Kinetics of reactions of hydroxide ion and water with .beta.-X-substituted .alpha.-nitrostilbenes (X = Cl, I, SEt, OMe, SCH2CH2OH) in 50% Me2SO-50% water. Search for the intermediate in nucleophilic vinylic substitution

1991 ◽  
Vol 113 (13) ◽  
pp. 4937-4946 ◽  
Author(s):  
Claude F. Bernasconi ◽  
Julianne Fassberg ◽  
Robert B. Killion ◽  
David F. Schuck ◽  
Zvi Rappoport
Keyword(s):  
Hydroxide Ion ◽  
Nucleophilic Vinylic Substitution ◽  
Vinylic Substitution ◽  
Kinetics Of

Kinetics of the Imidazolium Ring-Opening of mRNA 5'-cap Analogs in Aqueous Alkali

2006 ◽  
Vol 71 (4) ◽  
pp. 567-578 ◽  
Author(s):  
Alicja Stachelska ◽  
Zbigniew J. Wieczorek ◽  
Janusz Stępiński ◽  
Marzena Jankowska-Anyszka ◽  
Harri Lönnberg ◽  
...  
Keyword(s):  
Electrostatic Interaction ◽  
Ring Opening ◽  
Nucleophilic Attack ◽  
Amino Groups ◽  
Hydroxide Ion ◽  
Methyl Group ◽  
Structural Modifications ◽  
Alkyl Groups ◽  
Imidazolium Ring ◽  
Kinetics Of

Second-order rate constants for the hydroxide-ion-catalyzed imidazolium ring-opening of several mono- and dinucleosidic analogs of mRNA 5'-cap have been determined. Intramolecular stacking of the two nucleobases in the dinucleosidic analogs, m7GpppN (m7G = 7-methylguanosine, N = 5'-linked nucleoside), and electrostatic interaction between the N-alkylated imidazolium ring and phosphate moiety have been shown to shield the m7G moiety against the nucleophilic attack of hydroxide ion. In addition, the effect of methylation of the nucleobase amino groups and replacement of the 7-methyl group with other alkyl groups have been studied. The influence of all the structural modifications studied turned out to be modest, the cleavage rates of the most and least reactive analogs (with the exception of non-phosphorylated nucleosides) differing only by a factor of 5.

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