Glyculosonic acids synthesis

Chain-extension reactions constitute a more widely used approach. Thus, the cyanohydrin synthesis followed by base-catalyzed cyclization and /1-elimination to iminolactones, which then undergo stepwise hydrolysis, affords 3-deoxy-2-glyculosonic acids.313 The overall yield of this reaction is low. Paerels314 used this method to prepare the first crystalline members of this group, namely 3-deoxy-D-m //iro-hex-2-ulosopyranosonic acid (2-keto-3-deoxy-D-gluconic acid, KDG, 119), and the L isomer, starting from D-ribose and L-arabinose, respectively. The synthesis of 119 is illustrated in Scheme 10. 

Fourthly, biotransformations have been used for the synthesis of 3-deoxy-2-glyculosonic acids, using whole cells or purified enzymes. For instance, 3-deoxy-D-araZu rao-heptulosonic acid (DAH) and its 7-phosphate (DAHP, 122) have been produced directly from D-glucose by mutants of E. coli JB-5, that lack dehydroquinate synthase, the enzyme that converts DAHP into the cyclic intermediate dehydroquinic acid (DHQ, Scheme 14). Both DAH and DAHP are secreted into the medium. The dephosphorylated product could be generated in vivo by a phosphatase acting on DAHP.312... 

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