CA2195856C - Substituted o6-benzylguanines and use thereof - Google Patents

Abstract

The present invention provides AGT inactivating compounds such as substituted O6-benzylguanines of formula (I) wherein 7- or 9-substituted 8-aza-O6-benzylguanines, 7,8-disubstituted O6-benzylguanines, 7,9-disubstituted O6-benzylguanines, 4(6)-substituted 2-amino-5-nitro-6(4)-benzyloxypyrimidines, and 4(6)--substituted 2-amino-5-nitroso-6(4)-benzyloxypyrimidines, as well as pharmaceutical compositions comprising such compounds along with a pharmaceutically acceptable carrier. The present invention further provides a method of enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent which causes cytotoxic lesion at the O6-position of guanine, by administering to a mammal an effective amount of one of the aforesaid compounds, 2,4-diamino-6-benzyloxy-s-triazine, 5-substituted 2,4-diamino-6-benzyloxypyrimidines, or 8-aza-O6-benzylguanine, and administering to the mammal an effective amount of an antineoplastic alkylating agent which causes cytotoxic lesions of the O6-position of guanine.

Description

TECHNICAL FIELD OF THE INVENTION
The present invention relates to substituted 06-benzylguanines, 06-benzyl-8-azaguanines, and 6(4)-benzyloxypyrimidines, pharmaceutical compositions comprising such compounds, and methods of using such compounds. The subject compounds are particularly useful in inactivating the human DNA repair protein 06-alkylguanine-DNA alkyltransferase.

BACKGROUND OF THE INVENTION
The inactivation of the human DNA repair protein 06-alkylguanine-DNA alkyltransferase (AGT) by 06-benzylguanine leads to a dramatic enhancement in the cytotoxic response of human tumor cells and tumor xenografts to chemotherapeutic.drugs whose mechanism of action involves modification of DNA guanine residues at the 06-position (Dolan et al., Proc. Natl. Acad. Sci. U.S.A., 87, 5368-5372 (1990); Dolan et al., Cancer Res., 51, 3367-3372 (1991);
Dolan et al., Cancer Commun., 2, 371-377 (1990); Mitchell et al., Cancer Res., 52, 1171-1175 (1992); Friedman et al., J. Natl. Cancer Inst., 84, 1926-1931 (1992); Felker et al., Cancer Chem. Pharmacol., 32, 471-476 (1993); Dolan et al., Cancer Chem. Pharmacol., 32, 221-225 (1993); Dolan et al., Biochem. Phazmacol., 46, 285-290 (1993)). The AGT
inactivating activity of a large number of 06-benzylguanine analogs have been compared with the aim of obtaining information about the types of substituent groups and the sites at which they could be attached to 06-benzylguanine without significantly lowering its AGT-inactivating activity (Moschel et al., J. Med. Chem., 35, 4486-4491 (1992); Chae et al., J. Med. Chem., 37, 342-347 (1994)).
While these studies led to the production of a variety of analogs that were as potent or somewhat less potent than 06-, benzylguanine, none of the analogs were better than 06-benzylguanine.

WO 96/04281 21()5Q5[1 L pCT/US95/09702 ' O

Thus, there remains a need for additional compounds which are capable of enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent which causes cytotoxic-lesions at the 06-position of guanine. The present invention provides such compounds and associated pharmaceutical compositions and treatment methods. These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

BRIEF SL?V~ OF THE INVENTION
The present invention provides 7- and 8-substituted 06-benzylguanine derivatives, 7,8-disubstituted 06-benzylguanine derivatives, 7,9-disubstituted 06-benzylguanine derivatives, 8-aza-06-benzylguanine derivatives, and 4(6)-substituted 2-amino-5-nitro-6(4)-benzyloxypyrimidine and 2-amino-5-nitroso-6(4)-benzyloxypyrimidine derivatives which have been found to be effective AGT inactivators, a's well as pharmaceutical compositions comprising such derivatives along with a pharmaceutically acceptable carrier. The present invention further provides a method of enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent which causes cytotoxic lesions at the 06-position of guanine, by administering to a mammal an effective amount of one of the aforesaid derivatives, 2,4-diamino-6-benzyloxy-s-triazine, 5-substituted 2,4-diamino-6-benzyloxypyrimidines, or 8-aza-06-benzylguanine, and administering to the mammal an effective amount of an antineoplastic alkylating agent which causes cytotoxic lesions at the 06-position of guanine. -WO 96/04281 PCTIUS95l09702 ~ , . . _ I2ESCRIPTION*OF THE PRSFERRED EMBODIMENTS
The present invention provides a compound of the formula I

(I) N
Ii '\- gs R2~ s N
x R, wherein-R1 is a substituent selected from the group consisting of amino, hydroxy, C1-C4 alkylamino, C1-C4 dialkylamino, and C1-C4 acylamino (although, as explained in further detail below, other substituents can be placed at this 2-position), R2 is a substituent selected from the group consisting of hydrogen, C;-C4 alkyl, C1-C4 aminoalkyl, C1-C4 hydroxyalkyl, C1-C4 alkylaminoalkyl, C1-C4 dialkylaminoalkyl, Ci-C4 cyanoalkyl, C1-C4 carbamoylalkyl, C1-C4 pivaloylalkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, carbo C2.-C4 alkoxyalkyl, ribose, 2'-deoxyribose, the conjugate acid.form of a C1-C4 carboxyalkyl, and the carboxylate anion of a C1-C4 carboxyalkyl as the sodium salt (although, as explained in further detail below, other substituents can be placed at this N9-position), and R3 is a substituent selected from the group consisting of hydrogen, halo,C1-C4 alkyl, C1-C4 hydroxyalkyl, thiol, C1-C4 alkylthio, trifluoromethylthio, C1-C4 thioacyl, hydroxy, C1-CQ alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, Cl-Ca acyloxy, amino, C1-C4 aminoalkyl, C1-C4 alkylamino, C1-C4 dialkylamino, trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, C1-C4 aminoacyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, C1-C4 alkyldiazo, CS-C6 aryldiazo, trifluoromethyl, C1-C4 haloalkyl, halomethyl, C1-C4 cyanoalkyl, cyanomethyl, cyano, ~

C1-C4 alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, C1-C4 alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SOnR' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl, with the proviso that R1 is not amino when both R2 and R3 are hydrogen, and with the proviso that R1 is not amino or methylamino when R. is ribose or 2'-deoxyribose and R. is hydrogen. It is to be understood that the substituents are defined herein such that the group farthest from the point of attachment of the substituent is named first. By way of illustration, C1-C6 alkylcarbonyloxy C1-C4 alkyl includes pivaloyloxymethyl.
Suitable compounds of the above formula include those compounds wherein R. is selected from the group consisting of amino, hydroxy, C1-C4 alkylamino, C1-C4 dialkylamino, and C1-C4 alkylcarbonylamino, R2 is selected from the group consisting of hydrogen, C1-C4 alkyl, and C1-C6 alkylcarbonyloxy C1-C. alkyl, and R3 is selected from the group consisting of amino, halo, C1-C4 alkyl, hydroxy, and trifluoromethyl. Other suitable compounds include those wherein R1 is selected from the-group consisting of amino, hydroxy, methylamino, dimethylamino, and acetylamino, R2 is selected from the group consisting of hydrogen, methyl, and pivaloyloxymethyl, and R3 is selected from the group consisting of amino, bromo, methyl, hydroxy, and trifluoromethyl. Examples of suitable compounds include 8-amino-06-benzylguanine, 8-methyl-06-benzylguanine, 8-hydroxy-06-benzylguanine, 8-bromo-06-benzylguanine, 8-trifluoromethyl-06-benzylguanine, 06-benzylxanthine, 06-benzyluric acid, N2-acetyl-06-benzyl-8-oxoguanine, 06-benzyl-N2-methylguanine, 06-benzyl-NZ,N2-dimethylguanine, 06-benzyl-8-trifluoromethyl-9-methylguanine, 06-benzyl-8-bromo-9-methylguanine, and 06-benzyl-8-bromo-9-(pivaloyloxymethyl)guanine.

4a In one aspect of the present invention there is a pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound of the formula \
/
O ~
/CH=
~\ s N, N
~
, Ri 'N/= N
' RZ

wherein R1 is a substituent selected from the group consisting of amino, hydroxy, C1-C4 alkylamino, C1-C4 dialkylamino, and C1-C4 alkylcarbonylamino, R2 is a substituent selected from the group consisting of hydrogen, Cl-C4 alkyl, Cl-C4 aminoalkyl, Cl-C4 hydroxyalkyl, Cl-C4 alkylamino Cl-C4 alkyl, Cl-C4 dialkylamino alkyl, Cl-C4 cyanoalkyl, Cl-C4 carbamoylalkyl, Cl-C4 pivaloylalkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkoxycarbonylalkyl, 2' -deoxyribose, the conjugate acid form of a Cl-C4 carboxyalkyl, and the carboxylate anion of a Cl-C4 carboxyalkyl as the sodium salt, and R3 is a substituent selected from the group consisting of halo, C1-C4 alkyl, Cl-C4 hydroxyalkyl, mercapto, Cl-C4 alkylthio, trifluoromethylthio, C1-C4 alkylthiocarbonyl, hydroxy, C1-C4 alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, C1-C4 alkylcarbonyloxy, amino, Cl-C4 aminoalkyl, Cl-C4 alkylamino, Cl-C4 dialkylamino, trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, amino C1-C4 alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, Cl-C4 alkyldiazo, CS-C6 aryldiazo, trifluoromethyl, Cl-C4 4b haloalkyl, C1-C4 cyanoalkyl, cyano, C1-C4 alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, C1-C4 alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SOnR' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl.

In another aspect of the present invention there is a use of a compound of the formula O
/C H O

N s N
~ ~
,~Rs R 2~
i N
Rz wherein R1 is a substituent selected from the group consisting of amino, hydroxy, Cl-C4 alkylamino, C1.-C4 dialkylamino, and C1.-C4 alkylcarbonyl, R2 is a substituent selected from the group consisting of hydrogen, C1-C4 alkyl, Cl-C4 aminoalkyl, Cl-C4 hydroxyalkyl, Cl-C4 alkylamino Cl-C4 alkyl, Cl-C4 dialkylamino alkyl, Cl-C4 cyanoalkyl, Cl-C4 carbamoylalkyl, C1-C4 pivaloylalkyl, Cl-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkoxycarbonylalkyl, 2'-deoxyribose, the conjugate acid form of a C1-C4 carboxyalkyl, and the carboxylate anion of a C1-C4 carboxyalkyl as the sodium salt, and R3 is a substituent selected from the group consisting of halo, Cl-C4 alkyl, C3.-C4 hydroxyalkyl, mercapto, Cl-C4 alkylthio, trifluoromethylthio, Cl-C4 alkylthiocarbonyl, hydroxy, C1-C4 alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, C1-C4 alkylcarbonyloxy, amino, C1-C4 aminoalkyl, C1-C4 alkylamino, Cl-C4 dialkylamino, 4c trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, amino C1-C4 alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, C1-C4 alkyldiazo, C5-C6 aryldiazo, trifluoromethyl, C1-C4 haloalkyl, C1-C4 cyanoalkyl, cyano, C1-C4 alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, C1.-C4 alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SOnR' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl, in the manufacture of a medicament for enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent that causes cytotoxic lesions at the 06-position of guanine.

In yet another aspect of the present invention there is a product containing.compound of the formula \
~
/
O/CH=

e\s N, N

i RZ
wherein R1 is a substituent selected from the group consisting of amino, hydroxy, C1-C4 alkylamino, C1-C4 dialkylamino, and C1-C4 alkylcarbonyl, R2 is a substituent selected from the group consisting of hydrogen, C1-C4 alkyl, C1-C4 aminoalkyl, C1-C4 hydroxyalkyl, Cl-C4 alkylamino C1-C4 alkyl, C1-C4 dialkylamino alkyl, C1-C4 cyanoalkyl, C1-C4 carbamoylalkyl, C1-C4 pivaloylalkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkoxycarbonylalkyl, 2'-deoxyribose, the conjugate acid form of a C1-C4 carboxyalkyl, and the carboxylate anion of a Cl-C4 4d carboxyalkyl as the sodium salt, and R3 is a substituent selected from the group consisting of halo, C1-C4 alkyl, C1-C4 hydroxyalkyl, mercapto, C1-C4 alkylthio, trifluoromethylthio, C1-C4 alkylthiocarbonyl, hydroxy, C1-C4 alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, C1-C4 alkylcarbonyloxy, amino, C1-C4 aminoalkyl, C1-C4 alkylamino, C1-C4 dialkylamino, trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, amino C1-C4 alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, C1-C4 alkyldiazo, C5-C6 aryldiazo, trifluoromethyl, C1-C4 haloalkyl, C1-C4 cyanoalkyl, cyano, C1-C4 alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, Cl-C4 alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SOnR' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl, and an antineoplastic alkyating agent which causes cytotoxic lesions at the 06-position of guanine, for simultaneous, separate or sequential use for enhancing chemotherapeutic treatment of tumor cells in a mammal.

The following terms are understood as equivalent:
C1_4 acylamino - C1_4 alkylcarbonylamino;
thiol - mercapto;

C1_4 thioacyl - C1_4 alkylthiocarbonyl; and C1_4 acyloxy - C1_4 alkylcarbonyloxy.

WO 96/04291 21/ 58,50 PCT/QS95/09702 s The present invention also provides a compound of the formula II

\
~CR~I /

= (II) Rt Hs Ra wherein R1 is NOa or NO, and R2 is a substituent selected from the group consisting of hydrogen, halo, C1-C4 alkyl, C1-C4 hydroxyalkyl, thiol, C1-C4 alkylthio, trifluoromethylthio, C1-C4 thioacyl, hydroxy, C1-C4 alkyloxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, Cl-C& acyloxy, C1-C4 aminoalkyl, C1-C& alkylamino, C1-C4 dialkylamino, trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, amino C1-C4 alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, C1-C4 alkyldiazo, CS-C6 aryldiazo, trifluoromethyl, C1-C4 haloalkyl, cyanomethyl, C1-C4 cyanoalkyl, cyano, C1-Cy alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, C1-C4 alkoxymethyl, phenoxymethyl, C2-Cq vinyl, C2-C4 ethynyl, and SOnR' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl.
Suitable compounds include those compounds wherein R1 is NO2 and R. is hydrogen or a C1-C4 alkyl. Examples of suitable compounds include 2-amino-4-benzyloxy-5-nitropyrimidine and 2-amino-4-benzyloxy-6-methyl-5-nitropyrimidine.
The present invention further provides a compound of the formula III

WO 96104281 2195856 PCTlUS95/09702 ~

\
dCHll ~
(III) / N
I \
~ N
H
s N
k R
wherein R is selected from the group consisting of C1-C4 alkyl, C1-C4 alkyloxycarbonyl C1-C4 alkyl, carboxy Cl-C4 alkyl, cyano C1-CQ alkyl, aminocarbonyl C1-C4 alkyl, hydroxy Cl-C4 alkyl, and C1-C4 alkyloxy C1-Cy alkyl. Suitable compounds of the above formula include those wherein R is selected from the group consisting of C1-C4 alkyl and C1-C6 alkylcarbonyloxy C1-C4 alkyl. Examples of suitable compounds include 8-aza-06-benzyl-9-methylguanine and 8-aza-06-benzyl-9-(pivaloyloxymethyl)guanine.
The present invention further provides a compound of the formula IV

\
CHZI ~
Q
d R (IV) N
N
H
a M" N

wherein R is selected from the group consisting of Ci-C4 alkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkyloxycarbonyl C1-C4 alkyl, carboxy C1-C4 alkyl, cyano C1-C4 alkyl, aminocarbonyl C1-C4 alkyl, hydroxy C1-C4 alkyl, and C1-C4 alkyloxy Cl-C4 alkyl. Suitable compounds include those wherein said R is C1-C6 alkylcarbonyloxy C1-C4 alkyl.
An example of a suitable compound is 8-aza-06-benzyl-7-(pivaloyloxymethyl)guanine.

