Furanodictine A and B: amino sugar analogues produced by cellular slime mold Dictyostelium discoideum showing neuronal differentiation activity

Isolation and Structure Determination of New Pyrones from Dictyostelium spp. Cellular Slime Molds Coincubated with Pseudomonas spp

Cellular slime molds are excellent model organisms in the field of cell and developmental biology because of their simple developmental patterns. During our studies on the identification of bioactive molecules from secondary metabolites of cellular slime molds toward the development of novel pharmaceuticals, we revealed the structural diversity of secondary metabolites. Cellular slime molds grow by feeding on bacteria, such as Klebsiella aerogenes and Escherichia coli, without using medium components. Although changing the feeding bacteria is expected to affect dramatically the secondary metabolite production, the effect of the feeding bacteria on the production of secondary metabolites is not known. Herein, we report the isolation and structure elucidation of clavapyrone (1) from Dictyostelium clavatum, intermedipyrone (2) from D. magnum, and magnumiol (3) from D. intermedium. These compounds are not obtained from usual cultural conditions with Klebsiella aerogenes but obtained from coincubated conditions with Pseudomonas spp. The results demonstrate the diversity of the secondary metabolites of cellular slime molds and suggest that widening the range of feeding bacteria for cellular slime molds would increase their application potential in drug discovery.

Easy Access to Sauropunols A-D: Synthesis and Spectroscopy Correlation of Their Natural Methyl and Ethyl Glycosides

3,6-Anhydro-2-deoxy-hexofuranoside, the natural product core, is present in natural sauropunols (A-D) and in their natural methyl and ethyl glycosides, now, namely, sauropunol H and sauropunol F. The easily synthesized d-glucose-derived 3,6-anhydro-1,2-O-isopropylidene-5-O-benzoyl-α-d-glucofuranose was elaborated to final targets employing the TsOH·H2O-catalyzed glycosylation reaction with seven different alcohols, subsequent radical deoxygenation, and appropriate deprotection reactions involving mild conditions with excellent functional group tolerance. A short total synthesis of sauropunols (A-D), sauropunol H, and the first total synthesis of sauropunol F are reported herein. The correlation of spectroscopy data of sauropunol H and sauropunol F has been derived through these syntheses.

Towards Shell Biorefinery: Advances in Chemical-Catalytic Conversion of Chitin Biomass to Organonitrogen Chemicals

Chitin is the most abundant biopolymer after cellulose but it has not been fully utilized yet. Because of biologically fixed nitrogen, effective conversion of chitin or its derivatives to value-added organonitrogen compounds is a promising strategy to valorize chitin biomass, which has attracted increasing attention. Recently, a novel concept of shell biorefinery has been proposed on account of the huge potentials of chitin valorization. Until now, a number of valuable organonitrogen chemicals, including amino sugars, amino alcohols, amino acids, and heterocyclic compounds, have been produced from chitin biomass. In this Minireview, the focus is on the recent advances in the synthesis of organonitrogen chemicals employing chitin biomass as starting material via different catalytic processes. An outlook on the challenges and opportunities for more effective valorization of chitin will be given.

Laboratory culture and bioactive natural products of myxomycetes

Myxomycetes, one of the lowest classes of eukaryote (true slime molds), are an unusual group of primitive organisms. Their life cycle consists of two stages, namely the free-living plasmodium and the fruiting body with unique structures and colors. The chemical studies on the secondary metabolites of the myxomycetes are limited due to a lack of understanding of their laboratory cultivation. In this review, 93 natural products from myxomycetes, including their chemical structures and bioactivities were described. We also provided a conceptual overview over five culture methods of myxomycetes, including moist chamber culture, feeding culture, pure culture, liquid culture and hanging drop culture.

Two New Terpenes Isolated from Dictyostelium Cellular Slime Molds

We report a protoilludane-type sesquiterpene, mucoroidiol, and a geranylated bicyclogermacranol, firmibasiol, isolated from Dictyostelium cellular slime molds. The methanol extracts of the fruiting bodies of cellular slime molds were separated by chromatographic methods to give these compounds. Their structures have been established by several spectral means. Mucoroidiol and firmibasiol are the first examples of more modified and oxidized terpenoids isolated from cellular slime molds. Mucoroidiol showed moderate osteoclast-differentiation inhibitory activity despite demonstrating very weak cell-proliferation inhibitory activity. Therefore, cellular slime molds produce considerably diverse secondary metabolites, and they are promising sources of new natural product chemistry.

