Fig. 1. Cleavage of a higher-order ganglioside by Vibrio cholerae sialidase to give GM₁, the putative receptor for cholera toxin

Fig. 2. Structure of Vibrio cholerae sialidase. The central domain is the sialidase function and is flanked by lectin domains

Fig. 3. A view of 2-α-Neu5Ac modelled in the active site of Vibrio cholerae sialidase

Fig. 4. Important interactions between the active site residues of Vibrio cholerae sialidase and Neu5Ac2en 3

Fig. 5. Contour map showing the most favourable interactions (in magenta) at −7 kcal mol⁻¹ for the carboxyl group probe with 2-α-Neu5Ac modelled in the active site

Fig. 6. Contour map showing the most favourable interactions (in blue) at −11 kcal mol⁻¹ for the hydroxyl group probe with 2-α-Neu5Ac modelled in the active site

Fig. 7. Contour map showing the most favourable interactions (in yellow) at −4 kcal mol⁻¹ for the chloro probe with 2-α-Neu5Ac modelled in the active site

Fig. 8. Contour map showing the most favourable interactions (in blue) at −18 kcal mol⁻¹ for the amino group probe with 2-α-Neu5Ac modelled in the active site

Fig. 9. Contour map showing the most favourable interactions (in red) at −3 kcal mol⁻¹ for the methyl group probe with 2-α-Neu5Ac modelled in the active site

Scheme 1. Reagents and conditions: (a) Ba(OH)₂, H₂O, 90°C; (b) (i) Et₃N, THF, H₂O, rt; (ii) R′COOH, DCC, rt; (c) Et₃N, MeOH, R′COCl, −60°C

Table 1. The important conserved residues in the active site of Vibrio cholerae sialidase[17]

Table 2. Inhibition data against Vibrio cholerae sialidase for Neu5Ac2en and C-5-modified derivatives of Neu5Ac2en

Table 3. Inhibition data against Vibrio cholerae sialidase for Neu5Ac2en and N-haloacetyl-Neu2en derivatives; N-C(O)R-Neu2en[39]

Table 4. Inhibition data against Vibrio cholerae sialidase for Neu5Ac2en and C-5-modified derivatives with different acyl-group chain lengths; N-C(O)R-Neu2en[38]