Enantioselective syntheses and sensory properties of 2‐Alken‐4‐olides

Due to the disadvantages of low fragrance threshold and high volatility of pyrrole monomer under high‐temperature process in tobacco or food, it cannot meet the market requirements. In order to develop pyrrole flavour precursors, 2,5‐dimethyl‐N‐pyrroleacetic acid was synthesized by the Paal–Knorr reaction using 2,5‐hexanedione and glycine as raw materials. Various pyrrole fragrance precursors such as 2‐ethyl‐4‐oxo‐4H‐pyran‐3‐yl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5a), 4‐formyl‐2‐methoxyphenyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5b), pyridine‐2‐ylmethyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5c) and thiophen‐2‐ylmethyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5d) were synthesized by esterification from 2,5‐dimethyl‐N‐pyrroleacetic acid with ethyl maltol, vanillin, 2‐pyridinemethanol and 2‐thiophenemethanol, respectively. As part of the study, IR, NMR and HRMS were used to characterize the target compounds. Using gas chromatography–mass spectrometry‐olfactometer (GC–MS‐O), the pyrrole esters obtained were evaluated for the characteristics of their aromas. The thermal stability was analysed using thermogravimetric analysis and pyrolysis gas chromatography/mass spectrometry. In addition, the pyrolysis mechanism was speculated. With TG‐DTG results, the main mass loss phase of 5a occurred between 108°C and 450°C, with a dramatic mass loss reduction of 83.07%. At 118.60°C and 450°C, 5b showed a mass loss reduction of 60.80%. Furthermore, according to the Py‐GC/MS analysis results, compounds 5a and 5b formed 8 and 7 pyrolysis products. The main pyrolysis products of 5a and 5b were 1‐ethyl‐2,5‐dimethyl‐1H‐pyrrole, ethyl maltol, and vanillin, which are all aroma components used to blend cigarette smoke, can slow down the rate at which aromas are lost and mask unpleasant smoke. Study results provide a reference for the tobacco industry to further develop new high‐temperature release aroma ingredients.

Section: Sensory Panelmentioning

confidence: 99%

Synthesis and pyrolysis of various novel pyrrole ester fragrance precursors

Tian

Han

et al. 2023

“…Sensory panels were determined according to the procedure described by Dai and Liu. 33 The panel consisted of ten healthy, nonsmoking judges, four men and six women, aged 23-29 years old. All the panel members belonged to the Henan Agricultural University.…”

Section: Sensory Panelmentioning

confidence: 99%

Synthesis and pyrolysis of ethyl maltol ester

Dong

Pan

et al. 2023

Ethyl maltol is one of the most important aromatic components in food and cigarettes because of its caramel flavour. However, the development of ethyl maltol is limited by problems such as heavy smell, low threshold, strong volatility and poor stability. In order to develop a new class of high‐temperature resistance and caramel flavours for cigarettes, eight new ethyl maltol flavours were synthesized using the reaction of ethyl maltol with a carboxylic acid. The target compounds were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), infrared spectroscopy (IR) and high‐resolution mass spectrometry (HRMS). By gas chromatography–mass spectrometry‐olfactometer (GC–MS‐O), the aroma characteristics of esters were evaluated. Four compounds with strong aroma were conducted with thermogravimetry (TG), derivative thermogravimetry (DTG) and pyrolysis‐gas chromatography/mass spectrometry (Py–GC/MS) to analyse their heating stability. TG–DTG results showed that the degradation temperature of ethyl maltol esters was significantly higher than that of ethyl maltol, which could effectively slow down the volatilization of ethyl maltol. Py‐GC/MS results showed that a large amount of ethyl maltol and many esters with aroma were formed during thermal degradation of the four compounds at 300°C, 350°C and 400°C. The above results show that the esterification of ethyl maltol was a good strategy to slow release flavours, and ethyl maltol ester latent aroma compounds have significant applications in high‐temperature processed food and tobacco. This work may provide a new method to improve the stability of spices and expand their multifunctional application.

“…In addition, a series of optically active 2‐alken‐4‐olides of C 6 –C 11 were also prepared by the Sharpless asymmetric dihydroxylation of methyl ( E )‐3‐alkenoates, followed by elimination via mesylates in our laboratory in order to examine the odour properties. The odour evaluation revealed that all of the samples exhibited stereospecific differences in sensory properties; however, the application of these optically active 2‐alken‐4‐olides is impossible for the time being, as those chiral oxidants are too expensive for industrial production. Like the saturated γ ‐lactones, the racemic mixtures still predominate over the enantiomers in the market, even with these well‐known stereospecific differences in sensory properties.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of butenolides by reactions of 3‐alkenoic acids with diphenyl sulfoxide/oxalyl chloride

Ding

Liu

et al. 2018

Self Cite

Butenolides are of high interest as potential flavouring compounds. Efficient and general methods for the production of these compounds remain to be developed. A series of butenolides were prepared starting from 3‐alkenoic acids with diphenyl sulfoxide/oxalyl chloride, followed by treatment with bases. The 3‐alkenoic acids with alkyl substitutents on the double bond were converted into the corresponding 2‐butenolides with yields of greater than 77%, whereas those with aryl groups on the double bond produced the corresponding 3‐butenolides with yields of about 80%. The butenolides were produced by β eliminations of the corresponding chlorolactones, which were generated from the chlorolactonization of 3‐alkenoic acids. The chlorodiphenylsulfonium salt produced from the reaction between diphenyl sulfoxide and oxalyl chloride was supposed to be the chlorinating reagent for the chlorolactonization. This is a very simple and convenient method for the preparation of butenolides.