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941.
A. M. O. Abdul Raheem E. U. Adah 《International journal of environmental analytical chemistry》2013,93(13):1340-1352
ABSTRACTThe polluting effects of Iponri-Alaka Canal in Surulere area of Lagos State on the environment have been studied using six sampling points. The study aimed at assessing the effects of exposure to pollutants on humans and other life forms. The quality of air, wastewater and sediments was assessed between March and August 2017. The concentrations of SO2 and H2S were measured using MSA Altair 5X. Temperature, pH and DO were measured in-situ using Thermometer, pH meter and Winkler method, respectively. TSS, TDS, TS, TA, TH, BOD, chloride Cl?, PO43-, SO42- and NO3? were determined using appropriate standard methods in the laboratory. EC and some heavy metals (Cr, Pb, Mn, Cd and Ni) concentrations were determined using conductivity meter and Atomic Absorption Spectroscopy, respectively. The results showed that pH, TS, DO and TH were well within the WHO and FEPA maximum limits. EC, SO42- and TDS were observed to be higher than guideline values only at one sampling point. The TSS, BOD, TA, NO3? and PO43- were higher than WHO and FEPA guideline limits at all sampling points. Cr was seen to be within, while Pb and Mn were higher than WHO and FEPA guideline values. Cd was higher than guideline values only at two sampling points. Ni was below detection concentration at all the sampling points.The concentration of SO2 was seen to be higher than WHO and NESREA guideline values at two sampling points, while H2S concentration was higher than WHO limit at all the six sampling points. 相似文献
942.
《Journal of carbohydrate chemistry》2013,32(8-9):443-452
Abstract An efficient synthesis of the protected branched trisaccharide (2′S,3′S)‐(7‐O‐benzyl‐6‐O‐chloroacetyl‐3,4‐O‐(2′,3′‐dimethoxybutane‐2′,3′‐diyl)‐2‐O‐p‐methoxybenzyl‐L‐glycero‐α‐D‐manno‐heptopyranosyl)‐(1 → 3)‐[(2,3,4,6‐tetra‐O‐benzoyl‐β‐D‐glucopyranosyl)‐(1 → 4)]‐7‐O‐acetyl‐1,6‐anhydro‐2‐O‐benzyl‐L‐glycero‐β‐D‐manno‐heptopyranose, which is a key intermediate in the synthesis of inner core structures of Haemophilus and Neisseria LPSs, is described. The heptoses were formed by Grignard reactions using a benzyloxymethyl chloride or a commercial vinyl reagent. The anhydro bridge was formed by treatment of a 6‐OH methyl α‐heptoside precursor with FeCl3. The protecting group pattern allows modifications at the 2‐, 3‐, 4‐, and 6‐positions of the second heptose moiety and also, after acetolysis of the anhydro bridge, elongation at the reducing end, all known alterations found in the bacterial LPSs. 相似文献
943.
Shaogan Niu Lifen Zhang Jian Zhu Wei Zhang Zhenping Cheng Xiulin Zhu 《Journal of polymer science. Part A, Polymer chemistry》2013,51(5):1197-1204
Well‐defined polyacrylonitrile (PAN) of high viscosity‐average molecular weight (Mη = 405,100 g/mol) was successfully synthesized using reversible addition‐fragmentation chain transfer polymerization. The polymerization exhibits controlled characters: molecular weights of the resultant PANs increasing approximately linearly with monomer conversion and keeping narrow molecular weight distributions. The addition of 0.01 equiv (relative to monomer acrylonitrile) of Lewis acid AlCl3 in the polymerization system afforded the obtained PAN with an improved isotacticity (by 8%). In addition, the influence of molecular weights and molecular weight distributions of PANs on the morphology of the electrospun fibers was investigated. The results showed that, under the same conditions of electrospinning, average diameter (247–1094 nm) of fibers increased with molecular weights of PANs, and it was much easier to get “uniform” diameter fibers while using PANs with narrow molecular weight distributions as the precursor of electrospinning. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
944.
945.
