Patent ID: 7709470

Claim:
A compound of formula (I) or a pharmaceutically acceptable salt thereof, wherein R1 and R2, independently of each other, represent hydrogen, or C 1 -C 7 -alkyl, or R1 and R2 together with the carbon atoms of the phenyl ring to which they bind form a 5-, 6- or 7-membered cycloalkyl ring, which ring may optionally be substituted by one or more C 1 -C 7 -alkyl groups, which alkyl groups may also together form one or more 3-, 4-, 5-, 6- or 7-membered rings; R3 represents —CN, —CO— R 5 , or hydrogen, provided that, if R3 is hydrogen, R4 must represent C 3 -C 7 -alkenyl or C 3 -C 7 -alkynyl; R 5 represents aryl, or alkyl being unsubstituted or substituted by halogen, cyano, nitro, hydroxy, C 1 -C 7 -alkoxy, carboxyl or aryl; R4 represents C 1 -C 7 -alkyl, C 2 -C 7 -alkenyl or C 2 -C 7 -alkynyl or R4 represents C 2 -C 7 -alkanoyl; and X represents ligand (a), wherein Y may be in ortho, meta or para position and wherein Y represents carboxyl, C 1 -C 7 -alkoxy-carbonyl, aryloxycarbonyl, tetrazolyl, SO 3 H or P(O)(OH) 2 ; and wherein Z represents hydrogen or a substituent selected from the group consisting of C 1 -C 7 -alkyl, C 1 -C 7 -alkoxy, halogen, CF 3 , cyano and NO 2 .