合成路线1

The esterification of 4(R)-hydroxypyrrolidine-2(S)-carboxylic acid (I) gives the methyl ester (II), which is N-protected to yield 1-Boc-4(R)-hydroxypyrrolidine-2(S)-carboxylic acid methyl ester (III). Compound (III) which is mesylated to afford 1-Boc-4(R)-(mesyloxy)pyrrolidine-2(S)-carboxylic acid methyl ester (IV). The reaction of (IV) with sodium azide affords (V), which is reduced with H2 over Pd/C in ethanol to provide 4(S)-amino-1-Boc-pyrrolidine-2(S)-carboxylic acid methyl ester (VI). The reductocondensation of (VI) with 3-methoxybenzaldehyde (VII) by means of NaBH(OAc)3 provides the secondary amine (VIII), which is acylated with 3,3-dimethylbutyryl chloride (IX) and TEA in dichloromethane to give the amide (X). The deprotection of the pyrrolidine NH of (X) by means of TFA yields the pyrrolidine (XI), which is reductocondensed with piperonal (XII) by means of NaBH3CN to afford the N-substituted pyrrolidine (XIII). The hydrolysis of the ester group of (XIII) with LiOH in methanol/water provides the carboxylic acid (XIV), which is condensed with N-Boc-piperazine (XV) by means of TBTU and DIEA in DMF to give the protected intermediate (XVI). Finally, this compound is deprotected by means of TFA in dichloromethane to furnish the target carboxamide.