Ligand effects in the rhodium-catalyzed addition of alkynes to aldehydes and diketones. Modification of the β-diketonate ligand

A catalytic amount of dicarbonylacetonato rhodium(I) and a phosphine ligand bearing bulky electron-donating alkyl groups has been shown to generate an effective catalyst for the addition of alkynes to aldehydes and activated ketones under mild, neutral conditions. While previous studies have shown that modification of the phosphine has significant effects on the activity of the catalyst, the role of the β-diketonate ligand has not been probed. Six different β-diketonate rhodium complexes were synthesized and their ability to catalyze the alkyne addition reaction was evaluated. Changing the structure of the β-diketonate ligand can have a noticeable effect on the reaction rate. Acetylacetonate derivatives with strong electron withdrawing groups have a detrimental effect on the catalytic activity, while bulky and electron rich β-diketonate derivatives provide more efficient catalysts.     

Boron-Dependency of Molybdenum Boride Electrocatalysts for the Hydrogen Evolution Reaction

Molybdenum-based materials have been considered as alternative catalysts to noble metals, such as platinum, for the hydrogen evolution reaction (HER). We have synthesized four binary bulk molybdenum borides Mo₂B, α-MoB, β-MoB, and MoB₂ by arc-melting. All four phases were tested for their electrocatalytic activity (linear sweep voltammetry) and stability (cyclic voltammetry) with respect to the HER in acidic conditions. Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy (XPS) for the first time; MoB₂ and β-MoB show excellent activity in the same range as the recently reported α-MoB and β-Mo₂C phases, while the molybdenum richest phase Mo₂B show significantly lower HER activity, indicating a strong boron-dependency of these borides for the HER. In addition, MoB₂ and β-MoB show long-term cycle stability in acidic solution.     

Asymmetric Synthesis of β, γ-β-Hydroxyl-γ-butyrolactones

Chiral β-hydroxyl-γ-butyrolactones have attracted substantial interest in recent years due to their presence inmany strongly active natural products having antitumor, fungicidal, anti-inflammatory activity, and their use as important precursors in natural product synthesis. [1] In the course of the total synthesis of the natural product Tuxpano lide ,[2] we found a concise and efficient strategy on the stereocontrolled synthesis of β-hydroxyl-γ-butyrolactonederivatives from cheap and achiral starting material.     

Synthesis of new 9-hydroxy-α- and 7-hydroxy-β-pyran naphthoquinones and cytotoxicity against cancer cell lines

A synthetic method to obtain α- and β-pyran naphthoquinones 10 and 11 with a hydroxyl substituent on the aromatic ring was developed. Two series of α- and β-pyran naphthoquinones were obtained from the 8-hydroxy-lawsone, and their anticancer properties were evaluated against four tumor cell lines. In general, the new compounds displayed good activity, possibly indicating that these compounds have increased pro-oxidant capacity. The 9-hydroxy-α-lapachone and 7-hydroxy-β-lapachone analogues of the natural products α-lapachone and β-lapachone were successfully produced by this methodology.     

Syntheses Characterization of Chloro-cyclopentadienyltricarbonyl-molybdenum with β-Cyclodextrin Supramolecular

Organotransition metal complex have been extensively used as homogeneous catalysts in organic reactions and much effort has been paid to improve their activity and selectively. Cyclodextrins have been studied as a model of enzyme for selective catalysis. However, so far there are only a few reports on the inclusion compounds of organometallic complexes with cyclodextrins. Breslow et al.repored high acylation rates for β-CD using ferrocene derivatives and assumed β-CD substrate complexes as intermediate [1]..larad et al reported the preparation and propertics of cyclodextrin-ferrocen inclusion compounds as the first example of cyclodextrin inclusion compounds of organotransition metal complexes[2]. Song Le-Xin et al reported the supramolecular inclusion compound of β-cyclodextrin with cyclopentadieny-tricarbonylmanganese [3] .To our knowledge, there are no reports of inclusion compounds of β-CD with molybdenum organometallic complexes. In the present work we described the preparation and properties of the supramolecular of CpMo(CO)3Cl with β-CD in details.     

