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A new method for the preparation of 3-amino-2-quinoxalinecarbonitrile ( 1 ) was studied. A successful condensation reaction between bromomalononitrile and o-phenylenediamine in the presence of Lewis acid catalyst (AlCl3) was achieved to produce compound 1 . 相似文献
14.
Yanliang Ren Bo Chi Osama Melhem Ke Wei Lingling Feng Yongjian Li Xinya Han Ding Li Ying Zhang Jian Wan Xin Xu Minghui Yang 《Journal of computational chemistry》2013,34(12):1005-1012
In the present study, the electronic energy transfer pathways in trimeric and hexameric aggregation state of cyanobacteria C‐phycocyanin (C‐PC) were investigated in term of the Förster theory. The corresponding excited states and transition dipole moments of phycocyanobilins (PCBs) located into C‐PC were examined by model chemistry in gas phase at time‐dependent density functional theory (TDDFT), configuration interaction‐singles (CIS), and Zerner's intermediate neglect of differential overlap (ZINDO) levels, respectively. Then, the long‐range pigment‐protein interactions were approximately taken into account by using polarizable continuum model (PCM) at TDDFT level to estimate the influence of protein environment on the preceding calculated physical quantities. The influence of the short‐range interaction caused by aspartate residue nearby PCBs was examined as well. Only when the protonation of PCBs and its long‐ and short‐range interactions were properly taken into account, the calculated energy transfer rates (1/K) in the framework of Förster model at TDDFT/B3LYP/6‐31+G* level were in good agreement with the experimental results of C‐PC monomer and trimer. Furthermore, the present calculated results suggested that the energy transfer pathway in C‐PC monomer is predominant from β‐155 to β‐84 (1/K = 13.4 ps), however, from α‐84 of one monomer to β‐84 (1/K = 0.3–0.4 ps) in a neighbor monomer in C‐PC trimer. In C‐PC hexamer, an additional energy flow was predicted to be from β‐155 (or α‐84) in top trimer to adjacent β‐155 (or α‐84) (1/K = 0.5–2.7 ps) in bottom trimer. © 2013 Wiley Periodicals, Inc. 相似文献
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8-Chloro-7-formyl-4-oxo-2-phenyl-4H-pyrimido[1,2-a]pyrimidine-3-carbonitrile ( 3 ) is constructed using N-(5-cyano-6-oxo-4-phenyl-1,6-dihydropyrimidin-2-yl) acetamide ( 2 ) via Vilsmeier-Haack formylation reaction. Compound 3 reacted with 3-(triethoxysilyl)propan-1-amine under different conditions. Condensation of pyrimidopyrimidine 3 with thiosemicarbazone derivative gave Schiff base 8 , which upon treating with Vilsmeier-Haack reagent afforded pyrazole carbothioamide 9 . Cyclocondensation of compound 3 with some binucleophiles namely thiocarbohyrazide, hydrazine carbodithioic acid, benzyl hydrazinecarbodithioate and/or 2-thioxopyrimidinone was investigated. Structures of the new synthesized compounds were confirmed by their analytical and spectral data. 相似文献
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Brønsted Acid Catalyzed,Conjugate Addition of β‐Dicarbonyls to In Situ Generated ortho‐Quinone Methides—Enantioselective Synthesis of 4‐Aryl‐4H‐Chromenes
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M. Sc. Osama El‐Sepelgy M. Sc. Stefan Haseloff Dr. Santosh Kumar Alamsetti Prof. Dr. Christoph Schneider 《Angewandte Chemie (International ed. in English)》2014,53(30):7923-7927
We describe herein a catalytic, enantioselective process for the synthesis of 4H‐chromenes which are important structural elements of many natural products and biologically active compounds. A sequence comprising a conjugate addition of β‐diketones to in situ generated ortho‐quinone methides followed by a cyclodehydration reaction furnished 4‐aryl‐4H‐chromenes in generally excellent yields and high optical purity. A BINOL‐based chiral phosphoric acid was employed as a Brønsted acid catalyst which converted ortho‐hydroxy benzhydryl alcohols into hydrogen‐bonded ortho‐quinone methides and effected the carbon–carbon bond‐forming event with high enantioselectivity. 相似文献
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Durgaramani Sivadasan Muhammad H. Sultan Osama Ali Madkhali Shahd Hassan Alsabei Asia Abdullah Alessa 《Molecules (Basel, Switzerland)》2022,27(3)
