4-PIPERIDONES FROM ENANTIOMERICALLY PURE ENONES - SYNTHESIS OF 6-ALKYLSUBSTITUTED 4-OXO-PIPECOLIC ACID-DERIVATIVES

The cyclization of the enantiomerically pure alpha,beta-unsaturated ke tone 1, an aliphatic aldehyde 3 and ammonia or benzylamine gives diast ereoselectively cis-piperidones 4/4'. Although only modest yields were obtained, the presented cyclization has the advantage of being a sing le step reaction. The products 4 can serve as precursors for all-cis-4 -hydroxypiperidones 5 and novel pipecolic acid derivatives 9.