Dictyostelium: An Important Source of Structural and Functional Diversity in Drug Discovery

The cellular slime mold Dictyostelium discoideum is an excellent model organism for the study of cell and developmental biology because of its simple life cycle and ease of use. Recent findings suggest that Dictyostelium and possibly other genera of cellular slime molds, are potential sources of novel lead compounds for pharmacological and medical research. In this review, we present supporting evidence that cellular slime molds are an untapped source of lead compounds by examining the discovery and functions of polyketide differentiation-inducing factor-1, a compound that was originally isolated as an inducer of stalk-cell differentiation in D. discoideum and, together with its derivatives, is now a promising lead compound for drug discovery in several areas. We also review other novel compounds, including secondary metabolites, that have been isolated from cellular slime molds.

Natural Products from Social Amoebae

Natural products are invaluable sources of structural diversity and complexity ideally suited for the development of therapeutic agents. The search for novel bioactive molecules has prompted scientists to explore various ecological niches. Microorganisms have been shown to constitute such an important source. Despite their biosynthetic potential, social amoebae, that is, microorganisms with both a uni- and multicellular lifestyle, are underexplored regarding their secreted secondary metabolome. In this review, we present the structural diversity of amoebal natural products and discuss their biological functions as well as their total syntheses.

Isolation, Synthesis, and Biological Activity of Chlorinated Alkylresorcinols from Dictyostelium Cellular Slime Molds

Eight chlorinated alkylresorcinols, monochasiol A-H (1-8), were isolated from the fruiting bodies of Dictyostelium monochasioides. Compounds 1-8 were synthesized to confirm their structures and to obtain sufficient material for performing biological tests. Monochasiol A (1) selectively inhibited the concanavalin A-induced interleukin-2 production in Jurkat cells, a human T lymphocyte cell line. Monochasiols were biogenetically synthesized by the combination of biosynthetic enzymes relating to the principal polyketides, MPBD and DIF-1, produced by Dictyostelium discoideum.

Total synthesis, structural elucidation and anti-inflammatory activity evaluation of 2-deoxy-3,6-anhydro hexofuranoside derivatives isolated from Sauropus rostratus

The first total synthesis of four 2-deoxy-3,6-anhydro hexofuranoside derivatives isolated from Genus Sauropus rostratus was accomplished.

Weight loss by Ppc-1, a novel small molecule mitochondrial uncoupler derived from slime mold

Mitochondria play a key role in diverse processes including ATP synthesis and apoptosis. Mitochondrial function can be studied using inhibitors of respiration, and new agents are valuable for discovering novel mechanisms involved in mitochondrial regulation. Here, we screened small molecules derived from slime molds and other microorganisms for their effects on mitochondrial oxygen consumption. We identified Ppc-1 as a novel molecule which stimulates oxygen consumption without adverse effects on ATP production. The kinetic behavior of Ppc-1 suggests its function as a mitochondrial uncoupler. Serial administration of Ppc-1 into mice suppressed weight gain with no abnormal effects on liver or kidney tissues, and no evidence of tumor formation. Serum fatty acid levels were significantly elevated in mice treated with Ppc-1, while body fat content remained low. After a single administration, Ppc-1 distributes into various tissues of individual animals at low levels. Ppc-1 stimulates adipocytes in culture to release fatty acids, which might explain the elevated serum fatty acids in Ppc-1-treated mice. The results suggest that Ppc-1 is a unique mitochondrial regulator which will be a valuable tool for mitochondrial research as well as the development of new drugs to treat obesity.

Construction of 3,6-anhydrohexosides via intramolecular cyclization of triflates and its application to the synthesis of natural product isolated from leaves of Sauropus rostratus

A novel synthetic approach to construct various 3,6-anhydrohexosides via an intramolecular cyclization of corresponding triflates is described. The nucleophilic attack from C3 p-methoxybenzylated hydroxyl to C6 trifluoromethanesulfonate on triflate structures triggered the cyclization reaction to provide 3,6-anhydrohexosides in excellent yields, making the strategy more efficient with respect to the reported protocols. By applying this methodology, a concise first total synthesis of natural product isolated from leaves of Sauropus rostratus was accomplished.

