The stereoselectivity of some Diels-Alder reactions was investigated by means of ABEEM-oTr model. Combined with local hard-soft and acid-base （HSAB） principle, we made reasonable explanation by calculating local sof...The stereoselectivity of some Diels-Alder reactions was investigated by means of ABEEM-oTr model. Combined with local hard-soft and acid-base （HSAB） principle, we made reasonable explanation by calculating local softness of atom and bond regions for the stereoselectivity of four Diels-Alder reactions involving cyclopentadiene.展开更多
Molecular structures of reactants were characterized by molecular electronegativity distance vector （VHMED） considering hydrogen association. A reasonable molecular modeling equation with 4-parameters was achieved f...Molecular structures of reactants were characterized by molecular electronegativity distance vector （VHMED） considering hydrogen association. A reasonable molecular modeling equation with 4-parameters was achieved for quantitative structure-property/activity relationship （QSPR/QSAR） by stepwise multiple regression （SMR） that the variable was introduced item by item in significant level order. A high correlation coefficient （R = 0.980） demonstrates that the model is able to well express a quantitative relation between stereoselectivity and the reactant structures as quantitative structure-reactivity/stereoselectivity relationship （QSRR/QSSR）. The multiple correlation coefficient （Rcv= 0.964） was tested through cross-validation with the leave-one-out （LOO） procedure. The above results show that the model possesses high estimation stability and good prediction ability between the amount of both cis and trans isomers in products and reactants.展开更多
(R)-1,3-butanediol is an important pharmaceutical intermediate, and the synthesis of(R)-1,3-butanediol using green biological methods has recently been of interest for industrial application. Here, a novel strain QC-1...(R)-1,3-butanediol is an important pharmaceutical intermediate, and the synthesis of(R)-1,3-butanediol using green biological methods has recently been of interest for industrial application. Here, a novel strain QC-1 that efficiently transforms 4-hydroxy-2-butanone to(R)-1,3-butanediol was isolated from soil samples. Based on morphological, physiological, and biochemical tests and 5.8 S-internal transcribed spacer sequencing, the strain was identified as Pichia kudriavzevii QC-1. The reaction conditions were optimized to 35 ℃, pH 8.0, rotation speed 200 rpm, and 6:5 mass ratio of glucose to 4-hydroxy-2-butanone. Evaluation of the effects of 4-hydroxy-2-butanone concentrations on yield and cell survival rate showed that 85.60 g·L^-1 product accumulated, with an enantiomeric excess of more than 99%, when 30 g·L^-14-hydroxy-2-butanone was added at 0, 10, and 30 h in a 3-L bioreactor. Thus, strain QC-1 showed excellent catalytic activity and stereoselectivity for the synthesis of(R)-1,3-butanediol from 4-hydroxy-2-butanone.展开更多
Stereoselective chemical glycosylation reactions are pivotal for preparing manifold biologically and medically important compounds,while mechanisms of chemical glycosylation reactions remain obscure and largely specul...Stereoselective chemical glycosylation reactions are pivotal for preparing manifold biologically and medically important compounds,while mechanisms of chemical glycosylation reactions remain obscure and largely speculative.Herein,we performed DFT calculations to delve into the multifaceted mechanistic details of glycosylation reactions,including the equilibria among reactive glycosyl triflate intermediates in solution,the stereoselectivity imparting protecting groups,solvent effects,base,and the anomeric effect.Our results provided theoretical corroboration to 2-OAc neighbouring group participation(NGP),the arming/disarming effect,the coordination theory of solvent effect on glycosylation stereochemistry,and the influence of solvent polarity on the reaction kinetics spanning the S_(N)1-S_(N)2 continuum.For the first time,the existence of putative contact-ion-pairs(CIP)of glycosyl oxocarbenium and triflate anion in organic solutions was theoretically confirmed with the identification of multiple ground state structures employing an implicit Solvation Model based on Density(SMD).Kinetics of nucleophilic attack of model glucosyl triflates by simple alcohol acceptors ethanol(EtOH)and trifluoroethanol(TFE),complexed with 2,4,6-tri-tert-butylpyrimidine(TTBP)were explored,revealing the essential role of the close accompanying base for rendering glycosidic bond formation thermodynamically favourable.Our work deepens the comprehension of the glycosylation mechanism,paving the way for the rational design and future advancement of efficient and environmentally friendly stereoselective glycosylation reactions.展开更多
