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Biomedical subjects

Jun-ichi Yoshida

Publications and source records attributed to Jun-ichi Yoshida.

At least 19 recordsLinked to original sources
PubMed2006

Oxidative generation of diarylcarbenium ion pools.

"Cation pools" of diarylcarbenium ions have been generated by the oxidative C-H bond dissociation of diarylmethanes using anodic oxidation. "Diarylcarbenium ion pools" thus generated react with various nucleophiles, such as allylsilanes, ketene silyl acetals, and aromatic compounds. The reductive homocoupling of the "diarylcarbenium ion pool" has been achieved. The dimer thus obtained also serves as a precursor of the "diarylcarbenium ion pool" via oxidative C-C bond dissociation. [reaction: see text]

Journal Article↗
PubMed2006

Indirect cation pool method. Rapid generation of alkoxycarbenium ion pools from thioacetals.

A sequential one-pot indirect cation pool method has been developed. The method involves the electrochemical generation and accumulation of ArS(ArSSAr)+ at low temperature (step 1) and the follow-up reaction with a thioacetal to generate an alkoxycarbenium ion pool (step 2), which reacts with various carbon nucleophiles (step 3). Steps 2 and 3 are extremely fast. The electrogenerated ArS(ArSSAr)+ was well-characterized by 1H NMR and CSI-MS. The alkoxycarbenium ion pool generated by the present indirect method exhibited 1H and 13C NMR spectra and thermal stability similar to those of the alkoxycarbenium ion pool generated by the direct electrochemical method.

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PubMed2006

Platform synthesis: A useful strategy for rapid and systematic generation of molecular diversity.

Emergence of library-based approaches have changed the way of developing new functional molecules in materials science and pharmaceutical science. Therefore, reliable methods for rapid and systematic generation of functional molecules are highly called for in this field. We herein describe our concept of "platform synthesis" as a useful strategy for generating molecular diversity. This simple yet powerful strategy realizes the synthesis of a number of interesting multifunctional molecules, such as multisubstituted olefins, in a programmable and diversity-oriented format. As well as applications to the synthesis of pharmaceutically important molecules, such as tamoxifen and CDP840, applications to materials science, which have led to the discovery of interesting fluorescent materials and properties, are also described.

Journal Article↗
PubMed2005

Combinatorial synthesis of an oligosaccharide library by using beta-bromoglycoside-mediated iterative glycosylation of selenoglycosides: rapid expansion of molecular diversity with simple building blocks.

A new method for constructing an oligosaccharide library composed of structurally defined oligosaccharides is presented based on an iterative glycosylation of selenoglycosides. Treatment of 2-acyl-protected selenoglycosides with bromine selectively generates beta-bromoglycosides, which serve as glycosyl cation equivalents in the oligosaccharide synthesis. Thus, the coupling of the bromoglycosides with another selenoglycoside affords the corresponding glycosylated selenoglycosides, which can be directly used to next glycosylation. The iteration of this sequence allows the synthesis of a variety of oligosaccharides including an elicitor active heptasaccharide. A characteristic feature of the iterative glycosylation is that glycosyl donors and acceptors with the same anomeric reactivity can be selectively coupled by activation of the glycosyl donor prior to coupling with the glycosyl acceptor. Therefore, same selenoglycosides can be used for both the glycosyl donors and the acceptors. This feature has been exemplified by a construction of an oligosaccharide library directed to elicitor-active oligosaccharides. The library composed of stereochemically defined oligoglucosides with considerable structural diversity can be constructed starting from simple selenoglycosides.

Carbohydrate Sequence↗
PubMed2005

Intramolecular participation in alkoxycarbenium ion pools.

[reaction: see text] Alkoxycarbenium ions having no substituents on the cationic carbon have been accumulated as "cation pools" by the introduction of an ether group in an appropriate position. Intramolecular participation of the ether oxygen is suggested to be responsible for stabilization of the alkoxycarbenium ions.

Journal Article↗
PubMed2005

Rapid synthesis of CDP840 with 2-pyrimidyl vinyl sulfide as a platform.

A rapid synthesis of CDP840 (a potential therapeutic agent for asthma), using 2-pyrimidyl vinyl sulfide as a platform, has been established. This method includes a stereoselective double Mizoroki-Heck-type arylation, a Liebeskind-Srogl-type cross-coupling reaction, and a Pd/C-catalyzed hydrogenation.

Journal Article↗
PubMed2005

Triarylethene-based extended pi-systems: programmable synthesis and photophysical properties.

[reaction: see text] On the basis of an efficient Pd-catalyzed triarylation to a vinylsilane platform, four types of structurally well-defined triarylethene-based extended pi-systems have been prepared very rapidly. From a compound library constructed by the present method, it was possible to find a number of interesting fluorescent materials, as well as interesting fluorescent properties such as aggregation-induced enhanced emission. A useful method for the rapid synthesis and property evaluation has also been developed.

Journal Article↗
PubMed2005

Iron-catalyzed cross-coupling of alkenyl sulfides with Grignard reagents.

[reaction: see text] The iron-catalyzed cross-coupling reaction of alkenyl sulfides with Grignard reagents is described. While the cross-coupling proceeds efficiently at alkenyl-S bonds, almost no cross-coupling takes place at aryl-S bonds, attesting to a unique selectivity of iron catalysis. The beneficial effect of potentially coordinating 2-pyrimidyl group on sulfur is also described.

Journal Article↗
PubMed2005

Stereoselective synthesis of multisubstituted alkenes via conformationally labile alkenyllithium species.

Stereoselective synthesis of tri- and tetrasubstituted alkenylsilanes has been realized by the selective intramolecular silicon migration in the rapidly equilibrating alkenyllithium species. Subsequent copper- and palladium-mediated coupling with allyl and aryl halides provides tri- and tetrasubstituted alkenes possessing all different carbon-substituents with complete stereoselectivity. [structure: see text]

Journal Article↗
PubMed2005

Effect of synthetic protease inhibitor gabexate mesilate on the attenuation of ischemia/reperfusion injury in canine kidney autotransplantation.

BACKGROUND: Kidneys from non-heart-beating donors are associated with delayed graft function and a high rejection rate due to the long period of warm ischemia. Gabexate mesilate (GM), a synthetic serine protease inhibitor, has been shown to improve organ function by suppressing cytokine activity and neutrophil function after ischemia/reperfusion. In this study, we evaluated the effect of GM on renal function after warm ischemia in a canine kidney autotransplantation model. METHODS: After 60 minutes of warm ischemia, the left kidney was transplanted into the iliac fossa, and the right kidney was removed. The control group (n = 7) and GM group (n = 7) were evaluated for serum creatinine and blood urea nitrogen (BUN) concentrations, renal tissue blood flow, resistive index, pulsatility index, interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha mRNA expression levels in peripheral blood mononuclear cells, apoptotic index, CD10 immunolabeling as an indicator of brush border injury, and standard histopathology. RESULTS: Compared with controls, administration of GM resulted in lower serum creatinine concentrations (11.3 +/- 2.4 vs 5.2 +/- 3.3 mg/dL at 72 hours; P = .04) and BUN concentrations (188 +/- 26 mg/dL vs 98 +/- 41 mg/dL at 72 hours; P = .04), as well as better tissue blood flow, improvement of brush border injury and apoptotic index (each P < .05). The expression of IL-1beta and TNF-alpha mRNA did not change after administration of GM. CONCLUSIONS: The present study shows that GM protected renal function after warm ischemia/reperfusion by inhibition of serine proteases, maintenance of tissue blood flow, and amelioration of tubular apoptosis.

Animals↗