Tricalysiosides A-G: rearranged ent-kauranoid glycosides from the leaves of Tricalysia dubia.

Seven rearranged ent-kaurane glycosides, named tricalysiosides A-G (1-7), were isolated from the leaves of Tricalysia dubia collected on Okinawa Island. Their C-18 and 19 methyls were found to have rearranged to form an alpha,beta-unsaturated gamma-lactone ring, with other functional groups remotely located only on C-15, -16, and -17 of the five-membered ring. Information available from various kinds of two-dimensional NMR spectra was limited and insufficient to allow total characterization of the structures. Finally, using X-ray crystallographic analysis, the structure of tricalysioside A (1) was determined to be 4-nor-18-homo-ent-kauran-4(18)-en-15beta,16beta,17-triol-3beta,19-olide 16-O-beta-D-glucopyranoside (1). On the basis of the crystal structure of 1, the structures of the other tricalysiosides (2-7) were also established.