Whisky Lactone Research Articles

Catalytic Enantioselective Synthesis of Naturally Occurring Butenolides via Hetero-Allylic Alkylation and Ring Closing Metathesis

An efficient catalytic asymmetric synthesis of chiral γ-butenolides was developed based on the hetero-allylic asymmetric alkylation (h-AAA) in combination with ring closing metathesis (RCM). The synthetic potential of the h-AAA-RCM protocol was illustrated with the facile synthesis of (-)-whiskey lactone, (-)-cognac lactone, (-)-nephrosteranic acid, and (-)-roccellaric acid.

Impact of Oak-Derived Compounds on the Olfactory Perception of Barrel-Aged Wines

Barrel-aged wine is a complex mixture and its olfactory perception results from the interaction of many flavors. To estimate the role of oak-derived flavor compounds, it is necessary to consider odor activity values (OAV) and to perform a correlation study to assess the impact of flavor compounds on the flavor attributes. Twenty Spanish and French wines, each aged in different types of barrels, were studied using both sensory (descriptive) and chemical (GC-MS) analysis. Paired-sample <i>t</i>-tests were used to assess whether there were systematic differences in the concentrations of oak-derived compounds between wines aged in different barrels and evaluated differently in the sensory tests. Regardless of their low OAVs, furanic compounds (furfural, furfuryl alcohol, and 5-methylfurfural) increased the “overall oak” intensity rating and decreased the “fruity” intensity rating. It is hypothesized that these compounds indirectly impacted the respective intensities. The presence of <i>cis</i>- and <i>trans</i>-whisky lactones, eugenol, and vanillin increased the intensity rating of the vanilla/pastry descriptor, while furfural and 5-methylfurfural diminished it. Regardless of the volatile phenols (guaiacol, 4-methylguaiacol, eugenol) described as smoky and spicy in their pure state, no reliable links were found between these compounds and the respective sensory descriptors in wines. Samples described as having higher olfactory persistence were richer in relatively high-boiling wood compounds, such as <i>trans-</i> and <i>cis</i>-whisky lactone, maltol, eugenol, and vanillin, than their paired samples, explaining their retronasal persistence.

Aroma substance of fragrant tree Platycarya strobilacea and change of phenolic constituents on toasting

The wood of Platycarya strobilacea (PSW) is a fragrant tree and has been used as a substitute for expensive agarwood (Aquilaria agallocha). PSW was burned when it is used as fragrant tree, and the aim of our study is characterization of the aroma substance and chemical change of the constituents during the heating. Previously, we reported that PSW contains 3-hydroxy-α-calacorene, oak lactone (syn. whisky lactone) precursor (1), gallotannins, such as pentagalloyl-β-D-glucose, and ellagitannins, such as pedunculagin, 1(β)-O-galloylpedunculagin (5)1,2.

ChemInform Abstract: Synthesis of β-Halobutenolides and Their Pd(0)-Catalyzed Cross-Coupling Reactions with Terminal Alkynes and Organozinc Reagents. A General Route to β-Substituted Butenolides and Formal Synthesis of cis-Whisky Lactone.

Abstract An improved procedure for the efficient synthesis of β-halobutenolides was developed. The Pd(0)-catalyzed coupling reactions of β-halobutenolides with terminal alkynes or organozinc reagents, i.e., 1-alkenyl, aryl, and alkyl zinc reagents, to afford β-substituted butenolides were carefully studied. Using the coupling protocol of γ-(n-butyl)-β-iodobutenolide with methylzinc halide, we performed an efficient formal synthesis of whisky lactone.

Oxidative rearrangement of 2-alkoxy-3,4-dihydro-2 H-pyrans: stereocontrolled synthesis of 4,5-cis-disubstituted tetrahydrofuranones including whisky and cognac lactones and crobarbatic acid

Oxidation of 2-alkoxy-3,4-dihydro-2 H-pyrans 3 with dimethyldioxirane or MTO/urea–H 2O 2 followed by Jones oxidation leads to rearrangement and stereocontrolled formation of 4,5-cis-disubstituted tetrahydrofuranones. The method is applied to the synthesis of the whisky lactone 9, cognac lactone 10 and crobarbatic acid 17.

