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91.
Subhash K. Batra 《Journal of Macromolecular Science: Physics》2013,52(3):405-422
The force-temperature history of polyethylene terephthalate (PET) and nylon 66 monofilaments was explored at annealing temperatures of 100,125, 150,175, and 200°C. Annealing was carried out at constant length with 0, 5, 10, and 15% pre-strain. Unexpected difference in behavior was observed during the cooling stage subsequent to the annealing stage. The PET monofilament behavior is attributed to its very high degree of crystallinity. 相似文献
92.
Wu Y Zakharova VM Kashemirov BA Goodman MF Batra VK Wilson SH McKenna CE 《Journal of the American Chemical Society》2012,134(21):8734-8737
Deoxynucleoside 5'-triphosphate analogues in which the β,γ-bridging oxygen has been replaced with a CXY group are useful chemical probes to investigate DNA polymerase catalytic and base-selection mechanisms. A limitation of such probes has been that conventional synthetic methods generate a mixture of diastereomers when the bridging carbon substitution is nonequivalent (X ≠ Y). We report here a general solution to this long-standing problem with four examples of β,γ-CXY dNTP diastereomers: (S)- and (R)-β,γ-CHCl-dGTP (12a-1/12a-2) and (S)- and (R)-β,γ-CHF-dGTP (12b-1/12b-2). Central to their preparation was conversion of the prochiral parent bisphosphonic acids to the P,C-dimorpholinamide derivatives 7 of their (R)-mandelic acid monoesters, which provided access to the individual diastereomers 7a-1, 7a-2, 7b-1, and 7b-2 by preparative HPLC. Selective acidic hydrolysis of the P-N bond then afforded "portal" diastereomers, which were readily coupled to morpholine-activated dGMP. Removal of the chiral auxiliary by H(2) (Pd/C) gave the four individual diastereomeric nucleotides 12, which were characterized by (31)P, (1)H, and (19)F NMR spectroscopy and by mass spectrometry. After treatment with Chelex-100 to remove traces of paramagnetic ions, at pH ~10 the diastereomer pairs 12a,b exhibit discrete P(α) and P(β)(31)P resonances. The more upfield P(α) and more downfield P(β) resonances (and also the more upfield (19)F NMR resonance in 12b) are assigned to the R configuration at the P(β)-CHX-P(γ) carbons on the basis of the absolute configurations of the individual diastereomers as determined from the X-ray crystallographic structures of their ternary complexes with DNA and polymerase β. 相似文献
93.
Syntheses of a variety of aza-polycycles employing 2-(N-allylaminomethyl)cinnamaldehydes derived from Morita–Baylis–Hillman adducts of acrylates via intramolecular 1,3-dipolar cycloaddition, or Aza-Diels–Alder or domino Knoevenagel/hetero Diels–Alder cycloaddition reactions are described. Whereas the Aza-Diels–Alder afforded a mixture of cis- and trans-isomers of substituted 1,2,3,4,4a,5,10,10a-octahydrobenzo[b][1,6]naphthyridines, the 1,3-dipolar cycloaddition and domino Knoevenagel/hetero Diels–Alder were diastereoselective to produce exclusively cis-derivatives of 1,2,3,4,4a,6,7,8,9,9a-decahydro-1H-pyrido[3,4-b]pyrrolizine-8a-carboxylates and 3,4,4a,5,7,8,9,10b-octahydro-1H-chromeno[3,4-c]pyridin-10(2H)-ones, respectively. 相似文献
94.
The thermotolerant yeast Pichia etchellsii produces multiple cell bound β-glucosidases that can be used for synthesis of important alkyl- and aryl-glucosides. Present work focuses on enhancement of β-glucosidase I (BGLI) production in Pichia pastoris. In the first step, one-factor-at-a-time experimentation was used to investigate the effect of aeration, antifoam addition, casamino acid addition, medium pH, methanol concentration, and mixed feed components on BGLI production. Among these, initial medium pH, methanol concentration, and mixed feed in the induction phase were found to affect BGLI production. A 3.3-fold improvement in β-glucosidase expression was obtained at pH 7.5 as compared to pH 6.0 on induction with 1 % methanol. Addition of sorbitol, a non-repressing substrate, led to further enhancement in β-glucosidase production by 1.4-fold at pH 7.5. These factors were optimized with response surface methodology using Box–Behnken design. Empirical model obtained was used to define the optimum “operating space” for fermentation which was a pH of 7.5, methanol concentration of 1.29 %, and sorbitol concentration of 1.28 %. Interaction of pH and sorbitol had maximum effect leading to the production of 4,400 IU/L. The conditions were validated in a 3-L bioreactor with accumulation of 88 g/L biomass and 2,560 IU/L β-glucosidase activity. 相似文献
95.
A relatively mild, efficient, and inexpensive method for the nucleophilic aromatic substitution of the N–H heterocycles with various aryl and heteroaryl iodides using copper nanoparticles (Cu-NP) is reported. The coupling reaction has been successfully achieved with moderate to good yields. 相似文献
96.
