Novel chemical probes for the investigation of nonribosomal peptide assemblyElectronic supplementary information (ESI) available: General methods for the synthesis of chemical probes and LC-HRMSn analysis of the biosynthetic intermediates isolated from S. lasaliensis strains. See DOI: 10.1039/c7cc02427d

Chemical probes were devised and evaluated for the capture of biosynthetic intermediates involved in the bio-assembly of the nonribosomal peptide echinomycin. Putative intermediate peptide species were isolated and characterised, providing fresh insights into pathway substrate flexibility and paving the way for novel chemoenzymatic approaches towards unnatural peptides. Newly devised chemical probes capture biosynthetic intermediates in the bio-assembly of the nonribosomal peptide echinomycin.