The molecule is a zwtterion obtained by transfer of a proton from the 2-hydroxy to the primary amino group of 4-amino-4-de(dimethylamino)anhydrotetracycline. It is the major microspecies at pH 7.3 (according to Marvin v 6.2.0.). It is a tautomer of a 4-amino-4-de(dimethylamino)anhydrotetracycline.
(4S,4aS,12aR)-4-azaniumyl-2-carbamoyl-10,11,12a-trihydroxy-6-methyl-3,12-dioxo-4a,5-dihydro-4H-tetracen-1-olate