Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pyrones”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed1996

Characterization of the Potent Insulin Mimetic Agent Bis(maltolato)oxovanadium(IV) (BMOV) in Solution by EPR Spectroscopy.

Bis(maltolato)oxovanadium(IV) (abbreviated BMOV or VO(ma)(2)) has been characterized by electron paramagnetic resonance (EPR) spectroscopy in CH(2)Cl(2), H(2)O, MeOH, and pyridine at both room and low temperatures. Spin Hamiltonian parameters for mono- and bis(maltolato)oxovanadium(IV) complexes [VO(ma)](+) (=[VO(ma)(H(2)O)(n)()](+), n = 2 or 3) and VO(ma)(2) (Hma = 3-hydroxy-2-methyl-4-pyrone, maltol) have been obtained by computer simulation (SOPHE). Configurations of solvated vanadyl/maltol complexes, VO(ma)(2)S, in solution (S = solvent) are proposed on the basis of a comparison of their hyperfine coupling constants with those obtained for related vanadium(IV) compounds in the literature. Whereas at room temperature pyridine coordinates to VO(ma)(2) in a position cis to the oxo ligand (cis isomer), in H(2)O or in MeOH solvated and unsolvated cis and trans adducts of VO(ma)(2) are all formed, with the cis isomer dominant. As expected, the coordinating ability was found to be in the order py > H(2)O approximately MeOH > CH(2)Cl(2). In aqueous solutions at room temperature and neutral pH, cis- and trans-VO(ma)(2)(H(2)O) complexes are present as major and minor components, respectively.

Journal Article↗
PubMed2002

Asymmetric total synthesis of spongistatins 1 and 2.

The total synthesis of spongistatin 1 (1) and spongistatin 2 (2) has been achieved through an advanced-stage intermediate. The synthesis is highlighted by a highly convergent assembly of the four key fragments (the C1-C15 AB fragment 2, the C16-C28 CD fragment 3, the C29-C43 EF fragment 4, and the C44-C51 side chain 5) at a very advanced stage of the synthesis with minimal functional group interconversion. The CD fragment 3 functions as the central building block to which the other fragments are attached. The synthesis of the AB and CD spiroketal fragments is accomplished through the addition of a metalated gamma-pyrone to a beta-alkoxy aldehyde followed by spiroketalization. The EF subunit was assembled with high diastereoselectivity relying on asymmetric aldol reactions of chlorotitanium enolates of N-propionyl oxazolidinethiones and a double diastereoselective boron aldol to join the E and F fragments. Wittig coupling of the CD and EF fragments followed by a diastereoselective aldol reaction between the CDEF ketone and an AB aldehyde set the stage for attachment of the C44-C51 side chains and final macrolactonization and deprotection.

Antineoplastic Agents↗
PubMed2006

Total synthesis of (+/-)-haouamine A.

The first total synthesis of the highly complex and potent anticancer agent haouamine A is reported through an eight-step sequence. Brevity of the sequence and complete control of chemo-, position-, and stereoselectivity (both planar and axial chirality) were possible through the invention of chemistry specifically tailored for the problems at hand, namely a cascade annulation proceeding via a hitherto unknown chemical entity for the indeno-tetrahydropyridine ring system as well as a pyrone-assisted stitching of the daunting bent-aromatic ring.

Alkylation↗
PubMed2002

Determination of soyasaponins in soy with LC-MS following structural unification by partial alkaline degradation.

High-performance liquid chromatography coupled with electrospray ionization mass spectrometer was used to study the soyasaponins in soy. It was found that each soyasaponin belonging to group A existed mainly in their genuine acetylated forms. The partially to fully deacetylated structures coexisted in various proportions. Likewise, the soyasaponins belonging to group B in soy were detected as both 2,3-dihydro-2,5-dihydroxy-6-methyl-4-pyrone (DDMP) conjugated forms and non-DDMP forms. The structural diversity of soyasaponins hinders the separation and determination of the individual compounds in soy. In the present studies, the soyasaponins extracted from soy were treated with sodium hydroxide under mild conditions to cleave the acetyl groups from soyasaponins in group A as well as the DDMP from soyasaponins in group B, while the glycoside structures remained unaffected. By doing so, all soyasaponins originating from the same initial structures were unified into well-defined structures and then quantified individually using the selective ion recording of their [M-H](-) ions. The pure deacetyl and non-DDMP soyasaponins were used as the external standards. The quantification limits of soyasaponins in group A and group B were 1.74 and 1.89 ng injected on column with recovery rates of 94.1% +/- 4.2% and 96.9% +/- 2.9%, respectively.

Chromatography, High Pressure Liquid↗
PubMed2003

Kinetic study of the oxidation of quercetin by mushroom tyrosinase.

