Synthesis and Photophysical Properties of Aromatic L‐Amino Acids Functionalized Tricyanofuran (TCF) Derivatives

Abstract

The fluorescent labeling using chemical dyes are extensively used in biological and medicinal research. The amino acid incorporated chromophores with significant fluorescence properties are commonly used as fluorescent imaging agents allowing to tap a wide range of biological and biophysical processes. The dyes with large size can disrupt protein folding and function. Therefore, the development of new fluorophores remains a challenging task for the design of new fluorescent probes. To achieve the desired applications, small fluorescence chromophore is required. Herein, inspired by the earlier report on fluorescent fluorophore, we report the new class of small organic chromophores containing (E)-2-(4-(4-aminostyryl)-3-cyano-5,5-dimethylfuran-2(5H)-ylidene) malononitrile (TCF-1) that can be conjugated with the natural aromatic amino acids i.e. L-phenylalanine, L-tryptophan and L-tyrosine.  In this connection, a series of six TCF-1 fluorescently labeled aromatic amino acids were designed and synthesized. At first, the theoretical calculations were performed to establish the frontier molecular orbitals and energy band gap. Further, the synthesized aromatic amino acid functionalized TCF-1 was evaluated with respective to their spectroscopic properties using UV-Vis absorption and fluorescence spectroscopic techniques. The promising photophysical properties of Boc protected derivatives Boc-L-Phe-TCF-1, Boc- L-Tyr-TCF-1 and Boc- L-Trp-TCF-1 were observed in different solvents. Moreover, the Boc deprotected derivatives L-Phe-TCF-1, L-Tyr-TCF-1 and L-Trp-TCF-1 showing different photophysical properties at various pH ranging from 3 to 11.