Synthesis and Fluorogenic Properties of Some 1-(Coumarin-7-yl)-4,5-dihydro-1,2,4-triazin-6(1H)-ones

Abstract

Herein, we have synthesized and tested a selected set of N1-(coumarin-7-yl)-4,5-dihydro-1,2,4-triazin-6(1H)-ones (8) incorporating masked a-amino acids within the triazinone skeleton as synthetic fluorogenic substrates for amino peptidases using human nasal epithelium that expressed aminopeptidases. These chiral triazinones, obtained via direct interaction of a-amino esters with N1-(coumarin-7-yl) nitrile imine (generated in situ from its hydrazonoyl chloride by the action of triethylamine), bear close resemblance to 7-amino-4-methylcoumarin (AMC) with labeled a-amino acids (AA-AMC's/7). The aminopeptidase activity of the synthesized compounds (0.125 and 0.5 mM) was compared with that of a model compound L-alanine-4-methylcoumaryl-7-amide (Ala-MCA), following in-house validation of the aminopeptidase activities of the human nasal primary culture. In comparison to the model aminopeptidase substrate (Ala-MCA), the synthesized compounds yielded fluorescent 7-amino-4-methylcoumarin following incubation with nasal epithelial cells. However, the yield was significantly lower than was observed for the control compound.