Scheme 3. Synthesis of daurinol (17). Reagents and conditions: (a) BnBr, K2CO3 and EtOH, 50 °C; (b) triethyl phosphonoacetate, NaH and THF, 0 °C; (c) n-BuLi and THF, −78 °C, then (CH2O)n, −78 °C to rt; (d) compound number 20, DCC, DMAP and THF, rt; (e) Ac2O, 140 °C; (f) DDQ and benzene, 80 °C; (g) H2, Pd/C and MeOH, rt.
