RES-701-1, comparative study of the synthetic and the microbial-origin compounds

RES-701-1 is an ETB receptor selective antagonist obtained from Streptmyces sp. (IC50 = 10 nM). The chemically synthesized RES-701-1 which exhibits only micromolar affinity for ETB receptor was examined by 1H NMR and FAB-MS. The results indicated that the primary structures of the synthetic and the authentic RES-701-1 are identical but the 3D structure is completely different between them.