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Biomedical subjects

S Umezawa

Publications and source records attributed to S Umezawa.

At least 91 records · Page 5Linked to original sources
PubMed1981

Syntheses of 9-substituted josamycin, 13-substituted isojosamycin and their tetrahydro derivatives.

Derivatives of josamycin and isojosamycin modified at C-9 and C-13 have been prepared by reaction sequences involving treatment of josamycin with alcohols, phenol or 1-methyl-1H-tetrazol-5-ylthiol in acidic media. Several tetrahydro derivatives of josamycin and isojosamycin have also been prepared by reaction sequences involving catalytic hydrogenation. From the 1H NMR studies, it was found that the conformation of the macro-lactone portion of 13-O-methylisojosamycin dimethylacetal, a key intermediate, is flexible and changeable with variation of the solvent.

Anti-Bacterial Agents↗
PubMed1980

Chemical modification of the ester group of diketocoriolin B.

5,8-Di-O-tetrahydropyranylcoriolin B (2) was synthesized and its two expoxide groups were found to be resistant to alkaline hydrolysis to give di-O-tetrahydropyranldihydrocoriolin (3). Acylation or alkylation of the free hydroxyl group at C-1 of 3 followed by hydrolysis of the tetrahydropyranylether groups and oxidation of the hydroxyl groups at C-5 and C-8 afforded a numer of 1-O-acyl or alkyl analogs of diketocoriolin B. All of them showed antibacterial and antitumor activities.

Animals↗
PubMed1980

Syntheses of corliolin, 1-deoxy-1-ketocoriolin and 1,8-dideoxy-1,8-diketocoriolin from coriolin B.

Hydrolysis of 5,8-di-O-tetrahydropyranyl-5-deoxo-5-hydroxycoriolin which was prepared from coriolin B, followed by oxidation of the hydroxy groups at C-5, or C-1 and C-5, or C-1, C-5 and C-8 afforded coriolin (2), 1-deoxy-1-ketocoriolin (3) and 1,8-dideoxy-1,8-diketocoriolin (4). All three ketones were found to have antitumor activity, whereas antibacterial activity was observed in 2 and 3 but not in 4.

Animals↗
PubMed1978

A synthesis of dihydrostreptomycin.

A key protected streptidine derivative (3) useful for the synthesis of antibiotics of streptomycin series was prepared by hydrolysis of an acylated dihydrostreptomycin (DHSM) derivative (2), and it was condensed with a protected dihydrostreptobiosaminyl chloride (5) to give two condensation products (6 and 7). By deblocking, 6 was led to DHSM and 7 to a biologically inactive isomer (8) of DHSM. From the PMR spectrum of 4-O-mesyl derivative (4) of 3, the benzyloxycarbonyl and acetyl groups were concluded to be attached to the end nitrogens of the guanidine groups.

Chemical Phenomena↗
PubMed1978

Cyclic phosphates of formycin.

The syntheses of N1- and N2-isopropylformycin (10, 11), formycin 3',5'-cyclic and 2',3'-cyclic phosphate (3,7) and their N-methyl and N-isopropyl derivatives (13, 15, 19, 23) are described. It was observed that substitution at N1 or N2 with a bulky alkyl group or cyclic phosphorylation of the ribose moiety made formycin resistant to adenosine deaminase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

Synthesis of 5''-amino-3,5''-dideoxybutirosin A.

The titled compound was prepared by condensation of 3'-deoxyparomamine derivative (5) with 2,3-O-bis(p-nitrobenzoyl)-5-O-tosyl-D-xylofuranosyl bromide followed by 1-N-acylation with the active ester of (S)-4-benzyloxycarbonylamino-2-hydroxybutyric acid. The compound was slightly more active than 3'-deoxybutirosin A against Pseudomonas.

Anti-Bacterial Agents↗