Involved in the biosynthesis of dTDP-6-deoxy-D-allose, an intermediate in the biosynthesis of mycinose, which is one of the two unusual sugars attached to the 16-membered macrolactone ring of the aglycone antibiotic dihydrochalcomycin (GERI-155). Catalyzes the conversion of dTDP-4-oxo-6-deoxyglucose to dTDP-4-oxo-6-deoxyallose, via a C-3 epimerization. dTDP-4-dehydro-6-deoxy-alpha-D-glucose = dTDP-4-dehydro-6-deoxy-alpha-D-allose Antibiotic biosynthesis. Homodimer. Belongs to the dTDP-4-dehydrorhamnose 3,5-epimerase family.