Synthesis of oxygen heterocycles via alkynyltungsten compounds

This short review article covers some useful applications of alkynyltungsten compounds to the syntheses of complex lactones. Two types of cyclizations will be emphasized: (1) cycloalkenylation of tungsten-alkynol compounds with aldehydes to give a-alkylidene oxacarbeniums, further leading to a-alkylidene lactones and (2) intramolecular [3+2]-cycloaddition of epoxides to give bicyclic lactones. The new methodologies can provide a short synthesis of enantiopure lactones such as (-) -epilitsenolide C₂, (+) -listenolide C₁, (+) -isodihydromahubanolide A, (+) -blastmycinone, and (-) -epi-blastmycinone.