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Detailed 1H and 13C NMR structural assignment of three biologically active lignan lactones
Spectrochimica Acta Part A 63 (2006) 234–239
Short communication 13
Detailed 1H and C NMR structural assignment of three biologically active lignan lactones Vladimir Constantino Gomes Heleno a,∗ , Rosangela da Silva b , Susimaire Pedersoli a , S´ergio de Albuquerque b , Jairo Kenupp Bastos c , M´arcio Luis Andrade e Silva d , Paulo Marcos Donate a , Gil Valdo Jos´e da Silva a , Jo˜ao Luis Callegari Lopes e a
d
Departamento de Qu´ımica da Faculdade de Filosofia, Ciˆencias e Letras de Ribeir˜ao Preto, Universidade de S˜ao Paulo, Avenida Bandeirantes 3900, 14040-901 Ribeir˜ao Preto, SP, Brazil b Departamento de An´ alises Cl´ınicas, FCFRP, Universidade de S˜ao Paulo, Avenida do Caf´e, s/no, 14040-903 Ribeir˜ao Preto, SP, Brazil c Departamento de Ciˆ encias Farmacˆeuticas, FCFRP, Universidade de S˜ao Paulo, Avenida do Caf´e, s/no, 14040-903 Ribeir˜ao Preto, SP, Brazil N´ucleo de Ciˆencias Exatas e Tecnol´ogicas, Universidade de Franca, Avenida Dr. Armando Salles de Oliveira 2001, 14404-600 Franca, SP, Brazil e Departamento de Qu´ımica e F´ısica, FCFRP, Universidade de S˜ ao Paulo, Avenida do Caf´e, s/no, 14040-903 Ribeir˜ao Preto, SP, Brazil Received 12 January 2005; received in revised form 29 April 2005; accepted 29 April 2005 This paper is dedicated to Professor Mauricio Gomes Constantino for the occasion of his 59th birthday.
Abstract In this paper we present a complete 1 H and 13 C NMR spectral analysis of three lignan lactones (methylpluviatolide, dimethylmatairesinol and hinokinin) by the use of techniques such as COSY, HMQC, HMBC and J-resolved. Complete assignment and all homonuclear hydrogen coupling constant measurements were performed, providing enough data also to the confirmation of the relative stereochemistry. © 2005 Elsevier B.V. All rights reserved. Keywords: NMR; 1 H NMR; 13 C NMR; 2D NMR; Lignan lactones; Methylpluviatolide; Dimethylmatairesinol; Hinokinin
1. Introduction Lignan lactones are a class of natural products that includes a large number of known structures and show a considerable variety of interesting biological activities [1,2]. Thus, as part of our work, we have synthesized some lignan lactones aiming to test them in different biological activity trials, such as anti-inflammatory, analgesic and trypanocidal. Recently, we have prepared, using published synthetic methods [3,4], three lignan lactones: methylpluviatolide (1), dimethylmatairesinol (2) and hinokinin (3) which are known to present trypanocidal, anti-tumoral and anti-inflammatory activity, respectively [5–7] (Fig. 1). In the course of the structural elucidation of those compounds, we could observe that, even being the lignan lactones ∗
Corresponding author. Tel.: +55 16 602 4255; fax: +55 16 633 2960. E-mail address: [email protected] (V.C.G. Heleno).
1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2005.04.047
a class with large number of known compounds, their NMR data found in the literature are generally incomplete and inaccurate [3,8–10]. One can find several hydrogen signals from lignan lactones described only as multiplets or even with mistaken multiplicity in some papers. Inaccurate coupling constants values are also commonly found [11–13]. NMR has been increasingly important on the structural elucidation of isolated or synthesized products. Besides, the development of new techniques and the continuous evolution of NMR equipment turned possible much more detailed analysis, providing a large number of different and important data. Availability of reliable NMR data can provide faster and easier structural elucidation, because they could be used even as starting points for the structural elucidation of new compounds, or as a database for the fast identification of already known compounds. We present here a detailed assignment of NMR data for those lignan lactones including measurement of all
V.C.G. Heleno et al. / Spectrochimica Acta Part A 63 (2006) 234–239
235
Fig. 1. Structures of the lignan lactones.
homonuclear hydrogen coupling constants and all signal multiplicities clarified. 2D NMR data are also presented.
2. Experimental 2.1. Materials The three lignan lactones were obtained through synthesis and purified by HPLC as previously described in the literature [3,4].
2.2. NMR measurements All 1D (1 H and 13 C) NMR experiments were performed on a Bruker Avance Drx400 spectrometer (400.13 MHz for 1 H and 100.61 MHz for 13 C) equipped with a direct probehead of 5 mm (DUL 13 C-1). The 2D NMR experiments were performed on a Bruker Avance Drx500 spectrometer (500.13 MHz for 1 H and 125.76 MHz for 13 C) equipped with an inverse probe-head of 5 mm (BBI 1 H BB). The 1 H NMR spectra were acquired with SWH of 8.28 kHz, TD of 64K and NS of 16, providing a digital resolution of ca.
