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Publication numberUSRE33033 E
Publication typeGrant
Application numberUS 07/098,171
Publication dateAug 22, 1989
Filing dateSep 18, 1987
Priority dateJul 5, 1985
Fee statusLapsed
Publication number07098171, 098171, US RE33033 E, US RE33033E, US-E-RE33033, USRE33033 E, USRE33033E
InventorsJoseph E. Lynch, Ichiro Shinkai, Ralph P. Volante
Original AssigneeMerck & Co., Inc.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process for the preparation of HMG-CoA reductase inhibitors intermediates
US RE33033 E
Abstract
.Iaddend.hypercholesterolemic compounds of the HMG-CoA reductase type of the following general formula (1): ##STR1## involving an enantioselective aldol condensation is disclosed.
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Claims(7)
What is claimed is:
1. A process for the preparation of a compound represented by the following general formula (I): ##STR25## wherein R is: ##STR26## wherein Q is ##STR27## R5 is H or OH;
R6 is hydrogen or methyl; and a, b, c, and d represent optional double bonds, especially where b and d represent double bonds or a, b, c and d are all single bonds; or ##STR28## wherein E is --C═CH-- or --CH2 CH2 --; and
R1, R2 and R3 are each selected from halo such as chloro, bromo or fluoro,
C1-4 alkyl,
C1-4 haloalkyl,
phenyl
phenyl with one or more substituents independently selected from halo,
C1-4 alkyl, and
C1-4 alkoxy, or
R4 O in which R4 is phenyl, halophenyl, or
substituted phenyl-C1-3 alkyl wherein the substituents are selected from halo and C1-4 haloalkyl;
which comprises:
(1) reacting a compound of the formula (II)
RCHO (II)
wherein R is defined above, with the enolate of .[.(R)-2-acetoxy-1,2,2-triphenylethanol.]. .Iadd.(S)-2-acetyloxy-1,1,2-triphenylethanol .Iaddend.of the formula (III) ##STR29## wherein M+ is a cation derived from sodium, potassium, lithium, magnesium, or zinc, to afford a compound of the formula (IV) ##STR30## wherein R and M+ are defined above; and (2) reacting the compound of the formula (IV) with the enolate of a C1-5 alkylacetate, followed by mild acid hydrolysis to obtain the compounds of the formula (I).
2. A process according to claim 1 wherein the compound of the formula (III) is prepared by treating .[.(R)-2-acetoxy-1,2,2-triphenylethanol.]. .Iadd.(S)-1-acetyloxy-1,1,2-triphenylethanol .Iaddend.with a non-nucleophilic base .[.employed to form the enolate of the compound of the formula (III) is an alkali metal amide of the formula:.]. .Iadd.of formula: .Iaddend.
M+ N- R7 R8 
wherein M+ is a cation derived from sodium, potassium lithium, magnesium or zinc and R7 and R8 independently are C1-3 alkyl or when taken together with the nitrogen to which they are attached form a 5 or 6-membered heterocyclic ring.
3. A process according to claim 1 wherein the compound of the Formula (IV) is not isolated and the reactions are conducted in an aprotic solvent.
4. A process according to claim 1 wherein R is the radical (B).
5. A process according to claim 4 wherein E is --CH═CH--, R1 is in the 6-position and represents a phenyl with 1 or 2 substituents independently selected from chloro, fluoro, methyl and methoxy and R2 and R3 are independently selected from halo and C1-3 alkyl in the 2- and 4-position.
6. A process according to claim 5 for the preparation of C1-5 alkyl (E)-7-(4'-fluoro-3,3',5-trimethyl-[1,1 '-biphenyl]-2-yl)-3-oxo-5-hydroxy-6-heptenoate.
Description
BACKGROUND OF THE INVENTION

Hypercholesterolemia is known to be one of the prime etiological components of cardiovascular disease such as atherosclerosis, and there is still no effective antihypercholesterolemic agent available that has found wide patient acceptance. The bile acid sequestrants seem to be moderately effective but they must be consumed in large quantities, i.e. several grams at a time and they are not very palatable.

