Theoretical and experimental CD of conformationally flexible complex molecules - Application to ouabain pentanaphthoate and analogs

Theoretical calculation of circular dichroic exciton-coupled spectra of oua bain 1,19,2',3',4'-pentanaphthoate and its analogs was executed by a combin ation of conformational analysis with molecular mechanics and quantum-chemi cal calculation. Most of the calculated CD spectra show good agreement with the corresponding experimental data, which suggests that the method may be generalized for applications to other conformationally flexible natural pr oducts. The CD calculation was then used to evaluate the plausibility of "f ortuitous CD cancellation," which was observed in the microscale naphthoyla tion study of hypothalamic inhibitory factor, a presumed ouabain isomer fro m bovine hypothalamus. (C) 1999 Wiley-Liss, Inc.