An oxidative trimerization of three amino acids has been realized to furnish 2,3,5-trisubstuitued pyridines in both cross- and homo-trimerization types. This method is capable of converting simple linear biomass material to heterocycles, which features in the assembly of three amino acid branched chains into one aromatic ring. Molecular iodine triggers the sequential decarboxylation and deamination of amino acids and then promotes the selective formation of new C-N and C-C bonds.