2-Ethyl-3-methoxypyrazine

Ethyl-3-methoxypyrazine (3-Ethyl-2-methoxy pyrazine) C2H5 och3... 

Three extremely odorous pyrazines, 3-isopropyl-2-methoxypyrazine, 2-s-butyl-3-methoxypyrazine, and 2-isobutyl-3-methoxypyrazine have been shown to be present in green peas, and are likely to be of major significance in the flavor of peas (59). The volatile oil of green bell peppers has been found to contain 2-isobutyl-3-methoxypyrazine as a major component (60,61). The alkylpyrazines in potato chips (62,63) and roasted peanuts (63) have been examined. 2-Isopropyl-3-methoxypyrazine has been characterized in the vacuum steam volatile oil of potatoes (64), 2-ethyl-3-methoxypyrazine in cooked potato (65), and 3-ethyl-2,5-dimethylpyrazine and 2-ethyl-3,5-dimethylpyTazine as the components important to the aroma of baked potato (66). A variety of alkylpyrazines have been identified in roasted sesame seeds (67) and 21 pyrazines have been identified in the aroma components isolated from roasted green tea (68). 

Ethylmethoxypyrazine. Unlike the isobutyl-, isopropyl- and sec-butyl methoxypyrazines, the existence of 2-ethyl-3-methoxypyrazine (4) (ethylmethoxypyrazine) in fruits and vegetables has not been consistently confirmed in the past. While evidence for its existence was found, unambiguous identification by mass spectrometry was prevented by the trace concentration of this component. Of all the methoxypyrazines so far mentioned, it has an aroma most similar to raw potatoes 16) and synthetic material adds potato flavor to processed potato products (18). It is also described as earthy 15), and it has a sensory detection threshold of 425 ng/L (17). Given its aroma, it is not surprising that its possible occurrence in potatoes has been the subject of several studies. 

Pyrazine, 2-ethyl-3-methoxy-, 2-ethyl-3-methoxypyrazine, 2-methoxy-3-ethylpyrazine [25680-58-4]... 

Shading (Leaf layer index Isobutyl- methoxypyrazine (ng/L) Ethyl- methoxypyrazine (ng/L) ... 

The odor threshold of the pyrazines range from 0.006 ppb in water for 2—propyl—3-methoxypyrazine (29) to 43 ppm in water for 2,5—dimethyl—3-ethyl pyrazine (30). A excellent review of the pyrazines found in food products has been prepared by Maga (31). 

Benzyloxy-6-hydroxymethyl-3-isobutylpyrazine 4-oxide 2-Benzyloxy-6-iodomethyl-3-isobutyl-5-methoxypyrazine 4-oxide 2-Benzyloxy-3-isobutyl-6-mesyloxy-methyl-5-methoxypyrazine-4-oxide 1 - Benzyloxy-3 - (2-methoxycarbonyl-ethyl)-5,6-dimethyl-2(l/7)-pyrazinone... 

A suitable tool for the quantitation of trace compounds in foods is a stable isotope dilution assay (IVA) 16, 17). Allen et al. (18) used the IVA for the quantification of two methoxypyrazines in red wines, Guth (77) quantified wine lactone in various red and white wines and Aubry et al. (7P) used the technique for the determination of four esters (ethyl dihydrocinnamate, ethyl cinnamate, methyl anthranilate and ethyl anthranilate) in Pinot Noir wines. 

Deuterolysis of 3-chloro-2-chloromethyl-5-methoxypyrazine over 5% palladium on alumina in the presence of sodium isopropoxide in 2-propanol afforded 3-deutero-2-monodeuteromethyl-5-methoxypyrazine (687) and methylation of the bromomagnesium derivative from 2-bromomethyl-3,5,6-trimethylpyrazine with methyl sulfate or methyl iodide gave 2-ethyl-3,5,6-trimethylpyrazine (330). 

