J.P. Ma et al. / Chinese Chemical Letters 22 (2011) 1454–1456
1455
HO
9
R1
H
R2
OH
6'
1
2
3
4
5
6
Api(1 6)Glc 7S
Api(1 6)Glc 7R
H
H
Glc
Glc
8
7
7'
8'
4'
O
6
1
H
O
1'
Glc
Glc
H
7S
7R
7R
7R
9'
3'
OR2
3
4
R1O
O
Glc
Fig. 1. Chemical structures of 1–6.
Table 1
1H NMR (500 MHz) and 13C NMR (125 MHz) and HMBC data for 1 (CD3OD, d in ppm, J in Hz).
No.
dC
dH
HMBC
No.
dC
dH
HMBC
H-90
H-70, 80, 100
1
2
3
4
5
6
7
8
9
134.5
112.3
149.2
147.5
116.1
121.5
74.5
H-5, 7, 8
80
90
125.6
71.5
6.22 (dt, 1H, 15.9, 6.2)
4.46 (dd, 1H, 13.4, 6.6)
4.28 (dd, 1H, 13.3, 6.8)
3.79 (s, 3H)
7.01 (br s, 1H)
H-6, 7
H-2, 5, 3-OCH3
H-2, 5, 6
3000-OCH3
57.0
103.7
75.6
78.5
72.2
77.4
69.2
6.72 (d, 1H, 8.1)
1
4.34 (d, 1H, 7.8)
H-9000, 200
H-300
6.83 (dd, 1H, 8.1, 1.7)
4.82 (d, 1H, 5.8)
H-2, 7
200
300
400
500
600
3.21 (dd, 1H, 8.8, 7.8)
3.34 (m, 1H)
H-2, 6, 8, 9
H-7, 9
H-200, 400
H-3 , 500, 600
H-400, 600
H-400, 1000
86.6
4.36 (dt, 1H, 7.3, 5.7)
3.84 (dd, 1H, 12.1, 6.8)
3.80 (dd, 1H, 12.2, 6.3)
3.79 (s, 3H)
3.28 (t, 1H, 9.0)
62.7
H-7, 8
3.39 (m, 1H)
3.99 (dd, 1H, 11.4, 1.7)
3.61 (dd, 1H, 11.2, 6.1)
5.03 (d, 1H, 2.6)
3-OCH3
56.8
10
20
30
40
50
60
70
133.2
111.9
152.3
149.6
119.2
121.5
134.3
H-20, 50, 70, 80
H-60, 70
H-20, 50, 30-OCH3
H-8, 20, 50, 60
111.5
78.5
81.0
75.5
H-2000, 4000, 600
H-4000, 5000
H-1000, 4000, 5000
H-1000, 5000
7.01 (br s, 1H)
1000
2000
3000
4000
3.91 (d, 1H, 2.5)
3.98 (d, 1H, 9.7)
3.76 (d, 1H, 9.7)
3.57 (s, 2H)
6.90 (d, 1H, 8.2)
6.86 (br d, 1H, 8.2)
6.58 (d, 1H, 15.9)
H-20, 70
H-20, 60
66.0
H-2000, 4000
5000
J = 8.2 Hz), 6.83(dd, 1H, J = 8.1, 1.7 Hz) and 6.72 (d, 1H, J = 8.1 Hz), one 1-ol-2(E)-propenyl moiety at d 6.58 (d, 1H,
J = 15.9 Hz), 6.22 (dt, 1H, J = 15.9, 6.2 Hz), 4.46 (dd, 1H, J = 13.4, 6.6 Hz) and 4.28 (dd, 1H, J = 13.3, 6.8 Hz), two
oxygenated methines at d 4.82 (d, 1H, J = 5.8 HZ) and 4.36 (dt, 1H, J = 7.3, 5.7 Hz), one oxygen-bearing methylene at
d 3.84 (dd, 1H, J = 11.9, 6.8 Hz) and 3.80 (dd, 1H, J = 12.2, 6.3 Hz), and two methoxy groups at d 3.79 (s, 6H),
demonstrating a citrusin A-like 8,40-oxyneolignan diglycoside [6]. Moreover, the 13C NMR (125 MHz, CD3OD)
signals at d 111.5 (C), 81.0 (C), 78.5 (CH), 75.5 (CH), 66.0 (CH2) and a +5.8 ppm downfield shift at C-6 of glucose,
revealed a b-D-apiofuranosyl-(1!6)-b-D-glucopyranosyl moiety. In the HMBC spectrum, significant correlations of
3-OCH3/C-3, 30-OCH3/C-30, H-100/C-90, H-90/C-100, H-600/C-1000 and H-1000/C-600 were observed (Fig. 2), confirming the
connectivities of two methoxyls with C-3 and C-30, a b-D-apiofuranosyl-(1!6)-b-D-glucopyranosyloxy group at C-90
of the aglycone, respectively. By enzymatic hydrolysis, erythro-form aglycone was obtained (400 MHz, acetone-d6,
J
7,8 = 5.4 Hz) [7]. A negative chirality appearing around 250–300 nm (c 1.0 g/L, MeOH, u: ꢁ360,000 (281 nm),
ꢁ160,000 (271 nm), 200,000 (265 nm), 250,000 (257 nm)) in the CD spectrum of the aglycone consolidated the
absolute configuration of 8R. Therefore, compound 1, named ligusinenoside D was elucidated to be (7S, 8R)-90-[b-D-
apiofuranosyl-(1!6)-b-D-glucopyranosyloxy]-3,30-dimethoxy-8,40-oxyneolign-70-ene-4,7,9-triol.
The five known analogues were identified as ligusinenoside C (2), alaschanioside A (3), citrusin A (4), hyuganoside
IIIb (5) and ligusinenoside B (6) [6,8,9].
Ligusinenoside C (2) was previously deduced to be threo-form relative configuration. By enzymatic hydrolysis,
threo-form aglycone was obtained (J7, 8 = 5.8 Hz) [7]. A negative chirality appearing at 250–300 nm (c 2.3 g/L,
MeOH, u: ꢁ60,000 (281 nm), ꢁ30,000 (275 nm), 60,000 (267 nm), 90,000 (257 nm)) in the CD spectrum of the
aglycone demonstrated the absolute configuration of 8R. Therefore, the absolute configuration of ligusinenoside C (2)
was further clarified to be (7R, 8R)-90-[b-D-apiofuranosyl-(1!6)-b-D-glucopyranosyloxy]-3,30-dimethoxy-8,40-
oxyneolign-70-ene-4,7, 9-triol.