Dihydroisocoumarin constituents from the leaves of Hydrangea macrophylla var. thunbergii (2). Absolute stereostructures of hydrangenol, thunberginol I, and phyllodulcin glycosides and isomerization reaction at the 3-positions of phyllodulcin and its glycosides

Following the characterization of 3S-phyllodulcin, 3R- and 3S-phyllodulcin 3'-O-glucosides, and 3R- and 3S-thunberginol H 8-O-glucosides, six new dihy droisocoumarin glycosides, 3R- and 3S-hydrangenol 4'-O-apiosylglucosides, 3 R- and 3S-thunberginol I 4'-O-glucosides, thunberginol I 8-O-glucoside, and 3S-phyllodulcin 8-0-glucoside, were isolated from the dried leaves of Hydr angea macrophylla var, thunbergii and their structures were determined on t he basis of chemical and physicochemical evidence. In addition, isomerizati on reaction at the 3-positions of phyllodulcin and its glycosides was exami ned.