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Mukherji A, Rotta MKV, Sarmah BK, Kancharla PK. Influence of Various Silyl Protecting Groups on Stereoselective 2-Deoxyrhamnosylation. J Org Chem 2023; 88:245-260. [PMID: 36524596 DOI: 10.1021/acs.joc.2c02285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The influence of various silyl protecting groups on 2-deoxyrhamnosylation using 2-deoxyrhamnosyl acetates, thioglycosides, and (p-methoxyphenyl)vinylbenzoate (PMPVB) donors has been presented. C-Glycosylation reactions reveal that tert-butyldimethylsilyl (TBDMS), triisopropylsilyl (TIPS), and tert-butyldiphenylsilyl (TBDPS) silyl protected rhamnosyl oxocarbenium ions have no facial selectivity except for the conformationally (4H3) locked tetraisopropyldisiloxane (TIPDS) protected rhamnose donor, which provides complete α-selectivity. However, TBDPS protected rhamnosyl donors are found to be superior protecting groups for α-stereoselective O-glycosylation reactions with various acceptors. The observed results are found consistent across donors and donor activation conditions. Most importantly, the study was conducted at room temperature unlike the other energy-intensive low-temperature studies and was bound to have more practical utility. The outcomes have been explained using kinetic and thermodynamic analyses.
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Affiliation(s)
- Ananya Mukherji
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Mahendra K V Rotta
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Bikash K Sarmah
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Pavan K Kancharla
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
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Demkiw KM, Hu CT, Woerpel KA. Hyperconjugative Interactions of the Carbon-Halogen Bond that Influence the Geometry of Cyclic α-Haloacetals. J Org Chem 2022; 87:5315-5327. [PMID: 35363473 PMCID: PMC9036965 DOI: 10.1021/acs.joc.2c00148] [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
The analysis of the structures of low-energy conformers of different α-haloacetals reveals changes in bond lengths and geometries that correspond to stabilizing orbital interactions that contribute to the ground-state structures of these systems. Several factors, including the electron-donating and electron-accepting abilities of the substituents on the ring, affect the degree of the electronic interactions in these carbohydrate-like systems. The presence of an α-halogen atom that can participate in hyperconjugation has been shown to contribute to the structural characteristics of the low-energy conformer. The experimental evidence is supported by natural bond order (NBO) analysis to identify the types of interactions and to assess their relative importance.
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Affiliation(s)
- Krystyna M Demkiw
- Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States
| | - Chunhua T Hu
- Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States
| | - K A Woerpel
- Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States
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Addanki RB, Halder S, Kancharla PK. TfO -···H-O-H Interaction-Assisted Generation of a Silicon Cation from Allylsilanes: Access to Phenylallyl Ferrier Glycosides from Glycals. Org Lett 2022; 24:1465-1470. [PMID: 35142527 DOI: 10.1021/acs.orglett.2c00062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We demonstrate here that the strained and bulky protonated 2,4,6-tri-tert-butylpyridine (TTBPy) triflate salt serves as a mild and efficient organocatalyst for the diastereoselective C-Ferrier glycosylation of various glycals. The importance of the role of the 1/2 H2O molecule trapped in the catalyst has been disclosed. The mechanism of action involves unique anionic triflate and H2O hydrogen-bond interactions that assist the activation of allylsilanes, providing unprecedented access to diastereoselective phenylallyl Ferrier glycosides.
