一种含末端炔喹啉酮类化合物的波谱学研究

通过Cu(I)催化有机叠氮化物和端基炔之间的1,3-偶极Huisgen环加成反应,又称“点击化学”, 可快速、高效合成专一的1,4-二取代-1,2,3-三唑产物. 为得到含有末端炔的喹啉酮衍生物,以7,8-二氢-2,5(1H,6H)-二酮（1）为原料,通过烷基化反应将端基炔引入到化合物1中,合成了1-(2-炔丙基)-7,8-二氢喹啉-2,5(1H, 6H) 二酮（3）,并利用重结晶和硅胶柱分离两种化学手段,得到了该化合物的两种构型异构体. 采用DEPT、¹H NMR、¹³C NMR、¹H-¹H COSY、NOESY、HMQC多种NMR实验测试分析方法,对该化合物的构型异构体进行了验证和区分,并分别对其¹H NMR和¹³C NMR谱的信号进行了归属.     

2个半合成偏诺皂苷的NMR研究

应用¹H NMR、¹³C NMR、HSQC、HMBC等多种NMR实验测试方法,结合MS技术,确认了2个半合成偏诺皂苷的结构,即：偏诺皂苷元-3-O-α-L-鼠李吡喃糖基(1→2)-α-D-葡萄吡喃糖苷(1),偏诺皂苷元-3-O-{α-L-鼠李吡喃糖基(1→2)-[α-L-鼠李吡喃糖基(1→4)]}-α-D-葡萄吡喃糖苷(2),并对这2个化合物的1D NMR谱数据进行了全归属. 这2个化合物目前没有天然产物的报道. 通过药理实验发现,这2个连接α-D葡萄糖的偏诺皂苷则没有缩宫止血活性,表明该类化合物3位糖苷键的构型决定其是否具有生物活性.      

对氯苯氧基氯苯乙酮异构体的NMR分析

2-氯-4-(4-氯苯氧基)苯乙酮和2-(4-氯苯氧基)-4-氯苯乙酮互为同分异构体,它们的核磁共振谱十分相似,只通过一维核磁共振谱对其结构确定有很大的困难. 本文借助2-(4-氯苯氧基)-4-氯苯乙酮的分子晶体结构信息,利用二维核磁共振方法,对两个化合物的¹H NMR和¹³C NMR进行了指认,为这两种化合物的结构鉴定提供了重要依据.     

取代基对2-(2-羟基苯基)苯并噻唑分子内氢键及质子转移的影响:密度泛函理论研究

运用密度泛函(DFT)和含时密度泛函(TD DFT)理论方法研究了在2-(2-羟基苯基)苯并噻唑(HBT)苯环羟基的邻位或对位分别引入羟基和醛基后的衍生物分子内质子转移过程,考察了取代基的电子效应及取代位置对分子内氢键和质子转移反应的影响,模拟计算了各分子的IR振动光谱和电子光谱.研究发现,HBT及其衍生物分子可以形成分子内氢键,且激发态时氢键增强.基态时以醇式构型稳定存在,激发态时酮式结构为优势构象.分子的最大吸收峰和发射峰主要源于电子从前线分子轨道HOMO到LUMO之间的跃迁.基态分子内质子转移需要越过较高的能垒因而难以发生,而激发态时只需越过较低能垒就很容易发生激发态分子内质子转移.取代基的电子效应和取代位置对HBT分子氢键强度、互变异构体的相对稳定性、电子光谱及质子转移反应的能垒均有一定影响.     

