Sodium Iodide → (3S)-N-[N-[3-[[(t-Butyloxy)carbonyl]amino]-2-oxo-4-phenylbutyl]-L-phenylalanyl]-L-leucine, t-butyl ester

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Reaction Steps

To a stirred solution of L-phenylalanyl-L-leucine, t-butyl ester (4.13 g, 12 mmol) in 60 ml of dimethylformamide under argon was added N-[(t-butyloxy)carbonyl]-L-phenylalanine chloromethyl ketone (3.57 g, 12 mmol, see example 4A), sodium bicarbonate (1.01 g, 12 mmol) and sodium iodide (900 mg, 6 mmol, 0.5 equiv.). The reaction mixture was allowed to stir overnight, then the solvent was evaporated (<25° C., vacuum pump). The residue was taken up into ethyl acetate (300 ml) and washed with water (3×40 ml) and brine (40 ml), then dried (sodium sulfate) and evaporated to give 6.63 g of a yellow oil. This oil was purified by flash chromatography on 450 g of Merck silica gel (230-400 mesh), eluting with 3:1 hexane-ethyl acetate, to yield 5.05 g of the title compound as a light yellow solid. A portion was recrystallized from ethyl acetate-hexane to give a white solid, melting point 85°-87° C.

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