Benzyl Alcohol → 3-[2-(3-Benzyloxycarbonylamino-2-oxo-2H-pyridin-1-yl)-2-tert-butoxycarbonyl-ethyl]-indole-1-carboxylic acid tert-butyl ester

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To a stirred solution of (S)-3-[2-tert-Butoxycarbonyl-2-(3-carboxy-2-oxo-2H-pyridin-1-yl)-ethyl]-indole-1-carboxylic acid tert-butyl ester (1.8 g, 3.7 mmol) in dioxane was added triethylamine (580 mg, 5.9 mmol), diphenylphosphoryl azide 91.5 g, 5.6 mmol) and benzyl alcohol (680 mg, 6.3 mmol) and the mixture refluxed at 100 C for 18 hours. The mixture was concentrated and partitioned between ethylacetate and saturated bicarbonate. The organic layer was washed with brine, dried (MgSO4), filtered and evaporated to afford the crude product, which was purified by flash chromatography (30-70% ethylacetate/petroleum ether) to afford the title compound as a white solid (1.3 g, 59%); 1H NMR (400 MHz, CDCl3) δ 1.48 (9H, s), 1.73 (9H, s), 3.45 (1H, m), 3.65 (1H, m), 5.2-5.25 (2H, m), 5.60 (1H, m), 6.15 (1H, t), 6.85 (1H, m), 7.25-7.55 (9H, m), 7.95 (1H, m), 8.02-8.18 (2H, m);

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