Design, synthesis and anti-itch activity evaluation of aromatic amino acid derivatives as gastrin-releasing peptide receptor antagonists.

Eight aromatic amino acid derivatives (9a-9h) as gastrin-releasing peptide receptor (GRPR) antagonists were designed and synthesized. For the design, the tertiary structure of GRPR was predicted by blast searching in the premise of 1u19 protein as the template. Eight target compounds were docked into the binding pocket to investigate their possible binding interactions. Their anti-itch activities were tested by intrathecal injection using Kunming mice as experimental animals and chloroquine phosphate as a modeling medium. Compounds 9e and 9f significantly inhibited scratching behaviors. The anti-itch activities of these compounds decreased with the following sequence: 9e > 9f = 9d > 9b > 9g > 9a > 9h > 9c predicted by computer-aided drug design (CADD) and 9e > 9f > 9b > 9h > 9g > 9d > 9a > 9c evaluated by preliminary test. They were broadly in line with activity order pretested by CADD. It showed that the predicted tertiary structure of GRPR could be used for antipruritic drug design.