1. Structural Characterization by NMR Spectroscopy. Conventional and two dimensional studies of the alkaloid undulatine have been compared. 2. Nitrogen-15 NMR Studies: N-15 Spectra of the tautomers of 3,5-dipyrrolidinophenol have revealed an unsuspected component. 3. Poison Frog Toxins: A structure has been assigned to be alkaloid 239AB.