Differential operator realizations of superalgebras and free field representations of corresponding current algebras

Based on the particular orderings introduced for the positive roots of finite-dimensional basic Lie superalgebras, we construct the explicit differential operator representations of the osp(2r|2n)$\mathit{osp}(2r|2n)$ and osp(2r+1|2n)$\mathit{osp}(2r+1|2n)$ superalgebras and the explicit free field realizations of the corresponding current superalgebras ospk_(2r|2n)$\mathit{osp}{(2r|2n)}_k$ and ospk_(2r+1|2n)$\mathit{osp}{(2r+1|2n)}_k$ at an arbitrary level k. The free field representations of the corresponding energy–momentum tensors and screening currents of the first kind are also presented.     

Selective acylation of ribonucleotides and ribonucleosides with acylimidazoles

Selective acylation of ribonucleotides and ribonucleosides can be achieved by using N-acylimidazole on a preparative scale with good yields (50–80%). For uridine 3′-phosphate (Up): in the presence of MDCAI, the 2′-O-acyl-derivative is the main product, while in the presence of an excess of TEAH, the 5′-O-acyl-derivative is the main product. For ribonucleosides (U_R or A_R or ψ_R): in the presence of MDCAI, the acylations take place preferably at 2′-OH or 3′-OH of ribonucleosides and only 3′-O-acyl-derivatives can be isolated by crystallization; in the presence of an excess of TEAH. 5′-O-acyl-derivative is obtained as the main product. Arabinonucleoside and deoxyribonucleoside are only slowly acylated to form 5′-O-acyl-derivatives as the main products by acylimidazole in the presence of MDCAI. Possible mechanisms of these acylations have been discussed.     

2-酰肼基-5-(2,4-二氯苯基)-1,3,4-(口恶)二唑的合成及环化反应研究

(口恶)二唑衍生物具有抗菌、消炎和调节植物生长等活性[1～5].(口恶)二唑硫醚衍生物也具有一定抗菌活性[6].     

Stereoselective Synthesis via Chiral Pinanone Imine

A serious of new pinanone ketimine, and of which asymmetric alkylation, carbonyl additionand double chiral induction reaction have been studied. The ketimine with π-structure are essential toobtain excellent stereoselectivities in 90%～99%e.e. They are explained by the transition model thatwe proposed.     

系列手性二齿配体在硫醚的不对称氧化反应中的应用

设计合成了系列手性二齿配体,并将它们与Ti(OPr-i)4生成的配合物用于催化硫醚的不对称氧化,考察了配体的结构对反应活性和对映选择性的影响,阐明了手性配体的构型与产物亚砜过量异构体构型间的关系.     

(R)-α-取代苄胺的立体控制合成

通过(+)-樟脑酮亚胺体系的不对称反应已有不少文献报道。近年来,我们曾先后用(+)-樟脑缩甘氨酸特丁酯和(+)-樟脑缩苄胺体系作手性模板,合成了多种生理活性的(R)-α-氨基酸,(R)-α-取代苄胺和β-氨基醇。但产物的光学收率除个别在90％以上外,多数都不高。因此,为寻找具有高的立体选择性的手性模板,我们对天然(+)-樟脑进行结构改造,按Bartlett's方法将樟脑氧化成10-樟脑酸(1),经酰氯化后,在二氯甲烷     

固-液相转移催化合成 Ⅳ.α-甲基丝氨酸及其它氨基酸

利用活化了的氨基酸酯,通过烷基化反应合成α-氨基酸是近年来使用的简便方法。特别是以苯甲醛与简单的氨基酸酯反应生成的Schiff碱为底物,用固-液相转移催化烷基化反应合成a-氨基酸,不仅条件温和,而且操作简便,原料易得,选择性好。我们采用上述方法成功地合成了α-甲基     

Asymmetric Diethylzinc Addition to N-Diphenylphosphinoyl Benzalimine Mediated by Imino Alcohols

As our continuous efforts to search for easily accessible ligands for dialkylzinc addition to imines,[1] in this paper,we would like to present a family of chiral imino alcohols 3 derived from 1,2-diphenyl-2-aminoethanol which will be evaluated for the titled reaction. We believed that this kind of chiral ligands could be good chiral ligands for the diethylzinc addition to imines based on two points: (1) The excellent asymmetrically inductive properties of 1,2-diphenyl-2-aminoethanol and its derivatives have been proven in many reactions. (2) The conformation of the nitrogen in the chiral imines 3 is restricted by imine function which is similar to chiral oxazolines reported in our recent work.     

Determination of nine organophosphorus pesticides in cereals and kidney beans by capillary gas chromatography with flame photometric detection

A method is developed for the determination of nine organophosphorus pesticide residues in cereals and kidney beans by capillary gas chromatography with flame-photometric detection. In this method, dichloromethane is used for clean-up after liquid-liquid extraction. It is shown that good separations are obtained using a fused-silica capillary column (DB-1701) by the optimized temperature program. In the spiked levels of 0.012-0.43 mg/kg, the recoveries are from 83.7% to 107%, with the relative standard deviation between 3.2% and 13% and limits of detection from 8.2 to 15 microg/kg. The method is rapid, sensitive, and practical.