The condensation between 3-methoxybenzaldehyde (I), S-methylisothiourea (II) and ethyl cyanoacetate (III) in the presence of K2CO3 in hot EtOH leads to pyrimidine (IV). Subsequent chlorination of (IV) by means of POCl3 and dimethylaniline furnishes the 6-chloropyrimidine (V). Reaction of (V) with ethyl mercaptoacetate (VI) and potassium tert-butoxide gives rise to the thienopyrimidine (VII). The ethyl ester group of (VII) is then hydrolyzed to the carboxylic acid (VIII) employing LiOH. Finally, coupling of acid (VIII) with tert-butylamine by means of TBTU produces the target N-tert-butyl amide