REGIO- AND STEREOSPECIFIC CONSTRUCTION OF VICINAL QUATERNARY CARBONS: TOTAL SYNTHESIS OF (+/-)-ALBENE

Article abstract of DOI:10.1016/0031-9422(95)00592-U

A regiospecific and stereoselective total synthesis of the trisnorsesquiterpene (+/-)-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. - Keywords: Albene; quaternary carbons; Claisen rearrangement; diazo ketone; cyclopropanation; reductive cyclopropane cleavage; Shapiro reaction.