磷酰化丝氨酸六配位磷中间体的结构及其反应

用MNDO方法对磷酰化丝氨酸仿生化反应机理中所形成的六配位磷中间体(3)可能的3个异构体的结构及其反应活性进行了研究.在六配位磷中间体3的6根键中,丝氨酸的羧基氧O3与磷之间的键最弱,最易断裂生成新的五配位磷中间体4,4的P_N键断裂得到磷酰基的N→O转位反应产物5.对于六配位磷中间体3中的两个异丙氧基,位于丝氨酸侧链羟基O6对面的异丙氧基较另一个易于离去(约低37kJ/mol)并得到中间体6,接着甲醇从O6对面新产生的空隙进攻中间体6中的磷,生成磷上酯交换产物9.六配位磷中间体机理比较好地解释了实验中所发现的磷酰化丝、苏氨酸仿生化反应的多样性和复杂性.     

磷酰化线氨酸六配位磷中间体的结构及其反应

用ＭＮＤＯ方法对磷酰化丝氨酸仿生化反应机理中所形成的六配位磷中间体（３）可能的３个异构体的结构及其反应活性进行了研究。在六配位磷中间体３的６根键中,丝氨酸的羧基氧Ｏ３与磷之间的键最弱,最易断裂生成新的五配位磷中间体４,４的Ｐ－Ｎ键断裂得到磷酰基的Ｎ→Ｏ转位反应产物５。对于六配位磷中间体３中的两个异丙氧基,位于丝氨酸铡链羟基Ｏ６对面的异丙氧基较另一个易于离去（约低３７ｋＪ／ｍｏｌ）并得到中间体６,接     

磷酰氨基酸的酯交换反应研究

本文利用^3^1P NMR , 对比研究了磷酰化组氨酸与其它磷酰化氨基酸和一级醇的磷上酯交换的反应速度,实验表明磷酰化组氨酸的反应速度最快. 由此提出了以下机理:由于咪唑环的参与,磷可以形成六配位过渡态,从而加快了反应速度.     

咪唑催化磷酰化丝,苏氨酸及其酯的活化反应

咪唑对磷酰化氨基酸的活化反应具有较强的催化作用，磷酰化丝、苏氨酸在咪唑催化下不仅能发生溶剂解反应，如磷酯交换，羧基活化成酯、成肽及磷酰基的Ｎ－Ｏ迁移等，而且还会发生分子内环化反应，对于化学性质非常稳定的磷酰化丝、苏氨酸酯在咪唑催化下也会发生上述反应，反应机理推测为丝、苏氨酸的侧链基团羟基在咪唑的存在下亲核进攻磷原子形成五配位中间体。     

含磷五元环五配位化合物的合成

三配位磷化物与烷氧基苯硫醚反应合成了一系列含磷五元环的五配位化合物。在不同温度下,测定了这些化合物的¹⁹FNMR。化合物(7)与三氟乙氧基苯硫醚反应生成化合物(19)以及(20)和(21);化合物(11)与六氟异丙氧基苯硫醚反应生成化合物(18)和(21),并对这些反应机理进行了讨论。     

含六氟异丙氧基五配位磷化合物的合成及其NMR的研究

最近Schmutzler等人合成了几种含有甲基六氟异丙氧基的五配位磷化合物,通过在不同温度下~(19)FNMR测试以及计算活化能,表明这类化合物在分子内配位基重组过程(intramolecula ligand reorganization)中,各配位基的空间效应是主要因素。我们采用另一路线合成了几种含有苯基六氟异丙氧基的五配位磷化合物,通过NMR的研究,进一步提供了关于这类化合物在假旋转(pseudorotation)时,配位基空间效应的影响。     

五配位磷化合物与生物化学

综述了五配位磷化合物与生物化学的关系, 发现当a-氨基酸的氨基接上磷酰基团以后, 化学性质发生了许多奇特的现象, 在室温下可发生自身活化现象而成肽、成酯、磷上酯交换及N→O磷酰基转位; 丝氨酸和苏氨酸与核苷缀合以后, 在弱碱性条件下能够对不同的碱基进行识别; 磷酰化组氨酸和丝组二肽可以在中性条件下切割核酸、蛋白、酯. 发现上述现象的发生都经历了一个五配位磷中间体, 认为五配位磷中间体是决定它们活性的结构因素.     

尾式金属卟啉配合物的研究（Ⅲ）—咪唑基尾式卟啉及其铁（Ⅲ…

合成了咪唑基尾式卟啉－５－邻［４－（１－咪唑基）丁氧基］苯基－１０，１５，２０－三苯基卟啉及其铁（Ⅲ）配合物。以元素分析，质谱，＾１ Ｈ ＮＭＲ，ＩＲ和紫外可见吸收光谱等进行了表征，初步研究了在氯仿和苯中某些含氮配体与铁（Ⅲ）配合物的轴向配位性质，表明，Ｆｅ（Ⅲ）Ｃｌ通常与含氮配体生成低自旋的六配位加合物，但在苯溶液中与咪唑作用时，一定条件下还能生成稳定的高自旋五配位加合物。     

磷酰化丝氨酸形成六配位磷中间体的理论研究

用MNDO方法对磷酰化丝氨酸仿生化反应机理中六配位磷中间体的形成过程进行了研究.磷酰化丝氨酸(1)形成分子内磷酸-羧酸分子内混酐的五配位磷中间体(2)后,其酸性质子解离,分子经过具有氢桥键结构的过渡态,使氨基酸侧链羟基上的氢通过氢键作用向磷上的O₁进行转移,然后再经过构型由三角双锥向八面体的转变,形成六配位磷中间体(3).氢桥键的存在使反应过渡态能量降低,其相对能量为148.5kJ/mol.理论计算较成功的解释了六配位磷中间体的形成机理以及磷酰化丝氨酸仿生化反应中羧基和侧链羟基共同参与的实验结果.     

