Kemeng Shi,Christian Marcus Pedersen,Zhaohui Guo,Yanqiu Li,Hongyan Zheng,Yan Qiao,Tuoping Hu,Yingxiong Wang
The tautomer distributions of d ‑fructose, a popular model compound for biorefinery , in various lower alcohols and DMSO‑ d 6 (ROHs/DMSO‑ d 6 ) mixtures at 298 K were investigated by quantitative 13 C NMR. The tautomer distributions of d ‑fructose in ethanol/DMSO‑ d 6 and methanol/DMSO‑ d 6 with different volume ratios of alcohols to DMSO‑ d 6 were also examined. For these normal alcohols (methanol, ethanol, n ‑propanol and n ‑butanol)/DMSO‑ d 6 , the tautomer distribution of d ‑fructose in methanol/DMSO‑ d 6 exhibited the shortest equilibration time (46 h) and the lowest concentration of β‑furanose (39.0%) at equilibrium. The fraction of fructofuranose (α‑furanose and β‑furanose) at equilibrium and time needed to reach equilibrium in branched chain alcohols/DMSO‑ d 6 obey the following order: 2‑propanol/DMSO‑ d 6 (62.2%, 320 h) > tert ‑butanol/DMSO‑ d 6 (61.6%, 307 h) > 2‑butanol/DMSO‑ d 6 (60.6%, 216 h) > isobutanol/DMSO‑ d 6 (57.8%, 134 h). For the diols/DMSO‑ d 6 , the time for the tautomer distribution of d ‑fructose to reach the equilibrium was found to be: 1,4‑butanediol/DMSO‑ d 6 (113 h) > 1,2‑propanediol/DMSO‑ d 6 (38 h) > ethylene glycol/DMSO‑ d 6 (36 h). For ethanol/DMSO‑ d 6 and methanol/DMSO‑ d 6 with respectively different volume ratios, the experimental results showed that the high concentration of ethanol or methanol increases the conversion rate of tautomers.
Aromatic sulfones are the prevailing scaffolds in pharmaceutical and material sciences. However, compared to their widespread application, the selective deuterium labeling of these structures is restricted due to their electron-deficient properties. This study presents two comprehensive strategies for the deuteration of aromatic sulfones. The base-promoted deuteration uses DMSO-d6 as the deuterium source, resulting in a rapid H/D exchange within 2 h. Meanwhile, a silver-catalyzed protocol offers a much milder option by using economical D2O to furnish the labeled sulfones.
Yulin You,Dongxiao Guo,Weiliang Cui,Zhifan Wang,Chunguo Yang,Yongqiang Lin,Shuqi Wang
Matrix-assisted diffusion-ordered spectroscopy (MA DOSY) technology enables efficient the virtual separation of components in a mixture according to their coefficients (D). In the current research, MA DOSY technology was applied for the analysis of a flavonoid mixture. To establish the method, five representative active flavonoid ingredients, including baicalein, baicalin, quercetin, puerarin and rutinum, were selected for the mixture model. The effects of the type and concentration of the matrix, solvent polarity, and nuclear magnetic resonance (NMR) experimental conditions on the resolution of the DOSY spectrum were investigated. It turned out that sodium dodecyl sulfate (SDS) showed the best performance in increasing the resolution of different analytes, which initially increased to the peak below the added amount of 9 mg, and decreased upon the addition of more SDS. In addition, the five flavonoids showed higher resolution in DMSO–d6than in MeOD. Experimental parameters of DOSY, including the number of scans (NS), dummy scans (DS), and value of the FID data points (TD), were also optimized. Finally, the above optimized method was used for the qualitative analysis of the total flavonoid mixture extracted fromScutellaria baicalensisGeorgi. A total of nine compounds were identified and confirmed by comparing them with mass spectrometry data, which further verifies the practical value of this method upon analyzing flavonoid mixtures and provides some reference significance for the follow-up research.Keywords:NMR;MA-DOSY;flavonoids;mixture separation
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