H-1-nmr Conformational Study of Fusicoccin and Related-compounds - Molecular-conformation and Biological-activity

A H-1 NMR study of the phytotoxin fusicoccin (FC) and of a group of related compounds has been carried out at 500 MHz in chloroform-d solutions. Among the seven investigated compounds five were biologically active while two were not. The NMR spectra were completely analysed in terms of chemical shifts and coupling constants. A computer program, designed to provide all possible conformations compatible with the experimental values of a molecular set of vicinal coupling constants, was then employed to attain the structural conformations of the aglycones of all the compounds. The procedure afforded one conformation for each compound, except in one case wherein the experimental data are better interpreted in terms of a mixture of two interconverting conformers. The results of the present investigation seem to suggest that the occurrence of a given overall conformation of the carbotricyclic system whilst contributory to, is not sufficient to account for the biological activity of these compounds.