C-13 NUCLEAR MAGNETIC-RESONANCE SPECTRAL ASSIGNMENTS FOR PYRROLIZIDINE ALKALOIDS

The natural abundance carbon-13 nmr spectra of some pyrrolizidine alkaloids, and their derivatives: retronecine, retronecine diacetate, retronecine hydochloride, platynecine, heliotrine, heliotrine acetate, supinine, lasiocarpine, crispatine, monocrotaline and maduresine, have been determined at 15.03 MHz. Several important chemical shift trends have been described which identify the basic pyrrolizidine alkaloid skeleton and the various ester groups in these alkaloids. On the basis of 13C nmr data for crispatine, monocrotaline and madurensine, the chemical shift assignments reported earlier for C-3, C-9, C―12’ and C-16, in retrorsine have been revised. © 1979, American Chemical Society. All rights reserved.