合成路线1

Synthesis of intermediate (XIV): Protection of 4-piperidone (I) with (Boc)2O in presence of DMAP and Et3N yields (II), which is converted into hydantoin (III) by means of NaCN in presence of (NH4)2CO3. Hydantoin (III) is then fully protected to provide (IV) by treatment with (Boc)2O and DMAP in THF. Alternatively (IV) can be obtained by treatment of 4-piperidone (I) with KCN in presence of (NH4)2CO3 to yield hydantoin (V), which is then protected with (Boc)2O and DMAP in DME. Hydrolysis of (IV) with NaOH affords aminoacid (VI) whose free amine is protected to provide carboxylic acid (VII). Treatment of (VII) with isobutyl chloroformate (IBCF) in DME in presence of NMM, followed by aqueous ammonia, yields amide (VIII), which is converted to (IX) by hydrogenation with H2 over Pd/C. Reductive amination of (IX) with aldehyde (X) affords amino amide (XI), which is treated with triethyl orthoformate to provide spirocycle (XII). Reduction of (XII) with NaBH4 in EtOH gives (XIII), which is alkylated with ethyl bromoacetate (A) followed by hydrolysis with NaOH to yield intermediate (XIV).