Mutsuo Okamura

Stereochemical control in microbial reduction. Part 31: Reduction of alkyl 2-oxo-4-arylbutyrates by baker's yeast under selected reaction conditions

Abstract Treatment of bakers yeast with phenacyl chloride in an aqueous–organic solvent has been proven to be an effective method of inhibiting the enzymes that afford (S)-enantiomers of α-hydroxy esters in the reduction of α-keto esters. The procedure is effective for the whole-cell system to produce the (R)-product with high chemical yield and high enantiomeric excess.

Catalytic hydrogenation of linoleic acid on nickel, copper, and palladium

The catalytic activity and selectivity for hydrogenation of linoleic acid were studied on Ni, Cu, and Pd catalysts. A detailed analysis of the reaction product was performed by a gas-liquid chromatograph, equipped with a capillary column, and Fourier transform-infrared spectroscopy. Geometrical and positional isomerization of linoleic acid occurred during hydrogenation, and many kinds of linoleic acid isomers (trans-9,trans-12; trans-8,cis-12 orcis-9,trans-13; cis-9,trans-12; trans-9,cis-12 andcis-9,cis-12 18∶2) were contained in the reaction products. The monoenoic acids in the partial hydrogenation products contained eight kinds of isomers and showed different isomer distributions on Ni, Cu, and Pd catalysts, respectively. The positional isomers of monoenoic acid were produced by double-bond migration during hydrogenation. On Ni and Pd catalysts, the yield ofcis-12 andtrans-12 monoenoic acids was larger than that ofcis-9 andtrans-9 monoenoic acids. On the contrary, the yield ofcis-9 andtrans-9 monoenoic acids was larger than that ofcis-12 andtrans-12 monoenoic acids on Cu catalyst. From these results, it is concluded that the double bond closer to the methyl group (Δ12) and that to the carboxyl group (Δ9) show different reactivity for hydrogenation on Ni, Cu, and Pd catalysts. Monoenoic acid formation was more selective on Cu catalyst than on Ni and Pd catalysts.

Photochemical bis-silylation of C60: synthesis of a novel C60 main chain polysilane

Abstract The photoreaction of polysilanes and cyclic oligosilanes with C 60 has been investigated. Photoirradiation of a solution of C 60 and polysilanes in benzene in a degassed quartz tube at 20°C with a low-pressure mercury-arc lamp has afforded the C 60 –polysilane adduct in moderate yield, in which C 60 is incorporated into the polysilane chain. A unique electronic property of the C 60 main chain polysilane has also been elucidated.

A comparison of the photochemical reactivity of N@C60 and C60: photolysis with disilirane

N@C60 has a lower photochemical reactivity toward disilirane than C60, although N@C60 does not differ from C60 in its thermal reactivity; theoretical calculations reveal that N@C60 and C60 have the same orbital levels and that N@3C60* has a shorter lifetime than 3C60*.

C60-sensitized bis-silylation of nitrile and carbonyl compounds with disilirane

The photochemical reaction of disilirane with unsaturated compounds such as nitrile, ketone and aldehyde in the presence of C60 with a halogen lamp (cutoff <400 nm) affords the corresponding adducts of disilirane and unsaturated compounds as bis-silylated products. The experimental results by using laser flash photolysis technique confirm the formation of the adducts via a photoinduced electron transfer process between 1 and 3C60*. In this bis-silylation reaction, C60 serves as a sensitizer.

Stereospecificity observed in base-catalyzed electrochemical oxidation☆

Abstract A mechanism for amine-catalysis of stereospecificity in electrochemical oxidation of (4 R )-Me 3 MQPH and (4 R )-Me 3 PNPH is discussed.

A novel coenzyme NAD(P)+–NAD(P)H model with axial chirality. Its preparation and stereoselectivity

An axially chiral NAD(P)H model 1 bearing a 2′-methoxy-1′-naphthyl group at the C-2 position is prepared; the reduction of methyl benzoylformate with the optically active model, (+)- or (–)-1, in the presence of magnesium ion gives (R)- or (S)-isomer of methyl mandelate, respectively, in over 95% enantiomeric excess.

STEREOSPECIFIC REDOX REACTION DIRECTED BY A SULFINYL GROUP

Stereochemistry of reductions of a pyridinium and quinoliniums with an asymmetric sulfinyl group has been studied. Dithionite and borohydride prefer the face characterized by a lone pair on sulfur atom. Dihydropyridine prefers the face characterized by a S-O bond.