2.7.7.24 glucose-1-phosphate thymidylyltransferase dTDP-L-daunosamine biosynthesis 4.2.1.46 dTDP-glucose 4,6-dehydratase dTDP-L-daunosamine biosynthesis 5.1.3.13 dTDP-4-dehydrorhamnose 3,5-epimerase dTDP-L-daunosamine biosynthesis