1
|
Damico A, Shrestha G, Das A, Stine KJ, Demchenko AV. SFox imidates as versatile glycosyl donors for chemical glycosylation. Org Biomol Chem 2024; 22:5214-5223. [PMID: 38867654 DOI: 10.1039/d4ob00679h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2024]
Abstract
Described herein is a continuation of our studies dedicated to the development of novel classes of leaving groups based on O- and S-imidates. The main focus of the study presented herein is the synthesis of novel 3,3-difluoro-3H-indol-2-ylthio (SFox) imidates and their application as glycosyl donors in chemical glycosylation. Being thioimidates, these compounds are more stable than O-imidates albeit much more reactive than conventional alkyl/arylthio glycosides. This study demonstrates that SFox imidates can be activated either with soft thiophilic reagents (N-iodosuccinimide or transition metal salts), typical for the activation of thioglycosides or thioimidates, or hard electrophilic reagents (protic or Lewis acids) common for the activation of O-imidates. Expectedly, complete β-selectivity was obtained from SFox donors equipped with 2-O-benzoyl group. Surprisingly, complete α-selectivity was obtained from 2-O-benzylated SFox imidates in all investigated cases.
Collapse
Affiliation(s)
- Alessandra Damico
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St Louis, Missouri, 63103, USA.
| | - Ganesh Shrestha
- Department of Chemistry and Biochemistry, University of Missouri - St Louis, One University Boulevard, St Louis, Missouri 63121, USA
| | - Anupama Das
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St Louis, Missouri, 63103, USA.
| | - Keith J Stine
- Department of Chemistry and Biochemistry, University of Missouri - St Louis, One University Boulevard, St Louis, Missouri 63121, USA
| | - Alexei V Demchenko
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St Louis, Missouri, 63103, USA.
- Department of Chemistry and Biochemistry, University of Missouri - St Louis, One University Boulevard, St Louis, Missouri 63121, USA
| |
Collapse
|
2
|
Forsythe N, Liu L, Kashiwagi GA, Demchenko AV. Activation of thioglycosides under mild alkylation conditions. Carbohydr Res 2023; 531:108872. [PMID: 37348387 PMCID: PMC10528260 DOI: 10.1016/j.carres.2023.108872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/08/2023] [Accepted: 06/09/2023] [Indexed: 06/24/2023]
Abstract
Reported herein is the development of a novel method for the activation of thioglycosides and thioimidates using benzyl trichloroacetimidate in the presence of catalytic triflic acid. Excellent yields have been achieved with reactive substrates, whereas efficiency of reactions with unreactive glycosyl donors and/or acceptors was modest.
Collapse
Affiliation(s)
- Nicholas Forsythe
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri, 63103, USA
| | - Leah Liu
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri, 63103, USA
| | - Gustavo A Kashiwagi
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri, 63103, USA
| | - Alexei V Demchenko
- Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, Missouri, 63103, USA.
| |
Collapse
|
3
|
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 PMCID: PMC9417321 DOI: 10.1021/acs.chemrev.2c00029] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [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.
Collapse
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
| |
Collapse
|
4
|
Chooppawa T, Janprasert P, Padungros P. One-Pot Synthesis of Glycosyl Chlorides from Thioglycosides Mediated by Bromodiethylsulfonium Salt as A Mild Oxidant. Synlett 2022. [DOI: 10.1055/a-1852-6889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Conventional synthesis of glycosyl chlorides from thioglycosides relies on the two sequential oxidation and chlorination. A one-pot synthesis of glycosyl chlorides is warranted as an alternative method. Herein, we report the one-pot synthesis of glycosyl chlorides from thioglycoside precursors. The transformation was mediated at low temperature by bromodiethylsulfonium bromopentachloroantimonate (BDSB) as a mild oxidant and n-Bu4NCl as an additive. The armed thioglycosides afforded the corresponding α-glycosyl chlorides in moderate to good yields under the optimized conditions. Low conversions and yields were obtained when the less reactive disarmed thioglycosides were used. Unexpectedly, BDSB-mediated oxidation of thioglycosides without the addition of n-Bu4NCl also afforded the α-glycosyl chlorides in moderate yields. We suggest a mechanism involving the transfer of chloride ions from the non-nucleophilic bromopentachloroantimonate (SbCl5Br) anion to the oxocarbenium ion.
