SYNTHESIS OF METHYL 4,6-O-BENZYLIDENE-2,3-DI-O-TOLUENE-p-SULPHONYL-𝛼-D-GLUCOPYRANOSIDE

• Place 40 ml of pure dry redistilled pyridine in a conical flask and add 14.9 g (0.066 mol) of toluene-p-sulphonyl chloride (1) with cooling. 

• Allow the yellow solution to stand for about half an hour at room termperature (2) before adding 8.5g (0.03 mol) of methyl 4,6-O-benzylidene-𝛼-D-glucopyranoside with shaking and cooling. 

• Leave the reaction mixture in the stoppered flask for five days at room temperature and then pour on to 75g of crushed ice. 

• Stir vigorously, extract the mixture of syrup and water with three 25 ml portions of dichloromethane and wash the combined extracts successively with cold dilute hydrochloric acid (2 m), water, saturated aqueous sodium hydrogen carbonate, and water, and then dry over magnesium sulphate. 

• Remove the dichloromethane by evaporation under reduced pressure and triturate the gummy residue with ether until solid. 

• Recrystallise from dichloromethane-ether to obtain the pure product, m.p. 152-154 °C, [𝛼]ᴅ²⁰ +11.8° (c1 in CHCl₃). The yield is 13.5g (75%).

Notes to keep in mind:

1.  The toluene-p-sulphonyl chloride may be purified by suggested procedure.

2.  In all sulphonylations performed in these laboratories this procedure of allowing the mixture of toluene-p-sulphonyl chloride in pyridine to stand for about half an hour before the addition of the material to be sulphonylated has been found to be beneficial.