Synthesis of trifluoromethylated analogues of β-l-fucofuranose and β-l-4,6-dideoxyxylohexopyranose

Efficient strategy to trifluoromethylated trans-disubstituted alkene 3 was developed starting from commercially available 4,4,4-trifluoro-3-oxo-butyric acid ethyl ester 12. 6-Deoxy-6,6,6-trifluorosugars 21 and 30 were synthesized from 3 in high stereoselectivity and in a straightforward fashion. The key steps were Sharpless AD reaction, regioselective ring opening of trifluoromethylated cyclic sulfate, Horner–Wadsworth–Emmons reaction and TEMPO oxidation. It was noteworthy that the oxidation of alcohols 20 and 29 followed by deprotection and acetylation gave the single isomer target molecules 21 and 30, respectively.