Synthesis of (+)-L-733,060, (+)-CP-99,994 and (2S,3R)-3-hydroxypipecolic acid: application of an organocatalytic direct vinylogous aldol reaction.

The γ-butenolide obtained from an organocatalyzed, direct vinylogous aldol reaction of γ-crotonolactone and benzaldehyde serves as the key starting material in the expedient synthesis of a 3-hydroxy-2-phenyl piperidine intermediate which is converted to the target 2,3-disubstituted piperidines.