Structural Variations of N‐Acetylneuraminic Acid, 10. Synthesis of 2,7‐, 2,8‐, and 2,9‐Dideoxy‐ and 2,4,7‐Trideoxy‐2,3‐didehydro‐N‐acetylneuraminic Acids and Their Behavior Towards Sialidase from Vibrio cholerae

Abstract The peracetylated methyl ester derivatives of 7‐deoxy‐Neu5Ac ( 2a ), 8‐deoxy‐Neu5Ac ( 3a , 9‐deoxy‐Neu5Ac ( 4a ), and 4,7‐dideoxy‐Neu5Ac ( 5a ) were transformed by trimethylsilyl trifluoromethanesulfonate into the corresponding 2‐deoxy‐2,3‐didehydro derivatives 2b–5b . As additional products, the 4,5‐oxazolino derivatives 6b–8b were formed. Hydrolysis of 2b–5b yielded the free acids 7‐deoxy‐Neu5Ac2en ( 2c ), 8‐deoxy‐Neu5Ac2en ( 3c ), 9‐deoxy‐Neu5Ac2en ( 4c ), and 4,7‐dideoxy‐Neu5Ac2en ( 5c ). They showed significantly different inhibitory influences on the hydrolysis of 4‐methylumbelliferyl‐α‐Neu5Ac by sialidase from Vibrio cholerae . The comparison of their evaluated α‐side profiles with that of Neu5Ac2en ( 1c ) enables a suitable explanation of their different inhibitory potencies.