1
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Alom NE, Rani N, Schlegel HB, Nguyen HM. Highly stereoselective synthesis of α-glycosylated carboxylic acids by phenanthroline catalysis. Org Chem Front 2024:d4qo00710g. [PMID: 39211000 PMCID: PMC11347974 DOI: 10.1039/d4qo00710g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 08/15/2024] [Indexed: 09/04/2024]
Abstract
Carbohydrate molecules with an α-glycosylated carboxylic acid motif provide access to biologically relevant chemical space but are difficult to synthesize with high selectivity. To address this challenge, we report a mild and operationally simple protocol to synthesize a wide range of functionally and structurally diverse α-glycosylated carboxylic acids in good yields with high diastereoselectivity. Although there is no apparent correlation between reaction conversion and pK a of carboxylic acids, we found that carboxylic acids with a pK a of 4-5 provide high selectivity while those of a pK a of 2.5 or lower do not. Our strategy utilizes readily available 2,9-dibutyl-1,10-phenanthroline as an effective nucleophilic catalyst to displace a bromide leaving group from an activated sugar electrophile in a nucleophilic substitution reaction, forming phenanthrolinium intermediates. The attack of the carboxylic acid takes place from the α-face of the more reactive intermediate, resulting in the formation of α-glycosylated carboxylic acid. Previous calculations suggested that the hydroxyl group participates in the hydrogen bond interaction with the basic C2-oxygen of a sugar moiety and serves as a nucleophile to attack the C1-anomeric center. In contrast, our computational studies reveal that the carbonyl oxygen of the carboxylic acid serves as a nucleophile, with the carboxylic acid-OH forming a hydrogen bond with the basic C2-oxygen of the sugar moiety. This strong hydrogen bond (1.65 Å) interaction increases the nucleophilicity of the carbonyl oxygen of carboxylic acid and plays a critical role in the selectivity-determining step. In contrast, when alcohol acts as a nucleophile, this scenario is not possible since the -OH group of the alcohol interacts with the C2-oxygen and attacks the C1-anomeric carbon of the sugar moiety. This is also reflected in alcohol-OH's weak hydrogen bond (1.95 Å) interaction with the C2-oxygen. The O(C2)-HO (carboxylic acid) angle was measured to be 171° while the O(C2)-HO (alcohol) angle at 122° deviates from linearity, resulting in weak hydrogen bonding.
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Affiliation(s)
- Nur-E Alom
- Department of Chemistry, Wayne State University Detroit Michigan 48202 USA
| | - Neha Rani
- Department of Chemistry, Wayne State University Detroit Michigan 48202 USA
| | | | - Hien M Nguyen
- Department of Chemistry, Wayne State University Detroit Michigan 48202 USA
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2
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Haisha S, Nguyen HM, Schlegel HB. Stereoselective glycosylation reactions with 2-deoxyglucose: a computational study of some catalysts. COMPUT THEOR CHEM 2023; 1224:114122. [PMID: 37214423 PMCID: PMC10195097 DOI: 10.1016/j.comptc.2023.114122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2023]
Abstract
2-Deoxy glycosides are important components of many oligosaccharides with antibiotic and anti-cancer activity, but their synthesis can be very challenging. Phenanthrolines and substituted pyridines promote stereoselective glycosylation of 1-bromo sugars via a double SN2 mechanism. Pyridine reacting with α-bromo, 2-deoxyglucose was chosen to model this reaction. The first step involves displacement of bromide by pyridine which can be rate limiting because bromide ion is poorly solvated in the non-polar solvents used for these reactions. We examined a series of small molecules to bind bromide and stabilize this transition state. Geometry optimization and vibrational frequencies were calculated using M06-2X/6-31+G(d,p) and SMD implicit solvation for diethyl ether. More accurate energies were obtained with M06-2X/aug-cc-pVTZ and implicit solvation. Urea, thiourea, guanidine and cyanoguanidine bind bromide more strongly than alkylamines, (NH2CH2CH2)nNH3-n. Compared to the uncatalyzed reaction, urea, thiourea and cyanoguanidine lower the free energy of the transition state by 3 kcal/mol while guanidine lowers the barrier by 2 kcal/mol.
