Synthesis, structure-activity relationships and biological evaluation of caudatin derivatives as novel anti-hepatitis B virus agents

Article abstract of DOI:10.1016/j.bmc.2012.03.023

A series of caudatin derivatives were synthesized, and their anti-hepatitis B virus (HBV) activity was evaluated in HepG 2.2.15 cells. Most of the 3-O-substituted caudatin derivatives showed effective anti-HBV activity. Among the tested compounds, six compounds (2e-2h, 2l, 2r) exhibited significantly inhibitory activity against HBV DNA replication with IC₅₀ values in the range of 2.82-7.48 μM. Interestingly, two compounds (2e, 2f) had potent activity inhibiting not only the secretion of HBsAg (IC₅₀ = 18.68 μM, 21.71 μM), HBeAg (IC₅₀ = 13.16 μM, 33.73 μM), but also HBV DNA replication (IC₅₀ = 7.48 μM, 3.63 μM). The structure-activity relationships (SARs) of caudatin derivatives had been discussed, which were useful for caudatin derivatives to be explored and developed as novel anti-HBV agents.

Full text of DOI:10.1016/j.bmc.2012.03.023

Bioorganic & Medicinal Chemistry 20 (2012) 2877–2888
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis, structure–activity relationships and biological evaluation
of caudatin derivatives as novel anti-hepatitis B virus agents
Li-Jun Wang a,b, Chang-An Geng a, Yun-Bao Ma a, Xiao-Yan Huang a, Jie Luo a, Hao Chen a,b
,
Rui-Hua Guo a,b, Xue-Mei Zhang a, Ji-Jun Chen a,
⇑
a State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, PR China
b Graduate University of the Chinese Academy of Sciences, Beijing 100049, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of caudatin derivatives were synthesized, and their anti-hepatitis B virus (HBV) activity was eval-
uated in HepG 2.2.15 cells. Most of the 3-O-substituted caudatin derivatives showed effective anti-HBV
activity. Among the tested compounds, six compounds (2e–2h, 2l, 2r) exhibited significantly inhibitory
Received 1 February 2012
Revised 8 March 2012
Accepted 9 March 2012
Available online 16 March 2012
activity against HBV DNA replication with IC50 values in the range of 2.82–7.48
compounds (2e, 2f) had potent activity inhibiting not only the secretion of HBsAg (IC50 = 18.68
21.71 M), HBeAg (IC50 = 13.16 M, 33.73 M), but also HBV DNA replication (IC50 = 7.48
3.63
were useful for caudatin derivatives to be explored and developed as novel anti-HBV agents.
Ó 2012 Elsevier Ltd. All rights reserved.
lM. Interestingly, two
lM,
l
l
l
lM,
Keywords:
Synthesis,
Caudatin derivatives
Anti-HBV activity
Structure–activity relationships
lM). The structure–activity relationships (SARs) of caudatin derivatives had been discussed, which
1. Introduction
and anti-HBV activity of caudatin derivatives by modification of
the A, B and D rings.
Hepatitis B virus (HBV) infection is a significant health problem
throughout the world.1 Despite the current therapies (immuno-
2. Results and discussion
2.1. Chemistry
modulator,
a-interferon, and nucleoside drugs) are effective for
the treatment of HBV infection patients clinically, but still remain
unsatisfactory,2–5 which have been commented in detail in our
previous articles.6 Therefore, the search for anti-HBV agents with
novel antiviral targets and mechanisms are urgently needed.7
Currently, many potent non-nucleoside anti-HBV agents have been
reported,8–19 which would provide many clues to find the novel
inhibitors.
