(i) DCC, CF3CO2H, Py, DMSO, benzene, (ii) oxalic acid, aq. MeOH, EtOH; Multistep reaction;

1: 99 percent / pyridine 2: 1.) NaBH4 / 1.) MeOH 3: 22 percent / pyridine / tetrahydrofuran / Ambient temperature 4: 80 percent / dicyclohexyl carbodiimide, dimethyl sulfoxide, pyridine, trifluoroacetic acid / benzene / 5 h / Ambient temperature 5: 86 percent / KOH / methanol; tetrahydrofuran; H2O / Ambient temperature 6: 1.) conc HCl, 2.) dicyclohexyl carbodiimide, dimethyl sulfoxide, pyridine, trifluoroacetic acid / 1.) methanol, reflux, 2 h; 2.) benzene, r.t., 5 h View Scheme