含绿色荧光蛋白发色团双自由基分子的非线性光学性质

采用密度泛函理论(DFT)方法研究了系列含绿色荧光蛋白发色团双自由基分子光学异构体的几何结构、极化率(αs)和第一超极化率(βtot).结果表明,引入电子给受体取代基使分子的极化率增大,而对第一超极化率有不同影响.对于光照前的反式结构,引入电子受体βtot值增加,且βtot值随取代基吸电子能力的增强而增大;引入电子给体βtot值降低,且βtot值随取代基给电子能力的增强而减小.当分子变成相应的顺式结构时,其βtot值变化趋势与反式结构的结果正好相反.光异构化前后分子的βtot值变化不同,引入电子受体使顺式结构的βtot值比反式结构的小,其中―NO2使顺式结构的βtot值减小为反式结构的1/6;引入电子给体使反式结构的βtot值比顺式结构的小,其中―NH2使反式结构的βtot值减小为顺式结构的1/6.从而,光异构化起到调节非线性光学(NLO)响应的作用.     

An Investigation of the Metabolism of Amitriptyline Using High Performance Liquid Chromatography

Abstract

A systematic study of the metabolism of the antidepressant amitriptyline was conducted using an inbred strain of rats. Variables affecting rat liver metabolism in vitro that were examined include age of the rat, the substrate concentration, and pH. A liquid-liquid extraction with hexane-butanol and back extraction into phosphoric acid was developed to provide efficient extraction for the wide range of polarity exhibited by amitriptyline and seven metabolites (amitriptyline-N-oxide, cis and trans isomers of 10-hydroxy-amitriptyline, cis and trans isomers of 10-hydroxynortriptyline, nortriptyline, and desmethylnortriptyline). HPLC was performed with 5 μm C-8 reversed phase column and a methanol/sodium phosphate buffer/amine modifier mobile phase.     

Spectroscopic Characterization of the Geminal Isomer of Lewisite

Abstract

Lewisite is generally a mixture of several components with the trans isomer of lewisite being the predominant compound. A geminal isomer has not been previously reported as one of the components of the mixture. In the lewisite samples we examined, the geminal isomer, dichloro(l-chlorovinyl)arsine, comprised 2.7 per cent of the total material compared to 95.2 and less than 1 per cent, respectively, for the trans and cis isomers. The remaining fraction was not identified. The geminal isomer of lewisite has been characterized along with the trans and cis isomers using several spectroscopic techniques. Proton NMR of the geminal isomer produced a coupling constant consistent with vinylic protons in a geminal configuration. Mass spectrometry and infrared spectroscopy characterizations were based on an ethanedithiol derivative of the lewisite isomers with gas chromatography used to first separate the derivatized isomers. The electron ionization massspectra of the trans and cis derivatives were very similar, but significant differences were observed in the mass spectrum of the geminal form. Infrared absorption spectra were obtained for the trans and geminal derivatives with significant differences observed between the two, but the method was not sensitive enough to detect the cis isomer.

     

GC/FTIR Potential for Structural Analysis of Marine Origin Complex Mixtures

Abstract

In this paper, we show the GC/FTIR contribution to the structural elucidation of marine origin complex mixtures. Three examples are given concerning aromatic hydrocarbons, fatty acid methyl esters and polychlorobiphenyls. These examples show the capability of GC/FTIR to differentiate isomers of aromatic hydrocarbons and polychlorobiphenyls and to rapidly characterize the different classes of fatty acid methyl esters (ramification, insaturation, cis/trans isomerism, hydroxyl group, cyclopropane ring).     

SYNTHESIS AND CONFORMATIONAL STUDIES OF A NUMBER OF SATURATED BICYCLIC SIX-MEMBERED RING PHOSPHITES

Abstract

An ¹H NMR study of the conformation of the dioxaphosphorinane ring of a number of diastereoisomeric bicyclic saturated six-membered ring phosphites (3ab-10ab) has been performed. The dioxaphosphorinane ring of these phosphites is transannelated with a tetrahydrofuran, cyclopen-tane, tetrahydropyran or cyclohexane ring. The substituent on the phosphorus atom is a methoxy or phenoxy group. It is shown that the cis isomers 3a-10a prefer a chair conformation of the dioxaphosphorinane ring, independent of the substituent on the phosphorus atom and of the nature of the transannelated ring. In contrast, for the trans isomers 3b-10b a twist rather than a chair conformation of the dioxaphosphorinane ring is preferred. The fraction of the twist conformer in the trans isomers is mainly determined by the substituent on phosphorus. The size and composition of the transannelated ring are relatively unimportant in this respect. For both cis and trans isomers the preferred geometry is solvent-independent. The measured ^3JPOCH couplings of the cis isomers 3a-10a are used to formulate an expression for the dependence of such couplings upon dihedral angles in bicyclic phosphites.     

