- Syntheses and CD Studies of 5α-Cholesteno-, -- and -pyrimidines
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Syntheses of 5α-cholesteno- (5a), - (12a), and pyrimidines (15a) have been achieved by using hydroxymethylene derivatives of relevant cholestanones prepared from cholesterol (1).Their CD spectra exhibit at least three Cotton effects between 300 to 200 nm, a first CD band around 290, a second one around 260 and a third one around 220 nm.A quadrant rule is developed and applied to the determination of the first CD band, while a helicity rule is applicable to the third CD band.The first band is positive in the series, whereas it is negative in the and the series.The third band is negative in all three series. - Key Words: Cholestenopyrimidines / Circular dichroism / Quadrant rule of cholestenopyrimidines
- Hasan, Mashooda,Rashid, Naghmana,Khan, Khalid Mohammed,Snatzke, Guenther,Duddeck, Helmut,Voelter, Wolfgang
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p. 889 - 896
(2007/10/02)
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- Syntheses of Steroidal trans-Iodo Acetates
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The reaction of the following streoidal olefins with iodine-copper(II) acetate in acetic acid afforded the corresponding steroidal trans-iodo acetates: 5α-cholest-1, -2-, and -3-ene; and 5β-cholest-1-, -2-, and -3-ene.
- Horiuchi, C. Akira,Satoh, J. Yasuo
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p. 426 - 428
(2007/10/02)
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- Anoid Acetamidosulphenylation and Trifluoroacetoxysulphenylation of Steroidal Alkenes
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Electrochemical acetamidosulphenylation of a number of steroidal alkenes is described via oxidation of diphenyl, di-p-tolyl, dibenzyl and dipropyl disulphide in acetonitrile.The regiochemistry and stereochemistry of addition are established by analysis of
- Mellor, John M.,Milano, Doris L. Bruzco de
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p. 1069 - 1076
(2007/10/02)
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- REDUCTION OF TRITERPENOID KETONES BY CHLOROIRIDIC ACID AND TRIMETHYL PHOSPHITE
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Selective reduction of keto groups on triterpenoid pentacyclic skeleton by chloroiridic acid and trimethyl phosphite (Henbest method) was studied.The 2-oxo group is stereospecifically reduced to give axial 2β-hydroxy group whereas oxo groups in positions 1, 3, 11, 12, 16, 20, 21, 22, and 28 do not react.An analogous reduction was observed with a 2-oxo steroid.
- Protiva, Jiri,Klinotova, Eva,Klinot, Jiri,Kusiak, Miroslav,Vystrcil, Alois
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p. 2029 - 2033
(2007/10/02)
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- The Octant Rule VIII. Variable Temperature Circular Dichroism Spectra of α-Methyl- and Methoxyl-Substituted 5α-Cholestan-2- and -3-ones.
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2α- and 2β-methyl- and methoxy-5α-cholestan-3-ones and 3α- and 3β-methyl- and methoxy-5α-cholestan-2-ones have been synthesized and their variable temperature circular dichroism spectra obtained and analyzed.Rotatory strength (R) values for α-axial and equatorial CH3 and OCH3 groups are determined by difference measurements with the parent ketone.The (small) equatorial CH3 R-values do not consistently follow the Octant Rule.Axial OCH3 groups do not obey the Octant Rule ("anti-octant" behavior) and impose a bathochromic shift on the C=O n-?* transition.Equatorial OCH3 groups do not consistently follow octant or "anti-octant" behavior.
- Lightner, D. A.,Eng, F. P. C.
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p. 189 - 207
(2007/10/02)
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- Stereocontrolled catalytic hydrogenations of 3-oxocholestanes and some related compounds to the corresponding axial 3-alcohols
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Catalytic hydrogenations of 5α-cholestan-3-ones and related compounds with Urushibara nickel A catalyst in cyclohexane gave a distinct preponderance of unstable axial 3α-ols.Product ratios of axial alcohols decreased with increasing solvent polarity.For 3-oxo-5α-steroids, the cobalt catalyst was less selective for the axial alcohol formation.On the other hand, conversion of 5β-cholestan-3-one into the corresponding axial 3β-ol was most successfully attained by hydrogenation catalyzed by Urushibara cobalt A catayst in methanol.For such a 5β-ketone, alcoholic media with higher polarities were more favorable for giving the product rich in axial alcohol.The stereochemistry of the products obtained from hydrogenations conducted in nonpolar solvents may be understood in terms of steric congestion around the ketone carbonyl group.However, when alcohols were used as solvents, the product ratios obtained did not correlate well with the congestion ratios of substrates.
- Ishige, Masayoshi,Shiota, Michio
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p. 1061 - 1068
(2007/10/02)
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