Electrochemical oxidation of xanthosine |
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| Institution: | 1. Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia;2. Department of Materials, Imperial College London, London SW7 2AZ, United Kingdom;3. Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan;1. School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China;2. School of Materials Science and Engineering, Central South University, Changsha 410083, China;3. Key Laboratory of Ministry of Education for Non-ferrous Materials Science and Engineering, Changsha 410083, China;1. Key Laboratory of Hunan Province for Advanced Carbon-based Functional Materials, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China;2. College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, Hunan, China;3. College of Mechanical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan, China;1. Laboratório de Processos de Separação e Reacção - Laboratório de Catálise e Materiais (LSRE-LCM), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto. R. Dr Roberto Frias s/n, 4200-465, Porto, Portugal;2. Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto. R. Dr Roberto Frias s/n, 4200-465, Porto, Portugal;3. Universidade do Minho, LAB2PT- Laboratório de Paisagens, Património e Território, Portugal |
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| Abstract: | The electrochemical oxidation of xanthosine in aqueous solution at pH 2.0 at the pyrolytic graphite electrode has been studied. The primary electrochemical oxidation reaction is an irreversible 1 e−, 1 H+ reaction giving the C(8) free radical. In order to account for the ultimate products formed, the latter primary radical reacts with xanthosine to give at least one N free radical and with water to give an 8-hydroxylated free radical. The C(8) and N radicals couple to give a xanthosylxanthosine dimer which rapidly loses one ribosyl residue to give a xanthosylxanthine dimer. The 8-hydroxylated radical reacts with the C(8) and N radicals to give two isomeric hydroxylated xanthosylxanthosines. The 8-hydroxylated radical can also undergo further electrochemical oxidation (1 e−, 1 H+) to 9-β-D-ribofuranosyluric acid which is immediately oxidized (2 e−, 2 H+) to a very reactive quinonoid. Attack by water on the quinonoid gives two isomeric tertiary alcohol intermediates which have been isolated and characterized by their UV and mass spectra and by their reaction with water to give a diol. The latter diol decomposes to 5-hydroxyhydantoin-5-carboxamide-3-riboside. |
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