1: 96 percent / Et3N / acetonitrile / 6 h 2: 1.) acetic anhydride, 2.) trifluoroacetic acid, 3.) anion exchange resin Bio-Rad AG-3, 200-400 mesh / 1.) pyridine, r.t., 12 h, 2.) 12 h View Scheme

1: 96 percent / Et3N / acetonitrile / 6 h 2: 1.) acetic anhydride, 2.) trifluoroacetic acid, 3.) anion exchange resin Bio-Rad AG-3, 200-400 mesh / 1.) pyridine, r.t., 12 h, 2.) 12 h View Scheme

1: 96 percent / Et3N / acetonitrile / 6 h 2: 1.) acetic anhydride, 2.) trifluoroacetic acid, 3.) anion exchange resin Bio-Rad AG-3, 200-400 mesh / 1.) pyridine, r.t., 12 h, 2.) 12 h 3: 45 percent / 6N HCl / H2O / 75 °C View Scheme

1: 96 percent / Et3N / acetonitrile / 6 h 2: 1.) acetic anhydride, 2.) trifluoroacetic acid, 3.) anion exchange resin Bio-Rad AG-3, 200-400 mesh / 1.) pyridine, r.t., 12 h, 2.) 12 h View Scheme