WO 96104281 2195856 .PCT/US95109702 The present invention further provides a compound of the formula V

IRa ( V ) / N
N/I~~ />-R, ~
, N
wherein R1 is selected from the group consisting of hydrogen, halo, C1-C4 alkyl, halo C1-C4 alkyl, C1-C6 alkylcarbonyloxy C1-C. alkyl, C1-C4 alkyloxycarbonyl C1-C4 alkyl, carboxy C1-C4 alkyl, cyano Cl-Cy alkyl, aminocarbonyl Cl-C4 alkyl, hydroxy C1-C4 alkyl, and C1-C4 alkyloxy C1-C4 alkyl, and R2 is selectd from the group consisting of C1-C4 alkyl, halo C1-C4 alkyl, C1-C6 alkylcarbonyloxy Cl-C4 alkyl, C1-C4 alkyloxycarbonyl C1-C4 alkyl, carboxy C1-C4 alkyl, cyano C1-C4 alkyl, aminocarbonyl C1-C4 alkyl, hydroxy C1-C4 alkyl, and C1-C4 alkyloxy C1-C4 alkyl, with the proviso that when R1 is hydrogen, R. is selected from the group consisting of halo C1-C4 alkyl, Cl-C~ alkyloxy C1-C4 alkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C3-C4 alkyloxycarbonyl C1-C4 alkyl, carboxy Ca-C4 alkyl, cyano C2-C4 alkyl, aminocarbonyl C2-C4 alkyl, and hydroxy Cl-C3 alkyl.
Suitable compounds include those wherein R1 is hydrogen or halo, and R2 is C1-C6 alkylcarbonyloxy C1-C4 alkyl.
Examplesof suitable compounds include 06-benzyl-8-bromo-7-(pivaloyloxymethyl)guanine and 06-benzyl-7-(pivaloyloxymethyl)guanine.
The present invention additionally provides treatment methods, which are generally administered via pharmaceutical compositions comprising one or more of the 06-substituted compounds of the present invention. In particular, the present invention provides a method of enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent that causes cytotoxic lesions at the O6-position of guanine,-which method comprises administering to a mammal an effective amount of one or more of the aforedescribed present inventive compounds of formulas I-V1 and administering to the mammal an effective amount of an antineoplastic alkylating agent that causes cytotoxic lesions at the 06-position of guanine. The present invention also includes the method of enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent that causes cytotoxic lesions at the 06-position of guanine, which method comprises (i) administering to a mammal an effective amount of - -(a) 8-aza-06-benzylguanine N
~ N
H N
a g (b) a compound of the formula VI -(VI) R

Hy NHy - -wherein R is a substituent selected from the group ' consisting of hydrogen, halo, C1-C4 alkyl, C1-C4 hydroxyalkyl, thiol, C1-C4 alkylthio, trifluoromethylthio, C1-C4 thioacyl, hydroxy, C1-C4 alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, C1-C4 acyloxy, amino, C1-C4 aminoalkyl, Cl-Cy alkylamino, Cl-C4 . 2195856 ~

dialkylamino,,trifluoromethylamino;-ditrifluoromethylamino, aminomethanesulfonyl, amino CI-Ca alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, Ci-C4 alkyldiazo, C5-C6 aryldiazo, trifluoromethyl, Cz-CQ
haloalkyl, halomethyl, cyanomethyl,Ci-Ca cyanoalkyl, cyano, C1-C4 alkyloxycarbonyl, C1-C9 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, C1-C4 alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SOõR' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1 C4 alkyl, amino, or phenyl, or (c) 2,4-diamino-06-benzyl-s-triazine, and (ii) administering to the mammal an effective amount of an antineoplastic alkylating agent which causes cytotoxic lesions at the 06-position of guanine.
Several 06-substituted compounds were tested for their ability to inactivate the human DNA repair protein, 06-alkylguanine-DNA alkyltransferase (AGT, alkyltransferase).
Two classes oLf compounds were identified as being significantly better than 06-beniylguanine (the prototype low-molecular-weight inactivator) in inactivating AGT in human HT29 colon tumor cell extracts. These were 8-substituted O6-benzylguanines bearing electron-withdrawing groups at the 8-position and 5-substituted 2,4-diamino-6-benzyloxypyrimidines bearing electron-withdrawing groups at the 5-position. The latter derivatives were also more effective than-06-benzylguanine in inactivating AGT in intact HT29 colon tumor cells. Both types of compounds were as effective or more effective than 0'6-benzylguanine in enhancing cell killing by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) of colon, breast and prostate cancer cells grown in culture. Provided 8-substituted 06-benzylguanine derivatives bearing electron-withdrawing substituents at the 8-position and 5-substituted 2,4-diamino-6-benzyloxypyrimidines bearing electron-withdrawing substituents at the 5-position do not exhibit undesirable toxicity, they should be superior to 06-benzylguanine as chemotherapeutic adjuvants for enhancing the effectiveness of antitumor drugs whose mechanism of action involves t~ME~'DED SNEET

= 21953.56 modification of the Ob-position of DNA guanine residues.
The specific-compounds surveyed for AGT inactivating activity are illustrated below.

0~CH2 0 O~CH2 0 ~ N -~
H2N N H H2N \N H
1aa 2 1 a, R-NH2 ib, R-CH3 1o,R-OH
1d, R-Br ie, R-CF3 0 ~CH2 0 C~CH2 ~R2 N - N
N I I ~R2 Ri~N NH2 RiN~~
3a-f 4a-f 3a, R,-H; R2-NO2 4a, Ri-HO; R2-H
3b, Ri-NH2; R2-H 4b, Ri-HO; R2-OH
30, Rl-NHZ; RZ-NH2 40, Rj-F; R2-H
3d, Ri-NH2; R2-NO 4d, RI-CH3CONH; R2-OH
Se, RI-NHZ R2-N02 4e, R,-CH3NH; R2-H
8f, RI-NH2; R2-9r 4f, Ri-(CH3)2N; R2-H

O,CN2 0 0 ~CH2 ~ I O'CH2 N NOZ N J~', N N N
I ~-CF3 5a,b Sa, R-H
5b, R - CH3 AMEIDED SHEET

2 195356.
_ = - _, .,-\
/C H

CH i N/ N O H=OCOC(CH
\ I N / ~
H=N~N N ~ I ~N
HiN N N
8a-b 9 8a, R = CH3 8b, R = CHZOCOC (CH3) 3 I /
~
/CHa CH= /
N CH=OCOC(CHI);
\>8r N N
N /Br HaN N ~
H=N N N

lOa-b 10a, R = CH3 10b, R = CH2OCOC(CH3)3 ~,CH I /
~
i H=OCOC(CH3)3 NC
/
N

/>
~
H=N N N

AMENDED SK-ET

Preparations of the 8-substituted O6-benzylguanine derivatives 8-amino-06-benzylguanine (la) and O6-benzyl-8-methylguanine(ib) were accomplished by treating 2,8-diamino-6-chloropurine and 2-amino-6-chloro-8-methylpurine, respectively, with sodium benzyloxide in benzyl alcohol.
O6-Benzyl-8-oxoguanine (06-benzyl-7, 8-dihydro-8-oxoguanine, lc) was prepared by reacting 1,1'-carbonyldiimidazole with 2,4,5-triamino-6-benzyloxypyrimidine (pfleiderer et al., Chem. Ber., 94, 12-18 (1961)). For convenience, the compound is illustrated in the B-hydroxy tautomeric form although it most probably exists in solution in the 8-keto form with a hydrogen attached to the 7-nitrogen atom. O6-Benzyl-8-broinoguanine (1d) was prepared by bromination of 06-benzylguanine. O6-Benzyl-8-trifluoromethylguanine (le) was preparad by reacting 2-amino-6-chloro-8-trifluoro-methylpurine with sodium benzyloxide in benzyl alcohol. 8-Aza-Og-benzylguanine (2) was prepared through nitrous acid treatment of 2,4,5-triamino-6-benzyloxypyrimidine.
Compound 2 had been prepared previously by another route (Shealy et al., J. Org. Cheta., 27, 4518-4523 (1962)).
With respect to the pyrimidine derivatives (3a-f), 4-amino-6-benzyloxy-5-nitropyrimidine (3a) was prepared by treating 4-amino-6-chloro-5-nitropyrimidine (Boon et al., J. Chem. Soc., 96-102 (1951)) with sodium benzyloxide in benzyl alcohol. Derivatives 3b-d were prepared by the method of Pfleiderer et al. (Chem. Ber., 94, 12-18 (1961)).
2,4-Diamino-6-benzyloxy-5-nitropyrimidine (3e) and 2,4-diamino-6-benzyloxy-5-bromopyrimidine (3f) were prepared previously by Kosary et al. (Acta Pharm. Hung., 49, 241-247 (1989) );.
The purines, 06-benzylxanthine (4a) and O6-benzyluric acid (4b) uiere prepared by nitrous acid deamination of 06-benzylguanine and 06-benzyl-8-oxoguanine, respectively. AF-Acetyl-06-benzyl-8-oxoguanine (Af-acetyl-O6-benzyl-7,8-dihydro-8-oxoguanine)(4d) was prepared through acetylation IfMEND~D SHEET

i of OS-benzyl-8-oxoguanine (1c). o6-Benzyl-2-fluorohypoxanthine (4c) was prepared previously by Robins and Robins (J. Org. Chem., 34, 2160-2163 (1969)). This material was treated with methylamine and dimethylamine to produce OB-benzyl-N2-methylguanine (4e) and O6-benzyl-l~,t?-dimethylguanine (4f), respectively.
Compounds Sa (2-amino-4-benzyloxy-5-nitropyrimidine) and 5b (2-amino-4-benzyloxy-6-methyi-5-nitropyrimidine) were prepared by treating 2-amino-4-chloro-5-nitropyrimidine and 2-amino-4-chloro-6-methyl-5-nitropyrimidine (Boon et al., J. Chem. Soc., 96-102 (1951)), respectively, with sodium benzyloxide in benzyl alcohol. Compound 6 (2,4-diamino-6-benzyloxy-s-triazine) was prepared previously under similar conditions (Wakabayashi et al., Nippon Dojo-Hiryyogaku Zasshi, 41, 193-200 (1970)): 06-Benzyl-8-trifluoromethyl-9-methylguanine _(7) was prepared by treating the anion of le with methyl iodide in N,IF-dimethylformamide.
Compound 8a was prepared by methylating the sodium salt of 8-aza-O6-benzylguanine using methyl iodide as the methylating agent. Compounds 8b and 9 were prepared by the reaction of the sodium salt of 8-aza-O6-benzylguanine and chloromethyi pivalate. Compound 10a was prepared by direct bromination of O6-benzyl-9-methylguanine. Compounds lOb and 11 were prepared by the reaction of the sodium salt of O6-benzyl-8-bromoguanine and chloromethyl pivalate. Compound 12 was prepared by the reaction of the sodium salt of 06-benzylguanine and chloromethyl pivalate.
Theability of these compounds to inactivate the AGT
protein in HT29-human colon tumor ce11 extracts and in intact HT29 cells is summarized in Tables 1 and 2. The data represent the dose of compound required to produce 50%
inactivation in cell-free extracts upon incubation for 30 min or in cells upon incubation for 4 hr.

AMENDED SHEET

;2195856 Table 1. AGT-Inactivating Activity of 6-Benzyloxypurine, 6(4)-Benzyloxypyrimidine, and 6-Benzyloxy-s-triazine Derivatives ED5o (mM) In HT29 In cell-free HT29 Compound - extract cells 2,4-diamino-6-benzyloxy-5- 0.06 0.02 nitrosopyrimidine (3d) 2,4-diamino-6-benzyloxy-5-nitropyrimidine 0.06 0.02 (3e) 8-aza-06-benzylguanine (2) 0.07 0.06 06-benzyl-8-bromoguanine (id) 0.08 0.06 O6-benzylguanine 0.2 0.05 06-benzyl-8-methyl-guanine (lb) 0.3 0.1 06-benzyi-B-oxoguanine (lc) 0.3 0.15 06-benzyl-8-trifluoromethylguanine (le) 0.4 0.25 2,4,5-triamino-6-benzyloxypyrimid'ine (3c) 0.4 0.3 2-amino-4-benzyloxy-6-methyl-5- 0.4 0.06 nitropyrimidine (5b) 2-amino-4-benzyloxy-5-nitropyrimidine (5a) 0.4 0.05 8-am.ino-06-benzylguanine (la) 0.7 2 2,4-diamino-6-benzyloxy-5-bromopyrimidine 2 0.8 (3f) 2,4-diamino-6-benzyloxy-s-triazi.ne (6) 4 1.0 2,4-diamino-6-benzyloxypyrimidine (3b) 15 5 06-benzyluric acid (4b) 25 45 4-amino-6-benzyloxy-5-nitropyrimidine (3a) 28 8 06-benzyl-2-fluorohypoxanthine (4c) 48 12 06-benzylxanthine (4a) 60 35 1~-acetyl-O6-benzyl-8-oxoguanine (4d) 65 11 06-benzyl-l~-methylguanine (4e) 160 60 06-benzyl-N2, NZ-dimethylguanine (4f) 200 110 The effective dose required to produce 50% inactivation in cell-free extracts upon incubation for 30 min or in cells upon incubation for 4 hr. The values for O6-benzylguanine are from Moschel et al., J. Med. Chem., 35, 4486-4491 (1992).

