CA1132136A

CA1132136A - Amino acid derivatives

Info

Publication number: CA1132136A
Application number: CA294,939A
Authority: CA
Inventors: Miguel A. Ondetti; Michael E. Condon
Original assignee: ER Squibb and Sons LLC
Current assignee: ER Squibb and Sons LLC
Priority date: 1977-01-17
Filing date: 1978-01-13
Publication date: 1982-09-21
Also published as: NO150397B; US4154960A; US4129571A; IE46364B1; JPS6126781B2; HU180529B; BE862944A; DE2801911A1; DK149594C; NO150397C; US4146611A; US4156786A; DE2801911C2; GB1600461A; FR2377374A1; US4113715A; AU518282B2; CH632991A5; US4154946A; JPS5390218A

Abstract

ABSTRACT
New substituted acyl derivatives of amino acids which have ]the general formula

Description

~3~3~ HA1~6 This invention relates to new substituted acyl deri-vatives of amino acids which have the general formula Rl- N- R2 (~H2)m 1 1 R3 S - ~CH2)n ~CH CO N ~CH- CO- R

and salts thereof, wherein R is hydroxy or lower alkoxy; R
is hydrogen, lower alkanoyl or amino(imino)methyl; R2 is hydrogen, lower alkyl or phenyl-lower alkylene; R3 is hydrogen, lower alkanoyl, benzoyl or Rl- N- R2 ( IcH2)m 1 7 -S- (CH2)n CH - CO - N CH CO - R

A is hydrogen, lower alkyl or hydroxy-lower alkylene; B is hydrogen, lower alkyl, phenyl, phenyl-lower alkylene, hydroxy-lower alkylene, hydroxyphenyl-lower alkylene, amino-lower alkyl-ene, guanidino-lower alkylene, mercapto-lower alkylene, lower alkyl-thio-lower alkylene, imidazolyl-lower alkylene, indolyl-lower alkylene, carbamoyl-lower alkylene or carboxy-lower alkylenP; or A and B together form a (CH2)p bridge which completes a ring of 5 or 6 atoms with the nitrogen and carbon to which they are joined, one carbon optionally bearing a hydroxy group; n is 0 or 1; m is 0, 1, 2, 3 or 4; at least one of m and n is other than 0, provided that when m=0, A and B together form a (CH2)p bridge which completes a ring of 5 or 6 atoms with the nitrogen and carbon to which they are joined, one carbon optionally bearin~ a hydroxy group; and p is 3 or 4. The asterisks denote centers of asymmetry.

1132~3~

The invention in its broad aspects includes substituted acyl derivatives of amino acids having Formula I above. The substituted acyl groups re~er to the side chains on the carbon beta to the nitrogen atom. The one side chain has one or two sulfur containing groups and the second side chain has one nitrogen containing group. Within the class defined by Formula I, because of their properties, certain subgroups are preferred.
Compounds in the group represented by Formula I which are derived from or include the structure of the amino acids glycine, alanine, leucine, threonine, phenylalanine, lysine, arginine! glutamine, histidine, methionine, serine, cysteine, tyrosine, valine, asparagine, glutamic acid, proline, hydroxy-proline, phenylglycine or tryptophane are broadly preferred.
Preferred modifications are compounds of Formula I wherein R is hydroxy; Rl is hydrogen, lower alkanoyl or amino(imino)-methyl (particularly hydrogen, methyl, acetyl or amino(imino~-methyl); R~ is hydrogen, lower alkyl (particularly hydxogen or methyl) or phenyl-lower alkylene (particularly benzyl), most particularly R2 is hydrogen; R3 is hydrogen, lower alkanoyI or benzoyl (particularly hydrogen or acetyl); A is hydrogen; B is lower alkyl, guanidino lower alkylene (particularly quanidino-propyl), amino-lower alkylene (particularly amino-C3-C4-lower alkylene) or phenyl-lower alkylene (particularly phenylmethyl);
or A and B complete a 5- or 6~membered ring; m is 0, 3 or 4 and n is 0 or 1, but not both m and n are 0.

~3~3~ ~A146 Especially preferred are those compounds of formula I
which are derived from proline and have the formula (II) Rl-N-R2 R3 S - (CH2)n CH - C0 N- - CH-C0-R

The symbols have the same preferred meanings described a~ove.
The lower alkyl groups represented by any of the variables include straight and branched chain hydrocarbon radicals from methyl to heptyl, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, iso-pentyl and the like. The lower alkylene groups are of the same kind also having 1 to 7 carbons. Similarly, the lower alkoxy groups are of the same kind with a link to oxygen, for example, methoxy, ehtoxy, propoxy, isopropoxy, butoxy, isobutoxy, t-butoxy and the like. The Cl-C4 members, especially Cl and C2 members, of all types are preferred.
Phenylmethyl is the preferred phenyl-lower alkylene group and methoxy and t-butoxy the preferred lower alkoxy groups.
The lower alkanoyl groups are the acyl radicals of the lower (up to 7 carbons) fatty acids, e.g., acetyl, propionyl, butyryl and the like, acetyl being preferred.
The amino(imino)methyl group represented by Rl is the residue of the guanidino radical (-C-NH2).
The products of formula I and the preferred subgroups can be produced by various methods of synthesis. ~ccording to a preferred method, the amino acid of the formula ~ B
H~-CH-C0~ III

~13~ç; HA146 wherein A, B and R are defined as above, and R is hydroxy is acylated with an acid of the formula (CH ) IV
1 2 m R3 S (CH2)n CH COOH

wherein R is an acyl group, and R2, R3, m and n have the meaning defined above, by one of the known procedures in which the acid IV, prior to reaction with the amino acid III, is transformed into an activated carboxylic acid derivative, such as a mixed anhydride, symmetrical anhydride, acid chloride, active ester, Woodward reagent K, N,N'-carbonylbisimidazolc, EEDQ (N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline) or the like. When R is lower alkoxy, this or other known methods of coupling such moieties can be used [For a review of these methods, see Methoden der Organischen Chemie (Houben-Weyl), Vol. XV, parts 1 and 2 (1974)~.
When the product obtained is an ester, e.g., R is t-butoxy, the ester can be converted to the free carboxy group (R is hydroxy) by cleavage with acids, e.g., trifluoroacetic acid. Conversely the free acid can be esterified by conventional proce`dures.
Starting materials of Formula IV wherein m is 0 are deri-vatives of the amino acid cysteine which can be produced by known procedures.
The acids of Formula IV wherein n is 2, 3, or 4 can be synthesized, according to a preferred method, by the addition of a thiol acid to the substituted acrylic acid of the formula ~n ,~ _ :

f j ~3~3~;

Rl-N-R2 (CH ) (V) C 2 m D \

The latter are obtained by hydrolysis, e.g., with 6N hydrochloric acid, of the methylene lactams of the formula (VI) (C ~ 7H

H2C= C=O

[J. Org. Chem. 39, 893 (1974)]
The compounds of formula I wherein m is 1 are obtained by the Curtius rearrangement of an acid of the formula (VII) COOII

CH A B

R3~s-(cH2)m-cH-co-N-cH-co-R
The preferred method for producing compounds of formula I wherein n is 0 is hy displacement of the halo derivative of the formula (VIII) R -N~R