芳香性取代基对2-(2-羟基苯基)苯并咪唑激发态质子转移和光谱性质影响的理论研究

运用密度泛函(DFT)和含时密度泛函(TD DFT)理论方法研究了在2-(2-羟基苯基)苯并咪唑(HBI)苯环羟基的对位分别被呋喃基、吡咯基等五种芳香性取代基后的衍生物(HBI-R)分子内质子转移过程,考察了取代基的电子离域效应对分子结构、分子内氢键和质子转移的影响,模拟计算了各分子的IR振动光谱和电子光谱。研究发现,基态的HBI与HBI-R分子内氢键O—H…N比O…H—N强度大,因氢键中的O—H增长和H—N的缩短,激发态氢键O—H…N弱于O…H—N强度,基态和激发态的稳定构型分别为醇式和酮式结构,取代基总体上使酮式构型相对稳定性有所增加,但呋喃基、吡咯基和噻吩基却略降低了激发态酮式构型相对稳定性。取代基降低了HBI基态和激发态分子内质子转移反应的能垒,但影响不大。电子吸收光谱的最大吸收峰和荧光光谱的最大发射峰主要源于前线分子轨道HOMO与LUMO之间的电子跃迁,芳环取代基增强了电子离域效应,使光谱的吸收峰和发射峰波长均有较大的红移。     

N-磷酰化叉肽结构与NMR波谱

测定了N-磷酰化叉肽(2-5)在溶液中的NMR谱.发现它们具有非对映异位,分子无规卷曲及氢键相互作用.波谱分析表明,磷酰基的参与,主要影响其结合部位的氨基酸.由于肽平面的生成及分子内、分子间氢键影响的改变,致使叉肽中支链的Dipp-Ala磷酰基与β位羰基的相对位置发生变化.磷酰基与N-C_α基团仍处于反式位置,这可能是该氨基酸侧链无极性基团的缘故.     

牛磺熊去氧酮胆酸分子结构的1H、13C NMR研究

应用多种二维核磁共振波谱方法研究并证实了熊胆汁中由牛磺熊去氧胆酸氧化生成的衍生物是牛磺熊去氧酮胆酸,同时详细介绍了根据2D-MAXY和MAXY-TOCSY谱进行谱峰归属和结构分析的过程.     

荧光猝灭法研究单羰基姜黄素衍生物与酪氨酸酶间的相互作用

用二烯酮结构代替不稳定的二烯二酮结构合成了3个结构稳定的单羰基姜黄素衍生物1,5-双(4-羟基)-1,4-戊二烯-3-酮(1a)、2,5-双(4-羟基-苯亚甲基)环戊酮(1b)和2,6-双(4-羟基-苯亚甲基)环己酮(1c).运用荧光光谱法研究了化合物与酪氨酸酶间的相互作用.实验结果表明,酪氨酸酶可致使合成化合物的荧光...     

氧化异佛尔酮缩酮化产物的NMR特征

报道了由乙二醇有选择性的与氧化异佛尔酮4位或1位羰基形成缩酮化产物的NMR研究,介绍了通过与已知的缩酮化产物(2)的文献核磁图谱对照,以及与原料氧化异佛尔酮相应位置的NMR谱图对比来确定另一未见文献报道的缩酮化产物(3)的结构的方法,并对化合物(3)(3,5,5-三甲基-4,4-乙二氧基-2-环己烯酮)的氢谱和碳谱进行了归属.     

皂苷Tb2个糖基化产物的NMR研究

利用¹H NMR、¹³C NMR、COSY、HSQC和HMBC等多种核磁共振技术,结合MS技术,确认了皂苷Tb的2个糖基化产物的结构,即偏诺皂苷元-3-O-α-D-葡萄糖-(1→3)[α-L-鼠李糖(1→2)]-β-D-葡萄糖苷（1）和偏诺皂苷元-3-O-α-D-葡萄糖-(1→4)-α-D-葡萄糖-(1→3)[α-L-鼠李糖-(1→2)]-β-D-葡萄糖苷（2）. 化合物1和2为新化合物,对其¹H NMR和¹³C NMR信号分别进行了全归属和详细分析.     

