Synthesis
To a stirred solution of δ-Boc-L-ornithine (0.5 g, 2.15 mmol, 1 eq.) dissolved in 5% aqueous NaHCO3 (30 mL) was slowly added benzyl chloroformate (0.4 mL, 2.80 mmol, 1.3 eq.) at room temperature. The reaction mixture was stirred continuously for 12 hours at room temperature. Upon completion of the reaction, extraction was performed by adding ether (20 mL) to remove unreacted benzyl chloroformate. The aqueous phase was adjusted to pH 1 with aqueous 6N hydrochloric acid and subsequently extracted with dichloromethane (50 mL x 3). The organic phases were combined, dried with anhydrous MgSO4, filtered and concentrated under reduced pressure to afford the target compound N-benzyloxycarbonyl-N'-tert-butoxycarbonyl-L-ornithine (Compound 13) as a colorless solid (0.71 g) in 90% yield.
References
[1] European Journal of Medicinal Chemistry, 2018, vol. 149, p. 122 - 128
[2] Helvetica chimica acta, 1966, vol. 49, # 3, p. 1013 - 1022
[3] Patent: US2004/6062, 2004, A1. Location in patent: Page/Page column 42
[4] FEBS Journal, 2013, vol. 280, # 8, p. 1807 - 1817
