手性化合物的质谱分析研究

运用不含手性碳的非对称化合物Ｓ－ＢＮＰ酸（Ｓ－ｐｈｏｓｐｈｏｒｓａｅｕｒｅ－（１，１＇－ｂｉｎａｐｈｔｈｙｌ－２，２＇－ｄｉｙｌｅｓｔｅｒ））作反应试剂用快原子轰击反应质谱法（ＦＡＢ－ＲＭＳ）测定手性化合物的绝对构型．发现非对称手性化合物可与不对称手性化合物在质谱中发生立体选择性反应，Ｓ－ＢＮＰ酸可作为一种新的反应试剂来测定手性化合物的绝对构型．     

P10原子簇的电子结构

利用Ｇａｕｓｓｉａｎ－９４从头算程序，选择６－３１Ｇ￣＊基组对Ｐ_１０原子簇的３种构型Ｐ_１０（Ｃ_２ｖ）、Ｐ_１０（Ｄ_５ｈ）与Ｐ１０（Ｃ_３ｖ）进行几何全优化。３种构型总能量相对值表明，原子簇Ｐ１０（Ｃ_３ｖ）具有热力学稳定性；ＨＯＭＯ与ＬＵＭＯ的能级差表明，原子簇Ｐ_１０（Ｃ_３ｖ）具有动力学稳定性。相反，原子簇Ｐ_１０（Ｄ_５ｈ）ＬＵＭＯ的能级值较低，易于得到电子而成为负离子。     

2′-Methyl taxanes: synthesis and NMR configurational assignment

Capitalizing on an oxidation-alkylation approach, a non-diastereoselective entry into 2′-methyl taxanes was developed. The issue of configurational assignment at the newly formed side-chain quaternary stereocenter was solved and put into a more general context by integrating information from an alternative diastereoselective synthesis of model compounds and from spectroscopic measurements, critically comparing the J-Based and the Universal NMR Database approaches.     

Synthesis and absolute configuration of (−)-chettaphanin I and (−)-chettaphanin II

An efficient synthesis of chettaphanin I and II has been achieved from ent-halimic acid. The absolute configuration of the natural products was established by nOe experiment and by X-ray analysis of chettaphanin II.     

An expeditious total synthesis of kalkitoxins: determination of the absolute stereostructure of natural kalkitoxin

Kalkitoxin, a potent neurotoxin isolated from the marine cyanobacteria Lyngbya majuscula, and its congeners (1-7) were efficiently synthesized utilizing Hruby's diastereoselective 1,4-addition and the Wipf's oxazoline-thiazoline conversion as key steps. These synthetic efforts in combination with spectral studies of natural kalkitoxin clearly determined the absolute stereostructure of kalkitoxin to be 7.     

Triblock copolymer Pluronic®F127 sustains insulin release and reduces initial burst of microspheres—in vitro and in vivo study

In many cases, initial release of drugs from microparticles is undesirable. In the present study, Pluronic^®F127, which shows thermosensitive characteristic, was used for controlling both the initial release and the sustained release of insulin from microspheres. Calcium-alginate insulin microspheres were prepared by emulsion technology and dispersed in a thermosensitive semisolid gel, the PF127. In vitro study demonstrated that PF127 could protect the activity of insulin in some extent and control the initial release and sustained release of insulin well. The results of in vivo hypoglycemic experiment carried out on diabetic rats also displayed a well correlation with in vitro release patterns. The results suggested that PF127 could sustain insulin release through a subcutaneous injection, and this material was available to deliver insulin aiming for prolonged and smooth hypoglycemic function.     

华佗豆碱甲氢溴酸盐晶体结构和绝对构型

(+)华佗豆碱甲已经从中草药华佗豆(Ipomoea hardwickii Hemsl.)中分离到。它的氢溴酸盐晶体属正交晶系,空间群P 2_12_12_1。晶胞参数:a=10.078(2)(?),b=17.303(3)(?),c=9.022(1)(?),Z=4。用四圆衍射仪收集强度数据,得到独立可观察点共1248个。用重原子法确定结构,经块对角矩阵最小二乘法修正结构参数,最终的偏离因子R为0.051。根据Br的反常散射确定华佗豆碱甲阳离子的绝对构型为S型,命名为S-1,2,3,5,8,9-六氢-6-对苯酚基-7-甲基吲嗪。晶胞内四个分子两两一对,通过氢键NH…Br…HOH…OHAr形成在晶体内沿b方向无限伸展的分子链。     

Computational Evidence for the Smallest Boron Nanotube

One-dimensional boron nanostructures have being actively studied experimentally1 and theoretically2 in the recent years, due to their promising applications in field emission devices and high-temperature electronics. Amorphous3 and crystalline1 nanowires,…     

Enantioselektive Katalysen. 155 [1] (Cymol)Ruthenium‐Halbsandwich‐Komplexe mit Pyrroloxazolin‐Liganden — Synthese,Stereochemie, Katalyse

Asymmetric Catalysis. 155 [1] (Cymene)Ruthenium Halfsandwich Complexes with Pyrroleoxazoline Ligands — Synthesis, Stereochemistry, Catalysis The (cymene)ruthenium halfsandwich complexes K1 and K2 with chiral pyrroleoxazoline ligands were synthesized and characterized. The complexes form diastereomers, which only differ in the metal configuration. Complex K1 crystallized as the pure diastereomer S_Ru, S_C4, R_C5. In solution epimerization S_Ru, S_C4, R_C5 ? R_Ru, S_C4, R_C5 occurred via change of the configuration at the ruthenium atom. The half‐life for the first‐order reaction at 0.4 °C in CD₂Cl₂ was 50.6 min. Thus, the two diastereomers equilibrate at room temperature. The equilibrium mixtures of K1 und K2 were used as catalysts for the transfer hydrogenation of acetophenone and for the Diels‐Alder reaction of cyclopentadiene with methacrolein. Enantiomeric excesses of up to 60 % ee were achieved.     

△~9(11)雌甾四烯类化合物的硼氢化-铬酸氧化(Ⅰ)

雌甾-11-酮化合物是合成11-烃基取代甾体化合物的关键中间体。文献多采用硼氢化-过氧化氢氧化得11α-羟基物,再经进一步氧化得雌甾-11-酮化合物。两步反应均有副产物生成,总收率很低(31%)。Brown 等报道有机硼烷化合物用重铬酸钠的硫酸水溶液氧化可直接得到酮。我们将此