General procedure: 1,4-Diazabicyclo[2.2.2]octane (DABCO, 1.0 mole equivalent) was added to a suspension of (2R,3S,4S,5R,6S)-2-(hydroxymethyl)-6-(phenylthio)tetrahydro-2H-pyran-3,4,5-triol (10.0 g, 51.5 mmol) in acetic anhydride (1.2 mole equivalents/hydroxy group) The mixture was stirred at room temperature. The progress of the reaction was monitored by thin layer chromatography (TLC) and the eluent was ethyl acetate:hexane (2:3). Upon completion of the reaction, the mixture was poured into crushed ice and stirred for a few minutes to induce precipitation of (2R,3R,4S,5R,6R)-2-(acetyloxymethyl)-6-(phenylthio)tetrahydro-2H-pyran-3,4,5-triyltriacetate, while the DABCO was dissolved in water (as confirmed by TLC and iodine vapor color development). The product was separated by diafiltration and subsequently washed with ice water and dried. The resulting product was pure enough to be used directly in the subsequent reaction in a yield of 18.3 g in 98% yield. Analytically pure samples can be obtained by recrystallization from 95% ethanol. It should be noted that the temperature of the reaction mixture increases during the addition of DABCO and stirring. In experiments on the scale of 10-20 g, this phenomenon favors a significant increase in the reaction rate. However, for larger scale reactions (50-100g and above), it is recommended to add DABCO in batches to avoid overheating the reaction mixture.
