Bruce L. Onisko

Synthesis and biological activity of 3-deoxy-1α-hydroxyvitamin D3+†

A vitamin D 3 analog, 3-deoxy-1 α -hydroxyvitamin D 3 has been synthesized. The compound is active in promoting intestinal calcium transport and bone mineral mobilization.

Inhibitors of the 25-hydroxylation of vitamin D3 in the rat

Abstract Two new sidechain-modified analogs of vitamin D 3 , 25-azavitamin D 3 and 25-fluorovitamin D 3 , were prepared; both compounds were found to inhibit the in vivo 25-hydroxylation of vitamin D 3 in the rat. 25-Azavitamin D 3 was chemically synthesized from a degradation product of stigmasterol by a six-step process. The desired carbon skeleton was efficiently assembled by alkylation of a suitably protected C-20 bromomethylpregnane with the enolate of N,N -dimethylacetamide (70%). The completion of the synthesis utilized the known photochemistry of steroidal 5,7-dienes to prepare the vitamin D triene system. In contrast, 25-fluorovitamin D 3 was prepared by direct vitamin modification. 25-Hydroxyvitamin D 3 3-acetate was fluorinated with diethylaminosulfur trifluoride to give 25-fluorovitamin D 3 3-acetate (59%); saponification provided the desired analog. When vitamin D-deficient rats on a low calcium diet were dosed with [3- 3 H]vitamin D 3 (0.05 μg), 10% of the dose was found in serum as 25-hydroxyvitamin D 3 4 hr after administration. If 25-azavitamin D 3 (50 or 200 μg) was given 2 hr before the radiolabeled vitamin D 3 , however, serum 25-hydroxyvitamin D 3 concentration was markedly reduced. 25-Fluorovitamin D 3 caused similar reduction when administered at much lower doses.

Excretion of metabolites of 1α,25-dihydroxyvitamin D3 in rat bile☆

Abstract Bile is the major excretory route for 1,25-dihydroxyvitamin D3 and its metabolites. The amount of radioactivity as a percentage of the total dose found in either urine or combined feces and intestinal contents of bile duct-cannulated rats does not vary with the dose of 1α,25-dihydroxy-[3α-3H]vitamin D3 whereas the percentage of the dose found in bile (24-h collection) increases with increasing dose. When rats were administered 1α,25-dihydroxy-[3α-3H]vitamin D3 and 1α,25-dihydroxy-[26,27-14C]vitamin D3, metabolites with low 14 C 3 H (indicative of side chain-cleaved metabolites) were detected in bile, but not in either the urine or combined feces and intestinal contents. Bile had the lowest 14 C 3 H ratio 8–12 h after the dose.

Synthesis and bioassay of 3-deoxy-1α-hydroxyvitamin D3, an active analog of 1α,25-dihydroxyvitamin D3

Abstract Two synthetic routes to 3-deoxy-1α-hydroxyvitamin D3, an analog of 1α,25-dihydroxyvitamin D3, are described. One involved the six-step conversion of 1α,2α-epoxy-6,6-ethylenedioxy-5α-cholestan-3- one to 1α-acetoxycholest-5-ene, whereas, in the second, the same intermediate was prepared from 1α-hydroxycholesterol. Conversion of the Δ5-sterol to the required 5,7-diene was accomplished most efficiently via 7-keto and 7-tosylhydrazone intermediates. Bioassay of 3-deoxy-1α-hydroxyvitamin D3 in the rat establishes that the analog can fulfill all common vitamin D functions including stimulation of intestinal calcium transport, mobilization of calcium and phosphate from bone, stimulation of growth, and calcification of bone. Direct comparison indicates the compound to have 1 20 to 1 50 of the activity of 1α-hydroxyvitamin D3, but it acts with a time course indistinguishable from the latter.