Abstract
The advantageous properties of ethylene glycol diacetate (EGDA) qualify it as a useful substitute for glycerol triacetate (GTA) for various green applications. We scrutinised the lipase-mediated acetylation of structurally diverse alcohols in neat EGDA furnishing the range of naturally occurring fragrant acetates. We found that such enzymatic system exhibits high reactivity and selectivity towards activated (homo) allylic and non-activated primary/secondary alcohols. This feature was utilised in the scalable multigram synthesis of fragrant (Z)-hex-3-en-1-yl acetate in 70% yield. In addition, the Lipozyme 435/EGDA system was also found to be applicable for the chemo-selective acetylation of (hydroxyalkyl) phenols as well as for the kinetic resolution of chiral secondary alcohols. Lastly, its discrimination power was demonstrated in competitive experiments of equimolar mixtures of two isomeric alcohols. This enabled the practical synthesis of 1-pentyl acetate isolated as a single product in 68% yield from the equimolar mixture of 1-pentanol and 3-pentanol.
Highlights
In perfumery and the flavour industry, acetates are the most important aliphatic esters used and valued for their typical aromas [1]
The Lipozyme 435/ethylene glycol diacetate (EGDA) system was found to be applicable for the chemo-selective acetylation of phenols as well as for the kinetic resolution of chiral secondary alcohols
In combination with Lipozyme 435, we have successfully employed EGDA as a useful acetylation reagent and solvent for chemo-selective and/or stereoselective enzymatic preparation of natural acetates for perfumery and/or flavour purposes. We found that such a green system exhibits high reactivity and selectivity toward activated allylic and non-activated primary/secondary alcohols
Summary
In perfumery and the flavour industry, acetates are the most important aliphatic esters used and valued for their typical aromas [1]. The use of lipases gained considerable attention due to their high reactivity and remarkable selectivity under diverse reaction conditions [4]. Their stability in a non-aqueous environment, under solvent-free conditions, gives lipases a comparative advantage over other biocatalysts [5]. In this context, glycerol-based solvents [6,7,8]
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