An efficient procedure for the direct C-1 hydroxylation of vitamin D compounds has been developed. The method involves conversion of vitamin D3 tosylates to 3,5-cyclovitamin D derivatives, allylic oxidation with selenium dioxide, and acid-catalyzed solvolysis to the 1 alpha-hydroxyvitamin D analogs. When applied to vitamin D3,25-hydroxyvitamin D3, and vitamin D2, this sequence give the corresponding 1alpha-hydroxylated derivatives in 10-15% yield.