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At least 631 records · Page 35Linked to original sources
PubMed2003

Novel synthesis and reactions of 5,7-dialkyl-4,6-dioxo-4,5,6,7-tetrahydro- isothiazolo[3,4,-d]pyrimidine-3-carbonitriles and 6-methyl-4-oxo-4H-1-aza-5-oxa-2- thiaindene-3-carbonitrile.

[reaction: see text] 5,7-Dialkyl-4,6-dioxo-4,5,6,7-tetrahydroisothiazolo[3,4-d]pyrimidine-3-carbonitriles 4, prepared from 6-amino-1,3-dialkyluracils 3 and 4,5-dichloro-5H-1,2,3-dithiazolium chloride (Appel's salt) 1, are utilized for the preparation of new derivatives of 4 bearing amino, alkylthio, amido, thioamido, tetrazolyl, and carboximidic acid ethyl ester groups at position 3. Similarly, the reactions of 6-methyl-4-oxo-4H-1-aza-5-oxa-2-thiaindene-3-carbonitrile 8, prepared from 4-amino-6-methyl-2-pyrone 6 and 1, with alkyl- and arylamines in DMF at 50 degrees C and reflux afforded different isothiazole derivatives 11 and 17, respectively. On the other hand, treatment of 8 with 1,3-diaminopropane in THF at room temperature, followed by chromatography on silica gel, gave 3-(2-oxopropyl)-6,7,8-trihydro-4H-1-thia-2,5,9-triazacyclopentacyclononene-4,10-dione 12 in 59% yield.

Journal Article↗
PubMed2005

A unique highly oxygenated pyrano[4,3-c][2]benzopyran-1,6-dione derivative with antioxidant and cytotoxic activities from the fungus Phellinus igniarius.

[structure: see text] A unique pyrano[4,3-c][2]benzopyran-1,6-dione derivative with an unprecedented carbon skeleton, phelligridin G (1), has been isolated from the fruiting body of the fungus Phellinus igniarius. Its structure was elucidated by detailed spectroscopic analysis. A possible biogenetic origin of 1 mediated by the fungal metabolite precursor 4-hydroxy-6-methyl-2-pyrone was postulated. Phelligridin G (1) showed antioxidant activity inhibiting rat liver microsomal lipid peroxidation and moderate selective cytotoxic activities against human cancer cell lines.

Animals↗
PubMed2005

A short total synthesis of aureothin and N-acetylaureothamine.

The total synthesis of the nitrophenyl pyrones, (+/-)-aureothin and (+/-)-N-acetylaureothamine, starting from known 2-ethyl-6-methoxy-3,5-dimethyl-4H-pyran-4-one are described. The key steps involved in the synthesis are the construction of the tetrahydrofuran motif using a palladium-catalyzed cycloaddition and the ruthenium-catalyzed cross-metathesis reaction of an alkenyl boronic ester. [reaction: see text]

Acetylation↗
PubMed2005

Synthesis of the aglycones of altromycins and kidamycin from a common intermediate.

The aglycone structures 1 and 2, respectively corresponding to the antitumor antibiotic natural products altromycin and kidamycin, have been efficiently synthesized from a common advanced intermediate 3. A series of Claisen condensations and aromatizations affords the anthracene section of 3, followed by annulation of the pyrone ring. The functional groups of 3 can be manipulated for enantioselective introduction of the epoxide side-chain of altromycin aglycone 1, as well as synthesis of the kidamycin aglycone 2. [reaction: see text]

Aminoglycosides↗
PubMed2005

A novel oxidative rearrangement of 6-methoxypyran-2-ones.

As part of our continuing studies of pyrone-containing natural products, a series 6-methoxypyran-2-ones were synthesized. These were found to react with molecular oxygen at 20 degrees C, and this novel reaction yielded a series of highly functionalized alpha,beta-butenolides. [reaction: see text]

Journal Article↗
PubMed2000

Synthesis of the C1-C13 fragment of leucascandrolide A.

[reaction: see text] The synthesis of the C1-C13 fragment 3 of leucascandrolide A has been completed utilizing a stereoselective and regioselective reductive cleavage of a highly functionalized spiroketal to incorporate the cis-2,6-disubstituted tetrahydropyan. The spiroketal was constructed by addition of a lithiated pyrone 5 to aldehyde 6.

