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PubMed1984

8-Methoxypsoralen-nucleic acid photoreaction. Effect of methyl substitution on pyrone vs. furan photoaddition.

We have synthesized a series of 8-[3H]methoxypsoralens in which methyl and hydrogen are systematically varied at the 4- and 5'-positions. Analysis of the products resulting from the photoaddition of these four psoralens with the nucleic acid poly(dA-dT) reveals that the product distribution depends on the presence or absence of a 4-methyl substituent. Compounds with the 4-methyl group show an overwhelming preference (approximately 98%) for addition to the furan double bond, while compounds without the 4-methyl show a substantial amount (approximately 18%) of addition to the pyrone double bond.

Chemical Phenomena↗
PubMed2003

Synthesis of isocoumarins and alpha-pyrones via electrophilic cyclization.

A variety of substituted isocoumarins and alpha-pyrones are readily prepared in excellent yields under very mild reaction conditions by the reaction of o-(1-alkynyl)benzoates and (Z)-2-alken-4-ynoates with ICl, I(2), PhSeCl, p-O(2)NC(6)H(4)SCl, and HI. This methodology accommodates various alkynyl esters and has been successfully extended to the synthesis of polycyclic aromatic and biaryl compounds.

Journal Article↗
PubMed2003

Studies on K2CO3-catalyzed 1,4-addition of 1,2-allenic ketones with diethyl malonate: controlled selective synthesis of beta,gamma-unsaturated enones and alpha-pyrones.

The K2CO3 (10 mol %)-catalyzed 1,4-addition reaction of diethyl malonate with various substituted 1,2-allenic ketones leading to polyfunctionalized beta,gamma-unsaturated enones 3 or 4 was studied. With 3-unsubstituted 1-substituted-1,2-allenyl ketones, the highly selective formation of beta,gamma-unsaturated enones 4 was observed; with 1,2-allenyl ketones bearing one or two 3-substituents in the allenyl group, only beta,gamma-unsaturated enones 3 with an unmigrated carbon-carbon double bond were produced; with 3-monosubstituted-1,2-allenyl ketones Z-beta,gamma-unsaturated enones 3 were formed with excellent stereoselectivity (E:Z > 96:4); with propadienyl ketones, mixtures of beta,gamma-unsaturated enones 3 and 4 were formed. alpha-Pyrone derivatives were synthesized via the K(2)CO(3)-catalyzed or -promoted reaction of 1,2-allenic ketones with diethyl malonate via a sequential Michael addition-carbon-carbon double bond migration-lactonization process.

Journal Article↗
PubMed1996

3-Hydroxy-4-pyrones as Precursors of 4-Methoxy-3-oxidopyridinium Ylides. An Expeditious Entry to Highly Substituted 8-Azabicyclo[3.2.1]octanes.

3-Hydroxy-4-pyridones, which are easily prepared from commercially available 3-hydroxy-4-pyrones, can be readily transformed into 4-methoxy-3-oxidopyridinium ylides by treatment with methyl trifluoromethanesulfonate and subsequent deprotonation with a non-nucleophilic base. These ylides are capable of undergoing cycloaddition to several electron-deficient alkenes, thus allowing the synthesis of highly functionalized azabicyclo[3.2.1]octane moieties. The rich substitution patterns of these frameworks might allow their divergent conversion to a variety of natural and non-natural tropane alkaloids.

Journal Article↗
PubMed2006

Photochemical ring-opening and intramolecular hydrogen shift reactions in sulfur analogues of alpha-pyrone.

A combined matrix isolation FTIR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the photochemistry of sulfur analogues of alpha-pyrone [2H-thiopyran-2-one (TP) and 2H-pyran-2-thione (PT)] was carried out. The vibrational spectra of monomers of the compounds isolated in low-temperature argon matrixes were studied experimentally and assigned completely on the basis of theoretical calculations. UV irradiation (lambda > 337 nm) of the studied compounds isolated in low-temperature matrixes results mainly in the ring-opening reaction by means of the cleavage of the alpha-bond. Other photoprocesses, not involving the alpha-bond-cleavage step (such as generation of Dewar valence isomer), correspond to the minor reaction channels in both studied compounds. The ring-opening photoreaction in PT represents the first reported case of an alpha-bond cleavage in a compound with a C=S group attached to a six-membered ring, in which the internal strain practically does not exist, whereas the corresponding reaction in TP (a cleavage of a C-S bond in the alpha position with respect to a carbonyl group) is now reported for the first time. Following the ring-opening reactions, isomerization processes and intramolecular hydrogen shift reactions were observed, enabling production of TP from PT and vice versa. A detailed study of such processes was undertaken, and kinetical and mechanistical data are presented and discussed.

