合成路线1

Reaction of 4-hydroxy-3-nitrobenzaldehyde (I) with hydroxylamine and sodium formate in refluxing formic acid gives 4-hydroxy-3-nitrobenzonitrile (II), which is treated with thioacetamide in hot DMF to yield the corresponding thiobenzamide (III). The cyclization of (III) with 2-chloroacetoacetic acid ethyl ester (IV) in refluxing ethanol affords 2-(4-hydroxy-3-nitrophenyl)-5-methylthiazole-4-carboxylic acid ethyl ester (V), which is alkylated at the phenolic group by means of isobutyl bromide (VI) and K2CO3 in hot DMF, providing the isobutyl ether (VII). The reduction of the NO2 group of (VII) with H2 over Pd/C in ethanol/ethyl acetate gives the expected amino derivative (VIII), which is converted into 2-(3-cyano-4-isobutoxyphenyl)-4-methylthiazole-5-carboxylic acid ethyl ester (IX) by diazotation with NaNO2/HCl and treatment with CuCN and KCN. Finally, this compound is hydrolyzed with NaOH in hot THF.