N-(4-Nitrophenyl)oxamic Acid and Related N-Acylanilines Are Non-competitive Inhibitors of vibrio cholerae sialidase but do not inhibit trypanosoma cruzi or trypanosoma brucei trans-sialidases

N‐(4‐Nitrophenyl)oxamic acid 1, N‐(2‐fluoro‐4‐nitrophenyl)oxamic acid 7, N‐(4‐nitrophenyl)‐trifluoroacetamide 3, and N‐(2‐methoxy‐4‐nitrophenyl)trifluoroacetamide 9 are non‐competitive inhibitors of Vibrio cholerae sialidase with Ki‐values ranging from 2.66 to 5.18 · 10−4 M. These compounds, and the N‐acetylneuraminic‐acid analogues 11–13 do not inhibit the sialidase and trans‐sialidase activities from Trypanosoma cruzi; nor does N‐(4‐nitrophenyl)oxamic acid (1) inhibit the corresponding enzyme activities from T. brucei.