Step 4: Synthesis of (2S,4R)-1-((S)-2-amino-3,3-dimethylbutanoyl)-4-hydroxy-N-(4-(4-methylthiazol-5-yl)benzyl)pyrrolidine-2-carboxamide hydrochloride (ULM-1)
To a stirred solution of tert-butyl N-[(2S)-1-[(2S,4R)-4-hydroxy-2-({[4-(4-methyl-1,3-thiazol-5-yl)phenyl]methyl}carbamoyl)pyrrolidin-1-yl]-3,3-dimethyl-1-oxobutan-2-yl]carbamate (12 g, 22.61 mmol) in dioxane (20 mL) at room temperature was added to a dioxane solution of hydrogen chloride (4N, 80 mL). The reaction mixture was stirred at room temperature for 2 h. LC-MS monitoring showed formation of the target product. The precipitated solid was collected by filtration to give ULM-1 in 48% yield as a yellow solid.
1H NMR (400 MHz, CD3OD): δ 9.84-9.82 (s, 1H), 7.58-7.54 (m, 4H), 4.71-4.41 (m, 4H), 4.13-4.08 (m, 1H), 3.86-3.71 (m, 2H), 3.36 (s, 1H), 2.60-2.58 (s, 3H), 2.35-2.07 (m, 2H), 1.19-1.12 (m, 9H).
LC-MS (ES+): m/z 431.11 [MH+], tR = 0.73 min (run time 2.0 min).
