Abstract: In order to find an effective hypotensive agent, the authors prepared tetrahydropalmatine from Berberine, which has been obtained from Chinese drugs, "Huang-Lien" (Coptis Teeta Wall.) For the purpose of securing a more effective preparation, its methyl rhodanate, m. p. 208--210°, was prepared by the cleavage of methylene-dioxy, linkage in the isoquinoline nucleus Spath, Mosettig: Ber. 59, 1496 (1926) and subsequent methylation by means of diazomethane. The pharmacological examinations are in progress. The following derivatives have been prepared: 1. Desmethylenedioxy-tetrahydroberberine, m. p. 201--203°. 2. Tetrahydropalmatine C₂₁H₂₅O₄N m.p. 145--146°. 3. Desmethylenedioxy-tetrahydroberberine, acetate C₂₃H₂₅O₆N HI, m. p. 238°. 4. Tetrahydropalmatine methyl rhodanate C₂₃H₂₈O₄ N₂ S, m. p. 208--210°. (Probably belongs to α-type.)