The synthesis of N-glycosides has received significant attention due to their crucial role in carbohydrate chemistry.Despite considerable advancements developed in the construction of N-glycosides,methods for the ster...The synthesis of N-glycosides has received significant attention due to their crucial role in carbohydrate chemistry.Despite considerable advancements developed in the construction of N-glycosides,methods for the stereoselective construction of 2-deoxy-α-N-glycosides are still limited.Herein,we disclosed a nickel-catalyzed hydroamination of glycals under mild conditions.This transformation could allow for the stereoselective synthesis of an array of 2-deoxy-α-N-glycosides with excellentα-stereoselectivity.Nickel-catalyzed glycosylation reactions,particularly those involving anomeric C(sp")-metal bond formation,have proven to be an effective and stereoselective strategy for producing various N-glycosides.Additionally,with highlight of the application of this reaction,y-sugar amino acidderivatives weresynthesized.展开更多
Efficiently modifying glycals by directly introducing functional groups into their double bonds is a longstanding challenge.Here,the strategy of introducing two different functional groups into 1-iodoglycals to obtain...Efficiently modifying glycals by directly introducing functional groups into their double bonds is a longstanding challenge.Here,the strategy of introducing two different functional groups into 1-iodoglycals to obtain modified glycals in one step through palladium catalysis was reported for the first time,and the modified glycals contained stereodefined tetrasubstituted olefins.Using this method,various difunctionalized glycals that were difficult to form by other routes were synthesized in moderate to good yields.Control experiments and density functional theory calculations show that the palladium catalyst played dual roles in this transformation,namely,inducing nucleophilic substitution and catalyzing Suzuki coupling.The reaction intermediate was isolated and confirmed by X-ray crystallographic analysis.Furthermore,the gram-scale synthesis and facile deprotection of the target compound enhances the practicality of this strategy.展开更多
A convenient and environmentally benign procedure for the synthesis of glycals from glycosyl bromides with very low zinc dust loading （1.5 equiv.） is described. The process is activated by β-cyclodextrin and ultras...A convenient and environmentally benign procedure for the synthesis of glycals from glycosyl bromides with very low zinc dust loading （1.5 equiv.） is described. The process is activated by β-cyclodextrin and ultrasound. Based on 19 samples, this method has been demonstrated to be highly effective for a broad range of glycosyl bromides, including acidor base-sensitive and disaccharide glycosyl bromides. A yield of 85%--96% of glycals was obtained.展开更多
A new protocol for the synthesis of 2-deoxy-C-aryl-glycosides and 2-deoxy-C-alkyl-glycosides via iridium-catalyzed directed C—H glycosylation with glycals is reported.The method is amenable for both the C_(2)C—H gly...A new protocol for the synthesis of 2-deoxy-C-aryl-glycosides and 2-deoxy-C-alkyl-glycosides via iridium-catalyzed directed C—H glycosylation with glycals is reported.The method is amenable for both the C_(2)C—H glycosylation of indoles and the methyl C—H glycosylation of secondary methyl amines under the control of an N-linked benzoxazole directing group.The benzoxazole group can be cleanly removed by the treatment of KOH or LiAlH_(4).展开更多
以经过致密化处理的废旧涤棉军装（废旧涤棉）为原料,以乙二醇（EG）为醇解剂,通过改变EG与废旧涤棉的配比、醇解时间、醇解液循环使用次数等研究了废旧涤棉的醇解效率,以及不同循环次数对醇解产物对苯二甲酸乙二醇酯（BHET）和涤棉织...以经过致密化处理的废旧涤棉军装（废旧涤棉）为原料,以乙二醇（EG）为醇解剂,通过改变EG与废旧涤棉的配比、醇解时间、醇解液循环使用次数等研究了废旧涤棉的醇解效率,以及不同循环次数对醇解产物对苯二甲酸乙二醇酯（BHET）和涤棉织物中的棉纱性能的影响。结果表明：在废旧涤棉与EG质量比为1∶（10～12）,废旧涤棉与Na2CO3质量比为1∶0.003,反应温度196℃,反应时间1 h的醇解条件下,醇解液可以循环使用,最佳循环使用次数为4,醇解后产物绝大部分仍为BHET单体,醇解物产率高于60%;醇解后棉纱表面虽有一定程度破坏,但其断裂强度最高仍达1.76 c N/dtex,满足开松再纺纱的要求,可实现棉纱的二次回收利用。展开更多
