- The involvement of xanthone and (E)-cinnamoyl chromophores for the design and synthesis of novel sunscreening agents
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Excessive UV exposure contributes to several pathological conditions like skin burns, er-ythema, premature skin aging, photodermatoses, immunosuppression, and skin carcinogenesis. Effective protection from UV radiation may be achieved with the use of sunscreens containing UV filters. Currently used UV filters are characterized by some limitations including systemic absorp-tion, endocrine disruption, skin allergy induction, and cytotoxicity. In the research centers all over the world new molecules are developed to improve the safety, photostability, solubility, and absorption profile of new derivatives. In our study, we designed and synthesized seventeen novel molecules by combining in the structures two chromophores: xanthone and (E)-cinnamoyl moiety. The ultraviolet spectroscopic properties of the tested compounds were confirmed in chloroform solutions. They acted as UVB or UVA/UVB absorbers. The most promising compound 9 (6-meth-oxy-9-oxo-9H-xanthen-2-yl)methyl (E)-3-(2,4-dimethoxyphenyl)acrylate) absorbed UV radiation in the range 290–369 nm. Its photoprotective activity and functional photostability were further evaluated after wet milling and incorporation in the cream base. This tested formulation with compound 9 possessed very beneficial UV protection parameters (SPFin vitro of 19.69 ± 0.46 and UVA PF of 12.64 ± 0.32) which were similar as broad-spectrum UV filter tris-biphenyl triazine. Additionally, compound 9 was characterized by high values of critical wavelength (381 nm) and UVA/UVB ratio (0.830) thus it was a good candidate for broad-spectrum UV filter and it might protect skin against UVA-induced photoaging. Compound 9 were also shown to be photostable, non-cytotoxic at con-centrations up to 50 μM when tested on five cell lines, and non-mutagenic in Ames test. It also possessed no estrogenic activity, according to the results of MCF-7 breast cancer model. Addition-ally, its favorable lipophilicity (miLogP = 5.62) does not predispose it to penetrate across the skin after topical application.
- Popió?, Justyna,Gunia-Krzy?ak, Agnieszka,S?oczyńska, Karolina,Koczurkiewicz-Adamczyk, Paulina,Piska, Kamil,Wójcik-Pszczo?a, Katarzyna,?elaszczyk, Dorota,Krupa, Anna,?mudzki, Pawe?,Marona, Henryk,P?kala, El?bieta
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- New 3-O-substituted xanthone derivatives as promising acetylcholinesterase inhibitors
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A new series of 3-O-substituted xanthone derivatives were synthesised and evaluated for their anti-cholinergic activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The results indicated that the xanthone derivatives possessed good AChE inhibitory activity with eleven of them (5, 8, 11, 17, 19, 21-23, 26-28) exhibited significant effects with the IC50 values ranged 0.88 to 1.28 μM. The AChE enzyme kinetic study of 3-(4-phenylbutoxy)-9H-xanthen-9-one (23) and ethyl 2-((9-oxo-9H-xanthen-3-yl)oxy)acetate (28) showed a mixed inhibition mechanism. Molecular docking study showed that 23 binds to the active site of AChE and interacts via extensive π–π stacking with the indole and phenol side chains of Trp86 and Tyr337, besides the hydrogen bonding with the hydration site and π–π interaction with the phenol side chain of Y72. This study revealed that 3-O-alkoxyl substituted xanthone derivatives are potential lead structures, especially 23 and 28 which can be further developed into potent AChE inhibitors.
