Synthesis of 5-substituted analogues of 1a
aReagents and conditions: (a) (i) 6N HCl, reflux, 12 h; (ii) H2SO4, MeOH, reflux, 5 h; (b) KOH, DMSO, 35% H2O2, EtOH, 60 °C, 2 h; (c) Ni-Al, 85% formic acid, reflux, 3 h; (d) LiAlH4, THF, reflux, 2 h; (e) corresponding secondary amine, Na(OAc)3BH, dichloroethane, RT, 12 h. (f) (i) corresponding aldehyde, MeOH, RT, 12 h; (ii) NaBH4, 30 min; (g) HCHO, Na(OAc)3BH, dichloroethane, 12 h.