β-环糊精功能化碳纳米管高效催化氧化肉桂油制备天然苯甲醛

天然苯甲醛是一类重要的食品添加剂.在温和液相反应条件下催化氧化肉桂醛制天然苯甲醛是一个有效的手段,但该过程需要活性高、选择性好和易循环利用的高效催化剂.环糊精(CD)一般是由6-8个D-吡喃葡萄糖单元构成,具有"内疏水、外亲水"的特殊结构,能够与尺寸和形状相近的分子通过分子间的非共价键作用力(如氢键、范德华力及疏水性作用力)形成主客体分子包结物.利用环糊精模拟天然酶来提高反应活性和产物选择性一直是研究者追求的目标,并已被广泛用于调控不同的有机反应过程,如氧化、还原、水解和开环等反应.然而,由于β-环糊精易溶于水,需要将其固载至合适的载体上才能实现其循环重复利用.近年,文献中报道了将β-环糊精固定至纤维素或壳聚糖用于催化肉桂油制天然苯甲醛,结果表明,环糊精与载体的功能基团通过弱相互作用的协同能明显提高肉桂醛氧化性能.然而,从实际应用角度看,这些催化剂的循环使用性能和机械强度还需进一步增强.碳纳米管具有良好的化学稳定性、较强的机械性能和环境兼容性,广泛应用于液相吸附或反应系统.例如,碳纳米管作为一种无金属催化剂被成功用于芳族烃和烷烃的氧化脱氢、氧还原反应、烃或酚的氧化和氨分解以及催化苯甲醇制备苯甲醛等反应体系中.基于环糊精能通过形成主客体包结物的形式明显提高反应选择性,以及多壁碳纳米管能通过形成共轭配合物的形式对溶液中芳香化合物具有良好的吸附能力,本文制备了一种β-环糊精功能化多壁碳纳米管,并将其成功用于溶液中肉桂油催化氧化制天然苯甲醛的反应.β-环糊精功能化碳纳米管表现出比环糊精聚合物催化剂更优异的催化性能,在10 min内,肉桂醛转化率和天然苯甲醛选择性能分别达到95%和85%,并且反应体系的活化能从45.66 kJ/mol降至16.33 kJ/mol.循环使用结果显示,这种复合催化剂还具有良好的稳定性和可循环使用性.利用拉曼光谱、透射电镜、红外光谱、X射线衍射、比表面积和热重分析对催化剂进行了系统表征.结果表明,多壁碳纳米管和β-环糊精的协同催化作用是其具有高效催化性能的重要原因.为了进一步研究其催化反应机理,利用量子化学计算对主客体之间的相互作用力进行了探究.结果表明,肉桂醛易通过电子相互作用力吸附至碳纳米管表面,由于环糊精空腔的弱相互作用力更强,肉桂醛更容易进入环糊精空腔,通过环糊精上的羟基与肉桂醛之间O?H···O的氢键相互作用,并通过体系生成的高碳酸根氧化剂(HCO4-),促使肉桂醛C=C不饱和双键断裂生成苯甲醛,而生成的苯甲醛与环糊精之间的弱相互作用低于肉桂醛与环糊精之间的相互作用,苯甲醛可迅速地离开环糊精空腔.因而,β-环糊精和碳纳米管的协同作用可明显提高底物选择性.     