- Loh, Zi Han,Kwong, Huey Chong,Lam, Kok Wai,Teh, Soek Sin,Ee, Gwendoline Cheng Lian,Quah, Ching Kheng,Ho, Anthony Siong Hock,Mah, Siau Hui
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p. 627 - 639
(2021/02/16)
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- Mild C?F Activation in Perfluorinated Arenes through Photosensitized Insertion of Isonitriles at 350 nm
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Fluorinated compounds have become important in the fields of agrochemical industry, pharmaceutical chemistry and materials sciences. Accordingly, various methods for their preparation have been developed in the past. Fluorinated compounds can be accessed via conjugation with fluorinated building blocks, via C?H fluorination or via selective activation of perfluorinated compounds to give the partially fluorinated congeners. Especially the direct activation of C?F bonds, one of the strongest σ-bonds, still remains challenging and new strategies for C?F activation are desirable. Herein a method for the photochemical activation of aromatic C?F bonds is presented. It is shown that isonitriles selectively insert into aromatic C?F bonds while aliphatic C?F bonds remain unaffected. Mechanistic studies reveal the reaction to proceed via the indirect excitation of the isonitrile to its triplet state by photoexcited acetophenone at 350 nm. Due to the relatively mild light used, the process shows high functional group tolerance and various compounds of the class of benzimidoyl fluorides are accessible from aryl isonitriles and commercially available perfluorinated arenes. (Figure presented.).
- Weidlich, Frauke,Esumi, Naoto,Chen, Dongyang,Mück-Lichtenfeld, Christian,Zysman-Colman, Eli,Studer, Armido
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supporting information
p. 376 - 383
(2019/11/19)
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- A Green Nanopalladium-Supported Catalyst for the Microwave-Assisted Direct Synthesis of Xanthones
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We report an efficient, selective, rapid and eco-friendly protocol for the one-step synthesis of a small xanthone library via an intermolecular catalytic coupling from readily available salicylaldehydes and 1,2-dihaloarenes under ligand-free conditions. To achieve this advantageous direct annulation, we used a novel recoverable palladium nanocatalyst supported on a green biochar under microwave irradiation. Unlike other existing palladium-based approaches, our synthetic strategy showed a greater operational simplicity, drastic reduction in reaction times, and an excellent tolerance to diverse functional groups. The reaction proceeds in very good yields and with high regioselectivity. The novel heterogeneous catalyst can be recycled and reused up to four times without significant loss of activity.
- Diez, Alejandra S.,Gerbino, Darío C.,Mendioroz, Pamela,Steingruber, H. Sebastián
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supporting information
p. 619 - 628
(2020/02/13)
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- Design, synthesis and cardiovascular evaluation of some aminoisopropanoloxy derivatives of xanthone
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A series of aminoisopropanoloxy derivatives of xanthone has been synthesized and their pharmacological properties regarding the cardiovascular system has been evaluated. Radioligand binding and functional studies in isolated organs revealed that title compounds present high affinity and antagonistic potency for α1-(compound 2 and 8), β-(compounds 1, 3, 4, 7), α1/β-(compounds 5 and 6) adrenoceptors. Furthermore, compound 7, the structural analogue of verapamil, possesses calcium entry blocking activity. The title compounds showed hypotensive and antiarrhythmic properties due to their adrenoceptor blocking effect. Moreover, they did not affect QRS and QT intervals, and they did not have proarrhythmic potential at tested doses. In addition they exerted anti-aggregation effect. The results of this study suggest that new compounds with multidirectional activity in cardiovascular system might be found in the group of xanthone derivatives.
- Kubacka,Szkaradek,Mogilski,Pańczyk,Siwek,Grybo?,Filipek,?mudzki,Marona,Waszkielewicz
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p. 3773 - 3784
(2018/05/04)
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- Synthesis and molecular docking studies of xanthone attached amino acids as potential antimicrobial and anti-inflammatory agents
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A series of novel xanthone conjugated amino acids were synthesised and characterised by analytical and spectroscopic methods. All the synthesized analogues (2-23) were screened for their in vitro antimicrobial and anti-inflammatory activities. Compounds 7, 8, 9, 12, 18, 19, 20, 21 and 23 showed excellent antimicrobial activities compared to antibacterial and antifungal reference drugs gentamicin and bavistin, respectively. Compounds 7-12 and 18-23 showed good anti-inflammatory activity compared to a standard drug, indomethacin. The preliminary structure-activity relationship revealed that tryptophan, tyrosine, phenylalanine, proline and cysteine conjugated compounds showed excellent antimicrobial and anti-inflammatory activities. This may be explained by the contribution of aromaticity and hydrophobicity of amino acids. Molecular docking studies were performed for all the synthesised compounds, among which compounds 20, 21 and 23 showed the highest docking scores for antimicrobial activity while compounds 9, 20 and 22 showed the highest docking scores for anti-inflammatory activity. Different amino acids conjugated xanthone derivatives were synthesized and evaluated for their in vitro biological activities. The conjugation was found to play a major role in improving the biological activities of those compounds.
