Carbon Dioxide → 1-Chloro-4-(beta-glucopyranos-1-yl)-2-(4-hydroxybenzyl)-benzene

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Reaction Conditions

Reaction Steps

A solution of 4.0 g [4-(5-bromo-2-chloro-benzyl)-phenoxy]-tert-butyl-dimethyl-silane in 42 ml dry diethyl ether is cooled to −80° C. under argon. 11.6 ml of a 1.7 M solution of tert-butyllithium in pentane are slowly added dropwise to the cooled solution, and then the solution is stirred for 30 min at −80° C. This solution is then added dropwise through a transfer needle, which is cooled with dry ice, to a solution of 4.78 g 2,3,4,6-tetrakis-O-(trimethylsilyl)-D-glucopyranone in 38 ml diethyl ether chilled to −80° C. The resulting solution is stirred for 3 h at −78° C. Then a solution of 1.1 ml methanesulfonic acid in 35 ml of methanol is added and the solution is stirred for 16 h at ambient temperature. The solution is then neutralised with solid sodium hydrogen carbonate, ethyl acetate is added and the methanol is removed together with the ether. Aqueous sodium hydrogen carbonate solution is added to the remaining solution which is extracted four times with ethyl acetate. The organic phases are dried over sodium sulfate and evaporated down. The residue is dissolved in 30 ml acetonitrile and 30 ml dichloromethane and the solution is cooled to −10° C. After the addition of 4.4 ml triethylsilane 2.6 ml boron trifluoride etherate are added dropwise so that the temperature does not exceed −5° C. After the addition is complete the solution is stirred for another 5 h at −5 to −10° C. and then quenched by the addition of aqueous sodium hydrogen carbonate solution. The organic phase is separated off and the aqueous phase is extracted four times with ethyl acetate. The combined organic phase are dried over sodium sulfate, the solvent is removed and the residue is purified using silica gel. The product then obtained is an approx. 6:1 mixture of β/α which can be converted into the pure β-anomer by global acetylation of the hydroxy groups with acetic anhydride and pyridine in dichloromethane and recrystallising the product in ethanol. The product thus obtained is converted into the title compound by reacting in methanol with 4 M potassium hydroxide solution.

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