Coelobillardin, an iridoid glucoside dimer from Coelospermum billardieri

A new iridoid glucoside dimer, coelobillardin (1), was isolated from the aerial parts of Coelospermum billardieri. Its structure has been elucidated on the basis of MS and NMR data. From a biogenetic point of view, this compound, which includes a cyclobutane basic core, should be considered as a [2+2] dimerization product of (E)-10-(4-hydroxycinnamoyloxy)loganin, which is the major iridoid isolated from the plant.