نتایج جستجو برای: pyrimidine quinoxalines
تعداد نتایج: 10165 فیلتر نتایج به سال:
We compared the removal of pyrimidine(6-4)pyrimidone photoproducts [(6-4) photoproducts] and cyclobutane pyrimidine dimers (CPDs) from the genome of repair-proficient Escherichia coli, using monoclonal antibodies specific for each type of lesion. We found that (6-4) photoproducts were removed at a higher rate than CPDs in the first 30 min following a moderate UV dose (40 J/m2). The difference i...
4,6-Dichloro-2-(methylthio)pyrimidine (3) reacts with EtONa in EtOH, at ca. 20 ◦C, for 2 h, to give exclusively 4-chloro-6-ethoxy-2-(methylthio)pyrimidine (5) in 89% yield. The latter is presented as a useful multifunctionalised pyrimidine scaffold.
The formation of pyridine-pyrimidine- and pyrimidine-pyrimidine base pairs after in vitro DNA replication with the large fragment of Escherichia coli DNA polymerase I indicates that Watson-Crick-like base pairing between pyrimidine bases can occur in the enzyme due to the presence of the rare tautomers of deoxycytidylate and thymidylate in the template strand. The implications to mispair format...
Analogs of alternating purine-pyrimidine DNA polymers such as poly(dA-dT)-poly(dA-dT) can be made with phosphorothioate groups in the DNA backbone. A phosphorothioate diester at the 5'-purine-pyrimidine-3' step causes a significant lowering of the polymer's melting temperature compared to a phosphorothioate diester at the 5'-pyrimidine-purine-3' step. This may occur because sulfur substitution ...
Fused pyrimidine cores are privileged kinase scaffolds, yet few examples of the 2-amino-pyrido[3,4-d]pyrimidine chemotype have been disclosed in the context of kinase inhibitor programs. Furthermore, no general synthetic route has been reported to access 2-amino-pyrido[3,4-d]pyrimidine derivatives. Here we report a versatile and efficient chemical approach to this class of molecules. Our strate...
Spectroscopic and computational insight into weak noncovalent interactions in crystalline pyrimidine
Effects of weak C-H· · ·N interactions on the vibrational spectrum of crystalline pyrimidine are studied using Raman spectroscopy and electronic structure computations. When pyrimidine transitions from the liquid to solid state, peaks in the Raman spectrum exhibit non-uniform shifts. Calculations performed on a cluster of nine pyrimidine molecules (one pyrimidine molecule embedded in a field of...
With reference to the impending transition of chemical industry from depleting fossil raw materials to renewable feedstocks--the end of cheap oil is predicted for 2040 at the latest--this account gives an overview on chemically transforming carbohydrates, by far the major part of the annually regrowing biomass, into the following unsaturated O- and N-heterocycles with versatile industrial appli...
Neuroblastoma is an aggressive pediatric malignancy with significant chemotherapeutic resistance. In order to obtain new compounds active on neuroblastoma cell lines, we investigated the reactivity of carbanion formed via TDAE in quinoxaline series. The new synthesized compounds were tested for their anti-proliferative activity on two neuroblastoma cell lines, and seven oxirane derivatives obta...
The additive effects of amines were realized in the asymmetric hydrogenation of 2-phenylquinoxaline, and its derivatives, catalyzed by chiral cationic dinuclear triply halide-bridged iridium complexes [{Ir(H)[diphosphine]}(2)(μ-X)(3)]X (diphosphine = (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [(S)-BINAP], (S)-5,5'-bis(diphenylphosphino)-4,4'-bi-1,3-benzodioxole [(S)-SEGPHOS], (S)-5,5'-bis(...
We describe the clinical. hematologic. and biochemical findings in eight patients with pyrimidine-5’-nucleotidase deficiency occurring in six unrelated families. In most cases, a profound lowering of red cell pyrimidine-5’-nucleotidase activity. associated with the characteristic change in the u.v. spectrum brought about by increased levels of pyrimidine nucleotides was observed. One patient ha...
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