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Affiliation(s)
- Spencer Haisha
- Department of Biology, Wayne State University, Detroit, Michigan 48202, United States
| | - Hien M Nguyen
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - H Bernhard Schlegel
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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3
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Li J, Nguyen HM. Phenanthroline Catalysis in Stereoselective 1,2- cis Glycosylations. Acc Chem Res 2022; 55:3738-3751. [PMID: 36448710 DOI: 10.1021/acs.accounts.2c00636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The National Research Council's report in 2012 recognized glycosidic bond forming (glycosylation) reactions as critical due to the central importance of carbohydrates to the glycosciences. This report emphasized the need for the development of reproducible and broadly applicable glycosylation technologies to facilitate the stereoselective synthesis of biomedically relevant glycan libraries for tool development and for research applications by nonspecialists. In response to this report with NIH Common Fund support, the publications of new catalytic diastereoselective glycosylation protocols, some with broad generality under mild conditions, have been recently reported by our group and others. These recent discoveries have also advanced the understanding of the glycosylation reaction mechanism involving the coupling of a sugar electrophile bearing a leaving group at its C1-anomeric center with an alcohol nucleophile. This glycosidic bond forming reaction can lead to a mixture of two stereoisomers that differ in the configuration of the anomeric center.In our group, we discovered that readily available phenanthroline, a rigid and planar organic compound with two fused pyridine rings, could be utilized as a nucleophilic catalyst to promote highly diastereoselective glycosylation of an alcohol nucleophile with a sugar bromide electrophile. The phenanthroline catalysis process allows access to a myriad of high yielding and diastereoselective 1,2-cis pyranosides and furanosides. This catalyst-controlled approach has been applied to the synthesis of a potential vaccine adjuvant α-glucan octasaccharide. For pyranosyl bromide electrophiles, an extensive mechanistic investigation illustrated that two phenanthrolinium ion intermediates, a 4C1 chair-liked equatorial-conformer and a B2,5 boat-like axial-conformer, are formed in a ratio of 2:1 (equatorial/axial). To obtain high levels of axial-1,2-cis selectivity, a Curtin-Hammett scenario was proposed wherein interconversion of the 4C1 equatorial-conformer and B2,5 axial-conformer is more rapid than nucleophilic addition. Hydroxyl attack takes place from the axial-face of the more reactive 4C1 chairlike equatorial intermediate to afford an axial-1,2-cis glycoside product. The phenanthroline catalysis system is applicable to a number of furanosyl bromide electrophiles to provide the challenging 1,2-cis substitution products in good yield and diastereoselectivity. NMR experiments and density-functional theory (DFT) calculations support an associative mechanism in which the rate-determining step takes place from an invertive displacement of the faster reacting furanosyl phenanthrolinium ion intermediate with an alcohol nucleophile. Overall, this work stands at the underdeveloped intersection of operationally simple conditions, catalysis, and stereocontrolled glycosidic bond formation, each of which represents an important theme in the preparation of biologically important oligosaccharides and glycopeptides for applications to human health and medicine.
