Crystal structure and theoretical study of IR and 1 H and 13 C NMR spectra of cordatin, a natural product with antiulcerogenic activity

Cordatin is a furan diterpenoid with a clerodane skeleton isolated from Croton palanostigma Klotzsch (Euphorbiaceae). This natural product shows significant antiulcerogenic activity, similar to cimetidine (Tagamet®), a compound used for the treatment of peptic ulcers. The crystal structure of cordatin was obtained by X‐ray diffraction and its geometrical parameters were compared with theoretical calculations at the B3LYP theory level. The IR and NMR ( 1 H and 13 C chemical shifts and coupling constants) spectra were obtained and compared with the theoretical calculations. The B3LYP theory level, with the 6‐31G(d,p) and 6‐311G(d,p) basis set, provided IR absorption values close to the experimental data. Moreover, theoretical NMR parameters obtained in both gas phase and chloroform solvent at the B3PW91/DGDZVP, B3LYP/6‐311+G(2d,p), and B3PW91/6‐311+G(2d,p) levels showed good correlations with the experimental results. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008