A1 Refereed original research article in a scientific journal
Buffer-catalyzed interconversion of ribonucleoside 2 '/3 '-methylphosphonates and 2 '/3 '-alkylphosphates
Authors: Maki E, Oivanen M, Poijarvi P, Lonnberg H
Publisher: ROYAL SOC CHEMISTRY
Publication year: 1999
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: 11
First page : 2493
Last page: 2499
Number of pages: 7
ISSN: 0300-9580
DOI: https://doi.org/10.1039/a905516i
Abstract
The O-2' = O-3' isomerization of uridine 2'/3'-methylphosphonates, 2'/3'-isopropyl phosphates and 2'/3'-(2-ethoxy-ethyl) phosphates has been studied in buffer solution. In imidazole buffers, all these isomerizations exhibit only weak general acid catalysis. This low susceptibility of isomerization to buffer catalysis appears to be an inherent property of this reaction, and not a consequence of competitive buffer-catalyzed breakdown of the phosphorane intermediate to 2',3'-cyclic phosphate: uridine 3'-(2-ethoxyethyl) phosphate and 3'-isopropyl phosphate exhibit a similar susceptibility of isomerization to buffer catalysis in spite of the fact that the former undergoes concurrent buffer-catalyzed cleavage and the latter does not. In carboxylic acid buffers (pH < 3), the 2'/3'-methylphosphonates were observed to undergo another buffer-catalyzed isomerization, which was first order in the concentration of both hydronium ion and the buffer acid. Plausible mechanistic interpretations-for the buffer-catalyzed isomerizations are described.
The O-2' = O-3' isomerization of uridine 2'/3'-methylphosphonates, 2'/3'-isopropyl phosphates and 2'/3'-(2-ethoxy-ethyl) phosphates has been studied in buffer solution. In imidazole buffers, all these isomerizations exhibit only weak general acid catalysis. This low susceptibility of isomerization to buffer catalysis appears to be an inherent property of this reaction, and not a consequence of competitive buffer-catalyzed breakdown of the phosphorane intermediate to 2',3'-cyclic phosphate: uridine 3'-(2-ethoxyethyl) phosphate and 3'-isopropyl phosphate exhibit a similar susceptibility of isomerization to buffer catalysis in spite of the fact that the former undergoes concurrent buffer-catalyzed cleavage and the latter does not. In carboxylic acid buffers (pH < 3), the 2'/3'-methylphosphonates were observed to undergo another buffer-catalyzed isomerization, which was first order in the concentration of both hydronium ion and the buffer acid. Plausible mechanistic interpretations-for the buffer-catalyzed isomerizations are described.
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