Numerous attempts to overcome the poor water solubility of cam ptothecin (CPT) by various nano drug delivery systems are described in various sources in the literature. However, the results of these approaches may be hampered by the incomplete separation of free CPT from the formulations, and this issue has not been investigated in detail. This study aimed to promote the solubility and continuous delivery of CPT by developing long-lasting liposomes using various weights (M.W. 2000 and 5000 Daltons) of the hydrophilic polymer polyethylene glycol (PEG). Conventional and PEGylated liposomes containing CPT were formulated via the lipid film hydration method (solvent evaporation) using a rotary flash evaporator after optimising various formulation parameters. The following physicochemical characteristics were investigated: surface morphology, particle size, encapsulation efficiency, in vitro release, and formulation stability. Different molecular weights of PEG were used to improve the encapsulation efficiency and particle size. The stealth liposomes prepared with PEG5000 were discrete in shape and with a higher encapsulation efficiency (83 ± 0.4%) and a prolonged rate of drug release (32.2% in 9 h) compared with conventional liposomes (64.8 ± 0.8% and 52.4%, respectively) and stealth liposomes containing PEG2000 (79.00 ± 0.4% and 45.3%, respectively). Furthermore, the stealth liposomes prepared with PEG5000 were highly stable at refrigeration temperature. Significant changes were observed using various pharmacokinetic parameters (mean residence time (MRT), half-life, elimination rate, volume of distribution, clearance, and area under the curve) of stealth liposomes containing PEG2000 and PEG5000 compared with conventional liposomes. The stealth liposomes prepared with PEG5000 showed promising results with a slow rate of release over a long period compared with conventional liposomes and liposomes prepared with PEG2000, with altered tissue distribution and pharmacokinetic parameters. 相似文献
18.
Osama Elsallabi Antonia Patruno Mirko Pesce Amelia Cataldi Simone Carradori Marialucia Gallorini 《Molecules (Basel, Switzerland)》2022,27(3)
Like other organs, brain functions diminish with age. Furthermore, for a variety of neurological disorders—including Alzheimer’s disease—age is one of the higher-risk factors. Since in many Western countries the average age is increasing, determining approaches for decreasing the effects of aging on brain function is taking on a new urgency. Neuroinflammation and oxidative stress are two convoluted key factors in brain aging and chronic neurodegenerative diseases. The diverseness of factors, causing an age-related decrease in brain functions, requires identifying small molecules that have multiple biological activities that can affect all these factors. One great source of these small molecules is related to polyphenolic flavonoids. Recently, 3,3′,4′,7-tetrahydroxyflavone (fisetin) has been reported as a potent senotherapeutic capable of extending lifespan by reducing peroxidation levels and enhancing antioxidant cell responses. The neuroprotective effects of fisetin have been shown in several in vitro and in vivo models of neurological disorders due to its actions on multiple pathways associated with different neurological disorders. The present work aims to collect the most recent achievements related to the antioxidant and neuroprotective effects of fisetin. Moreover, in silico pharmacokinetics, pharmacodynamics, and toxicity of fisetin are also comprehensively described along with emerging novel drug delivery strategies for the amelioration of this flavonol bioavailability and chemical stability. 相似文献
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Osama Saber Hideyuki Tagaya 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(1-2):107-115
The layered double hydroxide (LDH) well known for its abilityto intercalate anionic compounds has been prepared conventionallyonly with bivalent and trivalent cations. In this study, Zn–Ti LDH consisting of bivalent and tetravalent cations was prepared, andreacted with organic monocarboxylic, dicarboxylic and aromatic acidsat high or room temperature. XRD patterns of the prepared LDH(Zn–Ti-CO3) showed that interlayer spacing of the LDH was 0.67 nm. The value was small compared to the usual LDH (Zn–Al–CO3)of 0.76 nm in the case of carbonate anion as the guest. Also, DTA,TG and DTG analysis indicated that the electrostatic force betweenthe layers and carbonate anions increased where the carbonate anionsin Zn–Ti LDH decomposed at 255 °C while those inZn–Al–CO3 decomposed at 230–240 °C. 相似文献
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