There are agents known, however, that are very active antihypercholesterolemic agents that function by limiting cholesterol biosynthesis by inhibiting the enzyme, HMG-CoA reductase. These agents include the natural fermentation products compactin and mevinolin and a variety of semi-synthetic and totally synthetic analogs thereof. These compounds have the following general structural formula: ##STR2## wherein R is ##STR3##

One group of totally synthetic analogs are disclosed in U.S. Pat. No. 4,375,475 and have the same general structural formula: ##STR4## wherein R is ##STR5## In the usual course of synthesis of these lactones an intermediate ester and dihydroxy acid are encountered: ##STR6## Each of these entities, as well as the lactone, demonstrate antihypercholesterolemic activity in vivo, of comparable magnitude. However, for these compounds to manifest a useful degree of activity, it.Iaddend. ve.ionship shown in the structures.[...].r .[.3R:5S/3S:5R.].

One of the prior art synthesis of these compounds comprises reduction of β-hydroxyketones 2a or 2b ##STR7## A stereoselective process for the reduction of β-hydroxyketones 2a.Iaddend.been described and disclosed in a copending U.S. patent application Ser. No. 725,891, filed Apr. 25, 1985.

SUMMARY OF THE INVENTION

This invention relates to a novel two step process for the preparation of the intermediate ester 2a in the synthesis of antihypercholesterolemic agents which contain a 4-hydroxy-3,4,5,6-tetrahydro-2H-pyran-2-one moiety. The process involves the enantiomeric aldol condensation of an appropriately substituted aldehyde with the enolate of.Iaddend.with an alkyl acetate. resultant .[.enolate.].

DETAILED DESCRIPTION OF THE INVENTION

A process for the preparation of a compound represented by the following general formula (I): ##STR8## wherein R is: ##STR9## wherein Q is ##STR10## R5 is H or OH; R6 is hydrogen or methyl; and a,b,c, and d represent optional double bonds, especially where b and d represent double bonds or a,b,c and d are all single bonds; or ##STR11## wherein E is --CH═CH-- or --CH2 CH2 --; and

R1, R2 and R3 are each selected from halo such as chloro, bromo or fluoro,

C1-4 alkyl,

C1-4 haloalkyl,

phenyl

phenyl with one or more substituents independently selected from halo C1-4 alkyl, and C1-4 alkoxy, or

R4 O in which R4 is phenyl, halophenyl, or

substituted phenyl-C1-3 alkyl wherein the substituents are selected from halo and C1-4 haloalkyl;

comprises:

(1) reacting a compound of the formula (II)

RCHO (II)

wherein R is defined above, with the enolate of.Iaddend.of the formula (III) riphenylethanol ##STR12## wherein M+ is a cation derived from sodium, potassium, lithium, magnesium or zinc, to afford a compound of the formula (IV) ##STR13## wherein R and M+ defined above; and

(2) reacting the compound of the formula (IV) with the enolate of a C1-5 alkylacetate, followed by mild acid hydrolysis to obtain the compounds of the formula (I).

In a first preferred embodiment R is the radical (A). Illustrative of this embodiment are the compounds of the formula I wherein R5 is H, R6 is H or CH3 and b and d represent double bonds or a, b, c and d are all single bonds.

In a second preferred embodiment, R is the radical (B). Illustrative of this embodiment are the compounds of the formula I wherein E is --CH═CH--, R1 is in the 6-position and represents phenyl with 1 or 2 substituents independently selected from chloro, fluoro, methyl and methoxy; and R2 and R3 are independently selected from halo and C1-3 alkyl in the 2- and 4-positions.

In the most preferred embodiment, R is: ##STR14##

The preparation of the compound of formula (IV) is accomplished by an aldol condensation of the appropriately substituted aldehyde with the enolate of.Iaddend.under standard aldol conditions as described in Braun et al., Tetrahedron Letters, Vol. 25, No. 44, pp 5031-5034 (1984). Specifically.Iaddend.is formed under anhydrous conditions in an aprotic solvent utilizing a non-nucleophilic base. Then the appropriately substituted aldehyde is added at low temperatures, between -100 C. and -30 C., preferrably -78 C. and the reaction allowed to go to completion.

