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排序方式: 共有78条查询结果,搜索用时 15 毫秒
41.
Karol Al Ayed Ross D. Ballantine Michael Hoekstra Samantha J. Bann Charlotte M. J. Wesseling Alexander T. Bakker Zheng Zhong Yong-Xin Li Nora C. Brüchle Mario van der Stelt Stephen A. Cochrane Nathaniel I. Martin 《Chemical science》2022,13(12):3563
Brevicidine and laterocidine are two recently discovered lipopeptide antibiotics with promising antibacterial activity. Possessing a macrocyclic core, multiple positive charges, and a lipidated N-terminus, these lipopeptides exhibit potent and selective activity against Gram-negative pathogens, including polymyxin-resistant isolates. Given the low amounts of brevicidine and laterocidine accessible by fermentation of the producing microorganisms, synthetic routes to these lipopeptides present an attractive alternative. We here report the convenient solid-phase syntheses of both brevicidine and laterocidine and confirm their potent anti-Gram-negative activities. The synthetic routes developed also provide convenient access to novel structural analogues of both brevicidine and laterocidine that display improved hydrolytic stability while maintaining potent antibacterial activity in both in vitro assays and in vivo infection models.Convenient solid-phase approaches are described for the synthesis of brevicidine and laterocidine. Also reported are novel analogues including a laterocidine variant with enhanced hydrolytic stability and potent in vivo antibacterial activity. 相似文献
42.
Ping Zhang Tehreem Munawar Raya Soltane Mohsin Javed Guocong Liu Shahid Iqbal Muhammad Azam Qamar Ayed A. Dera Hamad Alrbyawi M. Alfakeer Sameh Rabea Eslam B. Elkaeed 《Molecules (Basel, Switzerland)》2022,27(19)
There has been a lot of interest in the manufacture of stable, high-efficiency photocatalysts. In this study, initially Cr doped ZnFe2O4 nanoparticles (NPs) were made via surfactant-assisted hydrothermal technique. Then Cr-ZnFe2O4 NPs were modified by incorporating S-g-C3N4 to enhance their photocatalytic efficiency. The morphological, structural, and bonding aspects were analyzed by XRD, FTIR, and SEM techniques. The photocatalytic efficiency of the functional Cr-ZnFe2O4/S-g-C3N4 (ZFG) heterostructure photocatalysts was examined against MB under sunlight. The produced ZFG-50 composite has the best photocatalytic performance, which is 2.4 and 3.5 times better than that of ZnFe2O4 and S-g-C3N4, respectively. Experiments revealed that the enhanced photocatalytic activity of the ZFG nanocomposite was caused by a more effective transfer and separation of photo-induced charges. The ZFG photocatalyst can use sunlight for treating polluted water, and the proposed modification of ZnFe2O4 using Cr and S-g-C3N4 is efficient, affordable, and environmentally benign. Under visible light, Gram-positive and Gram-negative bacteria were employed to ZFG-50 NCs’ antimicrobial activity. These ZFG-50 NCs also exhibit excellent antibacterial potential. 相似文献
43.
Brahim Ayed 《Comptes Rendus Chimie》2012,15(7):603-608
Single crystals of a new phosphate AgCr2(PO4)(P2O7) have been prepared by the flux method and its structural and the infrared spectrum have been investigated. This compound crystallizes in the monoclinic system with the space group C2/c and the parameters are, a = 11.493 (3) Å, b = 8.486 (3) Å, c = 8.791 (2) Å, β = 114.56 (2)°, V = 779.8 (3) Å3and Z = 4. Its structure consists of CrO6 octahedra sharing corners with P2O7 units to form undulating chains extending infinitely along the [110] direction. These chains are connected by the phosphate tetrahedra giving rise to a 3D framework with six-sided tunnels parallel to the [101] direction, where the Ag+ ions are located. The infrared spectrum of this compound was interpreted on the basis of P2O74? and PO43? vibrations. The appearance of νsP–O–P in the spectrum suggests a bent P–O–P bridge for the P2O74? ions in the compound, which is in agreement with the X-ray data. The electrical measurements allow us to obtain the activation energy of (1.36 eV) and the conductivity measurements suggest that the charge carriers through the structure are the silver captions. 相似文献
44.
A novel and efficient one-pot preparation of 6-substituted pyrido-[2,3-d]pyrimidines by cyclocondensation of 6-amino-1,3-dimethyluracil with symmetrical vinamidinium salts under basic conditions has been developed. Regioselectivity was observed with an unsymmetrical chloropropeniminium salt. 相似文献
45.
46.
The ammonium 6 salt resulting from the reaction of the DABCO and the allyl bromide 2 was converted with good yields into a new family of dimethyl 3-amino itaconates 5. 相似文献
47.
Thouraya GmizaMohamed Adnen Hadj Ayed Jamel Eddine KhiariBéchir Ben Hassine 《Tetrahedron letters》2011,52(7):764-766
Α series of substituted 3-acyl-6-aryl-2-pyridones have been prepared in one-step reactions via condensation of 3-aryl-3-chloropropeniminium salts with β-keto-amides. This efficient synthesis has the advantages of high yields and simple reaction procedures. 相似文献
48.
A highly efficient and versatile method for the synthesis of 3‐acyl‐5‐aryl or arylsulfonylpyridin‐2‐ones and 3‐alkyl‐5‐aryl‐2‐hydroxybenzamides in one step via regiospecific cyclocondensation reaction of β‐keto‐amides with vinamidinium salts is described. 相似文献
49.
Khouloud Jebri Marie-Rose Mazières Stéphanie Ballereau Taïcir Ben Ayed Jean-Christophe Plaquevent Michel Baltas Frédéric Guillen 《Tetrahedron letters》2014
Ionic liquids are solvents general enough to conduct a multi-step process in organic synthesis. We show that both the preparation of starting materials (thioacetals and enoxysilane) as well as their coupling can be realized in such medium. 相似文献
50.
Mahamed G.H. Omran Andries P. Engelbrecht Ayed Salman 《European Journal of Operational Research》2009
The barebones differential evolution (BBDE) is a new, almost parameter-free optimization algorithm that is a hybrid of the barebones particle swarm optimizer and differential evolution. Differential evolution is used to mutate, for each particle, the attractor associated with that particle, defined as a weighted average of its personal and neighborhood best positions. The performance of the proposed approach is investigated and compared with differential evolution, a Von Neumann particle swarm optimizer and a barebones particle swarm optimizer. The experiments conducted show that the BBDE provides excellent results with the added advantage of little, almost no parameter tuning. Moreover, the performance of the barebones differential evolution using the ring and Von Neumann neighborhood topologies is investigated. Finally, the application of the BBDE to the real-world problem of unsupervised image classification is investigated. Experimental results show that the proposed approach performs very well compared to other state-of-the-art clustering algorithms in all measured criteria. 相似文献