Synthesis and Photolysis of Sugar Nitrates. Trifluoromethanesulfonate (Triflate) Displacement by the Nitrate Anion

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Abstract
1,2:3,4-Di-O-isopropylidene-6-O-nitro-a-d-galacto-pyranose (13), 1,2:5,6-di-O-isopropylidene-3-O-nitro-ct-d-glucofuranose (14), 2,3:4,5-di-O-isopropylidene-l-O-nitro-β-d-fructopyranose (15), methyl 2,3-O-iso-propylidene-5-O-nitro-α-d-ribofuranoside (16), and 1,2:5,6-di-O-isopropylidene-3-O-nitro-α-d-allofuranose (17) were synthesized by reacting the appropriate triflates (1, 5, 3, 4, and 2, respectively) with tetra-butylammonium nitrate in refluxing benzene. These compounds (13-17) and 1,2:4,5-di-O-isopropylidene-3-O-nitro-β-d-fructopyranose (19) also were prepared by reacting the appropriate alcohols (7, 11, 9, 10, 8, and 12, respectively) with fuming nitric acid in acetic anhydride. The nitrates 13-16 and 19 were photolyzed in 2-propanol to give the corresponding deprotected alcohols. Photolysis of the nitrate 17, however, gave the C3 inverted alcohol 11. A mechanism is proposed for the deprotection and rearrangement of 17 upon irradiation.