MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2005; 43: 864–866 Published online 18 July 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/mrc.1621 Spectral Assignments and Reference Data 1 H and 13 C NMR spectra of 3,8-dimethoxyfuro[3,2-g]coumarin and maculine from Esenbeckia grandiflora Martius (Rutaceae) F. M. Nunes, 1 B. A. Barros-Filho, 1 M. C. F. de Oliveira, 1 * M. Andrade-Neto, 1 M. C. de Mattos, 1 J. Mafezoli 2 and J. R. Pirani 3 1 Departamento de Qu´ ımica Org ˆ anica e Inorg ˆ anica, Curso de P ´ os- Gradua ¸ c˜ ao em Qu´ ımica Org ˆ anica, Universidade Federal do Cear ´ a, Cx. Postal 6044, Fortaleza-CE, 60.450-970, Brazil 2 Curso de Farm ´ acia, Universidade de Fortaleza, Av. Washington Soares, 1321, Cx. Postal 1258, Fortaleza-CE, 60.811-905, Brazil 3 Departamento de Bot ˆ anica, Instituto de Bioci ˆ encias, Universidade de S˜ ao Paulo, Cx. Postal 11.461, S ˜ ao Paulo-SP, 05422-970, Brazil Received 21 March 2005; revised 23 May 2005; accepted 25 May 2005 One- and two-dimensional NMR experiments were used for the unambiguous assignment of the 1 H and 13 C NMR chemical shifts of the furoquinoline alkaloid maculine (1) and the new furanocoumarin 3,8-dimethoxyfuro[3,2- g]coumarin (2). Copyright  2005 John Wiley & Sons, Ltd. KEYWORDS: 3,8-dimethoxyfuro[3,2-g]coumarin; maculine; Esenbeckia grandiflora; Rutaceae; 1 H NMR; 13 C NMR; HMQC; HMBC INTRODUCTION Esenbeckia species (Rutaceae) are well-recognized as a source of furoquinoline alkaloids and furocoumarins. 1 The phytochemical investigation of species from this genus contributes for the study of Rutaceae’s chemotaxonomy. The phytochemical investigation of the hexane extract from the roots of Esenbeckia grandiflora Martius subsp. grandiflora var. grandiflora (Rutaceae) allowed isolation of the furoquinoline alkaloid maculine (1) previously found in some Rutaceae species, 1–5 and the new 3,8-dimethoxyfuro[3,2-g]coumarin (2). From the hexane extract of the trunk of E. grandiflora, a 9 : 1 mixture of the triterpenes ˛- and ˇ-amirin was isolated. Herein we report the first complete 1 H and 13 C NMR chemical shift assignments of 2 and the correction of the previously 6 reported 13 C NMR chemical shift assignment of 1 based on one- and two-dimensional NMR techniques. L Correspondence to: M. C. F. de Oliveira, Curso de P ´ os-gradua¸ c˜ ao em Qu´ ımica Orgˆ anica, Departamento de Qu´ ımica Orgˆ anica e Inorg ˆ anica, Centro de Ciˆ encias, Universidade Federal do Cear ´ a, Cx. Postal 6044, Fortaleza-CE, 60.455-970, Brazil. E-mail: mcfo@ufc.br Contract/grant sponsor: Funda¸ c˜ ao Cearense de Apoio a Pesquisa (FUNCAP). Contract/grant sponsor: Conselho Nacional do Desenvolvimento Cient´ ıfico e Tecnol ´ ogico (CNPq/Pronex). Contract/grant sponsor: Coordena¸ c˜ ao de Aperfei¸ coamento de Pessoal de N´ ıvel Superior (CAPES). EXPERIMENTAL Plant material E. grandiflora Martius subsp. grandiflora var. grandiflora (Rutaceae) was collected at Chapada farm, Maranh˜ ao state, northeast Brazil, in October 2002 and identified by Dr Jos´ e Rubens Pirani, Instituto de Biociˆ encias, Universidade de S˜ ao Paulo, Brazil. A voucher specimen (nr 21 018) was deposited at the Herbarium Prisco Bezerra (EAC), Universidade Federal do Cear´ a, Brazil. Isolation of 1 and 2 Dried powdered roots (654.0 g) of E. grandiflora were exhaustively extracted with