The 13C NMR spectra of some isoquinoline and tetrahydroisoquinoline alkaloids and their corresponding N-methosalts and of the bisbenzylisoquinoline alkaloid isochondodendrine were recorded and the signals assigned. The substituent shielding effects and the 13C1H long range couplings were analysed and utilized in the spectral interpretation. © 1978.17916551658Wenkert, Buckwalter, Burffit, Gasić, Gottlieb, Hagaman, Schell, Wovkulich, (1976) Topics in Carbon-13 NMR Spectroscopy, 2. , G.C. Levy, Wiley-Interscience, New YorkHughes, Holland, Maclean, (1976) Can. J. Chem., 54, p. 2252Takao, Iwasa, Kamigauchi, Sigiura, (1977) Chem. Pharm. Bull., 25, p. 1426Ferreira, de, Barata, Rúveda, (1977) Phytochemistry, , in pressCompound 3 has a papaverine-like activity which is under study. Meirelles, U. M. F., Reis, F. A. M., Simioni, L. R., Magalhães, A. F., unpublished resultsJohns, Willing, 13C N.M.R spectra of quinoline and methylquinolines. The magnitude of the vicinal (peri)3JCCCHcoupling constants (1976) Australian Journal of Chemistry, 29, p. 1617Marshall, Miiller, Conn, Seiwell, Ihrig, (1974) Accounts Chem. Res., 7, p. 333Levy, Nelson, (1972) Carbon-13 Nuclear Magnetic Resonance for Organic Chemists, , Wiley-Interscience, New YorkClark, Ewing, Scrowston, NMR studies of sulphur heterocycles: III—13C spectra of benzo[b]thiophene and the methylbenzo[b]thiophenes (1976) Organic Magnetic Resonance, 8, p. 252Wenkert, E., pers. commBreitmaier, Spohn, (1973) Tetrahedron, 29, p. 1145Yoshikawa, Morishima, Kunitomo, Ju-ichi, Yoshida, (1975) Chem. Lett., 961, p. 13. , A 3J(C8-H1) = 5.0 Hz observed in a fully coupled spectrum of 13, indicative of a close to 45° dihedral relationship, gives further support to this explanationCastelão, Jr., Gottlieb, de, Mesquita, Gottlieb, Wenkert, (1977) Phytochemistry, 16, p. 735The fine structure of C7|3 3J(C7-H5) = 7.4 Hz| of 17, which becomes a multiplet in 18 and again a doublet | 3J(C7-H5) = 8.0 Hz | in 19, confirms the previous assignment. Methylation of 17 produces a crowded system in which the o-methyl group of C7 resonates, as expected, at lower fieldGaleffi, Marini-Bettolo, Vecchi, (1975) Gazz. Chim. Ital., 105, p. 1207Franca, Giesbrecht, Gottlieb, Magalhães, Magalhães, (1975) Phytochemistry, 14, p. 1671Pschorr, Ueberführung des Papaverins in eine vom Phenanthren sich ableitende Isochinolinbase (1904) Berichte der deutschen chemischen Gesellschaft, 37, p. 1926