- Synthesis of sodium androst-5-ene-17-one-3β-methylene sulfonate
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The synthesis of sodium androst-5-ene-17-one-3β-methylene sulfonate 2, a stable analog of memory-enhancing neurosteroid dehydroepiandrosterone sulfate, is described.The synthesis of compound 2 is carried out in six steps from dehydroepiandrosterone. - Keywords: steroids; steroid sulfatase; memory enhancement; dehydroepiandrosterone sulfate
- Vhu, Guo-Hua,Li, Pui-Kai
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- Stereoretentive chlorination of cyclic alcohols catalyzed by titanium(IV) tetrachloride: Evidence for a front side attack mechanism
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A mild chlorination reaction of alcohols was developed using the classical thionyl chloride reagent but with added catalytic titanium(IV) chloride. These reactions proceeded rapidly to afford chlorination products in excellent yields and with preference for retention of configuration. Stereoselectivities were high for a variety of chiral cyclic secondary substrates including sterically hindered systems. Chlorosulfites were first generated in situ and converted to alkyl chlorides by the action of titanium tetrachloride which is thought to chelate the chlorosulfite leaving group and deliver the halogen nucleophile from the front face. To better understand this novel reaction pathway, an ab initio study was undertaken at the DFT level of theory using two different computational approaches. This computational evidence suggests that while the reaction proceeds through a carbocation intermediate, this charged species likely retains pyramidal geometry existing as a conformational isomer stabilized through hyperconjugation (hyperconjomers). These carbocations are then essentially "frozen" in their original configurations at the time of nucleophilic capture.
- Mondal, Deboprosad,Li, Song Ye,Bellucci, Luca,Laino, Teodoro,Tafi, Andrea,Guccione, Salvatore,Lepore, Salvatore D.
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p. 2118 - 2127
(2013/04/10)
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- Hydroxylation of steroids by Fusarium oxysporum, Exophiala jeanselmei and Ceratocystis paradoxa
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The potential of Fusarium oxysporum var. cubense UAMH 9013 to perform steroid biotransformations was reinvestigated using single phase and pulse feed conditions. The following natural steroids served as substrates: dehydroepiandrosterone (1), pregnenolone (2), testosterone (3), progesterone (4), cortisone (5), prednisone (6), estrone (7) and sarsasapogenin (8). The results showed the possible presence of C-7 and C-15 hydroxylase enzymes. This hypothesis was explored using three synthetic androstanes: androstane-3,17-dione (9), androsta-4,6-diene-3,17-dione (10) and 3α,5α-cycloandrost-6- en-17-one (11). These fermentations of non-natural steroids showed that C-7 hydroxylation was as a result of that position being allylic. The evidence also pointed towards the presence of a C-15 hydroxylase enzyme. The eleven steroids were also fed to Exophiala jeanselmei var. lecanii-corni UAMH 8783. The results showed that the fungus appears to have very active 5α and 14α-hydroxylase enzymes, and is also capable of carrying out allylic oxidations. Ceratocystis paradoxa UAMH 8784 was grown in the presence of the above-mentioned steroids. The results showed that monooxygenases which effect allylic hydroxylation and Baeyer-Villiger rearrangement were active. However, redox reactions predominated.
- Peart, Patrice C.,McCook, Kayanne P.,Russell, Floyd A.,Reynolds, William F.,Reese, Paul B.
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experimental part
p. 1317 - 1330
(2011/11/06)
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- Chlorination of 3β-hydroxyl-5-Δ steroids with anhydrous ferric chloride
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Treatment of 3β-hydroxyl-5-Δ steroids with anhydrous FeCl 3 in CH2Cl2 afforded reasonable yields of the corresponding alkyl chlorides with a retention of configurations. The structures of the chlorine-exchanging products were determined by NMR and HRMS spectra. The absolute configurations were confirmed by X-ray crystal analysis of 3β-chloro-androst-5-en-17-one. The generality and scope of the reaction were also investigated.
