ent-Labdane Diterpenes from the Stems of Mallotus japonicus

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ent-Labdane Diterpenes from the Stems of Mallotus japonicus De-Zheng Li,† Chunping Tang,†,‡ Ronald J . Quinn,‡ Yunjiang Feng,‡ Chang-Qiang Ke,† Sheng Yao,*,† and Yang Ye*,† †

State Key Laboratory of Drug Research & SIMM-CUHK Joint Research Laboratory for Promoting Globalization of Traditional Chinese Medicines, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu-Chong-Zhi Road, Zhangjiang Hi-Tech Park, Shanghai 201203, People’s Republic of China ‡ Eskitis Institute, Griffith University, Brisbane, QLD4111, Australia S Supporting Information *

ABSTRACT: Eight new ent-labdane diterpenoids, mallonicusins A−H (1−8), were isolated from the stems of Mallotus japonicus. Their structures, including the absolute configurations, were determined by extensive analyses of spectroscopic data and the ECD spectra of the Pr(FOD)3 complex of substrates in CCl4. The absolute configuration of compound 1 was confirmed by single-crystal X-ray crystallography using Cu Kα radiation. Mallotus japonicus (Thunb.) Muell. -Arg. var.. floccosus (Muell. -Arg.) S. M. Huang, belonging to the Euphorbiaceae family, is distributed mainly in the southern area of China. Its roots and bark have long been used in folk medicines for the treatment of diseases including gastropathy, cancer, and scald.1 Previous research of M. japonicus had resulted in the isolation of rutins,2 tannins,3 cardiac glycosides,4 bergenins,5 chromenes,6 and phloroglucinols.7 Those compounds were reported to have diverse bioactivities such as antitumor, antiviral, and antiinflammatory.8−14 In our efforts to seek structurally diverse terpenoids from natural sources, we investigated the constituents of the stems of M. japonicus and identified eight new entlabdane diterpenes, namely, mallonicusins A−H (1−8). The method based on the ECD spectra of Pr(FOD)3 diol complexes15 was applied to confirm the absolute configuration of C-14 of the side chain. The absolute configuration of compound 1 was confirmed by single-crystal X-ray diffraction using Cu Kα radiation. Herein, we report the isolation and structural elucidation of mallonicusins A−H (1−8).

partition between H2O and CH2Cl2 yielded a CH2Cl2 fraction, which was purified by multiple steps of column chromatography over silica gel, Sephadex LH-20, and preparative HPLC, leading to the isolation of mallonicusins A (1, 130 mg, 0.0012%), B (2, 20 mg, 0.000 18%), C (3, 8 mg, 0.000 07%), D (4, 4 mg, 0.000 036%), E (5, 20 mg, 0.0002%), F (6, 8 mg, 0.000 07%), G (7, 2 mg, 0.000 018%), and H (8, 2 mg, 0.000 018%). Mallonicusin A (1) was obtained as white needles. Its molecular formula was established by HRESIMS as C20H32O4, indicating five indices of hydrogen deficiency. The IR absorption bands at 3384 and 1722 cm−1 indicated the presence of hydroxy and carbonyl functional groups. The 1H NMR spectrum (Table 1) displayed signals attributable to three methyls [δH 0.66, 0.67, and 1.18 (s, 3H each)], an exocyclic methylene [δH 4.59 and 4.93 (s each)], an olefinic methylene [δH 4.96 and 5.14 (s each)], one oxygenated methylene [δH 3.51 (dd, J = 7.5, 11.2 Hz) and 3.68 (dd, J = 3.4, 11.2 Hz)], and two oxygenated methines [δH 3.94 (s) and 4.17 (dd, J = 3.4, 7.5 Hz)]. The 13C NMR spectrum (Table 2) showed 20 resonances including three methyl, eight methylene (including two olefinic and one oxygenated), four methine (including two oxygenated), and five quaternary carbons (including two olefinic and one carbonyl). Since the double bonds and the carbonyl group contributed to three indices of hydrogen deficiency, the remaining two indicated the presence of two rings. The 1H−1H COSY and HSQC spectra revealed the presence of partial structures of −C(14)H−C(15)H2−, −C(5)H−C(6)H2−C(7)H2−, and −C(9)H−C(11)H2−C(12)H2−. In the HMBC spectrum (Figure 1), the protons of the oxymethine (H-14), methylene (H2-12) and the olefinic H2-16