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Affiliation(s)
- Jiayi Li
- Department of Chemistry, Wayne State University 5101 Cass Avenue, Detroit, Michigan 48202, United States
| | - Hien M Nguyen
- Department of Chemistry, Wayne State University 5101 Cass Avenue, Detroit, Michigan 48202, United States
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4
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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] [Key Words] [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)
| | - 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
| | - Yukishige Ito
- RIKEN Cluster for Pioneering Research, Saitama, Japan
- Graduate School of Science, Osaka University, Osaka, Japan
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5
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Li KJ, Bennett CS. New chemical processes to streamline carbohydrate synthesis. Curr Opin Chem Biol 2022; 70:102184. [PMID: 35863085 DOI: 10.1016/j.cbpa.2022.102184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/13/2022] [Accepted: 06/14/2022] [Indexed: 12/01/2022]
Abstract
Carbohydrates hold potential for the future of therapeutic development due to their important role in essential biological processes. However, it is still challenging to produce homogenous materials, especially for non-mammalian sugars that are considered rare. Recent developments in this field have focused on catalytic methods, including organometallic and organocatalytic approaches to regioselective functionalization. Many approaches to glycosylations also utilize catalysts, increasingly in combination with photoredox conditions, to achieve stereoselectivity. Additionally, there have been significant advancements in the automation of glycosylation to synthesize oligosaccharides in less time and with fewer manually conducted steps by the user.
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Affiliation(s)
- Karen J Li
- Department of Chemistry, Tufts University, 62 Talbot Ave. Medford, MA 02155, USA
| | - Clay S Bennett
- Department of Chemistry, Tufts University, 62 Talbot Ave. Medford, MA 02155, USA.
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6
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Mukherjee MM, Ghosh R, Hanover JA. Recent Advances in Stereoselective Chemical O-Glycosylation Reactions. Front Mol Biosci 2022; 9:896187. [PMID: 35775080 PMCID: PMC9237389 DOI: 10.3389/fmolb.2022.896187] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 04/21/2022] [Indexed: 12/26/2022] Open
Abstract
Carbohydrates involving glycoconjugates play a pivotal role in many life processes. Better understanding toward glycobiological events including the structure–function relationship of these biomolecules and for diagnostic and therapeutic purposes including tailor-made vaccine development and synthesis of structurally well-defined oligosaccharides (OS) become important. Efficient chemical glycosylation in high yield and stereoselectivity is however challenging and depends on the fine tuning of a protection profile to get matching glycosyl donor–acceptor reactivity along with proper use of other important external factors like catalyst, solvent, temperature, activator, and additive. So far, many glycosylation methods have been reported including several reviews also. In the present review, we will concentrate our discussion on the recent trend on α- and β-selective glycosylation reactions reported during the past decade.
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Affiliation(s)
- Mana Mohan Mukherjee
- Laboratory of Cell and Molecular Biology, NIDDK, National Institutes of Health, Bethesda, MD, United States
| | - Rina Ghosh
- Department of Chemistry, Jadavpur University, Kolkata, India
- *Correspondence: John A. Hanover, ; Rina Ghosh,
| | - John A. Hanover
- Laboratory of Cell and Molecular Biology, NIDDK, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: John A. Hanover, ; Rina Ghosh,
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7
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McMillan TF, Crich D. Influence of 3-Thio Substituents on Benzylidene-Directed Mannosylation. Isolation of a Bridged Pyridinium Ion and Effects of 3- O-Picolyl and 3- S-Picolyl Esters. European J Org Chem 2022; 2022:e202200320. [PMID: 36340645 PMCID: PMC9632450 DOI: 10.1002/ejoc.202200320] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Indexed: 08/08/2023]
Abstract
The influence on glycosyl selectivity of substituting oxygen for sulfur at the 3-position of 4,6-O-benzylidene-protected mannopyranosyl thioglycosides is reported and varies considerably according to the protecting group employed at the 3-position. The substitution of a thioether at the 3-position for the more usual 3-O-benzyl ether results in a significant loss of selectivity. The installation of a 3-S-picolinyl thioether results in a complex reaction mixture, from which a stable seven-membered bridged bicyclic pyridinium ion is isolated, while the corresponding 3-O-picolinyl ether affords a highly α-selective coupling reaction. A 3-O-picolyl ester provides excellent β-selectivity, while the analogous 3-S-picolyl thioester gives a highly α-selective reaction. The best β-selectivity is seen with a 3-deoxy-3-(2-pyridinyldisulfanyl) system. These observations are discussed in terms of the influence of the various substituents on the central glycosyl triflate - ion pair equilibrium.