Natural products and their derivatives possessing various skel-
etons are important sources for novel HBV inhibitors.20–23 In our
continuing research for active leads from traditional Chinese
medicinal herbs, we investigated the anti-HBV constituents of
Cynanchum auriculatum (baishouwu) which were traditionally
used as a folk medicine for replenishing the liver and kidney, nour-
ishing the blood and prolonging life. By the anti-HBV assay, caud-
atin was found to have inhibiting HBV DNA replication activity
We probed several structural changes based on the characteris-
tics of caudatin, including acylation, oxidation, epoxidation, and
hydrogenation, at positions C-3, C-5, C-6, C-7, C-8, C-14, C-17, and
C-20.10,24,25 The syntheses of caudatin derivatives were summa-
rized in Scheme 1–3. Many potent anti-HBV inhibitors with nitro-
gen heterocylic ring were reported in previous investigation, such
as quinolines,6,8,12,13 tryptamines,17 benzimidazoles,26 indoles,27
etc. Therefore, some nitrogen heterocylic rings were introduced into
the caudatin in order to obtain the active derivatives. Derivatives
2a–2r were synthesized by the reaction of corresponding acids with
caudatin in the presence of N0,N0-dicyclohexylcarbodiimide (DCC)
and 4-dimethylaminopyridine (DMAP). Derivative 2s changed from
compound 2r was chromatographed using a silica gel column with
petroleum ether and acetone. Compound 1 was treated with
anhydride and a catalytic amount of DMAP in dry pyridine to afford
the derivatives 2t and 2u as the major product, together with by-
product 3 [3-O-(2-hydroxyacetyl)caudatin] from compound 2t by
cleavage one 2-hydroxyacetic acid molecular. The compounds 2v
and 2w were obtained by caudatin with phosphoryl chloride in
the mixture of pyridine and CH2Cl2.
(IC50 = 40.62 lM, SI = 6.0). In view of the novel structural template,
we synthesized analogues of caudatin to determine structure–
activity relationships (SARs) and possibly develop more potent
anti-HBV agents. In this article, we reported the synthesis, SARs,
⇑
Corresponding author. Tel.: +86 871 5223265; fax: +86 871 5227197.
E-mail address: chenjj@mail.kib.ac.cn (J.-J. Chen).
0968-0896/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2012.03.023

2878
L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
O
O
O
O
O
OH
O
O
OH
O
O
OH
a
OH
OH
OH
or b or c
or
O
OH
OH
OH
HO
O
HO
RO
1
3
2
Scheme 1. Synthesis of compounds 2a–2w, 3. Reagents and conditions: (a) DMAP, DCC, CH2Cl2, rt; (b) (RCO)2O, DMAP, anhydrous pyridine, reflux; (c) diphenylphosphoryl
(dimethoxyphosphoryl) chloride, pyridine, CH2Cl2, rt.
O
O
O
O
O
O
O
O
O
OR
OH
OH
OH
OR
OH
or
RO
a or b
OH
OH
OH
RO
HO
1
4
5
Scheme 2. Synthesis of compounds 4a–4h, 5. Reagents and conditions: (a) DMAP, DCC, CH2Cl2, rt; (b) (RCO)2O, DMAP, anhydrous pyridine, reflux.
O
O
O
O
OH
O
O
OH
a
c
OH
O
O
OH
O
O
OH
HO
HO
8
O
O
6
OH
O
OH
O
HO
O
OH
OH
O
O
1
OH
b
d
OH
OH
OH
OH
O
HO
O
9
7
Scheme 3. Synthesis of compounds 6–9. Reagents and conditions: (a) BF3ꢀOEt2, acetone, rt; (b) PCC, CH2Cl2, rt; (c) m-CPBA, CH2Cl2, rt; (d) NaBH4, EtOH, rt.
A solution of compound 1 with an excess of organic acids and
DCC in the presence of DMAP was stirred in CH2Cl2 at room tem-
perature to give the 3,17-O-disubsituted derivatives 4a–4f, except
for 3,8-O-dinicotinic acyl caudatin (5). Compound 1 with excess
anhydride was refluxed in dry pyridine yielding the 3,17-O-
disubsituted derivatives 4g–4h. From those results, it suggested
that the steric hindrance and rigid backbone of the caudatin
influenced the acylation sequence of the hydroxyl groups as
3-OH > 17-OH > 8-OH, 14-OH.
was necessary for biological activity. The structures of the synthe-
sized derivatives were identified by comparing their spectroscopic
data (1H, 13C NMR and MS) with those of caudatin. For instance,
compounds 4a and 5 were determined based on the obvious
down-field shift of C-17 (from 91.5 to 98.6) and C-8 (from 74.3
to 91.3), respectively, compared to caudatin.
2.2. Anti-HBV activity
In order to evaluate the hydroxyl groups of C-8 and C-14 were
the necessarily for anti-HBV activity, compound 6 was synthesized
by compound 1 with BF3ꢀOEt2 as the catalyst in acetone. Oxidation
derivative 7 was successfully obtained by treatment of compound
1 with pyridinium chlorochromate (PCC) in CH2Cl2. Epoxidation of
compound 1 with m-chloroperoxybenzoic acid (m-CPBA) in CH2Cl2
at room temperature gave epoxide 8. In the 1H NMR spectrum of
derivative 8, the splitting pattern and the coupling constants of
All the newly synthesized derivatives of caudatin were tested
for their anti-HBV activity, namely inhibiting the secretion of
HBsAg, HBeAg, and HBV DNA replication in HepG 2.2.15 cells using
tenofovir as a positive control. The results of their anti-HBV activity
and cytotoxicity were listed in Table 1.