What is the most favorite and original chemistry developed in your research group? Developing PIP amine for regio-and enantioselective methylene C-H activation. How do you get into this specific field? Could you pleas...What is the most favorite and original chemistry developed in your research group? Developing PIP amine for regio-and enantioselective methylene C-H activation. How do you get into this specific field? Could you please share some experiences with our readers?展开更多
Recently, there has been considerable attention focused on the binding of metal complexes to DNA. Since the middle 1980s, Barton et al. have found that the chirl octahedral complexes that contain planar aromatic ligan...Recently, there has been considerable attention focused on the binding of metal complexes to DNA. Since the middle 1980s, Barton et al. have found that the chirl octahedral complexes that contain planar aromatic ligands can bind to double-helical DNA stereoselectively, and the chirl intercalator [Ru（phen）<sub>3</sub>]<sup>3+</sup> has been used as the probe to recognize B and Z-form DNA. The photophysical studies indicated that the complexes containing 1, 10-phenanthroline or larger planar aromatic ligands can be intercalated into DNA stereoselectively and the complexes containing smaller ligands such as 2, 2’-展开更多
From (+)- camphor, six new (+)-camphor derivatives were synthesized. According tothe structure and chemical properties of the derivatives, the relation between the substitutedgroups and the stereoselectivity of alkyla...From (+)- camphor, six new (+)-camphor derivatives were synthesized. According tothe structure and chemical properties of the derivatives, the relation between the substitutedgroups and the stereoselectivity of alkylations and reduction was examined. It is found thatthe chemical shift of protons of C(8), C(9) methyl groups and chemical properties of carbonylO(2) are associated with the substituted groups.展开更多
Twenty one 1,3 dioxolanes with varieties of substituents at 2,4 positions were synthesized by acid catalyzed acetalization and ketalization reactions of glycerol and its modified derivatives. The assignment and qua...Twenty one 1,3 dioxolanes with varieties of substituents at 2,4 positions were synthesized by acid catalyzed acetalization and ketalization reactions of glycerol and its modified derivatives. The assignment and quantitative analyses of thermodynamically equilibrated cis and trans 1,3 dioxolanes were completed by 1H NMR. The stereoselective regularity was found in acetalization and ketalization reactions of glycerol and its modified derivatives. The stereoselective regularity of the condensation reactions was reasonably explained by anomeric effect and 2,4 nonbonded interaction.展开更多
3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have rec...3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.展开更多
The authors regret that in the original article,the structure of(–)-swainsonine(1)in Graphical abstract,Fig.1,Schemes 1 and 3 was incorrect.The correct structure is shown here.
To investigate a new glycosylation method. Methods In the presence of TMSOTfas catalyst, 1-O-(3, 5-dinitrobenzoyl)-2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranose 1 reacted with aseries of carboxylic acid, phenols, alcoh...To investigate a new glycosylation method. Methods In the presence of TMSOTfas catalyst, 1-O-(3, 5-dinitrobenzoyl)-2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranose 1 reacted with aseries of carboxylic acid, phenols, alcohols and saccharides respectively to give the correspondingglycosylation products. The compounds were determined by ~1H NMR and ^(13)C NMR spectra. ResultsThe α-glu-co-pyranosides and related oligosaccharides were prepared in high yields. Conclusion The3, 5-dinitro-benzoyl group was found to be a good leaving group at the anomeric position andO-glucopyranosides and oligosaccharides were stereoselectively synthesized in good yield.展开更多
