• Bulletin of the Korean Chemical Society
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• v.8 no.2
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• pp.102-105
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• 1987

2-Methoxy-6-methyl-3,4-dihydro-2H-pyran ($1_a$), 2-ethoxy-3,6-dimethyl-3,4-dihydro-2H-pyran ($1_b$), and 2-ethoxy-3-methyl-6-ethyl-3,4-dihydro-2H-pyran ($1_c$) were prepared by (4 + 2) cycloaddition reaction from the corresponding vinyl ketones and alkyl vinyl ethers. Compounds $1_{a-c}$ were ring-open polymerized by cationic catalyst to obtain alternating head-to-head (H-H) copolymers. For comparison, copolymer of head-to-tail (H-T) was also prepared by free radical copolymerization of the mixture of the corresponding monomers. The H-H copolymer exhibited some differences in its $^1H$ NMR and IR spectra. However, significant differences were showed between the H-H and H-T copolymers in the $^{13}C$ NMR spectra. Also noteworthy was that$T_g$ value of H-H copolymer was higher than that of the corresponding H-T structure. Decomposition temperature of the H-H copolymer was lower than that of the H-T copolymer. All the H-H and H-T copolymers were soluble in common solvents.

• Journal of the Korean Magnetic Resonance Society
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• v.13 no.2
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• pp.108-116
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• 2009

The HP0902, a homodimeric 22.1 kDa protein, has been suggested as a putative secretory protein from Helicobacter pylori, although the protein possesses no signal peptide for secretion. Since it may be associated with the virulence of the bacterium, NMR study has been initiated in terms of structural genomics. In our previous effort to assign the backbone NMR resonances, using 800MHz NMR machine at pH 7.8, the resonances from eight of the 99 residues could not be assined due to missing of the signals. In this work, to enhance the extent of assignments, a 900 MHz machine was employed and the sample pH was reduced down to 6.5. Finally, almost all signals, except for those from G9 and S24, could be clearly assigned. The determined secondary structure using the assined chemical shifts indicated that the HP0902 consists of 11 ${\beta}$-strands with no helices. In our database search result, HP0902 was predicted to interact with VacA (Vacuolating cytotoxin A), which is a representative virulence factor secreted from Helicobacter pylori. Thus, molecular interaction between HP0902 and VacA would be worthy of investigation, on the basis of the present results of NMR assignments.

• Applied Biological Chemistry
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• v.46 no.2
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• pp.69-73
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• 2003

A novel antifungal antibiotic for azole-resistant Candida albicans was purified from the culture broth of Bacillus subtilis LAM 97-44 by butanol extraction, Diaion HP-20 and Dowex-50 adsorption chromatography, silica gel flash chromatography followed by HPLC and designated LAM-44A. LAM-44A was stable for 60 min at $100^{\circ}C$, and pH range from 2 to 10. MIC values were observed at $0.5-3.5\;{\mu}g/ml$ against various Candida albicans strains. The antibiotic showed no cytotoxicity for S180, MKN-45, P388, HeLa and 373 at the concentration of 1 mg/ml. LAM-f4A was colorless powder soluble in water, methanol, ethanol, butanol and negative to ninhydrin reaction. The antibiotic had maximum absorption at 273 nm in methanol, and melting point was $202^{\circ}C$. The molecular weight and formula were determined to be 282 and $C_{14}H_{34}O_5$ by $^1H-NMR,\;^{13}C-NMR$, IR spectrum and elemental analysis.

• Journal of the Korean Chemical Society
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• v.36 no.5
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• pp.685-691
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• 1992

The $d^8$-transition metal complexes containing diphosphine, $MCl_2PP$ were prepared by using $K_nMCl_m$ as starting materials, wherein M were Ni(II), Pd(II), Pt(II) and Au(III) and PP were bis(diphenylphosphino)methane(dppm), bis(diphenylphosphino)ethane(dppe), bis(diphenylphosphino)propane (dppp) and bis(diphenylphosphino)ethylene(dppety). The complexes were characterized by the spectral property $(^H-NMR$, $^{31}P-NMR$ and UV-Visible spectra) together with elemental analysis. The complexes were tested for the catalytic activity on the formation reactions of 3(2H)-furanone and cyclic carbonate. The only Ni(II)- and Pd(II)-diphosphine complexes displayed a good catalytic effects in the production of 3(2H)-furanone from 2-methyl-3-butyn-2-ol [reaction (1)]. But all the diphosphine complexes as catalyst were almost inactive towards cyclic carbonate production preaction [reaction (2)].

• Applied Biological Chemistry
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• v.37 no.2
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• pp.100-104
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• 1994

From the 48 hour-cultured mycelial broth of Phellinus linteus, six compounds were isolated by means of ethyl acetate extraction, silica gel column chromatography and preparative thin layer chromatography, consecutively. Compound 1 was identified as a succinic acid by the comparison of its spectral data with authentic sample. Compounds 2 and 3 were identified as p-hydroxyphenyl acetic acid methyl ester and p-hydroxybenzaldehyde by spectroscopic studies, respectively. NMR and MS studies of compound 6 revealed that it was 2,5-dihydroxymethyl furan. Compound 4, which showed similar NMR absorptions and MS fragmentation pattern with those of compound 6 was identified as 2-hydroxymethyl-5-methoxymethylfuran. These structures were verified by the spectral data of the acetate derivatives of the compounds. Compound 5 was supposed to be a N-acetyltyramine from its $^1H-NMR$ and EI-MS data, and its structure was confirmed by a synthesis starting from tyramine.

