Synthesis of the spirosuccinimide moiety of Asperparaline A

2,6,6-Trimethyl-2-azaspiro[4.4]nonane-1,3-dione (9), a spirosuccinimide moiety of asperparaline A (1), was synthesized by starting from 2,2-dimethylcyclopentanone (4) via trinitrile 6 in five steps in a moderate yield. This conversion establishes a model study for synthesis of the spirosuccinimide moiety of asperparaline A (1).     

A fungal metabolite asperparaline a strongly and selectively blocks insect nicotinic acetylcholine receptors: the first report on the mode of action

Asperparalines produced by Aspergillus japonicus JV-23 induce paralysis in silkworm (Bombyx mori) larvae, but the target underlying insect toxicity remains unknown. In the present study, we have investigated the actions of asperparaline A on ligand-gated ion channels expressed in cultured larval brain neurons of the silkworm using patch-clamp electrophysiology. Bath-application of asperparaline A (10 μM) had no effect on the membrane current, but when delivered for 1 min prior to co-application with 10 μM acetylcholine (ACh), it blocked completely the ACh-induced current that was sensitive to mecamylamine, a nicotinic acetylcholine receptor (nAChR)-selective antaogonist. In contrast, 10 μM asperparaline A was ineffective on the γ-aminobutyric acid- and L-glutamate-induced responses of the Bombyx larval neurons. The fungal alkaloid showed no-use dependency in blocking the ACh-induced response with distinct affinity for the peak and slowly-desensitizing current amplitudes of the response to 10 μM ACh in terms of IC(50) values of 20.2 and 39.6 nM, respectively. Asperparaline A (100 nM) reduced the maximum neuron response to ACh with a minimal shift in EC(50), suggesting that the alkaloid is non-competitive with ACh. In contrast to showing marked blocking action on the insect nAChRs, it exhibited only a weak blocking action on chicken α3β4, α4β2 and α7 nAChRs expressed in Xenopus laevis oocytes, suggesting a high selectivity for insect over certain vertebrate nAChRs.     

Selective cytotoxicity of recombinant STXA1-GM-CSF protein in hematopoetic cancer cells

Chimeric proteins are composed of a cell-targeting moiety and a cell-killing moiety. In this study, a chimeric protein, STXA1-GM-CSF, composed of catalytic domain of Shiga toxin (A1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) was constructed and expressed in E. coli. Cytotoxicity, receptor blocking, and neutralization experiments revealed that the chimeric protein induced cytotoxic effect on different cell lines. This effect was found to be specific, due to the presence of the killing moiety (A1), which exerts its effect through a specific GM-CSF-targeting domain, by binding to its receptor present on those cell lines. These initial investigations indicate that the chimeric protein was functional; further analyses are required for its application.     

Biosynthesis of the nargenicin A<Subscript>1</Subscript> pyrrole moiety from <Emphasis Type="Italic">Nocardia</Emphasis> sp. CS682

A number of structurally diverse natural products harboring pyrrole moieties possess a wide range of biological activities. Studies on biosynthesis of pyrrole ring have shown that pyrrole moieties are derived from l-proline. Nargenicin A₁, a saturated alicyclic polyketide from Nocardia sp. CS682, is a pyrrole-2-carboxylate ester of nodusmicin. We cloned and identified a set of four genes from Nocardia sp. CS682 that show sequence similarity to the respective genes involved in the biosynthesis of the pyrrole moieties of pyoluteorin in Pseudomonas fluorescens, clorobiocin in Streptomyces roseochromogenes subsp. Oscitans, coumermycin A₁ in Streptomyces rishiriensis, one of the pyrrole rings of undecylprodigiosin in Streptomyces coelicolor, and leupyrrins in Sorangium cellulosum. These genes were designated as ngnN4, ngnN5, ngnN3, and ngnN2. In this study, we presented the evidences that the pyrrole moiety of nargenicin A₁ was also derived from l-proline by the coordinated action of three proteins, NgnN4 (proline adenyltransferase), NgnN5 (proline carrier protein), and NgnN3 (flavine-dependent acyl-coenzyme A dehydrogenases). Biosynthesis of pyrrole moiety in nargenicin A₁ is initiated by NgnN4 that catalyzes ATP-dependent activation of l-proline into l-prolyl-AMP, and the latter is transferred to NgnN5 to create prolyl-S-peptidyl carrier protein (PCP). Later, NgnN3 catalyzes the two-step oxidation of prolyl-S-PCP into pyrrole-2-carboxylate. Thus, this study presents another example of a pyrrole moiety biosynthetic pathway that uses a set of three genes to convert l-proline into pyrrole-2-carboxylic acid moiety.     

