- PHOTO-OXIDATIVE CYCLISATION OF 2'-HYDROXYCHALCONES LEADING TO FLAVONES INDUCED BY HETEROCYCLE N-OXIDES: HIGH EFFICIENCY OF PYRIMIDOPTERIDINE N-OXIDE FOR THE PHOTOCHEMICAL DEHYDROGENATION
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Irradiation of 2'-hydroxychalcones (3) with UV-visible light in the presence of heterocycle N-oxides such as pyrimidopteridine N-oxide (I) results in the formation of the corresponding flavones (4) and flavanones (5).The photooxidative cyclisation of (3) induced by (1) to give (4) most efficiently occurred among the heterocycle N-oxides examined and could be reasonably explained by considering an initial single-electron oxidation of (3) by (1) under the photochemical conditions and subsequent intramolecular cyclisation.
- Maki, Yoshifumi,Shimada, Kaoru,Sako, Magoichi,Hirota, Kosaku
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Read Online
- Organocatalytic Approach for Assembling Flavanones via a Cascade 1,4-Conjugate Addition/oxa-Michael Addition between Propargylamines with Water
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A DBU-catalyzed one-pot cascade reaction of propargylamines and water for the synthesis of flavanones has been developed. This process proceeds via a sequence of 1,4-conjugate addition of water to alkynyl o-quinone methide (o-AQM), followed by the alkyne-allene isomerization and subsequent intramolecular oxa-Michael addition. This strategy provides a convenient method for accessing a broad range of flavanones in good to excellent yields with good functional-group tolerance, in particular, the reactive halo functional groups.
- He, Xinwei,He, Xinwei,Xie, Mengqing,Li, Ruxue,Choy, Pui Ying,Tang, Qiang,Shang, Yongjia,Kwong, Fuk Yee
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p. 4306 - 4310
(2020/06/05)
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- Synthesis and kinetic study for the interconversion process of some 2'-hydroxychalcones to their corresponding flavanones
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In this work, five substituted2'-Hydroxychalconeswere prepared using Claisen - Schmidt condensation and used as a synthone for substituted flavanones via base catalyzed isomerization process. The latter process has been studied kinetically using HPLC technique in (8:2) (CH3CN:CH3OH) medium at different temperatures (298 K - 318 K). The obtained results were inconsonance with a four-step mechanism which considered the existence of phenoxide ion as the key intermediate. The reaction was achieved as a pseudo first order reaction in which the rate of the studied compounds followed the sequence 1>2>3>4>5, and the activation energy had the same sequence for these compounds. The reaction rate was affected by the electronic behavior of the different substituents at ring B since they played an important role in the stability of the intermediate that led to the final product.
- Majed, Zainab Waleed,Said, Said Abdelqader,Shareef, Omar Adil
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p. 4379 - 4386
(2020/12/09)
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- Synthesis of Flavanones via Palladium(II)-Catalyzed One-Pot β-Arylation of Chromanones with Arylboronic Acids
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A total of 47 flavanones were expediently synthesized via one-pot β-arylation of chromanones, a class of simple ketones possessing chemically unactivated β sites, with arylboronic acids via tandem palladium(II) catalysis. This reaction provides a novel route to various flavanones, including natural products such as naringenin trimethyl ether, in yields up to 92percent.
- Cho, Yang Yil,Jang, Hyu Jeong,Kim, Dong Hwan,Kim, Nam Yong,Kim, Nam-Jung,Kim, Young Min,Lee, Soo Jin,Lee, Yong Sup,Park, Boyoung Y.,Son, Seung Hwan,Yoo, Hyung-Seok
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p. 10012 - 10023
(2019/08/30)
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- Discovery of a Prenylated Flavonol Derivative as a Pin1 Inhibitor to Suppress Hepatocellular Carcinoma by Modulating MicroRNA Biogenesis
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Peptidyl-prolyl cis-trans isomerase Pin1 plays a crucial role in the development of human cancers. Recently, we have disclosed that Pin1 regulates the biogenesis of miRNA, which is aberrantly expressed in HCC and promotes HCC progression, indicating the therapeutic role of Pin1 in HCC therapy. Here, 7-(benzyloxy)-3,5-dihydroxy-2-(4-methoxyphenyl)-8-(3-methylbut-2-en-1-yl)-4H-chromen-4-one (AF-39) was identified as a novel Pin1 inhibitor. Biochemical tests indicate that AF-39 potently inhibits Pin1 activity with an IC50 values of 1.008 μm, and also displays high selectivity for Pin1 among peptidyl prolyl isomerases. Furthermore, AF-39 significantly suppresses cell proliferation of HCC cells in a dose- and time-dependent manner. Mechanistically, AF-39 regulates the subcellular distribution of XPO5 and increases miRNAs biogenesis in HCC cells. This work provides a promising lead compound for HCC treatment, highlighting the therapeutic potential of miRNA-based therapy against human cancer.
