MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2003; 41: 545–548 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/mrc.1205 Spectral Assignments and Reference Data Complete 1 H and 13 C NMR spectral assignment of hydrogenated oxoisoaporphine derivatives Eduardo Sobarzo-S ´ anchez, 1* Bruce K. Cassels 1 and Luis Castedo 2 1 Department of Chemistry, Faculty of Sciences, and Millennium Institute for Advanced Studies in Cell Biology and Biotechnology, University of Chile, Casilla 653, Santiago, Chile 2 Department of Organic Chemistry and CSIC Associated Unit, Faculty of Chemistry, University of Santiago, 15706 Santiago de Compostela, Spain Received 13 January 2003; accepted 10 March 2003 2,3,8,9,10,11-Hexahydro-7H-dibenzo[de,h]quinolin-7- one, 5-methoxy-2,3,8,9,10,11-hexahydro-7H-dibenzo[de,h] quinolin-7-one, 5-methoxy-6-hydroxy-1,2,3,7a,8,9,10,11, 11a,11b-decahydro-7H-dibenzo[de,h]quinolin-7-one, 5- methoxy-5,6,8,9,10,11-hexahydro-4H-dibenzo[de,h]quin- olin-7-ol, 5,6,8,9,10,11-hexahydro-4H-dibenzo[de,h]quin- olin-7-ol and 5,6-dihydro-4H-dibenzo[de,h]quinolin-7-ol were prepared by catalytic hydrogenation of oxoisoa- porphines or their 2,3-dihydro derivatives over PtO 2 in acetic acid under mild conditions. Their structures were confirmed and 1 H and 13 C NMR spectra were completely assigned using a combination of one- and two-dimensional NMR techniques. Copyright  2003 John Wiley & Sons, Ltd. KEYWORDS: NMR; 1 H NMR; 13 C NMR; 1 H– 1 H COSY; HMBC; HMQC; 7H-dibenzo[de,h]quinolin-7-one; 4H-dibenzo[de,h]quinolin-7-ol INTRODUCTION ‘Oxoisoaporphines’ is the generic name given to a series of unusual natural products with the 7H-dibenzo[de,h]quinolin-7-one skeleton, 1 because of their isomeric relationship to the better known oxoa- porphines or 7H-dibenzo[de,g]quinolin-7-ones, which are formed by oxidation of the relatively abundant (nor)aporphine alkaloids. 2 The fact that aporphines usually co-exist with oxoaporphines suggests the possibility of finding ‘isoaporphines’ together with oxoisoapor- phines. However, ‘isoaporphines’ have never been found in nature, and do not seem to have been described as synthetic products. This situation prompted us to study the reduction chemistry of oxoisoaporphines as a possible route to ‘isoaporphines.’ We have previously reported the complete 1 H and 13 C NMR spectral assignments of a series of 2,3-dihydrooxoisoaporphines. 3 In this paper, we describe the structure determination, conducted entirely by the use of NMR spectroscopy, and the complete chemical shift assignments of the 1 H and 13 C NMR spectra of the hydrogenation products of several oxoaporphines and 2,3- dihydrooxoisoaporphines. This was achieved through the concerted application of a variety of one- and two-dimensional techniques such as COSY, 4 and gradient-enhanced 5 HMQC and HMBC, 6,7 experiments. These new and novel compounds were separated into two groups: (i) two 2,3,8,9,10,11-hexahydrooxoisoaporphines (4, 5) con- sisting of one two-spin (two meta aromatic protons), one four-spin and one eight-spin 1 H systems (two and four methylenes, respec- tively), and a 1,2,3,7a,8,9,10,11,11a,11b-decahydrooxoisoaporphine L Correspondence to: Eduardo Sobarzo-S ´ anchez, Department of Chemistry, Faculty of Sciences, and Millennium