AN ASYMMETRIC SYNTHESIS OF 4,4- AND 6,6-DIALKYLCYCLOHEXENONES AND 4,4- AND 5,5-DIALKYLCYCLOPENTENONES. APPLICATION TO THE TOTAL SYNTHESIS OF (-)-SILPHIPERFOL-6-ENE

Article abstract of DOI:10.1016/S0040-4020(01)87745-0

Chiral amino alcohols have been transformed into bicyclic lactams 1 and 6 which, after metalation and alkylation, gave high diastereomeric ratios of 2,2-dialkyl quaternaly products, 29 and 12, respectively.Addition of organolithium reagents to the carbonyl of these lactams, followed by acidic cleavage, leads to enantiomerically pure cyclohex-2-enones and cyclopent-2-enones.This process was also applied to a key, chiral cyclopentenone 39, which was used by Curran, in racemic form, to prepare the angular triquinane, silphiperfol-6-ene.The total asymmetric synthesis was carried out in 6.6percent yield over nine steps.