Ethyl 2-hydroxy-2-methylpropanoate,

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... 

A patent describes the synthesis of ethyl 2-fluoro-2-methylpropanoate (9) from ethyl 2-hydroxy-2-methylpropanoate (8) with sulfur tetrafluoride/hydrogen fluoride. 1... 

C6H120S S-tert-butyl thioacetate 999-90-6 407.10 35.035 1,2 8540 C6H1203 ethyl 2-hydroxy-2-methylpropanoate 80-55-7 423.15 36.552 1,2... 

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. 

The volatiles of fresh pineapple (Ananas comosus [L] Merr.) crown, pulp and intact fmit were studied by capillary gas chromatography and capillary gas chromatography-mass spectrometry. The fnjit was sampled using dynamic headspace sampling and vacuum steam distillation-extraction. Analyses showed that the crown contains Cg aldehydes and alcohols while the pulp and intact fruit are characterized by a diverse assortment of esters, h rocarbons, alcohols and carbonyl compounds. Odor unit values, calculated from odor threshold and concentration data, indicate that the following compounds are important contributors to fresh pineapple aroma 2,5-dimethyl-4-hydroxy-3(2H)-furanone, methyl 2-methybutanoate, ethyl 2-methylbutanoate, ethyl acetate, ethyl hexanoate, ethyl butanoate, ethyl 2-methylpropanoate, methyl hexanoate and methyl butanoate. 

The reaction of 1,5,2-dioxazepine 66 with zinc and AcOH results in the reductive cleavage of the N-O bond, furnishing either methyl 2-(3-benzyl-7-hydroxy-l,4-oxazocan-5-yl)-2-methylpropanoate or methyl 2-(3-ethyl-7-hydroxy-l,4-oxazocan-5-yl)-2-methylpropanoate 67 (Scheme 11) <1999ZNB519>. 

Benzyloxy)-2-fluoro-2-methylpropanal (8) is prepared in optically active form from ethyl (5 )-2-fluoro-3-hydroxy-2-methylpropanoate (7). Ester 7 is readily obtained from ethyl (S)-2-fiuoro-2-methylmalonate (6) which can, itself, be prepared by enzymatic hydrolysis. ... 

Our first synthesis of the natural (2S,3R,VR)- 4 was published in 1986.124 As shown in Figure 4.71, the required building block B was prepared from ethyl (,R)-3-hydroxybutanoate of 100% ee via A. Another building block C was synthesized from methyl (,R)-3-hydroxy-2-methylpropanoate (97% ee). Esterification of B with C gave the key intermediate D, whose intramolecular cyclization afforded the required pyra-none system. The synthetic (2S,3R,VR)- 4 showed spectral properties identical to those of the natural stegobinone, although it remained as an oil due to the contamination with trace amounts of impurities. Our... 

Dihydroisoxazole 1066 is obtained in nearly quantitative yield from the cycloaddition of ethyl methacrylate with ethoxycarbonylformonitrile oxide. Treatment of 1066 with protease from Aspergillus oryzae in a two-phase system (toluene and pH 7.0 buffer) results in an enantio-selective hydrolysis of the 5-carboxylate group, producing a mixture of (/ )-1067 (44.5% yield, 97% ee) and (5)-1068 (55% yield, 77% ee) when the reaction is terminated at 55% conversion. Hydrolysis of the diester 1067 and thermal decarboxylation of the resulting diacid (1069) affords (i )-3-cyano-2-hydroxy-2-methylpropanoic acid (1070). Acid catalyzed methanolysis of the nitrile group gives 1059 with > 97% ee. 

S) -(-)-Lactic acid butyl ester see Butyl (S)-(-)-2-hydroxy-2-methylpropanoate (S)-(-)-Lactic acid ethyl ester see Ethyl (S)-(-)-2-hydroxypropanoate (S)-(-)-Lactic acid isopropyl ester see Isopropyl (S)-(-)-2-hydroxy-2-methylpropanoate Lauryl alcohol Dodecan-l-ol... 

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