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显示 61-90 共 1014 条结果 关于 "pyrans" 范围 论文
Maud Reiter et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 12(27), 7190-7203 (2006-07-05)
Structurally diverse beta-hydroxyenones are shown to undergo nonoxidative 6-endo-trig ring closure to form highly substituted tetrahydropyranones. Amberlyst-15, Al(ClO(4))(3) x 9 H(2)O and [Pd(MeCN)(4)](BF(4))(2) were found to be suitable catalysts for these intramolecular conjugate additions, preventing side reactions, such as dehydration
Shen Z-W et al.
Phytochemistry, 57(1), 33-42 (2001-05-05)
The biosynthesis of chelidonic acid was studied in cell suspension cultures of Leucojum aestivum. Cell cultures were supplied with [U-13C]glucose, [l-13C]glucose or [U-13Cs]ribose/ribulose in standard medium containing unlabeled glucose. 13C labeling patterns of amino acids obtained by hydrolysis of biomass
Jigar A Makawana et al.
Bioorganic & medicinal chemistry letters, 21(20), 6166-6169 (2011-09-06)
A new series of fused pyran derivatives 5a-x bearing 2-morpholinoquinoline nucleus has been synthesized under microwave irradiation by a reaction of 2-morpholinoquinoline-3-carbaldehyde 2a-c, malononitrile 3 and compounds 4a-h in presence of NaOH as basic catalyst. All the compounds were screened
Srinivas Kantevari et al.
European journal of medicinal chemistry, 46(10), 4827-4833 (2011-07-05)
A series of novel hexahydro-2H-pyrano[3,2-c]quinoline analogues derived from dibenzo[b,d]furan and 9-methyl-9H-carbazole has been synthesized in very good yields through SnCl(2)·2H(2)O catalyzed one-pot Povarov reaction (imino-Diels-Alder reaction). The imines generated in situ from dibenzo[b,d]furan-2-carbaldehyde or 9-methyl-9H-carbazole-3-carbaldehyde and aromatic amines, were reacted
Shengqiang Tong et al.
Phytochemical analysis : PCA, 17(6), 406-408 (2006-12-06)
The bioactive component harpagoside was successfully separated from the crude extract of Scrophularia ningpoensis Hemsley by one-step purification using high-speed counter-current chromatography (HSCCC). A two-phase solvent system containing n-butanol:ethyl acetate:water (1:9:10) was selected following consideration of the partition coefficient of
Yasuyuki Ogawa et al.
The Journal of organic chemistry, 78(1), 104-115 (2012-11-06)
The Prins cyclization of syn-β-hydroxy allylsilanes and aldehydes gives cis-2,6-disubstituted 4-alkylidenetetrahydropyrans as sole products in excellent yields regardless of the aldehyde (R″) or syn-β-hydroxy allylsilane substituent (R') used. By reversing the R″ and R' groups, complementary exocyclic stereocontrol can be
Total synthesis of natural myriaporones.
Marta Pérez et al.
Angewandte Chemie (International ed. in English), 43(13), 1724-1727 (2004-03-24)
Yong-hong Zhang et al.
Zhongguo Zhong yao za zhi = Zhongguo zhongyao zazhi = China journal of Chinese materia medica, 27(3), 206-208 (2003-05-31)
To investigate the chemical constituents of Galeopsis bifida. Various chromatographic techniques were employed for isolation and purification of the constituents. The structures were elucidated by chemical and spectral analyses. Ten compounds were isolated and identified as chrysoeriol(1), 5,7-dihydroxy-3',4'-dimethoxyflavone(2), hederagenin(3), daucosterol(4)
Rodrigo S Bitzer et al.
Carbohydrate research, 340(13), 2171-2184 (2005-08-02)
An ab initio conformational study of the alpha- and beta-glycosidic C1-O1 bonds has been carried out on the axial and equatorial forms of 2-methoxytetrahydropyran (2-MTHP) at the HF/6-31G(d,p) and GVB-PP/6-31G(d,p) levels of calculation. Six conformers of 2-MTHP were fully optimized
Yangbin Liu et al.
The Journal of organic chemistry, 77(8), 4136-4142 (2012-03-22)
A simple chiral diamine catalyst (1a) was successfully applied in the asymmetric Michael reaction between cyclic dimedone and α,β-unsaturated ketones. Both acyclic enones with aryl or alkyl β-substituents and cyclic enones were tolerated well in the reaction. The desired adducts
Z Szendi et al.