Most of the 3-O-acylated caudatin derivatives showed high-
potency activity against of the secretion of HBsAg and HBV DNA
replication. Derivatives (2a–2d) showed inhibitory potency to the
secretion of HBsAg. Meanwhile, compounds 2c and 2d exhibited
significant efficacy on suppressing the secretion of HBeAg. Among
of the acetyl derivatives, only compound 2b showed highly inhibi-
tory activity on HBV DNA replication with the IC50 value of
H-6 with H
,6 -epoxysteroids and 5
ide oxygen is -oriented. Furthermore, as outlined in Scheme 3, C-
a-7 (d, J6-H,7-H = 4.0 Hz), similar to that of reported
a
5a
a
a,6a
-epoxycaudatin,28,29 thus the epox-
a
20 keto of compound 1 was reduced to give derivative 9 with
NaBH4 for further evaluation that a carbonyl function at C-20
13.82 lM, which indicated that the hydroxyl group at C-3 of

L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
2879
Table 1
Anti-HBV activity and cytotoxicity of the caudatin derivatives in vitroa
b
Compd
R
CC50
(
lM)
HBsAgc
M)
HBeAgd
M)
DNA replication
SIf
IC50
(
l
SIf
IC50
(lM)
SIf
e
e
e
IC50
(l
1
244.58
101.92
142.67
1.7
1.4
>183.44
<1.3
40.62
6.0
O
g
2a
70.42
>835.85
—
103.59
—
H3CO
AcO
O
2b
115.6
68.20
1.7
4.2
>152.59
—
13.82
8.4
7.8
O
O
2c
2d
2e
319.11
25.34
76.66
51.64
18.68
96.11
78.62
13.16
3.3
—
40.97
>105.00
7.48
O
O
—
—
O
H3CO
N
O
>1457.34
>78.0
1.7
>110.7
>194.8
10.1
N
2f
36.66
21.71
33.73
1.1
—
3.63
N
H
O
N
2g
2h
2i
50.42
14.28
48.42
64.06
61.34
10.08
20.84
15.59
76.46
26.48
95.52
14.52
2.4
—
>1038.05
>687.36
>626.11
28.16
4.05
4.97
12.4
2.9
3.9
5.1
1.3
3.6
O
N
F
O
N
Br
—
—
12.49
12.60
47.92
2.82
O
N
H3CO
2j
2.4
—
2.3
>1.2
—
O
N
N
2k
2l
<50.28
O
N
N
—
>720.99
O
H3CO
N
2m
2n
132.72
39.91
201.23
19.68
—
—
>1179.08
>32.80
—
—
16.97
7.8
—
O
O
O
>414.10
N
O
O
2o
105.99
70.72
1.5
>638.23
—
65.72
1.6
N
N
2p
2q
2r
62.13
50.48
93.20
87.21
—
<62.13
>749.30
>161.49
>1.0
54.84
13.77
7.32
1.1
3.6
O
O
CH3
N
O
—
H3C
NC
O
122.02
100.48
1.2
—
10.5
N
H3C
H3C
2s
452.23
136.14
3.3
221.14
2.0
30.55
14.8
O
O
O
2t
273.61
309.96
523.67
—
—
115.45
2.4
—
163.84
288.71
1.7
1.1
O
HO
O
O
2u
>384.74
>384.74
HO
Me
O
P
O
O
2v
560.05
>1754.97
—
>1754.97
—
104.93
5.3
Me
(continued on next page)

2880
L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
Table 1 (continued)
b
Compd
R
CC50
(
lM)
HBsAgc
M)
HBeAgd
M)
DNA replication
e
e
e
IC50
(l
SIf
IC50
(l
SIf
IC50
(
lM)
SIf
O
P
O
O
O
2w
>1938.25
>1938.25
—
>1938.25
—
>484.56
—
3
135.97
192.07
331.07
—
146.84
—
—
219.23
288.40
—
HO
O
4a
>1403.12
>4.2
>1403.12
>4.9
O
H3C
Cl
O
4b
4c
>537.70
598.80
575.26
1.6
>256.63
407.48
—
>148.21
>200.74
—
—
O
F
O
>1018.70
>1.8
>2.5
O
4d
4e
>1580.93
>809.48
>1580.93
>809.48
—
—
>1580.93
>809.48
—
182.67
>8.7
—
F
O
O
N
—
>202.37
O
O
4f
602.23
483.08
90.00
>6.7
—
134.54
>2.4
24.69
>24.4
—
N
O
4g
653.48
>965.75
—
—
>241.43
HO
O
O
O
4h
5
>267.96
349.87
>267.96
198.81
—
>267.96
203.66
>267.96
97.00
—
HO
N
O
1.8
1.7
—
3.6
6
7
8
9
511.52
154.53
226.15
217.00
>1820.42
168.06
205.43
189.12
306.55
1446.35
3.0
—
1.2
—
>1716.00
>1632.49
1144.89
>1054.81
1236.61
218.32
112.78
184.30
171.95
0.77
2.3
1.4
1.2
1.3
—
—
>1.5
h
TF
>1.3
>2364.2
a
Values are means determined from at least two experiments.