Platelet activating factor-acetylhydrolase in insects: Identification and partial characterization of a 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine acetylhydrolase in a cell-free system of Heliothis

A specific acetylhydrolase that inactivates platelet activating factor (PAF; 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine), a potent cellular mediator in mammalian cells, by removal of the sn-2 acetyl moiety, has been found in the cytosolic fraction of several postembryonic developmental stages and specific tissues of the corn earworm, Heliothis zea (Boddie). Effects of magnesium, calcium, EGTA, deoxycholate, dithiothreitol, diisopropylfluorophosphate, egg phosphatidylcholine, and an acylacetyl-glycerophosphocholine show that hydrolysis of the acetate moiety is due to a specific acetylhydrolase for PAF. The activity does not appear to be due to a typical cellular phospholipase A₂ that utilizes phospholipid substrates with a long-chain acyl group at position sn-2 of glycerol. Specific activities and properties of the acetylhydrolase from this insect match closely with those described from tissues of vertebrate animals.     

Partial Structure of Glycopeptide Obtained from Scytalidium lignicolum Acid Protease A

The partial structure of glycopeptide moiety of new acid protease A isolated from Scytalidium lignicolum ATCC 24568 was studied by Smith degradation, methylation and partial acetolysis techniques. The main product, glycopeptide V (GP-V), obtained by Pronase digestion was composed of mannose, glucosamine, asparagine, serine and glycine in an approximate molar ratio of 10: 3: 2: 1: 1, and a possible structure was proposed as follows:     

Capsule polysaccharide-protein-peptidoglycan complex in the cell envelope of Rhodobacter capsulatus

The capsule polysaccharide-protein-peptidoglycan complex (insoluble in boiling sodium dodecyl sulfate and hot phenol-water) from cell envelopes of Rhodobacter capsulatus St. Louis was characterized. Hydrofluoric, hydrochloric acid or alkaline hydrolysis solubilized the polysaccharide moiety, whereas the protein-peptidoglycan moiety remained insoluble. On treatment of the protein-peptidoglycan moiety with lysozyme, the protein with peptidoglycan-residues bound was solubilized. It showed a single, broad peptide band (M _r=about 17,000) on sodium dodecyl sulfate polyacrylamide gel-electrophoresis. The same protein was obtained by lysozyme digestion (without preceding hydrofluoric or hydrochloric acid treatment) of the protein-peptidoglycan complex of the phage-resistant mutant Rhodobacter capsulatus St. Louis RC1^-, in which the capsule polysaccharide is present in a free form. A protein-peptidoglycan complex was isolated also from the capsulefree Rhodobacter capsulatus 37b4. Covalent binding between the protein and peptidoglycan moieties is likely for all three strains as is the lipoprotein nature of the protein moiety. The polysaccharide moiety of the complete complex from the wild-type Rhodobacter capsulatus St. Louis was at least partly removable from the complex in the presence of high salt concentrations or ethylene diamine tetraacetate. A specific amino acid pattern (with Ser, Gly, Glu, and Ala dominating) remained constantly associated with the capsule polysaccharide moiety independent of the separation procedure.Abbreviations A₂pm diaminopimelic acid - Cetavlon cetyltrimethyl-ammonium bromide - EDTA ethylene-diaminetetraacetate, disodium salt - HF hydrofluoric acid - HPLC high-performance liquid chromatography - PAGL polyacrylamide gel-electrophoresis - SDS sodium dodecyl sulfate - TCA trichloroacetic acid     

Relation between structure of bacterial lipopolysaccharide and the stimulation of B lymphocytes into colony formation.

