Title full: Structure and synthesis of menisporphine, a new type of isoquinoline alkaloid. Alkaloids of menispermum dauricum dc. (9)1 1 Part 8. Y. Okamoto, S. Tanaka, K. Kitayama, M. Isomoto, M. Masaishi, H. Yanagawa and J. Kunitomo, Yakugaku Zasshi 91, 684 (1971). This paper constitutes Part 279 in the series Studies on the Alkaloids of Menispermaceous Plants (Part 278, see S. Kondo, M. Matsui and Y. Watanabe, Chem. Pharm. Bull. Tokyo in press (1983). Part of the contents was reported by rapid publication in J. Kunitomo and M. Satoh, Chem. Pharm. Bull Tokyo 30, 2659 (1982). The structure of an unknown yellow base from Menispermum dauricum DC. (Menispermaceae) was determined to be 5,6,9-trimethoxy-7H-dibenzo[de, h]quinolin-7-one from various spectral data and synthesis, and was named menisporphine. This is a new isoquinoline-type alkaloid having a 7H-dibenzo[de, h]quinolin-7-one skeleton for which the general term "oxoisoaporphine" is proposed. © 1983.