In this paper, circular dichroism (CD), sector projection and reverse octant 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 first application to the configuration determination of diterpenoid dilactone. By using these rules, the predicted Cotton effects of these compounds coincided with the result of previous determinations, so, their absolute configurations are assigned.