Collapse
Affiliation(s)
- Tianchai Chooppawa
- Chemistry, Chulalongkorn University Faculty of Science, Bangkok, Thailand
| | | | - Panuwat Padungros
- Chemistry, Chulalongkorn University Faculty of Science, Bangkok, Thailand
| |
Collapse
|
5
|
Ramdular A, Woerpel KA. Diastereoselective Substitution Reactions of Acyclic β-Alkoxy Acetals via Electrostatically Stabilized Oxocarbenium Ion Intermediates. Org Lett 2022; 24:3217-3222. [PMID: 35446592 PMCID: PMC9817112 DOI: 10.1021/acs.orglett.2c01004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Substitution reactions of acyclic β-alkoxy acetals proceeded with generally high diastereoselectivities (>90:10) to form the anti product. Mechanistic experiments supplemented with computational studies suggest that, upon activation of the acetal, the resulting oxocarbenium ion is electrostatically stabilized by the β-alkoxy group. This stabilization defines the conformation of the reactive intermediate, which can be attacked preferentially from the more exposed face, leading to the observed products.
Collapse
Affiliation(s)
- Amanda Ramdular
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003 (USA)
| | - K. A. Woerpel
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003 (USA),Corresponding Author: K. A. Woerpel – Department of Chemistry, New York University, New York, New York 10003, United States;
| |
Collapse
|
6
|
Njeri DK, Pertuit CJ, Ragains JR. 1,2-cis-Selective glucosylation enabled by halogenated benzyl protecting groups. Org Biomol Chem 2020; 18:2405-2409. [PMID: 32195525 DOI: 10.1039/d0ob00373e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report on our initial results from a systematic effort to implement electron-withdrawing protecting groups and Lewis basic solvents/additives as an approach to 1,2-cis(α)-selective O-glucosylation. 1,2-cis-Selective O-glucosylations are reported with thioglucosides and glucosyl trichloroacetimidates and a range of acceptors. A correlation between electron-withdrawing effects and 1,2-cis selectivity has been established. This phenomenon may prove to be broadly applicable in the area of chemical O-glycosylation.
Collapse
Affiliation(s)
- Dancan K Njeri
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Claude J Pertuit
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Justin R Ragains
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803, USA
| |
Collapse
|
7
|
Meng L, Wu P, Fang J, Xiao Y, Xiao X, Tu G, Ma X, Teng S, Zeng J, Wan Q. Glycosylation Enabled by Successive Rhodium(II) and Brønsted Acid Catalysis. J Am Chem Soc 2019; 141:11775-11780. [DOI: 10.1021/jacs.9b04619] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- 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
| | - Peng 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
| | - Jing Fang
- 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
| | - Ying Xiao
- 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
| | - Xiong Xiao
- 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
| | - Guangsheng Tu
- 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
| | - Xiang Ma
- 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
| | - Shuang Teng
- 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
| |
Collapse
|
8
|
Moons SJ, Mensink RA, Bruekers JPJ, Vercammen MLA, Jansen LM, Boltje TJ. α-Selective Glycosylation with β-Glycosyl Sulfonium Ions Prepared via Intramolecular Alkylation. J Org Chem 2019; 84:4486-4500. [PMID: 30808170 PMCID: PMC6454400 DOI: 10.1021/acs.joc.9b00022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Indexed: 02/07/2023]
Abstract
Stereoselective glycosylation remains the main challenge in the chemical synthesis of oligosaccharides. Herein we report a simple method to convert thioglycosides into β-sulfonium ions via an intramolecular alkylation reaction, leading to highly α-selective glycosylations for a variety of glycosyl acceptors. The influence of the thioglycoside substituent and the protecting group pattern on the glycosyl donor was investigated and showed a clear correlation with the observed stereoselectivity.
Collapse
Affiliation(s)
| | | | - Jeroen P. J. Bruekers
- Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
| | - Maurits L. A. Vercammen
- Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
| | - Laura M. Jansen
- Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
| | - Thomas J. Boltje
- Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, Nijmegen 6525 AJ, The Netherlands
| |
Collapse
|
9
|
Bradshaw GA, Colgan AC, Allen NP, Pongener I, Boland MB, Ortin Y, McGarrigle EM. Stereoselective organocatalyzed glycosylations - thiouracil, thioureas and monothiophthalimide act as Brønsted acid catalysts at low loadings. Chem Sci 2019; 10:508-514. [PMID: 30713648 PMCID: PMC6334493 DOI: 10.1039/c8sc02788a] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 10/15/2018] [Indexed: 01/21/2023] Open
Abstract
Thiouracil catalyzes stereoselective glycosylations with galactals in loadings as low as 0.1 mol%. It is proposed that in these glycosylations thiouracil, monothiophthalimide, and the previously reported catalyst, Schreiner's thiourea, do not operate via a double H-bonding mechanism but rather by Brønsted acid/base catalysis. In addition to the synthesis of 2-deoxyglycosides and glycoconjugates, we report the first organocatalytic synthesis of 1,1'-linked trehalose-type sugars.
