On the basis of physical and chemical studies nudiflorine, the new pyridone alkaloid isolated from the leaves of Trewia nudiflora Linn. has been assigned the 1-methyl-5-cyano-2-pyridone (II) structure which has been confirmed by an unambiguous synthesis. Nudiflorine is an isomer of ricinidine (I, R = H; R1 = CN) the demethoxylation product of ricinine (I, R = OCH3; R1 = CN). Biogenesis of nudiflorine and ricinidine has been discussed and their simultaneous synthesis accomplished. © 1966.