SYNTHESIS OF EPIMERIC PURE SPIRO N,S-ACETALS OF L-MENTHONE

By acetalisation of L-menthone (2) with mercaptoacetic acid and deriva tives of benzylamine, the spirocyclic N,S-acetals 3 were obtained as s ingle diastereomers. The reaction of an epimeric mixture of unsubstitu ted thiazolidinones 4 with acetic anhydride or allyliodide afforded ho mochiral N-acetyl (5) or N-allyl N,S-acetals (6), respectively. The co nfiguration of the new stereogenic centres were proven by X-ray crysta llography.