Reagents and conditions: a) triethylamine,
dry ethanol, 80 °C; b) Zn(0), NH4Cl, H2O:1,4-dioxane 1:1, 50 °C; c) 1) trichloroacetyl chloride, dry
dichloroethane, 70 °C; 2) 2 N KOH aqueous solution, ethanol/tetrahydrofuran
1:1; d) N,N-dimethylformamide di-tert-butyl acetal, dry toluene, 90 °C; e) triethylamine,
dry dichloromethane, RT; f) trifluoroacetic acid, dry dichloromethane,
RT; g) triethylamine, TBTU reagent, dry N,N-dimethylformamide, RT; h) LiOH(aq), tetrahydrofuran, RT;
(i) 1) triethylamine, TBTU reagent, O-(tetrahydro-2H-pyran-2-yl)hydroxylamine, dry N,N-dimethylformamide, RT; 2) 4 N hydrogen chloride solution
in 1,4-dioxane, dry tetrahydrofuran, RT.