The natural abundance 13C nmr spectra of the Aspidosperma alkaloids tabersonine and vincadifformine, of the structurally related, new bases vandrikidine, vandrikine, and hazuntinine, of the indole-indoline alkaloid vincaleukoblastine (VLB) and leurosine, and of the indoline alkaloid vindoline and suitable models have been recorded. Chemical shift assignments have been made for all carbons of the alkaloids except some of the carbomethoxyvelbanamine portions of the indole-indoline alkaloids. The data have been used for the structure determination of the new indole bases and for ascertaining the presence of an epoxide linkage in leurosine. Anomalous, hence potentially misleading single frequency off-resonance data are described. A structurally diagnostic, endo-cyclic homoallyl shielding effect is portrayed by the use of a variety of models. © 1973, American Chemical Society. All rights reserved.