青霉素G亚砜对-甲氧基苄基酯的制备

青霉素亚砜;合成;青霉素G亚砜对-甲氧基苄基酯的制备     

Experimental and Theoretical Study of Fluorescent Properties of Morin

Morin (M) is one of the most widely distributed flavonoids with several beneficial effects on human health, and has the potential of being used as a possible treatment for COVID-19. To achieve a better understanding of the process of M dissolution, the fluorescent (FL) emission from M solutions prepared with different polar and nonpolar solvents (methanol, DMSO, and chloroform) was measured and compared with the FL emission from M powder and M crystals. In the FL spectra of the solutions with high M concentration, as well as in the spectra of M in solid state, two features, at 615 nm and 670 nm, were observed. As the solution concentration decreases, the maxima of FL spectra of the M solutions in all considered solvents shift to the blue side of the spectrum until reaching the value of 520 nm. To explain the experimental results, the TDDFT-M06-2X/6-31++G(d,p) method was used to determine the possible electronic transitions in the M molecule. The computations show that the FL emission in the spectral range of detection of our setup (405–800 nm) is related to the excited state intramolecular proton transfer (ESIPT). Comparison of the experimental data with the computations strongly suggests that in low-concentrated solutions, the FL emission is mostly due to electronic transitions in the keto OH3 form, whereas in aggregated states, the dominate contribution to the FL emission spectra is due to the transitions in keto OH5 form. Moreover, the time evolution of the M solutions FL spectra was observed, measured and explained for the first time.     

灵芝多糖的结构特征分析

采用沸水回流法从灵芝子实体中提取多糖,经Sevage法除蛋白,乙醇沉淀,离心、透析、膜分离,浓缩、冻干后得灵芝多糖。经HIO4氧化、Smith降解及甲基化反应,并利用多糖及刚果红混合液在碱性溶液中的波长的红移变化,通过UV-VIS,IR,GC,GC-MS,NMR对灵芝水提多糖的结构特征及三螺旋体结构进行分析研究。结果表明:灵芝多糖含有三螺旋体构型,GC-MS分析灵芝多糖的主要单糖组分为葡萄糖,还有少量的半乳糖、甘露糖、木糖和艾杜糖,IR及1HNMR分析多糖为β-构型,HIO4氧化、Smith降解和甲基化分析表明:多糖主要为(1→3)糖苷键连接构型,并伴有少量的1→6位支链键连接的结构,灵芝多糖是由D-葡萄糖单元通过β-(1→3)糖苷键连接葡聚多糖,其主要构型特征为(1→3)β-D-线性连接的骨架结构。     

新的异体四氢键二聚体结构的理论研究

研究了一系列由不同单位通过DAAD－ADDA方式结合的新的异体二聚体体系。运 用密度泛函B31YP方法在3－21g水平上完全优化了单位和二聚体的结构，通过对体 系的结构特征、能量、相互作用能的分析研究，证实了这类新的超分子聚集体可通 过四重氢键自组装形成。     

A Facile Method for the Separation of Methionine Sulfoxide Diastereomers,Structural Assignment,and DFT Analysis

Methionine (Met) oxidation is an important biological redox node, with hundreds if not thousands of protein targets. The process yields methionine oxide (MetO). It renders the sulfur chiral, producing two distinct, diastereomerically related products. Despite the biological significance of Met oxidation, a reliable protocol to separate the resultant MetO diastereomers is currently lacking. This hampers our ability to make peptides and proteins that contain stereochemically defined MetO to then study their structural and functional properties. We have developed a facile method that uses supercritical CO₂ chromatography and allows obtaining both diastereomers in purities exceeding 99 %. ¹H NMR spectra were correlated with X-ray structural information. The stereochemical interconversion barrier at sulfur was calculated as 45.2 kcal mol⁻¹, highlighting the remarkable stereochemical stability of MetO sulfur chirality. Our protocol should open the road to synthesis and study of a wide variety of stereochemically defined MetO-containing proteins and peptides.     

有机磷化合物硫逐-硫赶重排反应的理论研究

有机磷化合物硫逐┐硫赶重排反应的理论研究彭万华（湖北三峡学院化学系宜昌４４３０００）刘述斌（Ｄｅｐｔ．ｏｆｃｈｅｍ．，Ｕｎｉｖ．ｏｆＮｏｒｔｈｃａｒｏｌｉｎａ，ｃｈａｐｅｌＨｉｌ，２７５９９－３２９０，ＵＳＡ）杨小平（湘潭师范学院化学系湘潭４１１１０...     

