Non-enzymic tetramisation of ethyl 3-(4-ethoxycarbonylmethyl-1H-pyrrol-3-yl)propionate with formaldehyde follows a similar course to the non-enzymic tetramisation of porphobilinogen

The octaethyl esters of uroporphyrins were formed directly from ethyl 3-(4-ethoxy-carbonylmethyl-1H-pyrrol-3-yl)propionate and formalin in a yield of ca. 30% with the isomers I, II, III and IV being formed in the ratio 1:1:4:2. Under anaerobic conditions, the colourless uroporphyrinogen esters were formed in a similar ratio. These observations parallel the non-enzymic formation of uroporphyrinogens from the naturally occurring tetrapyrrole precursor, porphobilinogen, highlighting the similarity in both tetramisation and isomerisation reactions.