Rrans-2-Heptene

Further efforts to design chiral ligands led to the highly enantioselective oxidation of rranj-/3-methylstyrene (99% ee), mms-stilbene (97% ee), styrene (90%) rrans-3-heptene (90% ee), and dimethyl fumarate (93% ee) (87b-f). Although this reaction is a reliable synthetic method, the metal s cost and toxicity necessitate its use as a catalyst. In 1988, Sharpless found that the desired enantioselective reaction can be achieved... 

The hydroperoxy epidioxides formed from photosensitized oxidized methyl linoleate are important precursors of volatile compounds, which are similar to those formed from the corresponding monohydroperoxides. Thus, 13-hydroperoxy-10,12-epidioxy-tra 5 -8-enoic acid produces hexanal and methyl lO-oxo-8-decenoate as major volatiles (Figure 4.24). The 9-hydroperoxy-10,12-epidioxy-rrans-13-enoic acid produces 2-heptenal and methyl 9-oxononanoate. Other minor volatile products include two volatiles common to those formed from the monohydroperoxides, pentane and methyl octanoate, and two that are unique, 2-heptanone and 3-octene-2-one. The hydroperoxy epidioxides formed from autoxidized methyl linolenate produce the volatiles expected from the cleavage reactions of linolenate hydroperoxides, and significant amounts of the unique compound 3,5-octadiene-2-one. This vinyl ketone has a low threshold value or minimum detectable level, and may contribute to the flavor impact of fats containing oxidized linolenate (Chapter 5). 

A large number of volatile compounds have been identified in beef fat (Table 11.17). The flavor significance of individual volatile compounds can be calculated on the basis of their threshold values. Thus, two of the carbonyl compounds formed in the smallest concentrations, c/5-4-heptenal and rran, tran5 -2,6-nonadienal, were the most flavor significant. More sensitive GC-MS analyses reported odor threshold values of 1260 ppb for cw-4-heptenal and 1231 for tra 5, d5 -2,6-nonadienal found among fish oil volatiles (Section E.3 and Chapter 5). On the other hand, the most abundant carbonyl, 2-decenal, was the least flavor significant. 

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