Diastereoselective synthesis of functionalized tetrahydro-γ-carbolines via a [3 + 3] cycloaddition of 2,2′-diester aziridines with β-(indol-2-yl)-α,β-unsaturated ketones

A Sc(OTf)₃-catalyzed [3 + 3] cycloaddition of 2,2′-diester aziridines with β-(indol-2-yl)-α,β-unsaturated ketones was developed, affording polysubstituted tetrahydro-γ-carbolines in single diastereoisomers in good to excellent yields.     

Asymmetric Negishi reaction for sterically hindered couplings: synthesis of chiral binaphthalenes

A new synthetic approach affording, for the first time chiral binaphthalene derivatives via an asymmetric Negishi reaction, in good yields (55–95%) and good enantioselectivities (49–85% ee), is reported.     

Increasing the enantioselectivity of cyclopentanone monooxygenase (CPMO): profile of new CPMO mutants

A series of cyclohexanones substituted at the 4-position with a selection of hydrophobic and hydrophilic groups were used as substrates in the evaluation of six new cyclopentanone monooxygenase (CPMO) mutants. These mutants were obtained through evolutionary modifications in two specific regions of the CPMO’s putative active site. Several mutant enzymes with improved enantioselectivity were identified. Analysis of the results, in terms of a diamond model, illustrates how a family of cyclohexanone substrates may be used to explore putative active sites of Baeyer–Villiger monooxygenases (BVMOs) and to design productive mutations for specific substrates.     

光敏型季铵盐类阳离子表面活性剂的合成及表面活性和泡沫性质

本文报道了一种光敏型的阳离子表面活性剂（AZO），其分子结构中含有偶氮苯基团，并研究了光照对表面活性和泡沫性能的影响。经紫外光照射后，表面活性剂的饱和吸附量（Г_max）减小，临界胶束浓度（cmc）、最低表面张力（γ_cmc）和分子极限占有面积（A_min）增大；气泡数目增多，直径变小，发泡能力和泡沫稳定性降低。实验结果证实，该表面活性剂的表面活性和泡沫稳定性可以用光照进行调控。     

Conformation and size of humic substances: Effects of major cation concentration and type,pH, salinity,and residence time

The macromolecular structure of humic substances (HS), i.e. molecular size, shape, conformation, and weight is believed to control key physico-chemical reactions in aquatic systems. However, these properties of HS are still deeply a matter of debate. Furthermore, they are affected by solution physico-chemical parameters such as ionic strength, pH, and chemical composition, etc. To better understand aggregation processes of HS in natural waters, the effects of cation concentration and type, water composition, and pH on the size and conformation of the Suwannee River Humic Acid (SRHA) were investigated with synthetic solutions. The size and the conformation of the SRHA in NaCl and CaCl₂ solutions at different concentrations (0.001–0.5 M) and pH (4.5–9.3) were determined using the photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM), respectively. In addition, dissolved organic matter (DOM) samples collected from the Adour estuary along a salinity gradient were imaged by TEM. The average size of the SRHA measured by PCS increased with pH and ionic strength. This behavior was confirmed by TEM micrographs. The increase in pH and CaCl₂ engendered aggregation of the SRHA. Two aggregation steps were identified, a big increase in HS size occurred for small changes in CaCl₂ concentrations in the range <0.02 M CaCl₂, and a slight increase occured for higher concentrations in the range >0.02 M CaCl₂. The parallel analysis of SRHA by PCS and TEM allowed overcoming the limits for both techniques.Comparable results were found for the DOM samples from the Adour estuary (South West of France). The conformation and size of the HS network of these samples varied with the salinity gradient. TEM images demonstrated that, HS have a branched open network in freshwater whereas they have a more compacted and close network with increasing salinity.     