Kinetic Studies of the Thermal cis-to-trans Isomerization of Dioxaphospholanes

By following a previously reported method,¹ the synthesis of r-2-alkoxy-cis-4-cis-5-dimethyl-1,3,2-λ³-dioxaphospholanes ligands (1 and 3) was carried out. The purpose of this work is the kinetic study of the inversion barrier at phosphorus for 1 and 3 and the comparison with the already informed dioxaphospholane 2. The kinetic measurements of the thermal isomerization cis-to-trans were performed by ³¹P NMR spectroscopy, observing a first order kinetics for both compounds. The energy of activation (E_a) for the epimerization of compounds cis-1 and cis-3 was calculated to be 16.0 ± 0.6 and 11.8 ± 0.8 kcal/mol, respectively. The values of the thermodynamic parameters of the transition state (Δ H^≠, Δ S^≠, Δ G^≠) suggest that the inversion at phosphorus not only depends on the spatial requirements of the alkoxy substituent but also on entropic effects. The thermodynamic parameters Δ H°, Δ S°, and Δ G° were also evaluated and they show that the cis isomers are preferred from enthalpic point of view, but entropic effects dominate the equilibrium trans ? cis leading to the entropically favored trans isomers. Furthermore, the results are supported by density functional theory calculations of 1–4 at the B3LYP/6-31G** level.     

Tris(dialkylamino)phosphine Chalcogenide Complexes of Tin(IV) Chloride: A Multinuclear (31P, 77Se,and 119Sn) NMR Characterization

Abstract

Four octahedral complexes of the type SnCl₄.2L [L = (R₂N)₃P(E): E = Se; R = Me(1), Et(2) and E = S; R = Me(3), Et(4)] have been studied in solution by multinuclear (³¹P, ⁷⁷Se, and ¹¹⁹Sn) NMR spectroscopy. ³¹P and ⁷⁷Se NMR data were informative of changes associated with complex formation. The solution structure of the complexes was confirmed by their ¹¹⁹Sn NMR spectra that showed two triplet features for each complex, attributed to a mixture of the expected cis and trans isomers. The triplet signal is due to the coupling with two equivalent phosphorus atoms, consistent with an octahedral geometry around the tin center. In addition, density functional theory (DFT)/B3LYP calculations have been carried out to support the interpretations of NMR data. The results are discussed and compared with those reported for related complexes.

GRAPHICAL ABSTRACT      

Donor-Acceptor Complexes in Copolymerization. XXXV. Alternating Diene-Dienophile Copolymers. 3. Copolymerization of cis- and trans-1, 3-Pentadiene with Maleic Anhydride and Acrylonitrile… AlEt1.5CI1.5

Abstract

The copolymerization of the cis or trans isomers of 1,3-pentadiene with maleic anhydride in the presence of a peroxide catalyst yields identical equimolar, alternating copolymers in which the pentadiene units have a cis-1, 4 configuration (IR, NMR). The copolymerization of the cis or trans isomers of 1, 3-pentadiene with acrylonitrile in the presence of ethyl aluminum sesquichloride yields identical equimolar, alternating copolymers in which the pentadiene units have a trans-1,4 configuration (IR, NMR). Although the trans isomer forms cyclic adducts with both maleic anhydride and acrylonitrile, the cis isomer does not undergo the Diels-Alder reaction with these dienophlles. The formation of identical copolymers from cis- and trans-1, 3-pentadiene is attributed to isomerization of the diene-dienophile charge transfer complex in the excited state, resulting in the generation of the same homopolymerizable exciplex from both isomers.     