Table 1 1 H and 13 C NMR data for methylpluviatolide (1) δC (ppm)
H
δH (ppm)
Multiplicity
Coupling constants (Hz)
1 2 3 4 5 6 7
131.58 108.75 146.35 147.87 108.28 121.56 38.33
8 9
41.05 71.18
10
101.07
11 12 1 2 3 4 5 6 7
55.86 55.80 130.10 112.09 149.04 147.92 111.04 121.34 34.62
8 9
46.52 178.66
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11 12 – 2 – – 5 6 7 a 7 b 8 –
– 6.32 – – 6.61 6.18 2.19 1.90 2.10 3.65 3.29 5.45 5.42 3.48 3.40 – 6.67 – – 6.61 6.67 2.89 2.84 2.15 –
– d – – d dd dd dd ddddd dd dd d d s s – d – – d dd dd dd ddd –
– J(2, 6) = 1.6 – – J(5, 6) = 7.9 J(6, 5) = 7.9; J(6, 2) = 1.6 J(7a, 7b) = 13.2; J(7a, 8) = 6.0 J(7b, 7a) = 13.2; J(7b, 8) = 8.0 J(8, 8 ) = 15.2; J(8, 7b) = 8.0; J(8, 9b) = 7.8; J(8, 9a) = 7.3; J(8, 7a) = 6.0 J(9a, 9b) = 8.8; J(9a, 8) = 7.3 J(9b, 9a) = 8.8; J(9b, 8) = 7.8 J(10a, 10b) = 1.4 J(10b, 10a) = 1.4 – – – J(2 , 6 ) = 1.9 – – J(5 , 6 ) = 8.6 J(6 , 5 ) = 8.6; J(6 , 2 ) = 1.9 J(7 a, 7 b) = 13.9; J(7 a, 8 ) = 5.3 J(7 b, 7 a) = 13.9; J(7 b, 8 ) = 6.5 J(8 , 8) = 15.2; J(8 , 7 b) = 6.5; J(8 , 7 a) = 5.3 –
C
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Table 2 H H and C H correlation NMR data for methylpluviatolide (1) C 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9
H
COSY
HMQC
HMBC
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11 12 – 2 – – 5 6 7 a 7 b 8 –
– H6 – – H6 H2, H5 H7b, H8 H7a, H8 H7a, H7b, H8 , H9a, H9b H8, H9b H8, H9a H10b H10a – – –
– H2 – – H5 H6 H7a, H7b
H5, H7a, H7b H6, H7a, H7b H2, H5, H6, H10a, H10b H2, H5, H6, H10a, H10b H2, H6 H2, H5, H7a, H7b H2, H6, H8, H8 , H9a, H9b
H8 H9a, H9b
H7a, H7b, H7 a, H7 b, H8 , H9a, H9b H7a, H7b, H8, H8
– – H7 b, H8 H7 a, H8 H7 a, H7 b, H8 –
0.126 Hz. For 13 C NMR spectra, SWH of 23.98 kHz was used with TD of 32K and NS of 1024, giving a digital resolution of ca. 0.732 Hz. DEPT (512 scans), 1 H/1 H and 13 C/1 H 2D chemical shift correlation experiments were performed
H10a, H10b H11 H12 – H2 – – H5 H6 H7 a, H7 b
H2 , H5 , H6 , H7 a, H7 b, H8 H6 , H7 a, H7 b H2 , H5 , H11 H2 , H5 , H6 , H12 H6 H2 , H5 , H7 a, H7 b H2 , H6 , H8, H8
H8 –
H7a, H7b, H7 a, H7 b, H8, H9a, H9b H7 a, H7 b, H8, H8 , H9a, H9b
using standard pulse sequences supplied by the spectrometer manufacturer. Long-range 13 C/1 H chemical shift correlations were obtained in experiments with delay values optimized for 2 J(C, H) = 8 Hz; in some cases, experiments were acquired
Table 3 1 H and 13 C NMR data for dimethylmatairesinol (2) δC (ppm)
H
δH (ppm)
Multiplicity
Coupling constants (Hz)
1 2 3 4 5 6 7
130.76 112.21 148.27 149.38 111.45 120.88 38.48
8 9
41.37 71.52
10 11 12 13 1 2 3 4 5 6 7
56.20 56.16 56.13 56.16 130.52 112.72 148.21 149.36 111.69 121.66 34.80
8 9
46.86 178.98
– 2 – – 5 6 7a 7b 8 9a 9b 10 11 12 13 – 2 – – 5 6 7 a 7 b 8 –
– 6.33 – – 6.59 6.40 2.32 2.05 2.20 3.74 3.40 3.55 3.50 3.46 3.52 – 6.70 – – 6.61 6.69 2.95 2.91 2.26 –
– d – – d dd dd dd ddddd dd dd s s s s – d – – d dd dd dd ddd –
– J(2, 6) = 2.1 – – J(5, 6) = 8.1 J(6, 5) = 8.1; J(6, 2) = 2.1 J(7a, 7b) = 13.4; J(7a, 8) = 5.8 J(7b, 7a) = 13.4; J(7b, 8) = 8.0 J(8, 8 ) = 9.1; J(8, 9b) = 8.2; J(8, 7b) = 8.0; J(8, 9a) = 7.3; J(8, 7a) = 5.8 J(9a, 9b) = 8.8; J(9a, 8) = 7.3 J(9b, 9a) = 8.8; J(9b, 8) = 8.2 – – – – – J(2 , 6 ) = 2.0 – – J(5 , 6 ) = 8.3 J(6 , 5 ) = 8.3; J(6 , 2 ) = 2.0 J(7 a, 7 b) = 14.0; J(7 a, 8 ) = 6.3 J(7 b, 7 a) = 14.0; J(7 b, 8 ) = 5.6 J(8 , 8) = 9.1; J(8 , 7 a) = 6.3; J(8 , 7 b) = 5.6 –