Lipopolysaccharide (LPS) was analyzed in order to determine which component, lipid A or polysaccharide (PS), is able to stimulate B lymphocytes from ICR lymph nodes and spleen cells from nude (nu/nu) mice into forming colonies in soft agar culture. Lipid A, obtained by acid hydrolysis of LPS and solubilized by complex-formation with bovine serum albumin, was found to be the active moiety of LPS capable of stimulating colony growth of lymphoid cells in soft agar culture. The PS portion exhibited no significant activity at the concentrations used. Glycolipids from mutant strains of S. minnesota which contain the intact lipid moiety but are deficient in PS content, were as potent as S. abortus equi LPS in stimulating B cells into colony growth. Alkaline hydrolysis of LPS which cleaves ester-linked fatty acids, substantially decreased the number of lymphocyte colonies formed. This indicates that the intact lipid moiety is required for stimulating lymphocytes into colony formation. The synthetic glycolipid, N-palmitoyl-D-glucosamine (NPG), whose structure is similar to some components of lipid A, was also able to induce B lymphocyte colony development. In summary, our data point to lipid A as the active moiety of the endotoxin which induces B lymphocytes to grow and develop into colonies in the 2-layer soft agar culture system.     

Application of click chemistry towards an efficient synthesis of 1,2,3-1H-triazolyl glycohybrids as enzyme inhibitors

An efficient synthesis of novel 1,2,3-1H-triazolyl glycohybrids with two or more than two sugar units or a chromenone moiety via copper-catalysed azide–alkyne cycloaddition (CuAAC), a 1,3-dipolar cycloaddition of glycosyl azides to 2,3-unsaturated alkynyl glycosides or propargyloxy coumarins is described. The synthesised glycohybrids were screened for their α-glucosidase, glycogen phosphorylase and glucose-6-phosphatase inhibitory activities. A few of the glycohybrids showed promising inhibitory activities against these enzymes.     

Ideamine N-Oxides: Pyrrolizidine Alkaloids Sequestered by the Danaine Butterfly,Idea leuconoe

Two new pyrrolizidine alkaloids, ideamines A and B, together with other analogs (lycopsamine and parsonsine) were isolated in the N-oxide forms from adult bodies of the Apocynaceae-feeding danaine butterfly, Idea leuconoe. Ideamine A was characterized as a homolog of lycopsamine, in which the viridifloric acid moiety was replaced by a 2-ethyl-2,3-dihydroxybutanoic moiety. Likewise, ideamine B was identified as a nor-derivative of parsonsine, in which the trachelanthic acid moiety was replaced by a 2-ethyl-2,3-dihydroxybutanoic moiety diastereomeric to the necic acid from ideamine A.     

Synthesis and Characteristics of Fluorescent BODIPY-Labeled Gangliosides

A series of new fluorescent-labeled gangliosides bearing the residues of acids labeled by 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene(BODIPY) in the polar or/and apolar moiety were synthesized. These are ganglioside GM1 labeled with the residue of 4,4-difluoro-4-bora-3a,4a-diaza-5,7-dimethyl-s-indacenyl-3-propanoic (BODIPY-FL-propanoic) and -indacenyl-5-pentanoic (BODIPY-FL-pentanoic) acid in the oligosaccharide moiety of the molecule, and ganglioside GD1a labeled with two residues of BODIPY-FL-pentanoic acid in the oligosaccharide moiety and also with the residue of BODIPY-FL-pentanoic acid and the residue of 4,4-difluoro-4-bora-3a,4a-diaza-5-octyl-s-indacenyl-5-pentanoic acid in the ceramide part of the molecule. Some spectral characteristics and the behavior in the model membrane systems of the synthesized probes were studied. In their emission spectra, the BODIPY-labeled gangliosides included into phosphatidylcholine liposomes at high concentrations (>1 mol %) exhibit a long-wavelength maximum (at 630 nm) in addition to the usual maximum (at 510–515 nm).     

Controlled transformation from nanorods to vesicles induced by cyclomaltoheptaoses (β-cyclodextrins)

A modified cyclomaltoheptaose (β-cyclodextrin) containing an anthraquinone moiety, mono[6-deoxy-N-n-hexylamino-(N′-1-anthraquinone)]-β-cyclodextrin (1), which can self-assemble into nanorods in aqueous solution, was synthesized. Interestingly, upon the addition of natural cyclodextrin, the nanorods could transform into bilayer vesicles, which were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), and epi-fluorescence microscopy (EFM). A transformation mechanism is suggested based on the results of ¹H NMR, 2D NMR ROESY, FTIR, and UV–vis spectra. The response of the vesicles to changing pH and adding Cu²⁺ was also tested. Our research may pave the way to the development of new intelligent materials and biomaterials.     

