STUDIES ON DERIVATIVES OF 2,3-DIHYDRO-4H-1,3,2-BENZOXAZAPHOSPHORINE——SYNTHESIS AND STRUCTURE ANALYSIS OF 2,3-DISUBSTITUTED-2,3-DIHYDRO-4H-1,3,2-BENZOXAZAPHOSPHORIN-4-ONE-(THIONE)-2-SULFIDE(OXIDE)

A series of novel organocyclophosphorus compounds including twenty-three 2, 3-disubsti-tuted-2,3-dihydro-4H-1,3,2-benzoxazaphosphorin-4-one-2-sulfide (compounds Ⅰ) and three 2, 3-disubstituted-2,3,-dihydro-4H-1,3,2-benzoxazaphosphorin-4-thione-2-oxide (compounds Ⅱ) havebeen synthesized. Their structures were determined by IR, UV, HNMR, X-ray diffractionand elemental analysis. Each of compounds Ⅰ showed a strong absorption between 1290-1319em~(-1) in the IR spectrum. Comprehensive studies of the spectral data and experimental re-sults indicated that this strong characteristic absorption is different from that of the P = Olinkage and thus could be considered as a result of the stretching vibration of (unsaturatedC)-N single bond. In the course of synthesis of the compounds, an abnormal productisomers could be made predominantly in yield and be readily isolated from the other byrecrystallizing for several times from appropriate solvent. Data for the melting point, IR,UV and HNMR spectra of three pairs o     

苄氧羰酰脯氨酰丙氨酰苏氨酰叔丁酯晶体结构的研究

用X射线晶体学方法测定了含有保护基的三肽(Z-Pro-Ala-Thr(But)_2)的晶体结构和分子构象.其结晶属正交晶系,空间群为P2_12_12_1,晶胞参数a=29.557A,b=11.583A,c=8.830A,z=4.用PW-1100四圆衍射仪收集衍射强度数据,用直接法解结构,使用MULTAN-80计算机程序系统.用块矩阵最小二乘方法修正结构,最终的R=0.088(不包括氢原子). 分子中丙氨酸的构象趋近屏蔽式,形成肽链的转折.脯氨酸与保护基之间形成的“肽键“是顺式结构.脯氨酸侧链的吡咯烷环五个原子不在一个平面上,C~β和C~γ分别向相反方向偏离平面.相邻的肽基团平面之间的交角都接近90°.分子之间存在氢键,它使分子沿晶体z方向无限伸展形成分子链.晶体沿x和y方向的分子间作用力为范氏力.保护基(Z)在分子堆积中起重要作用。     

晶体结构修正的最小二乘方法

通过晶体结构分析的方法,可以从电子密度计算得到原子在三维空间的坐标。从而,可在原子水平上研究分子的构型、构象、配位情况等等。无论是研究物质结构与性能间的关系,还是探讨化学键的变异,以及建立量子化学的计算模型等方面,都不可缺少精密的结构分析数据。因此开展晶体结构修正具有重要意义。 Hughes 首先将最小二乘法用于修正晶体中原子位置坐标,以获得更精确的结构参数。但是,由于方     

叔丁氧羰酰-L-甲硫氨酰甘氨酸乙脂的晶体结构

本文测定了叔丁氧羰酰-L-甲硫氨酰甘氨酸乙脂的晶体结构。晶体学参数是P2_1,a=14.504(6),b=5.015(2),c=12.762(6),β=93.63(3)°,z=2。最终的R因子是0.066,使用了1495个反射。甲硫氨酸侧链的扭角是x~1=-177.7°,x~2=-178.6°,x~3=71.7°。侧链平面与酰胺平面近于垂直(90.8°)。该二肽主链在晶胞中的堆积构成了平行β-折叠结构。甲硫氨酸残基的主链扭角甲φ,Φ分别为-118.9°,115.4°。该二肽与Naider等人在研究肽的运输系统时所使用的某些小肽十分相似。     

