| Co-Investigator(Kenkyū-buntansha) |
OHNO Teruhisa Kyushu University, Department of Organic Synthesis, Associate Professor, 工学部, 助教授 (10203887)
HISAEDA Yoshio Kyushu University, Department of Organic Synthesis, Associate Professor, 工学部, 助教授 (70150498)
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| Research Abstract |
We prepared an octopus cyclophanes having L-aspartate residues as connector units interposed between a macrocyclic ring and four double-chain hydrocarbon segments. This cationic host strongly binds anionic and nonionic hydrophobic guests and exercises the induced-fit guest-binding behavior originating from both hydrophobic and electrostatic interactions. We also prepared a hexapus cyclophane having three catechol moieties and six hydrocarbon chains, the former acting as the metal binding sites. The inclusion behavior of a Fe-complex of the hexapus cyclophane was examined in water. When the catechol segments of the cyclophane are coordinated to Fe^<3+>, the binding constant for hydrophobic guests becomes larger than that of the hexapus cyclophane without metal coordination. The present metal-bound hexapus cyclopahne exhibits marked inclusion capability toward organic guests, as arising from hydrophobic, electrostatic, and coordination effects. Vitamin B_<12>-dependent enzymes catalyze v
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arious isomerization reactions accompanied with carbon-skeleton rearrangements. In order to simulate catalytic functions of vitamin B_<12>-dependent enzymes, we have been dealing with hydrophobic vitamin B_<12> derivatives. We succeeded in constructing an artificial vitamin B_<12>-dependent holoenzyme composed of an octopus cyclophane as an apoenzyme model and hydrophobic vitamin B_<12> as a coenzyme model. The octopus cyclophane acts as an effective apoenzyme model for constitution of an artificial vitamin B_6-dependent holoenzyme by simultaneous incorporation of pyridoxal-5'-phosphate and a hydrophobic alkylammonium substrate into the host cavity to give the Schiff-base species, showing the substrate selectivity.
We prepared cyclophanes of another structural feature ; a cage-type cubical molecule with six faces each consisting of a 2, 11, 20, 29-tetraaza[3.3.3.3] paracyclophane ring. This host possesses eight tertiary aminomoieties and acts as a polycationic host in acidic media. The host shows size-sensitive and regioselective molecular discrimination. The second cage-type cyclophane is composed of two macrocyclicskeletons, 1, 6, 20, 25-tetraaza[6.1.6.1.] paracyclophane 2, 11, 20, 29-tetraaza[3.3.3.3] paracyclophane segments. This cationic host incorporates anionic and nonionic hydrophobic fluorescent guests into its in ternal cavityand exercises marked chiral discrimination toward selected amino acids in aqueous media. Less
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