Penta-Coordinate Phosphorus Intermediates Analysis on Phospho-related Proteins

In this paper, based on known crystal structures of square pyramid （SP） and trigonal bipyramid （TBP） penta coordinated phosphorus compounds containing amino acid side chains, such as amino, carboxyl, hydroxyl or thiol, a software for survey the P（5）-structure of phosphorylated proteins was derived. By this software, it was found that 382 of 398 phosphorus related kinases （96%） from current PDB could go through the penta-coordinated phosphorus transition state or intermediate.     

Synthesis of L-Aspartic Acid and Lactone Copolymers

Recently,thesynthesisandapplications0fbiodegradablepolydepsipeptides,alternatingcopolymersofa-aminoacidanda-hydroxyacidwithfunctionalside-chaingroupshavedrawnmoreandmoreattentionl'2.Thisisbecausethefunctionalizedpendantgroups0fthep0lydepsipeptidesmakethemusefulf0rthepreparationofavarietyofpolymer-drugconjugates.However,thepolymerizati0nofdepsipeptideswithfuncti0nalgr0upsisratherdifficultduetotheirbigstructuresandsterichindrance.Furthermore,high-molecular-weightpr0ductsofsuitablephysicalpropert…     

(S)-异丝氨酸的合成研究

以L -天冬氨酸为原料 ,经酯化、重氮化 -水解、氨解、Hofmann降解等反应合成了具有良好光学纯度的 (S) -异丝氨酸。总收率不低于35 %     

L-天门冬氨酸二肽的结构与甜味的一些关系

本文报导了一系列L-天门冬氨酸二肽衍生物,NH_2CH(CH_2COOH)CONHCH(COOCH_3)-(COX)(X为烷氧基,烷氨基,邻位取代苯胺基及N-甲基苯胺基)的合成和它们的甜度。这些二肽尾部的电性能、憎水性、以及整个分子的链长(在满足一定立体要求的条件下)都影响着二肽的甜度。     

磷酸体系中微量稀土元素萃取回收技术研究

研究了从磷矿硫酸湿法制备磷酸过程中回收伴生稀土元素的萃取分离技术,首先进行了不同萃取剂的筛选,同时考察了萃取剂浓度、磷酸浓度、相比、反应温度、杂质元素等对稀土萃取率的影响.结果表明:在该体系下,P204(二(2-乙基己基)磷酸)单独萃取稀土的能力最强,而且较高的萃取剂浓度、较大相比及低的磷酸浓度有利于稀土的萃取,不同杂质对稀土萃取存在不同程度的影响;并对萃取反应机制进行了考察,得到P204在磷酸介质中萃取微量稀土的反应式,该萃取反应的焙变△H<0,为放热反应.     

“可乐”与磷酸

“可乐”亦称可口可乐,是一种软饮料(与含酒精的“硬”饮料相区别)。因起初由可乐豆提取汁配料制成而得名。“可乐”以其特有的臻予佳境的美味深受消费者青睐,盛行世界各国,尤其在青年学生中最为流行,其消费量在食品中占第一位。     

Carbohydrate Phosphorylation with Phosphoric Acid,Polyphosphoric Acid,Pyrophosphoric Acid,and Anhydrous Phosphoric Acid

Abstract

Pyrophosphoric acid was first reported as a phosphorylating agent for highmolecular weight alcohols in 1934¹. Direct phosphorylating of sugars and sugar derivatives was first carried out by Cherbuliez² who used polyphosphoric acid on alcohols, amines and glycols. These precedents suggested to Seegmiller and Horecker in 1951³ to try tetraphosphoric (polyphosphoric) acid, as supplied by commercs, as the phosphorylating agent of carbohydrate phosphorylation. Carbohydrates can be phosphorylated when all but one of the positions is blocked by suitable protective groups, or, on rare occasions, in the unblocked, “natural” stata.? The latter method can be used only on terminal, C₅ or C₆ positions as the 5-phosphates of pentoses and the 6-phosphates of hexoses are more stable at low pH than other phosphates and can withstand an acidic hydrolysis of the mixture of phosphorylated sugars resulting from such phosphorylation. For the phosphorylation of easily available, cheap pentoses and hexoses in the 5- and 6-positions respectively, with cheap polyphosphoric acid, this is the method of choice.     

