Catalyzes synthesis of paratose and tyvelose, unusual 3,6-dideoxyhexose sugars that form part of the O-antigen in the lipopolysaccharides of several enteric bacteria. CDP-alpha-D-paratose + NADP(+) = CDP-4-dehydro-3,6-dideoxy-alpha-D-glucose + H(+) + NADPH Nucleotide-sugar biosynthesis; CDP-3,6-dideoxy-D-mannose biosynthesis; CDP-3,6-dideoxy-D-mannose from CTP and alpha-D-glucose 1-phosphate: step 4/5. The functional difference between abequose synthase and paratose synthase lies in the side of the pyranose ring from which the keto group on carbon 4 is attacked in the reduction of CDP-4-keto-3,6-dideoxy-D-glucose. Belongs to the NAD(P)-dependent epimerase/dehydratase family.