Identification of Molecular Crystals Capable of Undergoing an Acyl‐Transfer Reaction Based on Intermolecular Interactions in the Crystal Lattice

Investigation of the intermolecular acyl‐transfer reactivity in molecular crystals of myo‐inositol orthoester derivatives and its correlation with crystal structures enabled us to identify the essential parameters to support efficient acyl‐transfer reactions in crystals: 1) the favorable geometry of the nucleophile (? OH) and the electrophile (C?O) and 2) the molecular assembly, reinforced by C? H???π interactions, which supports a domino‐type reaction in crystals. These parameters were used to identify another reactive crystal through a data‐mining study of the Cambridge Structural Database. A 2:1 co‐crystal of 2,3‐naphthalene diol and its di‐p‐methylbenzoate was selected as a potentially reactive crystal and its reactivity was tested by heating the co‐crystals in the presence of solid sodium carbonate. A facile intermolecular p‐toluoyl group transfer was observed as predicted. The successful identification of reactive crystals opens up a new method for the detection of molecular crystals capable of exhibiting acyl‐transfer reactivity.     

Modeling of Osmotic Pressure of Aqueous Poly(Ethylene Glycol) Solutions Using the Artificial Neural Network and Free Volume Flory Huggins Model

In this work, the modified Flory-Huggins coupled with the free-volume concept and the artificial neural network models were used to obtain the osmotic pressure of aqueous poly(ethylene glycol) solutions. In the artificial neural network, the osmotic pressure of aqueous poly(ethylene glycol) solutions depends on temperature, molecular weight and the mole fractions of poly(ethylene glycol) in aqueous solution. The network topology is optimized and the (3-1-1) architecture is found using optimization of an objective function with batch back propagation (BBP) method for 134 experimental data points. The results obtained from the neural network in obtaining of the osmotic pressure of aqueous poly(ethylene glycol) were compared with those obtained from the free volume Flory-Huggins model (FV-FH). The results showed that the modified Flory-Huggins model and also the artificial neural network can accurately predict the osmotic pressure of aqueous poly(ethylene glycol) solutions but the accuracy of ANN is much better than the modified Flory-Huggins model.     

Dess-Martin Periodinane on Silica: Rapid Oxidation of Alcohols using Microwaves

Adsorbed on silica gel. Dess-Martin periodinane can rapidly oxidize alcohols to the corresponding carbonyl compounds upon exposure to microwave under solvent-free condition.     

The rapid and efficient synthesis of disulfides from alkyl and acyl halides

Various symmetrical dialkyl and diacyl disulfides are prepared easily in high yields from the corresponding alkyl and acyl halides under mild and nonaqueous conditions using N,N′-dibutyl-N,N,N′,N′-tetramethyl-ethylenediammonium tetrahydroborate (BTMETB) or N,N′-dibenzyl-N,N,N′,N′-tetramethylethylenediammonium tetrahydroborate (BZTMETB) and elemental sulfur. The quaternary diammonium borohydrides were easily prepared by treatment of the corresponding quaternary diammonium chloride or bromide with alkaline solution of sodium borohydride at room temperature. Correspondence: Mahmood Tajbakhsh, Department of Chemistry, Mazandaran University, Babolsar, Iran.     

A Rh(II)-catalyzed cycloaddition approach toward the synthesis of komaroviquinone

Using a rhodium(II)-catalyzed cyclization/cycloaddition sequence as the key reaction step, the icetexane core of komaroviquinone was constructed by an intramolecular dipolar-cycloaddition of a carbonyl ylide dipole across a tethered π-bond. The ylide was arrived at by cyclization of a rhodium carbenoid intermediate onto a proximal ester group. Efforts toward the preparation of the required precursor for elaboration to the natural product are discussed.     