Rhodium(ii)-catalysed tandem aziridination and ring-opening: stereoselective synthesis of functionalised tetrahydrofurans

Rh(ii) mediated tandem aziridination and cycloetherification achieves a direct, stereoselective synthesis of the 2-(1-amino-2-hydroxyethyl)tetrahydrofuran motif.

Total synthesis of the cytotoxic anhydrophytosphingosine pachastrissamine (jaspine B)

A short, 8-step synthesis of the marine natural product pachastrissamine has been developed that relies on a diastereoselective aldol reaction between a suitably protected hydantoin and an optically enriched α-chloroaldehyde. This synthetic route provides new opportunities for exploring structure activity relationships within this family of natural products.

Novel chlorinated dibenzofurans isolated from the cellular slime mold, Polysphondylium filamentosum, and their biological activities

Cellular slime molds are expected to have the huge potential for producing secondary metabolites including polyketides, and we have studied the diversity of secondary metabolites of cellular slime molds for their potential utilization as new biological resources for natural product chemistry. From the methanol extract of fruiting bodies of Polysphondylium filamentosum, we obtained new chlorinated benzofurans Pf-1 (4) and Pf-2 (5) which display multiple biological activities; these include stalk cell differentiation-inducing activity in the well-studied cellular slime mold, Dictyostelium discoideum, and inhibitory activities on cell proliferation in mammalian cells and gene expression in Drosophila melanogaster.

Derivatives of Dictyostelium discoideum differentiation-inducing factor-3 suppress the activities of Trypanosoma cruzi in vitro and in vivo

Chagas disease (human American trypanosomiasis), which is caused by the protozoan parasite Trypanosoma cruzi, is responsible for numerous deaths each year; however, established treatments for the disease are limited. Differentiation-inducing factor-1 (DIF-1) and DIF-3 are chlorinated alkylphenones originally found in the cellular slime mold Dictyostelium discoideum that have been shown to possess pharmacological activities. Here, we investigated the effects of DIF-3 derivatives on the infection rate and growth of T. cruzi by using an in vitro assay system utilizing host human fibrosarcoma HT1080 cells. Certain DIF-3 derivatives, such as butoxy-DIF-3 (Bu-DIF-3), at micro-molar levels strongly suppressed both the infection rate and growth of T. cruzi in HT1080 cells and exhibited little toxicity for HT1080 cells. For example, the IC50 of DIF-3 and Bu-DIF-3 versus the growth of T. cruzi in HT1080 cells were 3.95 and 0.72μM, respectively, and the LD50 of the two compounds versus HT1080 cells were both greater than 100μM. We also examined the effects of DIF-3 and Bu-DIF-3 on T. cruzi activity in C57BL/6 mice. Intraperitoneally administered Bu-DIF-3 (50mg/kg) significantly suppressed the number of trypomastigotes in blood with no apparent adverse effects. These results strongly suggest that DIF-3 derivatives could be new lead compounds in the development of anti-trypanosomiasis drugs.

Natural product-like synthetic libraries

There is a paucity of chemical matter suitably poised for effective drug development. Improving the quality and efficiency of research early on in the drug discovery process has been a long standing objective for the drug industry and improvements to the accessibility and quality of compound screening decks might have a significant and positive impact. In the absence of specific molecular information that can be modeled and used predicatively we are far from identifying which small molecules are most relevant to emerging biological targets such as protein-protein interactions. Natural products have been historically successful as an entry point for drug discovery and recently screening libraries are being synthesized to emulate natural product like features.

The Henry reaction of (1R)-(1,4:3,6-dianhydro-D-mannitol-2-yl)-1,4:3,6-dianhydro-D-fructose 5,5'-dinitrate. Different reactive features of nitromethane to nitroethane

Henry reactions of a novel higher sugar derivative, (1R)-(1,4:3,6-dianhydro-D-mannitol-2-yl)-1,4:3,6-dianhydro-D-fructose 5,5'-dinitrate (Alternate nomenclature: (1R)-(isomannid-2-yl)-1,4:3,6-dianhydro-D-fructose 5,5'-dinitrate), with nitromethane and nitroethane were studied. The kinetic and thermodynamic reactions with nitromethane under different conditions were carried out to afford (2S)- and (2R)-beta-nitroalcohols, respectively. But when using nitroethane the reaction gave a (2S)-beta-nitroalcohol with an inverted configuration at vicinal carbon C-1. Two stereogenic centers were generated, and one was altered in the reaction.

