溶剂调控布洛芬乙烯酯酶促水解的立体选择性的热力学研究

采用高效液相色谱研究了不同溶剂体系中褶皱假丝酵母菌脂肪酶（CRL）催化布洛芬乙烯酯水解反应的立体选择性.研究发现,在单一溶剂体系中Eyring曲线呈线性,在10~50 ℃的实验温度内均呈S选择性;在混合溶剂体系中Eyring曲线呈非线性,且观察到不同的转变温度（T_inv）.研究还发现：在亲水性有机溶剂二氧六环/水均相混合溶剂体系中,Eyring曲线的T_inv处立体选择性E 值为极小值,在疏水性有机溶剂异辛烷/水两相混合溶剂体系中,T_inv处E 值为极大值,而在氯仿/水两相混合溶剂体系中,随着温度的变化,立体选择性发生了反转.     

One-Pot Stereoselective Synthesis of Alkyl (Z)-2-[4-Oxo-3-phenyl-2-(phenylimino)-1,3-thiazolan-5-yliden]acetates from Acetylenic Esters and N,N′ -Diphenylthiourea

N, N′ -diphenylthiourea reacts with dialkyl acetylenedicarboxylates in acetone to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl (Z)-2-[4-oxo-3-phenyl-2-(phenylimino)-1,3-thiazolan-5-yliden]acetates in fairly good yields. NMR spectra indicated that the reaction is completely stereoselective.     

The Synthesis of Amino Acid Methyl Ester 5′-Phosphoamidates of Protected Uridine

In this article, we used the Atherton–Todd reaction to synthesize amino acid methyl ester 5′-phosphoamidates of uridine as prodrugs. Their structures were confirmed by ¹H NMR, ³¹P NMR, ¹³C NMR, IR, and mass spectrometry.

Supplemental materials are available for this article. Go to the publisher′s online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Anti‐static Agent Containing Zinc Oxide and its Modification for PA6 Fiber

A new anti‐static agent was synthesized from zinc oxide‐adipic acid‐polyethylene glycol and caprolactam by three‐step reactions. The antistatic agent (called poly(ether ester amide zinc oxide) or PEEAZ) was analyzed by IR and DSC. The results showed that zinc oxide existed in the main chain of PEEAZ. The glass temperature and melt temperature of poly(ether ester amide zinc oxide) (referred to as PEEAZ in the following) decreased with increasing poly(ether ester zinc oxide) increasing in PEEAZ. Antistatic PA6 fiber was obtained by adding PEEAZ 2–8% (wt/wt) to PA6 during blend spinning. The specific resistance and the static half‐value period of PA6 fiber was less than 10⁹Ω · cm and 60 sec, respectively. Excellent antistatic property remained after being washed 30 times.     

Hypervalent Iodine in Synthesis XXXIV: Palladium-Catalyzed Coupling Reaction of o-Hydroxyarylaldehydes with Hypervalent Iodonium Salts Via Cleavage of the Aldehyde C-H Bond

A novel way of preparation for o-hydroxyarylketones with mild conditions and good yields by palladium-catalyzed coupling reaction of o-hydroxyarylaldehydes with hypervalent iodonium salts via the cleavage of the aldehyde C-H bond has been reported.     

An appraisal of the Suzuki cross-coupling reaction for the synthesis of novel fluorescent coumarin derivatives

We report the chemical design and development of 3-aryl-substituted 7-alkoxy-4-methylcoumarins with enhanced fluorogenic properties. The 3-aryl substituents are installed via an optimized Suzuki–Miyaura cross-coupling (SMC) reaction between a 7-alkoxy-3-bromo-4-methylcoumarin and aryl boronic MIDA esters using Pd(OAc)₂/XPhos in a catalytic system with K₂CO₃ in aqueous THF. Under these conditions, an exocyclic ester functionality is found to be unaffected. Subsequent saponification revealed a carboxylic acid functionality that is suitable for conjugation reactions. Evaluation of their fluorescence properties indicated that the installed 3-heteroaryl substituent, particularly benzofuran-2-yl, resulted in a significant red shift of both the excitation and emission wavelengths.     