Journal Article↗
PubMed2004

Water-in-CO2 emulsions: reaction vessels for the production of tetra-ethyl pyrone.

Water-in-CO2 (W/C) emulsions formed using a nickel Triton X-100 surfactant complex (Ni-surfactant) were used as microreactors for the carbon-carbon coupling reaction between hex-3-yne and CO2 to produce tetra-ethyl pyrone (TEP). The structure of the product, which was isolated in the CO2 phase, was determined using gas chromatography mass spectrometry (GC-MS) and infrared spectroscopy. The Ni-surfactant acted as both an emulsion forming agent and a water soluble catalyst for this carbon-carbon coupling reaction. The optimum yield of TEP was determined to be 69% after 72 h, at a temperature of 70 degrees C and a pressure of 206 bar. The ease with which the emulsion could be collapsed allowed the facile separation of products from the catalyst and any unreacted starting material. Product selectivity in the W/C emulsions was found to be greater than that obtained using conventional organic methodologies.

Journal Article↗
PubMed1994

Murayalactone, a dibenzo-alpha-pyrone from Streptomyces murayamaensis.

Murayalactone, 6, has been isolated from Streptomyces murayamaensis, and its structure assigned with the use of inverse nmr spectroscopy. This constitutes the first occurrence of a dibenzo-alpha-pyrone in a Streptomyces species, and the first biogenesis of this ring system from a decaketide.

Chromatography, High Pressure Liquid↗
PubMed2001

Reversal of stereoselectivity in [5 + 2] pyrone--alkene cycloadditons using a sulfoxide-to-sulfoximine switch. Enantiodivergent synthesis of 8-oxabicyclo[3.2.1]octane systems.

[reaction: see text] Switching from a sulfinyl to a sulfonimidoyl group allows the reversal of the sense of asymmetric induction in thermal [5C + 2C] intramolecular pyrone-alkene cycloadditions. Removal of the sulfoximine unit from the resulting cycloadducts yields optically active oxabicyclic systems that are enantiomeric to those obtained using the sulfinyl chiral auxiliary.

Journal Article↗
PubMed2005

Aurovertin E, a new polyene pyrone from the basidiomycete Albatrellus confluens.

A new polyene pyrone, aurovertin E (2), was isolated along with aurovertin B (1) from the culture mycelia of the basidiomycete Albatrellus confluens. Their structures were elucidated on the basis of spectroscopic studies including 2D NMR experiments. This is the first example of the occurrence of aurovertins in basidiomycetes.

Aurovertins↗
PubMed1993

Sex pheromone for the brownbanded cockroach is an unusual dialkyl-substituted alpha-pyrone.

Female brownbanded cockroaches, Supella longipalpa, emit a sex pheromone that attracts males from a distance. This pheromone was isolated and identified as 5-(2,4-dimethylheptanyl)-3-methyl-2H-pyran-2-one (which we refer to as supellapyrone), and its structure was confirmed by synthesis. A racemic blend of the synthetic compound elicited behavioral and electrophysiological responses comparable to the natural pheromone across a range of doses. This compound is not only a very different type of cockroach pheromone but also makes up an additional class of natural products--namely, 3,5-dialkyl-substituted alpha-pyrones.

Journal Article↗
PubMed1989

The effects of 5,6 benzo-[a]-pyrone (coumarin) and DEC on filaritic lymphoedema and elephantiasis in India. Preliminary results.

A randomized double-blind, placebo-controlled, trial of 5,6 benzo-[alpha]-pyrone (coumarin, '56 BaP') and of diethylcarbamazine (DEC) is being performed on patients with filaritic lymphoedema and elephantiasis over two years, using matched groups. In 169 patients there were significant (1% level) reductions in the amounts of oedema for the patients taking 56 BaP. The excess limb volumes were reduced from 40 to 25% over two years. A similar, but less significant (5% level), improvement was found for the circumference measurements. The rate of reduction was increased when the initial amount of oedema was greater. This therapy, while much slower than many other methods of treatment, does convert a slowly worsening condition into a slowly improving one. There were no significant reductions in the amount of oedema following DEC treatment.

Analysis of Variance↗
PubMed1980

Improved Procedure for the Estimation of Nanogram Quantities of Indole-3-acetic Acid in Plant Extracts using the Indolo-alpha-pyrone Fluorescence Method.

