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At least 163 records · Page 9Linked to original sources
PubMed1990

Chemotherapeutic agents, XVIII: Synthesis of pi-deficient pyrimidines and fused pyrimidines as leishmanicidal agents.

Synthesis of 6-aryl-5-cyano-2-thiouracils 1a-d from the condensation-cyclization of an aromatic aldehyde, thiourea and ethyl cyanoacetate has been described. Alkylation of 1a-d under different reaction conditions with mono- and dihalo-alkanes yielded 2, 3, and 6. Interaction of 1 with POCl3 provided halopyrimidines 8a,b. Nucleophilic substitution on 8 and 3 with aromatic amines gave 9a-d and 7a-d respectively. 6-Chloro-5-nitro-3-methyluracil (11) obtained by nitration of 10 underwent nucleophilic substitution with amines providing 12. Some of the compounds screened as leishmanicides did not exhibit any significant activity.

Animals↗
PubMed1994

Imidazo[1,5-a]pyrimidine and benzo[4,5]imidazo-[1,2-a]pyrimidine derivatives as calcium antagonists.

Several bicyclic dihydropyrimidines were synthesized and evaluated for their calcium antagonistic activities by comparison with the usual 1,4-dihydropyridine calcium antagonist reference compound nifedipine. The solid-state structure of the isopropyl 2-methyl-4-(3'-nitrophenyl)-1,4-dihydrobenzo[4,5]imidazo[1,2- a]pyrimido-3-carboxylate shows that these compounds can adopt the most important structural features of the 1,4-dihydropyridine and 1,4-dihydropyrimidine calcium channel blockers. The high-potassium depolarized rat aorta assay was used for testing the compounds as calcium channel blockers. Some compounds showed interesting vasorelaxant activity.

Animals↗
PubMed1995

Comparison of the effects of UV irradiation on 5-methyl-substituted and unsubstituted pyrimidines in alternating pyrimidine-purine sequences in DNA.

We previously demonstrated the UV-induced formation of cytosine hydrate in DNA and its deamination product, uracil hydrate, via their release from the DNA backbone by the DNA glycosylase activity of Escherichia coli endonuclease III. Subsequently, endonuclease III-mediated release of thymine hydrate from UV-irradiated poly(dA-dT) was reported. Therefore, we asked whether 5-methylcytosine residues in DNA underwent photohydration and deamination to thymine hydrate in analogy to UV-induced deamination of cytosine. An alternating DNA copolymer containing 5-methylcytosine was irradiated with UVC and incubated with endonuclease III. No 5-methylcytosine hydrate was released. Instead, UV-induced nonenzymatic release of 5-methylcytosine occurred. Similarly, incubation of UV-irradiated poly(dA-dT) with endonuclease III did not release thymine hydrate; nonenzymatic release of thymine occurred. Nonenzymatic release of 5-methylpyrimidines was oxygen dependent, enhanced by ferric ion and inhibited by free radical scavengers. In contrast, photohydration of cytosine was oxygen independent, and only small amounts of cytosine were nonenzymatically released. Thus, 5-methylpyrimidine residues within alternating Pu-Py sequences in DNA do not undergo photohydration, but instead undergo cleavage of their N-glycosyl bonds yielding abasic (AP) sites. The inability to repair such AP sites may explain the UV sensitivity of E. coli xthnfo mutants, which lack AP endonuclease activity. We suggest that N-glycosyl bond cleavage is mediated by radical species formed via transfer of an electron from UV-excited triplet 5-methylpyrimidines to ground state oxygen and/or ferric ions.

DNA↗