The carbon-13 nuclear magnetic resonance chemical shift assignments for several canthin-6-one alkaloids isolated from Ailanthus altissima SWINGLE and Picrasma quassioides BENNET, made on the basis of two-dimensional ¹³C-¹H chemical shift correlation, ¹³C-¹H heteronuclear couplings, and long-range selective ¹H decoupling experiments, are reported.