1
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Hoard DJ, Sutar Y, Demchenko AV. Direct Synthesis of Glycosyl Chlorides from Thioglycosides. J Org Chem 2024; 89:6865-6876. [PMID: 38669055 DOI: 10.1021/acs.joc.4c00244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
Reported herein is a new method for the direct synthesis of glycosyl chlorides from thioglycosides using sulfuryl chloride at rt. A variety of thioglycosides and thioimidates could be used as substrates. Both acid- and base-sensitive protecting groups were found compatible with these reaction conditions. Preliminary investigation of the reaction mechanism indicates chlorination of the leaving group at the anomeric sulfur as the key step of the reaction.
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Affiliation(s)
- Daniel J Hoard
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri 63103, United States
| | - Yogesh Sutar
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri 63103, United States
| | - Alexei V Demchenko
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri 63103, United States
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2
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Demchenko AV, De Meo C. The 4K reaction. Carbohydr Res 2024; 538:109102. [PMID: 38569333 DOI: 10.1016/j.carres.2024.109102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Revised: 03/22/2024] [Accepted: 03/26/2024] [Indexed: 04/05/2024]
Abstract
The classical Koenigs-Knorr glycosidation of bromides or chlorides promoted with Ag2O or Ag2CO3 works only with reactive substrates (ideally both donor and acceptor). This reaction was found to be practically ineffective with unreactive donors such as per-O-benzoylated mannosyl bromide. Recently, it was discovered that the addition of catalytic (Lewis) acids to a silver salt-promoted reaction has a dramatic effect on the reaction rate and yield. A tentative mechanism for this cooperatively-catalyzed glycosylation reaction has been proposed, and the improved understanding of the reaction led to more efficient protocols and broader applications to a variety of glycosidic linkages. Since Ag2O-mediated activation was introduced by German chemists Koenigs and Knorr, and "cooperatively catalyzed" is Kooperativ Katalysiert in German, we refer to this new reaction as "the 4K reaction."
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Affiliation(s)
- Alexei V Demchenko
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri, 63103, United States.
| | - Cristina De Meo
- Department of Chemistry, Southern Illinois University Edwardsville, 1 Hairpin Dr., Edwardsville, IL, 62025, United States
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3
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Ishiwata A, Tanaka K, Ito Y, Cai H, Ding F. Recent Progress in 1,2- cis glycosylation for Glucan Synthesis. Molecules 2023; 28:5644. [PMID: 37570614 PMCID: PMC10420028 DOI: 10.3390/molecules28155644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 06/30/2023] [Accepted: 07/02/2023] [Indexed: 08/13/2023] Open
Abstract
Controlling the stereoselectivity of 1,2-cis glycosylation is one of the most challenging tasks in the chemical synthesis of glycans. There are various 1,2-cis glycosides in nature, such as α-glucoside and β-mannoside in glycoproteins, glycolipids, proteoglycans, microbial polysaccharides, and bioactive natural products. In the structure of polysaccharides such as α-glucan, 1,2-cis α-glucosides were found to be the major linkage between the glucopyranosides. Various regioisomeric linkages, 1→3, 1→4, and 1→6 for the backbone structure, and 1→2/3/4/6 for branching in the polysaccharide as well as in the oligosaccharides were identified. To achieve highly stereoselective 1,2-cis glycosylation, including α-glucosylation, a number of strategies using inter- and intra-molecular methodologies have been explored. Recently, Zn salt-mediated cis glycosylation has been developed and applied to the synthesis of various 1,2-cis linkages, such as α-glucoside and β-mannoside, via the 1,2-cis glycosylation pathway and β-galactoside 1,4/6-cis induction. Furthermore, the synthesis of various structures of α-glucans has been achieved using the recent progressive stereoselective 1,2-cis glycosylation reactions. In this review, recent advances in stereoselective 1,2-cis glycosylation, particularly focused on α-glucosylation, and their applications in the construction of linear and branched α-glucans are summarized.
