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see............http://process-nmr.com/WordPress/?cat=7
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Sunday, 21 December 2014
The Power of MestReNova Data Processing and Analysis Applied to 60 MHz 1H NMR Real Time Reaction Monitoring
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see............http://process-nmr.com/WordPress/?cat=7
Solution structures by NMR of a novel antifungal drug: Petriellin A
Petriellin A is a novel cyclic depsipeptide antifungal compound consisting of nine L-configured residues, one D-phenyllactic acid (PhLac) and three unknown chiral centres: two N-methyl-threonines (MeThr1 & MeThr2) and one N-methyl-isoleucine (MeIle). NMR experiments including 2D ROESY, NOESY along with structural and energy calculations predicted that the unknown chiral centres were all L-configured, which was later verified chemically. Simulated annealing, dynamics calculations and minimisation processes showed Petriellin A to have a folded “C-shaped” structure.
Org. Biomol. Chem., 2006,4, 3802-3807
DOI: 10.1039/B608434F http://pubs.rsc.org/en/content/articlelanding/2006/ob/b608434f#!divAbstract
Integration of NMR signals as a function of time.
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A 7Li RINMR experiment at -135 °C (3:1 Me2O / THF): Reaction of n-BuLi dimer and tetramer with trimethylsilylacetylene (Jones, A. C., Sanders, A. W., Bevan, M. J., Reich, H. J. J. Am. Chem. Soc. 2007, 129, 3492).
read
http://www.chem.wisc.edu/areas/reich/nmr/08-tech-03-dnmr.htm
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Simple preparation of new N-aryl-N-(3-indolmethyl) acetamides and their spectroscopic analysis
http://www.scielo.org.co/scielo.php?pid=S0122-74832009000300005&script=sci_arttext
The new compound 9 gave a molecular ion peak at m/z 331, corresponding to the molecular formula C20H17N3O2 as indicated by its EI-MS. The loss of 43 units (one acetyl group) generates the same mass spectrum as the acetamide 8.
The IR spectrum shows bands at 1704 and 1654 cm-1, assignable to two carbonyl groups. The N-H absorption bands were not observed in the region of 3300-3400 cm-1.
The 1H NMR spectrum showed, as expected, two singlets at d 22.4 and 23.9 ppm, which integrated three protons each. To the methylenic protons Figure 3.
X-Ray structure of the diacetamide 9 case, they appeared to be diasterotopic resonating at the high field frequencies d 4.75 and 5.46 ppm with a coupling constant J = 15 Hz, usual constant value to a germinal coupling. Of course, the aromatic protons were also assigned.
The 13C NMR spectrum showed all expected characteristic peaks at d 169.4 (ArN-CO-), 168.5 (ArindolN-CO-) ppm, in addition to a signal at d 117.3 ppm showing the presence of TCN in the molecule. Besides, methyl carbons at 23.9 (ArindolNCO-CH3) and 22.4 (ArNCO-CH3) ppm and the methylene carbon at d 42.8 ppm were also displayed in the 13C NMR.
N-(1-Acethyl-1H-indol-3-ylmethyl)-N-(2-cyanophenyl) acetamide (9)
A mixture of the amine 7 (0.50 g, 2.02 mmol), acetic anhydride (10.80 g, 98 mmol), and Et3N (0.44 g, 4.30 mmol) was heated at 100°C for 3 hours. Then, the reaction mixture was allowed to reach room temperature and then treated with 50 mL of aqueous NaOH and extracted with ethyl acetate (3 x 30 mL). The organic layer was dried over Na2SO4 and later dried in vacuum. Silica gel preparative chromatography (petroleum ether / ethyl acetate, 2:1) of the crude product afforded diacetamide 9 (0.53 g, 80%) as a white and stable solid. Rf 0.50 (petroleum ether/ethyl acetate, 1:1).
A mixture of the amine 7 (0.50 g, 2.02 mmol), acetic anhydride (10.80 g, 98 mmol), and Et3N (0.44 g, 4.30 mmol) was heated at 100°C for 3 hours. Then, the reaction mixture was allowed to reach room temperature and then treated with 50 mL of aqueous NaOH and extracted with ethyl acetate (3 x 30 mL). The organic layer was dried over Na2SO4 and later dried in vacuum. Silica gel preparative chromatography (petroleum ether / ethyl acetate, 2:1) of the crude product afforded diacetamide 9 (0.53 g, 80%) as a white and stable solid. Rf 0.50 (petroleum ether/ethyl acetate, 1:1).
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Impurity analysis of gentamicin bulk samples by improved liquid chromatography-ion trap mass spectrometry
Several gentamicin bulk samples from different origins were investigated using an LC/MS method. LC equipped with ion trap MS with positive ionization was performed on a Capcell Pak C18 (AQ) column with the mobile phase containing 50 mM trif-luoroacetic (TFA) and methanol. Impurities present in batches of gentamicin bulk samples were elucidated and compared ac-cording to their fragmentation behavior. In total seventeen impurities present in samples, five impurities were not elucidated and two compounds were identified preliminarily. It was observed that the impurity profiles were different in samples from different origins which indicate necessity in the quality control of gentamicin.
Impurity analysis of gentamicin bulk samples by improved liquid chromatography-ion trap mass spectrometry
ZHENG Chao, WANG BoChu, WANG MingJuan, HOOGMARTENS Jos, SCHEPDAEL Ann Van, ADAMS Erwin
SCIENCE CHINA Chemistry 2011, 54 No. 9
2011 Vol. 54 (9): 1518-1528 [Abstract] ( 306 ) [ PDF (909 KB) ] ( 5767 ) [Supporting Information] DOI: 10.1007/s11426-011-4304-0
http://chem.scichina.com:8081/sciBe/EN/abstract/abstract504534.shtml
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