Success or Failure of Chiral Crystallization of Similar Heterocyclic Compounds

Single crystals of two achiral and planar heterocyclic compounds, C₉H₈H₃O(CA1) and C₈H₅NO₂ (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P2₁2₁2₁ (# 19), whereas it was not observed for CA4 P2₁/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites.     

Copper-Catalyzed Oxidative Benzylic C(sp3)−H Cyclization for the Synthesis of β-Lactams

β-Lactams are important structural motifs because of their ubiquity in natural products and pharmaceuticals. We report herein a Cu-catalyzed intramolecular oxidative C(sp³)−H amidation for the synthesis of β-lactams using tBuOOtBu. This method is based on Kharasch–Sosnovsky amidation and does not require prefunctionalization of C(sp³)−H bonds or the installation of a directing group, thereby allowing for the straightforward synthesis of β-lactams. Our intramolecular functionalization protocol can be extended to diverse benzylic C(sp³)−H bonds and shows excellent functional-group tolerance.     

The outersphere complex of EuCl2+ in a mixed system of methanol and water of 1.0M (H, Na) (Cl, ClO4)

The stability constans, ₁, of each monochloride complex of Eu(III) have been determined in the methanol and water mixed system with 1.0 mol·dm^–3 ionic strength using a solvent extraction technique. The values of ₁ increase with an increase in the mole fraction of methanol (X _S ) in the mixed solvent system when 0X _S 0.40. The, distance of Eu³⁺–Cl^– in the mixed solvent system was calculated using the Born-type equation and the Gibbs' free energy derived from ₁. Calculation of the Eu³⁺–Cl^– distance and the preferential solvation, of Eu³⁺ by water proposed the variation of the outersphere complex of EuCl²⁺ as follows: (1) [Eu(H₂O)₉]³⁺Cl^–, [Eu(H₂O)₈]³⁺Cl^– and [Eu(H₂O)₇(CH₃OH)³⁺Cl^– inX _S0.014, (2) [Eu(H₂O)₈]^3–Cl^– and [Eu(H₂O)₇(CH₃OH)]³⁺Cl^– in 0.014<X _S <0.25 and (3) [Eu(H₂O)₇(CH₃OH)]^3–Cl^– and [Eu(H₂O)₆(CH₃OH)[₂ ³⁺Cl^– in 0.25<X _S 0.40.     

Post-synthetic modification of oligonucleotides containing 5-trifluoromethylpyrimidine bases

A practical and operationally simple post-synthetic modification of oligonucleotides containing 5-trifluoromethylpyrimidine bases is described. Trifluoromethyl group was used as a post-synthetic precursor and 5-trifluoromethylpyrimidine bases within oligonucleotides were converted into the corresponding 5-carboxy-, 5-cyano-, 5-amidinyl-, and 5-carbamoyl derivatives by treatment with an alkaline solution and amines. Moreover, post-synthetic treatment of fully protected and controlled pore glass (CPG)-attached oligonucleotides proceeded successfully with the simultaneous removal of all protecting groups, cleavage from CPG, and conversion of the trifluoromethyl group to afford the corresponding modified oligonucleotides.     

Measurement of the electrophoretic mobility of sheep erythrocytes using microcapillary chips

Cell electrophoretic mobility (EPM) can be used to characterize individual cells. The purpose of this study is to establish reproducible and reliable cell EPM values obtained using microcapillary electrophoresis (microCE) chips. We studied cell electrophoresis on microCE chips through the comprehensive measurement of EPM and zeta potential. The inner wall of microchannels in microCE chips was coated with three kinds of reagents, namely bovine serum albumin (BSA), gelatin, and 2-methacryloyloxyethylphosphorylcholine (MPC) polymer to prevent nonspecific adhesion and interaction between cells and the inner wall. Electrophoresis was conducted in phosphate-buffered saline (pH 4-9) using erythrocytes extracted from sheep whole blood. Electroosmotic flow (EOF) mobility was measured using noncharged particles, and then the true EPM was calculated by subtracting the EOF mobility from the electromigration. MPC polymer coatings in microCE chips reduced the zeta potential of the inner wall and fully prevented nonspecific adhesion. EPM data obtained using microCE chips were almost the same and reproducible over a wide range of pH irrespective of the coating reagent used. In conclusion, reliability in the measurement of cell EPM using microCE chips was realized.     