C
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Table 4 H H and C H correlation NMR data for dimethylmatairesinol (2) C 1 2 3 4 5 6 7 8 9 10 11 12 13 1 2 3 4 5 6 7 8 9
H
COSY
HMQC
HMBC
– 2 – – 5 6 7a 7b 8 9a 9b 10 11 12 13 – 2 – – 5 6 7 a 7 b 8 –
– H6 – – H6 H2, H5 H8, H7b H8, H7a H7a, H7b, H8 , H9a, H9b H8, H9b H8, H9a
– H2 – – H5 H6 H7a, H7b
H2, H5, H7a, H7b, H8, H8 H6, H7a, H7b H2, H5, H6, H10, H11 H2, H5, H6, H10, H11 H6, H7a, H7b H2, H5, H7a, H7b H2, H6, H8, H8 , H9a, H9b
H8 H9a, H9b
H7a, H7b, H7 a, H7 b, H8 , H9a, H9b H7a, H7b, H8
H10 H11 H12 H13 – H2 – – H5 H6 H7 a, H7 b
H2 , H5 , H6 , H7 a, H7 b, H8, H8 H6 , H7 a, H7 b H2 , H5 , H6 , H12, H13 H2 , H5 , H6 , H12, H13 H2 , H6 , H7 a, H7 b H2 , H5 , H7 a, H7 b H2 , H6 , H8, H8
H8 –
H7a, H7b, H7 a, H7 b, H8, H9a H7 a, H7 b, H8 , H9a, H9b
– – – H6 H5 H8 H8 H7 a, H7 b, H8 –
with this delay values optimized for 2 J(C, H) = 4 Hz and 2 J(C, H) = 12 Hz. Experiments were all performed at 300 K and the concentration for all samples were in a range of 20–30 mg mL−1 in C6 D6 with TMS as internal reference.
3. Results and discussion The NMR data, from 1 H and 13 C, for methylpluviatolide (1) are presented in Tables 1 and 2; for dimethylmatairesinol
Table 5 1 H and 13 C NMR data for hinokinin (3) δC (ppm)
H
δH (ppm)
1 2 3 4 5 6 7
132.18 109.17 146.89 148.34 108.43 121.73 38.13
8 9
41.29 70.47
10
100.95
11
100.98
1 2 3 4 5 6 7
132.31 108.46 146.73 148.29 109.92 122.61 34.97
8 9
46.44 177.46
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11a 11b – 2 – – 5 6 7 a 7 b 8 –
– 6.24 – – 6.54 6.08 2.05 1.74 1.92 3.53 3.18 5.30 5.28 5.34 5.33 – 6.56 – – 6.57 6.39 2.76 2.56 1.96 –
C
Multiplicity d
d dd dd dd ddddd dd dd d d d d – d – – d dd dd dd ddd –
Coupling constants (Hz) – J(2, 6) = 1.9 – – J(5, 6) = 7.9 J(6, 5) = 7.9; J(6, 2) = 1.9 J(7a, 7b) = 13.4; J(7a, 8) = 5.8 J(7b, 7a) = 13.4; J(7b, 8) = 8.2 J(8, 8 ) = 14.2; J(8, 7b) = 8.2; J(8, 9b) = 8.0; J(8, 9a) = 7.5; J(8, 7a) = 5.8 J(9a, 9b) = 9.0; J(9a, 8) = 7.5 J(9b, 9a) = 9.0; J(9b, 8) = 8.0 J(10a, 10b) = 1.2 J(10b, 10a) = 1.2 J(11a, 11b) = 1.4 J(11b, 11a) = 1.4 – J(2 , 6 ) = 1.9 – – J(5 , 6 ) = 7.9 J(6 , 5 ) = 7.9; J(6 , 2 ) = 1.9 J(7 a, 7 b) = 13.9; J(7 a, 8 ) = 5.0 J(7 b, 7 a) = 13.9; J(7 b, 8 ) = 7.1 J(8 , 8) = 14.2; J(8 , 7 b) = 7.1; J(8 , 7 a) = 5.0 –
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Table 6 H H and C H correlation NMR data for hinokinin (3) C 1 2 3 4 5 6 7 8 9 10 11 1 2 3 4 5 6 7 8 9
H
COSY
HMQC
HMBC
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11a 11b – 2 – – 5 6 7 a 7 b 8 –
– H6 – – H6 H2, H5 H7b, H8 H7a, H8 H7a, H7b, H8 , H9a, H9b H9b, H8 H9a, H8 H10b H10a H11b H11a – H6 – – H6 H2 , H5 H7 b, H8 H7 a, H8 H7 a, H7 b, H8 –
– H2 – – H5 H6 H7a, H7b
H2, H5, H6, H7a, H7b, H8 H5, H6, H7a, H7b H2, H5, H6, H10 H2, H5, H6, H10 H2, H6, H7a, H7b H2, H5, H7a, H7b H2, H6, H8, H8 , H9a, H9b,
H8 H9a, H9b
H7a, H7b, H7 a, H7 b, H8 , H9a, H9b H7a, H7b, H8
H10a, H10b
H6
H11a, H11b
H6
– H2 – – H5 H6 H7 a, H7 b
H2 , H5 , H6 , H7 a, H7 b, H8 H5 , H6 , H7 a, H7 b H2 , H5 , H6 , H11 H2 , H5 , H6 , H11 H2 , H6 , H7 a, H7 b H2 , H5 , H7 a, H7 b H2 , H6 , H8, H8
H8 –
H6 , H7a, H7b, H7 a, H7 b, H8, H9a H7 a, H7 b, H8, H8 , H9a, H9b
