Tetrahydroisoquinoline-monoterpene and iridoid glycosides from Alangium lamarckii

From the water soluble fraction of the dried fruits of Alangium lamarckii, four tetrahydroisoquinoline-monoterpene glycosides, 6- O-methyl- N-deacetylisoipecosidic acid, 7- O-methyl- N-deacetylisoipecosidic acid, 6,7-di- O-methyl- N-deacetylisoipecosidic acid and 6″- O-α- d-glucopyranosyl-6- O-methyl- N-deacetylisoipecosidic acid, and an iridoid glycoside, 6′- O-α- d-glucopyranosylloganic acid, were isolated, together with six known compounds. The structures of the previously unknown compounds were determined by spectroscopic and chemical means. The significance of these glucosides in the biogenesis of Alangium alkaloids is discussed; 6- O-methyl- N-deacetylisoipecosidic acid was also chemically converted into 10- O-demethylprotoemetine and dihydroisoalangine.