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Biomedical subjects

T Miyasaka

Publications and source records attributed to T Miyasaka.

At least 109 records · Page 6Linked to original sources
PubMed1985

Diazaquinomycin A, a new antifolate antibiotic, inhibits thymidylate synthase.

The inhibitory effect of diazaquinomycin A (DQM) on the growth of Enterococcus faecium was completely reversed by thymidine. Relatively large amounts of folate, dihydrofolate or leucovorin also reversed the activity of DQM. DQM showed cytotoxicity against Vero and Raji cells and the cytotoxicity was partially reversed by leucovorin or thymidine. With enzyme experiments, it was found that DQM inhibits TMP synthases from E. faecium and Ehrlich ascites carcinoma competitively with 5,10-methylenetetrahydrofolate, one of the substrates for the enzyme reaction.

Animals↗
PubMed1985

Synthesis and pharmacological activities of 2-alkynyl- and 2-alkenyladenine nucleosides.

A variety of 2-alkynyladenosines (2a-1) were evaluated for biological activity in antiallergic and cardiovascular tests. Compounds bearing 2-C identical to CCH(R)OH side-chain structure exhibited the most potent antiallergic activity at 0.4 mg/kg iv, in rat. These compounds, however, possessed hypotensive activity accompanied by a decrease in heart rate. Compounds substituted at the 2-position by n-pentynyl, n-hexynyl and n-octynyl showed potent hypotensive effect without showing antiallergic activity and a decrease in heart rate. Synthesis and pharmacological activities of 2-alkenyl-adenosines and 2-alkynyl-2'-deoxy- or 3'-deoxyadenosines were also described.

Adenosine↗
PubMed1985

On the mechanism of lithiation of uridine derivatives with lithium dialkylamides.

Efficiency and regioselectivity (C-6 or C-5) in the lithiation of uridine derivatives were examined by using LDA (lithium diisopropylamide) and LTMP (lithium 2,2,6,6-tetramethylpiperidide). It revealed that rotation of the C-2' substituent caused steric hindrance on approaching the lithiating agent to the C-6 position, providing evidence that the lithiation takes place through their syn-conformers.

Amides↗
PubMed1985

Evaluation of the affinity of new N atom-containing tumor inhibitors for nucleic acids.

Interaction between new N atom-containing tumor inhibitors (1-9) and nucleic acids has been investigated utilizing the spectroscopic methods efficiently. On the basis of their data, it is well suggested that FNT-4 (4) and benzo[c]phenanthridine alkaloids (6-8) bind to nucleic acids by a fashion involving intercalation of aromatic molecule(s).

Animals↗
PubMed1984

Synthesis and properties of 2'-deoxy-8,2'-methylene-cyclopurine nucleosides.

A method was developed to synthesize 2'-deoxy-8,2'-methylene-cycloadenosine (1) and -cycloguanosine (2) which were new carbon-bridged cyclopurine nucleosides fixed in a high-anti torsional angle region. 3',5'-Di-O-acetyl-8-methanesulfonyl-2'-O-p-toluene-sulfonyladenosine+ ++ (3) or 2-acetamido-9- (3,5-di-O-acetyl-2-O-p-toluenesulfonyl-beta-D-ribofuranosyl)-6- ethoxy-8-methanesulfonyl-purine (9) was treated with sodium salt of ethyl malonate to give the cyclized nucleosides (4 and 10) in good yields, respectively. Subsequent decarboxylation and deblocking of 4 and 10 afforded 1 and 2 in crystalline form, respectively.

Chemical Phenomena↗
PubMed1984

Anti-parasite activity of nucleoside analogues in Leishmania tropica promastigotes.

Many nucleoside analogs were screened for anti-protozoa activity on Leishmania tropica in an in vitro culture system. 3'-Deoxyinosine and several tubercidin derivatives were found to be potent inhibitors for growth of the promastigote form of L. tropica. EC50 value of 3'-deoxyinosine was 4.43 X 10(-7)M. This compound was remarkably less toxic towards mouse mammary tumor FM3A cells (EC50, 1.25 X 10(-4) M). 3'-Deoxyinosine is metabolized by Leishmania promastigote to give 3'-deoxyinosine-5'-monophosphate, 3'-deoxy-adenosine(cordycepin)-5'-mono, di-, and triphosphates. This means that Leishmania can aminate the 6-position of 3'-deoxyinosine-5'-monophosphate, thereby converting it into a highly toxic compound.

Animals↗
PubMed1983

Introduction of carbon substituents at C-2 position of purine nucleosides.

A series of new purine nucleosides which have carbon substituents at their C-2 position were synthesized by non-aqueous diazotization/deamination of 2-amino-6-chloro-9-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)purine (1) with isoamyl nitrite in aromatic solvents and by palladium-catalyzed alkynylation of 2-iodo-adenosine (4) with terminal alkynes.

Alkylation↗