Ketones polyunsaturated

The branched-chain polyunsaturated ketones tagetone and ocimenone, the odor impact compounds ia tagettes, are unstable and presumably responsible for the resiniftcation of the oil. 

Many selective epoxidations are possible with polyunsaturated steroids. In general, oc, -unsaturated ketones are not attacked by peracid, although linear dienones react slowly at the y,5-double bond. Aw-Chloroperbenzoic acid is the reagent of choice for this reaction.When two isolated double bonds are present in the steroid nucleus, e.g. (27) and (30), the most highly substituted double bond reacts preferentially with the peracid. Selective epoxidation of the nuclear double bond of stigmasterol can likewise be achieved.However, one exception to this general rule has been reported [See (33) (34)]. ... 

Brain Coordination of the nervous system Glycolysis, amino acid metabolism Glucose, amino acid, ketone bodies (in starvation) Polyunsaturated fatty acids in neonate Lactate ... 

A mild, Fe(CO)5-catalyzed isomerization of this type was reported by Gree and coworkers [173]. Allylic alcohols having mono-, di-, trisubstituted alkene are readily converted into their corresponding ketones, whereas polyunsaturated derivatives do not rearrange (Scheme 54). 

Oxidative damage to membrane polyunsaturated fatty acids leads to the formation of numerous lipid peroxidation products, some of which can be measured as index of oxidative stress, including hydrocarbons, aldehydes, alcohols, ketones, and short carboxylic acids. 

Hydroperoxide formation by the ene reaction path may lead to formation of conjugated double bonds in polyunsaturated fatty acids (see Section V.A) this reaction is concurrent with POV increase. An increase of the CDV, as measured from the absorbance at 233 nm, therefore indicates oxidation of polyunsaturated lipids. A strong correlation exists between CDV predicted from the absorbance in the 1100 to 2200 nm NIR region and CDV determined by the Ti Ia-64 AOCS official method , by UV spectrophotometry at 233 nm. The method was applied to determine CDV for oxidized soybean oil. A secondary absorption maximum of lesser intensity appears in the 260-280 mn range, and is assigned to ketone dienes . 

A significant portion of the neutral ethyl ether extract from the salts of carboxylated methyl linoleate consists of ,/3-unsaturated cyclic ketones. This material is produced in small but significant amounts (4-10%) (Table I) from the carboxylation of polyunsaturates but not from the corresponding monounsaturated fatty acids and esters (19). These ,/ -unsaturated cyclic ketones were identified spectroscopically (IR, UV, and NMR) as 4. This structural assignment was firmly established by mass spectral analyses before and after hydrogenation of the carbon-carbon double bond. 

Such is most often the case when the dehydration product is a polyunsaturated conjugated aldehyde or ketone. 2-Propanone and benzenecarbaldehyde (benz-aldehyde), for instance, give the unsaturated ketone 12 in cold aqueous sodium hydroxide solution ... 

The aldehydes are generated at temperatures as low as 60 C. O-f particular note is the oxidation o-f phospholipids and polyunsaturated -fatty acids. It is the oxidative products o-f arachidonic acid -from the phospholipid -fraction in chicken, yielding cis—4-decenal, trans-2-cis—5—undecadienal, and trans-2-cis—4— trans-7—tridecatrienal that are responsible -for the species identity o-f chicken. At temperatures o-f 200 to 300 C the thermal oxidative reactions allow the -formation o-f ketones and lactones as well as aldehydes. 

Further examples of a, 3-unsaturated ketones include molecules such as steroid derivatives that were not originally designed as photoaffinity reagents. Polyunsaturated compounds that may be photolysed efficiently at wavelengths above 300 nm are preferred (e.g. Fig. 2.6 Dureetal., 1980 Nordeen et al., 1981 Sadler and Mailer, 1982). 

Within the Lymantriidae, patterns of pheromone use are not yet clear, and there appears to be the greatest diversity of pheromone structures. Roughly two-thirds of the approximately thirty species for which pheromones or sex attractants have been reported have polyenes, epoxides, ketones, or polyunsaturated esters that could be classified as belonging to the Type n class, whereas the remainder use branched-chain epoxyalkane pheromones. Remarkably, even within a genus (e.g., Lymantria or Euproctis), congeners produce pheromones of different classes (Table 18.4). 

Polyunsaturated aliphatic alkohols, aldehydes, ketones, and esters occur as fragrance components in fats, oils, fruits and plants 158). As an example the synthesis of ethyl (2 ,4Z)-2,4-decadienoate (232, pear ester ), which is responsible for the aroma of bartlett pears 161) is given. 2,4-Diunsaturated ester 232 may be obtained by a number of highly stereoselective syntheses, a lot of them making use of the Wittig reaction. Ohloff and Pawlak condensed 4,5-epoxy-( )-2-pentenal 228 with the ylide generated from 229 (butyllithium/ether) to the alkadiene epoxide 230 which was oxidized with periodic acid to the 2,4-decadienal 231. 231 is subsequently converted with MnOj/NaCN in ethanol to the pear ester 232162) [75 % (Z)-amount of the C-4 double bond] (Scheme 44). 

Lipoxygenase Bean, potato, tomato, maize, strawberry, canola, fish, meat Oxidation of polyunsaturated fatty acids to hydroperoxides and further into aldehydes, acids, ketones, etc. 

The aromas associated widi very fi esh fish are usually mild, delicate and fi esh (53,54), and generally described as green (hexanal), melon-like ((E,Z)-3,6-nonadienal), iodine-like (bromophenols). Fresh fish and seafood aromas are due to volatile carbonyls and derive fi om lipoxygenase catalyzed oxidation of polyunsaturated fatty acids. The oxidation of Eicosapentaenoic acid (C20 5) leads to C5 to C9 alcohols, aldehydes, ketones and hydrocarbons. The formation of methyl mercaptan, dimethyl sulfide and dimethyl disulfide in fi esh fish at the time of harvest has been reported by Shiomi et al. (55). Although these compounds are usually associated with fish deterioration, they contribute to the fi esh aroma ch cter at low concentrations. For instance, dimethyl sulfide is... 

Brunengraber H. Potential of ketone body esters for parenteral and oral nutrition. Nutrition 1997 13 233-235. Carrie 1, Clement M, Javel DD, Frances H, Bourre J. Learning deficits in first generation OFl mice deficient in (n-3) polyunsaturated fatty acids do not result from visual alteration. Neurosci Lett 1999 266 69-72. 

Without deviating from the theme of this review, the 3-azapyrylium (1,3-oxazi-nylium , l,3-oxazin-l-ium ) salts formed by the reactions described above deserve particular attention. Their conversions to both jS-A -acyl amino vinyl ketones 49 and 200 and to polyunsaturated A -acylimines 50-52 have been shown above (equations 18 and 63). Their properties and methods of their synthesis were investigated in detail by Schmidt and coworkers ° and summarized in a number of revie 19.123 3-azapyrylium salts are easily converted in reactions with amino... 

---