Reagents and conditions: (a)
Lawesson’s reagent, DME, room temperature, 12 h. (b) BrCH2COCOOEt, KHCO3, TFAA, 2,6-lutidine, DME, room temperature,
10 h. (c) LiOH, MeOH/H2O, room temperature, 8 h. (d) EDCI,
HOBt, i-Pr2NEt, DMF, room temperature,
12 h. (e) Grubbs’ second generation catalyst, toluene, reflux,
8 h. (f) TFA, Et3SiH, CH2Cl2, room
temperature, 2 h. (g) Et3N, TFAA, THF, room temperature,
2 h. (h) Et3N, MeOH, 50 °C, 12 h. (i) NH2OH·HCl, KOH, MeOH, room temperature, 2 h. (j) Zn, dry THF, reflux,
2 h. (k) Pd(OAc)2, PPh3, toluene, reflux, 8
h. (l) NaOH, MeOH/H2O, reflux, 1 h.