58 孤立水酸基の絶対配置決定の新方法 : アセテートおよびメトキシグリオギザレートのCDスペクトル(ポスター発表の部)

概要

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CD Spectra of acetates of chiral cyclic and acyclic aliphatic alcohols exhibit the Cotton effects near 215nm, and their signs are dependent on the absolute configuration of the adjacent carbinyl carbons. Thus the esters with R configuration show a positive Cotton effect, while that of S structure exhibit a negative peak (Table 1). Although the parent alcohols are almost transparent, their contributions are subtracted from the acetate curves. The above phenomena may be explained by the asymmetric interactions between the chiral center and the ester group. The sign of the Cotton effectmay be predicted by the models 9 and 10. Analogusly, methoxyglyoxalates exhibit the peaks at 247nm with the same sign as those of corresponding acetates (Table 1). Further, the difference spectra of the respective pairs disclosed a pair of maxima at 247 and 214nm (see Fig. 3), indicating the presence of excitone coupling between the vicinal ester groups. Practical usefulness of this investigation is demonstrated by the determination of absolute configuration of a side chain hydroxyl group of 11, isolated from Aconitum carmiehaeli leaves. The difference CD spectrum of the acetates 12.A and 13.A, derived from 11, exhibited a negative Cotton effect due solely to the contribution of 24-acetoxyl group. The configuration at this center was thus assigned to be S.
1991-09-07