Fig. 1

Synthesis, preparation and characterization of HACB. A Synthetic route of HACB. Reagents and conditions: (i) (1) H₂O, HCl, NaNO₂, 0–4 ℃; (2) Phenol, 0–4 ℃, 24 h. (ii) 1-Methylpyrrolidine, DMF, room temperature, 20 h. (iii) Tert-butoxide, DMF, nitrogen atmosphere, room temperature, 6 h. (iv) (1) HA, EDC, NHS, H₂O, room temperature, 0.5 h; (2) Nitrogen atmosphere, 40 ℃, 48 h. B ¹H NMR spectrum of compound c, HA and HACB: inset is a blown up of spectrum 5.5–8.2 ppm. C FT-IR spectrum of compound a, compound b, compound c, HA and HACB, from the bottom to the top