Scheme 2. Synthesis of Compounds 14–17a.

a Reagents and conditions: (i) (CF3CO)2O, toluene, reflux, 4 h, 1 for 14, 2 for 15; (ii) KHCO3, MeOH, room temp. The definitions of X and Y are indicated in Chart 1.

a Reagents and conditions: (i) (CF3CO)2O, toluene, reflux, 4 h, 1 for 14, 2 for 15; (ii) KHCO3, MeOH, room temp. The definitions of X and Y are indicated in Chart 1.