• 약학회지
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• 제33권3호
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• pp.203-205
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• 1989

A method is presented for calculating the $^{13}C$ chemical shifts produced in liquid solution by referenced relative to RF frequency. The method is useful to get the real variations of chemical shifts in magnetic field by eliminating the affects of the variation of a reference substance.

• 약학회지
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• 제32권3호
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• pp.164-169
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• 1988

$^{13}C$ NMR chemical shifts for 18 ${\alpha}-susbstituted$ toluenes at high dilution in $CCl_4$ solution have been determined. Substituents are as follows: H, Me, Et, n-Pr, iso-Pr, Ph, F, Cl, Br, $NH_2$, NHMe, $NMe_2$, OH, OMe, OCOMe, $CO_2Me$, $CO_2Et$, CN. Those chemical shifts of the methylene carbon of the toluene and the ${\alpha}-carbon$ of the n-butane systems are correlated well. (r=.975, slope=.962)

• 생약학회지
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• 제18권3호
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• pp.151-167
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• 1987

The $^{13}C-NMR$ chemical shifts of amyrins and their derivatives published up to an early spring of 1987 are listed and a number of methods for signal assignment are explained. A list of 214 amyrins, the $^{13}C-NMR$ chemical shifts of which have been assigned, is included.

• Bulletin of the Korean Chemical Society
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• 제20권6호
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• pp.667-671
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• 1999

A series of the para-substituted 7-aryl-norbornadienyl cation (3) was prepared in FSO3H/SO2ClF solution at -100℃ and their 13C NMR shifts were measured at -80℃. The plots of the chemical shifts (changes in chemical shifts) of cationic carbon, ΔδC+, aganist our calculated new substituent constant, σc+s, gave an excellent correlation (r=0.994), with a ρc+ value of 12.63. These results indicate that the new substituent constants, σc+s, can be successfully employed to compare the relative charge demand of the carbonium ion by π-and πσ-participation.

• Bulletin of the Korean Chemical Society
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• 제19권8호
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• pp.847-851
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• 1998

13C, 15N, and 29Si NMR chemical shifts have been computed for selected X-substituted silatranes (X=Cl, F, H, CH3) using Gauge-Including Atomic Orbitals (GIAO) and Continuous Set of Gauge Transformations (CSGT) at the Hartree-Fock level of theory. The isotropic 13C chemical shifts are largely insensitive to substituent-induced structural changes. In this study, the isotropic 13C chemical shifts GIAO and CSGT calculations at the HF/6-31G and HF/6-31G* levels are sufficiently accurate to aid in experimental peak assignments. The isotropic 13C chemical shifts X-substituted silatranes at HF/6-31G* level are approximately 4 ppm different from the experimental values. In contrast, the isotropic 15N and 29Si chemical shifts and the chemical shielding tensors are quite sensitive to substituent-induced structural changes. These trends are consistent with those of the experiment. The 15N chemical shift parameters demonstrate a very clear correlation with Si-N distance, especially when we use the polarization function. Changes in anisotropy, 3a as well as in the 15N isotropic chemical shifts are due primarily to changes in the value of a.. But in case of "Si the correlations are not as clean as for the 15N chemical shift.

• 분석과학
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• 제7권2호
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• pp.213-224
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• 1994

선택적으로 중수소를 치환시킨 싸이클로옥타논의 여러 동위원소 이성질체들을 합성하였다. 고유동위원소 효과에 의해 영향을 받는 $^{13}C$ NMR 화학적 이동값들을 각 이성질체에 대해 저온에서 계통적으로 관찰하였다. 특히 싸이클로옥타논이 선호하는 안정한 형태 이성질체인 클 boat-chair 형과 연관시켜 이 효과들을 논의하였다.

• Bulletin of the Korean Chemical Society
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• 제19권8호
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• pp.836-840
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• 1998

The intrinsic and equilibrium isotope effects on the 13C NMR chemical shift of the cyclooctanone-2-D were investigated. Equilibrium constants and changes in the free energies, enthalpy, entropy, which are derived from the temperature dependence of the isotope shifts, are reported for this isotopomer.

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.81-84
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• 2008

In the present study, we report 1H and 13C NMR data of 19 methoxyflavonol derivatives with different substitution patterns on A- and B-ring. In addition, the influence of the methoxy substituents in A- and B-ring on the 1H and 13C NMR chemical shifts is discussed: the 1H and 13C chemical shifts of and the number of methoxyl groups provided information allowing elimination of many structural isomers from consideration and in certain instances greatly simplified structural elucidation.

• 생약학회지
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• 제11권3_4호통권43호
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• pp.153-162
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• 1980

1) The hydroxy-substitution in the simple phenolic compounds follows an additivity rule in the chemical shifts of their aromatic carbon atoms. In para-and ortho-effects is a good agreement between calculated and measured values, but the meta-effect is not certain. 2) The additivity rule was applied to assign the chemical shifts of catechins. 3) The nuclear overhauser effect was applied to assign the chemical shifts of C-8 and C-6 atoms of catechins and their polymer. The signal of C-8 is lower in intensity and appear in lower field than C-6. 4) The results of the NOE were applied to determine the bonding positions of catechin units in the catechin dimer and trimer. The bonding positions are C-8a and C-8b atoms of the second and third catechin units. 5) It was tried to determine the conformation of the catechin dimer and trimer by analysing the signal shapes of C-3' and C-4' atoms in the catechol moieties. The catechol moieties lie in opposite side in the dimer and trimer structure. A combined analysis of $^{13}C-and\;^1H-NMR$ results lead to the suggestion that such a catechin polymer is a zigzag planar form.

• Journal of Ginseng Research
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• 제20권1호
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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.