Ribocil C antibiotics effective for Gram-negative pathogens

A compound of Formula III:

• or a pharmaceutically acceptable salt thereof;
• wherein
• X1 is selected from the group consisting of NR6 and C(R7a)(R7b);
• X2 is selected from the group consisting of N and CR8;
• X3 is selected from the group consisting of OR9, SR9 and N(R10a)(R10b);
• each R1, R2, R4, and R5 is independently selected from the group consisting of halogen, hydroxyl, —O(C1-C6)alkyl, nitro, cyano, —(C1-C6)alkyl, N(R11a)(R11b), —((C1-C6)alkylene)N(R11a)(R11b), cycloalkyl, heterocyclyl, aryl, heteroaryl, aralkyl, and heteroaralkyl;
• R3a and R3b are each independently selected from the group consisting of hydrogen, —(C1-C6)alkyl, N(R11a)(R11b), and ((C1-C6)alkylene)N(R11a)(R11b);
• or R3a and R3b together form an oxo;
• R6 is selected from the group consisting of hydrogen, aryl, heteroaryl, cycloalkyl, heterocyclyl, aralkyl, —(C1-C6)alkyl, and ((C1-C6)alkylene)N(R11a)(R11b);
• R7a and R7b are each independently selected from the group consisting of hydrogen, —(C1-C6)alkyl, N(R11a)(R11b), and ((C1-C6)alkylene)N(R11a)(R11b);
• or together R7a and R7b form an oxo;
• R8 is selected from the group consisting of hydrogen, N(R11a)(R11b), —((C1-C6)alkylene)N(R11a)(R11b), and —(C1-C6)alkyl;
• R9 is selected from the group consisting of hydrogen, aryl, heteroaryl, cycloalkyl, heterocyclyl, aralkyl, and —(C1-C6)alkyl;
• R10a and R10b are each independently selected from the group consisting of hydrogen, aryl, heteroaryl, cycloalkyl, heterocyclyl, aralkyl, —(C1-C6)alkyl, C(O)(C1-C6)alkyl, and C(O)O(C1-C6)alkyl;
• R11a and R11b are each independently selected from the group consisting of hydrogen, aryl, heteroaryl, cycloalkyl, heterocyclyl, aralkyl, —(C1-C6)alkyl, C(O)(C1-C6)alkyl, and C(O)O(C1-C6)alkyl;
• n and q are each independently an integer from 0-3;
• m is an integer from 0-7;
• and
• p is an integer from 0-2;
• provided that:
• a) at least one of R1, R2, R3a, R3b, R4, and R5 is N(R11a)(R11b) or ((C1-C6)alkylene)N(R11a)(R11b), and at least one of n, q, m and p is 1;
• b) X1 is NR6 or C(R7a)(R7b), and at least one of R7a and R7b is N(R11a)(R11b);
• or
• c) X2 is CR8 and R8 is N(R11a)(R11b) or ((C1-C6)alkylene)N(R11a)(R11b).