Sesquiterpenes↗
PubMed1999

Production of mycotoxins on artificially and naturally infested building materials.

In this study, the ability to produce mycotoxins during growth on artificially infested building materials was investigated for Penicillium chrysogenum, Pen. polonicum, Pen. brevicompactum, Chaetomium spp., Aspergillus ustus, Asp. niger, Ulocladium spp., Alternaria spp., and Paecilomyces spp., all isolated from water-damaged building materials. Spores from the different isolates of the above mentioned species were inoculated on gypsum board with and without wallpaper and on chipboard with and without wallpaper. Fungal material was scraped off the materials, extracted, and analyzed using high performance liquid chromatography-diode array detection and thin layer chromatography. All six isolates of C. globosum produced the toxic chaetoglobosins A and C, at levels of up to 50 and 7 microg/cm2 respectively. The quantities of secondary metabolites produced by Penicillia were generally low, and no toxin production was detected from any of the five isolates of Pen. chrysogenum. Both isolates of Pen. polonicum produced 3-methoxy-viridicatin, verrucosidin, and verrucofortine. Two of five isolates of Pen. brevicompactum produced mycophenolic acid. From five out of six isolates of Alternaria spp., altenariol and alternariol monomethyl ether were detected. From Ulocladium spp., Paecilomyces spp., and Asp. ustus no known mycotoxins were detected, although the latter two are known mycotoxin producers. Asp. niger produced several naphtho-gamma-pyrones and tetra-cyclic compounds. All investigated species, especially Asp. ustus and Asp. niger produced many unknown secondary metabolites on the building materials. Analyses of wallpaper and glass-fibre wallpaper naturally infested with Asp. versicolor revealed sterigmatocystin and 5-methoxysterigmatocystin. Analyses of naturally infested wallpaper showed that C. globosum produced the chaetoglobosins A and C, and Pen. chrysogenum produced the antibiotic meleagrin.

Chromatography, High Pressure Liquid↗
PubMed2001

Behavioral and chemical analysis of venom gland secretion of queens of the ant Solenopsis geminata.

Bioassays in a Y-tube olfactometer showed that workers of Solenopsis geminata (Hymenoptera: Formicidae) were attracted to venom gland extracts of queens. Gas chromatography coupled mass spectrometry analysis of individual glands of queens of S. geminata showed that the secretion is composed mainly of a large amount of 2-alkyl-6-methylpiperidine alkaloids and a tiny amount of a delta-lactone and a a-pyrone, which have been earlier identified as components of the queen attractant pheromone of Solenopsis invicta Buren. However, additional small amounts of a mixture of sesquiterpenes and pentadecene were found. The possible function of the sesquiterpenoid compounds is discussed.

Animals↗
PubMed1999

Characterization of Sphingomonas paucimobilis SYK-6 genes involved in degradation of lignin-related compounds.

Sphingomonas paucimobilis SYK-6 is able to grow on a wide variety of dimeric lignin compounds. These compounds are degraded via vanillate and syringate by a unique enzymatic system, composed of etherases, O demethylases, ring cleavage oxygenases and side chain cleaving enzymes. These unique and specific lignin modification enzymes are thought to be powerful tools for utilization of the most abundant aromatic biomass, lignin. Here, we focus on the genes and enzymes involved in beta-aryl ether cleavage and biphenyl degradation. Two unique etherases are involved in the reductive cleavage of beta-aryl ether. These two etherases have amino acid sequence similarity with the glutathione S-transferases, and use glutathione as a hydrogen donor. It was found that 5,5'-dehydrodivanillate, which is a typical lignin-related biphenyl structure, was transformed into 5-carboxyvanillate by the reaction sequence of O-demethylation, meta-ring cleavage, and hydrolysis, and the genes involved in the latter two reactions have been characterized. Vanillate and syringate are the most common intermediate metabolites in lignin catabolism. These compounds are initially O-demethylated and the resulting diol compounds, protocatechuate (PCA) and 3-O-methylgallate, respectively, are subjected to ring cleavage catalyzed by PCA 4,5-dioxygenase. The ring cleavage products generated are further degraded through the PCA 4,5-cleavage pathway. We have isolated and characterized genes for enzymes involved in this pathway. Disruption of a gene for 2-pyrone-4,6-dicarboxylate hydrolase (ligI) in this pathway suggested that an alternative route for 3-O-methylgallate degradation, in which ligI is not involved, would play a role in syringate catabolism. In this article, we describe the genetic and biochemical features of the S. paucimobilis SYK-6 genes involved in degradation of lignin-related compounds. A possible application of the SYK-6 lignin degradation system to produce a valuable chemical material is also described.

