Sulfuric Acid → methyl (1S,2S,3S,4R,5S)-2,3,4-tribenzyloxy-5-[3-[(4-benzyloxyphenyl)methyl]-4-chloro-phenyl]-6,8-dioxabicyclo[3.2.1]octane-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

To a solution of (1S,2S,3S,4R,5S)-2,3,4-tribenzyloxy-5-[3-[(4-benzyloxyphenyl)methyl]-4-chloro-phenyl]-6,8-dioxabicyclo[3.2.1]octane-1-carboxylic acid 25m (0.45 g, 0.57 mmol) in a methanol/tetrahydrofuran mixture (v/v=6/5, 22 mL) was added concentrated sulphuric acid (0.05 mL) at room temperature. The mixture was warmed up to 60° C. and stirred for 14 hours. The reaction mixture was adjusted with saturated aqueous sodium bicarbonate to pH 7 at room temperature and extracted with ethyl acetate (60 mL). The organic layer was washed with saturated brine (20 mL×2), dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo and the residue was purified by silica gel chromatography eluted with PE/EtOAc(v/v)=6/1 to give the title compound 25n as a pale yellow solid (0.38 g, 84.4%). The compound was characterized by the following spectroscopic data: 1H NMR (600 MHz, CDCl3) δ(ppm): 7.48 (m, 1H), 7.47 (m, 2H), 7.41 (m, 4H), 7.33 (m, 7H), 7.25 (m, 3H), 7.21 (m, 4H), 7.16 (m, 2H), 7.08 (m, 2H), 6.87 (m, 2H), 5.01 (s, 2H), 4.81-4.75 (m, 3H), 4.78 (m, 1H), 4.63 (d, 1H), 4.52 (d, 1H), 4.26 (d, 1H), 4.19 (m, 2H), 4.09 (m, 1H), 4.01 (m, 2H), 3.87 (m, 1H), 3.74 (d, 1H), 3.71 (s, 3H).

Provenance & Evidence