Trunkwood of Guatteria dielsiana afforded eight alkaloids and one triterpene. Three of the alkaloidal constituents are oxoaporphines: liriodenine, O-methylmoschatoline and isomoschatoline; four are 1-azafluorenones: onychine, the only previously known representative of this group, and three novel compounds of this rare type, 6-methoxyonychine, dielsine (1-aza-4-methyl-2-oxo-1,2-dihydrofluorenone) and dielsinol (1-aza-4-hydroxymethyl-2 oxo-1,2-dihydrofluorenone). The last alkaloid is dielsiquinone (1-aza-3-methoxy-4-methyl-2-oxo-1,2-dihydro-9,10-anthracenedione), the second representative of a new class of quinones of which cleistopholine was the only one previously known. The triterpene is polycarpol whose presence is of chemotaxonomic significance since this metabolite seems to be exclusive to the Annonaceae. © 1986.