Journal Article↗
PubMed2006

Synthesis of the bis-potassium salts of 5-hydroxy-3-oxopent-4-enoic acids and their use for the efficient preparation of 4-hydroxy-2H-pyran-2-ones and other heterocycles.

5-Hydroxy-3-oxopent-4-enoic acid esters can be efficiently transformed into the stable bis-potassium salts of the corresponding 5-hydroxy-3-oxopent-4-enoic acids, from which the sensitive acids are released in situ, the latter being converted into substituted 4-hydroxy-2H-pyran-2-ones, pyrazoles and isoxazoles under mild conditions; the efficiency of this method is demonstrated by the first synthesis of two naturally occurring pyrones.

Acids↗
PubMed1992

Site-specific DNA cleavage by mammalian DNA topoisomerase II induced by novel flavone and catechin derivatives.

Four naturally occurring flavones (baicalein, quercetin, quercetagetin and myricetin) and two novel catechins [(-)-epicatechin gallate and (-)-epigallocatechin gallate, from the tea plant Camellia sinensis], which are known inhibitors of reverse transcriptase, were shown to induce mammalian topoisomerase II-dependent DNA-cleavage in vitro. The flavones differed from the catechins in causing unwinding of duplex DNA, but both classes of compound induced enzymic DNA breakage at the same sites on DNA. Moreover, the cleavage specificity was the same as that for the known intercalator 4'-(acridin-9-ylamino)methanesulphon-m-anisidide, suggesting that these agents trap the same cleavable complex. Analysis of some 30 flavonoid compounds allowed elucidation of the structure-function relationships for topoisomerase II-mediated DNA cleavage. For flavonoid inhibitors an unsaturated double bond between positions 2 and 3 of the pyrone ring and hydroxy groups at the 5, 7, 3' and 4' positions favoured efficient cleavage. Hydroxy substitutions could be tolerated at the 3, 6 and 5' positions. Indeed, the absence of substituents at the 3', 4' and 5' positions could be compensated by a hydroxy group at position 6 (baicalein). Similar requirements have been reported for flavonoid inhibitors of protein kinase C that act competitively with ATP, suggesting interaction with a conserved protein feature. Formation of the cleavable complex is a cytotoxic lesion that may contribute to the growth-inhibitory properties of flavones observed for three human tumour cell lines. These results are discussed in regard to the selectivity of antiviral agents.

Animals↗
PubMed1999

p-Coumaroyltriacetic acid synthase, a new homologue of chalcone synthase, from Hydrangea macrophylla var. thunbergii.

Chalcone synthase and stilbene synthase are plant-specific polyketide synthases. They catalyze three common consecutive decarboxylative condensations and specific cyclization reactions. They are highly homologous to each other, and are likely to fall into a family of polyketide synthases along with acridone synthase and bibenzyl synthase. Two cDNA clones (named HmC and HmS), both of which show high homology to the known chalcone synthases, were obtained from leaves of Hydrangea macrophylla var. thunbergii. They were expressed in Escherichia coli in order to determine their enzyme functions. Detection of chalcone formation clearly indicated that HmC encoded chalcone synthase, while HmS protein catalyzed the formation of neither chalcone nor stilbene. However, a novel pyrone, a lactonization product of a linear tetraketide was detected in reaction products of HmS protein. This proves that HmS encodes a novel polyketide synthase that catalyzes only chain elongation without cyclization.

Acyltransferases↗
PubMed1999

New 4(1H)-pyridinone derivatives as analgesic agents.

