Constituents of a fern, Diplazium subsinuatum. III. Four new hopane-triterpene lactone glycosides

Abstract

From a whole plant of a fern, Diplazium subsinuatum, three new hopane-triterpene lactone glycosides, diplaziosides V-VII (1-3), were isolated, together with a new monoacetyl derivative (4) of diplazioside VII (3). Compounds 1-3 were defined as the respective 3-O-[β-D-glucopyranosyl-(1→2)]-β-D-glucopyranosides of 3β,24-dihydroxyhopan-28,22-olide (1), of 3β,17,24-trihydroxyhopan-28,22-olide (2), and of (22R)-3β,24,30-trihydroxy-hopan-28,22-olide (3), and 4 as the 6″-O-acetate of 3, respectively, on the basis of spectral evidence. 1-3 are new in their glycoside structures but also in their triterpene structures. Furthermore, in compounds 1-4, the coupling between the 24-hydroxy proton and one of the 24-methylene protons showed a very large J-value (11.4 Hz); based on this 1H-NMR evidence, etc., preferred conformations of the 24-hydroxymethylene groups in 1-4 are also inferred. In a similar manner, 1H-NMR coupling patterns of the 24-hydroxymethylene in the monoglucoside (2a) and aglycone (2b), derived from 2, are also reported and discussed here.