The regiospecific oxidation of alkyl group of both sterically hindered and unhindered aromatic amine to corresponding carbonyl compound was done in aq. medium by using DDQ. The optimized reaction protocol was found to...The regiospecific oxidation of alkyl group of both sterically hindered and unhindered aromatic amine to corresponding carbonyl compound was done in aq. medium by using DDQ. The optimized reaction protocol was found to be most simple, high yielding and novel method for oxidation of alkyl group of aromatic amine in to its carbonyl compound.展开更多
The reaction mechanism of the intramolecular cycloaddition of N-3-butenyl nitrone has been investigated theoretically by using AM1 MO method and transition state theory.There are two parallel reactions leading to two ...The reaction mechanism of the intramolecular cycloaddition of N-3-butenyl nitrone has been investigated theoretically by using AM1 MO method and transition state theory.There are two parallel reactions leading to two different regioisomers.The ratio of the rate constants of these two reactions was calculated to be 124.1(at 383.75 K).The obtained results can be used to explain the high regiospecificity of the reaction product.展开更多
A stereoselective and regiospecific synthesis of procursors(2),(4),(6)and(7)of prostacyclin analogues from 2,3-epoxylbicyclo[3.2.0]hept-6-one(1)are described.
An easy and efficient method for the aminobromination of β,β-dicyanostyrene derivatives with NBS as the aminobrominating reagent in CH3CN catalyzed by NaOAc （10 mol%） is developed. This protocol provides con- veni...An easy and efficient method for the aminobromination of β,β-dicyanostyrene derivatives with NBS as the aminobrominating reagent in CH3CN catalyzed by NaOAc （10 mol%） is developed. This protocol provides con- venient process to convert β,β-dicyanostyrene derivatives into the vicinal haloamines with full regiospecificity and high stereoselectivety in the ice-water bath in air. The reaction is high efficient in yielding the corresponding ami- nobrominated products in excellent yields （up to 95%） under these conditions. The outcome indicated that the reac- tion has an electrophilic addition feature. 12 Eexamples of β,β-dicyanostyrene derivatives have been investigated.展开更多
The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH_3O-phenyl (1a), phenyl(1b), 4-Cl-phenyl(1e), 4-Br-phenyl(1d), 4-NO2-phenyl(1e), 2-furyl (1f), 2-thienyl (1g), 2-pyrryl(1h)] and their thermochem...The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH_3O-phenyl (1a), phenyl(1b), 4-Cl-phenyl(1e), 4-Br-phenyl(1d), 4-NO2-phenyl(1e), 2-furyl (1f), 2-thienyl (1g), 2-pyrryl(1h)] and their thermochemical reactions have been investigated. The thermocycloadditions of 1a-1h are regiospecific in forming a novel heterobicyclic ring system. Exo-aryl-1-aza-7-oxabicyclo- [2.2.1]heptane.展开更多
The eme reactions of α-ionones with singlet oxygen were examined to ascertain the effect of secondary Me interaction between the reactants on the reaction regiospecificity. Exclusive formation of 3-hydroxy-γ-ionones...The eme reactions of α-ionones with singlet oxygen were examined to ascertain the effect of secondary Me interaction between the reactants on the reaction regiospecificity. Exclusive formation of 3-hydroxy-γ-ionones found in the reactions reveals favorable interaction of singlet oxygen with the acyclic α-hydrogen atom,On the other hand,no formation of 3-hy- droxy-β-ionones implies that the steric requirement was not met for the bond formation between zwitterionic perepoxide with C_1-hydrogen in the process.The MMP21 and MNDO calculations indicate minus value of the secondary interaction energy for the aeyelie α-hydrogen abstrac- tion and a repulsion between the oxygen with C_1-hydrogen atom.Twisting tilting of the double bond may account for favorable attack of singlet oxygen on C_3.An explanation of the excellent regiospecificity was addressed and placed in proper mechanic prospective.展开更多