XL.jr5d[;FV JRLCT

:2 195 856 is Within-these series of compounds, 06-benzyl-le-methyl-and 06-benzyl-1~f,1~-dimethylguanine (4e and 4f) were the least active agents exhibiting ED50 values for inactivation of AGT in HT29 cell extracts of 160 and 200 mM, respectively. - For comparison, the ED50 value exhibited by 06-benzylguanine was 0.2 mM (Table 1) The other 2- and/or 8-substituted6-benzyloxypurines, N2-acetyl-06-benzyl-8-oxoguanine (4d), 06-benzylxanthine (4a), 06-benzyl-2-fluorohypoxanthine (4c) and 0s-benzyluric acid (4b), together with the substituted pyrimidines 4-amino-6-benzyloxy-5-initropyrimidine (3a) and 2,4-diamino-6-benzyloxypyrimidine (3b), comprised a group of increasingly more active-AGT inactivating agents exhibiting intermediate ED5o values in the range of 65 to 15 mM. 2, 4-Diamino-6-benzyloxy-s-triazine (6) and 2,4-diamino-6-benzyloxy-5-bromopyrimidine (3f) were considerably more active than 3b indicating that electron-withdrawing groups at the 5-position of a 2,4-diamino-6-benzyloxypyrimidine derivative-are positive contributors to efficient AGT inactivation.
This is further emphasized by the very high activity exhibited by 2,4-diamino-6-benzyloxy-5-nitrosopyrimidine (3d) and 2,4-diamino-6-benzyloxy-5-nitropyrimidine (3e), which contain strongly electron-withdrawing nitroso and nitro substituents, respectively. These two derivatives are the most active AGT inactivators tested to date. The observation that 2-amino-4-benzyloxy-5-nitropyrimidine (5a) is much more active than 3a indicates that a 2-amino group is critical_for high activity for a6(4)-benzyloxy-5-nitropyrimidine derivative. An additional alkyl group at the 4(6)-position (e.g., as in 5b) does not enhance activity significantly over that for 5a although an amino group at the 4(6)-position significantly enhances activity.
Thus, AGT inactivating activity increases substantially over the series-5a=5b<3d=3e. With these considerations in mind the activity of 2,4,5-triamino-6-benzyloxypyrimidine (3c) seems exceptional and the reasons for its relatively high activity are unclear at present. It is also AMENDED SHEET

-Z l 9,-85b .:; .
_ ~ . . ....16 significant that pyrimidines 5a and 5b are quite active in cells, which is not totally predicted by their corresponding activity in HT29 ce11_extracts.
All the 06-benzylguanine analogs la-d were much more active than the purines in the series 4a-f and the activity differences among la-d also reflect enhancements due to introduction of electron withdrawing groups. Thus, activity increased in the series 8-amino-06-benzylguanine (la) <06-benzyl-8-oxoguanine (1c) <Og-benzyl-8-methylguanine (ib) <Os-benzyl-8-bromoguanine (1d) <8-aza-06-benzylguanine (2). Indeed, derivatives ld and 2 were essentially as active as pyrimidines 3d and 3e in cell-free extracts although ld and 2 were somewhat less active in cells than expected from their activity in cell-free extracts.
- The compounds listed in Table 2 also had AGT-inactivating activity in cell free extracts and in cells.
The activity of 7, 8a, and 10a in cells is significantly higher than their activity in cell-free extracts. Thus the ratio of EDso values in cell-free extracts/intact cells is 1.6, 1.6, 1.1, respectively, for derivatives ld, le, and 2 (Table l). This ratio increases to 7.2, 6.3 and 6.3, respectively, for the corresponding methylated derivatives 10a, 7, and Ba. It is believed that the higher activity of the methylated derivatives in the cells is due to the fact that these compounds do not possess readily dissociable hydrogens in the imidazole portion of the purine ring system and therefore they can readily enter the cells as neutral.molacules.

AMENDED SHEET

195.556 ~

Table 2. AGT-Inactivatinq Activity of 7,8- and 8,9-Disubstituted.0 -Benzylguanine Derivatives and Related Compounds ED50 value (mM)' In HT29 In cell-free HT29 Compound extract cells 06-benzyl-8-trif.l.uoromethyl-9-methylguanine 2.5 0.4 (7) 8-aza-0s-benzyl-9-methylguanine (8a)--__ 0.5 0.08 8-aza-06-benzyl-9- 0.28b 0.23 (pivaloyloxyinethyl)guanine (8b) 8-aza-06-benzyl-7- 0.11' 0.16 (pivaloyloxymethyl)guanine (9) Og-benzyl-8-bromo-9-methylguanine (10a) 1.9 0.25 Og-benzyl-8-bromo-9- 0.08d 0.05 _ (pivaloyloxymethyl)guanine (lOb) Os-benzyl-7-(pivaloyloxymethyl)guanine (12) 9e 0.3 O6-benzyl-9-(pivaloyloxymethyl)guanine 3.1t'4 0.3 06-benzyl-9-methylguanine 2. 6; 0.4 The dose required to produce-508 inactivation in ce11-.
free.extracts upon incubation for 30 min. or in cells upon incubation for 4 hr. 6ED5o=4with 9 urified human AGT. ED50=2 with purified human AGT. ED5o > 100 with P urified human AGT. 'ED50 >> 100 with purified human AGT.
EDSo = 95 with purified human AGT. 4Data from Chae et al., J. Med. Chem., 37, 342-347 (1994) The ability of,increasing concentrations of la-d, 2, and 3c-e to enhance the killing of human HT29 colon cancer cells, DU-145 prostate cancer cells, and MCF-71 breast cancer cells by BCNU (40 mM) is shown in Tables 3, 4, and 5, respectively. The data reflect the number of cell colonies that result followiing exgosure to AGT inactivator alone or AGT inactivator 2 hr before exposure to BCNU as described in Dolan et al. (Proc. Nat1. Acad. Sci., U.S.A., 87, 5368-5372 (1990)). Data for e-benzylguanine are included for comparison. As indicated, at 10 mM

AMMDED ~~~

2 1-:95856 :: .

concentrations, all the 8-substituted purines with the exception of la were as effective as 06-benzylguanine in enhancing the cytotoxicity of BCNU (40 mM); such treatment killed essentially all the tumor cells. Treatment of the cells with the modified 8-substituted e-benzylguanine alone or BCNU alone had no significant effect on cell colony number. The comparatively low activity of la in all but the breast cancer cells may reflect its poor transport into other tumor cell types or its rapid metabolic conversion to an ineffective AGT inactivator: Its ineffective enhancement of BCNU cytotoxicity parallelsits relatively poor AGT inactivating ability in colon tumor cells (Table 1).
For the pyrimidines tested, 2,4,5-triamino-6-benzyldxypyrimidine (3c) was as effective as the 8-substituted Og-be_nzylguanine derivatives and OS-benzylguanine itself in enhancing BCNU toxicity although the nitroso- and nitropyrimidine derivatives (3d and 3e) were similarly effective at a 4-fold lower dose.

Table 3. Killing of HT-29 Colon Cancer Cells by BCNU
Combined with AGT inactivators Inactivator Inactivator BCNTJ Colony Concentration (mM) Formation (mM) per 1000 cells None None 435t63 None 40 442t34 06-benzylguanine 10 None 431 33 2.5 40 38t15 8-aza-06-benzylguanine 10 None 537 48 (2) . 10 40 2 1 1 40 423t42 06-benzyl-8-bromoguanine 10 None 401 22 (id) 10 40 1 0 AMENDED SFEEET"

21.~-)5850 : =

06-benzyl-8-oxoguanine 10 None 401 22 (ic) 10 40 <1 06-benzyl-8- 10 None 513t76 methylguanine_(lb) 10 40 <1 1 40 230f51 O6-benzyl-8-aminoguanine 10 None 504 30 (la) 10 40 430t41 1 40 475t26 2,4,5-triamino-6- 10 None 453i59 benzyloxypyrimidine (3c) 10 40 3 1 2,4-diamino-6-benzyloxy- 2.5 None 528 64 5-nitrosopyrimidine (3d) 2.5 40 <1 1 40 19t4 2,4-diamino-6-benzyloxy- 2.5 None 438t25 5-nitropyrimidine (3e) 2.5. 40 <1 Table 4. Killing of DU-145 Prostate Cancer Cells by BCNU
Combined with AGT Inactivators Colony Inactivator Formation Concentration BCNU per 1000 Inactivator ... (mM) . (mM) cells None None 453 81 None 40 394f76 06-benzylguanine 10 . None 462t68 40 _28 5 1 40 299t18 8-aza-06-benzylguanine 10 None - 452 72 (2) 10 . . 40 28 5 06-benzyl-8- 10 None 493 90 bromog,uanine (1d) 10 40 16 3 06-benzyl-8-oxoguanine 10 . . None 379t34 (1c) 10 40 34 3 1 40 329t43 06-benzyl-8- 10 . . None 357 43 10 40 50t7 AIb!E~lDED SFfÃE7"

= : : ..
methylguanine (lb) 1 40 306 157 O6-benzyl-8- 10 None 380t36 aminoguanine (la) 10 40 435 70 1 40 295t45 2,4,5-triamino-6- 10 None 429 101 benzyloxypyrimidine 10 40 57 7 (3c) 1 40 378 60 2,4-diamino-6- 2.5 None 403t35 benzyloxy-5- 2.5 40 7t3 nitrosopyrimidine 1 40 25 4 (3d) 0.25 40 192 17 2,4-diamino-6- 2.5 None 407 80 benzyloxy-5- 2.5 - 40 9t2 nitropyrimidine (3e) 1 40 59t6 0.25 .40 129t26 Table 5. Killing of MCF-71 Breast Cancer Cells by BCNU
Combined with AGT Inactivators Colony Inactivator Formation Inactivator Concentration BCNU per 1000 (mM) (mM) cells None - None 426 78 None 40 364 60 06-benzylguanine 10 None 455 63 2.5 40 12 6 8-aza-06-benzylguanine 10 None 483 27 (2) 10 40 2t1 06-benzyl-8-bromoguanine 10 None 380 109 (id) 10 40 3 1 2.5 40 4 3 06-benzyl-8-oxoguanine 10 None 522 78 (1c) 10 40 4 2 06-benzyl-8-methylguanine 10 None 376 76 (lb) . 10 40 2}1 06-benzyl-8-aminoguanine 10 None 432t36 (la) 10 40 95 8 AMENDED SFI;:ET

w ..

2,4,5-triamino-6- 10 None 448 55 benzyloxypyrimidine (3c) 10 40 12 4 2,4-diamino-6-benzyloxy- 2.5 None 447 87 5-nitrosopyrimidine (3d) 2.5 40 2 1 2,4-diamino-6-benzyloxy- 2.5 None 314 49 5-nitropyrimidine (3e) 2.5 40 2 1 Although the human alkyltransferase is very sensitive to inactivation by 0s-benzylguanine. and the_various compounds described above, a number of mutants have been generated that are resistant to 06-benzylguanine (Crone and Pegg, Cancer Res., 53, 4750-4753 (1993)). This resistance is probably caused by a reduction in the space surrounding the active site of the alkyltransferase, which limits the access to O6-benzylguanine. These mutants are produced by single base changes in the alkyltransferase DNA-coding sequence causing changes in one or two_amino acids in the alkyltransferase (Crone and Pegg, Cancer Res., 53, 4750-4753 (1993)). Thus, as indicated i.n Table 6, changing the proline residue at position 140 to alanine (protein P140A) or the glycineresidue at position 156 to an alanine (protein G156A) causes a 20-fold and a 240-fold increase in resistance to 06-benzylguanine, respectively. The alkyltransferase containing an arginine in place of a p-roline at residue 138 together with an arginine in place of a proline at-residue 140-(protein P138A/P140A) is 88-fold more resistant'to inactivation by 06-benzylguanine. It is possible that such resistant mutants wilL arise or be selected for in_tumors under the selective pressure generated by treatment with Og-benzylguanine plus an alkylat,ing agent. More potent inhibitors andlor those of a smaller size that are better able to fit into the space of the active site of-the mutant alkyltransferase can be used to advantage to overcome this resistance.
AMÃMDED SHFET

- ~ .. ' .. ..~

Table 6. Inhibition of Mutant Alkyltransferase Proteins by 06-Benzylguanine or 2, 4-Di amino- 6-benzyloxy-5-nitrosopyrimidine ED50 value (mM)' 2,4-diamino-6-Protein 06-benzylguanine --benzyloxy-5-nitroso-pyrimidine Control 0.25_- 0.05 -P140A - 5 0.1 P138A/P140A 22 0.3 'The concentration needed to inactivate 50% of the activity in 30 minutes.

As shown in Table 6, 2,4-diamino-6- . benzyloxy-5-nitrosopyrimidine (3d) was 50 to 60times better at inactivating the mutant alkyltransferases than 06-benzylguanine. Doses of 2,4-diamino-6-benzyloxy-5-nitrosopyrimidine leading to intracellular concentrations greater than 5 mM will therefore be effective at inactivating such resistant alkyltransferases.
Concentratiohs greater than 200 mM of 06-benzylguanine would be needed to get such inactivation, and these are much more than can be achieved with this compound in current formulations. However, 8-substituted 06-benzylguanine derivatives that are significantly more potent than O6-benzylguanine may be useful in inactivating mutant alkyltransferases provided their required intracellular concentrations can be achieved. These data for mutant alkyltransferase inactivation and the data presented earlier indicate that pyrimidine derivatives bearing electron-withdrawing groups at the 5-position as well as substituted 06-benzylguanine derivatives bearing electron-withdrawing groups at the 8-position are superior to 06-benzylguanine for useas adjuvants in chemotherapy with agents whose mechanism of action, like that of BCNU, AMENDED SHEET

= 585 6 ..=

involves modification of the 06-position of DNA guanine residues.
Other 8-substituted Os-benzylguanine derivatives bearing electron-withdrawing 8-substituents (e.g., NOZ) are readily available. For example, 06-benzyl-8-nitroguanine could be prepared by treatment of 8-nitroguanine (Jones and Robins, J. Am. Chem. Soc., 82, 3773-3779 (1960)) with phosphorus oxychloride to produce 2-amino-6-chloro-8-nitropurine which when treated with.sod.ium benzyloxide in benzyl alcohol would produce the desired 06-benzyl-8-nitroguanine.
Additional 2,4-diamino-6-benzyloxypyrimidine derivatives bearing electron-withdrawing groups other than halogen or nitro groups (e.g., formyl or cyano groups) could also be readily prepared. 2;4-Diamino-5-formyl-6-hydroxypyrimidine, a known compound (Delia and Otteman, Heterocycles, 20, 1805-1809 (1983)), can be treated with phosphorus oxychloride to produce a 2,4-diamino-6-chloro-5-formylpyrimidine intermediate, which on treatment with sodium benzyloxide in benzyl alcohol produces 2,4-diamino-.6-benzyloxy-5-formylpyrimidine. Treatment of the formyl pyrimidine with hydroxylamine affords 2,4-diamino-6-benzyloxy-5-cyanopyrimidine. The preparation of a large number of 5-substituted 6(4)-benzyloxypyrimidines or 8-substituted 06-benzylguanine derivatives is possible for those skilled in the art of synthesis of heterocyclic aromatic compounds (D.J. Brown, "The Pyrimidines," in The Chemistry of Heterocyclic Compounds, Vol. 16, A.
Weissberger, Ed., Wiley Interscience, New York, 1962; D.J.
Brown, "The Pyrimidines," Supplement I, in The Chemistry of Heterocyclic Compounds, Vol. 16, A. Weissberger and E.C.
Taylor,.. Eds., Wiley Interscience, New York, 1970; J.H.
Lister; "Fused Pyrimidines Part II Purines," in The Chemistry of Heterocyclic Compounds, Vol. 24 Part II, A.
Weissberger and E.C. Taylor, Eds., Wiley Interscience, New York, 1971).

ANltNO~D SHEET

.~195356 - ~ ~ . .:: ..

