PubMed · 5022092
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J R Evans. 1972. A solid sampler with single sample leading for gas chromatography.. https://doi.org/10.1016/0009-8981(72)90444-5
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Cholestane-3beta,5alpha,6beta-triol is an extensively studied biologically important oxysterol. The full set of eight cholestane-3,5,6-triol stereoisomers was synthesised in diastereomerically pure forms by the stereoselective cleavage of eight diastereomerically pure 4,5-epoxycholestane-3,6-diols with LiAlH4, in high yields on multigram scales and without chromatography for most of them. However, applying various reportedly successful combinations of a hydride donor and a Lewis acid to the same substrates under a variety of conditions failed to generate a single unsubstituted cholestane-3,4,6-triol. The products of the eight cholestane-3,5,6-triol stereoisomers will serve as a good probe in the study of biological functions of oxysterols in a biological process.
[reaction: see text] A facile approach for the conversion of a spirostan saponin into its furostan counterpart, as illustrated by the transformation of dioscin to methyl protodioscin (and its 26-thio-analogue), has been developed.
A crystallographic comparison of some geometrical and structural features for a series of steroids (cholestane derivatives) is made in the present paper. Selected bond distances and bond angles of interest are discussed in detail. Conformations of individual ring systems in a series of 28 cholestane derivatives are calculated and discussed. Graphical presentations of ring conformations are made for all the five- and six-membered rings to show the frequency of their occurrence. X--H...A intra- and intermolecular interactions in the identified molecules are discussed with the standard distance and angle cut-off criteria. Distance-angle scatter plots for both kinds of interactions are presented for better understanding of packing interactions existing in cholestane molecules.