The indolo-alpha-pyrone fluorescence method of determining indole-3-acetic acid (IAA) is improved by adding butylated hydroxytoluene (BHT), an antioxidant, to samples: addition of BHT increases the fluorescence intensities and decreases their variability so that amounts of IAA as small as 0.1 to 1 nanogram become measurable. Interfering compounds, 4-chloroindole-3-acetic acid and 5-hydroxyindole-3-acetic acid, can be separated from IAA by thin-layer chromatography using polyamide as the solid support, and benzene-ethyl acetate-acetic acid (70:25:5, v/v) as the developing solvent. Polyamide thin-layer chromatography is also superior in purifying IAA without significant loss or decomposition.A serious problem in extracting IAA from plant tissues is the considerable loss. Losses can result from decomposition of IAA when its solutions in organic solvents are evaporated to dryness, apparently due to some impurity in the solvents. Decomposition can be eliminated by simple treatments of the solvents, i.e. addition of BHT, washing with water, and passage through cotton wool. The latter is particularly effective in the case of ethyl acetate and ether. Loss of IAA by photodecomposition is also substantial even in dried samples. Ways to minimize the conversion of indole-3-pyruvic acid to IAA during extraction procedure are also described.A revised procedure of IAA extraction and determination is proposed. Applied to etiolated shoots of maize seedlings, it enables content to be estimated (18 nanograms per gram fresh weight) with over 90% recovery in terms of [(14)C]IAA added at the beginning of the extraction.

Journal Article↗
PubMed1982

Estimation of Free, Conjugated, and Diffusible Indole-3-acetic Acid in Etiolated Maize Shoots by the Indolo-alpha-pyrone Fluorescence Method.

Procedures for estimating free indoleacetic acid (IAA extracted from tissue homogenates by aqueous acetone), conjugated IAA (extracted by aqueous acetone and hydrolyzed by 1 n KOH), and diffusible IAA (diffused from the excised tissue into water), in shoots of etiolated 3-day-old maize (Zea mays L. cv. GH 390) seedlings are described, the indolo-alpha-pyrone fluorescence method being used to assay IAA. The reliability of the procedure is shown by comparative IAA determinations of the extracts using the gas chromatography-mass spectrometry method in which the methyl ester, heptafluorobutyryl derivative of IAA is assayed using the selected-ion-monitoring technique with deuterated IAA as an internal standard. A 3-millimeter-long coleoptile tip, a coleoptile with its included leaves and nodal region (whole coleoptile), and a mesocotyl each contains 0.2, 1.7, and 1.5 nanograms of free IAA, respectively. The whole coleoptile and the mesocotyl contain slightly less conjugated IAA than their content of free IAA. IAA diffuses from the coleoptile tip at the rate of 1.0 nanograms per tip per hour; from the base of the whole coleoptile and a set of leaves excised from a coleoptile, IAA diffuses at the rate of 0.62 and 0.17 nanogram per plant part per hour, respectively. The data obtained support the classical assumption that the coleoptile tip produces IAA. It is also suggested that some IAA is decomposed during its downward transport in the coleoptile.

Journal Article↗
PubMed1988

[Structure of a psoralen-thymine photoproduct: model for the interaction with DNA on the pyrone ring of psoralen].

Photoadduct 4-ethoxypsoralen-thymine (4a-methyl-11,1-epoxyethanofuro [3'',2'',:6',7']chromeno-[2',3':1,2]cyclobutal[4,3-d]pyrimid in e-2,4, 5-trione), C18-H14N2O6, Mr = 354.1, monoclinic, P21/c, a = 9.021 (3), b = 11.504 (1), c = 16.397 (3) A, beta = 110.45 (1) degrees, V = 1594.4 A 3, Z = 4, Dm = 1.46, D chi = 1.475 Mg m-3, lambda (Mo K alpha) = 0.71069 A, mu = 0.072 mm-1, F(000) = 736, T = 298 K, R = 0.032 for 1442 observed reflections. This original structure of an intramolecular photoproduct obtained photochemically gives structural information about the cycloaddition of the thymine base on the pyrone ring of the psoralen. The crystal structure displays deformations of the planes of the two rings which form a dihedral angle of 40.5 degrees and a cis-anti conformation relative to the cyclobutane bridging component.

Cross-Linking Reagents↗
PubMed1999

Genetic and biochemical characterization of a 2-pyrone-4, 6-dicarboxylic acid hydrolase involved in the protocatechuate 4, 5-cleavage pathway of Sphingomonas paucimobilis SYK-6.

