Synthesis and Reactivity of 4′-Deoxypentenosyl Disaccharides

• Published in: Journal of organic chemistry 2014-06, Vol.79 (11), p.4878-4891
• Main Authors: Padungros, Panuwat, Fan, Ren-Hua, Casselman, Matthew D, Cheng, Gang, Khatri, Hari R, Wei, Alexander
• Format: Article
• Language: English
• Subjects: Disaccharides - chemical synthesis; Disaccharides - chemistry; Epoxy Compounds - chemistry; Glycosylation; Oligosaccharides - chemical synthesis; Oligosaccharides - chemistry; Oxidation-Reduction; Stereoisomerism
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo500449h

4-Deoxypentenosides (4-DPs) are versatile synthons for rare or higher-order pyranosides, and they provide an entry for structural diversification at the C5 position. Previous studies have shown that 4-DPs undergo stereocontrolled DMDO oxidation; subsequent epoxide ring-openings with various nucleophiles can proceed with both anti or syn selectivity. Here, we report the synthesis of α- and β-linked 4′-deoxypentenosyl (4′-DP) disaccharides, and we investigate their post-glycosylational C5′ additions using the DMDO oxidation/ring-opening sequence. The α-linked 4′-DP disaccharides were synthesized by coupling thiophenyl 4-DP donors with glycosyl acceptors using BSP/Tf2O activation, whereas β-linked 4′-DP disaccharides were generated by the decarboxylative elimination of glucuronyl disaccharides under microwave conditions. Both α- and β-linked 4′-DP disaccharides could be epoxidized with high stereoselectivity using DMDO. In some cases, the α-epoxypentenosides could be successfully converted into terminal l-iduronic acids via the syn addition of 2-furylzinc bromide. These studies support a novel approach to oligosaccharide synthesis, in which the stereochemical configuration of the terminal 4′-DP unit is established at a post-glycosylative stage.