We report a novel P-directing effect of imidazolium based ionic liquid,which was observed when we conducted the glycosylation of a 6-O-acetyl-2,3,4-tri-O-benzyl-mannose trichloroacetimidate donor with a modified ionic...We report a novel P-directing effect of imidazolium based ionic liquid,which was observed when we conducted the glycosylation of a 6-O-acetyl-2,3,4-tri-O-benzyl-mannose trichloroacetimidate donor with a modified ionic liquid support acceptor. The mechanism was investigated and a hypothesis was proposed.After optimization of the reaction conditions,an innovative method for the selective construction of 1,2-cis-β-D-mannopyranosyl linkage was developed.展开更多
The protein binding of non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac with human serum albumin （HSA） was investigated using indirect chiral high performance liquid chromatography （HPLC...The protein binding of non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac with human serum albumin （HSA） was investigated using indirect chiral high performance liquid chromatography （HPLC） and ultrafiltration techniques. S-（-）-1-（1-naphthyl）- ethylamine （S-NEA） was utilized as chiral derivatization reagent and pre-column derivatization RP-HPLC method was established for the separation and assay of the three pairs of enantiomer. The method had good linear relationship over the investigated concentration range without interference. The average extraction efficiency was higher than 85% in different systems, and the intra-day and inter-day precisions were less than 15%. In serum albumin, the protein binding of etodolac enantiomers showed significant stereoselectivity that the affinity of S-enantiomer was stronger than R-enantiomer, and the stereoselectivity ratio reached 6.06; Flurbiprofen had only weak stereoselectivity in HSA, and ketoprofen had no stereoselectivity at all. Scatchard curves showed that all the three chiral drugs had two types of binding sites in HSA.展开更多
β-Iminophosphonamide ligated lanthanum bis（benzyl） complex（NPNDipp）La（CH2Ph-4-Me）2（THF）（NPNDipp = Ph2P（NC6H3iPr2-2,6）2）, upon activation of Al Et3 and [Ph3C][B（C6F5）4], exhibited high catalytic activity...β-Iminophosphonamide ligated lanthanum bis（benzyl） complex（NPNDipp）La（CH2Ph-4-Me）2（THF）（NPNDipp = Ph2P（NC6H3iPr2-2,6）2）, upon activation of Al Et3 and [Ph3C][B（C6F5）4], exhibited high catalytic activity and high trans-1,4 stereoselectivity for the polymerization of bio-sourced b-myrcene（MY）. Based on which, a series of novel trans-1,4 regulated elastomers could be generated by random/block copolymerization of MY and isoprene（IP）.展开更多
AIM: To study the stereoselectivity of phase Ⅱ glucuronidation metabolism of side-chain propranolol in Chinese Han population. METHODS: Sixteen adult Chinese Han volunteers with an average age of 20 years were given ...AIM: To study the stereoselectivity of phase Ⅱ glucuronidation metabolism of side-chain propranolol in Chinese Han population. METHODS: Sixteen adult Chinese Han volunteers with an average age of 20 years were given a single oral dose of 20 mg racemic propranolol. Human urine at indicated time after administration was collected and S-(-)-propranolol glucuronide and R-(+)-propranolol glucuronide were determined simultaneously by using RP-HPLC. RESULTS: The mean values of k were 0.19±0.04 h-1 and 0.28±0.06 h-1, of t1/2 3.56±0.73 h and 2.45±0.50 h, of Tmax 2.21±0.45 and 1.75±0.33 h, and of Xu0-24 5.65±0.98 and 2.95±0.62 μmoL for S-(-)- and R-(+)-propranolol glucuronide, respectively. The cumulative excretion percentages in urine of closes were 14.7±2.46% and 7.68±1.60% for S-(-)-and R-(+)-propranolol glucuronide, respectively. The results showed the elimination rate constant k of S-(-)-propranolol glucuronide was less than that of R-(+)-propranolol glucuronide; and the elimination half-life (t1/2), Tmax and the cumulative excretion amount (Xu0-24) of R-(+)-propranolol glucuronide were significantly less than that of S-(-)-propranolol glucuronide. CONCLUSION: The propranolol glucuronidation of the side-chain undergoes stereoselective excretion in Chinese Han population after an oral administration of racemic propranolol.展开更多
Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization（ROP） of rac-lactide（rac-LA）, well-controlled stereoselective rac-LA ROP by organic catalys...Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization（ROP） of rac-lactide（rac-LA）, well-controlled stereoselective rac-LA ROP by organic catalyst still remains a scientific challenge. Here we report our investigations into organocatalytic stereoselective ROP of rac-LA by utilizing novel bulky chiral and achiral N-heterocyclic carbenes（NHC）, 1,3-bis-（1′-naphthylethyl）imidazolin-2-ylidene. The effect of polymerization conditions（e.g. solvent, temperature, alcohol initiator） on ROP behavior by these bulky NHCs has been fully studied, leading to the formation of isotactic-rich stereoblock polylactide（Pi = 0.81） under optimized conditions with high activity（Conv. = 98% in 30 min） and narrow molecular weight dispersity（D = 1.05）.展开更多
An efficient and E-selective monoisomerization of 1-alkenes is developed with a bis(phosphine)-based PCP-type Co complex as the catalyst.The protocol provides an atom-economical approach to trans-2-alkenes with high r...An efficient and E-selective monoisomerization of 1-alkenes is developed with a bis(phosphine)-based PCP-type Co complex as the catalyst.The protocol provides an atom-economical approach to trans-2-alkenes with high regio-and stereoselectivity,featuring mild conditions and wide substrate scope.Mechanistic investigation supports a cobalt-hydride pathway involving reversible alkene insertion/β-H elimination,and the step ofβ-H elimination at the allylic position is likely the rate-determining step.展开更多
Cu-catalyzed endo-selective asymmetric 1,3-dipolar cycloaddition of azomethine ylides with ethenesulfonyl fluorides(ESFs) was successfully developed, this protocol provided an efficient and facile method to a wide ran...Cu-catalyzed endo-selective asymmetric 1,3-dipolar cycloaddition of azomethine ylides with ethenesulfonyl fluorides(ESFs) was successfully developed, this protocol provided an efficient and facile method to a wide range of chiral pyrrolidine-3-sulfonyl fluorides with good to excellent results(up to 87% yield,>20:1 dr, 94% ee). Some other chiral sulfonyl derivatives, such as sulfonamide and sulfonate, were easily accessible through simple transformations with high yields, which demonstrated that the cycloaddition products could be synthetically useful in the sulfur(VI) fluoride exchange(Su FEx) chemistry.展开更多
Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21（DE3） and further functionally characterized. Under optimal conditions（10 mmo...Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21（DE3） and further functionally characterized. Under optimal conditions（10 mmol/L substrate, p H 6.0, 2 h at 40 ℃）, this esterase can hydrolyze racemic methyl mandelate to（ R）-methyl mandelate with very high optical purity（e. e. 〉99%） and yield（nearly 90%）. Interestingly, the stereoselectivity of this esterase is opposite to that of two previously reported lipases that can generate（ S）-methyl mandelate through the hydrolysis of racemic methyl mandelate. No organic solvents or other additives were required to optimize the optical purity and production of the fi nal chiral product（R）-methyl mandelate, which can potentially simplify the production procedure of（ R）-methyl mandelate catalyzed by esterase.展开更多
基金the grants from the National Natural Science Foundation of China.(No.20633050 and 20403007).
文摘The stereoselectivity of some Diels-Alder reactions was investigated by means of ABEEM-oTr model. Combined with local hard-soft and acid-base （HSAB） principle, we made reasonable explanation by calculating local softness of atom and bond regions for the stereoselectivity of four Diels-Alder reactions involving cyclopentadiene.
文摘Molecular structures of reactants were characterized by molecular electronegativity distance vector （VHMED） considering hydrogen association. A reasonable molecular modeling equation with 4-parameters was achieved for quantitative structure-property/activity relationship （QSPR/QSAR） by stepwise multiple regression （SMR） that the variable was introduced item by item in significant level order. A high correlation coefficient （R = 0.980） demonstrates that the model is able to well express a quantitative relation between stereoselectivity and the reactant structures as quantitative structure-reactivity/stereoselectivity relationship （QSRR/QSSR）. The multiple correlation coefficient （Rcv= 0.964） was tested through cross-validation with the leave-one-out （LOO） procedure. The above results show that the model possesses high estimation stability and good prediction ability between the amount of both cis and trans isomers in products and reactants.
