- N6-Substituent Effect on the Photooxidation of 2',3'-O-Isopropylideneadenosines with a Pyrimidopteridinetetraone N-Oxide. Chemical Evidence for the Generation and Reactivity of Adenosyl Cation Radicals
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A comparative study on the photooxidation of 2',3'-O-isopropylideneadenosine 1a and its N6-benzoyl, N-6-monomethyl, and N6,N6-dimethyl derivatives, 1b-d, with a pyrimidopteridinetetraone N-oxide (PPO) was carried out.The ease of photooxidative consumption of the adenosines by the PPO is in the order 1d > 1c > 1a > 1b, which is parallel to their oxidation-peak potentials.Although substrates 1a and 1b underwent oxidative intramolecular cyclisation to the corresponding 5'-O,8-cycloadenosines, 2a and 2b, even in low yield, substrates 1c and 1d were exclusively oxidised at the N6-methyl group to give the corresponding N6-formyl derivatives, 3 and 4, together with minor amounts of demethylated products, 1a and 1c.The present observations provide chemical evidence for the generation and reactivity of adenosyl cation radicals.
- Sako, Magoichi,Makino, Toru,Kitada, Yukio,Hirota, Kosaku,Maki, Yoshifumi
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p. 1801 - 1806
(2007/10/02)
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- A 15N-STUDY ON THE DEAMINATION OF 1-AMINOPURINIUM SALTS WITH AMINES
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Reaction of 1-aminoadenosinium mesitylenesulphonate, 1a, with methanolic ammonia for 10 h at 80 deg C yields adenosine, 7a, and nebularine, 6a.With methanolic methylamine 1a gives 6-methylamino-9-β-D-ribofuranosylpurine, 8a, and adenosine, 7a, respectively.Similar results are obtained with the salt of 1-amino-2',3'-O-isopropylideneadenosine, 1b. 1-Aminoadeninium mesitylenesulphonate, 1c, with methanolic methylamine only yields 6-(methylamino)purine, 8c.In contrast, the mesitylenesulphonate salt of 1,2-diaminopurine, 11, with methanolic methylamine gives only deamination at N1, affording 2-aminopurine, 12.Studies with 15N-labelled methanolic ammonia or 15N-labelled purinium compounds show that in all these reactions, except that of 11, a ring-opening mechanism (ANRORC-mechanism) is involved.
- Kos, Nico J.,Jongejan, Hugo,Plas, Henk C. van der
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p. 369 - 374
(2007/10/02)
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