Convergent Synthesis of Taxol Skeleton via Decarbonylative Radical Coupling Reaction.

The highly oxygenated 6/8/6-membered ABC-ring 2 of taxol was assembled in a convergent fashion. A decarbonylative radical reaction between α-alkoxyacyl telluride 4 and cyanocyclohexenone 5 linked the A- and C-rings and stereoselectively installed the C2- and C3-tertiary carbon centers of 3. After the C8-quaternary stereocenter was constructed, the C9-methyl ketone and the C11-vinyl triflate of 30 participated in Pd(0)-promoted cyclization of the eight-membered B-ring, giving rise to the taxol skeleton 2.