(CH ) A B
l 2 m X-CEI-CO ~ N- CH- CO--~wherein X is halogen, preferably chlorine or bromine, with the thiol acid R3-COSH.
The disulfides of formula I, wherein R3 is R -~-R

(CH ) A B
1 2 m I I
-S- (CH2)n-CH-CO-N-CEI-COR

_5_ ~3~ HA146 are obtained by oxidation of the compound of the formula (IX) Rl-N-R2 (I 2)m 1 7 HS-(CH2)n-CH-C0-N-C~I-COR
e~g., with an alcoholic solution of iodine.
The compounds of formula I wherein Rl is amino(imino)-methyl are obtained by reacting a compound of formula I
wherein R1 or R2 is hydrogen with a guanyl-forming reagent e.g., guanyl-3,~-dimethylpyrazole nitrate, S-methyliso-thiourea, or 0-methylisourea.
Products of formula I have two asymmetric carbon atoms. These carbon atoms are indicated by an asterisk in formula I. The compounds accordingly exist in diastereo-isomeric forms or in racemic mixtures thereof. All of these are within the scope of the invention~ The ahove described syntheses can utilize the racemate or one of the enantiomers as starting material. When the racemic starting material is used in the synthetic procedure, the stereoisomers obtained in the product can be ser)arated by conventional chroma-tagraphic or fractional crystallization'methods. In general,the L-isomer with respect to the carbon of the amino acid constitutes the preferred isomeric form.
The compounds of formula I form salts which are also part of this invention. The salts include acid-addition salts which are formed by reaction with a variety of inorganic and organic acids providing acid addition salts including, for example, hydrohalides (especially hydrochloride and hydrobromide), sulfate, nitrate, borate, phosphate, oxalate, tartrate, ma]t-(lte, citratc, acctatc, a-corbatc, succinatc, ben enesulfonate, mcthalle-;ulfonate, cycloht-~xancsulfamatc and toluenesulfonate.

11~19~
~3~3~

The salts ~re formed in con~entional manner by reacting the free form of the product with one or more equivalents of the appropriate acid or base providing the desired anion or cation in a solvent or medium in which the salt is insoluble, or in water and removing the water hy freeze drying. ~y neutrali~ing the salt with an insoluble acid like a cation exchange resin in the hydrogen form ~e.g., polystyrene sulfonic acid resin - Dowex 50 (Mikes, Laboratory Handbook of Chromatographic Methods (Van Nostrand, 1~61) page 2563 eluting with a volatile buffer (e.g. pyridine-acetic acid) and extraction with an organic solvent, the free form can be obtained, and, if desired, another salt formed.
~ dditional experimental details are found in the examples which are preferred embodiments and also serve as models for the preparation of other members of the group.
The compounds of this invention inhibit the conversion of the decapeptide angiotensin I to angiotensin II and therefore are useful in reducing or relieving angiotensin related hypertension. Thè action of the enzyme renin on angiotensinogen, a pseudo~lobulin in blood plasma, produces angiotensin I. Angiotensin I is converted by angiotensin converting enzyme (ACE) to angiotensin II. The latter is an active pressor substance which has been implicated as the causative agent in various forms of hypertension in various mammalian species, e.g., rats, dogs, and so forth.
The compounds of this invention intervene in the angioten-sinogen ~ angiotensin I ~ angiotensin II sequence by inhibit-ing angiotensin converting enzyme and reducing or eliminating the formation of the pressor substance angiotensin II.

~ *Trade Mark Ihl4~

The inhibition of the angiotensin converting enzyme by compounds of formula I can be measured in vitro with isolated angiotensin converting enzyme from rabbit lungs following the procedure described by Cushman and Cheung [Biochem. Pharmacol., 20, 1637 (1971)], and with an excised smooth muscle assay [E O'Keefe, et al., Federation Proc.
31, 511 (1972)] in which these compounds have been shown to be powerful inhibitors of the contractile activity of angiotensin I and potentiators of the contractile activity of bradykinin.
The administration of a composition containing one or a combination of compounds of formula I or physiologically acceptable salt thereof to ~he species of hyperténsive mammal alleviates or reduces hypertension. A single dose, or prefer- -ably two to four divided daily doses, provided on a ~asis of about 5 to 1000 mg. per kilogram per day, preferably about 10 to 500 mg. per kilogram per day is appropriate to reduce blood pressure. The animal model experiments described by S. L. Engel, T. R. Schaeffer, M. H. Waugh and B. Rubin, Proc. Soc. Exp. Biol. Med. 143, 483 (1973) serve as a useful guide.
The substance is preerably administered orally, but parenteral routes such as subcutaneously, intramuscularly, intravenously or intraperitoneally can also be employed.
The compounds of this invention can be utilized to achieve the reduction o blood pressure by formulating in compositions such as tablets, capsules or elixirs for oral administration or in sterile solution or suspensions for parenteral adminlstration. About 10 to 500 mg. of a compound or mixture of compounds of ~ormula I or physiologically 1~14~

acceptable salt is compounded with a physiologically accept-able vehicle, carrier, excipient, binder, preservative, stabilizer, flavor and so forth, in a unit dosage fGrm as called for by accepted pharmaceutical practice. The amount of active substance in these compositions or preparations is such that a suitable dosage in the range indicated is obtained.
The following examples are illustrative of the inven-tion. All temperatures are in degrees celsius.
Example 1 N~ ButYloxycarbonyl-s-p-methoxybenzyl-D-cysteinyl-L
~rollne tert-butyl ester.

To a solution of L-proline t _ -butyl ester (0.85 g) and hydroxybenzotriazole (0.67 g) in methylene chloride (10 ml) chilled in an ice bath, dicyclohexylcarbodiimide (1.03 g) and N-tert-butyloxycarbonyl-S-p-methoxybenzyl-D-cysteine (1.7 g) are added in that order. After fifteen minutes, the ice bath is removed and the mixture is stirred at room temperature overnight. The precipitate is filtered off and the filtrate is washed with 10% potassium bisulfate, water, saturated sodium bicarbonate, and water. The organic phase is dried and concentrated to dryness ln vacuo to give N-tert-butyloxycarbonyl-S-p-methoxybenzyl-D-cysteinyl-L-proline tert-butyl ester as an oil. Rf=0.2 (silica gel, chloroform).
Example 2 D-Cysteinyl-L-proline acetate To a solution of N-tert-butyloxycarhonyl-S-p-methoxy-benzyl-D-cysteinyl-L-proline tert butyl ester tl.8 9) ~nd ~nisole (4.4 ml) in dichloromethane (8 ml) chilled in an _g_ ~ 3~ ~Ihl~

ice bath, trifluoromethane sulfonic acid (6.0 g) is added.
The ice bath is removed and the mixture is stirred at room temperature for thirty minutes. The dichloromethane is removed ln vacuo and the residue is triturated with hexane (2 X 200 ml). The residue is dissolved in water and extracted twice with ether. The aqueous phase is applied to a column of 200 ml of cation exchange resin [Dowex 50] in the hydrogen cycleO The column is washed with water until no more acidic material is eluted. The D-cysteinyl-L-proline acetate is eluted with a pyridine-acetic acid buffer pH 6.5, yield 0.66 g. Rf=0.38 (silica gel, chloroform:methanol:acetic acid:water).
Example 3 N,~S-Diacetyl-DL-cysteinyl-L-proline tert-butyl ester By substituting N~S-diacetyl-DL-cysteine for the N-tert-butyloxycarbonyl-S-p-methoxybenzyl-D-cysteine in the procedure of Example 1, N,S-diacetyl-DL-cysteinyl-L-proline tert-butyl ester is obtained. Rf=0.25 (silica gel, ethyl acetate).

