Discovery of the first non-planar flavonoid that can strongly inhibit xanthine oxidase: protoapigenone 1′-O-propargyl ether

Xanthine oxidase (XO) is a key enzyme in purine metabolism with an important role in various pathologies. Several flavonoids have been reported for their capacity to inhibit this enzyme, and, for these compounds, the ability to adopt a planar 3D structure has been accepted as fundamental prerequisite for such activity. Here we report the in vitro investigation of a series of non-planar protoflavone derivatives as XO inhibitors, among which protoapigenone 1′-O-propargyl ether was found to be an efficient competitive inhibitor of the enzyme with an IC₅₀ value of 3.61 μM, significantly (p <0.001) stronger than the anti-gout drug allopurinol (IC₅₀ = 8.72 μM). Methoxy substitution at C-7, however, resulted in complete loss of activity. In silico docking supported the observed structure–activity relationships, based on which a ‘planar structure’ itself can no longer be considered as a criterion for flavonoid-type inhibitors of XO.     

Synthetic study on neoponkoranol and its side chain epimer as potent α-glucosidase inhibitors,optimization of protecting group

Coupling reaction between thiosugar and triflate as the key protocol to synthesize neoponkoranol, a naturally occurring potent α-glucosidase inhibitor, and its related sulfonium salts was optimized by applying different esters as protecting group, with the yields of desired products being greatly improved. Our proposed mechanism of the coupling reaction indicated that the nucleophilicity of C3-hydroxyl moiety on monosaccharide structure is closely related to the reaction mode.     

Stereoselective quantitation of mecoprop and dichlorprop in natural waters by supramolecular solvent-based microextraction,chiral liquid chromatography and tandem mass spectrometry

Liquid chromatography (LC)/tandem mass spectrometry (MS/MS) after supramolecular solvent-based microextraction (SUSME) was firstly used in this work for the enantioselective determination of chiral pesticides in natural waters. The method developed for the quantitation of the R- and S-enantiomers of mecoprop (MCPP) and dichlorprop (DCPP) involved the extraction of the herbicides in a supramolecular solvent (SUPRAS) made up of reverse aggregates of dodecanoic acid (DoA), analyte re-extraction in acetate buffer (pH = 5.0), separation of the target enantiomers on a chiral column of permethylated α-cyclodextrin under isocratic conditions, and detection of the daughter ions (m/z = 140.9 and 160.6 for MCPP and DCPP, respectively) using a hybrid triple quadrupole mass spectrometer equipped with an electrospray source operating in the negative ion mode. Similar recoveries (ca. 75%) and actual concentration factors (ca. 94) were obtained for both phenoxypropanoic acids (PPAs). The quantitation limits were 1 ng L⁻¹ for R- and S-MCPP, and 4 ng L⁻¹ for R- and S-DCPP, and the precision, expressed as relative standard deviation (n = 6) was in the ranges 2.4–2.7% ([R-MCPP] = [S-MCPP] = 5 ng L⁻¹ and [R-DCPP] = [S-DCPP] = 15 ng L⁻¹) and 1.6–1.8% (100 ng L⁻¹ of each enantiomer). The SUSME-LC–MS/MS method was successfully applied to the determination of the enantiomers of MCPP and DCPP in river and underground waters, fortified at concentrations between 15 and 180 ng L⁻¹ at variable enantiomeric ratios (ER = 1–9).     

Diastereoselective Synthesis of N,N-Dibenzyl-Protected Aminoalkyl Hydroxyethylamines: Key Building Blocks for Hydroxyethylamine-Based BACE1 Inhibitor

L-Amino acids were reduced with NaBH₄ followed by reacting with benzyl bromide to give N,N-dibenzyl-protected aminoalkyl ethanol 3, which in turn underwent a Swern oxidation, a Johnson–Corey–Chaykovsky reaction, and a nucleophilic reaction to afford N,N-dibenzyl-protected aminoalkyl hydroxyethylamine 6 with a diastereomer ratio 2.5～2.9:1 of (2R, 3S)-6:(2S, 3S)-6.     

