For the biological activity evaluation, 1 mM stock solutions of all compounds were prepared in dimethylsulfoxide (DMSO). H-NMR spectra of conjugates 4, 24, 28, 33 and 39 in DMSO-d6, recorded at 25°C 5 min and 100 days after sample preparation showed no modifications (see Supporting information), demonstrating particularly good stability of the compounds in this highly complexing solvent.