Tetracyclic lactone substrate

A diastereoselective epoxidation of a tetrasubstituted double bond was accomplished with mCPBA in the total synthesis of (-)-21-isopentenylpaxilline by A.B. Smith et al." The tetracyclic lactone substrate containing the tetrasubstituted double bond was exposed to mCPBA in toluene at room temperature. The reaction mixture also contained sodium bicarbonate to neutralize the by-product m-chloro benzoic acid. The epoxidation exclusively took place from the less hindered a-face of the molecule. At a later stage, this epoxide was converted to the y-hydroxy enone moiety present in the natural product. 

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