Three new derivatives of porphobilinogen (PBG; 1) were designed and synthesized to study the mechanism of ammonia loss during the tetramerization of PBG, catalyzed by the enzyme PBG deaminase. Two of these compounds are substituted at the C-11 carbon with CH3 or CF3, while the third analog is the N-methyl derivative of PBG wherein the pyrrole proton is replaced with methyl. All three compounds reacted, to varying degrees of completion, with ...