The Experts below are selected from a list of 441 Experts worldwide ranked by ideXlab platform
Michael R. Buchmeiser - One of the best experts on this subject based on the ideXlab platform.
-
A Spirocyclic Parabanic Acid Masked N‐Heterocyclic Carbene as Thermally Latent Pre‐Catalyst for Polyamide 6 Synthesis and Epoxide Curing
Macromolecular Rapid Communications, 2020Co-Authors: Hagen J. Altmann, Wolfgang Frey, Michael R. BuchmeiserAbstract:1,3-Dicyclcohexyl-6,9-dimethyl-1,3,6,9-tetraazaspiro[4.4]non-7-ene-2,4-dione, a spirocyclic Parabanic Acid derivative of N,N-dimethylimidazole, is used as thermally latent, protected N-heterocyclic carbene (NHC) in polymerizing anhydride-cured epoxide resins, and azepan-2-one, respectively. The protected carbene is synthesized from 1,3-dimethylimidazolium-2-carboxylate in the presence of two equivalents of cyclohexyl isocyanate. In the synthesis of epoxide resin thermosets, this class of latent NHC allows the production of fast and fully cured materials with high crosslinking content. Fast and complete conversion is found in the anionic ring opening polymerization (AROP) of azepan-2-one (e-caprolactam, CLA) with and without additional activators.
-
a spirocyclic Parabanic Acid masked n heterocyclic carbene as thermally latent pre catalyst for polyamide 6 synthesis and epoxide curing
Macromolecular Rapid Communications, 2020Co-Authors: Hagen J. Altmann, Wolfgang Frey, Michael R. BuchmeiserAbstract:1,3-Dicyclcohexyl-6,9-dimethyl-1,3,6,9-tetraazaspiro[4.4]non-7-ene-2,4-dione, a spirocyclic Parabanic Acid derivative of N,N-dimethylimidazole, is used as thermally latent, protected N-heterocyclic carbene (NHC) in polymerizing anhydride-cured epoxide resins, and azepan-2-one, respectively. The protected carbene is synthesized from 1,3-dimethylimidazolium-2-carboxylate in the presence of two equivalents of cyclohexyl isocyanate. In the synthesis of epoxide resin thermosets, this class of latent NHC allows the production of fast and fully cured materials with high crosslinking content. Fast and complete conversion is found in the anionic ring opening polymerization (AROP) of azepan-2-one (e-caprolactam, CLA) with and without additional activators.
Bernard Meunier - One of the best experts on this subject based on the ideXlab platform.
-
guanine oxidation in double stranded dna by mn tmpyp khso5 5 8 dihydroxy 7 8 dihydroguanine residue as a key precursor of imidazolone and Parabanic Acid derivatives
Journal of the American Chemical Society, 2000Co-Authors: Corine Vialas, Catherine Claparols, And Geneviève Pratviel, Bernard MeunierAbstract:The mechanism of oxidation of guanine residues on double-stranded oligonucleotides (ODNs) by the chemical nuclease Mn-TMPyP/KHSO5 is reported. By using HPLC coupled to an electrospray mass spectrometer (ESI/MS) the different oxidized ODN strands were directly analyzed, and labeling experiments in H218O allowed us to propose a two-electron oxidation mechanism for guanine residues engaged in double-stranded DNA. We found that the imidazolone derivative (dIz) was formed by trapping of a guanine-cation by a water molecule. Two reaction intermediates on the pathway of the formation of dIz were observed: 5,8-dihydroxy-7,8-dihydroguanine and an oxidized guanidinohydantoin intermediate. Furthermore, a secondary route of guanine oxidation leading to Parabanic Acid was also evidenced. The mechanism of the different routes of guanine oxidation in double-stranded DNA has been discussed in detail.
-
Guanine Oxidation in Double-Stranded DNA by Mn-TMPyP/KHSO5: 5,8-Dihydroxy-7,8-dihydroguanine Residue as a Key Precursor of Imidazolone and Parabanic Acid Derivatives
Journal of the American Chemical Society, 2000Co-Authors: Corine Vialas, Catherine Claparols, And Geneviève Pratviel, Bernard MeunierAbstract:The mechanism of oxidation of guanine residues on double-stranded oligonucleotides (ODNs) by the chemical nuclease Mn-TMPyP/KHSO5 is reported. By using HPLC coupled to an electrospray mass spectrometer (ESI/MS) the different oxidized ODN strands were directly analyzed, and labeling experiments in H218O allowed us to propose a two-electron oxidation mechanism for guanine residues engaged in double-stranded DNA. We found that the imidazolone derivative (dIz) was formed by trapping of a guanine-cation by a water molecule. Two reaction intermediates on the pathway of the formation of dIz were observed: 5,8-dihydroxy-7,8-dihydroguanine and an oxidized guanidinohydantoin intermediate. Furthermore, a secondary route of guanine oxidation leading to Parabanic Acid was also evidenced. The mechanism of the different routes of guanine oxidation in double-stranded DNA has been discussed in detail.
