Enantioselective synthesis of R-(-)-ligularenolide and the progesterone receptor ligand R-(-)-PF1092C starting from S-(+)-carvone

Article abstract of DOI:10.1016/S0040-4020(98)00233-6

A new enantioselective synthesis of cremophilane sesquiterpenes was developed starting from S-(+)-carvone 3, using a conjugate addition- annelation sequence. The synthesis of R-(-)-ligularenolide 1 was accomplished in a staightforward manner with the annelation of the lactone as the last step. For the synthesis of the progesterone receptor ligand R-(-)-PF1092C 2 a different strategy was followed in which first the lactone was annelated. The concomitant isomerization of the double bond of the isopropenyl group into the conjugate position then offered an alternative way to remove the side chain and simultaneously provide for an ideal functionally for the introduction of the cis β-diol function at the C2,C3 position.