基金Financial supports from the National Key R&D Program of China(2018YFC1604100)the National Natural Science Foundation of China(NSFC)[21676120,31872891]+8 种基金the 111 Project[111-2-06]the Highend Foreign Experts Recruitment Program[G20190010083]the Program for Advanced Talents within Six Industries of Jiangsu Province[2015-NY007]the National Program for Support of Top-notch Young Professionalsthe Fundamental Research Funds for the Central Universities[JUSRP51504]the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education InstitutionsTop-notch Academic Programs Project of Jiangsu Higher Education Institutionsthe Jiangsu Province“Collaborative Innovation Center for Advanced Industrial Fermentation”Industry Development Programthe National First-Class Discipline Program of Light Industry Technology and Engineering[LITE2018-09]。
文摘(R)-1,3-butanediol is an important pharmaceutical intermediate, and the synthesis of(R)-1,3-butanediol using green biological methods has recently been of interest for industrial application. Here, a novel strain QC-1 that efficiently transforms 4-hydroxy-2-butanone to(R)-1,3-butanediol was isolated from soil samples. Based on morphological, physiological, and biochemical tests and 5.8 S-internal transcribed spacer sequencing, the strain was identified as Pichia kudriavzevii QC-1. The reaction conditions were optimized to 35 ℃, pH 8.0, rotation speed 200 rpm, and 6:5 mass ratio of glucose to 4-hydroxy-2-butanone. Evaluation of the effects of 4-hydroxy-2-butanone concentrations on yield and cell survival rate showed that 85.60 g·L^-1 product accumulated, with an enantiomeric excess of more than 99%, when 30 g·L^-14-hydroxy-2-butanone was added at 0, 10, and 30 h in a 3-L bioreactor. Thus, strain QC-1 showed excellent catalytic activity and stereoselectivity for the synthesis of(R)-1,3-butanediol from 4-hydroxy-2-butanone.
基金X.W.L.would like to sincerely appreciate Nanyang Technological University(No.MOE Tier 1,RG9/20)Ministry of Education,Singapore(No.MOE-T2EP30120-0007)+1 种基金A*STAR(No.A20E5c0087)for their generous financial supportT.P.L.thanks the Startup Grant(No.21470001)from Henan University of Technology for the financial support.
文摘Stereoselective chemical glycosylation reactions are pivotal for preparing manifold biologically and medically important compounds,while mechanisms of chemical glycosylation reactions remain obscure and largely speculative.Herein,we performed DFT calculations to delve into the multifaceted mechanistic details of glycosylation reactions,including the equilibria among reactive glycosyl triflate intermediates in solution,the stereoselectivity imparting protecting groups,solvent effects,base,and the anomeric effect.Our results provided theoretical corroboration to 2-OAc neighbouring group participation(NGP),the arming/disarming effect,the coordination theory of solvent effect on glycosylation stereochemistry,and the influence of solvent polarity on the reaction kinetics spanning the S_(N)1-S_(N)2 continuum.For the first time,the existence of putative contact-ion-pairs(CIP)of glycosyl oxocarbenium and triflate anion in organic solutions was theoretically confirmed with the identification of multiple ground state structures employing an implicit Solvation Model based on Density(SMD).Kinetics of nucleophilic attack of model glucosyl triflates by simple alcohol acceptors ethanol(EtOH)and trifluoroethanol(TFE),complexed with 2,4,6-tri-tert-butylpyrimidine(TTBP)were explored,revealing the essential role of the close accompanying base for rendering glycosidic bond formation thermodynamically favourable.Our work deepens the comprehension of the glycosylation mechanism,paving the way for the rational design and future advancement of efficient and environmentally friendly stereoselective glycosylation reactions.
文摘What is the most favorite and original chemistry developed in your research group? Developing PIP amine for regio-and enantioselective methylene C-H activation. How do you get into this specific field? Could you please share some experiences with our readers?
文摘Recently, there has been considerable attention focused on the binding of metal complexes to DNA. Since the middle 1980s, Barton et al. have found that the chirl octahedral complexes that contain planar aromatic ligands can bind to double-helical DNA stereoselectively, and the chirl intercalator [Ru（phen）<sub>3</sub>]<sup>3+</sup> has been used as the probe to recognize B and Z-form DNA. The photophysical studies indicated that the complexes containing 1, 10-phenanthroline or larger planar aromatic ligands can be intercalated into DNA stereoselectively and the complexes containing smaller ligands such as 2, 2’-
基金Project supported by the National Natural Science Foundation of China.
文摘From (+)- camphor, six new (+)-camphor derivatives were synthesized. According tothe structure and chemical properties of the derivatives, the relation between the substitutedgroups and the stereoselectivity of alkylations and reduction was examined. It is found thatthe chemical shift of protons of C(8), C(9) methyl groups and chemical properties of carbonylO(2) are associated with the substituted groups.
