Echinothiophene, a novel benzothiophene glycoside from the roots of Echinops grijissii

The structure of echinothiophene, the beta-D-glucoside of a benzo[b]thiophene lactone bearing a novel skeleton, has been deduced from extensive NMR and MS studies. The compound undergoes facile epimerization at the C-6 center, perhaps through the enol 2. Molecular mechanics and dynamics calculations indicated that the structure 1 (C-6, R) is more stable than 3 (C-6, S).