Biomimetic synthesis of (±)-aculeatin D

A practical, efficient and diastereoselective synthesis of the cytotoxic and antiprotozoal compound aculeatin D (1) is described, employing a biomimetic oxidative cyclisation cascade reaction to generate the tricyclic system of the natural product. The synthesis proceeds in ten steps from commercially available 1-tetradecanol.     

Optimization of polystyrene-supported triphenylphosphine catalysts for aza-Morita-Baylis-Hillman reactions

A series of polar group functionalized polystyrene-supported phosphine reagents were examined as catalysts in the aza-Morita-Baylis-Hillman reactions of N-tosyl arylimines and a variety of Michael acceptors with the aim of identifying the optimal polymer/solvent combination. For these reactions JandaJel-PPh₃ (1 mmol PPh₃/g loading) resin containing methoxy groups (JJ-OMe-PPh₃) on the polystyrene backbone in THF solvent provided the highest yield of all the catalyst/solvent combinations examined. The methyl ether groups were incorporated into JJ-OMe-PPh₃ using commercially available 4-methoxystyrene, and thus such polar polystyrene resins are easily accessible and should find utility as nucleophilic catalyst supports.     

Methods for the synthesis of mono- and polynuclear NH-tetrazoles. (Review)

Data on methods for the synthesis of monocyclic and polynuclear NH-unsubstituted tetrazoles are reviewed.Dedicated to Prof. H. Elguero on the occasion of his 65th birthday.St. Petersburg State Technological Institute (Technical University), St. Petersburg 198013, Russia; Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 867–884, July, 2000.     

Dynamic supported liquid membrane tip extraction of glyphosate and aminomethylphosphonic acid followed by capillary electrophoresis with contactless conductivity detection

A dynamic supported liquid membrane tip extraction (SLMTE) procedure for the effective extraction and preconcentration of glyphosate (GLYP) and its metabolite aminomethylphosphonic acid (AMPA) in water has been investigated. The SLMTE procedure was performed in a semi-automated dynamic mode and demonstrated a greater performance against a static extraction. Several important extraction parameters such as donor phase pH, cationic carrier concentration, type of membrane solvent, type of acceptor stripping phase, agitation and extraction time were comprehensively optimized. A solution of Aliquat-336, a cationic carrier, in dihexyl ether was selected as the supported liquid incorporated into the membrane phase. Quantification of GLYP and AMPA was carried out using capillary electrophoresis with contactless conductivity detection. An electrolyte solution consisting of 12 mM histidine (His), 8 mM 2-(N-morpholino)ethanesulfonic acid (MES), 75 μM cetyltrimethylammonium bromide (CTAB), 3% methanol, pH 6.3, was used as running buffer. Under the optimum extraction conditions, the method showed good linearity in the range of 0.01–200 μg/L (GLYP) and 0.1–400 μg/L (AMPA), acceptable reproducibility (RSD 5–7%, n = 5), low limits of detection of 0.005 μg/L for GLYP and 0.06 μg/L for AMPA, and satisfactory relative recoveries (90–94%). Due to the low cost, the SLMTE device was disposed after each run which additionally eliminated the possibility of carry-over between runs. The validated method was tested for the analysis of both analytes in spiked tap water and river water with good success.     

Mediated Electron Transfer Across Supported Bilayer Lipid Membrane with TCNQ‐Based Organometallic Compounds

Supported bilayer lipid membrane (s‐BLM) containing one‐dimensional compound 1, TCNQ‐based (TCNQ=7,7,8,8‐tetracyanoquinodimethane) organometallic compound {(Cu₂(μ‐Cl)(μ‐dppm)₂)(μ₂‐TCNQ)}_∞, was prepared and characterized on the self‐assembled monolayer (SAM) of 1‐octadecylmercaptan (C₁₈H₃₇SH) deposited onto Au electrode. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results showed that the compound 1, dotted inside s‐BLM, can act as mediator for electron transfer across the membrane. Two redox peaks and the charge‐transfer resistance of 400 kΩ were observed for compound 1 inside s‐BLM. The mechanism of the electron transfer across s‐BLM by TCNQ is by electron hopping while TCNQ‐based organometallic compound is by conducting. Further conclusion drawn from this finding is that the TCNQ‐based organometallic compound embedded inside s‐BLM exhibits excellent electron transfer ability than that of free TCNQ. This opens a new path for the development of s‐BLM sensor and/or biosensor by incorporation with TCNQ‐based organometallic compounds.     