The preparation of the compound of the formula (I) is accomplished by a condensation of the compound of the formula (IV), with or without isolation, and with an enolate of a C1-5 alkyl acetate. When the compound of (IV) is isolated from the reaction mixture of the previous step, it is treated with between 2.0 and 3.0 equivalents, preferrably 2.5 equivalents, of a non-nucleophilic base, in an aprotic solvent, followed by the addition of the enolate of C1-5 alkyl acetate which is formed in an aprotic solvent with a non-nucleophilic base. When the compound of (IV) is not isolated the enolate of C1-5 alkyl acetate is added directly to the reaction mixture of the previous step. This condensation is conducted at a temperature between 0 C. and -50 C., preferably -10 for a period of 30 minutes to 16 hours.

Illustrative of the non-nucleophilic bases which may be employed in both steps of this process are alkali metal amides of the formula:

 M+ N- R7 R8 .8.].

wherein M+ is a cation derived from sodium, potassium, lithium, magnesium or zinc and R7 and R8 independently are C1-3 alkyl or when taken together with the nitrogen atom to which they are attached form a .Badd.5 or 6-membered heterocyclic ring and alkyl metals such as butyllithium. The preferred non-nucleophilic base is lithium diisopropylamide. Examples of the aprotic solvents that may be employed in both steps of this process are ethers, such as diethyl ether, tetrahydrofuran, 1,2-dimethoxyethane and the like. The preferred solvent is tetrahydrofuran.

The reactions may conveniently be worked up by quenching with saturated ammonium chloride solution, and extracting into an organic solvent.

The starting materials wherein R is the radical (A) may be prepared by using the synthetic methods described by HSU et al., J. Am. Chem. Soc., 1983, 105, pp. 593-601. The starting materials wherein R is the radical (B) are known in the art.

The following examples illustrate the present invention and as such are not to be considered as limiting the invention set forth in the claims appended hereto.

EXAMPLE 1 Preparation of .[.(R)-2-[(E)-4-[4'-fluoro-3,3',5-trimethyl[1,'1-bipehnyl]-2-yl]-3-hydroxy .Iadd.(S)-2-hydroxy-1,2,2-triphenylethyl (E)-5-(4'fluoro-3,3',5-trimethyl[1,1'-biphenyl]-2-yl)-3-hydroxy-4-pentenoa.Iaddend.

.[.To a suspension of (R)-2-acetoxy-1,2,2-triphenylethanol (332 mg, 1 .Iadd.To a suspension of (S)-2-acetyloxy-1,1,2-triphenylethanol (332 mg, 1 mmol), prepared according to the general procedure of Braun but.Iaddend.in tetrahydrofuran (2 ml) at -78 C. under nitrogen was added lithium diisopropylamide (prepared from 2.2 mmol of butyllithium and 2.42 mmol of diisopropylamine) in tetrahydrofuran (1 ml) and the reaction allowed to warm to 0 C. To the reaction mixture which was recooled to -78 C. was added E-3-(4'-fluoro-3,3',5-trimethyl[1,1'-biphenyl]-2-yl)-propenal in. After 30 minutes at -78 C. the reaction was quenched with a saturated solution of ammonium chloride. The desired product was extracted into ethyl acetate, dried over magnesium sulfate, and flash chromatographed over silica gel with hexane:ethylacetate(4:1) to give a yellow wax.

EXAMPLE 2 Preparation of tert-butyl (E)-7-(4'-fluoro-3,3',5-trimethyl-[1,1-biphenyl]-2-yl)-3-oxo-5-hydroxy-6-heptenoate

Lithium diisopropylamide (6.65 mmol) was prepared by the addition of 4.75 ml of 1.4M n-butyllithium in hexanes to a solution of diisopropylamine (665 mg, 6.65 mmol) in 10 ml of tetrahydrofuran at -25 C. to -35 C. The mixture was stirred for 30 minutes at -25 C. and cooled to -78 C. t-Butylacetate (771 mg, 6.65 mmol) was added dropwise and the solution was stirred for 30 minutes at -78 C. and then warmed to -25 C. over 1 hour. A solution of .[.(R)-2-[(E)-4-(4'-fluoro-3,3',5-trimethyl]1,1'-biphenyl]-2-yl]-3-hydroxy .Iadd.(S)-2-hydroxy-1,2,2-triphenylethyl(E)-5-(4'-fluoro-3,3',5-trimethyl-[.Iaddend.(800 mg, 1.33 mmol) in 2 ml tetrahydrofuran was added and the mixture was stirred for 1 hour at -25 C. and warmed to 22-24 C. and stirred for 16 hours. The reaction mixture was quenched with a saturated solution of ammonium chloride and the product was extracted into methylene choride, dried over sodium sulfate and concentrated in vacuo to give the titled product.

