Isocyanurates with planar chirality: design, optical resolution, and isomerization.

Designs and syntheses of isocyanurates (1-3) are described on the basis of a novel concept that two enantiotopic faces of C(s) -symmetric, prochiral planar molecules are differentiated with a location of groups at the top or bottom of the planar skeleton using a rigid linker. Such isocyanurates are atropisomeric. The planar-chiral structures of 1 and 2(anti) (anti-conformer of 2) were confirmed by single-crystal X-ray analyses, and the space groups were P1 (for 1) and P2(1)/c (for 2(anti)), resulting that the crystals were racemates. Optical resolutions of 1-3 were successfully accomplished by using chiral high-performance liquid chromatography technique in combination with circular dichroism, absorption, and nuclear magnetic resonance spectroscopies and mass spectrometry. Furthermore, the rotational barriers (ΔG(‡)s) related to isomerizations of 1-3 were estimated to be 27.2 (for 1 at 50 °C), 27.6 (for 2(anti) at 50 °C), and 40.6 (for 3(syn) at 150 °C) kcal/mol. The ΔG(‡)s of 2 and 3 were higher than that of 1 and, in particular, that of 3 was highest among them. This result indicates that an introduction of bulky substituents and an intramolecular bridging are effective for inhibitions of the isomerizations.

Planar-chiral metal complexes comprised of square-planar metal and achiral tetradentate ligands: design, optical resolution, and thermodynamics.

Planar-chiral palladium complexes {[[N,N'-[1,4-butanediylbis(oxy-7,1-naphthalenediyl)]bis(2-pyridinecarboxamidato)](2-)-κN(1),κN(1)',κN(2),κN(2)']palladium (PdL(4)) and [[2,2'-[1,4-butanediylbis[[(oxy-7,1-naphthalenediyl)imino]methyl]]dipyrrolato](2-)-κN(1),κN(1)',κN(2),κN(2)']palladium (PdL(5))} were synthesized from achiral tetradentate ligands N,N'-[1,4-butanediylbis(oxy-7,1-naphthalenediyl)]bis(2-pyridinecarboxamide) (H(2)L(4)) and N,N'-bis[(1H-pyrrol-2-yl)methylidene]-7,7'-(1,4-butanediyldioxy)bis(1-naphthalenamine) (H(2)L(5)) bearing two dissymmetric bidentate units at both ends and a Pd(II) ion, respectively. The palladium complexes were crystallized in the monoclinic space group P2(1)/n with the unit cell parameters a = 16.5464(6) Å, b = 11.3534(4) Å, c = 17.6697(7) Å, ß = 115.5300(10)°, and Z = 4 for PdL(4) and a = 17.2271(8) Å, b = 10.1016(5) Å, c = 17.9361(9) Å, ß = 105.6310(10)°, and Z = 4 for PdL(5). The planar-chiral structures of PdL(4) and PdL(5) were confirmed by single-crystal X-ray analyses, resulting in the fact that the crystals were racemic mixtures. The racemic mixtures were successfully resolved by using chiral high-performance liquid-chromatography techniques. Racemizations of the complexes were found to be drastically dependent on the arrangement of the charged or uncharged metal-binding N atoms of the ligands.

Simplest homoleptic metal-centered tetrahedrons, [M(OH2)4]2+, in 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (M = Co, Ni, Cu).

Dissolution of a tetrafluoroborate or perchlorate salt of [M(OH(2))(6)](2+) (M = Co, Ni, Cu) in 1-ethyl-3-methylimidazolium tetraluforoborate ionic liquid ([emim]BF(4)) results in significant solvatochromism and increasing intensity of color. These observations arise from partial dehydration from the octahedral [M(OH(2))(6)](2+) and formation of the tetrahedral [M(OH(2))(4)](2+). This reaction was monitored by the intense absorption band due to the d-d transition in the UV-vis absorption spectrum. The EXAFS investigation clarified the coordination structures around M(2+) {[Co(OH(2))(4)](2+), R(Co-O) = 2.17 Å, N = 4.2; [Cu(OH(2))(4)](2+), R(Cu-O) = 2.09 Å, N = 3.8}. (1)H and (19)F NMR study suggested that both [emim](+) and BF(4)(-) are randomly arranged in the second-coordination sphere of [M(OH(2))(4)](2+).

Fab fragment labeled with ICG-derivative for detecting digestive tract cancer.

BACKGROUND: In previous studies, we generated infrared ray fluorescence-labeled monoclonal antibodies and developed an infrared ray fluorescence endoscope capable of detecting the monoclonal antibodies to establish a novel diagnostic technique for gastrointestinal cancer. Although the whole IgG molecule has commonly been used for preparation of labeled antibodies, labeled IgG displays insufficient sensitivity and specificity, probably resulting from non-specific binding of the Fc fragment to target cells or interference between fluorochromes on the identical labeled antibody, which might be caused by molecular structure. In this in vitro study, we characterized an Fc-free fluorescence-labeled Fab fragment, which was expected to yield more specific binding to target cells than the whole IgG molecule. METHODS: An anti-mucin antibody and ICG-ATT, an ICG derivative, were used as the labeled antibody and labeling compound, respectively. Paraffin sections of excised gastric cancer tissues were subjected to staining. The labeled whole IgG molecule (ICG-ATT-labeled IgG) and the labeled Fab fragment (ICG-ATT-labeled Fab) were prepared according to a previous report, and the fluorescence properties, antibody activities, and features of fluorescence microscope images obtained from paraffin sections were compared. RESULTS: Both ICG-ATT-labeled Fab and ICG-ATT-labeled IgG were excited by a near infrared ray of 766nm, and maximum emission occurred at 804nm. Antibody activities of ICG-ATT-labeled Fab were shown to be similar to those of unlabeled anti-MUC1 antibody. The fluorescence intensity obtained from paraffin sections of excised gastric cancer tissues revealed a tendency to be greater with ICG-ATT-labeled Fab than with ICG-ATT-labeled IgG. CONCLUSIONS: The infrared ray fluorescence-labeled Fab fragment was likely to be more specific than the conventionally labeled antibodies. Fragmentation of antibodies is considered to contribute to improved sensitivity and specificity of labeled antibodies for detection of micro gastrointestinal cancers.