Lithium hydroxide, monohydrate → 5-(4-tert-butoxycarbonyl-[1,4]diazepane-1-carbonyl)-1-isopropyl-1H-indole-2-carboxylic acid

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Reaction Steps

To a solution of 5-(4-tert-butoxycarbonyl-[1,4]diazepane-1-carbonyl)-1-isopropyl-1H-indole-2-carboxylic acid ethyl ester (1.60 g, 3.5 mmol) in tetrahydrofuran (10 ml), methanol (10 ml) and water (2 ml) was added lithium hydroxide monohydrate (2 eq., 168 mg). The mixture was stirred two days at room temperature. The solvent was removed under vacuum and the residue was quenched with 1M aq. dihydrogen potassium phosphate solution to pH 5. The aqueous phase was extracted with ethyl acetate (2×) and the combined organic phases washed with brine, dried over MgSO4 and filtered. The crude product was purified by column chromatography on silica gel (3:1 heptane/ethyl acetate eluant) to afford the product as an off-white powder (644 mg, 42%). MS (m/z): 430.3 (M+H)+.

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