How is N-{[(2-Methyl-2-propanyl)oxy]carbonyl}-L-norleucine - N-cyclohexylcyclohexanamine (CAS: 21947-32-0) typically synthesized?

N-{[(2-Methyl-2-propanyl)oxy]carbonyl}-L-norleucine - N-cyclohexylcyclohexanamine (CAS: 21947-32-0) is synthesized via multi-step organic synthesis, involving coupling reactions, amide formation, and cyclohexylation. Commonly, it is synthesized using protecting groups and catalysts such as DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene) to achieve high selectivity and yield. The process is optimized for purity and efficiency by employing techniques like recrystallization and chromatography.