The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Hiroyuki Suga - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective synthesis of tetrahydrofurans by lewis acid catalyzed intermolecular carbenoid Carbonyl Reaction cycloaddition sequences unusual diastereoselectivity of lewis acid catalyzed cycloadditions
Journal of Organic Chemistry, 2013Co-Authors: Yuta Hashimoto, Kennosuke Itoh, Akikazu Kakehi, Motoo Shiro, Hiroyuki SugaAbstract:The effects of including metal salts for three-component Reactions involving α-alkyl-α-diazo esters, aromatic aldehydes, and 3-(2-alkenoyl)-2-oxazolidinones are described, in terms of yields and diastereoselectivities. Metal tetrafluoroborates (10–30 mol %) such as Co(BF4)2·6H2O, Ni(BF4)2·6H2O, and AgBF4 were effective in delivering high yields and diastereoselectivities (93:7 to 99:1) of the corresponding tetrahydrofuran derivatives while suppressing the competitive formation of 1,3-dioxolane. Using (S)-3-(2-alkenoyl)-4-isopropyl-2-oxazolidinones as the dipolarophiles in the three-component Reactions, in the presence of Ni(BF4)2·6H2O or Co(ClO4)2·6H2O (10–30 mol %), optically active tetrahydrofurans that possess four successive asymmetric centers were synthesized in high diastereoselectivities (99:1). On the basis of the configuration of the cycloadduct using the X-ray analysis, the high diastereoselectivity could be explained by the unusual Re-face approach to the dipolarophile in the presence of the Le...
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diastereoselective synthesis of tetrahydrofurans by lewis acid catalyzed intermolecular carbenoid Carbonyl Reaction cycloaddition sequences unusual diastereoselectivity of lewis acid catalyzed cycloadditions
Journal of Organic Chemistry, 2013Co-Authors: Yuta Hashimoto, Kennosuke Itoh, Akikazu Kakehi, Motoo Shiro, Hiroyuki SugaAbstract:The effects of including metal salts for three-component Reactions involving α-alkyl-α-diazo esters, aromatic aldehydes, and 3-(2-alkenoyl)-2-oxazolidinones are described, in terms of yields and diastereoselectivities. Metal tetrafluoroborates (10-30 mol %) such as Co(BF4)2·6H2O, Ni(BF4)2·6H2O, and AgBF4 were effective in delivering high yields and diastereoselectivities (93:7 to 99:1) of the corresponding tetrahydrofuran derivatives while suppressing the competitive formation of 1,3-dioxolane. Using (S)-3-(2-alkenoyl)-4-isopropyl-2-oxazolidinones as the dipolarophiles in the three-component Reactions, in the presence of Ni(BF4)2·6H2O or Co(ClO4)2·6H2O (10-30 mol %), optically active tetrahydrofurans that possess four successive asymmetric centers were synthesized in high diastereoselectivities (99:1). On the basis of the configuration of the cycloadduct using the X-ray analysis, the high diastereoselectivity could be explained by the unusual Re-face approach to the dipolarophile in the presence of the Lewis acid, proceeding through the s-cis conformer of the 3-(2-alkenoyl)-2-oxazolidinone with the two Carbonyls in opposing directions (dipole-dipole interaction).
Tsukasa Matsuda - One of the best experts on this subject based on the ideXlab platform.
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Effects of the Glycoprotein Sugar Chains on the Amino-Carbonyl Reaction of Chicken and Japanese Quail Ovomucoids with Glucose
Bioscience biotechnology and biochemistry, 1996Co-Authors: Yasuko Kato, Tsukasa MatsudaAbstract:The amino-Carbonyl Reactions of two glycoproteins, chicken ovomucoid and quail ovomucoid, which have similar amino acid sequences but different sugar chains, were compared. The free guanidino groups, but not amino groups, of chicken ovomucoid decreased more rapidly than those of quail ovomucoid during Reaction with glucose. Protein polymerization and formation or brownish or fluorescent compounds also occurred more quickly in the chicken ovomucoid. These results suggested that the sugar chain moieties affect the amino-Carbonyl Reaction of glycoproteins with deducing sugars, especially at advanced stages of the Reaction.