Interfacial and emulsifying properties of designed β-strand peptides

The structural and surfactant properties of a series of amphipathic β-strand peptides have been studied as a function of pH. Each nine-residue peptide has a framework of hydrophobic proline and phenylalanine amino acid residues, alternating with acidic or basic amino acids to give a sequence closely related to known β-sheet formers. Surface activity, interfacial mechanical properties, electronic circular dichroism (ECD), droplet sizing and zeta potential measurements were used to gain an overview of the peptide behavior as the molecular charge varied from ±4 to 0 with pH. ECD data suggest that the peptides form polyproline-type helices in bulk aqueous solution when highly charged, but may fold to β-hairpins rather than β-sheets when uncharged. In the uncharged state, the peptides adsorb readily at a macroscopic fluid interface to form mechanically strong interfacial films, but tend to give large droplet sizes on emulsification, apparently due to flocculation at a low droplet zeta potential. In contrast, highly charged peptide states gave a low interfacial coverage, but retained good emulsifying activity as judged by droplet size. Best emulsification was generally seen for intermediate charged states of the peptides, possibly representing a compromise between droplet zeta potential and interfacial binding affinity. The emulsifying properties of β-strand peptides have not been previously reported. Understanding the interfacial properties of such peptides is important to their potential development as biosurfactants.     

Synthesis of β-Amino Acid Derivatives

In recent years, β-amino acids and their derivatives have attracted considerable attention due to their occurrence in biologically active natural products, such as dolastatins,cyclohexylnorstatine and Taxol. β-Amino acids also find application in the synthesis of β-lactams,piperidines, indolizidines. Moreover, the peptides consisting of β-amino acids, the so-called β-peptides, have been extensively studied recently. Consequently, considerable efforts have been directed to the synthesis of β-amino acids and their derivatives1. In particular, stereoselective synthesis of β-amino acids has been a challenging project, and there are only limited methods available. In this presentation, we report our efforts in this area.     

Preparation,crystal and molecular structure,and evaluation of plant growth regulating activity of guanidinoalkanephosphinates and phosphonates

A series of previously unknown α-guanidinoalkanephosphonous, α- and β-guanidinoalkanephosphonic acids has been prepared in order to study their structures and biological activity. Aminoalkanephosphonous and phosphonic acids have been converted into their guanidino derivatives by means of S-methylisothiourea hydroiodide or cyanamide amidination. The crystal and molecular structures of three guanidino acids have been determined by single-crystal X-ray diffraction. The plant growth regulating activity of all synthesized guanidinoalkanephosphinates and phosphonates has been evaluated on Lepidium sativum. © 1995 John Wiley & Sons, Inc.     

Chalcones XXI: Studies in Potential Germicides of Homocyclic and Heterocyclic Nature

Seventeen heterocyclic and homocyclic chalcone analogues have been synthetically prepared by interaction of respective methyl aryl ketones and substituted benzaldehydes with a view to narrate their germicidal activity against E. coli and S. aureus. Tbe absorption spectra in infrared region has been recorded to show the presence of α, β-unsaturated carbonyl group.     

Cephem-Pyrazinoic Acid Conjugates: Circumventing Resistance in Mycobacterium tuberculosis

Tuberculosis (TB) is a leading source of infectious disease mortality globally. Antibiotic-resistant strains comprise an estimated 10 % of new TB cases and present an urgent need for novel therapeutics. β-lactam antibiotics have traditionally been ineffective against M. tuberculosis (Mtb), the causative agent of TB, due to the organism's inherent expression of β-lactamases that destroy the electrophilic β-lactam warhead. We have developed novel β-lactam conjugates, which exploit this inherent β-lactamase activity to achieve selective release of pyrazinoic acid (POA), the active form of a first-line TB drug. These conjugates are selectively active against M. tuberculosis and related mycobacteria, and activity is retained or even potentiated in multiple resistant strains and models. Preliminary mechanistic investigations suggest that both the POA “warhead” as well as the β-lactam “promoiety” contribute to the observed activity, demonstrating a codrug strategy with important implications for future TB therapy.     

Synthesis of β-Dimethylaminoethyl and α-Hydroxy-β-Dimethylaminoethyl Derivatives from Organolithium Compounds and Tetramethyoxamide

The important biological activity of a variety of aromatic and heterocyclic systems having β-dimethylaminoethyl side chains and their α-hydroxy analogs (c.f. bufotenin, N-methylepinephrine, etc.) has focused the attention of the organic chemist on methods of introducing these functions, and a variety of approaches have been developed. A convenient synthesis has recently been reported³, which utilizes the α-hydroxy-β-dimethylaminoethyl function as an intermediate in the preparation of β-dimethylaminoethyl derivatives, thus providing either or both of these pharmacophoric groups.     

