• Journal of Ginseng Research
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• v.19 no.1
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• pp.45-50
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• 1995

(20S)- and (20R)-protopanaxadiol were prepared from crude ginseng saponin by chemical treatment. The $^{1}H$- and $^{13}C$-NMR signals of these compounds were fully assigned by various NMR techniques such as DEPT, 1H-1H COSY, HMQC, HMBC and NOESY.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.255-259
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• 1985

The NMR chemical shift arising from 4d electron orbital angular momentum and 4d electron spin dipolar-nuclear Spin angular momentum interactions for a $4d^2$ system in a strong crystal field environment of octahedral symmetry has been investigated when the four fold axis is taken as the quantization axis. The NMR results are comparted with the multipolar shift at various R-values and we find that the exact results are in agreement with the multipolar shift when $R{\geqslant}0.20 nm.$ We also separate the NMR shift into the contribution of the $1/R^5$ and $1/R^7$ terms. It is found that the contribution of the $1/R^5$term to the NMR shift is dominant than the contribution of the $1/R^7$ term. Temperature dependence analysis shows that the $1/T^2$ term is the dominant contribution to the NMR shift for a $4d^2$ system but the contribution of the 1/T term may not negligible. The similar results are obtained for a $4d^1$ system from the temperature dependence analysis.

• Bulletin of the Korean Chemical Society
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• v.4 no.2
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• pp.64-67
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• 1983

NMR shift arising from the electron orbital angular momentum and the electron spin dipolar-nuclear spin angular momentum interactions has been investigated for a $4d^{1}$ system in a strong crystal field of octahedral symmetry. To examine the NMR shif for a $4d^{1}$ system in a strong crystal field of octahedral symmetry, we derive a general expression for ${\Delta}$B/B using a nonmultipole expansion technique. From this expression all the multipolar terms are determined. For the $4d^{1}$ system in a strong crystal field of octahedral symmetry the exact solution for NMR shift, ${\Delta}$B, is compared with the multipolar results. ${\Delta}$B/B for the $4d^{1}$ system is also compared with that for the $3d^{1}$ system. It is found that the $1/R^{7}$ term contributes dominantly to the NMR shift. However, there is good agreement between the nonmultipole and multipolar results for R-values larger than 0.2 nm for the $4d^{1}$ system but for R-values larger than 0.4 nm for the $3d^{1}$ system.

• Bulletin of the Korean Chemical Society
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• v.6 no.2
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• pp.63-67
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• 1985

The NMR chemical shift arising from 3d electron spin dipolar nuclear spin angular momentum interactions for a 3d$^2$ system in a strong crystal field environment of octahedral symmetry has been investigated when the fourfold axis is chosen to be our axis of quantization. The NMR shift is separated into the contribution of 1/R$^5$ and 1/R$^7$ terms. A comparision of the multipolar terms with nonmultipolar results shows that the 1/R$^5$ term contributes dominantly to the NMR shift and there is in good agreement between the exact solution and the multipolar results when R ${\ge}$ 0.25. A temperature dependence analysis may lead to the results that the 1/T$^2$ term has the dominant contribution to the NMR shift for a paramagnetic 3d$^2$ system but the contribution of the 1/T term may not be negligible.

• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.961-965
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• 1997

1H NMR spectra of 3,3-dimethylpiperidine (1) at -70 to 30 ℃ exhibit gradual change from slow to rapid exchange between two alternate chair forms. The exchange rate constant was determined as a function of temperature by simulating the line shape of the signal from the two methyl groups using the modified Bloch equations. The resulting free energy of activation is ΔG* = 44.4±1.9 kJ mol-1 at 298 K. The 1H NMR spectrum of a D2O or dimethylsulfoxide-d6 (DMSO-d6) solution containing 1 and [SiW11CoⅡO39]6- exhibits separate signals for the free ligand and the complex, indicating that the ligand exchange is slow on the NMR time scale. In D2O the piperidine ring is frozen as a chair form even at room temperature with the cobalt ion bonded to the axial position of the nitrogen atom. When DMSO-d6 is added to the D2O solution, the NMR spectral change suggests that a rapid exchange occurs between the chair form and another conformer. It is proposed that the conformation of ^b1^b coordinated to [SiW11CoⅡO39]6- in DMSO-d6 is close to a twist form.