Intra- and intermolecular proton transfer in methyl-2-hydroxynicotinate

Spectral characteristics of methyl 2-hydroxynicotinate (MEHNA) have been studied using absorption, fluorescence excitation and fluorescence spectroscopy, as well as, using single photon counting nanosecond spectrofluorimeter. MEHNA is present as enol in less polar solvents and keto in polar media. In non-polar solvents, large Stokes shifted fluorescence band is assigned to phototautomer, formed by excited state intramolecular proton transfer (ESIPT), whereas fluorescence is only observed from keto form in polar solvents. In aqueous and polar solvents monocation (MC) is formed by protonating the exo carbonyl oxygen atom in the ground state (S₀) and in the first excited singlet state (S₁), MC is obtained by protonating carbonyl oxygen atom of the ester. It is formed by ESIPT from exo carbonyl proton to carbonyl oxygen atom of the ester. Dication is formed by protonating both the oxygen atoms. Two kinds of monoanions formed by deprotonating phenolic proton or >N-H proton of keto suggest the presence of enol and keto in aqueous solution. In cyclohexane MC is formed by protonating carbonyl oxygen in both S₀ and S₁ states. The electronic structure calculations were performed on each species using semi-empirical quantum mechanical AM1 method and density functional theory B3LYP with 6-31G^** basis set using Gaussian 98 program, along with potential energy mapping, to characterize the particular species.     

Excited-state inter- and intramolecular proton transfer in methyl 3-hydroxy-2-quinoxalinate: effects of solvent and acid or base concentrations

Absorption, fluorescence excitation and fluorescence spectroscopy, combined with time-dependent spectroscopy and semi-empirical (AM1) and density functional theory using Gaussian 98 program calculations have been used to study the effects of solvent and acid or base concentration on the spectral characteristics of methyl 3-hydroxy-2-quinoxalinate (M3HQ). M3HQ is present as enol in less polar solvents and as keto in polar media. In non-polar solvents, large Stokes shifted fluorescence band is assigned to the phototautomer, formed by the excited-state intramolecular proton transfer, whereas fluorescence is only observed from keto in the polar solvents. In aqueous and polar solvents the monocation (MC5/MC6) is formed by protonating the carbonyl oxygen atom in the ground (S₀) and the first excited singlet states (S₁). Dication is formed by protonating one of N- atom of MC5/MC6. Monoanion is formed by deprotonating the phenolic proton of enol in the basic solution. pK_a values for different prototropic equilibriums were determined in S₀ and S₁ states and discussed.     

铂催化3-炔-1-醇分子内加氢烷氧基化反应的理论研究

用密度泛函理论(DFT) M06-2X方法对铂催化的3-炔-1-醇分子内加氢烷氧基化反应机理和区域选择性进行了计算研究.计算结果表明:(1)通过羟基氧原子分别进攻分子内不同的炔烃碳原子形成两种竞争机制;(2)反应的关键步骤是分子内成环过程和氢迁移得到目标产物并释放催化剂的过程;(3)对于5-外切形成五元环产物的反应路径,具有相对较低的活化自由能;(4)两个竞争通道有一定的能量差,表明反应具有选择性但也会有副产物.计算研究结果与实验合成一致,并对实验报道给予了很好的补充和解释.     

糖与氨基酸反应产物结构的EPR和13C NMR研究

应用EPR和¹³C NMR技术系统地研究了糖与氨基酸反应的产物。EPR波谱分析表明,反应产物的结构主要取决于氨基酸的结构。¹³C NMR波谱的化学位移表明、反应产物的结构应该是2,5-哌嗪二酮,糖是作为1,4位取代的配位基。本文还提出了一种可能的反应机制。     

糖与氨基酸反应产物结构的EPR和~(13)C NMR研究(英文)

应用EPR和~(13)C NMR技术系统地研究了糖与氨基酸反应的产物。EPR波谱分析表明,反应产物的结构主要取决于氨基酸的结构。~(13)C NMR波谱的化学位移表明、反应产物的结构应该是2,5-哌嗪二酮,糖是作为1,4位取代的配位基。本文还提出了一种可能的反应机制。     

Experimental study on the reaction pathway of α‐haloacetophenones with nucleophiles: direct substitution or carbonyl addition?

The reaction of PhCOCH₂Cl with OH^– gave the expected α‐substituted alcohol (PhCOCH₂OH) in addition to three dimer products. To clarify whether the substitution product is formed by direct S_N2 or via carbonyl addition, the reaction of PhCOCH₂Cl and OMe^– was examined. The reaction gave two products, PhCOCH₂OH as the major product after acid hydrolysis and PhCOCH₂OMe as the minor product. An electron‐withdrawing substituent on the phenyl ring enhanced the overall reactivity and gave more alcohol than ether. It was concluded that the alcohol was formed via carbonyl addition‐epoxidation route, whereas the ether was formed by the direct substitution route. Copyright © 2012 John Wiley & Sons, Ltd.     

