Total synthesis of (-)-blepharocalyxin D and analogues.

An efficient strategy for the total synthesis of (-)-blepharocalyxin D and an analogue is described. The key step involves an acid-mediated cascade process in which reaction of methyl 3,3-dimethoxypropanoate with γ,δ-unsaturated alcohols possessing diastereotopic styrenyl groups gives trans-fused bicyclic lactones with the creation of two rings and four stereocenters in one pot.

Bicyclic oxygen heterocycles from γ,δ-unsaturated alcohols: synthetic targets inspired by blepharocalyxin D.

trans-2,8-Dioxabicyclodecanes were prepared in high yield with the creation of up to three stereocenters in a single pot by the acid-mediated reaction of γ,δ-unsaturated alcohols with aldehydes (see scheme, Bn=benzyl). This versatile reaction enables the stereoselective introduction of substituents at the C3, C4, C7, and C9 positions of the bicyclic framework.