Enantiospecific synthesis of shikimic acid from D-mannose: formation of a chiral cyclohexene by intramolecular olefination of a carbohydrate-derived intermediate

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Abstract
An enantiospecific synthesis of (–)-shikimic acid from D-mannose in an overall yield of 39% is described, in which the key step is an intramolecular Wadsworth–Emmons olefination reaction of a phosphonate. Nucleophilic displacement of triflate from benzyl 2,3-O-isopropylidene-5-O-trifluoro-methylsulphonyl-α-D-lyxofuranoside by the sodium salt of t-butyl dimethoxyphosphorylacetate provides a rare example of substitution at the C-5 position of a furanose derivative by a carbanion.