- Zheng, Yuanyuan,Pu, Wenchen,Li, Jiao,Shen, Xianyan,Zhou, Qiang,Fan, Xin,Yang, Sheng-Yong,Yu, Yamei,Chen, Qiang,Wang, Chun,Wu, Xin,Peng, Yong
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supporting information
p. 130 - 134
(2018/11/30)
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- A Borane-Catalyzed Metal-Free Hydrosilylation of Chromones and Flavones
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A Piers-type hydrosilylation of chromones and flavones has been successfully realized for the first time using 0.1 mol % of borane catalyst generated in situ by hydroboration of pentafluorostyrene with HB(C 6 F 5) 2 to afford a variety of chromanones and flavanones in 60-99% yields. An attempt for the asymmetric transformation with chiral diyne and HB(C 6 F 5) 2 gave chromanones and flavanones in high yields with up to 32% ee.
- Ren, Xiaoyu,Han, Caifang,Feng, Xiangqing,Du, Haifeng
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p. 2421 - 2424
(2017/11/04)
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- Palladium-Catalyzed [3+3] Annulation of Vinyl Chromium(0) Carbene Complexes through Carbene Migratory Insertion/Tsuji–Trost Reaction
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Vinyl chromium(0) Fischer carbene complexes were employed as the source of π-allylic palladium species for catalytic [3+3] annulation under palladium catalysis. Mechanistically, this transformation is proposed to involve carbene migratory insertion and intramolecular Tsuji–Trost reaction as the key steps. Substituted six-membered heterocyclic flavonones and quinolines are obtained, depending on the nucleophilic functional group on the coupling partners.
- Wang, Kang,Ping, Yifan,Chang, Taiwei,Wang, Jianbo
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supporting information
p. 13140 - 13144
(2017/10/11)
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- Guanidino-graphene catalysed synthesis of flavones via Aldol-Michael-oxidation
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Guanidino-graphene has been synthesized by the reaction of bromoamine with reduced graphene oxide and characterized by FT-IR, Raman, TGA, powder XRD, TEM, SEM, and zeta potential. It is a cheap, heterogeneous and environmentally benign solid base catalyst used for cascade Aldol-Michael-oxidation in the synthesis of chalcone, flavonoids.
- Mishra, Sweta,Arora, Smriti,Nagpal, Ritika,Chauhan, Shive Murat Singh
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p. 2525 - 2530
(2017/03/09)
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- An efficient synthesis of flavanones and their docking studies with aldose reductase
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A series of flavanone derivatives have been synthesized from 2-hydroxy acetophenone and benzaldehyde using fused calcium chloride in good to moderate yields, and their in vitro aldose reductase inhibitory activity has been tested on aldose reductase purified enzyme from Bovine lens. Most of the synthesized compounds exhibited potent aldose reductase inhibitory activity, and the obtained results are supported by the docking studies. Among the tested derivatives, 2, 3, 4-methoxy derivative 19 (IC50 5.88 ± 0.03 μM) exhibited the highest inhibitory activity whereas 2-methoxy derivative 12 showed the lowest, and the remaining compounds exhibited moderate activity with IC50 in the range of 6.09–7.89 μM. The spatial configuration of the most active derivative 19 was compared with pharmacophore requirements of the aldose reductase inhibitor site using a molecular modeling system.
- Kondhare,Gyananath,Tamboli, Yasinalli,Kumbhar, Santosh S.,Choudhari, Prafulla B.,Bhatia, Manish S.,Zubaidha
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p. 987 - 998
(2017/04/14)
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- Synthesis of pyrazole-substituted chromene analogues with selective anti-leukemic activity
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We report design and synthesis of a series of flavanone/chromene derivatives containing pyrazoles 6a–6h and 8a–8e with potent anti-leukemic activity. Anti-leukemic activity of novel flavanone derivatives was tested using the K562 cell line. The parental flavanone was selected as the reference compound in identification of analogues with superior anti-leukemic activity. More than two-thirds of the derivatives displayed higher activity than the initial flavanone. Positions of substituents that promoted anti-leukemic activity were identified on both the chromene and pyrazole fragments. Compounds 6b and 6c showed the highest activity against K562 cell line, with IC50 values 3.0 and 0.5 μM respectively. Notably, compounds 6b and 6c displayed very high selectivity in inhibition of leukemic cells (K562) but not of healthy HEK293 cells or solid cancer cell lines HeLa, MCF7 and BT474. Moreover, both the 6b and 6c compounds were predicted to have good ADME properties.
- Madhu,Sudhakar,Santosh Kumar,Rajashekher Reddy,Sravani,Ramakrishna,Prasad Rao, Ch.