尾式金属卟啉配合物的研究(Ⅲ)──咪唑基尾式卟啉及其铁(Ⅲ)配合物的合成和性质

合成了咪唑基尾式卟啉──5-邻[4-(1-咪唑基)丁氧基]苯基-10,15,20-三苯基卟啉(o-ImBPTPP)及其铁(Ⅲ)配合物[Fe(Ⅲ)(o-ImBPTPP)Cl],以元素分析、质谱、¹HNMR、IR和紫外可见吸收光谱等进行了表征.初步研究了在氯仿和苯中某些含氮配体与铁(Ⅲ)配合物的轴向配位性质.结果表明,Fe(Ⅲ)(o-ImBPTPP)Cl通常与含氮配体生成低自旋的六配位加合物,但在苯溶液中与咪唑作用时,一定条件下还能生成稳定的高自旋五配位加合物.     

Sequential Nucleophilic Substitution of Phosphorus Trichloride with Alcohols in a Continuous-Flow Reactor and Consideration of a Mechanism for Reduced Over-reaction through the Addition of Imidazole

We demonstrate a sequential nucleophilic substitution of highly electrophilic and inexpensive phosphorus trichloride with three different alcohols in a continuous-flow reactor. A variety of alcohols including ones that contained acid- and/or basic-labile functionalities were rapidly reacted. A over nucleophilic substitution that occurred during reaction of the second alcohol was suppressed by the addition of imidazole. Density functional theory calculations of the sequential nucleophilic substitutions of alcohols were performed both with and without imidazole, and Berry pseudorotation was suggested as a rate-limiting step in both cases. Herein, we discuss the reasons for the decreased selectivity in the absence of imidazole as well as those for improved selectivity in the presence of imidazole during the second nucleophilic substitution.     

Electrochemically induced processes in the formation of phosphorus acid derivatives. 2. The role of polymerization processes in the electrosynthesis of the esters of phosphorus acids from white phosphorus

The mechanism of the electrosynthesis of phosphate esters from white phosphorus was investigated. It was shown that the reaction takes place by two paths, i.e., monomeric (with the participation of dissolved phosphorus) and polymeric (with the participation of phosphorus on the surface of an emulsion drop). It was established that in an alcohol solution of tetraethylammonium iodide the main part of the final product is formed through an intermediate polymeric compound. It was noticed that by studying the dynamics of the accumulation of the dissolved product during electrolysis it is possible to trace the mechanism of reaction of the phosphorus at the individual stages of the process.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420028 Kazan'. V. I. Ul'yanov-Lenin Kazan' State University, 420028 Kazan'. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1328–1333, June, 1992.     

Electrochemically induced processes in the formation of phosphorus acid derivatives. 1. Synthesis of trialkyl phosphates from white phosphorus

An electrochemical method, based on the joint action of nucleophilic and electrophilic reagents on P₄, is proposed in order to utilize white phosphorus in the formation of the esters of phosphorus acids. The action of alkoxide ions on white phosphorus in an alcohol medium in the presence of iodine generated at the anode leads to the formation of phosphate esters. A scheme in which the intermediate products are dialkyl and trialkyl phosphites and the side product is dialkyl alkylphosphonate is proposed for the process.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420028 Kazan'. V. I. Ul'yanov-Lenin Kazan State University, 420028 Kazan'. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1322–1328, June, 1992.     

Penta-coordinate phosphorous compounds and biochemistry

The relationship between penta-coordinate phosphorus compounds and biochemistry is briefly reviewed. Some interesting phenomena such as peptide formation, ester formation, ester exchange on phosphorus and N to O migration occur at room temperature when the amino group of amino acid is associated with phosphoryl group. Serine or threonine in conjugate of nucleo-side-amino acid could recognize different nucleobases. N-phosphoryl Histine and Ser-His dipep-tide could cleavage nucleic acid, protein and ester in neutral medium. It is found that the above phenomena all undergo penta-coordinate intermediate of phosphorus atom, which is proposed as the key factor to determine their activities.     

Penta-coordinated phosphorus structure analysis on kinases

Phosphorus element was discovered in organismin the 17th century. In the past decades, it has beenfound that phosphorus plays crucial roles in many as-pects of bio-systems. For example, many biologicalprocesses are regulated by the phosphorylation anddephosphorylation of amino acid residues in proteins[1].However, there are still some unsolved problems[2],such as whether the process goes through a penta-co-ordinated phosphorus or a metaphosphate dianionicintermediate. The X-ray crystals struc…     

A Simple Synthesis of Stable Phosphoranes Derived from Imidazole Derivatives

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, in the presence of strong NH-acids, such as imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, benzimidazole, and 5,6-dimethylbezimidazole. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon–carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group.     

Structure and Properties of Violet Phosphorus and Its Phosphorene Exfoliation

Black phosphorene has attracted much attention as a semiconducting two‐dimensional material. Violet phosphorus is another layered semiconducting phosphorus allotrope with unique electronic and optoelectronic properties. However, no confirmed violet crystals or reliable lattice structure of violet phosphorus had been obtained. Now, violet phosphorus single crystals were produced and the lattice structure has been obtained by single‐crystal x‐ray diffraction to be monoclinic with space group of P2/n (13) (a=9.210, b=9.128, c=21.893 Å, β=97.776°). The lattice structure obtained was confirmed to be reliable and stable. The optical band gap of violet phosphorus is around 1.7 eV, which is slightly larger than the calculated value. The thermal decomposition temperature was 52 °C higher than its black phosphorus counterpart, which was assumed to be the most stable form. Violet phosphorene was easily obtained by both mechanical and solution exfoliation under ambient conditions.