• Journal of the Korean Chemical Society
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• v.51 no.6
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• pp.520-525
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• 2007

Three-component coupling of thiourea/urea, various structurally diverse aromatic aldehydes and ammonium acetate is catalyzed by activated fly ash in dry media under microwave irradiation to give 6-aryl-1,2,4,5-tetrazinan- 3-thiones/ones in good yields. The structure of 6-aryl-1,2,4,5-tetrazinan-3-thiones/ones have been elucidated on the basis of their melting points, elemental analysis, MS, IR, 1H NMR, D2O exchange, 13C NMR and two dimensional NMR spectral studies including Homonuclear Correlation (HOMOCOR) and Heteronuclear Single Quantum Correlation (HSQC) spectra.

• Journal of the Korean Chemical Society
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• v.46 no.2
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• pp.99-116
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• 2002

The thiazolylazo compounds and their Co(II), Ni(II) and Cu(II) complexes of barbituric acid, uracil, thiouracil, citrazinic acid, chromotropic acid, gallic acid, pyrogallol and salicylic acid were pre-pared and characterized by $^1H$ NMR , IR and the effect of pH on the electronic absorption spectra . The mode of ionization, the electronic transitions and the dissociation constants were discussed. The stoichiometries of the complexes were of 1:1, 2:1 and 3:2 (M:L). The copper complexes are of isotropic ESR spectra (except that of gallic acid which showed a complicated one) and are of magnetically diluted behaviour with orbital con-tribution. Detailed DTA data were obtained and discussed.

• Journal of the Korean Magnetic Resonance Society
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• v.22 no.3
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• pp.54-63
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• 2018

Nymphaea tetragona, also known as waterlilies, is aquatic plant in the family of Nymphaeceae. Three flavonoids(3, 4, and 5) and one mixed flavonoids were separated from this plant. The mixed flavonoid consisted of two flavonoids; a well-known quercetin(1) and a new natural flavonoid(2). The latter also has two chiral centers and their configurations were established by ROESY experiment. Two glycoflavonoids were determined as isoquercetin and quercetin-3-O-${\beta}$-xyropyranosyl-($1{\rightarrow}2$)-${\beta}$-galactopyroside. The $^1H$ NMR spectra for 4 and 5 dissoloved in $DMSO-d_6$ solvent showed resonance proximity and and severely overlap in the glycoside region, hindering the determination of the configurations of the stereogenic centers of the sugar moieties. This problem was solved through the spin simulation. Here, the exact NMR parameters for the sugar moieties of 4 and 5 were listed.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1094-1099
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• 1997

The rotational barriers of thioacetamide (TA) and acetamide (AA) were studied using the ab-initio molecular orbital theory and NMR spectroscopy. The calculated rotational barriers using MP2/6-31G**//MP2/6-31G** for TA was 72.26 kJ/mol and 58.19 kJ/mol for AA, respectively. These results are good agreement with the experimental data. The tendency for the change of structural parameters is consistent with the result of formamide. In both amides, the rotational barrier arises from the pyramidalization of nitrogen. The chemical shifts of both amides are shifted upfield when temperature is raised, which confirms pyramidalization of nitrogen. The lineshape of 1H-NMR spectra of TA shows quintet which is contributed from two triplet spectra. This means that the distribution of electrons around the nitrogen is rather symmetric. Ab-initio calculations of electric field gradient for both amides confirm the above results. The above experimental results are well understood by Keith's view on thioamides, which excludes the contribution of resonance structure and considers the origin of rotational barrier to be the same in both thioamides and in corresponding amides.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1244-1248
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• 1998

Ozonolysis reactions of cyclic olefins 1a-c and norbomene In in the presence of trifluoroactophenone 6 provided the corresponding cross-ozonides 7a-c and 7n. Further reactions of ozonides 7a-c and 7n with the independently prepared carbonyl oxide 11 gave diozonides of structure l0a-c and 10n. The ozonolysis of 1methylcyclopentene 12a and 1-methylcyclohexene 12b in the presence of trifluoroactophenone 6 provided exclusively ozonide 15 and 16 derived from capture of carbonyl oxide 13. All of the new ozonides have been isolated as pure substances and characterized by their 1H NMR and 13C NMR spectra.

