Preparation of 2,3,6,2',3',4',6'-hepta-O-acetyl-maltose/cellobiose by enzymatic hydrolysis of maltose/cellobiose octaacetate.

Partially protected monosaccharides with free anomeric hydroxyl groups are useful in the synthesis of oligosaccharides [ l-31. A number of chemical methods are reported to remove the anomeric acyl group of peracylated carbohydrates [ 4-61, providing a useful route to partially protected saccharides [ 7,8]. Enzymatic reactions have also been used for this purpose [ 9-231. According to previous reports, primary acetyl esters in peracetylated sucrose are the most reactive sites for enzymatic hydrolysis [ 19-221, whereas the anomeric position in peracylated monosaccharides, including furanoses and pyranoses, is the most reactive site [ 231. Fink and Hay reported that maltose and cellobiose octaacetates ( 1 and 2) were hydrolyzed by wheat germ lipase with low regioselectivity and a mixture of products was obtained [ 91. In our work, compounds 1 and 2 were hydrolyzed by various hydrolytic enzymes exclusively at the anomeric position. More than ten enzymes were examined for the hydrolysis of 1 and 2; the results are listed in Tables 1 and 2. All enzymes tested preferentially cleaved the anomeric esters (Scheme 1). Among the enzymes, lipase AP-6 had the greatest rate of hydrolysis toward both substrates; protease II, protease N, and lipase N had moderate rates; lipase P, lipase AK, lipase GC, and lipase CE showed only a small rate. Lipase OF, lipase FAP-15, and alcalase had a moderate rate toward 1, but a small rate toward 2.