Hydroxyl-Assisted trans-Reduction of 1,3-Enynes: Application to the Formal Synthesis of (+)-Aspicilin

Abstract

1,3-Enynes are hardly amenable to trans-hydrometalation reactions, because they tend to bind the standard ruthenium catalysts too tightly. However, catalysts comprising a [Cp*Ru–Cl] unit allow such compounds to be used, provided they contain an OH group next to the triple bond. This aspect is illustrated by a formal synthesis of the lichen-derived macrolide aspicilin. The required macrocyclic enyne precursor was formed by an efficient ring-closing alkyne metathesis reaction.