Syntheses of shuttlecock- and bowl-equipped phenylazopyridines and photomodulation of their coordination ability to Zn-porphyrin

Shuttlecock- and bowl-equipped 4-(phenylazo)pyridine derivatives, which bear substituents that allow the pyridine moiety to protrude in the trans form but hinder it in the cis form, have been designed and synthesized. These molecules show cis/trans photoisomerization despite the presence of bulky substituents. ¹H NMR titration with Zn-porphyrin showed that the trans isomers coordinate to Zn-porphyrin much stronger than the cis isomers.     

31P-NMR-SPEKTROSKOPISCHER NACHWEIS VON SUPERMESITYL-SUBSTITUIERTEM TRIPHOSPHAALLYLLITHIUM UND 2-ARSA-1,3-DIPHOSPHAALLYLLITHIUM

Abstract

The compounds 1.3-bis(2,4,6-tri-tert.butylphenyl)triphosphaallyllithium (5) and 1.3-bis(2,4,6-tritert.butylphenyl)-2-arsa-1,3-diphosphaallyllithium (7) are prepared by deprotonation of a phosphino-substituted diphosphene and arsaphosphene, resp. The presence of trans/trans and cis/trans isomers has been proven by ³¹P-NMR spectroscopy.

Die Verbindungen 1.3-Bis(2,4,6-tri-tert.butylphenyl)triphosphaallyllithium (5) und 1.3-Bis-(2,4,6-tri-tert.butylphenyl)-2-arsa-1,3-diphosphaallyllithium (7) werden durch Deprotonierung eines phosphino-substituierten Diphosphens bzw. Arsaphosphens dargestellt. Das Vorliegen von trans/trans und cis/trans-Isomeren wird durch ³¹P-NMR-Spektroskopie nachgewiesen.     

The Structure of 2,4-Diorganyl-2,4-Dithioxo-1,3,2λ5,4λ5-Dithiadiphosphetanes in Solution

Abstract

Compounds of the overall composition RPS₂, so called perthiophosphonic acid anhydrides, prefer a dimeric structure in szlution, as it has already been known for the solid compounds. Following compounds [RP(S)S]₂ with R=methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, cyclohexyl, phenyl, 4-methoxy-phenyl and 3,5-dimethyl-piienyl were prepared and characterized by iJJR spectroscopy. The 3,5-ditert-butyl-4-hydroxy-phenyl-compound [1] was also investigated. NHR investigations give evidence for the existence of conligurational isomers of the 2,4-Diorganyl-2,4-dithi-oxo-1,3,2λ⁵,4λ⁵-dithiadiphosphetanes. In solutions an equllibrium between cis and trans isomers is established. The concentration of the two isomers depends on the kind of P and the solvent used. In general the trans isomer has a nigher concentration than the cis isomer. The easy preparation of unsymmetrical compounds by mixing solutions of compounds with different R shows a continous dissociation and association process of the PSPS-ring. This result underlines the existence of a monomeric compound of low concentration as intermediate. An interesting result is obtained for the isopropyl compound. After dissolving e.g. in CDC1₃ almost 90% of the compound is transformed into the other isomer. The progress of the transformation can be followed by NXR spectroscopy. In all other cases the equilibrium state is immediately achieved after preparation of the solution.     

Tin(IV) Tetrachloride Complexes with Bis-(Dialkylamino)phosphoryl Fluoride: A Multinuclear (119Sn, 31P, 19F,and 1H) NMR Characterization in Solution

The two octahedral complexes SnCl₄·2(O)PF(NR₂)₂ (R = Me or Et) were prepared from reaction of SnCl₄ with the ligand (R₂N)₂P(O)F in anhydrous CHCl₃. The new adducts have been characterized by elemental analysis, IR, and multinuclear (¹¹⁹Sn, ³¹P, ¹⁹F, and ¹H) NMR spectroscopy. The NMR data show that the adducts exist in solution as a mixture of cis and trans isomers with markedly different proportions. When compared with previously described hexamethylphosphoramide (HMPA) and trimethylphosphate (TMPA) analogues, our results indicate that the cis isomer is the predominant species in solution. Low temperature ³¹P and ¹¹⁹Sn NMR spectra show that the compounds partially dissociate in dichloromethane.     