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Modification of Ovalbumin with Glucose 6-Phosphate by Amino-Carbonyl Reaction. Improvement of Protein Heat Stability and Emulsifying Activity
Journal of Agricultural and Food Chemistry, 1995Co-Authors: Yasuko Kato, Takayoshi Aoki, Natsuki Kato, Ryo Nakamura, Tsukasa MatsudaAbstract:Ovalbumin (OVA) was modified with glucose (Glu) and glucose 6-phosphate (G6P) through the amino-Carbonyl Reaction (Maillard Reaction), and heat-induced aggregation and emulsifying activity of the modified proteins were investigated. G6P reacted with the free amino groups in a similar manner to Glu; about 70-80% of the total amino groups were blocked by the Reaction at 50 o C, and 65% relative humidity for 3 days. However, the Reaction with G6P induced protein polymerization and brown-color development more strongly than that of Glu. OVA modified with G6P was much more acidic than either native OVA or the Glu-modified OVA, and it was highly soluble and quite resistant to heat-induced aggregation, i.e., its high-concentration solution (5%) was still completely soluble and transparent even after being heated at 100 o C for 10 min. Furthermore, OVA emulsifying activity was increased about 5-fold by the modification with G6P
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Lysine loss and polymerization of bovine .beta.-lactoglobulin by amino Carbonyl Reaction with lactulose (4-O-.beta.-D-galactopyranosyl-D-fructose)
Journal of Agricultural and Food Chemistry, 1991Co-Authors: Tsukasa Matsuda, Yasuko Kato, Ryo NakamuraAbstract:Loss of lysine, protein polymerisation, and production of fluorescent substances were investigated for bovine β-lactoglobulin stored with lactulose at 50°C and 65% relative humidity for 10 days as a model system for dried milk and milk products supplemented with lactulose.
Yuta Hashimoto - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective synthesis of tetrahydrofurans by lewis acid catalyzed intermolecular carbenoid Carbonyl Reaction cycloaddition sequences unusual diastereoselectivity of lewis acid catalyzed cycloadditions
Journal of Organic Chemistry, 2013Co-Authors: Yuta Hashimoto, Kennosuke Itoh, Akikazu Kakehi, Motoo Shiro, Hiroyuki SugaAbstract:The effects of including metal salts for three-component Reactions involving α-alkyl-α-diazo esters, aromatic aldehydes, and 3-(2-alkenoyl)-2-oxazolidinones are described, in terms of yields and diastereoselectivities. Metal tetrafluoroborates (10–30 mol %) such as Co(BF4)2·6H2O, Ni(BF4)2·6H2O, and AgBF4 were effective in delivering high yields and diastereoselectivities (93:7 to 99:1) of the corresponding tetrahydrofuran derivatives while suppressing the competitive formation of 1,3-dioxolane. Using (S)-3-(2-alkenoyl)-4-isopropyl-2-oxazolidinones as the dipolarophiles in the three-component Reactions, in the presence of Ni(BF4)2·6H2O or Co(ClO4)2·6H2O (10–30 mol %), optically active tetrahydrofurans that possess four successive asymmetric centers were synthesized in high diastereoselectivities (99:1). On the basis of the configuration of the cycloadduct using the X-ray analysis, the high diastereoselectivity could be explained by the unusual Re-face approach to the dipolarophile in the presence of the Le...
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diastereoselective synthesis of tetrahydrofurans by lewis acid catalyzed intermolecular carbenoid Carbonyl Reaction cycloaddition sequences unusual diastereoselectivity of lewis acid catalyzed cycloadditions
Journal of Organic Chemistry, 2013Co-Authors: Yuta Hashimoto, Kennosuke Itoh, Akikazu Kakehi, Motoo Shiro, Hiroyuki SugaAbstract:The effects of including metal salts for three-component Reactions involving α-alkyl-α-diazo esters, aromatic aldehydes, and 3-(2-alkenoyl)-2-oxazolidinones are described, in terms of yields and diastereoselectivities. Metal tetrafluoroborates (10-30 mol %) such as Co(BF4)2·6H2O, Ni(BF4)2·6H2O, and AgBF4 were effective in delivering high yields and diastereoselectivities (93:7 to 99:1) of the corresponding tetrahydrofuran derivatives while suppressing the competitive formation of 1,3-dioxolane. Using (S)-3-(2-alkenoyl)-4-isopropyl-2-oxazolidinones as the dipolarophiles in the three-component Reactions, in the presence of Ni(BF4)2·6H2O or Co(ClO4)2·6H2O (10-30 mol %), optically active tetrahydrofurans that possess four successive asymmetric centers were synthesized in high diastereoselectivities (99:1). On the basis of the configuration of the cycloadduct using the X-ray analysis, the high diastereoselectivity could be explained by the unusual Re-face approach to the dipolarophile in the presence of the Lewis acid, proceeding through the s-cis conformer of the 3-(2-alkenoyl)-2-oxazolidinone with the two Carbonyls in opposing directions (dipole-dipole interaction).
Yasuko Kato - One of the best experts on this subject based on the ideXlab platform.
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Effects of the Glycoprotein Sugar Chains on the Amino-Carbonyl Reaction of Chicken and Japanese Quail Ovomucoids with Glucose
Bioscience biotechnology and biochemistry, 1996Co-Authors: Yasuko Kato, Tsukasa MatsudaAbstract:The amino-Carbonyl Reactions of two glycoproteins, chicken ovomucoid and quail ovomucoid, which have similar amino acid sequences but different sugar chains, were compared. The free guanidino groups, but not amino groups, of chicken ovomucoid decreased more rapidly than those of quail ovomucoid during Reaction with glucose. Protein polymerization and formation or brownish or fluorescent compounds also occurred more quickly in the chicken ovomucoid. These results suggested that the sugar chain moieties affect the amino-Carbonyl Reaction of glycoproteins with deducing sugars, especially at advanced stages of the Reaction.
