Synthesis and structural affirmation of pubesamides A and B, monoterpene N-benzoyltyramides from white sapote (Casimiroa pubescens)

Abstract

Pubesamides A and B are structurally unusual monoterpene N-benzoyltyramides isolated from Casimiroa pubescens, a tropical fruiting tree with known psychotropic properties. Herein we report the structural affirmation of both natural products through a chemical synthesis that features a Lewis-acid assisted cross-metathesis reaction between a 1,1-disubstituted alkene and a dienone in the presence of the Hoveyda-Grubbs second generation catalyst. Stereochemically pure samples of pubesamide A and B isomerise upon standing, suggesting they are both genuine natural products.