How is 2-[(9H-Fluoren-9-ylmethoxy)carbonyl]-8-{[(2-methyl-2-propanyl)oxy]carbonyl}-2,8-diazaspiro[4.5]decane-3-carboxylic acid (CAS: 849928-23-0) typically synthesized?

2-[(9H-Fluoren-9-ylmethoxy)carbonyl]-8-{[(2-methyl-2-propanyl)oxy]carbonyl}-2,8-diazaspiro[4.5]decane-3-carboxylic acid can be synthesized via multi-step processes involving protection and deprotection steps. Typical synthetic methods include coupling reactions using DCC (dicyclohexylcarbodiimide) as a coupling agent, followed by acid-labile protecting group removal. The yield is typically around 70-80%, and the purity can be enhanced through recrystallization.