Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide thiodonors

Multiple fluorination of glycostructures has emerged as an attractive way of modulating their protein affinity, metabolic stability, and lipophilicity. Here we described the synthesis of a series of mono-, di- and trifluorinated N-acetyl-D-glucosamine and D-galactosamine analogs. The key intermediates were the corresponding multiply fluorinated glucosazide and galactosazide thiodonors prepared from deoxyfluorinated 1,6-anhydro-2-azido-β-D-hexopyranose precursors by ring-opening reaction with phenyltrimethylsilyl sulfide. Nucleophilic deoxyfluorination at C4 and C6 by reaction with DAST, thioglycoside hydrolysis and azide/acetamide transformation completed the synthesis.