Synthesis and X-ray crystallographic study of cyclobis-(1 → 2)-α-d-glucopyranosyl peracetate

Treatment of O-(3,4,6-tri-O-acetyl-2-O-benzyl-α-d-glucopyranosyl)-(1 → 2)-3,4,6-tri-O-acetyl-α-d-glucopyranosyl trichloroacetimidate with BF3 - Et2O gave a high yield of the peracetate of cyclobis-(1 → 2)-α-d-glucopyranosyl (6). Compound 6 crystallizes in the space group P21 [a = 6.888(2), b = 24.771(5), c = 9.105(2) Å, β = 111.49(2)°, Z = 2] and shows a high degree of symmetry. In 6 the two α-d-glucopyranosyl residues are in a slightly distorted chair conformation. The glucose moieties are interconnected by a 1,4-dioxane moiety which is in a boat conformation, with the anomeric carbon atoms in the bow positions.