Selective protection of the secondary amino group of 4-(aminomethyl)piperidine (I) was achieved via conversion to imine (III) upon condensation with benzaldehyde (II), followed by treatment with di-tert-butyl dicarbonate to afford carbamate (IV). Subsequent acid hydrolysis of the imine function of (IV) furnished the mono-protected diamine (V). Coupling of amine (V) with 3-methoxy-4-(3-o-tolylureido)phenylacetic acid (VI) using HATU furnished amide (VII). Acidic cleavage of the N-Boc protecting group of (VII) gave piperidine (VIII). Aziridine (X) was prepared from ethyl 2,3-dibromopropionate (IX) by treatment with ammonia in acetonitrile. Condensation of (X) with N-(benzyloxycarbonyloxy)succinimide produced the benzyl carbamate (XI). Regioselective ring opening of the aziridine (XI) with piperidine (VIII) yielded adduct (XII). The ethyl ester group of (XII) was finally hydrolyzed to the target carboxylic acid under basic conditions.

Selective protection of the secondary amino group of 4-(aminomethyl)piperidine (I) was achieved via conversion to imine (III) upon condensation with benzaldehyde (II), followed by treatment with di-tert-butyl dicarbonate to afford carbamate (IV). Subsequent acid hydrolysis of the imine function of (IV) furnished the mono-protected diamine (V). Coupling of amine (V) with 3-methoxy-4-(3-o-tolylureido)phenylacetic acid (VI) using HATU furnished amide (VII). Acidic cleavage of the N-Boc protecting group of (VII) gave piperidine (VIII). Aziridine (X) was prepared from ethyl 2,3-dibromopropionate (IX) by treatment with ammonia in acetonitrile. Condensation of (X) with N-(benzyloxycarbonyloxy)succinimide produced the benzyl carbamate (XI). Regioselective ring opening of the aziridine (XI) with piperidine (VIII) yielded adduct (XII). The ethyl ester group of (XII) was finally hydrolyzed to the target carboxylic acid under basic conditions.