Structural and Stereochemical Studies of Hydroxyanthraquinone Derivatives from the Endophytic Fungus Coniothyrium sp

Four known hydroxyanthraquinones ( 1–4 ) together with four new derivatives having a tetralone moiety, namely coniothyrinones A–D ( 5–8 ), were isolated from the culture of Coniothyrium sp., an endophytic fungus isolated from Salsola oppostifolia from Gomera in the Canary Islands. The structures of the new compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. The absolute configurations of coniothyrinones A ( 5 ), B ( 6 ), and D ( 8 ) were determined by TDDFT calculations of CD spectra, allowing the determination of the absolute configuration of coniothyrinone C ( 7 ) as well. Coniothyrinones A ( 5 ), B ( 6 ), and D ( 8 ) could be used as ECD reference compounds in the determination of absolute configuration for related tetralone derivatives. This is the first report of anthraquinones and derivatives from an isolate of the genus Coniothyrium sp. These compounds showed inhibitory effects against the fungus Microbotryum violaceum, the alga Chlorella fusca, and the bacteria Escherichia coli and Bacillus megaterium. Chirality 25:141–148, 2013. © 2012 Wiley Periodicals, Inc.     

Coleifolides A and B,Two New Sesterterpenoids from the Aerial Parts of Scutellaria coleifolia H.Lév.

Coleifolides A and B ( 1 and 2 ), two new sesterterpenoids with a β‐methyl‐α,β‐unsaturated‐γ‐lactone moiety, were isolated from the aerial parts of Scutellaria coleifolia H.Lév . (Lamiaceae), together with three known compounds. Their structures were elucidated by NMR and MS examinations. Coleifolides A and B were concluded to be partially racemic compounds by the HPLC analysis using a chiral column or introduction of chiral derivatizing agents. The absolute configuration of the major isomer was determined by analyses of the CD spectrum as well as NMR data of (R)‐ and (S)‐2‐NMA derivatives. Coleifolides A and B are structurally similar to manoalide derivatives, previously isolated from marine sponges, and appear to be the first examples of this type of compounds being isolated from higher plants.     

abeo‐Taxane Diterpenoids from the Taiwanese Yew Taxus sumatrana

Chemical investigation of the acetonic extract of the leaves and twigs of Taxus sumatrana (Taxaceae) led to the isolation of four new taxane diterpene esters, taiwantaxins A–D ( 1 – 4 , resp.). Their structures were determined primarily on the basis of 1D‐ and 2D‐NMR techniques as well as MS. Compound 1 is a rearranged taxane diterpenoid possessing an opened oxetane ring moiety containing C(4), C(5), and C(20). The metabolites 2 and 3 belong to a 5/6/6 taxene system having a rare five‐membered γ‐lactone ring comprising C(8), C(9), C(10), and C(19). Compound 4 is an example of a taxane diterpene containing a 6/8/6 ring system with a tetrahydrofuran ring comprising C(2), C(3), C(4), and C(20). The 11(15→1)abeo‐taxane diterpenoids, taiwantaxins A–C ( 1 – 3 , resp.) are lacking an O‐bearing functionality at either C(13) or C(14). Compound 2 showed significant cytotoxic activity against human PC‐3 tumor cells.     

Conformational Preferences of Hypermodified Nucleoside Lysidine (k2C) Occurring at “Wobble” Position in Anticodon Loop of tRNAIle

Conformational preferences of hypermodified nucleoside, 4-amino-2-(N⁶-lysino)-1-(β-D-ribofuranosyl) pyrimidinium (Lysidine or 2-lysyl cytidine), usually designated as k²C, have been investigated theoretically by the quantum chemical perturbative configuration interaction with localized orbitals (PCILO) method. The zwitterionic, non-zwitterionic, neutral, and tautomeric forms have been studied. Automated geometry optimization using molecular mechanics force field (MMFF), semi-empirical quantum chemical PM3, and ab initio molecular orbital Hartree-Fock SCF quantum mechanical calculations have also been made to compare the salient features. The predicted most stable conformations of zwitterionic, non-zwitterionic, neutral, and tautomeric form are such that in each of these molecules the orientation of lysidine moiety (R) is trans to the N(1) of cytidine. The preferred base orientation is anti (χ = 3°) and the lysine substituent folds back toward the ribose ring. This results in hydrogen bonding between the carboxyl oxygen O(12a) of lysine moiety and the 2′-hydroxyl group of ribose sugar. In all these four forms of lysidine O(12a)…H-C(9) and O(12b)…H-N(11) interactions provide stability to respective stable conformers. Watson-Crick base pairing of lysidine with A is feasible only with the tautomeric form of usual anti oriented lysidine. This can help in recognition of AUA codon besides in avoiding misrecognition of AUG.     

