The known 3,5-dimethylpyrrole-2,4-dicarboxylic acid 2-benzyl ester 4-t-butyl ester (I) is subjected to benzyl group hydrogenolysis over Pd/C to provide the corresponding pyrrole-2-carboxylic acid (II). Subsequent coupling of acid (II) with 1-propanol (III) in the presence of trifluoroacetic anhydride furnishes the 2-propyl ester (IV). The 4-t-butyl ester of (IV) is then cleaved by means of trifluoroacetic acid, yielding the pyrrole-4-carboxylic acid (V). This is finally coupled to 3,3-dimethyl-2-butanol (VI) by using trifluoroacetic anhydride to furnish the target pyrrole diester.

Nitrosation of tert-butyl acetoacetate (I) with NaNO2 in cold AcOH leads to oxime (II), which is further condensed with benzyl acetoacetate (III) in the presence of Zn and ammonium acetate, to produce pyrrole (IV). The 4-benzyl ester of (IV) is selectively removed by catalytic hydrogenolysis over Pd/C, yielding the pyrrole-4-carboxylic acid (V). Subsequent coupling of acid (V) with 3,3-dimethyl-2-butanol (VI) employing trifluoroacetic anhydride furnishes the target pyrrole diester.