苯骈-1-氧-2-磷-3-氮杂环己烷衍生物的研究——2,3-二取代苯骈-1-氧-2-硫(氧)化磷-3-氮杂环己-4-(硫)酮的合成及结构分析

本文合成了23个2,3-二取代苯骈-1-氧-2-硫化磷-3-氮杂环已-4-酮(化合物Ⅰ)和3个2,3-二取代苯骈-1-氧-2-氧化磷-3-氮杂环已-4-硫酮(化合物Ⅱ)新的有机环磷化合物,并用红外吸收光谱、氢核磁共振谱、紫外吸收光谱、X射线衍射分析和元素分析等方法鉴定了它们的组成和结构.并研究了23个化合物Ⅰ的红外吸收光谱,发现它们在指纹区1290—1319cm~(-1)范围内均有强吸收峰.经综合分析各光谱数据和实验结果,肯定了此强峰与P=O基因吸收峰的区别,并确认为不饱和碳原子C—N键伸缩振动所造成的特征吸收。 在合成上述化合物的过程中,往往在反应溶液中得到“正常产物”Ⅰ及其同分异构体“异常产物”Ⅱ 的混合物.通过选择适宜的缩合条件,可使其中某一异构体成为主要产物,并可在合适的溶剂中经多次重结晶将它们分离.本文提供了三对此类同分异构体的融点、红外吸收光谱、紫外吸收光谱和氢核磁共振谱等方面的数据,并对各谱图作了初步解析。     

STUDIES ON ORGANOMETALLIC COMPOUNDS OF TITANIUM,ZIRCONIUM AND HAFNIUM——THE CRYSTAL AND MOLECULAR STRUCTURES OF OXO-BRIDGED TETRAKIS(CYCLOPENTADIENYL)BIS (o.TOLYL)AND TETRAKIS(METYLCYCLOPEN-TADIENYL) BIS(p-TOLYL)BINUCLEATED ZIRCONIUM COMPOUNDS

This paper reports the crystal and molecular structures of tetrakis (cyclopentadienyl) bis(o-tolyl)-μ-oxo-dizirconium [dimer (Ⅰ)] and tetrakis (methylcyclopentadienyl) bis (p-tolyl)-μ-oxo-dizirconium [dimer (II)]. Both of them belong to monoclinic system and possess the same spacegroup C_2~5h- 2_1/a. The cell dimer (Ⅰ) containing four molecules is defined by a=19.122A,b=16.319A, c = 9.296A, β= 92°1′; the cell dimer (Ⅱ) containing two molecules is defined bya = 20.076A, b = 8.205A, c = 10.016A, β= 104°41′. The important difference of molecular configurations between the two dimers lies in thatthe dimer (Ⅰ) has no symmetry center and its Zn-O-Zr oxo-bridge presents a slightly bentconfiguration while the dimer (Ⅱ) takes the oxgen atom as a symmetry center and its oxo-bridge present linear linkage. In accordance with the above-mentioned molecular configuration, steric effect and elec-tronic structure have been further discussed.     

天花粉蛋白分子的三维结构

本文报道了我们最近建立的单斜晶胞内一个不对称单元中两个天花粉蛋白分子的模型,指出蛋白分子结构可以划分为大小两个结构域以及二级结构的一些特点,描述了独立单元中以一种非对称方式相关联的两个蛋白分子的差异及其相互作用,并解释了重原子衍生物的结合位置。     

1.73分辨率天花粉蛋白晶体中的水结构

本文报道的天花粉蛋白晶体中水的结构模型,包括了133个水分子,其中118个同蛋白的原子成氢键。天花粉蛋白内部有4个分立的水分子,其中2个水分子W251和W252分剔与A5螺旋变形部位的残基156Gln和157Ser的侧链成氢键,对维持活性部位的构象有贡献。晶体中水结构的比较结果表明,核糖体接近蛋白时,会诱导蛋白活性部位残基的构象发生变化,使各催化基团按催化效果最佳的构象排布,并激活一个水分子(W257)直接参与核糖体失活作用。     

STRUCTURAL STUDY OF BENZYLOXYCARBONYL-PROLYL-ALANYL-THREONYL-TERT-BUTYL ESTER

The crystal structure and molecular conformation of the synthetic oligopeptide (Z-Pro-Ala-Thr (But)_2) have been determined by X-ray analysis. The crystal is orthorhombic, spacegroup P2_12_12_1, with four molecules per unit cell of dimensions: a = 29.557, b = 11.583 andc = 8.830A. The diffraction data were collected using a PW-1100 four-circle diffractometer.The strueture was solved by direct methods, using the MULTAN-80 system of computerprograms and refined by the block-diagonal least-squares method. 7he final R value is 0.088(for non-hydrogen atoms). The Ala residue in this peptide is nearly in an eclipsed conformation. The peptide bondbetween Z and Pro is cis. The two atoms, C~β aud C~γ, are displaced on opposite sides of thepyrrolidine ring plane. The dihedral augles between the neighbouring peptide or carboxylgroups are all close to 90°. Hydrogen bonds link the peptides forming a chain in the zdireetion. The stacking of the peptides in the x and y directions is the result of the van derWaals fo