Quinazolines of Zanthoxylum arborescens

Dreyer and Brenner 62) isolated two new quinazoline alkaloids from seed husks of Zanthoxylum arborescens. The major compound, C17H16N2O2 exhibits a blue fluorescence on TLC. In the H-nmr spectrum the downfield aromatic quartet at 8 8.12 (J = 7.1 Hz) and a one-proton triplet at 8 7.8 (J = 7 Hz), each further split (J = 1 Hz) suggest the presence of four adjacent aromatic protons on an ortho-substituted benzene ring. The aromatic quartet farthest downfield at 8 8.12 indicates the presence of a / r/-related carbonyl group. Two two-proton multiplets (8 2.93—4.40) are consistent with the presence of a 2-phenylethyl system. Other nmr data, in light of the mass spectrum, suggest the presence of an N-methylanthranilic acid system. These characteristics could be assembled in two different ways, leading to structures (7) (Chart 1) and (31). C-spectroscopy and synthesis from N-methylisatoic anhydride and 2-phenylethylamine finally allowed elucidation of the structure. The synthetic product, l-methyl-3-(2 -phenylethyl)-lH,3H-quinazolin-2,4-dione (7) was identical with the alkaloid. 

A second alkaloid from the mother liquors of the major constituent, had prominent infrared absorptions at 1700, 1660 and 1620 cm its H-nmr spectrum exhibited many similarities to that of the major component. The aromatic region contained an A2B2 system (8 6.90 and 7.20) as well as signals associated with an N-methylanthranilic acid system. Two three- 

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