Antibacterial activity of cystobactamids with optimized A-rings and isopropoxy/hydroxyl-substituted E-ring, given as minimal inhibitory concentrations (MICs) in μg mL⁻¹, and inhibitory activity against DNA gyrase in μM^e.

Compound	R	MIC [μg mL−1]					EC gyrase IC50 [μM]
		E. coli ΔtolCa	E. coli WTb	P. ae. ΔmexABa	P. ae. WTc	S. aureus d
Reference 78		0.125	0.5	1	>64	0.05	0.2
79		≤0.03	0.25	1	2	≤0.03	0.6
80		≤0.03	0.06	0.5	>64	≤0.03	nd
81		0.06	0.125	2	>64	0.06	nd
82		≤0.03	0.125	0.25	1	0.06	0.2

^aStrain provided by collaborators, see ESI.

^bDSM-1116.

^cPA14.

^dATCC29213.

^end = not determined, P. ae. = P. aeruginosa.