Compound of general formula wherein Y is selected from a group consisting of nitrogen; N-oxide; R 1 is selected from the group consisting of H; halogen; -OH; -N 3; -(CH 2) n N 3, wherein n is an integer in the range of from 1 to 3; -NR 2, wherein R is independently selected from H or C 1 to C 6 alkyl, which may be branched or linear; -(CH 2) n NR 2, wherein n and R are as defined above; C 6 to C 10 aryl, which can optionally be substituted with -NH 2, -NO 2, -N 3, -COOH, -CH 2 Cl and/or -CH 2 COOH; C 7 to C 10 arylalkyl, which can optionally be substituted with -NH 2, -NO 2, -N 3, -COOH, -CH 2 Cl and/or -CH 2 COOH; -CF 3; -COOR, wherein R is as defined above; -(CH 2) n COOR, wherein n and R are as defined above; -CH 2 CH(OMe) 2; -SH; -SO 3 H; -SO 2 Ar, wherein Ar is phenyl; NO 2; R 2 is wherein n is an integer in the range of from 1 to 3; A are independently selected from the group consisting of H; -(CH 2) n COOH, wherein n is an integer from 1 to 3; -CH(CH 3)COOH; -CH((CH 2) n CH 3)COOH, wherein n is as defined above; -CH 2 P(=O) 2, wherein R is as defined above; -CH((CH 2) n COOH)COOH, wherein n is an integer from 1 to 3; -CH((CH 2) n NH 2)COOH, wherein n is an integer from 1 to 3; -CH 2 C(=O)(NH 2); -CH 2 C(=O) -CH 2 COOH; -CH 2 P(=O) (Ar), wherein Ar is phenyl, which can optionally be substituted with C 1 to C 6 alkyl; Z is selected from a group consisting of wherein R 3 is R 4 is selected from the group consisting of H; halogen; piperidinyl; trimethylsilyl; triisopropylsilyl; phenyl; C 1 to C 6 alkyl, which may be branched or linear; C 3 to C 6 cycloalkyl; -CF 3; -(CH 2) n NHR 6, wherein n is an integer in the range of from 1 to 3 and R 6 is selected from H, fluorenylmethyloxycarbonyl, tertbutyloxycarbonyl and benzyloxycarbonyl; -C(CH 3) 2 (NHR 6), wherein R 6 is as defined above; adamantyl; -(CH 2) n COOH, wherein n is as defined above; C 6 to C 10 aryl, which can optionally be substituted with -NH 2, -NO 2, -N 3, -COOH, -CH 2 Cl and/or -CH 2 COOH; R 5 is R 1 or wherein R 4 is as defined above; and/or R 2 and R 3 together form a 1,2,3-triazole group of formula wherein R 4 is defined above; with the proviso that at most one A is H. Y is selected from a group consisting of nitrogen; N-oxide; R 1 is selected from the group consisting of H; halogen; -OH; -N 3; -(CH 2) n N 3, wherein n is an integer in the range of from 1 to 3; -NR 2, wherein R is independently selected from H or C 1 to C 6 alkyl, which may be branched or linear; -(CH 2) n NR 2, wherein n and R are as defined above; C 6 to C 10 aryl, which can optionally be substituted with -NH 2, -NO 2, -N 3, -COOH, -CH 2 Cl and/or -CH 2 COOH; C 7 to C 10 arylalkyl, which can optionally be substituted with -NH 2, -NO 2, -N 3, -COOH, -CH 2 Cl and/or -CH 2 COOH; -CF 3; -COOR, wherein R is as defined above; -(CH 2) n COOR, wherein n and R are as defined above; -CH 2 CH(OMe) 2; -SH; -SO 3 H; -SO 2 Ar, wherein Ar is phenyl; NO 2; R 2 is wherein n is an integer in the range of from 1 to 3; A are independently selected from the group consisting of H; -(CH 2) n COOH, wherein n is an integer from 1 to 3; -CH(CH 3)COOH; -CH((CH 2) n CH 3)COOH, wherein n is as defined above; -CH 2 P(=O) 2, wherein R is as defined above; -CH((CH 2) n COOH)COOH, wherein n is an integer from 1 to 3; -CH((CH 2) n NH 2)COOH, wherein n is an integer from 1 to 3; -CH 2 C(=O)(NH 2); -CH 2 C(=O) -CH 2 COOH; -CH 2 P(=O) (Ar), wherein Ar is phenyl, which can optionally be substituted with C 1 to C 6 alkyl; Z is selected from a group consisting of wherein R 3 is R 4 is selected from the group consisting of H; halogen; piperidinyl; trimethylsilyl; triisopropylsilyl; phenyl; C 1 to C 6 alkyl, which may be branched or linear; C 3 to C 6 cycloalkyl; -CF 3; -(CH 2) n NHR 6, wherein n is an integer in the range of from 1 to 3 and R 6 is selected from H, fluorenylmethyloxycarbonyl, tertbutyloxycarbonyl and benzyloxycarbonyl; -C(CH 3) 2 (NHR 6), wherein R 6 is as defined above; adamantyl; -(CH 2) n COOH, wherein n is as defined above; C 6 to C 10 aryl, which can optionally be substituted with -NH 2, -NO 2, -N 3, -COOH, -CH 2 Cl and/or -CH 2 COOH; R 5 is R 1 or wherein R 4 is as defined above; and/or R 2 and R 3 together form a 1,2,3-triazole group of formula wherein R 4 is defined above; with the proviso that at most one A is H.