Showing papers on "Pyran published in 2007"
TL;DR: A chiral pyran derivative containing two cholesteryl groups is synthesized, and its optical properties are investigated, showing a novel phenomenon of aggregation-induced emission (AIE).
Abstract: A chiral pyran derivative containing two cholesteryl groups (1) is synthesized, and its optical properties are investigated. Whereas the isolated molecule of 1 is virtually nonluminescent in dilute solutions, it becomes highly emissive with a 2 orders of magnitude increase in fluorescence quantum yield upon aggregation in poor solvents or in solid state, showing a novel phenomenon of aggregation-induced emission (AIE). The color and efficiency of the AIE of 1 can be tuned by varying the morphology of its aggregates: photoluminescence of its aggregates formed in a tetrahydrofuran/water mixture progressively red-shifts (green → yellow → red) with increasing water content of the mixture, with the crystalline aggregates emitting bluer lights in higher efficiencies than their amorphous counterparts.
212 citations
TL;DR: Tetra-methyl ammonium hydroxide has been used as a mild, efficient, neutral and cheap catalyst for the synthesis of various 4H-benzo[b]pyran derivatives via a one-pot three-component condensation in aqueous media as mentioned in this paper.
146 citations
TL;DR: Diammonium hydrogen phosphate was used as a mild, efficient, neutral, and cheap catalyst for the synthesis of various 4H•benzo[b]pyran derivatives via a one-pot, three-component condensation of aromatic aldehydes, active methylene compounds, and dimedone in aqueous media as mentioned in this paper.
127 citations
TL;DR: The computational models have facilitated the identification of structural elements of the ligands that are key for antitumoral properties and provide a valuable tool in designing new and more potent cytotoxic analogues.
Abstract: Catalyst/HypoGen pharmacophore modeling approach and three-dimensional quantitative structure-activity relationship (3D-QSAR)/comparative molecular similarity indices analysis (CoMSIA) methods have been successfully applied to explain the cytotoxic activity of a set of 51 natural and synthesized naphthoquinone derivatives tested in human promyelocytic leukemia HL-60 cell line. The computational models have facilitated the identification of structural elements of the ligands that are key for antitumoral properties. The four most salient features of the highly active beta-cycled-pyran-1,2-naphthoquinones [0.1 microM < IC50 < 0.6 microM] are the hydrogen-bond interactions of the carbonyl groups at C-1 (HBA1) and C-2 (HBA2), the hydrogen-bond interaction of the oxygen atom of the pyran ring (HBA3), and the interaction of methyl groups (HYD) at the pyran ring with a hydrophobic area at the receptor. The moderately active 1,4-naphthoquinone derivatives accurately fulfill only three of these features. The results of our study provide a valuable tool in designing new and more potent cytotoxic analogues.
118 citations
TL;DR: In this article, an electrogenerated base of the anion of malononitrile was used to synthesize tetrahydrobenzo[b]pyrans.
110 citations
TL;DR: In this article, a three-component condensation of isatins with 3-methyl-pyrazolone-5 and respective methylene active nitriles in the presence of basic catalysts was proved unambiguously by X-ray diffraction.
90 citations
TL;DR: In this article, an iodine/DMSO system was introduced as an excellent catalyst in three-component coupling reactions of tetrahydrobenzo[b]pyran synthesis.
72 citations
TL;DR: Three new naphtho-γ-pyrones and nine related known compounds were characterized from Aspergillus niger EN-13, an endophytic fungus isolated from the marine brown alga Colpomenia sinuosa and showed weak antifungal activity against Candida albicans and moderate activity on DPPH scavenging.
Abstract: Three new naphtho-gamma-pyrones, 5-hydroxy-6,8-dimethoxy-2-hydroxymethyl-4H-naphtho[2,3-b]pyran-4- one (1, nigerasperone A), 3,3'-dihydro-2,2',5,5'-tetrahydroxy-8,8', 10,10'-tetramethoxy-2,2'-dimethyl-(6',9-bi-4H-naphtho[1,2-b]pyran)-4,4'-dione (2, nigerasperone 13), and 3'-hydro-2',5,5',8-tetrahydroxy-6,6',8'-trimethoxy-2,2'- dimethyl-(7,10'-bi-4H-naphtho[2,3-b]pyran)-4,4'-dione (3, nigerasperone C), together with nine related known compounds were characterized from Aspergillus niger EN-13, an endophytic fungus isolated from the marine brown alga Colpomenia sinuosa. Their structures were elucidated by detailed analysis of spectroscopic data and by comparison with literature reports. In the cytotoxic assay, these compounds did not show remarkable inhibitory effects against A549 and SMMC-7721 tumor cell lines. However, 3 and several known compounds showed weak antifungal activity against Candida albicans and moderate activity on DPPH scavenging.