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RESULTS AND DISCUSSION The stems of M. japonicus were collected in 2009 in Hunan Province, China. The plant material (11 kg) was ground and extracted with 95% EtOH. After evaporation of EtOH, solvent © XXXX American Chemical Society and American Society of Pharmacognosy

Received: March 22, 2013

A

dx.doi.org/10.1021/np400241p | J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products

Article

Table 1. 1H NMR Data of Compounds 1, 2, 3, and 4 (δ in ppm, J in Hz) position

1a

2b

1

2.59, d (12.2) 2.33, d (12.2)

2 3 5 6 7 9 11 12 14 15

16 17 18 19 20 a

3.94, s 1.75, dd (3.0, 12.3) 1.87, m 1.45, m 2.47, m 2.05, m 1.92, d (9.4) 1.55, 2H, m 2.24, m 1.75, m 4.17, dd (3.4, 7.5) 3.51, dd (7.5, 11.2) 3.68, d (3.4, 11.2) 4.96, s 5.14, s 4.59, s 4.93, s 1.18, 3H, s 0.66, 3H, s 0.67, 3H, s

3a

1.82, m 1.20, m 1.64, 2H, m 3.18, t (8.1) 1.11, dd (2.7, 12.5) 1.75, m 1.38, m 2.40, m 1.97, m 1.61, m 1.68, m 1.53, m 2.25, m 1.78, m 4.05, dd (4.2, 7.5) 3.55, dd (4.2, 11.3) 3.42, dd (7.5, 11.3) 5.07, s 4.90, s 4.84, s 4.56, s 0.97, 3H, s 0.75, 3H, s 0.71, 3H, s

4a

1.49, 2H, m

1.52, 2H, m

1.91, 1.64, 3.43, 1.57,

1.95, 1.67, 3.44, 1.60,

m m t (3.0) m

1.63, m 1.37, m 2.40, m 1.99, m 1.71, m 1.69, m 1.51, m 2.23, m 1.76, m 4.18, dd (3.3, 7.3) 3.68, dd (3.3, 11.2) 3.50, dd (7.3, 11.2) 4.99, s 5.12, s 4.84, s 4.51, s 0.96, 3H, s 0.83, 3H, s 0.70, 3H, s

m m t (2.9) m

Figure 1. Selected COSY () and HMBC correlations (H→C) of 1.

that C-7, C-9, and C-17 were connected to C-8. HMBC correlations from the methyl (H3-20), the methylene (H2-1), and two methines (H-5 and H-9) to the quaternary C-10 suggested that C-1, C-5, C-9, and C-20 were connected to C10. HMBC correlations from two methyls (H3-18 and H3-19), the oxymethine (H-3), and the methine (H-5) to the quaternary C-4 indicated that C-3, C-5, C-18, and C-19 were connected to C-4. HMBC correlations from the methylene (H2-1) and the methyl (H3-18) to the carbonyl carbon were also observed, suggesting that the carbonyl carbon was situated at C-2 and connected to C-1 and C-3. On the basis of these data, 1 was elucidated to be a labdane- or ent-labdane-type diterpene. The structure was further confirmed by HMBC correlations from H2-1 to C-3, H2-6 to C-10, H2-7 to C-9, H-9 to C-1, C-5, and C-7, H2-12 to C-14, H-14 to C-12, H3-18 and H3-19 to C-3, and H3-20 to C-1. The relative configuration of 1 was determined by the analysis of the ROESY data. The ROESY correlations between H-3/H-5 and H-5/H-9 indicated that these three protons were cofacial, whereas the correlation of CH2-11/CH3-20 suggested that these two were on opposite faces. However, the relative configuration of C-14 of the flexible side chain was difficult to determine on the basis of the ROESY experiment. Therefore, a Pr(FOD)3 method used for absolute configurational studies of acyclic secondary/tertiary vicinal glycols was introduced.15 The ECD spectrum of 1 measured in CCl4 containing Pr(FOD)3 showed a positive dichroic absorption (Δε +0.33) at 311 nm, which led to the assignment of the 14S configuration (Figure

