Chemical Synthesis of Coelenterazine and Its Analogs: New Route toward Four Segment-Couplings
摘要:
A novel and improved synthetic route includes four segment-couplings toward coelenterazine and its analogs as luminescent molecules. Regio- and chemo-selective cross coupling reactions using palladium catalysts with 5-iodo-3-bromo-2-aminopyrazine have enabled providing various aminopyrazine derivatives having different substituents. The improved synthesis of coelenterazine and its analogs employed advanced condensation with the aminopyrazines using various keto-acetal segments, which resulted in much higher yields to give the final imidazopyrazinone heterocycles than the previous method using keto-aldehydes.
Molecular mechanism of Symplectoteuthis bioluminescence—Part 4: Chromophore exchange and oxidation of the cysteine residue
作者:Chun-Ming Chou、Yu-Wen Tung、Minoru Isobe
DOI:10.1016/j.bmc.2014.05.044
日期:2014.8
Symplectin is one of the few photoproteins, which forms covalent bonds with the dehydro-coelenterazine (DCL) at the binding sites and the active site. This binding takes place through the SH's of the cysteine residues via conjugate addition reaction. This photoprotein contains the chromophore molecules at the binding cites first, and then moves to the active cite Cys-390 for the luminescence. The current study focuses on these dynamic aspects of the chromophore using the natural photoprotein by analyzing the fluorescence changing of the DCL chromophores analogs with 8-(4'-methoxyphenyI)- or 8-(2'-naphthyl)-group and 2-(2',4'-difluorophenyl)-group. Exchanges of these chromophores were monitored the fluorescence at slightly acidic media and also from the luminescence function observed at the optimum pH 7.8. The non-fluorescent naphthyl analogs was even proven to make the covalent bond formation at pH 6.0 and evidently to obtain the corresponding luminescent product amide by liquid chromatographic detection from the spent solutions. (C) 2014 Elsevier Ltd. All rights reserved.