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p. 2421 - 2428
(2017/11/24)
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- CuO nanoparticles as an efficient catalyst for the synthesis of flavanones
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CuO nanoparticle was found to be an efficient catalyst for the synthesis of flavanones derivatives from the reactions between 2-hydroxyacetophenones and aromatic aldehydes at room temperature. The protocol offers advantages in terms of higher yields, short reaction times, and mild reaction conditions, with reusability of the catalyst. The structures of the synthesized substituted flavanones were confirmed by their Melting point, FT-IR,1 HNMR,13 CNMR and mass spectral analysis.
- Ahmady, Amanollah Zarei,Keshavarz, Mosadegh,Kardani, Maryam,Mohtasham, Neda
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p. 1841 - 1846
(2016/01/25)
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- Nanosilica-supported dual acidic ionic liquid as a heterogeneous and reusable catalyst for the synthesis of flavanones under solvent-free conditions
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[Figure not available: see fulltext.] A nanosilica-supported dual acidic ionic liquid on the basis of 1-methyl-3-(4-sulfobutyl)imidazolium hydrogen sulfate was synthesized and used as an efficient, green, non-corrosive, non-toxic, heterogeneous, and reusable catalyst for the synthesis of some new and known substituted flavanones. The synthesis was done by the condensation of 2'-hydroxyacetophenone with different aldehydes and the subsequent cyclization of the resulting 2'-hydroxychalcone in the presence of the catalyst. High yields of the products, short reaction times, and solvent-free conditions characterize this new method.
- Rostamizadeh, Shahnaz,Zekri, Negar,Tahershamsi, Leili
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p. 526 - 530
(2016/02/16)
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- Rhodium/chiral diene-catalyzed asymmetric 1,4-addition of arylboronic acids to chromones: A highly enantioselective pathway for accessing chiral flavanones
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Chromone has been noted to be one of the most challenging substrates in the asymmetric 1,4-addi-tion of α,β-unsaturated carbonyl compounds. By employing the rhodium complex associated with a chiral diene ligand, (R,R)-Ph-bod, the 1,4-addition of a variety of aryl-boronic acids was realized to give high yields of the corresponding flavanones with excellent enantioselectivities (≥97% ee, 99% ee for most substrates). Ring-opening side products, which would lead to erosion of product enantioselectivity, were not observed under the stated reaction conditions.
- He, Qijie,Wang, Jun,So, Chau Ming,Hayashi, Tamio,Bian, Zhaoxiang
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supporting information
p. 540 - 543
(2015/05/05)
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- Facile one-pot synthesis of flavanones using tetramethylguanidinum-based ionic liquids as catalysts
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Several tetramethylguanidinum-based ionic liquids (TMGILs) were prepared, characterized and used as catalysts in one-pot synthesis of flavanones. The results indicated that TMGILs composed of phenolate anion was beneficial for one-pot synthesis of flavanones, and [TMG][4-MeO-PhO] induced the good yields of flavanones owing to the electron-donating effect of methoxy substituent on phenolate anion. Furthermore, [TMG][4-MeO-PhO] was found to be used repetitively at least five times without obvious decrease in activity and quantity.
- Zhou, Yan,Huang, Wei,Chen, Xiang-Shu,Song, Zhi-Bin,Tao, Duan-Jian
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p. 1830 - 1836
(2019/11/28)
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- Fe(HSO4)3/SiO2: An efficient and heterogeneous catalyst for one-pot synthesis of 2-aryl-chromene-4-ones (flavanones)
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Silica ferric hydrogensulphate is an efficient heterogeneous catalyst for cyclisation of 2-hydroxychalcones to their corresponding flavanones (chromanone). This intramolecular oxa-Michael reaction was carried out in high yields in the presence of electron donating and electron withdrawing groups in the chalcone structure. Also, we found that aniline can act as an organic co-catalyst in direct synthesis of flavanones from 2-hydroxyacethophenone and aldehydes in the presence of Fe(HSO4)3/SiO2. Flavanones were prepared in high yields in a new catalytic system with similar substituted effect in the indirect cyclisation method. The catalyst in all the above reactions is reusable without significant decreases in its activity after four times of recycling.