64 citations
TL;DR: Functionalized dibenzo[b,d]pyran-6-ones were prepared by formal [3 + 3] cyclization of 3-silyloxy-2-en-1-ones or 1,1-diacetylcyclopropane to give functionalized salicylates, Suzuki cross-coupling reactions of the corresponding triflates, and subsequent BBr3-mediated lactonization.
Abstract: Functionalized dibenzo[b,d]pyran-6-ones were prepared by formal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 3-silyloxy-2-en-1-ones or 1,1-diacetylcyclopropane to give functionalized salicylates, Suzuki cross-coupling reactions of the corresponding triflates, and subsequent BBr3-mediated lactonization. A second approach to dibenzo[b,d]pyran-6-ones relies on the [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 1-(2-methoxyphenyl)-1-(trimethylsilyloxy)alk-1-en-3-ones and subsequent BBr3-mediated lactonization.
53 citations
TL;DR: The ring-closing metathesis (RCM) reactions of homoallylic acrylates bearing alkyl substituents on various positions of their skeleton afford the corresponding pentenolides in the presence of carbene ruthenium catalysts.
Abstract: The ring-closing metathesis (RCM) reactions of homoallylic acrylates bearing alkyl substituents on various positions of their skeleton afford the corresponding pentenolides in the presence of carbene ruthenium catalysts. For R3 = R4 = H, or R3 = Me, R4 = H, the reactions are catalyzed by complex [RuCl2(PCy3)2(CHPh)], while a second-generation Grubbs catalyst is required when R3 = H and R4 = Me, R3 = R4 = Me, or R3 = i-Pr and R4 = H. Alkyl substitution at the homoallylic carbon (R1, R2) increases the yield of the reaction when both the acrylic and/or homoallylic double bonds are methyl-substituted. The interaction of the catalyst with the substrate in the initiation stage involves the homoallylic double bond rather than the acrylic moiety, and the resulting alkylidene species from the first-generation Grubbs catalyst can be observed by 1H and 31P NMR. The racemic tobacco constituents 4-isopropyl-5,6-dihydropyran-2-one and 4-isopropyltetrahydropyran-2-one are prepared via a short reaction sequence, involvin...
49 citations
TL;DR: A series of 2H-pyrano[3,2-c]chromen-5-one derivatives were synthesized and characterized by the UV-vis absorption spectroscopy as discussed by the authors.
TL;DR: In this article, an environmentally friendly three-component condensation reaction of an activated C-H acid, an aldehyde, and alkyl nitriles to afford the corresponding pyran annulated heterocyclic systems in water in good yields, avoiding the addition of any catalyst, is reported.
TL;DR: In this article, a 3,4-methylenedioxy cinnamic acid ester of kojic acid was synthesized as a new retinoidal compound, which showed broad biological activities such as inhibition of tyrosinase, scavenging of the free radicals, chelating activity of metal ions and prevention of photodamage.
Abstract: Kojic acid, 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4one, is produced from carbohydrate sources in an aerobic process by a variety of microorganisms. It showed broad biological activities such as inhibition of tyrosinase, scavenging of the free radicals, chelating activity of metal ions and prevention of photodamage. Its various activities are due to γ-pyranone structure having enolic hydroxyl group. Recently, enolic hydroxyl group of kojic acid has been focused as an alternative of carboxylic acid in retinoid structure. We synthesized 3,4-methylenedioxy cinnamic acid ester of kojic acid as a new retinoidal compound. In this study, we evaluated biological activities of new kojic acid derivative 1, 2-((3E)-4(2H,3H-benzo[3,4-d]1,3-dioxolan-5yl)-2-oxo-but-3-enyloxy)-5-hydroxy-4H-pyran-4-one.
TL;DR: Readily available 2,2',6,6'-tetramethoxy-1,1'-biphenyl was transformed in 14 synthetic steps into the natural product cardinalin 3 using a bidirectional approach and one of the key steps was the formation of the cis-3-dimethylnaphtho[2,3-c]pyran ring.
Abstract: Readily available 2,2′,6,6′-tetramethoxy-1,1′-biphenyl was transformed in 14 synthetic steps into the natural product cardinalin 3 using a bidirectional approach. One of the key steps was the formation of the cis-1,3-dimethylnaphtho[2,3-c]pyran ring. (±)-1,1′-[6,6′-Diallyl-5,5′-bis(benzyloxy)-1,1′,3,3′-tetramethoxy-2,2′-binaphthalene-7,7′-diyl]diethanol was treated with O2 in the presence of CuCl2 and catalytic PdCl2 to afford 5,5′-bis(benzyloxy)-7,7′,9,9′-tetramethoxy-1,1′,3,3′-tetramethyl-1H,1′H-8,8′-bibenzo[g]isochromene. Hydrogenation of this compound afforded 7,7′,9,9′-tetramethoxy-cis-1,3-cis-1′,3′-tetramethyl-3,3′,4,4′-tetrahydro-1H,1′H-8,8′-bibenzo[g]isochromene-5,5′-diol in quantitative yield, which was converted in 3 steps to cardinalin 3.
