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
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
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
Ribosomally synthesized and post-translationally modified peptides(RiPPs)constitute a vast and diverse family of bioactive peptides.These peptides,synthesized by ribosomes and subsequently modified by various tailorin...Ribosomally synthesized and post-translationally modified peptides(RiPPs)constitute a vast and diverse family of bioactive peptides.These peptides,synthesized by ribosomes and subsequently modified by various tailoring enzymes,possess a wide chemical space.Among these modifications,radical S-adenosylmethionine(rSAM)enzymes employ unique radical chemistry to introduce a variety of novel peptide structures,which are crucial for their activity.This review examines the major types of modifications in RiPPs catalyzed by rSAM enzymes,incorporating recent advancements in protein structure analysis techniques and computational methods.Additionally,it elucidates the diverse catalytic mechanisms and substrate selectivity of these enzymes through an analysis of the latest crystal structures.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
The hydrolysis reaction of (±)-2-acetamido-3-hydroxy-1-(4-nitrophenyl)-1-propanone[(±)-[STHZ]1], an intermediate of chloramphenicol, was studied and three different products were obtained respectively under ...The hydrolysis reaction of (±)-2-acetamido-3-hydroxy-1-(4-nitrophenyl)-1-propanone[(±)-[STHZ]1], an intermediate of chloramphenicol, was studied and three different products were obtained respectively under different reaction conditions. The resolution of hydrolysis product (±)-2-amino-3-hydroxy- 1-(4-nitrophenyl)-1-propanone, an intermediate of chloramphenicol, was studied and three different products were obtained respectively under different reaction conditions. The resolution of hydrolysis product (±)-2-amino-3-hydroxy- 1-(4-nitrophenyl)-1-propanone[(±)-[STHZ]3] was carried out. A process of crystallization-induced asymmetric transformation was observed and up to 76% of the optically pure enantiomer was obtained in the resolution of (±)- was carried out. A process of crystallization-induced asymmetric transformation was observed and up to 76% of the optically pure enantiomer was obtained in the resolution of (±)-3.展开更多
Using the potent anticancer agent 2-deoxy-2-chloro-1-amino sugar as a lead compound, its analogs were prepared in 6 steps starting from D-glucal. The key step was the synthesis of 2-chloro-1-acetamido sugars using （C...Using the potent anticancer agent 2-deoxy-2-chloro-1-amino sugar as a lead compound, its analogs were prepared in 6 steps starting from D-glucal. The key step was the synthesis of 2-chloro-1-acetamido sugars using （COCl） 2-AgNO 3-CH 3 CN system in high yields. 2-Deoxy-2-chloro-1-amino sugars were obtained by treating the corresponding acetamido sugars with HCl in MeOH. All the compounds, including the reference compound, displayed almost no cytotoxic activity to the selected cancer cell lines.展开更多
A detailed analysis of benzofuranone compounds under multiple tandem mass spectrometry （ESI-MS^n） conditions is reported. Element composition data of the fragment ions were obtained with the aid of comparison of the...A detailed analysis of benzofuranone compounds under multiple tandem mass spectrometry （ESI-MS^n） conditions is reported. Element composition data of the fragment ions were obtained with the aid of comparison of the multiple tandem mass spectra of four compounds, and the structures of which are identical except for some substituted groups or epimers or cis-trans-isomers. Attempts have been made to provide rational pathways for the formation of the fragment ions from these protonated compounds. And the structure-fragmentation relationships will facilitate the characterization of the structures of other analogs.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.
A pair of epimers of highly-oxygenated monoterpenes were isolated from the traditional Chinese medicine Eupatorium fortunei. Their structures were elucidated on the basis of the spectral analysis as （1R＊, 2S＊, 3R＊...A pair of epimers of highly-oxygenated monoterpenes were isolated from the traditional Chinese medicine Eupatorium fortunei. Their structures were elucidated on the basis of the spectral analysis as （1R＊, 2S＊, 3R＊, 4R＊, 6S＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （1） and （1S＊, 2S＊, 3S＊, 4R＊, 6R＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （2）.展开更多
The maremycin biosynthetic gene cluster has been identified in Streptomyces sp. B9173. Comparative metabolic profiling with knockout mutant strains led to the identification of new products correlated to the maremycin...The maremycin biosynthetic gene cluster has been identified in Streptomyces sp. B9173. Comparative metabolic profiling with knockout mutant strains led to the identification of new products correlated to the maremycin biosynthesis, in particular the ＂demethyl＂-maremycins with an unexpected D-tryptophan unit. A biosynthetic pathway for the maremycins is proposed and plausible reasoning for tryptopban epimerization in the demethylmaremycin biosynthesis is also provided.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
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
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
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.
