An expedient total synthesis of optically active piperidine and indolizidine alkaloids (−)-β-conhydrine and (−)-lentiginosine

Attempts directed toward the stereocontroled total synthesis of piperidine and indolizidine alkaloids resulted in the synthesis of (−)-β-conhydrine 1 and (−)-lentiginosine 3. The synthesis of 1 and 3 were developed from protected d-mannitol as the chiral precursor, which involved nucleophilic addition and azide nucleophilic substitution, Barbier allylation, ring closing metathesis, and Sharpless asymmetric dihydroxylation as the key steps.