CC50 is 50% cytotoxicity concentration in HepG2 2.2.15 cells.
HBsAg: hepatitis B surface antigen.
HBeAg, hepatitis B e antigen.
IC50 is 50% inhibitory concentration.
b
c
d
e
f
SI (selectivity index) = CC50/IC50
No SI can be obtained.
.
g
h
Tenofovir as the positive control.
caudatin might be a good target for further lead optimization by
introduction the rational substitutions. Based on many active
anti-HBV agents with nitrogen heterocylic ring, caudatin deriva-
tives with diverse heterocylic ring containing the nitrogen atoms
were synthesized to obtain the significantly anti-HBV agents. The
compounds 2e and 2f had the highest activity inhibiting not only
and cytotoxicity was on the same level. Compounds with pyrazolyl
or isioxazolyl moiety usually had good antiviral activity, so that the
pyrazolyl and isioxazolyl groups were incorporated into caudatin.
Compound 2l [3-O-(1-methyl-1H-pyrazole-5-carbonyl)] caudatin,
showed significantly activity inhibiting the replication of HBV
DNA (IC50 = 2.82
the highest cytotoxicity with the CC50 value 10.08
2m with an isioxazolyl moiety only exhibited potent activity
against HBV DNA replication with the IC50 value 16.97 M. From
lM) among the synthesized derivatives, but had
the secretion of HBsAg (IC50 = 18.68
(IC50 = 13.16 M, 33.73 M), but also HBV DNA replication
(IC50 = 7.48 M, 3.63 M). More the interesting was that compound
2e had low cytotoxicity (CC50 >1457.34 M), resulting in the high
lM, 21.71
lM,) and HBeAg
lM. Compound
l
l
l
l
l
l
the above results, it is indicated that the introduction of nitrogen
aromatic moiety could enhance the anti-HBV activity. However,
the anti-HBV activities of compounds 2o and 2p were at the same
level as caudatin when the nitrogen non-aromatic rings were intro-
duced. Derivative 2r was more effective on inhibiting HBV DNA rep-
selectivity index (SIHBsAg >78.0, SIHBeAg >110.7, SIHBV DNA >194.8).
The inhibiting HBV DNA replication of compounds 2g–2j with one
nicotinic acyl moiety was significantly enhanced with the IC50 value
of 4.05 lM, 4.97 lM, 12.49 lM, 12.60 lM, respectively, along with
better activity of against the secretion of HBsAg. Compound 2k
showed good activity inhibiting both of the secretion of HBsAg,
HBeAg, and HBV DNA replication, but its concentration of activity
lication with the IC50 values of 7.32 lM (SI = 10.5) than that of
caudatin. The anti-HBV activity and cytotoxicity of compound 2s
was weaker than that of compound 2r, which suggested that double

L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
2881
bond affected the activity and cytotoxicity. Both of the mono-3-O-
DNA replication with IC50 values in the range of 2.82–7.48 lM,
diglycolyl and glutaryl derivatives of caudatin (2t, 2u) showed
lower antiviral activity and cell cytotoxicity than that of caudatin.
Compound 3 with the 2-hydroxyacetyl group, by-product of
compound 2t, showed weaker activity than that of caudatin. The
anti-HBV activity of two phosphate esters (2v, 2w) also obviously
decreased, along with the cytotoxicity. These results suggested
that rational groups introduced at position C-3 could influence on
the antiviral activities.
