3-Methoxy-5a-cholest-2-ene

Levisalles and co-workers have prepared A-homo-5a-cholestan-4-one by the dibromocarbene procedure starting with 3-methoxy-5a-cholest-2-ene. Wieland and Anner have converted 19-mesyloxy-A -3-keto steroids into... 

The methyl ester (100, R = CH3), derived from this A-nor acid by treatment with diazomethane, is different from the ester (102) obtained either by Favorskii rearrangement of 2a-bromo-5a-cholestan-3-one (101) or by the action of cyanogen azide on 3-methoxy-5a-cholest-2-ene (103) followed by hydrolysis on alumina. The ketene intermediate involved in photolysis of (99) is expected to be hydrated from the less hindered a-side of the molecule to give the 2j -carboxylic acid. The reactions which afford (102) would be expected to afford the 2a-epimer. These configurational assignments are confirmed by deuteriochloroform-benzene solvent shifts in the NMR spectra of esters (100) and (102). ... 

Anodic decarboxylation of the glycidates (415) derived from 5a-cholestan-3-one gave 3-acetal-5a-cholest-2-ene (416) and a 3-acetyl-3-methoxy-derivative (417). "... 

The anaesthetic steroid 3a-hydroxy-5a-pregnane-ll,20-dione has normal conformational features, both in the crystal and in solution. X-Ray data show that deoxycholic acid can form an inclusion complex in which alternate molecules of dimethyl sulphoxide and water are held in canals formed by helically arranged host molecules.Six different crystalline forms of 17a-ethynyloestradiol have been recognized. X-Ray structural data are reported for 3-methoxy-2-aza-oestra-l,3,5(10)-trien-17/3-yl acetate, 3/3-hydroxypregn-5-en-20-one (pregnenolone), 5a-cholest-2-ene, 3/3-bromo- and 3/3-chloro-cholest-5-enes, and cholesteryl acetate (at 123 K), benzoate, chloroformate, ° laurate, methyl carbonate, and 24-norcholesteryl acetate. ... 

Conflicting reports relating to the products obtained from the Tiffeneau-Demjanov ring-expansion of 5a-cholestan-3-one have appeared. G.Lc. analysis has failed to reveal the presence of the A-homo-3-ketone, although it has been detected by o.r.d. and c.d. measurements. The pure A-homo-4-ketone has now been obtained via solvolysis of the dibromocarbene adduct (309) of 3-methoxy-cholest-2-ene to afford the unsaturated halogenoketone (310) which was then reduced to the 4-one. In a similar manner, 3-acetoxycholest-3-ene afforded the isomeric unsaturated halogenoketone (311) which on reduction produced A-homo-5a-cholestan-3-one. 

Cholest-4-ene and -5-ene add methanol photochemically to give 5-methoxy-5a-and -5)3-cholestanes, the latter predominating. Propan-2-ol affords only the 5/S-isopropoxy-derivative, along with the 5a- and 5)3-ols as major products. 

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