Bonded Cyclodextrin Stationary Phase Columns for the Separation of Cis/Trans Cyclohexane Derivatives

Abstract

Cyclohexane derivatives are important in the manufacture of monomers for the preparation of polyester polymers. The separation of cis/trans isomers of these derivatives has been investigated by using a bonded cyclodextrin column. This stationary phase offers excellent selectivity for the separation of these compounds. Although the efficiency of this column with the cyclohexane derivatives is less than the efficiency with nitroanalines, its excellent selectivity enabled adequate separation of the isomers of all but one of the compounds studied. A strategy for enhancing the efficiency and selectivity of this stationary phase is presented.     

Environmental Analysis of Cypermethrin and its Degradation Products After Forestry Applications

Abstract

Cypermethrin and alphamethrin ([1R, cis, αS]- and [1S, cis, αR]-cypermethrin) are pyrethroid insecticides used in agriculture, forestry, and public health hygiene. After forestry applications of cypermethrin against bark beetles diastereo- and enantioselective analyses of pyrethroid residues are performed by gas chromatography (GC) with electron capture (ECD) and mass spectrometric (MS) detection, or by achiral and chiral high performance liquid chromatography (HPLC). The major soil metabolites of cypermethrin, i.e. 2,2-dimethyl-3-(1,1-dichlorovinyl)-cyclopropylic acid and 3-phenoxybenzoic acid, are analyzed as methyl esters by GC-MS with electron-impact (EI) ionization. On spruce bark cypermethrin persists several months as surface films of 1 μg/cm^2. In soil it is detected as long as seven months after treatment at levels of 0.15–0.7 μg/g. Sunlight-induced cis, trans isomerization on bark and leaves results in an excess of trans-cypermethrin isomers. In soil cis-cypermethrin isomers are more persistent than their corresponding trans-isomers. Enantioselective HPLC demonstrates chiral discrimination of a pair of trans-cypermethrin enantiomers. Analysis of soil metabolites is less meaningful since traces of the investigated products are formed from pyrethroid residues during the extraction and derivatization procedures.     

Asymmetric Cyclic Phosphorothonamides Containing Substituted Pyridine

In order to find high-acitivity and low-toxicity pesticidal lead compounds, a type of novel, asymmetric cyclic phosphorothonamides containing substituted pyridine were synthesized via the condensation reactions of 2-chloro-4-substitutedphenyl-5,5-dimethyl-1,3,2-dioxaphosphinane 2-sulfide with 3-aminomethylpyridine. The cis and trans isomers of the products were isolated by column chromatography on silica gel. The structures of the products were characterized by ¹ H NMR, ³¹ P NMR, MS, and elemental analyses. The configuration of 3a was determined by X-ray diffraction analysis. The results of the preliminary bioassay showed that the new compounds possess potential fungicidal activities.     

Selective 1Hα NMR Methods Reveal Functionally Relevant Proline cis/trans Isomers in Intrinsically Disordered Proteins: Characterization of Minor Forms,Effects of Phosphorylation,and Occurrence in Proteome

It is important to identify proline cis/trans isomers that appear in several regulatory mechanisms of proteins, and to characterize minor species that are present due to the conformational heterogeneity in intrinsically disordered proteins (IDPs). To obtain residue level information on these mobile systems we introduce two ¹H^α-detected, proline selective, real-time homodecoupled NMR experiments and analyze the proline abundant transactivation domain of p53. The measurements are sensitive enough to identify minor conformers present in 4–15 % amounts; moreover, we show the consequences of CK2 phosphorylation on the cis/trans-proline equilibrium. Using our results and available literature data we perform a statistical analysis on how the amino acid type effects the cis/trans-proline distribution. The methods are applicable under physiological conditions, they can contribute to find key proline isomers in proteins, and statistical analysis results may help in amino acid sequence optimization for biotechnological purposes.     

Selective 1Hα NMR Methods Reveal Functionally Relevant Proline cis/trans Isomers in Intrinsically Disordered Proteins: Characterization of Minor Forms,Effects of Phosphorylation,and Occurrence in Proteome

It is important to identify proline cis/trans isomers that appear in several regulatory mechanisms of proteins, and to characterize minor species that are present due to the conformational heterogeneity in intrinsically disordered proteins (IDPs). To obtain residue level information on these mobile systems we introduce two ¹H^α-detected, proline selective, real-time homodecoupled NMR experiments and analyze the proline abundant transactivation domain of p53. The measurements are sensitive enough to identify minor conformers present in 4–15 % amounts; moreover, we show the consequences of CK2 phosphorylation on the cis/trans-proline equilibrium. Using our results and available literature data we perform a statistical analysis on how the amino acid type effects the cis/trans-proline distribution. The methods are applicable under physiological conditions, they can contribute to find key proline isomers in proteins, and statistical analysis results may help in amino acid sequence optimization for biotechnological purposes.     

