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11.
A new germanium-based linker for solid phase synthesis of aromatics: synthesis of a pyrazole library
An efficient synthesis of chlorogermane linker 12 is described. Economic introduction of germanium into this linker is accomplished by insertion of dichlorogermylene [from germanium(IV) chloride] into the homobenzylic C-Cl bond of 4-(2-chloroethyl)phenol 1. Using linker 12, transmetalation with lithiated 4-acetophenone, 3-acetophenone, and 4-(4'methoxy)biphenyl followed by Mitsunobu-type coupling to Argogel gives functionalized resins 14, 16, and 18, respectively. Treatment of resin 18 with TFA, ICl, Br2, or NCS effects clean ipso-degermylation releasing biphenyls 19-22, respectively. Resins 14 and 16 are employed for the parallel synthesis of a library of pyrazoles by enaminone formation (using Bredereck's reagent), condensative ring-closure (using a series of monosubstituted hydrazines), and cleavage (using TFA and Br2). Analysis of this library reveals the influence of the hydrazine substituent on both the regioselectivity of ring-closure and the propensity for electrophilic substitution at the 4-position of the pyrazoles during ipso-degermylative cleavage. 相似文献
12.
A.A. Kamel CM. Ma M.S. El-Aasser F.J. Micale J.W. Vanderhoff 《Journal of Dispersion Science and Technology》2013,34(2-3):315-330
The electrophoretic mobility behavior of well-characterized polystyrene latex particles, carrying one type of surface functional endgroups, has been studied as a function of pH. At low pH, the interaction of protons with the functional endgroups increased in the order: Hydroxyl > carboxyl > sulfate; at high pH the order of interaction was reversed; and at intermediate pH no interactions were observed. The particles of the polystyrene latexes in their different forms at the intermediate pH range, dispersed in deionized water, all exhibited the same mobility irrespective of the functional endgroup. The origin of charge in these systems is explained as being the result of either the preferential adsorption of hydroxyl ions or an electron - injection mechanism due to the overlap of local intrinsic molecular - ion states in polystyrene and water. At low concentrations of functional endgroups, the surface properties of the polystyrene latexes are largely dependent upon the hydrophobic nature of the surface. 相似文献
13.
Tobias Frank Johannes CM Schlachetzki Bettina G?ricke Katrin Meuer Gundula Rohde Gunnar PH Dietz Mathias B?hr Armin Schneider Jochen H Weishaupt 《BMC neuroscience》2009,10(1):49-10
Background
The hematopoietic Granulocyte-Colony Stimulating Factor (G-CSF) plays a crucial role in controlling the number of neutrophil progenitor cells. Its function is mediated via the G-CSF receptor, which was recently found to be expressed also in the central nervous system. In addition, G-CSF provided neuroprotection in models of neuronal cell death. Here we used the retinal ganglion cell (RGC) axotomy model to compare effects of local and systemic application of neuroprotective molecules. 相似文献14.
15.
16.
Marijke WA de Backer Carlos P Fitzsimons Maike AD Brans Mieneke CM Luijendijk Keith M Garner Erno Vreugdenhil Roger AH Adan 《BMC neuroscience》2010,11(1):81
Background
This study compared the transduction efficiencies of an adeno-associated viral (AAV) vector, which was pseudotyped with an AAV1 capsid and encoded the green fluorescent protein (GFP), with a lentiviral (LV) vector, which was pseudotyped with a VSV-G envelop and encoded the discosoma red fluorescent protein (dsRed), to investigate which viral vector transduced the lateral hypothalamus or the amygdala more efficiently. The LV-dsRed and AAV1-GFP vector were mixed and injected into the lateral hypothalamus or into the amygdala of adult rats. The titers that were injected were 1 × 108 or 1 × 109 genomic copies of AAV1-GFP and 1 × 105 transducing units of LV-dsRed. 相似文献17.
AM Cardoso SM Alexandre CM Barros AJ Correia NM Nibbering 《Rapid communications in mass spectrometry : RCM》1999,13(19):1885-1888
The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
18.
AM Johnston CM Scrimgeour MO Henry LL Handley 《Rapid communications in mass spectrometry : RCM》1999,13(14):1531-1534
The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
19.
S Rayaprol Krushna Mavani CM Thaker DS Rana Keka Chakravorty SK Paranjape M Ramanadham Nilesh A Kulkarni DG Kuberkar 《Pramana》2002,58(5-6):877-880
A new series of mixed oxide superconductors with the stoichiometric composition La2−x
Dy
x
Ca
y
Ba2Cu4+y
O
z
(x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La2−x
(Y/Er)
x
Ca
y
Ba2Cu4+y
O
z
series, show a strong dependence of T
c on hole concentration (p
sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant
displacement of La onto Ba site. Superconductivity studies show that maximum T
c is obtained for x=0.5, y=1.0 sample (T
c ∼ 75 K), for La1.5Dy0.5Ca1Ba2Cu5O
z
(La-2125). 相似文献
20.