New non-protienogenic fluorescent amino acids: Benzoxazol-5-yl-alanine derivatives containing acetylene unit. Synthesis, spectral and photophysical properties

New derivatives of non-proteinogenic amino acids benzoxazol-5-yl-alanine containing substituted acetylene derivative were synthesized according to Sonogashira coupling reaction. All of the obtained compounds are fluorescent. They are characterized by high or moderate molar absorption coefficients, large Stokes shifts, high fluorescence quantum yields and very high brightness. All of these parameters as well as the positions of absorption and emission bands depend on the type and size of substituent and the solvent polarity. Their high brightness enables working with low concentrations, simple and easy detection of spectral absorption and fluorescence analyzes. Moreover, amino acid part of studied compounds allow to use them as covalently attached to a peptide or protein fluorescent probes in biological system studies.