Constituents of Geranium thunbergii Sieb. et Zucc. Part 12. Hydrated stereostructure and equilibration of geraniin

Abstract

The structure of geraniin is (1), in which the cyclohexenetrione moiety is attached to O-4 of glucose. It forms a hydrated six-membered hemiacetal-ring structure (1a) in the crystalline state, and an equilibrium mixture of (1a) and a hydrated five-membered hemiacetal-ring structure (1b) upon the mutarotation. The absolute configurations are also represented by (1a) and (1b).