Because many 9-substituted O6-benzylguanine derivatives exhibit excellent AGT inactivation properties (Moschel et al., J. Med. Chem., 35, 4486-4491 (1992); Chae et al., J. Med. Chem., 37, 342-347 (1994)), 8,9-disubstituted analogs are expected to be similarly active.
These can be readily prepared by reacting the anion of 8-substituted Og-benzylguanines (e.g., la-e) or the anion of 8-aza-e-benzylguanine (2) with any of the range of compounds already described (Moschel et al., J. Med. Chem., 35, 4486-4491 (1992); Chae et al., J. Med. Chem., 37, 342-347 (1994)) to produce a mixture of isomeric 7,8- and 8,9-disubstituted 06-benzylguanine derivatives. The desired 8,9-disubstituted derivative can be isolated and purified by silica gel_-column chromatography as alreadydescribed (Moschel et al., J. Med. Chem., 35, 4486-4491 (1992); Chae et al., J. Med. Chem., 37, 342-347 (1994)). Compound 7 was prepared by treating the anion of compound le with methyl r iodide in N,N-dimethylformamide. Compounds 8-12 were prepared using similar procedures.-The OB-substituted compounds of the present invention can be administered in any suitable manner to a mammal for the purpose of enhancing the chemotherapeutic treatment of a particular cancer. Although more than one route can be used to administer a particular compound, a particular route can provide a more immediate and more effective reaction than another route. Accordingly, the described methods provided herein are merely exemplary and are in no way limiting.
Generally, the 06-substituted compounds of the present invention as described above will be administered in a pharmaceutical composition to an individual afflicted with a cancer. Those undergoing or about to undergo chemotherapy can be treated with the O6-substituted compounds separately or in conjunction with other treatments, as appropriate. In therapeutic applications, compositions are administered to a patient in an amount sufficient to elicit an effective depression of AGT

AWLMDED SHEET

activity thereby potentiating the cytotoxicity of the aforedescribed chemotherapeutic treatment. An amount adequate to accomplish this is defined.as a "therapeutically effective dose," which is also an "AGT
5 inactivating effective amount." Amounts effective for a therapeutic orprophylactic use will depend on, e.g., the stage and severity of the disease being treated, the age, weight, and general state of health of the patient, and the judgment of theprescribing physician. The size of the 10 dose will also be determined by the 06-substituted compound selected, method of administration, timing and frequency of administration as well as the existence, nature, and extent of any adverse side-effects that might accompany the administration of a particular 06-substituted compound and 15 the desired physiological effect. It will be appreciated by one of skill in the art that various disease states may require prolonged treatment involving multiple administrations, perhaps using a series of different AGT
inactivators and/or chemotherapeutic agents in each or 20 various rounds of administration.
Suitable chemotherapeutic agents usefully administered in coordination with the 06-substituted compounds of the present invention include alkylating agents, such as chloraethylating and methylating agents. Such agents may 25 be administered using conventional techniques such as those described in Wasserman et al., Cancer, 36, pp. 1258-1268 (1975), and Physicians' Desk Reference, 48th ed., Edward R.
Barnhart publisher (1994). For example, 1,3-bis(2-chloroethyl)-l-nitrosourea (carmustine or BCNU, Bristol-Myers, Evansville, IN) may be administered intravenously at a dosage of from about 150 to 200 mg/m2 every six weeks.
Another, alkylating agent, 1-(2-chloroethyl)-3-cyclohexyl-l-nitrosourea (lomustine or CCNU, Bristol-Myers), may be administered orally at a dosage of about 130 mg/mZ every six weeks. Other alkylating agents may be administered in appropriate dosages via appropriate routes of administration known to skilled medical practitioners.

RM~ND~D c.urc ~

. = ; ~~~

Suitable doses and dosage regimens can be determined by conventional range-finding techniques known to those of ordinary skill in the art. Generally, treatment is initiated with smaller dosages that are less than the 5. optimum dose of the compound. Thereafter, the dosage is increased by small increments until the optimum effect under the circumstances is reached. The present inventive method typically will involve the administration of about 0.1 mg to about 50 mg of one or more of the compounds described above per kg body weight of the individual. For a 70 kg patient, dosages of from about 10 mg to about 200 mg of 06-substituted compound would.be more commonly used, possibly followed by further lesser dosages from about 1 mg to about 1 mg of e-substituted compound over weeks to months, depending on a patient's physiological response, as determined by measuring cancer-specific antigens or other measurable parameters related to the tumor load of a patient.
It must be kept in mind that the compounds and compositions of the present invention generally are employed in serious disease states, that is, life-threatening or potentially life-thteatening situations. In such cases, in view of the minimization of extraneous substances and the relative nontoxic nature of the Os--substituted compounds, it is possible and may be felt desirable by the treating physician to administer substantial excesses of these Os-substituted compounds.
Single or multiple administrations of the compounds can be carried out with dose levels and pattern being selected by the treating physician. In any event, the pharmaceutical formulations should provide a quantity of AGT-inactivatinq compounds of the invention sufficient to effectively enhance the cytotoxic impact of the chemotherapy.
The pharmaceutical compositions for therapeutic treatment are intended for parenteral, topical, oral or local administration and generally comprise a AINF'NOEQ SN.cF:T

pharmaceutically acceptable carrier.and an amount of the active inqredient sufficient to reduce, and preferably prevent, the activity of the AGT protein. The carrier may be any of those conventionally used and is limited only by chemico-physical considerations, such as solubility and lack of reactivity with the compound, and by the route of administration.
Examples of pharmaceutically acceptable.acid addition salts for use in the present inventive pharmaceutical composition include those derived from mineral acids, such as hydrochloric, hydrobromic, phosphoric, metaphosphoric, nitric and sulfuric acids, and organic acids, such as tartaric, acetic, citric, malic, lactic, fumaric, benzoic, glycolic, gluconic, succinic, p-toluenesu.lphonic acids, and arylsulphonic, for example.
The pharmaceutically acceptable excipients described herein, for example, vehicles, adjuvants, carriers or diluents, are well-known to those who are skilled in the art and are readily available to the public. It is preferred that the pharmaceutically acceptable carrier be one that is chemically inert to the active compounds and one that has no detrimental side effects or toxicity under the conditions of use. Such pharmaceutically acceptable excipients preferably include saline (e.g., 0.9% saline), Cremophor EL (which is a derivative of castor oil and ethylene oxide available from Sigma Chemical Co., St.
Louis, MO) (e.g., 5% Cremophor EL/5B ethanol/90% saline, 10% Cremophor EL/90%r saline, or 50% Cremophor EL/50%
ethanol), propylene glycol (e.g., 40% propylene glycol/10%
ethanol/50% water), polyethylene glycol (e.g., 40% PEG
400/60% saline), and alcohol (e.g., 40% t-butanol/60%
water)., The most preferred pharmaceutical excipient for use in conjunction with the present invention is polyethylene glycol, such as PEG 400, and particularly a composition comprising 40% PEG 400 and 60% water or saline.
The choice.of excipient will be determined in part by the particular 06-substituted compound chosen, as well as by AA~NOED S4fET

4 ~195856=
. = . . ~., ~~ ' =
=..

the particular method used to administer the composition.
Accordingly, thereis a wide variety of suitable formulations of the pharmaceutical composition of the present invention.
The following formulations for oral, aerosol, parenteral, subcutaneous, intravenous, intraarterial, intramuscular, interperitoneal, rectal, and vaginal administration are merely exemplary and are in no way limiting.
The pharmaceutical compositions can be administered parenterally, e.g., intravenously, intraarterially, subcutaneously, intradermally, or intramuscularly. Thus, the invention provides compositions for parenteral administration that comprise a solution of the 06-substituted compound dissolved or suspended in an acceptable carrier suitable for parenteral administration, including aqueous and non-aqueous, isotonic sterile injection solutions.
Overall, the requirements for effective pharmaceutical -20_ carriers for parenteral compositions are well known to those of ordinary skill in the art. See Pharmaceutics and Pharmacy Practice, J.B. Lippincott Company, Philadelphia, PA, Banker and Chalmers, eds., pages 238-250-(1982), and ASHP Handbook on Injectable Drugs, Toissel, 4th ed., pages 25- 622-630 (1986) Such solutions cancontain anti-oxidants, buffers, bacteriostats, and solutes that render the formulation isotonic with the bloodof the intended recipient, and aqueo=us and non-aqueous sterile suspensions that can include suspending agents, solubilizers, 30 thickening agents, stabilizers, and preservatives. The compound may be administered in a physiologically acceptable diluent in a pharmaceutical carrier, such as a sterile liquid nr mixture of liquids, including water, saline, aqueous dextrose and related sugar solutions, an 35 alcohol, such as ethanol, isopropanol, or hexadecyl alcohol, glycols, such as propylene glycol or polyethylene glycol, dimethylsulfoxide, glycerol ketals, such as 2,2-AA~y ~en SNEET

- = ~ . ~.. . ' :: ..

dimethyl-1,3-dioxolane-4-methanol, ethers, such as poly(ethyleneglycol) 400, an oil, a fatty acid, a fatty acid ester or_glyceride, or an acetylated fatty acid glyceride with or without the addition of a pharmaceutically acceptable surfactant, such as a soap or a detergent, suspending agent, such as pectin, carbomers, methylcellulose, hydroxypropylmethylcellulose, or carboxymethylcellulose, or emulsifying agents and other pharmaceutical adjuvants.
Oils useful in parenteral formulations include petroleum, animal, vegetable, or synthetic oils. Specific examples of oils useful in such formulations include peanut, soybean, sesame, cottonseed, corn, olive, petrolatum, and mineral. Suitable fatty acids for use in parenteral formulations include oleic acid, stearic acid, and isostearic acid. Ethyl oleate and isopropyl myristate are examples of suitable fatty acid-esters.
Suitable soaps for use in parenteral formulations include fatty alkali metal, ammonium; and triethanolamine salts, and suitable detergents include (a) cationic detergents such as, for example, dimethyl dialkyl ammonium halides, and alkyl pyridinium halides, (b) anionic detergents such as, for example, alkyl, aryl, and olefin sulfonates, alkyl, olefin, ether, and monoglyceride sulfates, and sulfosuccinates, (c) nonionic detergents such as, for example, fatty amine oxides, fatty acid alkanolamides, and-polyoxyethylenepolypropylene copolymers, (d) amphoteric detergents such as, for example, alkyl-b-aminopropionates, and 2-alkyl-imidazoline quaternary ammonium salts, and (e) mixtures thereof.
The parenteral formulations typically will contain from abput 0.5% to about 25% by weight of the active ingredient in solution. Preservatives and buffers may be used. In order to minimize or eliminate irritation at the site of injection, such compositions may contain one or more nonionic surfactants having a hydrophile-lipophile balance (HLB) of from about.12 to about 17. The quantity AflcNnFn currT

2195856:
of surfactant in such formulations will typically range from about 5% to about 15% by weight. Suitable surfactants include polyethylene sorbitan fatty acid esters, such as sorbitan monooleate and the high molecular weight adducts 5 of ethylene oxide with a hydrophobic base, formed by the condensation of propylene oxide with propylene glycol. The parenteral formulations can be presented in unit-dose or multi-dose sealed containers, such as ampules and vials, and can be stored in a freeze-dried (lyophilized) condition 10 requiring only the addition of the sterile liquid excipient, for example, water, for injections, immediately prior to use. Extemporaneous injection solutions and suspensions can be prepared from sterile powders, granules, and tablets of the kind previously described.
15 Topical formulations, including those that are useful for transdermal drug release, are well-known to those of skill in the art and are suitable in the context of the present invention for application to skin.
Formulations suitable for oral administration require 20 extra considerations considering the peptidyl and/or carbohydrate nature of-some of the 06-substituted compounds of the present invention and the likely breakdown thereof if such compounds are administered orally without protecting them from the digestive secretions of the 25 gastrointestinal tract. Such a formulation can consist of -(a) liquid solutions, such as an effective amount of the compound dissolved indiluents, such as water, saline, or orange juice; (b) capsules, sachets, tablets, lozenges, and troches, each containing a predetermined amount of the 30 active ingredient, as solids or granules; (c) powders; (d) suspensions inan appropriate liquid; and (e) suitable emulsions. Liquid formulations may include diluents, such as water and alcohols, for example, ethanol, benzyl alcohol, and the polyethylene alcohols, either with or without the addition of a pharmaceutically acceptable surfactant, suspending agent, or emulsifying agent.
Capsule forms can be of the ordinary hard- or soft-shelled 21 95356.
.. =
' . ~ ~ . ...... .. .=

gelatin type containing, for example, surfactants, lubricants, and inert fillers, such as lactose, sucrose, calcium phosphate, and corn starch. Tablet forms can include one or more of lactose, sucrose, mannitol, corn starch, potatostarch, alginic acid, microcrystalline cellulose, acacia, gelatin, guar gum, colloidal silicon dioxide, croscarmellose sodium, talc, magnesium stearate, calcium stearate, zinc stearate, stearic acid, and other excipients, colorants, diluents, buffering agents, disintegrating agents, moistening agents, preservatives, flavoring agents and pharmacologically coinpatible excipients. Lozenge forms can comprise the active ingredient in a flavor, usually sucrose and acacia or tragacanth, as well as pastilles comprising the active ingredient in an inert base, such as gelatin and glycerin, or sucrose and acacia, emulsions, gels, and the like containing, in addition to the active ingredient, such excipients as are known in the art.
The 06-substituted compounds _of the present invention, alone or in combination with other suitable components, can be made into aeroso1 formulations to be administered via inhalation. The compounds are preferably supplied in finely divided form along with a surfactant and propellant. Typical percentages of active compound are 0_01%-20% by weight, preferably 1%-10%. The surfactant must, of course, be nontoxic, and preferably soluble in the propellant. Representative of-such surfactants are the esters or partial esters of fatty acids containing from 6 to 22 carbon atoms, such as caproic; octanoic, lauric, palmitic, stearic, linoleic, 1inole~nic, olesteric and oleic acids with an aliphatic polyhydric alcohol or its cyclic anhydri,de. Mixed esters, such as mixed or natural glycerides maybe employed. The surfactant may constitute 0.1%-20% by weight of the composition, preferably 0.25-5%.
The balance of the composition is ordinarily propellant.
A carrier can also be included as desired, e.g., lecithin for intranasal delivery. These aerosol formulations can be Ah!El~D[D SNfET

r= 2195356 ~ _. - = . .. .... . ==

placed into acceptable pressiurized propellants, such as dichl.orodifluosomethane, propane, nitrogen, and the like.
They also may be formulated as pharmaceuticals for non-pressured preparations, such as in a nebulizer or an atomizer. Such spray formulations may be used to spray mucosa. -Additionally, the compounds and polymers useful in the present inventive methods may be made into suppositories by mixing with a variety of bases, such as emulsifying bases or water-soluble bases. Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams, or spray formulas containing, in addition to the active ingredient, such carriers as-are known in the art to be appropriate.
--The concentration of the 06-substituted compounds of the present invention in the pharmaceutical formulations can vary widely, i.e., from less than about 1%, usually at or at least about 10%, to as much as 20% to 50% or more by weight, and will be selected_primarily by fluid volumes, viscosities, etc., in accordance with the particularmode of administration selected_ Thus, a typical pharmaceutical composition for intravenous infusion could be made up to contain 250 ml of sterile Ringer's solution, and 100 mg of the 06-substituted compound. Actual methods for preparing parenterally administrable compounds will be known or apparent to those skilled in the art and are described in more detail in, for example, Remington's Pharmaceutical Science (17th ed., Mack Publishing Company, Easton, PA, 1985).
It will be appreciated by one of ordinary skiil in the art that, in addition to the aforedescribed pharmaceutical compositions, the 0's-substituted compounds of the present inventive method may be formulated as inclusion complexes, such as cyclodextrin inclusion complexes, or liposomes.
Liposomes serve to target the compounds to.a particular tissue, such as lymphoid tissue or cancerous hepatic cells.
Liposomes can-also be used to increase the half-life of srEEr ..=

