Intermediates in the reduction of the antituberculosis drug PA-824, (6S)-2-nitro-6-{[4-(trifluoromethoxy)benzyl]oxy}-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazine, in aqueous solution
作者:Robert F. Anderson、Sujata S. Shinde、Andrej Maroz、Maruta Boyd、Brian D. Palmer、William A. Denny
DOI:10.1039/b801859f
日期:——
The reduction chemistry of the new anti-tuberculosis drug PA-824, together with a more water-soluble analogue, have been investigated using pulse and steady-state radiolysis in aqueous solution. Stepwise reduction of these nitroimidazo-dihydrooxazine compounds through electron transfer from the CO2˙− species revealed that, unlike related nitroimidazoles, 2-electron addition resulted in the reduction of the imidazole ring in preference to the nitro group. In mildly acidic solution a nitrodihydroimidazo intermediate was formed, which was reduced further to the amine product. In both alkaline and neutral solution, an intermediate produced on 2-electron reduction was resistant to further reduction and reverted to parent compound on extraction or mass spectrometric analysis of the solution. The unusual reduction chemistry of these nitroimidazole compounds, exhibiting ring over nitro group reduction, is associated with alkoxy substitution in the 2-position of a 4-nitroimidazole. The unique properties of the intermediates formed on the reduction of PA-824 need to be considered as playing a possible role in its bactericidal action.
我们利用水溶液中的脉冲和稳态辐射分解法研究了新型抗结核药物 PA-824 和一种水溶性更强的类似物的还原化学性质。通过 CO2˙-物种的电子传递逐步还原这些硝基咪唑二氢恶嗪化合物,发现与相关的硝基咪唑不同,2 电子加成导致咪唑环优先于硝基还原。在弱酸性溶液中会形成硝基二氢咪唑中间体,然后进一步还原成胺产物。在碱性和中性溶液中,2 电子还原产生的中间产物无法进一步还原,在萃取或对溶液进行质谱分析时会还原成母体化合物。这些硝基咪唑化合物不寻常的还原化学性质表现出环比硝基还原,这与 4-硝基咪唑 2 位的烷氧基取代有关。需要考虑 PA-824 还原过程中形成的中间体的独特性质在其杀菌作用中可能发挥的作用。