Stereoselective approach to C-aryl pyranoside synthesis which addresses the problem of C7-substitution in blepharocalyxin E

A general route to a series of aryl- substituted pyranoside derivatives has been developed as a model for the synthesis of blepharocalyxin E. Two exo-substituted tetrahydro-4H-furo[2,3-b]pyran-2-one derivatives, 8a and 8b, were prepared and treated separately with anisole and phenoxytriisopropylsilane under Lewis acid conditions to effect C-aryl pyranoside synthesis. In each case, a gamma-lactone was formed, which rearranged to the desired structure on acid treatment. Four compounds (12, 14, 16, and 18) were prepared by this route as single isomers in good overall yield.