Synthesis of cyclobutane fused γ-butyro lactones through intramolecular [2+2] photocycloaddition. Application in a formal synthesis of grandisol

Abstract

An approach to the synthesis of cyclobutane fused γ-butyrolactones is described. The key step involves a Cu(I) catalysed intramolecular [2+2] photocycloaddition of 1,6-dienes in which the two alkene units are tethered through acetal oxygen. The resulting bicyclic lactols were then oxidised to provide the title compounds. The synthetic potential of these lactones is illustrated by a formal synthesis of grandisol.