基于二维相关红外光谱的鱼糜品质检测可行性分析

对二维相关光谱在鱼糜品质检测中的可行性进行了分析。利用二维相关技术结合中红外光谱技术对冻融处理后白鲢鱼糜蛋白二级结构变化进行了分析。在冻融次数和温度双重外扰的作用下对样品进行了分析。以冻融次数为外扰的二维相关光谱分析结果揭示了鱼糜蛋白二级结构的变化顺序： α-螺旋结构、分子内聚集的β-折叠结构→反平行的β-折叠结构→羰基结构;基于温度外扰的二维相关光谱分析结果表明： 冻融处理1次和2次后鱼糜蛋白二级结构变化轻微。而冻融处理3次之后鱼糜蛋白二级结构已遭到严重破坏。结果分析还发现： 外扰温度为45℃时,温度对羰基的影响比大大小于冻融循环对鱼糜蛋白二级结构的影响。以上结果说明二维相关光谱技术可以探测并直观的反应出鱼糜蛋白二级结构变化程度。如果能将这种变化程度量化,则可以利用该技术对鱼糜新鲜度等品质进行快速检测。     

Time-dependent density functional theory study on excited state intramolecular proton transfer of 3-hydroxy-2-(pyridin-2-yl)-4H-chromen-4-one

The time-dependent density functional theory (TDDFT) method was carried out to investigate the excited state intramolecular proton transfer (ESIPT) process of 3-hydroxy-2-(pyridin-2-yl)-4H-chromen-4-one (1a). 1a has two tautomeric forms: one is 1a(O), which is induced by intramolecular hydrogen bond O-H?O=C, and the other one is 1a(N), which is caused by intramolecular hydrogen bond O-H?N. From excited state to tautomer excited state coming from ESIPT, the hydroxyl hydrogen breaks away and the dissociated hydrogen adsorbed on pyridinic nitrogen or carbonyl oxygen formed new intramolecular HB and the corresponding bond length and bond angle varied greatly. In comparison, a similar process of proton transfer for 1a(N)H⁺ protonated 1a(N) from ground state to excited state was obtained. This detailed proton transfer mechanism was provided by molecular orbitals analysis and it may be applied to molecular switch and organic Lewis acid/base. We investigated the excited state proton transfer mechanism of the four molecules through the theoretical method for the first time and gave unambiguous geometry of excited state.     

Solvent Effect on the Isotopic Ratios vo OH/vOD and AOH/AOD in a Tetrachlorosubstituted Mannich Base

Mannich bases are compounds formed from phenols and amines, characterized by intramolecular hydrogen bonds whose strength depends on the substituent implanted on the phenol ring; moreover, as shown by uv measurements, the strength of the interaction for a given phenol derivative depends strongly on the solvent In this work, we have studied the ir spectra of 2,3,4,5-tetrachloro-6-[(diethylamino)methyl]phenol (TCMBH)     

环戊二烯与二氢呋喃类化合物Diels-Alder反应的理论研究

采用量子化学密度泛函理论(DFT)在B3LYP/6-311++G **水平上对环戊二烯与2(5H)-呋喃酮、丁烯二酸酐和2,5-二氢呋喃的Diels-Alder反应机理进行了理论研究,并且考虑了溶剂化效应和取代基效应对反应机理及能垒的影响。结果表明,本文所涉及的环戊二烯与二氢呋喃类化合物的Diels-Alder加成反应是以协同方式进行的;羰基取代基的吸电子作用是造成产物中C(1)-C(2)、C(3)-C(4)键键长增加的主要原因;反应所涉及到的FMO相互作用主要是环戊二烯的HOMO与二氢呋喃类化合物的LUMO之间的相互作用,羰基对反应活化能的影响主要是通过降低呋喃类化合物的LUMO能级,减小与环戊二烯的HOMO的能级差异,从而有利于反应进行的;反应2的活化能垒最低,从动力学的角度考虑在室温下可以进行。