By treatment with ethyl-alcoholic HCl, it was possible to eliminate from the four desmo troposantonins (A, B, C, D) the asymmetric centers at C₅ and C₆, giving compounds having only one asymmetric center at C₁₁. With the antipodes so obtained, (Ⅳ) and (Ⅴ), it was possible to prove that the disagreement observed on the desmotroposantonins for optical change resulting from alkali inversion was really due to the vicinal effect(see p. 493, B→C and D→A), and further that an experimental proof was offered for the mechanism of the acid inversion of the desmotroposantonins.