5 3-Cholesta-1,3-diene synthesis

Irradiation of the 5,7-diene gave the previtamin, which was isomerized and saponified to give la-hydroxy-vitamin D3. For the last synthesis of la-hydroxy-7-dehydrocholesterol recorded here, cholesta-l,4,6-triene-3-one was again used as starting steroid.122 Deconjugation of this trienone with strong base followed by immediate reduction with calcium borohydride led to the unstable 3/3-hydroxycholesta-l,5,7-triene which, without isolation, was converted into the 1,4-addition product (265) upon reaction with 4-phenyl-l,2,4-triazoline-3,5-dione. 

Another synthesis of side-chain-hydroxylated cholesta-5,7-dien-3/S-ol derivatives uses the aldehyde (386), prepared by ozonolysis of the adduct of ergosteryl acetate with 4-phenyl-l,2,4-triazoline-3,5-dione. An aldol condensation between the aldehyde (386) and the pre-formed enolate of 3-methyl-3-tetrahydro-pyranyloxybutan-2-one (387) led to the enone (388), after acidic work-up. Reduc-... 

The 2-methoxy-4a-methyl-5Q -androst-2-en-l-one system (500), corresponding to the ring a substitution pattern of quassin, has been elaborated from a 5a-androst-l-en-3-one by application of a sequence of familiar transformations.5,6(8-Epoxy-4/3-hydroxy-5/3-cholest-2-en-l-one (501) has been synthesized as a model for rings A and B of withaferin A (502). The synthesis involved multiple steps from cholesta-2,5-dien-l-one related compounds were synthesized from the 2,4-dien-l-one." ... 

Musumeci, D. and Sica, D. (2002) CHsReOs-catalyzed oxidation of cholesta-5,7-dien-3 3-yl acetate with the urea-hydrogen peroxide adduct under various conditions. Synthesis of the natural epoxy sterol 9a,lla-epoxy-5a-cholest-7-en-3 3,5,6 3-triol. Steroids, 67, 661-668. 

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