Design and synthesis of a novel imidazolium-based ionic liquid with planar chirality

As the first example of a planar chiral ionic liquid, a cyclophane-type imidazolium salt was synthesized; its potential use in chiral recognition was demonstrated by 1H NMR studies.     

The conjugative metabolism of 4-methylumbelliferone and deconjugation to the parent drug examined by isolated perfused liver and in vitro liver homogenate of rats

We examined the disposition of 4-methylumbelliferone (4-MU) and its conjugative metabolites, glucuronide (4-MUG) and sulfate (4-MUS), using a single-pass rat liver perfusion system. When 4-MU was delivered, the steady-state hepatic extraction ratio for 4-MU was very high (approximately 1.0) and its conjugative metabolites, 4-MUG and 4-MUS, appeared to a large extent in the effluent perfusate. The biliary excretion rate of the 4-MUG conjugated from 4-MU was 44% of the infusion rate at the steady-state, whereas those of 4-MU and 4-MUS were less than 1% of the infusion rate. When 4-MUG was delivered, the steady-state hepatic extraction ratio for 4-MUG was very low (less than 0.05) and the removal rate of 4-MUG from the perfusate was almost identical to the excretion rate of 4-MUG into the bile, while 4-MU and 4-MUS were slightly excreted into the bile (1% of the total biliary excretion rate), suggesting that a little deconjugation of 4-MUG to 4-MU occurred in the liver. Similarly, 4-MU and 4-MUS were not detectable in the effluent perfusate. The apparent extraction ratio (Eapp) for the intracellularly conjugated 4-MUG was approximately twenty times higher than that for the pre-conjugated 4-MUG. This discrepancy between the values of Eapp for the intracellularly conjugated and pre-conjugated 4-MUG might be attributed mainly to the diffusional barrier for the metabolite between the blood and hepatocytes, as suggested in the previous simulation (J. Pharmacokin, Biopharm., 15, 399 (1987].(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanism of asymmetric sulfimidation with N-alkoxycarbonyl azide in the presence of (OC)Ru(salen) complex

Spectroscopic analysis of imidation of alkyl aryl sulfides with N-2,2,2-trichloro-1,1-dimethylethyloxycarbonyl azide 2 in the presence of (OC)Ru(salen) complex 1 strongly suggests that an addition compound of the azide 2 to 1 is the active species for the imidation, while the addition compound undergoes the undesired intramolecular CH insertion onto the salen ligand of the complex in the absence of sulfide, directly or via the corresponding nitrene-ruthenium species.     

Interaction of the halobacterial transducer to a halorhodopsin mutant engineered so as to bind the transducer: Cl- circulation within the extracellular channel

An alkali-halophilic archaeum, Natronomonas pharaonis, contains two rhodopsins that are halorhodopsin (phR), a light-driven inward Cl- pump and phoborhodopsin (ppR), the receptor of negative phototaxis functioning by forming a signaling complex with a transducer, pHtrII (Sudo Y. et al., J. Mol. Biol. 357 [2006] 1274). Previously, we reported that the phR double mutant, P240T/F250Y(phR), can bind with pHtrII. This mutant itself can transport Cl-, while the net transport was stopped upon formation of the complex. The flash-photolysis data were analyzed by a scheme in which phR --> 4 P1 --> P2 --> 4 P3 --> P4 --> phR. The P3 of the wild-type and the double mutant contained two components, X- and O-intermediates. After the complex formation, however, the P3 of the double mutant lacked the X-intermediate. These observations imply that the X-intermediate (probably the N-intermediate) is the state having Cl- in the cytoplasmic binding site and that the complex undergoes an extracellular Cl- circulation because of the inhibition of formation of the X-intermediate.     

Asymmetric catalysis of metal complexes with non-planar ONNO ligands: salen, salalen and salan

Chiral metal (M)-salen complexes are one of the most versatile asymmetric catalysts and the catalysis of trans-M(salen) complexes has been well cultivated. On the other hand, non-planar cis-beta M(salen) complexes were recently found to show unique asymmetric catalysis that cannot be attained by trans-M(salen) complexes. Moreover, related non-planar M(salalen) and M(salan) complexes were also found to exert unprecedented asymmetric catalysis. This Feature Article summarizes the seminal studies on asymmetric catalysis of non-planar M(ONNO) complexes, full utilization of which will provide marked improvement in asymmetric synthesis.     

Synthesis and Electronic Properties of Directly Linked Dihydrodiazatetracene Dimers

5,12-Dihydro-5,12-diazatetracene (DHDAT) dimers with different substitution patterns are synthesized: a symmetric one with a C−C bond between the monomer units ( 1 ) and two asymmetric ones with a C−N bond between the monomer units ( 2 and 3 ). The DHDAT units are planar in the C−C linked dimer 1 but perpendicularly oriented in the C−N linked dimers 2 and 3 (from X-ray analysis). The electronic ground-state interaction between the two units is large in 1 and small in 2 and 3 . The emission behavior of 3 is different from that of other dimers and its monomer; it displays positive solvatochromism, characteristic for electron donor–acceptor molecules, despite its donor–donor type structure. Compound 3 exhibits a unique multi-step thermochromic emission behavior. The emission behavior is attributed to the asymmetric distribution of the HOMO and LUMO of DHDAT.