Abstract
The laxaphyci’s B family constitutes a group of five related cyclic lipopeptides isolated from diverse cyanobacteria from all around the world. This group shares a typical structure of 12 amino acids from the l and d series, some of them hydroxylated at the beta position, and all containing a rare beta-amino decanoic acid. Nevertheless, they can be differentiated due to slight variations in the composition of their amino acids, but the configuration of their alpha carbon remains conserved. Here, we provide the synthesis and characterization of new laxaphycin B-type peptides. In doing so we discuss how the synthesis of laxaphycin B and analogues was developed. We also isolate minor acyclic laxaphycins B, which are considered clues to their biosynthesis.
Highlights
Among marine organisms, filamentous cyanobacteria occupy a special place and/or are of great interest for chemists because they produce a wide range of bioactive molecules, mainly cyclic lipopeptides [1,2,3]
Laxaphycins are cyclic lipopeptides synthesized through a hybrid polyketide synthases (PKS)/non‐ribosomal peptide synthases (NRPS) biosynthetic pathway by different marine or freshwater cyanobacteria
They need to prepare non‐natural amino acids and use them sparingly when developing the synthesis or even have recourse to use related analogs, before extending the synthesis to the natural compound. Taking these limitations into account, especially the uncertainty concerning the stereochemistry of the residue in position 3, we proposed an analog of the ((2S,3S)‐Hle3)laxaphycin B, the compound initially described for laxaB, in which the 2‐aminodecanoic acid (Ade), the 3‐hydroxyleucines (Hle), and the 3‐hydroxyasparagine (HAsn) were replaced by the simplest and commercially available β‐alanine, threonine, and asparagine, respectively, leading to analog 1 (Figure 2)
Summary
Filamentous cyanobacteria occupy a special place and/or are of great interest for chemists because they produce a wide range of bioactive molecules, mainly cyclic lipopeptides [1,2,3]. They produce this class of secondary peptide metabolites via a non‐ribosomal pathway that is responsible, for example, for the modification of natural amino acids into D‐, N‐methyl, β‐hydroxylated, or dehydrated amino acids. Laxaphycin A‐type and laxaphycin B‐type peptides are generally found in the same cyanobacteria
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