(2) in Tables 3 and 4 and for hinokinin (3) presented in Tables 5 and 6. In the spectra initially performed, CDCl3 was used as solvent and some overlapping of several signals could be observed. Thus, C6 D6 was used and that provided very clearer spectra in all cases. Hydrogen signals appeared isolated from each other for the three structures, except only for a few and comprehensive overlapping. So, we could observe the chemical shift, measure the coupling constants and verify the multiplicities for every signal in each case. The hardest part to clarify was the signals from H-8 and H-8 that are a little hardly defined and excessively coupled. The use of J-resolved spectra, allied to the use of the software first order multiplet simulator [14], in the analysis of those data could provide the necessary information to clarify them totally. Double irradiation experiments as well as changes in LB and GB parameters in spectra processing were also applied to understand some cases. This way, we could verify all signal multiplicities and determine all values of homonuclear hydrogen coupling constants for these molecules. Those J values are important to determine the relative stereochemistry of the substituents on the lactone ring. In our case, due to the fact that the lignan lactones were obtained by synthesis, and the synthetic method used only furnish the trans isomer [15], we used the J values only for confirmation. The homonuclear coupling constants between H8 and H8 showed in Tables 1, 3 and 5 were compared to values obtained in preliminary calculations using PCMODEL
software [16]. This comparison indicates a trans configuration for all cases as expected. Once the stereochemistry plays crucial roles in the activity [17], this is an important information. Most 13 C signals could be assigned based on the information from HMQC spectra. For quaternary carbons, further investigations were necessary. Calculated spectra and information from HMBC experiments were enough to achieve complete assignment.
4. Conclusion The assignment of all hydrogen and carbon signals were effected as well as the measurement of all 1 H/1 H coupling constants for the lignan lactones 1, 2 and 3. HMQC and COSY spectra provided information that allowed determination of most chemical shifts and coupling constants; information from HMBC, J-resolved and double irradiation spectra turned possible the solution of the more complicated cases. Spectral simulations confirmed all results.
Acknowledgements The authors thank the Fundac¸a˜ o de Amparo a` Pesquisa do Estado de S˜ao Paulo (FAPESP), the Coordenadoria de Aperfeic¸oamento de Pessoal do Ensino Superior (CAPES) and the Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnol´ogico (CNPq) for financial support.
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References [1] W.D. Macrae, G.N.H. Towers, Phytochemistry 23 (1984) 1207. [2] D.C. Ayres, J.D. Loike, Lignans. Chemical, Biological and Clinical Properties, Cambridge University Press, Cambridge, 1990. [3] L. Udino, J. Abaul, P. Bourgeois, L. Gorrichon, H. Duran, C. Zedde, Planta Medica 65 (1999) 279. [4] Y. Landais, J. Robin, A. Lebrun, Tetrahedron 47 (1991) 3787. [5] J.K. Bastos, S. Albuquerque, M.L.A. Silva, Planta Medica 65 (1999) 541. [6] S.T. Chang, S.Y. Wang, Y.H. Kuo, J. Wood Sci. 49 (2003) 1. [7] R. Silva, G.H.B. Souza, A.A. Silva, V.A. Souza, A.C. Pereira, V.A. Royo, M.L.A. Silva, P.M. Donate, A.L.S.M. Ara´ujo, J.C.T. Carvalho, J.K. Bastos, Bioorg. Med. Chem. Lett. 15 (2005) 1033. [8] G. Matth´ee, A.D. Wright, G.M. K¨onig, Planta Medica 65 (1999) 496.
