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

Cleavage of five different nucleoside diphosphosugars has been studied in the presence of Cu2+ and Zn2+ complexes. The results show that metal ion catalysts promote the cleavage via intramolecular transesterification whenever a neighbouring HO group can adopt a cis-orientation with respect to the phosphate. The HO group attacks the phosphate and two monophosphate products are formed. If such a nucleophile is not available, Cu2+ complexes are able to promote a nucleophilic attack of an external nucleophile, e.g. a water molecule or metal ion coordinated HO ligand, on phosphate. With the Zn2+ complex, this was not observed