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Chaesang Ihm 《Tetrahedron letters》2007,48(18):3263-3266
Hetero dimer between tetrakis(m-ammonium)cavitand and tetrakis(dibenzo-25-crown-8)cavitand 5 was formed in CDCl3 at room temperature. The effects of solvent polarity and temperature on the stability of were studied and the thermodynamic parameters for the formation of are , ΔH0 = −67.4 kcal mol−1 and ΔS0 = −201.6 cal mol−1 K−1. 相似文献
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Neil Vasdev Raman Chirakal Rezwan Ashique Gary J. Schrobilgen Karen Gulenchyn 《Journal of fluorine chemistry》2003,121(1):9-14
The detection of 3-nitro-l-tyrosine has been used as a biomarker of “reactive nitrogen species” in biological matrices and has been an ongoing challenge in analytical chemistry. In this work, fluorine-18 labelled 5-fluoro-3-nitro-l-tyrosine (FNT) was synthesized as a potential radiotracer to probe the biological fate of 3-nitro-l-tyrosine. The synthesis of []FNT was carried out by reaction of []3-fluoro-l-tyrosine with NaNO3 in TFA solvent for 5 min at 4 °C. The radiochemical yield (RCY) of []FNT was 96±2% and []3-fluoro-l-tyrosine, was 29±1%, relative to []3-fluoro-l-tyrosine and []F2, respectively. The syntheses of []FNT were also accomplished by direct fluorination of 3-nitro-l-tyrosine with []F2 and by nitration of l-tyrosine with NaNO3, followed by fluorination, in TFA (4 °C) or anhydrous HF (−65 °C) solvent. The latter two synthetic routes produced []FNT in 13.5±1.5% RCY, within 1 h. Products were characterized by use of , and NMR spectroscopy and mass spectrometry. 相似文献