Hagen J. Altmann - One of the best experts on this subject based on the ideXlab platform.
-
A Spirocyclic Parabanic Acid Masked N‐Heterocyclic Carbene as Thermally Latent Pre‐Catalyst for Polyamide 6 Synthesis and Epoxide Curing
Macromolecular Rapid Communications, 2020Co-Authors: Hagen J. Altmann, Wolfgang Frey, Michael R. BuchmeiserAbstract:1,3-Dicyclcohexyl-6,9-dimethyl-1,3,6,9-tetraazaspiro[4.4]non-7-ene-2,4-dione, a spirocyclic Parabanic Acid derivative of N,N-dimethylimidazole, is used as thermally latent, protected N-heterocyclic carbene (NHC) in polymerizing anhydride-cured epoxide resins, and azepan-2-one, respectively. The protected carbene is synthesized from 1,3-dimethylimidazolium-2-carboxylate in the presence of two equivalents of cyclohexyl isocyanate. In the synthesis of epoxide resin thermosets, this class of latent NHC allows the production of fast and fully cured materials with high crosslinking content. Fast and complete conversion is found in the anionic ring opening polymerization (AROP) of azepan-2-one (e-caprolactam, CLA) with and without additional activators.
-
a spirocyclic Parabanic Acid masked n heterocyclic carbene as thermally latent pre catalyst for polyamide 6 synthesis and epoxide curing
Macromolecular Rapid Communications, 2020Co-Authors: Hagen J. Altmann, Wolfgang Frey, Michael R. BuchmeiserAbstract:1,3-Dicyclcohexyl-6,9-dimethyl-1,3,6,9-tetraazaspiro[4.4]non-7-ene-2,4-dione, a spirocyclic Parabanic Acid derivative of N,N-dimethylimidazole, is used as thermally latent, protected N-heterocyclic carbene (NHC) in polymerizing anhydride-cured epoxide resins, and azepan-2-one, respectively. The protected carbene is synthesized from 1,3-dimethylimidazolium-2-carboxylate in the presence of two equivalents of cyclohexyl isocyanate. In the synthesis of epoxide resin thermosets, this class of latent NHC allows the production of fast and fully cured materials with high crosslinking content. Fast and complete conversion is found in the anionic ring opening polymerization (AROP) of azepan-2-one (e-caprolactam, CLA) with and without additional activators.
Akio Fujisawa - One of the best experts on this subject based on the ideXlab platform.
-
(2,5-Dioxoimidazolidin-4-ylidene)aminocarbonylcarbamic Acid as a Precursor of Parabanic Acid, the Singlet Oxygen-Specific Oxidation Product of Uric Acid.
The Journal of Organic Chemistry, 2019Co-Authors: Sayaka Iida, Yorihiro Yamamoto, Akio FujisawaAbstract:Previously, we identified that Parabanic Acid (PA) and its hydrolysate, oxaluric Acid (OUA), are the singlet oxygen-specific oxidation products of uric Acid (UA). In this study, we investigated the PA formation mechanism by using HPLC and a time-of-flight mass spectrometry technique and identified unknown intermediates as (2,5-dioxoimidazolidin-4-ylidene)aminocarbonylcarbamic Acid (DIAA), dehydroallantoin, and 4-hydroxyallantoin (4-HAL). DIAA is the key to PA production, and its formation pathway was characterized using 18O2 and H218O. Two oxygen atoms were confirmed to be incorporated into DIAA: the 5-oxo- oxygen from singlet oxygen and the carboxylic oxygen from water. Isolated DIAA and 4-HAL gave PA stoichiometrically. A plausible reaction scheme in which two pathways branch out from DIAA is presented, and the potential for PA as an endogenous probe for biological formation of singlet oxygen is discussed.
