How is N~2~-[(Benzyloxy)carbonyl]-N~5~-{[(2-methyl-2-propanyl)oxy]carbonyl}-L-ornithine (CAS: 7733-29-1) typically synthesized?

N~2~-[(Benzyloxy)carbonyl]-N~5~-{[(2-methyl-2-propanyl)oxy]carbonyl}-L-ornithine is typically synthesized through a multi-step process involving the protection of the amino group, followed by the introduction of the benzyloxy and 2-methyl-2-propanyl groups via esterification and amidation reactions. Commonly, triphenylphosphine and triethylamine are used as catalysts, and the overall yield is around 75-85%. This synthesis is performed under anhydrous conditions to avoid unwanted side reactions.