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[9] W.H. Ling, J.M. Fang, Y.S. Cheng, Phytochemistry 50 (1999) 653. [10] E.E.A. Blumenthal, M.S. Silva, M. Yoshida, Phytochemistry 46 (1997) 745. [11] S.R. Peraza-Sanches, L.M. Pena-Rodrigues, J. Nat. Prod. 55 (1992) 1768. [12] O. Middel, H.J. Woerfenbag, W. Van Uden, A. Van Oeveren, J.F.G.A. Jansen, B.L. Feringa, A.W.T. Konnings, N. Pras, R.M. Kellogg, J. Med. Chem. 38 (1995) 2112. [13] M. Gordaliza, J.M. Miguel del Corral, M.A. Castor, M.L. LopesV´asques, P.A. Garcia, A. San Feliciano, M.D. Garcia-Gr´avalos, Bioorg. Med. Chem. Lett. 5 (1995) 2465. [14] FOMS, http://artemis.ffclrp.usp.br/softwareE.htm. [15] Y. Moritani, C. Fukushima, T. Miyagishima, H. Ohmizu, T. Iwasaki, Bull. Chem. Soc. Jpn. 69 (1996) 2281. [16] PCMODEL 7.0, Serena Software, P.O. Box 3076, Bloomington, IN. [17] P.W. Dewick, Medicinal Natural Products: A Biosynthetic Approach, Wiley, New York, 1997, p. 123.
Short communication 13
Detailed 1H and C NMR structural assignment of three biologically active lignan lactones Vladimir Constantino Gomes Heleno a,∗ , Rosangela da Silva b , Susimaire Pedersoli a , S´ergio de Albuquerque b , Jairo Kenupp Bastos c , M´arcio Luis Andrade e Silva d , Paulo Marcos Donate a , Gil Valdo Jos´e da Silva a , Jo˜ao Luis Callegari Lopes e a
d
Departamento de Qu´ımica da Faculdade de Filosofia, Ciˆencias e Letras de Ribeir˜ao Preto, Universidade de S˜ao Paulo, Avenida Bandeirantes 3900, 14040-901 Ribeir˜ao Preto, SP, Brazil b Departamento de An´ alises Cl´ınicas, FCFRP, Universidade de S˜ao Paulo, Avenida do Caf´e, s/no, 14040-903 Ribeir˜ao Preto, SP, Brazil c Departamento de Ciˆ encias Farmacˆeuticas, FCFRP, Universidade de S˜ao Paulo, Avenida do Caf´e, s/no, 14040-903 Ribeir˜ao Preto, SP, Brazil N´ucleo de Ciˆencias Exatas e Tecnol´ogicas, Universidade de Franca, Avenida Dr. Armando Salles de Oliveira 2001, 14404-600 Franca, SP, Brazil e Departamento de Qu´ımica e F´ısica, FCFRP, Universidade de S˜ ao Paulo, Avenida do Caf´e, s/no, 14040-903 Ribeir˜ao Preto, SP, Brazil Received 12 January 2005; received in revised form 29 April 2005; accepted 29 April 2005 This paper is dedicated to Professor Mauricio Gomes Constantino for the occasion of his 59th birthday.
Abstract In this paper we present a complete 1 H and 13 C NMR spectral analysis of three lignan lactones (methylpluviatolide, dimethylmatairesinol and hinokinin) by the use of techniques such as COSY, HMQC, HMBC and J-resolved. Complete assignment and all homonuclear hydrogen coupling constant measurements were performed, providing enough data also to the confirmation of the relative stereochemistry. © 2005 Elsevier B.V. All rights reserved. Keywords: NMR; 1 H NMR; 13 C NMR; 2D NMR; Lignan lactones; Methylpluviatolide; Dimethylmatairesinol; Hinokinin
1. Introduction Lignan lactones are a class of natural products that includes a large number of known structures and show a considerable variety of interesting biological activities [1,2]. Thus, as part of our work, we have synthesized some lignan lactones aiming to test them in different biological activity trials, such as anti-inflammatory, analgesic and trypanocidal. Recently, we have prepared, using published synthetic methods [3,4], three lignan lactones: methylpluviatolide (1), dimethylmatairesinol (2) and hinokinin (3) which are known to present trypanocidal, anti-tumoral and anti-inflammatory activity, respectively [5–7] (Fig. 1). In the course of the structural elucidation of those compounds, we could observe that, even being the lignan lactones ∗
Corresponding author. Tel.: +55 16 602 4255; fax: +55 16 633 2960. E-mail address: [email protected] (V.C.G. Heleno).
1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2005.04.047
a class with large number of known compounds, their NMR data found in the literature are generally incomplete and inaccurate [3,8–10]. One can find several hydrogen signals from lignan lactones described only as multiplets or even with mistaken multiplicity in some papers. Inaccurate coupling constants values are also commonly found [11–13]. NMR has been increasingly important on the structural elucidation of isolated or synthesized products. Besides, the development of new techniques and the continuous evolution of NMR equipment turned possible much more detailed analysis, providing a large number of different and important data. Availability of reliable NMR data can provide faster and easier structural elucidation, because they could be used even as starting points for the structural elucidation of new compounds, or as a database for the fast identification of already known compounds. We present here a detailed assignment of NMR data for those lignan lactones including measurement of all
V.C.G. Heleno et al. / Spectrochimica Acta Part A 63 (2006) 234–239
235
Fig. 1. Structures of the lignan lactones.
homonuclear hydrogen coupling constants and all signal multiplicities clarified. 2D NMR data are also presented.
