The object of this study was the isolation and elucidation of the structure of unknown quaternary alkaloids occurring in the stem and root bark of Hunteria eburnea Pichon. We succeeded in isolating ten quaternary bases, the structure of five of which have been elucidated and makes the subject of this thesis. The isolation and separation of the alkaloids were extremely difficult and time consuming especially the chromatography on cellulose columns. Hunterburnine α- and β-methochlorides have been easily identified according to their published physical constants since they have been reported to occur in different plants. We isolated a quaternary salt and for which we propose the structure as 21 -methoxyhunterbumine methochloride. Another pair of quaternary alkaloids belonging to the same skeletal type as hunterburnine has been isolated. One being desoxyhunterburnine α-methochloride which we called antirhine α-methochloride, the second being its dihydro derivative occurring naturally and could be easily prepared from antirhine α-methochloride by hydrogenation. The striking feature in this pair of bases is the α-configuration of the N⁺-CH₃ groups. By déméthylation and subsequent méthylation of the resulting tertiary bases, only the β-isomers were obtained. We isolated for the first time from this plant Pleiocarpamine methods lor ide and this is contrary to the proposal of W.I. Taylor that none of the quaternary alkaloids of Hunteria eburnea originates from the co-occurring tertiary base. Pleiocarpamine has previously been reported to occur in this plant. Yohimbol, Huntrabrine and Akuammicine methochlorides have been easily identified mainly by spectroscopic methods. The final quaternary alkaloid was difficult to attack by the conventional chemical methods for elucidation of structure. We have proposed a structure which has been confirmed by X-ray analysis. Hunteracine nitrogen being at represents a new structural class where the quaternary the junction of three rings does not bear an alkyl group. / Montréal Trigonix inc. 2018