N,S-Diacetvl-DL-cvsteinyl-L-r~roline ~ Al . ~.
N,S-Diacetyl-DL-cysteinyl-L-proline tert-butyl ester (1.9 g) is dissolved in a mixture of anisole (6 ml) and trifluoroacetic acid (12 ml) and the solution is stored at room temperature for one hour. The solvents are removed in vacuo and the residue is precipitated from ethyl acetate-ether-hexane,to obtain N,S-diacetyl-DL-cysteinyl-L-proline, yield 1.08 g, m.p. 80-1~0.

--.1 O--~3~3~ ~IA146 Example 5 ~ ~ = .
N-Acetyl-DL-cysteinyl-L-proline -N,S-Diacetyl-DL-cysteinyl~L-proline (0.3 g) is dissolved in a mixture of water (4 ml) and concentrated ammonia (4 ml) under a blanket of argon. The solution is stored for thirty minutes at room temperature, saturated with sodium chloride and extracted with ethyl acetate and chloroform. The organic layers are pooled and concentrated to dryness ln vacuo to obtain N-acetyl-DL-cysteinyl-L-proline, yield 0.1 g, Rf=0.25 (silica gel; benzene:acetic acid, 75:25).
Example 6 Methyl N-(p-methoxybenzyl)nipecotate h~_rochloride A mixture of 23 g of methyl nipecotate, 24.3 g of potassium carbonate, and 52 g of p-methoxybenzyl tri-chloroacetate in 800 ml of toluene is refluxed under nitrogen for seventy-two hours. The mixture is cooled, the toluene removed in vacuo, the residue dissolved in chloroform, and this solution washed once with 400 ml of aqueous potassium carbonate and then with ~00 ml of 10% hydrochloric acid. The chloroform solution is dried and concentrated in vacuo to a viscous brown oil Tri-turation of this oil with ethyl acetate affords 30.7 g of methyl N-(p-methoxybenzyl)nipecotate hydrochloride as an off-white crystalline solid. Recrystallization from ethyl acetate yields the analytical sample, m.p. 150-154.
- Example 7 1-( -Methox benz 1)-3-meth lene-2- i eridone P_ . Y Y . Y . P P
A solution of methyl N-(p-methoxybenzyl)nipecotate hydrochloride (30.7 g) and 8.4 g of sodium hydroxide in ~IA146 900 ml of methanol and 45 ml of ~later is stirred at room temperature for seventeen hours. The solution is evaporated to dryness ln vacuo, the residue diluted with tolu~ne, and this again evaporated to dryness in vacuo. To the residue is added 1 liter of acetic anhydride and 140 ml of triethyl-amine, and the resulting mixture is heated under reflux for four hours. The reaction mixture is evaporated to dryness in vacuo, the residue taken up in chloroform, washed with __ water, dried, and concentrated in vacuo. The residual oil is chromatographed on silica gel using 1:1 hexane-ethyl acetate as the eluant, and yields 16.9 g of l-(p-methoxy-benzyl)-3-methylene-2-piperidone as a chromatographically pure yellow oil. Alternatively~ the oil can be distilled to give analytically pure l-(p~methoxybenzyl)-3-methylene-

2-piperidone, b.p. 145-155/0.05 mm.
Example 8

3-Methylene-2-piperidone A solution of l-(p-methoxybenzyl)-3-methylene-2-piperidone (16.9 g) and 21.3 g of anisole in 400 ml of trifluoroacetic acid is refluxed under nitrogen for forty-eight hours. The solution is evaporated to dryness ln vacuo, and the residue chromatographed on 900 g of silica gel using ethyl acetate as eluant, yielding 6.5 g of 3-methylene-2-piperidone as a crystalline solid.
Examp~e 9 2-Meth~lene-5-aminopentanoic acid hydrochloride A solution of 2.6 g of 3-methylene-2-piperidone in 150 ml of 6N hydrochloric acid is refluxed for twenty-four hours. The cooled solution is extracted with chloroform, and the aqueous layer concentrated in vacuo to 3.8 g o~

~13~

glassy foam. The foam is heated with methanol, filtered through Celite ~diatomaceous earth clarifying agent~ to remove a small amount of insoluble material, and the filtrate is evaporated to dryness in vacuo, yielding 2.5 g of 2-methylene-5-aminopentanoic acid hydrochloride as a tan crystalline solid. Recrystallization from isopropanol gives the analytical sample, m.p. 138-144.
Example 10 2-Methylene-5-(p-methoxyhenzyloxycarbonyl)aminopentanoic acid To a solution of 8.8 g of 2-methylene-5-aminopentanoic acid hydrochloride in 100 ml of water is added with stirring 6.36 g of magnesium oxide, followed by a solution of 12.2 g of p-methoxybenzyloxycarbonyl azide in 100 ml of dioxane, and the resulting mixture is stirred at room temperature for two days. The reaction mixture is filtered, and the filtrate diluted with 200 ml of ethyl acetate, two equivalents of Dowex 50 ion exchange resin is added, and the mixture is stirred at room temperature for two hours. The resin is then filtered of and washed with water. The layers in thc filtrate are separated and the aqueous layer is extracted - twice with ethyl acetate. The combined organic layers are dried and concentrated ln vacuo to give I8.2 g of 2-methyl-ene-S-(p-methoxybenzyloxycarbonyl)aminopentanoic acld as an amber oil which crystallizes on standing~ This is used without further purification.
Example 11 2-Acetylthiomethyl-5-(p-methoxybenzyloxycarbon~l)amino-pentanoic acid A solution of 2-methylene-5-(p-methoxybenzyloxycarbonyl)-amino pentanoic acid (53 rnmoles) in 50 ml of thiolacetic acid ~.3~ 3~ ~14~

is allowed to stand at room temperature for forty-eiyht hours. The solution is evaporated to dryness in vacuo, and the residue taken up in chloroform and applied to a silica gel column (700 g). Elution with 5~ methanol in chloroform affords 14.2 y of 2-acetylthiomethyl-5-(p-methoxybenzyloxycarbonyl)aminopentanoic acid as an oil.
Treatment of this oil with one equivalent of dicyclo-hexylamine in ether, followed by recrystallization from ethyl acetate affords the corresponding dicyclohexyl-amine salt, m.p. 112-114.
Example l_ 2-Acetylthiometh~1-5-(p-methoxybenzyloxycarbonyl)amino pentanoic acid ~l-hydroxysuccinimide ester To a solution of 3.7 g of 2-acetylthiomethyl-5 (p-methoxybenzyloxycarhonyl)aminopentanoic acid and 1.21 g of N-hydroxysuccinimide in 60 ml of dichloromethane at 0-5 is added 2.16 g of N,N'-dicyclohexylcarbodiimide over twenty minutes with stirring. The resulting mixture is stirred overnight at 0-5. The precipitated dicyclohexylurea is 2~ filtered off, the filtrate concent~ated in vacuo and the residue taken up in ethyl acetate and washed through a silica g~l column to give 4.~ g of 2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonyl)amino pentanoic acid N-hydroxysuccinimide ester as an oil, which crystallizes on trituration with ether. Recrystallization from ethyl acetate-hexane affords the analytical sample, m.p. ~5-87.
~xample 13 1-[(2-Acetylthiomethyl-5-(p-methoxybenzyloxycarbonylamino)-pentanoy~?~L-proline ~L~-butyl ester 3~ By substituting 2-acetylthiomethyl-5-(p-methoxybenzyl-oxycarbonylamino)pentanoic acid for the N-tert-butyloxy-~Ihl46 ~13~

