MD-Based CD calculations for the assignment of the absolute axial configuration of the naphthylisoquinoline alkaloid dioncophylline A

The circular dichroism (CD) of the biaryl alkaloid dioncophylline A (2) was investigated by CD calculations; the structures were generated by molecular dynamics (MD) simulations using the force field CVFF. From these structures the CD spectra were calculated with the semiempirical method CNDO/2S. Summing up the single CD spectra yielded the final spectrum. In contrast to our earlier method based on the Boltzmann weighting, the MD-assisted approach permitted to assign the flexible biaryl axis of dioncophylline A (2), which is found to be P. (C) 2001 John Wiley & Sons, Inc.