A number of 2-methyl/ethyl-3-hydroxy-4(1H)-pyridinones have been synthesized by reacting with 4-pyrones and primary aromatic amines in ethanol. Their structures were confirmed by microanalysis, IR and 1H-NMR spectral analysis. Possible analgesic and anti-inflammatory activities of the synthesized compounds were investigated by acetic acid-induced writhing and carrageenan rat paw edema tests. All compounds exhibited higher analgesic activities than acetylsalicylic acid, 1-(2-Piperidinoethyl)-2- methyl-3-hydroxy-4-(1H)-pyridinone.2HBr(1), 1-[2-(1-methyl-pyrrolidine-2- yl)-ethyl]-2- methyl-3-hydroxy-4(1H)-pyridinone.2HBr (3) and 1-[2-(1-methyl-pyrrolidine- 2-yl)-ethyl]-2- ethyl-3-hydroxy-4(1H)-pyridinone.2HBr (6) showed higher anti-inflammatory activities than indometacin.

Analgesics, Non-Narcotic↗
PubMed2005

Anti-staphylococcal and cytotoxic compounds from Hyptis pectinata.

Bioassay-guided fractionation of a CHCl (3) extract prepared from the Mexican medicinal plant Hyptis pectinata led to the isolation of four pyrones, pectinolides A-C ( 1-3) and H ( 4). Activity was tracked using cultured KB cells. Multidrug-resistant strains of Staphylococcus aureus were sensitive to pectinolide H ( 4; KB > 20 microg/mL) in the concentration range of 32-64 microg/mL. The absolute stereochemistry of this new compound was established as 5 S-[(4 S-acetyloxy)-(1 S-hydroxy)-2 Z-octenyl]-2(5 H)-furanone on the basis of spectral, chiroptical data and chemical correlation with pectinolide A ( 1). Mosher ester derivatives were used with pectinolide B ( 2) for confirmation of the 3'-( S) absolute stereochemistry on the side chain chiral center of pectinolides A-C.

Anti-Bacterial Agents↗
PubMed1996

Chemical and biological investigation of the root bark of Clerodendrum mandarinorum.

A 70% EtOH extract of Clerodendrum mandarinorum root bark was assessed for CNS activity against 18 radioligand receptor binding assays. The results showed that the extract was able to bind to opiate, adenosine-1, alpha 2-adrenergic, 5HT-1, 5HT-2, dopamine-2, histamine-1, GABA(A), and GABA(B) receptors. Fourteen compounds were isolated and identified by El-MS, 1H-NMR and 13C-NMR spectra as known triterpenoids (friedelanone, lupeol, betulinic acid), steroids (24S-stigmata-5,25-dien-3 beta-ol,22E,24S-stigmata-5,22,25-trien-3 beta-ol), flavonoids (cirsimaritin, cirsimaritin-4'-glucoside, quercetin-3-methyl ether), tetra-hydro-alpha-pyrone and saccharides (sucrose, alpha-D- and beta-D-glucopyranose, ethyl-alpha-D-glucopyranoside, 2-ethyl-beta-D-fructofuranoside). The isolated compounds were assessed for activity by the radioligand receptor binding assays. Betulinic acid and ethyl-alpha-D-glucopyranoside showed weak activities against sulphonylureas (IC50 = 7.5 microM) and muscarinic receptors (IC50 = 5.5 microM), respectively. Cirsimaritin-4'-glucoside was weakly active in the adenosine-1 binding assay (IC50 = 3.0 microM), whereas seven structurally related flavonoids, not isolated from C.mandarinorum, were inactive.

Animals↗
PubMed2006

A theoretical insight into the photophysics of psoralen.

Psoralen photophysics has been studied on quantum chemistry grounds using the multiconfigurational second-order perturbation method CASPT2. Absorption and emission spectra of the system have been rationalized by computing the energies and properties of the low-lying singlet and triplet excited states. The S1 pipi* state has been determined to be responsible of the lowest absorption and fluorescence bands and to initially carry the population in the photophysical processes related to the phototherapeutic properties of psoralen derivatives. The low-lying T1 pipi* state is, on the other hand, protagonist of the phosphorescence, and its prevalent role in the reactivity of psoralen is suggested to be related to the elongation of the pyrone ring C3-C4 bond, where the spin density is distributed on both carbon atoms. Analysis of energy gaps and spin-orbit coupling elements indicates that the efficient photophysical process leading to the population of the lowest triplet state does not take place at the Franck-Condon region but along the S1 relaxation path.

Absorption↗