Scheme 12.a.
a Reagents and conditions: (a) Me2C(OMe)2, p-TsOH, CH2Cl2; (b) p-O2NPhSO3NHCO2Me, K2CO3, CH2Cl2; (c) Bu3SnH, AIBN, THF; (d) BF3·Et2O, THF, −78 °C to −30 °C; (e) AcOH, THF, H2O, 65 °C; (f) t-BuOOH, VO(acac)2, PhH, 60 °C; (g) BzONa (cat.), H2O, 100 °C; (h) Ac2O, DMAP, py; (i) Tf2O, DMAP, CH2Cl2, 5 °C; (j) MeONa, MeOH.
