lα, 25-Dihydroxyvitamin D
4 (22, 23-dihydro-lα, 25-dihydroxyvitamin D
2) (1) and D
7 (24-epi22, 23-dihydro-1α, 25-dihydroxyvitamin D2) (3) were synthesized via 25-hydroxyvitamin D
4 (18a) and D
7 (18b) respectively. Condensation of phenylsulfonyl derivatives (6a, b) with 22-iodo derivative (13)obtained from ergosterol followed by deprotection of hydroxyl groups and reductive desulfonylation of coupling product (14a, b) and elimination of the protecting group of ergost-6-ene nucleus on 15a, b afforded 5, 7-diene (16a, b). Irradiation of 16a, b and thermal isomerzation of 25-hydroxyprevitamin D
4(17a) and D
7 (17b) gave 18a and 18b. Conversion of 18a, b into 25-hydroxycyclovitamin D
4 (19a) and D
7 (19b), allylic oxidation of 19a, b, acetolysis of 1-hydroxycyclovitamin D
4 (20a) and D
7 (Mb), and removal of protecting groups of hydroxyl groups of acetolysis product (21a, b) produced 1 and 3. laHydroxyvitamin D
4 (2) and D
7 (4) were prepared via vitamin D
4 (18c) and D
7 (18d).
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