文摘Twenty one 1,3 dioxolanes with varieties of substituents at 2,4 positions were synthesized by acid catalyzed acetalization and ketalization reactions of glycerol and its modified derivatives. The assignment and quantitative analyses of thermodynamically equilibrated cis and trans 1,3 dioxolanes were completed by 1H NMR. The stereoselective regularity was found in acetalization and ketalization reactions of glycerol and its modified derivatives. The stereoselective regularity of the condensation reactions was reasonably explained by anomeric effect and 2,4 nonbonded interaction.
基金supported by the National Key R&D Program of China(Nos.2022YFF1203005,2022YFC2303700)supported by the National Natural Science Foundation of China(Nos.81930097,82151223).
文摘3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.
文摘The authors regret that in the original article,the structure of(–)-swainsonine(1)in Graphical abstract,Fig.1,Schemes 1 and 3 was incorrect.The correct structure is shown here.
文摘To investigate a new glycosylation method. Methods In the presence of TMSOTfas catalyst, 1-O-(3, 5-dinitrobenzoyl)-2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranose 1 reacted with aseries of carboxylic acid, phenols, alcohols and saccharides respectively to give the correspondingglycosylation products. The compounds were determined by ~1H NMR and ^(13)C NMR spectra. ResultsThe α-glu-co-pyranosides and related oligosaccharides were prepared in high yields. Conclusion The3, 5-dinitro-benzoyl group was found to be a good leaving group at the anomeric position andO-glucopyranosides and oligosaccharides were stereoselectively synthesized in good yield.
基金National Natural Science Foundation of China (Grant No.20732001) the State New Drug Innovation(the Ministry of Science and Technology of China,Grant No. 2009ZX09501-011)
文摘We report a novel P-directing effect of imidazolium based ionic liquid,which was observed when we conducted the glycosylation of a 6-O-acetyl-2,3,4-tri-O-benzyl-mannose trichloroacetimidate donor with a modified ionic liquid support acceptor. The mechanism was investigated and a hypothesis was proposed.After optimization of the reaction conditions,an innovative method for the selective construction of 1,2-cis-β-D-mannopyranosyl linkage was developed.
基金supported by National Major Projects for Science and Technology Development of Ministry Science and Technology of China (2009ZX09304-003)
文摘The protein binding of non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac with human serum albumin （HSA） was investigated using indirect chiral high performance liquid chromatography （HPLC） and ultrafiltration techniques. S-（-）-1-（1-naphthyl）- ethylamine （S-NEA） was utilized as chiral derivatization reagent and pre-column derivatization RP-HPLC method was established for the separation and assay of the three pairs of enantiomer. The method had good linear relationship over the investigated concentration range without interference. The average extraction efficiency was higher than 85% in different systems, and the intra-day and inter-day precisions were less than 15%. In serum albumin, the protein binding of etodolac enantiomers showed significant stereoselectivity that the affinity of S-enantiomer was stronger than R-enantiomer, and the stereoselectivity ratio reached 6.06; Flurbiprofen had only weak stereoselectivity in HSA, and ketoprofen had no stereoselectivity at all. Scatchard curves showed that all the three chiral drugs had two types of binding sites in HSA.
基金financially supported by the National Natural Science Foundation of China(Nos.51321062 and 21304088)the Department of Science and Technology of Jilin Province for Project No.20150204079GX
文摘β-Iminophosphonamide ligated lanthanum bis（benzyl） complex（NPNDipp）La（CH2Ph-4-Me）2（THF）（NPNDipp = Ph2P（NC6H3iPr2-2,6）2）, upon activation of Al Et3 and [Ph3C][B（C6F5）4], exhibited high catalytic activity and high trans-1,4 stereoselectivity for the polymerization of bio-sourced b-myrcene（MY）. Based on which, a series of novel trans-1,4 regulated elastomers could be generated by random/block copolymerization of MY and isoprene（IP）.
