title: Synthesis of 25-hydroxy-[26,27-3H]vitamin D2, 1,25-dihydroxy-[26,27-3H]vitamin D2 and their (24R)-epimers.
abstract: Synthesis of a C-24-epimeric mixture of 25-hydroxy-[26,27-3H]vitamin D2 and a C-24-epimeric mixture of 1,25-dihydroxy-[26,27-3H]vitamin D2 by the Grignard reaction of the corresponding 25-keto-27-nor-vitamin D2 and 1 alpha-acetoxy-25-keto-27-nor-vitamin D3 with tritiated methyl magnesium bromide is described. Separation of epimers by high-performance liquid chromatography afforded pure radiolabeled vitamins of high specific activity (80 Ci/mmol). The identities and radiochemical purities of 25-hydroxy-[26,27-3H[vitamin D2 and 1,25-dihydroxy-[26,27-3H]vitamin D2 D2 were established by cochromatography with synthetic 25-hydroxyvitamin D2 or 1,25-dihydroxyvitamin D2. Biological activity of 25-hydroxy-[26,27-3H]vitamin D2 was demonstrated by its binding to the rat plasma binding protein for vitamin D compounds, and by its in vitro conversion to 1,25-dihydroxy-[26,27-3H]vitamin D2 by kidney homogenate prepared from vitamin D-deficient chickens. The biological activity of 1,25-dihydroxy-[26,27-3H]vitamin D2 was demonstrated by its binding to the chick intestinal receptor for 1,25-dihydroxyvitamin D3.
mesh_terms: D015652:25-Hydroxyvitamin D 2; D000818:Animals; D001667:Binding, Competitive; D004872:Ergocalciferols / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism; D011485:Protein Binding; D013237:Stereoisomerism; D014316:Tritium; D014808:Vitamin D Deficiency / Q000378:metabolism; D014809:Vitamin D-Binding Protein / Q000378:metabolism
chemical_list: D004872:Ergocalciferols; D014809:Vitamin D-Binding Protein; D014316:Tritium; D015652:25-Hydroxyvitamin D 2; C003564:1,25-dihydroxyergocalciferol