H2-antihistaminics. 20. Structure-activity relationships in H2-receptor antagonists containing a 4-pyrimidone moiety.

In a series of 5,6-substituted 4- pyrimidones 1 a-v the H2-antihistaminic activity was determined (guinea-pig atrium) and lipophilicity data are given in form of Rmo -values. The influence of different substituents at position 5 or 6 of a pyrimidone moiety has been studied. Quantitative structure-activity analyses showed the importance of lipophilicity for drug activity. Additionally other physicochemical substituent-properties may play a major role.