- Eshghi, Hossein,Rahimizadeh, Mohammad,Mousavi, Seyed Mohsen
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supporting information
p. 438 - 443
(2014/04/17)
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- SAR studies of o-hydroxychalcones and their cyclized analogs and study them as novel inhibitors of cathepsin B and cathepsin H
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Cathepsins have emerged as a potential target for anti-cancer drug development. In the present study, we have synthesized three structurally related series of flavanoids i.e., 2′-hydroxychalcones, flavanones and flavones and assayed in vitro to study their inhibitory potency against cathepsin B and H, promising drug candidate for cancer therapy. Enzyme kinetics studies were carried out in presence of these compounds after preliminary proteolytic studies on endogenous protein substrates. SAR studies suggested that open chain flavanoids were better inhibitors as compared to their cyclized analogs. The most potent inhibitors among the three series were nitro substituted compounds 1g, 2g and 3g with Ki values of ~6.18 × 10-8 M, 4.8 × 10-7 M and 7.85 × 10-7 M for cathepsin B and Ki values of ~2.8 × 10-7 M, 31.8 × 10-6 M and 33.7 × 10 -6 M for cathepsin H, respectively. The relationship between chalcone, flavanones and flavone structures interpreted by docking studies on cathepsin B and H also provided useful insights.
- Raghav,Garg
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- Palladium-catalyzed asymmetric conjugate addition of arylboronic acids to heterocyclic acceptors
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Flava Flavanone: Asymmetric conjugate additions to chromones and 4-quinolones are reported utilizing a single catalyst system formed in situ from Pd(OCOCF3)2 and (S)-tBuPyOX. Notably, these reactions are performed in wet solvent under ambient atmosphere, and employ readily available arylboronic acids as the nucleophile, thus providing ready access to these asymmetric heterocycles (see scheme).
- Holder, Jeffrey C.,Marziale, Alexander N.,Gatti, Michele,Mao, Bin,Stoltz, Brian M.
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supporting information
p. 74 - 77
(2013/02/25)
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- An efficient and facile synthesis of flavanones catalyzed by N-methylimidazole
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The use of N-methylimidazole as an efficient catalyst for the cyclization of 2'-hydroxychalcones to the corresponding flavanones in DMSO was investigated. The scope of this process was studied and various flavanones were obtained exclusively in good yields. Copyright
- Wang, Peng,Yang, Jiabin,Cai, Jin,Sun, Chunlong,Li, Lushen,Ji, Min
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p. 917 - 920
(2013/08/23)
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- Silica supported-double metal cyanides (DMCs): A green and highly efficient catalytic protocol for isomerisation of 2′-hydroxychalcones to flavanones
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Four different double metal cyanides (NiHCFe, CrHCFe, MnHCFe and ZnHCFe) were synthesized, followed by adsorbed on silica gel and used as Lewis acid catalyst in the isomerisation of substituted 2′-hydroxychalcones to flavanones under solvent-free (dry) condition. Optimization of the reaction condition, temperature effects, DMC catalysts loading and re-useable catalytic activity were further studied during the reaction. Among these catalysts, NiHCFe at 35 mol% loading gave excellent yield (90%) at 100 C temperature in 1.15 h. Catalyst (NiHCFe) easily recovered and re-used six times without much loss of its catalytic activity which gave 80-85% product yields each time. However, these DMCs were failed to give product in the solution phase even prolonging the reaction time at reflux temperature. Similarly, isomerization of substituted 2′-aminochalcones gave 2-5% yields either in solution phase or under solvent-free condition.
- Ahmed, Naseem,Konduru, Naveen Kumar,Praveen,Kumar, Anand,Kamaluddin
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p. 135 - 141
(2013/06/26)
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- Sodium perborate tetrahydrate-mediated transformations of 2′-hydroxychalcones to flavanones, flavones, and 3′, 5′-diiodoflavone under mild, environmentally friendly conditions
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Sodium perborate tetrahydrate has been utilized as a nucleophilic catalyst for facile conversion of 2′-hydroxychalcones to flavanones in warm aqueous acetonitrile, and then these chalcones, upon oxidative cyclization in warm acetic acid with an excess of the same reagent, afforded flavones in acceptable yields. One-pot synthesis of 3′,5′-diiodoflavone has been accomplished by diacetoxyiodobenzene-catalyzed iodination of 2′-hydroxychalcone with tetra-n-butylammonium iodide in acetic acid in the presence of sodium perborate as a terminal oxidant.
- Ganguly, Nemai C.,Chandra, Sumanta,Barik, Sujoy Kumar
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p. 1351 - 1361
(2013/05/09)
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- Hydromagnesite as an efficient recyclable heterogeneous solid base catalyst for the synthesis of flavanones, flavonols and 1,4-dihydropyridines in water
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A form of hydromagnesite (HM) with flower-like thin-sheet morphology was synthesized by an environmentally benign approach using simple conventional heating at moderate temperature without using any template in water as medium. The versatility of this HM catalyst was studied in the synthesis of flavanones, flavonols and the multicomponent synthesis of 1,4-dihydropyridines in water. The recyclability of catalyst was studied for six times and there was no appreciable loss in its catalytic activity. Copyright
- Rajesh, U. Chinna,Manohar, Sunny,Rawat, Diwan S.