C-aryl glycosides are an important kind of carbohydrate derivatives for drug discovery,due to their distinctive attributes of resistance to hydrolysis from enzymes.Herein,C-aryl glycosylation was established for the s...C-aryl glycosides are an important kind of carbohydrate derivatives for drug discovery,due to their distinctive attributes of resistance to hydrolysis from enzymes.Herein,C-aryl glycosylation was established for the synthesis of 2-sulfur C-aryl glycals and 1,2-dihydrobenzofuran-fused C-aryl glycosides via interrupted Pummerer process,featured with sulfonium-tethered[3,3]-sigmatropic rearrangement between sulfoxide glycals and phenols.This protocol offers a broad substrate scope with diverse glycosyl and phenols.Dapagliflozin,Empagliflozin,and Ipragliflozin analogs were straightforward achieved,respectively.展开更多
Most bacterial cell surface glycans are structurally unique, and have been considered as ideal target molecules for the developments of detection and diagnosis techniques, as well as vaccines. Chemical synthesis has b...Most bacterial cell surface glycans are structurally unique, and have been considered as ideal target molecules for the developments of detection and diagnosis techniques, as well as vaccines. Chemical synthesis has been a promising approach to prepare well-defined oligosaccharides, facilitating the structure-activity relationship exploration and biomedical applications of bacterial glycans. L-Galactosaminuronic acid is a rare sugar that has been only found in cell surface glycans of gram-negative bacteria. Here, an orthogonally protected L-galactosaminuronic acid building block was designed and chemically synthesized. A synthetic strategy based on glycal addition and TEMPO/BAIB-mediated C6 oxidation served well for the transformation of commercial L-galactose to the corresponding L-galactosaminuronic acid. Notably, the C6 oxidation of the allyl glycoside was more efficient than that of the selenoglycoside. In addition, a balance between the formation of allyl glycoside and the recovery of selenoglycoside was essential to improve efficiency of the NIS/TfOH-catalyzed allylation. This synthetically useful L-galactosaminuronic acid building block will provide a basis for the syntheses of complex bacterial glycans.展开更多
基金supported by the National Natural Science Foundation of China(22122107).
文摘The synthesis of N-glycosides has received significant attention due to their crucial role in carbohydrate chemistry.Despite considerable advancements developed in the construction of N-glycosides,methods for the stereoselective construction of 2-deoxy-α-N-glycosides are still limited.Herein,we disclosed a nickel-catalyzed hydroamination of glycals under mild conditions.This transformation could allow for the stereoselective synthesis of an array of 2-deoxy-α-N-glycosides with excellentα-stereoselectivity.Nickel-catalyzed glycosylation reactions,particularly those involving anomeric C(sp")-metal bond formation,have proven to be an effective and stereoselective strategy for producing various N-glycosides.Additionally,with highlight of the application of this reaction,y-sugar amino acidderivatives weresynthesized.
基金We thank the National Natural Science Foundation of China(NSF 22171114 and 21772075)for its financial support.
文摘Efficiently modifying glycals by directly introducing functional groups into their double bonds is a longstanding challenge.Here,the strategy of introducing two different functional groups into 1-iodoglycals to obtain modified glycals in one step through palladium catalysis was reported for the first time,and the modified glycals contained stereodefined tetrasubstituted olefins.Using this method,various difunctionalized glycals that were difficult to form by other routes were synthesized in moderate to good yields.Control experiments and density functional theory calculations show that the palladium catalyst played dual roles in this transformation,namely,inducing nucleophilic substitution and catalyzing Suzuki coupling.The reaction intermediate was isolated and confirmed by X-ray crystallographic analysis.Furthermore,the gram-scale synthesis and facile deprotection of the target compound enhances the practicality of this strategy.
文摘A convenient and environmentally benign procedure for the synthesis of glycals from glycosyl bromides with very low zinc dust loading （1.5 equiv.） is described. The process is activated by β-cyclodextrin and ultrasound. Based on 19 samples, this method has been demonstrated to be highly effective for a broad range of glycosyl bromides, including acidor base-sensitive and disaccharide glycosyl bromides. A yield of 85%--96% of glycals was obtained.