The kinetic behavior of mushroom tyrosinase in the presence of the flavonol quercetin was studied. This flavonol was oxidized by mushroom tyrosinase and the reaction was followed by recording spectral changes over time. The spectra obtained during the reaction showed two isosbectic points, indicating a stable o-quinone. When quercetin was oxidized by tyrosinase in the presence of cysteine and 3-methyl-2-benzothiazolone hydrazone (Besthorn's hydrazone, MBTH) isosbestic points were also observed indicating a definite stoichiometry. From the data analysis of the initial rate in the presence of MBTH, the kinetic parameters: = (16.2 +/- 0.6) microM/min, = (0.12 +/- 0.01) mM, (/) = (V(max)/K(S)(')()) = (13.5 +/- 1.4) x 10(-)(2) min(-)(1), = (6.2 +/- 0.6) s(-)(1) were determined. We propose that quercetin acts simultaneously as a substrate and a rapid reversible inhibitor of mushroom tyrosinase, depending on how it binds to the copper atom of the enzyme active site. Thus, if the binding occurs through the hydroxylic groups at the C3' and C4' positions, quercetin acts as a substrate, while if it occurs through the hydroxylic group at the C3 position of the pyrone ring, quercetin acts as an inhibitor.

Agaricales↗
PubMed2006

Determination of kavalactones in dried kava (Piper methysticum) powder using near-infrared reflectance spectroscopy and partial least-squares regression.

Kava (Piper methysticum Forst F.), or àwa in the Hawaiian language, has been used for thousands of years by the people of the South Pacific Islands, in particular Fiji, Vanuatu, Tonga, and Samoa, for social and ceremonial occasions. Kava has the unique ability to promote a state of relaxation without the loss of mental alertness. Kava recently became part of the herbal pharmacopoeia throughout the United States and Europe because of its anxiolytic properties. The active compounds are collectively called kavalactones (or kava pyrones). The need for a less time-consuming and costly method to determine the concentration of kavalactones in dried kava is urgent. The combination of near-infrared reflectance spectroscopy (NIRS) and partial least-squares (PLS) methods has been found to be a convenient, versatile, and rapid analytical tool for determination of kavalactones in dried kava powder. Calibration equations were developed based on the analyses of 110 samples with variable physical and chemical properties collected over time from Hawaii kava growers and validated by analyses of a set of 12 samples with unknown kavalactones concentration. All six major kavalactones and the total kavalactones were measured using NIRS with accuracy acceptable for commercial use. The NIRS measurements are reproducible and have a repeatability on a par with HPLC methods.

Anti-Anxiety Agents↗
PubMed1995

1-Thiomethoxsalen and 1-thiopsoralen: synthesis, photobiological properties, and site specific reaction of thiopsoralens with DNA.

The sulfur analogues of psoralen and 8-methoxypsoralen (8-MOP) in the pyrone moiety were synthesized and compared to the parent compounds in terms of photoreactivity with viral M13mp19 RF DNA. The damaged viral DNA was transfected into Escherichia coli and scored for infectivity toward Ca-treated wild-type E. coli. This allowed a comparative study of the sulfur and oxygen analogues to be made in terms of photoreactivity. Furthermore, the DNA sequence specificity for the formation of monoadducts and cross-links of the four analogues was determined with 32P-labeled oligonucleotides containing thymidine in different sequences. The most site specific of the studied psoralens is 8-MOP, while 1-thiopsoralen is the most reactive analogue. This new thio analogue of psoralen leads to the efficient formation of monoadducts and cross-links in any pyrimidine-purine site.

Base Sequence↗
PubMed1995

Structure-taste correlations in sweet dihydrochalcone, sweet dihydroisocoumarin, and bitter flavone compounds.

The dihydrochalcone derivatives of the bitter flavonoids naringin and neohesperedin are intensely sweet. Phyllodulcin is as sweet as the dihydrochalcones with similar taste properties although its structure apparently resembles that of bitter flavanone or flavone. Multifaceted approaches, including X-ray crystal structure analysis, energy calculation, and structure comparison, have been employed to clarify the structure-taste correlations in these classes of compounds. In the crystal, naringin dihydrochalcone assumes a 'J'-shaped conformation with a fully-extended dihydrochalcone moiety while neohesperidin dihydrochalcone assumes the same overall conformation but with a partially-extended moiety. A 2D conformational energy map of dihydrochalcone obtained using molecular mechanics revealed nine local minima. The pseudoequatorial and pseudoaxial forms of phyllodulcin have the same AM1 energies with a low energy barrier between them. The partially-extended form of dihydrochalcone and the pseudoequatorial form of phyllodulcin which are the maximally superposable conformers are proposed to be the active conformers. The major difference between the structures of flavone and phyllodulcin is not in the overall planarity but in the relative orientation of the pyrone and phenyl ring systems.