The 3,8-O-di and 3,17-O-diacyl derivatives of caudatin (4a–4e,
4g–4h, 5) lost suppressant properties on the HBV, suggesting that
the C-8 and C-17 hydroxy groups were the important feature in the
antiviral activity. However, there was an exception, 3,17-O-dini-
cotinic acyl derivative (4f) maintained the good activity inhibiting
the secretion of HBsAg and HBV DNA replication with the IC50 val-
which were comparative to that of positive control tenofovir. Inter-
estingly, compounds 2e and 2f had the potent activity inhibiting not
only the secretion of HBsAg (IC50 = 18.68
(IC50 = 13.16 M, 33.73 M), but also HBV DNA replication
(IC50 = 7.48 M, 3.63 M). Moreover, the derivative 2e showed
lM, 21.71 lM), HBeAg
l
l
l
l
low cytotoxicity resulting in high selectivity index values. The active
derivatives of caudatin might have the different anti-HBV mecha-
nisms or unique antiviral targets from the nucleoside drugs.
According to the above results, the SARs were summarized in Fig-
ure 1 and following conclusion could be drawn: (1) for 3-O-substi-
tuted caudatin derivatives, the anti-HBV activity largely depended
on the size and character of the substituent. The introduction of
nitrogen aromatic moiety could significantly enhance the anti-
HBV activity of the caudatin derivatives. However, the antiviral
activity decreased when the substitutions were diglycolyl, glutaryl,
and phosphate esters. (2) Hydroxyl groups were an important fea-
ture in the anti-HBV activity of caudatin derivatives. (3) Oxidation
of C-3 and C-7 to the carbonyl led to loss of anti-HBV activity. (4)
Epoxidefunctionalityat C-5(6) wouldcause the decreaseof suppres-
sant property on anti-HBV activity. (5) The present investigation
indicated that the C-20 carbonyl was crucial for anti-HBV inhibition.
This study provided valuable information for making those caudatin
derivatives to be explored and developed as novel non-nucleoside
anti-HBV agents.
ues of 90.00 lM and 24.69 lM. The cytotoxicity of the 3,8-O-di and
3,17-O-diacyl derivatives reduced when the hydroxyl group was
acylated, indicating that the free hydroxyl groups were not only
the necessary for the activity, but also the factor of leading the
cytotoxicity.
In an effort to gain more information of the SARs of caudatin
derivatives, we studied additional structure changes. The weak
anti-HBV activity was observed when compound 1 was converted
to derivative 6 by treatment with BF3ꢀOEt2 in acetone. This result
further demonstrated that the functionality at the position of C-8
and C-14 was important for potent anti-HBV activity. Modification
of the C-3 and C-7 of caudatin produced the oxidative derivative 7
which exhibited low anti-HBV activity relative to that of caudatin.
Compound 8 showed decreased inhibition to the secretion of
HBsAg, HBeAg and HBV DNA replication compared to compound
1, which revealed that epoxide group at C-5 (6) led to the decrease
of suppressant property on HBV. Comparing caudatin with 9, con-
version of the C@O (C-20) to OH decreased activity lightly, postu-
lated to possibly be due to the loss of hydrogen-bonding
capacity, which proposed that the C-20 carbonyl was crucial for
anti-HBV inhibition. The HBsAg and HBeAg, playing the role in
HBV infection, seroconversion was suggested that was an impor-
tant end point in the treatment of chronic hepatitis B.30–32 Part
of the derivatives had the higher activity against the secretion of
HBsAg or HBeAg than that of the tenofovir (positive control, nucle-
oside drug), suggesting the mechanisms of caudatin derivatives
might be different from the nucleoside analogs.
4. Experimental
4.1. General experimental procedures
1H and 13C NMR spectra were recorded on Bruker AM 400 MHz
or Bruker DRX 500 MHz or Bruker Avance III 600 MHz spectrome-
ters with tetramethylsilane (TMS) as the internal standard (Bruker,
Bremerhaven, Germany). MS and HRMS spectra were determined
on AutoSpec Premier P776 (VG, Manchester, UK) or API QSTAR Pul-
sar (AB, Foster City, USA) mass spectrometers. Column chromatog-
raphy (CC): silica gel (200–300 mesh; Qingdao Makall Group Co.,
Ltd; Qingdao; China). All reactions were monitored using thin-
layer chromatography (TLC) on silica gel plates. Caudatin was iso-
lated from Cynanchum auriculatum (Bai-Shou-Wu) and had the
purity of >95.0%. Reaction reagents were purchased from Alfa Ae-
sar or J&K Scientific Ltd. Organic solvents were analytical reagent
grade and purchased from Tianjin Chemical Reagent Co., Ltd.