STEPWISE ELIMINATION OF ETHANE TO SYNTHESISE NEW CYCLIC AND CAGE-LIKE GALLIUM-PHOSPHORUS COMPOUNDS

The reaction of GaEt₃ with H₂PSiMe₂R (R = CMe₂] initially yields the cyclic compound [(Et₂Ga)₂{P(H)SiMe₂R}₂] 1. 1 appears as a mixture of cis and trans isomers and has been characterized by ³¹P NMR spectroscopy, IR spectroscopy, and mass spectrometry. 1 decomposes at 180°C under elimination of ethane during 1 h to form the cage-like compound [EtGaPSiMe₂R]₄ (2). Central structural motif of 2 is a Ga₄P₄ heterocubane cage.     

Synthesis of 3-Ethoxy-2-Oxo-3-Phenyl-1,2-Oxaphosphorinane-3,5-Diene

Abstract

In view of the limited number of examples of 2-oxo-l,2-oxaphosphorinane3,5diene derivatives^1,2, we investigated the preparation of the title compound and derivatives of the same. Of additional interest were the spectroscopic propertits of this class of compounds, their stability, and the outcome of their reaction with nucleophilts. Prior work in our laboratory on the synthesis of simple phostones and their derivatives³, led us to use these as starting mataials. The presence of the phenyl substituent in la, (cis and trans isomers) permitted facile introduction of a bromo group through free radical bromination with NBS/AIBN to give 2a,b in 79% overall yield. The individual isomers of 2 were separated; tentative stereochemical assignments were made using NMR spectroscopy. Treatmnt of 2 with LiCl/DMF gave 3; the trans isomer (phenyl and OEt trans) 2b reacted much faster than the cis isomer. Treatmnt of 3 with NBS/AIBN gave 4a,b and 5 which were separated by flash chromatography. Dehydrobromination of 4 (71% yield) was achieved by heating with an excess of Et₃N in toluenc at 95°C to produce 6; likewise, dehydrobromination of 5 at 70°C gave 7.     

Competitive formation of cis and trans derivatives in the nucleophilic substitution reactions of cyclophosphazenes having a mono-spiro P-NHR group

Nucleophilic substitution reactions of N(3)P(3)Cl(4)[NH(CH(2))(3)NMe] (1) and N(3)P(3)Cl(4)[NH(CH(2))(3)O] (2) with mono-functional alcohols (methanol, 2,2,2-trifluoroethanol, phenol) and a secondary amine (pyrrolidine) were used to investigate the relationship between the incoming nucleophile and the proportions of products with substituents that are cis or trans to the spiro NH moiety. The reaction products were characterized by elemental analysis, mass spectrometry, (1)H and (31)P NMR spectroscopy and the configurational isomers by X-ray crystallography. Six products have been characterised with the substituent cis to the spiro NH group for the alcohol (methanol, phenol) and pyrrolidine derivatives of both compounds 1 and 2, compared to just one derivative with the substituent trans to the spiro NH group, that for the pyrrolidine derivative of compound 2. For each reaction the relative proportions of cis and trans isomers were determined by (31)P NMR measurements of the reaction mixtures. It was found that the reactions of compound 1 with all three alcohols and of compound 2 with methanol lead to exclusive formation of isomers with the substituent cis to the NH moiety, whereas all other reactions lead to mixtures of cis and trans isomers in different ratios under standard reaction conditions. However, when crown ether is included in the reaction medium for the reactions of compound 2 with both 2,2,2-trifluoroethanol and phenol, it is found that only cis isomers are formed. All these results are rationalised in terms of the competition between at least two effects; the cis-directing effect by hydrogen bonding of the incoming nucleophile to the spiro N-H group already present on the cyclophophazene ring and the cis-directing effect of the sodium cation coordinating to the oxygen lone pairs of the P-O moiety of the spiro ring.