Abstract: In this paper, circular dichroism (CD), sector projection and reverseoctant rule projection of four diterpenoid dilactones and five tylophorines (two of them,6,8,are new compounds) are reported in which reverse octant rule projection is the firstapplication to the configuration determination of diterpenoid dilactone. By using theserules, the predicted Cotton effects of these compounds coincided with the result of previousdeterminations, so, their absolute configurations are assigned.