Phenylethanoid glycosides(PhGs)are a group of important natural products widely distributed in medicinal plants and known for their remarkable pharmacological properties.Uridine diphosphate(UDP)glycosyltransferase 79G...Phenylethanoid glycosides(PhGs)are a group of important natural products widely distributed in medicinal plants and known for their remarkable pharmacological properties.Uridine diphosphate(UDP)glycosyltransferase 79G15(UGT79G15)from Rehmannia glutinosa catalyzes the conversion of osmanthuside A to osmanthuside B,a key intermediate in the PhG biosynthetic pathway,through the formation of a(1→3)glycosidic bond.In this study,we present the crystal structures of UGT79G15 in its apo form,UDP-bound form,and,notably,its ternary complex containing UDP and a mimic acceptor,forsythiaside A,within its active site.Structural and comparative analyses revealed that UGT79G15 possesses a distinctive funnel-shaped acceptor-binding pocket with a small auxiliary cavity capable of accommodating the 4′-hydroxycinnamoyl group of PhGs,explaining the enzyme’s regiospecificity toward the 3′-OH of the acceptor.Additional structural examination and site-directed mutagenesis identified key residues that recognize and stabilize UDP-rhamnose and the sugar acceptor.Among the variants generated,I204W exhibits enhanced catalytic efficiency for osmanthuside A conversion,reaching up to 2.2-fold higher activity than the wild type.This study provides mechanistic insight into the donor specificity and acceptor regioselectivity of PhG 1,3-rhamnosyltransferase and expands the structural understanding of plant UGTs.展开更多
A regioselective C8-H alkylation of polyaromatics exampled with inert alkyl chloride is reported.The reaction proceeds via the synergistic participation of inexpensive transition metals nickel and cobalt.This approach...A regioselective C8-H alkylation of polyaromatics exampled with inert alkyl chloride is reported.The reaction proceeds via the synergistic participation of inexpensive transition metals nickel and cobalt.This approach enables the coupling of various substituted polyaromatic rings with a broad range of primary and secondary alkyl chlorides.Further synthetic applications provide a series of simple conversions to useful building blocks,suggesting its potency in the late-stage functionalization of complex molecules.Mechanistic investigation illustrates that the reaction goes through a radical process with an unusual Ni(Ⅱ)→Ni(Ⅲ)-Ni(Ⅰ)cycle being responsible for the rate-determining C-H insertion of alkyl radicals,which are generated by the homolysis of chloroalkane with 2-electrons oxidative addition of Co(Ⅰ).展开更多
The reaction of chiral N-（tert-butanesulfinyl）ketimines and α,β-unsaturated trifluorotuethyl ketones catalyzed by DBU was achieved under mild conditions. 1,2-Addition products, precursors of chiral trifluoromethyl...The reaction of chiral N-（tert-butanesulfinyl）ketimines and α,β-unsaturated trifluorotuethyl ketones catalyzed by DBU was achieved under mild conditions. 1,2-Addition products, precursors of chiral trifluoromethylated 1,3-amino alcohols, were obtained diastereoselectively （dr value up to 95 ： 5） in moderate yields （up to 76%）. A possible catalytic cycle was proposed.展开更多
文摘The regiospecific oxidation of alkyl group of both sterically hindered and unhindered aromatic amine to corresponding carbonyl compound was done in aq. medium by using DDQ. The optimized reaction protocol was found to be most simple, high yielding and novel method for oxidation of alkyl group of aromatic amine in to its carbonyl compound.
文摘The reaction mechanism of the intramolecular cycloaddition of N-3-butenyl nitrone has been investigated theoretically by using AM1 MO method and transition state theory.There are two parallel reactions leading to two different regioisomers.The ratio of the rate constants of these two reactions was calculated to be 124.1(at 383.75 K).The obtained results can be used to explain the high regiospecificity of the reaction product.
文摘A stereoselective and regiospecific synthesis of procursors(2),(4),(6)and(7)of prostacyclin analogues from 2,3-epoxylbicyclo[3.2.0]hept-6-one(1)are described.
文摘An easy and efficient method for the aminobromination of β,β-dicyanostyrene derivatives with NBS as the aminobrominating reagent in CH3CN catalyzed by NaOAc （10 mol%） is developed. This protocol provides con- venient process to convert β,β-dicyanostyrene derivatives into the vicinal haloamines with full regiospecificity and high stereoselectivety in the ice-water bath in air. The reaction is high efficient in yielding the corresponding ami- nobrominated products in excellent yields （up to 95%） under these conditions. The outcome indicated that the reac- tion has an electrophilic addition feature. 12 Eexamples of β,β-dicyanostyrene derivatives have been investigated.
文摘The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH_3O-phenyl (1a), phenyl(1b), 4-Cl-phenyl(1e), 4-Br-phenyl(1d), 4-NO2-phenyl(1e), 2-furyl (1f), 2-thienyl (1g), 2-pyrryl(1h)] and their thermochemical reactions have been investigated. The thermocycloadditions of 1a-1h are regiospecific in forming a novel heterobicyclic ring system. Exo-aryl-1-aza-7-oxabicyclo- [2.2.1]heptane.
