Five kinds of 4-methyl sterol and also their oxo, acetoxy (OAc), trifluoracetoxy (TFA) and trimethylsiloxy (TMS) derivatives at the position of C-3 were prepared from cholesterol. Relationship between the molecular structure of 4-methyl sterols and their retention time has been studied.
The retention data were expressed as the relative retention time and the methylene unit value (Table-2, 3). The increment of the retention time due to the introduction of 4-methyl group was shown in Table-4 as retention factor. Main results obtained were as follows.
1) The retention times of 4-methyl sterols and their derivatives were found to be larger than those of the corresponding non-methylated sterols and their derivatives.
2) The retention factor of 4-methyl group was affected by its number and stereochemical configuration, the nature of C-3 functional group and unsaturated bond adjacent to the 4-methyl group.
3) The retention times for the derivatives at C-3 functional group were in the following increasing order : TFA<hydroxyl<TMS<OAc on SE-30; TFA<TMS<hydroxyl<OAc on OV-17. The change of C-3 functional group from hydroxyl to oxo resulted in an increase in retention time for 4α-methyl compound, while it decreased for 4β-methyl-, 4, 4-dimethyl- and 4, 4-dimethyl-Δ
5 compounds.
4) 4α- and 4β-methyl compounds could be separated each other finely well on SE-30 and on OV-17, and the latter was eluted after the former, while the both isomers with oxo and TMS group at C-3 exhibited almost equal retention times.
5) The retention time of the compounds with 4, 4-dimethyl group was smaller than might be expected, especially 4, 4-dimethyl-Δ
5-cholesten-3-one was eluted faster than the corresponding non-methylated Δ
5-cholesten-3-one.
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