Studies on peptide antibiotics, leucinostatins. II. The structures of leucinostatins A and B.

Structures I and II have been assigned to leucinostatins A and B based on fast atom bombardment, secondary ion, field desorption and chemical ionization mass spectrometry, NMR studies and chemical degradation methods of the intact antibiotics and their acid hydrolysis products. The essential difference between leucinostatins A and B is concluded to be the replacement of (2S)-N1,N1-dimethylpropane-1,2-diamine in leucinostatin A by (2S)-N1-methylpropane-1,2-diamine in leucinostatin B. This was further confirmed from the evidence that methylation with methyl iodide led each antibiotic to the identical compound which was named leucinostatin A-M (III).