- Epoxide Cleavage Reactions of 7α,8α- and 7β,8β-Epoxycholestanol Acetates
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In a search for an alternative synthetic route to 32-oxygenated sterol derivatives such as 5, 7α,8α- and 7β,8β-epoxycholestanol acetate (9 and 10) were subjected to various conditions of epoxide cleavage.The trans-diaxial opening of the α-epoxide 9 with lithium/ethylamine gave the 7α-ol 11, whereas the 8β-ol 12 was produced from the β-epoxide 10 on reduction with lithium aluminum hydride.However, the trans-diaxal 8β-halo(or hydroxy)-7α-ols were not obtained at all on treatment of the α-epoxide 9 with various mineral acids or BF3-etherate in benzene.Under these conditions, the C-8 carbenium ion would be the intermediate, from which the 7-ketone 13 and a mixture of Δ6,8-, Δ7,14- and/or Δ8,14-diene compounds 16, as well as Δ8(9)- and Δ8(14)-7α-ol 14 and 4a, were produced.The latter allylic alcohol 4a, a possible synthetic precursor of 32-oxygenated sterol was prepared in 63percent yield when benzene was replaced with tetrahydrofuran in the BF3-etherate-catalyzed reaction of the α-epoxide 9.Keywords-epoxide cleavage; 32-oxygenated sterol; 7α,8α-epoxycholestanol acetate; 7β,8β-epoxycholestanol acetate; 3β-acetoxycholest-8(14)-en-7α-ol; reduction; acid treatment; boron trifluoride-etherate; long-range 13C-1H COSY
- Eguchi, Sanae,Yamaguchi, Sanae,Furuya, Mitsuko,Morisaki, Masuo
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p. 2813 - 2818
(2007/10/02)
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- SYNTHESIS OF POTENTIAL ECDYSTEROID PRECURSORS FROM Δ7,22 STEROLS
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Two routes for the conversion of 5α-cholest-7-ene-3β-ol (11) into 7, which has the typical ecdysteroid substitution pattern in rings B, C, and D, have been developed.Making use of one of the methods, 5,6-dihydroergosterol (31) was converted into the 38, p
- Hedtmann, Udo,Hobert, Kurt,Milkova, Tsenka,Welzel, Peter
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p. 1941 - 1952
(2007/10/02)
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