Addition of Pseudohalogens to Unsaturated Carbohydrates. V. Addition of Iodine Trifluoroacetate

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Abstract
Treatment of 5,6-dideoxy-1,2-O-isopropylidene-α-D-xylo-hex-5-enofuranose (1) with silver trifluoroacetate and iodine in acetonitrile gave 3,6-anhydro-5-deoxy-5-iodo-1,2-O-isopropylidene-α-D-gluco(and β-L-ido)furanose (2) and 5-deoxy-5-iodo-1,2-O-isopropylidene-6-O-trifluoroacetyl-α-D-gluco(and/or β-L-ido)furanose (3). Component 2 was converted into 3,6-anhydro-5-deoxy-1,2-O-isopropylidene-α-D-xylo-hexofuranose (5) by hydrogenation over Raney nickel, and component 3 was converted into 5-deoxy-1,2-O-isopropylidene-α-D-xylo-hexofuranose (6) by treatment with methanol, followed by hydrogenation. Treatment of 5,6-dideoxy-1,2-O-isopropylidene-3-O-trifluoroacetyl-α-D-xylo-hex-5-enofuranose (7) with silver trifluoroacétate and iodine in acetonitrile gave the addition product 8, but no 3,6-anhydro derivative; 8 was converted into the iodohydrin 4 by treatment with methanol. The preparation of the 5-deoxy derivative 6 by way of the iodohydrin 4 represents an overall anti-Markovnikov hydration of the olefin 1; the reactions described are a convenient alternative to the hydroboration–oxidation procedure for the preparation of 6.

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