hexane at room temperature. Solvent distillation under reduced pressure provided 2.9 g of a yellowish viscous liquid denominated EGRH. A 2.2 g aliquot of the extract was purified by silica gel column chromatography using a gradient mixture of hexane and ethyl acetate as eluent to provide 11 fractions (EGRH-1 to EGRH-11). Fraction EGRH-8 (280.5 mg), eluted with 100% ethyl acetate, showed the presence of a precipitate that was washed with methanol and crystallized from hot methanol to provide 5.0 mg of 1. Fraction EGRH-9 (114.0 mg), also from the elution with ethyl acetate 100%, was rechromatographed by PTLC using benzene : acetone (19 : 1) to yield 9.8 mg of 2. Maculine (1) C 13 H 9 NO 3 ; white crystals; mp 197.2–197.9 ° C [lit. 5 200–201 ° C]; IR (KBr)  max : 2925, 2855, 1622, 1522, 1471, 1374, 1252, 632, 574 cm 1 EIMS m/z (rel. int.): 243 ([M Cž ], 96.9), 228 (100), 200 (44.6), 172 (41.6), 142 (21.5), 128 (7.7), 114 (38.5), 100 (15.4), 76 (77), 62 (15.4); 1 H and 13 C NMR see Table 1. 3,8-Dimethoxyfuro[3,2-g]coumarin (2) C 13 H 10 O 5 ; Yellow solid; mp 179.9 – 180.5 ° C; IR (KBr)  max : 2925, 2854, 1723, 1622, 1594, 1544, 872, 768 cm 1 ; EIMS m/z (rel. int.): 246 ([M Cž ] 100), 217 (17.6), 203 (68.9), 188 (5.4), 175 (12.2), 160 (18.9), 147 (11.5), 132 (21.6), 76 (22.3); HRESMS m/z 247.0534 ⊲[M C 1] Cž , calculated for C 13 H 11 O 5 247.0607); 1 H and 13 C NMR see Table 2. NMR spectra Compounds 1 and 2 were dissolved in 0.50 mL of CDCl 3 and analyzed on a Bruker DRX 500 spectrometer (500 MHz for 1 H and 125 MHz for 13 C) and Bruker DPX 300 spectrometer (300 MHz for 1 H and 75 MHz for 13 C), respectively. TMS was used as internal standard and the temperature was stabilized at 298 K for all experiments. Two-dimensional experiments were performed using Bruker software on an Aspect X32 and the pulse programs for HMQC and HMBC were taken from the Bruker software library. Comparative analysis of the broad-band (BB) decoupled and DEPT 13 C NMR spectra provided the numbers of hydrogens attached to the carbon atoms (C, CH, CH 2 and CH 3 ⊳. One-bond ( 1 J⊳ hydrogen–carbon connectivity patterns were established by 2D HMQC spectra. Long-range coupling ( 2 J CH and 3 J CH ⊳ patterns were obtained by HMBC. RESULTS AND DISCUSSION Table 1 shows one- and two-dimensional NMR shift correlation of maculine (1). The 13 C NMR spectrum exhibited 12 carbon signals associated to one methoxyl group (OMe), with a chemical shift (υ 58.9 ppm) characteristic for steric hindrance, one methylenedioxy group (–OCH 2 O–, υ 101.5 ppm) and 10 sp 2 carbons. The 1 H NMR spectrum showed a singlet at υ4.40 ppm characteristic of a methoxyl group attached to a furoquinoline system at C-4 position, two doublets (J D 2.4 Hz) at υ 7.02 and υ 7.56 ppm characteristic of a disubstituted furan ring, two singlets at υ 7.29 and υ 7.50 ppm associated to hydrogens in para position of an aromatic ring and one singlet at υ 6.08 ppm associated to a methylenedioxy group. The HMQC spectrum showed the correlation of the hydrogens at υ 7.02 ppm (H-3 0 ) and υ 7.29 ppm (H-8) with the signal at υ 104.4 ppm suggesting the presence of two carbons with the same chemical shift. Additionally, the hydrogens at υ 7.50 ppm (H-5) and υ 6.08 ppm (H-9) were correlated to carbons υ 98.0 and 101.5 ppm respectively. These Copyright  2005 John Wiley & Sons, Ltd.