Collapse
Affiliation(s)
- G A Bradshaw
- Centre for Synthesis & Chemical Biology , UCD School of Chemistry , University College Dublin , Belfield , Dublin 4 , Ireland .
| | - A C Colgan
- Centre for Synthesis & Chemical Biology , UCD School of Chemistry , University College Dublin , Belfield , Dublin 4 , Ireland .
| | - N P Allen
- Centre for Synthesis & Chemical Biology , UCD School of Chemistry , University College Dublin , Belfield , Dublin 4 , Ireland .
| | - I Pongener
- Centre for Synthesis & Chemical Biology , UCD School of Chemistry , University College Dublin , Belfield , Dublin 4 , Ireland .
| | - M B Boland
- Centre for Synthesis & Chemical Biology , UCD School of Chemistry , University College Dublin , Belfield , Dublin 4 , Ireland .
| | - Y Ortin
- Centre for Synthesis & Chemical Biology , UCD School of Chemistry , University College Dublin , Belfield , Dublin 4 , Ireland .
| | - E M McGarrigle
- Centre for Synthesis & Chemical Biology , UCD School of Chemistry , University College Dublin , Belfield , Dublin 4 , Ireland .
| |
Collapse
|
10
|
Panza M, Pistorio SG, Stine KJ, Demchenko AV. Automated Chemical Oligosaccharide Synthesis: Novel Approach to Traditional Challenges. Chem Rev 2018; 118:8105-8150. [PMID: 29953217 PMCID: PMC6522228 DOI: 10.1021/acs.chemrev.8b00051] [Citation(s) in RCA: 216] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Advances in carbohydrate chemistry have certainly made common oligosaccharides much more accessible. However, many current methods still rely heavily upon specialized knowledge of carbohydrate chemistry. The application of automated technologies to chemical and life science applications such as genomics and proteomics represents a vibrant field. These automated technologies also present opportunities for their application to organic synthesis, including that of the synthesis of oligosaccharides. However, application of automated methods to the synthesis of carbohydrates is an underdeveloped area as compared to other classes of biomolecules. The overarching goal of this review article is to present the advances that have been made at the interface of carbohydrate chemistry and automated technology.
Collapse
Affiliation(s)
- Matteo Panza
- Department of Chemistry and Biochemistry, University of Missouri–St. Louis, One University Boulevard, St. Louis, Missouri 63121, United States
| | - Salvatore G. Pistorio
- Department of Chemistry and Biochemistry, University of Missouri–St. Louis, One University Boulevard, St. Louis, Missouri 63121, United States
| | - Keith J. Stine
- 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
| |
Collapse
|
11
|
Kulkarni SS, Wang CC, Sabbavarapu NM, Podilapu AR, Liao PH, Hung SC. "One-Pot" Protection, Glycosylation, and Protection-Glycosylation Strategies of Carbohydrates. Chem Rev 2018; 118:8025-8104. [PMID: 29870239 DOI: 10.1021/acs.chemrev.8b00036] [Citation(s) in RCA: 207] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Carbohydrates, which are ubiquitously distributed throughout the three domains of life, play significant roles in a variety of vital biological processes. Access to unique and homogeneous carbohydrate materials is important to understand their physical properties, biological functions, and disease-related features. It is difficult to isolate carbohydrates in acceptable purity and amounts from natural sources. Therefore, complex saccharides with well-defined structures are often most conviently accessed through chemical syntheses. Two major hurdles, regioselective protection and stereoselective glycosylation, are faced by carbohydrate chemists in synthesizing these highly complicated molecules. Over the past few years, there has been a radical change in tackling these problems and speeding up the synthesis of oligosaccharides. This is largely due to the development of one-pot protection, one-pot glycosylation, and one-pot protection-glycosylation protocols and streamlined approaches to orthogonally protected building blocks, including those from rare sugars, that can be used in glycan coupling. In addition, new automated strategies for oligosaccharide syntheses have been reported not only for program-controlled assembly on solid support but also by the stepwise glycosylation in solution phase. As a result, various sugar molecules with highly complex, large structures could be successfully synthesized. To summarize these recent advances, this review describes the methodologies for one-pot protection and their one-pot glycosylation into the complex glycans and the chronological developments associated with automated syntheses of oligosaccharides.