TL;DR: In this article, a stereoselective total synthesis of (6R)-6-[(4R, 6R)-4,6-dihydroxy-10-phenyldec-1-enyl]-5, 6-dhydro-2H-pyran-2-one is reported.
TL;DR: This is the first example of cyclisation leading to a substituted pyran rather than 1,4-DHP under typical Hantzsch reaction conditions and a plausible mechanism for its formation is postulated.
Abstract: Hantzsch condensation of two equivalents of methyl-3-aminocrotonate with (m- and p)-methoxybenzaldehyde afforded the expected products 2,6-dimethyl-3,5-dimethoxycarbonyl-4-(m-methoxyphenyl)-1,4-dihydropyridine and 2,6-dimethyl-3,5-dimethoxycarbonyl-4-(p-methoxyphenyl)-1,4-dihydropyridine, whereas o-methoxy-benzaldehyde produced mainly 1-amino-2-methoxycarbonyl-3,5-bis(o-methoxy-phenyl)-4-oxa-cyclohexan-1-ene. The structure of the product, not previously reported in the literature, was determined by 1D and 2D NMR spectra and its MS fragmentation. This is the first example of cyclisation leading to a substituted pyran rather than 1,4-DHP under typical Hantzsch reaction conditions. A plausible mechanism for its formation is postulated.
TL;DR: One-pot, three-component condensation reactions of aromatic aldehydes 1, 3-methylpyrazol-5-one (2) and ethyl trifluoroacetoacetate (3) provided an efficient methodology for the preparation of ethyl (4S*,5R*)-4-aryl-6-hydroxy-3-methyl-6-(trifluoromethyl)-2,4,5,6-tetrahydropyrazolo[3,4-b]pyran-5 carboxylate
TL;DR: Substituted 7-methyl-2H,5H-pyrano[4,3-b]pyran-5-ones and related heterocycles 3 were synthesized through an efficient domino Knoevenagel condensation/6pi-electron electrocyclization and exhibited necrotic effects on the human IPC melanoma cells.
TL;DR: In this paper, the title compound, C21H16FNO3·CH3OH, was synthesized by the reaction of 1-naphthol with methyl cyanoacetate and 3-fluoro-benzaldehyde in methanol under microwave irradiation.
Abstract: The title compound, C21H16FNO3·CH3OH, was synthesized by the reaction of 1-naphthol with methyl cyanoacetate and 3-fluorobenzaldehyde in methanol under microwave irradiation. The pyran rings of the two independent molecules in the asymmetric unit adopt boat conformations. The crystal packing is stabilized by intermolecular N—H⋯O, O—H⋯O and C—H⋯π interactions.
TL;DR: In this paper, the reaction of 1,3-dicarbonyl compounds such as acetoacetate, acetylacetone, dibenzoylmethane, and benzoylacetate with electron-deficient internal alkynes in the presence of catalytic amount of ReBr(CO)5 in toluene under neutral conditions resulted in the formation of 4,5,6-trisubstituted 2H-pyran-2-ones in moderate to high yield.
TL;DR: A palladium-catalyzed tandem Stille-oxa-electrocyclization reaction has been developed for the convergent preparation of highly substituted polycyclic pyran systems.
TL;DR: In this article, the synthesis of tetrahydrobenzo[b]pyran derivatives has been carried out by means of an uncatalyzed, three-component, one-pot clean condensation of aromatic aldehydes, reactive methylene compounds, and dimidone in aqueous medium Simple workup, and mild and neutral conditions that give quantitative yields of products in pure form, are the attractive features of this method.
Abstract: The synthesis of various tetrahydrobenzo[b]pyran derivatives has been carried out by means of an uncatalyzed, three-component, one-pot clean condensation of aromatic aldehydes, reactive methylene compounds, and dimidone in aqueous medium Simple workup, and mild and neutral conditions that give quantitative yields of products in pure form, are the attractive features of this method
Patent•
26 Sep 2007
TL;DR: In this paper, photochromic materials are provided that are essentially free of polymerizable unsaturated groups, and comprise: a) an indeno[2',3':3,4]naphtho[1,2-b]pyran; and b) an electron-withdrawing, non-conjugating group bonded at the 11 position of the indeno [2,3': 3,4], naphthoe[ 1, 2-b], pyran.