Microwave‐Assisted Synthesis of cAMP Phosphodiesterase Inhibitor 8‐Hydroxy‐6,7‐dimethoxy‐3‐hydroxymethylisocoumarin

An efficient microwave‐assisted synthesis of 8‐hydroxy‐6,7‐dimethoxy‐3‐hydroxymethyl isocoumarin (1), a metabolite of Streptomyces mobaraensis and structural relative of reticulol and cytogenin that possesses potent cyclic nucleotide phosphodiesterase inhibitor activity, is described. 3,4,5‐Trimethoxyhomophthalic acid (2) was condensed with acetoxyacetyl chloride under microwave irradiation and the acid hydrolysis of resulting 6,7,8‐trimethoxy‐3‐acetoxymethylisocoumarin (3) afforded the 6,7,8‐trimethoxy‐3‐hydroxymethylisocoumarin (4). Regioselective demethylation of the latter using magnesium iodide in THF yielded the title compound (1).     

Asymmetric Synthesis of (S,S,S)-2-Aza-bicyclo-[3.3.0]-octane-3-carboxylic Acid Benzyl Ester: Formal Synthesis of Ramipril

An asymmetric synthesis of (S,S,S)-2-aza-bicyclo-[3.3.0]-octane-3-carboxylic acid benzyl ester 2 as an intermediate of angiotensin converting enzyme (ACE) inhibitor, ramipril 1, is described.

Study of the Inhibition Efficiency for Some Novel Surfactants on the Carbon Steel (Type H-11) Pipelines in 0.5 M HCl Solution by Potentiodynamic Technique

In this article, three deferent surfactants as corrosion inhibitor were prepared in two steps. In the first step, maleic anhydride was amidated with dodecylamine to produce 2-ene-4-dodecanamide butanoic acid. In the second step, the resulting product was further esterified with different molecular weights of polyethylene glycol (m.wt. = 200, 400, and 600), namely, polyoxy ethylenyl-x-ene-4-dodecanamide butanoic acid, where x = 2, 4, or 6 according to molecular weights of polyethylene glycol used). The chemical structures of these inhibitors were confirmed by FTIR and ¹H NMR. The corrosion inhibition effect of the synthesized inhibitors has been investigated on the carbon steel (type H-11) pipelines in 0.5 M HCl solution by the potentiodynamic polarization method. From the obtained results, it was found that the maximum inhibition efficiency (90.44%) was exhibited by polyoxy ethylenyl-6-ene-4-dodecanamide butanoic acid, while the minimum inhibition efficiency (79.84%) was obtained by polyoxy ethylenyl-2-ene-4-dodecanamide butanoic acid at 200 ppm and 35°C. Also, the values of activation energy and thermodynamic parameters were calculated and discussed. Adsorption of the synthesized inhibitors was found to follow the Langmuir's adsorption isotherm. Mixed physical and chemical adsorption mechanism is proposed.     

基于机器学习方法的H1N1神经氨酸苷酶抑制剂的分类预测

流感是一种主要的呼吸道传染病, 在普通人群中有着较高的发病率, 而对于一些年老和高危病人还有较高的死亡率. 研究显示抑制神经氨酸苷酶(NA)可以阻断病毒RNA复制, 因此NA是有效治疗H1N1型流感病毒的重要药物靶标. 通过计算机方法进行虚拟筛选和预测NA抑制剂已经变得越来越重要. 针对酶活性位点进行基于结构的合理药物设计, 开发H1N1 病毒神经氨酸苷酶抑制剂, 已成为药物研究的热点之一. 本文通过多种机器学习方法(支持向量机(SVM)、k-最近相邻法(k-NN)和C4.5决策树(C4.5DT))对已知的神经氨酸苷酶抑制剂(NAIs)与非神经氨酸苷酶抑制剂(non-NAIs)建立分类预测模型. 其中227个结构多样性化合物(72个NAIs与155个non-NAIs)被用于测试分类预测系统, 并用递归变量消除法选择与神经氨酸苷酶抑制剂分类相关的性质描述符以提高预测精度. 本研究对独立验证集的总预测精度为75.9%-92.6%, NA 抑制剂的预测精度为64.3%-78.6%, 非H1N1抑制剂的预测精度为77.5%-97.5%. SVM法给出最好的总预测精度(92.6%). 本研究表明支持向量机等机器学习方法可以有效预测未知数据集中潜在的NA抑制剂, 并有助于发现与其相关的分子描述符.