C-Glycofuranosides with an activated methylene group at C1 of the glycosyl residue are amenable to epimerisation via a retro-Michael–Michael addition sequence. Advantage is taken of this phenomenon by converting methyl 2,3-O-isopropylidene-β,D-ribo-octofuranosid-6-ulose (8) into the corresponding α,L-lyxo isomer (15) by treatment with base. Both 8 and 15 are then converted into the (−) and (+) enantiomers of methyl nonactate (14) respectively, in ~45 percent yield.