The synthesis of (R)-1-(pyridin-4-yl)ethyl acetate was achieved over tandem palladium-lipase catalyst with 100% selectivity using 4-acetyl pyridine as a reactant. The 2% w/w palladium and lipase catalyst was successfully co-immobilized in the microenvironment of the mesocellular foam and characterized by various techniques. The palladium metal from catalyst hydrogenated 4-acetyl pyridine to form 1-(pyridin-4-yl)ethanol. The generated intermediate product then underwent kinetic resolution over lipase and selectively gave (R)-1-(pyridin-4- yl)ethyl acetate. The catalytic conditions were then studied for optimal performance of both steps. The reaction conditions were optimized to 50 °C and toluene as a solvent. Both chemical and enzymatic kinetic models of the reaction were developed for a given set of reaction conditions and kinetic parameters were predicted. At optimal conditions, the obtained selectivity of intermediate (1-(pyridin-4-yl)ethanol) was 51.38%. The final product yield of ((R)-1-(pyridin-4-yl)ethyl acetate) was 48.62%.
To achieve transition from lab scale enzyme studies to industrial applications, understanding of enzyme kinetics plays a critical role. The widely applied Michaelis Menten equation of the single substrate kinetics, sequential and double replacement mechanism of bisubstrate reaction and the relevant kinetics, inhibition and activation of enzyme are all integral parts of this discussion. In this chapter, we have discussed different types of inhibition and kinetic modelling. Systematic approach to generate data and its interpretation as well as designing of inhibitors is also explained.
acetamide is an intermediate for the complete natural synthesis of antimalarial drugs. Chemoselective monoacetylation of the amino group of 2-aminophenol to N-(2-hydroxyphenyl)acetamide was carried out by employing Novozym 435 as the catalyst. Different acyl donors such as vinyl acetate, vinyl butyrate, acetic anhydride, and ethyl acetate were studied. The effect of various parameters such as different acyl donors, speed of agitation, solvent, catalyst loading, mole ratio, and temperature was studied. Vinyl acetate was found to be the best acyl donor among the studied acyl donors since it leads to an irreversible reaction. It is a kinetically controlled synthesis since vinyl acetate was used as the activated acyl donor. The substrate to acyl donor ratio was 1:3. The mechanism for the given reaction system was predicted based on the observations of Lineweaver− Burk plots. It was observed that the reaction followed a ternary complex model with inhibition by vinyl acetate, and kinetic constants were estimated using the Polymath 6.0 software. Under the final optimized conditions, the conversion for the reaction was found to be 74.6% in 10 h.
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