JBIR-78 and JBIR-95: phenylacetylated peptides isolated from Kibdelosporangium sp. AK-AA56

Dilarmycins A-C, Calcium-Dependent Lipopeptide Antibiotics with a Non-canonical Ca2+-Binding Motif

Genome analysis of strain Streptomyces sp. CA-278952 revealed a biosynthetic gene cluster encoding a putative lipopeptide with a sequence containing an Asp-Gly-Glu-Ala motif. We envisioned that this motif could mimic the canonical Asp-X-Asp-Gly sequence found in previously reported calcium-dependent lipopeptide antibiotics. Chemical investigation of the producing strain led to the discovery of three novel lipodepsipeptides, dilarmycins A-C. The calcium-dependent antibacterial activity of the new compounds was confirmed against the Gram-positive pathogens methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus.

Viennamycins: Lipopeptides Produced by a Streptomyces sp

Extracts from Streptomyces sp. S4.7 isolated from the rhizosphere of edelweiss, an alpine medicinal plant, exhibited activity against Gram-positive bacteria. LC-HRMS analyses of the extracts resulted in the detection of two unknown, structurally related lipopeptides that were assumed to be responsible for the antibiotic activity. LC-MS guided isolation and structure elucidation of viennamycins A and B (1 and 2) by HR-MS/MS, 1D and 2D NMR, and Marfey's analyses revealed them to be novel compounds, with viennamycin A containing cysteic acid, a unique feature for lipopeptides. Tests for antibacterial, antifungal, and cytotoxic activities of purified viennamycins, both with and without divalent cations, did not reveal any bioactivity, suggesting that their biological function, which could not be determined in the tests used, is atypical for lipopeptides. The genome of Streptomyces sp. S4.7 was sequenced and analyzed, revealing the viennamycin biosynthetic gene cluster. Detailed bioinformatics-based analysis of the viennamycin gene cluster allowed elucidation of the biosynthetic pathway for these lipopeptides.

Enantioselective total synthesis of pyrrolo-[2,1-c][1,4]-benzodiazepine monomers (S)-(−)-barmumycin and (S)-(+)-boseongazepine B

An efficient enantioselective total synthesis of pyrrolo-[2,1-c][1,4]benzodiazepine (PBD) monomers (S)-(−)-barmumycin and (S)-(+)-boseongazepine B was achieved through a stereocontrolled strategy, which relies on a proline catalysed asymmetric α-amination and ester α-ethylenation.

N-Phenylacetylation and Nonribosomal Peptide Synthetases with Substrate Promiscuity for Biosynthesis of Heptapeptide Variants, JBIR-78 and JBIR-95

JBIR-78 (1) and JBIR-95 (2), both of which are heptapeptide derivatives isolated from Kibdelosporangium sp. AK-AA56, have the same amino acid sequences except for the second amino acid: phenylacetic acid (Paa)-l-Val-d-Asp (1)/d-cysteic acid (2)-l-Ala-(3S)-3-hydroxy-d-Leu-Gly-d-Ala-l-Phe. Heterologous expression of the biosynthetic gene cluster including genes encoding nonribosomal peptide synthetases (NRPS) and in vitro assays with recombinant Orf3, an l-cysteic acid synthase homologue, suggested the single A domain in module 2 activates both l-Asp and l-cysteic acid to yield 1 and 2, respectively, although the substrate specificities of the A domains of NRPSs are usually strict. Biosynthetic mechanism of introduction of N-terminal Paa was also investigated. Recombinant Orf1 and Orf2 similar to subunits of pyruvate dehydrogenase complex catalyzed the conversion of phenylpyruvate into phenylacetyl-CoA together with dihydrolipoyl dehydrogenase whose encoding gene is located outside of the gene cluster. Moreover, we showed that phenylacetyl-CoA was directly condensed with l-Val, which was tethered to a peptidyl carrier protein, at the first condensation domain in the NRPS.

Long-range proton-carbon coupling constants: NMR methods and applications

A general review of novel NMR methods to measure heteronuclear long-range proton-carbon coupling constants ((n)JCH; n>1) in small molecules is made. NMR experiments are classified in terms of NMR pulse scheme and cross-peak nature. A discussion about simplicity, general applicability and accuracy for each particular NMR experiment is presented and exemplified. Important aspects such as the sign determination and measurement of very small coupling values involving protonated and non-protonated carbons as well as the complementarity between different experiments are also discussed. Finally, a compilation of applications in structural and conformational analysis of different types of molecules since 2000 is surveyed.