Boron trifluoride etherate → 2-Bromoethyl 2,3,6-tri-O-acetyl-4-O-{2,3,6-tri-O-acetyl-4-O-[2,3,4-tri-O-acetyl-6-O-(2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl)-alpha-D-glucopyranosyl]-alpha-D-glucopyranosyl]-beta-D-glucopyranoside

Participants

Reaction Steps

Compound 92 (12.54 g, 9.85 mmol) and 2-bromoethanol (2.5 g, 1.4 ml, 20 mmol) were dissolved in dichloromethane (50 ml). Borontrifluoride etherate (7.1 g, 6.3 ml, 50 mmol) was added dropwise at room temperature and the mixture was stirred until the reaction was finished (48 h, TLC: SiO2, ethyl acetate:isooctane 3:1). The mixture was washed (water, saturated sodium hydrogen carbonate), dried (Na2SO4) and evaporated. The residue (12.3 g) was chromatographed (SiO2, ethyl acetate:isooctane 3:2) to give 93 (4.95 g, 63% based on transformed 92 and unreacted 92 (5.05 g). Compound 93 had [α]D25 +109° (c 1.3, chloroform). 1H-NMR (CDCl3, Me4Si) δ 5.35, 5.28, 5.18 (3d, each 1H, J=3.8, 2.8 and 3.6 Hz, H1', H1", H1"'), 4.60 (d, 1H, J=7.9 Hz, H1), 3.42-3.49 (m, 2H, CH2 -Br). 13C-NMR (CDCl3, TMS) δ 170.6-169.3 (CO), 100.4 (Cl), 95.9, 95.7, 95.3 (Cl', Cl", Cl"'), 77.3. 75.0, 73.7, 72.7, 72.2, 71.9, 71.8, 70.7, 70.4, 70.1, 69.9, 69.8, 69.7, 69.4, 69.3, 68.9, 68.5, 68.4, 67.4, 63.0, 61.8, 29.9, 21.1-20.6.

Provenance & Evidence