- Synthesis of a tritiated 3-dehydroecdysteroid putative precursor of ecdysteroid biosynthesis in Locusta migratoria
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We have synthesized a tritiated form of 14α-hydroxy-5β-cholest-7-ene-3,6-dione (5β-diketol) of high specific activity (1.74 TBq/mmol) from 7-dehydrocholesterol in seven steps with stereoselective introduction of the A/B cis ring junction as the key reaction. We have examined the ability of endocrine glands (prothoracic glands) of Locusta migratoria to use this molecule as a precursor of 3-dehydroecdysone and of ecdysone biosynthesis. A very efficient conversion of 5β-diketol to ecdysone and to 3-dehydroecdysone was monitored, which opens up new possibilities for the understanding of the role of 3-dehydro-compounds in ecdysteroid biosynthesis.
- Dolle,Hetru,Roussel,Rousseau,Sobrio,Luu,Hoffmann
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p. 7067 - 7080
(2007/10/02)
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- 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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