• Analytical Science and Technology
• /
• v.12 no.6
• /
• pp.509-514
• /
• 1999

The systematic modification of titanium(IV) isopropoxide with acetic acid as a organic additive was done and identifided by FT-IR, $^1H$, $^{13}C$ NMR and UV-Vis spectroscopy. The structure was cbanged after hydrolysis-condensation reaction and drying process. The hydrolysis-condensation rates of modified Ti alkoxide with acetic acid were investigated by $^1H$ NMR spectroscopy. This modified Ti(IV) alkoxide was less reactive toward hydrolysis-condensation reaction than $Ti(OPr^i)_4$, which can be attributed to the stable ligand structure between Ti alkoxide and ligand. The structural change on obtained from gel powders with heat treatment was also observed by FT-IR spectroscopy.

• Archives of Pharmacal Research
• /
• v.3 no.1
• /
• pp.57-64
• /
• 1980

Carbon-13 NMR spectroscopy(abbreviated CMR) is an extremely powerful strategy for the study of natural organic molecules. The information derivable from CMR is often complementary to that obtianed form proton NMR spectroscopy (PMR). Because of low natural abundance of $^{13}C$ nucleus (1.1%) coupled with low inherent sensitivity relative to $^{1}H$ (about 1/64), CMR experiment is approximately 6000 times less sensitive than PMR. Despite of this, now it is possible to measure CMR of small amount of compound by the development of three significant ingenious techniques, i. e. a) computer time-averaging, b) wide-band (or noise modulated) proton decoupling, and c) pulsed Fourier transform (FT) NMR : For general recognition of CMR, its fundamental aspects of CMR are briefly reviewed.

• Archives of Pharmacal Research
• /
• v.17 no.6
• /
• pp.393-397
• /
• 1994

Rhomobifoline and 5,6-dehydrolupanine were isolated for the frist time from the leaves and stems of A. foetida L. indigenous to Saudil Arabia. In addition, five other alkaloids, previously identified in A, foetidia L., namely N-methylcytisine, sparteine, anagyrine, lupanine and cytisine, were isolated. The isolated alkaloids were characterized by UV, $^1-NMR,{\;}^{13}H-NMR,{\;}^{13}C-NMR{\;}and{\;}Mass{\;}spectral{\;}data.{\;}^{13}C-NMR$ data of rhombifoline and 5,6-dehydroupanine are reported for the first time.

• Journal of the Korean Chemical Society
• /
• v.39 no.4
• /
• pp.301-305
• /
• 1995

The cytotoxic metabolites, against the KB cell line, halenaquinone, epispongiatriol and aldisin were isolated from the sponge Spongia sp. collected in September 1992, Manado Bay, Sulawesi in Indonesia. Their structures were elucidated by 1H, 13C NMR, 1H 13C(1 bond) Heteronuclear Multiple Quantum Coherence Spectroscopy (HMQC), 1H 13C(2 and 3 bond) Heteronuclear Multiple Bond Correlation Spectroscopy (HMBC), Electron Impact Mass Spectroscopy (EI ms) and Infrared Spectroscopy (IR).

• Bulletin of the Korean Chemical Society
• /
• v.13 no.2
• /
• pp.179-183
• /
• 1992

A stable solid new inclusion complex with benzaldehyde and $permethyl-\beta-cyclodextrin$ was obtained by recrystallization method. The structure of the $benzaldehyde-permethyl-\beta-cyclodextrin$ inclusion complex in the solid and solution state have been studied by UV, IR, $^1H-NMR$, $^{13}C-NMR$ and FAB-mass spectroscopy.

• Journal of the Korean Magnetic Resonance Society
• /
• v.13 no.1
• /
• pp.15-26
• /
• 2009

The NMR detection of methyl groups is of keen interest because they provide the long-range distance information required to establish global folds of high molecular weight proteins. Using longitudinal $^1H$ relaxation optimization, we achieve a gain in sensitivity of approximately 1.6-fold in the methyl-TROSY and its NOESY experiments for the 38 kDa protein mitogen activated protein kinase p38 in its fully protonated and $^{13}C$ and $^{15}N$ labeled state.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.4
• /
• pp.603-608
• /
• 2005

The $^1H\;and\;^{13}C$ chemical shifts of flavone and its five derivatives were determined completely using the basic 1D and 2D NMR experiments and molecular modeling. Of the six compounds used for our experiments, the NMR data of three compounds were published previously, but we found that the data of two compounds included wrong assignments. Therefore, we report the corrected data and the complete assignments of NMR data of the other three compounds.

• Natural Product Sciences
• /
• v.26 no.2
• /
• pp.171-175
• /
• 2020

Liriodendron tulipifera, belonging to the family Magnoliaceae, is commonly called tulip tree. Four N-acetylated aporphine alkaloids, N-acetylnornuciferine (1), N-acetylanonaine (2), N-acetyl-3-methoxynornuciferine (3), and N-acetyl-3-methoxynornantenine (4) were isolated from the roots of L. tulipifera. Although the purity of each compound (1 - 4) was determined to be 97, 96, 99, and 98%, respectively, the ¹H and ¹³C NMR spectroscopic data of the aporphine alkaloids 1 - 4 displayed all signals in duplicate, indicating the presence of two rotamers due to restricted rotation of N-COCH₃ functionality in solution status. The absolute configurations of 1 - 4 w ere established by measuring specific rotation and comparison with the reported data. This is the first report on the ¹H and ¹³C NMR assignments of N-acetyl-3-methoxynornuciferine (3) and N-acetyl-3-methoxynornantenine (4). This study provides advanced NMR spectroscopic data for the structure determination of rotameric aporphine alkaloids.

• YAKHAK HOEJI
• /
• v.39 no.3
• /
• pp.268-275
• /
• 1995

A novel polyacetylene was isolated from Cirsium spp., as well as five known ones, and its chemical structure was determined as heptadeca-1-en-11.13-diyne-8R, 9S, 10R-triol(1) on the basis of spectral data and chemical reactions. $^{1}$H-and $^{13}$C-NMR data of these polyacetylenes were completely assigned by the appfication of 2D-NMR techniques.

• Bulletin of the Korean Chemical Society
• /
• v.13 no.1
• /
• pp.87-91
• /
• 1992

The structures of the compounds, 1, 2, 3, and 4, which were precursors of analgesics, were confirmed by modern NMR techniques. The complete $^{13}C-NMR$ assignments of these systems were established by applying COLOC (COrrelated spectroscopy for LOng range Couplings), HETCOR (HETeronuclear CORrelated spectroscopy), RCT (Relay Coherence Transfer), and NOE difference spectroscopy. The limitation of COLOC approach which has been widely used recently is discussed.