Synthetic studies of vitamin D analogues. XVII. Synthesis and differentiation-inducing activity of 1 alpha,24-dihydroxy-22-oxavitamin D3 analogues and their 20(R)-epimers.

Four vitamin D3 analogues, 1 alpha,24(S)- and 1 alpha,24(R)-dihydroxy-22-oxavitamin D3 (5 and 6) and their 20(R)-epimers (7 and 8) were synthesized from the 20(S)-alcohol (10). In tests of activity to induce differentiation of human myeloid leukemia cells (HL-60) to macrophages, 5 showed comparable activity to 1 alpha,25-dihydroxy-22-oxavitamin D3 (OCT) (2), and the other three analogues (6, 7 and 8) were less active than OCT (2). The binding properties of these analogues to the chick embryonic intestinal 1 alpha,25-dihydroxyvitamin D3 (1) receptor were evaluated. Furthermore, 20(R)-OCT (9) was synthesized and its biological properties were compared with those of OCT(2) and the 20(R)-epimers (7 and 8).