the 06-substituted compound. Liposomes useful in the present invention include emulsions, foams, micelles, insoluble monolayers, liquid crystals, phospholipid dispersions, lamellar layers and the like. In these preparations, the 06-substituted compound to be delivered is incorporated as part of a liposome, alone or in conjunction with a suitable chemotherapeutic agent. Thus, liposomes filled with a desired Os-substituted_compound of the invention can be directed to the site of a specific tissue type, hepatic cells, forexample, where the liposomes then deliver the selected chemotherapeutic-enhancement compositions. Liposomes for use in the invention are formed from standard vesicle-forming lipids, which generally include neutral and negatively_charged phospholipids and a sterol, such as cholesterol. The selection of lipids is generally guided-by consideration of, for example, liposome size and stability of the liposomes in the blood stream. Arvariety of methods are available.for preparing liposomes, as described in, for example, Szoka et al., Ann. Rev. Biophys. Bioeng., 9, 467 (1980), and U.S. Patents 4,235,871, 4,501,728, 4,837,028, and 5,019,369. For targeting to the cells of a particular tissue-type, a ligand to be incorporated into the liposome can include, for example, antibodies or fragments thereof specific for cell surface determinants of the targeted tissue type. A liposome suspension containing an 06-substituted compound may be administered intravenously, locally, topically,.etc. in a dose that varies according to the mode of administration, the 06-substituted compound being delivered, the stage of disease being treated, etc.
While the efficacy of the 06-substituted compounds of the pre,sent invention has been demonstrated with respect to particular types of cancerous cells; e.g., colon, prostate, and breast cancer cells, the present invention has applicability to the treatment of any type of cancer capable of-being treated with an antineoplastic alkylating agent which causes cytotoxic lesions at the OS-position of AWENDED cucF7 ; 2195856 ==

guanine. Such cancers include, for example, colon tumors, prostrate tumors, brain tumors, lymphomas, leukemias, breast tumors, ovarian tumors, lung tumors, Wilms' tumor, rhabdomyosarcoma, multiplemyeloma, stomach tumors, soft-tissue sarcomas, Hodgkin's disease, and non-Hodgkin's lymphomas.
Similarly, in view of the mode of action of the 06-substituted compounds of the present invention, such compounds can be used in conjunction with any type of antineoplastic alkylating agent which causes cytotoxic lesions at the O6-position of guanine. Such antineoplastic alkylating agents include, for example, chloroethylating agents (e.g. chloroethylnitrosoureas and chloroethyltriazines) and monofunctional alkylating agents such as Streptozotocin, Procarbazine, Dacarbazine, and Temozolomide.
Among the chloroethylating agents, the most frequently used chemotherapeutic drugs are 1-(2-chloroethyl)-3-cyclohexyl-1-initrosourea (CCNU, lomustine), 1,3-bis(2-chloroethyl)-7.-nitrosourea (BCNU, carmustine), 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (MeCCNU, semustine), and 1-(2-chloroethyl)-3-(4-amino-2-methyl-5-pyrimidinyl)methyl-l-nitrosourea (ACNU). These agents have been used clinically against tumors of the central nervous system, multiple myeloma, melanoma, lymphoma, gastrointestinal tumors, and other solid tumors (Colvin and Chabner, Alkylating Agents. In: Cancer Chemotherapy:
Principles and Practice, Chabner and Collins, eds., Lippincott, Philadelphia, pp. 276-313 (1990); McCormick and McElhinney, Eur. J. Cancer, 26, 207-221 (1990)), Chloroethylating agents currently under development with fewer s,ide effects are 1-(2-chloroethyl)-3-(2-hydroxyethyl)-1-nitrosourea (HECNU), 2-chloroethyl-methylsulfonylmethanesulfonate (Clomesone), and 1-[N-(2-chloroethyl)-N-nitrosoureido]ethylphosphonic acid diethyl ester (Fotemustine) (Colvin and Chabner, Alkylating Agents.
.Ln: Cancer Chemotherapy: Principles and Practice, Chabner AWrlrKO SHEET

and Collins, eds., Lippincott, Philadelphia, pp. 276-313 (1990); McCormick and McElhinney, Eur. J. Cancer, 26, 207-221 (1990)). Methylating chemotherapeutic agents include Streptozotocin (2-deoxy-2-(3-methyl-3-nitrosoureido)-D-5 glucopyranose), Procarbazine (N-(1-methylethyl)-4-[(2-methylhydrazino)methyl]benzamide), Dacarbazine or DTIC (5-(3,3-dimethyl-l-triazenyl)-1H-imidazole-4-carboxamide), and Temozolomide (8-carbamoyl-3-methylimidazo[5,1-d]-1,2,3,5-tetrazine-4-(3H)-one). Temozolomide is active against 10 malignant melanomas, brain tumors, and mycosis fungoides.
Streptozotocin is effective against pancreatic tumors.
Procarbazine is used to treat Hodgkin's disease and brain tumors, and DTIC is used in treatment of melanoma and lymphomas (Colvin and Cabner, Alkylating Agents. In:
15 Cancer Chemotherapy: Principles and Practice, Chabner and -Collins, eds., Lippincott, Philadelphia, pp. 276-313 (1990) ; Longo, Semin. Concol., 17, 716-735 (1990) ).
The examples set forth below describe the syntheses of the aforedescribed compounds. As regards the methods and 20 materials set forth in these examples, 1H-NMR spectra were recorded on a Varian'"VXR 500S spectrometer equipped with Sun 2/110 data stations or a VarianMXL 200 instrument interfaced to an Advanced data system. Samples were dissolved in DMSO-d6 with Me4Si as an internal standard. EI
25 mass spectra were obtained on a reversed geometry VG
MicromassTmZAB-2F spectrometer interfaced to a VG 2035-data system. Elemental analyses were performed by Galbraith Laboratories, Inc.,=Knoxville, TN.
Most of the reagents and solvents were from Aldrich ' 30 Chemical Co., Inc., Milwaukee, WI. 8-Aza-06-benzylguanine (2) (Shealy et al., J. Org. Chem., 27, 4518-4523 (1962) ), 2,4-diamino-6-benzyloxypyrimidine (3b) (Pfleiderer and Lohrmann, Chem. Ber., 94, 12-18 (1961)), 2,4,5-triamino-6-benzyloxypyrimidine (3c) (Pfleiderer and Lohrmann, Chem.
35 Ber., 94, 12-18 (1961)), 2,4-diamino-6-benzyloxy-5-nitrosopyrimidine (3d) (Pfleiderer and Lohrman, Chem. Ber., 94, 12-18 (1961)), 2,4-diamino-6-benzyloxy-5-21.95856 nitropyrimidine (3e) (Kosary et al., Acta Phazzn. Hung., 49, 241-247 (1989)), 2,4-diamino-6-benzyloxy-5-bromopyrimidine (3f) (Kosary et al., Acta Pharm. Hung., 49, 241-247 (1989)), 4-amino-6-benzyloxy-5-nitropyrimidine (3a) and O6-benzyl-2-fluorohypoxanthine (4c) (Robins and Robins, J.
Org. Che.m., 34, 2160-2163 (1969)) were prepared previously.
Alternative synthetic methods are provided below for some of these compounds together with spectroscopic data not provided previously. AGT inactivation studies were carried out as described in Moschel et a7.., J. Med. Cheni., 35, 4486-4491 (1992). Cell killing experiments involving various AGT inactivators in combination with BCNU were carried out as in Dolan, et al. (Proc. Nat1. Acad. Sci.
U.S.A., 87, 5368-5372 (1990)). Cells were treated for 2 h with AGT inactivator prior to exposure to BCNU.
Example 1: 2,8-Diamino-6-chloropurine A suspension of 8-aminoguanine (Fischer, Z. Physiol.
Chem., 60, 69 (1909); Beaman et al., in Zorbach and Tipson, Synthetic Procedures in Nucleic Acid Chemistry, Vol. 1, pp 41 - 43, John Wiley & Sons, New York, 1968) (3.0 g, 18.1 mmol) in phosphorus oxychloride (90 mL) and N,N-diethylaniline (3 mL) was refluxed for 30 min and the excess phosphorus oxychloride was evaporated under reduced pressure. Ice (20 g) was added slowly to the resulting solution and the pH was adjusted to 6 with a concentrated aqueous sodiumhydroxide solution. A yellow solid formed and was collected by filtration, washed with water, and dried to give a green solid. Crystallization from water with charcoal treatment produced 2,8-diamino-6-chloropurine as a white solid: yield, 2.11 g(63%); mp >275 C dec.; 'H
NMR d 6'.09 (s, 2 H, NH2, exchange with D20), 6.71 (s, 2 H, NH2, exchange with D20) ; MS (EI) calcd. m/z for C5H5N635C1 184.0264, found 184.0266; calcd. m/z C5H5N637 C1 186.0235, found 186.0237.

Ahr-nalir-n SFtEET

Example 2: 8-Amino-d-benzylguanine (la) 2, 8 -Di amino- 6-chloropurine (0.9 g, 4.9 mmol) was added to the solution of sodium (0.22 g, 10 mmol) in benzyl alcohol (9.0 mL). The solution was heated in a 130 C oil bath for 5 h, and was poured into water (100 mL) with constant stirring for 10 min. Undissolved solid was removed by filtration and the filtrate was neutralized with glacial acetic acid. The solution was mixed with methanol (100 mL), and half of the aqueous methanol solution was loaded on a 3 x 80 cm Sephadex LH-20 column eluted with methanol/water (1:1) at 1 mL/min. Column eluent was continuously monitored at 280 nm and fractions (10 mL) were collected. The remainder of the reaction mixture in MeOH/H20 was chromatographed separately under identical conditions. The desired product eluted in fractions 100 -130. Evaporation of solvent from the pooled fractions 100-130 from both chromatographic runs afforded analytically pure la: yield, 0.26 g(21%); mp 269 - 271 C dec.; UV (pH
1) 1a, 241 nm (e = 0. 699 x 104) , 300 (1.109 x 104) ; (pH

6.9) 250 (sh) (0.447 x 104) , 292 (1.027 x 104) ; (pH 13) 255 (sh) (0.355 x 10 ), 295 (0.932 x 104) ; 1H NMR d 5.41 (s, 2 H, ArCH2) , 5.70 (s, 2 H, NH2, exchange with D20), 6.18 (s, 2 H, NH2, exchange with D20), 7.25-7.55 (m, 5 H, ArH), 11.1 (br s, 1 H, NH, exchanges with D20); MS (EI) calcd. m/z for C12H12N60 256.1072, found 256.1059; Anal. (C12H12N60) C, H, N.
Example 3: 2-Amino-6-chloro-8-methylpurine A suspension of 8-methylguanine (Daves et al., J. Am.
Chem. Soc., 82, 2633 - 2640 (1960) )(1.0 g, 6.1 mmol) in phosphorous oxychloride (30 mL) and N,N-diethylaniline (1 mL) was refluxed for 3 h. The excess phosphorous oxychloride was evaporated under reduced pressure. The resulting brown oil was dissolved in ice-water and was neutralized with a concentrated aqueous NaOH solution.
After evaporation of the solvent, the solid residue was suspended in 70 mL of H20. Undissolved solid was filtered off, and the filtrate was loaded on a 3 x 80 cm Sephadex LH-20 column eluted with methanol/water (1:1) at 1 mL/min.
Column eluent was continuously monitored at 280 nm and fractions (10 mL) were collected. Evaporation of pooled fractions 50-60 produced 2-amino-6-chloro-8-methylpurine as a crude solid. Crystallization from ethanol/water with charcoal treatment afforded 2-amino-6-chloro-8-methylpurine as a white solid: yield, 0.57 g(51$); mp > 265 C dec.; 'H
NMR d 2.39 (s, 3 H, CH3) , 6.62 (s, 2 H, NH2, exchange with D20), 12.56 (s, 1 H, NH, exchanges with D20) ; MS (EI) calcd.
m/z for C6H6N535C1 183.0312, found 183.0309; calcd. m/z for C6H6N537C1 185.0283, found 185.0286.

Example 4: 06-Benzyl-8-methylguanine (lb) Sodium (0.1 g, 4.4 mmol) was stirred in 4.1 mL of benzyl alcohol until all sodium had reacted. 2-Amino-6-chloro-8-methylpurine (0.41 g, 2.2 mmol) was added, and the reaction mixture was heated in a 130 C oil bath for 5 h.
After cooling to room temperature 40 mL of ether was added to remove excess benzyl alcohol. The sticky precipitate that formed was collected by filtration and was dissolved in water (50 mL). The pH of the yellow solution was adjusted to 5 - 6 with glacial acetic acid. The solution was mixed with methanol (50 mL) and was loaded on a 3 x 80 cm Sephadex LH-20 column eluted with methanol/water (1:1) at 1 mL/min. Column eluent was continuously monitored at 280 nm and fractions (10 mL) were collected. Evaporation of pooled fractions-78-93 afforded analytically pure ib:
yield, 0.25 g (44%); mp 214 - 216 C; W(pH 1) 1,,,ax 238 nm (sh) (e = 0. 648 x 104) , 290 (1.136 x 104) ;(pH 6.9) 242 (0.758 x 10'), 284 (0.897 x 10 ); (pH 13) 240 (sh) (0.495 x 10 ), 286 (0.932 x 104); 'H NMR d 2.33 (s, 3 H, CH3), 5.46 (s, 2 H, ArCH2), 6.17 (s, 2 H, NH2, exchange with D20) , 7.34-7.51 (m, 5 H, ArH), 12.18 (br s, 1 H, NH, exchanges with D20),; MS (EI) calcd. m/z for C13H13N50 255.1120, found 255.1125; Anal. (C13H13N50.1/4 H20) C, H, N.

Example 5: O!6-Benzyl-8-oxoguanine (1c) 2,4,5-Triamino-6-benzyloxypyrimidine (Pfleiderer et al., Chem. Ber., 94, 12 - 18 (1961) )(1.85 g, 8 mmol) and 1,1'-carbonyldiimidazole (1.30 g, 8 mmol) were dissolved in anhydrous N,N-dimethylformamide (5 mL) under argon. The solution was stirred at room temperature overnight and was mixed with water (200 mL) to precipitate a white solid.
The solid was collected by filtration, and dissolved in 250 mL of aqueous 2 N NaOH solution. Undissolved material was removed by filtration, and the filtrate was neutralized with glacial acetic acid to precipitate a white solid. The solid was collected by filtration, was washed with water, and was recrystallized from 50% aqueous ethanol to afford analytically pure lc: yield, 1.63 g (79 %); mp 256 - 257 C dec.; UV (pH 1) 1. 243 nm (e = 0.717 x 104) , 306 (1.499 x 104) ; (pH 6.9) 243 (0.915 x 104) , 290 (1. 108 x 109) ;(pH
13) 249 (sh) (0.443 x 104) , 293 (1.368 x 104) ; 'H NMR d 5.41 (s, 2 H, ArCH2), 6.13 (s, 2 H, NH2, exchange with D20), 7.33 - 7.51 (m, 5 H, ArH), 10.46 (s, 1 H, exchanges with D20), 11.04 (s, 1 H, exchanges with D20); MS (EI) Calcd. m/z for C12H11N502: 257.0912. Found: 257.0914. Anal. (C12HI1N502. 1/2 H20) C, N, H.
Example 6: Ob-Benzyl-8-bromoguanine (1d) Bromine (0.26 mL, 5.1 mmol) was added slowly to the solution of 06-benzylguanine (1.205 g, 5.0 mmol) in anhydrous DMF (10 mI,) under argon. The resulting deep green solution was stirred at room temperature overnight.
The solution was mixed with water (70 mL) to precipitate crude product. This product was collected by filtration and was dissolved in 50% aqueous methanol (100 mL). The solution was loaded on a 3 x 80 cm SephadexMLH-20 column eluted with methanol/water (1:1) at 1 mL/min. Column eluent was continuously monitored at 280 nm and fractions (10 mL) were collected. The desired product eluted in 21 ~=5856 fractions 110 = 190.. _Evaporation of solvent from the pooled fractions 110 - 190 afforded id as a pale yellow solid. Crystallization from ethanol/water (1:1) produced analytically pure 2d: yield, 0.166 g (10%); mp 135 - 137 5 C dec.; W(pH 1) l,,.Y 236 nm (sh) (e = 0.517 x 104), 294 (1.429 x 104); (pH 6.9) 244 (0.666 x 104), 287 (1.043 x 104) ;(pH 13) 245 (sh) (0.544 x 10 ) , 289 (1.030 x 104) ; 1H
NMR d.5.45 (s, 2 H, ArCH2), 6.35 (s, 2 H, NH2, exchange with DZO), 7.34 - 7.52 (m, 5 H, ArH), 13.08 (b s, 1 H, NH, 10 exchanges with D20) ; MS (EI) calcd. m/z for CiZH1qN50'9Br 319.0068, fouhd 319.0069; calcd. m/z for CiZH2oN5081Br 321.0048, found 321.0048; Anal. (C1.zH1oN50Br3/2 HZ0) C, H, N, Br.

