AN EXPEDITIONS ROUTE TO N-GLYCOLYLNEURAMINIC ACID-BASED ON ENZYME-CATALYZED REACTION

A new preparative way of N-glycolylneuraminic acid (NeuGc), one of the important family of sialic acids, from N-acetylglucosamine (GlcNAc) v ia N-acetylmannosamine (ManNAc) was established based on the combinati on of chemical and enzymatic reactions. In a kinetic study of the key enzymatic reaction for this process, aldolase-catalyzed synthesis of s ialic acid, an inhibitory effect of gluco-isomer on the enzymatic reac tion was quantitatively clarified, and the importance of isomerically pure substrate with manno-configuration for aldolase-catalyzed reactio n was suggested. A newly developed method, selective degradation of Gl cNAc contaminating in the substrate by use of Rhodococcus rhodochrous IFO 15564 provided pure ManNAc to avoid such inhibitory effect of the gluco-isomer for aldolase. Starting from pure ManNAc, via mannosamine hydrochloride, acetoxyacetyl chloride was applied for introducing a pr otected form of glycolyl group to give N-acetylglycolylmannosamine. Fo r the removal of acetyl protective group, a lipase from Aspergillus ni ger was effectively used under a mild and neutral condition to afford N-glycolylmannosamine (ManNGc), the substrate of aldolase. NeuGc was p repared in 25% yield and 7 steps from GlcNAc. (C) 1997, Elsevier Scien ce Ltd.