46 Zeorinの構造について

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Previously we have discussed the atereostructures of seorin, leucotylin, and leucotylic acid, three major triterpenoids obtained from a lichen Parmelia leucotylisa Nyl., and have presented the structures as (1), (2), and (3) respectively. Among them the structure of leucotylin(2) having C-21βH configuration has been established unambiguously both chemically and X-ray crystallographically. The structures of the other two triterpenoids have been based on the chemical correlations between those and leucotylin and been proposed as possessing C-21αH configuration (as (1) and (3)). In addition, it has been proposed that the C-21 configuration of hopane and isohopane might be expressed as α and β rather than β and α respectively. However, further experiment on the stereostructure of seorin has enabled us to reifies the structures of seorin and ieucotylic acid as (18) and (28), having C-21βH, same as leucotylin(2) and also as hopane stereostructure(22) which was initially presented by Jones et al. and has later been confirmed by Ageta et al. chemically and by Koyama et al. by means of X-ray analysis. Thus, X-ray analysis of seorin-6-O-p-bromobensoate, C_<37>H_<55>O_3Br, mp. 224-227°(orthorhombic, space group P2_12_12_1), has disclosed that seorin should be formulated as (18) with C-21βH. Consequently, it follows that there must be some discrepancy among our previous chemical correlations and the subject has been discussed.
天然有機化合物討論会の論文
1970-10-01

46 Zeorinの構造について

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