基金project supported by the National Natural Science Foundation of China.
文摘The eme reactions of α-ionones with singlet oxygen were examined to ascertain the effect of secondary Me interaction between the reactants on the reaction regiospecificity. Exclusive formation of 3-hydroxy-γ-ionones found in the reactions reveals favorable interaction of singlet oxygen with the acyclic α-hydrogen atom,On the other hand,no formation of 3-hy- droxy-β-ionones implies that the steric requirement was not met for the bond formation between zwitterionic perepoxide with C_1-hydrogen in the process.The MMP21 and MNDO calculations indicate minus value of the secondary interaction energy for the aeyelie α-hydrogen abstrac- tion and a repulsion between the oxygen with C_1-hydrogen atom.Twisting tilting of the double bond may account for favorable attack of singlet oxygen on C_3.An explanation of the excellent regiospecificity was addressed and placed in proper mechanic prospective.
基金supported by the National Key Research and Development Program(2020YFA0907800)the Innovation Fund of Haihe Laboratory of Synthetic Biology(22HHSWSS00023)+3 种基金the Science and Technology Program of Tianjin(24ZYJDSS00300)the National Natural Science Foundation of China(31970065)the Tianjin Synthetic Biotechnology Innovation Capacity Improvement Project(TSBICIP-PTJJ-007-07)the Competitive Support Program of the Tianjin Institute of Industrial Biotechnology,Chinese Academy of Sciences(JZ2024-037).
文摘Phenylethanoid glycosides(PhGs)are a group of important natural products widely distributed in medicinal plants and known for their remarkable pharmacological properties.Uridine diphosphate(UDP)glycosyltransferase 79G15(UGT79G15)from Rehmannia glutinosa catalyzes the conversion of osmanthuside A to osmanthuside B,a key intermediate in the PhG biosynthetic pathway,through the formation of a(1→3)glycosidic bond.In this study,we present the crystal structures of UGT79G15 in its apo form,UDP-bound form,and,notably,its ternary complex containing UDP and a mimic acceptor,forsythiaside A,within its active site.Structural and comparative analyses revealed that UGT79G15 possesses a distinctive funnel-shaped acceptor-binding pocket with a small auxiliary cavity capable of accommodating the 4′-hydroxycinnamoyl group of PhGs,explaining the enzyme’s regiospecificity toward the 3′-OH of the acceptor.Additional structural examination and site-directed mutagenesis identified key residues that recognize and stabilize UDP-rhamnose and the sugar acceptor.Among the variants generated,I204W exhibits enhanced catalytic efficiency for osmanthuside A conversion,reaching up to 2.2-fold higher activity than the wild type.This study provides mechanistic insight into the donor specificity and acceptor regioselectivity of PhG 1,3-rhamnosyltransferase and expands the structural understanding of plant UGTs.
基金supported by the National Natural Science Foundation of China(Nos.22177052,YZ)the Key Industrial and Research Program of Jiangsu Provincial"333 Talent"(No.2022-2-245,YZ)+1 种基金University Distinguished Professor Research Funding of Nanjing University of Chinese Medicine(No.013038030002,YM)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX23_2196,WS).
文摘A regioselective C8-H alkylation of polyaromatics exampled with inert alkyl chloride is reported.The reaction proceeds via the synergistic participation of inexpensive transition metals nickel and cobalt.This approach enables the coupling of various substituted polyaromatic rings with a broad range of primary and secondary alkyl chlorides.Further synthetic applications provide a series of simple conversions to useful building blocks,suggesting its potency in the late-stage functionalization of complex molecules.Mechanistic investigation illustrates that the reaction goes through a radical process with an unusual Ni(Ⅱ)→Ni(Ⅲ)-Ni(Ⅰ)cycle being responsible for the rate-determining C-H insertion of alkyl radicals,which are generated by the homolysis of chloroalkane with 2-electrons oxidative addition of Co(Ⅰ).
基金Project supported by the National Natural Science Foundation of China （No. 20872166）.
文摘The reaction of chiral N-（tert-butanesulfinyl）ketimines and α,β-unsaturated trifluorotuethyl ketones catalyzed by DBU was achieved under mild conditions. 1,2-Addition products, precursors of chiral trifluoromethylated 1,3-amino alcohols, were obtained diastereoselectively （dr value up to 95 ： 5） in moderate yields （up to 76%）. A possible catalytic cycle was proposed.