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.
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supported by the National Key Research and Development Program of China(No.2023YFA0916000)the National Natural Science Foundation of China(No.32371324)the High-level Talent Startup Fund provided by China Pharmaceutical University.
文摘Ribosomally synthesized and post-translationally modified peptides(RiPPs)constitute a vast and diverse family of bioactive peptides.These peptides,synthesized by ribosomes and subsequently modified by various tailoring enzymes,possess a wide chemical space.Among these modifications,radical S-adenosylmethionine(rSAM)enzymes employ unique radical chemistry to introduce a variety of novel peptide structures,which are crucial for their activity.This review examines the major types of modifications in RiPPs catalyzed by rSAM enzymes,incorporating recent advancements in protein structure analysis techniques and computational methods.Additionally,it elucidates the diverse catalytic mechanisms and substrate selectivity of these enzymes through an analysis of the latest crystal structures.
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Supported by the Science and Technology Fund of Wuhan City( No.9960 0 10 16G)
文摘The hydrolysis reaction of (±)-2-acetamido-3-hydroxy-1-(4-nitrophenyl)-1-propanone[(±)-[STHZ]1], an intermediate of chloramphenicol, was studied and three different products were obtained respectively under different reaction conditions. The resolution of hydrolysis product (±)-2-amino-3-hydroxy- 1-(4-nitrophenyl)-1-propanone, an intermediate of chloramphenicol, was studied and three different products were obtained respectively under different reaction conditions. The resolution of hydrolysis product (±)-2-amino-3-hydroxy- 1-(4-nitrophenyl)-1-propanone[(±)-[STHZ]3] was carried out. A process of crystallization-induced asymmetric transformation was observed and up to 76% of the optically pure enantiomer was obtained in the resolution of (±)- was carried out. A process of crystallization-induced asymmetric transformation was observed and up to 76% of the optically pure enantiomer was obtained in the resolution of (±)-3.
基金National Natural Science Foundation of China(NSFC,Grant No.21072017)
文摘Using the potent anticancer agent 2-deoxy-2-chloro-1-amino sugar as a lead compound, its analogs were prepared in 6 steps starting from D-glucal. The key step was the synthesis of 2-chloro-1-acetamido sugars using （COCl） 2-AgNO 3-CH 3 CN system in high yields. 2-Deoxy-2-chloro-1-amino sugars were obtained by treating the corresponding acetamido sugars with HCl in MeOH. All the compounds, including the reference compound, displayed almost no cytotoxic activity to the selected cancer cell lines.
文摘A detailed analysis of benzofuranone compounds under multiple tandem mass spectrometry （ESI-MS^n） conditions is reported. Element composition data of the fragment ions were obtained with the aid of comparison of the multiple tandem mass spectra of four compounds, and the structures of which are identical except for some substituted groups or epimers or cis-trans-isomers. Attempts have been made to provide rational pathways for the formation of the fragment ions from these protonated compounds. And the structure-fragmentation relationships will facilitate the characterization of the structures of other analogs.
文摘The natural product, neoclausenamide was synthesized through the 'biomimetic' route and the stereoselective reduction of the ketone group wherein were described.
基金This work was supported by the NNSFC(No.20372029 and No.20021001-QT Program)by the Key Project of Chinese Ministry of Education(No.104178).
文摘A pair of epimers of highly-oxygenated monoterpenes were isolated from the traditional Chinese medicine Eupatorium fortunei. Their structures were elucidated on the basis of the spectral analysis as （1R＊, 2S＊, 3R＊, 4R＊, 6S＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （1） and （1S＊, 2S＊, 3S＊, 4R＊, 6R＊）-1, 2, 3, 6-tetrehydroxy-p-menthane （2）.
基金supported by the National Natural Science Foundation of China (NNSFC, 31425001 and 31070057 for SL)the Leopoldina Fellowship Program (German National Academy of Sciences Leopoldina, LPDS 2013-12 for NLB)
文摘The maremycin biosynthetic gene cluster has been identified in Streptomyces sp. B9173. Comparative metabolic profiling with knockout mutant strains led to the identification of new products correlated to the maremycin biosynthesis, in particular the ＂demethyl＂-maremycins with an unexpected D-tryptophan unit. A biosynthetic pathway for the maremycins is proposed and plausible reasoning for tryptopban epimerization in the demethylmaremycin biosynthesis is also provided.
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.
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.
