Preparation of β-amino-α-mercapto acids and amides: stereocontrolled syntheses of 2′-sulfur analogues of the taxol C-13 side chain, both syn and anti S-acetyl-N-benzoyl-3-phenylisocysteine

Stereoselective syntheses of both syn and anti S-acetyl-N-benzoyl-3-phenylisocysteine as coupling-ready reagents via the ring-opening reactions of trans- and cis-oxazoline-5-carboxylates with thiolacetic acid were demonstrated. In addition, we report upon ring-opening reactions of oxazoline-5-carboxamides. Ab initio molecular calculations were used to explain the different reactivities of these oxazolines with respect to the ring-opening reaction.