The transformation of aldose to ketose or common sugars into rare saccharides,including rare ketoses and aldoses,is of great value and interest to the food industry and for saccharidic biomass utilization,medicine,and...The transformation of aldose to ketose or common sugars into rare saccharides,including rare ketoses and aldoses,is of great value and interest to the food industry and for saccharidic biomass utilization,medicine,and the synthesis of drugs.Nowadays,high-fructose corn syrup(HFCS)is industrially produced in more than 10 million tons annually using immobilized glucose isomerase.Some low-calorie saccharides such as tagatose and psicose,which are becoming popular sweeteners,have also been produced on a pilot scale in order to replace sucrose and HFCS.However,current catalysts and catalytic processes are still difficult to utilize in biomass conversion and also have strong substrate dependence in producing high-value,rare sugars.Considering the specific reaction properties of saccharides and catalysts,since the pioneering discovery by Fischer,various catalysts and catalytic systems have been discovered or developed in attempts to extend the reaction pathways,improve the reaction efficiency,and to potentially produce commercial products.In this review,we trace the history of sugar isomerization/epimerization reactions and summarize the important breakthroughs for each reaction as well as the difficulties that remain unresolved to date.展开更多
A rapid, sensitive and specific ultra-high-performance liquid chromatography tandem mass spectrometry （UPLC-MS） method was developed for the analysis of tetracycline antibiotics, including tetracycline （TC）, oxyte...A rapid, sensitive and specific ultra-high-performance liquid chromatography tandem mass spectrometry （UPLC-MS） method was developed for the analysis of tetracycline antibiotics, including tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and their 4-epimers （4-epiTCs） in agricultural soil fertilized with swine manure. Soil samples were extracted and cleaned-up with 10 mL EDTA-McIlvaine buffer solution （pH 4.0）, then cleaned-up and pre-concentrated using the Oasis MAX cartridge and then eluted with 1 mL solution by mixing formic acid, methanol and water at a ratio of 2：15：83 （v/v/v）. The purified samples were separated by an ACQUITY UPLC BEH C18 column using acetonitrile and water containing 0.1% formic acid mobile phase and detected by a single quadrupole MS. The limits of detection for the soil extraction method （LODsoil） ranged from 0.6-2.5 lag kg-~ with recoveries from 23.3-159.2%. Finally, the method was applied to an agricultural field in an area with intensive pig-fattening farming. Tetracyclines were detected in soil from 2.8 to 42.4 μg kg-1 soil. These results demonstrate that soil from swine farms can become severely contaminated with tetracycline antibiotics and their metabolites.展开更多
The natural product, neoclausenamide was synthesized through the 'biomimetic' route and the stereoselective reduction of the ketone group wherein were described.
Compound 2 with 14β-hydroxyl group was successfully converted into its epimerized α-counterpart via oxidation - reduction.The elimination product (6) was auto-oxidized to epoxide 8,even in the solid state
: The microbiological transformaion of a natural taxoid 10-deacetylbaccatin III into its C-7 epimer, 10-deacetylbaccatin V with Microsphaeropsis onychiuri, a fungus isolated from the inner bark of Taxus yunnanensis is...: The microbiological transformaion of a natural taxoid 10-deacetylbaccatin III into its C-7 epimer, 10-deacetylbaccatin V with Microsphaeropsis onychiuri, a fungus isolated from the inner bark of Taxus yunnanensis is described.展开更多
D-Allose and its derivatives play important roles in the field of health care and food nutrition. Pure and well-defined Dallose derivatives can facilitate the elucidation of their structure-activity relationship as an...D-Allose and its derivatives play important roles in the field of health care and food nutrition. Pure and well-defined Dallose derivatives can facilitate the elucidation of their structure-activity relationship as an essential step for drug design. The LattrellDax epimerization, refers to the triflate inversion using nitrite reagent, is known as valuable method for the synthesis of rare D-allose derivatives. Here, the influence of protecting group patterns on the transformation efficiency of D-glucose derivatives into synthetically useful D-alloses and D-allosamines via the Lattrell-Dax epimerization was studied. For C3 epimerization of D-glucose derivatives bearing O2-acyl group, an anomeric configuration-dependent acyl migration from O2 to O3 was found. In addition, a neighbouring group participation effect-mediated SN1 nucleophilic substitution of the D-glucosamine bearing C2 trichloroacetamido(TCA) group in the Lattrell-Dax epimerization was dependent upon anomeric configuration. Thus, the effect of anomeric configuration on the LattrellDax epimerization of D-glucose suggests that β-D-glucosides with low steric hindrance at C2 should be better substrates for the synthesis of D-allose derivatives. Significantly, the efficient synthesis of the orthogonally protected D-allose 13 and D-allosamine 18 will serve well for further assembly of complex glycans.展开更多
Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of...Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of-principle report of a novel DMS–MS/MS method to separate and simultaneously quantify epimers, taking PGF2α and its 8-epimer, 8-iso-PGF2α, as an example. Good accuracy and precision were achieved in the range of 10–500 ng/m L with a run time of only 1.5 min. Isopropanol as organic modifier facilitated a good combination of sensitivity and separation. The method is the first example of the quantitation of epimers without chromatographic separation.展开更多
A pair of new tirucallane triterpenoid epimers,picraquassins M and N(1 and 2),were isolated from the stems of Picrasma quassioides(D.Don)Benn.Their structures were determined based on comprehensive spectroscopic and X...A pair of new tirucallane triterpenoid epimers,picraquassins M and N(1 and 2),were isolated from the stems of Picrasma quassioides(D.Don)Benn.Their structures were determined based on comprehensive spectroscopic and X-ray crystallographic analyses.In addition,their ACh E inhibitory activity,cytotoxicity against five human tumour cell lines(SW480,MCF-7,HepG2,Hela,and PANC-1),and antimicrobial activity against two bacteria(Staphylococcus.aureus 209 P and Escherichia coli ATCC0111)and two fungi(Candida albicans FIM709 and Aspergillus niger R330)were evaluated.展开更多
Baogongteng A is a tropane alkaloid with cholinergic activity. It has been used clinically for the treatment of glaucoma, and its pharmacological activity on heart function has also been reported.In the synthesis of b...Baogongteng A is a tropane alkaloid with cholinergic activity. It has been used clinically for the treatment of glaucoma, and its pharmacological activity on heart function has also been reported.In the synthesis of baogongteng A, the cycloadducts of Katritzky cycloaddition of 1-benzyl-3-oxidepyridinium with a-chloroacrylonitrile were ketalized with ethylene glycol in benzene by azeotropic distillation. After recrystallization from ethanol, two compounds（A, prisms, m.p.127—129℃; B, needles, m.p.75—77℃） were obtaines.Their MS, IR spectral data and elemental analysis were consistent with the proposed structures. They were assigned as C<sub>6</sub>-chloro nitrile epimers by <sup>1</sup>H-<sup>1</sup>H展开更多
Two remarkable epimerization processes were uncovered during our pursuit of an enantioselective synthesis of(+)-aigialospirol featuring a cyclic acetal tethered ring-closing metathesis.Through modeling,we were able to...Two remarkable epimerization processes were uncovered during our pursuit of an enantioselective synthesis of(+)-aigialospirol featuring a cyclic acetal tethered ring-closing metathesis.Through modeling,we were able to turn these two unexpected epimerizations to our advantage via modeling to ensure a successful and concise total synthesis,thereby firmly establishing cyclic acetal tethered RCM as a powerful strategy in natural product synthesis.Most importantly,calculations allowed us to fully understand the nature and the mechanistic course of these two epimerizations that were imperative to the total synthesis efforts.展开更多
γ-Lupane (2) and iso-γ-lupane (10) (3α-isopropyl, 5αH) were synthesized from lupeol. The reaction conditions of conversion of lupeol into lupenes and γ-lupenes and the results of catalytic hydrogenation of lupene...γ-Lupane (2) and iso-γ-lupane (10) (3α-isopropyl, 5αH) were synthesized from lupeol. The reaction conditions of conversion of lupeol into lupenes and γ-lupenes and the results of catalytic hydrogenation of lupenes and γ-lupenes under different conditions were studied.展开更多
The singlet-singlet intramolecular energy transfer between naphthalene moiety and dansyl group held apart by a rigid steroid bridge was investigated for two molecules:3β-(1-naphthyl)acetoxy- 17α-dansyl-△~5androsten...The singlet-singlet intramolecular energy transfer between naphthalene moiety and dansyl group held apart by a rigid steroid bridge was investigated for two molecules:3β-(1-naphthyl)acetoxy- 17α-dansyl-△~5androstene(3a)and 3β-(1-naphthyl)acetoxy-17β-dansyl-△~5androstene(3b).The rates of energy transfer for 3a and 3b in cyclohexane are 6.9×10~6 and 1.1×10~8s^(-1) respectively.The difference in energy transfer rate between 3a and 3b is attributed to the different donor-acceptor separation and orientation.The ratio of the two epimers in the synthesized product mixture was obtained from the fluorescence decay measurements.展开更多
基金Financial support by Dual Initiative Project of Jiangsu Province and Changzhou University is gratefully acknowledgedSample analysis supported by Analysis and Testing Center,NERC Biomass of Changzhou University was also greatly acknowledged.
