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DOI: 10.1055/s-0032-1321294
New insights on the structure of the anti-TB peptide H14: Crystal structure, 1H NMR full spin analysis, and biosynthetic pathway
Previous anti-TB HTS of actinomycete extracts led to the extract of strain E5123, a Nonomuraea sp., from which two cyclic depsipeptides, H14 and H16, with potent and selective anti-TB activity were isolated. Three distinctive approaches to structural analysis of compound H14 are presented and discussed. An X-ray crystallographic analysis of H14 provided information on its tertiary structure and stereochemistry. From the X-ray structure, a 1H NMR iterative full spin analysis (HiFSA) of H14 was carried out, giving all parameters of the spectrum (all δH and J HH). The biosynthesis was investigated by genome sequencing. A portion of the presumed NRPS responsible for the four C-terminal amino acids in H14/H16 and several tailoring enzymes leading to the unusual amino acids, were identified. The lack of any epimerization domains in this sequence is strong presumptive evidence that at least 12 out of the 13 amino acids are L.