As part of our studies on the constituents of the medicinal plant, Piper guineense (West African Black or Ashanti pepper), a novel amide alkaloid (piperx) (1) was isolated from the root bark of the plant by Addae-Mensah et al. (1). The ir and 1H-nmr spectra of piperx indicated that it was identical with synthetic Npiperidyl-5-(2-methoxy-4, 5-methylenedioxyphenyl)-trans-2-cis-4-pentadienamide (2) and hence a trans-cis-isomer of the pharmacologically active amide alkaloid, wisanine (2) (3). The present X-ray analysis of piperx, the first naturally occurring mixed-isomer pipertine-type alkaloid to be reported (1), was undertaken to confirm the structure. © 1984, American Chemical Society. All rights reserved.