基金We gratefully acknowledge the National Natural Science Foundation of China(NSFC 21725204,NSFC-22071119)the“111”project(B06005)of MOE China,and NCC2020FH02 for financial support of this work.
文摘A new protocol for the synthesis of 2-deoxy-C-aryl-glycosides and 2-deoxy-C-alkyl-glycosides via iridium-catalyzed directed C—H glycosylation with glycals is reported.The method is amenable for both the C_(2)C—H glycosylation of indoles and the methyl C—H glycosylation of secondary methyl amines under the control of an N-linked benzoxazole directing group.The benzoxazole group can be cleanly removed by the treatment of KOH or LiAlH_(4).
文摘以经过致密化处理的废旧涤棉军装（废旧涤棉）为原料,以乙二醇（EG）为醇解剂,通过改变EG与废旧涤棉的配比、醇解时间、醇解液循环使用次数等研究了废旧涤棉的醇解效率,以及不同循环次数对醇解产物对苯二甲酸乙二醇酯（BHET）和涤棉织物中的棉纱性能的影响。结果表明：在废旧涤棉与EG质量比为1∶（10～12）,废旧涤棉与Na2CO3质量比为1∶0.003,反应温度196℃,反应时间1 h的醇解条件下,醇解液可以循环使用,最佳循环使用次数为4,醇解后产物绝大部分仍为BHET单体,醇解物产率高于60%;醇解后棉纱表面虽有一定程度破坏,但其断裂强度最高仍达1.76 c N/dtex,满足开松再纺纱的要求,可实现棉纱的二次回收利用。
基金The authors are grateful for financial support provided by NSFC(22125103and21971065)STCSM(22JC1401000,20xD1421500 and 20JC1416800)the Fundamental Research FundsfortheCentral Universities.
文摘C-aryl glycosides are an important kind of carbohydrate derivatives for drug discovery,due to their distinctive attributes of resistance to hydrolysis from enzymes.Herein,C-aryl glycosylation was established for the synthesis of 2-sulfur C-aryl glycals and 1,2-dihydrobenzofuran-fused C-aryl glycosides via interrupted Pummerer process,featured with sulfonium-tethered[3,3]-sigmatropic rearrangement between sulfoxide glycals and phenols.This protocol offers a broad substrate scope with diverse glycosyl and phenols.Dapagliflozin,Empagliflozin,and Ipragliflozin analogs were straightforward achieved,respectively.
基金supported by the National Natural Science Foundation of China(Nos.22077052,21877052,21907039)the China Postdoctoral Science Foundation(2020M681487)+5 种基金the National Key R&D Program of China(2020YFA0908304)the Natural Science Foundation of Jiangsu Province(BK20180030,BK20190575)the National First-class Discipline Program of Light Industry Technology and Engineering(LITE2018-14)the 111 Project(111-2-06)the Open Project of Key Laboratory of Carbohydrate Chemistry and Biotechnology(Jiangnan University),Ministry of Education(KLCCB-KF202005)the Natural Science Foundation of Xuzhou(KC19154).
文摘Most bacterial cell surface glycans are structurally unique, and have been considered as ideal target molecules for the developments of detection and diagnosis techniques, as well as vaccines. Chemical synthesis has been a promising approach to prepare well-defined oligosaccharides, facilitating the structure-activity relationship exploration and biomedical applications of bacterial glycans. L-Galactosaminuronic acid is a rare sugar that has been only found in cell surface glycans of gram-negative bacteria. Here, an orthogonally protected L-galactosaminuronic acid building block was designed and chemically synthesized. A synthetic strategy based on glycal addition and TEMPO/BAIB-mediated C6 oxidation served well for the transformation of commercial L-galactose to the corresponding L-galactosaminuronic acid. Notably, the C6 oxidation of the allyl glycoside was more efficient than that of the selenoglycoside. In addition, a balance between the formation of allyl glycoside and the recovery of selenoglycoside was essential to improve efficiency of the NIS/TfOH-catalyzed allylation. This synthetically useful L-galactosaminuronic acid building block will provide a basis for the syntheses of complex bacterial glycans.
