SYNTHETIC APPROACHES TO HOMOGYNOLIDE-A AND HOMOGYNOLIDE-B

A four step, efficient and general methodology for the conversion of a cyclic ketone into the corresponding alpha-spiro-beta-methylene-gamma -butyrolactone, the key structural feature present in tricyclic sesqui terpenes bakkanes, has been developed employing a regiospecific 5-exo dig radical cyclisation reaction as the key step. The methodology has been extended to the total synthesis of bakkanes including homogynolid e-B and chiral homogynolide-A.