Sheu Chimin, Kang Ping, Khan Saeed, Foote Christopher S
Department of Chemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA.
J Am Chem Soc. 2002 Apr 17;124(15):3905-13. doi: 10.1021/ja011696e.
An organic-soluble guanosine derivative, 2',3',5'-O-(tert-butyldimethylsilyl)guanosine (1), was prepared and its photosensitized oxidation was carried out in several solvents at various temperatures. Singlet oxygen is the reactive oxidizing agent responsible for this reaction. Neither an endoperoxide nor a dioxetane intermediate was detected by low-temperature NMR even at -78 degrees C. A product (A) with an oxidized imidazole ring was the only major product detected at room temperature; this compound could be isolated by low-temperature column chromatography and was characterized by (1)H and (13)C and mass spectroscopy. CO(2) was the other major product. A small amount of the corresponding 8-oxo-7,8-dihydroguanosine derivative B was detected during the initial stage of the photooxidation and was shown to be intermediate in the formation of two products of extensive degradation, C and D. Reaction of 1 with the singlet oxygen analogues 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) gave products consistent with a proposed mechanism involving the rearrangement of an initially formed endoperoxide to give A and B from reaction of 1 with singlet oxygen.
制备了一种有机可溶性鸟苷衍生物，2',3',5'-O-(叔丁基二甲基甲硅烷基)鸟苷(1)，并在几种溶剂中于不同温度下进行了其光敏氧化反应。单线态氧是该反应的活性氧化剂。即使在-78℃下，通过低温核磁共振也未检测到内过氧化物或二氧杂环丁烷中间体。在室温下检测到的唯一主要产物是一种咪唑环被氧化的产物(A)；该化合物可通过低温柱色谱法分离，并通过(1)H、(13)C和质谱进行表征。二氧化碳是另一种主要产物。在光氧化反应的初始阶段检测到少量相应的8-氧代-7,8-二氢鸟苷衍生物B，并且表明它是两种大量降解产物C和D形成过程中的中间体。1与单线态氧类似物4-甲基-1,2,4-三唑啉-3,5-二酮(MTAD)和4-苯基-1,2,4-三唑啉-3,5-二酮(PTAD)的反应产物与所提出的机理一致，该机理涉及最初形成的内过氧化物重排，从而由1与单线态氧反应生成A和B。
