Reaction of Methyl 2-O-Benzoyl-3-0-methyl-4,6-di-Omethylsulfonyl-/$-D-mannopyranoside (10) with Potassium Benzoate in Refluxing JV,jV-Dimethylformamide (10 hr). An N, N-dimethylformamide solution (10 ml) containing 10 (105 mg, O. 22 mmol) and potassium benzoate (250 mg, 1.56 mmol) was heated at reflux for 10 hr. The precipitate was filtered off and the filtrate was evaporated in vacuo. The residue was chromatographed on silica gel (30 g). Elution with 7:1 benzene-ethyl acetate gave two fractions. The first fraction (23 mg, 20%) was pure 4, whereas the second fraction (75 mg, 65%) was pure 6, the 6:4 ratio being 3.2:1.Methyl 3-O-Methyl-2-0-methylsulfonyl-¡8-D-galactopyranoside (12). To a methanolic solution (10 ml) of 7 (220 mg, 0.44 mmol), metallic sodium (55 mg, 2.30 mmol) was added and the reaction mixture was heated at 60°for 30 min. The solution was neutralized with acetic acid and the solvents were evaporated in vacuo. The residue was chromatographed on A1203 (12 g). Elution with benzene (20 ml), ethyl acetate (20 ml), and 1:1 ethyl acetatemethanol (40 ml) gave pure 12 (125 mg, 98%): mp 164-165°; [a]27D +3°(c 1.12, CHgOH); ir (CHC13) 3500 cm"1 (broad peak, OH); NMR (CDCls) S 3.37 and 3.28 (two s, 6, C-l and C-3 methoxy groups), 3.07 (s, 3, methyl from C-2 methylsulfonyl group).

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