43 ゲンノショウコ,アカメガシワ,ザクロ等のellagitanninの構造について

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Geraniin (I) (from Geranium thunbergii and Mallotus japonicus), mallotusinic acid (II) (from M. japonicus) and granatin A (from Punica granatum) were found to be ellagitannins which have dehydro-hexahydroxydiphenoyl (DHHDP) group in their molecules. The CMR signals of these ellagitannins were assigned by comparing them with those of corilagin (IV) for which the CMR signals were assigned by comparisons with those of the derivatives substituted at O-2 or O-4, and also by deuterium-induced differential isotope shifts (DIS). The CMR spectral investigation was then applied to geraniin before and after the equilibration, and also to "phenazine A" which is produced by condensation of geraniin with o-phenylenediamine. The CMR shifts and DIS showed that the equilibration is induced by transformation of a six-membered hemiacetal ring into a five-membered ring. The shielding effect on H-1 in the glucopyranose moiety upon the transformation of "phenazine A" into "phenazine B" indicates that the atropisomerism in the phenylphenazine moiety in "phenazine B" is R, and hence that the absolute configuration at the methine in geraniin is R. The specific rotation of dimethyl hexamethoxydiphenoate produced by methanolysis of nona-O-methylcorilagin (V) indicates that the atropisomerism of hexahydroxydiphenoyl group in geraniin and corilagin is R. The hydrated and equilibrated structure of geraniin is then shown by (Ia)⇄(Ib). Mallotusinic acid and granatin A have analogous hydrated and equilibrated structures. Granatin B was found to be an isomer of geraniin concerning the DHHDP moiety.
1979-09-20

43 ゲンノショウコ,アカメガシワ,ザクロ等のellagitanninの構造について

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