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Affiliation(s)
- Rupa Bai Addanki
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Suvendu Halder
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Pavan K Kancharla
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
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Javed, Tiwari A, Azeem Z, Mandal PK. 4,5-Dioxo-imidazolinium Cation-Promoted α-Selective Dehydrative Glycosylation of 2-Deoxy- and 2,6-Dideoxy Sugars. J Org Chem 2022; 87:3718-3729. [DOI: 10.1021/acs.joc.1c02650] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Javed
- Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute, BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, P.O. Box 173, Lucknow, 226031, India
| | - Ashwani Tiwari
- Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute, BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, P.O. Box 173, Lucknow, 226031, India
| | - Zanjila Azeem
- Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute, BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, P.O. Box 173, Lucknow, 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Pintu Kumar Mandal
- Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute, BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, P.O. Box 173, Lucknow, 226031, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Mukherji A, Addanki RB, Halder S, Kancharla PK. Sterically Strained Brønsted Pair Catalysis by Bulky Pyridinium Salts: Direct Stereoselective Synthesis of 2-Deoxy and 2,6-Dideoxy-β-thioglycosides from Glycals. J Org Chem 2021; 86:17226-17243. [PMID: 34794312 DOI: 10.1021/acs.joc.1c02305] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A sterically strained ionic Brønsted pair complex obtained from a sterically bulky base 2,4,6-tri-tert-butylpyridine and hydrochloric acid imbues unusual reactivity to the anionic chloride. The complete shielding of the cationic [N-H]+ by the bulky ortho-tert-butyl groups weakens the possible hydrogen-bonding interactions with the chloride anion, and the [N-H]+···Cl- distance is unusually longer (3.10 Å). This results in strained/frustrated electrostatic interactions between the ion-pair, thus infusing an increased reactivity in both of the ions, which results in the activation of a third molecule like thiol via hydrogen-bonding. This intriguing weak interaction-based reactivity has been utilized to develop an organocatalytic synthesis of 2-deoxy-β-thioglycosides from glycals. While the 1H NMR studies showcase the diamagnetic activation of thiols in the presence of the catalyst, the electron paramagnetic resonance (EPR) studies reveal the generation of a radical species that suggests a possible frustrated radical pair catalysis. Besides, IR spectroscopic studies explain the intriguing influence of size/charge density of the anion on the solvation-insusceptible, cationic [TTBPyH]+ and on the observed reactivity.
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Affiliation(s)
- Ananya Mukherji
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Rupa Bai Addanki
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Suvendu Halder
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Pavan K Kancharla
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
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Exploiting non-covalent interactions in selective carbohydrate synthesis. Nat Rev Chem 2021; 5:792-815. [PMID: 37117666 DOI: 10.1038/s41570-021-00324-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/10/2021] [Indexed: 02/08/2023]
Abstract
Non-covalent interactions (NCIs) are a vital component of biological bond-forming events, and have found important applications in multiple branches of chemistry. In recent years, the biomimetic exploitation of NCIs in challenging glycosidic bond formation and glycofunctionalizations has attracted significant interest across diverse communities of organic and carbohydrate chemists. This emerging theme is a major new direction in contemporary carbohydrate chemistry, and is rapidly gaining traction as a robust strategy to tackle long-standing issues such as anomeric and site selectivity. This Review thus seeks to provide a bird's-eye view of wide-ranging advances in harnessing NCIs within the broad field of synthetic carbohydrate chemistry. These include the exploitation of NCIs in non-covalent catalysed glycosylations, in non-covalent catalysed glycofunctionalizations, in aglycone delivery, in stabilization of intermediates and transition states, in the existence of intramolecular hydrogen bonding networks and in aggregation by hydrogen bonds. In addition, recent emerging opportunities in exploiting halogen bonding and other unconventional NCIs, such as CH-π, cation-π and cation-n interactions, in various aspects of carbohydrate chemistry are also examined.
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Zhao X, Wu B, Shu P, Meng L, Zeng J, Wan Q. Rhenium(V)-catalyzed synthesis of 1,1'-2-deoxy thioglycosides. Carbohydr Res 2021; 508:108415. [PMID: 34358864 DOI: 10.1016/j.carres.2021.108415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 07/17/2021] [Accepted: 07/27/2021] [Indexed: 11/29/2022]
Abstract
As stable glycomimetics, thioglycosides are important tools for the investigation of biological processes and discovery of new drugs. In this note, we report a ReOCl3(SMe2)(OPPh3) catalyzed coupling reaction between β-glycosyl thiols (1-thio sugars) and glycals for the preparation of 1,1'-α,β-2-deoxy thioglycosides, which are glycomimetics of natural trehalose and 2-deoxy glycosides. Furthermore, an S-linked trisaccharide was successfully obtained by successive employment of the Re(V) catalyzed thioglycosylation protocol.
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Affiliation(s)
- Xiang Zhao
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, Hubei, 430030, China
| | - Bin Wu
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, Hubei, 430030, China
| | - Penghua Shu
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, Hubei, 430030, China
| | - Lingkui Meng
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, Hubei, 430030, China
| | - Jing Zeng
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, Hubei, 430030, China
| | - Qian Wan
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, Hubei, 430030, China; Institute of Brain Research, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, Hubei, 430030, China.
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