Single enantiomer synthesis of alpha-(trifluoromethyl)-beta-lactam

Abstract

The first synthesis of alpha-(trifluoromethyl)-beta-lactam ((S)-1) is reported. The route starts from alpha-(trifluoromethyl)acrylic acid (2). Conjugate addition of alpha-(p-methoxyphenyl)ethylamine ((S)-3b), generated an addition adduct 4b which was cyclised to beta-lactam 5b. Separation of the diastereoisomers by chromatography gave ((alpha S,3S)-5b). N-Debenzylation afforded the desired alpha-(trifluoromethyl)-beta-lactam ((S)-1). The absolute stereochemistry of diastereoisomers 5 was determined by X-ray crystallographic determination of a close structural analogue, (alpha S,3S)-5c, and then H-1 and F-19 NMR correlation to the individual diastereoisomers of 5a and 5b.