EXAMPLE 3 .Iaddend.-biphenyl]-2-yl)-3-oxo-5-hydroxy-6-heptenoate (one-pot)

.Iaddend.(166 mg, 0.5 mmol) in tetrahydrofuran (1 ml) at -78 C. under nitrogen was added lithium diisopropylamide (prepared from 1.2 mmol butyllithium and 1.2 mmol of diisopropylamine) in tetrahydrofuran (0.5 ml) and the reaction was allowed to warm to 0 C. To the reaction mixture which was recooled to -78 C. was added.Iaddend.-biphenyl]-2-yl)-propenal (132 mg, 0.5 mmol) in tetrahydrofuran (0.5 ml). After 30 minutes at -78 C., to the reaction mixture lithium tert butylacetate (prepared from tert butyl acetate 3.0 mmol, butyllithium 3.0 mmol and diisopropylamine 3.0 mmol) in tetrahydrofuran (3.0 ml) was added and the reaction mixture allowed to warm to -20 C. over 30 minutes. The mixture was then warmed to 22 and stirred.Iaddend.16 hours. The reaction was quenched with a saturated solution of ammonium chloride and the product extracted into methylene chloride. The organic phase was washed with saturated sodium chloride, dried over sodium sulfate and concentrated in vacuo to afford the above tilted product.

EXAMPLES 4 TO 13

Utilizing the general procedures of Examples 1 and 2 or 3, the following compounds of the Formula I are prepared from the appropriate starting materials.

______________________________________CompoundNumber   .[.R1.].tep .Iadd.R.Iaddend.______________________________________     ##STR15##5     ##STR16##6     ##STR17##7     ##STR18##8     ##STR19##9     ##STR20##10     ##STR21##11     ##STR22##12     ##STR23##13     ##STR24##______________________________________
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4137322 *Oct 31, 1977Jan 30, 1979Sankyo Company LimitedML-236B carboxylic acid derivatives and their use as antihyperlipemic agents
US4346227 *Jun 5, 1981Aug 24, 1982Sankyo Company, LimitedML-236B Derivatives and their preparation
US4375475 *Feb 11, 1981Mar 1, 1983Merck & Co., Inc.Substituted pyranone inhibitors of cholesterol synthesis
US4438277 *Apr 15, 1982Mar 20, 1984Sankyo Company, LimitedHydronaphthalene derivatives
US4444784 *Dec 18, 1980Apr 24, 1984Merck & Co., Inc.Antihypercholesterolemic compounds
US4447626 *Jul 7, 1982May 8, 1984Sankyo Company LimitedML-236B Derivatives
GB2055100A * Title not available
GB2075013A * Title not available
GB2077264A * Title not available
Non-Patent Citations
Reference
1 *J. E. Lynch, Tetrahedron Letters, 28, No. 13, 1385, (1987).
2 *M. Braun, Angew. Chem. Int. Ed., Engl., 26, 24, (1987).
Classifications
U.S. Classification560/53, 560/60, 568/592, 560/119
International ClassificationC07C69/76, C07C69/732, C07C69/675
Cooperative ClassificationC07C69/732, C07C69/76, C07C69/675
European ClassificationC07C69/732, C07C69/76, C07C69/675
Legal Events
DateCodeEventDescription
Nov 22, 1994FPExpired due to failure to pay maintenance fee
Effective date: 19940914
Sep 11, 1994LAPSLapse for failure to pay maintenance fees
Apr 19, 1994REMIMaintenance fee reminder mailed
Feb 16, 1990FPAYFee payment
Year of fee payment: 4