Chalcone↗
PubMed1994

Mobilization of iron by chiral and achiral anionic 3-hydroxypyrid-4-ones.

In the search for 3-hydroxypyrid-4-ones with enhanced iron-mobilizing ability, seven chiral, anionic amino acid derivatives of maltol (3-hydroxy-2-methyl-4-pyrone) have been synthesized, utilizing L-methionine, L-serine, L-leucine, L-phenylalanine, L-glutamic acid, and the D- and L-isomers of alanine. Two achiral, aromatic compounds were also synthesized and compared with the phenylalanine derivative. The biliary iron excretion following iv injection and the urinary iron excretion following po administration were measured using female Sprague-Dawley rats and compared to that of the standard, 1,2-dimethyl-3-hydroxypyrid-4-one (L1). While none of the compounds was as effective as L1 in enhancing the urinary excretion of iron, all monoanionic chelators increased excretion relative to the controls. All monoanionic compounds were at least equivalent to L1 in enhancing the biliary excretion of iron, with the methionine, leucine, and benzoate derivatives surpassing the standard and the other aromatic compounds also showing strong activity. The dianionic glutamate derivative showed low activity relative to the controls for both urinary and biliary iron excretion. No significant difference in iron excretion was observed due to variation in chirality; molecular weight and the number of negative charges appeared to have the greatest influence on the ability of the various derivatives to enhance iron excretion. In order to evaluate the relative purity of the stereoisomers, the alanine derivatives were analyzed by circular dichroism. Further characterization was provided by UV/vis spectroscopy for all compounds and X-ray crystallography for the novel dianionic derivative.

Animals↗
PubMed1992

New vitamin D3 derivatives with unexpected antiproliferative activity: 1-(hydroxymethyl)-25-hydroxyvitamin D3 homologs.

Surprisingly, both of the synthetic 1-(hydroxymethyl)-25-hydroxyvitamin D3 diastereomers (-)-2 and (+)-3 retained the antiproliferative activity of natural calcitriol in murine keratinocytes. Preliminary studies indicated, however, that both of these synthetic diastereomers were less than 0.1% as effective as calcitriol for binding to the 1,25-(OH)2-D3 receptor and that they were less than 0.1% as potent as calcitriol for calbindin-D28K induction in organ-cultured embryonic chick duodenum. 1-(Hydroxymethyl)-25-hydroxyvitamin D3 homologs (-)-2 and (+)-3 were synthesized in a convergent manner by combining enantiomerically pure C,D-ring ketone 12 with highly enantiomerically enriched A-ring phosphine oxides (-)-11a and (+)-11b. These A-ring chirons were prepared starting from thermal [2 + 4] cycloaddition of 3-bromo-2-pyrone and acrolein.

Animals↗
PubMed1976

Cycloalkanones. 9. Comparison of analogues which inhibit cholesterol and fatty acid synthesis.

A number of 2,8-dibenzylcyclooctanone analogues inhibited the HMG-CoA reductases activity of Holtzman male rat liver, whereas only 2-octanone, 2-hexadecanone, 2,8-dibenzylcyclooctanone derivatives, and 2-bis(4-chlorophenyl)-3,5-dimethyltetrahydro-4-pyrone inhibited fatty acid synthetase activity. 2-Octanone significantly lowered serum cholesterol, triglycerides, and glycerol levels in Holtzman male rats and serlm cholesterol in male CF1 mice. Serum lipase activity was significantly elevated in rats administered 20 mg/kg/day of 2-octanone for 16 days. The activity of liver HMG-CoA reductase was inhibited in mice administered 10 mg/kg/day of 2-octanone for 10 days and in mouse and rat liver in vitro by 10 mg of 2-octanone. In mice, fecal excretion of [14C]cholesterol and tripalmitin was accelerated whereas palmitic acid and cholesteryl oleate were not affected by 10 mg/kg/day of 2-octanone. The LD50 in male mice for 2-octanone was 1.6g/kg.

Acetate-CoA Ligase↗
PubMed1975

Studies on antianaphylactic agents. 4. Synthesis and structure-activity relationships of 3-(4-oxo-4H-1-benzopyran-3)acrylic acids, a new series of antiallergic substances, and some related compounds.

The syntheses of trans-3-(4-oxo-4H-1-benzypyran-3)acrylic acid and a number of analogs shown to be highly active in antiallergic bioassays are described. These compounds are of possible value in the treatment of asthma. The structural requirements for biological activity are discussed with reference to the type of the substituents on the chromone ring or positions of linkage of the acrylic acid on the pyrone ring.