• Bulletin of the Korean Chemical Society
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• v.5 no.3
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• pp.93-97
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• 1984

A general expression using the nonmultipole expansion method is derived for the NMR shift arising from 3d electron angular momentum and the 3d electron spin dipolar-nuclear spin angular momentum interactions for a 3$d^2$ system in a strong crystal field environment of octahedral symmetry when the threefold axis is chosen as the quantization axis. The NMR shift is separated to the contribution of constant, $1/R^5\;and\;1/R^7$ terms and compared with the multipolar terms. We find that $1/R^5$ term contributes dominantly to the NMR shift but the contribution of $1/R^7$ term may not be negligible. It is also found that the exact values of the NMR shift are in agreement with the multipolar results for distances larger than 0.35 nm.

• Bulletin of the Korean Chemical Society
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• v.5 no.2
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• pp.55-60
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• 1984

The NMR shift arising from the electron angular momentum and electron spin dipolar-nuclear spin angular momentum interactions has been investigated for a $4d^1$system in a strong crystal field environment of tetragonal symmetry. A general formula for NMR shift is used to compute the NMR shifts along the (100), (010), (001), (110) and (111) axes. We find that from the computed results, the NMR shift along the (100) and (010) axes is consistent with each other in a strong crystal field environment of tetragonal symmetry, but the NMR shift along the (001) axis is about triply greater in magnitude than those along the (100) and (010) axes and is opposite in sign to those along (100) and (010) axes. In this work, we express the expansion coefficients $a_1^{(i)}$ and $b_1^{(i)}$ of $A_i$ and $B_i$ in terms of $g_m^{(i)}$ and $h_m^{(i)}$ and two matrices $c_{lm}$ and $d_{lm}$ of radial dependence. The NMR shift is also separated into the contributions of multipolar terms. We find that $1/R^3$ term contributes dominantly to the NMR shift along the (100), (010), (001) and (110) axes while along the (111) axis $1/R^5$ term dominantly contributes. However, the contribtions of the other terms may not be negligible.

• Journal of the Korean Magnetic Resonance Society
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• v.4 no.2
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• pp.125-132
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• 2000

The detailed $^1$H and $^{13}$ C NMR assignments of a novel sucrose isovaleryl ester isolated from the seed of Euphorbia Lathyris L., were achieved by one-and two-dimensional techniques. The new sucrose ester was characterized as an $\alpha$-D-glucopyranoside, 3,4,6-tris-O-(3-methyl-1-oxobutyl)-$\beta$-D-fructofuranosyl, 2,6-bis(3-methylbutanoate); sucrose 4,7,8,11,12-pentaisovalerate by MS and NMR experiments.

• Journal of Ginseng Research
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• v.20 no.1
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• pp.111-112
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• 1996

The chemical shifts of C-21 and C-23 in the $^{13}C$-NMR for (20R)-protopanaxatriol, (20R)-ginsenoside $Rh_1$ and (20R)-ginsenoside $Rg_3$ were revised by employing some extensive 2D-NMR techniques.

• Journal of the Korean Magnetic Resonance Society
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• v.27 no.2
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• pp.10-15
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• 2023

The Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC) is a powerful method for synthesizing triazoles, even under physiological conditions, without a copper catalyst. This technique provides an efficient means for everyone to synthesize complex triazole derivatives rapidly. In order to investigate the configuration of triazole derivatives using bicyclo[6.1.0.]-nonyne (BCN) and chiral azide, it is necessary to employ the 2D NMR. Both 1D and 2D NMR (COSY, HSQC, ¹⁵N HMBC) are used to analyze the complex triazole product containing cyclooctyne, a diastereomeric product. The stereometric difference of the proton bonded to the same carbon is determined through the HSQC assignment. The intriguing splitting pattern of carbon resonances also reveals their diastereomeric configuration and will aid in further research based on physiological knowledge.