1.1: 4.3 mg / EDCI; DMAP / dimethylformamide / 16 h / 25 °C 2.1: 98 percent / aq. LiOH / tetrahydrofuran; methanol / 8 h / 60 °C 3.1: EDCI; DMAP / dimethylformamide / 1 h / 25 °C 3.2: 68 percent / dimethylformamide / 13 h / 25 °C 4.1: HCl / ethyl acetate / 1 h / 25 °C 5.1: 3.8 mg / CDI / tetrahydrofuran / 3 h / 25 °C View Scheme

1: 4.3 mg / EDCI; DMAP / dimethylformamide / 16 h / 25 °C 2: 98 percent / aq. LiOH / tetrahydrofuran; methanol / 8 h / 60 °C 3: EDCI; DMAP / dimethylformamide / 14 h / 25 °C 4: HCl / ethanol / 2.5 h / 0 - 25 °C 5: NH3 / ethanol / 1 h / 25 °C 6: methanol; tetrahydrofuran / 1 h / -40 °C View Scheme