5- alkanoic acid 2-alkenoate ester

The formation of acyl conjugates of vanillamine (capsaicinoids, 20) or vanillic alcohol (capsinoids, 21) with various Cg/Ci3 alkenoic and alkanoic acids is a unique chemical trait of plants from the genus Capsicum. Hot peppers are characterized by the presence of vanillyl conjugates of the amide type, absent or replaced by their nonpungent ester isosters (capsinoids) in bell (sweet) peppers [19]. Indeed, the difference between the sensory properties of capsaicin (la) and its naturally occurring ester analog capsiate (22) is a remarkable example of the biological relevance of isosterism. 

A bifnnctional enol-CoA hydratase and 3-hydroxyacetyl-CoA dehydrogenase are used in the degradation of CoA-alkenoic esters to the p-keto acid. This is then degraded to acetyl-CoA and the lower alkanoate ester by 3-ketoacetyl CoA thiolase and acetyl-CoA thiolase. 

The reaction of the phosphonium salts 28, generated from the -halogencarboxylic esters 26, with sodium ethoxide in DMF or sodium hydride in DMSO yields the phosphoranes 29 which, on treatment with aldehydes 30, are converted into (Z)-alkenoic esters 31 49,51 53). To synthesize As-unsaturated acids and higher homologous acids of type 31 (m 11) Bergelson et al. 49,54) olefinated ethyl co-formyl-alkanoates 34, obtained from co-iodoalkanoic esters 32, with alkylidenephosphoranes 35 to the ethyl esters 31 (Scheme 7). 

Formation of AllylEsters. AEyl esters are formed by reaction of aEyl chloride with sodium salts of appropriate acids under conditions of controEed pH. Esters of the lower alkanoic, alkenoic, alkanedioic, cycloalkanoic, benzenecarboxyEc, alkylbenzene carboxyEc, and aromatic dicarboxyEc acids maybe prepared in this manner (25). More information can be found about the reactivity of aEyl compounds (see Allyl alcohol and mono allyl derivatives). 

In Candida sp., degradation of the CoA-alkanoic esters to the alkenoic acid esters is catalyzed by an acyl-CoA oxidase and results in the production of H2O2 that is converted into O2 by catalase activity. The enzyme from C. tropicalis contains FAD (Jiang and Thorpe 1983), and in C. lipolytica carries out a stereospecific antielimination of hydrogen (Kawagnchi et al. 1980). 

Some alkanoic and alkenoic acids derived from biphenyl, stilbene and diphenylethane were reported to have potential antirheumatic and hypo-cholesterolaemic properties. Some of these compounds were later investigated by Milla and Grumelli for anti-inflammatory activity the only compound which showed activity was 3-(4-biphenylyl) acrylic acid, p-PhCgH4 GH = CH-CO-OH. Some of the alkylamine esters of this acid prepared by Carissimi , and the acid itself, were then examined for antiinflammatory activity in dextran oedema of the rat-foot, experimental granuloma in the rat, and synovial permeability in the rabbit, and for their ability to modify the reactions of subcutaneous connective tissue in mice. 

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