Tsutomu Fukuda

Mechanism of one oxygen atom transfer from oxo (salen) manganese(V) complex to olefins

Abstract In the Mn-salen catalyzed asymmetric epoxidation of some olefins, non-linear relationship between reaction temperature and enantioselectivity was observed. For example, the epoxidation of 1,3-cycloalkadiene with complex 3a as a catalyst showed the maximum enantioselectivity at 0 °C. It was also found that the electronic nature of the aromatic substituent in the salen ligand affects enantioselectivity but its effect does not necessarily correspond to the Hammets σ-values. Based on these new experimental results, we propose a reaction mechanism which proceeds through metallaoxetane intermediate, for one oxygen atom transfer reaction from oxo (salen)manganese(V) complex to olefins.

Highly enantioselective cyclopropanation of styrene derivatives using Co(III)-salen complex as a catalyst

Abstract Optically active (salen)cobalt(III) bromide complex 6-Br was found to be an efficient catalyst for asymmetric cyclopropanation of styrene derivatives. For example, the reaction of 4-chlorostyrene and tert -butyl diazoacetate in the presence of 6-Br proceeded with high enantioselectivity of 96% ee as well as high trans-cis selectivity (97:3) to give tert -butyl 2-(4-chlorophenyl)cyclopropane-1-carboxylate as a major product.

Catalytic and asymmetric [2,3]sigmatropic rearrangement: Co(III)-salen catalyzed S-ylide formation from allyl aryl sulfides and their rearrangement

Abstract Reaction of allyl aryl sulfides and α-diazoacetic acid esters in the presence of optically active Co(III)-salen complex (8-Br) provided 3-substituted 2-arylthio-4-pentenoic acid esters stereoselectively by way of enantioselective S-ylide formation and subsequent diastereoselective [2,3]sigmatropic rearrangement. For example, the reaction of cinnamyl phenyl sulfide and (−)-menthyl α-diazoacetate provided (−)-menthyl (2R,3S)-2-phenylthio-3-phenyl-4-pentenoate of 74% de preferentially.

Mn-salen catalyzed asymmetric oxidation of enol derivatives

Abstract Mn-salen complex 1 was found to catalyze highly enantioselective oxidation of enol ethers with iodosylbenzene as a terminal oxidant giving the corresponding hydroxy acetals, when the reaction was carried out in an alcoholic solvent. The reactions in the usual solvents such as dichloromethane and acetonitrile showed irregular and lower enantioselectivity, partly due to racemization of the resulting α-hydroxy ketones.

Co(III)-salen catalyzed carbenoid reaction: Stereoselective [2,3]sigmatropic rearrangement of S-ylides derived from allyl aryl sulfides

Allyl aryl sulfides and diazoacetic acid esters react in the presence of optically active Co(III)-salen complex (4) with good enantioselectivity, to give the [2,3]sigmatropic rearrangement products, 2-arylthio-3-aryl-4-pentenoic acid esters, via the corresponding S-ylides.

Mn-salen catalyzed asymmetric epoxidation of (±)-3-alkylindene: Reagent-dependent stereoselectivity

Abstract Epoxidation of (±)-3-alkylindenes was examined with various (salen)manganese(III) complexes as catalysts and, from the analysis of the obtained data, it was found that the location and nature of C3- and C3′-substituents of the Mn-catalysts strongly influenced the stereochemistry of the epoxidation.

Metabolism of [131I]gamma globulins in patients with chronic liver disease

Abstract The turnover of injected 131 I-labelled γ-globulins has been observed in control subjects and patients with non-alcoholic liver diseases. In control subjects, the half-life of γG was 14.1 days and the synthetic rate 52 mg/kg/day. In patients with chronic active hepatitis and liver cirrhosis, the half-life was reduced and the synthetic rate increased. Following treatment with corticosteroids, the synthetic rate was reduced in patients with liver cirrhosis. In γA studies, the normal values of the half-life and the synthetic rate were 6.2 days and 29 mg/kg/day, respectively. In cirrhosis patients the synthetic rate increased. In γM studies, the normal values of the half-life and the synthetic rate were 6.0 days and 6 mg/kg/day, respectively. In cirrhosis patients, the half-life was prolonged and the synthetic rate increased.