Synthesis of purine nucleoside—amino acid conjugates and their photophysical properties

2,6-Bis-(1,2,3-triazol-1H-1-yl)purine nucleosides react at C(6) with the N- and S-termini of various amino acids by expelling the corresponding 1,2,3-triazole as a leaving group in nucleophilic aromatic substitution reaction. This gives rise to a novel type of conjugate between purine nucleosides and amino acids. The obtained amino acid—derived 6-amino-2-(1,2,3-triazol-1H-1-yl)-purine derivatives showed useful levels of fluorescence with quantum yields up to 38% and Stokes shifts up to 91 nm. Glutathione and a cysteine-containing nonapeptide selectively reacted with their S-termini and produced the expected C(6) conjugates in good to excellent yields. [Display omitted]