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2-NHR-Pyridines (R=H, CH3) on the reaction with 3-halogenopropionic acids have been found to give 1-R-2-oxo-pyrido[2,1b][3,4]dihydro-pyrimidinium halides (1 (R=Me), 2 (R=H). Their structures have been confirmed by the H, C NMR spectra in DMSO-d6 solution using 2D NMR techniques (HETCOR, COSY, HMBC), FTIR spectra and B3LYP/6-31G(d,p) calculations. Only 2 on the reaction with propylene oxide is converted into betaine, 3-(2-aminopyridinium)-propionate (4). This suggest that in solution 1-H-2-oxo-pyrido[2,1b][3,4]dihydropyrimidinium chloride is in an equilibrium with N-carboxyethyl-2-amino-pyridinium chloride (2 3).

Synthesis, spectral and B3LYP analysis of 1-R-2-oxo-pyrido[2,1b][3,4]dihydro-pyrimidinium halides