| abstract |
A carboxylic acid derivative of the formula I, where R is carboxy; X is nitrogen or CR14, where R14 is hydrogen, or CR14 forms together with CR3 a 5- or 6-membered alkylene ring in which one methylene group can be replaced by oxygen; R2 and R3 are independently C1-C4-alkyl or C1-C4-alkoxy; R4 and R5 are independently phenyl or halophenyl; R6 is C1-C8-alkyl, the radicals being substituted by hydroxyl, carboxyl, H2N-CO- or cyano; Z is oxygen. |