SIALYL ALDOLASE IN ORGANIC-SYNTHESIS - FROM THE TROUT EGG ACID, 3-DEOXY-D-GLYCERO-D-GALACTO-2-NONULOSONIC ACID (KDN), TO BRANCHED-CHAIN HIGHER KETOSES AS POSSIBLE NEW CHIRONS

N-Acetylneuraminate pyruvate lyase accepts as substrates varied non-nitrogeneous sugars. Condensation of pyruvate with D-mannose yields 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) a component of rainbow trout egg polysialoglycoprotein. From some easily available monosaccharides were prepared other ulosonic acids: 3-deoxy-D-galacto-2-octulosonic 35dideoxy-D-gluco-2-nonulosonic and 37-dideoxy-D-galacto-2-nonulosonic acids. Glucose was not a good substrate and D-arabinose gave a mixture of the expected 3-deoxy-D-gluco-2-octulosonic acid (19%) with 3-deoxy-D-manno-2-octulosonic acid (16%). The latter is the well-known sugar acid KDO from bacterial polysaccharides and results from an anomalous orientation at the condensation step. The relative indifference of the enzyme to the nature of the substituent at C(2) of the sugar provided the D-manno configuration is retained is demonstrated by the conversion in 76% yield of 2-deoxy-2-C-phenyl-D-mannose into 35-dideoxy-5-C-phenyl-D-gluco-2-nonulosonic acid. All these preparations utilized immobilized lyase and can be scaled up ad libitum. © 1990.