- Liu, Feng-Wu,Liu, Hong-Min,Zhang, Yan-Bing,Zhang, Jing-Yu,Tian, Li-Huan
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p. 825 - 830
(2007/10/03)
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- Steroidal Allylic and Homoallylic Rearrangements during Halogenation with Triphenylphosphine and Carbon Tetrachloride
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Treatment of 3β-hydroxyandrost-5-en-17-one with triphenylphosphine and carbon tetrachloride under various conditions affords 3α- and 3β-chloroandrost-5-en-17-one, 3α,5-cycloandrost-6-en-17-one, and minor amounts of 17-dichloromethylene derivatives.In contrast, 4β-acetoxy-3β-hydroxyandrost-5-en-17-one affords 4β-acetoxy-3α-chloro- and 3β-acetoxy-4α-chloro-androst-5-en-17-ones. 3β-Acetoxy-4β-hydroxyandrost-5-en-17-one affords 3β-acetoxyandrost-4,6-dien-17-one and minor amounts of the 3β-acetoxy-4α-chloro-5-ene and 3β-acetoxy-6α-chloro-4-ene.
- Hanson, James R.,Hitchcock, Peter B.,Reese, Paul B.,Truneh, Almaz
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p. 1469 - 1472
(2007/10/02)
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- Azasteroids from 3β-Chloroandrost-5-en-17-one
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The Beckmann rearrangement of 3β-chloroandrost-5-en-17-one oxime using p-toluenesulphonyl chloride and pyridine or using thionyl chloride affords the lactam 3β-chloro-17a-aza-D-homoandrost-5-en-17-one (IIa).The Schmidt reaction of the corresponding ketone using sodium azide and sulphuric acid furnishes the same lactam.However, the Schmidt reaction of this ketone using hydrazoic acid and boron trifluoride diethyletherate gives 3β-chloro-13,17-seco-17-azidoandrost-5-ene-16-nitrile (III) and 3β-chloro-D-homoandrost-5-enotetrazole (IV).
- Siddiqui, A. H.,Afzal, M. N.,Baig, M. H.,Lingam, G. Vajra,Rao, N. Sathyanarayan
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p. 1108 - 1109
(2007/10/02)
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- TRIMETHYLSILYL TETRAFLUOROBORATE A CONVENIENT REAGENT FOR SOLVOLYSIS REACTIONS
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Conversions of cyclopropyl carbinols (or their acetates) and ketones into homoallyl and γ-substituted ketone derivatives, respectively, are accomplished by trimethylsilyl tetrafluoroborate efficiently and under mild conditions.
- Caputo, Romualdo,Ferreri, Carla,Palumbo, Giovanni,Wenkert, Ernest
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p. 577 - 578
(2007/10/02)
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- Microbial Oxidation of Sterol Side-Chains
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Several sterol metabolising microorganisms, Pseudomonas convexa, P. stutzeri, Micrococcus sp., Cephalosporium longisporum and Moraxella sp. were isolated from soil on 2-cyclopentyl-6-methyl heptane and cholestane as carbon sources.All these organisms were shown to have the capacity of oxidizing the eight carbon side chain of cholesterol.Excepting P. convexa, the organisms needed a chelating agent for prevention of steroid ring degradation.The Moraxella sp. proved to be the most versatile as it degraded cholesterol derivatives such as 3β-methoxy cholest-5-ene, 3β-chloro cholest-5-ene, 3,5-cyclocholestan-6-one and potassium cholesteryl sulphate to the corresponding 17-keto steroids in 10-50percent yield in shake flasks.It also gave high yields of estrone from both 19-hydroxy-3β-acetoxy cholest-5-ene and 19-hydroxy-3β-acetoxy sitost-5-ene.Two new enzymes one carrying out the oxidative O-demethylation of 6β-methoxy 3,5-cyclocholestane and the other, the isomerisation of i-steroids to normal 3β-hydroxy-Δ5 steroids were discovered.Immobilized Moraxella cells in agar carried out the side chain degradation of cholesteryl sulphate to yield 3β-hydroxy androst-5-en-17-one sulphate and the 19-hydroxy-3β-acetoxy derivatives of both cholesterol and sitosterol to estrone in high yields.The half life of entrapped cells was estimated to be 28 days.
- Bhattacharyya, P. K.,Rao, M. Krishna,Natarajan, Rama Devi,Ramgopal, Malathi,Madyastha, Prema,Madyastha, K. M.
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