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

A regiospecific and stereoselective total synthesis of the trisnorsesq uiternene (+/-)-albene, via a prochiral precursor is described. The or tho ester Claisen rearrangement of the allyl alcohol, obtained in two regiospecific reactions from a Diels-Alder adduct, followed by hydroly sis of the resultant ester furnished an ene acid in a highly stereosel ective manner. Anhydrous copper sulphate catalysed intramolecular cycl opropanation reaction of the diazo ketone derived from the ene acid, g enerated a cyclopropyl ketone. The regiospecific reductive cleavage of this cyclopropyl ketone resulted in a prochiral ketone. Finally, Shap iro reaction on the tosylhydrazone, derived from the latter ketone, fu rnished (+/-)-albene.