The title compound3, which is the first member of a new class of anhydroglycosides, was initially isolated from the methanolysis mixture of the pyranoid isomer1in about 1% yield. Improved yields of greater than 30 % of3are obtained by treating the main product of the aforementioned methanolysis, the dimethylacetal2, with a catalytic amount of p-toluenesulfonic acid in boiling xylene.3(C7H12O5) crystallizes from diisopropyl ether in the monoclinic space group P21 (Z=2) with a = 552.4(1), b = 685.2(1), c = 1052.9(3) pm, α = 90.0, β = 98.95(6) and Y = 90.0°. The structure was solved by X-ray crystal structure analysis using direct methods to R indices of 0.036 and 0.045, respectively, for 1180 independent reflections. The furanoid ring in3adopts a conformation intermediate between2T3(D) and E3(D) (puckering parameters: Q = 48.9 pm; Φ = 102.4°). The oxane ring adopts ana2Ca5(D) conformation, which is heavily distorted by flattening at C-6 (puckering parameters: Q = 64.2 pm; Φ = 58.1° and 0 = 159.5°). Orientation of the glycosidic methyl group is in accord with theexo-anomeric effect. The molecules of3are interchained in three dimensions by a system of hydrogen bonds.