Compounds for the detection of senescent cells

A compound that functions as a senescent cell detector of the general formula (1) or (2), shown below:

• wherein:
• R1 and R2 are each independently selected from:
• i) hydrogen, with the proviso that R2 is not hydrogen in general structure (1) above and only one of R1 and R2 can be hydrogen in general structure (2) above.
• ii) an optionally substituted (1-10C)alkyl group;
• iii) an optionally substituted aryl group;
• iv) an optionally substituted (1-10C)alkyl-aryl group;
• v) an optionally substituted aryl-(1-10C)alkyl group;
• or
• vi) R1 and R2 are linked so as to form part of a spiranic cycloalkane group, selected from cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or adamantanyl;
• R3 is hydrogen or (1-10C)alkyl group;
• R4 is hydrogen, or one or more of the following substituents:
• i) a halogen selected from F, Cl, Br and I;
• ii) NO2;
• iii) CF3,
• iv) SCH3;
• v) an optionally substituted (1-5C)alkyl group;
• vi) a (1-10C)alkoxy group which optionally comprises one or more heteroatoms;
• and
• Z is either Z1 or —Ar—Z1— and Z1 is selected from OH, NH2, O(CH2)nCH2OH, (CH2)qOH or COOH, wherein n is an integer selected from 1 to 9, and wherein q is an integer selected from 1 to 4, and wherein Ar is an aryl group optionally substituted with one or more of the following substituents halogen, (1-6C)alkyl, (1-6C)alkenyl or (1-5C)alkoxy.