Methoxypyrazines (31) have been prepared by diazomethane methylation of 2-hydroxy-3-isobutylpyrazine (60, 311, 367), 2-hydroxy-3-isopropylpyrazine (59, 367), 2-hydroxy-3-propyl(ethyl or hexyl)pyrazine (367), 3-hydroxy-2-isobutyl-5(and 6)methylpyrazine and 2-hydroxy-3-isobutyl-5,6-dimethylpyrazine (368), 2,3-dihydroxypyrazine (832), 2-hydroxy-5-methoxy- and 2,5-dihydroxy-3,6-diphenyl-pyrazine (832), 2-hydroxy-6-methoxy(and benzyloxy)pyrazine (832), 2,6-dihydroxy-3,5-diphenylpyrazine (873), 2,3,5-trifluoro-6-hydroxypyrazine (851), 2-chloro-6-hydroxy-3,5-diphenylpyrazine (873), 2-chloro-6-hydroxy-5-methyl-3-phenylpyrazine (873), 2-chloro-6-hydroxy-3-methyl-5-phenylpyrazine (873), 5,6-dichloro-1 -cyclohexyl-34iydroxy-2-oxo-l, 2-dihydropyrazine (853), 2-chloro-5-hydroxy-3-methoxy-6-methoxycarbonylpyrazine (881), 2-(4 -amino-3, 5 -dibromo-phenylsulfonamido)-3Tiydroxy-6-methoxypyrazine (881), 2-amino-3-hydroxy-... 

Diisobutyl-3-methoxypyrazine 1,4-dioxide with phosphorus trichloride in ethyl acetate at 40° gave 2,5-diisobutyl-3-methoxypyrazine (and 2,5-diisobutyl-4-methoxy-3-oxo-3,4-dihydropyrazine 1-oxide similarly treated gave 3,6-diisobutyl-I-methoxy-2-oxo-l, 2-dihydropyrazine) (see Section 15) (980). 

Methylation (666, 912) of 2-methoxypyrazine with methyl iodide in dimethyl sulfoxide at room temperature gave 3-methoxy-l-methylpyrazinium iodide with a rate of methylation relative to pyrazine of 1.05 (666). 2-Methoxypyrazine with tetracyanoethylene oxide gave a small yield of 3 ethoxypyrazinium dicyano-methylide (53) (1094). Alkylation of 2-methoxypyrazine with ethyl methyl ketone in the presence of sodium in liquid ammonia to give 2-s-butyl-6-methoxypyrazine (17%) has been described (614). The reactions of 3-hydroxy-2,5-dimethylpyrazine and alkylhalides have been examined (1095). 

The odorants of dry sweet bell pepper powder have been analysed in detail [84, 85]. Omission experiments established ethyl methylpropanoate, methyl 2- and 3-methylb-utanoate, ethyl 2- and 3-methylbutanoate, 3-isopropyl-, 3-isobutyl- and 3-sec-butyl-2-methoxypyrazine as character impact odorants. 

Figure 4.10. Extracted ion chromatograms of GC/IT-MS/MS analysis of a 1 2.5 diluted wine spiked with four methoxypyrazines at 0.25 ng/L and two ethoxypyrazines at 45 ng/L as internal standards. The chromatographic conditions are described in Table 4.3. (49) 3-Ethyl-2-methoxypyrazine (m/z 119) (50) 3-isopropyl-2-methoxypyrazine (IPMP) (m/z 109) (51) 3-ethyl-2-ethoxypyrazine (internal standard 1) (m/z 124) (52) 3-isopropyl-2-ethoxypyrazine (I.S. 2) (m/z 123) (53) 3-seobutyl-2-methoxypyrazine (SBMP) (m/z 81) (54) 3-isobutyl-2-methoxypyrazine (IBMP) (m/z 109).

Ethyl-6-methoxypyrazine 204 3-Hexenoic acid 252 Linalool oxide... 

Potatoes 2-Isopropyl-3-methoxypyrazine together with 2,5-dimethylpyrazine (see pyrazines) dominate in raw potatoes. Key compounds in boiled potatoes are meAional and 2-ethyl-3,6-dimethylpyrazine. Tomatoes The highest flavor values in fresh tomatoes are exhibited by (Z)-3- and ( )-2-hexenals (see alkenals), j3- ionone, hexanal (see alkanals), 8-damascenone, I-penten-3-one (CsHgO, Mr 84.12, CAS [1629-58-9], 3-methylbutanal (see alkanals), and 2-isobutylthiazole. The most important flavor components in tomato pulp are dimethyl sulfide, )8-damascenone, )5-ionone, 3-methylbutanal, I-nitro-2-phenylethane (CgH,N02, Mr 151.16, CAS [24330-46-91), eugenol, methional, and 3-methylbutanoic acid. ... 

