1: 25percent HBr, acetic acid 2: 58 percent / 1-hydroxybenzotriazole, Et3N, N,N'-dicyclohexylcarbodiimide / dimethylformamide / Ambient temperature 3: 5.4N HCl / dioxane 4: 53 percent / 1-hydroxybenzotriazole, Et3N, N,N'-dicyclohexylcarbodiimide / dimethylformamide / Ambient temperature View Scheme

Multi-step reaction with 2 steps 1: 25percent HBr, acetic acid2: 58 percent / 1-hydroxybenzotriazole, Et3N, N,N'-dicyclohexylcarbodiimide / dimethylformamide / Ambient temperature