Biocatalysis Applied to the Synthesis of Nucleoside Analogs

Selective biotransformations of polyhydroxylated compounds, such as carbohydrates, have been used since some time ago for the activation or protection of some of their hydroxyl groups, allowing different chemical transformations to be carried out without the need for using tedious protection and deprotection steps. Monoesters of some monosaccharides and disaccharides have been obtained using lipases or proteases in polar organic solvents [3]. In addition, the utility of biotransformations in other natural products such as nucleosides [4] or steroids [5] has also been reviewed. 

Modem Biocatalp Stereoselective and Environmentally Friendly Reactiojts. Edited by Wolf-Dieter Fessner and Thorleif Anthonsen Copyright 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32071-4 

In recent years biotransformations have also shown their potential when applied to nucleoside chemistry [7]. This chapter will give several examples that cover the different possibiUties using biocatalysts, especially lipases, in order to synthesize new nucleoside analogs. The chapter will demonstrate some applications of enzymatic acylations and alkoxycarbonylations for the synthesis of new analogs. The utQity of these biocatalytic reactions for selective transformations in nucleosides is noteworthy. In addition, some of these biocatalytic processes can be used not only for protection or activation of hydroxyl groups, but also for enzymatic resolution of racemic mixtures of nucleosides. Moreover, some possibilities with other biocatalysts that can modify bases, such as deaminases [8] or enzymes that catalyze the synthesis of new nucleoside analogs via transglycosylation [9] are also discussed. 

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