• Archives of Pharmacal Research
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• v.12 no.1
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• pp.48-51
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• 1989

A new polyacetylene compound with cytotoxic activity against L1210 cells having diyne-ene and epoxy moiety, named panaxyne epoxide, was isolated from Panax ginseng C.A. Meyer. The chemical structure of the polyacetylene was determined to be tetradeca-13-ene-1,3-diyne-6,7-epoxide by UV, IR, $^1H-NMR,\;^{l3}$C-NMR and mass spectra.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.43-48
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• 1993

The $^1H-NMR$ spectra of the NH-group were obtained for N-ethylacetamide (NEAA) in the series of n-alcohols over a temperature range of 310∼350K by using NMR spectroscopy. The $^1H-NMR$ lineshape coupled to $^{14}N$ nucleus were analyzed to obtain the reorientational correlation times ${\tau}_c$ of NEAA. The data indicate that the coupling of solute and solvent decreases as the chain length of n-alcohols increases. But in the n-alcohols the reorientational motion depends almost linearly on η/T of solvents over our temperature range. The results are discussed in the context of the subslip phenomenon.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.864-869
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• 1995

Investigation of the structures of the gangliosides has proven to be very important in the understanding of their biological roles such as regulation of differentiation and growth of cells. We used nuclear magnetic resonance spectros-copy in order to investigate the structure of GA1. In order to do this, the assignment of spectra is a prerequisite. Since GA1 does not have polar sialic acid, the spectral overlap is severe. In order to solve this problem, we use 2D NMR spectroscopy and heteronuclear 1H/13C correlated spectroscopy in this study. Here, we report the complete assignment of the proton and the carbon spectra of the GA1 in DMSO-d6-D20 (98:2, v/v). These assignments will be useful for interpreting 1H and 13C NMR data from uncharacterized oligosaccharides and for determining the linkage position, the number of sugar rings, and the sequence of new ganglioside. Amide proton in ring Ⅲ shows many interring nOes and has intramolecular hydrogen bonding. This appears to be an important factor in tertiary folding of GA1. Based on this assignment, determination of three dimensional structure of GA1 will be carried out. Studies on the conformational properties of GA1 may lead to a better understanding of the molecular basis of its functions.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.936-942
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• 2013

Series of (E)-1-aryl-3-(2-pyrrolyl)-2-propenones, that were aldol condensation products between pyrrole-2-carbaldehyde and m- and p-substituted acetophenones, were prepared and their $^1H$ and $^{13}C$ NMR spectra were examined to obtain the information on the conformation of the enone system. Similar studies were carried out with (E)-3-aryl-1-(2-pyrrolyl)-2-propenones that were prepared from 2-acetylpyrrole and m- and p-substituted benzaldehydes. The substituent chemical shifts were studied by applying the Hammett relationship.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.372-378
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• 2010

Membrane disruption by an antimicrobial peptide, protegrin-1 (PG-1), was investigated by measuring the $^2H$ solid-state nuclear magnetic resonance (SSNMR) spectra of 1-palmitoyl-$d_{31}$-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC_$d_{31}$) in the mixture of PG-1 and POPC_$d_{31}$ lipids deposited on thin cover-glass plates. The experimental line shapes of anisotropic $^2H$ SSNMR spectra measured at various peptide-to-lipid (P/L) ratios were simulated reasonably by assuming the mosaic spread of bilayers containing pore structures or the coexistence of the mosaic spread of bilayers and a fast-tumbling isotropic phase. Within a few days of incubation in the hydration chamber, the pores were formed by the peptide in the POPC_$d_{31}$ and POPC_$d_{31}$/cholesterol membranes. However, the formation of the pores was not clear in the POPC_$d_{31}$/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG) membrane. Over a hundred days after hydration, a rapidly rotating isotropic phase increased in the POPC_$d_{31}$ and the POPC_$d_{31}$/cholesterol membranes with the higher P/L ratios, but no isotropic phase appeared in the POPC_$d_{31}$/POPG membrane. Cholesterol added in the POPC bilayer acted as a stabilizer of the pore structure and suppressed the formation of a fast-tumbling isotropic phase.