- Synthesis of 3β-methyl ether of dehydroepiandrosterone by biotransformation of 3β-methyl ether of cholesterol with cells of mycobacteria Mycobacterium sp.
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3p-Methyl ether of dehydroepiandrosterone was obtained by microbiological transformation of 3?-methyl ether of cholesterol with Mycobacterium sp. Androstane-3,17-dione, androst-4-ene-3,17-dione, and androsta-1,4-diene-3,17-dione were minor transformation products.
- Andryushina,Stytsenko,Karpova,Yaderets,Zavarzin,Kurilov
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p. 2355 - 2358
(2020/02/18)
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- Electrochemical cholesterylation of sugars with cholesteryl diphenylphosphate
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Electrochemical cholesterylation of various sugars with cholesteryl diphenylphosphate was studied. The reaction afforded mono-, di-, tri-, and tetra-cholesterylated products using equivalent amounts of the reagent. The reactions turned out to be completel
- Tomkiel, Aneta M.,Siergiejczyk, Leszek,Naróg, Dorota,P?oszyńska, Jolanta,Sobkowiak, Andrzej,Morzycki, Jacek W.
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- Optimised conditions for the synthesis of 17O and 18O labelled cholesterol
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Conditions are described for the preparation of cholesterol with 17O and 18O labels from i-cholesteryl methyl ether using minimal amounts of isotopically enriched water. Optimum yields employed trifluoromethanesulfonic acid as catalyst in 1,4-dioxane at room temperature with 5 equivalents of water. An isotopic enrichment >90% of that of the water used for the reaction could be attained. Tetrafluoroboric acid could also be used as catalyst, at the expense of a lower overall reaction yield. Byproducts from the reaction included dicholesteryl ether, methyl cholesteryl ether, compounds formed by ether hydrolysis, and olefins arising from elimination reactions. Reactions in tetrahydrofuran yielded significant amounts of cholesteryl ethers formed by reaction with alcohols arising from hydrolysis of the solvent.
- De La Calle Arregui, Celia,Purdie, Jonathan A.,Haslam, Catherine A.,Law, Robert V.,Sanderson, John M.
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- 3α,5α-Cyclocholestan-6β-yl ethers as donors of the holesterol moiety for the electrochemical synthesis f cholesterol glycoconjugates
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3α,5α-Cyclocholestan-6β-yl alkyl and aryl ethers were proved to be efficient cholesteryl donors in the electrochemical synthesis of glycoconjugates. 3α,5α-Cyclocholestan-6β-ol (i-cholesterol) and its tert-butyldimethylsilyl ether can also be used for this
- Tomkiel, Aneta M.,Biedrzycki, Adam,Ploszyska, Jolanta,Narg, Dorota,Sobkowiak, Andrzej,Morzycki, Jacek W.
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supporting information
p. 162 - 168
(2015/02/05)
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- Determination of total cholesterol in serum by gas chromatography-mass spectrometry
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In this study, a reliable protocol for determination of total cholesterol in serum using gas chromatography-mass spectrometry was established. The total free cholesterol was extracted from the serum with chloroform and derivatized with bis(trimethylsilyl)trifluoroacetamide, analyzed without the saponification step commonly used. Linear calibration curves of cholesterol were obtained from the concentration 0.1 to 15 mmol L-1. The limit of detection was 0.04 mmol L-1. Finally, the proposed method was to explore the influence of high cholesterol diet on total cholesterol in serum of rats.
- Lian, Kaoqi,Zhang, Pingping,Wang, Wei,Dai, TIngting,Li, Lei
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p. 2646 - 2648
(2014/06/09)
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- Synthesis and characterisation of new types of side chain cholesteryl polymers
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A series of cholesterol derivatives have been synthesised via the alkylation reaction of the 3-hydroxyl group with the aliphatic bromide compounds with different chain lengths, namely 3β-alkyloxy-cholesterol. The double bond between the C5 and C6 positions in these cholesterol derivatives was oxidised into epoxy, followed by an epoxy-ring-opening reaction with the treatment with acrylic acid, resulting in a series of 3β-alkyloxy-5α- hydroxy-6β-acryloyloxycholesterol, CnOCh (n = 1, 2, 4, 6, 8, 10, 12), The acrylate group is connected to the C6 position, which is confirmed by the single crystal structure analysis. The corresponding polymers, PC nOCh, were prepared via free radical polymerisation. The structure of monomers and the resulting polymers were characterised with nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The thermal properties of PCnOCh were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). To determine the secondary structure of polymers, circular dichroism (CD) spectra were performed. It was found that not all monomers produce high-molecular-weight polymers because of steric hindrance. However, all polymers have a helical structure, which can be enhanced by increasing the alkoxy chain length. In addition, increasing the alkoxy chain length decreases the glass transition temperature and increases the decomposition temperature of the polymers.
