7-(1-Isobutoxy-ethoxycarbamoyl)-heptanoic acid (5.0 g, 1.72 mmol, 1.0 eq) and 4-trimethylsilanyloxymethyl-phenylamine (3.38 g, 1.72 mmol, 1.0 eq) were stirred together in DMF (140 mL). To the mixture was added PyBroP (10.5 g, 2.25 mmol, 1.3 eq) and DiPEA (3.9 mL, 2.25 mmol, 1.3 eq). The reaction was stirred under a nitrogen atmosphere overnight at room temperature. Ethyl acetate (200 mL) and water (200 mL) were added. The aqueous phase was isolated and re-extracted with ethyl acetate (2×100 mL). The combined organic phases were washed with water (2×50 mL) and brine (50 mL), then dried (MgSO4), filtered and concentrated in vacuo. The crude product was dissolved in the minimum of ethyl acetate and purified by passing through a pad of silica. The product was washed through the silica using ethyl acetate and collected in 100 mL conical flasks until elution ceased by LCMS analysis. Purification gave a yellow oil (3.59 g, 53% yield). LCMS purity 61%, m/z 417 [M++Na]+
