Spectroscopic and theoretical study on peramine and some pyrrolopyrazinone compounds

The comparative analysis of IR and Raman spectra of peramine and its four derivatives in solid state was carried out. The harmonic vibrational frequencies, infrared intensities, and Raman scattering activities were calculated at density functional B3LYP methods with 6-311++G(d,p) basis set. For the predicted spectra, a potential energy distribution of normal modes was also calculated. For peramine derivatives the conjugation effect of pyrrole with pyrazinone ring was observed as a result of introduction of double bond. Moreover, ¹H NMR analysis indicated that pyrrole protons are deshielded in comparison with the pyrrolopyrazinone model ring system.