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Modification of Ovalbumin with Glucose 6-Phosphate by Amino-Carbonyl Reaction. Improvement of Protein Heat Stability and Emulsifying Activity
Journal of Agricultural and Food Chemistry, 1995Co-Authors: Yasuko Kato, Takayoshi Aoki, Natsuki Kato, Ryo Nakamura, Tsukasa MatsudaAbstract:Ovalbumin (OVA) was modified with glucose (Glu) and glucose 6-phosphate (G6P) through the amino-Carbonyl Reaction (Maillard Reaction), and heat-induced aggregation and emulsifying activity of the modified proteins were investigated. G6P reacted with the free amino groups in a similar manner to Glu; about 70-80% of the total amino groups were blocked by the Reaction at 50 o C, and 65% relative humidity for 3 days. However, the Reaction with G6P induced protein polymerization and brown-color development more strongly than that of Glu. OVA modified with G6P was much more acidic than either native OVA or the Glu-modified OVA, and it was highly soluble and quite resistant to heat-induced aggregation, i.e., its high-concentration solution (5%) was still completely soluble and transparent even after being heated at 100 o C for 10 min. Furthermore, OVA emulsifying activity was increased about 5-fold by the modification with G6P
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Lysine loss and polymerization of bovine .beta.-lactoglobulin by amino Carbonyl Reaction with lactulose (4-O-.beta.-D-galactopyranosyl-D-fructose)
Journal of Agricultural and Food Chemistry, 1991Co-Authors: Tsukasa Matsuda, Yasuko Kato, Ryo NakamuraAbstract:Loss of lysine, protein polymerisation, and production of fluorescent substances were investigated for bovine β-lactoglobulin stored with lactulose at 50°C and 65% relative humidity for 10 days as a model system for dried milk and milk products supplemented with lactulose.
Akikazu Kakehi - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective synthesis of tetrahydrofurans by lewis acid catalyzed intermolecular carbenoid Carbonyl Reaction cycloaddition sequences unusual diastereoselectivity of lewis acid catalyzed cycloadditions
Journal of Organic Chemistry, 2013Co-Authors: Yuta Hashimoto, Kennosuke Itoh, Akikazu Kakehi, Motoo Shiro, Hiroyuki SugaAbstract:The effects of including metal salts for three-component Reactions involving α-alkyl-α-diazo esters, aromatic aldehydes, and 3-(2-alkenoyl)-2-oxazolidinones are described, in terms of yields and diastereoselectivities. Metal tetrafluoroborates (10–30 mol %) such as Co(BF4)2·6H2O, Ni(BF4)2·6H2O, and AgBF4 were effective in delivering high yields and diastereoselectivities (93:7 to 99:1) of the corresponding tetrahydrofuran derivatives while suppressing the competitive formation of 1,3-dioxolane. Using (S)-3-(2-alkenoyl)-4-isopropyl-2-oxazolidinones as the dipolarophiles in the three-component Reactions, in the presence of Ni(BF4)2·6H2O or Co(ClO4)2·6H2O (10–30 mol %), optically active tetrahydrofurans that possess four successive asymmetric centers were synthesized in high diastereoselectivities (99:1). On the basis of the configuration of the cycloadduct using the X-ray analysis, the high diastereoselectivity could be explained by the unusual Re-face approach to the dipolarophile in the presence of the Le...
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diastereoselective synthesis of tetrahydrofurans by lewis acid catalyzed intermolecular carbenoid Carbonyl Reaction cycloaddition sequences unusual diastereoselectivity of lewis acid catalyzed cycloadditions
Journal of Organic Chemistry, 2013Co-Authors: Yuta Hashimoto, Kennosuke Itoh, Akikazu Kakehi, Motoo Shiro, Hiroyuki SugaAbstract:The effects of including metal salts for three-component Reactions involving α-alkyl-α-diazo esters, aromatic aldehydes, and 3-(2-alkenoyl)-2-oxazolidinones are described, in terms of yields and diastereoselectivities. Metal tetrafluoroborates (10-30 mol %) such as Co(BF4)2·6H2O, Ni(BF4)2·6H2O, and AgBF4 were effective in delivering high yields and diastereoselectivities (93:7 to 99:1) of the corresponding tetrahydrofuran derivatives while suppressing the competitive formation of 1,3-dioxolane. Using (S)-3-(2-alkenoyl)-4-isopropyl-2-oxazolidinones as the dipolarophiles in the three-component Reactions, in the presence of Ni(BF4)2·6H2O or Co(ClO4)2·6H2O (10-30 mol %), optically active tetrahydrofurans that possess four successive asymmetric centers were synthesized in high diastereoselectivities (99:1). On the basis of the configuration of the cycloadduct using the X-ray analysis, the high diastereoselectivity could be explained by the unusual Re-face approach to the dipolarophile in the presence of the Lewis acid, proceeding through the s-cis conformer of the 3-(2-alkenoyl)-2-oxazolidinone with the two Carbonyls in opposing directions (dipole-dipole interaction).