2. Experimental 2.1. Materials The three lignan lactones were obtained through synthesis and purified by HPLC as previously described in the literature [3,4].
2.2. NMR measurements All 1D (1 H and 13 C) NMR experiments were performed on a Bruker Avance Drx400 spectrometer (400.13 MHz for 1 H and 100.61 MHz for 13 C) equipped with a direct probehead of 5 mm (DUL 13 C-1). The 2D NMR experiments were performed on a Bruker Avance Drx500 spectrometer (500.13 MHz for 1 H and 125.76 MHz for 13 C) equipped with an inverse probe-head of 5 mm (BBI 1 H BB). The 1 H NMR spectra were acquired with SWH of 8.28 kHz, TD of 64K and NS of 16, providing a digital resolution of ca.
Table 1 1 H and 13 C NMR data for methylpluviatolide (1) δC (ppm)
H
δH (ppm)
Multiplicity
Coupling constants (Hz)
1 2 3 4 5 6 7
131.58 108.75 146.35 147.87 108.28 121.56 38.33
8 9
41.05 71.18
10
101.07
11 12 1 2 3 4 5 6 7
55.86 55.80 130.10 112.09 149.04 147.92 111.04 121.34 34.62
8 9
46.52 178.66
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11 12 – 2 – – 5 6 7 a 7 b 8 –
– 6.32 – – 6.61 6.18 2.19 1.90 2.10 3.65 3.29 5.45 5.42 3.48 3.40 – 6.67 – – 6.61 6.67 2.89 2.84 2.15 –
– d – – d dd dd dd ddddd dd dd d d s s – d – – d dd dd dd ddd –
– J(2, 6) = 1.6 – – J(5, 6) = 7.9 J(6, 5) = 7.9; J(6, 2) = 1.6 J(7a, 7b) = 13.2; J(7a, 8) = 6.0 J(7b, 7a) = 13.2; J(7b, 8) = 8.0 J(8, 8 ) = 15.2; J(8, 7b) = 8.0; J(8, 9b) = 7.8; J(8, 9a) = 7.3; J(8, 7a) = 6.0 J(9a, 9b) = 8.8; J(9a, 8) = 7.3 J(9b, 9a) = 8.8; J(9b, 8) = 7.8 J(10a, 10b) = 1.4 J(10b, 10a) = 1.4 – – – J(2 , 6 ) = 1.9 – – J(5 , 6 ) = 8.6 J(6 , 5 ) = 8.6; J(6 , 2 ) = 1.9 J(7 a, 7 b) = 13.9; J(7 a, 8 ) = 5.3 J(7 b, 7 a) = 13.9; J(7 b, 8 ) = 6.5 J(8 , 8) = 15.2; J(8 , 7 b) = 6.5; J(8 , 7 a) = 5.3 –
C
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Table 2 H H and C H correlation NMR data for methylpluviatolide (1) C 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9
H
COSY
HMQC
HMBC
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11 12 – 2 – – 5 6 7 a 7 b 8 –
– H6 – – H6 H2, H5 H7b, H8 H7a, H8 H7a, H7b, H8 , H9a, H9b H8, H9b H8, H9a H10b H10a – – –
– H2 – – H5 H6 H7a, H7b
H5, H7a, H7b H6, H7a, H7b H2, H5, H6, H10a, H10b H2, H5, H6, H10a, H10b H2, H6 H2, H5, H7a, H7b H2, H6, H8, H8 , H9a, H9b
H8 H9a, H9b
H7a, H7b, H7 a, H7 b, H8 , H9a, H9b H7a, H7b, H8, H8
– – H7 b, H8 H7 a, H8 H7 a, H7 b, H8 –
0.126 Hz. For 13 C NMR spectra, SWH of 23.98 kHz was used with TD of 32K and NS of 1024, giving a digital resolution of ca. 0.732 Hz. DEPT (512 scans), 1 H/1 H and 13 C/1 H 2D chemical shift correlation experiments were performed
