2-Alkylpyrrole formation from 4,5-epoxy-2-alkenals.

N-Substituted 2-pentylpyrrole formation has been related to the etiology or the consequences of several diseases in which lipid oxidation is involved. This study describes the formation of N-substituted 2-alkylpyrroles in the reaction of 4,5-epoxy-2-alkenals with amino compounds and suggests an alternative pathway for the formation of these compounds that are nowadays commonly accepted to be produced by reaction of the lipid oxidation product 4-hydroxy-2-nonenal with primary amino compounds. The described reaction constitutes a new route for pyrrole production in the lipid peroxidation pathway when it takes place in the presence of amino compounds and implies the loss of one carbon in the 4,5-epoxy-2-alkenal during the formation of the heterocyclic ring, which is proposed to be released as formaldehyde. This reaction also confirms the high reactivity of 4,5-epoxy-2-alkenals, which are usually found in smaller amounts than other lipid oxidation products. Their importance in vivo may be underappreciated in part as a consequence of this high reactivity that brings about their rapid disappearance.