5417-13-0Relevant articles and documents
Complexes with 6-amino-5-nitroso-2-thiouracil and violuric acid derivatives containing the fac-ReI(CO)3 core: Synthesis, XRD structural and photoluminescence characterization
Illán-Cabeza, Nuria A.,García-García, Antonio R.,Moreno-Carretero, Miguel N.
, p. 262 - 267 (2011)
The fac-tricarbonylrhenium(I) complexes of the 6-amino-1,3-dimethyl-5- nitroso-2-thiouracil (DANTU) and violuric acid (VIO) and its mono- (MVIO) and dimethyl (DVIO) derivatives have been prepared. The complexes have been characterized by elemental analysis, IR, 1H and 13C NMR spectral methods and luminescence spectroscopy. The structures of [ReCl(CO) 3(DANTU)], [Re(H2O)(CO)3(VIOH-1)] and [Re(H2O)(CO)3(DVIOH-1)] complexes were solved from single-crystal X-ray diffraction experiments. The coordination environment around the Re(I) may be described as a distorted octahedron in which the ligand behaves in a bidentate fashion through the nitrogen atom of the nitroso group and an adjacent carbonylic oxygen, making a five-membered chelate ring. The coordination sphere is completed with three carbonyl groups in fac-arrangement and one chlorine atom (DANTU complex) or water molecule (VIO complexes). The higher acidity of violuric acids, if compared with DANTU one, may explain both synergic deprotonation and chloride substitution in the [ReCl(CO)3]+ moiety to form the Re-violurato complexes.
Supramolecular interactions through lone pair(lp)-π and hydrogen bonding in cobalt(III) and manganese(II) derivatives of N,N′-dimethylvioluric acid: A combined experimental and theoretical study
Banik, Rupak,Roy, Subhadip,Bauza, Antonio,Frontera, Antonio,Rodríguez-Diéguez, Antonio,Salas, Juan M.,Kirillov, Alexander M.,Chowdhury, Shubhamoy,Das, Saroj Kr.,Das, Subrata
, p. 178 - 186 (2015)
The reactivities of cobalt(II) and manganese(II) salts toward HDMV (N,N′-dimethylvioluric acid monohydrate) were studied. Reaction of cobalt(II) chloride hexahydrate with HDMV in water-methanol medium at pH = 8.0 led to the formation of a cobalt(III) complex [CoIII(DMV)3]·0.5H2O (1), whereas the interaction of manganese(II) chloride tetrahydrate with HDMV under similar reaction conditions afforded [MnII(H2O)6](DMV)2 (2). Dimethylviolurate anion behaves as a bidentate ligand in 1 and counteranion in 2. Both compounds were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, cyclic voltammetry and thermogravimetric analysis. Presence of Co(III) in 1 indicates the aerial oxidation of the cobalt(II) precursor. In 1, Co(III) adopts a distorted octahedral [CoN3O3] coordination environment through bonding to the three dimethylviolurato anions. In 2, the [Mn(H2O)6]2+ cations and (DMV)- anions are assembled by multiple hydrogen bonds into a complex 3D H-bonded network. It was analyzed from the topological viewpoint, disclosing a binodal 4,8-connected underlying net with the flu (fluorite) topology. Electrochemical studies reveal that the compounds undergo a quasi-reversible one electron metal centered redox process. DFT studies were carried out to analyze the supramolecular assemblies in the solid state structures, especially lone pair(lp)-π interactions in 1 and H-bonding network in 2.
