is protonated form of is tautomer of 6-aminopenicillanic acid 6-aminopenicillanate amino-acid zwitterion 6-aminopenicillanic acid zwitterion Zwitterionic form of 6-aminopenicillanic acid arising from migration of a proton from the carboxy group to the 6-amino group; major species at pH 7.3. (2S,5R,6R)-6-azaniumyl-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate 6-azaniumyl-2,2-dimethylpenam-3alpha-carboxylate 6-aminopenicillanate 6-azaniumyl-2,2-dimethylpenam-3alpha-carboxylate