Fluorocarbohydrates-XXVIII: Synthesis and characterisation of 2-deoxy-2-fluoro-derivatives of l-rhamnose and l-epirhamnose

Addition of CF₃OF to 3,4-di-O-acetyl-l-rhamnal gave four products separable by fractional crystallisation and column chromatography. The two principal products were in the epirhamnose series, i.e. trifluoromethyl 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-α-l-glucoside and 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-α-l-glucosyl fluoride. The lesser products were in the rhamnose series viz. trifluoromethyl 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-β-1-mannoside and 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-β-l-mannosyl fluoride. The structures were confirmed by ¹H and ¹⁹F NMR spectral measurements. Deacylation and acidic hydrolysis gave the free 2-deoxy-2-fluoro sugars of both series.