Pyrimidine derivatives

A compound of the formula ##STR44## R.sub.5a is a single bond or --(CH.sub.2).sub.m --, Y.sub.a is biphenyl unsubstituted or substituted by at least one member of the group consisting of hydroxyl;

• halogen;
• alkyl and alkoxy of 1 to 4 carbon atoms;
• trifluoromethyl;
• cyano;
• nitro, amino;
• carbamoyl;
• free, salified or esterified carboxy;
• tetrazolyl;
• isoxazolyl;
• phenoxy;
• benzyl;
• R.sub.1a is selected from the group consisting of alkyl, alkenyl, alkynyl, alkylthio of up to 10 carbon atoms, or cycloalkyl of 3 to 7 carbon atoms, all unsubstituted or substituted by at least one member of the group consisting of halogen, hydroxyl, alkoxy of 1 to 6 carbon atoms, alkylthio, acyl, free, salified or esterified carboxy, formyl, cyano, nitro, amino unsubstituted or substituted by one of two individual alkyl of 1 to 6 carbon atoms, cyclo-alkyl of 3 to 7 carbon atoms and aryl unsubstituted or substituted by at least one member of the group consisting of halogen, hydroxyl, alkyl, alkenyl and alkoxy of up to 6 carbon atoms, haloalkyl, alkylthio, haloalkylthio, haloalkoxy, aryloxy, aryl-alkoxy, carbamoyl, acyl, acyloxy, free, salified or esterified carboxy, tetrazolyl, cyano, nitro, amino unsubstituted or substituted by at least one alkyl of 1 to 6 carbon atoms and phenyl unsubstituted or substituted by at least one member of the group consisting of halogen, hydroxyl, alkyl and alkoxy of 1 to 4 carbon atoms, trifluoromethyl, free, salified or esterified carboxy and tetrazolyl, R.sub.2a is chosen from the group consisting of hydrogen, halogen, hydroxyl, mercapto, cyano, nitro, formyl, benzoyl, acyl of 1 to 6 carbon atoms, alkyl, alkenyl, alkoxy, alkylthio of up to 10 carbon atoms, phenyl, phenoxy, naphthyl, benzyl, phenylthio, biphenyl, biphenylmethyl and indole, all unsubstituted or substituted by at least one member of the group consisting of halogen, hydroxyl, alkoxy of 1 to 4 carbon atoms, trifluoromethyl, cyano, acyl, formyl, free, salified or esterified carboxy, tetrazolyl, isoxazolyl and pyridyl and R.sub.3a is alkyl substituted with carboxy or esterified carboxy.