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Acid Acceptor (acid + acceptor)
Selected AbstractsSynthesis and Biological Evaluation of Non-Hydrolyzable 1,2,3-Triazole-Linked Sialic Acid Derivatives as Neuraminidase InhibitorsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2009Michel Weïwer Abstract ,-Sialic acid azide 1 has been used as a substrate for the efficient preparation of 1,2,3-triazole derivatives of sialic acid using the copper-catalyzed azide,alkyne Huisgen cycloaddition ("click chemistry"). Our approach is to generate non-natural N-glycosides of sialic acid that are resistant to neuraminidase-catalyzed hydrolysis as opposed to the natural O-glycosides. These N-glycosides would act as neuraminidase inhibitors to prevent the release of new virions. As a preliminary study, a small library of 1,2,3-triazole-linked sialic acid derivatives has been synthesized in 71,89,% yield. A disaccharide mimic of sialic acid has also been prepared using the ,-sialic acid azide 1 and a C-8 propargyl sialic acid acceptor in 68,% yield. A model sialic acid coated dendrimer was also synthesized from a perpropargylated pentaerythritol acceptor. These novel sialic acid derivatives were then evaluated as potential neuraminidase inhibitors using a 96-well plate fluorescence assay; micromolar IC50 values wereobserved, comparable to the known sialidase inhibitorNeu5Ac2en.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Phylogenetic analysis of condensation domains in the nonribosomal peptide synthetasesFEMS MICROBIOLOGY LETTERS, Issue 1 2005Niran Roongsawang Abstract Condensation (C) domains in the nonribosomal peptide synthetases are capable of catalyzing peptide bond formation between two consecutively bound various amino acids. C-domains coincide in frequency with the number of peptide bonds in the product peptide. In this study, a phylogenetic approach was used to investigate structural diversity of bacterial C-domains. Phylogenetic trees show that the C-domains are clustered into three functional groups according to the types of substrate donor molecules. They are l -peptidyl donors, d -peptidyl donors, and N -acyl donors. The fact that C-domain structure is not subject to optical configuration of amino acid acceptor molecules supports an idea that the conversion from l to d -form of incorporating amino acid acceptor occurs during or after peptide bond formation. l -peptidyl donors and d -peptidyl donors are suggested to separate before separating the lineage of Gram-positive and Gram-negative bacteria in the evolution process. [source] Synthesis and comparative physicochemical investigation of partly aromatic cardo copolyestersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007N. B. Joshi Abstract Copolyesters were synthesized through the condensation of 0.0025 mol of 1,1,-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 0.0025 mol of ethylene glycol/propylene glycol/1,4-butanediol/1,6-hexane diol, and 0.005 mol of terephthaloyl chloride with water/chloroform (4:1 v/v) as an interphase, 0.0125 mol of sodium hydroxide as an acid acceptor, and 50 mg of cetyl trimethyl ammonium bromide as an emulsifier. The reaction time and temperature were 2 h and 0°C, respectively. The yields of the copolyesters were 81,96%. The structures of the copolyesters were supported by Fourier transform infrared and 1H-NMR spectral data and were characterized with the solution viscosity and density by a floatation method (1.1011,1.2697 g/cm3). Both the intrinsic viscosity and density of the copolyesters decreased with the nature and alkyl chain length of the diol. The copolyesters possessed fairly good hydrolytic stability against water and 10% solutions of acids, alkalis, and salts at room temperature. The copolyesters possessed moderate-to-good tensile strength (11,37.5 MPa), good-to-excellent electric strength (19,45.6 kV/mm), excellent volume resistivity (3.8 × 1015 to 2.56 × 1017 , cm), and high glass-transition temperatures (148,195°C) and were thermally stable up to about 408,427°C in a nitrogen atmosphere; they followed single-step degradation kinetics involving 38,58% weight losses and 34,59% residues. The copolyesters followed 2.6,2.9-order degradation kinetics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Temperature and pH sensitive ionic hydrogels based on new crosslinkersPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2005Ayman M. Atta Abstract New crosslinkers were synthesized from reaction of melamine with acryloyl and methacryloyl chloride in the presence of 1-methyl-2-pyrrolidone as a solvent and triethyl amine as acid acceptor. The chemical structures of the prepared crosslinkers were elucidated from FT-IR, 1H-NMR and 13C-NMR analyses. Linear 2-acrylamido-2-methyl-1-propane sulfonic acid and methacrylic acid (AMPS/MAA) copolymers were prepared and their viscometric properties in aqueous solution were investigated. Different weight percentages of the prepared crosslinkers were used as crosslinking agent (AMPS/MAA) to prepare ionic copolymers using ammonium persulfate as initiator. The percentage of crosslinkers was varied from 0.5 to 4,wt%. The swelling behaviors of crosslinked AMPS/MAA gels in deionized water were measured at different pH and temperatures. All AMPS/MAA copolymers exhibit faster deswelling rate at 50°C except for the copolymer containing 0.9 (mol ratio) AMPS. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||