1α-Hydroxyvitamin D3 (XIVa) was synthesized from cholesterol (Ia) in ca. 1.5% overall yield. 1α, 2α-Epoxycholest-4-en-3-one (IVa) readily obtained from Ia was converted to 1α, 2α-epoxycholest-5-en-3-one (Va) by the modified deconjugation reaction with t-BuOK in DMSO. Reduction of Va with Ca (BH4)2 and then with LiAlH4 gave 1α-hydroxycholesterol (VIIIa) in 15.6% yield from Ia. Allylic bromination and subsequent dehydrobromination of the diacetate of VIIIa afforded 1α, 3β-diacetoxycholesta-5, 7-diene (XIa), whose saponification gave the corresponding diol (XIIa). 1α-Hydroxyprovitamin D3 (XIIa) in ethanol was irradiated with the ultraviolet lights in the range between 275 and 310 nm through a newly found filter solution. The formed 1α-hydroxyprevitamin D3 (XIIIa) was thermally isomerized into 1α-hydroxyvitamin D3. The yield of XIVa from XIIa was ca. 25%. These procedures were applied to 25-hydroxycholesterol (Ib) and 1α, 25-dihydroxyvitamin D3 (XIVb) was obtained ca. 0.4% overall yield from Ib.
1α-羟基
维生素 D3(XIVa)由
胆固醇(Ia)合成,总收率约为 1.5%。1α,2α-环氧胆甾烷-4-烯-3-酮(IVa)很容易从 Ia 中获得,通过在
DMSO 中与 t-BuOK 的改进脱钩反应转化为 1α,2α-环氧胆甾烷-5-烯-3-酮(Va)。用 Ca (
BH4)2 还原 Va,然后用 LiAlH4 还原,从 Ia 得到 1α-hydroxycholesterol (VIIIa),收率为 15.6%。对 VIIIa 的二
乙酸酯进行烯丙基
溴化和随后的脱氢
溴化,可得到 1α,3β-
二乙酰氧基胆甾烷-5,7-二烯(XIa),对其进行皂化可得到相应的二醇(XIIa)。
乙醇中的 1α-羟基
维生素 D3(XIIa)通过新发现的滤液,在 275 至 310 纳米范围内接受紫外线照射。生成的 1α-羟基
维生素 D3(XIIIa)经热异构化为 1α-羟基
维生素 D3。从 XIIa 生成 XIVa 的产率约为 25%。将这些步骤应用于 25-羟基
胆固醇(Ib),从 Ib 中得到 1α,25-二羟基
维生素 D3(XIVb),总产率约为 0.4%。