Theoretical Studies on the Conformation of mono-6-O-p-nitrobenzoyl-β-cyclodextrin in Aqueous Solution

The conformation of mono-6-O-p-nitrobenzoyl-β-cyclodextrin was studied with B3LYP/6-311g**//PM3 calculations in vacuum and in water solution. It was concluded that the p-nitrobenzoyl group of the molecule should be located above the primary hydroxyls of the cyclodextrin instead of being completely enclosed by the cavity. It was proposed that the behavior might be caused by the requirement of a cis ester bond in the self-included conformation of the molecule.

Cu(I)/Diamine-catalyzed Aryl-alkyne Coupling Reactions

CuI/ethylene diamine/K2CO3/dioxane is shown to be a useful system for the cross coupling reactions of various aryl iodides and bromides with aryl and alkyl alkynes. Compared to the conventional Sonogashira reactions, the new procedure is free of palladium and phosphines.

A Theoretical Study on the Stereoisomerism in the Complex of Cucurbit[8]uril with 2,6-Bis(4,5-dihydro-1H-imidazol-2-yl)naphthalene

Semiempirical PM3 and density function theory B3LYP/3-21g* calculations in vacuum and in water indicated that the 'syn' orientation was preferred in the 1:2 complex of cucurbit[8]uril with protonated 2, 6-bis(4, 5-dihydro-1H-imidazol-2-yl)naphthalene. The pi-pi stacking interaction between the two substrate molecules was proposed as the physical origin of such a behavior.

On the Structure of the Arginine-carboxylate Salt Bridge:A Density Functional Theory Study

High level density functional theory (DFT) calculations are performed for the first time to answer the question whether the arginine-carboxylate salt bridge stays in a zwitterionic state or a neutral one. The results indicate that in the gas phase, the neutral form is more stable and hence proton transfer occurs from guanidinium to carboxylate. However, in an aqueous solution the zwitterionic form should be favored. The difference might he caused by the electrostatic interaction between the salt bridge and its molecular environment. Therefore, the solvation effect has to be considered in the modeling of proteins, whose stabilization depends heavily on the salt-bridges.

Hartree-Fock and Density Functional Theory Studies on the Molecular Recognition of the Cyclodextrin

This study involves initial Hartree-Fock and Density Functional theory calculations onthe molecular recognition of the cyclodextrins. The α-cyclodextrin-acetophenone complexationsystem was investigated with PM3, HF/3-21G* and B3LYP/3-21G* methods. The results indicatedthat the inclusion orientation in which the acetyl group of the acetophenone points towards thesecondary hydroxyls of the a-cyclodextrin was preferable in energy. The steric effect wassupposed as the physical reason of such a behavior Hence, the simple rule the anti-parallelarrangement of the dipoles of the host and guest molecules in the cyclodextrin complexqtion is notgenerally applicable.

Triphenylphosphine-catalyzed isomerization of alkynyl ketones in aqueous solution

An efficient isomerization of alkynyl ketones to (E,E)-diene ketones was developed. The reaction catalyzed by 20 mol% triphenylphosphine in aqueous media gave the desired products in good yields.

A Novel Palladium-Catalyzed Reaction and Its Application in Preparation of Derivatives of Stilbazols

A novel palladium-catalyzed coupling reaction for the preparation of derivatives of stilbazoles was presented. A series of stilbazoles were synthesized firstly by this highly efficient method. From this reaction it was found that reaction solvent is one of important factors in this catalytic system.

A Statistical Examination on the Compensation between the Enthalpies and Entropies Obtained from the Calorimetric Methods

The validity of the compensation between the enthalpies and entropies obtained from the calorimetric methods was statistically examined for the first time based on computer simulations. It turned out that several claimed enthalpy-entropy compensations in literature based upon the calorimetric measurements were statistically correct. Interestingly, a linear relationship between the slopes and correlation coefficients of the T DeltaS-DeltaH plots of different physical origin of the compensation behavior.

Quantitative Structure-Activity Relationships in the Lithium and Sodium Affinities of n-Alkyl Fluorides

B3LYP/6-31+g (d, p) method was used to calculate the lithium and sodium affinities of n-alkyl fluoride. These affinities were found to obey the Holmes relationship, i.e. they correlate linearly with the quotient n/(n+1), where n is the number of carbon atoms in the alkyl chain. From the correlation the limiting values of lithium and sodium affinities for very long alkyl chain were predicted to be 153.3 kJ/mol and 108.4 kJ/mol, respectively.

1,3-Dicarbonyl compounds as phosphine-free ligands for Pd-catalyzed Heck and Suzuki reactions

Some 1,3-dicarbonyl compounds (such as pentane-2,4-dione and 3-oxo-N-phenylbutanamide) were found to constitute highly efficient, yet low-priced and phosphine-free ligands for the Pd-catalyzed Heck and Suzuki reactions of aryl bromides and iodides with very high turnover numbers (ca. 103–104).