Improved Stabilities of Labeling Probes for the Selective Modification of Endogenous Proteins in Living Cells and In Vivo

To date, various affinity-based protein labeling probes have been developed and applied in biological research to modify endogenous proteins in cell lysates and on the cell surface. However, the reactive groups on the labeling probes are also the cause of probe instability and nonselective labeling in a more complex environment, e. g., intracellular and in vivo. Here, we show that labeling probes composed of a sterically stabilized difluorophenyl pivalate can achieve efficient and selective labeling of endogenous proteins on the cell surface, inside living cells and in vivo. As compared with the existing protein labeling probes, probes with the difluorophenyl pivalate exhibit several advantages, including long-term stability in stock solutions, resistance to enzymatic hydrolysis and can be customized easily with diverse fluorophores and protein ligands. With this probe design, endogenous hypoxia biomarker in living cells and nude mice were successfully labeled and validated by in vivo, ex vivo, and immunohistochemistry imaging.     

Synthesis of a C(sp2)-bridged Phosphine-Borane by Ionic Coupling

The vinyl carbenoid H₂C=CBr(Li) has been used as key precursor to prepare a geminal C(sp²)-bridged phosphine-borane. Starting from bromoethene, two sequences of lithiation/electrophilic trapping, with ClPiPr₂ and FBMes₂ respectively, affords iPr₂P–C(=CH₂)–BMes₂ 3 [Mes = 2,4,6-(H₃C)₃C₆H₂]. This new phosphine-borane 3 was characterized by multi-nuclear NMR and mass spectroscopy. It adopts a monomeric open structure without P→B interaction. A few crystals of a secondary product 4 were analyzed by X-ray diffraction, revealing an unusual dimeric structure.     

Asymmetric Synthesis of Some Chiral Aryl and Hetero Aryl-Substituted β-, γ-, δ-Hydroxy Esters

Sixteen chiral β-, γ-, and δ-hydroxy esters with aryl, substituted aryl, and heteroaryl groups 2a–2s were synthesized by the asymmetric reduction of their corresponding keto esters 1a–1s as chiral pure reference compounds and starting materials. The asymmetric reduction was achieved by (R)-Me-CBS-oxazaborolidine. Ten new chiral γ- and δ-hydroxy esters 2d, 2e, and 2j–2s were obtained with high ee values and characterized by infrared, NMR (¹H and ¹³C), mass spectrometry, chiral high-performance liquid chromatography, and specific rotation.     

Proton exchange membrane prepared by blending polybenzimidazole with poly (aminophosphonate ester)

In this article, we report a new amorphous-crystalline polymer blend system consisting of poly (4, 4′-diphenylether-5, 5′-bibenzimidazole) (OPBI) and poly (aminophosphonate ester) (PAPE) polymers, the membranes of which were fabricated using the solution blending route. A series of blend membranes at different ratios were prepared and systematically analysed for chemical interactions, morphological changes and their physico-chemical properties studied for use as proton exchange membrane. While FT-IR spectroscopy established the hydrogen bonding interactions between N–H of OPBI and phosphonate ester group of PAPE, X-ray diffraction studies revealed the development of crystallinity in the membrane matrix. Interestingly, the gradual induction of crystallinity in an amorphous OPBI matrix was found to influence the properties of the blend membranes favourably. For instance, the blend membrane containing 25 wt% PAPE in OPBI matrix displayed the maximum property enhancement in terms of storage modulus, glass transition temperature (T_g), phosphoric acid (PA) doping level (37 mol/OPBI repeat unit) and most importantly proton conductivity (0.135 S/cm at 180 °C) which is almost twice the value for pristine OPBI (0.05 S/cm at 180 °C) under identical conditions. Although improved properties were observed at other blend ratios as well, the studies ascertain that the membrane with 25 wt% PAPE was found to be the threshold ratio up to which properties increase and beyond which i.e. at >25 wt% PAPE, there is a decrement in properties like mechanical stability and proton conductivity. An important reason for this was attributed to the creation of a right balance of amorphous and crystalline domains and appropriate intra and inter-polymer hydrogen bonding interactions in the matrix of 75/25 (OPBI/PAPE) blend membrane.