- Synthesis of fluorinated steroids using a novel fluorinating reagent tetrabutylammonium difluorodimethylphenylsilicate (TAMPS)
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Steroidal 3-fluoroderivatives were prepared from corresponding tosylates using tetrabutyl-ammonium difluorodimethylphenylsilicate as fluorinating agent. The reaction was tested on all four possible C-3 and C-5 stereoisomers of cholestane and 17-oxoandrostane skeletons. In this reaction only one isomer was always formed with opposite configuration at C-3 to starting tosylate. The reaction is accompanied by elimination which affords a mixture of corresponding olefines.
- Herrmann, Pavel,Kvicala, Jaroslav,Pouzar, Vladimir,Chodounska, Hana
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experimental part
p. 1825 - 1834
(2009/06/19)
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- Preparation of steroid olefins from heptafluorobutyrates
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Steroids with hydroxyl group in positions 2, 3, 6, 7, 17 and 20 were esterified with heptafluorobutyric anhydride. The obtained esters on treatment with lithium bromide in N,N-dimethylacetamide in the presence of pyridinium tosylate afforded the corresponding olefins in high yields.
- Dalibov, Lucie,Kohout, Ladislav
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p. 549 - 556
(2007/10/03)
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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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- A Simple Method for the Reduction of the 7,8-Double Bond of Steroidal 5,7-Dienes
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1,4-Cycloadducts of various steroidal 5,7-dienes and 4-phenyl-1,2,4-triazoline-3,5-dione gave a separable mixture (3 : 2) of the corresponding Δ5- and Δ7-sterols in good yield when treated with lithium dissolved in refluxing ethylamine.
- Anastasia, Mario,Ciuffreda, Pierangela,Fiecchi, Alberto
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p. 1169 - 1170
(2007/10/02)
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- Studies on the Constituents of Pollen. X. On the Constituents of Pollen Grains of Ambrosia elatior LINNE
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The new sterols 4α,14-dimethyl-9,19-cyclocholestan-3β,24ξ-diol (IIIa) and 4α,14-dimethyl-9,19-cyclocholestan-3β,24ξ,25-triol (IVa) were isolated, together with lophenone, lophenol, and cholest-7-en-3β-ol, from the pollen grains of Ambrosia elatior LINNE.The structures were elucidated on the basis of spectroscopic studies and chemical evidence.Keywords-Ambrosia elatior LINNE; Compositae; pollen grains; lophenone; lophenol; cholest-7-en-3β-ol; 4α,14-dimethyl-9,19-cyclocholestan-3β,24ξ-diol; 4α,14-dimethyl-9,19-cyclocholestan-3β,24ξ,25-triol
- Ohmoto, Taichi,Ikeda, Keiji,Chiba, Takeo
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p. 2780 - 2786
(2007/10/02)
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