Synthesis And Properties Of Boron And Phosphorus Substituted Xanthenes

Recently,fluorescence bioimaging technology has become more and more important due to its simple operation,straight forward results,and high sensitivity in bioimaging both in vivo and in vitro.Fluorescent probes are fundermental for fluorescence bioimaging.Among the extensively applied fluorescent probes,probes based on small organic molecules are favored due to their simple,specific structures and extensive application.Recent studies have shown that the introduction of main group elements into the traditional xanthene framework can improve its photochemical properties.For example,replacement of the bridging oxygen by boron and phosphorus atoms with unique electronic structures,has resulted in the decreased LUMO energy levels and red-shifted spectra,which are extremely favored for biological imaging in vivo.In this dissertation,we designed a new synthetic route for boron-substituted rhodamine and boron-substituted fluorescein.We have further synthesized a boron-substituted rhodamine fluorescent probe MMBR and a phosphor-substituted rhodamine probe PR-SNAP.Spectral analysis and cellular imaging experiments with probe MMBR have proved that the probe can sensitively detect H₂O₂ and HOCl in vivo.Probe PR-SNAP was used for spontaneous blinking super-resolution imaging with high positioning accuracy.The specific content includes the following:(1)Synthesis and properties of boron-substituted rhodamine and boron-substituted fluorescein dyesThe traditional route for the synthesis of boron-substituted xanthenes suffered from some problems,including cumbersome operation,multiple steps,low yield,difficult post-treatment,and multiple-steps of using high-activity organometallic lithium reagents.We designed a new synthetic route on this basis,which has the advantages of higher overall yield,safer operation,simpler post-processing,and wider application range.In addition,we analyzed the performance of the probes,and the unique boron-substituted xanthenes provide a new idea for the development of ratiometric sugar detection fluorescent probes.(2)Bioimaging of boron-substituted rhodamine based ratiometric fluorescent probe for HOCl and H₂O₂Reactive oxygen species(ROS)are closely related to oxidative stress and various diseases in vivo.There are many probes that only respond to single type of ROS.However,in complex biological systems,signal transduction is often associated with a group of ROS and often transforms into each other through intracellular reactions.We designed and synthesized a ratiometric fluorescent probe boron-substituted rhodamine that simultaneously monitors HOCl and H₂O₂ with high selectivity,sensitivity,reliable photostability,solubility,and biocompatibility.(3)Phosphorus-substituted rhodamine fluorescent probe for spontaneously blinking super-resolution imagingSuper-resolution microscopy technology can break the physical diffraction limit and detect subcellular structures with high accuracy.Combining the unique properties of phosphorous-substituted rhodamine dyes with the imaging principle of super-resolution fluorescence microscopy,we chose the stochastic optical reconstruction microscopy(STORM)for fluorescence imaging experiments.In this work,we designed and synthesized a spontaneously blinking phosphor-substituted rhodamine fluorescent probe,which has significant selectivity and good reversibility to glutathione(GSH)in super-resolution fluorescence imaging.In this dissertation,we mainly focus on the development of a new synthetic method for boron-substituted xanthenes and the functional construction of boron-substituted and phosphorus-substituted xanthenes fluorescent probes,and carefully study the the photophysical and chemical properties of boron-substituted and phosphorus-substituted xanthenes.The probe MMBR is used to simultaneously detect H₂O₂ and HOCl in vivo,and the probe PR-SNAP is used for super-resolution fluorescence imaging,which has high positioning accuracy.