文摘The transformation of aldose to ketose or common sugars into rare saccharides,including rare ketoses and aldoses,is of great value and interest to the food industry and for saccharidic biomass utilization,medicine,and the synthesis of drugs.Nowadays,high-fructose corn syrup(HFCS)is industrially produced in more than 10 million tons annually using immobilized glucose isomerase.Some low-calorie saccharides such as tagatose and psicose,which are becoming popular sweeteners,have also been produced on a pilot scale in order to replace sucrose and HFCS.However,current catalysts and catalytic processes are still difficult to utilize in biomass conversion and also have strong substrate dependence in producing high-value,rare sugars.Considering the specific reaction properties of saccharides and catalysts,since the pioneering discovery by Fischer,various catalysts and catalytic systems have been discovered or developed in attempts to extend the reaction pathways,improve the reaction efficiency,and to potentially produce commercial products.In this review,we trace the history of sugar isomerization/epimerization reactions and summarize the important breakthroughs for each reaction as well as the difficulties that remain unresolved to date.
文摘A rapid, sensitive and specific ultra-high-performance liquid chromatography tandem mass spectrometry （UPLC-MS） method was developed for the analysis of tetracycline antibiotics, including tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and their 4-epimers （4-epiTCs） in agricultural soil fertilized with swine manure. Soil samples were extracted and cleaned-up with 10 mL EDTA-McIlvaine buffer solution （pH 4.0）, then cleaned-up and pre-concentrated using the Oasis MAX cartridge and then eluted with 1 mL solution by mixing formic acid, methanol and water at a ratio of 2：15：83 （v/v/v）. The purified samples were separated by an ACQUITY UPLC BEH C18 column using acetonitrile and water containing 0.1% formic acid mobile phase and detected by a single quadrupole MS. The limits of detection for the soil extraction method （LODsoil） ranged from 0.6-2.5 lag kg-~ with recoveries from 23.3-159.2%. Finally, the method was applied to an agricultural field in an area with intensive pig-fattening farming. Tetracyclines were detected in soil from 2.8 to 42.4 μg kg-1 soil. These results demonstrate that soil from swine farms can become severely contaminated with tetracycline antibiotics and their metabolites.
文摘The natural product, neoclausenamide was synthesized through the 'biomimetic' route and the stereoselective reduction of the ketone group wherein were described.
文摘Compound 2 with 14β-hydroxyl group was successfully converted into its epimerized α-counterpart via oxidation - reduction.The elimination product (6) was auto-oxidized to epoxide 8,even in the solid state
文摘: The microbiological transformaion of a natural taxoid 10-deacetylbaccatin III into its C-7 epimer, 10-deacetylbaccatin V with Microsphaeropsis onychiuri, a fungus isolated from the inner bark of Taxus yunnanensis is described.
基金the National Natural Science Foundation of China(Nos.21877052 and 21907039)the Natural Science Foundation of Jiangsu Province(Nos.BK20180030and BK20190575)+1 种基金the National First-class Discipline Program of Light Industry Technology and Engineering(No.LITE2018-14)the 111 Project(No.111-2-06)。
文摘D-Allose and its derivatives play important roles in the field of health care and food nutrition. Pure and well-defined Dallose derivatives can facilitate the elucidation of their structure-activity relationship as an essential step for drug design. The LattrellDax epimerization, refers to the triflate inversion using nitrite reagent, is known as valuable method for the synthesis of rare D-allose derivatives. Here, the influence of protecting group patterns on the transformation efficiency of D-glucose derivatives into synthetically useful D-alloses and D-allosamines via the Lattrell-Dax epimerization was studied. For C3 epimerization of D-glucose derivatives bearing O2-acyl group, an anomeric configuration-dependent acyl migration from O2 to O3 was found. In addition, a neighbouring group participation effect-mediated SN1 nucleophilic substitution of the D-glucosamine bearing C2 trichloroacetamido(TCA) group in the Lattrell-Dax epimerization was dependent upon anomeric configuration. Thus, the effect of anomeric configuration on the LattrellDax epimerization of D-glucose suggests that β-D-glucosides with low steric hindrance at C2 should be better substrates for the synthesis of D-allose derivatives. Significantly, the efficient synthesis of the orthogonally protected D-allose 13 and D-allosamine 18 will serve well for further assembly of complex glycans.
