合成路线1

Coupling between N-Boc-glycine (I) and 4-aminobenzonitrile (II) via activation with CDI yields amide (III). Subsequent acidic N-Boc group cleavage provides the amino acetanilide (IV). Reductive alkylation of amine (IV) with ethyl 4-oxopiperidine-1-acetate (V) leads to the aminopiperidine (VI). This is reductively alkylated with chloroacetaldehyde in the presence of NaBH3CN, to produce the chloroethyl amine (VII). Cyclization of (VII) by means of NaH in DMF furnishes the piperazinone (VIII). The cyano group of (VIII) is then converted to the corresponding ethyl imidate, which is further displaced with ammonium carbonate producing amidine (IX). Finally, saponification of the ethyl ester group of (IX) with LiOH gives rise to the title amidino acid