Scheme 3. Preparation of 2-amino-5-carboxamide thiazole derivatives (19–21) on solid phase: reagents and conditions (a) 4-hydroxy-2-methoxybenzaldehyde, K2CO3, KI, 60 °C, 16 h. (b) NaBH(OAc)3, 1,2-dichloroethane, rt, 1.5 h. (c) DCM, rt, 19 h. (d) DMF, 80 °C, 12 h. (e) TEA, DMF, rt, 2–12 h. (f) 2 M NaOH, DMSO, 60 °C, 72 h (g) EDC HCl, HOBt, DMF, rt, 24 h. (h) TFA/DCM (1 : 2, v/v), rt, 12 h.
