合成路线1

Addition of 3-methyl-2-butenoic acid (II) to 4-methoxythiophenol (I) in the presence of piperidine at 105 C afforded adduct (III). After conversion of (III) to the corresponding acid chloride (IV) with oxalyl chloride, Friedel-Crafts cyclization using SnCl4 produced thiochromanone (V). Cleavage of the methyl ether of (V) by means of BBr3 gave phenol (VI), which was converted to triflate (VII) with trifluoromethanesulfonic anhydride in pyridine. Coupling of (VII) with trimethylsilyl acetylene (VIII) using a palladium catalyst provided (IX). Subsequent desilylation of (IX) with K2CO3 in MeOH, followed by palladium-catalyzed coupling of the resulting alkyne with ethyl 4-iodobenzoate (X) afforded the diaryl acetylene (XI). Introduction of the 4-aryl group in (XI) was achieved by conversion of (XI) to vinyl triflate (XIII) upon treatment of the sodium enolate with the bis-triflimide reagent (XII), and further condensation with 4-ethyl-phenylzinc chloride (XIV) yielding (XV). Finally, basic hydrolysis of the ethyl ester (XV) furnished the target carboxylic acid.