4,6-O-Benzylidene-D-allal,1a, undergoes the Eschenmoser–Claisen rearrangement giving the unsaturated α-C-hex-2-enopyranoside,4(3,7-anhydro-6,7-O-benzylidene-4,5-dideoxy-D-lyxo-oct-4 -N,N-dimethyl amide) in 85% yield. The corresponding β-anomer13a(methyl 3,7-anhydro-6,7-O-benzylidene-4,5-dideoxy-D-ribo-oct-4- enonate) is prepared by reductive elimination of the β-C-glucopyranoside11. The latter is obtained as the sole product from 4,6-O-ethylidene-D-glucose in two steps involving Wittig addition of carboxymethylene followed by cyclization of the resulting α,β-unsaturated ester under thermodynamic conditions.