15 Example 7: 8-Aza-O6-benzylguanine (2) Glacial acetic acid (1 mL) was added into the mixture of 2,4,5-triamino-6-benzyloxypyrimidine (0.231 g, 1.0 mmol) and sodium nitrite (0.069 g, 1.0 mmol) in acetone (5 mL).
20 The resulting mixture was stirred at room temperature for 2 h. The solution was poured in water (100 mL) with stirring to precipitate a crude solid. The solid was collected by filtration and air dried. Crystallization from ethanol/water (1:1) with charcoal treatment produced 2 as a 25 white solid: yield, 105 mg (43%); mp 191 - 192 C (192 -193 C; Shealy et. al., J. Org. Chem., 27, 4518 - 4523 (1962)); 'H NMR d 5.56 (s, 2 H, ArCHz), 7.00 (s, 2 H, NHz, exchange with DZO), 7.41 - 7.58 (m, 5 H, ArH) ; MS (EI) calcd. m/z for CL1H16N60 242.0916, found 242.0924.
ao Example 8: 4-Arnino-6-benzyloxy-5-nitropyrim.idine (3a) 4-Amino-6-chloro-5-nitropyrimidine (Boon et al., J.
Chem. Soc., 96-102 (1951)) (1.5 g, 8.6 mmol) was added to a 35 solution of sodium (0.23 g, 9.9 mmol) in benzyl alcohol (14 mL). The solution was heated in a 130 C oil bath for 3.5 h, and was poured into benzene (50 mL). A yellow solid was collected by filtration and washed with benzene.

AW-rto fo !z.N-=

21 t5856 = ;:

Crystallization from benzene/ether afforded an analytically pure sample of 3a: yield, 0.71 g (34%); mp 149 - 150 C;
UV (pH 1) 1,,,,x 284 nm (e = 0.368 x 10'), 333 (0:488 x 10 );
(pH 6.9) 284 (0-:329 x 104) , 336 (0.470 x 104) ; (pH 13) 290 5(0.344 x 104), 333 (0.494 x 10 ); 'H NMR d 5.50 (s, 2 H, ArCH2), 7.33 - 7.49 (m, 5 H, ArH), 8.12 - 8.24 (br d, 2 H, NH, and NHb, exchange with D20), 8.24 (s, 1 H, H-2); MS (EI) calcd. m/z for_C11H1oN403 246.0752, found 246.0751; Anal.
(CiiH,oN403) C, H, N.
Example 9: 2,4-Diamino-6-benzyloxy-5-nitropyrimidine (3e) 2,4-Diamino-6-chloro-5-nitropyrimidine (O'Brien et.
al., J. Med. Chem., 9, 573 - 575 (1966)) (1.0 g, 5.28 mmo1) was added to_a solution of sodium (0.14 g, 6.08 mmol) in benzyl alcohol (9 inL). The solution was heated in a 160 C
oil bath for 3.5 h and the solvent was evaporated under reduced pressure to provide a yellow solid. This solid was washed with water, and air dried. Crystallization from benzene/ether gave a pale yellow filamentous solid: yield, 0.69 g (50 %); mp 194 - 195 C (171 C; Kosary et. al., Acta. Pha.rni. Hung., 49, 241 - 247 (1989) ) ; UV (pH 1) 1~
236 nm (sh) (e = 1.452 x 10'), 264 (0.522 x 10 ), 321 (1.294 x 104) ; (pH 6.9) 242 (sh) (0.965 x 10") , 337 (1.493 x 10 ) ;
(pH 13) 242 (sh) (0.952 x 104), 338 (1.479 x 104); 'H NMR d 5.43 (s, 2 H, ArCH2), 7.26 (br s, 2 H, NH2, exchange with D20) , 7.33 - 7.51 (m, 5 H, ArH), 7.93 (br s, 2 H, NH21 exchange with D20); MS (EI.) calcd. m/z for C11H11N5O3 261.0861, found 261.0866; Anal. (C11H11N503).
Example 10: 06-Benzylxanthine (4a) A=.suspension of 06-benzylguanine (0.83 g, 3.4 mmo1) in acetone (15 mL) was poured into a solution of sodium nitrite (5 g) in 15 mL of HZ0. Acetic acid (8 mL) was added to the suspension with stirring. Minimum amounts of acetone were added as necessary to dissolve any suspended solid. The resulting pale yellow-green solution was AMENDED StlEET

stirred for 3 h. A pale green precipitate that formed was collected by filtration and washed with water (200 mL).
Recrystallization of the air-dried solid from ethanol/water (1:1) afforded analytically pure 4a: yield, 0.43 g(52%-);
mp 145 - 147 C dec.; W(pH 1) l. 270 nm (e = 0.749 x 104); (pH 6.9) 286 (1.143 x 104) ; (pH 13) 290 (0.914 x 10') 'H NMR d 5.49 (s, 2 H, ArCH2), 7.36-7.54 (m, 5 H, ArH), 8.02 (s, 1 H, H-8), 11.8 (br s, 1 H, NH, exchanges with D20), 13.2 (br s, 1 H, NH, exchanges with D20); MS (EI) calcd. m/z for C12HioN402 242.0803, found 242.0828; Anal. (C12H1oN402 H20) C, H, N.

Example 11: e-Senzyluric acid (4b) Sodium nitrite (1.5 g, 43 mmol) dissolved in water (5 mL) was added to a suspension of Os-benzyl-8-oxoguanine (1c) (0.257 g, 1.0 mmol) in acetone (5 mL). Glacial acetic acid (3 mL) was added to the suspension with stirring. After stirring for 3 h at room temperature a bright yellow precipitate formed. The suspension was mixed with water (150 mL) and undissolved solid wasfiltered off. Saturated aqueous sodium carbonate solution was added to the filtrate to adjust the pH to approximately 5.---A yellow precipitate (130 mg) was collected and washed with water. This solid was crystallized from 50% aqueous ethanol to give an analytically pure sample of 4b: yield, 75 mg (29 $); mp >230 C; UV (pH 1) 1, 236 nm (sh) (e = 0.972 x 10') , 299 (1.427 x 104); (pH 6.9) 240 (sh) (0.821 x 104), 304 (2.134 x 104) ; ( p H 13) 245 (sh) (0.846 x 104) , 297 (1.861 x 10') ;;H
NMR d 5.43 (s, 2 H, ArCH2), 7.35-7.51 (m, 5 H, ArH), 10.76 (s, 1 H, NH, exchanges with D20), 11.23 (s, 1 H, NH, exchanges with D2O), 11.39 (s, 1 H, NH, exchanges with D20);
MS (EI)' calcd. m/z for Ci2H1oN403 258.0752, found 258.0753;
Anal. (Ci2HfoNa03.5/2 H20) C, H, N.

AKNIDEO S!-!EET

Example 12:. -Diacetyl-d -benzyl-8-oxoguanine Acetic anhydride (2 mL) was added to the suspension of 06-benzyl-8-oxoguanine (1c) (0.257 g, 1.0 mmol) in dry toluene (10 mL). The suspension was vigorously refluxed for 24 hr, and was cooled to room temperature. After storing at 4 C for 4 hr, the resulting precipitate was collected by filtration, washed with benzene and air dried to give an analytically pure sample of a diacetylated product: yield, 0.287 g(84$)) mp272 - 274 C dec.; W
(100% MeOH) 1~ 275 nm (e = 1.313 x 10 ); (pH 1) 275 (1.143.-x 104) ; (pH 6.9) 238 (0.995 x 104.) , 276 (1.115 x 10 ) ; (pH
13) 285 (2.138 x 104); 'H NMR d 2.18-(s, 3 H, CH3), 2.57 (s, 3 H, CH3), 5.51 (s, 2 H, ArCH2), 7.30 - 7.57 (m, 5 H, ArH), 10.41 (s, 1 H, exchanges with D20), 12.30 (s, 1 H, exchanges with D20) ; MS (EI) Ca1cd. m/z for C16H15N504: 341.1123.
Found: 341.1130. Anal. (C16H15N504) C, N, H.
Example 13: D7 -Acetyl-O -benzyl-8-oxoguanine (4d) _ : -Diacetyl-O6-benzyi-8-oxoguanine (85 mg, 0.25 mmo1) was dissolved in methanol (10 mL) and ammonium hydroxide (28%, 5 mL) and was allowed stand for 1 hr. The clear solution became cloudy and a precipitate formed on standing. The precipitate was collected by filtration, washed with water, and dried to give an analytically pure sample of 4d:
yield, 48 mg (65%); mp 335 - 337 C dec.-; W(pH 1) 1~x 276 rim (e = 1.723 x 10{), 303.(sh) (0.679 x 10 ); (pH 6.9) 276 (1.379 x 10 ); (pH 13) 284 (1.683 x 10') ; 1H NMR d 2.15 (s, 3 H, CH3), 5.49 (s, 2 H, ArCH2) , 7.30 - 7.55 (m, 5 H, ArH), 10.21 (s, 1 H, exchanges with D20), 10.99 (s, 1 H, exchanges with D20), 11.60 (s, 1 H, exchanges with D20; MS (EI) Calcd.
m/z for C14H13N303: 299.1018. Found: 299.1023. Anal.
(C14H13N503) C, N, H.
. .
Example 14: O'-Benzyl-2-fluorohypoxanthine (4c) 06-Benzylguanine (1.21 g, 5 mmol) was added to 100 mL
of 48% fLuoboric acid at -20 C. Sodium nitrite (1.23 g, WFhDR) SNEET

35 mmole) was dissolved in water (5 mL) and 2.5 mL of this sodium nitrite solution was added slowly to the cold fluoboric acid solution. The resulting mixture was stirred for 1 h at or below -15 C. Additional fluoboric acid (25 mL) was added followed by an additional 2.5 mL of the aqueous sodium nitrite solution. After stirring for an additional 1 h below -15 C, fluoboric acid (25 mL) was again added and stirring was continued for 1 h. The resulting solution was neutralized with saturated aqueous sodium carbonate solution at -20 C and was allowed to warm to room temperature. A white precipitate that formed was collected by filtration and was washed with water and dried under vacuum to afford crude 4c: yield, 0.52 g, 43%. An analytical sample was prepared by chromatography on a Sephadex LH-20 column (3 x 80 cm) eluted with methanol/water (1:1) at 1 mL/min. The desired 4c eluted in fractions 66 - 77: mp 182 - 183 C (184 - 185 C; Robins and Robins, J. Org. Chein., 34, 2160-2163 (1969) ) ; UV (pH 1) 1,,,aX 256 run (e = 1.117 x 104) ; (pH 6.9) 257 (1.078 x 104) (pH 13) 264 (1.063 x 10 ) ; iH NMR d 5. 60 (s, 2 H, ArCH2), 7.37-7.57 (m, 5 H, ArH), 8.40 (s, 1 H, H-8), 13.60 (s, 1 H, NH, exchanges with DZ0) ,19F NMR d 23.54 downfield from trifluoroacetic acid standard; MS (EI) calcd. rn/z for C12H9FN40 244.0760, found 244.0756; Anal. (C12H9FN40.2/3 H20) C, H, N.

Example 15: d6-Benzyl-N2-methylguanine (4e) Fluoboric acid1 (48%, 30 mL) was cooled to -20 C in an dry ice-acetone bath. 06-Benzylguanine (0.362 g, 1.5 mmol) was added with stirring. Sodium nitrite (0.369 g, 10.5 mmol) was dissolved in water (1 mL) and 0.5 mL of this solutio'n was added slowly to the cold fluoboric acid solution. The resulting solution was stirred at or below -15 C for 1 h. More fluoboric acid (5 mL) was then added followed by 0.5 mL of the sodium nitrite solution. After stirring-for 1 h at or below -15 C, fluoboric acid (5 mL) was again added and stirring was continued for an additional 1 h. Methylamine (40% in water, 60 mL) was then added at -20 C, and the resulting basic solution was stirred at room temperature for 2 days. The solvent was 5 evaporated under reduced pressure to produce a white solid.
The solid was suspended in 50 mL of H20 with stirring for 10 min. Undissolved material was collected by filtration and washed with water. This solid was dissolved in 40 mL
methanol/water (1:1) to which was added 1.2 mL of 28%
10 aqueous ammonia solution. The solution was loaded on a 3 x 80 cm Sephadex LH-20 column eluted with MeOH/H20/NH40H
(30:70:3) at 1 mL/min. Column eluent was continuously monitored at 280 nm and fractions (10 mL) were collected.
Evaporation of the pooled fractions 106-127 gave an 15 analytically pure sample of 4e: yield, 85 mg (22%); mp 189 -- 190 C; UV (pH 1) 1,,,, 238 nm (sh) (e = 0.665 x 104) , 297 (0.904 x 104) ;(pH 6.9) 246 (0.898 x 104) , 290 (0.676 x 104) ;(pH 13) 240 (sh) (0. 615 x 104) , 294 (0.674 x 104) ; 1H
NMR d 2.30 (d, 3 H, CH3), 5.50 (s, 2 H, ArCH2), 6.75 (m, 1 20 H, MeNH, exchanges with D20), 7.31-7.53 (m, 5 H, ArH), 7.82 (s, 1 H, H-8) , 12.53 (s, 1 H, NH, exchanges with D20) ; MS
(EI) calcd. m/z for C13H13N50 255.1120, found 255.1107; Anal.
(C13H13N50.1/2 H20) C, H, N.

