INTRAMOLECULAR C-H INSERTION BY AN ALKYLIDENE CARBENE - DIASTEREOSELECTIVE SYNTHESIS OF A TAXOL A-RING SYNTHON

The first stage in a proposed total synthesis of the clinically effective anticancer agent taxol 1 is reported. A key step in this synthesis is the development of a new procedure for the generation and cyclization of the alkylidene carbene derived from ketone 9, to give cyclopentene 10 (formation of three new carbon-carbon bonds) in 72% yield. Ozonolysis of 10 followed by aldol condensation furnished the crystalline cyclohexenone 4.