C-13 NMR化学シフトの図表化 : ステロイド及び関連化合物中のメチル炭素の化学シフト

概要

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To be continued from the previous reports, the chemical shifts of methyl carbons, which are very important as the starting informations for the compounds consisted of similar carbons such as steroids at structure analysis with C-13 NMR, are shown in three schematic figures of the relationships with the chemical structures. Figure 1 shows that the chemical shifts of axial methyl carbons in cyclohexanes and decalins are (6〜7) ppm higher field and are influenced more effectively by the other neighbor substituents than equatorial ones. In Fig. 2, the chemical shifts of methyl carbons in steroids are described in order of higher field except the methoxy methyl ones. As a result, it was clear that 19-methyl carbons in the AB trans structure of steroids were observed in the wider region from 11 to 20 ppm, but that ones in the AB cis structure had the chemical shifts in the narrower region between 23 and 25 ppm. The other kind of methyl carbons, 18-, 21-, 26-, 27-methyl and acetyl methyl carbons, have the characteristic chemical shifts respectively. In Fig. 3, 18- and 19-methyl in the AB trans structures are taken up to be shown in detail. 18-Methyl of steroids with 17β-substituents have the highest chemical shifts and ones with a double bond near 13- carbon have the lower chemical shifts. And also, 19- methyl carbons in steroids with 3-keto or 7-keto have the higher chemical shifts.
社団法人日本分析化学会の論文
1976-03-10