Collapse
Affiliation(s)
- Suvarn S Kulkarni
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India
| | | | | | - Ananda Rao Podilapu
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India
| | - Pin-Hsuan Liao
- Institute of Chemistry , Academia Sinica , Taipei 115 , Taiwan
| | - Shang-Cheng Hung
- Genomics Research Center , Academia Sinica , Taipei 115 , Taiwan
| |
Collapse
|
12
|
Abstract
Previously, we communicated 3,3-difluoroxindole (HOFox)-mediated glycosylations wherein 3,3-difluoro-3H-indol-2-yl (OFox) imidates were found to be key intermediates. Both the in situ synthesis from the corresponding glycosyl bromides and activation of the OFox imidates could be conducted in a regenerative fashion. Herein, we extend this study to the synthesis of various glycosidic linkages using different sugar series. The main outcome of this study relates to enhanced yields and/or reduced reaction times of glycosylations. The effect of HOFox-mediated reactions is particularly pronounced in case of unreactive glycosyl donors and/or glycosyl acceptors. A multistep regenerative synthesis of oligosaccharides is also reported.
Collapse
Affiliation(s)
- Yashapal Singh
- Department of Chemistry and Biochemistry, University of Missouri—St. Louis, One University Boulevard, St. Louis, Missouri 63121, United States
| | - Tinghua Wang
- 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
| | - Keith J. Stine
- 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
| |
Collapse
|
13
|
Bols M, Pedersen CM. Silyl-protective groups influencing the reactivity and selectivity in glycosylations. Beilstein J Org Chem 2017; 13:93-105. [PMID: 28228850 PMCID: PMC5301963 DOI: 10.3762/bjoc.13.12] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 12/23/2016] [Indexed: 11/26/2022] Open
Abstract
Silyl groups such as TBDPS, TBDMS, TIPS or TMS are well-known and widely used alcohol protective groups in organic chemistry. Cyclic silylene protective groups are also becoming increasingly popular. In carbohydrate chemistry silyl protective groups have frequently been used primarily as an orthogonal protective group to the more commonly used acyl and benzyl protective groups. However, silyl protective groups have significantly different electronic and steric requirements than acyl and alkyl protective groups, which particularly becomes important when two or more neighboring alcohols are silyl protected. Within the last decade polysilylated glycosyl donors have been found to have unusual properties such as high (or low) reactivity or high stereoselectivity. This mini review will summarize these findings.
Collapse
Affiliation(s)
- Mikael Bols
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | | |
Collapse
|
14
|
Dewitte G, Walmagh M, Diricks M, Lepak A, Gutmann A, Nidetzky B, Desmet T. Screening of recombinant glycosyltransferases reveals the broad acceptor specificity of stevia UGT-76G1. J Biotechnol 2016; 233:49-55. [DOI: 10.1016/j.jbiotec.2016.06.034] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/21/2016] [Accepted: 06/30/2016] [Indexed: 12/23/2022]
|
15
|
Mensink RA, Elferink H, White PB, Pers N, Rutjes FPJT, Boltje TJ. A Study on Stereoselective Glycosylations via Sulfonium Ion Intermediates. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600898] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Rens A. Mensink
- Synthetic organic chemistry; Institute for Molecules and Materials; Heyendaalseweg 135 Nijmegen The Netherlands
| | - Hidde Elferink
- Synthetic organic chemistry; Institute for Molecules and Materials; Heyendaalseweg 135 Nijmegen The Netherlands
| | - Paul B. White
- Synthetic organic chemistry; Institute for Molecules and Materials; Heyendaalseweg 135 Nijmegen The Netherlands
| | - Nathalie Pers
- Synthetic organic chemistry; Institute for Molecules and Materials; Heyendaalseweg 135 Nijmegen The Netherlands
| | - Floris P. J. T. Rutjes
- Synthetic organic chemistry; Institute for Molecules and Materials; Heyendaalseweg 135 Nijmegen The Netherlands
| | - Thomas J. Boltje
- Synthetic organic chemistry; Institute for Molecules and Materials; Heyendaalseweg 135 Nijmegen The Netherlands
| |
Collapse
|
16
|
Smith R, Müller-Bunz H, Zhu X. Investigation of α-Thioglycoside Donors: Reactivity Studies toward Configuration-Controlled Orthogonal Activation in One-Pot Systems. Org Lett 2016; 18:3578-81. [PMID: 27399930 DOI: 10.1021/acs.orglett.6b01572] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The influence of anomeric configuration upon thioglycoside donors remains relatively unexplored. Utilizing methodology developed for the stereoselective and high-yielding synthesis of α-glycosyl thiols, a series of α-thioglycosides were synthesized, and their reactivity was compared to that of their β-counterparts. The highly selective activation observed for anomeric pairs containing a 2-O-acyl moiety and additional findings are reported. Application of a pair of "superarmed" thioglycosides to a one-pot oligosaccharide system is also described, in which selectivity is a result of configuration-based orthogonal activation.
