Ethyl 5-nitroindole-2-carboxylate (I) was hydrogenated over Pd/C to give amino indole (II), which was condensed with methanesulfonyl chloride, affording sulfonamide (III). Subsequent hydrolysis of the ester group of (III) furnished the intermediate indolecarboxylic acid (IV).

Deprotonation of 2-bromopyridine (V) with LDA and subsequent quenching with dimethylformamide provided 2-bromo-3-formylpyridine (VI). Nucleophilic substitution of the bromine of (VI) with N-Boc-4-(methylamino)piperidine (VII) in diisopropylethylamine at 100 C in a sealed tube yielded aminopyridine derivative (VIII). Then, Wittig olefination of (VIII) with the ylide resulting from isopropyl triphenylphosphonium iodide and n-BuLi introduced the isobutenyl substituent giving (IX), and further catalytic hydrogenation furnished the isobutyl derivative (X). The Boc group of (X) was deprotected by treatment with HCl in dioxan to give piperidine (XI). Finally, coupling of (XI) with indolecarboxylic acid (IV) via activation with carbonyl diimidazole yielded the title carboxamide.

Deprotonation of 2-bromopyridine (V) with LDA and subsequent quenching with dimethylformamide provided 2-bromo-3-formylpyridine (VI). Nucleophilic substitution of the bromine of (VI) with N-Boc-4-(methylamino)piperidine (VII) in diisopropylethylamine at 100 C in a sealed tube yielded aminopyridine derivative (VIII). Then, Wittig olefination of (VIII) with the ylide resulting from isopropyl triphenylphosphonium iodide and n-BuLi introduced the isobutenyl substituent giving (IX), and further catalytic hydrogenation furnished the isobutyl derivative (X). The Boc group of (X) was deprotected by treatment with HCl in dioxan to give piperidine (XI). Finally, coupling of (XI) with indolecarboxylic acid (IV) via activation with carbonyl diimidazole yielded the title carboxamide.