Characterization of a biosurfactant, mannosylerythritol lipid produced from Candida sp. SY16

One yeast strain, SY16, was selected as a potential producer of a biosurfactant, and identified as a Candida species. A biosurfactant produced from Candida sp. SY16 was purified and confirmed to be a glycolipid. This glycolipid-type biosurfactant lowered the surface tension of water to 29 dyne/cm at critical micelle concentration of 10 mg/l (1.5 × 10⁻⁵ M), and the minimum interfacial tension was 0.1 dyne/cm against kerosene. Thin-layer and high-pressure liquid chromatography studies demonstrated that the glycolipid contained mannosylerythritol as a hydrophilic moiety. The hydrophilic sugar moiety of the biosurfactant was determined to be β-d-mannopyranosyl-(1 → 4)-O-meso-erythritol by nuclear magnetic resonance (NMR) and fast atom bombardment mass–spectroscopy analyses. The hydrophobic moiety, fatty acids, of the biosurfactant was determined to be hexanoic, dodecanoic, tetradecanoic, and tetradecenoic acid by gas chromatography–mass spectroscopy. The structure of the native biosurfactant was determined to be 6-O-acetyl-2,3- di-O-alkanoyl-β-d-mannopyranosyl-(1 → 4)-O-meso-erythritol by NMR analyses. We newly determined that an acetyl group was linked to the C-6 position of the d-mannose unit in the hydrophilic sugar moiety. Received: 18 December 1999 / Received last revision: 2 June 1999 / Accepted: 4 June 1999     

Prenylated Benzophenone Peroxide Derivatives from Hypericum sampsonii

Two new prenylated benzophenone peroxide derivatives, peroxysampsones A and B ( 1 and 2 , resp.), together with a known compound, plukenetione C ( 3 ), were isolated from the roots of the Chinese medicinal plant Hypericum sampsonii, and their structures were elucidated by detailed spectral analysis. These compounds are the unusual peroxides of polyprenylated benzophenone derivatives, containing the unique caged moiety of 4,5‐dioxatetracyclo[9.3.1.1^9,13.0^1,7]hexadecane‐12,14,15‐trione. In the biological test, peroxysampsone A ( 1 ) showed comparable activity with norfloxacin against a NorA over‐expressing multidrug‐resistant (MDR) strain of Staphylococcus aureus SA‐1199B.     

Synthesis of symmetric disulfides as potential alternative substrates for trypanothione reductase and glutathione reductase: Part 1

Summary The synthesis of a series of symmetrical disulfides as potential substrates of trypanothione reductase and glutathione reductase was described. The key intermediate in the synthetic approach was the choice of S-^tbutylmercapto-L-cysteine (1). The spermidine ring in the native substrate, trypanothione disulfide (TSST), was replaced with 3-dimethyl-aminopropylamine (DMAPA), while the-Glu moiety was replaced by phenylalanyl or tryptophanyl residues. The same modifications in the-Glu moiety of glutathione disulfide (GSSG) were applied.     

Cycloartane Triterpenes from Dikamali,the Gum Resin of Gardenia gummifera and Gardenia lucida

We report on the chemical investigation of dikamali gum, which is the resin of Gardenia gummifera and G. lucida (Rubiaceae). Six new cycloartane triterpenes, dikamaliartanes A–F ( 1 – 6 , resp.), together with a known flavonoid ( 7 ), were isolated and identified by NMR spectroscopy. All six cycloartanes are characterized by an open A‐ring with a free COOH group at C(3). In four of them, the C‐atoms C(23)–C(27) form a 4‐methylfuran‐2‐yl moiety. Bacterial assays using Staphylococcus aureus, Candida albicans, and Mycobacteria have been carried out but did not reveal significant activity.