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

The rare actinobacterium Amycolatopsis sp. strain 195334CR was found to produce previ ously undescribed cyclic hexapeptides, which we named amycolatomycin A and B (1 and 2). Their planar structures were determined by high-resolution mass spectrometry as well as extensive 1D and 2DNMRspectroscopy, while the absolute stereochemistry of its amino acids were determined by Marfey’s method. Moreover, 1 and 2 differ by the incorporation of L-Ile and L-allo-Ile, respectively, whose FDVA (N-(2,4-Dinitro-5-fluorphenyl)-L-valinamide) derivatives were separated on a C4 column. Their hallmark in common is a unique 2,6-dichloro-tryptophan amino acid unit. Amy colatomycin A (1) exhibited weak activity against Bacillus subtilis DSM 10 (minimum inhibitory concentration (MIC) = 33.4 g/mL).