- Chen, Xing,Leng, Jing,Rakesh,Darshini,Shubhavathi,Vivek,Mallesha,Qin, Hua-Li
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p. 1706 - 1719
(2017/08/22)
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- Design, synthesis, and anticonvulsant activity of some derivatives of xanthone with aminoalkanol moieties
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A series of new xanthone derivatives have been synthesized and evaluated for their anticonvulsant properties in the maximal electroshock, subcutaneous metrazole tests and for neurotoxicity in the rotarod in mice, i.p. and rats, p.o. Compound 9: R,S-2-{2-[(1-hydroxybutan-2-yl]amino)ethoxy}-9H-xanthen-9-one and compound 12: R,S-2-{3-[(1-hydroxybutan-2-yl)amino]propoxy}-9H-xanthen-9-one exerted activity in rats, p.o. 2 and 4?h after administration, respectively. Therefore, metabolic stability of the compounds was evaluated with use of rat microsomes, resulting in half-life t1/2 136 and 108?min, respectively, indicating that either the metabolites are very active or the parent compounds exert ADME properties other than metabolism which influence the late onset of activity.
- Waszkielewicz, Anna M.,S?oczyńska, Karolina,P?kala, El?bieta,?mudzki, Pawe?,Siwek, Agata,Grybo?, Anna,Marona, Henryk
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p. 339 - 352
(2017/04/03)
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- Synthesis of xanthone derivatives and studies on the inhibition against cancer cells growth and synergistic combinations of them
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34 Xanthones were synthesized by microwave assisted technique. Their in?vitro inhibition activities against five cell lines growth were evaluated. The SAR has been thoroughly discussed. 7-Bromo-1,3-dihydroxy-9H-xanthen-9-one (3-1) was confirmed as the most active agent against MDA-MB-231?cell line growth with an IC50 of 0.46?±?0.03?μM. Combination of 3-1 and 5,6-dimethylxanthone-4-acetic acid (DMXAA) showed the best synergistic effect. Apoptosis analysis indicated different contributions of early/late apoptosis and necrosis to cell death for both monomers and the combination. Western Blot implied that the combination regulated p53/MDM2 to a better healthy state. Furthermore, 3-1 and DMXAA arrested more cells on G2/M phase; while the combination arrested more cells on S phase. All the evidences support that the 3-1/DMXAA combination is a better anti-cancer therapy.
