A new secopyrrolizidine alkaloid, acetylanonamine [1], was isolated from Senecio anonymus. The structure was established by high resolution nmr (1H−1H COSY and 1H−13C HETCOR), ms, comparison of these spectral data with those of anonamine [2], and synthesis of 1 from 2. © 1991, American Chemical Society. All rights reserved.