Studies towards the Synthesis of Rapamycin: Regiocontrol in the Addition of Carbanions to Enantiomerically Pure Epoxides and the Formation of a Highly Substituted Tetrahydrofuran

Reaction of trimethylaluminium, dimethyllithium cuprate and lithium tetramethylaluminate with the homochiral epoxide 8 has been studied. Intermolecular epoxide ring-opening was observed with dimethyllithium cuprate and lithium tetramethylaluminate, but acetal ring-opening followed by intramolecular epoxide ring-opening was observed with trimethylaluminium.