Ammonium Chloride → (3R,4S,5S)-tert-butyl 4-((S)-2-(((benzyloxy)carbonyl)amino)-N,3-dimethylbutanamido)-3-methoxy-5-methylheptanoate

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Reaction Steps

425 mg (1.7 mmol) N-[(benzyloxy)carbonyl]-L-valine were dissolved in 50 ml of DMF and mixed successively with 500 mg (1.7 mmol) of tert.-butyl-(3R,4S,5S)-3-methoxy-5-methyl-4-(methylamino)-heptanoate hydrochloride (starting compound 2), 356 mg (1.9 mmol) 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride, 285 mg (1.9 mmol) 1-hydroxy-1H-benzotriazol hydrate and 655 mg (5.1 mmol) of N,N-iiisopropylethylamine. The mixture was stirred for 20 h at RT. Another 142 mg (0.5 mmol) of N-[(benzyloxy)carbonyl]-L-valine, 119 mg (0.6 mmol) of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 95 mg (0.6 mmol) of 1-hydroxy-1H-benzotriazol hydrate and 218 mg (1.7 mmol) N,N-diisopropylethylamine were added and the mixture was treated with ultrasound for 90 min. The mixture was then poured into a solution of semi-saturated aqueous ammonium chloride and ethyl acetate. The organic phase was separated off, washed successively with saturated sodium hydrogen carbonate solution and saturated sodium chloride solution, then dried over magnesium sulphate, filtered and evaporated. The remainder was purified using preparative HPLC. 329 mg (40% o. th.) of the title compound were obtained as a colorless oil.

Provenance & Evidence