The alkaloids of the tulip tree Liriodendron tulipifera L., family Magnoliaceae, are considered. More then 20 alkaloids have been isolated during different vegetation periods from various organs of the plant growing in Uzbekistan, and these have been assigned to the aporphine alkaloids and their dehydro, oxo, and 7-hydroxy derivatives; only two alkaloids proved to be derivatives of proaphorphine and of tetrahydroberberine. On the basis of the results of a comparative study of the NMR spectra of aporphines unsubstituted in ring D and some chemical transformations, the structure and configuration of the (R)-3-hydroxy-1,2-dimethoxyaporphine have been proposed for the new alkaloid lirinine. The absolute configurations, possible biogenetic interconnections, and mutual transitions of the alkaloids of L. tylipifera that are derivatives of aporphine, oxoaporphine, and dehydroaporphine are discussed. A summery table is given which includes 41 alkaloids found in this plant. © 1988 Plenum Publishing Corporation.