The invention provides compounds of the general formula (I)
or a physiologically acceptable salt, solvate or non-toxic metabolically labile ester thereof wherein
R 1 represents a hydrogen atom or a halogen atom or a group selected from C 1-6 alkyl, C 2 - 6 alkenyl, fluoroC 1-6 alkyl, C 1-6 alkoxy, -CHO, -C0 2 H or ―COR 2 ; Ar represents the group
R 2 represents a group selected from C 1-6 alkyl, C 2-6 alkenyl, C 1-6 alkoxy or the group ―NR 10 R11 ; R 3 represents a group selected from ―CO 2 H, -NHS0 2 CF3 or a C-linked tetrazolyl group ; R 4 and R 5 , which may be the same or different, each independently represent a hydrogen atom or a halogen atom or a C 1-6 alkyl group ; Het represents an N-linked imidazolyl group optionally substituted at the 2-position by a C 1-6 alkyl, C 2-6 alkenyl or a C 1 - 6 alkylthio group, the imidazolyl group optionally being substituted at the 4- and 5- positions by one or two further substituents selected from a halogen atom or group selected from cyano, nitro, C 1-6 alkyl, C 2-6 alkenyl, fluoroC 1-6 alkyl, ―(CH 2 ) m R 6 , ―(CH 2 )nCOR 7 or ―(CH 2 ) p NR 8 COR 9 ; R 6 represents a hydroxy or C 1 - 6 alkoxy group ; R 7 represents a hydrogen atom or a group selected from hydroxy, C 1-6 alkyl, C 1-6 alkoxy, phenyl, phenoxy or the group -NR 10 R 11 ; R 8 represents a hydrogen atom or a C 1-6 alkyl group ; R 9 represents a hydrogen atom or a group selected from C 1-6 alkyl,C 1-6 alkoxy, phenyl, phenoxy or the group -NR 10 R 11 ; R 10 and R 11 , which may be the same or different, each independently represent a hydrogen atom or a C I - 4 alkyl group or -NR 10 R 11 forms a saturated heterocyclic ring which has 5 or 6 ring members and may optionally contain in the ring one oxygen atom; m represents an integer from 1 to 4 ; n represents an integer from 0 to 4; and p represents an integer from 1 to 4. The compounds may be used in the treatment or prophylaxis of hypertension and diseases associated with cognitive disorders.