Preparation of (S)-clopidogrel and related compounds

Abstract

A process for producing enantiomerically enriched (S)-α-(2-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5 (4H)-acetic acid hydrocarbyl ester, represented by the formula: Is provided, wherein R1 and R2 are hydrogens and R3 is methyl (i.e., (S)-Clopidogrel). The process includes the steps of: (a) contacting N-2-chlorobenz-aldehyde-ylidene-1-ethylamine-2 (2-thiophenyl)imine and an HCN source, in the presence of a non-metallic asymmetric Strecker catalyst to form enantiomerically enriched (S)-α,α-(2-thiophenylethylamino) (2-chlorophenyl) acetonitrile; (b) contacting the enantiomerically enriched (s)-α,α-(2-thiophenylethylamino) (2-chlorophenyl) acetonitrile and a formaldehyde equivalent, in the presence of an acid catalyst to form enantiomerically enriched α-5 (4,5,6,7-tetrahydro[3,2-c] thienopyridyl) (2-chlorobenzyl)-nitrile; and (c) contacting the enantiomerically enriched α-5(4,5,6,7-tetrahydro[3,2-c] thienopyridyl) (2-chlorobenzyl)-nitrile and a reagent capable of converting a cyano group into an ester group to form enantiomerically enriched hydrocarbyl ester of (S)-α-(2-chlorophenyl)-6,7-dihydrothieno-[3,2-c]pyridine-5(4H)-acetic acid.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for enantioselective preparation of (S)-Clopidogrel, a potent platelet aggregation inhibitor, and related compounds. More particularly, the present invention relates to a process for the preparation of (S)-Clopidogrel in high enantioselectivity and yield. (S)-Clopidogrel is used as an antithrombotic agent for treatment of patients with vascular diseases, myocardial infraction and stroke. 2. Description of the Prior Art Currently there are two known processes for the preparation of (S)-Clopidogrel. Each of these processes relies on classical resolution or enzymatic techniques to introduce the sole chiral center into the molecule. U.S. Pat. No. 4,847,265 describes a method of preparation of Clopidogrel employing classical resolution techniques. French Patent Applications Nos. 2,530,247 and 2,769,313 describe commercial methods that are currently used to synthesize Clopidogrel. When ...

AI Technical Summary

Benefits of technology

The advantages of the current process include the production of (S)-Clopidogrel in high ee, high yield and with good volumetric throughput without the need to resort to enzymatic or classical resolution techniques.

Problems solved by technology

The problems with enzymatic resolution techniques are similar to classical resolution techniques in that low yield of the desired enantiomer makes it necessary to isolate and racemize starting material from the mother liquor.

An added problem with enzymatic resolution is low volumetric throughput and tedious work up procedures.

To overcome these disadvantages of the prior art, laborious procedures and separations would be required to either enrich the racemic product in one or the other enantiomer or to efficiently and completely separate one enantiomer from the other.

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