Collapse
Affiliation(s)
- Raymond Smith
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin , Belfield, Dublin 4, Ireland
| | - Helge Müller-Bunz
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin , Belfield, Dublin 4, Ireland
| | - Xiangming Zhu
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin , Belfield, Dublin 4, Ireland
| |
Collapse
|
17
|
Goswami M, Ashley DC, Baik MH, Pohl NLB. Mechanistic Studies of Bismuth(V)-Mediated Thioglycoside Activation Reveal Differential Reactivity of Anomers. J Org Chem 2016; 81:5949-62. [PMID: 27295299 DOI: 10.1021/acs.joc.6b00860] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism of bismuth(V)-mediated thioglycoside activation was examined using reaction kinetics and quantum chemical reaction models. NMR experiments show an unusual nonlinear growth/decay curve for the glycosylation reaction. Further studies suggest an anomeric inversion of the β-glycoside donor to the α-donor during its activation, even in the presence of a neighboring 2-position acetate. Interestingly, in situ anomerization was not observed in the activation of an α-glycoside donor, and this anomer also showed faster reaction times and higher product diastereoselectivites. Density functional theory calculations identify the structure of the promoter triphenyl bismuth ditriflate, [Ph3Bi(OTf)2, 1], in solution and map out the energetics of its interactions with the two thioglycoside anomers. These calculations suggest that 1 must bind the thiopropyl arm to induce triflate loss. The computational analyses also show that, unlike most O-glycosides, the β- and α-donor S-glycosides are similar in energy. One energetically reasonable anomerization pathway of the donors is an SN1-like mechanism promoted by forming a bismuth-sulfonium adduct with the Lewis acidic Bi(V) for the formation of an oxacarbenium intermediate. Finally, the computed energy compensations needed to form these α vs β Bi adducts is a possible explanation for the differential reactivity of these donors.
Collapse
Affiliation(s)
- Manibarsha Goswami
- Department of Chemistry, Iowa State University , Ames, Iowa 50011, United States
| | - Daniel C Ashley
- Department of Chemistry, Indiana University , Bloomington, Indiana 47405, United States
| | - Mu-Hyun Baik
- Department of Chemistry, Indiana University , Bloomington, Indiana 47405, United States.,Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS) , Daejeon 305-701, Korea.,Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 305-701, Korea
| | - Nicola L B Pohl
- Department of Chemistry, Indiana University , Bloomington, Indiana 47405, United States.,Department of Chemical and Biological Engineering, Iowa State University , Ames, Iowa 50011, United States
| |
Collapse
|
18
|
Abstract
Anomeric sulfonium ions are attractive glycosyl donors for the stereoselective installation of 1,2-cis glycosides. Although these donors are receiving increasing attention, their mechanism of glycosylation remains controversial. We have investigated the reaction mechanism of glycosylation of a donor modified at C-2 with a (1S)-phenyl-2-(phenylsulfanyl)ethyl chiral auxiliary. Preactivation of this donor results in the formation of a bicyclic β-sulfonium ion that after addition of an alcohol undergoes 1,2-cis-glycosylation. To probe the importance of the thiophenyl moiety, analogs were prepared in which this moiety was replaced by an anisoyl or benzyl moiety. Furthermore, the auxiliaries were installed as S- and R-stereoisomers. It was found that the nature of the heteroatom and chirality of the auxiliary greatly influenced the anomeric outcome and only the one containing a thiophenyl moiety and having S-configuration gave consistently α-anomeric products. The sulfonium ions are sufficiently stable at a temperature at which glycosylations proceed indicating that they are viable glycosylation agents. Time-course NMR experiments with the latter donor showed that the initial rates of glycosylations increase with increases in acceptor concentration and the rate curves could be fitted to a second order rate equation. Collectively, these observations support a mechanism by which a sulfonium ion intermediate is formed as a trans-decalin ring system that can undergo glycosylation through a bimolecular mechanism. DFT calculations have provided further insight into the reaction path of glycosylation and indicate that initially a hydrogen-bonded complex is formed between sulfonium ion and acceptor that undergoes SN2-like glycosylation to give an α-anomeric product.
