1,6-Anhydro-2-azido-4-O-benzyl-2,3-dideoxy-β-D-ribo-hexoyranose (see Example 13) (1.0 g), phthalic anhydride (0.74 g), triphenylphosphine (1.21 g) and tetrabutylammonium cyanide (0.1 g) were heated under reflux in a nitrogen atmosphere in benzene (50 ml) for 40 h. Methanol (10 ml) was then added and the solution was allowed to stand at room temperature for 15 days. The solution was then evaporated and the residue was chromatographed on silica gel to yield the title compound as a crystaline solid (0.2 g, 14%) from amongst a variety of products (t.l.c.evidence). Recrystallised from ethanol it had m.p. 135°-136° C., [α]D -28.4°; 13C-nmr data: 100.4 (C-1), 51.1 (C-2), 25.0 (C-3), 76.5 and 75.7 (C-4 and C-5), 67.4 (C-6), 70.4 (PhCH2O), 167.7 (C=0), 156.0 and 131.8 (q-aromatic), 134.0, 128.3, 127.6, 127.5 and 123.3 (aromatic).