- Liu, Jie,Zhang, Jianrun,Wang, Huailing,Liu, Zhijun,Zhang, Cao,Jiang, Zhenlei,Chen, Heru
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- Cardiovascular activity of the chiral xanthone derivatives
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A series of 6 derivatives of xanthone were synthesized and evaluated for cardiovascular activity. The following pharmacological experiments were conducted: the binding affinity for adrenoceptors, the influence on the normal electrocardiogram, the effect on the arterial blood pressure, the effect on blood pressor response and prophylactic antiarrhythmic activity in adrenaline induced model of arrhythmia (rats, iv). Two compounds revealed nanomolar affinity for α1-adrenoceptor which was correlated with the strongest cardiovascular (antiarrhythmic and hypotensive) activity in animals' models. They were enantiomers of previously described (R,S)-4-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazin-1-yl)propoxy)-9H-xanthen-9-one hydrochloride and revealed similar antiarrhythmic potential in adrenaline induced model of arrhythmia in rats after intravenous injection (ED50 = 0.53 mg/kg and 0.81 mg/kg, respectively). These values were lower than values obtained for reference drug urapidil. These compounds were more active in this experiment than urapidil (ED50 = 1.26 mg/kg). The compound 5 administered iv at doses of 0.62-2.5 mg/kg at the peak of arrhythmia prevented and/or reduced the number of premature ventricular beats in a statistically significant manner. The ED50 value was 1.20 mg/kg. The S-enantiomer (6) given at the same doses did not show therapeutic antiarrhythmic activity in this model. These compounds significantly decreased the systolic and diastolic blood pressure throughout the whole observation period in anesthetized, normotensive rats. The studied enantiomers showed higher toxicity than urapidil, but imperceptibly higher that another cardiovascular drugs, that is, carvedilol or propranolol. They were also evaluated for mutagenic potential in the Ames (Salmonella) test. It was found that at the concentrations tested the compounds were non mutagenic when compared to solvent control. Results were quite promising and suggested that in the group of xanthone derivatives new potential antiarrhythmics and hypotensives might be found.
- Szkaradek, Natalia,Rapacz, Anna,Pytka, Karolina,Filipek, Barbara,Zelaszczyk, Dorota,Szafrański, Przemys?aw,S?oczyńska, Karolina,Marona, Henryk
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p. 6714 - 6724
(2015/10/19)
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- Microwave-assisted synthesis of xanthones promoted by ytterbium triflate
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Xanthones represent a class of naturally occurring compounds with valuable and promising reported pharmacological activities. One of the main disadvantages in the use of such products is related to the difficulties in their chemical synthesis. In this Letter a new and improved method for the chemical synthesis of xanthones is described. The title compounds have been synthesized in good yields under microwave irradiation from substituted 2-hydroxybenzoic acids and phenols in the presence of Yb(OTf)3 hydrate as the catalyst.
- Genovese, Salvatore,Fiorito, Serena,Specchiulli, Maria Carmela,Taddeo, Vito Alessandro,Epifano, Francesco
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supporting information
p. 847 - 850
(2015/01/30)
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- One-step synthesis of xanthones catalyzed by a highly efficient copper-based magnetically recoverable nanocatalyst
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A versatile and highly efficient strategy to construct a xanthone skeleton via a ligand-free intermolecular catalytic coupling of 2-substituted benzaldehydes and a wide range of phenols has been developed. For this purpose, a novel and magnetically recoverable catalyst consisting of copper nanoparticles on nanosized silica coated maghemite is presented. The reaction proceeds smoothly with easy recovery and reuse of the catalyst. The methodology is compatible with various functional groups and provides an attractive protocol for the generation of a small library of xanthones in very good yield.
- Menendez, Cintia A.,Nador, Fabiana,Radivoy, Gabriel,Gerbino, Dario C.
