تخليق وتشخيص مركبات جديدة: دراسة حركية تفاعلات ديلز-الدر المحفزة انزيميا

Synthesis and Characterization of Novel Compounds: Kinetic Study of Enzymatically Catalyzed Diels-Alder Reactions

Summary
Diels-Alder (D-A) reaction is one of the important chemical transformations between diene and dienophile in a coordinated thermal pericyclic reaction to create the C–C bonds with predicted regio- and stereo-selectivity, which lead to the forming of bulk organic molecules. Despite of the significant efforts in this filed, the control of the stereoselectivity of Diels-Alder reactions remain so difficult. Despite the significant efforts in this field, controlling of stereoselectivity of Diels-Alder reactions remains so difficult.
Biosynthetic enzymes, Diels-Alderases are functionally distinct enzymes that catalyze [4 + 2] cycloaddition processes. The design of the enzymatic Diels-Alder reactions provides scientists with a huge advantage in increasing the selectivity of Diels-Alder reaction products.
Morus alba Diels-Alderase has ability to catalyze non-redox D-A reactions of different dinophiles and different types of natural and artificial polyphenolic dienes. Morus alba Diels-Alderase only have endo-selectivity. Moreover, it was shown that the Morus alba Diels-Alderase had great enantioselectivity when it came to catalyzing the Diels–Alder reaction, producing only enantiopure products with high stereoselectivity.
This work focused on applying the friendly environmental method includes the application of the current approach in enzymatic D-A reactions by formation the new organic compounds through the enzymatic D-A reactions between anthracene derivatives as dines and pyrrole derivatives as dienophiles. in addition to control the stereoselectivity of the final products. Furthermore, monitoring the enzymatic reaction of Morus alba Diels-Alderase.
All D-A reactions were carried out in the inert environment using the nitrogen gas. The prepared compounds were characterized using various techniques including mass spectroscopy, nuclear magnetic resonance, and Fourier transform infrared.
The final products of Diels-Alder reaction were Meso 9-(hydroxymethyl)-13-methyl-9,10-dihydro-12H,14H-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracene-12,14-dione (P1), Meso9-(hydroxymethyl)-13-propyl-9,10-dihydro-12H,14H-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracene-12,14-dione (P2), Meso(9-(hydroxymethyl)-12,14-dioxo-9,10-dihydro-13H-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracen-13- yl)acetic acid (P3),Meso(13-methyl-12,14-dioxo-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracen-9(10H)- yl)boronic acid(P4),Meso(12,14-dioxo-13-propyl-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracen-9(10H)- yl)boronic acid (P5), Meso (9-(dihydroxyboranyl)-12,14-dioxo-9,10-dihydro-13H-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracen-13- yl)acetic acid (P6).
Depending on the results, the mechanisms of enzymatic Diels-Alder reaction was suggested.
The kinetics of preparation of these products in presence of Morus alba Diels-Alderase were studied by applying the Michaelis-Menten equation. The maximum velocity (Vmax) and the Michaelis-Menten constant (Km) for all the enzymatic Diels Alder reaction. The least affinity between diene and enzyme found in Meso(13-methyl-12,14-dioxo-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracen-9(10H)- yl)boronic acid (P4) because it had the highest Km value 0.3527. while, 2 Meso (9-(dihydroxyboranyl)-12,14-dioxo-9,10-dihydro-13H-9,10- (epiethane[1,1,2]triylazanoethane[1,2,2]triyl)anthracen-13- yl)acetic acid (P6) achieved the highest affinity by having the lowest Km value 0.2292.
In addition, the optimization of the enzymatic Diels Alder reactions which were included the concentration of the substrate, the enzymatic activity, and the temperature were performed to determine the best concentration of each substrate in addition to best enzyme activity at the optimum temperature. which found in P2 by using anthracen-9-ylmethanol as diene and in P6 by using anthracen-9-ylboronic acid as diene at 25°C
The thermodynamic parameters, which include enthalpy change (∆H), Gibbs free energy change (∆G) and entropy change (∆S) were determined. All of the products are spontaneous and thermodynamically favorable, While the most favorable is P2. in addition, all the products are endothermic except P3 is exothermic
However, there are other three compounds have been prepared by using 9,10-diphenylanthracene as diene but didn’t give the expected result based on FTIR, NMR, and Mass spectroscopy analysis.