25 Example 16: Oa-Benzyl-IV2,IV2-dimethy1guanine (4f) Fluoboric acid (48%, 40 mL) was cooled to -20 C in an dry ice-acetone bath. 06-Benzylguanine (0.482 g, 2.0 mmol) was added with stirring. Sodium nitrite (0.492 g, 14.0 30 mmol) was dissolved in water (2 mL) and 1 mL of this solution was added slowly to the cold fluoboric acid solution. The resulting solution was stirred at or below -15 C for 1 h. More fluoboric acid (10 mL) was added followed by the addition of 1 mL of the sodium nitrite 35 solution. After stirring for 1 h at or below -15 C, additional fluoboric acid (10 mL) was added with stirring for 1 h. Dimethylamine (40% in water, 60 mL) was then 2t95856 added to the solution at -20 C, and the resulting mixture was allowed to warm to room temperature. The suspension became a clear solution and a precipitate formed within 10 min. After standing overnight at room temperature the precipitate was collected by filtration and was washed with water.. The solid was crystallized from 50% aqueous ethanol to give an analytically pure sample of 4f: yield, 0.25 g (46%); mp 220 - 221 C dec.; W(pH 1) 1 . 248 nm (sh) (e =
0.512 x 104), 303 (0.908 x 10 ); (pH 6.9) 251 (1.152 x 104), 299 (0.686 x 10-0); (pH 13) 248 (sh) (0.766 x 104), 299 (0.710 x 10 ) ; 1H lZiR d 3.12 (s, 6 H, CH3), 5.54 (s, 2 H, ArCH2), 7.36-7.51 (m, 5 H, ArH), 7.84 (s, 1 H, H-8), 12.56 (s, 1 H, NH, exchanges with D20); MS (EI) calcd. m/z for C14H15N50 269.1276, found 269.1254; Anal. (C14H15N50) C, H, N.
Example 17: 2,4-Diam3.no-6-benzyloxy-5-bromopyrimidine (3f) 2,4-Diamino-5-bromo-6-chloropyrimidine (Phillips et.
al., J. Org. Chem., 29, 1488 - 1490-(1963)) (2.3 g, 10 mmol) was added to a solution of sodium (0.29 g, 12.5 mmo1) in benzyl alcohol (10 mL) under argon. The solution was heated in a 130 C oi1 bath for 3 h and the benzyl alcohol was evaporated under reduced pressure to give a white solid. This solid was washed with water, and air dried.
Crystallization from 50% aqueous ethanol gave white crystalline needles of 3f: yield, 2.32 g (76%); mp 165 -166 C (lit. 136 C; Kosary et. al., Acta Pharm. Hung., 49, 241 - 247 (1989) ); W(pH 1) 1~ 236 nm (e = 0.873 x 10 ) , 291 (1.388 x 104); (pH 6.9) 236 (0.850 x 10 ), 277 (0.835 x 10 ) ; (pH 13) 234 (0.869 x 104), 277 (0.827 x 10 ) ; 'H NMR d 5.30 (s, 2 H, ArCH2), 6.15 (s, 2 H, NH2, exchange with D20), 6.32 (s, 2 H, NH2, exchange with D20), 7.31 - 7.45 (m, 5 H, ArH) ; MS (EI) calcd. m/z for C11H11N4O"Br 294.0115, found 294.0127; calcd. m/z for C11H11N4O81Br 296.0094, found 296.0083; Anal. (C11H11N40Br) C, H, N.
pr,RPItir-D SkfIEC

21-95856 . .
= : , _. .:= .:= ~..

Example 18: 2-Amino-4-chloro-5-nitropyrimidine A suspension of 2-amino-4-hydroxy-5-nitropyrimidine (5.0 g, 32.1 mmol) in phosphorous oxychloride (100 mL) was refluxed overnIght, and the excess phosphorous oxychloride was evaporated under reduced pressure. The residue was mixed with ice (100 g) in an ice-bath, and the mixture was neutralized with concentrated aqueous sodium carbonate solution. A yellow precipitate was collected by filtration and washed with water: yield, 1.39 g(25%); mp 191 - 194 C dec.; 1H NM12 d 8.45 (br s, 2 H, NH2, exchange with D20), 9.03 (s; 1 H, H-6) ; MS (EI) calcd. m/z for C4H3N40235Ci 173.9944, found 173.9934; calcd. rn/z for C4H3N402 37C1 175.9915, found 175.9916.
Example 19: 2-Amino-4-benzyloxy-5-nitropyrimidine (5a) 2-Amino-4-chloro-5-nitropyrimidine (0.70 g, 4.0 mmo1) was added to a solution of sodium'(0.12 g, 5.2 mmol) in benzyl alcohol (8 mL) under argon. The solution was heated in a 130 C oil bath for 3 h, and approximately half of the benzyl alcohol was evaporated under reduced pressure. The residue was poured into water (50 mL) with constant stirring for 10 min. After neutralization with glacial acetic acid, a brown precipitate formed which was collected by filtration and washed with water. This solid was crystallized from benzene to give 5a as a golden crystalline solid: yield, 126 mg (13%); mp 164 - 167 C;
W(pH 1) l. 262 nm (e = 0.879 x 104) , 295 (sh) (0.571 x 104) ; (pH 6.9)_ 235 (sh) (0.448 x 104) , 273 (0.360 x 104) , 326 (1.085 x 10') ; (pH 13) 273 (0.404 x 10'), 327 (1.055 x 104); 1H NMR d 5.51 (s, 2 H, ArCH2) , 7.35 - 7.54 (m, 5 H, ArH), 8.05 (d, 2 H, NH2, exchange with D20), 8.92 (s, 1 H, H-6); MS (EI) calcd. m/z for C11H1oNa03 246.0752, found 246.0758; Anal. (CL1H1oN403) C, H, N.
pesr-r info SHfEf - i ..,.. ..

E
Rple 20: 2-Amino-4-benzyloxy-6-methyl-5-nitropyrimidine 2-Amino-4-chloro-6-methyl-5-nitropyrimidine (Boon et al., J. Chem. Soc., 96 - 102 (1951)) (1.24 g, 6.58 mmol) was added to a solution of sodium (0.21 g, 9.13 mmol) in benzyl alcohol (14 mL) under argon. The solution was heated in a 135 C oil bath for 3.5 h, and was poured into water (70 mL) with constant stirring for 10 min. After neutralization with glacial acetic acid, a yellow precipitate formed which was collected by filtration and washed with water. This solid was crystallized from benzene to give 5b as a bright yellow crystalline solid:
yield, 0.57 g (33%); mp 159 - 160 C; UV (pH 1) 1~ 268 nm (e = 0.783 x l04), 345 (sh) (0.104 x 10"); (pH 6.9) 282 (0.564 x 10'), 345 (sh) (0.338 x 10'); (pH 13) 282 (0.549 x 10 ) , 345 (sh) (0.332 x 10') ;''H NMR d 2.35 (s, 3 H, CH3), 5.44 (s, 2 H, ArCH2), 7.34 - 7.46 (m, 5 H, ArH), 7.64 (b s, 2 H, NH2, exchange with D2.0); MS (EI) calcd. m/z for C12H12N4O3 260.0908, found 260.0913; Anal. (CIZH12N403) C, H, N.
Example. 21: 2,4-Diamino-6-benzyloxy-s-triazine (6) 2,4-Diamino-6-chloro-s-triazine (2.25 g, 15.0 mmol) was added to a solution of sodium (0.43 g, 18.8 mmol) in benzyl alcohol (30 mL) under argon. The suspension was heated in a 130 C oil bath for 3.5 h. The excess benzyl alcohol was removed under vacuum and the resulting solid was collected with the aid of benzene, and washed with water (100 mL): yield, 1.83 g (56%); mp 184 - 185 C (lit.
186 - 188 C; Wakabayashi et al., Nippon Dojo-Hiryogaku Zasshi, 41, 193 - 200 (1970)); UV (pH 1) 1aõx 233 nm (sh) (e = 0.589 x 104); (pH 6.9) 238 (sh) (0.111 x 10 ); (pH 13) 240 (sh) (0'.073 x 10 ); 'H NMR d 5.25 (s, 2 H, ArCH2), 6.63 (s, 4 H, NH2, exchange with D20), 7.30 - 7.42 (m, S H, ArH); MS
(EI) calcd. um/z for C1oHi1N50 217.0963, found 217.0955.
~q~r~ni~p SHEET

Example 22: 2-Amino-6-chloro-8-trifluoromethylpurine A suspension of 8-trifluoromethylguanine (Pfleiderer and Shanshal, Liebigs Ann. Chern. , 726, 201 - 215 (1969) ) (2.0 g, 9.1 mmol) in phosphorous oxychloride (20 mL) was refluxed for 3 h. Excess phosphorous oxychloride was evaporated under reduced pressure. The resulting residue was mixed with ice-water (100 g), and the pH was adjusted to 3 - 4 with a concentrated aqueous NaOH solution. The resulting solution was mixed with MeOH (100 mL) and approximately half (i.e., 100 mL) of the aqueous methanol solution was loaded on a 3 x 80 cm SephadexmLH-20 column eluted with methanol/water (1:1) at 1 mL/min. Column eluent was continuously monitored_at 280 nm and fractions (10 mL) were collected. The remainder of the reaction mixture in MeOH/H20 was chromatographed separately under identical conditions. The desired product eluted in fractions 73 - 85. Evaporation of solvent from the pooled fractions 73 - 85 from both chromatographic runs afforded analytically pure 2-amino-6-chloro-8-trifluoromethylpurine:
yield, 0.94 g (43%); mp >225 C dec.; W(pH 1) l,,aX 245 nm (e = 0.501 x 10"), 314 (0.746 x x 104); (pH 6.9) 270 (0.265 x 104) , 315 (0. 612 x 104) ; (pH 13) 272 (0.269 x 104) , 314 (0. 612 x 104 ); 'H NMR d 7.19 (s, 2 H, NH2, exchange with D20), 14.25 (br s, 1 H, NH, exchanges with DZ0) ; MS (EI) calcd. rrr/z for C6H3N5F335C1 237.0029, found 237.0011; calcd.
rn/z for C6H3N5F337C1 239.0000, found 238.9987; Anal.
(C6H3N5F3C) C, H, N, F, Cl.

Example 23: 0'6-Henzyl-8-trifluoromethylguanine (le) Sodium (0.10 g, 4.3 mmol) was stirred in 5 mL of benzyl alcohol until all had reacted. 2-Amino-6-chloro-8-trifluoromethylpurine (0.475 g, 2.0 mmol) was added, and the reaction mixture was heated in a 135 C oil bath for 3.5 h. The benzyl alcohol was removed by vacuum distillation yielding a brown oil. The oil was dissolved in water (50 mL) and was acidified with glacial acetic"acid to produce a pale yellow precipitate. The precipitate was collected by filtration and washed with water. The crude product was loaded on a 2.5 x 35 cm silica gel column (DavisilTMgrade 633, 200 - 425 mesh, 60 A). Elution was 5 carried out with 5% EtOH in CHC13 to provide analytically pure 06-benzyl-8-trifluoromethylguanine (Ie): yield, 0.42 g (67$) ; mp 214 - 216 C dec.; UV (pH i) l,,,aX 291 nm (e =
1.229 x 104) ; (pH 6.9) 244 (0.470 x 109) , 289 (1.023 x 10") ;
(pH 13) 247 (sh) (0.393 x 104), 290 (0.923 x 104); 'H NMR d 10 5.51 (s, 2 H, ArCH2), 6.82 (s, 2 H, NH2, exchange with D20), 7.38 - 7.55 (m, 5 H, ArH), 13.75 (br s, 1 H, NH, exchanges with D20); MS (EI) calcd. m/z for C13H10N5OF3 309.0837, found 309.0827; Anal. (C13H,oN50F3) C, H, N, F.

15 Example 24: O'6-Benzyl-8-trifluoromethyl-9-methylguanine (7) To 06-benzyl-8-trifluoromethylguanine (le) (200 mg, 0.65 mmol) under argon was added 0.66 mL of a 1.0 M
solution of sodium ethoxide in ethanol. The solution was 20 stirred for 10 min and the ethanol was removed under vacuum. The remaining solid was dissolved in anhydrous DMF
(1.5 mL),, and methyl iodide (49 uL, 0.78 mmol) was added to the solution. This solution was stirred at room temperature for 1 h, and 1.5 mL additional DMF was added.
25 The solution was stirred at room temperature overnight.
The solvent was evaporated under reduced pressure. The crude solid was loaded on a 2.5 x 35 cm silica gel column (Davisil grade 633, 200 - 425 mesh, 60 A). Elution was carried out with chloroform/hexane (3:1) to provide 30 analytically pure 06-benzyl-8-trifluoromethyl-9-methylguanine (7): yield, 95 mg (45%); mp 86 - 89 C; UV
(pH 1) L. 244 nm (e = 0.581 x 104), 286 (1.274 x 104) ; (pH
6.9) 262 (0.608 x 104) , 288 "(1.022 x 104) ; (pH-13) 252 (0. 618 x 104) , 288 (1.038 x 104) ; 'H NMR d 3.70 (s, 3 H, 35 CH3 ),. 5.51 (s, 2 H, ArCH2 ), 6.91 (s, 2 H, NH2, exchange with D20), 7.38 - 7.54 (m, 5 H, ArH); MS (EI) calcd. m/z for C14H12N50F3 323.0994, found 323.0978; Anal. (C14HI2N5OF3) C, H, N, F.

Example 25: 8-Aza-06-benzyl-9-methylguanine (8a) 8-Aza-06-benzylguanine (0.484 g, 2.0 mmol) was mixed with 4 mL of 0.5 M sodium ethoxide in ethanol and stirred for 30 min. The ethanol was evaporated under reduced pressure. The residue was dissolved in anhydrous DMF (6 mL), and methyl iodide (0.15 mL, 2.4 mmol) was added. The clear solution became cloudy within 10 min, and the resulting mixture was stirred overnight at room temperature. DMF was evaporated under reduced pressure to give a brown solid. The solid was dissolved in chloroform and loaded on a silica gel column (DavisilTMgrade 633, 200-425 mesh, 60 A). Product 8a was eluted with chloroform;
yield, 138 mg (27$) ; mp 178-179 C; UV (pH 1) 243 nm (sh) (e = 0.556 x 104) , 284 (1. 112 x 10 ) ; (pH 6.9) 243 (0.553 x 104) , 290 (0. 998 x 10 ) ; (pH 13) 242 (0.549 x 104) 290 (1.010 x 104) ; 'H NMR d 3.96 (s, 3 H, CH3), 5.57 (s, 2 H, ArCH2), 7.18 (s, 2 H, NH2, exchange with D20), 7.38-7.57 (m, 5 H, ArH) ; MS (EI ) calcd m/z for C1ZHIZN60 256.1072, found 256.1086; Anal. (C12H12N60) C, H, N.