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Affiliation(s)
- Timothy F McMillan
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, USA
- Department of Pharmaceutical and Biomedical Sciences, 250 West Green Street, Athens, GA 30602, USA
| | - David Crich
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202, USA
- Department of Pharmaceutical and Biomedical Sciences, 250 West Green Street, Athens, GA 30602, USA
- Department of Chemistry, University of Georgia, 1001 Cedar Street, Athens, GA 30602, USA
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
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8
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Xu H, Schaugaard RN, Li J, Schlegel HB, Nguyen HM. Stereoselective 1,2- cis Furanosylations Catalyzed by Phenanthroline. J Am Chem Soc 2022; 144:7441-7456. [PMID: 35413194 DOI: 10.1021/jacs.2c02063] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Stereoselective formation of the 1,2-cis furanosidic linkage, a motif of many biologically relevant oligosaccharides and polysaccharides, remains an important synthetic challenge. We herein report a new stereoselective 1,2-cis furanosylation method promoted by phenanthroline catalysts under mild and operationally simple conditions. NMR experiments and density functional theory calculations support an associative mechanism in which the rate-determining step occurs from an inverted displacement of the faster-reacting phenanthrolinium ion intermediate with an alcohol nucleophile. The phenanthroline catalysis system is applicable to a number of furanosyl bromide donors to provide the challenging 1,2-cis substitution products in good yield with high anomeric selectivities. While arabinofuranosyl bromide provides β-1,2-cis products, xylo- and ribofuranosyl bromides favor α-1,2-cis products.
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Affiliation(s)
- Hengfu Xu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Richard N Schaugaard
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Jiayi Li
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - H Bernhard Schlegel
- 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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9
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Zhang M, Chen HW, Liu QQ, Gao FT, Li YX, Hu XG, Yu CY. De Novo Synthesis of Orthogonally-Protected C2-Fluoro Digitoxoses and Cymaroses: Development and Application for the Synthesis of Fluorinated Digoxin. J Org Chem 2021; 87:1272-1284. [PMID: 34964642 DOI: 10.1021/acs.joc.1c02592] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Inspired by Roush's pioneering work on rare sugars, we have developed a scalable, stereoselective, de novo synthesis of orthogonally protected C2-fluoro digitoxose and cymarose, utilizing Sharpless kinetic resolution and organocatalytic fluorination as key steps. The utility of this strategy is demonstrated by the synthesis of a fluorinated analogue of digoxin, which indicates the fluorine on the sugar ring may have a significant impact on biological activity.
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Affiliation(s)
- Ming Zhang
- National Engineering Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, China.,Beijing National Laboratory for Molecular Science (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hong-Wei Chen
- National Engineering Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, China
| | - Qing-Quan Liu
- National Engineering Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, China
| | - Feng-Teng Gao
- National Engineering Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, China
| | - Yi-Xian Li
- Beijing National Laboratory for Molecular Science (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiang-Guo Hu
- National Engineering Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, China
| | - Chu-Yi Yu
- Beijing National Laboratory for Molecular Science (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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10
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Abstract
With a view to reducing the notorious complexity and irreproducibility of glycosylation reactions, 12 guidelines for the choice of concentration, temperature, and counterions are adumbrated.
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Affiliation(s)
- Peter R. Andreana
- Department of Chemistry
and Biochemistry and School of Green Chemistry and Engineering, University of Toledo, 2801 West Bancroft Street, Toledo, Ohio 43606, United States
| | - David Crich
- Department of Pharmaceutical and Biomedical
Sciences, University of Georgia, 250 West Green Street, Athens, Georgia 30602, United States
- Department
of Chemistry, University of Georgia, 140 Cedar Street, Athens, Georgia 30602, United States
- Complex
Carbohydrate Research Center, University
of Georgia, 315 Riverbend
Road, Athens, Georgia 30602, United States
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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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