H10a, H10b H11 H12 – H2 – – H5 H6 H7 a, H7 b
H2 , H5 , H6 , H7 a, H7 b, H8 H6 , H7 a, H7 b H2 , H5 , H11 H2 , H5 , H6 , H12 H6 H2 , H5 , H7 a, H7 b H2 , H6 , H8, H8
H8 –
H7a, H7b, H7 a, H7 b, H8, H9a, H9b H7 a, H7 b, H8, H8 , H9a, H9b
using standard pulse sequences supplied by the spectrometer manufacturer. Long-range 13 C/1 H chemical shift correlations were obtained in experiments with delay values optimized for 2 J(C, H) = 8 Hz; in some cases, experiments were acquired
Table 3 1 H and 13 C NMR data for dimethylmatairesinol (2) δC (ppm)
H
δH (ppm)
Multiplicity
Coupling constants (Hz)
1 2 3 4 5 6 7
130.76 112.21 148.27 149.38 111.45 120.88 38.48
8 9
41.37 71.52
10 11 12 13 1 2 3 4 5 6 7
56.20 56.16 56.13 56.16 130.52 112.72 148.21 149.36 111.69 121.66 34.80
8 9
46.86 178.98
– 2 – – 5 6 7a 7b 8 9a 9b 10 11 12 13 – 2 – – 5 6 7 a 7 b 8 –
– 6.33 – – 6.59 6.40 2.32 2.05 2.20 3.74 3.40 3.55 3.50 3.46 3.52 – 6.70 – – 6.61 6.69 2.95 2.91 2.26 –
– d – – d dd dd dd ddddd dd dd s s s s – d – – d dd dd dd ddd –
– J(2, 6) = 2.1 – – J(5, 6) = 8.1 J(6, 5) = 8.1; J(6, 2) = 2.1 J(7a, 7b) = 13.4; J(7a, 8) = 5.8 J(7b, 7a) = 13.4; J(7b, 8) = 8.0 J(8, 8 ) = 9.1; J(8, 9b) = 8.2; J(8, 7b) = 8.0; J(8, 9a) = 7.3; J(8, 7a) = 5.8 J(9a, 9b) = 8.8; J(9a, 8) = 7.3 J(9b, 9a) = 8.8; J(9b, 8) = 8.2 – – – – – J(2 , 6 ) = 2.0 – – J(5 , 6 ) = 8.3 J(6 , 5 ) = 8.3; J(6 , 2 ) = 2.0 J(7 a, 7 b) = 14.0; J(7 a, 8 ) = 6.3 J(7 b, 7 a) = 14.0; J(7 b, 8 ) = 5.6 J(8 , 8) = 9.1; J(8 , 7 a) = 6.3; J(8 , 7 b) = 5.6 –
C
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Table 4 H H and C H correlation NMR data for dimethylmatairesinol (2) C 1 2 3 4 5 6 7 8 9 10 11 12 13 1 2 3 4 5 6 7 8 9
H
COSY
HMQC
HMBC
– 2 – – 5 6 7a 7b 8 9a 9b 10 11 12 13 – 2 – – 5 6 7 a 7 b 8 –
– H6 – – H6 H2, H5 H8, H7b H8, H7a H7a, H7b, H8 , H9a, H9b H8, H9b H8, H9a
– H2 – – H5 H6 H7a, H7b
H2, H5, H7a, H7b, H8, H8 H6, H7a, H7b H2, H5, H6, H10, H11 H2, H5, H6, H10, H11 H6, H7a, H7b H2, H5, H7a, H7b H2, H6, H8, H8 , H9a, H9b
H8 H9a, H9b
H7a, H7b, H7 a, H7 b, H8 , H9a, H9b H7a, H7b, H8
H10 H11 H12 H13 – H2 – – H5 H6 H7 a, H7 b
H2 , H5 , H6 , H7 a, H7 b, H8, H8 H6 , H7 a, H7 b H2 , H5 , H6 , H12, H13 H2 , H5 , H6 , H12, H13 H2 , H6 , H7 a, H7 b H2 , H5 , H7 a, H7 b H2 , H6 , H8, H8
H8 –
H7a, H7b, H7 a, H7 b, H8, H9a H7 a, H7 b, H8 , H9a, H9b
– – – H6 H5 H8 H8 H7 a, H7 b, H8 –
with this delay values optimized for 2 J(C, H) = 4 Hz and 2 J(C, H) = 12 Hz. Experiments were all performed at 300 K and the concentration for all samples were in a range of 20–30 mg mL−1 in C6 D6 with TMS as internal reference.
