CIRCULAR-DICHROISM OF MICHELLAMINES - INDEPENDENT ASSIGNMENT OF AXIALCHIRALITY BY CALCULATED AND EXPERIMENTAL CD-SPECTRA

The circular dichroic behavior of the michellamines, dimeric naphthyli soquinoline alkaloids, was investigated. Due to the molecular size and conformational flexibility, which makes direct calculations of the CD spectra very difficult, and because of the lack of direct standards f or an empirical comparison, there is no simple possibility for the int erpretation of the CD spectra of such quateraryls. The chiroptical con tributions of the particular stereogenic elements were shown to behave largely additively and thus allow comparison of spectra of the quater aryls with those of the corresponding 'monomeric' naphthylisoquinoline s. This comparison was performed first of all with the experimental an d theoretical CD spectra of ancistrobrevine B, then with the predicted spectra of the authentic molecular 'halves' of the michellamines.