Hydrochloric Acid → methyl [(2S)-3-methyl-1-oxo-1-{(2S)-2-[9-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-3,7-dihydroisochromeno[3',4': 5,6]naphtho[1,2-d]imidazol-2-yl]pyrrolidin-1-yl}butan-2-yl]carbamate

Participants

Reaction Steps

A solution of tert-butyl(2S)-2-[9-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-3,7-dihydroisochromeno[3′,4′:5,6]naphtho[1,2-d]imidazol-2-yl]pyrrolidine-1-carboxylate (0.98 g, 1.7 mmol), concentrated HCl (2 mL) and ethanol (20 mL) was heated to 60° C. for 2 hours. The reaction was concentrated and redissolved in a minimal amount of methanol. An equal volume of dichloromethane was added and the solution was again concentrated. Dichloromethane was added to the resulting residue and concentrated off two more times. The resulting crude material was dissolved in dimethylformamide (17 mL). To this solution was added (S)-2-(methoxycarbonylamino)-3-methylbutanoic acid (455 mg, 2.6 mmol), HATU (955 mg, 2.5 mmol) and diisopropylethylamine (3 mL, 17 mmol). The reaction was stirred at room temperature for one hour then diluted with ethyl acetate. The organics were washed with water (×2) and brine, dried with magnesium sulfate and concentrated. The resulting residue was purified by flash column chromatography to yield Intermediate methyl [(2S)-3-methyl-1-oxo-1-{(2S)-2-[9-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-3,7-dihydroisochromeno[3′,4′:5,6]naphtho[1,2-d]imidazol-2-yl]pyrrolidin-1-yl}butan-2-yl]carbamate (780 mg, 72% yield over 2 steps).

Provenance & Evidence