Chiral Primary Amine Catalyzed α-Arylation of Simple Ketones via Asymmetric Retro-Claisen Cleavage

Highly enantioselective α-arylation of simple ketones has been achieved by chiral primary amine catalyzed asymmetric retro-Claisen cleavage of β-diketones. This mild organocatalytic strategy enables the construction of α-aryl tertiary carbon stereocenters in good yields and excellent enantioselectivities (up to 98 % ee) with the para-quinone monoimines as aryl sources. Furthermore, oxidative catalytic asymmetric α-arylation has also been realized with free p-aminophenols.     

Nmp-based ionic liquids: Recyclable catalysts for both hetero-Michael addition and Knoevenagel condensation in water

A series of novel N-methyl piperidine (Nmp)-based ionic liquids with 1,2-propanediol group are synthesized and used as catalysts for both hetero-Michael addition of α,β-unsaturated amides and Knoevenagel condensation at room temperature in water; and all the examined substrates could be transformed into corresponding products in good to excellent yields. Meanwhile IL-catalyzed hetero-Michael addition of α,β-unsaturated amides in water has not been reported in the previous literatures. Additionally, the catalyst is recyclable for the two reactions. This finding provides a green catalyst for both hetero-Michael addition of α,β-unsaturated amides and Knoevenagel condensation in water.     

Squaramide catalyzed α-chiral amine synthesis

Enantiomerically pure α-chiral amines, have been commonly utilized as resolving agents and chiral auxiliaries and are currently found in 40% of active pharmaceutical ingredients. Hence, development of highly stereoselective metal-free protocols regarding atom-economy and large-scale applications becomes a major issue. In this respect, chiral bifunctional H-bonding squaramides have been successfully applied for both amine synthesis and functionalization of amines in the last decade. This survey summarizes asymmetric synthesis of chiral amines by various carbon-carbon and carbon-nitrogen bond formation with squaramide catalysis as a particular focus of interest.     

Synthesis,characterization, and biological activity of some complex combinations of nickel with α-ketoglutaric acid and 1-(o-tolyl)biguanide

The four divalent nickel complexes having α-ketoglutaric acid (H₂A) and 1-(o-tolyl)biguanide (TB) ligands have been synthesized, characterized, and tested for antibacterial and antitumor activity.The proposed formulas for these complexes are [Ni(TB)(HA)(H₂O)₂]Cl (C1), [Ni(TB)(HA)(H₂O)₂]Br (C2), [Ni(TB)(HA)]NO₃·H₂O (C3), and [Ni(TB)(HA)]CH₃COO (C4), where HA represents deprotonated H₂A.For the four complexes and for the ligands used in the synthesis, the antibacterial activity against Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853 and antitumor activity in HeLa tumor cells were tested. A moderate cytotoxic effect of C3 and C4 complexes has been observed on the development and metabolic activity of HeLa cells, whereas C1 and C2 ligands have a very low effect on them.The synthesized complexes (obtained) inhibit adherence to the inert substrate of bacterial strains S. aureus and P. aeruginosa; therefore, they may be candidates for (potential) therapeutic applications.     

高灵敏甲胎蛋白夹心免疫传感器的制备

构建了新型甲胎蛋白(AFP)夹心免疫传感器.采用金纳米粒子-氧化石墨烯-普鲁士蓝纳米立方体(AuNP-GO-PBNCs)纳米复合材料标记甲胎蛋白(AFP)二抗,将制备的金-聚多巴胺-四氧化三铁(Au-PDA-Fe3O4)磁性纳米复合物固定在自制的磁性电极表面,通过吸附作用固定AFP一抗,用牛血清白蛋白(BSA)封闭电极上的非特异性吸附位点.在37℃下与AFP抗原溶液孵育50 min,最后将电极放入AuNP-GO-PBNCs纳米复合材料标记的二抗溶液中孵育,基于此建立了采用普鲁士蓝(PB)标记的的夹心免疫传感器检测AFP的方法.在最佳实验条件下,PB催化H2O2氧化的响应电流与AFP的浓度表现出两段线性关系,线性范围分别为0.005~1.000 ng/mL和1~20 ng/mL, 检出限(LOD, S/N=3)为1.0 pg/mL.本方法具有灵敏度高、选择性好的特点.     