Dissecting the functional role of polyketide synthases in Dictyostelium discoideum: biosynthesis of the differentiation regulating factor 4-methyl-5-pentylbenzene-1,3-diol

Dictyostelium discoideum exhibits the largest repository of polyketide synthase (PKS) proteins of all known genomes. However, the functional relevance of these proteins in the biology of this organism remains largely obscure. On the basis of computational, biochemical, and gene expression studies, we propose that the multifunctional Dictyostelium PKS (DiPKS) protein DiPKS1 could be involved in the biosynthesis of the differentiation regulating factor 4-methyl-5-pentylbenzene-1,3-diol (MPBD). Our cell-free reconstitution studies of a novel acyl carrier protein Type III PKS didomain from DiPKS1 revealed a crucial role of protein-protein interactions in determining the final biosynthetic product. Whereas the Type III PKS domain by itself primarily produces acyl pyrones, the presence of the interacting acyl carrier protein domain modulates the catalytic activity to produce the alkyl resorcinol scaffold of MPBD. Furthermore, we have characterized an O-methyltransferase (OMT12) from Dictyostelium with the capability to modify this resorcinol ring to synthesize a variant of MPBD. We propose that such a modification in vivo could in fact provide subtle variations in biological function and specificity. In addition, we have performed systematic computational analysis of 45 multidomain PKSs, which revealed several unique features in DiPKS proteins. Our studies provide a new perspective in understanding mechanisms by which metabolic diversity could be generated by combining existing functional scaffolds.

First example of 5/6-O-linked pseudosaccharides: synthesis of bicyclic nucleosides containing azido or extended carbohydrate moiety

Treatment of the d-glucose-derived substrate 1 with sodium hydride in tetrahydrofuran provided 3,6-anhydro monosaccharide 2, along with the 5,6-ether linked pseudodisaccharide 3, and pseudotrisaccharide 4. However, reaction of 1 with sodium ethoxide in ethanol afforded 2 as the sole product, elaborated to the bicyclic azidonucleosides 9 and 16. Acetylated bicyclic nucleosides 17-19 with extended carbohydrate residues have been synthesized from 3.

[Novel biologically active compounds isolated from unexploited organisms, cellular sime molds]

Cellular slime molds are thought to be excellent model organisms for the study of cell and developmental biology because of their simple pattern of development. However, there have been few reports on secondary metabolites of them. We have focused on the utility of cellular slime molds as novel resources for natural product chemistry, and have studied the diversity of secondary metabolites produced by them as well as their physiological and pharmacological activities. We have recently isolated many novel compounds from the fruiting bodies of various species of Dictyostelium cellular slime molds. Total syntheses and biological evaluation of these compounds have been carried out. It was shown that dictyopyrones and dictyomedins may regulate Dictyostelium development. Amino sugar derivatives such as furanodictines and dictyoglucosamines induced neuronal differentiation of rat PC-12 cells. In addition, brefelamide inhibited the cellular proliferation of 1321N1 human astrocytoma cells. These results show that cellular slime molds are promising sources in natural product chemistry.

GrlJ, a Dictyostelium GABAB-like receptor with roles in post-aggregation development

BACKGROUND

The G-protein-coupled receptor (GPCR) family represents the largest and most important group of targets for chemotherapeutics. They are extremely versatile receptors that transduce signals as diverse as biogenic amines, purins, odorants, ions and pheromones from the extracellular compartment to the interior via biochemical processes involving GTP-binding proteins. Until recently, the cyclic AMP receptors (cARs) were the only known G protein coupled receptors in Dictyostelium discoideum. The completed genome sequence revealed the presence of several families of GPCRs in Dictyostelium, among them members of the family 3 of GPCRs, the GABAB/glutamate like receptor family, which in higher eukaryotes is involved in neuronal signaling.

RESULTS

D. discoideum has seventeen Family 3 members of GPCRs, denoted GrlA through GrlR. Their transcripts are detected throughout development with increased levels during early and late development. We have examined here GrlJ. GFP-tagged GrlJ localises to the plasma-membrane and to internal membranes. Inactivation of the grlJ gene leads to precocious development, and the mutant completes development ~6 hours earlier. Alterations were also noted at the slug stage and in spore formation. grlJ- slugs were longer and broke apart several times on their way to culmination forming smaller but proportionate fruiting bodies. Spores from grlJ- fruiting bodies were malformed and less viable, although the spore differentiation factors were synthesized and sensed normally. Expression of a GFP-tagged full length GrlJ rescued the phenotype.

