Amycolatomycins A and B, Cyclic Hexapeptides Isolated from an sp. 195334CR.

The rare actinobacterium sp. strain 195334CR was found to produce previously undescribed cyclic hexapeptides, which we named amycolatomycin A and B ( and ). Their planar structures were determined by high-resolution mass spectrometry as well as extensive 1D and 2D NMR spectroscopy, while the absolute stereochemistry of its amino acids were determined by Marfey's method. Moreover, and differ by the incorporation of l-Ile and l--Ile, respectively, whose FDVA (Nα-(2,4-Dinitro-5-fluorphenyl)-L-valinamide) derivatives were separated on a C column. Their hallmark in common is a unique 2,6-dichloro-tryptophan amino acid unit. Amycolatomycin A () exhibited weak activity against DSM 10 (minimum inhibitory concentration (MIC) = 33.4 µg/mL).