1.68, m 1.39, m 2.41, m 2.00, m 1.72, m 1.65, m 1.49, m 2.14, m 1.95, m 4.19, dd (3.2, 7.2) 3.68, dd (3.2, 11.0) 3.49, dd (7.2, 11.0) 4.97, s 5.14, s 4.84, s 4.49, s 0.95, 3H, s 0.83, 3H, s 0.70, 3H, s

In CDCl3, 400 MHz. bIn methanol-d4, 400 MHz.

correlated to the quaternary olefinic C-13, suggesting C-12, C14, and C-16 were connected to C-13. HMBC correlations were observed from the methylene (H2-7), the methine (H-9), and the olefinic H2-17 to the quaternary olefinic C-8, revealing

Table 2. 13C NMR Data of Compounds 1−8 (100 MHz, δ in ppm) position 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 a

1a 51.3, 210.8, 82.5, 45.3, 53.8, 23.8, 37.5, 146.3, 56.1, 45.6, 22.6, 30.9, 148.6, 75.2, 65.6, 110.8, 108.1, 29.2, 16.3, 15.2,

CH2 C CH C CH CH2 CH2 C CH C CH2 CH2 C CH CH2 CH2 CH2 CH3 CH3 CH3

2b 38.8, 29.1, 79.9, 40.9, 56.4, 25.7, 39.8, 149.9, 58.1, 40.6, 24.2, 32.7, 151.7, 77.2, 66.9, 111.3, 107.8, 29.4, 16.5, 15.6,

CH2 CH2 CH C CH CH2 CH2 C CH C CH2 CH2 C CH CH2 CH2 CH2 CH3 CH3 CH3

3a 31.8, CH2 26.0, CH2 76.1, CH 37.9, C 48.6, CH 24.1CH2 38.3, CH2 148.4, C 56.4, CH 39.5, C 22.4, CH2 31.6, CH2 149.3, C 75.3, CH 65.7, CH2 110.6, CH2 106.7, CH2 28.6, CH3 22.3, CH3 14.5, CH3

4a 31.9, 26.1, 76.3, 38.0, 48.7, 24.2, 38.4, 148.5, 56.2, 39.5, 22.2, 31.7, 149.2, 75.0, 65.8, 110.7, 106.5, 28.7, 22.4, 14.6,

5a


37.5, 34.6, 217.0, 47.7, 55.1, 24.9, 37.7, 146.9, 55.5, 39.2, 22.6, 31.2, 148.8, 75.1, 65.6, 110.3, 107.5, 25.8, 21.6, 13.9,

CH2 CH2 C C CH CH2 CH2 C CH C CH2 CH2 C CH CH2 CH2 CH2 CH3 CH3 CH3

6b 38.0, 34.5, 222.1, 49.3, 59.6, 72.0, 49.3, 146.3, 56.1, 40.4, 24.6, 32.4, 151.3, 77.0, 66.7, 111.4, 109.3, 32.3, 20.5, 16.2,

CH2 CH2 C C CH CH CH2 C CH C CH2 CH2 C CH CH2 CH2 CH2 CH3 CH3 CH3

7b 37.3, 37.0, 218.8, 54.0, 48.3, 26.5, 39.1, 149.2, 56.8, 40.3, 24.4, 32.6, 151.4, 77.0, 66.8, 111.3, 108.3, 18.4, 67.4, 14.9,

CH2 CH2 C C CH CH2 CH2 C CH C CH2 CH2 C CH CH2 CH2 CH2 CH3 CH2 CH3

8b 32.9, 27.6, 76.8, 41.9, 44.2, 25.2, 39.4, 150.0, 58.0, 40.6, 23.9, 32.7, 151.7, 77.0, 66.8, 111.3, 107.3, 18.3, 71.6, 15.6,


In CDCl3. bIn methanol-d4. B



Article

planar structure. The ROESY spectra of compounds 3 and 4 showed a cross-peak between H-3 and CH3-20, indicating that H-3 was cofacial with CH3-20. ROESY correlations were also observed between H-5 and H-9, suggesting H-5 and H-9 were cofacial. The ECD spectra of the Pr(FOD)3 complexes (Figure 4) showed a positive Cotton effect at 306 nm for compound 3

2). Crystals of 1 were obtained from MeOH, and single-crystal X-ray crystallography with Cu Kα radiation unambiguously

Figure 2. ECD curves of the Pr(FOD)3 complexes of 1 (dash) and 2 (solid line).

confirmed its absolute configuration as 3S,5S,9R,10S,14S (Figure 3). This result was consistent with that deduced from the ECD spectrum. Consequently, 1 was identified as an entlabdane diterpene.


