Reaction of 2-(5-aminopyrazol-1-yl)quinoxaline 4-oxides with dimethyl acetylenedicarboxylate

The reaction of 6-chloro-2-hydrazinoquinoxaline 4-oxide 6 with ethyl 2-(ethoxymethylene)-2-cyanoacetate or (1-ethoxyethylidene)malononitrile gave 2-(5-amino-4-ethoxycarbonylpyrazol-1-yl)-6-chloroquinoxaline 4-oxide 7a or 2-(5-amino-4-cyano-3-methylpyrazol-1-yl)-6-chloroquinoxaline 4-oxide 7b , respectively. The reaction of compound 7a or 7b with dimethyl acetylenedicarboxylate resulted in the 1,3-dipolar cycloaddition reaction and then ring transformation to afford 4-(5-amino-4-ethoxycarbonylpyrazol-1-yl)-8-chloro-1,2,3-trismethoxycarbonylpyrrolo[1,2-α]quinoxaline 8a or 4-(5-amino-4-cyano-3-methylpyrazol-1-yl)-8-chloro-1,2,3-trismethoxycarbonylpyrrolo[1,2-α]quinoxaline 8b , respectively.     

A luminescence sensor of inositol 1,4,5-triphosphate and its model compound by ruthenium-templated assembly of a bis(Zn2+-cyclen) complex having a 2,2'-bipyridyl linker (cyclen = 1,4,7,10-tetraazacyclododecane)

A new supramolecular complex (Ru(Zn2L4)3) was designed and synthesized as a luminescence sensor for inositol 1,4,5-triphosphate (IP3), which is one of the important second messengers in intracellular signal transduction, and its achiral model compound, cis,cis-1,3,5-cyclohexanetriol triphosphate (CTP3), by a ruthenium(II)-templated assembly of three molecules of a bis(Zn2+-cyclen) complex having a 2,2-bipyridyl linker (Zn2L4). Single-crystal X-ray diffraction analysis of a racemic mixture of Ru(Zn2L4)3 showed that three of the six Zn2+-cyclen units are orientated to face the opposite side of the molecule with three apical ligands (Zn2+-bound HO-) of each of the three Zn2+ located on the same face. 1H NMR and UV titrations of Ru(Zn2L4)3 with CTP3 indicated that Ru(Zn2L4)3 forms a 1:2 complex with CTP3, (Ru(Zn2L4)3)-((CTP3)6-)2, in aqueous solution at neutral pH. In the absence of guest molecules, Ru(Zn2L4)3 (10 microM) has an emission maximum at 610 nm at pH 7.4 (10 mM HEPES with I = 0.1 (NaNO3)) and 25 degrees C (excitation at 300 nm). An addition of 2 equiv of CTP3 induced a 4.2-fold enhancement in the emission of Ru(Zn2L4)3 at 584 nm. In this article, we describe that Ru(Zn2L4)3 is the first chemical sensor that directly responds to CTP3 and IP3 and discriminates these triphosphates from monophosphates and diphosphates. The photodecomposition of Ru(Zn2L4)3, which is inhibited upon complexation with CTP3, and the stereoselective complexation of chiral IP3 by Ru(Zn2L4)3 are also described.     

Effect of pore size of FSM-16 on the entrapment of flurbiprofen in mesoporous structures

The interaction between FSM-16 and flurbiprofen (FBP) in the mesopores of FSM-16 was investigated by using three types of FSM-16 with different pore diameters, i.e., FSM-16(Oc), FSM-16(Do) and FSM-16(Doc) (pore diameters 16.0, 21.6, 45.0 A, respectively). Solid dispersions of 30% FBP-70% FSM-16 were prepared by solvent evaporation and sealed-heating of the physical mixture at 100 degrees C for 6 h. Changes in the molecular state of FBP were investigated using powder X-ray diffractometry, thermal analysis and FT-IR spectroscopy. The changes in pore diameter and specific surface area of FSM-16 systems were investigated by small angle X-ray scattering and nitrogen gas adsorption. Powder X-ray diffractometry and thermal analysis revealed that FBP was adsorbed onto the mesopores of FSM-16(Do) and FSM-16(Doc), leading to an amorphous state, while no change was observed for FSM-16(Oc). Fourier-transformed IR spectroscopy showed a hydrogen bond interaction between the carbonyl groups of FBP and the silanol groups of FSM-16. The pore diameter and specific surface area of FSM-16 in solid dispersions decreased due to the adsorption of FBP. Improved dissolution of FBP from solid dispersions prepared by the evaporation and the sealed-heating methods was observed in comparison with FBP crystals.     

Stereocontrolled synthesis and determination of the c-24 and 25 stereochemistry of glaucasterol

(24S,25S)- and (24R,25R)-24,26-Cyclocholesta-5,22E-dien-3β-ols (1a and 1b) were synthesized stereoselectively. Their ₁H NMR comparison with natural glaucasterol (1) allowed to conclude that 1 possesses 24S,25S stereochemistry.     

Molecular structure of benzene

The molecular structure of benzene has been determined by combining the average distances obtained by the present electron diffraction study and the moments of inertia reported by Cabana et al. The following thermal average bond distances have been determined: r_g(C-C) = 1.399 ± 0.001 Å and r_g (C-H) = 1.101 ± 0.005 Å. The uncertainties represent the estimated limits of error. The C-H distance of this molecule is similar to vinyl C-H distances.     

Production of 5′-mononucleotides using immobilized 5′-phosphodiesterase and 5′-amp deaminase

The preparations and properties of 5′-phosphodiesterase and 5′-AMP-deaminase immobilized on porous ceramics by covalent binding and the production of 5′mononucleotides from RNA using these immobilized enzymes are described. Comparison tests for the properties of both immobilized and native enzymes were carried out. It was found that the pH optima of these immobilized enzymes were shifted toward the acidic side, and their practically operable pH regions were much more broadened. In such acidic pH regions, these immobilized enzymes also showed more excellent heat stabilities. These special characteristics of the immobilized enzymes were quite satisfactory for eliminating possible microbial contamination during the long-term operation of these immobilized enzyme systems. In continuous-column operations, more than 85% hydrolysis of RNA and complete conversion of 5′-AMP to 5′-IMP were maintained for more than 23 days when a 4% RNA solution was charged as the substrate.     

Sound velocity dispersion in room temperature ionic liquids studied using the transient grating method

Sound velocity is determined by the transient grating method in a range from 10(6) to 10(10) Hz in three room temperature ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, and N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide. In all room temperature ionic liquids studied, the sound velocity increased with increasing frequency. The cause of this change is posited to be structural relaxation in the room temperature ionic liquids. Frequency dependence of the sound velocity is not reproduced by a simple Debye relaxation model. The sound velocity dispersion relation in 1-butyl-3-methylimidazolium hexafluorophosphate matches a Cole-Davidson function with parameters determined by a dielectric relaxation [C. Daguenet et al., J. Phys. Chem. B 110, 12682 (2006)], indicating that structural and reorientational relaxations are strongly coupled. Conversely, the sound velocity dispersions of the other two ionic liquids measured do not match those measured for dielectric relaxation, implying that structural relaxation is much faster than the reorientational relaxation. This difference is discussed in relation to the motilities of anions and cations.     

Palladium‐catalyzed dehalogenation of 5‐halopyrazoles

A new and efficient method for the dehalogenation of 5‐halopyrazoles was developed by using the catalytic amount of palladium (II) chloride and triphenylphosphine as a ligand at reflux under constant flow of hydrogen gas. The reaction gave the corresponding pyrazole products in good to excellent yields (≥83%). J. Heterocyclic Chem., (2012).