A 21st century HPLC workflow for process R&D.

A unique high-performance liquid chromatographic (HPLC) workflow specifically designed for the rigors of process development has been developed. A key feature of the workflow is the creation of an HPLC software-hardware platform designed to automatically and systematically screen samples using a matrix of columns and eluents to aggressively search for impurities. The workflow platform was assembled from commercial hardware components and both custom and commercial HPLC software.

Crystallization-induced chiral inversion as the key step for synthesis of (S)-2-acetylthio-3-phenylpropanoic acid from l-phenylalanine.

[reaction: see text] A novel crystallization-induced chiral inversion of (S)-2-bromo-3-phenylpropanoic acid to its (R)-enantiomer with excellent enantiomeric excess (96-99%) is achieved. Optically pure (S)-2-acetylthio-3-phenylpropanoic acid can be prepared in good yield from inexpensive and commercially available l-phenylalanine via diazotization/bromination, chiral inversion, and thioacetate substitution reactions.

Efficient crystallization-induced dynamic resolution of alpha-substituted carboxylic acids.

Herein we present a novel route to enantiomerically enriched chiral alpha-substituted carboxylic acids by crystallization-induced dynamic resolution (CIDR) of their diastereomeric salts with chiral amines. Thus, the racemic alpha-bromo acid 3 is converted reliably with (1R,2S)-2-amino-1,2-diphenylethanol in the presence of a catalytic amount of tetrabutylammonium bromide into its R-enantiomer 4 in 90% yield with 88% ee. Similarly, the racemic alpha-thiobenzoyl acid 5 could be resolved to 90% ee in 74% yield.