Dopaol 2-keto- and 2,3-diketoglycosides from Chelone obliqua.

Two unique 2-(3,4-dihydroxyphenyl)ethyl glycosides, namely, dopaol beta-D-2-ketoglucopyranoside and dopaol beta-D-2,3-diketoglucopyranoside, were isolated from Chelone obliqua together with the iridoid glucoside catalpol, dopaol beta-D-glucopyranoside, descaffeoylverbascoside, and verbascoside. Glycosides with a diketosugar have not so far been isolated from natural sources.