CONCLUSION

Our data suggest that GrlJ acts at several stages of Dictyostelium development and that it is a negative regulator in Dictyostelium development.

Anti-leukemic activities of Dictyostelium secondary metabolites: a novel aromatic metabolite, 4-methyl-5-n-pentylbenzene-1,3-diol, isolated from Dictyostelium mucoroides suppresses cell growth in human leukemia K562 and HL-60 cells

It has previously been shown that DIF-1, a differentiation-inducing factor of the cellular slime mold Dictyostelium discoideum, possesses antitumor activities in mammalian tumor cells and that neuronal differentiation of PC12 cells can be induced with furanodictines (FDs), aminosugar analogs found in D. discoideum, or dictyoglucosamines (DGs), N-acetyl glucosamine derivatives (DG-A from D. purpureum and DG-B from D. discoideum). Thus, cellular slime molds are attractive natural resources that may provide valuable lead compounds to be utilized in the field of pharmacology and medicine. In this study, we have isolated a novel aromatic compound, 4-methyl-5-n-pentylbenzene-1,3-diol (MPBD), from fruiting bodies of the cellular slime mold D. mucoroides and assessed the in vitro antiproliferative activities of MPBD, FDs, and DGs in human leukemia K562 and HL-60 cells. MPBD at 20-80 microM dose-dependently suppressed cell growth in both K562 and HL-60 cells. While FDs at 10-80 microM did not affect cell growth, DGs at 10-40 microM dose-dependently suppressed cell growth in the cells. Although we failed to find the roles of FDs and DGs in the original organisms, MPBD at 5-20 microM was found to promote stalk cell formation in D. discoideum. The present results indicate that MPBD, DGs or their derivatives may have therapeutic potential in the treatment of cancer and confirm our expectations regarding cellular slime molds as drug resources.

Discovery of protein phosphatase inhibitor classes by biology-oriented synthesis

Protein phosphatases have very recently emerged as important targets for chemical biology and medicinal chemistry research, and new phosphatase inhibitor classes are in high demand. The underlying frameworks of natural products represent the evolutionarily selected fractions of chemical space explored by nature so far and meet the criteria of relevance to nature and biological prevalidation most crucial to inhibitor development. We refer to synthesis efforts and compound collection development based on these criteria as biology-oriented synthesis. For the discovery of phosphatase inhibitor classes by means of this approach, four natural product-derived or -inspired medium-sized compound collections were synthesized and investigated for inhibition of the tyrosine phosphatases VE-PTP, Shp-2, PTP1B, MptpA, and MptpB and the dual-specificity phosphatases Cdc25A and VHR. The screen yielded four unprecedented and selective phosphatase inhibitor classes for four phosphatases with high hit rates. For VE-PTP and MptpB the first inhibitors were discovered. These results demonstrate that biology-oriented synthesis is an efficient approach to the discovery of new compound classes for medicinal chemistry and chemical biology research that opens up new opportunities for the study of phosphatases, which may lead to the development of new drug candidates.

Astonishing diversity of natural surfactants: 1. Glycosides of fatty acids and alcohols

Alkyl and fatty acid glycosides have become of great commercial interest in general and specifically for the pharmaceutical, cosmetic, and food industries. Natural surfactants are good sources for future chemical preparation of these glycosides. This review article shows an astonishing diversity of natural surfactants that could be used in laboratories and industry. More than 250 natural surfactants, including their chemical structures and biological activities, are described in this review article.

Secondary metabolites of slime molds (myxomycetes)

The compounds reported from the slime molds (myxomycetes) species are described. Almost 100 natural compounds including their chemical structures and biological activities are described in this review article. Only metabolites with a well-defined structure are included.

Discovery of the Chemical Function of Glycosidases: Design, Synthesis, and Evaluation of Mass-Differentiated Carbohydrate Libraries

[reaction: see text] Discovery of the catalytic chemical function of the many putative glycosidases coded in genomes currently relies on individual testing of possible substrates, usually as their p-nitrophenol conjugate. Herein, we present an alternative chemical proteomics approach using a synthetic mass-differentiated heat-stable substrate library with mass spectrometry readout. Library components do not serve as reaction inhibitors and both primary and secondary enzyme substrates can be delineated.