83823-87-4Relevant articles and documents
Synthesis of Anacardic Acids
Zehnter, Reinhard,Gerlach, Hans
, p. 2209 - 2220 (2007/10/03)
The anacardic acids 1-11, isolated from various plants, were synthesized by a new general method.Reaction of the methyl alkynoates 12-18 with 1-methoxy-1,4-cyclohexadiene at 200 deg C afforded directly the methyl 2-methoxybenzoates 19-25 with long chain substituents in 6-position in 74-85percent yield.The dienophiles 12-16 were prepared by pyrolysis of the corresponding acylphosphoranes 26-30, the dienophiles 17 and 18 by methoxycarbonylation of the corresponding alkynes 31 and 32 via the hydroxy esters 33 and 34.Demethylation of 19-23 with AlI3 gave the methyl salicylates 35-39 which could be hydrolized to the anacardic acids 1-4 and 7.Hydrolysis of 24 and 25 provided the hydroxy acids 40 and 41, which were converted by treatment with CBr4/PPh3 into the acids 42 and 43 bearing bromoalkyl side chains.These were transformed into 44-47 by reaction with 1-hexynyllithium and 1-octynyllithium.Stereoselective hydrogenation of 44-47 gave 48-51 with (Z)-alkene side chains.In a similar approach 42 was converted into 52 and then into 53, which gave upon treatment with 1-pentynylmagnesium bromide or 1-heptynylmagnesium bromide the acids 54 and 55 with alkadiyne side chains.Stereoselective hydrogenation provided 56 and 57 with (Z,Z)-alkadiene side chains.The 2-methoxy group in 48-51, 56, 57 was demethylated by treatment with AlI3 to give the anacardic acids 5, 6, 8-11. - Keywords: Anacardic acids; Benzoates, methyl 6-alkyl-2-methoxy-; 2-Alkynoates, methyl; Aluminium triiodide, demethylation by treatment with