Collapse
Affiliation(s)
- Tao Fang
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602, United States
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Yi Gu
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602, United States
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Wei Huang
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602, United States
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Geert-Jan Boons
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602, United States
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States
- Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, and Bijvoet Center for Biomolecular Research, University of Utrecht, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| |
Collapse
|
19
|
Komarova BS, Tsvetkov YE, Nifantiev NE. Design of α-Selective Glycopyranosyl Donors Relying on Remote Anchimeric Assistance. CHEM REC 2016; 16:488-506. [PMID: 26785933 DOI: 10.1002/tcr.201500245] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Indexed: 11/08/2022]
Abstract
Oligosaccharides have a variety of versatile biological effects, but unlike peptides and oligonucleotides, investigation of the roles of oligosaccharides is not easy. Since biosynthesis of oligosaccharides does not comply with direct genetic control, their isolation from natural sources and biotechnological preparation are complicated, due to the heterogeneous composition of raw carbohydrates. Oligosaccharide synthesis is needed for the establishment or confirmation of the structure of natural glycocompounds. Also, synthetically prepared, defined oligosaccharides and their derivatives are becoming increasingly important tools for many biological and immunological research projects. The key step of oligosaccharide synthesis involves glycosylation, a reaction that builds glycosidic bonds. Usually, construction of 1,2-trans-bonds is easy, and therefore, this reaction can even be included into automated syntheses. At this time, installation of the 1,2-cis-bond remains simultaneously frustrating and compelling. In our and other laboratories, a strategy of α-selective (1,2-cis) glycosylation, relying on remote anchimeric assistance with acyl groups, is studied. The state of the art in this work is summarized in this review.
Collapse
Affiliation(s)
- Bozhena S Komarova
- Laboratory of Glycoconjugate Chemistry, N. D. Zelinsky Institute of Organic Chemistry Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| | - Yury E Tsvetkov
- Laboratory of Glycoconjugate Chemistry, N. D. Zelinsky Institute of Organic Chemistry Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| | - Nikolay E Nifantiev
- Laboratory of Glycoconjugate Chemistry, N. D. Zelinsky Institute of Organic Chemistry Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| |
Collapse
|
20
|
Frihed TG, Bols M, Pedersen CM. Mechanisms of Glycosylation Reactions Studied by Low-Temperature Nuclear Magnetic Resonance. Chem Rev 2015; 115:4963-5013. [DOI: 10.1021/cr500434x] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | - Mikael Bols
- Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | | |
Collapse
|
21
|
Yasomanee JP, Demchenko AV. Hydrogen-Bond-Mediated Aglycone Delivery (HAD): A Highly Stereoselective Synthesis of 1,2-cisα-D-Glucosides from Common Glycosyl Donors in the Presence of Bromine. Chemistry 2015; 21:6572-81. [DOI: 10.1002/chem.201406589] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2014] [Revised: 02/09/2015] [Indexed: 11/06/2022]
|
22
|
Mulani SK, Hung WC, Ingle AB, Shiau KS, Mong KKT. Modulating glycosylation with exogenous nucleophiles: an overview. Org Biomol Chem 2014; 12:1184-97. [PMID: 24382624 DOI: 10.1039/c3ob42129e] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The major challenge in carbohydrate synthesis is stereochemical control of glycosidic bond formation. Different glycosylation methods have been developed that are based on the modulation effect of external nucleophiles. This review highlights the development, synthetic application, challenges and outlook of the modulated glycosylation methods.
Collapse
Affiliation(s)
- Shaheen K Mulani
- Applied Chemistry Department, National Chiao Tung University, 1001, Ta Hsueh Road, Hsinchu, Taiwan.
| | | | | | | | | |
Collapse
|
23
|
Ranade SC, Demchenko AV. Glycosyl alkoxythioimidates as building blocks for glycosylation: a reactivity study. Carbohydr Res 2014; 403:115-22. [PMID: 25043398 DOI: 10.1016/j.carres.2014.06.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 06/16/2014] [Accepted: 06/22/2014] [Indexed: 12/13/2022]
Abstract
Structural modifications of the leaving group of S-glycosyl O-methyl phenylcarbamothioates (SNea) involving change of substituents that express different electronic effects led to a better understanding of how the reactivity of these glycosyl donors can be modified by changing the structure of their leaving groups. Mechanistic studies involving the isolation of departed aglycones were indicative of the direct activation of both p-methoxy-SNea and p-nitro-SNea leaving groups via the anomeric sulfur rather than the remote nitrogen atom. The presence of an electron donating substituent (p-methoxy) has a strong effect on the nucleophilicity of the sulfur atom that becomes more susceptible toward the attack of thiophilic reagents, in particular. This key observation allowed to differentiate the reactivity levels of p-methoxy-SNea versus p-nitro-SNea and even unmodified SNea leaving groups. The reactivity difference observed in the series of SNea leaving groups is sufficient to be exploited in expeditious oligosaccharide synthesis via selective activation strategies.
