Coupled biocatalysts applied to the synthesis of nucleosides.

Biocatalytic procedures offer a good alternative to the chemical synthesis of nucleosides since biocatalyzed reactions are regio- and stereoselective and afford reduced by-products contents. Among them, enzymatic transglycosylation between a pyrimidine nucleoside and a purine base catalyzed by nucleoside phosphorylases or microorganisms that contain them, has attracted considerable attention. In addition, the combination to other enzymatic steps has been explored. In this work we investigate the coupled action of nucleoside phosphorylases with other enzymatic activities: deaminase and phosphopentomutase. Unlike the preparation of other purine nucleosides, transglycosylation from a pyrimidine nucleoside and guanine is difficult because of the low solubility of this base. Therefore, another strategy, based on microbial transglycosylation followed by deamination, is here explored. The direct use of furanose 1-phosphate, the intermediate in the transglycosylation reaction, is an attractive alternative when pyrimidine nucleosides are not available. Its preparation from the more stable furanose 5-phosphate and phosphopentomutase is here applied to different sugars and bases.