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[综合交流] 如何回复审稿人意见(标度法计算了核磁)

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发表于 2021-3-5 21:25:27 | 显示全部楼层 |阅读模式
老师好,我在文章中用了标度法计算了核磁。核磁部分表述如下:考拉  20:59:40
NMR calculation has become an effective means to predict the real structure of natural products, and it is a supplement to judge the geometry structure of natural products using only NMR experimental data. The calculated NMR chemical shifts can effectively screen out the real candidate structures, especially for prediction of the undiscovered crystal structures in natural products [16]. The chemical shifts for compounds 11αM12βTTB and 11αT12βTTB were calculated by the scaling method, which is accurate and time-saving [17]. The first step is to optimize the geometry structure using B3LYP/6-31+G (d,p) level in gas phase, the second step is to compute isotropic shielding constants in Chloroform by the GIAO method and DFT/ mPW1PW91/6-311+G (2d,p) basis set. Finally, the chemical shifts of hydrogen and carbon are converted by scaling method [18]. The experimental and computational datas of 13C and 1H NMR of 11αM12βTTB and 11αT12βTTB were presented in Table 1 and 2.

In addition, we focus on the chemical shifts of oriented hydrogen atoms. For 11αM12βTTB, the chemical shifts are δ3.59 (1H, m, H-3),δ2.02 (1H, d, J = 10.1 Hz, H-9),δ5.41 (1H, t, J = 10.1 Hz, H-11), δ5.05 (1H, d, J = 10.1 Hz, H-12) and δ2.92 (1H, d, J = 7.5 Hz, H-17), and the homologous chemical shifts calculated by scaling method are 3.73, 1.89, 5.43, 4.85 and 3.07 respectively, The absolute error is less than 0.2 ppm. Therefore, it can be considered that the relative conformation of 11αM12βTTB is correct. In the experiment, the chemical shift of H-3" is δ 6.80, while the calculated chemical shift is δ 6.83, which verifies that the substituent R2 is cis structure.

The mean absolute deviation calculated of the two compounds from the table are 1.6 ppm and 1.8 ppm for 13C-NMR, respectively. 0.04 ppm and 0.13 ppm for 1H-NMR chemical shifts, respectively. The theory chemical shifts have good coherence to experimental ones. It is indicated that this method is suitable for the prediction of NMR data of Polyoxypregnane Derivatives, and more importantly, it is of practical significance to judge the true geometric configuration and predict the undiscovered crystal structure. It provides a reliable material basis for the next study of physical and chemical properties, intramolecular and intermolecular interactions and structure-activity relationships of polyoxypregnane derivatives .
审稿人给出了如下的意见:What is the criterion for affirming that the differences are not significant? How does it compare with other possible conformations of the molecules?
请问,我该如何回复啊?



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发表于 2021-3-5 22:09:21 | 显示全部楼层
第一个问题语义不太清楚,如果是指和实验差异大小问题,就说通常小于多少就算差异较小了
如果体系是多构象的,拿molclus做构象搜索,看看其它构象的化学位移情况
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 楼主| 发表于 2021-3-6 04:10:12 | 显示全部楼层
好的卢老师,多谢啦
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