反应详情

L-glucose (−)-IV-12 (4.95 g, 27.4 mmol) was added acetic anhydride (25 mL) and HBr in acetic acid (5 mL, 33%) and stirred for 1 h until the solid dissolved. Another 25 mL of HBr in acetic acid was added and the reaction mixture stirred for 6 h. Concentration in vacuo with toluene and filtration through a silica gel plug (75% ether/hexanes) furnished pure bromo-α-L-glucopyranoside tetraacetate. The bromide was dissolved in ethyl acetate (140 mL), zinc (10.9 g, 166 mmol) added, and the mixture heated at reflux. N-methyl imidazole (2.21 mL, 27.7 mmol) was added in one portion and heating continued for 1 h. The mixture was concentrated in vacuo and purified by flash chromatography (33% ethyl acetate/hexane) to furnish (+)-IV-13 (5.89 g, 78% yield) as a clear oil: [α]D25 −24.04° (c 1.4, CHCl3); IR (CHCl3) 3010 (m), 1745 (s), 1655 (s), 1375 (s), 1230 (s), 1050 (s) cm−1; 1H NMR (500 MHz, CDCl3) s 6.48 (dd, J=6.2, 1.3 Hz, 1H), 5.36 (m, 1H), 5.24 (dd, J=7.6, 5.9 Hz, 1H), 4.86 (dd, J=6.2, 3.3 Hz, 1H), 4.41 (dd, J=12.1, 5.7 Hz, 1H), 4.27 (m, 1H), 4.21 (dd, J=12.1, 3.2 Hz, 1H), 2.11 (s, 3H), 2.09 (s, 3H), 2.06 (s, 3H); 13C NMR (125 MHz, CDCl3) s 170.5, 170.4, 169.5, 145.6, 99.0, 74.0, 67.4, 67.2, 61.4, 21.0, 20.8, 20.7; high resolution mass spectrum (Cl, NH3) m/z 290.1243 [(M+NH4)+; calcd for C12H16O7: 290.1239].

1. dissolutiondissolved
2. stirringthe reaction mixture stirred for 6 h
3. concentrationConcentration in vacuo
4. filtrationwith toluene and filtration through a silica gel plug (75% ether/hexanes)