- Wang, Bin,Du, Haiyan,Zhang, Junhua
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experimental part
p. 204 - 209
(2011/03/18)
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- Stereoselective synthesis of selenosteroids
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A stereoselective synthesis of selenosteroids 4 and 5 has been achieved. Starting from commercial available cholesterol 1, followed by asymmetric epoxidation, and subsequently, by stereoselective epoxide ring opening, employing a selenium nucleophilic spe
- Rodrigues, Oscar E.D.,de Souza, Diego,Soares, Letiére C.,Dornelles, Luciano,Burrow, Robert A.,Appelt, Helmoz R.,Alves, Camila F.,Alves, Diego,Braga, Antonio L.
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scheme or table
p. 2237 - 2240
(2010/05/19)
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- Tributylgermanium hydride as a replacement for tributyltin hydride in radical reactions
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Tributylgermanium hydride (Bu3GeH) can be used as an alternative to tributyltin hydride (Bu3SnH) as a radical generating reagent with a wide range of radical substrates. Tributylgermanium hydride has several practical advantages over tributyltin hydride, e.g. low toxicity, good stability and much easier work-up of reactions. The reagent can be easily prepared in good yield and stored indefinitely. Suitable substrates include iodides, bromides, activated chlorides, phenyl selenides, tert-nitroalkanes, thiocarbonylimidazolides and Barton esters. Alkyl, vinyl and aryl radicals can be generated in radical reactions including reduction and cyclisation processes. Common radical initiators such as ACCN and triethylborane can be used. The slower rate of hydrogen abstraction by carbon-centred radicals from Bu 3GeH as compared to Bu3SnH facilitates improved cyclisation yields. Polarity reversal catalysis (PRC) with phenylthiol can be used in reactions which generate stable radical intermediates which will not abstract hydrogen from Bu3GeH.
- Bowman, W. Russell,Krintel, Sussie L.,Schilling, Mark B.
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p. 585 - 592
(2007/10/03)
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- Sensitized photooxygenation of cholesterol and pseudo-cholesterol derivatives via singlet oxygen
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3-Substituted cholesterols and 7-substituted pseudocholesterols undergo a facile photooxygenation sensitized by 9, 10-dicyanoanthracene (DCA) and lumiflavin (LF) to give similar, oppositely-positioned enol derivatives. Both steroids showed the same reaction pattern associated with the endocyclic 5- and 4-olefin units, respectively. The reaction was proposed to proceed via the ene reaction of singlet oxygen and subsequent rearrangement of the initially formed 5α-hydroperoxides.
- Shuping, Wu,Zhiqin, Jiang,Heting, Li,Li, Yang,Daixun, Zeng
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- Improved procedure for the synthesis of methyl ethers from alcohols
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Alcohols can be conveniently converted to the corresponding methyl ethers with methyl iodide in the presence of KOH under solvent-free conditions.
- Rao, H. Surya Prakash,Senthilkumar,Reddy, D. Srinivasa,Mehta, Goverdhan
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p. 260 - 263
(2007/10/03)
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- Montmorillonite Clay Catalysis. Part 13.1 Etherification of Cholesterol Catalysed by Montmorillonite K-10
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The preparation of cholesteryl ethers from alcohols and phenols with cholesterol is carried out at 50-70 °C by using montmorillonite K-10 as an acid catalyst in chloroform or cyclohexane.
- Lu, Bo,Li, Li-Jun,Li, Tong-Shuang,Li, Ji-Tai
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p. 604 - 605
(2007/10/03)
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- A MILD PROCEDURE FOR ETHERIFICATION OF ALCOHOLS WITH PRIMARY ALKYL HALIDES IN THE PRESENCE OF SILVER TRIFLATE
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Alcohols were alkylated in good to excellent yield with primary alkyl halides by a method employing silver triflate and a non-nucleophilic amine base.
- Burk, Robert M.,Gac, Todd S.,Roof, Michael B.
