Synthesis Of A Novel Coumarin-quinazolinone Two-photon Fluorescent Probe For Celling Imaging Assay

Biological imaging has become an important strategy for understanding various biological processes in living cells and tissues with minimum perturbation.Compared to one-photon fluorescent imaging,two photon?TP?fluorescent imaging is a more attractive tool because of the increased penetration depth,higher spatial resolution,lower background fluorescence and reduced phototoxicity.In order to obtain high brightness TP fluorescence imaging in vivo,the TP fluorophores with large TP action cross-section?TPACS?value??37??max?are very desirable.Generally,the enhancement of intramolecular charge transfer?ICT?efficiency and extending conjugate structure could efficiently improve the TPACS of fluorophores.However,it is a dilemma that enlarging conjugate structure or increasing the push-pull character of TP fluorophores often shows poor biocompatibility,high toxicity or fluorescence quenching in physiological conditions.1.We synthesis a novel coumarin-quinazolinone?CQ?conjugate with the large TP action cross-section value by reaction of 7-diethylaminocoumarin-3-al and2-aminobenzamide.A novel scaffold based on the conjugate of coumarin and quinazolinone?CQ?exhibited brilliant TP fluorescence properties?action cross-section value?37??max=299 GM and TP action cross section per molecular weight?37??max/MW=0.83?in water.Besides,the reversible locking with intramolecular hydrogen bond between quinazolinone moiety and coumarin moiety was can significantly enhance the TP brightness of CQ.Therefore,the two-photon fluorophore CQ can be well used to the fields of two-photon cell imaging.2.CQ was further engineered with p-nitrobenzyl moiety to afford 2-?7-?diethylamino?-2-oxo-2H-chromen-3-yl?-3-?4-nitrobenzyl?quinazolin-4?3H?-one?NBCQ?.The structure of the probe NBCQ was identified by ¹H NMR,¹³C NMR,HR-MS and ¹H-¹H COSY.The probe NBCQ attached a nitro group to CQ scaffold has good selectivity,perfect biocompatibility and high sentivity for mitochondria nitroreductase?NTR?imaging in normoxia and hypoxia,which proved to be a“off-on”NTR fluorescent probe.In summary,this robust TP fluorescent scaffold CQ provides a novel platform for the development of TP fluorescent probes as molecular tools in biological systems.