First Total Synthesis of Piperenol B and Configuration Revision of the Enantiomers Piperenol B and Uvarirufol A

摘要

We report herein the first total synthesis of piperenol B, a polyoxygenated cyclohexene derivative with reported pharmacological activity isolated from Piper cubeb. The chiral building block for this synthetic approach is derived from microbial cis-ipso, ortho-dihydroxylation of sodium benzoate, which was optimized to the multi-ten-gram scale by reaction medium engineering. Final-stage deprotection of an acetonide was investigated in detail, leading to an efficient eight-step protocol for the synthesis of piperenol B with a total yield of 10%. Most importantly, the previously assigned absolute configuration of piperenol B was revised and unequivocally established by 2D NMR analysis and the Mosher's ester method.