Preparation of fluorinated galactosyl nucleoside diphosphates to study the mechanism of the enzyme galactopyranose mutase

A novel latent-->active phosphorylation strategy has been employed for the preparation of two fluorinated nucleoside diphosphates (compounds I and II). The strategy is based on the isomerisation of substituted allyl to vinyl glycosides which were subsequently phosphorylated by treatment with dibenzyl hydrogen phosphate, N-iodosuccinimide and a catalytic amount of trimethylsilyl triflate. This methodology is very suitable for the preparation of nucleoside diphosphates that have a modification in the saccharide moiety since the allyl moiety serves first as an anomeric protecting group, allowing for protecting-group manipulation and functionalisation of the sugar ring, but after isomerisation to the corresponding vinyl glycoside it acts as an anomeric leaving group. The 2-F and 4-F Gal-UDP derivatives I and II do not inhibit the enzyme galactopyranose mutase in the direction pyranose --> furanose but both compounds have been found to inhibit the reverse reaction.