Synthesis
First, the construction of the 2,8-diazaspiro[4.5]decane core skeleton typically involves the reaction of an N-protected 4-piperidinone with a reagent such as a cyanoacetate or malonic acid ester to form a spirocyclic succinimide structure, namely 2,8-diazaspiro[4.5]decane-1,3-dione, through a series of steps (such as Knoevenagel condensation, hydrolysis, and cyclization). Once the dione intermediate is formed, it can be reduced with a strong reducing agent (such as lithium aluminum hydride) to give the final 2,8-diazaspiro[4.5]decane, which converts the two carbonyl groups on the succinimide ring to methylene groups while removing the protecting group on the nitrogen atom (if present), thus effectively yielding the target spirocyclic diamine compound.
