Regio- and stereospecific construction of vicinal quaternary carbons: total synthesis of (±)-albene

Abstract

A regiospecific and stereoselective total synthesis of the trisnorsesquiternene (±)-albene, via a prochiral precursor is described. The ortho ester Claisen rearrangement of the allyl alcohol, obtained in two regiospecific reactions from a Diels-Alder adduct, followed by hydrolysis of the resultant ester furnished an ene acid in a highly stereoselective manner. Anhydrous copper sulphate catalysed intramolecular cyclopropanation reaction of the diazo ketone derived from the ene acid, generated a cyclopropyl ketone. The regiospecific reductive cleavage of this cyclopropyl ketone resulted in a prochiral ketone. Finally, Shapiro reaction on the tosylhydrazone, derived from the latter ketone, furnished (±)-albene.