A compound having the structure (I) or a pharmaceutically acceptable salt thereof, wherein R3 is hydrogen, deuterium, -OH, -OC1-6alkyl, or halogen R8 is hydrogen, deuterium, or C1-6alkyl R11 and R12 are independently hydrogen, -C1-6alkyl, -OH, -OC1-6alkyl, or halogen R13 and R14 are independently -C1-6alkyl, -(CH2)1-2OH, or -OC1-6alkyl, or, together with the nitrogen atom to which they are attached, form a 4- to 7-membered heterocyclic ring containing one nitrogen atom and 0 or 1 oxygen atoms, wherein said ring is unsubstituted or mono-, di- or tri-substituted with halogen or -C1-6alkyl R15 is -C(O)OH, -C(O)OCH2CH2N+CH3)3 wherein n is 0, 1 or 2, -C(O)NHCH(R17)OR16, or -C(O)NHCH(R17)C(O)NHCH(R18)C(O)OR16 R16 is hydrogen, C1-6alkyl, or (CH2)1-2N+R19R20R21 R1, R2, R4, R5, R6, R7, R9, R10, R17, R18, R19, R20, and R21 are independently hydrogen or -C1-6alkyl and stereoisomers thereof, and pharmaceutically acceptable salts thereof, and pharmaceutically acceptable salts of stereoisomers thereof.
