CHEMICAL-REACTIVITY TRENDS OF ERGOTAMINE AND BUTENOLIDE FROM ELECTROSTATIC POTENTIALS AND CHARGE SENSITIVITIES

A set of reactivity indices, including maps of the electrostatic poten tial and local and condensed Fukui function (FF) indices in the atomic resolution, are reported for two vasoconstricting mycotoxins: butenol ide and ergotamine; both the finite difference approach of Parr and Ya ng as well as charge sensitivity analysis, determining the charge resp onses via the inversion of the hardness tenser, have been used to gene rate the FF data. These two routes of arriving at the atomic FF indice s provide an opportunity to evaluate the available parametrizations of the semiempirical NDDO-type of methods which have been used to determ ine the input charge distribution; namely, the best parametrization sh ould generate consistent FF predictions resulting from both approaches . For butenolide, the MNDO parametrization was found to fulfill this c onsistency requirement. The chemical reactivity information has been u sed to trace possible similarities in reactivity trends of the butenol ide molecule and the related fragment of ergotamine, toward hypothetic al nucleophilic, electrophilic, and radical attacks. These predictions have been compared to experimental data available for other unsaturat ed lactones. (C) 1995 John Wiley & Sons, Inc.