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101.
Moritz Balkenhohl Harish Jangra Ilya S. Makarov Shu‐Mei Yang Hendrik Zipse Paul Knochel 《Angewandte Chemie (International ed. in English)》2020,59(35):14992-14999
The development of a predictive model towards site‐selective deprotometalation reactions using TMPZnCl?LiCl is reported (TMP=2,2,6,6‐tetramethylpiperidinyl). The pKa values of functionalized N‐, S‐, and O‐heterocycles, arenes, alkenes, or alkanes were calculated and compared to the experimental deprotonation sites. Large overlap (>80 %) between the calculated and empirical deprotonation sites was observed, showing that thermodynamic factors strongly govern the metalation regioselectivity. In the case of olefins, calculated frozen state energies of the deprotonated substrates allowed a more accurate prediction. Additionally, various new N‐heterocycles were analyzed and the metalation regioselectivities rationalized using the predictive model. 相似文献
102.
本文探讨了CT血管造影(CT angiography,CTA)在急性复杂性大咯血患者行介入栓塞术前的应用价值。回顾性选择49例急性复杂性大咯血患者CTA影像资料,通过与术中数字减影血管造影(digital subtraction angiography,DSA)结果进行对比,发现CTA对罪犯血管诊断准确率为89.33%,对多动脉交通吻合诊断准确率为86.96%。Kappa检验CTA与DSA检查结果一致性较高,受试者特征曲线(ROC)分析CTA诊断急性复杂性大咯血罪犯血管的曲线下面积(AUC)为0.947(95%CI:0.903~0.990,P=0.000),灵敏度89.33%,特异度100.00%。通过随访发现CTA指导下行介入栓塞术治疗有效率91.84%,术后1年无大咯血复发病例。 相似文献
103.
104.
FAAS法测钙时磷酸根离子的干扰及消除研究 总被引:1,自引:1,他引:0
研究了用火焰原子吸收光谱法测钙时PO3- 4对钙的测定的干扰情况以及用有关方法消除PO3-4对钙干扰的效果.用La(NO3)3和EDTA单独消除PO3-4的干扰进行了实验研究,同时对有关问题作了讨论.对测定各种样品中的钙时消除PO3-4的干扰有一定的指导意义. 相似文献
105.
壳聚糖混合膜酶降解的FTIR分析 总被引:2,自引:2,他引:0
生物可降解性是壳聚糖的重要性质之一,但利用傅里叶变换红外光谱(FTIR)研究降解过程中壳聚糖的变化则较少。文章制备了由高脱乙酰度壳聚糖(HDC)和中脱乙酰度壳聚糖(MDC)组成的混合膜。运用FTIR分析了壳聚糖混合膜组分变化对其红外谱图和脱乙酰度(DD)的影响,并研究了该混合膜在溶菌酶的降解作用下红外谱图和脱乙酰度的变化。发现壳聚糖混合膜材料的脱乙酰度与膜中MDC组分的比例呈线性关系;随降解的进行,混合膜的脱乙酰度增加。结果证实了溶菌酶对较低脱乙酰度壳聚糖的选择性降解作用,而且表明FTIR可用于分析壳聚糖混合膜降解过程中的化学变化。 相似文献
106.
107.
Caiyun Xu Haihong Wu Zhanrong Zhang Bingxiao Zheng Jianxin Zhai Kaili Zhang Wei Wu Xuelei Mei Mingyuan He Buxing Han 《Chemical science》2022,13(6):1629
Effective hydrodeoxygenation (HDO) of aromatic alcohols is very attractive in both conventional organic synthesis and upgrading of biomass-derived molecules, but the selectivity of this reaction is usually low because of the competitive hydrogenation of the unsaturated aromatic ring and the hydroxyl group. The high activity of noble metal-based catalysts often leads to undesired side reactions (e.g., saturation of the aromatic ring) and excessive hydrogen consumption. Non-noble metal-based catalysts suffer from unsatisfied activity and selectivity and often require harsh reaction conditions. Herein, for the first time, we report chemoselective HDO of various aromatic alcohols with excellent selectivity, using porous carbon–nitrogen hybrid material-supported Co catalysts. The C–OH bonds were selectively cleaved while leaving the aromatic moiety intact, and in most cases the yields of targeted compounds reached above 99% and the catalyst could be readily recycled. Nitrogen doping on the carbon skeleton of the catalyst support (C–N matrix) significantly improved the yield of the targeted product. The presence of large pores and a high surface area also improved the catalyst efficiency. This work opens the way for efficient and selective HDO reactions of aromatic alcohols using non-noble metal catalysts.Porous carbon–nitrogen hybrid material-supported Co catalysts can effectively promote the chemoselective hydrodeoxygenation reaction of a various of aromatic alcohols in ethanol and hydrogen atmosphere, under relatively mild conditions. 相似文献
108.
Dong-Zhao Yang Zhen-Zhen Chen Mei Chi Ying-Ying Dong Shou-Zhi Pu Qi Sun 《Molecules (Basel, Switzerland)》2022,27(3)
5-Hydroxymethyl-2′-deoxycytidine (5hmdC) phosphoramidite and triphosphate are important building blocks in 5hmdC-containing DNA synthesis for epigenetic studies. However, efficient and practical methods for the synthesis of these compounds are still limited. The current research provides an intensively improved synthetic method that enables the preparation of commercially available cyanoethyl-protected 5hmdC phosphoramidite with an overall yield of 39% on 5 g scale. On the basis of facile and efficient accesses to cyanoethyl protected-5hmdU and 5hmdC intermediates, two efficient synthetic routes for 5hmdC triphosphate were also developed. 相似文献
109.
Nonlinear Dynamics - In this paper, a novel fixed-time second-order sliding mode (SOSM) controller has been developed for a class of nonlinear systems with output constraints. Based on the output... 相似文献
110.