Obtaining and Properties of L-Aspartic Acid Solutions of Chitosan

Russian Journal of Applied Chemistry - Conditions for obtaining L-aspartic acid solutions of chitosan were considered: dissolution of the polymer with the formation of chitosan aspartate occurs in...     

磷酸体系中微量稀土元素萃取动力学研究

采用新型恒界面池法进行了磷酸体系中用P204萃取La(Ⅲ),Sm(Ⅲ)和Y(Ⅲ)的动力学研究,考察了搅拌速度、温度、比界面积、磷酸浓度及萃取剂浓度等因素对萃取速率的影响.结果表明:磷酸体系中用P204萃取La(Ⅲ),Sm(Ⅲ)和Y(Ⅲ)的表观活化能E_a分别为27.0,22.2和21.1 kJ·mol~(-1),在体相P204浓度大于在液一液界面饱和吸附时的最低浓度C_(min)时,其在界面已达到吸附饱和,反应的主通道由界面变为体相,在该体系下P204萃取La(Ⅲ),Sm(Ⅲ)和Y(Ⅲ)反应为体相化学反应和扩散反应混合控制.     

Si-Containing Amides of Phosphoric Acid

Summary. The first representative of the N-silylmethylamides of phosphoric acid O=P[NMe(CH₂SiMe _n (OEt)_3-n ]₃ have been synthesized by interaction of MeNHCH₂SiMe _n (OEt)_3-n (n = 2, 3) with POCl₃. The interaction of the N,N′,N″-trimethyl-N,N′,N″-tris[(ethoxydimethyl- silyl)methyl]triamide phosphoric acid with BF₃·Et₂O or BCl₃ results in the formation of the N,N′,N″-trimethyl-N,N′,N″-tris[(fluorodimethyl-silyl)methyl]triamide phosphoric acid or N,N′,N″-trimethyl-N,N′,N″-tris[(chlorodimethylsilyl)methyl]triamide phosphoric acid. NMR data show on the tetracoordinate state of silicon in these products. Professor Vadim Aleksandrovich Pestunovich, our chief, teacher and friend died on July 4^th, 2004     

Nylon Intermediates from Bio‐Based Levulinic Acid

Use of ZrO₂/SiO₂ as a solid acid catalyst in the ring‐opening of biobased γ‐valerolactone with methanol in the gas phase leads to mixtures of methyl 2‐, 3‐, and 4‐pentenoate (MP) in over 95 % selectivity, containing a surprising 81 % of M4P. This process allows the application of a selective hydroformylation to this mixture to convert M4P into methyl 5‐formyl‐valerate (M5FV) with 90 % selectivity. The other isomers remain unreacted. Reductive amination of M5FV and ring‐closure to ?‐caprolactam in excellent yield had been reported before. The remaining mixture of 2‐ and 3‐MP was subjected to an isomerising methoxycarbonylation to dimethyl adipate in 91 % yield.     

Si-Containing Amides of Phosphoric Acid

The first representative of the N-silylmethylamides of phosphoric acid O=P[NMe(CH₂SiMe _n (OEt)_3-n ]₃ have been synthesized by interaction of MeNHCH₂SiMe _n (OEt)_3-n (n = 2, 3) with POCl₃. The interaction of the N,N′,N″-trimethyl-N,N′,N″-tris[(ethoxydimethyl- silyl)methyl]triamide phosphoric acid with BF₃·Et₂O or BCl₃ results in the formation of the N,N′,N″-trimethyl-N,N′,N″-tris[(fluorodimethyl-silyl)methyl]triamide phosphoric acid or N,N′,N″-trimethyl-N,N′,N″-tris[(chlorodimethylsilyl)methyl]triamide phosphoric acid. NMR data show on the tetracoordinate state of silicon in these products.     

Chemistry of Phosphoric Acid Phenylesterdiamide

Abstract

References of methanolytic splitting of the urease inhibitor (1) phosphoric acid phenylesterdiamide (PPDA) at 25°C are given from investigations of time dependent UV absorption behaviour of diluted methanolic PPDA-solutions (2). Exclusion of moisture and addition of solvate free nickel(II)-, cobalt(II)-, manganese(II)-or zinc(II)- acetates or chlorides accelerate solvolytic reactions. Kinetic investigations on this effects indicate catalytic influences in the following sequence Ni(II)<Co(II)<Mn(II) < Zn(II) and to be independent from the anion usedo The half-life value was determined to be 3,5 hours (25°C) for the most active salt (ZnCl₂). Identification of ester bond splitting by metal ions used here was enabled by HPLC and TLC techniques. These findings are confirmed by estimation of equilibrium and stability constants for metal ion : PPDA 1:2 complexes.     

