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Open AccessArticle

Scalable Preparation of Enantioenriched (S)-5-methylhept-2-en-4-one. Synthesis and Aroma Properties of Achiral Analogues Thereof

1
Department of Organic Chemistry, Slovak University of Technology, Radlinského 9, SK-812 37 Bratislava, Slovakia
2
Department of Analytical Chemistry, Slovak University of Technology, Radlinského 9, SK-812 37 Bratislava, Slovakia
*
Author to whom correspondence should be addressed.
Academic Editor: Domenico Montesano
Molecules 2019, 24(24), 4497; https://doi.org/10.3390/molecules24244497
Received: 29 October 2019 / Revised: 19 November 2019 / Accepted: 4 December 2019 / Published: 8 December 2019
(This article belongs to the Special Issue New Insights in Diversity Oriented Synthesis)
(S)-5-Methylhept-2-en-4-one is a key flavour compound in hazelnuts. We have performed its chiral-pool-based chemoenzymatic synthesis with 39% overall yield (73% ee). The four-step aldol-based sequence avoids the use of highly reactive and/or toxic reagents, does not require anhydrous conditions and uses only distillation as the purification method. Thus, such methodology represents a green and scalable alternative to only two stereoselective approaches towards this natural product known so far. In addition, we have designed and prepared a set of new (di)enones as achiral synthetic analogues of the title compound. The results of their sensory analyses clearly show that relatively minor structural changes of the natural molecule significantly alter its olfactory properties. Thus, simple (poly)methylation completely changes the original hazelnut aroma of (S)-5-methylhept-2-en-4-one and shifts the odour of its analogues to eucalyptus, menthol, camphor, and sweet aroma. View Full-Text
Keywords: hazelnut; enzymatic hydrolysis; fragrant enones; allylic oxidation; sensory analysis hazelnut; enzymatic hydrolysis; fragrant enones; allylic oxidation; sensory analysis
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MDPI and ACS Style

Puchľová, E.; Dendys, M.; Špánik, I.; Szolcsányi, P. Scalable Preparation of Enantioenriched (S)-5-methylhept-2-en-4-one. Synthesis and Aroma Properties of Achiral Analogues Thereof. Molecules 2019, 24, 4497.

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