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Cai J, Yuan X, Kong Y, Hu Y, Li J, Jiang S, Dong C, Ding K. Chemical approaches for the stereocontrolled synthesis of 1,2-cis-β-D-rhamnosides. Chin J Nat Med 2023; 21:886-901. [PMID: 38143103 DOI: 10.1016/s1875-5364(23)60408-x] [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: 03/07/2023] [Indexed: 12/26/2023]
Abstract
In carbohydrate chemistry, the stereoselective synthesis of 1,2-cis-glycosides remains a formidable challenge. This complexity is comparable to the synthesis of 1,2-cis-β-D-mannosides, primarily due to the adverse anomeric and Δ-2 effects. Over the past decades, to attain β-stereoselectivity in D-rhamnosylation, researchers have devised numerous direct and indirect methodologies, including the hydrogen-bond-mediated aglycone delivery (HAD) method, the synthesis of β-D-mannoside paired with C6 deoxygenation, and the combined approach of 1,2-trans-glycosylation and C2 epimerization. This review elaborates on the advancements in β-D-rhamnosylation and its implications for the total synthesis of tiacumicin B and other physiologically relevant glycans.
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Affiliation(s)
- Juntao Cai
- Henan Polysaccharide Research Center, Henan Key Laboratory of Chinese Medicine for Polysaccharides and Drugs Research, Academy of Chinese Medical Sciences, Henan University of Chinese Medicine, Zhengzhou 450046, China.
| | - Xin Yuan
- Henan Polysaccharide Research Center, Henan Key Laboratory of Chinese Medicine for Polysaccharides and Drugs Research, Academy of Chinese Medical Sciences, Henan University of Chinese Medicine, Zhengzhou 450046, China
| | - Yuanfang Kong
- College of Pharmacy, Henan University of Chinese Medicine, Zhengzhou 450046, China
| | - Yulong Hu
- Henan Polysaccharide Research Center, Henan Key Laboratory of Chinese Medicine for Polysaccharides and Drugs Research, Academy of Chinese Medical Sciences, Henan University of Chinese Medicine, Zhengzhou 450046, China
| | - Jieming Li
- Henan Polysaccharide Research Center, Henan Key Laboratory of Chinese Medicine for Polysaccharides and Drugs Research, Academy of Chinese Medical Sciences, Henan University of Chinese Medicine, Zhengzhou 450046, China
| | - Shiqing Jiang
- Henan Polysaccharide Research Center, Henan Key Laboratory of Chinese Medicine for Polysaccharides and Drugs Research, Academy of Chinese Medical Sciences, Henan University of Chinese Medicine, Zhengzhou 450046, China; Department of Oncology, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou 450000, China.
| | - Chunhong Dong
- Henan Polysaccharide Research Center, Henan Key Laboratory of Chinese Medicine for Polysaccharides and Drugs Research, Academy of Chinese Medical Sciences, Henan University of Chinese Medicine, Zhengzhou 450046, China.
| | - Kan Ding
- Henan Polysaccharide Research Center, Henan Key Laboratory of Chinese Medicine for Polysaccharides and Drugs Research, Academy of Chinese Medical Sciences, Henan University of Chinese Medicine, Zhengzhou 450046, China; Carbohydrate-Based Drug Research Center, CAS Key Laboratory of Receptor Research, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
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Dorst KM, Widmalm G. NMR chemical shift prediction and structural elucidation of linker-containing oligo- and polysaccharides using the computer program CASPER. Carbohydr Res 2023; 533:108937. [PMID: 37734222 DOI: 10.1016/j.carres.2023.108937] [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: 08/02/2023] [Revised: 09/01/2023] [Accepted: 09/01/2023] [Indexed: 09/23/2023]
Abstract
Carbohydrate structures containing alkyl groups as aglycones are useful for investigating enzyme activity and glycan-protein interactions. Moreover, linker-containing oligosaccharides with a spacer group are commonly used to print glycan microarrays or to prepare protein-conjugates as vaccine candidates. The structural accuracy of these synthesized glycans are essential for interpretation of results from biological experiments in which the compounds have been used and NMR spectroscopy can unravel and confirm their structures. An approach for efficient 1H and 13C NMR chemical shift assignments employed a parallel NOAH-10 measurement followed by NMR spin-simulation to refine the 1H NMR chemical shifts, as exemplified for a disaccharide with an azidoethyl group as an aglycone, the NMR chemical shifts of which have been used to enhance the quality of CASPER (http://www.casper.organ.su.se/casper/). The CASPER program has been further developed to aid characterization of linker-containing oligo- and polysaccharides, either by chemical shift prediction for comparison to experimental NMR data or as structural investigation of synthesized glycans based on acquired unassigned NMR data. The ability of CASPER to elucidate structures of linker-containing oligosaccharides is demonstrated and comparisons to assigned or unassigned NMR data show the utility of CASPER in supporting a proposed oligosaccharide structure. Prediction of NMR chemical shifts of an oligosaccharide, corresponding to the repeating unit of an O-antigen polysaccharide, having a linker as an aglycone and a non-natural substituent derivative thereof are presented to exemplify the diversity of structures handled. Furthermore, NMR chemical shift predictions of synthesized polysaccharides, corresponding to bacterial polysaccharides, containing a linker are described showing that in addition to oligosaccharide structures also polysaccharide structures having an aglycone spacer group can be analyzed by CASPER.
