1 -Hydroxy derivative of vitamin D 3 : a highly potent analog of 1 ,25-dihydroxyvitamin D 3 .

The 1alpha-hydroxy derivative of vitamin D(3) has been chemically synthesized and tested for its biological activity. This analog has comparable biological activity on a weight basis to 1,25-dihydroxyvitamin D(3) in the stimulation of intestinal calcium transport and bone calcium mobilization in normnal and anephric rats. Because the 1alpha-hydroxy derivative is synthesized from cholesterol, it is easier and less expensive to prepare than 1alpha,25-dihydroxy derivative, making it attractive as a drug in the treatment of renal osteodystrophy and hypopara-thyroidism.