The molecule is zwitterionic form of anhydrotetracycline arising from transfer of a proton from the 2-hydroxy to the tertiary amino group; major species at pH 7.3. It is a zwitterion and a tertiary alpha-hydroxy ketone. It is a tautomer of an anhydrotetracycline.
(4S,4aS,12aR)-2-carbamoyl-4-(dimethylazaniumyl)-10,11,12a-trihydroxy-6-methyl-3,12-dioxo-4a,5-dihydro-4H-tetracen-1-olate