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 'H-nmr spectra of piperx indicated that it was identical with synthetic N-piperidyl-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 piperine-type alkaloid to be reported (1), was undertaken to confirm the structure. The results of the X-ray analysis confirm that piperx is a trans-2-cis-4 isomer of wisanine.