115142-02-4Relevant articles and documents
The mechanism of the metal ion promoted cleavage of RNa phosphodiester bonds involves a general acid catalysis by the metal aquo ion on the departure of the leaving group
Mikkola, Satu,Stenman, Eeva,Nurmi, Kirsi,Yousefi-Salakdeh, Esmail,Stroemberg, Roger,Loennberg, Harri
, p. 1619 - 1625 (2007/10/03)
A series of uridine 3′-alkyl phosphates and 3′-aryl phosphates were synthesised and their cleavage was studied in the presence of Zn2+ aquo ions. A βlg value was determined for the Zn2+ promoted cleavage of both types of compounds. Comparison of the results obtained to those reported previously for the cleavage of the same substrates in the absence of metal ion catalysts suggests that the alkyl leaving group departs as an alcohol in the presence of metal ion catalysts. Furthermore, metal ion catalysts seem to enhance the departure. The aryl leaving group, in contrast, departs as an oxyanion.
Charge Description of Base-Catalyzed Alcoholysis of Aryl Phosphodiesters: A Ribonuclease Model
Davis, Andrew M.,Hall, Adrian D.,Williams, Andrew
, p. 5105 - 5108 (2007/10/02)
The release of substituted phenol from aryl uridine-3'-phosphates is catalyzed by bases and involves cyclization to form the 2',3'-cyclic nucleotide.The rate constants for imidazole and hydroxide ion catalysis (kim and kOH, respectively) obey the Broensted equations (25 deg C and 0.25 M ionic strength) log kim = -0.59 pKArOH + 1.40 (n = 7, r = 0.955) and log kOH = -0.54 pKArOH + 6.68 (n = 9, r = 0.967).General-base-catalyzed release of 4-nitrophenol from the 4-nitrophenyl ester (kB) obeys the Broensted relationship log kB = 0.67 pKBH - 7.50 (n = 7, r = 0.989).Charge changes on base and leaving group atoms as determined from the corresponding β and βeq values do not balance.Comparison with data in the literature indicates that the difference in charge may be assigned to the attacking oxygen (2'-hydroxyl) rather than to the phosphoryl oxygens in the O...PO2... group of atoms.Both P-O bond forming and bond fission components of the reaction are considered to be only weakly advanced in a transition state that lies on a concerted pathway.