aReagents and conditions: (a) n-BuLi, THF, −50 °C, then MeI; n-BuLi, −50 °C to rt, then (HCHO)n; (b) isobutyric acid, DCC, DMAP (10 mol %), CH2Cl2, rt; (c) LDA, THF, −78 °C, then TMSCl, −78 to 75 °C; (d) (i) TMSCHN2, MeOH/C7H8 (2:1), rt; (ii) MeLi, Et2O, 0 °C to rt; (e) BH3T·HF, THF, 50 °C, then H2O2, NaOH, 0 °C to rt; (f) (COCl)2, DMSO, CH2Cl2, −78 °C, then DIPEA, −78 to 0 °C; (g) KOH(aq), THF/ MeOH (1:1), 0 °C to rt; (h) (i) H2 (1 atm), Pd/C (1.50 mass equiv), EtOAc, rt; (ii) NH2OBn·HCl, NaOAc, MeOH/H2O (5:1), 85 °C; (i) Pd(OAc)2 (15 mol %), PhI(OAc)2, AcOH/Ac2O (1:1), 100 °C.