Epimerization of tilivalline (1) at the C11-position occurred by treatment with zinc chloride to give a mixture of 1 and its 11-epimer (epi-1) in a ratio of 83 : 17. The computational chemical analysis of the thermodynamic stability of 1 and epi-1 through MM3(92) also revealed the energetic preference of 1 and the calculated equilibrium ratio of 1 and epi-1 was consistent with the experimental results