The function of secondary metabolites has been a subject of debate since the first isolation and characterization of these often times structurally complex chemical compounds. By definition, secondary metabolites are naturally produced compounds that are not essential for the survival of the producing organism, as opposed to primary metabolites. Bioassays have revealed a wide range of biological activities, such as cytotoxicity, ichthyotoxicity, antimicrobial and antifeedant activity, antifoulant and anti-cancer activities. However, some of these activities are manifested against organisms that do not represent logical targets, since they would never be encountered by the producing organism in their natural habitat.

An efficient and facile one-pot, three-component protocol for the synthesis of pyrimido[4,5-b]quinoline-4-amines from the condensation of 2-aminoquinoline-3-carbonitrile, N,N-dimethylformamide dimethyl acetal and primary amines under microwave irradiation is reported. This efficient, straightforward procedure led to the desired products in high yields without the need for a catalyst or for a tandem addition–elimination–cyclisation reaction.