Q.Q. Gong et al. / Chinese Chemical Letters 21 (2010) 449–452
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C52H82O21. The 13C NMR spectral data of the sapogenin part of 1 were similar to those of 3, which is the known
oleanane type triterpene cyclamiretin A. In 3, the 13b,28-epoxy bridge and 16a-OH is evident from the 13C NMR
resonances at d 86.0 (C-13, C by DEPT), 77.3 (C-28, CH2) and 76.5 (C-16, C-H), respectively. However, in compound
1, no resonance was observed for C-16 at d 76.5; instead, a signal was seen at d 212.6 (C by DEPT), indicating that the –
OH at C-16 of compound 3 is oxidized to a carbonyl group. This assignment was confirmed low-field shifts at C-17
(+11.7), C-15 (+9.2) and C-14 (+5.9), and the high-field shifts at C-28 (ꢂ3.0). Furthermore, long-range coupling of H-
28 with C-16 in HMBC also supported the same conclusion. Further, in the 1H NMR spectrum, one carbinylic proton
signal assignable to H-3 of the aglycon were observed at d 3.25(dd, J = 12.0, 4.0 Hz), suggesting the carbinylic protons
could be placed at 3a [3]. Based on these findings, the aglycone was identified as 3b-hydrox-13b,28-epoxy-oleanan-
16-oxo-30-al (cyclamigenin B).
The monosaccharides obtained after acid hydrolysis of 1 were derivatized into aldononitrile peracetatederivative
and analyzed by GC–MS using authentic samples as References L-rhamaose, L-arabinose, D-xylose, and D-glucose in
the relative proportions of 1:1:1:1 were detected. The 1H NMR spectrum showed four anomeric proton signals at d 4.90
(d, 1H, J = 7.8 Hz, Glc-H-1), 4.91 (d, 1H, J = 8.0 Hz, Xyl-H-1), 4.66 (d, 1H, J = 5.2 Hz, Ara-H-1) and 6.00 (brs, 1H,
Rha-H-1). All proton signals due to sugars were assigned by careful analysis of the TOCSY, and HMQC spectra, and
the carbon signals were assigned by HMQC and DEPT spectra. The b-anomeric configurations for the glucopyranose
and xylopyranose units were determined from their 3JH-1, H-2 coupling constants (6.9–7.8 Hz). The small H-1 coupling
constant of arabinose, which indicated the arabinose should have an a-configuration at its anomeric carbon. The broad
singlet of the anomeric proton of the Rha unit indicated an a-orientation [4]. The sugar signals of 1 were similar with
known 3 [5], 1 was one glucopyranosyl unit less than 3. The arabinose was connected to C-3 of the aglycon, which was
Table 1
The NMR spectral data of compound 1 (400 MHz, pyridine-d5).a,b
.
No.
dC (DEPT)
dH (JHZ
)
No.
dC (DEPT)
dH (JHZ)
1
2
39.1 (CH2)
26.7 (CH2)
88.6 (CH)
39.7 (C)
0.78, 1.62
Arabinose (A)
A-1
1.84, 2.08
107.4 (CH)
73.8 (CH)
74.3 (CH)
81.5 (CH)
65.9 (CH2)
4.66 d (5.2)
3
3.25 dd (4.0, 12.0)
A-2
4.30
4
–
A-3
4.01
5
55.5 (CH)
17.7 (CH2)
33.8 (CH2)
43.0 (C)
0.69 d (9.2)
A-4
4.14
6
1.42
A-5
3.72 d (11.8), 4.64 dd (3.2, 11.8)
7
0.94
Glucose (G)
G-1
8
–
105.2 (CH)
81.8 (CH)
86.0 (CH)
70.6 (CH)
78.0 (CH)
62.1 (CH2)
4.90 d (7.8)
4.08
9
50.0 (CH)
36.7 (C)
1.06
G-2
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
–
G-3
4.12
18.8 (CH2)
31.5 (CH2)
86.1(C)
1.37, 1.75
G-4
4.13
2.05
G-5
3.69
–
G-6
4.32, 4.42
50.1(C)
–
Xylose(X)
X-1
45.7 (CH2)
212.6 (C)
55.3 (C)
1.27, 1.95
106.0 (CH)
75.3 (CH)
78.2 CH)
4.91 d (8.0)
–
X-2
4.03
–
X-3
3.99
55.7 (CH)
33.8 (CH2)
47.9 (C)
1.88
X-4
69.6 (CH)
66.8 (CH2)
4.10
1.36, 2.77
X-5
3.45 t-like (10.4) 4.20 m
–
Rhamnose(R)
R-1
29.6 (CH2)
33.7 (CH2)
28.0 (Me)
16.7 (Me)
16.1 (Me)
18.8 (Me)
21.8 (Me)
74.3 (CH2)
23.8 (Me)
206.1 (CH)
1.95
103.7 (CH)
72.3 (CH)
72.6 (CH)
73.7 (CH)
70.5 (CH)
18.5 (Me)
6.00 br s
5.04 br s
4.52 dd (9.0, 3.0)
4.32
0.97
R-2
1.26 s
R-3
1.00 s
R-4
0.82 s
R-5
4.85
1.28 s
R-6
1.65 d (6.4)
1.10 s
3.35 d (8.0), 3.87(8.0)
0.89 s
9.63 s
a
Assignments based on TOCSY, HMQC and HMBC experiments.
Overlapped signals are reported without designating multiplicity.
b