carbonyl-S-p-methoxybenzyl-D-cysteine in the procedure of Example 1, 1 ~2-acetylthiomethyl-5-(p-methoxybenzyloxy-carbonylamino)pentanoyl]-L-proline tert-butyl ester is obtained.
Example 14 1-(2-Acetylthiomethyl-5-aminopentanoyl?-L-proline trifluoro-acetate 1-[2-Acetylthiomethyl-5-(p-methoxybenzyloxycarbonyl-amino)pentanoyl]-L-proline tert-butyl ester (2 g) is dissolved in a mixture of trifluoroacetic acid (15 ml) and anisole (6 ml). The solution is stored at room temperature for one hour, the solvents are removed in vacuo and the residue is precipitated from ethyl acetate-ether to yieId 1-(2-acetylthiomethyl-5-aminopentanoyl)-L-proline trifluoro-acetate.
Example 15 1-(5-Amino-2-mercaptomethylpentanoyl)-L-proline 1-(2-Acetylthiomethyl-5-aminopentanoyl)-L-proline trifluoroacetate tl g) is dissolved in a mixture of water (12 ml) and concentrated ammonia (12 ml) under a blan~.et - of argon. The solution is stored twenty minutes at room temperature concentrated to 5 ml and applied to a column o~ Dowex 50 ion exchange resin in the hydrogen cycle.
The column is washed with water and 1-(5-amino-2-mercapto-methylpentanoyl)-L-proline is eluted with a buffer of pyridine-acetic acid at pH 6.5.
Example 16 2-Methvlene-4-methvlaminobutanoic acid hYdrochloride .

By substituting l-methyl-3-methylene-2-pyrrolidinone r~l. ('helr~ '3, ~93 (197~)~ for the 3-methy]ene-2-fl~,14~
3~

piperidone in the procedure of Example 9, 2-methylene-4-methylaminobutanoic acid hydrochloride is obtained.
Example 17 2-Methylene-4-(N-p-methoxybenz~loxycarbonvl-N-methylamino)-butanoic acid By substituting 2-methylene-4-methylaminobutanoic acid hydrochloride for the 2-methylene-5-aminopentanoic acid hydrochloride in the procedure of Example 10, 2-~ methylene-4-(N-p-methoxybenzyloxycarbonyl-N-methylamino)-butanoic acid is obtained.
Exam~le 1~

2-Acetylthiomethyl~ -methoxybenzyloxycarbonyl-N-methvlamino)butanoic ~acid By substituting 2-methylene-4-(N-p-methoxybenzyloxy-carbonyl-N-methylamino)butanoic acid for the 2-methylene-5-(p-methoxybenzyloxycarbonylamino)pentanoic acid ln the pro-cedure of Example 11, 2-acetylthiomethyl-4-(N-p-methoxy-benzyloxycarbonyl-N-methylamino)butanoic acid is obtained.
xample 19 1-(4-Amino-2-mercaptomethylbutanoyl)-I.-proline By substituting 2-acetylthiomethyl-4-(N-p-methoxy-benæyloxycarbonyl-N-methylamino)butanoic acid for the N-tert-butyloxycarbonyl-S-p-methoxybenzyl-D-cysteine in the procedure of Example 1, and then submitting the product to the procedures of Examples 14 and 15, 1-(2-acetylthiomethyl-

4-(M-p-methoxybenzyloxycarbonyl-N-methylamino)butanoyl)-L-proline t _ -butyl ester, l-(2-acetylthiomethyl-4-amino-butanoyl)-L-proline trifluoroacetate, and 1-(4-amino-2-mercaptomethylbutanoyl)-I-r~rolinc are obtained.

~1~3~ IA146 2-Acetylthiomethyl-6-(N-methyl-N-acetylamino)hexanoic acid By substituting 6-(N-methyl-N-aeetylamino)-2-methylene hexanoie aeid for the 2-methylene-5-(p-methoxybenzyloxy-earbonylamino)pentanoie acid in the proeedure of Example 11, 2-aeetylthiomethyl-6-(N-methyl-N-aeetylamino)hexanoie aeid is obtained.
Example 21 1-[(2-Mercaptomethyl-6-(N-methyl-N=acetylamino)hexano~l]-L-prollne By substituting 2-acetylthiomethyl-6-(N-methyl-N-acetylamino)hexanoic acid for the N-tert-butyloxycarbonyl-S-p-methoxybenzyl-D-cysteine in the procedure of Example 1, and then submitting the produet to the procedure of Examples 14 and 15, 1-[2-aeetylthiomethyl-6-(N-methyl-N-acetylamino)-hexanoyl]-L-proline tert-butyl ester, 1-[2-acetylthiomethyl-6-(N-methyl-N-acetylamino)hexanoyl]-L-proline, and 1-[2-mercaptomethyl-6-(N-methyl-N-acetylamino)hexanoyl~-L-proline are ohtained.
~xample 22 1-(5-Guanidino-2-mercaptomethylpentanoyl)-L-proline A solution of 1-(5-amino-2-mercaptomethylpentanoyl)-L-proline ~2.3 g), guanyl-3,5-dimethylpyrazole nitrate (2.41 g) and triethylamine (3.36 ml) in dimethylformamide (20 ml) is stored at room temperature under a blanket of argon for sixteen hours. The solvents are removed in vacuo, the residue is dissol~ed in 0.1 N hydroehloric aeid (10 ml) and zine dust (500 my) is ~dded. The suspension is stirred at roorn temI)er;lture rc,r two hours. ~tcr ilterin~,the ~iltrate is ~l~plied tO a eolumn oI l~c)wex 50 ion x(:han~e ~IA1~6 resin in the hydrogen cycle. The column is washed with water until no more acid is eluted and l-(S-guanidino-2-mercaptomethylpentanoyl)-L-proline is then eluted ~7ith a pyridine-acetate buffer at pH 6.5.
Example 23 N-(5-Amino-2-mercaptomethylpentanoyl)glycine By substituting glycine tert-butyl ester for the proline tert~butyl ester in the procedure of Example 13, and then submitting the product to the procedures of Examples 14 and lS, N-[2-acetylthiomethyl-5-(p-methoxybenzyloxy-carbonylamino)pentanoyl]glycine t _ -butyl ester, N-[2-acetylthiomethyl-5-aminopentanoyl]glycine and N-(5-amino-2-mercaptomethylpentanoyl)glycine are obtained.
Example 24 N-~5-Amino-2-mercaptomethylpentano~l)-L-leucine By substituting L-leucine tert-butyl ester for the proline tert-butyl ester in the procedure of Example 13, and then submitting the product to the procedures of Examples 14 and 15, N-[2-acetylthiomethyl-5-(p-methoxybenzyloxy-carbonylamino)pentanoyl]-L-leucine tert-butyl ester, N-[2-acetylthiomethyl-5-aminopentanoyl]-L-leucine and N-(5-amino-2-mercaptomethylpentanoyl)-L-leucine are obtained.
Example 25 N-~5-Amino-2-mercaptomethylpentanoyl)-L-phenylalani~e By substituting L-phenylalanine tert butyl ester for the L-proline tert-butyl ester in the procedure of ~xample 13, and then submitting the product to the procedures of Examples 14 and 15, N-[2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-L-phenylalanine tert-butyl ester, N-[2-acetylthiomethyl-5-aminopentanoyl)-L-2~3~;

