A1 Refereed original research article in a scientific journal
Mutual isomerization of uridine 2 '- and 3 '-alkylphosphates and cleavage to a 2 ',3 '-cyclic phosphate: the effect of the alkyl group on the hydronium- and hydroxide-ion-catalyzed reactions
Authors: Kosonen M, Youseti-Salakdeh E, Stromberg R, Lonnberg H
Publisher: ROYAL SOC CHEMISTRY
Publication year: 1997
Journal: Royal Society of Chemistry. Journal: Perkin Transactions 2
Journal name in source: JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
Journal acronym: J CHEM SOC PERK T 2
Issue: 12
First page : 2661
Last page: 2666
Number of pages: 6
ISSN: 0300-9580
DOI: https://doi.org/10.1039/a704636g
Abstract
Isopropyl, ethyl, 2-ethoxyethyl, 2-chloroethyl, 2,2-dichloroethyl and 2,2,2-trichloroethyl esters of uridine 3'-phosphate have been prepared. In aqueous acid the compounds undergo concurrent isomerization to 2'-alkylphosphates and cleavage to uridine 2',3'-cyclic phosphate, but in aqueous alkali only cleavage to the cyclic phosphate takes place. Buffer-independent rate constants for these reactions have been determined. The hydroxide-ion-catalyzed reaction to the 2',3'-cyclic monophosphate is exceptionally susceptible to the polar nature of the leaving group, the beta(1g) value being -1.28 +/- 0.05. By contrast, the hydronium-ion-catalyzed isomerization and cleavage are both rather insensitive to the electron-withdrawing ability of the alkyl group, the beta and beta(1g) values being -0.18 +/- 0.02 and -0.12 +/- 0.05, respectively. The transition state structures of the reactions are discussed on the basis of these structural-effects.
Isopropyl, ethyl, 2-ethoxyethyl, 2-chloroethyl, 2,2-dichloroethyl and 2,2,2-trichloroethyl esters of uridine 3'-phosphate have been prepared. In aqueous acid the compounds undergo concurrent isomerization to 2'-alkylphosphates and cleavage to uridine 2',3'-cyclic phosphate, but in aqueous alkali only cleavage to the cyclic phosphate takes place. Buffer-independent rate constants for these reactions have been determined. The hydroxide-ion-catalyzed reaction to the 2',3'-cyclic monophosphate is exceptionally susceptible to the polar nature of the leaving group, the beta(1g) value being -1.28 +/- 0.05. By contrast, the hydronium-ion-catalyzed isomerization and cleavage are both rather insensitive to the electron-withdrawing ability of the alkyl group, the beta and beta(1g) values being -0.18 +/- 0.02 and -0.12 +/- 0.05, respectively. The transition state structures of the reactions are discussed on the basis of these structural-effects.
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