Nonulosonic acid analogues

Many hexoses were tested in both D- and L-form, resulting in the formation of nonulosonic acid analogues. Table 2 demonstrates the most common enzymatic approach to the synthesis ofNeu5Ac (entry 1) and its analogues (entry 2-12) from modified A-acetylmannosamine derivatives. 

Some deaminated Neu5Ac analogues were also prepared (rows 13-21), including 3-deoxy-D-glycero-D-galacto-nonulosonic acid (KDN, entry 13). 

The stereochemical outcome of the hetero Diels-Alder reaction of the erythrose based diene with sodium glyoxylate was further rationalized by preparing the same compounds via decarboxylation of 2-carboethoxy-2-deoxy-2-ulosonic acid esters, obtained by cycloaddition with diethyl ketomalonate [146], A range of 2-nonulosonic acid derivatives - KDN analogues - were prepared including protected form of 2-deoxy-KDN,... 

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