Scheme 14. Synthetic protocol for the development of compounds (A) 29; (B) 30, 31, and 32; (C) 33. Reagents and conditions: (a) (i) Na, AcOEt, rt, (ii) conc. HCl, MeOH, rt, (iii) 4-chlorobenzaldehyde, NaOMe, MeOH, reflux; (b) K₂CO₃, DMF, 80 °C; (c) (i) H₂O₂, PhCH₂N⁺(CH₃)₃ OH⁻, Et₂O, 0 °C, (ii) cyclic amine, CH₃CN, and rt.