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Affiliation(s)
| | - Katsunori Tanaka
- RIKEN, Cluster for Pioneering Research, Saitama 351-0198, Japan
- Department of Chemical Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8552, Japan
| | - Yukishige Ito
- RIKEN, Cluster for Pioneering Research, Saitama 351-0198, Japan
- Graduate School of Science, Osaka University, Osaka 560-0043, Japan
| | - Hui Cai
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China
| | - Feiqing Ding
- School of Pharmaceutical Sciences (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China
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4
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Shadrick M, Stine KJ, Demchenko AV. Expanding the scope of stereoselective α-galactosylation using glycosyl chlorides. Bioorg Med Chem 2022; 73:117031. [PMID: 36202065 PMCID: PMC9677435 DOI: 10.1016/j.bmc.2022.117031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/19/2022] [Accepted: 09/20/2022] [Indexed: 11/20/2022]
Abstract
Recently, we reported that silver(I) oxide mediated Koenigs-Knorr glycosylation reaction can be dramatically accelerated in the presence of catalytic acid additives. We have also investigated how well this reaction works in application to differentially protected galactosyl bromides. Reported herein is the stereoselective synthesis of α-galactosides with galactosyl chlorides as glycosyl donors. Chlorides are easily accessible, stable, and can be efficiently activated for glycosylation. In this application, the most favorable reactions conditions comprised cooperative Ag2SO4 and Bi(OTf)3 promoter system.
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Affiliation(s)
- Melanie Shadrick
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, MO 63103, USA; Department of Chemistry and Biochemistry, University of Missouri - St. Louis, One University Boulevard, St. Louis, MO 63121, USA
| | - Keith J Stine
- Department of Chemistry and Biochemistry, University of Missouri - St. Louis, One University Boulevard, St. Louis, MO 63121, USA
| | - Alexei V Demchenko
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, MO 63103, USA; Department of Chemistry and Biochemistry, University of Missouri - St. Louis, One University Boulevard, St. Louis, MO 63121, USA.
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5
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Li SJ, Fang Q, Huang YW, Luo YY, Mu XD, Li L, Yin XC, Yang JS. Chemical Synthesis of the Nonreducing Hexasaccharide Fragment of Axinelloside A Based on a Stepwise Glycosylation Approach. Org Lett 2022; 24:7088-7094. [PMID: 36169189 DOI: 10.1021/acs.orglett.2c02618] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An expedient synthesis of the nonreducing hexasaccharide fragment of axinelloside A has been completed via a linear stepwise glycosylation approach. Challenges involved in the synthesis include the highly stereoselective construction of five consecutive 1,2-cis-glycosidic linkages and the formation of a sterically crowded 2,3-disubstituted l-fucoside subunit. Protecting group-directing glycosylation strategies such as the remote participation effect of the benzoyl substituent and the stereocontrolling effect of the 4,6-O-benzylidene group were employed for the synthesis of the desired 1,2-cis-glycosidic linkages. Moreover, the 2,3-branched l-fucoside framework was established through a 3-O and then 2-O glycosylation sequence in which the 3-hydroxyl group of the core l-fucose unit was glycosylated first and then the 2-hydroxyl. The synthetic hexasaccharide is properly protected, so it can be employed as a precursor to synthesize its natural form.
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Affiliation(s)
- Su-Jia Li
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
| | - Qing Fang
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
| | - Ying-Wen Huang
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
| | - Yi-Yang Luo
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
| | - Xiao-Dong Mu
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
| | - Ling Li
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
| | - Xiao-Chen Yin
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
| | - Jin-Song Yang
- Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
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6
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Ishiwata A, Tanaka K, Ao J, Ding F, Ito Y. Recent advances in stereoselective 1,2-cis-O-glycosylations. Front Chem 2022; 10:972429. [PMID: 36059876 PMCID: PMC9437320 DOI: 10.3389/fchem.2022.972429] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Accepted: 07/08/2022] [Indexed: 02/03/2023] Open
Abstract
For the stereoselective assembly of bioactive glycans with various functions, 1,2-cis-O-glycosylation is one of the most essential issues in synthetic carbohydrate chemistry. The cis-configured O-glycosidic linkages to the substituents at two positions of the non-reducing side residue of the glycosides such as α-glucopyranoside, α-galactopyranoside, β-mannopyranoside, β-arabinofuranoside, and other rather rare glycosides are found in natural glycans, including glycoconjugate (glycoproteins, glycolipids, proteoglycans, and microbial polysaccharides) and glycoside natural products. The way to 1,2-trans isomers is well sophisticated by using the effect of neighboring group participation from the most effective and kinetically favored C-2 substituent such as an acyl group, although high stereoselective synthesis of 1,2-cis glycosides without formation of 1,2-trans isomers is far less straightforward. Although the key factors that control the stereoselectivity of glycosylation are largely understood since chemical glycosylation was considered to be one of the useful methods to obtain glycosidic linkages as the alternative way of isolation from natural sources, strictly controlled formation of these 1,2-cis glycosides is generally difficult. This minireview introduces some of the recent advances in the development of 1,2-cis selective glycosylations, including the quite recent developments in glycosyl donor modification, reaction conditions, and methods for activation of intermolecular glycosylation, including the bimodal glycosylation strategy for 1,2-cis and 1,2-trans glycosides, as well as intramolecular glycosylations, including recent applications of NAP-ether-mediated intramolecular aglycon delivery.