JPC – Journal of Planar Chromatography – Modern TLC - The present paper deals with direct enantioresolution of (±)-bupropion using thin-layer chromatography and different... 相似文献
97.
K. Soni M. K. Samota P. Jhajharia Gita Seth 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2845-2853
Novel organophosphorus compounds have been conveniently prepared using 2-(2′-hydroxynapthyl)benzoxazole and 2-(2′-aminophenyl)benzoxazole as starting materials. Phosphorylation and thiophosphorylation was performed using different molar ratio (1:1, 1:2 and 1:3) of phosphorus oxychloride/thiophosphoryl chloride and substituted benzoxazole. The toxicity of newly synthesized phosphorylated/thiophosphorylated compounds was tested on Aspergillus niger and Fusarium oxysporium. All were found antifungal agents. Plausible structures have been proposed on the basis of IR, 1 H NMR, 31 P NMR spectral studies. 相似文献
98.
Reena Agrawal Jyoti Sharma Yashpal Singh Durgesh Nandani Amla Batra 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):516-525
Chloro bis(alkylenedithiophosphato)antimony(III) complexes of the type [OGOP(S)S]2SbCl (1–5) [where G = —C(Me)2—CH2—CH(Me)—1 —C(Me)2—C(Me)2—2, —CH2—C(Me)2—CH2—3, —CH(Me)—CH(Me)—4 and –CH(Me)—CH2—CH2—5] have been synthesized by the reaction of SbCl3 with sodium salts of alkylenedithiophosphoric acids in a 1:2 molar ratio in refluxing benzene. Reactions of chloro bis(alkylenedithiophosphato) antimony(III) compounds, [OGOP(S)S]2SbCl with sodium tetraisopropoxoborate, NaB(OPri)4, in a 1:1 molar ratio in refluxing benzene yielded some new heterobinuclear derivatives of antimony(III) and boron(III) of the type[OGOP(S)S]2Sb(μ—OPri)2B(OPri)2. These newly synthesized complexes have been characterized by elemental analysis and molecular weight measurement, and their plausible structures have been proposed on the basis of IR, NMR (1H, 13C,31P,11B), and FAB-mass spectral studies. On the basis of the spectroscopic evidence, a pseudo octahedral geometry around antimony and tetrahedral geometry around boron atom has been proposed. Cyclic O,O′-alkylenedithiophosphate ligands and their corresponding chloro bis(alkylenedithiophosphato)antimony(III) compounds have been screened for microbial activities. These compounds showed significant antifungal activity against Fusarium and Trichoderma and antibacterial activity against E. Coli and Pseudomonas. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
99.
Priyanka Jhajharia Mahesh Kumar Samota Gita Seth 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):1361-1368
Abstract A series of biologically active phenoxy derivatives of 2-substituted benzoxazole organophosphates have been synthesized by the reaction of O-(naphthyl benzoxazolyl-2-) phosphorodichloridate/phosphorodichloridothioate with phenol/4-chlorophenol/4-nitroph- enol in 1:1 and 1:2 molar ratios. These compounds have been characterized on the basis of elemental analysis, IR, 1H NMR, 31P NMR, and mass spectral studies. The antibacterial activity of these 2-substituted benzoxazole phenoxy derivatives has been evaluated against pathogenic bacteria Staphylococcus aureus (+ve) and Escherichia coli (?ve). The antifungal activity of these 2-substituted benzoxazole phenoxy derivatives has been evaluated against pathogenic fungi Aspergillus niger and Fusarium oxysporium. All compounds were found to have significant antibacterial and antifungal activity. 相似文献
100.
The formation of substituted 2-pyrrolidinones and indoles by the reduction of the secondary nitro group in appropriate 3-aryl-2-methylene-4-nitroalkanoates afforded by Baylis-Hillman chemistry via different reducing agents is described. The 3-aryl-2-methylene-4-nitroalkanoate obtained from SN2 nucleophilic reaction between the acetate of Baylis-Hillman adducts and ethyl nitroacetate upon reduction with indium-HCl furnishes a mixture of cis and trans substituted phenyl-3-methylene-2-pyrrolidinones. In contrast, similar reductions of analogous substrates derived from nitroethane stereoselectively furnished only the trans substituted phenyl-3-methylene-2-pyrrolidinones. On the other hand the SnCl2·2H2O-promoted reductions of substrates derived from nitro ethylacetate give oxime derivatives while the ones obtained from nitroethane yield a mixture of cis and trans 4-aryl-3-methylene-2-pyrrolidinones. Alternatively, the SnCl2·2H2O-promoted reduction of substituted 2-nitrophenyl-2-methylene-alkanoate furnished from ethyl nitroacetate yield 3-(1-alkoxycarbonyl-vinyl)-1H-indole-2-carboxylate while indium-promoted reaction of this substrate leads to a complex mixture. Analogous reactions with SnCl2·2H2O of substituted 2-nitrophenyl-2-methylene-alkanoate obtained from nitroethane yield 4-alkyl-3-methylene-2-quinolones in moderate yields. 相似文献