基金Supported by the National Natural Science Foundation of China, No. 30225047
文摘AIM: To study the stereoselectivity of phase Ⅱ glucuronidation metabolism of side-chain propranolol in Chinese Han population. METHODS: Sixteen adult Chinese Han volunteers with an average age of 20 years were given a single oral dose of 20 mg racemic propranolol. Human urine at indicated time after administration was collected and S-(-)-propranolol glucuronide and R-(+)-propranolol glucuronide were determined simultaneously by using RP-HPLC. RESULTS: The mean values of k were 0.19±0.04 h-1 and 0.28±0.06 h-1, of t1/2 3.56±0.73 h and 2.45±0.50 h, of Tmax 2.21±0.45 and 1.75±0.33 h, and of Xu0-24 5.65±0.98 and 2.95±0.62 μmoL for S-(-)- and R-(+)-propranolol glucuronide, respectively. The cumulative excretion percentages in urine of closes were 14.7±2.46% and 7.68±1.60% for S-(-)-and R-(+)-propranolol glucuronide, respectively. The results showed the elimination rate constant k of S-(-)-propranolol glucuronide was less than that of R-(+)-propranolol glucuronide; and the elimination half-life (t1/2), Tmax and the cumulative excretion amount (Xu0-24) of R-(+)-propranolol glucuronide were significantly less than that of S-(-)-propranolol glucuronide. CONCLUSION: The propranolol glucuronidation of the side-chain undergoes stereoselective excretion in Chinese Han population after an oral administration of racemic propranolol.
基金financially supported by the Science and Technology Commission of Shanghai Municipality(No.17JC1401200)
文摘Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization（ROP） of rac-lactide（rac-LA）, well-controlled stereoselective rac-LA ROP by organic catalyst still remains a scientific challenge. Here we report our investigations into organocatalytic stereoselective ROP of rac-LA by utilizing novel bulky chiral and achiral N-heterocyclic carbenes（NHC）, 1,3-bis-（1′-naphthylethyl）imidazolin-2-ylidene. The effect of polymerization conditions（e.g. solvent, temperature, alcohol initiator） on ROP behavior by these bulky NHCs has been fully studied, leading to the formation of isotactic-rich stereoblock polylactide（Pi = 0.81） under optimized conditions with high activity（Conv. = 98% in 30 min） and narrow molecular weight dispersity（D = 1.05）.
文摘An efficient and E-selective monoisomerization of 1-alkenes is developed with a bis(phosphine)-based PCP-type Co complex as the catalyst.The protocol provides an atom-economical approach to trans-2-alkenes with high regio-and stereoselectivity,featuring mild conditions and wide substrate scope.Mechanistic investigation supports a cobalt-hydride pathway involving reversible alkene insertion/β-H elimination,and the step ofβ-H elimination at the allylic position is likely the rate-determining step.
基金the financial support from the National Natural Science Foundation of China (Nos. 21772147, 22071186, 22071187)Natural Science Foundation of Hubei Province (No. 2020CFA036)+1 种基金Natural Science Foundation of Jiangsu Province (No. SKB2019041078)The Program of Introducing Talents of Discipline to Universities of China (111 Project) is also appreciated。
文摘Cu-catalyzed endo-selective asymmetric 1,3-dipolar cycloaddition of azomethine ylides with ethenesulfonyl fluorides(ESFs) was successfully developed, this protocol provided an efficient and facile method to a wide range of chiral pyrrolidine-3-sulfonyl fluorides with good to excellent results(up to 87% yield,>20:1 dr, 94% ee). Some other chiral sulfonyl derivatives, such as sulfonamide and sulfonate, were easily accessible through simple transformations with high yields, which demonstrated that the cycloaddition products could be synthetically useful in the sulfur(VI) fluoride exchange(Su FEx) chemistry.
基金Supported by the National Natural Science Foundation of China(No.21302199)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA11030404)+1 种基金the Project of“Engineering HighPerformance Microorganisms for Advanced Bio-Based Manufacturing”from the Chinese Academy of Sciences(No.KGZD-EW-606)the Guangzhou Science and Technology Plan Projects(No.201510010012)
文摘Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21（DE3） and further functionally characterized. Under optimal conditions（10 mmol/L substrate, p H 6.0, 2 h at 40 ℃）, this esterase can hydrolyze racemic methyl mandelate to（ R）-methyl mandelate with very high optical purity（e. e. 〉99%） and yield（nearly 90%）. Interestingly, the stereoselectivity of this esterase is opposite to that of two previously reported lipases that can generate（ S）-methyl mandelate through the hydrolysis of racemic methyl mandelate. No organic solvents or other additives were required to optimize the optical purity and production of the fi nal chiral product（R）-methyl mandelate, which can potentially simplify the production procedure of（ R）-methyl mandelate catalyzed by esterase.