青霉素亚砜催化扩环制备头孢G酸

保护性甲硅烷基化;青霉素亚砜催化扩环制备头孢G酸     

Structural Effects on the RhII-Catalyzed Rearrangement of Cyclopropenes

The thermocatalytic rearrangement of 2-alkylcycloprop-2-ene-1-carboxylates ( 1 ) in the presence of Rh^II perfluorobutyrate is regio- and stereospecific and leads to the substituted metallocarbenes 3 . The latter undergo intramolecular C? H bond insertion to form cyclopentylidenes ( 4 ). In contrast, the metallocarbenes 19 , derived from 2,3-dialkylcycloprop-2-ene-1-carboxylates 6c , d , react to dienes (Z)- 20 , via 1,2-H migration. The cyclopropenedicarboxylates 10 , in turn, rearrange exclusively to the more substituted metallocarbenes 26 , which cyclize to furans 28 , With 6e , and 12 , products derived from both modes of ring-opening are observed.     

CE Analysis of Cephalosporins in Environmental Waters

This study investigates an off-line solid phase extraction (SPE) for improving the sensitivity in the capillary electrophoretic (CE) analysis of four cephalosporins. Two sorbents—LiChrolut-C₁₈ and Oasis HLB—were used in a SPE process to detect cephalosporins in natural waters (tap, river and hospital sewage) and their performances were compared. By using Oasis HLB sorbent higher recoveries for river water were obtained (94–107% when 500 mL of sample were analyzed). The off-line SPE–CZE method was validated for river water with good detection limits (3 μg L⁻¹) and the linearity ranged between 5 and 200 μg L⁻¹.     

Theoretical Study on the Transition State of N-nitropyrazoles Rearrangement Reaction

Theoretical studies on the rearrangement reactions of nitropyrazoles have been investigated. In order to gain a better understanding of the intermediate process of rearrangement reactions, the transition states of the rearrangement reactions were obtained by TS method at the B3 LYP/6-311 G(d, p) level of theory. The natural bond orbital charge, electrostatic potential and frontier molecular orbital of the molecules in the process of rearrangement were analyzed, and the solvent effect was also discussed. The rearrangement of nitropyrazoles involves two transition states and one intermediate, and the nitro group and hydrogen atom are two transfer groups for rearrangement reactions. The migration of these two groups leads to the change of charge distribution and molecular structure. The structural changes of the molecules in different solvents are not significant, but the dipole moment of the molecule has obvious change.     

Structural Study of Mesoporous Titania Prepared from Titanium Alkoxide and Carboxylic Acids

Mesoporous titania with regulated pore size as well as high specific surface area was prepared from titanium alkoxide and various carboxylic acids with different alkyl-chain length [CH₃(CH₂) _n COOH : n = 0–20]. Although the pore size and pore volume of titania changed slightly at n < 10, they increased with increasing the alkyl-chain length of carboxylic acid at n 10. Each carboxylic acid forms a complex with titanium alkoxide in an organic-inorganic precursor, while the precursor prepared by using carboxylic acid with n 10 consists of a lamella-type mesophase. The interplanar distance of the lamella structure increases with increasing the alkyl-chain length of carboxylic acid. During calcination, the lamella structure collapses together with the combustion of organic moieties and titania particles crystallized to anatase aggregate to provide pores. Although carboxylic acid does not act as a true template, the formation of the lamella-type mesophase in the precursor plays an important role in controlling the pore size of titania.     

毛细管区带电泳法分析头孢菌素类药物的纯度

摘要：提出了以pH9.20的20mmol/L硼酸缓冲溶液、pH6.86的20mmol/L磷酸缓冲溶液和pH2.05的50mmol/L磷酸缓冲溶液作为背景电解质分析9种头孢菌素类抗生素药物纯度的毛细管区带电泳方法。用内部归一化法定量,方法简单快速。讨论了方法的优点和局限性。     

Structural Analysis and Properties of Organic-Inorganic Hybrid Ionic Conductor Prepared by Sol-Gel Process

