Figure 2: Synthetic routes. Reagents and conditions: (a) (CH3CO)2O, Py, reflux 4 h; (b) DCC, Py, reflux, 80°C, 4 h. (c) ClCH2COCl, NaHCO3, EA, r.t., 0.5 h; (d) K2CO3, KI, DMF, 24 h. (e) CCl4/Et3N, C2H5OH, 24 h. (f) K2CO3, CH3CH2OH, reflux 24 h. (g) DCC, Py, reflux, 80°C, 4 h. (h) CH3OH, 60°C, 1 h; (i) VO(acac)2, r.t., 0.5 h; (j) stand in air for a few days for crystallization. Parent compounds: R = OH, H; R′ = H, OCH3.