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 K_i-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.