Biosynthesis of 3,6-dideoxyhexoses: new mechanistic reflections upon 2, 6-dideoxy, 4,6-dideoxy, and amino sugar construction

Biosynthesis of deoxy sugars such as 2,6 and 4,76-dideoxyhexoses prevalent in a wide range of bioactive compounds and 3,6-dideoxyhexoses prevalent in the lipopolysaccharides of Yersinia follows a pathway similar to that of the biosynthesis of ascarylose. The pathway of the biosynthesis is characterized by an initial CDP-dextrorotary(D)-glucose 4,6-dehydratase (Eod)-catalyzed conversion of CDP-D-glucose to 6-deoxy-D-glycero-L-thero-4-hexulose. This is succeeded by a C-3 deoxygenation involving 2 successive reactions catalyzed by CDP-6-deoxy-laerorotatory(L)-threo-D-glycero-4-hexulose-3-dehydrase (EI), a PMP-dependent iron-sulfur containing enzyme and CDP-6-deoxy-delta-glucoseen reductase (E3), a (2Fe-2S)-containing flavoprotein. The biosynthesis terminates by a stereospecific C-4 reduction, concurrent with a probable C-5 epimerization, resulting in a field of the 3,6-dideoxyhexoses.