Synthesis And Properties Of Isodoline Nitroxide-Porphyrins

Electron paramagnetic resonance （EPR） spectroscopy is the most direct and powerfulmethod for the detection and identification of free radicals and other species with unpairedelectrons. Based on the EPR techniques, electron paramagnetic resonance imaging （EPRI）has received increasing attention as an important new clinical tool for non-invasivethree-dimensional spatial mapping of tissue oxygenation and potentially multidimensionalimaging of the spatial distribution of paramagnetic species such as free radicals inbiological tissues using several combinations of magnetic field gradients. Moreover, EPRIcan be used to study the tumor hypoxia, tissue heterogenicity with respect to oxygen andredox status, and vascular deficiencies in vivo. However, the naturally occurringparamagnetic species amenable for EPRI in the body are below the detection limits andmostly possess the short half-life. It is normally necessary to introduce prior intravenous orintramuscular infusion of stable or slowly metabolizable non-toxic water-solubleparamagnetic materials, or stable implantable particulate materials as spin probes（0.1mmol/kg） into the system.However, the commercially used nitroxides, such as2,2,6,6-tetramethylpiperidine-1-yloxyl （TEMPO） and5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CT_MIO), arethe low molecular weight compounds and have some limitations for spin probes due totheir weak water solubility, rapid excretion and nonspecific organ or tissue selectivity inthe body. An approach to improve the accuracy of EPRI and EPR oximetry is the designand synthesis of new spin labels with tissue or organ-targeting or selective-specific EPRand good chemical characteristics, such as high water solubility, superior EPR linewidth,and resistance to physiological reduction. In recent years, water-soluble specifically-designed nitroxides have led to low frequency EPRI to have a promising future to detectgreater sampling depths in clinical studies.In the thesis, the principle, classification, and research progress of EPRI spin probesand porphyrins were reviewed in detail herein.5,10,15-Trisphenyl-20-（1’,1’,3’,3’-tetramethylisoindolin-2’-yloxyl-5’-yl）porphyrin (TPT_MIOP) and5,15-bisphenyl-10,20-bis（1’,1’,3’,3’-tetramethylisoindolin-2’-yloxyl-5’-yl）por-phyrin (BPBT_MIOP) were synthesized by the cyclization reaction between5-（4’-phenyl） dipyrromethane and5-formyl-1,1,3,3-tetramethyl-isoindolin-2-yloxyl (FT_MIO) and furtherused to make a corresponding water-soluble5,10,15-Tris[（4’’-sulfuricacid）phenyl]-20-（1’,1’,3’,3’-tetrameth-yl-isoindolin-2’-yloxyl-5’-yl）porphyrin (TSPT_MIOP) and5,15-bis[（4’’-sulfuricacid）phenyl]-10,20-bis（1’,1’,3’,3’-tetramethyl-isoindolin-2’-ylox-yl-5’-yl）porphyrin(BSPBT_MIOP), respectively. These porphyrin-bound isoindoline nitroxides were reactedwith manganese chloride to produce the corresponding manganese-porphyrin complexes.The porphyrins and manganese-porphyrin complexes were characterized by1H NMR, UV,IR, etc. And their properties of EPR and fluorescent properties in vitro were also evaluated.Fluorescence-suppression was observed in the free base monoradical porphyrins, whilst thefree base biradical porphyrins exhibited highly suppressed fluorescence about three timesgreater than the monoradical porphyrins. The EPR spectra of porphyrin-bound isoindolinenitroxides all exhibited the hyperfine splittings and characteristic EPR spectra oftetramethyl isoindoline nitroxides, with typical nitroxide g-values and nitrogen isotropichyperfine coupling constants. Therefore these porphyrins and manganese-porphyrincomplexes may be considered as novel potential tumor-targeting spin probes for electronparamagnetic resonance （EPR）.5,10,15-Tris（4’’-carboethoxymethyleneoxyphenyl）-20-（1’,1’,3’,3’-tetramethylisoindolin-2’-yloxyl-5’-yl）porphyrin (TECPT_MIOP) and5,15-bis（4’’-carboethoxymethyleneoxyphe-nyl）-10,20-bis（1’,1’,3’,3’-tetramethylisoindolin-2’-yloxyl-5’-yl）porphyrin (BECPBT_MIOP)were synthesized by the Lindsedy cyclization reaction between5-（4’-carboethoxymethyl-eneoxyphenyl）dipyrromethane and5-formyl-1,1,3,3-tetramethylisoindolin-2-yloxyl （FTMIO） and further used to make a corresponding water-soluble5,10,15-tris[(4’’-carboxymethyleneoxyphenyl]-20-（1’,1’,3’,3’-tetramethyl-isoindolin-2’-yloxyl-5’-yl）porphyrin(TCPT_MIOP) and5,15-bis[（4’’-carboxymethyleneoxyphenyl）phenyl]-10,20-bis（1’,1’,3’,3’-tetr-amethylisoindolin-2’-yloxyl-5’-yl）porphyrin (BCPBT_MIOP), respectively. These porph-yrin-bound isoindoline nitroxides were reacted with manganese chloride to produce thecorresponding manganese-porphyrin complexes. The porphyrins and manganese-porphyrin complexes were characterized by1H NMR, UV, IR, etc. And their properties ofEPR and fluorescent properties in vitro were also evaluated. Fluorescence-suppression wasobserved in the free base monoradical porphyrins, whilst the free base biradical porphyrinsexhibited highly suppressed fluorescence about three times greater than the monoradical porphyrins. The EPR spectra of porphyrin-bound isoindoline nitroxides all exhibited thehyperfine splittings and characteristic EPR spectra of tetramethyl isoindoline nitroxideswith typical nitroxide g-values and nitrogen isotropic hyperfine coupling constants and anoxygen-concentration-dependent line width broadening. Therefore these porphyrins andmanganese-porphyrin complexes may be considered as novel potential tumor-targetingspin probes for electron paramagnetic resonance （EPR）.