A new alkaloid from Stemona sessilifolia

Peng Wang, Hai Lin Qin *, Zhi Hong Li, Ai Lin Liu, Guan Hua Du

Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China

Received 30 August 2006

Abstract

A new alkaloid, named sessilistemonamine D, was isolated from the roots of Stemona sessilifolia and the structure and relative

configuration were determined on the basis of NMR and MS spectrometric data analysis.

# 2006 Hai Lin Qin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Keywords: Sessilistemonamine D; Stemona sessilifolia

The roots of Stemona sessilifolia Miq., named ‘‘Bai Bu’’ in traditional Chinese herb medicine, has been used as an

antitussive agent and insecticide in China for a long time. Early phytochemical research on Stemona genus indicated

Stemona alkaloids were main chemical and bioactive ingredients [1,2]. In our recent chemical investigation of the

roots of S. sessilifolia, a new alkaloid, namely sessilistemonamine D, has been isolated. We report here the structure

elucidation of this new compound on the basis of NMR and MS spectrometric data analysis.

Sessilistemonamine D was obtained as colorless prisms and decomposed when heated to 208 8C. The HR-EI-MS

spectrum indicated its molecular formula as C22H33NO4 (m/z 375.2415, calcd. 375.2410). In EI-MS spectrum, the ion

peak at m/z 136 revealed the molecular structure contained a perhydroazaazulene skeleton [1,2], and the base peak at

m/z 276 indicated the presence of an a-methyl-g-butyrolactone ring [1,2]. The 1H NMR spectrum (d, ppm) suggested

three methyl groups at d 1.19 (s, 3H, Me-15), 1.25 (d, 3H, J = 7.0 Hz, Me-22) and 0.90 (t, 3H, J = 7.5 Hz, Me-17),

three methines and a methene bearing a hetero atom at d 4.58 (t, 1H, J = 5.0 Hz, H-11), 4.29 (dt, 1H, J = 10.5, 5.5 Hz,

H-18), 3.60 (dt, 1H, J = 10.5, 6.5 Hz, H-3), 3.34 (br d, 1H, J = 16.0 Hz, H-5a) and 3.00 (dd, 1H, J = 16.0, 12.5 Hz, H-

5b). The 13C NMR and DEPT spectra showed signals of 22 carbons including 3 methyls, 5 methenes, 7 methines and 7

quaternary carbons. The resonance peaks at d 179.5, 181.1, 76.8 and 83.1 suggested the presence of two saturated

lactones, which was also confirmed by the lower-field resonances of two methines bearing an oxygen atom at d 4.58 (t,

1H, J = 5.0 Hz, H-11) and d 4.29 (dt, 1H, J = 10.5, 5.5 Hz, H-18). The 1H–1H COSY experiment showed spin system

involving H-1, H-2, H-3, H-18, H-19, H-20 and Me-22, suggesting a lactone ring attached to C-3, which was

confirmed by the HMBC correlations between H-3 and C-18, C-19. Another lactone ring was determined by the1H–1H correlation of H-11 and H-12 in the 1H–1H COSY spectrum, as well as the long range 1H–13C correlations

between H-11 and C-14, H-12 and C-13, C-14, Me-15 and C-12, C-13 and C-14 in the HMBC spectrum. Location of

this lactone ring was established by the long range 1H–13C correlations between H-11 and C-10, H-12 and C-9a, C-10,

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Chinese Chemical Letters 18 (2007) 152–154

* Corresponding author.

E-mail address: qinhailin@imm.ac.cn (H.L. Qin).

1001-8417/$ – see front matter # 2006 Hai Lin Qin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

doi:10.1016/j.cclet.2006.12.007

Me-15 and C-9a in the HMBC spectrum. The full assignments and other relative connections were elucidated by 1H

and 13C NMR, DEPT, HSQC, 1H–1H COSY and HMBC experiments (Fig. 1; Table 1).

The relative configuration of sessilistemonamine D was established by NOE difference spectrum, which showed

significant NOE correlation between H-18 and H-20, and correlation between H-3 and H-5a. According to a

P. Wang et al. / Chinese Chemical Letters 18 (2007) 152–154 153

Fig. 1. Structure of sessilistemonamine D.

Table 1

NMR spectroscopic data of sessilistemonamine D (CDCl3, d in ppm, J in Hz)

Position 1H NMR (500 MHz) 13C NMR (125 MHz)

1 1.92, m, H-b; 1.82, m, H-a 30.5 (t)

2 1.84, m; 1.43, m 26.3 (t)

3 3.60, dt (J = 10.5, 6.5) 63.2 (d)

5 3.34, br d (J = 16.0), H-a; 3.00, dd (J = 16.0, 12.5), H-b 44.5 (t)

6 1.86, m; 1.28, m 21.7 (t)

7 1.71, m; 1.30, m 28.4 (t)

8 1.39, m; 1.27, m 27.3 (t)

9 2.28, t (J = 6.0) 44.3 (d)

9a 71.7 (s)

10 1.99, m 45.8 (d)

11 4.58, t (J = 5.0) 76.8 (d)

12 2.21, d (J = 12.5), H-a; 2.03, dd (J = 12.5, 5.0), H-b 37.8 (t)

13 51.4 (s)

14 1.19, s 181.1 (s)

15 1.61, m; 1.13, m 17.8 (q)

16 0.90, t (J = 7.5) 19.9 (t)

17 4.29, dt (J = 10.5, 5.5) 12.7 (q)

18 2.35, ddd (J = 5.0, 7.5, 12.5), H-b; 1.59, m, H-a 83.1 (d)

19 2.59, m 34.1 (t)

20 35.0 (d)

21 1.25, d (J = 7.0) 179.5 (s)

22 14.9 (q)

Fig. 2. Selective HMBC correlations and Key NOE correlations of sessilistemonamine D.

conventional a orientation of H-3 and b orientation of H-18 in most of Stemona alkaloids [1,2], configuration of H-20

and H-5a could be exactly deduced. Correlation between H-5b and H-9, as well as correlation between H-18 and Me-

15 revealed the trans connection of ring-B and -C, which result in almost vertical arrangement of ring-A and -B, and

therefore the nuclear overhauser effect between H-18 and H-5a could be observed. The facts that no correlation could

be observed between H-9 and H-12, but correlation between H-12a and H-1b was visibly determined the relative

arrangement of ring-D, as it was shown in Fig. 2. The a orientation of ethyl group was established by the NOE

correlation between H-12a and H-16.

References

[1] R.A. Pilli, G.B. Rosso, M.C.F. Oliveira, The Alkaloids, vol. 62, Elsevier, New York, 2005 , p. 77 (Chapter 2).

[2] H. Greger, Planta Med. 72 (2006) 99.

P. Wang et al. / Chinese Chemical Letters 18 (2007) 152–154154