Reinvestigation of structures of robustasides B and C, and isolation of (E)-2,5-dihydroxycinnamic acid esters of arbutin and glucose from the leaves of Grevillea robusta.

From the leaves of Grevillea robusta, compounds whose NMR data were superimposable on those of robustasides B and C were isolated along with two new compounds, (E)-2,5-dihydroxycinnamic acid esters of arbutin and D-glucose, and two known compounds, robustaside A and (E)-2,5-dihydroxycinnamic acid. The structures of robustasides B and C were not arbutin caffeates, being revised to arbutin (E)-2,5-dihydroxycinnamic acid esters.