Synthesis of BC Ring-Systems of Taxol by Ring-Closing Metathesis

Highly functionalized BC ring-systems of Taxol® having the required chemistry for the C1, C2 and C8 centers have been synthesized using a ring- closing metathesis (RCM) reaction as the key step. Silylene 26 and acetonide 27 were obtained in excellent yields with Schrock's and our recently reported catalyst. In the case of carbonate 23, a trans cyclooctene was formed when using Grubbs' catalyst, indicating that RCM does not always proceed to completion of thermodynamic equilibrium.