2-Nitrophenol → Nalpha-Boc-Ndelta-Cbz-(R)-ornithine o-nitrophenyl ester

Participants

Reaction Conditions

Reaction Steps

A solution Nα -Boc-Nδ -Cbz-(R)-ornithine (25.0 g; 68.2 mmol) and o-nitrophenol (19.0 g; 136.4 mmol) in pyridine (250 mL) was cooled to 0° C. Dicyclohexylcarbodiimide (13.4 g; 64.8 mmol) was added at 0° C. The solution was stirred at 0° C. for several hours, warmed to room temperature and stirred overnight. The resulting heterogeneous solution was diluted with EtOAc and filtered. The filtrate was concentrated under reduced pressure to afford a thick oil. The oil was dissolved in a minimal amount of warm isopropanol and stirred. The resultant precipitate was collected via vacuum filtration and washed with isopropanol, then diethyl ether. Concentration of the isopropanol/ether filtrate and crystallization from isopropanol provided a second crop. The combined product was dissolved in EtOAc at room temperature and filtered. Concentration of the EtOAc gave the sub-title compound as a solid.

Provenance & Evidence