NEW QUINOLIZIDINE ALKALOIDS FROM LUPINUS-ARGENTEUS AND ITS HOSTED ROOT PARASITE CASTILLEJA-SULFUREA - STEREOCHEMISTRY AND CONFORMATION OF SOME NATURALLY-OCCURRING CYCLIC CARBINOLAMIDES

At one Colorado location, Castilleja sulphurea (Scrophulariaceae) is a root parasite on Lupinus argenteus subsp. rubricaulis (Fabaceae). The new carbinolamide quinolizidine alkaloids 2(S),9(/2)-dihydroxyaphyllidine, 1; 2(R), 9(ft)-dihydroxyaphyUidine, 2; 2(/?)-hydroxyaphyllidine or (-)-argyrolobine, 4; and 2 (S)-hydroxy aphyllidine, 5, and the known (+)-aphyllidine, 6, were isolated from both plant species. The alkaloids are inherent to the Lupinus and are transferred via root parasitism to the Castilleja. The pairs 1–2 and 4–5 are interconvertible epimers of each other, although they can be isolated pure either as such or as ester derivatives. NMR and X-ray crystal data reveal that each of the four carbinolamides (or ester derivatives) adopts a conformation placing the functional group perpendicular to the plane of the conjugated amide bond system. Subspecies of the L. argenteus complex apparently differ in quinolizidine alkaloid patterns because of a differing order in the timing of ring-oxidation steps. © 1990, American Chemical Society. All rights reserved.