Steroids, 56(9), 458-463 (1991-09-01)
Pregnenolone 3-(2'-tetrahydropyranyl) ether (1) was condensed with 3,4-[2H]dihydropyran to mainly give (20R)-[6'-(3',4'-[2'H]dihydropyranyl)]-pregn-5-ene-3 beta,20-diol 3-(2'-tetrahydropyranyl) ether (20R-3), according to nuclear magnetic resonance (NMR). Cold, dilute HCl in ethanol removed the tetrahydropyranyl group at C-3 and also opened the dihydropyranyl ring at
Pipas Saha et al.
Organic & biomolecular chemistry, 10(12), 2470-2481 (2012-02-22)
An efficient method for the synthesis of 2,3,5,6-tetrasubstituted tetrahydropyrans has been developed from the reaction of aldehydes and ethyl 2-(1-hydroxyalkyl/hydroxy(phenyl)methyl)-5-methylhex-4-enoate using (3,5)-oxonium-ene reaction promoted by boron trifluoride etherate in good yields under mild conditions.
Andreas Rathjens et al.
Carbohydrate research, 438, 18-25 (2016-12-14)
2, 3-Di-ω-halo- as well as 2, 3-di-ω-toluenesulfonamide-alkylated glucopyranoside derivatives were prepared. Their condensation with α,ω-bis-toluenesulfonamide components under varying Richman-Atkins conditions with alkali carbonate in DMF led to carbohydrate-linked aza-macrocycles displaying 14-, 17-, 18-, 21-, 24-, and 25-membered ring structures. Isomeric
Hamidreza Shirvani-Mahdavi et al.
Optics express, 18(13), 13593-13599 (2010-07-01)
An amplified cholesteric liquid crystal (CLC) laser performance is demonstrated by utilizing a binary-dye mixture (with 62 wt% DCM and 38 wt% PM597) as the active medium and an external stable resonator. The measured results show that the laser efficiency
C L Cantrell et al.
Journal of agricultural and food chemistry, 53(20), 7741-7748 (2005-09-30)
Bioassay-guided fractionation of the hexane/ethyl acetate/water (H/EtOAc/H2O) crude extract of the aerial parts of Haplophyllum sieversii was performed because of preliminary screening data that indicated the presence of growth inhibitory components against Colletotrichum fragariae, Colletotrichum gloeosporioides, and Colletotrichum acutatum. Fractionation
[Isolation and identification of chemical constituents from Hedyotis chrysotricha (Palib.) Merr].
Z Fang et al.
Zhongguo Zhong yao za zhi = Zhongguo zhongyao zazhi = China journal of Chinese materia medica, 17(2), 98-100 (1992-02-01)
Surendra Singh et al.
The Journal of organic chemistry, 74(15), 5758-5761 (2009-07-04)
The ZrCl4-catalyzed deprotection of 1,3-dioxane/dioxalane and the simultaneous formation of 6-methoxy-substituted tetrahydropyrans proceeded under microwave irradiation in good yield. This synthetic methodology was used for the asymmetric synthesis of (+)-exo- and (+)-endo-brevicomin in 55% overall yield over 4 steps.
S B Turnipseed et al.
Journal of AOAC International, 84(3), 640-647 (2001-06-22)
A liquid chromatographic/mass spectrometric (LC/MS) electrospray confirmation method has been developed to confirm 4 ionophores (monensin, lasalocid, salinomycin, and narasin) in a variety of animal feeds using a single quadrupole mass spectrometer. The sodium ions of these compounds are dominant
Lucie Szücová et al.
Bioorganic & medicinal chemistry, 17(5), 1938-1947 (2009-02-24)
In an attempt to improve specific biological functions of cytokinins routinely used in plant micropropagation, 33 6-benzylamino-9-tetrahydropyran-2-ylpurine (THPP) and 9-tetrahydrofuran-2-ylpurine (THFP) derivatives, with variously positioned hydroxy and methoxy functional groups on the benzyl ring, were prepared. The new derivatives were
James R Frost et al.
Chemistry (Weinheim an der Bergstrasse, Germany), 21(38), 13261-13277 (2015-08-01)
Since their isolation almost 20 years ago, the callipeltosides have been of long standing interest to the synthetic community owing to their unique structural features and inherent biological activity. Herein we present our full research effort that has led to the
M Atef et al.