Jian‐Nan Xiang Li‐Hui Jiang Chao‐Yue Chen Zhi‐ying Fu Jun‐Fei Duan Xiao‐Xiao He 《Journal of carbohydrate chemistry》2013,32(7):595-614
New retinoyl sugar derivatives of 13‐cis‐retinoic acid were synthesized in three ways in this paper in order to enhance pharmacal effects, especially antiproliferative activities of 13‐cis‐retinoic acid. Their structures were confirmed by IR, 1H‐NMR, 13C‐NMR, and MS spectra and their antiproliferative activities were determined in vitro using human cancer lines. Results showed that some compounds possessed potential antitumor activities. 相似文献
946.
《Journal of carbohydrate chemistry》2013,32(5):305-311
Abstract Synthesis of 4‐aryl‐5‐phenylimino‐3‐(tetra‐O‐benzoyl‐β‐D‐glucopyranosylimino)‐1,2,4‐dithiazolidines (hydrochlorides) is described. These compounds were screened for their antibacterial and antifungal activity against Escherichia coli, Staphylococcus aureus, P. vulgaris, Pseudomonas, Bacillus, Salomonella sp., Aspergilus niger, and Fusarium. The identities of these new N‐glucosides have been established on the basis of usual chemical transformation IR, NMR, and mass spectral studies. 相似文献
947.
Highly α‐selective sialylation of sialic acid N‐phenyltrifluoroacetimidate with various galactose and lactose acceptors has been achieved by introducing the C‐5 N‐phthalyl group on the donor. The “fixed dipole effect” of the N‐phthalyl group was proposed to explain the high reactivity and α‐selectivity. The microfluidic system was applied to the present α‐sialylation, which is amenable to large‐scale synthesis. The N‐phthalyl group was removed by treatment with methylhydrazine acetate, for which protocol can be readily applied to the synthesis of a variety of sialic acid‐containing oligosaccharides. 相似文献
948.
《Journal of carbohydrate chemistry》2013,32(7-8):593-601
The crystal structure of methyl α‐d‐mannofuranoside was determined by X‐ray crystallography. The C‐1–C‐2, C‐2–C‐3, C‐3–C‐4, C‐4–O and O‐4–C‐1 distances within the furanoside ring are 1.513(2), 1.523(2), 1.516(2), 1.445(2) and 1.422(2) Å, respectively. The hydrogen bonding consists of O–H–O interactions which include the anomeric oxygen but exclude the ring oxygen atom. The two hydroxyls OH‐6 and OH‐2 are H‐bond acceptors and donors with H···O distances of 1.92–1.93 Å, whereas the OH‐3 and OH‐5 are only H‐bond donor [H···O distance of 2.04(2) Å]. Additionally, OH‐6 participates in a weak hydrogen bond to the anomeric oxygen [H···O distance of 2.19(3) Å]. The crystalline methyl α‐d‐mannofuranoside adopts an 3 E ring conformation. The analysis of 13C CPMAS NMR chemical shifts for solid methyl α‐d‐mannofuranoside confirm such H‐bonding pattern. 相似文献
949.
《Journal of carbohydrate chemistry》2013,32(7-8):613-629
1,3‐Dipolar cycloaddition of nitrones 1–3 to the α,β‐unsaturated δ‐lactones, non‐chiral 4, d‐glycero 5, dl‐glycero 5/5ent, d‐erythro 6, and d‐threo 7, provides an interesting example of a double asymmetric induction. In all cases, only the exo approach of reactants was observed. The high preference of anti addition of the nitrones to the terminal acetoxymethyl group in the lactones 5–7 is consistent with previous observations, and can be explained in terms of the axial approach of the nitrone oxygen atom. The 3‐t‐butoxy group of the nitrone plays a similar role. In the case of mismatched pairs, the location of the 4‐acetoxy substituent in the lactone and that of the 4‐t‐butoxy one in the nitrone become decisive for the outcome of the addition. CD‐spectroscopy proved to be an attractive tool to determine the absolute configuration of the cycloadducts. 相似文献
950.
The synthesis of the aliphatic subunit 9 of the macrolide LL‐Z1640‐2 (I), starting from a 4‐deoxy‐D‐mannose derivative 2a, is described. The procedure includes the first successful application of a Vasella ring opening reaction for a 4‐deoxypyranoside. Nucleophilic addition of an alkynyllithium reagent to the aldehyde 4 led to the propargylic alcohol 7, which was converted to the advanced building block 9 in two further steps. 相似文献