基金supported by the National Natural Science Foundation of China(Grant Nos.81430087 and 81673396)
文摘Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of-principle report of a novel DMS–MS/MS method to separate and simultaneously quantify epimers, taking PGF2α and its 8-epimer, 8-iso-PGF2α, as an example. Good accuracy and precision were achieved in the range of 10–500 ng/m L with a run time of only 1.5 min. Isopropanol as organic modifier facilitated a good combination of sensitivity and separation. The method is the first example of the quantitation of epimers without chromatographic separation.
基金supported by grants from the National Key Research and Development Program of China(Nos.2018YFA0903200 and 2018YFA0903201)the National Natural Science Foundation of China(No.31761143016)+6 种基金Chang Jiang Scholars Program(GAO Hao,2017)from the Ministry of Education of ChinaNational High-level Personnel of Special Support Program(No.2017RA2259)Guangdong Special Support Program(No.2016TX03R280)Young Elite Scientists Sponsorship Program by China Association of Chinese Medicine(No.QNRC2-B06)Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme(GAO Hao,2014)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01Y036)K.C.Wong Education Foundation(GAO Hao,2016)
文摘A pair of new tirucallane triterpenoid epimers,picraquassins M and N(1 and 2),were isolated from the stems of Picrasma quassioides(D.Don)Benn.Their structures were determined based on comprehensive spectroscopic and X-ray crystallographic analyses.In addition,their ACh E inhibitory activity,cytotoxicity against five human tumour cell lines(SW480,MCF-7,HepG2,Hela,and PANC-1),and antimicrobial activity against two bacteria(Staphylococcus.aureus 209 P and Escherichia coli ATCC0111)and two fungi(Candida albicans FIM709 and Aspergillus niger R330)were evaluated.
文摘Baogongteng A is a tropane alkaloid with cholinergic activity. It has been used clinically for the treatment of glaucoma, and its pharmacological activity on heart function has also been reported.In the synthesis of baogongteng A, the cycloadducts of Katritzky cycloaddition of 1-benzyl-3-oxidepyridinium with a-chloroacrylonitrile were ketalized with ethylene glycol in benzene by azeotropic distillation. After recrystallization from ethanol, two compounds（A, prisms, m.p.127—129℃; B, needles, m.p.75—77℃） were obtaines.Their MS, IR spectral data and elemental analysis were consistent with the proposed structures. They were assigned as C<sub>6</sub>-chloro nitrile epimers by <sup>1</sup>H-<sup>1</sup>H
基金PRF-AC(42106) for support and Dr.Victor Young and Ben Kucera(University of Minnesota) for X-ray analysis.CCG thanks UW for an NIH-CBI Training Grant
文摘Two remarkable epimerization processes were uncovered during our pursuit of an enantioselective synthesis of(+)-aigialospirol featuring a cyclic acetal tethered ring-closing metathesis.Through modeling,we were able to turn these two unexpected epimerizations to our advantage via modeling to ensure a successful and concise total synthesis,thereby firmly establishing cyclic acetal tethered RCM as a powerful strategy in natural product synthesis.Most importantly,calculations allowed us to fully understand the nature and the mechanistic course of these two epimerizations that were imperative to the total synthesis efforts.
基金The project was supported by the National Natural Science Foundation of China
文摘γ-Lupane (2) and iso-γ-lupane (10) (3α-isopropyl, 5αH) were synthesized from lupeol. The reaction conditions of conversion of lupeol into lupenes and γ-lupenes and the results of catalytic hydrogenation of lupenes and γ-lupenes under different conditions were studied.
文摘The singlet-singlet intramolecular energy transfer between naphthalene moiety and dansyl group held apart by a rigid steroid bridge was investigated for two molecules:3β-(1-naphthyl)acetoxy- 17α-dansyl-△~5androstene(3a)and 3β-(1-naphthyl)acetoxy-17β-dansyl-△~5androstene(3b).The rates of energy transfer for 3a and 3b in cyclohexane are 6.9×10~6 and 1.1×10~8s^(-1) respectively.The difference in energy transfer rate between 3a and 3b is attributed to the different donor-acceptor separation and orientation.The ratio of the two epimers in the synthesized product mixture was obtained from the fluorescence decay measurements.