phenylalanine and N-(5-amino-2-mercaptomethylpentanoyl)-L-phenylalanine are obtained.
Example 26 N-(5-Amino-2-mercaptomethylpentanoyl)-L-serine By substituting O-tert-butyl L-serine tert-butyl ester for the L-proline tert-butyl ester in the procedure of Example 13, and then submitting the product to the procedures of Examples 14 and 15, ~-[2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-O-tert-butyl L-serine tert-butyl ester, N-[2-acetylthiomethyl-5-aminopentanoyl)-L-serine and N-(5-amino-2-mercaptomethylpentanoyl)-L-serine are obtained.
Example 27 1-(5-Amino-2-mercaptomethylpentanoyl)-4-hydroxy-L-proline By substituting 4-hydroxy-L-proline p-methoxyhenzyl ester for th~ L-proline tert-butyl ester in the procedure of Example 13, and then submitting the product to the procedures of Examples 14 and 15, 1-[2-acetylthiomethyl-5-~p-methoxybenzyloxycarbonylamino)pentanoyl]-4-hydroxy-L-- proline p-methoxybenzyl ester, 1-(2-acetylthiomethyl~5-aminopentanoyl)-4-hydro~y-L proline, and 1-(5-amino-2-mercaptomethylpentanoyl)-4-hydroxy-L-prolin~ are obtained.
Example 23 1-(5-Amino-2-mercaptomethylpentanoyl)pipecolic acid By substituting pipecolic aeid tert-hutyl-ester (obtained from pipecolic acid by the procedure descrihed for the synthesis of L-proline tert-butyl ester) for the L-proline tert-butyl ester in the procedure of Example 13 and then submitting the product to the procedure of F.xamples 14 and 15, 1-[2-acetylthiomethyl-5-(p-methoxyhenzyloxycar~onyl-amino)pentanoyl~pipecolic acid tert-butyl ester, 1-[2-1~.1~6 3~

acetylthiomethyl-5-aminopentanoyl)pipecolic acid and 1-~5-amino-2-mercaptomethylpentanoyl)pipecolic acid are obtained.
Example 29 N -[2-Acetylthiomethyl-5-(p-methoxybenzyloxycarbonylamino)-pentanoyl -L-arglnlne A solution of 2-acetylthiomethyl-5-(p-methoxybenzyloxy-carbonylamino)pentanoic acid N-hydroxysuccinimide ester (4~6 g) in ethanol (16 ml) is added to a solution of L-arginine (1.47 g) in a mixture of water (15 ml) and sodium bicarbonate (1.68 g). The mixture is stirred at room tempexature for eight hours, acidified to p~ 3 and extracted with ethyl acetate. The aqueous phase is applied to a column of Dowex 50 ion exchange resin (100 ml) in the hydrogcn cycle. The column is washed with water until no more acidic material is eluted and then Na-[2-acetylthiomethyl-

5-(p-methoxybenzyloxycarbonylamino)pentanoyl]-L-arginine is eluted with pyridine-acetate buffer at p~l 6.5.
Rxample 30 N -(2-Acetylthiomethyl-5-aminopentanoyl)-L-arginine trifluoroacetate A solution of Na-[2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-L-arginine (1 g) in trifluoroacetic acid (10 ml) is stored at room temperature for fifteen minutes, and then concentrated to dryness in vacuo to yield N -(2-acetylthiomethyl-5-aminopentanoyl)-L-arginine trifluoroacetate.
Example 31 N -[5-Amino-2-mercaptomethylpentanoyl)-L-arginine Na-(2-acetylthiomethyl-5-aminopentano~l)-L-arginine trifluoroacetate (2 g) is dissolved in a mixture of w~ter . -2()-l~il4~
~13'~3~

(25 ml) and concentrated ammonia (25 ml) and this solution is stored at room temperature for twenty minutes. The solution is concentrated ln vacuo to ca. 5 ml and applied to a column of Dowex 50 ion exchange resin (50 ml) in the hydrogen cycle. After washing with water Na-[5-amino-2-mercaptomethylpentanoyl)-L-arginine is eluted with a pyridine-acetate buffer at pH 6.5.
Example 32 N -[2-Acetylthiomethyl-5-(p-me-thoxyben7y]oY~ycarhony]~mino)-PentanoYl -N -tert-butYloxYcarbonyl-L-lyslne tcrt-butyl cstex 1 0 ~ ~ ~
By substituting N~-tert-butyloxycarbonyl lysine tert-butyl ester for the L-proline tert-butyl ester in the procedure of Example 13, N -[2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-N-tert-butyloxycarbonyl-L-lysine tert-butyl ester is obtained.
Example 33 N -(2-Acetylthiomethyl-5-aminopentanoyl)-L-lysine trifluoro-acetate A solution of N -[2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-N -tert-butyloxy-carbonyl-L-lysine tert-butyl ester (1 g) in trifluoroacetic acid (5 ml) is stored at room temperature for one hour and then concentrated to dryness ln vacuo to yield Na-(2-acetylthiomethyl-5-aminopentanoyl)-L-lysine trifluoro-acetate.
Exarnple 3~
N -(5-Amino-2-mercaptomethylpentanoyl)-L-lysine By substitu-tiny N -(2-acetylthiomethyl-5-amino-pentanoyl)-l,-lyfiinc tri~luoroacetate for the N -(2-acetylthiomethyl-5-aminopentalloyl)-L-argininc in the procedure of lixample 31, N -(5-amino-2-mercaptometllyl-pentanoyl)-L-lysine is obtained.
Example 35 N -(5-Amino-2-mercaptomethylpentanoyl)-L-histidine By substituting L-histidine for the L-arginine in the procedure of Example 29 and then submitting the product to the procedures of Examples 30 and 31, N -[2-acetylthio-methyl-5-(p-methoxybenzyloxycarbonylamino)pentanoyl]-L-histidine, N -(2-acetylthiomethyl-5-aminopentanoyl)-I,-histidine, and Na-(5-amino-2-mercaptomethylpentanoyl)-L-histidine are obtained.
Example 36 N-(5-Amino-2-mercaptomethylpentanoyl)-L-methionine By substituting L-methionine diphenylmethyl ester for the L-proline tert-butyl ester in the procedure of Example 13, and then submitting the product to the procedures of Examples 14 and 15, N-[2-acetylthiomethyl-5-(p-methoxybenzyloxycarbonylamino)pentanoyl]-L-methionine diphenylmethyl ester, N-(2-acetylthiomethyl-5-amino~entanoyl)-L-methionine, and N-(5-amino-2~mercaptomethylpentanoyl)-L-methionine are obtained.
Example 37 N-[2-Acetylthiomethyl-5-(p-methoxybenzyloxycarbonylamino)-pentanoyl -L-tryptophane methyl ester A solution of L-tryptophane methyl ester hydrochloride (2.5 g), 2-acetylthiomethyl-5-(p-methoxybenzyloxycarbonyl-amino)pentanoic acid N-hydroxysuccinimide ester (4.6 g), and hydroxybenzotria~ole (1.35 g) in a mixture of dimethyl-~ormamide (20 ml) and triethylamine (l.6 ml) is stored at room temperature overnight. The solvent is removed 1n vacuo, the residue is dissolved in ethyl acetate and washed ~-~146 ~1~3~L3~à

