PAUCIN METHANOLATE

3aR-(3a-alpha,4a-beta,7-alpha,7a-alpha,8-alpha,9a-alpha)-7-[(6-O-Acetyl-beta-D-glucopyranosyl)oxy]decahydro-4a,8-dimethyl-3-methyleneazuleno[6,5-b]furan-2,5-dione methanol solvate, C23H32O10.CH3OH, M(r) = 500.55, monoclinic, P21, a = 10.819 (5), b = 6.591 (6), c = 18.044 (8) angstrom, beta = 92.91 (4)-degrees, V = 1284.9 (11) angstrom-3, Z = 2, D(x) = 1.294 g cm-3, lambda-(Cu K-alpha) = 1.5406 angstrom, mu = 8.198 cm-1, F(000) = 536, T = 253 K, R = 0.045, wR = 0.059 for 1969 observations, I greater-than-or-equal-to 3-sigma-(I). Paucin was isolated from the plant Hymenoxys rusbyi (Asteraceae) and crystallized from methanol. Crystals are isomorphous with those of a previously reported monohydrate. The structure was refined to a better residual. Conformational details are similar when compared to the monohydrate, but not identical. The cycloheptane ring adopts a twist-boat (C2) conformation. The alpha-methylene-gamma-lactone ring adopts an envelope conformation but with C8 at the flap rather than C7 as observed for the monohydrate. The weakest hydrogen bond from the monohydrate structure is absent in the methanolate, otherwise the hydrogen-bonding pattern is identical in both.