Ethyl 2-methylpropanoate

Analysis of grapefruit juice [71] gave high OAV for 4-mercapto-4-methylpentan-2-one (MMP), ethyl (S)-2-methylbutanoate, (Z)-3-hexenal, ethyl butanoate, decanal, ethyl methylpropanoate and l-p-menthen-8-thiol (MTO, probably the R-enantiomer). The aroma of a solution containing 19 odorants in the levels found in grapefmits was very similar to the natural aroma of this fmit [71 ]. 

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. 

A sweetish off-flavor formed during storage of beer is caused by an increase in 3-methyl-butanal, methional, phenylacetaldehyde, ethyl methylpropanoate and ethyl 2-methylbutanoate. The addition of ascorbic acid or glucose oxi-dase/catalase (cf. 2.7.2.1.1) is recommended to overcome color and flavor defects caused by oxidation. Therefore, low-oxygen bottling is of great importance. Bottled beer should not contain more than 1 mg O2 /I. 

Unless the p keto ester can form a stable anion by deprotonation as m step 4 of Figure 21 1 the Claisen condensation product is present m only trace amounts at equi librium Ethyl 2 methylpropanoate for example does not give any of its condensation product under the customary conditions of the Claisen condensation... 

The next step yields 1-(3-acetylthio-2-methylpropanoyl)-L-proline tert-butyl ester. L-proline tert-butyl ester (5.1 g) is dissolved in dichloromethane (40 ml) and the solution stirred and chilled in an ice bath. Dicyclohexylcarbodiimide (15 ml) is added followed immediately by a solution of 3-acetylthio-2-methylpropanoic acid (4.9 g) in dichloromethane (5 ml). After 15 minutes stirring in the ice bath and 16 hours at room temperature, the precipitate is filtered off and the filtrate is concentrated to dryness in vacuo. The residue is dissolved in ethyl acetate and washed neutral. The organic phase is dried over magnesium suifateand concentrated to dryness in vacuo. The residue 1-(3-acetylthio-2-methylpropanoyl)-L-proline tert-butyl ester is purified by column chromatography (silica gel-chloroform), yield 7.9 g. 

Chemical Name 2-(4-chlorophenoxy)-2-methylpropanoic acid ethyl ester Common Name Ethyl p-chlorophenoxylsobutyrate... 

Ethyl dimethylacetoacetate reacts instantly at room temperature when treated with ethoxide ion to y- ield two products, ethyl acetate and ethyl 2-methylpropanoate. Propose a mechanism for this cleavage reaction. 

RN 66195-31-1 MF CnH25N04 MW 307.39 EINECS 266-229-5 CN 2-methylpropanoic acid 4-[2-(methylamino)ethyl]-1,2-phenylene ester... 

Ethyl hexyl ketone, nlOO Ethyl hydrogen adipate, el77 /V-Ethyl-/V-(2-hydroxyethyl)-3-toluidine, e267 Ethyl 2-hydroxy-2-methylpropanoate, el82 Ethyl 2-hydroxypropionate, el94 Ethylidene bromide, d96... 

Ethyl butanoate Methyl hexanoate Methyl nonanoate Methyl 3-methylbutanoate Methyl 2-methylpropanoate Ethyl 3-acetamidobutanoate (70) Methyl 5-acetamidohexanoate (42) Methyl 4-acetamidohexanoate (11) Methyl 8-acetamidononanoate (25) Methyl 3-acetamido-3-methylbutanoate (68) Methyl 2-acetamido-2-methylpropanoate (58) Methyl 3-acetamidobutanoate (4)... 

Imino-substituted pyridazine 68 reacted in the 5-position with the lithium enolate of ethyl 2-methylpropanoate 69 via an interesting cascade of nucleophilic addition, ring closure via addition-elimination and tautomerization (Scheme 13) <1996JHC1731>. 

Wild and cultivated blackberries have been used as food and medicine for hundreds of years [106]. Approximately 150 volatiles have been reported from blackberries [107]. The aroma profile is complex, as no single volatile is described as characteristic for blackberry [108, 109]. Several compounds have been suggested as prominent volatiles in blackberries using AEDA, e.g. ethyl hexanoate, ethyl 2-methylbutanoate, ethyl 2-methylpropanoate, 2-heptanone, 2-undecanone, 2-heptanol, 2-methylbutanal, 3-methylbutanal, hexanal, ( )-2-hexenal, furaneol, thiophene, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, 2-methylthiophene, methional, a-pinene, limonene, linalool, sabinene. 

The highest OAVs were found for 4-hydroxy-2,5-dimethyl-3(2H)-fura-none, followed by ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, methyl 2-methylbutanoate and ( ,Z)-l,3,5-undecatriene. It is assumed that these odorants contribute strongly to the aroma of pineapples [50]. However, FD factors and OAVs are functions of the odorants concentrations in the extract, and are not psychophysical measures for perceived odour intensity [71,72]. To take this criticism into account, aroma models are prepared on the basis of the results of the quantitative analysis (reviewed in [9]) and in addition omission experiments are performed [9]. 

In the case of pineapples, the 12 odorants listed in Table 16.7 were dissolved in water in concentrations equal to those determined in the fruit [50]. Then the odour profile of this aroma model was evaluated by a sensory panel in comparison to fresh pineapple juice. The result was a high agreement in the two odour profiles. Fresh, fruity and pineapple-like odour notes scored almost the same intensities in the model as in the juice. Only the sweet aroma note was more intense in the model than in the original sample [50]. In further experiments, the contributions of the six odorants showing the highest OAV (Table 16.7) were evaluated by means of omission tests [9]. The results presented in Table 16.8 show that the omission of 4-hydroxy-2,5-dimethyl-3(2H)-furanone, ethyl 2-methylbutanoate or ethyl 2-methylpropanoate changed the odour so clearly that more than half of the assessors were able to perceive an odour difference between the reduced and the complete aroma model. Therefore, it was concluded that these compounds are the character-impact odorants of fresh pineapple juice. 

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