Indole Alkaloids from Alstonia angustifolia.

From the stem bark of ALSTONIA ANGUSTIFOLIA, eleven alkaloids were isolated. Seven of them are known ones: echitamine ( 1), N(b)-demethylechitamine ( 2), pseudoakuammigine ( 3), tubotaiwine ( 5), akuammicine ( 6), N(b)-beta-methylantirhine ( 12), and N(b)-methylakuammidine ( 13). The four others, pseudoakuammigine N-oxide ( 4), akuammicine N-oxide ( 7), N(b)-demethylalstogustine ( 8), and N(b)-demethylalstogustine N-oxide ( 11), are new alkaloids. Their structures were determined by means of spectroscopic analysis and chemical correlation with known alkaloids.