Mechanism for the synthesis of medium-chain 1-alkenes from fatty acids catalyzed by binuclear iron UndA decarboxylase

Terminal olefins synthesized by the decarboxylation of fatty acids are important platform chemicals. PfUndA is a nonheme di-iron oxidase capable of converting medium-chain (C-10 similar to C14) fatty acids into the corresponding 1-alkenes. Using density functional theory calculations, it is demonstrated that the PfUndA-catalyzed lauric acid decarboxylation is initiated by introducing one pair of H+/e(-). The subse-quent reaction mainly involves the O - O bond dissociation, the partial interconversion between active high-spin Fe(III)-O-center dot and inactive medium-spin Fe(IV) = O, the formation of triple-hydroxyl intermediates and substrate Cb radical resulted from successive hydrogen transfers, the stepwise decarboxylation of substrate radical, and the protonation of Fe-bound hydroxides with H+ and e(-) added. Other mechanistic possibilities have been excluded. It is further found that the low catalytic efficiency of UndA may be due to the energy penalty caused by the drop of active high-spin Fe(III)-O-center dot to a deeper minimum (inert medium-spin Fe(IV) = O). (c) 2023 Elsevier Inc. All rights reserved.