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 CF 3 COOH under standardized conditions as the mono‐cations. The chemical shifts of the vinyl‐, methyl‐ and NH 2 ‐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(NH 2 ) and p K a values.