纤维素二乙烯三胺负载钯配合物的制备及对Heck反应的催化性能

通过较简单的方法合成了纤维素二乙烯三胺负载钯(0)配合物,并利用XPS、TG、DTA等手段对其进行了表征。该配合物在室温至230℃范围内有很好的稳定性,在空气氛围、DMSO中能有效地催化丙烯酸、苯乙烯与芳基碘的Heck反应,立体选择性地生成取代的反式肉桂酸、1,2-二苯乙烯,在70℃时反应6h,产率≥66%(丙烯酸、苯乙烯与带取代基芳基碘的Heck反应产率接近100%)。催化剂中起催化作用的是金属态的钯。     

Post‐Grignard Reagents: Influence of the Coligands L on the Molecular Structures of Phenylcalcium Iodides [(L)nCa(R)I] and Calcium Diiodides [(L)nCaI2]

Iodide is a very soft and large anion and as such its extreme ability to be polarized leads to a flat energy surface with respect to the variation of the Ca–I distances in [(L)_nCaI₂] and [(L)_nCa(R)I]. The influence of the donor strength and the bulkiness of the neutral coligands L on the Ca–I distances is studied. The base adducts of calcium diiodide can be isolated after the addition of L to CaI₂ or from the Schlenk equilibrium after the direct synthesis of calcium powder with aryl iodides. As L the ethers diethyl ether (Et₂O), tetrahydrofuran (thf), tetrahydropyran (thp), 1,2‐dimethoxyethane (dme), 18‐crown‐6 (18C6), bis(methoxyethyl)ether (diglyme), and amines tetramethylethylenediamine (tmeda), and hexamethyltriethylenetetramine (hmteta) are studied yielding the adducts [(thp)₄Ca(Ph)I] ( 1a ), [(thf)₄Ca(Ph)I] ( 1b ), [(dme)₂(thf)Ca(Ph)I] ( 1c ), [(18C6)Ca(Ph)I] ( 1d ), and [(tmeda)₂Ca(Ph)I] ( 1e ), as well as [(thp)₄CaI₂] ( 2a ), [(thf)₄CaI₂] ( 2b ), [(Et₂O)₄CaI₂] ( 2c ), [(diglyme)(thf)₂CaI₂] ( 2d ), [(diglyme)(dme)CaI₂] ( 2e ), [(dme)₂(thf)CaI₂] ( 2f ), [(18C6)CaI₂] ( 2g ), [(tmeda)₂CaI₂] ( 2h ), and [(hmteta)CaI₂] ( 2i ). For comparison reasons, [(thf)₄Ca(Ph)Br] ( 3a ), [(thp)₄CaBr₂] ( 4a ), [(thf)₄CaBr₂] ( 4b ), and [(dme)₂(AcOH)CaBr₂] ( 4c ) with AcOH being acetic acid are included as well. The comparison shows that the coordination number of calcium itself only plays an insignificant role whereas bulkiness and donor strength of L represent the key influences.     

Photocatalytic degradation of an azo reactive dye,Reactive Yellow 84, in water using an industrial titanium dioxide coated media

The photocatalytic degradation of an azo reactive dye, Reactive Yellow 84 (RY84), in aqueous solutions using industrial titanium dioxide coated non-woven paper was studied. The experiments were carried out to investigate the factors that influence the dye photocatalytic degradation, such as adsorption, initial concentration of dye, temperature, and solution pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetics constant of degradation. The photocatalytic degradation rate was favored by a high concentration of solution in respect to Langmuir–Hinshelwood model. The degradation was enhanced by the temperature and was favored in acidic pH range.     

选矿药剂二次污染对尾矿重金属释放与迁移的影响

利用柱淋溶实验模拟研究了硫化矿尾矿在不同选矿药剂淋溶条件下的铜、铅、锌、铬重金属离子的污染规律;利用光降解实验模拟研究了选矿药剂二次污染物的产生问题。选矿药剂二次污染对重金属离子的释放与迁移起着重要作用。