合成路线1

Reductive condensation of 2-oxopiperazine (I) with 4-oxopiperidine-1-carboxylic acid t-butyl ester (XIV) in the presence of sodium cyanoborohydride (NaBH3CN) in MeOH/EtOH-HCl yields derivative (XV), which is then coupled to bromo derivative (IV) by means of sodium in refluxing toluene to give compound (XVI). Deprotection of (XVI) by treatment with TFA and anisole provides piperidine derivative (XVII), which is then treated with chloromethyl chloroformate (X) and proton sponge in CH2Cl2 to furnish derivative (XVIII). Finally, (XVIII) is coupled to pivalic acid (XII) by means of K2CO3 in DMF and converted into the corresponding hydrochloride salt by treatment with HCl-EtOH in EtOAc.