Mary A. Fivizzani

Synthesis of 25-hydroxy[26,27-3H]vitamin D3 with high specific activity

Abstract A synthesis of radiochemically pure 25-hydroxy[26,27- 3 H]vitamin D 3 with a specific activity of 160 Ci/mmol is reported. The structure and biological activity of the radiolabeled compound was verified by comigration on high-pressure liquid chromatography with synthetic 25-hydroxyvitamin D 3 to constant specific activity, and by conversion in vitro to 1α,25-dihydroxy[26,27- 3 H]vitamin D 3 with the chick kidney 1α-hydroxylase.

Synthesis of vitamin D5: Its biological activity relative to vitamins D3 and D2☆

Abstract The chemical synthesis, spectral characterization, and biological activity of vitamin D5 in vitamin D-deficient rats is reported. Vitamin D5 is about 180-fold less active than vitamin D3 in calcification of rachitic cartilage and about 100- to 200-fold less active in induction of bone-calcium mobilization. In stimulation of intestinal-calcium transport, vitamin D5 is about 80-fold less active than vitamin D3. Vitamins D2 and D3 appear to be equiactive in all three responses when low doses are administered.

The synthesis and activity in vitro of 25-masked-1α-hydroxylated vitamin D3 analogs

1alphaHydroxylated-25-masked-vitamin D3 and analogs were synthesized as probes to help evaluate the role of 25-hydroxyl group in hormone-receptor interactions of 1alpha,25-dihydroxyvitamin D3 (13a). Synthetic work on model systems showed that the steroidal 25-hydroxyl group could be easily fluorinated in high yield with diethylaminosulfur trifluoride. Treatment of 25-fluoro compound with acetic acid resulted in both elimination and displacement of fluorine by acetate. The desired 1alpha-hydroxy-25-fluoro-vitamin D3 (14b) was obtained efficiently by fluorination and subsequent deacetylation of 1alpha,25-dihydroxyvitamin D3 1,3-diacetate (13b). Also obtained was a mixture of 1alpha-hydroxyvitamin D3-24- and 25-enes (15b). Both 14b and 15b were 300-400 times less active than 13a in the chick intestinal cytosol protein binding assay, making these analogs similar in potency to 1alpha-hydroxyvitamin D3 in vitro. The essentially equivalent activity of 14b and 15b with 1alpha-hydroxyvitamin D3 indicates that in the absence of a 25-hydroxyl group some alterations to the side chain carbons of 13a may be tolerated without further weakening analog-protein interactions. The fluoroanalog 14b was also about 250 times less potent than 13a in stimulating bone resorption in vitro. These compounds should prove to be valuable tools in aiding understanding of the salient structural features of the vitamin D3 metabolites.

1α,25-Difluorovitamin D3: An inert vitamin D analog☆

Abstract 1α,25-Difluorovitamin D 3 has been synthesized by reacting 1,25-dihydroxyvitamin D 3 -3-acetate with diethylaminosulfurtrifluoride followed by hydrolysis. Retention of configuration of the fluoro group in this reaction was demonstrated by physical studies using 1α-fluoro and 1β-fluorovitamin D 3 models. The 1,25-difluorovitamin D 3 compound possessed no vitamin D-like activity demonstrating the importance of 1α- and 25-hydroxylations of vitamin D for activity. However, 1,25-difluorovitamin D 3 had no anti-25-hydroxylation activity and no antivitamin D activity. Since 25-fluorovitamin D 3 has anti-25-hydroxylase activity, it appears the introduction of a fluoro group on the 1 position diminishes interaction of the vitamin D molecule with the 25-hydroxylase system.

Synthesis of 25-hydroxyvitamin D3-26,23-lactone

Abstract All four possible C-23 and C-25 stereoisomers of the title compound have been synthesized. One of these isomers is identical to the natural product.