メチルステロイドのガスクロマトグラフィ--4-側鎖の構造が保持時間に及ぼす影響および4-メチル基と3位官能基の相互作用について

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Gas chromatographic behaviors of various 4- and 6-methyl sterols with cholestane, campestane, β-sitostane or stigmastane side chains at C-17 position were studied. From the retention times for these sterols and for their oxo, acetoxy, trimethylsiloxy and trifluoracetoxy derivatives at C-3 position, the increment of the retention times due to the introduction of an alkyl group at C-4 or C-6 position in the steroid skelton and at C-24 position in the side chain was expressed as retention factors, respectively. Moreover, interaction between functional group at C-3 and methyl group at C-4 or C-6 was expressed in terms of ΔR-values, which are ratios of the retention times for steryl derivatives to those for the cor responding free sterols. Main results obtained were as follows. 1) In spite of the variations of the side chain structures, no influences on the retention factors of 4- or 6-methyl group were observed. Whereas, the retention factors of C-24 alkyl group for methyl sterols were identical with those for non-methylated sterols, and were not affected by the natures of C-3 functional groups and liquid phases (SE-30, OV-17, DEGS). 2) It was observed that the ΔR-values for sterols examined differed from one another depending upon number, stereochemical configuration, position and the presence or absence of methyl groups adjacent to C-3 functional group, whereas, within a homologous series, were idetical. Thus, the ΔR-values decreased in the following order : non-methylated>4α-methyl>4β-methyl≅4, 4-dimethyl sterols on the ΔRAC-values (retention times of steryl acetate vs. the corresponding free sterol), 4α-methyl>non-methylated>4, 4-dimethyl>4β-methyl sterols on the ΔRTMS-values (retention times of the steryl trimethylsilyl ether vs. the corresponding free sterol), respectively. Changes of liquid phases were not affected on the orders of the ΔR-values described above. On the 6α-, 6β- and 6-methyl sterols, in general, the ΔR-values were approximately equal to each other because their methyl groups at C-6 are more apart from C-3 functional group compared to methyl group at C-4. It is, hence, concluded that the differentiation of sterol type can be easily carried out from their ΔRAC and ΔRTMS-values. The characteristics of these retention factors and ΔR-values shown in this study may be especially useful for the structural elucidation of unknown sterols.
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メチルステロイドのガスクロマトグラフィ--4-側鎖の構造が保持時間に及ぼす影響および4-メチル基と3位官能基の相互作用について

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