Synthesis and anti-influenza virus activity of 7-O-alkylated derivatives related to zanamivir

A series of 7-alkyl ether derivatives related to zanamivir were synthesized using direct alkylation of the C-7 alcohol of sialic acid. Alkyl ether moiety of less than 12 carbons in length showed low nanomolar inhibitory activity against influenza A virus sialidase. Furthermore, their moiety improved influenza A virus plaque reduction activity compared to zanamivir. However, removal of the 8,9-diol of the 7-O-alkyl derivatives resulted in loss of antiviral potency. This result suggests that 8,9-diol must play an important role in binding with both influenza A and B virus sialidases.