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supporting information
p. 2846 - 2849
(2014/06/23)
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- New chiral derivatives of xanthones: Synthesis and investigation of enantioselectivity as inhibitors of growth of human tumor cell lines
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A highly efficient and practical methodology for synthesis of new chiral derivatives of xanthones (CDXs) in enantiomerically pure form has been developed According to this approach, thirty CDXs (3-32) were synthesized by coupling a carboxyxanthone (1) and a carboxymethoxyxanthone (2) with both enantiomers of commercially available chiral building blocks, namely six amino alcohols, one amine and one amino ester The activation of the carboxylic acid group of the xanthonic scaffold was carried out with the coupling reagent O-(benzotriazol-1-yl)-N-N-N′-N′-tetramethyluronium tetrafluoroborate (TBTU), in the presence of a catalytic amount of TEA in anhydrous THF The coupling reactions with the chiral blocks were performed at room temperature with short reactions times, excellent yields (ranging from 94% to 99%), and very high enantiomeric excess The synthesized CDXs were evaluated for their effect on the in vitro growth of three human tumor cell lines, namely A375-C5 (melanoma), MCF-7 (breast adenocarcinoma), and NCI-H460 (non-small cell lung cancer) The most active compound was CDX 15 being active in all human tumor cell lines with values of GI50 of 32.15 ± 2.03 μM for A375-C5, 22.55 ± 1.99 μM for MCF-7, and 14.05 ± 1.82 μM for NCI-H460 Nevertheless, some CDXs showed cell-type selectivity Furthermore, the growth inhibitory effects, in some cases, demonstrated to be depending on the stereochemistry of the CDXs An interesting example was observed with the enantiomers 3 and 4, which demonstrated high enantioselectivity for MCF-7 and NCI-H460 cell lines It can be inferred that the effects on the growth of the human tumor cell lines can be ascribed not only to the nature and positions of substituents on the xanthonic scaffold but also to the stereochemistry of the CDXs Some considerations regarding structure-activity relationship within this class of compounds will be highlighted
- Fernandes, Carla,Masawang, Kamonporn,Tiritan, Maria Elizabeth,Sousa, Emília,De Lima, Virgínia,Afonso, Carlos,Bousbaa, Hassan,Sudprasert, Wanwisa,Pedro, Madalena,Pinto, Madalena M.
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p. 1049 - 1062
(2014/02/14)
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- Nanoporous metal oxides with tunable and nanocrystalline frameworks via conversion of metal-organic frameworks
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Nanoporous metal oxide materials are ubiquitous in the material sciences because of their numerous potential applications in various areas, including adsorption, catalysis, energy conversion and storage, optoelectronics, and drug delivery. While synthetic
- Kim, Tae Kyung,Lee, Kyung Joo,Cheon, Jae Yeong,Lee, Jae Hwa,Joo, Sang Hoon,Moon, Hoi Ri
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supporting information
p. 8940 - 8946
(2013/07/26)
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- Synthesis and evaluation of novel aza-caged Garcinia xanthones
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Inspired by the therapeutic potential of the simplified caged xanthones, we have developed a chemical strategy for synthesizing novel aza-caged Garcinia analogues through a regioselective Claisen/Diels-Alder cascade reaction. The origin of regioselectivity has been explained using the DFT method. We have further evaluated the cell proliferation and IKKβ inhibitory activities of these compounds and studied their binding mode with IKKβ by molecular docking. The results suggested that the aza-caged scaffold provides a suitable modification site and the introduction of a hydrophobic moiety leads to improvement in the cytotoxicity and IKKβ inhibitory activity. The aza-caged compound 6c exhibited an IC50 value of 2.68, 2.10, 8.02 μM against the HepG2, A549 cells and IKKβ, respectively. Mechanism studies with 6c showed that the aza-caged compounds induce apoptosis and cell cycle S phase arrest in A549 cells.
- Zhang, Xiaojin,Li, Xiang,Sun, Haopeng,Jiang, Zhengyu,Tao, Lei,Gao, Yuan,Guo, Qinglong,You, Qidong
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experimental part
p. 3288 - 3299
(2012/06/04)
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- Microwave-assisted efficient and green synthesis of hydroxyxanthone in water
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An efficient and green procedure has been developed for the synthesis of hydroxyxanthones from substituted 2,2-dihydroxybenzophenone precursors via microwave-assisted base-catalyzed cyclization in water. This method provides excellent yields of products in a short time, making it a useful strategy for the synthesis of structurally diverse hydroxyxanthones.
