6-aminopenicillanic acid is a penicillanic acid compound having a (6R)-amino substituent. The active nucleus common to all penicillins, it may be substituted at the 6-amino position to form the semisynthetic penicillins, resulting in a variety of antibacterial and pharmacologic characteristics. It has a role as an allergen. It is functionally related to a penicillanic acid. It is a conjugate base of a 6-aminopenicillanate. It is a tautomer of a 6-aminopenicillanic acid zwitterion.