Figure 3. Synthesis of target compounds 2–19.

Reagents and conditions: (a) pyridine, dichloromethane, rt, 15 h (2–6, 8–12, 14–19); (b) NaHCO3, acetonitrile, rt, 22 h (7, 13).

Reagents and conditions: (a) pyridine, dichloromethane, rt, 15 h (2–6, 8–12, 14–19); (b) NaHCO3, acetonitrile, rt, 22 h (7, 13).