Example 26: 8-Aza-O'6-benzyl-9-(pivaloyloxymethyl)guanine (8b) and 8-Aza-06-benzyl-7-(pivaloyloxymethyl)guanine (9) 8-Aza-06-benzylguanine (0.484 g, 2.0 mmol) was mixed with 4 mL of 0.5 M sodium ethoxide in ethanol and stirred for 30 min. The ethanol was evaporated under reduced pressure. The residue was dissolved in anhydrous DMF (6 mL), and chloromethyl pivalate (0.3 mL, 2.1 mmol) was added. The clear solution was stirred for 8 h at room temperature. DMF was evaporated under reduced pressure to give a brown solid. The solid was dissolved in chloroform and loaded on a silica gel column (DavisiiMgrade 633, 200 -425 mesh, 60 A). The 9-isomer (8b) was eluted from the column with CHC13:hexane (4:1) while the 7-isomer (9) was subsequently eluted with CHC13. 8-Aza-06-benzyl-9-.(pivaloyloxymethyl)guanine (8b): yield, 405 mg (57%); mp 119-120 C; W(pH 1) l,,a,, 246 nm (e = 0.494 x 104) , 286 (0.878 x 104) ;(pH 6.9) 247 (0.472 x 104) , 288 (0.819 x 10'); (pH 13) (decomposes to 8-aza-06-benzylguanine); 'H NMR
d 1.10 (s, 9 H, C(CH3)3), 5.50 (s, 2 H, ArCH2), 6.31 (s, 2 H, CHZ) , 7.38 (s, 2 H, NH2, exchange with D20), 7. 40-7. 54 (m, 5 H, ArH) ; MS (EI ) calcd m/z for C1,H2oN603 356.1596, found 356.1578; Anal. (C17H2ON603.1/5H20) C, H, N. 8-Aza-06-benzyl-7-(pivaloyloxymethyl)guanine (9): yield, 103 mg (15%); mp 153-154 C; UV (pH 1) lõaX 244 nm (e = 0.820 x 10 ) , 294 (1.249 x 104) ; (pH 6.9) 250 (sh) (0.296 x 104) 313.(0.503 x 104) ;(pH 13) (decomposes to 8-aza-06-benzylguanine) ; 1H NMR d 1.12 (s, 9 H, C(CH3) 3) , 5.56 (s, 2 H, ArCH2), 6.40 (s, 2 H, CH2), 7.04 (s, 2 H, NH2, exchange with D20), 7.4-7.58 (m, 5 H, ArH); MS (EI) calcd m/z for CL-7H2ON603 356.1596, found 356.1602; Anal. (C1-,H2ON503) .
Example 27: 06-Benzyl-8-bromo-9-methylguanine (l0a) 06-Benzyl-9-methylguanine (0.252 g, 1.0 mmol) and sodium bicarbonate (0.084 g, 1.0 mmol) were dissolved in anhydrous DMF (2 mL) under argon. Bromine (52 mL, 1.0 mmol) was added to the solution and the resulting mixture was stirred overnight at room temperature. The solvent was evaporated under reduced pressure. The residue was dissolved in chloroform, and loaded on a silica gel column "A
(Davisil grade 633, 200 - 425 mesh, 60 A). Product 10a was eluted with chloroform; yield, 180 mg (52%); mp 150-152 C;
UV (pHl) l,,,. 248 nm (e = 0.753 x 104) , 292 (1.398 x 104) ;
(pH 6.9) 251 (0.919 x 104), 287 (1.306 x 109); (pH 13) 251 (0.906 x 10") , 287 (1.296 x 104) ; 'H NMR d 3.53 (s, 3 H, CH3) , 5'. 47 (s, 2 H, ArCH2) , 6.61 (s, 2 H, NH2, exchange with D20), 7. 35-7 . 52 (m, 5 H, ArH) ; MS (EI) calcd m/z for C13H12N5O79Br 333.0225, found 333.0228; calcd m/z for C13H12N5O81Br 335.0205, found 335.0188; Anal. (C13H12N5OBr) C, H, N, Br.

Example 28: O6-Benzyl-8-bromo-9-(pivaloyloxymethyl)guanine (lOb) and 06-benzyl-8-bromo-7-(pivaloyloxymethyl)guanine (11) 06-Benzyl-8-bromoguanine (Chae et al., J. Med. Chem., 38, 342-347 (1995)) (0.48 g, 1.5 mmol) was mixed with 1.5 mL of a 1.0 M solution of sodium ethoxide in ethanol and was stirred for 20 min. The ethanol was removed under reduced pressure and the solid residue was dissolved in DMF
(5 mL). Chloromethylpivalate (0.24 mL, 1.65 mmol) was then added and the solution was stirred overnight. The DMF was removed under reduced pressure. The residue was dissolved in chloroform and was loaded on a silica gel column (Davisil grade 633, 200-425 mesh, 60A) eluted with chloroform. The 9-isomer (lOb) eluted earlier than the 7-isomer with chloroform and lOb was recovered in pure form under these conditions. 06-Benzyl-8-bromo-9-(pivaloyloxymethyl)guanine (lOb):-yield, 150 mg (23%); mp 217-218 C; UV (pH 1) l,,,,, 250 nm (e = 0.944 x 104) , 291 (1.166 x 104) ; (pH 6.9) 266 (0.916 x 104) , 295 (0.916 x 104) ; (pH 13) decomposes to 06-benzyl-8-bromoguanine; 'H NMR
d 1.13 (s, 9H, C(CH3) 3) , 5.48 (s, 2H, ArCH2), 5.93 (s, 2H, CH2), 6.80 (s, 2H, NH2, exchange with D20), 7.35-7.52 (m, 5H, ArH) . MS (EI) calcd rn/z for C18HZON5O379Br 433.0750, found 433.0725; calcd m/z for C1eHioNsOs81Br 435.0729, found 435.0672; Anal. (C18H2oN5O3Br) C, H, N, Br. The recovered 7-isomer (11) was rechromatographed on a silica gel column (Davisii'grade 633, 200-425 mesh, 60 A) which was eluted first with CHC13/hexane (1:1) followed by CHC13 to recover 06-benzyl-8-bromo-7-(pivaloyloxymethyl)guanine (11).
Example 29: &-Benzyl-7- (pivaloyloxymethyl) guanine (12) 06-Benzylguanine (2.41 g, 10 mmol) was mixed with 10 mL of a 1.0 M solution of sodium ethoxide in ethanol and was stirred for 30 min. The ethanol was evaporated under reduced pressure. The residue was dissolved in anhydrous DMF (30 mL), and chloromethyi- pivalate (Aldrich) (1.5 mL, , ~ = !=
2195$5b ::; = . :. ..

10.4 mmol) was added. The clear solution was stirred overnight at room temperature. DMF was evaporated under reduced pressure to give a pale peach-colored solid.- The solid was dissolved in chloroform/ethanol (9:1) and loaded on a silica gel column (Davisil grade 633, 200 - 425 mesh, 60 A). The column was eluted with_chloroform/ethanol (9:1) to elute the 9-isomer (Chae et al., J. Med. Chem., 37, 342-347 (1994)) followed by the 7-isomer. The 7-isomer (12) was further purified by silica gel column chromatography (Davisil grade 633, _200 - 425 mesh, 60 A) using chloroform/ethanol (98:2) as eluent: yield, 36 mg (1$); mp 166-168 C dec; W(pH 1) lm,x 240 nm (sh) (e =
0.656 x 104), 290 (1.164 x 10 ); (pH 6.9) 240 (sh) (0.635 x 10 ), 293 (0.528 x 104); (pH 13) decomposes to 0-benzylguanine; 1H NMR d 0.98 (s, 9 H, C(CH3)3); 5.51 (s, 2 H, ArCH2), 6.07 (s, 2 H, CH2), 6.32 (s, 2 H, NHZ, exchange with Da0), 7.36-7.58 (m, 5 H, ArH), 8.25 (s, 1 H, H-8); MS
(EI) calcd nt/z for CieH21Ne03 355.1644, found 355.1626.

AMft3DED SNEET

Claims (17)

CLAIMS:

1. A compound of the formula wherein R1 is a substituent selected from the group consisting of amino, hydroxy, C1-C4 alkylamino, C1-C4 dialkylamino, and C1-C4 alkylcarbonylamino, R2 is a substituent selected from the group consisting of hydrogen, C1-C4 alkyl, C1-C4 aminoalkyl, C1-C4 hydroxyalkyl, C1-C4 alkylamino C1-C4 alkyl, C1-C4 dialkylamino alkyl, C1-C4 cyanoalkyl, C1-C4 carbamoylalkyl, C1-C4 pivaloylalkyl, C1-C4 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkoxycarbonylalkyl, 2'-deoxyribose, the conjugate acid form of a C1-C4 carboxyalkyl, and the carboxylate anion of a C1-C4 carboxyalkyl as the sodium salt, and R3 is a substituent selected from the group consisting of halo, C1-C4 alkyl, C1-C4 hydroxyalkyl, mercapto, C1-C4 alkylthio, trifluoromethylthio, C1-C4 alkylthiocarbonyl, hydroxy, C1-C4 alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, C1-C4 alkylcarbonyloxy, amino, C1-C4 aminoalkyl, C1-C4 alkylamino, C1-C4 dialkylamino, trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, amino C1-C4 alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, C1-C4 alkyldiazo, C5-C6 aryldiazo, trifluoromethyl, C1-C4 haloalkyl, C1-C4 cyanoalkyl, cyano, C1-C4 alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, C1-C4 alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SO n R' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl.

2. The compound of claim 1, wherein R1 is selected from the group consisting of amino, hydroxy, C1-C4 alkylamino, C1-C4 dialkylamino, and C1-C4 alkylcarbonylamino, R2 is selected from the group consisting of hydrogen, C1-C4 alkyl, and C1-C6 alkylcarbonyloxy C1-C4 alkyl, and R3 is selected from the group consisting of amino, halo, C1-C4 alkyl, hydroxy, and trifluoromethyl.

3. The compound of claim 2, wherein R1 is selected from the group consisting of amino, hydroxy, methylamino, dimethylamino, and acetylamino, R2 is selected from the group consisting of hydrogen, methyl, and pivaloyloxymethyl, and R3 is selected from the group consisting of amino, bromo, methyl, hydroxy, and trifluoromethyl.

4. The compound of claim 3, wherein said compound is selected from the group consisting of 8-amino-O6-benzylguanine, 8-methyl-O6-benzylguanine, 8-hydroxy-O6-benzylguanine, 8-bromo-O6-benzylguanine, 8-trifluoromethyl-O6-benzylguanine, O6-benzylxanthine, O6-benzyluric acid, N2-acetyl-O6-benzyl-8-oxoguanine, O6-benzyl-8-trifluoromethyl-9-methylguanine, O6-benzyl-8-bromo-9-methylguanine, and O6-benzyl-8-bromo-9-(pivaloyloxymethyl)-guanine.

5. The compound of claim 1, where R1 is amino.

6. The compound of claim 1, wherein R1 is hydroxy, C1-C4 alkylamino, C1-C4 dialkylamino, or C1-C4 alkylcarbonylamino.

7. A compound of the formula wherein R1 is selected from the group consisting of hydrogen, halo, C1-C4 alkyl, halo C1-C4 alkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkyloxycarbonyl C1-C4 alkyl, carboxy C1-C4 alkyl, cyano C1-C4 alkyl, aminocarbonyl C1-C4 alkyl, hydroxy C1-C4 alkyl, and C1-C4 alkyloxy C1-C4 alkyl, and R2 is selected from the group consisting of C1-C4 alkyl, halo C1-C4 alkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkyloxycarbonyl C1-C4 alkyl, carboxy C1-C4 alkyl, cyano C1-C4 alkyl, aminocarbonyl C1-C4 alkyl, hydroxy C1-C4 alkyl, and C1-C4 alkyloxy C1-C4 alkyl, with the proviso that when R1 is hydrogen, R2 is selected from the group consisting of halo C1-C4 alkyl, C1-C4 alkyloxy C1-C4 alkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, carboxy C2-C4 alkyl, cyano C2-C4 alkyl, aminocarbonyl C2-C4 alkyl, and hydroxy C1-C3 alkyl.

8. The compound of claim 7, wherein said compound is selected from the group consisting of O6-benzyl-8-bromo-7-(pivaloyloxymethyl)guanine and O6-benzyl-7-(pivaloyloxymethyl)guanine.

9. A compound of the formula wherein R1 is hydroxy, R2 is a substituent selected from the group consisting of hydrogen, C1-C4 alkyl, C1-C4 aminoalkyl, C1-C4 hydroxyalkyl, C1-C4 alkylamino C1-C4 alkyl, C1-C4 dialkylamino alkyl, C1-C4 cyanoalkyl, C1-C4 carbamoylalkyl, C1-C4 pivaloylalkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkoxycarbonylalkyl, 2'-deoxyribose, the conjugate acid form of a C1-C4 carboxyalkyl, and the carboxylate anion of a C1-C4 carboxyalkyl as the sodium salt, and R3 is a substituent selected from the group consisting of hydrogen, halo, C1-C4 alkyl, C1-C4 hydroxyalkyl, mercapto, C1-C4 alkylthio, trifluoromethylthio, C1-C4 alkylthiocarbonyl, hydroxy, C1-C4 alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, C1-C4 alkylcarbonyloxy, amino, C1-C4 aminoalkyl, C1-C4 alkylamino, C1-C4 dialkylamino, trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, amino C1-C4 alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, C1-C4 alkyldiazo, C5-C6 aryldiazo, trifluoromethyl, C1-C4 haloalkyl, C1-C4 cyanoalkyl, cyano, C1-C4 alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, C1-C4 alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SO n R' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl.

10. A compound of the formula wherein R1 is a substituent selected from the group consisting of amino, hydroxy, C1-C4 alkylamino, C1-C4 alkylcarbonylamino, and C1-C4 dialkylamino, R2 is a substituent selected from the group consisting of C1-C4 aminoalkyl, C1-C4 alkylamino C1-C4 alkyl, C1-C4 dialkylamino alkyl, C1-C4 carbamoylalkyl, C1-C4 pivaloylalkyl, C1-C6 alkylcarbonyloxy C1-C4 alkyl, C1-C4 alkoxycarbonylalkyl, and 2'-deoxyribose, and R3 is a substituent selected from the group consisting of hydrogen, halo, C1-C4 alkyl, C1-C4 hydroxyalkyl, mercapto, C1-C4 alkylthio, trifluoromethylthio, C1-C4 alkylthiocarbonyl, hydroxy, C1-C4 alkoxy, trifluoromethoxy, methanesulfonyloxy, trifluoromethanesulfonyloxy, C1-C4 alkylcarbonyloxy, amino, C1-C4 aminoalkyl, C1-C4 alkylamino, C1-C4 dialkylamino, trifluoromethylamino, ditrifluoromethylamino, aminomethanesulfonyl, amino C1-C4 alkylcarbonyl, aminotrifluoromethylcarbonyl, formylamino, nitro, nitroso, C1-C4 alkyldiazo, C5-C6 aryldiazo, trifluoromethyl, C1-C4 haloalkyl, C1-C4 cyanoalkyl, cyano, C1-C4 alkyloxycarbonyl, C1-C4 alkylcarbonyl, phenyl, phenylcarbonyl, formyl, alkoxymethyl, phenoxymethyl, C2-C4 vinyl, C2-C4 ethynyl, and SO n R' wherein n is 0, 1, 2, or 3 and R' is hydrogen, C1-C4 alkyl, amino, or phenyl, with the provisos that R1 is not methylamino when R2 is ribose or 21 -deoxyribose and R3 is hydrogen and that when R1 is amino and R3 is hydrogen, R2 is not alkylcarbonyloxyalkyl, alkoxycarbonylalkyl, or carbamoylalkyl.

11. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and at least one compound of any one of claims 1 to 10.

12. The pharmaceutical composition of claim 11, wherein said pharmaceutically acceptable carrier comprises polyethylene glycol.

13. Use of a compound of any one of claims 1 to 10 in the manufacture of a medicament for enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent that causes cytotoxic lesions at the O6-position of guanine.

14. A product containing a compound of any one of claims 1 to 10 and an antineoplastic alkylating agent which causes cytotoxic lesions at the O6-position of guanine, for simultaneous, separate or sequential use for enhancing chemotherapeutic treatment of tumor cells in a mammal.

15. The pharmaceutical composition of claim 11, for enhancing the chemotherapeutic treatment of tumor cells in a mammal with an antineoplastic alkylating agent that causes cytotoxic lesions at the O6-position of guanine.

16. A method of inhibiting the reaction of O6 alkylguanine-DNA alkyltransferase in vitro with an alkylated DNA comprising reacting the O6-alkylguanine-DNA
alkyltransferase with a compound of any one of claims 1 to 10.

17. An enhancing chemotherapeutic pharmaceutical composition for treatment of tumor cells in a mammal with an antineoplastic alkylating agent which causes cytotoxic lesions at the O6-position of guanine comprising a therapeutically effective amount of a compound defined in any one of claims 1 to 10 in association with a pharmaceutically acceptable carrier.