Acrylates↗
PubMed2002

Synthetic approach to analogues of the original structure of sclerophytin A.

A route to analogues of the original structure of sclerophytin A is described. The beta-anomer of dideoxyribosyl nitriles 10a,b (prepared from glutamic acid) was converted into the methyl ketone 11. Addition of a silylated acetylide to 11 in diethyl ether/trimethylamine gave mainly 22a. Alkylation with methallyl halide and ozonolysis gave the ketone 24, which was then converted by hydrogenation and a second ozonolysis into the keto aldehyde 26. A two-step aldol process afforded the desired 3-pyrone 27 in good overall yield. However, several methods for the conversion of this enone 27 into the desired sclerophytin analogue 2 failed.

Animals↗
PubMed2003

Direct asymmetric Michael reactions of cyclic 1,3-dicarbonyl compounds and enamines catalyzed by chiral bisoxazoline-copper(II) complexes.

The catalytic direct Michael addition of cyclic 1,3-dicarbonyl compounds and enamines to unsaturated 2-ketoesters is presented. A series of different 4-hydroxycoumarins, 4-hydroxy-6-methyl-2-pyrone, 3-hydroxy-1H-phenalene-1-one, 2-hydroxy-1,4-naphthoquinone, 5,5-dimethyl-1,3-cyclohexanedione, and various enamines of cyclic 1,3-diketones all add to unsaturated 4-substituted 2-ketoesters in an enantioselective manner. The reaction is catalyzed by chiral bisoxazoline-copper(II) complexes and proceeds in the absence of base to afford Michael adducts in good to high yields and with up to 98% ee. The products formed are substructures found in skeletons of important biological and pharmaceutical molecules. The scope and potential of the new reaction are discussed as well as the mechanism for the catalytic enantioselective reaction.

Journal Article↗
PubMed2003

A theoretical rationalization of the asymmetric induction in sulfinyl-directed [5C + 2C] intramolecular cycloadditions.

A computational DFT examination (B3LYP/6-31G and B3LYP/6-311+G//B3LYP/6-31G) of the thermal [5C + 2C] cycloaddditions of 6-acetoxy-3-pyranones and 3-silyloxy-4-pyrones with tethered alkenyl sulfoxides confirms that the high level of diastereofacial selectivity obtained is ultimately due to the preference of the alkenesulfinyl group to adopt a well-defined conformation in the transition state of the reaction. This conformation, which is different from that found in the ground state, is most probably dictated by dipolar interaction effects between the sulfoxide and the oxidopyrylium ylide intermediate.

Journal Article↗
PubMed2003

Tandem or sequential coupling-IMDA cycloaddition approach to highly fused polycarbocycles.

The Diels-Alder cycloadduct made from 3,5-dibromo-2-pyrone and 2-bromo-styrene was successfully transformed stereoselectively into a series of novel benzotetracycles via a tandem or sequential Pd-catalyzed coupling-intramolecular Diels-Alder (IMDA) cycloaddition. The resulting polycarbocycles can be readily converted into a bicyclo[3.3.1]nonane system upon ozonolysis of the internal double bond.

Journal Article↗
PubMed2004

Synthesis and conformational studies of dipeptides constrained by disubstituted 3-(aminoethoxy)propionic acid linkers.

A series of cyclic compounds with dimethyl-substituted 3-(aminoethoxy)propionic acid linkers have been prepared as potential beta-turn mimics. The desired linkers were prepared from disubstituted pyrones, which were coupled with dipeptides and then subjected to macrocyclization using diethylcyanophosphonate to furnish cyclic compounds 1-5. Conformational analysis was carried out using NMR and X-ray crystallography. All of the five cyclic compounds were found to exist in type I or type II beta-turn conformations.

Cross-Linking Reagents↗
PubMed2005

Highly substituted tetrahydropyrones from hetero-Diels-Alder reactions of 2-alkenals with stereochemical induction from chiral dienes.

[reaction: see text] A new method for the stereoselective synthesis of libraries of 2,3,5-trisubstituted tetrahydro-gamma-pyrones and the corresponding tetrahydropyran-4-ols is reported. Dienes with a chiral moiety at position 5 were synthesized starting from (triphenylphosphoranylidene)acetone. In hetero-Diels-Alder (HDA) reactions, especially with alpha,beta-unsaturated aldehydes, they induce diastereomeric ratios from 4:1 to 14:1. Through selective epimerization and reduction, further building blocks are available. These constitute ideal starting points for their use in the total synthesis of complex polyketide macrocycles, especially with the vinyl group available for metathetic coupling.

Journal Article↗