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0 °C

A mixture that consists of 54.1 g (100 mmol) of 2,3,4,6-tetra-O-benzyl-mannopyranose, 1.39 g (5 mmol) of tetrabutylammonium chloride and 15.2 g (110 mmol) of anhydrous potassium carbonate in 500 ml of diethoxymethane is cooled to 0° C. At 0° C., 30.12 g (200 mmol) of chloroacetic acid-tert-butyl ester is added in drops over 20 minutes while being stirred vigorously. It is stirred for one hour at 10° C. 250 ml of methyl-tert-butyl ether is added, the organic phase is separated, and the aqueous phase is extracted twice with 250 ml of water. The solvent of the combined organic phases is washed with water, dried on sodium sulfate, filtered off and distilled off in a vacuum. The residue is taken up in 500 ml of ethanol. 40 ml of 50% aqueous sodium hydroxide solution is added, and it is refluxed for 0.5 hour. It is cooled to 0° C., set at pH 8 with 10% aqueous hydrochloric acid, and then the solvent is distilled off (vacuum). The residue is taken up in 300 ml of water and 500 ml of ethyl acetate, and the pH of the aqueous phase is set at 2 while being stirred (10% aqueous hydrochloric acid). The organic phase is separated, and the aqueous phase is extracted once more with 200 ml of ethyl acetate. The combined organic phases are dried on magnesium sulfate, the solvent is distilled off in a vacuum, and the residue is chromatographed on silica gel (mobile solvent: dichloromethane/n=hexane/ethanol/acetic acid=20:5:3:0.5). The product-containing fractions are concentrated by evaporation, dissolved in 400 ml of ethyl acetate and shaken out three times with 200 ml of water. Then, the organic phase is separated and evaporated to the dry state in a vacuum.

1. stirringIt is stirred for one hour at 10° C
2. customthe organic phase is separated
3. extractionthe aqueous phase is extracted twice with 250 ml of water
4. washThe solvent of the combined organic phases is washed with water
5. customdried on sodium sulfate
6. filtrationfiltered off
7. distillationdistilled off in a vacuum
8. addition40 ml of 50% aqueous sodium hydroxide solution is added
9. temperatureit is refluxed for 0.5 hour
10. temperatureIt is cooled to 0° C.
11. distillationthe solvent is distilled off (vacuum)
12. stirringwhile being stirred (10% aqueous hydrochloric acid)
13. customThe organic phase is separated
14. extractionthe aqueous phase is extracted once more with 200 ml of ethyl acetate
15. customThe combined organic phases are dried on magnesium sulfate
16. distillationthe solvent is distilled off in a vacuum
17. customthe residue is chromatographed on silica gel (mobile solvent: dichloromethane/n=hexane/ethanol/acetic acid=20:5:3:0.5)
18. concentrationThe product-containing fractions are concentrated by evaporation
19. dissolutiondissolved in 400 ml of ethyl acetate
20. stirringshaken out three times with 200 ml of water
21. customThen, the organic phase is separated
22. customevaporated to the dry state in a vacuum