Fluorescent conjugates of PSMA-targeting ligand with cyanine dyes: synthetic approaches and photochemical properties

Fluorescent conjugates of carbocyanine dyes with a ligand selective to prostate-specific membrane antigen were accessed by either peptide synthesis or CuAAC methodology, with the latter being more promising. The introduction of a propargylamino moiety at the meso-position of the polymethine chain of the fluorophores afforded the alkyne counterparts for the CuAAC reaction toward the ligand bearing azido group. The photochemical studies showed that the quantum yields of the obtained conjugates exceeded those for the unmodified fluorophores by more than 20 times.