Search results for "Nuclear magnetic resonance spectroscopy"

In-witro-NMR-Spektroskopie an gesunden, mastopathisch veränderten und karzinomatös befallenen Brustdrüsen-gewebsproben, korreliert mit histologischen…

1994

Es wurden bei 57 Patientinnen mit klinischem Verdacht auf Mammakarzinom 121 Gewebeproben entnommen und mittels der 1H-NMR-Spektroskopie bei 300 MHz in vitro nach Korrelation mit histologischen Befunden untersucht. Im interessanten Spektralbereich zwischen 2,7 und 4,1 ppm wurden starke Signale beobachtet, die Fett, (Phosphoryl-)Cholin, Kreatin(-phosphat) sowie Karnitin zugeordnet wurden. Weiterhin konnten mit hoher Regelmasigkeit 8 schwachere, zum Teil uberlappende Signale der Substanzen Glukose, Glyzin, Threonin, Serin, Inositol und Saccharose nachgewiesen werden. Hierbei wurden Linienintensitaten uber ein iteratives Fitprogramm bestimmt. Uber deren Quotienten konnten unterschiedliche Geweb…

NMR Spectroscopy, Heteronuclei, Y-Cd

2017

Total Correlation Spectroscopy (TOCSY) of Proteins Using Coaddition of Spectra Recorded with Several Mixing Times

1993

NMR Spectrum and Line Shape of Two Interacting Two-Spin Systems in Crystals

1967

Di-n-butyltin oxide as a chemical carbon dioxide capturer

2010

Abstract Several synthetic routes to the decakis(di-n-butyltin(IV)) oxocluster, (n-Bu2SnO)6[(n-Bu2SnOCH3)2(CO3)]2 (1), a diorganotin compound previously shown to belong to the class of organotins able to store carbon dioxide, as well as its reactivity toward dimethyl carbonate (DMC), are described. The synthetic route from n-Bu2SnO and DMC was applied for the preparation of the ethoxy analogue of 1, oxocluster 2, using diethyl carbonate. The structural relationship connecting cluster 1, with its precursor PRE-1 isolated from recycling experiments and n-Bu2SnO is discussed. For this purpose, the reactivity of PRE-1 with trifluoromethanesulfonic acid was investigated in order to trace structu…

Synthesis of 2-isoxazolines: enantioselective and racemic methods based on conjugate additions of oximes.

2010

The formation of 3-unsubstituted 2-isoxazolines by means of condensation reactions between α,β-unsaturated aldehydes and oximes proceeds readily in the presence of catalytic amounts of anilinium salts. Mechanistically, the process involves a fast conjugate addition of the oxime and a slower intramolecular oxime-transfer reaction. The rate of oxime transfer was found to correlate with the acidity of the catalyst. This finding enabled us to discover an enantioselective process in which the fragile conjugate-addition product generated in the first stage is rapidly cyclized into the stable isoxazoline under acidic conditions, with conservation of enantiomeric excess. In summary, herein we descr…

Mono-, bi- and polynuclear complexes of dimethyldiphenylsilane, diphenylether and biphenyl with Cr, Co and Ru. Synthesis and 1H, 13C, 17O and 29Si NM…

1995

Abstract Mono- and bimetallic transition metal carbonyls of dimethyldiphenylsilane, Ph 2 Si(CH 3 ) 2 (L1), diphenylether, Ph 2 O (L2) and biphenyl, Ph 2 (L3): Ph 2 Si(CH 3 ) 2 Cr(CO) 3 ( 1 ), Ph 2 Si(CH 3 ) 2 [Cr(CO) 3 ] 2 ( 2 ), Ph 2 Si(CH 3 ) 2 Co 4 (CO) 9 ( 3 ), Ph 2 Si(CH 3 ) 2 [Co 4 (CO) 9 ] 2 ( 4 ), Ph 2 Si(CH 3 ) 2 Cr(CO) 3 Co 4 (CO) 9 ( 5 ), Ph 2 OCr(CO) 3 ( 6 ), Ph 2 OCo 4 (CO) 9 ( 7 ), Ph 2 ORu 6 C(CO) 14 ( 8 ), Ph 2 OCr(CO) 3 Co 4 (CO) 9 ( 9 ) and Ph 2 Ru 6 C(CO) 14 ( 10 ) have been prepared and characterized by means of 1 H, 13 C, 17 O and 29 Si NMR spectroscopy. The same order of the shielding effects induced by the transition metal (Co 1 H NMR chemical shifts of the η 6 -coord…

Kinetics and Mechanism of the Nucleophilic Substitution of Tellurium(II) Dialkanethiolates, Te(SR1)2 with Thiols, HSR2

2005

The equilibrium reaction between tellurium(II) dithiolates and thiols, Te(SR1)2 + 2 HSR2 ⇌ Te(SR2)2 + 2 HSR1 was studied by means of 1H- and 125Te NMR spectroscopy and ab initio quantum chemical methods. It was found that the reaction is catalyzed by Bronsted acids and bases, the catalytic activity corresponding to the strength of the respective acid or base. Investigation of the initial step of the reaction, Te(SR1)2 + HSR2 ⇌ Te(SR1)(SR2) + HSR1, showed it to proceed according to first order kinetics for Te(SR1)2, HSR2 and for the catalyst. Ab initio geometry optimizations and frequency calculations suggest [Te(SR1)(HSR1)(HSR2)]+ and [Te(SR1)2(SR2)]− to be stable intermediates and not tran…

Electrochemical and chemical reduction of niobocene dichlorides in the presence of carbon dioxide

1995

Abstract The chemical and electrochemical reduction of the niobocene dichlorides [Nb(η5-C5H4SiMe3)2Cl2]1, [Nb(η5-C5Me5)2Cl2] 2 and [Nb(η5-C5Me4Et)2Cl2] 3, in the presence of carbon dioxide has been investigated. Formation of compounds of the type [Cp2Nb(CO2)] and [Cp2(∗)NbCl(CO2))] 1 has been established by means of IR, ESR and/or NMR spectroscopy. They contain a labile η2-CO2. The order of stability increases with the degree of substitution the Cp. Less stable intermediates in the reduction of the system [Cp2NbCl2]/CO2 are discussed on the basis of cyclovoltammetric and coulometric data.

Polycondensed nitrogen heterocycles. Part17. Isoxazolo[4,3-d]pyrazolo[3,4-f][1,2,3]triazepine. A new ring system

1987

The title compounds were prepared by nitration of compounds 2, reduction of the dinitro derivatives 4 and diazotization of the diamino derivatives 6 followed by an intramolecular coupling reaction. Compound 4a showed good activity against Salmonella cholerasuis and Clostridium perfringens bacteria.