Constituents of a Fern, Diplazium subsinuatum. II. Structure Elucidation of Five New Hopane-Triterpene Glycosides.

From whole fern, Diplazium subsinuatum (Wall. ex Hook. et Grev.) Tagawa, two new hopane-triterpene glycosides named diplaziosides III and IV were isolated, together with three new hopane glycosides with acetylated sugars. The structures of diplaziosides III and IV were established as (22S)-24-O-alpha-L-arabinofuranosyl-(1 --> 2)- [beta-D-glucopyranosyl-(1 --> 6)]-beta-D-glucopyranosyl-20 alpha-O-beta-D-glucopyranosyl-30-hydroxyhopan-28-oic acid (1) and (22R)-24-O-alpha-L-arabinofuranosyl-(1-->2)-[beta-D-glucopyranosyl-(1--> 6)]-beta-D-glucopyranosyl-30-carboxy-17-hydroxy-hopano-28,22-lacto ne (2), respectively, on the basis of spectral evidence. Diplazioside III (1) is novel not only in its glycoside structure, but also in its triterpene structure and moreover, 1 provides the first instance of a naturally occurring bisdesmoside with a hopane aglycone. The structures (3a, 3b, and 4a) of the acetylated glycosides were also elucidated, and this is the first report of naturally occurring acetates of hopane glycosides.

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