Characterization of the Key Aroma Compounds in an American Bourbon Whisky by Quantitative Measurements, Aroma Recombination, and Omission Studies

Thirty-one of the 45 odor-active compounds previously identified by us in an American Bourbon whisky were quantified by stable isotope dilution assays. Also for this purpose, new synthetic pathways were developed for the synthesis of the deuterium-labeled whisky lactone as well as for gamma-nona- and gamma-decalactone. To obtain the odor activity values (OAVs), the concentrations measured were divided by the odor thresholds of the odorants determined in water/ethanol (6:4 by vol.). Twenty-six aroma compounds showed OAVs >1, among which ethanol, ethyl (S)-2-methylbutanoate, 3-methylbutanal, 4-hydroxy-3-methoxybenzaldehyde, (E)-beta-damascenone, ethyl hexanoate, ethyl butanoate, ethyl octanoate, 2-methylpropanal, (3S,4S)- cis-whiskylactone, (E, E)-2,4-decadienal, 4-allyl-2-methoxyphenol, ethyl-3-methylbutanoate, and ethyl 2-methylpropanoate showed the highest values. The overall aroma of the Bourbon whisky could be mimicked by an aroma recombinate consisting of the 26 key odorants in their actual concentrations in whisky using water/ethanol (6:4 by vol.) as the matrix. Omission experiments corroborated the importance of, in particular, 4-hydroxy-3-methoxybenzaldehyde, (3S,4S)-cis-whiskylactone, ethanol, and the entire group of esters for the overall aroma of the Bourbon whisky.

Analysis of French and American oak chips with different toasting degrees by headspace solid-phase microextraction-gas chromatography–mass spectrometry

This paper describes the optimisation of headspace solid-phase microextraction (HS-SPME) conditions for the analysis of volatile compounds in oak chips used to accelerate wine aging as an alternative to traditional aging in oak barrels. The direct extraction of ground wood samples and the extraction of sample aqueous slurries using a divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre were studied and compared. Optimal conditions for direct extraction were 110 °C and 60 min, whereas for aqueous slurries they were obtained by adding 2 mL of a 7.1 mol L −1 sodium chloride solution, at 70 °C and for 60 min. The two optimised HS-SPME approaches were compared in terms of repeatability and extraction efficiency; water addition to the sample prior to HS-SPME was selected because it yielded better repeatability (6.6% versus 8.5% relative standard deviation) and efficiency (around 1.4–4.8 times higher analyte amount extracted for most of the compounds). Finally, the method was applied in the analysis of oak chip samples from American and French oak with different degrees of toasting. Principal component analysis (PCA) of the results showed that the first principal component was correlated with the toasting degree whereas the second, which was strongly influenced by whisky lactones and eugenol, allowed us to differentiate between American and French oak chips.

Determination of Aroma Compounds from Alcoholic Beverages in Spiked Blood Samples by Means of Dynamic Headspace GC–MS

Some aroma compounds found in alcoholic beverages are characteristic of a certain beverage (i.e. 2,4-decadienoic acid ethyl ester is characteristic of pear spirit and 5-butyltetrahydro-4-methylfuran-2-on “whiskey lactone” is characteristic of aged spirits like whiskey). These substances were detectable in beverages but not in blood samples. The aim of this investigation was to find a sensitive sampling technique for aroma compounds in whole blood samples. This technique may be used in forensic toxicology for examination of drinking claims. The method comprises dynamic headspace sampling using a purge and trap concentrator, followed by quantitative gas chromatography–mass spectrometry (dynamic HS–GC–MS). The influence of sample preparation, trap adsorbents and sample temperature as well as desorption time and purge time on the quality of the analytical results were investigated. The following optimal parameters were determined: stirred and diluted whole blood sample without salt addition, use of Carbotrap C as trap material, sample temperature at 80 °C, desorption time 20 min and purge time 30 min. These optimal parameters were used for the determination of detection limits (LOD). The LOD of aroma compounds by means of dynamic headspace sampling were compared with the results of conventional sampling: the static headspace technique. Limits of detection for the aroma compounds with conventional static headspace GC are in the range 400–10,000 μg L−1. Dynamic headspace–GC was found to be a more sensitive sampling technique for most of the aroma compounds investigated (e.g. C4–C8 ethyl esters, benzoic acid ethyl ester, linalool oxide and 4-ethylguaiacol) with detection limits between 1 and 50 μg L−1, but there were also limits to the sampling of substances with lower volatility like decanoic acid ethyl ester, 2,4-decadienoic acid ethyl ester, eugenol and whiskey lactone with detection limits of about 1,000 μg L−1.