Collapse
Affiliation(s)
- Sneha C Ranade
- Department of Chemistry and Biochemistry, University of Missouri - St. Louis, St. Louis, MO 63121, USA
| | - Alexei V Demchenko
- Department of Chemistry and Biochemistry, University of Missouri - St. Louis, St. Louis, MO 63121, USA.
| |
Collapse
|
24
|
Affiliation(s)
- Hongwen He
- College
of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China
| | - Xiangming Zhu
- College
of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China
- Centre
for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical
Biology, University College Dublin, Belfield, Dublin 4, Ireland
| |
Collapse
|
25
|
Heuckendorff M, Premathilake HD, Pornsuriyasak P, Madsen AØ, Pedersen CM, Bols M, Demchenko AV. Superarming of glycosyl donors by combined neighboring and conformational effects. Org Lett 2013; 15:4904-7. [PMID: 24006853 PMCID: PMC3823551 DOI: 10.1021/ol402371b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A novel glycosyl donor that combines the concepts of both conformational and electronic superarming has been synthesized. The reactivity and selectivity of the donor have been tested in competition experiments.
Collapse
Affiliation(s)
- Mads Heuckendorff
- Department of Chemistry, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Hemali D. Premathilake
- Department of Chemistry and Biochemistry, University of Missouri – St. Louis, One University Boulevard, St. Louis, MO 63121, USA
| | - Papapida Pornsuriyasak
- Department of Chemistry and Biochemistry, University of Missouri – St. Louis, One University Boulevard, St. Louis, MO 63121, USA
| | - Anders Ø. Madsen
- Department of Chemistry, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | | | - Mikael Bols
- Department of Chemistry, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Alexei V. Demchenko
- Department of Chemistry and Biochemistry, University of Missouri – St. Louis, One University Boulevard, St. Louis, MO 63121, USA
| |
Collapse
|
26
|
Chu AHA, Nguyen SH, Sisel JA, Minciunescu A, Bennett CS. Selective synthesis of 1,2-cis-α-glycosides without directing groups. Application to iterative oligosaccharide synthesis. Org Lett 2013; 15:2566-9. [PMID: 23646882 DOI: 10.1021/ol401095k] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A method for the highly selective synthesis of 1,2-cis-α-linked glycosides that does not require the use of the specialized protecting group patterns normally employed to control diastereoselectivity is described. Thioglycoside acceptors can be used, permitting iterative oligosaccharide synthesis. The approach eliminates the need for lengthy syntheses of monosaccharides possessing highly specialized and unconventional protecting group patterns.
Collapse
Affiliation(s)
- An-Hsiang Adam Chu
- Department of Chemistry, Tufts University , 62 Talbot Avenue, Medford, Massachusetts 02145, United States
| | | | | | | | | |
Collapse
|
27
|
Ranade SC, Demchenko AV. Mechanism of Chemical Glycosylation: Focus on the Mode of Activation and Departure of Anomeric Leaving Groups. J Carbohydr Chem 2013. [DOI: 10.1080/07328303.2012.749264] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Sneha C. Ranade
- a Department of Chemistry and Biochemistry , University of Missouri , St. Louis , MO , 63121 , USA
| | - Alexei V. Demchenko
- a Department of Chemistry and Biochemistry , University of Missouri , St. Louis , MO , 63121 , USA
| |
Collapse
|
28
|
Walvoort MTC, van der Marel GA, Overkleeft HS, Codée JDC. On the reactivity and selectivity of donor glycosides in glycochemistry and glycobiology: trapped covalent intermediates. Chem Sci 2013. [DOI: 10.1039/c2sc21610h] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
29
|
Desmet T, Soetaert W, Bojarová P, Křen V, Dijkhuizen L, Eastwick-Field V, Schiller A. Enzymatic glycosylation of small molecules: challenging substrates require tailored catalysts. Chemistry 2012; 18:10786-801. [PMID: 22887462 DOI: 10.1002/chem.201103069] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Glycosylation can significantly improve the physicochemical and biological properties of small molecules like vitamins, antibiotics, flavors, and fragrances. The chemical synthesis of glycosides is, however, far from trivial and involves multistep routes that generate lots of waste. In this review, biocatalytic alternatives are presented that offer both stricter specificities and higher yields. The advantages and disadvantages of different enzyme classes are discussed and illustrated with a number of recent examples. Progress in the field of enzyme engineering and screening are expected to result in new applications of biocatalytic glycosylation reactions in various industrial sectors.
