Several indolopyridoquinazoline alkaloids have been reported as constituents of the yellow bark of Euxylophora paraensis Hub. (Rutaceae) [1-5]. Further investigation of the fraction containing 1-hydroxyrutaecarpine yielded a new related compound, euxylophoricine F, for which we now assign by spectroscopic methods structure (I), a conclusion confirmed by synthesis. Euxylophoricine F, C₁₉H₁₅O₃N₃, M⁺ at m/e 333, mp 226° (C₆H₆-petrol), exhibits the same UV spectrum as the other euxylophoricines and similar NMR spectrum (CF₃COOH + 20% CDCl₃) which comprises two deceptively simple triplets at δ 3.53 and 4.90 (J 7.0 Hz) for the ind <CH₂-CH₂-N: system, a singlet at 4.20 for a methoxyl group, a singlet at 7.92 for an aromatic proton, deshielded by the neighbouring carbonyl group and a multiplet between 7.20 and 7.80 for 5 aromatic protons. The presence of a phenolic OH group was substantiated by IR absorption at 3300 cm⁻¹ and by bathochromic shift to 304 nm in N aq. NaOH in UV spectrum. Methylation of (1) with MeI-K₂CO₃ in Me₂CO yielded N₁₁-methyleuxylophoricine A (2) indicating that euxylophoricine F was a 2,3-disubstituted rutaecarpine [6]. That the hydroxyl group was located at carbon 2 was clarified by a 20% NOE for the integrated area of C-4H at δ 7.90 on irradiating the methoxyl group at δ 4.20. The relationship between (1) and the known indolopyridoquinazolines was confirmed by its conversion into 3-methoxyrutaecarpine (3) removing the OH group by hydrogenolysis of the respective urethane [7]. Finally, condensation of 4-benzyloxy-5-methoxyanthranilic acid methyl ester with 1,2,3,4-tetrahydronorharman-1-one in the presence of POCl₃ and subsequent hydrogenolysis gave (I) [cf 3]. The occurrence of euxylophoricine F with euxylophoricines A and C and paraensine [2] suggests that (1) may be the biogenetic precursor of the other three alkaloids.