CDP-D-glucose = CDP-4-dehydro-6-deoxy-D-glucose + H2O 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 2/5. Bacterial outer membrane biogenesis; LPS O-antigen biosynthesis. Belongs to the NAD(P)-dependent epimerase/dehydratase family.