- Zhang, Xiao-Jin,Ye, Suo-Fu,Zhang, Yu,Meng, Hu-Yan,Zhang, Ming-Qian,Gao, Wen-Lei,You, Qi-Dong
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experimental part
p. 2952 - 2958
(2012/08/13)
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- Synthesis, SAR and biological evaluation of natural and non-natural hydroxylated and prenylated xanthones as antitumor agents
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In order to explore the detailed structure-activity relationship (SAR) around xanthone scaffold bearing hydroxyl and prenyl moieties, twenty-nine natural and non-natural hydroxylated and prenylated xanthones have been synthesized and evaluated for their in vitro anti-proliferative activities against five human cancer cell lines, including HepG2 (hepatocelluar carcinoma), HCT-116 (colon carcinoma), A549 (lung carcinoma), BGC823 (gastric carcinoma) and MDAMB- 231 (breast carcinoma). The SAR analysis revealed that the anti-proliferative activity of the xanthones is substantially influenced by the position and number of attached hydroxyl and prenyl groups, and the presence of hydroxyl group ortho to the carbonyl function of xanthone scaffold contributes significantly to their cytotoxicity. The new prenylated xanthone 20 with a relatively simple structure, namely 1,3,8-trihydroxy-2-prenylxanthone, was found to exhibit potent antitumor activities comparable to mangostin against all the five cancer cell lines. Further mechanistic studies suggested that compound 20 induces apoptosis and causes cell cycle arrest at S phase in HepG2 cells. These results have highlighted compound 20 as a new potential lead candidate for future development of novel potent broad-spectrum antitumor agents.
- Zhang, Xiaojin,Li, Xiang,Tao, Lei,Gao, Yuan,Gong, Dandan,Xi, Meiyang,Xu, Xiaoli,Guo, Qinglong,You, Qidong,Ye, Suofu,Zhang, Yu,Meng, Huyan,Zhang, Mingqian,Gao, Wenlei
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p. 1012 - 1025,14
(2012/12/12)
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- Anti-AIDS agents 89. Identification of DCX derivatives as anti-HIV and chemosensitizing dual function agents to overcome P-gp-mediated drug resistance for AIDS therapy
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In this study, 19 dicamphanoyl-dihydropyranochromone (DCP) and dicamphanoyl-dihydropyranoxanthone (DCX) derivatives, previously discovered as novel anti-HIV agents, were evaluated for their potential to reverse multi-drug resistance (MDR) in a cancer cell line over-expressing P-glycoprotein (P-gp). Seven compounds fully reversed resistance to vincristine (VCR) at 4 μM, a 20-fold enhancement compared to the first generation chemosensitizer, verapamil (4 μM). The mechanism of action of DCPs and DCXs was also resolved, since the most active compounds (3, 4, and 7) significantly increased intracellular drug accumulation due, in part, to inhibiting the P-gp mediated drug efflux from cells. We conclude that DCPs (3 and 4) and DCXs (7, 11, and 17) can exhibit polypharmacologic behavior by acting as dual inhibitors of HIV replication and chemoresistance mediated by P-gp. As such, they may be useful in combination therapy to overcome P-gp-associated drug resistance for AIDS treatment.
- Zhou, Ting,Ohkoshi, Emika,Shi, Qian,Bastow, Kenneth F.,Lee, Kuo-Hsiung
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scheme or table
p. 3219 - 3222
(2012/06/18)
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- Antioxidant xanthone derivatives induce cell cycle arrest and apoptosis and enhance cell death induced by cisplatin in NTUB1 cells associated with ROS
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In an effort to develop novel antioxidant as anticancer agents, a series of xanthones were prepared. In vitro screening, the synthetic xanthones revealed significant inhibitory effects on xanthine oxidase and ABTS radical-cation scavenging activity. The selective compounds 2 and 8 induced an accumulation of NTUB1 cells in the G1 phase arrest and cellular apoptosis by the increase of ROS level. The combination of cisplatin and 2 significantly enhanced the cell death in NTUB1 cells. Compounds 2 and 8 did not show cytotoxic activity in selected concentrations against SV-HUC1 cells. The present results suggested that antioxidants 2 and 8 may be used as anticancer agent for enhancing the therapeutic efficacy of anticancer agents and to reduce their side effect.