Design and Synthesis of Lipids Bearing Nucleosides as Gene Vectors

Some novel lipids bearing nucleosides were designed and synthesized as gene vectors, and the structures of these compounds were characterized by UV, IR, 1HNMR, 13CNMR and elemental analysis.

Cu-catalyzed arylation of phosphinic amide facilitated by (±)-trans-cyclohexane-1,2-diamine

Cu-catalyzed cross coupling between phosphinic amides and aryl halides was accomplished for the first time by using (±)-trans-cyclohexane-1,2-diamine as the ligand. This reaction provided a novel approach for synthesizing arylated phosphinic amides. Both kinetic measurement and theoretical calculation indicated that phosphinic amides were much less reactive than amides by about 10 times in Cu-catalyzed cross coupling.

The Electron Transfer Reaction between ρ-Nitrobenzoates and β-N, N-Dimethylaminonaphthalene

A few of p-nitrobenzoates were synthesized, and the electron transfer of them with b-N, N-dimethylaminonaphthalene (DMAN) in methanol solution was studied. Steady-state fluore-scence results showed the cyclodextrin moiety in p-nitrobenzoyl-b-cyclodextrin would block the electron transfer pathway from DMAN compared with other electron acceptors, thus, reduced the electron transfer efficiency.

Inclusion Complexation of β-CD with Phenothiazine and N-Alkylphenothiazine Derivatives

Inclusion of Acyclodextrin (ACD) with phenothiazine 1 and Nalkylpheno-thiazine derivatives (alkyl = ethyl 2, isobutyl 3 and isopentyl 4) in aqueous solution was studied by means of UV-vis spectroscopy. The association constant Ka values for the inclusion of β-CD with 1, 2, 3 and 4 were determined to be 188, 214, 129 and 80 L/mol, respectively. It indicates that the stability of the inclusion complexes is dependent on the structure and the volume of the substituents in the guest compounds.

A Study on the Inclusion of α-Cyclodextrin with Mono-and 1,4-Disubstituted Benzenes by Neural Networks

The association constant (Ka) values were calculated by the function-strengthen ing neural networks (FNN) for the inclusion complexation of α-CD with mono- and 1,4-disubstituted benzenes. The lnKa predicted by FNN from Rm, π and σ constants of substituents are in great agreement with the experimental data.

A REGRESSION STUDY ON THE INCLUSION OF CYCLODEXTRIN WITH BENZENE DERIVATIVES

A set of regression models have been established for the inclusion of substituted benzenes by alpha- and beta-cyclodextrin with correlations of 0.96 and 0.94, respectively. The 1nK(a) values calculated by the models are in agreement with those determined experimentally. The inclusion process is mainly driven by the van der Waals force and the hydrophobic interactions.

PREDICTION OF STABILITY CONSTANTS FOR INCLUSION COMPLEXESOF β－CYCLODEXTRIN WITH SUBSTITUTED BENZENES BY ARTIFICIAL NEURAL NETWORKS

The stability constants (K.) for inclusion complexes of β-cyclodextrin (β-CD) with substituted benzenes were predicted by the Artificial Neural Networks (ANN). The stability constants obtained byANN from the substituent molar refraction (Rmn), hydrophobic coefficient (πn) and Hammett constant (σx) are very close to those determinedexperimentally. It suggested that the van der Waals force and hydrophobic interactions play important roles in CD inclusion complex formation.

ENTHALPY－ENTROPY COMPENSATION IN THE INCLUSION OF 1－SUBSTITUTED NAPHTHALENES BY β－CYCLODEXTRIN IN WATER

The association constants (K.), free energy (△G￣0), enthalpy (△H￣0) and entropy (△S0) changes were determined for the inclusion complexation of β-cyclodextrin with a series of 1-substituted naphthslenes in aqueous solution. The △H0-T△S0 plot for the β-cyclodextrin complexes with naphthalene derivatives show a linear relationship with slope of 0. 98and intercept of 14. 67. The results were discussed in terms of enthalpy-entropy compensation.

A highly selective and easy-to-synthesize Zn(Ⅱ) fluorescent probe based on 6-methoxyquinolin

A novel fluorescent Zn^2＋ probe based on 6-methoxyquinolin was synthesized in four steps from inexpensive starting materials. It exhibits very strong fluorescence responses and has a remarkably high selectivity to Zn^2＋ than other physiological relevant metal ions. This new compound could be used as low-priced yet high-quality Zn^2＋ probe.

Photoregulation of protein plasmid expression in vitro and in vivo using BHQ caging group

Green fluorescent protein（GFP） plasmid was caged by 8-bromo-7-hydroxyquinolinyl chromophore（BHQ） for controlling its expression with exact spatiotemporal resolution.In vitro and in vivo experiments clearly verified that,comparing with Bhc caging, the expression level of caged GFP plasmid was dramatically decreased and then efficiently restored after subsequent photolysis.