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p. 3170 - 3178
(2013/12/04)
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- Synthetic approach to flavanones and flavones via ligand-free palladium(ii)-catalyzed conjugate addition of arylboronic acids to chromones
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The remarkable catalytic effects of Fe(OTf)3 in the context of the Pd(ii)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO2 to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds.
- Kim, Donghee,Ham, Kyungrok,Hong, Sungwoo
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experimental part
p. 7305 - 7312
(2012/09/22)
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- Synthesis of flavanones, azaflavanones, and thioflavanones catalyzed by PMA-SiO2 as a mild, efficient, and reusable catalyst
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Cyclization of a variety of chalcones to flavanones catalyzed by 1 mol% phosphomolybdic acid (PMA) supported on silica as a mild, efficient, and reusable catalyst was carried out in high yields. PMA-SiO2 is an efficient, inexpensive, and green catalyst which gave high conversion yields and could be recycled up to three times without significant loss in activity. Springer-Verlag 2011.
- Sakirolla, Raghavendra,Yaeghoobi, Marzieh,Rahman, Noorsaadah Abd.
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experimental part
p. 797 - 800
(2012/09/07)
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- Iodine catalyzed one-pot synthesis of flavanone and tetrahydropyrimidine derivatives via Mannich type reaction
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A variety of functionalized flavanone derivatives and tetrahydropyrimidine derivatives were achieved under remarkably mild conditions. The combination of good to excellent yields, a simple work-up, and the high compatibility of functional groups makes this an attractive synthetic approach to access flavanone and tetrahydropyrimidine derivatives.
- Kavala, Veerababurao,Lin, Chunchi,Kuo, Chun-Wei,Fang, Hulin,Yao, Ching-Fa
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experimental part
p. 1321 - 1329
(2012/02/13)
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- Synthesis of 5-aryl-2-piperidino-5H-chromeno[3,4-c]pyridine-1-carbonitriles
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4-Chloro-2-aryl-2H-3-chromenecarbaldehydes 3a-g on reaction with malononitrile in ethanol in the presence of piperidine gave 5-aryl-2-piperidino- 5H-chromeno[3,4-c]pyridine-1-carbonitriles 4a-g in good yields. ARKAT-USA, Inc.
- Venkati,Reddy, S. Satyanarayana,Swamy,Ravikumar,Krupadanam, G. L. David
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scheme or table
p. 355 - 364
(2012/06/29)
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- Synthesis of flavanones by use of anhydrous potassium carbonate as an inexpensive, safe, and efficient basic catalyst
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Anhydrous potassium carbonate has been utilized as an inexpensive, safe, and efficient basic catalyst for the synthesis of flavanones starting either from 2′-hydroxychalcones or from 2′-hydroxyacetophenones. In both the cases the favored reaction condition was either refluxing in a solvent with added catalyst or microwave irradiation on the catalyst.
- Mondal, Rina,Gupta, Arpita Das,Mallik, Asok K.
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p. 5020 - 5024
(2011/10/19)
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- Ytterbium(III) triflate: An efficient and simple catalyst for isomerization of 2′-hydroxychalcone and 2′-aminochalcones in ionic liquid
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Isomerization of 2′-hydroxychalcone and 2′-aminochalcone have been investigated using ytterbium(III) trifluromethanesulfonate {Yb(OTf) 3} (30 mol %) as Lewis acid catalyst in [bmim][BF4] ionic liquid. The effect of different metal triflates as Lewis acid, catalyst loading and reaction media was studied for this isomerization reaction. Advantages of the methodology include short reaction time, excellent yields, catalytic use of Lewis acid, and recovery and reuse of the catalyst. Copyright
- Rao, V. Kameswara,Rao, M. Sudershan,Kumar, Anil
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experimental part
p. 1356 - 1360
(2012/01/04)
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- PH-Dependent conjugate addition of arylboronic acids to α,β-unsaturated enones catalyzed by a reusable palladium(II)/cationic 2,2'-bipyridyl system in water under air
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A reusable Pd(NH3)2Cl2/cationic 2,2'-bipyridyl system for the catalysis of the conjugate addition of arylboronic acids to α,β-unsaturated enones in water under air was developed. Addition of arylboronic acids to both cyclic and acyclic enones progressed smoothly, providing the products in good to high yields, the best result being obtained when HBF4 was used to adjust the pH value to 1.0. After the reaction, the residual aqueous solution could be reused several times,making the reaction greener and reducing wastage of precious metals. Copyright
- Huang, Shao-Hsien,Wu, Tzu-Min,Tsai, Fu-Yu
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experimental part
p. 619 - 624
(2010/11/04)
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- Synthesis and cytotoxic activity of 4-aryl-4H-chromeno[4,3-d] [1,2,3] selenadiazoles
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Fourteen 4-Aryl-4H-chromeno[4,3-d][1,2,3] selenadiazole derivatives were synthesized by the reaction of fla-vonone-4-semicarbazones with SeO2. The structures of the target compounds 1a-n were elucidated by 1H NMR, IR spectra, ESI-MS and elemental analyses. The preliminary cytotoxic activities of 1a-n against K562, KB, A549, SMC-7721 and SGC-7901 cell lines were evaluated by MTT method, indicating that most compounds displayed moderate to good antiproliferative activities against K562 and KB cell lines. Compounds 1m and 1n, the most potent ones, were promising template for development of novel potent antitumor agents.
