75 コウボウシバの抗菌性オリゴスチルベン類の構造解析(ポスター発表の部)

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Some Carex spp. (Cyperaceae) contain a considerable amount of oligostilbenes (oligomers of 3,5,4'-trihydroxystilbene). In this paper, we report the structural determination of the oligo-stilbenes found in C. pumila Thunb. Methanol extracts of the subterranean parts of C. pumila were fractionated by column and thin layer chromatography to afford five oligostilbenes, kobophenol B (1), miyabenol A (2) and hopeaphenol (3) as tetramers, miyabenol C (4) as a trimer and ε-viniferin (5) as a dimer. All isolates showed an antibacterial activity against Staphylococcus aureus. Compound 1 showed a molecular formula of C_<56>H_<40>O_<12> which corresponded to a tetrastilbene. Permethylation of 1 yielded an octamethyl ether (7). The plain structure was elucidated principally with the aid of 2D NMR (HH- and CH-COSY, and COLOC). The EIMS fragmentation pattern of 7 well supported this structure. The stereochemistry of 1 was determined as (7aR,8aR,10aR,12aS,7bR,8bS,7cR,8cS,7dR,8dR) by the 2D NOESY results and the biogenetic relationship with 5. The stereochemistry of 2 was also determined as (7aR,8aR,7bS,8bS,7cR,8cR) by taking the NOESY results of a related tetrastilbene, miyabenol B (6) into account. Compound 3 has an interesting C_2 symmetric structure. The spatial relationship between two equivalent units was elucidated by a 2D coupled HMQC-ROESY technique.
天然有機化合物討論会の論文
1991-09-07