Free Radical Studies and Solutions to the Synthesis of (+)-Cyclophellitol

d -Xylose serves as a starting material for approaches to the synthesis of the glucosidase inhibitors, (+)-cyclophellitol ( 1 ) and (+)-epi-cyclophellitol ( 2 ). An investigation of the cyclization of diastereomeric oxiranyl radicals to achieve this goal was moderately successful with the diastereomer that would have led to epi-cyclophellitol undergoing cyclization. An alternative route to cyclophellitol from d -xylose employed Grubbs' ring closure metathesis and radical transformations to complete the synthesis.