Stereoselective synthesis of 1,1-dialkyl-1-methoxymethyl glucosides (acetal-glucosides)

The synthesis is described of highly acid-sensitive, 1,1-dialkyl-1-methoxymethyl glucosides (acetal-glucosides) as potential anti-cancer prodrugs. Reaction of 2,3,4,6-tetra-O-acetyl-1-O-trimethylsilyl-beta-D-glucopyranose (4) severally with various aliphatic and alicyclic ketones and methyl trimethylsilyl ether, in the presence of catalytic amounts of trimethylsilyl trifluoromethanesulfonate, afforded the corresponding acetylated acetal-beta-glucosides, e.g., acetone gave 1-methoxy-1-methylethyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside (7a). Likewise the alpha-anomer (8a) of 7a was obtained from the alpha-anomer of 4. Deacetylation of the tetra-acetates then gave the acetal-alpha- and -beta-glucosides.