Facets of Click-Mediated Triazoles in Decorating Aminoacids and Peptides

Abstract

Decorating biomolecular building blocks, such as amino acids, to afford desired and tuneable photophysical/biophysical properties would allow chemical biologists to use them for several biotechnological and biosensing applications. While many synthetic methodologies have been explored in this direction, the advantages provided by click-derived triazole moieties are second to none. However, since the discovery, click-mediated triazoles have been majorly utilised as linkers for conjugating biomolecules, creating material with novel properties such as in polymers or drug conjugates. Despite exploring the profound role as linkers, click-mediated triazoles as an integral part of biomolecular building blocks have not been addressed. The 1,2,3-triazole, a transamide mimic, exhibits high aromatic stacking propensity, high associability with biomolecules through H-bonding, and high stability against enzymatic hydrolysis. Furthermore, the triazoles can be considered as donors useable for installation/modulation of the photophysics of a fluorophore. Therefore, triazole with a chromophoric unit may rightly be utilised as an integral part of the biomolecular building blocks to install microenvironment sensitive solvofluorochromic properties useable for biological sensing, studying inter-biomolecular interactions and bringing novel physicochemical properties onto a biomolecule. This feature article mainly focuses on the facets of click-derived triazole in designing novel fluorescent amino acids and peptides with particular emphasis on those wherein triazole acts as an integral part of the amino acids, i.e. the side chain, generating a new class of fluorescent unnatural triazolyl amino acids. Thus, the fluorescent triazolyl unnatural amino acids, peptidomimetics with such amino acids and aliphatic/aromatic triazolyl aminoacids as scaffolds for peptidomimetics are the central part. However, to start with, a brief history followed by the various other relevant facets of the triazoles as linkers in various fields ranging from therapeutics, material science, diagnostics, and bioconjugation to peptidomimetics are cited in brief. Additionally, the possible roles of CuAAC-mediated triazoles in shaping the future of bioorganic chemistry, medicinal chemistry, diagnostics, nucleoside chemistry and protein engineering have also been briefly discussed.