Polyoxygenated Bipyridine, Pyrrolylpyridine, and Bipyrrole Alkaloids from <i>Speranskia tuberculata</i>

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