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Affiliation(s)
- Akihiro Ishiwata
- RIKEN Cluster for Pioneering Research, Saitama, Japan
- *Correspondence: Akihiro Ishiwata, ; Feiqing Ding, ; Yukishige Ito,
| | - Katsunori Tanaka
- RIKEN Cluster for Pioneering Research, Saitama, Japan
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo, Japan
| | - Jiaming Ao
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-Sen University, Shenzhen, China
| | - Feiqing Ding
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-Sen University, Shenzhen, China
- *Correspondence: Akihiro Ishiwata, ; Feiqing Ding, ; Yukishige Ito,
| | - Yukishige Ito
- RIKEN Cluster for Pioneering Research, Saitama, Japan
- Graduate School of Science, Osaka University, Osaka, Japan
- *Correspondence: Akihiro Ishiwata, ; Feiqing Ding, ; Yukishige Ito,
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7
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Li G, Luo Y, Mo J, Noguchi M, Jing J, Luo Z, Shoda SI, Ye XS. Hydrogen bond-assisted 1,2-cis O-glycosylation under mild hydrogenolytic conditions. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2022.107754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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8
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Singh Y, Geringer SA, Demchenko AV. Synthesis and Glycosidation of Anomeric Halides: Evolution from Early Studies to Modern Methods of the 21st Century. Chem Rev 2022; 122:11701-11758. [PMID: 35675037 DOI: 10.1021/acs.chemrev.2c00029] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Advances in synthetic carbohydrate chemistry have dramatically improved access to common glycans. However, many novel methods still fail to adequately address challenges associated with chemical glycosylation and glycan synthesis. Since a challenge of glycosylation has remained, scientists have been frequently returning to the traditional glycosyl donors. This review is dedicated to glycosyl halides that have played crucial roles in shaping the field of glycosciences and continue to pave the way toward our understanding of chemical glycosylation.
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Affiliation(s)
- Yashapal Singh
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Boulevard, St. Louis, Missouri 63121, United States
| | - Scott A Geringer
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Boulevard, St. Louis, Missouri 63121, United States
| | - Alexei V Demchenko
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Boulevard, St. Louis, Missouri 63121, United States.,Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, St. Louis, Missouri 63103, United States
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9
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Zhang Y, Hu Y, Liu S, He H, Sun R, Lu G, Xiao G. Total synthesis of Lentinus giganteus glycans with antitumor activities via stereoselective α-glycosylation and orthogonal one-pot glycosylation strategies. Chem Sci 2022; 13:7755-7764. [PMID: 35865907 PMCID: PMC9258330 DOI: 10.1039/d2sc02176e] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 05/26/2022] [Indexed: 12/23/2022] Open
Abstract
The accessibility to long, branched and complex glycans containing many 1,2-cis glycosidic linkages with precise structures remains a challenging task in chemical synthesis. Reported here is an efficient, stereoselective and orthogonal one-pot synthesis of a tetradecasaccharide and shorter sequences from Lentinus giganteus polysaccharides with antitumor activities. The synthetic strategy consists of: (1) newly developed merging reagent modulation and remote anchimeric assistance (RMRAA) α-(1→6)-galactosylation in a highly stereoselective manner, (2) DMF-modulated stereoselective α-(1→3)-glucosylation, (3) RMRAA stereoselective α-(1→6)-glucosylation, (4) several orthogonal one-pot glycosylations on the basis of N-phenyltrifluoroacetimidate (PTFAI) glycosylation, Yu glycosylation and ortho-(1-phenylvinyl)benzoate (PVB) glycosylation to streamline oligosaccharide synthesis, and (5) convergent [7 + 7] glycosylation for the final assembly of the target tetradecasaccharide. In particular, this new RMRAA α-galactosylation method has mild reaction conditions, broad substrate scopes and significantly shortened step counts for the heptasaccharide synthesis in comparison with 4,6-di-tert-butylsilyene (DTBS) directed α-galactosylation. Furthermore, DFT calculations shed light on the origins of remote anchimeric assistance effects (3,4-OBz > 3,4-OAc > 4-OBz > 3-OBz) of acyl groups.
