Carbacephem β-lactam antibiotics

A compound having the chemical structure:

• or a salt thereof, wherein:
• n is 0 or 1, wherein:
• when n is 0:
• R1 is hydrogen;
• A1 is selected from the group consisting of oxygen and sulfur;
• R2 does not exist;
• A2 is carbon;
• A3 and A5 are independently selected from the group consisting of carbon and nitrogen such that the resulting ring is aromatic;
• and,
• R3 is selected from the group consisting of hydrogen, —NH2 and —CH2S(CH2)2NH2;
• when n is 1:
• A1 is carbon;
• one or two of A2, A3, A4 and A5 is/are nitrogen, the rest are carbon;
• R2 is —CH2S(CH2)2NH2;
• if A2 is carbon, R3 is hydrogen;
• if A2 is nitrogen, R3 does not exist;
• and,
• R1 is selected from the group consisting of:
• hydrogen;
• —CH3;
• —CH2CH3;
• —CH2F;
• and,
• —CH2CH2F.