Analytical Characterization of the Aroma of Five Premium Red Wines. Insights into the Role of Odor Families and the Concept of Fruitiness of Wines

The aroma profile of five premium red wines has been studied by sensory descriptive analysis, quantitative gas chromatography-olfactometry (GC-O), and chemical quantitative analysis. The most relevant findings have been confirmed by sensory analysis. Forty-five odorants, including the most intense, were identified. At least 37 odorants can be found at concentrations above their odor threshold. A satisfactory agreement between GC-O and quantitative data was obtained in most cases. Isobutyl-2-methoxypyrazine, (E)-whiskey lactone, and guaiacol were responsible for the veggie, woody, and toasted characters of the wines, respectively. The sweet-caramel notes are related to the presence of at least five compounds with flowery and sweet notes. The phenolic character can be similarly related to the presence of 12 volatile phenols. The berry fruit note of these wines is related to the additive effect of nine fruity esters. Ethanol exerts a strong suppression effect on fruitiness, whereas norisoprenoids and dimethyl sulfide enhance fruity notes.

Impact of ethanol on the perception of wine odorant mixtures

Several studies have focused on perceptual interactions in binary odor mixtures, but few on more complex mixtures. The aroma of wine is an example of a complex odor mixture. Our aim was to assess the impact of ethanol on the perception of mixtures of Woody (whiskey lactone) and Fruity (isoamyl acetate) odorants commonly found, physico-chemically and perceptually, in wine. Physico-chemically, reduced whiskey lactone volatility was observed in hydro-alcoholic solutions. Perceptually, a synergy effect by the Woody on the Fruity odor was observed in aqueous solutions, which disappeared with the addition of ethanol. Conversely, the Woody odor was masked in both aqueous and dilute alcohol solutions. In addition, mixed Woody and Fruity odors were found to mask the so-called Alcohol odor. These results underline the importance of perceptual interactions in the perception of wine bouquet.

Atom transfer radical cyclization (ATRC) applied to a chemoenzymatic synthesis of Quercus lactones

The natural fragrances (+)- trans whisky lactone 2 and (+)- trans cognac lactone 4, together with a minor amount of their (−)- cis stereoisomers, were prepared in 50% and 42% overall yield, respectively, starting from racemic 1-hepten-3-ol (±)- 5 and 1-octen-3-ol (±)- 6. The procedure involved first the enantioconvergent, lipase mediated transformation of the secondary allylic alcohols derived dichloroacetates (±)- 7 and (±)- 8 into the corresponding homochiral (+)- 7 and (+)- 8, combined with their cyclization under a transition metal catalyzed atom transfer process.

Microwave-Assisted Mild Conversion of Natural Dihydrotagetone into 5-Isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone, an Analogue of Whisky Lactone

A microwave-assisted mild protocol is developed for the synthesis of 5-isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone, an analogue of whisky lactone, from dihydrotagetone, an acyclic monoterpenoid obtained from Tagetes minuta. The methodology involved oxidation of dihydrotagetone in the presence of sodium metaperiodate/potassium permanganate/alumina to give 2,6-dimethyl-4-oxo-heptanoic acid, which upon reduction and subsequent lactonization provided 5-isobutyl-3-methyl-4,5-dihydro-2(3H)-furanone. The reaction is also conducted under conventional conditions and is compared with the microwave method.