Oxyma-B, an excellent racemization suppressor for peptide synthesis
Jad, Yahya E.,Khattab, Sherine N.,De La Torre, Beatriz G.,Govender, Thavendran,Kruger, Hendrik G.,El-Faham, Ayman,Albericio, Fernando
, p. 8379 - 8385 (2014)
Peptide-bond formation is a key process in the synthesis of peptide oligomers. Among the many coupling techniques reported, carbodiimides combine strong acylation potency and smooth reaction conditions and are commonly used in the presence of additives. Recently, ethyl 2-cyano-2-(hydroxyimino)acetate (OxymaPure) has emerged as a highly reactive alternative to the classic and explosion-prone benzotriazolic additives, namely 1-hydroxybenzotriazole (HOBt) and 1-hydroxy-7-azabenzotriazole (HOAt). Here we report on a new oxime additive 5-(hydroxyimino)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (Oxyma-B). This new additive showed satisfactory solubility in various solvents (DMF, ACN, and THF). It was also more effective in the control of optical purity during the synthesis of Z-Phg-Pro-NH2, Z-Phe-Val-Pro-NH2, H-Gly-Ser-Phe-NH2, H-Gly-Cys-Phe-NH2, H-Gly-Cys(Acm)-Phe-NH2 and H-Gly-His-Phe-NH2 than related Oxyma- and benzotriazole-based reagents. Oxyma-B also proved to be advantageous compared to the related HONM, because the latter cannot be used with the carbodiimide. Furthermore, Oxyma-B showed satisfactory performance in assembling demanding sequences such as the Aib-enkephalin pentapeptide (H-Tyr-Aib-Aib-Phe-Leu-NH2). This journal is
Enol nitrosation revisited: determining reactivity of ambident nucleophiles
Garcia-Rio, Luis,Mejuto, Juan C.,Parajo, Mercedes,Perez-Lorenzo, Moises
, p. 4525 - 4533 (2009)
Enols are one of the most Important types of ambident nucleophiles being widely used as reagents in organic chemistry, The relevance of enols has led to considerable interest in developing methods to determine the reactivity of their nucleophilic centers, In this sense, the mainstream, literature works on this topic make use of a. combination of overall rate constants together with the analysis of the reaction products, By knowing the product ratio it is possible to determine the ratio between the reaction rates on each site, Thus, the reactivity for each, nucleophilic position can be obtained, This is a reliable approach as long as the isolation or in situ characterization of the reaction products can be carried out, In the case of unstable and/or interconvertible products where the use of identification techniques is not possible, an alternative methodology must be found, For that: reason, our research group has developed a model that allows us to study and quantify separately the reaction rates of enol nucleophilic centers even if only one final reaction product is obtained, This model is based on the fact: that nitrosation of enols shows well-differentiated behavior depending on whether the reaction proceeds through the carbon or the oxygen atom, The present study provides insights into the ambident nature of enols as well as a methodology for determining the chemical reactivity of their nucleophilic centers.
5,5′-bipyridyl-2,4,6,2′,4′,6′-hexaone derivatives (hydurilic acids): Syntheses, mechanism of C-C-Bond formation and properties of the dimeric barbituric acid derivatives
Mueller, Christa E.,Roegler, Carolin,Hockemeyer, Joerg
experimental part, p. 703 - 720 (2009/12/26)
A series of hydurilic acid derivatives (5,5′-bipyrimidinyl-2,4,6,2′,4′,6′-hexaones) including several new derivatives was synthesized from 5,6-diaminouracils. Mechanisms for their formation are proposed and discussed. Furthermore, a new method for the preparation of pyrimidine-2,4,5,6-tetraone-5-oxime derivatives (violuric acids) was found starting from 5-amino-6-nitrosouracils.
Photoprotection compositions comprising certain chelating agents
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, (2008/06/13)
The subject invention relates to methods and compositions comprising: a) from about 0.1% to about 5% of a compound having the structure selected from the group consisting of: STR1 wherein each R is independently selected from the group consisting of hydrogen, alkyl, and aryl; each R' is independently selected from the group consisting of hydrogen, alkoxy, and alkyl; Z and Z' are independently selected from the group consisting of NH, O, and CH2 such that when Z or Z' is NH, the other is not O; or a pharmaceutically acceptable salt of any of the aforementioned compounds; and b) a pharmaceutically-acceptable topical carrier.
