X-ray diffraction structural analysis of zo-hydroxy-20-isoxazolinylsteroids

Verenich, A. I.; Govorova, A. A.; Galitskii, N. M.; Baranovskii, A. V.; Litvinovskii, R. P.; Хрипач, В. А.

doi:10.1007/bf00747088

Cited by 5 publications

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“…Thus, comparison of the values calculated and obtained by the method of x-structural analysis for dihedral angles of the molecules of three stereoisomeric isoxazolinyl steroids synthesized from alcohols 1, 3, and 4 [3,14,15] shows their good agreement: the scatter in the deviations of their values lies within 3-9 o . Good agreement between the calculated and experimental results was also observed for other geometric parameters of molecules (the scatter in the deviations of the valence angles lay within 1.0-1.5 o , whereas that of the bond lengths did not exceed 0.010 A°).…”

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confidence: 79%

“…Good agreement between the calculated and experimental results was also observed for other geometric parameters of molecules (the scatter in the deviations of the valence angles lay within 1.0-1.5 o , whereas that of the bond lengths did not exceed 0.010 A°). As the initial geometry in performing the quantum-chemical calculations, the corresponding experimental data obtained by the x-structural analysis method were used [3,14,15] for the aboveindicated isoxazolinyl steroids. The search for the most probable conformations of the side chain was carried out on the basis of the quantum-chemical calculation of the structures resulting from rotation of the side chain with a step of 5 o and of its separate parts successively around the bonds C 20 -C 22 and C 22 -C 23 followed by rotation of the hydroxyl group around the bonds C 20 -O 20 or C 22 -O 22 .…”

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confidence: 99%

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IR Spectroscopic Investigation and Conformational Analysis of Unsaturated C20 and C22 Steroid Alcohols

et al. 2005

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With the IR-spectroscopy method and the quantum-chemical AM1 method, the ∆ 22 and ∆ 23 steroids containing a hydroxyl group at C 20 or C 22 have been studied in order to elucidate the mutual arrangement in space of the hydroxyl group and of the double bond in the side chain of the molecules. The conformational analysis of steroid alcohols has been performed and the population of their stable conformers has been calculated. The frequencies of the bands in the IR spectra of alcohols in the region of the stretching vibration of OH groups have been assigned to certain conformers and the possibility of formation of the intramolecular hydrogen bond of the OH groups with the π-electron cloud of C=C bonds has been analyzed.Keywords: stretching vibrations of OH, unsaturated steroid alcohols, alcohol conformers, intramolecular hydrogen bond.Introduction. Terminal steroid alkenes (22-and 23-ens) are of interest in nitryloxide synthesis of biologically active modified steroids, the side chain of which contains a 2-isoxazoline fragment [1-3]. Addition of nitryloxides to steroid alkenes proceeds in regio-and stereoselective ways, with the degree of stereoselectivity depending substantially on the character of substitution at C 20 and C 22 , in particular, on the presence of a hydroxyl group in the allylic position [4][5][6]. To elucidate the characteristic features of the behavior of such steroid alcohols with the end C=C bond in the reaction of interaction with nitryloxides, it is necessary to carry out a detailed investigation of their spatial structure, including the mutual disposition of the hydroxyl group and double bond.In the present work, we carried out an IR spectroscopic investigation and a conformational analysis of tertiary ∆ 22 and ∆ 23 steroid C 20 alcohols 1 and 2 with a different spacing between the OH group and C=C bond as well as

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IR Spectroscopic Investigation and Conformational Analysis of Unsaturated C20 and C22 Steroid Alcohols

et al. 2005

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“…It is a complicated problem to study the structures of isoxazolinyl steroids and in particular to establish the stereochemistry of asymmetric centers on the side chains of the stereoisomers formed, requiring that we draw on a number of physicochemical methods. We have successfully used NMR spectroscopy [1, 2, 4-6], x-ray diffraction [3,7,8], and circular dichroism [9] to solve this problem.In this work, with the aim of determining the spectral features allowing us to identify the stereoisomers with the simple and accessible IR spectroscopy method, we have carried out an IR spectroscopy study and conformational analysis of the stereoisomers 5a-12c of 22(23)-isoxazolinyl steroids with a hydroxyl group at C 20 or C 22 : …”

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Intramolecular hydrogen bonding and structure of stereoisomeric 20(22)-hydroxy-22(23)-isoxazolinyl steroids

et al. 2006

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We have used IR spectroscopy and the quantum chemical AM1 method to study stereoisomeric 22(23)-isoxazolinyl steroids with a hydroxyl group at C 20 or C 22 , in order to establish the spectral features that will allow us to identify their stereoisomers. We have carried out a conformational analysis of isoxazolinyl steroid stereoisomers, and we have calculated the populations of their stable conformers. We have assigned the bands in the IR spectra of the stereoisomers in the region of the stretching vibrations of OH groups, and have analyzed the possibility of intramolecular hydrogen bond formation between the OH groups and proton-acceptor centers of the isoxazoline ring. Introduction.As was shown earlier in [1-6], 1,3-dipolar cycloaddition of nitrile oxides to form terminal steroid 22-enes and 23-enes leads to stereoisomeric isoxazolinyl steroids, which are of interest as potential bioregulators and also are valuable intermediates in synthesis of a number of natural steroids with a polyfunctionalized side chain. It is a complicated problem to study the structures of isoxazolinyl steroids and in particular to establish the stereochemistry of asymmetric centers on the side chains of the stereoisomers formed, requiring that we draw on a number of physicochemical methods. We have successfully used NMR spectroscopy [1, 2, 4-6], x-ray diffraction [3,7,8], and circular dichroism [9] to solve this problem.In this work, with the aim of determining the spectral features allowing us to identify the stereoisomers with the simple and accessible IR spectroscopy method, we have carried out an IR spectroscopy study and conformational analysis of the stereoisomers 5a-12c of 22(23)-isoxazolinyl steroids with a hydroxyl group at C 20 or C 22 :

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“…The crystal structure determination of (1) reveals that a single medium-strong intermolecular hydrogen bond exists between the carbonyl 029 atom and the O31--H31 group. Literature data suggest that compound (2) (C29H45NO4; Verenich et al, 1992) is isostructural with compound (1) (Figs. 2 and 3).…”

Section: Introductionmentioning

confidence: 99%