Volatile composition analysis by solid-phase microextraction applied to oak wood used in cooperage (Quercus pyrenaica and Quercus petraea): effect of botanical species and toasting process

The purpose of this study was to investigate the sorption of selected volatile substances from oak wood-chip samples (Quercus pyrenaica Willd. and Quercus petraea L.) subjected to different toasting levels, namely, without toasting, with medium toasting, and with strong toasting, through the use of solid-phase microextraction (SPME). The main volatile compounds identified as a function of the toasting level and botanical species were furfural, hexanal, α-pinene, d-limonene, decanal, vitispirane, ethyl hexanoate, cis-3-methyl-γ-octalactone (“oak lactone” or “whisky lactone”), α-terpineol, p-xylene, and nonanal. Considering the data obtained from the toasted woods (medium and strong intensity) in comparison with those of nontoasted woods, it can be pointed out that the average peak area and the number of compounds identified in the gas chromatogram decreased during the toasting process. In general, regarding the compounds analyzed, quantitative differences were found between the two oak wood species under study. High values of volatile compounds were found in Quercus pyrenaica oak wood chips. In addition, for the number of compounds identified in oak wood extracts and directly extracted from solid oak wood chips by SPME, it is concluded that the best extraction process for volatile compounds from oak wood is the use of oak wood-chip liquid extracts.

Influence of Geographical Origin and Botanical Species on the Content of Extractives in American, French, and East European Oak Woods

The chemical composition of East European (Republic of Moldova, Ukraine, and Romania) oaks was investigated profoundly for the first time in the present study and compared with American and French counterparts. Taking into account the high natural variability of oak extractives contents, the wide-ranging sampling was performed for all oak origins: 276 French oaks, 102 East European oaks of both species (Quercus robur L. and Quercus petraea Liebl.), and 56 American oaks (Quercus alba). These oaks were compared with great attention paid to the extractives, which are most important for sensorial impact in wine or spirit maturation, such as ellagitannins and principal odorant substances (aromatic aldehydes, lactones and phenols). The substances in question were studied by application of HPLC and GC-MS techniques. The pattern of all studied extractive contents allowed adequate separation of oak samples according to their geographical origin or botanical species. The highest separation rate was for American and French oaks, whereas East European samples could be partially misclassified in two sets mentioned above. The most important variables for species discrimination were whiskey lactone related variables and ellagitannins, whereas the most important features for distinguishing the origin were eugenol, 2-phenylethanol, vanillin, and syringaldehyde. These substances allowed the distinction of French and East European woods of the same species. With regard to chemical composition, East European wood held the intermediary place between American and French oaks according to their ellagitannin and whiskey lactone levels; nevertheless, it was characterized by specific high values of eugenol, aromatic aldehydes, and 2-phenylethanol.

Oxidative Rearrangement of 2‐Alkoxy‐3,4‐dihydro‐2H‐pyrans: Stereocontrolled Synthesis of 4,5‐cis‐Disubstituted Tetrahydrofuranones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Oxidative rearrangement of 2-alkoxy-3,4-dihydro-2 H-pyrans: stereocontrolled synthesis of 4,5-cis-disubstituted tetrahydrofuranones

Oxidation of 2-alkoxy-3,4-dihydro-2 H-pyrans with dimethyldioxirane followed by Jones oxidation leads to rearrangement and stereocontrolled formation of 4,5-cis-disubstituted tetrahydrofuranones; the method is applied to the synthesis of the whisky lactone 13 and cognac lactone 14 .

Chemical Markers for Tracking the Sensory Contribution of Production Stages in Muscat Wine Distillates

ABSTRACT:The main sensory contribution of each post‐fermentation production stage of muscat wine distillates can be tracked by following the concentration of just 1 corresponding chemical marker. Matching sample clusters of sensory and chemical data by using principal components analysis (PCA) revealed potential chemical markers. The data used in this study correspond to 12 sensory attributes that showed significant differences among products (P &lt; 0.05) and concentrations of 23 volatile compounds of 14 distillate fractions and 15 finished Piscos. Artificial fruit attribute, characteristic of the head fraction (FR1) can be tracked with esters. Linalool, main odor attribute of the 1st part of the heart (FR2) can be tracked with linalool molecule. The 2nd part of the heart (FR3) can be tracked with octanoic acid, decanoic acid, furfural and ethyl lactate, accounting for tails attribute. In blended and aged finished products, chemical markers accounting for the effects of distillate fractions were similar but not identical to the markers from samples obtained from the purely distilled samples. Chemical markers for FR1 are ethyl hexanoate, ethyl octanoate, ethyl decanoate. Differentiation between FR1 and FR2 is less evident than in the purely distilled samples due to the linalool and artificial fruit attribute correlation. Chemical markers for FR2, therefore, include linalool and esters ethyl hexanoate, ethyl octanoate, and ethyl decanoate. The blending of the 2nd part of the heart (FR3) can be tracked with 2‐phenylethanol, ethyl lactate, and decanoic acid. Oak aging was tracked with eugenol and whisky lactones, while 5‐hydroxy‐methyl‐2‐furfural accounted for added caramel.

