Nuclear magnetic resonance assignment

Table 3. Proton nuclear magnetic resonance assignments for spectrum of sodium valproate...

R. Morrison and D. Hare, /. Mol. Biol., 204, 483 (1988). Determining Stereospecific H Nuclear Magnetic Resonance Assignments from Distance Geometry Calculations. 

The absolute configuration of (-)-swainsonine (1) was deduced on the basis of its biosynthesis and unambiguous nuclear magnetic resonance assignments.The relative stereochemistry of swainsonine was determined by X-ray crystallography. Noncarbohydrates have been used for the total synthesis of swainsonine and its isomers.The first total synthesis of 1 has established its absolute stereochemistry as (15, 2i ,8i ,8ai )-... 

McEvoy, M.M., Zhou, H.J., Roth, A.F., Lowry, D.F., Morrison, T.B., Kay, L.E. and Dahlquist, F.W. (1995). Nuclear magnetic resonance assignments and global fold of a CheY-binding domain in CheA, the chemotaxis-specific kinase of Escherichia coli. Biochemistry 34,13871—13880. 

Pachler KGR, Ste)fn PS, Vleggaar R, Wessels PL, Scott DB (1976) C arbon-13 Nuclear Magnetic Resonance Assignments and Biosynthesis of Aflatoxin Bl and Sterigmatocystin. J Chem Soc Perkin Trans 1 1182... 

Osborne, MJ, Breeze, AL, Lian, LY, Reilly, A, James, R, Kleanthous, C, etal., Three-dimensional solution structure and 13C nuclear magnetic resonance assignments of the colicin E9 immunity protein lm9. Biochemistry 35 (1996) 9505-9512. 

De Jesus, A.E., P.S. Steyn, R. Vleggar, and P.L. Wessels Carbon-13 Nuclear Magnetic Resonance Assignments and Biosynthesis of the Mycotoxin Ochratoxin A.J. Chem. Soc. Perkin Trans. I 1980, 52. 

Nuclear Magnetic Resonance Spectroscopy. Bmker s database, designed for use with its spectrophotometers, contains 20,000 C-nmr and H-nmr, as weU as a combined nmr-ms database (66). Sadder Laboratories markets a PC-based system that can search its coUection of 30,000 C-nmr spectra by substmcture as weU as by peak assignments and by fiiU spectmm (64). Other databases include one by Varian and a CD-ROM system containing polymer spectra produced by Tsukuba University, Japan. CSEARCH, a system developed at the University of Vieima by Robien, searches a database of almost 16,000 C-nmr. Molecular Design Limited (MDL) has adapted the Robien database to be searched in the MACCS and ISIS graphical display and search environment (63). Projects are under way to link the MDL system with the Sadder Hbrary and its unique search capabiHties. 

Other spectroscopic methods such as infrared (ir), and nuclear magnetic resonance (nmr), circular dichroism (cd), and mass spectrometry (ms) are invaluable tools for identification and stmcture elucidation. Nmr spectroscopy allows for geometric assignment of the carbon—carbon double bonds, as well as relative stereochemistry of ring substituents. These spectroscopic methods coupled with traditional chemical derivatization techniques provide the framework by which new carotenoids are identified and characterized (16,17). 

Nuclear magnetic resonance spectra of all four parent compounds have been measured and analyzed.The powerful potentialities of NMR as a tool in the study of covalent hydration, tautomerism, or protonation have, however, as yet received no consideration for the pyridopyrimidines. NMR spectra have been used to distinguish between pyrido[3,2-d]pyrimidines. and isomeric N-bridgehead compounds such as pyrimido[l,2- ]pyrimidines and in several other structural assignments (cf. 74 and 75). 

Snyder and his co-workers assigned structures 48 and 49 to these j6-hydroxythiophene derivatives on the basis of chemical evidence and infrared and nuclear magnetic resonance spectral data. Infrared and nuclear magnetic resonance spectra further indicate that compounds of type 49 exist as dimers, probably hydrogen bonded, when R = OC2H5 or CH3, but as monomeric enols when R = H. ... 

Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool that can provide the binding sites of Ugand-DNA interactions at the molecular level. A prerequisite for the examination of ligand-DNA complexes is assignment of all resonances in the NMR spectra of the free DNA and the ligand and of both components in the complex. 

Most of the NMR work reported on B 12-derivatives has been concerned with interpreting spectra and assigning resonance positions. In certain cases some valuable information concerning the chemistry of B12 has been obtained. We will discuss the nuclear magnetic resonance work which has been reported for B12 plus some of our own unpublished results with particular emphasis on those results which give some insight into vitamin B 12-chemistry. 

The nuclear magnetic resonance spectrum of sodium valproate as shown in Figure 3 was obtained on a Varian Associates T-60 NMR Spectrometer in deuterium oxide containing tetramethylsilane as the internal standard. The spectral peak assignments (2) are presented in Table I. 

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