Reagents and conditions: (a) 2,5-hexanedione, pTsOH, toluene, Dean–Stark, 2 h, 82% (for 10), 91% (for 11); (b) CuI, Cs2CO3, BnOH, 90 °C, overnight, 86% (for 12), 82% (for 13); (c) NH2OH·HCl, NEt3, EtOH/H2O (2:1), reflux, 20 h, 81% (for 14), 76% (for 15); (d) CH3C(O)Cl, cat. DMAP, NEt3, CH2Cl2, rt, overnight, 81% (for 16), 69% (for 17); (e) Pd/C, H2, MeOH, rt, 3 h, 95% (for 2), 94% (for 3).