Process Development and Scale Up of a Glycine Antagonist

Abstract

A synthetic route amenable to large-scale synthesis of the glycine antagonist (2R,4E)-7-chloro-4-(2-oxo-1-phenyl-pyyrrolidin-3-ylidene)-1,2,3,4-tetrahydroquinoline-2-carboxylic acid, (2R,3R,4R,5S)-6-(methylamino)hexane-1,2,3,4,5-penta-ol 12 is presented. The route consists of four stages of chemistry. Stage 1 starts from 5-chloro-2-iodoaniline hydrochloride and is a three-step telescoped stage consisting of an imine formation with ethyl glyoxalate, Mannich reaction using vinyloxytrimethylsilane, and subsequent Wittig reaction with (2-oxo-1-phenyl-3-pyrrolidinyl)triphenylphosphonium bromide. The stage 1 product (4E)-2[(5-chloro-2-iodophenyl)amino]-4-(2-oxo-1-phenyl-pyrrolidin-3-ylidene)butanoic acid ethyl ester 17 is subjected to an enzyme-catalysed kinetic resolution to prepare the single (2R)-enantiomer 19 as the ethyl ester. Stage 3 is the intramolecular Heck reaction to yield (2R,4E)-7-chloro-4-(2-oxo-1-phenyl-pyrrolidin-3-ylidene)-1,2,3,4-tetrahydroquinoline-2-carboxylic acid ethyl ester 31. The final stage is ester saponification and meglumine salt formation to afford the drug candidate molecule 12. In total, more than 300 kg of target 12 was produced with a purity >99.9%. Aspects of route selection as well as elements of process understanding and control are discussed.