碳酸钾与相转移催化剂催化的硝基甲烷与α,β-不饱和酰基吡唑的Michael加成反应

在碳酸钾和18-冠-6的共同催化下,低活性的Michael受体α,β-不饱和酰基吡唑顺利与硝基甲烷发生Michael加成反应,以31%~78%收率合成了5个4-硝基-丁酰基-3,5-二甲基吡唑,其中4个为新化合物,其结构经~1H NMR,~(13)C NMR和HR-MS(ESI)表征。     

Sorption Catalytic Determination of Copper(II) and L-α-alanine on Mg-, Al-Layered Double Hydroxides

Mg-, Al and Mg-, Cu-, Al-layered double hydroxides well-known synthetic hydrotalcite-like sorbents, were used for the first time as carriers for indicators in the sorption catalytic determination of copper(II) and L-α-alanine. Mg-, Al and Mg-, Cu-, Al-layered double hydroxides were synthesized by coprecipitation and characterized using infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The adsorption of 0.50?mg?L^?1 copper(II) solution by Mg-, Al-layered double hydroxides followed a pseudo-second-order model with an equilibrium sorption capacity of 24.2?×?10^?3?mg?g^?1 (3.8?×?10^?4?mmol g^?1) and a reaction rate constant of 4.2?g mg^?1?min^?1. Mg-, Al-layered double hydroxide tablets were prepared and used for sorption concentration and subsequent sensitive and selective sorption catalytic determination of 5.5?×?10^?3 to 1.0?mg?L^?1 copper(II) at the sorbent phase. The method was used for the analysis of natural water. A method was developed for the determination of α-alanine in Mg-, Cu-, Al-layered double hydroxide tablets with a limit of detection of 4.0?×?10^?3 mol?L^?1. In addition, thin layers of Mg-, Cu-, Al-layered double hydroxide were used to separate α-alanine and determine α-amino acids by thin-layer chromatography.     

Unexpected transformations of 3-(bromoacetyl)coumarin provides new evidence for the mechanism of thiol mediated dehalogenation of α-halocarbonyls

The mechanism for the thiol mediated dehalogenation of α-halogenated carbonyls has remained an unresolved problem, despite its ongoing application in synthetic organic chemistry. Nakamura and co-workers first proposed that net dehalogenation occurs via sequential nucleophilic substitutions, while Israel and co-workers concluded that the rate at which dehalogenation occurred suggested that dehalogenation proceeds in a single concerted step. In this study, we investigated the debromination and nucleophilic substitution of 3-(bromoacetyl)coumarin with a variety of thiophenols, whose electron donating or withdrawing natures resulted in large variations in the degree of nucleophilic substitution and dehalogenation products, respectively. Results from these experiments, in addition to an unexpected formation of thioether containing dibenzo[b,d]pyran-6-ones from a Robinson annulation, has provided new evidence for this disputed mechanism.     

Cu(II)-catalyzed enantioselective 1,3-dipolar cycloaddition of nitrones with α, β-unsaturated acyl phosphonates

A highly enantioselective 1, 3-dipolar cycloaddition of nitrone with α, β-unsaturated acyl phosphonate was developed for the first time by using a chiral indane-bis(oxazoline)-copper(II) complex. The reaction proceeded smoothly under mild conditions to provide isoxazolidines with multi-stereocenters in good yields with high to excellent diastereo- (>20:1 dr) and enantioselectivities (up to 99% ee). The resulting products were readily converted to multi-functional isoxazolidines or γ-amino alcohol compounds.     

Regioselective protection of xylose for efficient synthesis of arabino-α-1,3-xylosides

We reported here an efficient regioselective protection strategy for xylose with two-step successive protections on 4- and 2-OH. This method enables the expeditious preparation of various xylose building blocks (3a–c, 5, 6). The rapid selective 2,4-protection especially facilitates the synthesis of 3-substituted xyloside structures. By this approach, typical arabino-α-1,3-xyloside disaccharide and trisaccharide, as fragment structure units from arabinoxylans, have been successfully synthesized.