Green Biocatalysis by Ramesh N. Patel

Author:Ramesh N. Patel
Language: eng
Format: epub
ISBN: 9781118822364
Publisher: Wiley
Published: 2016-07-12T00:00:00+00:00

14.1 INTRODUCTION

Due to the importance of chirality for the activity and properties of many compounds, synthesis of optically pure compounds is increasingly in demand in the pharmaceutical, fine chemicals, and agroalimentary industries. The exquisite regio-, chemo-, and enantioselectivity commonly displayed by enzymes have allowed the employment of these biocatalysts in the production of biologically active compounds, offering the development of more sustainable and economically attractive strategies for the synthesis of optically pure molecules [1–6]. Biocatalysis satisfies many of the 12 principles of green chemistry [7], such as the employment of gentle reaction conditions (physiological pH, temperature and water as the usual reaction medium, although many green solvents can also be used) or the evasion of protection and deprotection steps, producing less waste and shortening the production processes. Subsequently, the production of fine chemicals and drugs by using biotechnological methodologies is becoming widely implemented on an industrial scale [8–11].

Enzyme-catalyzed kinetic resolution (KR) of racemates have been widely employed for the preparation of enantiomerically pure compounds. In particular, the use of serine hydrolases as catalysts of the enantioselective hydrolysis of esters and amides or the stereoselective alcoholysis or aminolysis of esters is a common strategy to afford chiral compounds through KR processes [12–14]. However, a maximum 50% yield of chiral product can be afforded through this methodology, which restricts the real applicability of the process. Among the different approaches that have been proposed to circumvent this limitation, dynamic kinetic resolution (DKR) appears as a promising strategy to achieve maximum theoretical yield of 100% of optically pure compounds. The appropriate in situ combination of an enzyme-catalyzed KR and the racemization of the remnant substrate allow the complete transformation of a racemate into an enantiomerically pure product, as shown in Figure 14.1.

FIGURE 14.1 Dynamic kinetic resolution (DKR) process.

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