Effects of Trans -hydroxyl Groups in Alkaline Degradation of Glycosidic Bonds

The influence of ß-dihydroxyl groups in the alkaline hydrolysis of glucosidic bonds is examined. In deriva­ tives of ß-D-glucopyranosides, all hydroxyl groups are trans to each other, and the alkaline elimination of sub­ stituted methyl ethers in positions C-2 and C-4 can be explained, in part, by assistance from neighboring trans a-hydroxyls. The rate of degradation of ethyl 2-2-methyl-ß-D-glucopyranoside is two times slower than the corresponding 2-hydroxyl derivative, whereas the rate for ethyl 2-deoxy-D-glucopyranoside is 8 times slower in 2.5N NaOH at 170° C.