The structures of three alkaloids isolated from Guatteria dielsiana, 6-methoxyonychine, dielsine and dielsinol, originally described as 1-azafluoren-9-ones, are revised to 4-azafluoren-9-ones on the basis of previous synthetic work and current studies on alkaloids of the Annonaceae. Synthetic 6-methoxyonychine (6-methoxy-1-methyl-4-azafluoren-9-one) isshown to be id. © 1987.