-
Parabanic Acid is the singlet oxygen specific oxidation product of uric Acid
Journal of Clinical Biochemistry and Nutrition, 2017Co-Authors: Sayaka Iida, Yuki Ohkubo, Yorihiro Yamamoto, Akio FujisawaAbstract:Uric Acid quenches singlet oxygen physically or reacts with it, but the oxidation product has not been previously characterized. The present study determined that the product is Parabanic Acid, which was confirmed by LC/TOFMS analysis. Parabanic Acid was stable at Acidic pH (<5.0), but hydrolyzed to oxaluric Acid at neutral or alkaline pH. The total yields of Parabanic Acid and oxaluric Acid based on consumed uric Acid were ~100% in clean singlet oxygen production systems such as UVA irradiation of Rose Bengal and thermal decomposition of 3-(1,4-dihydro-1,4-epidioxy-4-methyl-1-naphthyl)propionic Acid. However, the ratio of the amount of uric Acid consumed to the total amount of singlet oxygen generated was less than 1/180, indicating that most of the singlet oxygen was physically quenched. The total yields of Parabanic Acid and oxaluric Acid were high in the uric Acid oxidation systems with hydrogen peroxide plus hypochlorite or peroxynitrite. They became less than a few percent in peroxyl radical-, hypochlorite- or peroxynitrite-induced oxidation of uric Acid. These results suggest that Parabanic Acid could be an in vivo probe of singlet oxygen formation because of the wide distribution of uric Acid in human tissues and extracellular spaces. In fact, sunlight exposure significantly increased human skin levels of Parabanic Acid.
-
Parabanic Acid is the singlet oxygen specific oxidation product of uric Acid.
Journal of Clinical Biochemistry and Nutrition, 2017Co-Authors: Sayaka Iida, Yuki Ohkubo, Yorihiro Yamamoto, Akio FujisawaAbstract:Uric Acid quenches singlet oxygen physically or reacts with it, but the oxidation product has not been previously characterized. The present study determined that the product is Parabanic Acid, which was confirmed by LC/TOFMS analysis. Parabanic Acid was stable at Acidic pH (
Corine Vialas - One of the best experts on this subject based on the ideXlab platform.
-
guanine oxidation in double stranded dna by mn tmpyp khso5 5 8 dihydroxy 7 8 dihydroguanine residue as a key precursor of imidazolone and Parabanic Acid derivatives
Journal of the American Chemical Society, 2000Co-Authors: Corine Vialas, Catherine Claparols, And Geneviève Pratviel, Bernard MeunierAbstract:The mechanism of oxidation of guanine residues on double-stranded oligonucleotides (ODNs) by the chemical nuclease Mn-TMPyP/KHSO5 is reported. By using HPLC coupled to an electrospray mass spectrometer (ESI/MS) the different oxidized ODN strands were directly analyzed, and labeling experiments in H218O allowed us to propose a two-electron oxidation mechanism for guanine residues engaged in double-stranded DNA. We found that the imidazolone derivative (dIz) was formed by trapping of a guanine-cation by a water molecule. Two reaction intermediates on the pathway of the formation of dIz were observed: 5,8-dihydroxy-7,8-dihydroguanine and an oxidized guanidinohydantoin intermediate. Furthermore, a secondary route of guanine oxidation leading to Parabanic Acid was also evidenced. The mechanism of the different routes of guanine oxidation in double-stranded DNA has been discussed in detail.
-
Guanine Oxidation in Double-Stranded DNA by Mn-TMPyP/KHSO5: 5,8-Dihydroxy-7,8-dihydroguanine Residue as a Key Precursor of Imidazolone and Parabanic Acid Derivatives
Journal of the American Chemical Society, 2000Co-Authors: Corine Vialas, Catherine Claparols, And Geneviève Pratviel, Bernard MeunierAbstract:The mechanism of oxidation of guanine residues on double-stranded oligonucleotides (ODNs) by the chemical nuclease Mn-TMPyP/KHSO5 is reported. By using HPLC coupled to an electrospray mass spectrometer (ESI/MS) the different oxidized ODN strands were directly analyzed, and labeling experiments in H218O allowed us to propose a two-electron oxidation mechanism for guanine residues engaged in double-stranded DNA. We found that the imidazolone derivative (dIz) was formed by trapping of a guanine-cation by a water molecule. Two reaction intermediates on the pathway of the formation of dIz were observed: 5,8-dihydroxy-7,8-dihydroguanine and an oxidized guanidinohydantoin intermediate. Furthermore, a secondary route of guanine oxidation leading to Parabanic Acid was also evidenced. The mechanism of the different routes of guanine oxidation in double-stranded DNA has been discussed in detail.
