Journal of the American Chemical Society, Vol.137, No.6, 2243-2246, 2015
Concise Synthesis of Alkaloid (-)-205B
Described herein is a short total synthesis of alkaloid (-)-205B (1) by means of an anti-selective S(N)2' alkylation of an attractively functionalized cyclopropanol and diastereoselective cyclization of the resulting aminoallene adduct for bicyclic ring formation. The synthesis features a general route to cis- or trans-2,6-disubstituted piperidines by lithium aluminum hydride reduction of the imine intermediate by an appropriate choice of solvent and cis- or trans-2,5-disubstituted pyrrolidines by an exceptional level of chirality transfer from a pendant allene. Particularly noteworthy are the brevity and convergence made possible by a segment-coupling strategy.