Effect of β-cyclodextrins Derivatives on Steroids Biotransformation by <Emphasis Type="Italic">Arthrobacter simplex</Emphasis>

β-cyclodextrins derivatives (CDs) have applied in steroids biotransformation industry because of their unique properties. However, the effect of β-CDs on the growth rate, activity, conversion, and characters of whole cells has not been concerned. In this study, the growth rate and cellular morphology of Arthrobacter simplex (ASP) pretreated by six kinds of β-CDs were measured. The results showed that most β-CDs inhibited the growth of ASP, among which randomly methylated-β-CDs has the most serve inhibition; however, sulfonic acid-β-CD promoted the growth of cells. The morphology size and the surface of all β-CDs-pretreated cells were changed compared with the control group. Besides, the conversion of cortisone acetate (CA) increased in β-CDs-pretreatment system and β-CDs-containing system, which reached 97.98% in hydroxypropyl-β-cyclodextrin (HP-β-CD) containing-system and 78.69% in HP-β-CD-pretreatment-system, but the dehydrogenase activity of all β-CDs-pretreated cells decreased. β-CDs with higher K value have stronger inclusion ability with CA, and along with the membrane permeability of β-CDs-pretreated cells increased more, but they also have more serve damage on the ASP cells, which is negative to increase the conversion of CA. This study improved our understanding of the effect of β-CDs when they were used in the steroids biotransformation by ASP whole cells, and provided data basis for the selection of suitable CDs for application.     

Novel approach for synthesis of 2:1 permethylated β-cyclodextrin-C60 conjugate

Amphiphilic cyclodextrin-fullerene conjugates have potential biological activity, due to their water solubility. In order to study the influence of the linker of these conjugates on solubility and aggregation, a permethylated β-cyclodextrin-C₆₀ conjugate with a short linker -(CH₂)₂NHCO-, which is attached to the secondary face of β-cyclodextrin was synthesized. Its solubility in water and its UV spectrum in CH₂Cl₂ and water were investigated.     

Synthesis of a number of derivatives of alkaloids and of nitrogen-containing heterocycles and their anticholinesterase activities

N-Methyl- and N-phenylcarbamates based on a number of alkaloids and nitrogen-containing heterocycles have been synthesized, and they have proved to be weak irreversible inhibitors of acetylcholinesterase and butyrylcholinesterase. It has been shown that the choline fragments of the above-mentioned carbamates and their β-methylcholine analogs are reversible inhibitors of both cholinesterases and make a substantial contribution to the anticholinesterase activity. Selective inhibitors of ACE and BuCE have been found among the compounds synthesized.     

A Set of Activity‐Based Probes to Visualize Human (Immuno)proteasome Activities

Proteasomes are therapeutic targets for various cancers and autoimmune diseases. Constitutively expressed proteasomes have three active sites, β1c, β2c, and β5c. Lymphoid tissues also express the immunoproteasome subunits β1i, β2i, and β5i. Rapid and simultaneous measurement of the activity of these catalytic subunits would assist in the discovery of new inhibitors, improve analysis of proteasome inhibitors in clinical trials, and simplify analysis of subunit expression. In this work, we present a cocktail of activity‐based probes that enables simultaneous gel‐based detection of all six catalytic human proteasome subunits. We used this cocktail to develop specific inhibitors for β1c, β2c, β5c, and β2i, to compare the active‐site specificity of clinical proteasome inhibitors, and to demonstrate that many hematologic malignancies predominantly express immunoproteasomes. Furthermore, we show that selective and complete inhibition of β5i and β1i is cytotoxic to primary cells from acute lymphocytic leukemia (ALL) patients.     

