Sadao Tsuboi

Facile and reversible synthesis of an acidic water-soluble poly(amidoamine) fullerodendrimer

Water-soluble fullerodendrimer was obtained by the use of a Diels–Alder reaction of C60 with a newly designed anthryl dendron under an extremely mild condition in 70% yield, which is more than five times as high as the yield described in our previous report.

Chemoenzymatic synthesis of the C-13 side chain of paclitaxel (Taxol) and docetaxel (Taxotere)

Abstract Reduction of methyl 3-chloro-2-oxo-3-phenylpropanoate with various reducing agents gave syn - and anti -3-chloro-2-hydroxy-3-phenylpropanoates 3 , which underwent an efficient lipase-catalyzed resolution. All four diastereomers were subsequently converted to N -benzoyl-(2 R ,3 S )-3-phenylisoserine methyl ester, C-13 side chain analogues of paclitaxel (Taxol).

A facile synthesis of optically pure L-armentomycin and its D-isomer.Highly enantioselective reduction of the CC double bond of methyl (E)- and (Z)-2,4,4-trichloro-2-butenoate by using baker's yeast

Optically pure L-armentomycin [(S)-2-amino-4,4-dichlorobutanoic acid] and its D-isomer [(R)-2-amino-4,4-dichlorobutanoic acid] were prepared by using methyl (E)- and (Z)-2,4,4-trichloro-2-butenoate as key intermediate, which were reduced with bakers yeast to (R)- and (S)-2,4,4-trichlorobutanoate in 84~92 and 97~98% ee, respectively, in 60~65% yields.

Simple, Extremely Fast, and High‐Yielding Oxidation of Thiols to Disulfides

Abstract Results of oxidation of thiols to disulfides with 1,3‐dibromo‐5,5‐dimethylhydantoin (DBDMH) are described. A simple addition of 0.20–0.25 mol equivalent of solid DBDMH to thiol in chloroform at room temperature yielded the disulfides in excellent yield. The reaction is extremely fast and gave no other oxidized side products.

A practical synthesis of chiral 3-chloro-2-hydroxyalkanoates and 2,3-epoxyalcohols

Abstract Asymmetric reduction of 3-chloro-2-oxoalkanoates with bakers yeast gave optically active 3-chloro-2-hydroxyalkanoates with ≥95% e.e. in most cases, which were converted to optically active 2,3-epoxyalcohols with ≥78.0% e.e.

Purification and Characterization of α-Keto Amide Reductase from Saccharomyces cerevisiae

An NADPH-dependent α-keto amide reductase was purified from Saccharomyces cerevisiae. The molecular mass of the native enzyme was estimated to be 33 and 36 kDa by gel filtration chromatography and SDS–polyacrylamide gel electrophoresis, respectively. The purified enzyme showed a reducing activity not only for aromatic α-keto amides but also for aliphatic and aromatic α-keto esters. The internal sequence of the enzyme was identical with that of a hypothetical protein (ORF YDL 124w) coded by yeast chromosome IV.

Synthesis and CD spectrum of chiral porphyrin dimer

Abstract Chiral porphyrin dimer 1 was synthesized. The UV-vis spectrum of 1 was almost identical with that of the corresponding monomer 2 . The circular dichroism induced in the Soret region of 1 was very strong and of the split type due to the chiral exction coupling.

An Isozyme of Earthworm Serine Proteases Acts on Hydrolysis of Triacylglycerol

An enzyme catalyzing the hydrolysis of triacylglycerol was purified from an earthworm. The N-terminal amino acid sequence and the catalytic function of the purified enzyme were identical to those of Isozyme C, an isozyme of the earthworm-serine proteases. No other lipase proteins were found in the earthworm cells. The isozyme might act on the hydrolysis of triacylglycerol as well as the protein decomposition.

Transformation of cis-Epoxy Compound to cis-2,3-Disubstituted Oxane and Investigation on Propagation Step in the Ring-Expansion Reactions of cis,trans-Diepoxy Systems

Abstract Conversion of cis-epoxy compounds by successive ring-expansion reaction into trans-fused cyclic ethers was examined from both the initiation step and the propagation step. The ring-expansion reaction of cis-4,5-epoxy compounds containing a leaving group on C-1 was attempted as a unit process for the successive reaction. When a chloromesyl group was used as a leaving group, the ring expansion proceeded to give an oxane derivative (endo-type product) preferentially. On the other hand, investigation of the propagation step was carried out with respect to epoxy oxane derivatives. It was clarified that the ring-expansion reaction of cis-2,3-disubstituted oxane derivatives provided spiro acetals as products, not the desired trans-fused cyclic ethers, owing to the reaction pathway triggered by 1,2-hydride rearrangement.

A facile synthesis of (R)-(−)-hexahydromandelic acid with fermenting baker's yeast

Abstract Optically pure (R)-(−)-hexahydromandelic acid has been prepared stereoselectively in two steps by the asymmetric reduction of ethyl α,2-dioxocyclohexaneacetate with fermenting bakers yeast followed by Clemmensen reduction.