COMBINED CHEMOENZYMATIC SYNTHESIS OF 2O-6-DEOXY-ALPHA-L-SORBOFURANOSYL-D-GLUCOSE

The chemoenzymatic synthesis of 20-6-deoxy-alpha-L-sorbofuranosyl-D-gl ucose has been performed by coupling four enzymatic and one simple che mical step on a preparative scale with 17% overall yield. At first, py ruvic aldehyde dimethyl acetal was reduced stereospecifically to L-lac taldehyde dimethyl acetal by the carbonyl reductase from Candida parap silosis with approximately 100% ee. Subsequently, the product was conv erted to L-lactaldehyde by simple treatment with a strong cation excha nger. Secondly, stereoselective condensation between dihydroxyacetone phosphate and L-lactaldehyde was catalyzed by fructose 1,6-bisphosphat e aldolase from Staphylococcus carnosus. The resulting sugar phosphate was dephosphorylated by acid phosphatase treatment and further purifi ed by cation exchange chromatography. The structure and stereochemistr y of the product, 6-deoxy-L-sorbose, was confirmed by H-1- and C-13-NM R analysis. In the last step sucrose synthase from rice grains was uti lized to catalyze the transfer of glucose from UDP-glucose to 6-deoxy- L-sorbose. The structure and stereochemistry of the disaccharide forme d, 20-6-deoxy-alpha-L-sorbo-furanosyl-D-glucose, was also confirmed by H-1- and C-13-NMR analysis.