- Yin, Hong,Huang, Yueyan,Song, Guojie
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p. 721 - 725
(2013/01/09)
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- A new series of flavones, thioflavones, and flavanones as selective monoamine oxidase-B inhibitors
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A new series of synthetic flavones, thioflavones, and flavanones has been synthesized and evaluated as potential inhibitors of monoamine oxidase isoforms (MAO-A and -B). The most active series is the flavanone one with higher selective inhibitory activity against MAO-B. Some of these flavanones (mainly the most effective) have been separated and tested as single enantiomers. In order to investigate the MAOs recognition of the most active and selective compounds, a molecular modeling study has been performed using available Protein Data Bank (PDB) structures as receptor models for docking experiments.
- Chimenti, Franco,Fioravanti, Rossella,Bolasco, Adriana,Chimenti, Paola,Secci, Daniela,Rossi, Francesca,Yá?ez, Matilde,Orallo, Francisco,Ortuso, Francesco,Alcaro, Stefano,Cirilli, Roberto,Ferretti, Rosella,Sanna, M. Luisa
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experimental part
p. 1273 - 1279
(2010/04/24)
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- Ionic liquid catalyzed expeditious synthesis of 2-aryl-2,3-dihydroquinolin- 4(1H)-ones and 2-aryl-2,3-dihydro-4H-chromen-4-ones under microwave irradiation
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(Chemical Equation Presented) A facile and convenient synthesis of 2-aryl-2,3-dihydroquinolin-4(1H)-one and 2-aryl-2,3-dihydro-4Hchromen-4-one has been described using ionic liquid catalyzed intramolecular cyclization of the corresponding 2′-aminochalcones and 2′-hydroxychalcones, respectively. The rapid and fairly general protocol affords product in good yield. Ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, was recovered and reused without loosing its efficiency.
- Kumar, Dalip,Patel, Gautam,Kumar, Anil,Roy, Ram K.
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experimental part
p. 791 - 795
(2009/12/01)
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- Asymmetric intramolecular oxa-Michael addition of activated α,β-unsaturated ketones catalyzed by a chiral N,N′-dioxide nickel(II) complex: Highly enantioselective synthesis of flavanones
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(Chemical Equation Presented) The title reaction provides a promising approach for the synthesis of chiral flavanones with broad substrate scope and is tolerant to air and moisture. Good to excellent enantioselectivities and high yields were achieved for most substrates under mild conditions.
- Wang, Lijia,Liu, Xiaohua,Dong, Zhenhua,Fu, Xuan,Feng, Xiaoming
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supporting information; body text
p. 8670 - 8673
(2009/05/16)
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- Synthesis of 2-alkyl-1-aryl-1,2-dihydrochromeno[2,3-c]pyrrole-3,9-dione derivatives
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A preparative procedure for the synthesis of 2-alkyl-1-aryl-1,2- dihydrochromeno[2,3-c]pyrrole-3,9-diones from methyl 4-(o-hydroxyphenyl)-2,4- dioxobutanoate, aromatic aldehyde, and aliphatic amine is described.
- Vydzhak,Panchishin, S. Ya.
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experimental part
p. 2391 - 2397
(2009/05/30)
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- Eco-friendly polyethylene glycol promoted Michael addition reactions of α,β-unsaturated carbonyl compounds
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Intra- and inter-nucleophilic addition reactions of different α,β-unsaturated carbonyl compounds were found to be highly effective without any additives in PEG-400 as a recyclable reaction medium under neutral conditions.
- Kumar, Dalip,Patel, Gautam,Mishra, Braja G.,Varma, Rajender S.
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scheme or table
p. 6974 - 6976
(2009/04/07)
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- A simple and facile solventless procedure for the cyclization of 2′-amino- and 2′-hydroxy-chalcones using silica-supported sodium hydrogen sulphate as heterogenous catalyst
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A simple environmentally friendly method for the cyclization of 2′-amino- and 2′-hydroxy-chalcones under solventless conditions using silica-supported sodium hydrogen sulphate has been reported.