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Affiliation(s)
- Yunqin Zhang
- State Key Laboratory of Phytochemistry and Plant Resources in West China Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Yanlei Hu
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University Jinan Shandong 250100 China
| | - Shanshan Liu
- State Key Laboratory of Phytochemistry and Plant Resources in West China Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Haiqing He
- State Key Laboratory of Phytochemistry and Plant Resources in West China Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Roujing Sun
- State Key Laboratory of Phytochemistry and Plant Resources in West China Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Gang Lu
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University Jinan Shandong 250100 China
| | - Guozhi Xiao
- State Key Laboratory of Phytochemistry and Plant Resources in West China Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
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10
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Lei J, Jiang Y, Xia Y, Fang Q, Duan S, Ruan Y, Yang J. Stereoselective Synthesis of a Tetrasaccharide Fragment from Rhamnogalacturonan
II
Side Chain A. CHINESE J CHEM 2022. [DOI: 10.1002/cjoc.202200177] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Jin‐Cai Lei
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant‐Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital Sichuan University Chengdu 610041 China
| | - Yuan‐Yuan Jiang
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant‐Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital Sichuan University Chengdu 610041 China
| | - Yi‐Fei Xia
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant‐Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital Sichuan University Chengdu 610041 China
| | - Qing Fang
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant‐Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital Sichuan University Chengdu 610041 China
| | - Shi‐Chao Duan
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant‐Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital Sichuan University Chengdu 610041 China
| | - Yu‐Xiong Ruan
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant‐Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital Sichuan University Chengdu 610041 China
| | - Jin‐Song Yang
- Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant‐Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital Sichuan University Chengdu 610041 China
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11
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Li J, Nguyen HM. A Mechanistic Probe into 1,2- cis Glycoside Formation Catalyzed by Phenanthroline and Further Expansion of Scope. Adv Synth Catal 2021; 363:4054-4066. [PMID: 35431716 PMCID: PMC9009828 DOI: 10.1002/adsc.202100639] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Indexed: 12/20/2022]
Abstract
Phenanthroline, a rigid and planar compound with two fused pyridine rings, has been used as a powerful ligand for metals and a binding agent for DNA/RNA. We discovered that phenanthroline could be used as a nucleophilic catalyst to efficiently access high yielding and diastereoselective α-1,2-cis glycosides through the coupling of hydroxyl acceptors with α-glycosyl bromide donors. We have conducted an extensive investigation into the reaction mechanism, wherein the two glycosyl phenanthrolinium ion intermediates, a 4C1 chair-liked β-conformer and a B2,5 boat-like α-conformer, have been detected in a ratio of 2:1 (β:α) using variable temperature NMR experiments. Furthermore, NMR studies illustrate that a hydrogen bonding is formed between the second nitrogen atom of phenanthroline and the C1-anomeric hydrogen of sugar moiety to stabilize the phenanthrolinium ion intermediates. To obtain high α-1,2-cis stereoselectivity, a Curtin-Hammett scenario was proposed wherein interconversion of the 4C1 chair-like β-conformer and B2,5 boat-like α-conformer is more rapid than nucleophilic addition. Hydroxyl attack takes place from the α-face of the more reactive 4C1 β-phenanthrolinium intermediate to give an α-anomeric product. The utility of the phenanthroline catalysis is expanded to sterically hindered hydroxyl nucleophiles and chemoselective coupling of an alkyl hydroxyl group in the presence of a free C1-hemiacetal. In addition, the phenanthroline-based catalyst has a pronounced effect on site-selective couplings of triol motifs and orthogonally activates the anomeric bromide leaving group over the anomeric fluoride and sulfide counterparts.
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Affiliation(s)
- Jiayi Li
- Department of Chemistry, Wayne State University, Detroit, Michigan, 48202, United States
| | - Hien M Nguyen
- Department of Chemistry, Wayne State University, Detroit, Michigan, 48202, United States
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12
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Abstract
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Polysaccharides are
Nature’s most abundant biomaterials
essential for plant cell wall construction and energy storage. Seemingly
minor structural differences result in entirely different functions:
cellulose, a β (1–4) linked glucose polymer, forms fibrils
that can support large trees, while amylose, an α (1–4)
linked glucose polymer forms soft hollow fibers used for energy storage.
A detailed understanding of polysaccharide structures requires pure
materials that cannot be isolated from natural sources. Automated
Glycan Assembly provides quick access to trans-linked
glycans analogues of cellulose, but the stereoselective installation
of multiple cis-glycosidic linkages present in amylose
has not been possible to date. Here, we identify thioglycoside building
blocks with different protecting group patterns that, in concert with
temperature and solvent control, achieve excellent stereoselectivity
during the synthesis of linear and branched α-glucan polymers
with up to 20 cis-glycosidic linkages. The molecules
prepared with the new method will serve as probes to understand the
biosynthesis and the structure of α-glucans.
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Affiliation(s)
- Yuntao Zhu
- Max Planck Institute for Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Martina Delbianco
- Max Planck Institute for Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
| | - Peter H Seeberger
- Max Planck Institute for Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany.,Institute for Chemistry and Biochemistry, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
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