Collapse
Affiliation(s)
- Tom Desmet
- University of Ghent, Centre for Industrial Biotechnology and Biocatalysis, Gent, Belgium
| | | | | | | | | | | | | |
Collapse
|
30
|
Fang T, Mo KF, Boons GJ. Stereoselective assembly of complex oligosaccharides using anomeric sulfonium ions as glycosyl donors. J Am Chem Soc 2012; 134:7545-52. [PMID: 22475263 DOI: 10.1021/ja3018187] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The development of selectively protected monosaccharide building blocks that can reliably be glycosylated with a wide variety of acceptors is expected to make oligosaccharide synthesis a more routine operation. In particular, there is an urgent need for the development of modular building blocks that can readily be converted into glycosyl donors for glycosylations that give reliably high 1,2-cis-anomeric selectivity. We report here that 1,2-oxathiane ethers are stable under acidic, basic, and reductive conditions making it possible to conduct a wide range of protecting group manipulations and install selectively removable protecting groups such as levulinoyl (Lev) ester, fluorenylmethyloxy (Fmoc)- and allyloxy (Alloc)-carbonates, and 2-methyl naphthyl ethers (Nap). The 1,2-oxathiane ethers could easily be converted into bicyclic anomeric sulfonium ions by oxidization to sulfoxides and arylated with 1,3,5-trimethoxybenzene. The resulting sulfonium ions gave high 1,2-cis-anomeric selectivity when glycosylated with a wide variety of glycosyl acceptors including properly protected amino acids, primary and secondary sugar alcohols and partially protected thioglycosides. The selective protected 1,2-oxathianes were successfully employed in the preparation of a branched glucoside derived from a glycogen-like polysaccharide isolated form the fungus Pseudallescheria boydii , which is involved in fungal phagocytosis and activation of innate immune responses. The compound was assembled by a latent-active glycosylation strategy in which an oxathiane was employed as an acceptor in a glycosylation with a sulfoxide donor. The product of such a glycosylation was oxidized to a sulfoxide for a subsequent glycosylation. The use of Nap and Fmoc as temporary protecting groups made it possible to install branching points.
Collapse
Affiliation(s)
- Tao Fang
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, USA
| | | | | |
Collapse
|
31
|
Kumar R, Whitfield DM. Could Diastereoselectivity in the Presence of O-2 Chiral Nonparticipating Groups Be an Indicator of Glycopyranosyl Oxacarbenium Ions in Glycosylation Reactions? J Org Chem 2012; 77:3724-39. [DOI: 10.1021/jo202563f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Rishi Kumar
- National Research Council, Institute for Biological Sciences, 100 Sussex Drive, Ottawa, Ontario,
Canada K1A 0R6
| | - Dennis M. Whitfield
- National Research Council, Institute for Biological Sciences, 100 Sussex Drive, Ottawa, Ontario,
Canada K1A 0R6
| |
Collapse
|
32
|
Christina AE, Es DVD, Dinkelaar J, Overkleeft HS, Marel GAVD, Codée JDC. β-Rhamnosides from 6-thio mannosides. Chem Commun (Camb) 2012; 48:2686-8. [DOI: 10.1039/c2cc17623h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
33
|
Kaeothip S, Yasomanee JP, Demchenko AV. Glycosidation of thioglycosides in the presence of bromine: mechanism, reactivity, and stereoselectivity. J Org Chem 2011; 77:291-9. [PMID: 22136383 DOI: 10.1021/jo2019174] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Elaborating on previous studies by Lemieux for highly reactive "armed" bromides, we discovered that β-bromide of the superdisarmed (2-O-benzyl-3,4,6-tri-O-benzoyl) series can be directly obtained from the thioglycoside precursor. When this bromide is glycosidated, α-glycosides form exclusively; however, the yields of such transformations may be low due to the competing anomerization into α-bromide that is totally unreactive under the established reaction conditions.
Collapse
Affiliation(s)
- Sophon Kaeothip
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Boulevard, St. Louis, Missouri 63121, United States
| | | | | |
Collapse
|
34
|
Kaeothip S, Demchenko AV. On orthogonal and selective activation of glycosyl thioimidates and thioglycosides: application to oligosaccharide assembly. J Org Chem 2011; 76:7388-98. [PMID: 21797272 DOI: 10.1021/jo201117s] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Discrimination among S-thiazolinyl (STaz), S-benzoxazolyl (SBox), and S-ethyl anomeric leaving groups was achieved by fine-tuning activation conditions. Preferential glycosidation of a certain leaving group is determined neither by the strength of the activating reagent nor by the stability of the leaving group itself; instead, the type of activation plays the key role. The activation conditions established herein were applied to a sequential five-step synthesis of a hexasaccharide using six monosaccharide building blocks equipped with six different leaving groups.
Collapse
Affiliation(s)
- Sophon Kaeothip
- Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Boulevard, St. Louis, Missouri 63121, USA
| | | |
Collapse
|