The naturally occurring ketene acetal benesudon: Total synthesis and assignment of relative and absolute stereochemistry

The densely functionalized ketene acetal benesudon, which is a bioactive fungal metabolite, was synthesized from D-glucose by a route involving radical cyclization to form the five-membered ring, and oxidative decarboxylation to generate the key central double bond. The originally suggested stereochemistry for the quaternary center C(5) must be revised, as both C(5) epimers were prepared and a comparison with an authentic sample was made. The absolute configuration of benesudon is 4S,5R,6S.