Nucleophilic catalysis of glycoside hydrolysis. The hydrolysis of 4-nitrophenyl α- and β-D-glucopyranoside tetraphosphates

The octaanion of the tetraphosphate of 4-nitrophenyl β-D-glucopyranoside is hydrolysed up to 100 times faster than model compounds, in a reaction which is pH-independent above pH 9. The mechanism involves intramolecular nucleophilic catalysis by the phosphate group in the 2-position: the intermediate five-membered 1,2-cyclic phosphate can be observed directly by 31P NMR spectroscopy under suitable conditions. In base this gives α-D-glucopyranose 1,3,4,6-tetraphosphate and inorganic phosphate: it appears that glucose 2,3,4,6-tetraphosphate is not stable under basic conditions, but is converted into the triphosphate of a saccharinic acid. The tetraphosphate of 4-nitrophenyl α-D-glucopyranoside shows no significant acceleration.