Abstract: Various photochromic materials are provided that are essentially free of polymerizable unsaturated groups, and comprise: a) an indeno[2',3':3,4]naphtho[1,2-b]pyran; and b) an electron-withdrawing, non-conjugating group bonded at the 11-position of the indeno[2',3':3,4]naphtho[1,2-b]pyran. Alternative embodiments include various substituents at other positions of the indeno[2',3':3,4]naphtho[1,2-b]pyran. Also provided are photochromic articles including a substrate and one of the above photochromic materials, in contact with at least a portion of the substrate.
TL;DR: Evidence is provided that a dimethylamino substituted side chain and the presence of 1,2 double bond play a key role in cell growth inhibition in 2,6-disubstituted pyrano- and 1,3-c]xanthen-7-ones synthesized and evaluated against MDA-MB-231 breast cancer cells.
TL;DR: In this paper, a stereoselective synthesis of (6S)-5,6-dihydro-6-[(2R)-2-hydroxy-6-phenylhexyl]-2H-pyran-2-one is reported.
Abstract: A stereoselective synthesis of (6S)-5,6-dihydro-6-[(2R)-2-hydroxy-6-phenylhexyl]-2H-pyran-2-one is reported. The strategy utilizes an olefin cross-metathesis, syn-benzylidene acetal formation and a preferential (Z)-Wittig olefination reaction and lactonization as the key steps.
TL;DR: A facile two-step procedure for the synthesis of 6-(trifluoromethyl)-1,4,5,6-tetrahydropyrazolo[3,4-b]pyran derivatives (4) from the reaction of 4-arylidene-3-methyl-1-phenyl-5-pyrazolones (1) with ethyl trifluoroacetoacetate (2), a versatile fluorinated building-block, was presented.
TL;DR: A novel C-27 norwithasteroid, withaphysanolide A (1) containing a pyran ring was isolated from the aerial parts of Physalis divericata.
TL;DR: In this article, the reaction of l-phenylpyrazolidine-3,5-dione with 3-formylchromone afforded 4-(chromenyl-methylene)pyrazinedione 2, which was reacted with hydrazine or hydroxylamine in different molar ratios and conditions to give the corresponding pyrazole and isoxazole derivatives 3-8, respectively.
Abstract: Condensation of l-phenylpyrazolidine-3,5-dione 1 with 3-formylchromone afforded 4-(chromenyl-methylene)pyrazolidinedione 2, which was reacted with hydrazine or hydroxylamine in different molar ratios and conditions to give the corresponding pyrazole and isoxazole derivatives 3-8, respectively. Compound 2 was subject to react with ammonia, N,S- or S,S-acetals, mercaptoacetic acid, cyanoacetamide or cyanothioacetamide to give the corresponding pyridine, dithiine, thiazine and thiophene, 9-14, respectively. The reaction of compound 2 with thiourea, guanidine, cystamine, o-aminothiophenol, ethylenediamine, o-phenelenediamine or barbituric acid afforded the corresponding thiazine, pyrimidine, thiazepine, diazepine, and pyran derivatives 17-23, respectively. The study of the reaction of compound 2 with nucleophiles via chromene ring opening was investigated.
TL;DR: A lipase catalyzed copolymerization of 4‐methylcoumarin diesters and polyethylene glycols (PEGs) has been carried out to give novel copolymers to increase the antioxidant potential and their hydrophilicity.
Abstract: Coumarins are well known for their antioxidant and anti‐edema activities. Their antioxidant property gets enhanced with a methyl group at the C‐4 position of the pyran ring. To increase the antioxidant potential and their hydrophilicity, a lipase (Novozyme 435) catalyzed copolymerization of 4‐methylcoumarin diesters and polyethylene glycols (PEGs) has been carried out to give novel copolymers.
TL;DR: The reactions of 5-arylidene derivatives of Meldrum's acid with ethyl vinyl ether or N-vinyl-2-oxazolidinone yielded trans-trans-(2,4:4,7)-pyrano[4,3-b]pyrans, cis-trans(2, 4: 4, 7)-Pyrano [4, 3-b]-pyran, or diastereoisomeric mixtures of pyrano•4, 4, 3b] pyrans and reactions with 3,
Abstract: The reactions of 5-arylidene derivatives of Meldrum’s acid with ethyl vinyl ether or N-vinyl-2-oxazolidinone yielded trans-trans-(2,4:4,7)-pyrano[4,3-b]pyrans, cis-trans-(2,4:4,7)-pyrano[4,3-b]pyrans, or diastereoisomeric mixtures of pyrano[4,3-b]pyrans and reactions with 3,4-dihydro-2H-pyran afforded Michael adducts. The reactions of 5-arylidene derivatives of Meldrum’s acid with cyanoacetic acid derivatives do not provide appropriate pyrans.