Biphasic Catalysis with Disaccharide Phosphorylases: Chemoenzymatic Synthesis of α-D-Glucosides Using Sucrose Phosphorylase

Thanks to its broad acceptor specificity, sucrose phosphorylase (SP) has been exploited for the transfer of glucose to a wide variety of acceptor molecules. Unfortunately, the low affinity (K-m > 1 M) of SP towards these acceptors typically urges the addition of cosolvents, which often either fail to dissolve sufficient substrate or progressively give rise to enzyme inhibition and denaturation. In this work, a buffer/ethyl acetate ratio of 5:3 was identified to be the optimal solvent system, allowing the use of SP in biphasic systems. Careful optimization of the reaction conditions enabled the synthesis of a range of alpha-D-glucosides, such as cinnamyl alpha-D-glucopyranoside, geranyl alpha-D-glucopyranoside, 2-O-alpha-D-glucopyranosyl pyrogallol, and series of alkyl gallyl 4-O-alpha-D-glucopyranosides. The usefulness of biphasic catalysis was further illustrated by comparing the glucosylation of pyrogallol in a cosolvent and biphasic reaction system. The acceptor yield for the former reached only 17.4%, whereas roughly 60% of the initial pyrogallol was converted when using biphasic catalysis.