DTW. Deutsche tierarztliche Wochenschrift, 96(6), 296-298 (1989-05-01)
Fetotoxic effects induced by three anticoccidial drugs: robenidine, salinomycin and arprinocid were elucidated in the chicken. Different doses of these drugs were inoculated in groups of embryonated chicken eggs by the yolk sac route. After inoculation, candling of the eggs
Citreoviridins from Aspergillus terreus.
B Franck et al.
Angewandte Chemie (International ed. in English), 19(6), 461-462 (1980-01-01)
Selvaraj Kanchithalaivan et al.
ACS combinatorial science, 15(12), 631-638 (2013-10-24)
An efficient one-pot four-component domino protocol for the combinatorial synthesis of novel 1,4-dihydropyrano[2,3-c]pyrazol-6-amines has been achieved. This transformation presumably occurs via cyclization-Knoevenagel condensation-Michael addition-tautomerism-intramolecular O-cyclization-elimination sequence of reactions. The significant features of this reaction include expedient one-pot process, short reaction
María I Mangione et al.
Carbohydrate research, 338(21), 2177-2183 (2003-10-14)
The oxirane ring-opening of an anhydro sugar with diethylaluminum cyanide (Et(2)AlCN) is a direct approach for obtaining a cyano derivative. Methyl 2,3-anhydro-4,6-O-benzylidene-alpha-D-allopyranoside showed anomalous chemical behavior when treated with Et(2)AlCN. The reaction afforded the corresponding beta-cyanohydrin as the minor component
Keith G McMillan et al.
Carbohydrate research, 341(1), 41-48 (2005-11-03)
5-(1,2,3,4-tetra-O-acetyl-alpha-D-xylopyranos-5S-C-yl)-1,3,4-oxathiazol-2-one (8) has been prepared from glucuronamide in two steps and 73% overall yield by conversion to the tetra-O-acetyl derivative 7 followed by reaction with chlorocarbonylsulfenyl chloride. 5-(2,3,4-Tri-O-acetyl-beta-D-xylopyranosyl)-1,3,4-oxathiazol-2-one (12) was synthesised from D-xylose by a four-step sequence involving conversion to
Vanajakshi Gudla et al.
Chemistry, an Asian journal, 8(2), 414-428 (2012-11-28)
Intermolecular and intramolecular reactions of a one-pot gold-catalyzed epoxide rearrangement followed by an electrophilic addition to arylalkynes to synthesize 1-arylnaphthalenes have been reported. The intramolecular reaction has been applied to synthesize 1-arylnaphthalenes fused with saturated furan, pyran, pyrrole, and cyclopentane
Abdullah S Al-Bogami et al.
Ultrasonics sonochemistry, 20(5), 1194-1202 (2013-04-18)
The present paper deal with the multi-component condensation of 8-hydroxy quinoline, aromatic aldehydes, and sulfone derivatives catalyzed by p-toluenesulfonic acid for the synthesis of a series of 4H-pyrano[3,2-h]quinoline derivatives in ethanol under ultrasonic irradiations. We provide a series of quinoline
James A Marshall et al.
Organic letters, 7(8), 1593-1596 (2005-04-09)
[reaction: see text] Additions of chiral allenylzinc and indium reagents to N-Boc alaninal were examined as a possible route to a C20-C26 segment of superstolide A. Allenylzinc reagents, prepared in situ by palladiozincation of (R)- and (S)-5-pivalyloxy-3-butyn-2-ol mesylate, showed excellent
C D Tran et al.
Analytical chemistry, 65(13), 1675-1681 (1993-07-01)
Advantages of the acousto-optic tunable filter (AOTF), namely its ability for fast scanning and multiple-wavelength diffraction, were exploited to develop a novel, all solid-state, nonmoving parts spectrofluorometer. This instrument is based on the use of two AOTFs: one for excitation
Erika Pistarino et al.
Food chemistry, 138(2-3), 2043-2049 (2013-02-16)
The influence of two operative parameters on the fermentation process of table olives from Taggiasca cultivar were investigated. Laboratory scale fermentations were performed using Lactobacillus plantarum as the only starter and in combination with Saccharomyces cerevisiae at three different temperatures
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