Figure 2: Preparation of 3-allyl-Neu5Ac2en (5) and 3-(p-tolyl)allyl-Neu5Ac2en (6).
From: Novel sialic acid derivatives lock open the 150-loop of an influenza A virus group-1 sialidase
Reagents and conditions: (a) NBS, DMSO/H2O (2.5:1), −30 °C, 2 h (38% di-equatorial bromohydrin 8, 28% di-axial bromohydrin); (b) Bu3SnAll, AIBN, dry toluene, N2, 100 °C, 8 h (57%); (c) Ac2O, dry pyridine, DMAP, N2, room temperature, 16 h (95%); (d) AcCl, dry MeOH, dry DCM, 5 °C to room temperature, 48 h; (e) DBU, dry DCM, N2, room temperature, 8 h (91% over steps d and e, based on recovered starting material); (f) Grubbs' catalyst second generation, 4-methylstyrene, dry DCM, N2, 40 °C, 24 h (69%; 77% based on recovered starting material). (g) 1 M aq. NaOH, MeOH, 5 °C to room temperature, 12–16 h (5 and 6, 60%, based on recovered starting material, and 94%, respectively).
