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Chemical syntheses of 5 alpha cholesta 6 8 14 dien 3 beta ol 15 one and related 15 oxygenated sterols



Chemical syntheses of 5 alpha cholesta 6 8 14 dien 3 beta ol 15 one and related 15 oxygenated sterols



Chemistry & Physics of Lipids 25(4): 381-394



Hydroboration of 5.alpha.-cholesta-8,14-dien-3.beta.-ol (I) gave 5.alpha.-cholest-8-en-3.beta.,15.alpha.-diol (IV) in 89% yield. 5.alpha.-Cholest-7-en-3.beta.,15.alpha.-diol (V) was prepared in 91% yield by hydroboration of 5.alpha.-cholesta-7,14-dien-3.beta.-ol (II). Hydroboration of 27:63 mixture of I and II gave IV and V in 18% and 70% yields, respectively. 5.alpha.-Cholest-8-en-15.alpha.-ol-3-one and 5.alpha.-cholest-7-en-15.alpha.-ol-3 one were prepared in high yields from IV and V, respectively, by either selective oxidation with silver carbonate-celite or by enzymatic oxidation using cholesterol oxidase. 7.alpha.,8.alpha.-Epoxy-5.alpha.-cholestan-3.beta.,15.alpha.-diol (VIII) was prepared in 93% yield by treatment of V with m-chloroperbenzoic acid. 5.alpha.-Cholest-8(14)-en-7.alpha.-ol-3,15-dione (IX) was prepared in 56% yield by oxidation of VIII with pyridinium chlorochromate followed by treatment of the crude product with acid. Compound IX was also obtained in 72% yield by selective chemical oxidation of 5.alpha.-cholest-8(14)-en-3.beta.,7.alpha.,15.alpha.-triol. 5.alpha.-Cholesta-6,8(14)-dien-3,15-dione (X) was prepared in 89% yield by treatment of IX with p-toluenesulfonic acid under controlled conditions. Reduction of X with lithium tri-tert-butoxyaluminum hydride under controlled conditions gave 5.alpha.-cholesta-6,8(14)-dien-3.beta.-ol-15-one in 84% yield.

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