A novel derivative of green fluorescent protein chromophore (Z)-5-((E)-3-(4-hydroxyphenyl)allylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one was synthesised. The desired compound was prepared by the synthetic approach based on the use of carboxyimidate. Comparison of optical properties of the obtained compound and of the classical GFP chromophore analogue (Z)-5-(4-hydroxybenzylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one showed the shift of absorption and emission maxima to the long-wavelength region induced by the increase of the conjugated π-system in the benzylidene fragment.