Total synthesis of quinolizidine (-)-217A.

We report here the construction of quinolizidine ring systems by intramolecular cyclization of suitable functionalized piperidines via a reductive amination sequence. This reaction proceeds with a total stereocontrol at C4. The preparation of the piperidine precursors is based on a chain elongation of a piperidine aldehyde either by aldolization or by Wittig reaction. We applied this second route to the total synthesis of quinolizidine (-)-217A from (S)-methyl 2-((S)-1-((R)-1-phenylethyl)piperidin-2-yl)propanoate 5.