Molecular modeling study of tubulosine and other related ipecac alkaloids

A molecular modeling study of two alkaloids, tubulosine and psychotrine, is olated from the sap of Pogonopus speciosus, and other related ipecac alkalo ids, showed that these flexible alkaloids favor a nonplanar structure. The biologically active compounds had conformations with a similar angle betwee n aromatic ring A, the nitrogen in ring B, and ring D. This angle was relat ed to the biological activity reported for these compounds. Our results sup port the hypothesis of two different types of receptor interactions, one fo r the nonplanar compounds and another for the planar compounds.