neutral. The organic phase is dried and concentrated to dryness to yield N-[2-acetylthiomethyl-5-(p-methoxybenzyl-oxycarbonylamino)pentanoyl]-L-tryptophane methyl ester.
Example 38 N- (2-Acetylthiomethyl-5-aminopentanoyl)-L-tryptophane methyl ester trifluoroacetate N- [2-Acetylthiomethyl-5-(p-methoxybenzyloxycarbonyl-amino)pentanoyl~-L-tryptophane methyl ester (l g) is dissolved in trifluoroacetic acid (lO ml), the solution is stored at room temperature for fifteen minutes, and then evaporated ln vacuo to yield N-(2-acetylthiomethyl-5-aminopentanoyl)-L-tryptophane methyl ester trifluoroacetate.
Example 39 N- (5-Amino-2-mercaptomethylpentano~l)-L-tryptophane To a solution of N-(2-acetylthiomethyl-5-amino-pentanoyl)-L-tryptophane methyl ester trifluoroacetate (3 g) in methanol (60 ml) N sodium hydroxide (60 ml) is added. After four hours the solution is applied to a column of Dowex 50 ion exchange resin in the hydrogen cycle. After washing with water, the N-(5-amino-2-mercaptomethylpentanoyl)-L-tryptophane is eluted with pyridine-acetic acid buffer at pH 6.5.
Example 40 N- ( 5-Amino-2-mercaptomethylpentanoyl)-L-glutamine By substituting L-glutamine tert-butyl ester for the L-proline t _ -butyl ester in the procedure of Example 13, and then submitting the product to the procedures of Examples 14 and 15, N-[2-acetylthiomethyl-5-(p-methoxybenzyloxy-carbonylamino)pentanoyl]-L-glutamine tert-butyl ester, N- (2-acetylthiomethyl-5-aminopentanoyl)-L-glutamine, and N-(S-HAl~
~3~

amino-2-mercaptomethylpentanoyl)-L-glutamine are obtained.
Example 41 N-(S-Amino-2-mercaptomethylpentanoyl) L-aspartic acid By substituting L-aspartic acid di tert-butyl ester for the L-proline tert-butyl ester in the procedure of Example 13, and then submitting the product to the procedures of Examples 14 and 15, N-[2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-L-aspartic di tert-butyl ester, N-(2-acetylthiomethyl-S-aminopentanoyl)-L-aspartic acid, and N-(5-amino-2-mercaptomethylpentanoyl)-L-aspartic acid are obtained.
Example 42 D-C~steinyl-L-alanine By substituting L-alanine tert-butyl ester for thc L-proline tert-butyl ester in the procedure of Examplc 1, and then submitting the product to the procedure of Example 2, D-cysteinyl-L-alanine is obtained.
Example 43 D-Cysteinyl-L-phenylglycine By substituting L-phenylglycine tert-butyl ester ~prepared from L-phenylglycine by the procedure described for L-proline tert-butyl ester) for the L-proline tert-butyl ester in the procedure o~ Example 1, and then suhmitting the-product to the procedure of Example 2, D-cysteinyl-L-phenylglycine is obtained.
Example 44 D-Cystein~1-L-threonine By substituting O-tert-butyl-L-threonine tert-butyl ester for the L-proline tert-butyl ester in the procedure of Example 1 and then submitting the product to the procedure fl~l46 ~3'~3~
f Example 2, D-cysteinyl-L-threonine is obtained.
xample 45 N-(5-Guanidino-2-merca~tomethylpentanoyl)-L-phenylalanine .

