Paraensidimerins E and F, two new alkaloids from the heartwood of Euxylophora paraensis (Rutaceae), are heptacyclic bis-quinolin-2-one derivatives (Ic) and (1d), which are stereoisomers of the previously isolated paraensidimerins A (la) and C (1b); the other two new members of this alkaloid group from the plant are paraensidimerins G (2) and B (3). Further separation of Euxylophora constituents has produced new monomeric and dimeric quinolinone alkaloids, including racemic dimers E and F (identified as stereoisomers Ic and 1d, respectively), such that all four possible stereoisomeric racemates have now been isolated from the same plant source. Paraensidimerin G (2) is an unsaturated derivative of dimers A and C, formed by the loss of two hydrogens to create a cyclohexene ring (double bond at 16-16a). Paraensidimerin B (3) is a tertiary alcohol that may be derived from the addition of water to the exocyclic double bond of paraensidimerin D. These structures were assigned based on ¹H and ¹³C NMR spectral measurements: dimers E, F, and G, like A and C, have three C-methyl, two methylene, and three methine groups, while dimer B has four C-methyl groups similar to dimer D. Paraensidimerin F (C₃₀H₃₀N₂O₄) crystallizes as rhombic crystals with coupling constants consistent with structure (1d); E (C₃₀H₃₀N₂O₄) is the fourth racemate with a trans-axial-equatorial BC ring junction; G (C₃₀H₂₈N₂O₄) shows five B-ring protons and characteristic ¹³C signals for a cyclohexene ring; B (C₃₀H₃₂N₂O₅) lacks exocyclic olefin signals and contains a methylene and an oxygen-linked carbon. Biosynthetically, dimeric quinolinone alkaloids may form via cycloaddition of N-methylflindersine with quinolinone quinone methides or dimerization of a quinolone diene, and the variety of racemic dimers from E. paraensis suggests non-enzymatic control and that these dimers are not artifacts from long-term storage of wood extracts.