Figure 3. Perspective ORTEP drawing for 1.

and a negative Cotton effect at 305 nm for compound 4, revealing a 14S configuration for 3 and a 14R configuration for 4. With the relative configuration of the ring system determined to be the same for 3 and 4 from the ROESY spectra, the absolute configuration was concluded to be 3R,5S,9R,10S,14S and 3R,5S,9R,10S,14R, respectively, on the basis of biosynthesis considerations. The molecular formula of mallonicusin E (5) was established as C20H32O3 by HRESIMS. Its 1H and 13C NMR data (Tables 2 and 3) showed similar resonances and coupling constants to those for 1−4. In comparison with 2, the signal of the hydroxymethine at C-3 of 2 does not exist in 5, while a carbon resonance of a carbonyl was observed at δC 217.0, suggesting that 5 was a C-3 oxidation product of 2. The proposed structure was confirmed by HMBC correlations from H-1, H-5, and H3-18 (19) to the carbonyl carbon. ROESY correlations between CH3-18/CH3-20, CH3-19/H-5, and H-5/H-9 suggested that CH3-18 and CH3-20 were on the same face, while CH3-19, H-5, and H-9 were on the opposite face of the ring system. The molecular formula of mallonicusin F (6) was assigned as C20H32O4 on the basis of its HRESIMS with one more oxygen atom than 5. Comparison of the NMR data of 6 and 5 (Tables 2 and 3) revealed the presence of an extra oxymethine group at δH 3.66 (1H, ddd, J = 5.0, 10.9, 11.4 Hz), indicating an additional hydroxy group in 6. The hydroxy group was located at C-6 by the observed 1H−1H COSY spin system of −CH(5)−CH(6)−CH(7)− and HMBC correlations from the oxymethine proton to C-4 and C-10. The observed ROESY correlation between H-6 and CH3-20 indicated its αorientation. The relative configurations of C-5, C-9, and C-10 were the same as those of compound 5 inferred from its ROESY spectrum. Mallonicusin G (7) gave a molecular formula of C20H32O4 by HRESIMS. Compared with 5, an oxymethylene at δH 3.30 (1H, d, J = 10.9 Hz) and 3.67 (1H, d, J = 10.9 Hz) replacing a methyl singlet revealed the presence of an additional hydroxy group in 7. This hydroxy group was assigned at C-18 or C-19 by the HMBC correlation from the oxymethylene to the C-3 carbonyl carbon. ROESY correlations between the oxymethylene and H-5 indicated the hydroxy substitution at C19. ROESY correlations between H-5/H-9 and CH3-18/CH320 further confirmed that the relative configurations of the

Mallonicusin B (2) possessed a molecular formula of C20H34O3 determined by HRESIMS. Comparison of 1H and 13 C NMR data of 1 and 2 (Tables 1 and 2) revealed that they possessed a similar ent-labdane skeleton except for a methylene group [δH 1.64 (2H, m); δC 29.1] in 2 replacing the C-2 carbonyl group in 1 (δC 210.8). The proposed structure was further confirmed by the fragment −C(1)H2−C(2)H2−C(3)H− deduced from the 1H−1H COSY spectrum, as well as the HSQC and HMBC correlations. The relative configuration of 2 was in agreement with that of 1 on the basis of similar ROESY correlations. The 14S absolute configuration of 2 was determined based on the positive Cotton effect at 311 nm (Δε +0.24) in the ECD spectrum of the Pr(FOD)3 complex in CCl4 (Figure 2). Therefore, the absolute configuration of 2 was determined as 3S,5S,9R,10S,14S. Mallonicusins C and D (3 and 4) had the same molecular formula of C20H34O3, deduced from the respective HRESIMS. Their 1H and 13C NMR data (Tables 1 and 2) were similar and resembled those of 2, suggesting that they shared the same C



