Bovine plasma amine oxidase (BPAO) was previously shown to be irreversibly inhibited by propargylamine and 2-chloroallylamine. 1, 4-Diamine versions of these two compounds are here shown to be highly potent inactivators, with IC50 values near 20 μM. Mono-N-alkylation or N, N-dialkylation greatly lowered the inactivation potency in every case, whereas the mono-N-acyl derivatives were also weaker inhibitors and enzyme activity was recoverable ...