[27] - Bromodeoxy Sugars from Epoxides: Methyl 5-O-Acetyl-3-bromo-3-deoxy-α-d-arabinofuranoside, Methyl 5-O-Acetyl-2-bromo-2-deoxy-β-d-xylofuranoside, and Methyl 5-O-Acetyl-3-bromo-3-deoxy-β-d-arabinofuranoside

Add time:09/06/2019    Source:sciencedirect.com

Publisher SummaryThis chapter describes an effective method for the preparation of a sugar containing a secondary bromide. The method involves cleavage of a sugar epoxide by magnesium bromide. The predominant product is generally the one that is expected by analogy to the nucleophilic cleavage of epoxides by other reagents. Steric considerations appear to control the direction of cleavage. Thereby, methyl 5-O-acetyl-2,3-anhydro-α-d-lyxofuranoside gives only methyl 5-O-acetyl-3-bromo-3-deoxy-α-d-arabinofuranoside, whereas methyl 5-O-acetyl-2,3-anhydro-β-d-lyxofuranoside gives a mixture of methyl 5-O-acetyl-2-bromo-2-deoxy-β-d-xylofuranoside and methyl 5-O-acetyl-3-bromo-3-deoxy-β-d-arabinofuranoside, which can be separated by preparative gas–liquid chromatography (GLC). Characterization of the 3-bromo arabinosides is accomplished by acetylation to the 2,5-diacetates followed by hydrogenation to methyl 2,5-di-O-acetyl-3-deoxy-α(and β)-O-threo-pentofuranosides.

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