A stereodivergent,two-directional synthesis of stereoisomeric C-linked disaccharide mimetics

Dipyranones, such as 1,2-bis[(2R,3S,6S)-3-hydroxy-6-methoxy-3-oxo-6H-pyran-2-yl]ethane, were exploited as templates for the synthesis of some novel C-linked disaccharide analogues. Efficient methods, such as stereoselective reduction and dihydroxylation, were developed for two-directional functionalisation of these templates. Peracetylated derivatives of ten stereoisomeric disaccharide analogues [acetic acid 4,5-diacetoxy-6-methoxy-[(3',4',5'-triacetoxy-6'-methoxytetrahydropyran- 2'-yl)ethyl]tetrahydropyran-3-yl esters] were synthesised from a virtual library of 136 compounds; furthermore, an additional eight stereoisomers could have been synthesised simply by using the enantiomeric ligand in the enantioselective step. The ability of (2S,3S,4R,5R,6R)-6-methoxy-2-[2'-((2'R,3'R,4'S, 5'R,6'S)-3',4',5'-trihydroxy-6'-methoxytetrahydropyran-2'-yl) ethyl]tetrahydropyran-3,4,5-triol to bind to the repressor protein, LacI, was estimated to be similar to that of isopropyl-beta-thiogalactoside. The disaccharide mimetics were concluded to be a new and interesting class of C-linked disaccharide mimetics with promising, though largely unstudied, biological activity.     

A solution- and solid-phase approach to tetrahydroquinoline-derived polycyclics having a 10-membered ring

With the goal of library generation using a polycyclic derivative 5 having an enamide functional group, a simple and practical, enantioselective synthesis of tetrahydroquinoline derivative 2 was achieved. The phenolic hydroxyl group in compound 2 was utilized as an anchoring site for solid-phase synthesis. The ring closing metathesis approach yielded the desired polycyclic product 5 on solid phase in five steps (overall 40% yield). Compound 5 is a novel scaffold for the library generation of natural product-like polycyclics having a functionalized medium ring for obtaining a new class of small molecules to be utilized as chemical probes.     

Syntheses,Characterization and X‐Ray Structures of the first Copper(I) and Silver(I) Complexes with ATT (ATT = 6‐Aza‐2‐thiothymine)

The reaction of copper(I) chloride with 6‐aza‐2‐thiothymine (ATT, 1 ) and triphenylphosphane in methanol/chloroform gives [(ATT)CuCl(PPh₃)] ( 2 ) as a neutral complex. [(ATT)Ag(NO₃)(PPh₃)₂]·MeOH ( 3 ) can be obtained by the reaction of 1 with silver(I) nitrate and triphenylphosphane in methanol/chloroform in excellent yields and the single crystals of 3 can be obtained from acetonitril solution. Both complexes were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for 2 at —80 °C: space group I2/a with a = 1859.3(1), b = 1143.2(1), c = 2208.2(1) pm, β = 104.84(1)°, Z = 8, R₁ = 0.0355 and for 3 at —80 °C: space group P2₁/c with a = 1344.1(1), b = 1553.6(1), c = 1977, 3(3) pm, β = 105.26(1)°, Z = 4, R₁ = 0.0436.     

Pd-Cu catalyzed heterocyclization during Sonogashira coupling: synthesis of 3-benzylthiazolo[3,2-a]benzimidazole

The reaction of 2-mercaptopropargyl benzimidazole with various iodobenzenes catalyzed by Pd-Cu leads to the formation of 3-benzylthiazolo[3,2-a]benzimidazoles.     

Gas Chromatography–Mass Spectrometry Determination of Pregabalin in Human Plasma Using Derivatization Method

A gas chromatography–mass spectrometry method for the determination of pregabalin in human plasma is described. The procedure involves precipitation of protein, liquid–liquid extraction with ethylene glycol monomethyl ether, and derivatization with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of N-hydroxysuccinimide as additive. Separation was attained on HP column (30 m × 0. 25 mm ID, 0.25 μm) coupled with mass spectrometric detector using electron impact selected ion monitoring. The assay showed an excellent linearity in the concentration range of 0.36–10 μg mL^?1 with correlation coefficient (r²) values of 0.999. The intra- and inter-day assay variations for three different concentration levels were less than 10%. The limit of quantification was detected at 0.36 μg mL^?1. The method is highly specific, precise, accurate, and reproducible and could also be applied for the determination of pregabalin in human plasma.