RADICAL CYCLIZATION ROUTES TO BRIDGED PYRANOSIDES AS PRECURSORS OF DENSELY FUNCTIONALIZED CYCLOALKANES

Glycals derived from hexopyranoses permit the incorporation of iodine at C-2 as well as elaboration of an olefinic residue via the C-5-hydroxymethyl group. Radical cyclization of these functionalities leads to bicyclic systems whose bridge sizes depend on the lengths of the olefinic appendages. Hydrolysis of the anomeric centers of the [2.2.1] structures leads spontaneously to cyclopentane derivatives. However, with [2.2.2] structures, the hemiacetal intermediates are stable in bicyclic forms but are opened readily upon mcerpatolysis with propane dithiol to give cyclohexane derivatives.