Multibiphenyl A, New biphenyls from Garcinia multiflora.

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Figure 2 Selected HMBC (H→C) and ¹H-¹H correlation spectroscopy (COSY) (–) correlations of 1. 

Compound 1 was obtained as a pale yellow gum. The molecular formula was determined to be C₂₀H₂₂O₆ from the molecular ion peak [M]⁺ at m/z 358.1408 in the EI-HRMS. The IR spectrum indicated that 1 possesses hydroxy (3422 cm^-1), phenyl (2939, 1498 cm^-1), and carbonyl (1721 cm^-1) functional groups. The ¹H and ¹³C NMR spectra (Table 1) revealed the signals for a 1,2,3,4,5-pentasubstituted benzene ring [d_H 6.26 (1H, s, H-6); δ_C 129.6 (C-1), 119.7 (C-2), 144.9 (C-3), 135.0 (C-4), 147.2 (C-5), 105.9 (C-6)], one p-substituted benzene ring [d_H 7.00 (2H, dd, J 8.8, 2.4 Hz, H-8, H-12), 6.74 (2H, dd, J 8.8, 2.4 Hz, H-9, H-11); δ_C 133.8 (C-7), 131.7 (C-8, C-12), 115.7 (C-9, C-11), 157.1 (C-10)], one acetoxyprenyl group [d_H 3.21 (2H, d, J 6.7 Hz, H-1′), 5.44 (1H, d, J6.7 Hz, H-2′), 4.33 (2H, s, H-4′), 1.39 (3H, s, H-5′), and 1.99 (3H, s, H-OAc); δ_C 26.8 (C-1′), 130.7 (C-2′), 134.6 (C-3′), 71.5 (C-4′), 14.0 (C-5′), 172.9, 20.8 (OAc)], and one methoxy group [d_H 3.76 (3H, s, OMe-5); δ_C 56.5 (OMe)], which implied that compound1 was a biphenyl derivative. This conclusion was confirmed by the heteronuclear multiple bond correlation (HMBC) correlations of H-6 with C-7, and of H-8 and H-12 with C-1 (Figure 2). HMBC correlations of H-1′ with C-1, C-2, and C-3, and of H-2′ with C-1 suggested the acetoxyprenyl group at C-2. The methoxy group was located at C-5 from the HMBC correlations of δ_H 3.76 (OMe) with C-5. Considering the signal for quarternary C-3, C-4, C-10 and the molecular formula of 1, three hydroxy groups were located at C-3, C-4, C-10, respectively. Thus, the structure of 1 was determined as shown (Figure 1), and named multibiphenyl A.

Figure 1 New biphenyls from Garcinia multiflora. 

Multibiphenyl A (1)

Pale yellow gum; [α]_D –11.0 (c 0.07, MeOH); UV (MeOH) l_max / nm (log ε) 570 (2.16), 205 (4.71); IR (KBr) n / cm^-1 3422, 2939, 1721, 1611, 1589, 1498, 1443, 1357, 1266, 1172, 1102, 1045, 1023, 838; ¹H and ¹³C NMR data (400 and 100 MHz, CD₃OD), see Table 1; ESI-MS (positive mode) m/z 381 [M + Na]⁺; EI-HRMS (M⁺) calcd.: 358.1416; found: 358.1408 (C₂₀H₂₂O₆).

Journal of the Brazilian Chemical Society

On-line version ISSN 1678-4790

J. Braz. Chem. Soc. vol.27 no.1 São Paulo Jan. 2016

http://dx.doi.org/10.5935/0103-5053.20150235

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