"Marking" the Nitrogen Atoms of Phenyl-(2-pyridyl)-(3-pyridyl)-(4-pyridyl)-methane. Synthesis and Absolute Configuration of the Corresponding Tris(pyridine N-oxide)

To "mark" the nitrogen atoms in phenyl-(2-pyridyl)-(3-pyridyl)- (4-pyridyl)methane (1), we have synthesized the corresponding tris(pyridine N-oxide) 2 by oxidation of 1 with m-chloroperbenzoic acid. The nitrogen atoms of 2 are unequivocally determined by the X-ray crystal analysis of a single crystal of rac-2 whereas the nitrogen atoms cannot be assigned at all in the case of rac-1. N-Oxide 2 can be resolved by chiral high-performance liquid chromatography under similar conditions to those used for the resolution of 1. The calculated circular dichroism (CD) curve for (R)-2 on the basis of time-dependent density functional theory reproduces the experimental spectra very well to suggest that the second-eluted fraction ([CD(+)283]-2) is the R isomer, namely (R)-[CD(+)283]-2. The independent absolute configuration determinations for 1 and 2 are in keeping with the chemical correlation between the two compounds by oxidation of (R)-1 into (R)-2

Development of a Universal Ellipsoidal Mirror Device for Fluorescence Detected Circular Dichroism (FDCD) - Elimination of Polarization Artifacts

We have developed an ellipsoidal mirror fluorescence detected circular dichroism (FDCD) device with enhanced detection sensitivity that eliminates the polarization artifact; this is applicable to samples with strongly polarized fluorescence. The device, JASCO FDCD465, has an ellipsoidal mirror structure with a framework consisting of three mirrors (one elliptical and two plane mirrors) that maximally collects light in the FDCD. All assemblies on the device including the ellipsoidal mirror, cylindrical cell, and photomultiplier tube (PMT) are aligned on the chamber-fitting sample mount as an attachment compatible with a standard CD spectropolarimeter. The new FDCD465 device eliminates the polarization artifact caused by anisotropic distribution of the emitted light. It represents a convenient, reliable, and sensitive FDCD attachment to the JASCO J-800 CD spectrometer series that can be used under both isotropic and photoselected conditions

Chiral Tetraarylmethane Derivative with Metal-Coordinating Ability

Phenyl-pyrazinyl-2-pyridyl-2-pyrimidinylmethane (1) has been synthesized in four steps from 2-(chloromethyl)pyridine. This compound is chiral and expected to show metal-coordinating ability because three of four aryl groups have the nitrogen atom at ortho-position with respect to the central carbon atom. The X-ray crystallographic analysis of rac-1 unambiguously revealed the tetraarylmethane framework, but the nitrogen atoms could not be assigned. The optical resolution of 1 was achieved by chiral HPLC. Besides the CD spectra of the two fractions exhibited opposite signs as expected, the solvent effect on the CD spectra was also observed. According to the calculated CD curve based on time-dependent density functional theory (TDDFT) method, the first eluted fraction is the R isomer in terms of absolute configuration. It should be noted that the CD spectrum of 1 was also changed by the addition of the transition metal ions because of the formation of the metal complexes of 1. The Job plot and the electrospray ionization (ESI) mass spectrum of the solution of rac-1 in the presence of Cu2+ ion revealed that the stoichiometry of 1 and Cu2+ was 2 : 1

Chiral Tetrakis(2-thienyl)methane Derivative: A Possible Precursor for Cryptochiral Tetraalkylmethanes

(5-Acetyl-2-thienyl)(5-benzoyl-2-thienyl)(5-bromo-2-thienyl)-(5-cyano-2-thienyl)methane has been synthesized as the first chiral tetrakis(2-thienyl)methane derivative. This compound can be resolved by chiral HPLC. Since Raney nickel reduction of tetrakis(2-thienyl)methane derivatives gave tetraalkylmethane derivatives, chiral tetrakis(2-thienyl)methane derivatives will be good precursors for a number of cryptochiral tetraalkylmethanes and their derivatives

Phenyl-(2-pyridyl)-(3-pyridyl)-(4-pyridyl)methane: Synthesis, Chiroptical Properties, and Theoretical Calculation of Its Absolute Configuration

The title compound, a prototypical chiral molecule based on a tetraarylmethane framework, has been synthesized in five steps from (2-pyridyl)-(3-pyridyl)ketone. X-ray crystallographic analysis revealed the tetraarylmethane framework of the molecule but did not determine the positions of the nitrogen atoms because the crystal is a racemic compound and the aryl groups are disordered in the crystal. The optical resolution of the title compound was achieved by chiral HPLC with a Chiralcel OD column. The CD spectra of the two fractions in acetonitrile exhibited opposite signs as expected for a pair of enantiomers. Their CD spectra are changed in 2m HCl due to protonation. The calculated CD curve for the target molecule based on time dependent density functional theory (TDDFT) reproduces the experimental result very well, thus suggesting that the first eluted fraction is the R isomer in terms of absolute configuration