- Cheng, Jen-Hao,Huang, A-Mei,Hour, Tzyh-Chyuan,Yang, Shyh-Chyun,Pu, Yeong-Shiau,Lin, Chun-Nan
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p. 1222 - 1231
(2011/04/22)
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- Compounds for the treatment of hepatoma
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Compounds of general Formula I in which the substituents of R1 -R7 are hydrogen, hydroxy group, C1-6 alkyl group, C1-6 alkoxy group, or epoxypropoxy, but at the most, six of the substituents can simultaneously be hydrogen, methoxy group, or hydroxy group, or epoxypropoxy group for activity against hepatoma. There are also described processes for the preparation of the novel compounds and useful intermediates. Substitute benzophenones are described.
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- Synthesis and pharmacological activity of a series of novel xanthone derivatives
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A compound, and salts thereof, represented by either formula I or formula II below: (1) Formula I: STR1 wherein substituents R1 -R7 can be, independently, hydrogen, hydroxy group, C1-6 alkyl(oxy) group, acetyl ester, or C1-12 alkyl propanolamine; at least three but no more than four of the substituents are alkyl(oxy) group, hydroxyl group or acetyl ester; no more than one of the substituents can be C1-12 alkyl propanolamines; R1, R3, R7 cnnnot all be hydroxy groups at the same time; and R6 is either an hydroxy group or an oxygen-containing glucose. (2) Formula II: STR2 wherein substituents R1 -R9 can be, indenpendently, hydrogen, hydroxy group and C1-6 alkyl(oxy) group; and no more then four of the substituents can be methoxy group, hydroxy group, or acetyl ester. These compounds were tested to be capable of inhibiting platelet aggregation, atrioventricular conduction, and calcium influx in myocardiac cells.
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- Preparation and applications of xanthenylamide (XAL) handles for solid-phase synthesis of C-terminal peptide amides under particularly mild conditions
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[[9-[(9-Fluorenylmethyloxycarbonyl)amino]xanthen-2(or 3)-yl]oxy]alkanoic acid (XAL) handles have been prepared by efficient four-step routes from 2- or 3-hydroxyxanthone and coupled onto a range of amino-functionalized supports. The resultant XAL supports are the starting points for solid-phase peptide synthesis by Fmoc chemistry. Upon completion of chain assembly, C-terminal peptide amides are released in excellent yields and purities by use of low concentrations [1-5% (v/v)] of trifluoroacetic acid (TFA) in dichloromethane, often without a need for added carbocation scavengers. These cleavage conditions allow retention of all or a significant portion of tert-butyl type and related side-chain protecting groups, which subsequently may be removed fully in a solution process carried out at higher acid concentration. XAL supports are particularly useful for the synthesis of acid-sensitive peptides, including tryptophan-containing sequences that are known to be susceptible to yield- and/or purity-reducing alkylation side reactions. The effectiveness of this chemistry was shown with the syntheses of prothrombin (1-9), acyl carrier protein (65-74), Tabanus atratus adipokinetic hormone, fragments of the protein RHK 1, CCK-8 sulfate, and oxytocin. Furthermore, the application of XAL supports for the preparation of fully protected peptide amides has been demonstrated.
- Han,Bontems,Hegyes,Munson,Minor,Kates,Albericio,Barany
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p. 6326 - 6339
(2007/10/03)
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- Design, Synthesis and Potential Use of 3,9-Substituted Xanthene Handles for Solid Phase Peptide Synthesis
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Theoretical calculations on different xanthene derivatives and related structures were performed and as a result conclusions could be drawn for the acid-lability of substituted xanthenes. (9-Hydroxyxanthene-3-oxy)acetic- and valeric acid (6a and 6b) were selected, synthesized in a six-step route, and 6b was tested for its applicability as a handle for solid phase synthesis of peptides.