Article

Table 3. 1H NMR Data of Compounds 5, 6, 7, and 8 (δ in ppm, J in Hz) 5a

position 1 2

m m m m

3 5 6

1.52, m 1.69, m

7

1.50, m 2.44, m

9

1.98, m 1.67, m

11

1.63, 2H, m

12

18 19

1.79, m 2.23, m 4.17, dd (3.2, 7.3) 3.67, dd (3.2, 11.2) 3.51, dd (7.3, 11.2) 4.92, s 4.60, s 5.13, s 4.97, s 1.09, 3H, s 1.02, 3H, s

20

0.87, 3H, s

14 15

16 17

a

2.06, 1.58, 2.26, 2.39,

6b 1.90, 2H, m 2.84, m 2.27, m 1.94, d (10.9) 3.66, ddd (5.0, 10.9, 11.4) 2.63, dd (11.4, 5.0) 2.11, d (11.4) 1.85, m 1.67, 1.58, 2.28, 1.85, 4.07,

m m m m dd (4.3, 7.4)

3.56, dd (4.3, 11.2) 3.45, dd (7.4, 11.2) 4.99, s 4.69, s 5.09, s 4.92, s 1.34, 3H, s 1.23, 3H, s 0.59, 3H, s

7b 2.10, 1.65, 2.59, 2.45,

m m m m

8b

2.25, m 1.63, m

1.57, 1.47, 1.88, 1.58, 3.63, 1.97, 1.60,

m m m m t (2.8) m m

1.50, m 2.40, m

1.37, m 2.40, m

2.08, m 1.83, dd (9.0, 10.4) 1.75, m 1.60, m 2.27, m 1.84, m 4.08, dd (4.2, 7.4) 3.56, dd (4.2, 11.2) 3.44, dd (7.4, 11.2) 4.94, s 4.67, s 5.08, s 4.93, s 0.88, 3H, s 3.30, d (10.9) 3.67, d (10.9) 0.89, 3H, s

2.05, m 1.78, m


1.73, m 1.51, m 2.27, m 1.76, m 4.07, d (4.1, 7.4) 3.57, dd (4.1, 11.1) 3.43, dd (7.4, 11.1) 4.85, s 4.57, s 4.93, s 5.08, s 0.72, 3H, s 3.33, d (11.2) 3.51, d (11.2) 0.76, 3H, s


vicinal glycol moiety at the side chain and oxygenation at C-2, C-3, C-6, or C-19. The absolute configuration of C-14 in the flexible side chain was successfully determined by a Pr(FOD)3based ECD method and verified by X-ray diffraction data using Cu Kα radiation.

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EXPERIMENTAL SECTION

General Experimental Procedures. Melting points were determined on an XT-4 microscopic thermometer without correction. Optical rotations were measured on a Perkin-Elmer 341 polarimeter. ECD data were collected in CCl4 on a JASCO 810 spectrometer with λmax(Δε) in nm. IR spectra were recorded on a Nicolet Magna FT-IR 750 spectrophotometer using KBr disks. NMR spectra were recorded on Bruker AM-300, AM-400, and INVOR-600 NMR spectrometers. The chemical shift (δ) values are given in ppm with TMS as internal standard, and coupling constants (J) in Hz. EIMS and HREIMS spectra were recorded on a Finnigan MAT-95 mass spectrometer. ESIMS and HRESIMS spectra were recorded on a Micromass LC-MSMS mass spectrometer. Column chromatographic separations were carried out using silica gel (200−300 mesh and H60, Qingdao Haiyang Chemical Group Corporation, People’s Republic of China), MCI gel CHP20P (75−150 μm, Mitsubishi Chemical Industries, Japan), and Sephadex LH-20 (Pharmacia Biotech AB, Uppsala, Sweden) as packing materials. TLC was carried out on precoated silica gel GF254 plates (Yantai Chemical Industrials), and the TLC spots were viewed at 254 nm and visualized by 5% H2SO4 in EtOH containing 10 mg/ mL vanillin. Analytical HPLC was performed on a Waters 2695 instrument with a 2998 PAD coupled with an ELSD 2424 and an SQDMS 3100 detector. Semipreparative and preparative HPLC were performed on a Varian SD1 instrument with a 320 single wave detector. Chromatographic separations were carried out on C18 columns (250 × 10 mm, 5 μm, Waters; 220 × 25 mm, 10 μm, Waters, respectively), using a gradient solvent system composed of H2O and MeCN, with a flow rate of 3.0 and 15.0 mL/min, respectively. Pr(FOD)3 was purchased from Sigma (purity ≥99%). Plant Material. The stems of M. japonicus were collected in Hunan Province of China in November 2009 and identified by Professor JinGui Shen of the Shanghai Institute of Materia Medica. A voucher specimen (No. 200911154) was deposited at the herbarium of the Shanghai Institute of Materia Medica, Chinese Academy of Sciences.

