Biomimetic Studies Of 4-hydroxyphenylpyruvate Dioxygenase Model Complexes And Molecular Oxygen Reaction

4-Hydroxyphenylpyruvate dioxygenase(HPPD)is a 2His-1COO active center mononuclear non-heme ferrous dioxygenase which can catalyzes 4-Hydroxyphenylpyuvic acid(HPPA)broken the C1-C2 bond and form 2,5-dihydroxyphenylacetic acid(Homogentisate,HG).HPPA can also serve as a substrate for ?-diketone dioxygenase(Dke1)in the active center of 3His,which is cleaved by C2-C3 to form p-hydroxybenzaldehyde.In the HPPD biomimetic study,the main product was DKe1 type product,and the existence of HG has not been confirmed in the degradation products so far.The main reason is that HPPA mainly exists in enol form.To mimic the catalytic process of HPPD at the molecular level and to confirm the presence of HG in the degradation products,it was demonstrated that the biological modelling of HPPD was consistent with the enzyme system.This article mainly did the following work:(1)Two model ligands were synthesized and characterized,2-{[(Benzyl-pyridin-2-ylmethyl)amino] methyl}-5-R-benzoic acid;R: 5-NO2,5-Br.The coordination site of 2N-1COO is the activity center of natural HPPD.(2)Synthesis and Characterization of Ketones and Enols of HPPA.(3)The structure and functional model of HPPD,three-dollar ferrous model complexes [FeIILBr(HPP)] was synthesized by the model ligand LBr H,HPPA(keto)and ferrous acetate(HPP)with a ratio of 1: 1: 1.And characterized by MS and FT-IR.(4)The mimic enzyme catalysed reaction product were analyzed by LC-MS and HPLC in quantity and quality,and to confirm the existence of HG,the method of reduce the polarity of product HG and its derivatives by esterification,and then separated by column chromatography were conducted.The results of product analysis of model complexes are as follows:(1)The enol tautomerism of HPPA can influence the reaction of model complexes [FeIILBr(HPP)] with oxygen.When HPPA is ketone-coordinated,the reaction product is HG and its derivatives(HPPD product),when HPPA is enolically coordinated,the reaction product is 4-hydroxybenzaldehyde(2DKe1 type product).(2)The use of water as the main solvent during the synthesis of the model complexes [FeIILBr(HPP)] and the reaction process favors the presence of HPPA(keto),which contributes to the reaction to the direction of HPPD,which can increases the yeild of HPPD-type product.