Synthesis,characterization of inclusion compounds of amygdalin with β-cyclodextrin and sod-like activity and cytotoxicity on hela tumor cells

In this work is presented the synthesis of the inclusion complexes of amygdalin with β-cyclodextrin by three methods: kneading, co-precipitation and freeze drying and their characterization.The inclusion compounds were synthesized using a molar ratio of amygdalin: β-cyclodextrin of 1:1. Synthesized compounds were analyzed by FTIR spectroscopy, X-rays, thermal analysis and the results confirm the formation of inclusion compounds by amygdalin with β-cyclodextrin.The studies carried out have shown the protective effect of amygdalin-β-cyclodextrin compounds obtained by freeze drying, kneading and coprecipitation against free radicals (SOD-like activity in vivo) and the results of in vitro cell cytotoxicity of the compounds on HeLa cell line compared to pure amygdalin. Compound obtained by freeze drying has the best SOD-like activity and cytotoxicity on HeLa tumor cells, so it may be considered as potential therapeutic agent.     

Synthesis and evaluation of N-phenyl-(2-aminothiazol-4-yl)acetamides with phenoxypropanolamine moiety as selective β3-adrenergic receptor agonists

In the search for potent and selective human β3-adrenergic receptor (AR) agonists as potential drugs for use in treating obesity and non-insulin dependent (type 2) diabetes, a series of N-phenyl-(2-aminothiazol-4-yl)acetamides with phenoxypropanolamine moiety were prepared and their biological activities against human β3-, β2-, and β1-ARs were evaluated. Among these compounds, N-phenyl-(2-phenylaminothiazol-4-yl)acetamide (4 g), N-phenyl-(2-benzylaminothiazol-4-yl)acetamide (4j), and N-phenyl-[2-(3-methoxyphenyl)aminothiazol-4-yl]acetamide (6g) derivatives showed potent agonistic activity against the β3-AR with functional selectivity over the β1- and β2-ARs. In addition, these compounds exhibited significant hypoglycemic activity in a rodent model of diabetes.     

Cytotoxic and insecticidal activities of derivatives of harmine, a natural insecticidal component isolated from Peganum harmala

In a continuing effort to develop novel β-carbolines endowed with better insecticidal activity, a simple high-yielding method for the synthesis of harmine compounds starting from L-tryptophan has been developed and a series of 1,3-substituted β-carboline derivatives have been synthesized and evaluated for their cytotoxicity against insect cultured Sf9 cell line in vitro and insecticidal activities against 4th instar larvae of mosquitos, Culex pipiens quinquefasciatus and mustard aphid, Lipaphis erysimi. The results demonstrated that 1-phenyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (compound 2) and methyl 1-phenyl-β-carboline-3-carboxylate (compound 13) represented the best potential compounds, with Sf9 cells inhibition rates of 71.55% and 60.21% after 24 h treatment at concentrations of 50-200 mg/L, respectively. Both compounds 2 and 13 also showed strong insecticidal activity towards 4th instar larvae of mosquitos with LC(50) values of 20.82 mg/L and 23.98 mg/L, and their LC(90) values were 88.29 mg/L and 295.13 mg/L, respectively. Furthermore, the LC(50) values of compounds 2 and 13 against mustard aphids were 53.16 mg/L and 68.05 mg/L, and their LC(90) values were 240.10 mg/L and 418.63 mg/L after 48 h treatment. The in vitro cytotoxicity of these compounds was consistent with the insecticidal activity in vivo. The results indicated that the 1- and 3-positions of the β-carboline ring deserve further investigation to develop biorational insecticides based on the natural compound harmine as a lead compound.     

Proline–cyclodextrin conjugates: synthesis and evaluation as catalysts for aldol reaction in water

The synthesis of six conjugates of l-proline and β-cyclodextrin and their evaluation as catalysts of aldol reaction in water are described. The results indicated that the nature of the linker between proline and β-cyclodextrin is important for catalytic activity; the one with the most flexible linker gave the best results. Inhibition experiments showed that the cavity of β-cyclodextrin plays a role in the catalysis. Permethylation of the cyclodextrin hydroxyl groups led to higher conversion rates.