摘要
A new approach for the synthesis of S-linked α(2→9) oligosialic acids was developed by using an asymmetric tert-butyl disulfide linkage as an anomeric thiol protecting group. Compared with conventional thiosialosides, the asymmetric disulfide sialosides can tolerate the conditions under which functional groups are modified without producing the undesired elimination and racemization products. In addition, the asymmetric tert-butyl disulfide protecting group can be efficiently removed to afford a thiol nucleophile at the a anomeric position without flipping the anomeric stereochemistry. By this strategy, the syntheses of a (2→9) tetra-, hexa-, and octasialic acids were achieved. Copyright © 2009 American Chemical Society.