- Solvolysis of sterol tosylates in aqueous dimethylformamide
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It has been established that the heating of the sterol tosylates (1a - c) in aqueous dimethylformamide in the presence of sodium acetate leads to the formation of the 3α,5-cyclo-6β-alcohols (2), the sterols (3), the 3,5-dienes (4), and the sterol formates (5).
- Kovganko,Survilo
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p. 324 - 327
(2007/10/03)
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- Dissolving Metal Reduction of Esters to Alkanes. A Method for the Deoxygenation of Alcohols
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Divers carboxylic esters have been reduced with dissolving Group 1A metals.Using lithium in ethylamine, sterically hindered esters (RCO2R') were deoxygenated giving the alkane (R'H) whereas non-hindered esters regenerated the parent alcohol (R'OH).This permitted the selective deoxygenation of diesters.Conversely, potassium-sodium eutectic solubilised with 18-crown-6 in t-butylamine and tetrahydrofuran (THF) efficiently deoxygenated both hindered and non-hindered esters.In the absence of nucleophiles at ambient temperture the principal reaction of carboxylic ester radical anions was deoxygenation.
- Barrett, Anthony G. M.,Godfrey, Christopher R. A.,Hollinshead, David M.,Prokopiou, Panayiotis A.,Barton, Derek H. R.,et al.
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p. 1501 - 1509
(2007/10/02)
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- The mass spectrometric behavior of 3α,5-cyclo-5α-cholestan-6β-yl alkyl ethers
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The 3α,5-cyclo-6β-methoxy (i-methyl ether) moiety is a common protective grouping in steroid partial synthesis.Therefore, the mass spectrometric behavior of 6β-hydroxy-3α,5-cyclo-5α-cholestane, the corresponding methyl, ethyl, and tert-butyl ethers, the analogous ketone, and the parent hydrocarbon has been investigated in order to determine the mechanisms of the characteristic fragmentations of these compounds.Such knowledge is essential for unequivocal structure elucidation by mass spectrometry and also bears on the current interest in the stereospecificity of electron impact induced eliminations.Deuterium labeling of carbon atoms 1,2,3,4,7,8,9, and 19 of 6β-methoxy-3α,5-cyclo-5α-cholestane established the course of methanol extrusion and the identity of the highly diagnostic A ring cleavage ion M.+ - 55.Mechanisms are proposed for these key fragmentations.The mass spectra of the methyl, ethyl, and tert-butyl ethers of cholesterol are analyzed, and the features distinguishing these compounds from the isomeric 3,5-cyclosteroids are noted.
- Brown, Frederick J.,Massey, Ian J.,Djerassi, Carl
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p. 2592 - 2599
(2007/10/02)
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