Two new quaternary alkaloids, alstogustine and 19-epialstogustine, have been isolated from the stem bark of Alstonia angustifolia. The structure of 1 was determined by means of spectroscopic methods and X-ray analysis. The structure of 19-epialstogustine could be elucidated by comparison of its spectra with those of alstogustine and confirmed by chemical correlation. The absolute configurations of both alkaloids were established by direct comparison of their CD spectra with that of the known alkaloid, akuammicine. © 1989.