Given the extreme complexity and diversity of carbohydrates,efficient approaches to the homogeneous oligosaccharide remain limited.Chemical synthesis represents one of the most reliable methods to access homogeneous s...Given the extreme complexity and diversity of carbohydrates,efficient approaches to the homogeneous oligosaccharide remain limited.Chemical synthesis represents one of the most reliable methods to access homogeneous samples,which mainly relies on the key glycosylation reaction.Consistent with enormous efforts to develop leaving groups for establishing robust glycosylation protocols,we herein disclose a structurally novel leaving group of 8-phenylethynyl-1-naphthoate that is able to enable efficient glycosylation reactions under the extremely mild condition of gold(I)-catalysis.Notably,the anomeric naphthoate possesses the unprecedent character of base-stability in sharp contrast to the conventional ester groups at anomeric position of carbohydrates,which endows high compatibility with a variety of chemical transformations.Furthermore,the present glycosylation protocol with 8-phenylethynyl-1-naphthoate as leaving group is able to realize minimally protected glycosylation processes.Mechanistic studies reveal a unique structure of 8-phenylethynyl-1-naphthoate that accounts for the reason for these characteristics.展开更多
Ubiquitous competition of stereospecific E2 elimination versus SN2 substitution is of central importance in chemical synthesis.Herein,we uncover how the nature of the leaving group affects the intrinsic competing dyna...Ubiquitous competition of stereospecific E2 elimination versus SN2 substitution is of central importance in chemical synthesis.Herein,we uncover how the nature of the leaving group affects the intrinsic competing dynamics that remains largely unknown as opposed to its role in reactivity.Results are presented for a prototype case of fluoride anion reacting with ethyl chloride,compared to reacting with ethyl iodide.Chemical dynamics simulations reproduce scattering signatures observed in experiments and reveal that the direct stripping/rebound mechanisms characterize the E2/S_(N)2 reactions,in line with their dynamic fingerprints identified.Quite similar structures and energetics are found for the Cl^(−)and I^(−)leaving halides,whereas the competing dynamics show markedly distinct features.A halogen-bonding attraction is found to be crucial that modifies the interaction potential in the entrance channel and essentially tunes the underlying atomistic behaviors causing a mechanistic shift.This work highlights the dynamical effects induced by a leaving group on the proceedings of baseinduced elimination and nucleophilic substitution,providing a unique insight into the reaction selectivity for complex chemical networks and environments.展开更多
基金the financial support from the National Natural Science Foundation of China(22007080)Zhongshan Science and Technology Bureau(CXTD2022012)+3 种基金Youth Innovation Promotion Association of CAS(2020258)grateful to Hi-Level New R&D Institute(2019B090904008)High-Level Innovative Research Institute(2021B0909050003)from Department of ScienceTechnology of Guangdong Province.Prof.Hongbin Zhang(Yunnan University)is appreciated for the assistance on this project.
文摘Given the extreme complexity and diversity of carbohydrates,efficient approaches to the homogeneous oligosaccharide remain limited.Chemical synthesis represents one of the most reliable methods to access homogeneous samples,which mainly relies on the key glycosylation reaction.Consistent with enormous efforts to develop leaving groups for establishing robust glycosylation protocols,we herein disclose a structurally novel leaving group of 8-phenylethynyl-1-naphthoate that is able to enable efficient glycosylation reactions under the extremely mild condition of gold(I)-catalysis.Notably,the anomeric naphthoate possesses the unprecedent character of base-stability in sharp contrast to the conventional ester groups at anomeric position of carbohydrates,which endows high compatibility with a variety of chemical transformations.Furthermore,the present glycosylation protocol with 8-phenylethynyl-1-naphthoate as leaving group is able to realize minimally protected glycosylation processes.Mechanistic studies reveal a unique structure of 8-phenylethynyl-1-naphthoate that accounts for the reason for these characteristics.
基金supported by the State Key Lab of Urban Water Resource and Environment of the Harbin Institute of Technology(No.ES202303)。
文摘Ubiquitous competition of stereospecific E2 elimination versus SN2 substitution is of central importance in chemical synthesis.Herein,we uncover how the nature of the leaving group affects the intrinsic competing dynamics that remains largely unknown as opposed to its role in reactivity.Results are presented for a prototype case of fluoride anion reacting with ethyl chloride,compared to reacting with ethyl iodide.Chemical dynamics simulations reproduce scattering signatures observed in experiments and reveal that the direct stripping/rebound mechanisms characterize the E2/S_(N)2 reactions,in line with their dynamic fingerprints identified.Quite similar structures and energetics are found for the Cl^(−)and I^(−)leaving halides,whereas the competing dynamics show markedly distinct features.A halogen-bonding attraction is found to be crucial that modifies the interaction potential in the entrance channel and essentially tunes the underlying atomistic behaviors causing a mechanistic shift.This work highlights the dynamical effects induced by a leaving group on the proceedings of baseinduced elimination and nucleophilic substitution,providing a unique insight into the reaction selectivity for complex chemical networks and environments.
