Nuclear magnetic resonance has been employed to characterize fourteen new antibiotics belonging to the quinoxaline group, produced by feeding aromatic acids to Streptomyces echinatus. Twelve of the antibiotics are the expected substituted quinomycins and adopt conformations very similar to that of echinomycin. This is discussed in relation to their different DNA-binding characteristics. The other two antibiotics are triostins, supporting the proposal that triostins serve as biosynthetic precursors of the quinomycins.