In CDCl3, 400 MHz. bIn methanol-d4, 400 MHz.

other stereogenic centers of the ring system remained the same as those of 5. The molecular formula of mallonicusin H (8) was determined to be C20H34O4 by HRESIMS. A detailed analysis of its NMR data revealed that 8 contained a similar structural skeleton to 3. The only difference was the replacement of a methyl group by a hydroxymethylene [(δH 3.33, d, J = 11.2 Hz) and 3.51 (1H, d, J = 11.2 Hz)] in 8, suggesting the presence of an additional hydroxy group. The hydroxymethylene was assigned as CH2-19 due to the HMBC correlations from this methylene and CH3-18 [δH 0.72 (3H, s)] to C-3 (δC 76.8) and the observed ROESY correlation with H-5. The ROESY correlations between H-5/H-9 and H-3/CH3-18 indicated that H-3 was cofacial with CH3-18, while H-5 and H-9 were on the opposite face of the ring system. The absolute configurations of C-14 in compounds 5−8 were all determined to be S on the basis of a positive Cotton effect around 310 nm in their respective ECD spectra of the Pr(FOD)3 complex (Figures 5 and 6). Assuming that these compounds all have the same biosynthetic formation as compound 1, the absolute configurations of compounds 5−8 were assigned as 5S,9R,10S,14S (5), 5S,6R,9R,10S,14S (6), 4S, 5S,9R,10S,14S (7), and 3S,4S, 5S,9R,10S,14S (8) on the basis of the relative configuration of the ring system and the established absolute configuration of C-14. In summary, this is the first report of ent-labdane diterpenoids from M. japonicus. Their structures feature a D