L-天门冬氨酸分子印迹电极的制备与性能研究

以邻苯二胺(OPD)为功能单体,L-天门冬氨酸(L-Asp)为模板分子,对L-Asp分子印迹电极的制备与性能进行了研究,建立了一种新的测定L-Asp的电化学分析方法。用循环伏安(CV)法和差分脉冲伏安(DPV)法研究了该电极的电化学性能,结果表明该分子印迹电极对L-Asp分子具有显著的催化还原和选择作用。在pH=5.4的磷酸盐缓冲溶液(PBS)中,还原峰电流与L-Asp的浓度在1.0~50.0mg/L范围内呈良好的线性关系,检出限为0.5mg/L。该方法操作简便,可用于保健品中L-Asp含量的测定。     

Production of a Concentrate of Rare-Earth Metals from Wet-Process Phosphoric Acid

Desorption of rare-earth metals (REMs) (lanthanum, yttrium, and ytterbium), as well as iron and aluminum, from the KU-2 sulfocation exchanger phase with solutions of mineral acids and ammonium nitrate and sulfate of various concentrations was studied. New data on the distribution of REMs in these systems were obtained. It was found that it is the most rational to use an ammonium nitrate solution with concentration of 300 g L^–1. It is recommended to precipitate a concentrate of REMs from the resulting desorbate with ammonium carbonate, with the subsequent separation of the suspension by the electrofl otation method.     

液膜萃取法回收磷酸体系中的微量镧

通过斜率分析法研究了P204和TOPO从磷酸体系中液液萃取微量镧的反应机制和热力学,推测出一种可能的反应历程和萃合物结构,得到萃取反应式和反应的平衡常数K=104.502,焓变ΔH=-13.02 kJ.mol-1,自由能ΔG=-25.686 kJ.mol-1,熵变ΔS=0.0425kJ.(mol.K)-1。在液液萃取反应机制研究的基础上,采用液膜萃取法进行磷酸体系中微量镧的富集回收研究,考察了载体P204(2%～10%w/w)和TOPO(1%～10%w/w)、表面活性剂磺化聚丁二烯LYF(1%～10%w/w)、内萃取剂HCl(1～5 mol.L-1)和水乳体积比A/O(2:1～7:1)对液膜萃取收率及稳定性的影响。在最优条件下,可回收94.10%～95.94%的镧,并且膜溶胀率为8%～17%,破损率为0.45%～1.93%,能够维持较好的液膜稳定性。研究结果对磷酸中的微量稀土镧回收利用具有一定的参考价值。     

Macroporous Activated Carbon Fibers from Rayon Precursors Impregnated with Phosphoric Acid

Novel activated carbon fibers (ACFs) from rayon precursors impregnated with phosphoric acid (H₃PO₄), containing abundant macropores (pore size>50 nm), were successfully obtained. The physical properties of these ACFs were examined. The BET surface was obtained; SEM observations showed that the concentration of H₃PO₄ impregnation strongly influenced the surface morphology and the porous texture of the resulting ACFs. The shape of the pores was nearly round and we could estimate the pore size was distributed between 20 and 150 nm. Infrared spectroscopy (IR) was applied to investigate the pyrolysis process of the rayon precursors with H₃PO_4. In addition, P‐containing substances, which should perhaps be acid phosphates or polyphosphates, can be observed on the surface of the resulting ACFs from SEM photos. Impregnation made the dehydration become more predominant during the pyrolysis process.     

A Practical Synthesis of (2S, 3R)-3-Amino-2-methylpentanoic Acid from L-Aspartic Acid

L -Aspartic acid by successive N-tosylation, anhydride formation, and reduction was converted into (3S)-3-(tosylamino)butano-4-lactone ( 4 ). Electrophilic methylation of 4 , subsequent iodo-esterification and nucleophilic methylation, followed by saponification and deprotection, gave (2S, 3R)-3-amino-2-methylpentanoic acid ( 2 ) with an ee of > 99% in seven steps and in an overall yield of 34%.