Stereoselective Synthesis of Oligo-α-(2,8)-Sialic Acids

Abstract
An efficient and elegant synthesis of α(2,8)-oligosialosides is described. The 5-N,4-O-carbonyl-protected sialyl donor undergoes α-sialylation in CH2Cl2 to give α(2,8)- and α(2,9)-disialosides in excellent yields. The 5-N,4-O-carbonyl protecting group was effective in improving the reactivity of the C8 hydroxyl groups toward glycosylation. Using the sialyl building block, the synthesis of tetra-α(2,8)-sialic acid was accomplished by using a simple glycosidation and deprotection protocol.