赖氨酸-Ag反应机理的研究

The interaction of silver(Ⅰ) ion with lysine has been investigated by UV-Vis, fluorescent spectra and electrophoresis method. The effect of pH medium and multicomponent concentration on interaction of lysine-silver has also been studied. Lysine-silver system showed maximum absorbance at 239 nm and 448 nm. Lysine showed fluorescence. The fluorescence excitation wavelength was about 356.6 nm (fluorescence emission wavelength was about 438.6 nm). When the reaction of silver(Ⅰ) ion with lysine happened, fluorescence was quenching. Lysine-silver system carried negative charge, and the electrokinetic potential of double electrode layer was -2.35×10^-4 V.     

3-氟-6-碘吡嗪-2-羧酸甲酯的合成及晶体结构

以3-氨基吡嗪-2-羧酸为原料，经酯化反应、亲电反应和重氮化反应合成了3-氟-6-碘吡嗪-2-羧酸甲酯（1），总收率62.34%，其结构经¹H NMR、¹³C NMR和MS确证，用X-单晶衍射法测定了化合物的晶体结构。结果表明：1（CCDC: 1986368）属单斜晶系，空间群C2/c，晶胞参数a=17.6566(5) Å, b=4.74850(10) Å，c=19.6368(6) Å，β=95.6540(10)°，V=1638.39(8) ų，Z=8，R_gt(F)=0.0173，wR_ref(F²)=0.0465，F(000)=1056，μ=3.885 mm^-1。      

THPep: A machine learning-based approach for predicting tumor homing peptides

In the present era, a major drawback of current anti-cancer drugs is the lack of satisfactory specificity towards tumor cells. Despite the presence of several therapies against cancer, tumor homing peptides are gaining importance as therapeutic agents. In this regard, the huge number of therapeutic peptides generated in recent years, demands the need to develop an effective and interpretable computational model for rapidly, effectively and automatically predicting tumor homing peptides. Therefore, a sequence-based approach referred herein as THPep has been developed to predict and analyze tumor homing peptides by using an interpretable random forest classifier in concomitant with amino acid composition, dipeptide composition and pseudo amino acid composition. An overall accuracy and Matthews correlation coefficient of 90.13% and 0.76, respectively, were achieved from the independent test set on an objective benchmark dataset. Upon comparison, it was found that THPep was superior to the existing method and holds high potential as a useful tool for predicting tumor homing peptides. For the convenience of experimental scientists, a web server for this proposed method is provided publicly at http://codes.bio/thpep/.     

Carbene-catalyzed enantioselective annulation of dinucleophilic hydrazones and bromoenals for access to aryl-dihydropyridazinones and related drugs

4,5-Dihydropyridazinones bearing an aryl substituent at the C6-position are important motifs in drug molecules. Herein, we developed an efficient protocol to access aryl-dihydropyridazinone molecules via carbene-catalyzed asymmetric annulation between dinucleophilic arylidene hydrazones and bromoenals. Key steps in this reaction include polarity-inversion of aryl aldehyde-derived hydrazones followed by chemo-selective reaction with enal-derived α,β-unsaturated acyl azolium intermediates. The aryl-dihydropyridazinone products accessed by our protocol can be readily transformed into drugs and bioactive molecules.

Polarity inversion of arylidene hydrazones to react with bromoenals via carbene organic catalysis is disclosed. The reaction enantioselectively affords 6-aryl-4,5-dihydropyridazinones and related drugs with proven commercial applications.     

Chemical composition of the volatile oil from Cynanchum stauntonii and its activities of anti-influenza virus

The volatile oil of the roots of Cynanchum stauntonii was examined by gas chromatography–mass spectrometry (GC–MS). Thirty-eight constituents were identified. (E,E)-2,4-Decadienal, 3-efhyl-4-methypentanol, 5-pentyl-3H-furan-2-one, (E,Z)-2,4-decadienal and 2(3H)-furanone,dihydro-5-pentyl were found to be the major components. The volatile oil exhibited the activities against influenza virus in vitro (IC₅₀s = 64 μg/ml). In in vivo experiment, it prevented influenza virus-induced deaths in a dose-dependent manner.