合成路线1

Friedel-Crafts acylation of N-methylpyrrole (I) with trichloroacetyl chloride (II) affords the pyrrolyl ketone (III), which is subsequently subjected to electrophilic nitration with in situ generated acetyl nitrate, producing nitropyrrole (IV). Cleavage of the trichloroketone group of (IV) under alkaline conditions, followed by Fischer esterification leads to methyl ester (V). The nitro group of (V) is then reduced to amine (VI) by catalytic hydrogenation over Pd/C. After protection of amine (VI) as the corresponding N-Boc derivative (VII), saponification of the methyl ester group of (VII) yields acid (VIII). Coupling between the pyrrolecarboxylic acid (VIII) and amino ester (VI) provides the amide adduct (IX). After alkaline ester hydrolysis in (IX), the resultant carboxylic acid (X) is coupled with a further moiety of methyl 4-amino-1-methylpyrrole-2-carboxylate (VI) to furnish the tripyrrolyl compound (XI). Subsequent methyl ester saponification in (XI) provides acid (XII).