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Affiliation(s)
- Kevin M Dorst
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden
| | - Göran Widmalm
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
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Frame NW, Allas MJ, Pequegnat B, Vinogradov E, Liao VCH, Al-Abdul-Wahid S, Arroyo L, Allen-Vercoe E, Lowary TL, Monteiro MA. Structure and synthesis of a vaccine and diagnostic target for Enterocloster bolteae, an autism-associated gut pathogen – Part II. Carbohydr Res 2023; 526:108805. [PMID: 37023666 DOI: 10.1016/j.carres.2023.108805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 03/25/2023] [Accepted: 03/29/2023] [Indexed: 04/03/2023]
Abstract
Enterocloster bolteae (formerly known as Clostridium bolteae) is a gastro-intestinal pathogenic bacterium often detected in the fecal microbiome of children in the autism spectrum. E. bolteae excretes metabolites that are thought to act as neurotoxins. This study is an update of our first E. bolteae investigation that discovered an immunogenic polysaccharide. Through a combination of chemical derivatizations/degradations, spectrometry and spectroscopy techniques, a polysaccharide composed of disaccharide repeating blocks comprised of 3-linked β-d-ribofuranose and 4-linked α-l-rhamnopyranose, [→3)-β-D-Ribf-(1 → 4)-α-L-Rhap-(1→]n, was identified. To confirm the structure, and to provide material for subsequent investigations, the chemical synthesis of a corresponding linker-equipped tetrasaccharide, β-D-Ribf-(1 → 4)-α-L-Rhap-(1 → 3)-β-D-Ribf-(1 → 4)-α-L-Rhap-(1→O(CH2)8N3, is also described. Research tools based on this immunogenic glycan structure can form the foundation for serotype classification, diagnostic/vaccine targets and clinical studies into the hypothesized role of E. bolteae in the onset/augmentation of autism related conditions in children.
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Affiliation(s)
- Nolan W Frame
- Department of Chemistry, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Mikel Jason Allas
- Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada; Institute of Biological Chemistry, Academia Sinica, Nangang, Taipei, 11529, Taiwan
| | - Brittany Pequegnat
- Department of Chemistry, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | | | - Victor C-H Liao
- Institute of Biological Chemistry, Academia Sinica, Nangang, Taipei, 11529, Taiwan
| | | | - Luis Arroyo
- Department of Clinical Studies, University of Guelph, N1G 2W1, Guelph, ON, Canada
| | - Emma Allen-Vercoe
- Department of Microbiology, University of Guelph, N1G 2W1, Guelph, ON, Canada
| | - Todd L Lowary
- Institute of Biological Chemistry, Academia Sinica, Nangang, Taipei, 11529, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, 106, Taiwan.
| | - Mario A Monteiro
- Department of Chemistry, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Abstract
Glycans, carbohydrate molecules in the realm of biology, are present as biomedically important glycoconjugates and a characteristic aspect is that their structures in many instances are branched. In determining the primary structure of a glycan, the sugar components including the absolute configuration and ring form, anomeric configuration, linkage(s), sequence, and substituents should be elucidated. Solution state NMR spectroscopy offers a unique opportunity to resolve all these aspects at atomic resolution. During the last two decades, advancement of both NMR experiments and spectrometer hardware have made it possible to unravel carbohydrate structure more efficiently. These developments applicable to glycans include, inter alia, NMR experiments that reduce spectral overlap, use selective excitations, record tilted projections of multidimensional spectra, acquire spectra by multiple receivers, utilize polarization by fast-pulsing techniques, concatenate pulse-sequence modules to acquire several spectra in a single measurement, acquire pure shift correlated spectra devoid of scalar couplings, employ stable isotope labeling to efficiently obtain homo- and/or heteronuclear correlations, as well as those that rely on dipolar cross-correlated interactions for sequential information. Refined computer programs for NMR spin simulation and chemical shift prediction aid the structural elucidation of glycans, which are notorious for their limited spectral dispersion. Hardware developments include cryogenically cold probes and dynamic nuclear polarization techniques, both resulting in enhanced sensitivity as well as ultrahigh field NMR spectrometers with a 1H NMR resonance frequency higher than 1 GHz, thus improving resolution of resonances. Taken together, the developments have made and will in the future make it possible to elucidate carbohydrate structure in great detail, thereby forming the basis for understanding of how glycans interact with other molecules.
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Affiliation(s)
- Carolina Fontana
- Departamento
de Química del Litoral, CENUR Litoral Norte, Universidad de la República, Paysandú 60000, Uruguay
| | - Göran Widmalm
- Department
of Organic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden,
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