Evolvulin III, a new resin glycoside isolated from Evolvulus alsinoides

A new resin glycoside named evolvulin III (1) was isolated from the whole plants of Evolvulus alsinoides. Compound 1 was identified as a pentasaccharide macrolactone with a distinctive 3S,11R,14R-trihydroxyhexadecanoic acid acting as the aglycone. Interestingly, evolvulin III (1) is interconvertible with a known resin glycoside, namely, evolvulin II (2), by intramolecular transesterification. The structure of compound 1 was determined by spectroscopic data and the chemical analysis of the equilibrium mixture of 1 and 2.