Polyenecarboxylic acid

Polyenecarboxylic acids add bromine most easily at the C=C bond furthest removed from the COOH group.54... 

C20H20O2, Mr 292.38, yellow amorphous powder, mp. 118°C. An unstable polyenecarboxylic acid with an oH/to-substituted benzene ring and possessing ( )- and (Z)-double bonds in the side chains, produced by Strep-... 

The Cs-phosphonium ester salts 95 + 99 and the Cs-phosphonate ester 100 (Scheme 11), as well as their corresponding methyl esters, are key building blocks for the manufacture of various polyenecarboxylic acid esters for use in the carotenoid field [34-36]. An efficient route uses as an intermediate 2-hydroxy-2-methylbut-3-enoic acid ethyl ester (101) [37,38], which can be prepared from methylvinyl ketone (102) by acidic ethanolysis of the cyanohydrin 103, prepared by reaction of 102 with HCN (104). Reaction of 101 with thionyl chloride under reflux conditions led to a 76% yield of distilled 4-chloro-2-methyl-but-2-enoic acid ethyl ester (105), from which the phosphonium chloride 98 was obtained in good yield [36]. 

Isomeric polyenecarboxylic acid esters from aldehydes GHg + OG G C... 

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