Diisopropylethylamine → Methyl 2-((s)-2-(benzyloxycarbonylamino)-3-methylbutanamido)-3-(7-bromo-1h-indol-3-yl)propanoate

Participants

Reaction Conditions

Reaction Steps

The title compound of Example 3 (256.6 g, 770 mmol), TBTU (296.4 g, 1.2 eq) and Cbz-L-valine (212.7 g, 1.1 eq) were dissolved in dimethylformamide (DMF, anhydrous, 2,700 mL) and cooled to 0° C. for 30 min. Diisopropylethylamine (DIEA, 268 mL) was added slowly and the solution was allowed to warm to room temperature. Stirring was continued for 4 hours at which time HPLC indicated completion of reaction. The reaction was diluted with ethyl acetate (11 L) and water (7.5 L). The mixture was stirred for 1 hour and allowed to separate. The organic layer was washed once with water (7.5 L), twice with brine (7.5 L) and twice with saturated NaHCO3 (7.5 L). The material was dried with sodium sulfate and concentrated to brown black solid. The material was taken up in methylene chloride (7.5 L) and combined with 22.2 g of another lot of similar quality material and silica gel (400 g). The solvent was removed to support the crude compound on silica. This material was divided in half and each half was chromatographed on a 6 in×4 ft silica gravity column. Each was eluted with methylene chloride (20 L) followed by 5% acetone in methylene chloride (20 L) followed by 8% acetone in methylene chloride (30 L) to give the title compound (383 g, 89% yield). 1H NMR (CDCl3): consistent with proposed structure.

Provenance & Evidence