Conformational studies of free and Li+ complexed jasplakinolide, a cyclic depsipeptide from the Fijian marine sponge Jaspis splendens

A ribosomally synthesised and post-translationally modified peptide containing a β-enamino acid and a macrocyclic motif

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are structurally complex natural products with diverse bioactivities. Here we report discovery of a RiPP, kintamdin, for which the structure is determined through spectroscopy, spectrometry and genomic analysis to feature a bis-thioether macrocyclic ring and a β-enamino acid residue. Biosynthetic investigation demonstrated that its pathway relies on four dedicated proteins: phosphotransferase KinD, Lyase KinC, kinase homolog KinH and flavoprotein KinI, which share low homologues to enzymes known in other RiPP biosynthesis. During the posttranslational modifications, KinCD is responsible for the formation of the characteristic dehydroamino acid residues including the β-enamino acid residue, followed by oxidative decarboxylation on the C-terminal Cys and subsequent cyclization to provide the bis-thioether ring moiety mediated by coordinated action of KinH and KinI. Finally, conserved genomic investigation allows further identification of two kintamdin-like peptides among the kin-like BGCs, suggesting the occurrence of RiPPs from actinobacteria.

The chemical diversity of peptides from ribosomal origin is a growing field of research. Here, the authors report the discovery, genomic and biosynthetic investigations of kintamdin, a ribosomally synthesized and post-translationally modified peptides featuring a beta-enamino acid and a bis-thioether macrocyclic motif.

Tavarua Deoxyriboside A and Jasplakinolide as Potential Neuroprotective Agents: Effects on Cellular Models of Oxidative Stress and Neuroinflammation

The oceans harbor a great reservoir of molecules with unknown bioactivities, which could be useful for the treatment of illnesses that nowadays have no cure, such as neurodegenerative diseases. In this work, we evaluated the neuroprotective potential of the marine Fijian compounds tavarua deoxyriboside A and jasplakinolide against oxidative stress and neuroinflammation, crucial mechanisms in neurodegeneration. Both metabolites protected SH-SY5Y human neuroblastoma cells from H₂O₂ damage, improving mitochondrial function and activating the antioxidant systems of cells. These effects were mediated by their ability of inducing Nrf2 translocation. In BV2 microglial cells activated with lipopolysaccharide, Fijian metabolites also displayed promising results, decreasing the release of proinflammatory mediators (ROS, NO, cytokines) through the reduction of gp91 and NFkB-p65 expression. Finally, we performed a coculture among both cell lines, in which treatment with compounds protected SH-SY5Y cells from activated microglia, corroborating their neuroprotective effects. These results suggest that tavarua deoxyriboside A and jasplakinolide could be used as candidate molecules for further studies against neurodegeneration.

Synthesis and biological evaluation of new jasplakinolide (jaspamide) analogs

Synthesis and biological evaluation of jasplakinolide analogs are described. The synthesis of analogs utilized a diastereoselective syn-aldol reaction and an orthoester Claisen rearrangement as key steps. All synthetic analogs were evaluated for their ability to disrupt the actin cytoskeleton. Compounds 2, 3, and 4 essentially displayed similar activity to jasplakinolide.

Cyclodepsipeptides from marine sponges: natural agents for drug research

A number of natural products from marine sponges, such as cyclodepsipeptides, have been identified. The structural characteristics of this family of cyclic peptides include various unusual amino acid residues and unique N-terminal polyketide-derived moieties. Papuamides are representatives of a class of marine sponge derived cyclic depsipeptides, including callipeltin A, celebesides A and B, homophymine A, mirabamides, microspinosamide, neamphamide A and theopapuamides. They are thought to have cytoprotective activity against HIV-1 in vitro by inhibiting viral entry. Jasplakinolide, a representative member of marine sponge-derived cyclodepsipeptides that include arenastatin A, geodiamolides, homophymines, spongidepsin and theopapuamides, is a potent inducer of actin polymerization in vitro. Although actin dynamics is essential for tumor metasasis, no actin targeting drugs have been used in clinical trials due to their severe cytotoxicity. Nonetheless, the actin cytoskeleton remains a potential target for anti-cancer drug development. These features imply the use of cyclodepsipeptides as molecular models in drug research.

Ribosomal peptide natural products: bridging the ribosomal and nonribosomal worlds

Ribosomally synthesized bacterial natural products rival the nonribosomal peptides in their structural and functional diversity. The last decade has seen substantial progress in the identification and characterization of biosynthetic pathways leading to ribosomal peptide natural products with new and unusual structural motifs. In some of these cases, the motifs are similar to those found in nonribosomal peptides, and many are constructed by convergent or even paralogous enzymes. Here, we summarize the major structural and biosynthetic categories of ribosomally synthesized bacterial natural products and, where applicable, compare them to their homologs from nonribosomal biosynthesis.

Enantioselective Total Synthesis of (+)-Jasplakinolide

An enantioselective total synthesis of (+)-jasplakinolide is described. The synthesis of the polyketide template utilized a diastereoselective syn-aldol, ortho-ester Claisen rearrangement followed by efficient conversion to a cyanide. The beta-amino acid unit was constructed in a highly diastereoselective manner utilizing nucleophilic addition to a chiral sulfinimine. Yamaguchi macrocyclization and removal of the protecting group provided a convenient access to (+)-jasplakinolide.

Amino Acid Derived Macrocycles—An Area Driven by Synthesis or Application?

The synthesis, structure, and physical properties of macrocycles have fascinated chemists for many years. Their inherent properties make them useful in areas as diverse as ion transport across membranes, development of new antibiotics, and catalysis. In this Review, the authors examine the chemistry of macrocycles containing non-peptidic amino acid derived molecules; the analysis is discussed in terms of function, rather than structure or synthesis. It is revealed that the diverse and imaginative structures created by synthetic chemists are not being fully exploited in application-driven endeavors.