Sphingomonas paucimobilis SYK-6 is able to grow on a wide variety of dimeric lignin compounds with guaiacyl moieties, which are converted into protocatechuate by the actions of lignin degradation enzymes in this strain. Protocatechuate is a key metabolite in the SYK-6 degradation of lignin compounds with guaiacyl moieties, and it is thought that it degrades to pyruvate and oxaloacetate via the protocatechuate 4,5-cleavage pathway. In a 10.5-kb EcoRI fragment carrying the protocatechuate 4,5-dioxygenase gene (ligAB) (Y. Noda, S. Nishikawa, K. Shiozuka, H. Kadokura, H. Nakajima, K. Yoda, Y. Katayama, N. Morohoshi, T. Haraguchi, and M. Yamasaki. J. Bacteriol. 172:2704-2709, 1990), we found the ligI gene encoding 2-pyrone-4, 6-dicarboxylic acid (PDC) hydrolase. PDC hydrolase is a member of this pathway and catalyzes the interconversion between PDC and 4-carboxy-2-hydroxymuconic acid (CHM). The ligI gene is thought to be transcribed divergently from ligAB and consists of an 879-bp open reading frame encoding a polypeptide with a molecular mass of 32,737 Da. The ligI gene product (LigI), expressed in Escherichia coli, was purified to near-homogeneity and was estimated to be a monomer (31.6 kDa) by gel filtration chromatography. The isoelectric point was determined to be 4.9. The optimum pH for hydrolysis of PDC is 8.5, the optimum pH for synthesis of PDC is 6.0 to 7.5, and the Km values for PDC and CHM are 74 and 49 microM, respectively. LigI activity was inhibited by the addition of thiol reagents, suggesting that the cysteine residue is a catalytic site. LigI is more resistant to metal ion inhibition than the PDC hydrolases of Pseudomonas ochraceae (K. Maruyama, J. Biochem. 93:557-565, 1983) and Comamonas testosteroni (P. J. Kersten, S. Dagley, J. W. Whittaker, D. M. Arciero, and J. D. Lipscomb, J. Bacteriol. 152:1154-1162, 1982). The insertional inactivation of the ligI gene in S. paucimobilis SYK-6 led to the complete loss of PDC hydrolase activity and to a growth defect on vanillic acid; it did not affect growth on syringic acid. These results indicate that the ligI gene is essential for the growth of SYK-6 on vanillic acid but is not responsible for the growth of SYK-6 on syringic acid.

Carboxylic Ester Hydrolases↗
PubMed1976

The use of a tissue tonometer as a diagnostic aid in extremity lymphoedema: a determination of its conservative treatment with benzo-pyrones.

With the aid of a tissue tonometer, we have been able to gain an estimate of the rate at which the lymphoedematous tissue loses its compressability and regains it upon treatment with the non-steroidal anti-inflammatory drugs: the benzo-pyrones. The values obtained by tonometry, unlike other objective methods of measurement of the effectiveness of a therapy, approximate closely to the patients subjective claims.

Coumarins↗
PubMed1985

[The behavior of blood clotting and its inhibitors under long term treatment with 5,6-benzo-alpha-pyrone (coumarin). Double blind study].

The analyses on hemostaseological variables are recorded in connection with blood tests in the course of a double-blind study in 41 patients suffering from chronic venous insufficiency of higher degrees of severity. They were treated in addition to compression measures with two active ingredients, a coumarin (5,6-benzo-alpha-pyrone)/troxerutin combination (Venalot Depot) (n = 20) or benzarone (n = 21) receiving 3 X 2 dragees daily for 6 weeks. Good clinical efficacy and the improvement of symptoms were observed together with almost no side-effects. The coagulation analysis showed no influence of the active principles on the global coagulation or the clotting factors and the inhibitors and factors of the fibrinolysis. In particular there was no phenprocoumon-like effect on the blood clotting system.

Anticoagulants↗
PubMed1977

Fine structural aspects of the influence of lymphatic blockage on cold injury of the brain and skin, and the effects of benzo-pyrones.

The fine structural changes of cold injury, lymphoedema, or both have been studied in the cerebral cortices and facial skin of rats, with and without treatment by a mixture of two benzo-pyrones (coumarin and rutin sulphate salts). It was found that cold injury opens the endothelial junctions of the blood vessels and injures their plasma membranes, thus allowing plasma protein and fluid to enter the tissues, producing oedema. Hence the lymphatics of the skin and the prelymphatics of the brain become dilated, contain excess protein, and the junctions of the former become opened. Macrophages (together with astrocytes in the brain) appear to phagocytise some of the protein. Apart from the injuries to the blood vessels, lymphostasis causes similar effects. The two injuries in combination considerably enhance the effects of either by itself. The benzopyrones greatly reduce the amounts of protein and fluid, particularly in the tissues: the lymphatics lag behind these, especially if they are obstructed.

Animals↗