Polyoxygenated bipyridine, pyrrolylpyridine, and bipyrrole alkaloids from Speranskia tuberculata

Five novel polyoxygenated alkaloids, speranculatines A-C (3-5), speranskilatine A (6), and speranberculatine A (7), have been isolated from Speranskia tuberculata. Compounds 3-5, 6, and 7, have bipyridine, pyrrolylpyridine, and bipyrrole skeletons, respectively. This is the first time that these three alkaloid structural types have been reported. The structures of 3-7 were elucidated by spectroscopic methods, including 2D NMR techniques and X-ray crystallographic analysis.