Metal ion-promoted cleavage of nucleoside diphosphosugars: a model for reactions of phosphodiester bonds in carbohydrates

Abstract

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Kinetic and NMR spectroscopic study of the chemical stability and reaction pathways of sugar nucleotides

“…S10 (Supporting material). As we have reported before, [16] glycosylic sugar nucleotides with an attacking HO-group in cis-position are generally more reactive: A second-order rate constant of (1.6 ± 0.2)Á10 À2 dm 3 mol À1 s À1 at a lower temperature (25 C) was determined for galactose-1-UDP (11).…”

“…[15] However, under alkaline conditions, a nucleoside diphosphate (5a,b) is formed as a minor product (Scheme 2). [15,16] A reaction sequence involving a series of keto-enol equilibria, followed by an elimination of the phosphate, similarly to a reaction proposed for a reaction of ribose phosphates, [19] has been tentatively proposed as a mechanism for the formation nucleoside diphosphate. [15] In the present article, we aim to gather further information on the chemical decomposition of sugar nucleotides.…”

“…[1,2,5] In chemical reactions, an intramolecular nucleophilic attack occurs under neutral and alkaline conditions. [13][14][15][16][17] A neighbouring HO-group in cis-orientation attacks on the a-phosphate (in this context a refers to the sugar bound phosphate in the pyrophosphate moiety) (Scheme 1). The reaction of 1 results in the formation of glycopyranose 1,2-cyclic monophosphate (3) and uridine 5 0 -monophosphate (5 0 -UMP, 4).…”

“…[6,7] In chemical reactions, the pyrophosphate moiety is the predominant reaction site, and an intramolecular displacement at the phosphate occurs. [15,16] As an evidence of such a reaction, a nucleoside monophosphate (4,4b) is released as the major product (Scheme 2). The neighbouring 4-OH group of the acyclic ribose moiety is believed to be the most probable nucleophile in the reaction.…”

“…[15] In the present article, we aim to gather further information on the chemical decomposition of sugar nucleotides. As we have previously utilised capillary zone electrophoresis (CZE) with UV-detection in the kinetic experiments, [15,16] we have been able to observe only the UV-active nucleic acid base containing products. In the present work, the alkaline cleavage of glucose 1-UDP (1) and ribose 5-UDP (6) were followed by 1 H and 31 P NMR experiments to obtain information on the processes taking place in the non-chromophoric sugar moiety.…”