2-Deoxy-2,3-didehydro-N-acetylneuraminic acid analogs structurally modified by thiocarbamoylalkyl groups at the C-4 position: Synthesis and biological evaluation as inhibitors of human parainfluenza virus type 1.

4-O-Thiocarbamoylmethyl-Neu5Ac2en 3 has strong inhibitory activity toward human parainfluenza virus type 1 (hPIV-1) sialidase compared with the parent Neu5Ac2en 2. We synthesized analogs having thiocarbamoylethyl- 4 and thiocarbamoylpropyl group 5 at the C-4 position of 2. The inhibition degrees of 4 and 5 were weaker than that of thiocarbamoylmethyl analog 3, indicating a remarkable effect of the carbon chain length in thiocarbamoylalkyl groups at the C-4 position on inhibitory activities against hPIV-1 sialidase.