Institute for Advanced Studies in Cell Biology and Biotechnology, University of Chile, Casilla 653, Santiago, Chile. E-mail: esobarzo@usc.es Contract/grant sponsor: FONDECYT; Contract/grant number: 2010056. (6) with one four-spin and one 11-spin 1 H systems (two methylenes, separated by the nitrogen atom from four methylenes and three methines); and (ii) three annelated quinolin-7-ols, one (9) with a two-spin (quinoline ˛- and ˇ-H), a four-spin vicinal aromatic and a six-spin (three methylene) 1 H systems, and two (10, 11) incorporating one five- or six-spin 1 H system on the B ring (two methylenes sepa- rated by a methine, or three methylenes), one two-spin (quinoline ˛- and ˇ-H), and one eight-spin (four methylene) 1 H systems. All 1 H signals could be assigned unequivocally on the basis of the 1 H– 1 H COSY spectra. However, the complexity of the coupling patterns in the 1 H NMR spectra due to the presence of several neighbor- ing methylenes and methines made it necessary to apply HMQC and HMBC techniques for the direct unequivocal assignment of the heteronuclear correlations. RESULTS AND DISCUSSION Several previously described 2,3-dihydrooxoisoaporphine and oxoisoaporphine derivatives were catalytically hydrogenated over PtO 2 at room temperature and at 60 – 70 psi in acetic acid. Thus, when 2,3-dihydro-7H-dibenzo[de,h]quinolin-7-one (1) 8 and 5-methoxy-2,3- dihydro-7H-dibenzo[de,h]quinolin-7-one (2) 9 were used as starting materials, they afforded in good yields 2,3,8,9,10,11-hexahydro- 7H-dibenzo[de,h]quinolin-7-one (4) and 5-methoxy-2,3,8,9,10,11- hexahydro-7H-dibenzo[de,h]quinolin-7-one (5), respectively, in which only ring D is saturated. 10 However, 5-methoxy- 6-hydroxy-2,3-dihydro-7H-dibenzo[de,h]quinolin-7-one (3) 9 gave the more highly reduced 1,2,3,7a,8,9,10,11,11a,11b-decahydro-7H- dibenzo[de,h]quinolin-7-one (6). 10 This difference could be attributed to the presence of the OH group at C-6 forming a hydrogen bond with the carbonyl at C-7 and affecting the reactivity of the conjugated C-7a C-11a and C-11b N bonds. On the other hand, reduction of the 7H-dibenzo[de,h]quinolin-7-ones 7 and 8 afforded annelated quinolin-7-ols. 10 Thus, 7 gave the ring B- saturated 5,6-dihydro-4H-dibenzo[de,h]quinolin-7-ol (9) in good yield as the only isolated product. Catalytic hydrogenation of the oxoisoaporphine 8 generated two more highly reduced products with saturation of rings B and D: 5-methoxy-5,6,8,9,10,11-hexahydro- 4H-dibenzo[de,h]quinolin-7-ol (10) and 5,6,8,9,10,11-hexahydro-4H- dibenzo[de,h]quinolin-7-ol (11), the latter with hydrogenolytic loss of the methoxyl group. The reactions leading to these new products and their structures are summarized in Schemes 1 and 2. The complete assignments of the NMR spectra of 4, 5, 6, 9, 10 and 11 are summarized in Tables 1–3. N O O N N O MeO HO NH O MeO HO 1 2 3 4 5 3a 3b 6 6a 7 7a 8 9 10 11 11a 11b H 2 /PtO 2 R.T. 1 2 3 4 5 3a 3b 6 7 7a 8 9 10 11 11a 11b A B C D 6a 1); R 5 = H 2); R 5 = OMe 4); R 5 = H 5); R 5 = OMe 1 2 3 4 5 3a 3b 6 6a 7 7a 8 9 10 11 11a 11b H 2 /PtO 2 R.T. 1 2 3 4 5 3a 3b 6 7 7a 8 9 10 11 11a 11b A B C D 6a 3) 6) R5 R5 Scheme 1. Preparation of new saturated 7H-dibenzo[de,h]quinolin-7- one derivatives (4 – 6). Copyright  2003 John Wiley & Sons, Ltd.