Enantioselective Total Synthesis of a Natural Norsesquiterpene of the Calamenene Group by a Silane-Terminated Intramolecular Heck Reaction

Abstract

The total synthesis of the natural norsesquiterpene 7-desmethyl-2-methoxycalamenene 1 by an enantioselective silane-terminated Heck reaction is described. The substrate 2 used for the Heck reaction was synthesized in 7 steps from 3-(3-methoxyphenyl)propanol in 41 % yield. Heck reaction of 2 with Pd2(dba)3⋅CHCl3, (R)-BINAP and Ag3PO4 gives 8 in 91 % yield with 92 % ee, which after hydroxylation, transformation in the p-toluenesulfonate and methylation with Me2CuLi gave 1 in 36 % yield.