By substituting N-(5-amino-2-mercaptomethylpentanoyl)-L-phenylalanine for the 1-(5-amino-2-mercaptomethylpentanoyl)-L-proline in the procedure of Example 22, N-(5-guanidino-2-mercaptomethylpentanoyl)-L-phenylalanine is obtained.
Example 46 N-(5-Guanidino-2-mercaptomethylpentanoyl)-L-leucine By substituting N-(5-amino-2-mercaptomethylpentanoyl)-L-leucine for the 1-(5-amino-2-mercaptome-thylpentanoyl)-L-proline in the procedure of Example 22, N-(5-guanidino-2-mercaptomethylpentanoyl)-L-leucine is obtained.
~xample 47 3-Acetylthio-2-methoxycarbonylmeth~propanoiC acid A mixture of thiolacetic aci~ (12.5 g) and 3-methoxy-carbonyl-2-methylenepropanoiC acid (17.1 g) are heated on the-steam bath for two hours. The reaction is concentrated in vacuo and the residue is dissolved in ethyl acetate (125 ml) and dicyclohexylamine (35 ml) i5 added. The crystals are filtered, dried and recrystallized from ethyl acetate to yield 37.8 g, of the dicyclohexylammonium salt of 3-acetyl-thio-2-methoxycarbonylmethylpropanoic acid, m.p. 120-121~.
This dicyclohexylammonium salt is converted to the free acid, 3-acetylthio-2-methoxycarbonylmethylprop acid, by distribution between ethyl acetate and 10% aqueous potassium bisulfate.
Example 48 1-[3-(~cetylthio)-2-met:hox~carbonylmeth~lr)ropan~yl r -T,-~ nr~ ~L~ ly~ r To a solution of I.-proline tert-butyl ester (1.71 (~) f~l4~
3~3'~
and 3-hydroxybenzotriazole (1.35 g) in dichloromethane ~15 ml), dlcyclohexylcarbodiimide (2.06 g) and 3-acetyl-thio-2-methoxycarbonylmethylpro~noic acid (2.2 g) are added. After eighteen hours stirring at room temperature, the precipitate formed is filtered off, the filtrate is washed neutral, dried, and concentrated to dryness to yield 3.7 g of l-[3-(acetylthio)-2-methoxycarbonylmethyl-propanoyl]-L-proline tert-butyl ester. Rf=0.8 (silica gel-ethyl acetate).
I0 xample 49 1-[3-(Acetylthio)-2-carboxymethylpropanoyl]-L-proline ~L~-butyl ester To a solution of 1-[3-(acetylthio)-2-methoxycarbonyl-methylpropanoyl]-L-proline tert-butyl ester (3.7 g) in methanol (60 ml), N sodium hydroxide (40 ml) is added. ~fter four hours, the reaction mixture is dilu-ted with water (lO0 ml) and extracted with ethyl acetate. The aqueous layer is acidified and extracted with ethyl acetate. This 1ast ethyl acetate layer is dried and concentrated to dryness in vacuo.
The residue is dilssolved in a mixture of pyridine and acetic anhydride (3:1 ) and the solution is stored at room temperature overnight. The reaction mixture is diluted with ethyl acetate (200 ml) and washed with 10% potassium bisulfate. The organic layer is dried and concentrated to dryness ln vacuo to yield 1-[3-(acetylthio)-2-carboxy-methylpropanoyl]-L-proline tert-butyl ester.
~xample 50 1-[3-(Acetylthio)-2-~L~-hutyloxycarbonylaminomethylpropanoyl]-I.-r~rollne ~eL~-hutvl estf~r ., l'o a ~ol~ ion of l-l3~ ccty]tllio)-~-car~/oxyl~ y]-propanoyl]~ roline tcrt-hutyl cstcr (3.h ~) in tcrt-hutanol ~3'~3~ 146 (60 ml), triethylamine (1~4 ml) and diphenylphosphoryl azide (2.75 g) are added. The mixture is refluxed for twenty-two hours, and concentrated to dryness in vacuo.
The residue is dissolved in ethyl acetate and the solution is washed neutral. The organic phase is dried and concen-trated to dryness in vacuo to yield l-[3-(acetylthio)-2-tert-butyloxycarbonylaminomethylpropanoyl]-L-proline tert-butyl ester.
Example 51 1-(3-Acetylthio-2-aminomethylpropanoyl)-L-proline 1-[3-(acetylthio)-2-tert-butyloxycarbonylaminomethyl-propanoyl]-L-proline tert-butyl ester (1.5 g) is dissolved in a mixture of anisole (6 ml) and trifluoroacetic acid (12 ml) and the solution is stored at room temperature for one hour. The solvent is removed ln vacuo, the residue is distributed between water and ether. The a~ueous phase is washed twice with ether and freeze-dried to yield 1-(3-acetylthio-2-aminomethylpropanoyl)-L-proline.
Example 52 1-(2-Aminomethyl-3-mercaptcpropanoyl)-L-proline By substituting 1-(3-acetylthio-2-aminomethylpropanoyl)-L-proline for the 1-(2-acetylthiomethyl-5-aminopentanoyl)-L-proline trifluoroacetate in the procedure of Example 15, 1-(2-aminomethyl-3-mercaptopropanoyl)-L-proline is ohtained.
Example 53 1-(5-Guanidino-2-mercaptomethylpentanoyl)pipecolic acid By substituting 1-(5-amino-2-mercaptomethylpcntanoyl)-pipecolic acid for thc ]-(5-amino-2-mcrcaL)to~cthylL~cntanoyl)-L-proline in thc procc(lll~c o~ Exam~lc 22, 1-(5--~uani(lino-2-mercaptomethylpentanoyl)pipecolic acid is obtained.
, ~ 13~ ~IA14fi Example S4 1-(5-Guanidino-2-mercaptomethylpentanoyl)-4-hydroxy-L-proline By substituting 1-(5-amino-2-mercaptomethylpentanoyl)-4-hydroxy-L-proline for the 1-(5-amino-2-mercaptomethyl-pentanoyl)-L-proline in the procedure of Example 22, 1-(5-guanidino-2-mercaptomethylpentanoyl)-4-hydroxy-L-proline is obtained.
Example 55 1,1'-Dithiobis-(2-D-amino-3-propanoyl)-bis-L-proline An alcoholic solution of iodine is added dropwise to a solution of D-cysteine-L-proline (1 g.) in ~Jater (10 ml.) while keeping the pH between 5 and 7 by careful addition of N sodium hydroxide. When a persistent yellow color is obtained, the solution is applied to a column of Dowex 50 ion exchange resin in the hydrogen cycle and washed with water. The 1,1'-dithiobis-(2-D-amino-3-propanoyl)-bis-L-proline is eluted with a pyridine-buffer at pll 6.5.
_xample 56 1-[2-Mercaptomethyl-5-(p-methoxybenzyloxycarbonylaminoj-pentanoyl]-L-proline By substituting 1-~2-acetylthiomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-L-proline for the N,S-diacetyl-DL-cysteinyl-L-proline in the procedure of Ex~ample 5, 1-[2 mercaptomethyl-5-(p-methoxybenzyloxy-carbonylamino)pentanoyl]-L-proline is obtained.
Example 57 l~l'-Dithiobis-[2-(p-methoxybenzyloxycarbonylamino~rop~l)-3 propanoyl]-bis-L-proline By substituting 1-[2-mercaptomethyl-5-(p-methoxy-benzyloxycarbonylamino)pentanoyl]-L-proline for the D-1~321~
~1~146 cysteinyl-L-proline in the procedure of Example 55, 1,1'-dithiobis-[2-(p-methoxybenzyloxycarbonylaminopropyl)-3-propanoyl]-bis-L-proline is obtained.
Example 58 1,1'-Dithiobis-~2-aminopropyl-3-propanoyl)-bis-L-proline By substituting 1,1'-dithiobis-[2-(p-methoxybenzyloxy-carbonylaminopropyl)-3-propanoyl]-bis-L-proline for the N -[2-acetylthiomethyl-5-(p-methoxybenzylcarbonylamino)-pentanoyl]-L-arginine in the procedure of Example 30, 1,1'-dithiobis-[2-aminopropyl-3-propanoyl)-bis-L-proline is obtained.
_xample 59 1,1'-Dithiobis-(2-aminopropyl-3-propanoyl)-bis-~-leucine By substituting N-(5-amino-2-mercaptomethylpentanoyl)-L-leucine for the D-cysteine-L-proline in the procedure of Example 55, 1,1'-dithiobis-(2-aminopropyl-3-propanoyl)-bis-L-leucine is obtained.
Example 60 L-Cysteinyl-L-proline acetate By substituting N-tert-butyloxycarbonyl-S-p-methoxy-benzyl-L-cysteine for the N-tert-butyloxycarbonyl-S-p-methoxybenzyl-D-cysteine in the procedure of Example 1 and submitting the product to the procedure of Example 2, N-tert-butyloxycarbonyl-S-_-methoxybenzyl-L-cysteinyl-L-proline tert-butyl ester and L-cysteinyl-L-proline acetate are obtained.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Process for preparing compounds of the formula and salts thereof, wherein R is hydroxy or lower alkoxy; R1 is hydrogen, lower alkanoyl or amino(imino)methyl; R2 is hydrogen, lower alkyl or phenyl-lower alkylene; R3 is hydrogen, lower alkanoyl, benzoyl or A is hydrogen, lower alkyl or hydroxy-lower alkylene; B is hydrogen, lower alkyl, phenyl, phenyl-lower alkylene, hydroxy-lower alkylene, hydroxyphenyl-lower alkylene, amino-lower alkyl-ene, guanidino-lower alkylene, imidazolyl-lower alkylene, indolyl-lower alkylene, mercapto-lower alkylene, lower alkylthio-lower alkylene, carbamoyl-lower alkylene or carboxy lower alkylene;
or A and B together form a (CH2)p bridge which completes an unsubstituted ring of 5 or 6 atoms with the nitrogen and carbon to which they are joined or said ring substituted with a hydroxy group; m is 0, 1, 2, 3 or 4; n is 0 or 1; at least one of m and n being other than 0 provided that when m=0, A and B
together form a (CH2)p bridge which completes an unsubstituted ring of 5 or 6 atoms with the nitrogen and carbon to which they are joined or said ring is substituted with a hydroxyl group; and p is 3 or 4 which comprises acylating an amino acid of the formula wherein A, B and R are defined as above with an acid of the formula wherein R1 is an acyl group, and R2, R3, m and n have the meaning defined above, the acid being transformed into an activated carboxylic acid derivative prior to reaction with the amino acid.

