The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
M E K Wahba - One of the best experts on this subject based on the ideXlab platform.
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analysis of clozapine in its tablets using two novel spectrophotometric reactions targeting its Tertiary Amino Group
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2020Co-Authors: Aya Ayman, Abdallah M Zeid, M E K Wahba, Yasser ElshabrawyAbstract:Abstract Two simple spectrophotometric methodologies have been proposed and validated for the measurement of an atypical antipsychotic drug Clozapine (CLZ). Method A depends on interaction of CLZ with N-bromosuccinimide(NBS) resulting in formation of a yellowish orange colored product, measured at 320 nm. The linearity range was 5.0–70.0 μg/mL. Method B depends on condensation of the same drug with acetic acid mixed anhydride reagent producing a purple colored product, measured at 319 nm. The linearity range was 8.0–24.0 μg/mL. All parameters affecting the reaction condition (volume of both reagent, temperature, time and the different diluting solvents) were optimized. Both methods were successfully applied to assay CLZ in its pure form and tablets giving mean percentage recoveries of (98.87 ± 1.8 and 100 ± 1.7) for method A, and corresponding values of (98.6 ± 0.96 and 99.5 ± 1) for method B. Besides, the study of reactions stoichiometry was performed and the reaction mechanisms were proposed.
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validated stability indicating spectrofluorimetric methods for the determination of ebastine in pharmaceutical preparations
Chemistry Central Journal, 2011Co-Authors: Fawzia Ibrahim, Mohie Sharaf K Eldin, Manal Eid, M E K WahbaAbstract:Two sensitive, selective, economic, and validated spectrofluorimetric methods were developed for the determination of ebastine (EBS) in pharmaceutical preparations depending on reaction with its Tertiary Amino Group. Method I involves condensation of the drug with mixed anhydrides (citric and acetic anhydrides) producing a product with intense fluorescence, which was measured at 496 nm after excitation at 388 nm. Method (IIA) describes quantitative fluorescence quenching of eosin upon addition of the studied drug where the decrease in the fluorescence intensity was directly proportional to the concentration of ebastine; the fluorescence quenching was measured at 553 nm after excitation at 457 nm. This method was extended to (Method IIB) to apply first and second derivative synchronous spectrofluorimetric method (FDSFS & SDSFS) for the simultaneous analysis of EBS in presence of its alkaline, acidic, and UV degradation products. The proposed methods were successfully applied for the determination of the studied compound in its dosage forms. The results obtained were in good agreement with those obtained by a comparison method. Both methods were utilized to investigate the kinetics of the degradation of the drug.
Chuchi Tang - One of the best experts on this subject based on the ideXlab platform.
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sugar derived bifunctional thiourea organocatalyzed asymmetric michael addition of acetylacetone to nitroolefins
European Journal of Organic Chemistry, 2008Co-Authors: Peng Gao, Chungui Wang, Zhenghong Zhou, Chuchi TangAbstract:A bifunctional chiral thiourea organocatalyst bearing a glycosyl scaffold and a Tertiary Amino Group proved to be an effective organocatalyst for the asymmetric Michael addition of acetylacetone to nitroolefins. The corresponding adducts were obtained in good to excellent yields with excellent enantioselectivities (up to 96 % ee). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Sugar‐Derived Bifunctional Thiourea Organocatalyzed Asymmetric Michael Addition of Acetylacetone to Nitroolefins
European Journal of Organic Chemistry, 2008Co-Authors: Peng Gao, Chungui Wang, Zhenghong Zhou, Chuchi TangAbstract:A bifunctional chiral thiourea organocatalyst bearing a glycosyl scaffold and a Tertiary Amino Group proved to be an effective organocatalyst for the asymmetric Michael addition of acetylacetone to nitroolefins. The corresponding adducts were obtained in good to excellent yields with excellent enantioselectivities (up to 96 % ee). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Yoshiji Takemoto - One of the best experts on this subject based on the ideXlab platform.
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discovery and application of asymmetric reaction by multi functional thioureas
Bulletin of the Chemical Society of Japan, 2008Co-Authors: Hideto Miyabe, Yoshiji TakemotoAbstract:Novel bifunctional organocatalysts, which possess a thiourea moiety and an Amino Group, were designed and synthesized. We discovered that bifunctional thiourea bearing a Tertiary Amino Group signif...
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The Amino thiourea-catalyzed asymmetric nucleophilic reactions
CHIMIA International Journal for Chemistry, 2007Co-Authors: Yoshiji Takemoto, Hideto MiyabeAbstract:Bifunctional Amino thiourea-catalyzed asymmetric additions of several nucleophiles into electron-deficient unsaturated compounds such as nitroolefins, α,β-unsaturated imides, imines, and azodicarboxylates are described. We discovered that bifunctional thioureas bearing a Tertiary Amino Group significantly accelerated several nucleophilic addition reactions of active methylene compounds to electron-deficient double bonds. In these reactions, a strong hydrogen-bonding ability of the thiourea moiety as well as an appropriate Bronsted basicity of the Tertiary amine is crucial for high enantioselectivity. This dual activation of both nucleophiles and electrophiles by the bifunctional thiourea expanded the applicability of the thiourea-catalyzed enantioselective reaction. In addition, these organocatalyzed asymmetric reactions were successfully applied to the concise asymmetric synthesis of natural products and medicinal candidates such as epibatidine, baclofen, and CP-99,994.
