Highly Efficient Diastereoselective Michael Addition of Various Thiols to (+)-Brefeldin A

The Michael addition of thiols to brefeldin A occurs with high diastereoselectivity, affording ratios of major to minor diastereomers of at least 30:1. On the basis of the X-ray structure of a crystalline dibenzoyl derivative, the major diastereomers are assigned the 3R configuration, while the minor diastereomers have the 3S configuration.