Currently, carbazoles are of high interest due to their pharmacological potential. 1 In 1990, Seto et al. at the University of Tokyo isolated the antiostatins A 1 to A 4 and B 2 to B 5 from Streptomyces cyaneus 2007-SV 1 (Fig. 1). 2 They exhibit a strong inhibitory activity against free radical induced lipid peroxidation. The antiostatins are structurally unique because of their nitrogen substituent at C-4, which is part of an isobutylbiuret side chain for the antiostatins B. So far, no ...