Absorption, emission, and chiroptical spectra of neurokinin 1 tachykinin receptor antagonists: The role of charge-transfer states on the biological activity

Abstract

A spectroscopic investigation, based on both electronic absorption and emission spectra as well as on chiroptical data, was performed on novel neurokinin 1 (NK1) tachykinin receptor antagonists, exhibiting interesting biological activity. These pseitdopeptides have MO fliiorophores, i.e., indole (1) and naphthalene (N), and a central scaffold with different conformational mobility. Absorption spectra in methanol show the presence of a new band with respect to the sum spectrum of the isolated chromophorcs at around 285 nm, the intensity of which linearly increases as the bioactivity increases. This absorption disappears by using dioxane as solvent. It is ascribed to an intramolecular I-N char..