4385-56-2Relevant academic research and scientific papers
Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment
Cheng, Xi-Chuang,Guo, Xin-Ran,Liu, Hua-Min,Liu, Yu-Lan,Qin, Zhao,Wang, Xue-De
, p. 4348 - 4358 (2020/09/22)
Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of β-O-4′ linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.
Method for selective demethylation of ortho-trimethoxybenzene compounds
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Page/Page column 6, (2017/04/03)
The invention relates to a method for selective demethylation of ortho-trimethoxybenzene compounds and provides a method for preparation of 2,6-dimethoxyphenol derivatives by selective demethylation of ortho-trimethoxybenzene in different substitution types. By taking substitutional or non-substitutional ortho-trimethoxybenzene as a raw material, taking ZrCl4 as a catalyst and taking anisole as an additive, a ratio of the raw material to the catalyst to the additive is optimized in a reaction process to realize selective demethylation at a low reaction temperature ranging from the room temperature to 60 DEG C. The method has the advantages of mild reaction conditions, safety, reliability, low cost and easiness in operation and acquisition of the additive and the catalyst for reaction, simplicity and easiness in separation of reaction products, wide substrate application range and the like. The method effectively improves reaction safety and controllability and has an extensive application prospect in preparation of medicines, material intermediates and fine chemicals.
2-Diazo-1-(4-hydroxyphenyl)ethanone: A versatile photochemical and synthetic reagent
Senadheera, Sanjeewa N.,Evans, Anthony S.,Toscano, John P.,Givens, Richard S.
, p. 324 - 341 (2014/02/14)
α-Diazo arylketones are well-known substrates for Wolff rearrangement to phenylacetic acids through a ketene intermediate by either thermal or photochemical activation. Likewise, α-substituted p-hydroxyphenacyl (pHP) esters are substrates for photo-Favorskii rearrangements to phenylacetic acids by a different pathway that purportedly involves a cyclopropanone intermediate. In this paper, we show that the photolysis of a series of α-diazo-p- hydroxyacetophenones and p-hydroxyphenacyl (pHP) α-esters both generate the identical rearranged phenylacetates as major products. Since α-diazo-p-hydroxyacetophenone (1a, pHP N2) contains all the necessary functionalities for either Wolff or Favorskii rearrangement, we were prompted to probe this intriguing mechanistic dichotomy under conditions favorable to the photo-Favorskii rearrangement, i.e., photolysis in hydroxylic media. An investigation of the mechanism for conversion of 1a to p-hydroxyphenyl acetic acid (4a) using time-resolved infrared (TRIR) spectroscopy clearly demonstrates the formation of a ketene intermediate that is subsequently trapped by solvent or nucleophiles. The photoreaction of 1a is quenched by oxygen and sensitized by triplet sensitizers and the quantum yields for 1a-c range from 0.19 to a robust 0.25. The lifetime of the triplet, determined by Stern-Volmer quenching, is 31 ns with a rate for appearance of 4a of k = 7.1 × 10 6 s-1 in aq. acetonitrile (1:1 v:v). These studies establish that the primary rearrangement pathway for 1a involves ketene formation in accordance with the photo-Wolff rearrangement. Furthermore we have also demonstrated the synthetic utility of 1a as an esterification and etherification reagent with a variety of substituted α-diazo-p- hydroxyacetophenones, using them as synthons for efficiently coupling it to acids and phenols to produce pHP protect substrates. The Royal Society of Chemistry and Owner Societies.
P-Hydroxyphenacyl photoremovable protecting groups Robust photochemistry despite substituent diversity
Givens, Richard S.,Stensrud, Kenneth,Conrad, Peter G.,Yousef, Abraham L.,Perera, Chamani,Senadheera, Sanjeewa N.,Heger, Dominik,Wirz, Jakob
, p. 364 - 384 (2011/06/22)
A broadly based investigation of the effects of a diverse array of substituents on the photochemical rearrangement of p-hydroxyphenacyl esters has demonstrated that common substituents such as F, MeO, CN, CO2R, CONH2, and CH3 have little effect on the rate and quantum efficiencies for the photo-Favorskii rearrangement and the release of the acid leaving group or on the lifetimes of the reactive triplet state. A decrease in the quantum yields across all substituents was observed for the release and rearrangement when the photolyses were carried out in buffered aqueous media at pHs that exceeded the ground-state pKa of the chromophore where the conjugate base is the predominant form. Otherwise, substituents have only a very modest effect on the photoreaction of these robust chromophores.
Synthesis and evaluation of 4-hydroxyphenylacetic acid amides and 4-hydroxycinnamamides as antioxidants
Jung, Young-Sik,Kang, Tae-Souk,Yoon, Joong-Ho,Joe, Bo-Young,Lim, Hee-Jong,Seong, Churl-Min,Park, Woo-Kyu,Kong, Jae-Yang,Cho, Jungsook,Park, No-Sang
, p. 2599 - 2602 (2007/10/03)
4-Hydroxyphenylacetic acid amides and 4-hydroxycinnamamides were synthesized and their antioxidant and neuroprotective activities were evaluated. Among the prepared compounds, 6f, 6g, 8b, and 9 exhibited potent inhibition of lipid peroxidation in rat brain homogenates, and marked DPPH radical scavenging activities. Furthermore, 6f, 6g, and 9 exhibited neuroprotective action against the oxidative damage induced by the exposure of primary cultured rat cortical cells to H2O2, xanthine/xanthine oxidase, or Fe2+/ascorbic acid. Based on these results, we found that 6f was the most potent antioxidant among the compounds tested.
Synthesis of 3-alkoxy-4-hydroxyphenylacetic acids from methyl 3-alkoxybenzoates
Jung,Kang,Lee,Seong,Ham,Park
, p. 455 - 462 (2007/10/03)
3-Alkoxy-4-hydroxyphenylacetic acids 4 were obtained from 3-alkoxyl-substituted methyl benzoates 1 by reductive alkylation, followed by allylic oxidation and hydrolysis.