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enantioselective michael reaction of malonates to nitroolefins catalyzed by bifunctional organocatalysts
Journal of the American Chemical Society, 2003Co-Authors: Tomotaka Okino, Yasutaka Hoashi, Yoshiji TakemotoAbstract:Michael reaction of malonates to nitroolefins with chiral bifunctional organocatalysts, bearing both a thiourea and Tertiary Amino Group, afforded Michael adducts with high yields and enantioselectivities (up to 95%, up to 93% ee).
Peng Gao - One of the best experts on this subject based on the ideXlab platform.
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sugar derived bifunctional thiourea organocatalyzed asymmetric michael addition of acetylacetone to nitroolefins
European Journal of Organic Chemistry, 2008Co-Authors: Peng Gao, Chungui Wang, Zhenghong Zhou, Chuchi TangAbstract:A bifunctional chiral thiourea organocatalyst bearing a glycosyl scaffold and a Tertiary Amino Group proved to be an effective organocatalyst for the asymmetric Michael addition of acetylacetone to nitroolefins. The corresponding adducts were obtained in good to excellent yields with excellent enantioselectivities (up to 96 % ee). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Sugar‐Derived Bifunctional Thiourea Organocatalyzed Asymmetric Michael Addition of Acetylacetone to Nitroolefins
European Journal of Organic Chemistry, 2008Co-Authors: Peng Gao, Chungui Wang, Zhenghong Zhou, Chuchi TangAbstract:A bifunctional chiral thiourea organocatalyst bearing a glycosyl scaffold and a Tertiary Amino Group proved to be an effective organocatalyst for the asymmetric Michael addition of acetylacetone to nitroolefins. The corresponding adducts were obtained in good to excellent yields with excellent enantioselectivities (up to 96 % ee). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Fawzia Ibrahim - One of the best experts on this subject based on the ideXlab platform.
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Validated stability-indicating spectrofluorimetric methods for the determination of ebastine in pharmaceutical preparations
Chemistry Central Journal, 2011Co-Authors: Fawzia Ibrahim, Mary Elias Kamel WahbaAbstract:Two sensitive, selective, economic, and validated spectrofluorimetric methods were developed for the determination of ebastine (EBS) in pharmaceutical preparations depending on reaction with its Tertiary Amino Group. Method I involves condensation of the drug with mixed anhydrides (citric and acetic anhydrides) producing a product with intense fluorescence, which was measured at 496 nm after excitation at 388 nm. Method (IIA) describes quantitative fluorescence quenching of eosin upon addition of the studied drug where the decrease in the fluorescence intensity was directly proportional to the concentration of ebastine; the fluorescence quenching was measured at 553 nm after excitation at 457 nm. This method was extended to (Method IIB) to apply first and second derivative synchronous spectrofluorimetric method (FDSFS & SDSFS) for the simultaneous analysis of EBS in presence of its alkaline, acidic, and UV degradation products. The proposed methods were successfully applied for the determination of the studied compound in its dosage forms. The results obtained were in good agreement with those obtained by a comparison method. Both methods were utilized to investigate the kinetics of the degradation of the drug.
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validated stability indicating spectrofluorimetric methods for the determination of ebastine in pharmaceutical preparations
Chemistry Central Journal, 2011Co-Authors: Fawzia Ibrahim, Mohie Sharaf K Eldin, Manal Eid, M E K WahbaAbstract:Two sensitive, selective, economic, and validated spectrofluorimetric methods were developed for the determination of ebastine (EBS) in pharmaceutical preparations depending on reaction with its Tertiary Amino Group. Method I involves condensation of the drug with mixed anhydrides (citric and acetic anhydrides) producing a product with intense fluorescence, which was measured at 496 nm after excitation at 388 nm. Method (IIA) describes quantitative fluorescence quenching of eosin upon addition of the studied drug where the decrease in the fluorescence intensity was directly proportional to the concentration of ebastine; the fluorescence quenching was measured at 553 nm after excitation at 457 nm. This method was extended to (Method IIB) to apply first and second derivative synchronous spectrofluorimetric method (FDSFS & SDSFS) for the simultaneous analysis of EBS in presence of its alkaline, acidic, and UV degradation products. The proposed methods were successfully applied for the determination of the studied compound in its dosage forms. The results obtained were in good agreement with those obtained by a comparison method. Both methods were utilized to investigate the kinetics of the degradation of the drug.