2. A process according to claim 1 wherein A and B
together are (CH2)3 completing a 5-membered ring and salts thereof, wherein R, R1, R2, R3, m and n have the same meaning as in claim 1.

3. A process as in claim 1 wherein is the radical of glycine, alanine, leucine, threonine, phenylalanine, lysine, arginine, glutamine, histidine, methionine, serine, cysteine, tyrosine, valine, asparagine, glutamic acid, proline, hydroxyproline, phenylglycine, tryptophane or N-methylphenyl-alanine.

4. A process as in claim 1 wherein A and B together are (CH2)4- completing a 6-membered ring.

5. A process as in claim 1 wherein R is hydroxy, R1 is hydrogen, lower alkanoyl or amino(imino)methyl; R2 is hydrogen, lower alkyl or phenyl-lower alkylene; R3 is hydrogen, lower alkanoyl or benzoyl; A is hydrogen; B is lower alkyl, guanidino-lower alkylene, amino-lower alkylene or phenyl-lower alkylene;
m is 3 or 4 and n is 0 or 1.

6. A process as in claim 1 wherein R3 is

7. A process as in claim 1 wherein A and B together are (CH2)3 completing a 5-membered ring; R is hydroxy; R1 is hydrogen, lower alkanoyl or amino(imino)methyl; R2 is hydrogen, lower alkyl or phenyl-lower alkylene; R3 is hydrogen, lower alkanoyl or benzoyl; m is 3 or 4 and n is 0 or 1.

8. A process as in claim 1 wherein R is hydroxy.

9. A process as in claim 1 wherein R is hydroxy and A and B together are (CH2)3 completing a 5-membered ring.

10. A process as in claim 1 wherein R is hydroxy, R1, R2 and R3 each is hydrogen and A and B together are (CH2)3 completing a 5-membered ring.

11. A process as in claim 1 wherein R is hydroxy, R1, R2 and R3 each is hydrogen, m is 0, n is 1 and A and B together are (CH2)3 completing a 5-membered ring.

12. A process as in claim 1 wherein R is hydroxy, R1, R2 and R3 each is hydrogen, m is 3 and n is 1 and A and B together are (CH2)3 completing a 5-membered ring.

13. A process as in claim 1 wherein R is hydroxy, R2 and R3 each is hydrogen, R1 is amino(imino)methyl, m is 3, n is 1 and A and B together are (CH2)3 completing a 5-membered ring.

14. A process as in claim 6 wherein each R is hydroxy, each R1 and R2 is hydrogen, each m is 0 and each n is 1 and R3 is

15. A process according to claim 1 wherein R1, R2, R3 are hydrogen, n and m are 0, R is OH and A and B together are (CH2)3 completing a 5 membered ring.

16. A compound of the formula and salts thereof, wherein R is hydroxy or lower alkoxy; R1 is hydrogen, lower alkanoyl or amino(imino)methyl; R2 is hydrogen, lower alkyl or phenyl-lower alkylene; R3 is hydrogen, lower alkanoyl, benzoyl or A is hydrogen, lower alkyl or hydroxy-lower alkylene; B is hydrogen, lower alkyl, phenyl, phenyl-lower alkylene, hydroxy-lower alkylene, hydroxyphenyl-lower alkylene, amino-lower alkylene, guanidino-lower alkylene, imidazolyl-lower alkylene, indolyl-lower alkylene, mercapto-lower alkylene, lower alkylthio-lower alkylene, carbamoyl-lower alkylene or carboxy lower alkylene; or A and B together form a (CH2)p bridge which com-pletes an unsubstituted ring of 5 or 6 atoms with the nitrogen and carbon to which they are joined or said ring substituted with a hydroxy group; m is 0, 1, 2, 3 or 4; n is 0 or 1; at least one of m and n being other than 0 provided that when m=0, A and B together form a (CH2) bridge which completes an unsub-stituted ring of 5 or 6 atoms with the nitrogen and carbon to which they are joined or said ring is substituted with a hydroxyl group; and p is 3 or 4 when prepared by the process of claim 1.

17. A compound according to claim 16 wherein A and B
together are (CH2)3 completing a 5-membered ring and salts thereof, wherein R, R1, R2, R3, m and n have the same meaning as in claim 1 when prepared by the process of claim 2.

18. A compound as in claim 16 wherein is the radical of glycine, alanine, leucine, threonine, phenylalanine, lysine, arginine, glutamine, histidine, methionine, serine, cysteine, gyrosine, valine, asparagine, glutamic acid, proline, hydroxyproline, phenylglycine, tryptophane or N-methylphenyl alanine when prepared by the process of claim 3.

19. A compound as in claim 16 wherein A and B together are (CH2)4- completing a 6-membered ring when prepared by the process of claim 4.

20. A compound as in claim 16 wherein R is hydroxy; R1 is hydrogen, lower alkanoyl or amino(imino)methyl; R2 is hydrogen, lower alkyl or phenyl-lower alkylene; R3 is hydrogen, lower alkanoyl or benzoyl; A is hydrogen; B is lower alkyl, guanidino-lower alkylene, amino-lower alkylene or phenyl-lower alkylene;
m is 3 or 4 and n is 0 or 1 when prepared by the process of claim 5.

21. A compound as in claim 16 wherein R3 is when prepared by the process of claim 6.

22. A compound as in claim 16 wherein R is hydroxy; R1 is hydrogen, lower alkanoyl or amino(imino)methyl; R2 is hydrogen, lower alkyl or phenyl-lower alkylene; R3 is hydrogen, lower alkanoyl or benzoyl; m is 3 or 4 and n is 0 or 1; A and B
together are (CH2)3 completing a 5-membered ring when prepared by the process of claim 7.

23. A compound as in claim 16 wherein R is hydroxy when prepared by the process of claim 8.

24. A compound as in claim 16 wherein R is hydroxy and A and B together are (CH2)3 completing a 5-membered ring when prepared by the process of claim 9.

25. A compound as in claim 16 wherein R is hydroxy, R1, R2 and R3 each is hydrogen and A and B together are (CH2)3 completing a 5-membered ring when prepared by the process of claim 10.

26. A compound as in claim 16 wherein R is hydroxy, R1, R2, and R3 each is hydrogen, m is 0, n is 1 and A and B
together are (CH2)3 completing a 5-membered ring when prepared by the process of claim 11.

27. A compound as in claim 16 wherein R is hydroxy, R1 R2 and R3 each is hydrogen, m is 3 and n is 1 and A and B
together are (CH2)3 completing a 5-membered ring when prepared by the process of claim 12.

28. A compound as in claim 16 wherein R is hydroxy, R2 and R3 each is hydrogen, R1 is amino(imino)methyl, m is 3, n is 1 and A and B together are (CH2)3 completing a 5-membered ring when prepared by the process of claim 13.

29. A compound as in claim 16 wherein each R is hydroxy, each R1 and R2 is hydrogen, each m is 0, each n is 1 and R3 is when prepared by the process of claim 14.

30. D-cysteinyl-L-proline when prepared by the process of claim 15.