合成路线1

The N-Boc group of the orthogonally protected beta-lysine (I) is removed by acidic treatment to provide amine (II), which is further reprotected as the trifluoroacetamide (III) by reaction with methyl trifluoroacetate. Transesterification of acid (III) with t-butyl acetate in the presence of HClO4 gives rise to the corresponding t-butyl ester (IV). Selective methylation of the trifluoroacetamide N of (IV) furnishes the N-methyl amide (V), which is subsequently hydrolyzed to the N-methyl amine (VI) under alkaline conditions. Guanidylation of amine (VI) with N,N'-bis-carbobenzoxy-1-amidinopyrazole (VII) leads to the protected guanidine (VIII). Then, acidic cleavage of the tert-butyl ester group of (VIII) provides carboxylic acid (IX)