Protonenresonanzspektren von Pteridinen V. 2-Amino-4-oxo-3,4-dihydropteridine

The proton magnetic resonance spectra of 20 pteridines, i.e. 2-amino-4-oxo-3,4-dihydropteridine and 19 derivatives, have been measured at 100 Mc/s and 60 Mc/s in CF₃COOH under standardized conditions as the mono-cations. The chemical shifts of the vinyl-, methyl- and NH₂-protons are tabulated, and some typical spectra are illustrated. The influence of the substrate concentration and of solvent effects upon the NH-signals have been studied. Protonation always takes place at N(1) or N(3), and an attempt is made to correlate δ(NH₂) and pK_a values.