- Hemanth Kumar,Perumal
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p. 1079 - 1083
(2007/10/03)
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- Synthesis of flavanones using nanocrystalline MgO
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The design and development of a truly nano heterogeneous catalyst for the Claisen-Schmidt condensation (CSC) of benzaldehydes with 2-hydroxyacetophenone to yield substituted chalcones followed by isomerization to afford flavanones with excellent yields and selectivity is described.
- Choudary,Ranganath,Yadav, Jagajit,Lakshmi Kantam
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p. 1369 - 1371
(2007/10/03)
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- New synthesis of flavanones catalyzed by L-proline
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L-Proline is utilized as an efficient organocatalyst for the synthesis of substituted flavanones and chalcones in good yields. The efficiency of the catalyst was proved with a variety of substrates ranging from electron-deficient to electron-rich aryl aldehydes and 2-hydroxyacetophenones.
- Chandrasekhar,Vijeender,Venkatram Reddy
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p. 6991 - 6993
(2007/10/03)
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- A facile synthesis of ethyl-2-methyl-5-aryl-5H-chromeno-[3,4-c]pyridine-1-carboxylates
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Flav-4-ones on reaction with DMF/POCl3 gave 4-chloro-2-aryl-2H-chromene-3-carbaldehydes which on reaction with ethyl-3-aminocrotonate give under Hantszch reaction conditions ethyl-2-methyl-5-aryl-5H-chromeno[3,4-c]pyridine-1-carboxylates in good yields.
- Venkati,Krupadanam
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p. 2589 - 2598
(2007/10/03)
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- A concerted synthesis of hydroxychalcones, flavanones and benzo[b]furans through palladium-catalysed reactions
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A convenient palladium-catalysed procedure for the synthesis of o-hydroxychalcones, flavanones and benzo[b]furans is described where o-iodophenyl acetate was used as a common precursor.
- De, Mahuya,Majumdar, Dyuti P.,Kundu, Nitya G.
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p. 665 - 674
(2007/10/03)
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- ONE-STEP CONVERSION OF FLAVANONES INTO ISOFLAVANONES: A NEW FACILE BIOMIMETIC SYNTHESIS OF ISOFLAVONES
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One-step chemical conversion of flavanones into isoflavones by use of thallium trinitrate (TTN) is reported, and the mechanism of a 2,3-aryl migration in this reaction is discussed in relation to in vivo rearrangement process of flavanone precursors in the isoflavone biosynthesis.
- Kinoshita, Takeshi,Ichinose, Koji,Sankawa, Ushio
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p. 7355 - 7356
(2007/10/02)
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- Stereoelectronic effects in ring closure reactions: the 2'-hydroxychalcone-flavanone equilibrium, and related systems
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The 2'-hydroxychalcone (2-HOC6H4COCH=CHC6H4X)-flavanone equilibrium in trifluoroacetic acid (TFA) has been examined.The influence of substituents X on the rate of attainment of equilibrium shows that the 6-endo-trig mode of ring closure by Michael addition is disallowed, by demonstrating a negative ρ value for the reaction rate when X is varied.Reaction therefore proceeds either on the carbonyl-protonated form, which allows twisting about the 2,3 double bond, its double bond character being reduced by resonance, or through direct rate-limiting protonation on the 2,3-double bond.Either pathway permits the allowed 6-exo-trig mode of ring closure to be followed.Alternative mechanism involving intermolecular Michael addition of trifluoroacetate, followed by intramolecular 6-exo-tet displacement are considered.Such Michael adducts can be detected in the ring closures of 2-crotonyl-4-methylphenol and 4,4-dimethyl-1-(2-hydroxyphenyl)-2-penten-1-one in TFA, but they do not appear to lie on the main pathway, because the reaction proceed with equal facility in methanesulphonic acid/chloroform medium, which does not contain a suitable nucleophile for such a mechanism.Further important mechanistic information is given by studying the reactions in TFA-d, together with measurements on the (E)-2-methyl-3-oxo-5-arylpent-4-en-2-ol and flight during the rate-limiting step, and provide evidence against the mechanism involving a preequilibrium carbonyl protonation, such as in the Nazarov rearrangement of 3'-methoxychalcones, where KH/kD is ca. 0.7.Some results are also reported for ring closure of the 2-aminochalcones in TFA.
- Brennan, Colin M.,Hunt, Ian,Jarvis, Terence C.,Johnson, C. David,McDonnell, Peter D.
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p. 1780 - 1785
(2007/10/02)
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- Cyclodehydrogenation of 2'-hydroxychalcones and dehydrogenation of flavanones using nickel peroxide
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Nickel peroxide oxidation of 2'-hydroxychalcones (1) gives flavones (3) in moderate yields, aurones (4) are also formed in cases where the 2/4 position of the starting 1 bears either a strong ?-donor or a ?-acceptor substituent.Flavanones (2) are dehydrogenated with this reagent to the corresponding flavones (3) in very good yields.
