Synthesis of (+)-Sesbanimide A. Structure of the Crucial Silyl Ether AB Ring Intermediate.

Attempts to protect the 8-hydroxy group (sesbanimide numbering) of the AB ring intermediate 2a, derived from D-xylose, by tert-butyldiphenylsilyl trifluoromethanesulfonate, led unexpectedly to the formation of a novel 2-O-silyl derivative possessing a tricyclic structure. This intermediate has been converted into (+)-sesbanimide A.