Acetic Anhydride → beta-D-Galactose pentaacetate

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The synthesis of compounds 26-31 are depicted in FIGS. 3A and 3B and are set forth in the examples hereinbelow. In this figure, the synthesis of compounds 26, 27, 28, and 36 parallels that of compounds 17, 18, 19, and 20 as set forth above and illustrated in FIG. 2. In this regard, benzyl 4,6-O-benzylidene-2-O-benzoyl-3-O-chloroacetyl-β-D-thiogalactopyranoside (compound 31) has been produced without the necessity of chromatography. D-Galactose pentaacetate 26 is produced by slurring D-galactose and about an equimolar amount (e.g., about 1.1 equivalents) of sodium acetate (NaOAc) in dichloroethane (DCE), heating to reflux and adding at least 5 equivalents of acetic anhydride (AcOAc) dropwise to the refluxing solution (about 80°-85° C.) and then maintaining the reaction system at this temperature for a sufficient period of time (about 16-32 hours) to result in formation of compound 26. This procedure optimizes the yield of β-D-galactose pentaacetate 26 and controls the exotherm of heretofore known procedures.

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