Synthetic studies of vitamin D analogues. IX: Synthesis and differentiation-inducing activity of 1α,25-dihydroxy-23-oxa-, thia-, and azavitamin D3

Three vitamin D3 analogues, 1α, 25-dihydroxy-23-oxavitamin D3 (3), 1α, 25-dihydroxy-23-thiavitamin D3 (4) and 1α, 25-dihydroxy-23-azavitamin D3 (5) were synthesized. In the differentiation-inducing activity of human myeloid leukemia cells into macrophages in vitro, the 23-aza analogue (5) showed the least activity, while no remarkable differences were observed between the 23-oxa analogue (3) and the 23-thia analogue (4), which were less active than 1α, 25-dihydroxyvitamin D3 (1).