3. Results and discussion The NMR data, from 1 H and 13 C, for methylpluviatolide (1) are presented in Tables 1 and 2; for dimethylmatairesinol
Table 5 1 H and 13 C NMR data for hinokinin (3) δC (ppm)
H
δH (ppm)
1 2 3 4 5 6 7
132.18 109.17 146.89 148.34 108.43 121.73 38.13
8 9
41.29 70.47
10
100.95
11
100.98
1 2 3 4 5 6 7
132.31 108.46 146.73 148.29 109.92 122.61 34.97
8 9
46.44 177.46
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11a 11b – 2 – – 5 6 7 a 7 b 8 –
– 6.24 – – 6.54 6.08 2.05 1.74 1.92 3.53 3.18 5.30 5.28 5.34 5.33 – 6.56 – – 6.57 6.39 2.76 2.56 1.96 –
C
Multiplicity d
d dd dd dd ddddd dd dd d d d d – d – – d dd dd dd ddd –
Coupling constants (Hz) – J(2, 6) = 1.9 – – J(5, 6) = 7.9 J(6, 5) = 7.9; J(6, 2) = 1.9 J(7a, 7b) = 13.4; J(7a, 8) = 5.8 J(7b, 7a) = 13.4; J(7b, 8) = 8.2 J(8, 8 ) = 14.2; J(8, 7b) = 8.2; J(8, 9b) = 8.0; J(8, 9a) = 7.5; J(8, 7a) = 5.8 J(9a, 9b) = 9.0; J(9a, 8) = 7.5 J(9b, 9a) = 9.0; J(9b, 8) = 8.0 J(10a, 10b) = 1.2 J(10b, 10a) = 1.2 J(11a, 11b) = 1.4 J(11b, 11a) = 1.4 – J(2 , 6 ) = 1.9 – – J(5 , 6 ) = 7.9 J(6 , 5 ) = 7.9; J(6 , 2 ) = 1.9 J(7 a, 7 b) = 13.9; J(7 a, 8 ) = 5.0 J(7 b, 7 a) = 13.9; J(7 b, 8 ) = 7.1 J(8 , 8) = 14.2; J(8 , 7 b) = 7.1; J(8 , 7 a) = 5.0 –
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Table 6 H H and C H correlation NMR data for hinokinin (3) C 1 2 3 4 5 6 7 8 9 10 11 1 2 3 4 5 6 7 8 9
H
COSY
HMQC
HMBC
– 2 – – 5 6 7a 7b 8 9a 9b 10a 10b 11a 11b – 2 – – 5 6 7 a 7 b 8 –
– H6 – – H6 H2, H5 H7b, H8 H7a, H8 H7a, H7b, H8 , H9a, H9b H9b, H8 H9a, H8 H10b H10a H11b H11a – H6 – – H6 H2 , H5 H7 b, H8 H7 a, H8 H7 a, H7 b, H8 –
– H2 – – H5 H6 H7a, H7b
H2, H5, H6, H7a, H7b, H8 H5, H6, H7a, H7b H2, H5, H6, H10 H2, H5, H6, H10 H2, H6, H7a, H7b H2, H5, H7a, H7b H2, H6, H8, H8 , H9a, H9b,
H8 H9a, H9b
H7a, H7b, H7 a, H7 b, H8 , H9a, H9b H7a, H7b, H8
H10a, H10b
H6
H11a, H11b
H6
– H2 – – H5 H6 H7 a, H7 b
H2 , H5 , H6 , H7 a, H7 b, H8 H5 , H6 , H7 a, H7 b H2 , H5 , H6 , H11 H2 , H5 , H6 , H11 H2 , H6 , H7 a, H7 b H2 , H5 , H7 a, H7 b H2 , H6 , H8, H8
H8 –
H6 , H7a, H7b, H7 a, H7 b, H8, H9a H7 a, H7 b, H8, H8 , H9a, H9b
(2) in Tables 3 and 4 and for hinokinin (3) presented in Tables 5 and 6. In the spectra initially performed, CDCl3 was used as solvent and some overlapping of several signals could be observed. Thus, C6 D6 was used and that provided very clearer spectra in all cases. Hydrogen signals appeared isolated from each other for the three structures, except only for a few and comprehensive overlapping. So, we could observe the chemical shift, measure the coupling constants and verify the multiplicities for every signal in each case. The hardest part to clarify was the signals from H-8 and H-8 that are a little hardly defined and excessively coupled. The use of J-resolved spectra, allied to the use of the software first order multiplet simulator [14], in the analysis of those data could provide the necessary information to clarify them totally. Double irradiation experiments as well as changes in LB and GB parameters in spectra processing were also applied to understand some cases. This way, we could verify all signal multiplicities and determine all values of homonuclear hydrogen coupling constants for these molecules. Those J values are important to determine the relative stereochemistry of the substituents on the lactone ring. In our case, due to the fact that the lignan lactones were obtained by synthesis, and the synthetic method used only furnish the trans isomer [15], we used the J values only for confirmation. The homonuclear coupling constants between H8 and H8 showed in Tables 1, 3 and 5 were compared to values obtained in preliminary calculations using PCMODEL
software [16]. This comparison indicates a trans configuration for all cases as expected. Once the stereochemistry plays crucial roles in the activity [17], this is an important information. Most 13 C signals could be assigned based on the information from HMQC spectra. For quaternary carbons, further investigations were necessary. Calculated spectra and information from HMBC experiments were enough to achieve complete assignment.
4. Conclusion The assignment of all hydrogen and carbon signals were effected as well as the measurement of all 1 H/1 H coupling constants for the lignan lactones 1, 2 and 3. HMQC and COSY spectra provided information that allowed determination of most chemical shifts and coupling constants; information from HMBC, J-resolved and double irradiation spectra turned possible the solution of the more complicated cases. Spectral simulations confirmed all results.
Acknowledgements The authors thank the Fundac¸a˜ o de Amparo a` Pesquisa do Estado de S˜ao Paulo (FAPESP), the Coordenadoria de Aperfeic¸oamento de Pessoal do Ensino Superior (CAPES) and the Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnol´ogico (CNPq) for financial support.
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