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Cesium carbonate-mediated stereoselective anomeric -alkylation of a 2,3-oxazolidinone-protected d-mannosamine with sugar-derived primary or secondary alkyl triflates afforded the corresponding 2-amino-2-deoxy-β-d-mannosides in moderate to good yields and excellent stereoselectivity. The oxazolidinone ring can be opened with aqueous alkali hydroxide to liberate the amine functionality. This method has been successfully applied to the synthesis of the trisaccharide repeating unit of 19F polysaccharide.
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http://dx.doi.org/10.1021/acs.orglett.3c01564 | DOI Listing |
Beilstein J Org Chem
August 2025
Department of Natural Sciences and Sustainable Resources, Institute of Organic Chemistry, BOKU University, 1190 Vienna, Austria.
Nonreducing disaccharides are prevalent in non-mammalian glycans and glycolipids, serving as pivotal structural components in mycobacterial glycans, microbial oligosaccharide and nucleoside antibiotics, as well as biologically active mimetics of bacterial pathogen-associated molecular patterns (PAMPs). As integral components of PAMPs, 1,1'-linked disaccharide-containing biomolecules play important roles in host-pathogen interactions, cellular signaling, and pathogenesis. Accessing complex biomolecules containing nonreducing disaccharides is often hindered by difficulties in isolating them from natural sources, which can result in impure or degraded products, particularly when sensitive functional groups are involved.
View Article and Find Full Text PDFCarbohydr Res
October 2025
Department of Chemistry, Indian Institute of Technology Patna, Bihta, Bihar, 801106, India. Electronic address:
Herein, we report the stereoselective synthesis of 2,3-unsaturated α-O-aryl glycosides from disarmed glycals and challenging phenol as glycosyl acceptors using tris(pentafluorophenyl)borane (BCF) as an optimal catalyst. The optimized reaction conditions operate under metal-free conditions, affording the valuable 2,3-unsaturated-O-aryl glycosides in good to excellent yields with exclusive α-anomeric selectivity. The BCF catalyst not only activates the disarmed glycal donors but also enhances the nucleophilicity of electronically challenging phenol acceptors.
View Article and Find Full Text PDFJ Org Chem
July 2025
Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States.
Tetrahydropyran acetals bearing a fluorine atom adjacent to the acetal carbon atom can undergo highly stereoselective substitution reactions with nucleophilic alkenes to give the 1,2- products. By contrast, the chlorine- and bromine-substituted acetals give the 1,2- products. These results can be understood by considering oxocarbenium ion intermediates and their conformational preferences, which are dictated by hyperconjugative effects from axial substituents, with F ≪ H < Cl < Br.
View Article and Find Full Text PDFStereoselective glycosidation of 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) has emerged as a focal point in glycoscience, attributed to the burgeoning identification of naturally occurring α- or β-Kdo glycosides within the glycoconjugate structures of various organisms. Nonetheless, advancements in α-/β-switchable stereoselective Kdo -glycosidation remain scarce due to the complicated synthesis of Kdo donors and the complex chemical environment at the anomeric carbon of Kdo. Herein, inspired by the property that the conditions of the photocatalytic reaction can be facilely controlled and mediated, we report an efficient photocatalytic Ir/Cu-catalysed Kdo -glycosidation for the stereoselective synthesis of both α- and β-Kdo -glycosides with the dual mediation of MeCN and (-Tol)SO.
View Article and Find Full Text PDFAcc Chem Res
July 2025
University College Dublin, UCD School of Chemistry, Belfield, Dublin 4, Ireland.
ConspectusDeriving inspiration from frontier catalytic paradigms has emerged as a major force to tackle long-standing stereoselectivity issues in carbohydrate synthesis. In particular, there is a strong momentum in the harnessing of and the use of in the functionalization of carbohydrate polyols.In this Account, we describe our pioneering contributions to advancing these two major directions.
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