Kentaro Okuma

Reaction of Benzyne with Salicylaldehydes: General Synthesis of Xanthenes, Xanthones, and Xanthols

The reaction of salicylaldehydes with benzyne prepared from o-trimethylsilyphenyl triflate and CsF gave xanthenes and xanthones. When the reaction was carried out under basic conditions, 9-hydroxyxanthenes (xanthols) were obtained in good yields.

REACTION OF ARYNES WITH CARBON-HETEROATOM DOUBLE BONDS

Recent achievements in the construction of heterocycles by the reaction of arynes with carbon-heteroatom double bonds are reviewed. Use of the Diels-Alder type, ionic, and radical mechanisms resulted in the formation of novel heterocycles containing oxygen, nitrogen, sulfur, and selenium atoms. Abstract This review focused on the application of nano-materials in heterocyclic chemistry. The main part of review is constituted by sections in which the reactions catalyzed by nanomaterials. In the last part of this review, emphasis is given to the heterocyclic supported nanomaterials and their importance in the catalysis. Abstract Aspergillides A, B, and C are cytotoxic macrolides produced by the marine-derived fungus Aspergillus ostianus strain TUF 01F313. The unique molecular architectures of the aspergillides featuring 14-membered marocyclic structures embedded with a tetrahydro- or dihydropyran unit have attracted significant attention from the synthetic chemistry community, and thereby various synthetic approaches to these structurally as well as pharmacologically intriguing molecules have been reported by as many as 12 research groups in the past 3 years. This review describes all of the syntheses disclosed to date, focusing mainly on the methodologies employed for the diastereoselective installation of the pyran ring systems.

Isolation, structure and reaction of selenobenzophenones. X-Ray molecular structure of 4,4′-dimethoxyselenobenzophenone and of 4,4-biphenyl-2,3-diselenabicyclo[3.3.0]oct-7-ene

4,4′-Dimethoxy-1a and 4,4′-dimethyl-selenobenzophenone 1b could be isolated in moderate yields by the reaction of the corresponding ylides 3 with elemental selenium in benzene at 80 °C. Their spectral data are described. Attempted isolation of unsubstituted selenobenzophenone afforded only its dimer 5. Compound 1a crystallizes in space group P21/n with unit-cell parameters a= 7.191(3), b= 7.505(4), c= 24.856(4)A, β= 90.32(1)°, Z= 4, R= 0.055. The oxidation and thiation of 4,4′-dimethoxyselenobenzophenone 1a afforded the corresponding benzophenone and thiobenzophenone in good yields. The reaction of compound 1 with cyclopentadiene afforded the corresponding cycloadducts 7(3,3-diaryl-2-selenabicyclo[2.2.1] hept-5-enes), whereas bicyclic diselenides 8(4,4-diaryl-2, 3-diselenabicyclo[3.3.0]oct-7-enes) were obtained by using an excess of selenium and a higher temperature. Oxidation of compound 8c gave the corresponding diol 12, aldehyde 13, and diphenylfulvene 11. The reaction of compound 1a with benzenediazonium carboxylate afforded 2,2- bis-(4-methoxyphenyl)-4H-3,1 -benzooxaselenin -4-one 17.

Synthesis of bifunctional P-chiral hydroxy phosphinates; lipase-catalyzed stereoselective acylation of ethyl (1-hydroxyalkyl)phenylphosphinates

Abstract Lipase-catalyzed acylation of ethyl (1-hydroxyalkyl)phenylphosphinates afforded a single diastereomer in high enantiomeric excess. The substituent effect of the alkyl group toward the acylation using Candida antractica (CAL) was larger than that of an immobilized lipase from Pseudomonas fluorescens lipase (lipase AK).

Lipase-catalyzed kinetic resolution of P-chiral phosphorus compounds: enantiopreference of Pseudomonas lipase and Candida antarctica lipase

Optically active 1-hydroxymethylalkylphenylphosphine oxides 1a–c were prepared by Pseudomonas fluorescens lipase (lipase AK) and Candida antarctica lipase (CAL)-catalyzed optical resolution. Lipase AK-catalyzed resolution of tert-butyl derivative 1c showed R-selectivity, whereas CAL preferred the S-enantiomer.

THE FIRST ISOLATION OF BENZYNE-THIOBENZOPHENONE ADDUCTS

Abstract Reaction of thiobenzophenones with phenyl[2-(trimethylsilyl)phenyl]iodonium trifluoromethanesulfonate in the presence of tetrabutylammonium fluoride afforded the corresponding adducts, which are the first examples of benzync-thiobenzophenone adducts.

Reactions of selenobenzophenones with dimethyl acetylenedicarboxylate or norbornadiene

Abstract Reactions of selenobenzophenones with dimethyl acetylenedicarboxylate or norbornadiene gave benzoselenapyranes or seven-membered cyclic selenides; these reactions might proceed through unusual type of cycloaddition reaction.

Synthesis and properties of fluorescence probe for detection of peroxides in mitochondria.

In this study, a new type of fluorescence probe, diphenylpyrenylphosphine-conjugated alkyltriphenylphosphonium iodide which was accumulated in mitochondria, has been synthesized. This probe was detected peroxide in living cell. Comparison of the reactivity toward several peroxide indicated that the probe was existed in mitochondrial membrane. Using this probe, generation of peroxide in mitochondria of living cell was successfully visualized.

Lipase-catalyzed kinetic resolution of racemic seven-membered substituted lactones

Abstract Optically active 3-, 4-, 5-, or 6-methyl substituted seven-membered lactones were prepared by Candida antarctica lipase (CAL)-catalyzed kinetic resolution of the racemic lactones. Among these lactones, only in the case of 5-methylhexanolide ( R )-isomer reacts faster than the other enantiomer, while the rest of lactones show ( S )-selectivity.

An efficient synthesis of (R)-(+)-recifeiolide and related macrolides by using enantiomerically pure (R)-(−)-5-methyl-2,2,2-triphenyl-1,2λ5-oxaphospholane

Abstract E-(R)-(+)-8-Dodece-11-olide, which is known as recifeiolide, was synthesized by a six-step reaction starting from (R)-(+)-propene oxide in a total yield of 53 %. The key step of this synthesis is the preparation of (R)-(−)-methyl 11-hydroxy-8-dodecenate using (R)-(−)-5-methyl-2,2,2-triphenyl-1,2λ5-oxaphospholane. Be using this method, enantiomerically pure 13- and 14-membered macrolides were also synthesized.