Asymmetric synthesis of 2,4,5-trisubstituted piperidines from sulfinimine-derived delta-amino beta-ketoesters. Formal synthesis of pseudodistomin B triacetate

[reaction: see text] N-Sulfinyl delta-amino beta-ketoester enaminones, a new sulfinimine-derived chiral building block, undergoes, on hydrolysis in one pot, an intramolecular Michael addition followed by a retro-Michael-type elimination to give enantiopure 2,4,5-trisubstituted piperidines, a structural motif found in numerous biologically active alkaloids. This new chiral building block is readily prepared by treating N-sulfinyl delta-amino beta-ketoesters with dimethylformamide dimethyl acetal. This new protocol was illustrated with a concise formal asymmetric synthesis of marine alkaloid pseudodistomin B triacetate.