Bromide ion → 5-Allyloxypentyl 2-deoxy-2-phthalimido-beta-D-glucopyranoside

Participants

Reaction Conditions

Reaction Steps

A solution of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-D-glucopyranosyl bromide 230 (5.0 g, 10.0 mmol) in dichloromethane (5 mL) was added dropwise to a mixture of the alcohol 229 (1.33 mL, 10 mmol), silver trifluoromethanesulphonate (2.57 g, 10.0 mmol) and collidine (1.23 mL, 9.0 mmol) in dichloromethane (10 mL) at -70° C. After stirring for 3 hours at -70°, t.l.c. (2:1-toluene and ethyl acetate) indicated that the starting bromide and the reaction product had the same Rf. After addition of some triethylamine, the reaction mixture was diluted with dichloromethane and worked up as usual. The syrupy residue was chromatographed on silica gel using a 5:1 mixture of toluene and ethyl acetate providing compound 231 (4.0 g, 71%). 1H-n.m.r. (CDCl3): 5.80 (m, 2 H, --CH= and H-3), 5.36 (d, 1 H, J1,2 8.5 Hz, H-1), 5.18 (m, 3 H, =CH2 and H-4), 2.13, 2.06, 1.87 (3 s, 3 H each, 3 OAc), 1.40 (2 H) and 1.15 (m, 4 H): methylenes. A 0.2M solution of sodium methoxide in methanol (0.500 mL) was added dropwise to a solution of compound 231 (4.00 g, 7.1 mmol) in dry methanol (30 mL) cooled at 0° C. The mixture was stirred at 0° C. for 2 hours until t.l.c. (10:1-chloroform and methanol) indicated the disappearance of the starting material. The reaction mixture was de-ionized with Dowex 50 (H+ form, dry) at 0° C. Filtration and evaporation of the solvent left a residue which was purified by chromatography on silica gel using a 100:5 mixture of chloroform and methanol as eluant providing compound 232 (2.36 g, 76%). 1H-n.m.r. (CDCl3): 7.70 and 7.80 (m, 4 H, aromatics), 5.82 (m, 1 H, --CH=), 5.17 (m, 3 H, =CH2 and H-1), 1.38 and 1.10 (m, 6 H, methylenes); 13C-n.m.r. (CDCl3): 134.9 and 116.6 (ethylenics), 98.3 (C-1), 56.6 (C-2).

Provenance & Evidence