Ethanol → 2,3,4,6-Tetra-O-benzyl-1-O-carboxymethyl-mannopyranose

Participants

Reaction Conditions

Reaction Steps

A mixture that consists of 500.0 g (924.2 mmol) of 2,3,4,6-tetra-O-benzyl-mannopyranose and 50.00 g (147.1 mmol) of tetrabutylammonium hydrogen sulfate in 2500 ml of diethoxymethane is cooled to a temperature of 0° C. 121.77 g (217.0 mmol) of fine-powder potassium hydroxide is then added thereto, and it is stirred for 10 more minutes. At a temperature of between 0° C. and 5° C., 180.39 g (1608 mmol) of bromoacetic acid tert-butyl ester is added in drops within 30 minutes while being stirred vigorously. Stirring is continued for two hours at 0° C. It is then allowed to reach room temperature within two hours, 500 ml of absolute ethanol (denaturized with cyclohexane) is added thereto, and the solvent is largely distilled off at a bath temperature of 105° C. 1000 ml of ethanol (absolute, denaturized with cyclohexane) is now added thereto, and the solvent is largely distilled off again at a bath temperature of 105° C. 1000 ml of ethanol (absolute, denaturized with cyclohexane) is again added thereto, as well as 60.89 g (1085 mmol) of potassium hydroxide (as a powder) as well as 1000 ml of completely demineralized water. It is refluxed for 7 hours and then concentrated by evaporation to an oil that can still be stirred. After cooling to room temperature, the residue is extracted 3 times with 500 ml each of hexane. The aqueous phase is mixed with 500 ml of MTB and set at a pH of 2 while being stirred vigorously with 37% hydrochloric acid. The aqueous phase is then extracted twice with 1000 ml each of MTB. The organic phases are combined, dried and evaporated to the dry state in a rotary evaporator at a bath temperature of 50° C. and a pressure of 70 mbar. The residue is chromatographed on 1000 g of silica gel 60 (grain size 40-63 μm). As an eluant, 2700 ml of nhexane, 5400 ml of dichloromethane as well as 1500 ml of methanol are used. The product-containing fractions are combined and evaporated to the dry state in a vacuum.

Provenance & Evidence