Chemo-Enzymatic Cascade for the Generation of Fragrance Aldehydes

Daniel Schwendenwein,Margit Winkler,Viktor Savic,Anna K Ressmann,Marcello Entner,Florian Rudroff

doi:10.3390/catal11080932

Abstract

In this study, we present the synthesis of chiral fragrance aldehydes, which was tackled by a combination of chemo-catalysis and a multi-enzymatic in vivo cascade reaction and the development of a highly versatile high-throughput assay for the enzymatic reduction of carboxylic acids. We investigated a biocompatible metal-catalyzed synthesis for the preparation of α or β substituted cinnamic acid derivatives which were fed directly into the biocatalytic system. Subsequently, the target molecules were synthesized by an enzymatic cascade consisting of a carboxylate reduction, followed by the selective C-C double bond reduction catalyzed by appropriate enoate reductases. We investigated a biocompatible oxidative Heck protocol and combined it with cells expressing a carboxylic acid reductase from Neurospora crassa (NcCAR) and an ene reductase from Saccharomyces pastorianus for the production fragrance aldehydes.

Highlights

Heck coupling subsequent steps; a: Trifluorborate, The results showed that E. coli cells expressing NcCAR [23] had the highest activity for all subsequent reductions steps; a: Trifluorborate, b: cinnamic acid, c: cinnamaldehyde, d: Pheb: cinnamicand acid, c: cinnamaldehyde, d: Phenylpropionaldehyde, e: cinnamyl alcohol; for tested substrates
The first step was the generation of cinnamic acids
Compounds were detected at 254 nm using a Diode Array Detector (Agilent, Santa Clara, CA, USA) (DAD). These results outline the proof of concept of the presented chemoenzymatic cascade reaction

Summary

Introduction

The combination of organic chemistry with enzyme catalysis is attracting more and more attention, with high yields, less toxic byproducts and in general more environmentally friendly processes [2]. Cascade reactions are defined as consisting of at least two consecutive transformations, where the product of the first step serves as substrate for the subsequent step [2]. The advantages of both fields can be combined if the protocols for both the organic and the biocatalytic step are compatible. Reactions with biocatalysts typically require atmospheric pressure, ambient temperatures, and a nearly neutral pH

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Conclusion