Abstract
6,8-Dioxabicyclo[3•2•1]octane (2), obtained from acid-catalyzed cyclization of the NaBH4 reduction product of acrolein dimer, has been converted to 4-bromo-6,8-dioxabicyclo[3•2•1]octane 3. Epoxidation of the base-catalyzed dehydrohalogenated product of 3, 6,8-dioxabicyclo [3•2•1]oct-3-ene (4), gave stereoselectively 1,6:2,3-dianhydro-4-deoxy-β-DL-ribo-hexopyranose (5) contaminated with < 5% of the isomeric 1,6:2,3-dianhydro-4-deoxy-β-DL-lyxo-hexopyranose (6). Compound 5, with the contaminating 6, subjected to treatment with aqueous KOH, gave 1,6-anhydro-4-deoxy-β-DL-xylo-hexopyranose (7) whose di-p-nitrobenzoate (8) gave a 100 MHz nuclear magnetic resonance (n.m.r.) spectrum superimposable on that obtained from an authentic sample of 1,6-anhydro-4-deoxy-β-D-xylo-hexopyranose di-p-nitrobenzoate.A first order analysis of the n.m.r. spectrum of 5 showed that the anomeric proton was coupled to all other protons except H-4 exo. Long range coupling over five bonds, as well as over four bonds, is observed. Couplings between H-1 and H-6 or H-5 illustrate that such effects can be obtained when an oxygen atom replaces carbon as in the structural feature [Formula: see text].
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