抄録
(1) Three new hydrolyzable tannin oligomers, hirtellins T_1, T_2 and T_3, were isolated from the dried leaf of Reaumuria hirtella (Tamaricaceae). The structural study based on the spectroscopic and chemical methods has revealed a trimeric structure (3) of hirtellin T_1, and 36-membered macrocyclic structure (4) of hirtellin T_2. They are trimers biogenetically producible by repetition of intermolecular C-O oxidative coupling between O-1 galloyl group of a molecule of tellimagrandin II (1) and O-2 galloyl group of an other molecule of 1, forming a dehydrodigalloyl (m-GOG) unit. Hirtellin T_3 (10) is also a trimer possessing a m-GOG and a hellinoyl (m-GO-m-GOG) unit as the linking units between monomers. A dimer of related structure, tamarixinin B (12), was isolated from the dried flower of Tamarix pakistanica of the same family, and its 26-membered macrocyclic structure with two isodehydrodigalloyl (p-GOG) units was established. (2) Oenothein F (17), a new isomer of oenotheins B (15) and D (16), macrocyclic dimers, was isolated besides 15 and 16, from the fresh leaf of Oenothera laciniata (Onagraceae). The structures of hirtellin T_2 (4), tamarixinin B (12), oenotheins D (16) and F (17), are unique among the oligomers, in that each glucose core in a symmetrical structure has the same substitution mode. (3) The stereostructures of camelliatannins C, D and E, complex tannins, previously isolated from the leaf of Camellia japonica (Theaceae), were established as 18, 20 and 19 on the basis of NMR spectral analysis including ROESY.