- Mallik, Uttam K.,Murari, M. Saha,Mallik, Asok K.
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p. 970 - 972
(2007/10/02)
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- Thermal Isomerization Equilibrium between 2'-Hydroxychalcones and Flavanones
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Nine substituted 2'-hydroxychalcones and the corresponding flavanones were heated separately at 230 +/- 0.2 deg C in nitrogen atmosphere.Both materials were mutually isomerized under these reaction conditions and the equilibrium constants of this isomerization were measured by means of HPLC analyses.The substituent effect on the equilibrium is discussed and thermodynamic functions (ΔG, ΔH, and ΔS) are calculated.
- Hoshino, Yukio,Takeno, Noboru
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p. 2903 - 2904
(2007/10/02)
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- Photochemical Cyclization of 2'-Hydroxychalcones
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A series of 4-substituted 2'-hydroxychalcones underwent photocyclization to give the corresponding flavones selectively, but in low quantum yields, on visible irradiation in polar aprotic solvents.Hydroxylic solvents, which disturbed the formation of a cyclic intramolecular hydrogen bond, strongly retarded the photoreaction, while neither triplet quenchers nor free radical inhibitors affected the reaction.The quantum yields were independent of the light intensity, implying a one-photon process, but strongly depended on the wavelength of irradiation.Mechanisms were proposed assuming ?, ?* excited states and Weller's postulate of a dynamic equilibrium in a proton-transfer double-minimum potential.
- Matsushima, Ryoka,Kageyama, Hiroyuki
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p. 743 - 748
(2007/10/02)
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- Synthesis and Reactions of 4-Aryloxyflavans
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4α-Aryloxyflavans unsubstituted in ring A have been synthesised by the reaction of phenols with flavan-4β-ols in the presence of boron trifluoride in ether.If reaction times are prolonged beyond disappearance of the starting 4β-ols, thermodynamic control leads to 4-arylflavans and the yields of 4-aryloxyflavans are negligible. 4-Arylflavans are the sole products when the catalyst is toluene-p-sulphonic acid.Thermal decomposition of flavan-4-yl phenol carbonate in the presence of phenols affords a synthesis of 4α-aryloxyflavans free from 4-arylflavans.Syntheses of 7-methoxy-4α-aryloxyflavans have not been successful, nor can 4-aryloxyflavan-3-ols be obtained from 3,4-diols by these methods.The 4-aryloxyflavans react rapidly with acids to yield 4-carbocations which can be trapped by a variety of nucleophiles yielding 4α-ols with water, 4α-alkoxyflavans with alcohols, 4α-arylflavans with phenols, and 4α-sulphides with thiols. 2,3-cis-Flav-3-ene epoxide reacts with phenols to give 2,3-cis-3,4-cis-4-aryloxyflavan-3-ols and with sodium salts of phenols to give 2,3-cis-3,4-trans-4-aryloxyflavan-3-ols.The 2,3-trans-epoxide similarly gives the 2,3-trans-4-aryloxyflavan-3-ols.A biflavonoid containing a 4-aryloxy link has been synthesised from the 2,3-trans-epoxide and 7-hydroxyflavan-4-one.A series of 2,3-trans-4'-methoxy-4-aryloxyflavan-3-ols has been synthesised from crude 2,3-trans-4'-methoxyflav-3-ene epoxide.The substitution of a methoxy group into position 7 of the flavonoid A-ring prevented the preparation of the epoxides, but the action of N-bromosuccinimide and sodium acetate in acetic anhydride and acetic acid on 7,4'-dimethoxyflav-3-ene gave 2,3-cis- and 2,3-trans-4-acetoxy-3-bromo-7,4'-dimethoxyflavans, the latter of which was converted by the action of sodium salts of phenols into the expected 4-aryloxyflavan-3-ols. 5,7,3',4'-Tetramethoxyflav-3-ene gave nuclear brominated products even with N-bromosuccinimide; thus, the synthesis of 5,6,3'4'-tetramethoxy-4-aryloxyflavan-3-ols has not been possible by this method.
- Bateman, Graham,Brown, Ben R.,Campbell, John B.,Cotton, Charles A.,Johnson, Philip,et al.
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p. 2903 - 2912
(2007/10/02)
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- STEREOELECTRONIC EFFECTS IN RING CLOSURE REACTIONS
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The mechanistic criterion of reversed substituent effects in reactions, formally classified as 5-endo-trig and 6-endo-trig, is examined.
- Bradley, Jeremy P.,Jarvis, Terence C.,Johnson, David C.,McDonnell, Peter D.,Weatherstone, Timothy A. P.
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p. 2851 - 2854
(2007/10/02)
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