Organic-inorganic hybrid lithium ion conductors were prepared by the sol-gel process. The hybrid ion conductor will be used as the electrolyte for Li based high-energy density batteries. The hybrid ion conductor was prepared from a mixture of tetramethyl orthosilicate (TMOS), polyethylene glycol 200 (PEG₂₀₀), lithium perchlorate (LiClO₄) and water. A wet gel was prepared at room temperature. The gels dried at 80°C under vacuum did not contain water. The dried hybrid ion conductor gel had homogeneity and high transparency. Ionic conductivity of the hybrid sample was measured by the complex impedance method and it increased with increasing PEG₂₀₀ content. The dried hybrid gel that contained no LiClO₄ did not show ion conduction. Conductivity on the order of 10^–5 S·cm^–1 at room temperature was obtained. Structural characterization was done by Fourier Transform Infrared Spectra (FTIR) and NMR measurement of ¹³C and ¹H, and the thermal stability and glass transition properties were studied by DSC. Glass transition temperature decreased with increasing PEG₂₀₀ content and increased with increasing [Li]/[O] ratio (the oxygen considered is from the polyethylene glycol). Existence of the Si–O–(C₂H₄O) _n –bond and the C–OH bond in the framework of the organic and inorganic phases was confirmed. TMOS and PEG₂₀₀ were hydrolyzed and condensed. The organic and inorganic phases were chemically bonded and the microstructure of the hybrid matrix was shaped as comb. The comb shape leads to high ionic conduction.     

温度对二甲基亚砜水溶液的结构和热力学性质的影响

应用参考作用格位模型理论计算了二甲基亚砜(DMSO)摩尔分数为0.002时不同温度下溶液的微观结构和热力学性质. 计算结果表明, DMSO加入到水中能够增强溶液的分子网络结构. 温度升高, 配位数减小, 溶液中分子排布趋向无序. 平均力势的波动增大表明分子间的诱导力表现为斥力. 计算得到的各种热力学性质显示: 温度升高, 溶液的熵和溶剂化自由能增加, 相互作用能和过剩化学位也增加, 即高温下溶液越来越偏离理想溶液; 空位形成能降低表明溶液分子结构在高温下更容易重组.     

Functionalization and Rearrangement of Spirocyclohexadienyl Oxindoles: Experimental and Theoretical Investigations

The preparation and functionalization of spirocyclohexa‐2,5‐diene oxindoles is described. The spirocyclic core of the title compounds was installed by using a SmI₂‐mediated cyclization of aryl iodobenzamides. Epoxidation with CF₃CO₃H was then carried out and was shown to occur with a high level of diastereocontrol: the reagent approaches the diene moiety syn to the amide group, which is likely to be as a consequence of hydrogen bonding between the amide C?O bond and the peracid hydrogen. Carbanionic functionalization of the spirocyclohexa‐2,5‐diene oxindoles was then examined, leading to an unprecedented rearrangement of the strained spiro system into dearomatized phenanthridinones. Upon treatment with lithium diisopropylamide (LDA) at ?40 °C, the dienes rearranged to provide a phenanthridinone lithium enolate intermediate that was trapped by electrophiles including alkyl halides and aldehydes. Interestingly, alkylation and hydroxyalkylation occurred with different regiocontrol. DFT calculations were performed that rationalize the observed skeleton rearrangement, emphasizing the role of LDA/diisopropylamine in this rearrangement. The proposed mechanism thus relies on a thermodynamically driven diisopropylamine‐mediated proton transfer with the cleavage of the diene–amide C?O bond as the key step.     

Theoretical Study of the AlEt3-Promoted Tandem Reductive Rearrangement of Epoxides

The AlEt3-promoted tandem reductive rearrangement reactions of epoxides was studied at B3LYP/6-31G(d,p) level. For the model compound σ-hydroxy epoxides, two possible reaction pathways I and II were calculated. The main difference is the order of ethylene release and six- to five-member ring rearrangement.The ring contraction rearrangement in pathway I is the first step and this step is the rate controlling step with a free energy barrier of 116.62 kJ/mol. For pathway II, the ethylene release occurs first, and is followed by a six-member ring opening reaction which is the rate controlling step, and the barrier is 251.38 kJ/mol.The reason for such high barrier is that the ethylene release results in the following reaction being moredifficult. The results show that pathway I (C-C rearrangement and then ethylene release) is more favorable,which is consistent with experimental results.