13C NMR Study of Dihydropyrimidinedione and Dihydropyrimidine-2-thione Derivatives

The C-13 NMR spectral data for 18 dihydropyrimidinediones and their 2-thio analogues are presented. The influence of substituents on the shielding of neighbouring atoms was analysed and the resonances were unambiguously assigned. C-13 NMR spectroscopy was shown to be useful for structural determination of dihydropyrimidinediones and thioanalogues and allowed the facile distinction of otherwise similar compounds from the two classes. (C) 1997 by John Wiley & Sons, Ltd.