Asperuloside monohydrate

The title compound, [2aS-(2a alpha,4a alpha,5 alpha,7b alpha)]-5-(beta-D-gl ucopyranosyloxy)-2a,4a,5,7b-tetrahydro-1-oxo-1H-2,6-dioxacyclopent[cd]inden -4-ylmethyl acetate monohydrate, C18H22O11. H2O, was extracted from the Tur kish plant Putoria calabrica (L. fil.) DC. The three fused rings have envel ope or distorted envelope conformations and form a bowl in which ring strai n causes distortion of some bond angles and significant pyramidalization of two of the Csp(2) atoms. The ring junction H atoms are all cis to one anot her and the glycosidic linkage is in the beta axial position. The structure incorporates two symmetry-independent water molecules, each of which is lo cated on a twofold axis. Intermolecular hydrogen bonds involving all the hy droxy groups and water molecules link the molecules into a complex three-di mensional framework.