Solid-Phase Synthesis of 5-Noranagrelide Derivatives

Abstract

Solid-phase synthesis of 1H-benzo[d]imidazo[1,2-a]imidazol-2(3H)-one derivatives employing Fmoc-α-amino acids and nitroaryl fluorides as key building blocks has been developed. The Fmoc-α-amino acids immobilized on Wang resin, equipped with a piperazine carbamate linker, were transformed to o-nitroanilines in two steps. After reduction of the nitro group, the corresponding o-phenylenediamines gave the 2-aminobenzimidazole scaffold by reaction either with cyanogen bromide or with Fmoc-NCS. Cleavage from the polymer support and further cyclization afforded the target compounds. The developed methodology represents a versatile and simple approach for the preparation of various corresponding 1H-benzo[d]imidazo[1,2-a]imidazol-2(3H)-ones from a large number of commercially available building blocks.