25724-34-9Relevant academic research and scientific papers
Characterization of Aroma-Active Compounds in Italian Tomatoes with Emphasis on New Odorants
Kreissl, Johanna,Schieberle, Peter
, p. 5198 - 5208 (2017/07/04)
An aroma distillate was prepared by solvent extraction and subsequent SAFE distillation from Italian vine-ripe tomatoes eliciting an intense overall aroma. Application of gc/olfactometry and the aroma extract dilution analysis revealed 44 odor-active compounds, 42 of which could be identified. The highest odor activity value of 2048 was established for the green, grassy (Z)-3-hexenal, the metallic smelling trans-4,5-epoxy-(E)-2-decenal, the potato-like 3-(methylthio)propanal, and the caramel-like 4-hydroxy-2,5-dimethyl-3(2H)-furanone. Of the further odorants, 13 compounds have previously not been reported as tomato odorants. Although most of these showed lower FD-factors, in particular, the coconut/dill-like smelling wine lactone ((3S,3aS,7aR)-3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one) appeared with a quite high FD factor. In addition, a fruity, almond-like odorant (6) with an FD factor of 1024 was detected. By application of high resolution mass spectrometry and polarity considerations, the structure of a methyl-2-ethoxytetrahydropyran isomer was suggested for 6. Four of the five possible isomers, the 3-methyl-, 4-methyl-, 5-methyl-, and 6-methyl-2-ethoxytetrahydropyran were synthesized and showed similar mass spectrometric patterns. However, these were excluded by their different retention indices. Although the synthesis of the remaining 2-methyl-2-ethoxytetrahydropyran resulted in only small yields, which were not sufficient for NMR measurements, this structure is very likely for 6. This compound was never reported as a food constituent before. Finally, quantitation of 23 odorants by stable isotope dilution assays allowed for the preparation of an aroma recombinate resembling the overall aroma of the tomatoes.
EXPERIMENTAL STUDIES OF THE ANOMERIC EFFECT. PART IV. CONFORMATIONAL EQUILIBRIA DUE TO RING INVERSION IN TETRAHYDROPYRANS SUBSTITUTED AT POSITION 2 BY THE GROUPS ETHOXY, 2'-FLUOROETHOXY, 2',2'-DIFLUOROETHOXY, AND 2',2',2'-TRIFLUOROETHOXY
Booth, Harold,Readshaw, Simon A.
, p. 2097 - 2110 (2007/10/02)
Equilibrium constants (K) for ring inversion equilibria in 2-(RO)-tetrahydropyrans (R = Et, CH2CH2F, CH2CHF2, CH2CF3) have been determined from 13C nmr spectra recorded at 145-160 K in CD2Cl2 and CFCl3/CDCl3 (85/15 by volume).Additional values of K were obtained at 250-270 K from the acid-catalysed equilibration of cis- and trans-2-(RO)-4-methyl-tetrahydropyran (R as above).Plots of lnK against T-1 gave values for ΔH0a->e of -0.26, -0.12, -0.05 and 0.13 kcal mol-1 for R = Et, CH2CH2F, CH2CHF2 and CH2CF3, respectively, in CD2Cl2.The corresponding values of ΔH0a->e for CFCl3/CDCl3 as solvent were -0.58, -0.15, -0.07 and 0.21 kcal mol-1, respectively.The derived ΔS0a->e values were -2.33, -2.22, -2.25 and -2.24 cal K-1mol-1, respectively, in CD2Cl2 and -4.65, -3.37, -3.30 and -3.03 cal K-1mol-1, respectively, in CFCl3/CDCl3. The trends in ΔH0 values are attributed to modifications of anti-periplanar n->o* stabilisation (itself partly responsible for endo- and exo-anomeric effects) which occur as the number of electronegative fluorine substituents increases.For all substituents, axial conformations are the most abundant in the temperature range 120 K to infinite.However, this finding is a consequence of the higher entropy of axial conformations; in at least two cases (R = Et and CH2CH2F) it is the equatorial conformation which has the lower enthalpy.The results confirm the importance of studying conformational equilibria over a wide range of temperature.