• Korean Journal of Pharmacognosy
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• v.27 no.3
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• pp.207-211
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• 1996

Cumambrin A has been isolated from the dried flowers of Chrysanthemum boreale Makino. The complete $^1H$ and $^{13}C$ NMR assignment of cumambrin A was achieved from two-dimensional $^1H$-$^1H$ COSY and $^{13}C$-$^1H$ COSY spectra with the aid of homonuclear and heteronuclear double resonance experiments. The its structure has been verified by single crystal X-ray diffraction.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.643-647
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• 1996

1,2-Disubstituted chiral calix[4]arene "25-(3,5-dinitrobenzoyloxy)-26-methoxy-27,28-dihydroxycalix[4]arene" was synthesized by the reaction of 25-(3,5-dinitrobenzoyloxy)-calix[4]arene with methyl iodide in the presence of K2CO3. Methylation was occurred at the 26-position of calix[4]arene. The partial cone conformation and 1,2-substitution were characterized based on the 1H NMR, 13C NMR and X-ray diffraction analysis. The crystal structure has been determined by X-ray diffraction method. The crystals are orthorhombic, Pbca, a=10.652(1), b=17.687(1), c=32.247(3) Å, Z=8, V=6075.4(9) Å3, Dc=1.38gcm-3. The intensity data were collected on an Enraf-Nonius CAD-4 Diffractometer with a graphite monochromated Cu-Kα radiation. The structure was solved by direct method and refined by full-matrix least-squares methods to a final R value of 0.050 for 2368 observed reflections. The molecule is in the partial cone conformation. It has two strong intramolecular hydrogen bonds of O(1D)-H…O(1C)-H…O(1B).

• Journal of the Korean Chemical Society
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• v.55 no.6
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• pp.940-951
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• 2011

Reaction of 1-methylpyrimidine-(1H,3H,5H)-2,4,6-trione (1-MBA 1) as an unsymmetrical barbituric acid with cyanogen bromide and various aldehydes in the presence of triethylamine and/or pyridine afforded diastereomeric mixtures of new class of heterocyclic stable 5-aryl-1,1'-dimethyl- and 5-aryl-3,1'-dimethyl-1H,1'H-spiro[furo[2,3-d]pyrimidine-6,5'-pyrimidine]2,2',4,4',6'(3H,3'H,5H)-pentaones which are dimeric forms of 1-methyl barbiturate at the range of $0^{\circ}C$ to room temperature. In the reaction of some aldehydes with 1-MBA and BrCN were afforded a mixture of diastereomers. Another two aldehydes such as 4-cyano- and 2-hydroxybenzaldehydes gave exclusively two diastereomers in which binded to the salt of triethylammonium hydrobromide by intermolecular H-bond in ratio of 1:1. 4-Hydroxybenzaldehyde and 2-pyridinecarbaldehyde gave exclusively one diastereomer under the same condition. Aldehydes possessing strong electron-donor were produced exclusively two geometric isomers of Knoevenagel adduct (E- and Z-isomers). The structures of compounds were deduced by $^1H$ NMR, $^{13}C$ NMR and FT-IR spectroscopy. Mechanism of the formation is discussed.

• Journal of the Korean Chemical Society
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• v.38 no.1
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• pp.41-49
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• 1994

Exchange reaction mechanisms of the Pb(II) ion for the complexes between Pb(II) ion and nitrogen oxygen donor macrocyclic ligands, such as 1,13-diaza-3,4 : $1011-dibenzo-59-dioxacyclohexa-decane(NtnOtnH_4)$, 1,15-diaza-3,4 : $1213-dibenzo-5811-trioxacycloheptadecane(NenOdienH_4)$, and 1,15-diaza-3,4 : $1213-dibenzo-5811-trioxacyclooctadecane(NtnOdienH_4)$, were studied by $^{207}Pb-NMR$ spectroscopy in N,N'-dimethylformamide(DMF) solutions. The associative-dissociative mechanism dominated in $NtnOtnH_4-Pb(II)$ and $NtnOdienH_4-Pb(II)$ system. For $NenOdienH_4-Pb(II)$ system, the bimolecular exchange mechanism prevailed below $-5^{\circ}C$, and both bimolecular exchange and associative-dissociative mechanism dominated above $+5^{\circ}C.$ The order of activation energies for dissociation was $NtnOdienH_4\;<\;NtnOtnH_4\;<\;NenOdienH_4$ which was reverse to the order of stabilities.

• Natural Product Sciences
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• v.4 no.1
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• pp.51-52
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• 1998

From the chloroform extract of the defatted seeds of jute a new coumarin $C_9H_6O_4$, $m.p.\;178-179^{\circ}C$, was isolated. The structure of the compound was established as 4,7-dihydroxy coumarin on the basis of physical methods viz. $^1H\;NMR,\;^{13}C\;NMR$ and Ms.