- Somlai, Csaba,Nyerges, Levente,Penke, Botond,Hegyes, Peter,Voelter, Wolfgang
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p. 429 - 433
(2007/10/02)
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- γ-Pyrone compounds. IV: Synthesis and antiplatelet effects of mono- and dioxygenated xanthones and xanthonoxypropanolamine
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Xanthodilol, mono- and dioxygenated xanthones, and 1,3-, 2,3-, 3,4-, 3,5- , 1,6-, 2,6-, and 3,6-dioxygenated xanthones were synthesized from benzophenone precursors by Friedel-Crafts acylation and subsequent base- catalyzed cyclization to eliminate methanol. 3-Hydroxyxanthone, xanthodilol, 2,3-dihydroxyxanthone diacetate, and 3,4-dihydroxyxanthone and its diacetate showed potent antiplatelet effects on arachidonate- and collagen-induced aggregation. 3,5-Dihydroxyxanthone and its diacetate, 1,6-dimethoxyxanthone, and 3,6-dihydroxyxanthone and its diacetate showed potent antiplatelet effects on arachidonate-induced aggregation.
- Lin,Liou,Ko,Teng
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- Aromatic Nitro-group Displacement Reactions. Part 3. Minor Products of the o-Cyanophenol Synthesis
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In dipolar aprotic solvents, the action of cyanide ions on a moderately activated aromatic or heteroaromatic nitro-compound yields, in addition to the o-cyanophenol, a range of products generated through nitro-group reduction.
- Gorvin, John H.
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p. 738 - 762
(2007/10/02)
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- Acylation of Phenols with Salicylic Acid Using Polyphosphoric Acid
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Acylation of 2-naphthol (2), 1-naphthol (6) and resorcinol (11) with salicylic acid (1) in the presence of PPA affords salicylate esters (4, 7, 13 and 14), 1,2-benzoxanthone (5), 3,4-benzoxanthone (8), 3-hydroxyxanthone (12), 2-salicoyl-1-naphthol (9) and 11-hydroxy-12H-benzoxanthen-12-one (10).Compounds (4, 5, 7, 8, 12, 13 and 14) are identical with those obtained by heating a mixture of phenyl salicylate (3) and phenols (2, 6 and 11).
- Kamat, S. P.,Paknikar, S. K.
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p. 773 - 774
(2007/10/02)
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- Cycloadditions of substituted benzopyran-4-ones to electron-rich dienes: a new route to xanthone derivatives
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The benzopyranones 1 and 3 reacted with 2,3-dimethyl-1,3-butadiene in the presence of titanium (IV) chloride to give the corresponding (4 + 2) cycloadducts 8 and 11, the former undergoing facile deformylation to give 9 and 10. Compounds 1, 3, and 4 underwent efficient uncatalysed cycloaddition to 1- methoxy-3-(trimethylsilyloxy)-l,3-butadiene 12 to give the respective adducts 13,14, and 18 as mixtures of C-l stereoisomers. Heating the 3-arylsulphinylchromone 5 with the diene 12 afforded 3-hydroxyxanthone 23 in 50% yield, the presumed cycloaddition - elimination sequence constituting a new route to xanthone systems. Desilylation of 13,14, and 18 in acidic media provided 25,26, and 27 respectively.
- Cremins, Peter J.,Saengchantara, Suthiweth T.,Wallace, Timothy W.
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p. 3075 - 3082
(2007/10/02)
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- Thermal Conversion of Salol into Xanthone: A Mechanistic Study
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The thermal conversion of salol (1) into xanthone has been rationalized as proceeding via the keto-ketene intermediate (7) which is trapped by phenols (9, 12 and 15).
- Kamat, S. P.,Paknikar, S. K.
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- Studies in Synthesis of Xanthone Derivatives: Part III+ - A New One-step Synthesis of Xanthones
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Ethyl salicylate condenses with different phenols in refluxing diphenyl ether to give various xanthones in good yields.In the case of resorcinol, hydroquinone, catechol and 3,4-xylenol corresponding phenyl salicylate derivatives are also obtained.Condensation with hydroxycoumarins affords pyranoxanthones, which can not be prepared by the Pechmann condensation of hydroxyxanthones.The structures of the intermediates and final products are established by spectral data (IR, PMR and 13C NMR).
- Patolia, Ravji J.,Trivedi, K. N.
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p. 444 - 447
(2007/10/02)
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