Keisuke Kato

Intermolecular Methoxycarbonylation of Terminal Alkynes Catalyzed by Palladium(II) Bis(oxazoline) Complexes

Boxing clever: Direct conversion of a terminal alkyne group into a beta-methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid-sensitive glycosidic bonds are not affected under the reaction conditions. The one-pot synthesis of (+/-)-dihydrokawain from the homopropargyl alcohol is also achieved. tfa = trifluoroacetate.

Total Synthesis of (+)-Gregatin B and E

The first total synthesis of (+)-gregatin E and a new total synthesis of (+)-gregatin B are described. Key features of our synthetic approach involve a palladium-catalyzed cyclization-methoxycarbonylation of optically active propargylic acetate and a Suzuki-Miyaura coupling or CuTC-mediated coupling reaction. The absolute configuration of (+)-gregatin E (5R,5S) is proposed.

Cyclization-Carbonylation-Cyclization Coupling Reaction of Propargyl Ureas with Palladium(II)-Bisoxazoline Catalyst

The cyclization-carbonylation-cyclization coupling reaction (CCC-coupling reaction) of propargyl ureas catalyzed by PdII(box) complexes afforded symmetrical ketones bearing two 2-amino-2-oxazoline groups in good to moderate yields.

Induction of the estrogen‐responsive genes encoding choriogenin H and L in the liver of male medaka (Oryzias latipes) upon exposure to estrogen receptor subtype‐selective ligands

Choriogenin (Chg) H and L are estrogen‐induced chorion precursors. We measured the induction of ChgH and ChgL mRNA in the livers of male medaka fish treated with Orthoester‐2k, a selective ligand for estrogen receptor (ER) α, and 2‐(4‐hydroxyphenyl)‐5‐hydroxy‐1,3‐benzoxazole (HPHB), a selective ligand of ERβ. Although both ChgH and ChgL mRNA were induced by treatment with Orthoester‐2k or HPHB separately, their combination induced much greater expression of each Chg. ChgH expression correlated more closely with Orthoester‐2k dosage when combined with a small fixed dose of HPHB (1 μm), whereas ChgL mRNA expression was more responsive to HPHB dose when combined with a fixed dose of Orthoester‐2k (2.8 nm). Moreover, upon long‐term treatment with Orthoester‐2k, ChgH mRNA and ERα mRNA expression showed similar patterns with peak expression between days 6 and 10. These results imply that ERβ primarily regulates ChgL mRNA expression and ERα action primarily regulates ChgH mRNA expression. Thus, it is necessary to develop screening methods for fish ER subtype‐specific ligands. Copyright

Novel concept of enzyme selective nicotinamide adenine dinucleotide (NAD)-modified inhibitors based on enzyme taxonomy from the diphosphate conformation of NAD

The dihedral angle θ of the diphosphate part of NAD(P) were investigated to distinguish the differences in the binding-conformation of NAD(P) to enzymes and to create an enzyme taxonomy. Furthermore, new inhibitors with fixed dihedral angles showed that enzymes could recognize the differences in the dihedral angle θ. We suggest the taxonomy and the dihedral angle θ are important values for chemists to consider when designing inhibitors and drugs that target enzymes.

Palladium(II) Catalyzed Cyclization-Carbonylation-Cyclization Coupling Reaction of (ortho-Alkynyl Phenyl) (Methoxymethyl) Sulfides Using Molecular Oxygen as the Terminal Oxidant.

An efficient PdII/Pd0-p-benzoquinone/hydroquinone-CuCl2/CuCl catalyst system was developed that uses environmentally friendly molecular oxygen as the terminal oxidant to catalyze the cyclization-carbonylation-cyclization coupling reaction (CCC-coupling reaction) of (o-alkynyl phenyl) (methoxymethyl) sulfides.