Perceptual Interactions in Odour Mixtures: Odour Quality in Binary Mixtures of Woody and Fruity Wine Odorants

The qualitative perceptual interactions in three binary mixtures of wine odorants were studied: isoamyl acetate (fruity note)/whisky lactone (woody note), ethyl butyrate (fruity note)/whisky lactone (woody note) and ethyl butyrate (fruity note)/guaiacol (woody note). For each binary mixture, the perceived quality and intensity of 24 stimuli (four supra-threshold concentration levels of each of the two compounds and their 16 possible combinations) were evaluated in five replications by a trained panel of 13 subjects. The application of the Olsson predictive model for odour intensity and quality perception gave quite a good estimation of the evolution of single component identification in the mixture when the intensity proportion of unmixed components varied. However, this model was unable to account for the odour quality dominance in mixtures of iso-intense components. An alternative linear logistic model was proposed to study the qualitative dominance of the woody note in the three mixtures when the perceived intensities of each unmixed compound were equal.

Aroma compounds in Oregon Pinot Noir wine determined by aroma extract dilution analysis (AEDA)

AbstractThe aroma profiles of Oregon Pinot Noir wines were investigated with aroma extract dilution analysis (AEDA). The wines were extracted with pentane‐diethyl ether, the aromas were distilled using solvent‐assisted flavour evaporation (SAFE) and separated into acidic/water‐soluble and neutral/basic fractions. In the acidic/water‐soluble fraction, 2‐phenylethanol and 3‐methyl‐1‐butanol showed the highest AEDA values, followed by 2‐methylpropanoic acid, butanoic acid, 2‐methylbutanoic acid, 3‐methylbutanoic acid, 2‐methylpropanol, hexanol, trans‐3‐hexenol, cis‐3‐hexenol, benzyl alcohol, 3‐methylthio‐1‐propanol, 3‐ethylthio‐1‐propanol, linalool and geraniol (all with FD ≥ 64). In the neutral/basic fraction, ethyl 2‐methylpropanoate, ethyl butanoate, 3‐methylbutyl acetate, ethyl hexanoate, and benzaldehyde had very high AEDA values (all with FD ≥ 64), followed by ethyl 3‐methylbutanoate, 3‐methylbutyl 2‐methylpropanoate, ethyl octanoate, ethyl decanoate, benzyl acetate, phenylethyl formate, phenylethyl acetate, ethyl dihydrocinnamate, ethyl anthranilate, 3‐methylthio‐1‐propanal, citronellal, whisky lactone and γ‐nonalactone (all with FD ≥ 16). Overall, the results indicated that there is no single compound that characterizes the aroma of Pinot Noir, and that the characteristic aroma comes from a blend of numerous compounds. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Perceptual interactions between fruity and woody notes of wine

AbstractThe quantitative olfactory interactions in three binary mixtures of wine aroma compounds were studied. For the first two mixtures, whisky lactone (woody note) was mixed separately with two esters (fruity note), ethyl butyrate and isoamyl acetate. For the third mixture, guaiacol (woody note) was mixed with ethyl butyrate (fruity note). Perceived odour intensity of 24 stimuli (four supra‐threshold concentration levels of two compounds and the respective 16 mixtures) were evaluated in five replications, by a trained panel of 13 subjects. The results showed that for the three binary mixtures studied, quantitative perceptual interactions were non‐level independent, non‐symmetrical, and reached the compromise level of hypo‐addition. The experimental data highlighted that generally mixtures with high whisky lactone levels led to the compromise level of mixture intensity perception, whereas mixtures with high fruity note intensity proportions did not. A tendency to hyper‐addition was observed in iso‐intense mixtures only at the lowest intensity level. Copyright © 2004 John Wiley &amp; Sons, Ltd.