Total syntheses of (±)-fawcettimine, (±)-fawcettidine, (±)-lycoflexine, and (±)-lycoposerramine B

Abstract

The total syntheses of (±)-fawcettimine, (±)-lycoflexine, (±)-fawcettidine, and (±)-lycoposerramine B have been accomplished through an efficient, unified, and stereocontrolled strategy that required sixteen, sixteen, seventeen, and seventeen steps, respectively, from commercially available materials. The key transformations involve: 1) a Diels-Alder reaction between a 1-siloxy diene and an enone to construct the cis-fused 6,5-carbocycles with one all-carbon quaternary center, and 2) a Fukuyama-Mitsunobu reaction to form the azonine ring. Access to the enantioselective syntheses of these alkaloids can be achieved by kinetic resolution of the earliest intermediate via a Sharpless asymmetric dihydroxylation.