排序方式: 共有38条查询结果,搜索用时 15 毫秒
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Sarah Straßmann Tillman Brehmer Maike Passon Andreas Schieber 《Molecules (Basel, Switzerland)》2021,26(5)
The approach presented in this study is the first for the hemisynthesis of methylated anthocyanins. It was possible to obtain cyanidin-3-O-glucoside derivatives with different degrees of methylation. Cautious identification of 4′-, 5-, and 7-OH monomethylated derivatives was also accomplished. The methylation agent used was the “green chemical” dimethyl carbonate (DMC), which is characterized by low human and ecological toxicity. The influence of the temperature, reaction time, and amount of the required diazabicyclo[5.4.0]undec-7-en (DBU) catalyst on the formation of the products was examined. Compared to conventional synthesis methods for methylated flavonoids using DMC and DBU, the conditions identified in this study result in a reduction of reaction time, and an important side reaction, so-called carboxymethylation, was minimized by using higher amounts of catalyst. 相似文献
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Roberta Bernini Enrico Mincione Fernanda Crisante Maurizio Barontini Giancarlo Fabrizi 《Tetrahedron letters》2007,48(39):7000-7003
The efficiency of dimethyl carbonate (DMC) as chemoselective carbomethoxylating agent of the alcoholic chain of phenols has been investigated. In the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or sulfuric acid as catalysts, new carbomethoxylated phenolic compounds were obtained in quantitative yields. A new efficient derivatization of the aliphatic alcoholic chain of the precious natural hydroxytyrosol is described, which increases the lipophilicity of the hydroxytyrosol. The antioxidant activity of this new carboxymethylated hydroxytyrosol 8 has been investigated using DPPH radical scavenging test. The results showed that this new compound has an antioxidant activity similar to hydroxytyrosol. 相似文献
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Vernica Ibez Gaspar Jasmin McCaul Hilary Cassidy Craig Slattery Tara McMorrow 《Molecules (Basel, Switzerland)》2021,26(20)
The natural compound curcumin has been shown to have therapeutic potential against a wide range of diseases such as cancer. Curcumin reduces cell viability of renal cell carcinoma (RCC) cells when combined with TNF-related apoptosis-inducing ligand (TRAIL), a cytokine that specifically targets cancer cells, by helping overcome TRAIL resistance. However, the therapeutic effects of curcumin are limited by its low bioavailability. Similar compounds to curcumin with higher bioavailability, such as demethoxycurcumin (DMC) and 3,5-bis(2-fluorobenzylidene)-4-piperidone (EF24), can potentially have similar anticancer effects and show a similar synergy with TRAIL, thus reducing RCC viability. This study aims to show the effects of DMC and EF24 in combination with TRAIL at reducing ACHN cell viability and ACHN cell migration. It also shows the changes in death receptor 4 (DR4) expression after treatment with these compounds individually and in combination with TRAIL, which can play a role in their mechanism of action. 相似文献
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新型的承载双金属氰化物络合催化剂 总被引:1,自引:0,他引:1
用双金属氰化物(DMC)络合催化剂可制得相对分子质量高、相对分子质量分布窄和不饱和度低的聚醚多元醇。为提高DMC催化剂的利用率,降低催化剂和聚醚的生产成本,国外开发了承载的DMC催化剂。它不仅可简化聚醚的后处理工艺,而且使聚醚的连续化大规模生产得以实现,因此代表了DMC催化剂的一个重要发展方向。 相似文献
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We employ density functional, post‐Hartree–Fock, and quantum Monte Carlo methods to study the electronic structure, geometries, and behavior of positively charged Hm+ clusters with m=3,5,…,17. Their structure consists of a tightly bound H3+ core ion surrounded by successive solvation shells of H2 molecules. For the largest clusters, we propose new geometries. We find that correlated methods yield the stepwise decrease of enthalpies for dissociation of H2 from the clusters observed in experiments. Our best results are obtained by the diffusion Monte Carlo method, and by including finite temperature entropic effects, we are able to reproduce the experimental dissociation enthalpies with an unprecedented accuracy of less than 0.5 kcal/mol. These benchmark results contrast with erroneous predictions discovered in the density functional approaches. Finally, our analysis of the cluster energy surfaces indicates that under quantum and thermal fluctuations, the outer solvation shells will exhibit pronounced fluctional behavior. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 86–95, 2001 相似文献
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Experimental results are presented for continuous conversion of pretreated hardwood flour to ethanol. A simultaneous saccharification
and fermentation (SSF) system comprised ofTrichoderma reesei cellulase supplemented with additional β-glucosidase and fermentation bySaccharomyces cerevisiae was used for most experiments, with data also presented for a direct microbial conversion (DMC) system comprised ofClostridium thermocellum. Using a batch SSF system, dilute acid pretreatment of mixed hardwood at short residence time(10 s, 220°C, 1% H2SO4) was compared to poplar wood pretreated at longer residence time (20 min, 160°C, 0.45% H2SO4). The short residence time pretreatment resulted in a somewhat (10–20%) more reactive substrate, with the reactivity difference
particularly notable at low enzyme loadings and/or low agitation. Based on a preliminary screening, inhibition of SSF by byproducts
of short residence time pretreatment was measurable, but minor. Both SSF and DMC were carried out successfully in well-mixed
continuous systems, with steady-state data obtained at residence times of 0.58–3 d for SSF as well as 0.5 and 0.75 d for DMC.
The SSF system achieved substrate conversions varying from 31% at a 0.58-d residence time to 86% at a 2-d residence time.
At comparable substrate concentrations (4–5 g/l) and residence times (0.5–0.58 d), substrate conversion in the DMC system
(77%) was significantly higher than that in the SSF system (31%). Our results suggest that the substrate conversion in SSF
carried out in CSTR is relatively insensitive to enzyme loading in the range 7–25 U/g cellulose and to substrate concentration
in the range of 5–60 g/L cellulose in the feed. 相似文献