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p. 8111 - 8112
(2007/10/02)
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- The mechanisms of the rearrangements of allylic hydroperoxides: 5α-hydroperoxy-3β-hydroxycholest-6-ene and 7α-hydroperoxy- 3β-hydroxycholest-5-ene
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The rearrangement of 5α-hydroperoxy-3β-hydroxycholest-6-ene in solution under 18O2, gives isotopically normal 7α-hydroperoxy-3β-hydroxycholest-5-ene, whereas the epimerization of this product to give 7β-hydroperoxy-3β-hydroxycholest-5-ene involves incorporation of 73-83% of 18O2 into the hydroperoxy group. These two reactions proceed through the corresponding hydroperoxyl radicals, which have different e.s.r. spectra and which therefore must exist as separate and distinct species. The former reaction shows a first-order dependence on hydroperoxide concentration, and a half-order dependence on t-butyl hyponitrite which was added as an initiator. It is suggested that the first reaction involves a sigmatropic [2,3]-rearrangement, whereas the second reaction proceeds through a dissociative mechanism.
- Beckwith, Athelstan L. J.,Davies, Alwyn G.,Davison, Ian G. E.,Maccoll, Allan,Mruzek, Margaret H.
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p. 815 - 824
(2007/10/02)
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- CLEAVAGES OF ETHERS BY CHLOROTRIMETHYLSILANE AND ACETIC ANHYDRIDE
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Methyl and benzyl ethers have been cleaved with a combination of reagents consisting of chlorotrimethylsilane and acetic anhydride containing a catalytic amount of concentrated sulfuric acid.Methylthiomethyl ethers yield the correponding acetoxymethyl ethers with chlorotrimethylsilane and acetic anhydride.Comparative study with the borontrifluoride etherate and acetic anhydride method of ether cleavage suggests that chlorotrimethylsilane and acetic anhydride (conc.H2SO4 catalysis) could be a useful alternative to it.
- Sarma, J. C.,Borbaruah, M.,Sarma, D. N.,Barua, N. C.,Sharma, R. P.
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p. 3999 - 4006
(2007/10/02)
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- Desorption Chemical Ionization Mass Spectrometry of Epimeric 3-Hydroxysteroids and Derivatives. Stereoselectivity and Nucleophilic Substitution with Ammonia
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The desorption chemical ionization mass spectra, using ammonia as reagent gas, of several epimeric 3-hydroxysteroids and their ether and carboxylic acid ester derivatives are reported.In the case of steroids possessing a Δ4- or Δ5-3α-benzoate moiety, stereospecific stabilization of the protonated molecular ion + is observed.This behaviour is rationalized in terms of interaction of the double bond and the protonated benzoate group at C-3.Nucleophilic substitution by NH3 is observed when a double bond is present in the vicinity of the substitution center.The nature and the stereochemistry of the leaving group influence this substitution reaction.Our results seem to indicate the operation of a two-step mechanism (e.g.SN1 type reaction) rather than a SN2 type mechanism for the formation of the substitution ion +.
- Tecon, Pierre,Hirano, Yutaka,Djerassi, Carl
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p. 277 - 285
(2007/10/02)
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- A NEW METHOD FOR DEOXYGENATION OF VICINAL DIOLS
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Cis and trans vicinal diols have been converted into olefins in one step reaction with chlorotrimethylsilane and sodium iodide.
- Barua, Nabin C.,Sharma, Ram P.
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p. 1365 - 1366
(2007/10/02)
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- SOLVOLYSIS OF 3β-CHLORO-5-CHOLESTENE IN THE PRESENCE OF ZINC SALTS
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When heated in alcohols in the presence of zinc chloride 3β-chloro-5-cholestene undergoes solvolysis, and cholesterol ethers are formed with high yields.The same direction of reaction is preserved if the zinc chloride is formed directly in the reaction mixture.
- Kutulya, L. A.,Oleinik, S. S.,Protsenko, L. I.,Tishchenko, V. G.
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p. 1467 - 1469
(2007/10/02)
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- Calciferol and its Relatives. Part 26. A Conversion of Cholesterol into 8-Hydroxymethyl-des-AB-cholest-8-ene
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The methoxy-ketone (7), derived from Westphalen's diol, was degraded to 8α-benzoyloxymethyl-des-AB-cholestan-9-one (10), from which the title compound (6) was obtained in a yield of 47percent based on the ketone (7), or 22.5percent overall from cholestero
- Kocienski, Philip J.,Lythgoe, Basil,Roberts, David A.
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p. 897 - 901
(2007/10/02)
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