Cm3+-F- interaction in a mixed system of methanol and water

The stability constants (b₁) of the monofluoro complex of Cm(III) have been determined in mixed solvents of methanol and water using the solvent extraction technique. The values of lnb₁ increase as the molar fraction of methanol (X_s) in the mixed solvent increases. The variation in the stability constants mainly depends on the solvation of F^- and slightly depends on both (1) the solvation of cations in connection with the complexation of CmF²⁺ and (2) the electrostatic attraction of Cm³⁺-F^-. The variation in lnb₁ for Cm(III) due to the effect of both (1) and (2) is similar to that for Sm(III). By variation of lnb₁ the coordination number in the primary hydration sphere (CN) of Cm(III) decreased from a value between CN = 9 and CN = 8 to CN = 8, at about X_s = 0.02. The X_s value of the inflection point of the CN for Cm is slightly lower than X_s = 0.06 for Sm(III) and X_s = 0.03 for Eu(III), previously obtained.     

A cation-exchange study of stability constants of complexes formed between bismuth/III/ and nitrate or chloride ions

A cation-exchange method was used for determining the stability constants of complexes formed between Bi/III/, present in tracer concentrations /ca. 10^–11M Bi/, and nitrate ion or chloride ion in 1.OM H/ClO₄, NO₃/ or 1.OM H/Cl, ClO₄/ solutions, respectively. The successive formation constants were calculated using the distribution data. The resulting 1g ₁, 1g ₂, and 1g ₃ values were 0.74, 1.22, and 1.54 for 1.OM H/ClO₄, NO₃/ solutions, and 2.36, 3.61, and 4.95 for 1.OM H/Cl, ClO₄/ solutions, respectively.     

A new method for the spectrophotometric determination of pertechnetate with tris(1,10-phenanthroline)iron(II) ion

A new spectrophotometric determination of technetium has been developed by means of the solvent extraction of tris(1,10-phenanthroline)iron(II) ([Fe(phen)₃ ²⁺]) with pertechnetate into nitrobenzene. The concentration of technetium can be determined by measuring the characteristic absorbance at 516 nm (=11,700M^–1·cm^–1) in the organic phase. An important feature of the proposed method is that the concentration of pertechnetate can be determined without complicated processes such as the reduction of pertechnetate and the subsequent formation of a colored chelate.     

The Coordination Number of Lu(III) in a Mixed System of Methanol and Water

The stability constants (_1(F)) of the monofluoro complex of Lu(III) and those (_1(Cl)) of the monochloride solvent-shared ion-pair of Lu(III) have been determined in mixed solvents of methanol and water at 0.10 and 1.00 mol·dm^–3 ionic strengths, respectively. The variation in ln_1(F) with an increase in the mole fraction of methanol (X _s) in the mixed solvent system showed an acute-angled convex inflection point at X _s 0.12, an acute-angled concave inflection point at X _s 0.22, and another acute-angled convex inflection point at X _s 0.27. It was concluded that the first and the second convex inflection points denoted the CN of Lu³⁺ from CN = 8 to a mixture of CN = 8 and 7 and from CN = 8 and 7 to a mixture containing CN = 6, respectively. The concave point is the starting point of a change in the CN of Lu(III) in LuF²⁺ from CN = 8 to a mixture of CN = 8 and 7. The values of two inflection points of the CN around Lu³⁺ are consistent with the inflection points of the variation in the values of ln_1(Cl) versus the dielectric constant of the mixed solvent.