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11.
Vogensen SB Greenwood JR Varming AR Brehm L Pickering DS Nielsen B Liljefors T Clausen RP Johansen TN Krogsgaard-Larsen P 《Organic & biomolecular chemistry》2004,2(2):206-213
(RS)-3-Hydroxy-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid (5-HPCA)(), which is a conformationally constrained cyclised analogue of AMPA has previously been described as causing glutamate receptor mediated excitations of spontaneously firing cat spinal interneurons in a similar fashion to AMPA. We have now prepared the enantiomers of through chiral chromatographic resolution of (RS)-3-(carboxymethoxy)-4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-5-carboxylic acid () followed by a stereoconservative hydrolysis resulting in the enantiomers of with high enantiomeric excess (% ee [greater-than-or-equal] 99). The absolute configurations indicated by an X-ray analysis of (-)- monohydrate were confirmed by comparing observed and ab initio calculated electronic circular dichroism spectra and by stereoconservative synthesis of (S)- from (S)-AMPA, the pharmacologically active form of AMPA. The pharmacological effects at native and cloned (GluR1-4) AMPA receptors were shown to reside exclusively with (R)-(+)-, in striking contrast to the usual stereoselectivity trend among AMPA receptor agonists. The reasons for this anomalous behaviour became clear upon docking both enantiomers of to the agonist binding site of GluR2. 相似文献
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Tommy Dreyfus† Theodore Eisenberg† 《International Journal of Mathematical Education in Science & Technology》2013,44(3):489-497
There is a definite movement to remove many of the topics concerning polynomials from the school curriculum. The purpose of this paper is to point out why this movement is misguided and should be reversed. 相似文献
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Abstract The title trisaccharides were synthesized from a common trisaccharide thioglycoside derivative, which was, in turn, prepared from monosaccharide thioglycoside precursors. An acyclic analogue, methyl 3-O-(α-D-galacto-pyranosyl)-6-O-[(2′-hydroxyethyl)oxymethyl]-α-D-glucopyranoside, which carries a 2′-hydroxyethyloxymethyl group in place of the 6-O-galactosyl residue, was also synthesized. 相似文献
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Abstract FMOC-serine phenacylester was glycosylated with a derivative of the disaccharide α-D-Xylp-(1→3)-β-D-Glcp, and the product was treated with zinc to remove the phenacyl group. The title derivative is useful for synthesis of blood clotting factor IX glycopeptide fragments by the solid-phase approach. 相似文献
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Abstract The first completed chemical synthesis of Agrocinopine A (5) is presented. The key step in the synthesis was the pivaloyl chloride promoted condensation of a blocked arabinose 2-H-phosphonate derivative 3 with a protected sucrose derivative 1 having a free hydroxyl at 4′-OH. The resulting H-phosphonic acid diester was oxidised in situ with iodine to produce the corresponding phosphodiester 4, which was subsequently deblocked to give Agrocinopine A. 相似文献
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In this study the effect of the mercerization degree on the water retention value (WRV) and tensile properties of compression molded sulphite dissolving pulp was evaluated. The pulp was treated with 9, 10, or 11 % aqueous NaOH solution for 1 h before compression molding. To study the time dependence of mercerization the pulp was treated with 12 wt% aqueous NaOH for 1, 6 or 48 h. The cellulose I and II contents of the biocomposites were determined by solid state cross polarization/magic angle spinning carbon 13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. By spectral fitting of the C6 and C1 region the cellulose I and II content, respectively, could be determined. Mercerization decreased the total crystallinity (sum of cellulose I and cellulose II content) and it was not possible to convert all cellulose I to cellulose II in the NaOH range investigated. Neither increased the conversion significantly with 12 wt% NaOH at longer treatment times. The slowdown of the cellulose I conversion was suggested as being the result from the formation of cellulose II as a consequence of coalescence of anti-parallel surfaces of neighboring fibrils (Blackwell et al. in Tappi 61:71–72, 1978; Revol and Goring in J Appl Polym Sci 26:1275–1282, 1981; Okano and Sarko in J Appl Polym Sci 30:325–332, 1985). Compression molding of the partially mercerized dissolving pulps yielded biocomposites with tensile properties that could be correlated to the decrease in cellulose I content in the pulps. Mercerization introduces cellulose II and disordered cellulose and lowered the total crystallinity reflected as higher water sensitivity (higher WRV values) and poorer stiffness of the mercerized biocomposites. 相似文献
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Structural Manipulation of Ruthenium(II) Polypyridine Nitrone Complexes to Generate Phosphorogenic Bioorthogonal Reagents for Selective Cellular Labeling
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Tommy Siu‐Ming Tang Dr. Hua‐Wei Liu Prof. Kenneth Kam‐Wing Lo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9649-9659
We report a new class of ruthenium(II) polypyridine complexes functionalized with a nitrone group as phosphorogenic bioorthogonal probes. These complexes were very weakly emissive owing to rapid C=N isomerization of the nitrone moiety, but exhibited significant emission enhancement upon strain‐promoted alkyne–nitrone cycloaddition (SPANC) reaction with bicyclo[6.1.0]nonyne (BCN)‐modified substrates. The modification of nitrone with a dicationic ruthenium(II) polypyridine unit at the α‐C‐position and a phenyl ring at the N‐position led to remarkably accelerated reaction kinetics, which are substantially greater (up to ≈278 fold) than those of other acyclic nitrone–BCN systems. Interestingly, the complexes achieved specific cell membrane/cytosol staining upon specific labeling of an exogenous substrate, BCN‐modified decane (BCN‐C10), in live cells. Importantly, the in situ generation of the more lipophilic isoxazoline adduct in the cytoplasm resulted in increased cytotoxicity, highlighting a novel approach to apply the SPANC labeling technique in drug activation. 相似文献
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