Chang et al. [73] and Nawar et al. [74] have identified many of the volatiles formed during deep fat frying. They have found numerous acids, alcohols, aldehydes, hydrocarbons, ketones, lactones, esters, aromatics, and a few miscellaneous compounds (e.g., pentylfuran and 1,4-dioxane) as products of deep fat frying. More recently, Wagner and Grosch [75] have studied the key contributors to French fry aroma. The list of key aroma compounds in French fries includes 2-ethyl-3,5-dimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, 3-isobutyl-2-methoxypyrazine, (E,Z), (E,E)-2,4-decadienal, trans-4,5-epoxy-(E)-2-decenal, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, methylpropanal, 2- and 3-methylbutanal, and methanethiol. If one examines this list, it is obvious that the Maillard reaction (pyrazines, branched chain aldeydes, furanones, and methional), and lipid oxidation (nnsaturated aldehydes) are the primary sources of this characteristic aroma. 

Cherry Benzaldehyde, Tolyl aldehyde (para) Chocolate 5-Methyl-2-phenyl-2-hexenal. Isoamyl butyrate, vanillin, ethyl vanillirt, methyl methoxypyrazine... 

Fig. 5.8. FD chromatogram of the volatile fraction of French fries. Ordinate n, number of 1 + 1 dilutions. Abscissa retention index (RI) on the capillary SE-54. The following odorants were identified 1 methional, 2 2-acetyl-1-pyrroline, 3 dimethyltrisulfide, 4 l-octen-3-one, 5 phenylacetaldehyde, 6 2-ethyl-3,6-dimethyl-pyrazine, 7 2-ethyl-3,5-dimethylpyrazine, 8 nonanal, 9 (Z)-2-nonenal, 10 2,3-diethyl-5-methylpyrazine, 11 (E)-2-nonenal, 12 2-ethenyl-3-ethyl-5-methylpyrazine, 13 2-isobutyl-3-methoxypyrazine, 14 dimethyltetrasulfide, 15 (E,E)-2,4-nonadienal, 16 (Z)-2-decenal, 17 (E,Z)-2,4-decadienal, 75 (E,E)-2,4-decadienal, 79trans-4,5-epoxy-(E)-2-decenal (according to Wagner and Grosch, 1997)...

The difference between the aroma of the beverage and that of ground coffee is the more intensive phenolic, buttery, caramel-like note and a we iker roasty note. These changes are caused by shifts in the concentrations of the aroma substances during brewing (Table 21.8). Compounds hke 2,3-butandione, the furanones 6, 7 and 27, 2-ethyl-3,5-pyrazine, the thiols 17 and 18 are extracted with yields of >75%, while only 25% or less of 2-ethenyl-3-ethyl-5-methylpyrazine, 3-iso-butyl-2-methoxypyrazine, 2-furfurylthiol and P-damascenone pass into the beverage. The low yield of 2-furfurylthiol is partly due to reactions which occur during percolation of the coffee powder. 

Important components of hard cheeses (Gouda type) include some carboxylic acid esters (ethyl butanoate, ethyl hexanoate), as well as carboxylic acids (acetic, butyric, isobutyric, valeric, isovaleric, 2-methylbutyric and caproic acids). Cheeses manufactured using bacteria of the genus Propionibacterium (such as Emmental and Gruyere) contain propionic acid and other lower fatty acids, methyl thioacetate, some oxocarboxylic acids, various alcohols, esters (such as ethyl butanoate), lactones (such as 8-decalactone), amines and other basic compounds (also skatole in addition to aliphatic amines), alkylpyrazines (e.g. 2-sec-butyl-3-methoxypyrazine), 4-hydroxy-2,5-dimethyl-2H-furan-3-one (furaneol), 2-ethyl-4-hydroxy-5-methyl-2H-furan-3-one (homofuraneol) and a range of other compounds. 

Significant aliphatic sulfur compounds are methional, 3-methyl-but-2-ene-1-thiol, 3-mercapto-3-methylbutan-l-ol (8-124), its ester 3-mercapto-3-methylbutyl formate, methanethiol and dimethyltrisulfide. 3-Mercapto-3-methyl-l-ol also occurs in passion fruit and blackcurrant, and as a putative cat pheromone in cat urine, where it is formed as a degradation product of amino acid L-felinine (see Section 2.2.1.2.2). Of more than 70 known pyrazines, the most important compounds in roasted coffee are isopropylpyrazine, 2-isobutyl-3-methoxypyrazine, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, 2,6-dimethyl-3-vinylpyrazine and 2-ethyl-6-methyl-3-vinylpyrazine. Pyridine and its alkyl derivatives and bicyclic pyridines have a negative impact on the quality of coffee aroma. Important aromatic... 

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