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Biomedical subjects

H Miyabe

Publications and source records attributed to H Miyabe.

6 recordsLinked to original sources
PubMed2005

Detection of heat shock proteins but not superantigen by isolated oral bacteria from patients with Behcet's disease.

We isolated bacteria from periodontal sites and mixed saliva in eight patients with Behcet's disease and surveyed them to determine whether they produced heat shock proteins (HSPs) and superantigen. Cultivable bacterial compositions from periodontal sites and saliva were examined by anaerobic culture using blood agar plates. Gram-negative anaerobic rods such as Prevotella intermedia, Fusobacterium nucleatum, and Capnocytophaga species were predominant in the isolates from the subgingival plaque samples. The Streptococcus mitis group was the most common type isolated from the saliva samples. To detect the production of HSPs, Western blot analyses were performed using a polyclonal rabbit antibody to Escherichia coli DnaK and a monoclonal antibody to Helicobacter pylori Gro-EL. Sonic extracts of 27 of the strains (79.4%) reacted with the antibody against E. coli DnaK. Nine of these 34 strains (26.5%) were found to produce HSPs that reacted with antibody to H. pylori Gro-EL. A total of 54 isolates were examined for superantigen activity against human peripheral leukocytes. Twenty-five gram-negative clinical strains isolated from chronic periodontitis lesions and 20 ATCC strains of microorganisms were also examined. We could not detect any superantigen activity in 500x diluted supernatant of the strains isolated from the eight patients with Behcet's disease. The present study indicates that the anaerobic strains isolated from the oral cavity of these patients produce HSPs, the production being related to Bechet's disease.

Adult↗
PubMed2000

A new alternative to the mannich reaction: tandem radical addition-cyclization reaction for asymmetric synthesis of gamma-butyrolactones and beta-amino acids

The radical addition-cyclization reaction of substrates having two different radical acceptors such as acrylate and aldoxime ether moieties was studied. This new free radical-mediated Mannich-type reaction proceeded smoothly via a tandem C-C bond-forming process. Furthermore, the diastereoselective tandem reaction provides the novel method for asymmetric synthesis of gamma-butyrolactones and beta-amino acid derivatives.

Journal Article↗
PubMed2000

Stereocontrol in solid-phase radical reactions: radical addition to oxime ether anchored to polymer support

A high degree of stereocontrol in solid-phase radical reactions was achieved by using triethylborane and diethylzinc as a radical initiator at low reaction temperature. Alkyl radical addition to Oppolzer's camphorsultam derivatives of oxime ether anchored to polymer support proceeded smoothly to give the alpha-amino acid derivatives with excellent diastereoselectivities.

Journal Article↗
PubMed2000

Asymmetric synthesis of alpha-amino acids based on carbon radical addition to glyoxylic oxime ether

The first asymmetric synthesis of alpha-amino acids based on diastereoselective carbon radical addition to glyoxylic imine derivatives is reported. The addition of an isopropyl radical, generated from i-PrI, Bu(3)SnH, and Et(3)B in CH(2)Cl(2) at 25 degrees C, to achiral glyoxylic oxime ether 1 proceeded regioselectively at the imino carbon atom of the oxime ether group to give an excellent yield of the C-isopropylated product 2. The competitive reaction using glyoxylic oxime ether 1 and aldoxime ether 4 showed that the reactivity of the glyoxylic oxime ether toward nucleophilic carbon radicals was enhanced by the presence of a neighboring electron-withdrawing substituent. Thus, the alkyl radical addition to glyoxylic oxime ether 1 proceeded smoothly even at -78 degrees C, in contrast to the unactivated aldoxime ether 4. A high degree of stereocontrol in the carbon radical addition to the glyoxylic oxime ether was achieved by using Oppolzer's camphorsultam as a chiral auxiliary. The stannyl radical-mediated reaction of the camphorsultam derivative 6 with an isopropyl radical at -78 degrees C afforded a 96:4 diastereomeric mixture, 7a, of the C-isopropylated product. The reductive removal of the benzyloxy group of the major diastereomer (R)-7a, by treatment with Mo(CO)(6) and the subsequent removal of the sultam auxiliary by standard hydrolysis, afforded the enantiomerically pure D-valine (R)-12 without any loss of stereochemical purity. To evaluate the new methodology, a variety of alkyl radicals were employed in the addition reaction which gave the alkylated products 7 with excellent diastereoselectivity, allowing access to a wide range of enantiomerically pure natural and unnatural alpha-amino acids. Even in the absence of Bu(3)SnH, treatment of 6 with alkyl iodide and Et(3)B at 20 degrees C gave the C-alkylated products 7 with moderate diastereoselectivities. The use of Et(2)Zn as a radical initiator, instead of Et(3)B, was also effective for the radical reaction. The enantioselective isopropyl radical addition to 1 using (R)-(+)-2, 2'-isopropylidenebis(4-phenyl-2-oxazoline) and MgBr(2) gave excellent chemical yield of the valine derivative 2 in 52% ee.

Journal Article↗
PubMed2000

[Development of solid-phase radical reactions using oxime ethers as a radical acceptor].

Triethylborane has the potential to induce radical reactions on solid support and the solid-phase radical reactions were achieved by using triethylborane as a radical initiator. The intermolecular carbon radical addition to glyoxylic oxime ether anchored to Wang resin proceeded under very mild conditions to give alpha-amino acid derivatives in good yield without interference of the polystyrene skeleton of the resin. Diethylzinc also worked well as a radical initiator at low reaction temperature. Thus, the employment of triethylborane or diethylzinc at low reaction temperature facilitated the control of stereochemistry in solid-phase reactions. Alkyl radical addition to Oppolzer's camphorsultam derivatives of oxime ether anchored to a polymer support proceeded smoothly even at -78 degrees C to give the alpha-amino acid derivatives with excellent diastereoselectivities. The radical cyclization of oxime the ethers anchored to a polymer support also proceeded effectively to provide functionalized pyrrolidines via a carbon-carbon bond-forming process.

Amino Acids↗