- OCCURRENCE AND SEASONAL VARIATION OF 19-NORCHOLEST-4-EN-3-ONE AND 3β-MONOHYDROXY STEROLS IN THE CALIFORNIAN GORGONIAN, MURICEA CALIFORNICA
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The first natural occurrence of 19-norcholestenone is reported, together with 17 sterols and one other Δ4-3-ketone in the extracts of the Californian gorgonian, Muricea californica (Aurivillius).Six additional demethyl sterols and five additional 4-monomethyl sterols which remain unidentified were also detected.Lipid extracts of M. californica from a winter and summer collection were split by various chromatographic methods into free sterol, steryl ester, and steryl conjugate fractions.Sterol compositions (determined by GC and GC-MS) of each fraction, subsequent to hydrolysis, are tabulated and discussed with respect to plausible origins of observed variations.The possible relationship of the Muricea 19-nor-steroidal ketone to other naturally occurring 19-nor-steroids is discussed.
- Popov, S.,Carlson, R. M. K.,Djerassi, Carl
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- Biosynthetic studies of marine lipids. 39.1 19-norsterols: The course of c-19 methyl elimination
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The biosynthesis of 19-norstanols in the Mediterranean sponge, Axinella polypoides, was investigated through the use of radiotracer experiments. It was found that the conversion of cholesterol (7) to 19-nor-5α-chotestan-3β-ol (8) involved oxidation at C-3 with the distribution of the abstracted hydride from the 3α-position of dietary cholesterol into all of the 19-norstanols of the native mixture. Furthermore, while the efficiency of conversion of Δ5-19-oxygenated sterol precursors 19-hydroxycholesterol (9) and 3β-hydroxycholest-5-en-19-oic acid (10) to 8 was low, the efficiency of the conversion of 19-hydroxycholest-4-en-3-one (23) to 8 was high, suggesting that the principal pathway for 19-norstanol biosynthesis involves oxidative isomerization of a dietary Δ5-3β-hydroxy sterol to the δ4-3-ketone before oxidation at C-19. It was also shown that the conversion of cholesterol to 19-nor-5α-cholestan-3β-ol involves the stereospecific loss of the 4β-hydrogen atom. It was further determined that the biological demethylation pathway is suppressed for dietary sterols bearing an unconventional configuration at C-20 in the hydrocarbon side chain.
- Rabinowitz, Michael H.,Djerassi, Carl
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p. 304 - 317
(2007/10/02)
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- Photoinduced Molecular Transformations. Part 112.Transformation of Steroids into Ring-A-Aromatized Steroids and 19-Norsteroids involving a Regioselective β-Scission of Alkoxyl Radicals; Synthesis of Two Marine Natural Products, 19-Nor-5α-cholestan-3β-ol and 19-norcholest-4-en-3-one...
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A new transformation of steroids into 19-norsteroids and ring-A-aromatized steroids is described.The transformation method involves the removal of the 10β-methyl group by a regioselective β-scission of alkoxyl radicals.Cholesterol was transformed into two marine natural products, 19-nor-5α-cholestan-3β-ol and 19-norcholest-4-en-3-one, and into 19-norcholesta-1,3,5(10)-trien-3-ol.Transformations of 3β-hydroxyandrost-5-en-17-one into 19-nortestosterone, estrone, and the related estranes are also described.
- Suginome, Hiroshi,Senboku, Hisanori,Yamada, Shinji
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p. 2199 - 2205
(2007/10/02)
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