SYNTHETIC STUDIES ON ACTIVE FORMS OF VITA MIN-D AND THEIR ANALOGS

Active forms of vitamin D derivatives in addition to the traditional r ole in calcium homeostasis play an role in cellar differentiation. The hydroxylation at C-1 alpha position of vitamin D molecule is essentia l to elicit the physiological activities. We have developed a new meth od for the selective 1 alpha-hydroxylation process in the steroidal mo lecule via enol esterification rearrangement of the 1,4,6-trien-3-ones . This review deals with the syntheses ses of important intermediates for the preparation of active forms of vitamin D and their conversion into the active forms of vitamin D. The steroidal synthon, 1 alpha, 3 beta-dihydroxy-5,7-choladiene derivatives obtained from ergosterol or stigmasterol was converted into the various active forms of vitamin D compounds by coupling with phenylsulfonyl derivatives. Similar treatme nt of pregnenolone afforded (20 R and 20 S)-1 alpha, 3 beta-dihydroxy- 5, 7-pregnadiene derivatives. According to the procedure described her e, 1 alpha-hydroxy and 1 alpha, 25-dihydroxyvitamin D-2, D-3, D-4, and D-7, 24-epi-1 alpha, 25-dihydroxyvitamin D-2, 1 alpha, 24-dihydroxyvi tamin D-3, 24,24-dihomo-1 alpha, 25-dihydroxyvitamin D-3, and 1 alpha, 25-dihydroxy-2 beta-(3-hydroxypropoxy) vitamin D-3 were synthesized.