Asymmetric Synthesis of 2,4,5-Trisubstituted Piperidines from Sulfinimine-Derived δ-Amino β-Ketoesters. Formal Synthesis of Pseudodistomin B Triacetate

N-Sulfinyl δ-amino β-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 δ-amino β-ketoesters with dimethylformamide dimethyl acetal. This new protocol was illustrated with a concise formal asymmetric synthesis of marine alkaloid pseudodistomin B triacetate.