Yan YL, Guo JR, Liang CF. Sequential Dy(OTf)
3 -Catalyzed Solvent-Free Per-O-Acetylation and Regioselective Anomeric De-O-Acetylation of Carbohydrates.
Chem Asian J 2017;
12:2471-2479. [PMID:
28688169 DOI:
10.1002/asia.201700867]
[Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 07/04/2017] [Indexed: 11/06/2022]
Abstract
Dysprosium(III) trifluoromethanesulfonate-catalyzed per-O-acetylation and regioselective anomeric de-O-acetylation of carbohydrates can be tuned by adjusting the reaction medium. In this study, the per-O-acetylation of unprotected sugars by using a near-stoichiometric amount of acetic anhydride under solvent-free conditions resulted in the exclusive formation of acetylated saccharides as anomeric mixtures, whereas anomeric de-O-acetylation in methanol resulted in a moderate-to-excellent yield. Reactions with various unprotected monosaccharides or disaccharides followed by a semi-one-pot sequential conversion into the corresponding acetylated glycosyl hemiacetal also resulted in high yields. Furthermore, the obtained hemiacetals could be successfully transformed into trichloroimidates after Dy(OTf)3 -catalyzed glycosylation.
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