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Extraction and Isolation. The air-dried stems (11 kg) of M. japonicus were ground into a powder and extracted with 95% EtOH (40, 20, and 20 L, successively). After evaporation of EtOH, the remaining aqueous solution was extracted with CH2Cl2 (3 × 5 L). The CH2Cl2-soluble portion (50 g) was chromatographed on a silica gel column eluted in a step manner with petroleum ether/acetone (from 10:1 to 1:1) to afford fractions 1−11. Fraction 8 (2.3 g) was subjected to Sephadex LH-20 (CHCl3/MeOH, 1:1, and then MeOH) to yield subfraction 8C1 (700 mg), which was further separated by preparative HPLC (MeCN/H2O, 51−66%, 0−90 min) to afford 1 (130 mg), 2 (20 mg), 3 (8 mg), and 4 (4 mg). Fraction 9 (3.0 g) was chromatographed using repeated Sephadex LH-20 chromatography (CHCl3/MeOH, 1:1, and then MeOH) to obtain subfraction 9C1 (330 mg). Subfraction 9C1 was further purified by preparative HPLC (MeCN/H2O, 41−62%, 0−90 min) to afford 5 (20 mg), 6 (8 mg), 7 (2 mg), and 8 (2 mg). X-ray crystal data for 1: colorless, needles, C20H32O4, fw 336.46, orthorhombic, crystal size 0.20 × 0.08 × 0.06 mm, space group P212121, a = 6.08540(10) Å, b = 13.6015(2) Å, c = 22.6317(3) Å, V = 1873.24(5) Å3, Z = 4, Dcalcd = 1.193 mg/m3, F(000) = 736, reflections collected 12 882, reflections unique 3433 (Rint = 0.1070), final R indices for I > 2σ(I), R1 = 0.0448, wR2 = 0.1299, R indices for all data R1 = 0.0471, wR2 = 0.1327, completeness to 2θ (27.50) 99.5%, maximum transmission 0.9622, minimum transmission 0.8813. The structure was solved by direct methods using the program SHELXS97. Refinement method was full-matrix least-squares on F2, and goodness-of-fit on F2 is 1.047. The X-ray diffraction material has also been deposited in the Cambridge Crystallographic Data Center (CCDC) as deposit no. CCDC 684765.16 Mallonicusin A (1): white needles from MeOH; mp 140−141 °C; [α]20D −12 (c 0.2, MeOH); ECD (CCl4) λmax (Δε) 287 (−0.24), 311 (+0.33); IR (KBr) νmax 3384, 2954, 2848, 1722, 1644, 1452, 1390, 1139, 1093, 889 cm−1; 1H and 13C NMR data, see Tables 1 and 2; ESIMS m/z 359.2 [M + Na]+; HRESIMS m/z 359.2196 [M + Na]+ (calcd for C20H32O4Na, 359.2193). Mallonicusin B (2): white needles from MeOH; mp 139−140 °C; [α]20D −13 (c 0.2, MeOH); ECD (CCl4) λmax (Δε) 288 (−0.24), 311 (+0.24); IR (KBr) ν max 3311, 2938, 2867, 1644, 1455, 1384,1184,1079,1037, 896 cm−1; 1H and 13C NMR data, see Tables 1 and 2; ESIMS m/z 345.2 [M + Na]+; HRESIMS m/z 345.2403 [M + Na]+ (calcd for C20H34O3Na, 345.2400). Mallonicusin C (3): colorless gum; [α]20D −11 (c 0.2, CHCl3); ECD (CCl4) λmax (Δε) 283 (−0.22), 306 (+0.16); 1H and 13C NMR data, see Tables 1 and 2; ESIMS m/z 345.2 [M + Na]+; HRESIMS m/ z 345.2404 [M + Na]+ (calcd for C20H34O3Na, 345.2400). Mallonicusin D (4): colorless gum; [α]20D −14 (c 0.2, CHCl3); ECD (CCl4) λmax (Δε) 287 (+0.19), 305 (−0.14); 1H and 13C NMR data, see Tables 1 and 2; ESIMS m/z 345.2 [M + Na]+; HRESIMS m/ z 345.2404 [M + Na]+ (calcd for C20H34O3Na, 345.2400). Mallonicusin E (5): colorless gum; [α]20D −5 (c 0.2, MeOH); ECD (CCl4) λmax (Δε) 288 (−0.25), 323 (+0.13); 1H and 13C NMR data, see Tables 2 and 3; ESIMS m/z 343.2 [M + Na]+; HRESIMS m/ z 343.2245 [M + Na]+ (calcd for C20H32O3Na, 343.2244). Mallonicusin F (6): colorless gum; [α]20D −41 (c 0.2, MeOH); ECD (CCl4) λmax (Δε) 289 (−0.20), 310 (+0.29); 1H and 13C NMR data, see Tables 2 and 3; ESIMS m/z 359.2 [M + Na]+; HRESIMS m/ z 359.2194 [M + Na]+ (calcd for C20H32O4Na, 359.2193). Mallonicusin G (7): colorless gum; [α]20D −5 (c 0.2, MeOH); ECD (CCl4) λmax (Δε) 289 (−0.35), 315 (+0.33); 1H and 13C NMR data, see Tables 2 and 3; ESIMS m/z 359.2 [M + Na]+; HRESIMS m/ z 359.2195 [M + Na]+ (calcd for C20H32O4Na, 359.2193). Mallonicusin H (8): colorless gum; [α]20D −24 (c 0.2, MeOH); ECD (CCl4) λmax (Δε) 287 (−0.25), 315 (+0.24); 1H and 13C NMR data, see Tables 2 and 3; ESIMS m/z 361.2 [M + Na]+; HRESIMS m/ z 361.2353 [M + Na]+ (calcd for C20H34O4Na, 361.2349).

Article

ASSOCIATED CONTENT

S Supporting Information *

1 H and 13C NMR, 1H−1H COSY, HSQC, HMBC, and ROESY spectra for compounds 1−8 and a CIF file of compound 1. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*Tel: 86-21-50806726. Fax: 86-50806726. E-mail: syao@mail. shcnc.ac.cn. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the “Key New Drug Creation and Manufacturing Program” (2011ZX09307-002-03, 2012ZX09301001-001) for financial support. We also thank the NNSF for Distinguished Young Scholar (30925043), MOST (2010DFA30980), and the Shanghai Commission of Science and Technology (10DZ1972700, 11DZ1970700, 12JC1410300).

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REFERENCES

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ent-Labdane Diterpenes from the Stems of Mallotus japonicus

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