3. Conclusions
4.2. Chemistry
In conclusion, a series of caudatin derivatives were synthesized
and examined for their anti-HBV activities and cytotoxicities
in vitro. Ten tested compounds (2a–2c, 2e–2g, 2j, 2n, 2o, 4f) with
higher inhibitory activity against the secretion of HBsAg than caud-
atin were obtained. Compounds 2c, 2e, 2f, 2j, 4f showed better
activity inhibiting the secretion of HBeAg than that of caudatin.
Six compounds (2e–2h, 2l, 2r) exhibited significant inhibition HBV
4.2.1. General procedure for preparation of compounds 2a–2r
The DCC (1.2 equiv) was added to the solution of 1 (0.2 mmol),
DMAP (0.2 equiv), and appropriate carboxylic acid (1.2 equiv) in
anhydrous CH2Cl2 (8 mL) at 0 °C. The resulting mixture was stirred
at room temperature until the starting material was not observed
by TLC. The reaction mixture was filtered, and the residue was
washed with CH2Cl2 (2 ꢁ 10 mL). Then, the CH2Cl2 solution was
washed with 5% HCl (3 ꢁ 30 mL), saturated NaHCO3 (3 ꢁ 30 mL)
and saturated NaCl (3 ꢁ 30 mL), respectively. Subsequently, the or-
ganic layer was dried over anhydrous Na2SO4 and concentrated to
dryness under reduced pressure. At last, the residue was purified
by column chromatography over the silica gel to yield the pure tar-
get compounds.
O
O
OH
O
OH
OH
H
Nitrogen aromatic moiety
HO
H
Diglycolyl, glutaryl and phosphoryl
4.2.1.1. 3-O-(Methoxyacetyl)caudatin (2a).
White amor-
Epoxidation
phous power, yield 70.6% (after chromatography with petroleum
ether/acetone, 85:15); 1H NMR (CDCl3, 500 MHz): d 1.04 (6H, d,
J = 6.8 Hz, CH3-50, 60), 1.14 (3H, s, CH3-19), 1.38 (3H, s, CH3-18),
1.60 (1H, m, H-9), 1.80–1.97 (9H, overlap, H-1, 2, 11, 15, 16),
2.10 (3H, s, CH3-70), 2.14 (3H, s, CH3-21), 2.18 (2H, s, H-7), 2.40
: Anti-HBV activity increased
: Anti-HBV activity decreased
Oxidation
Figure 1. Structure–activity relationships of caudatin derivatives anti-HBV activity.

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L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
(3H, overlap, H-40, 4), 2.83 (1H, m, H-16), 3.42 (3H, s, OCH3), 3.98
(2H, s, CH2CO), 4.53 (1H, dd, J = 5.0, 10.6 Hz, H-12), 4.71 (1H, m,
H-3), 5.39 (1H, s, H-6), 5.50 (1H, s, H-20); 13C NMR (CDCl3,
125 MHz): d 9.4 (C-18), 16.4 (C-70), 18.3 (C-19), 20.8 (2C-50, 60),
24.1 (C-11), 26.8 (C-2), 27.1 (C-21), 31.7 (C-16), 33.2 (C-7), 34.2
(C-15), 36.8 (C-10), 37.8 (C-1), 38.1 (C-40), 38.3 (C-4), 43.5 (C-9),
57.8 (C-13), 59.2 (C-300), 69.9 (C-200), 71.5 (C-12), 74.1 (C-3), 74.2
(C-8), 87.9 (C-14), 91.4 (C-17), 112.9 (C-20), 119.0 (C-6), 138.9 (C-
5), 165.9 (C-30), 166.9 (C-10), 169.6 (C-100), 208.8 (C-20); ESIMS:
m/z 585 [M+Na]+ HRESIMS: calcd for C31H46O9Na [M+Na]+
585.3039, found 585.3040.
4.2.1.5.
(2e).
3-O
-[(E)-3-(1H-Imidazol-1-yl)acryloyl]caudatin
White amorphous power, yield 79.6% (after chromatog-
raphy with petroleum ether/acetone, 70:30); 1H NMR (CDCl3,
400 MHz): d 1.04 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.17 (3H, s, CH3-
19), 1.41 (3H, s, CH3-18), 1.58 (1H, m, H-9), 1.82–1.90 (9H,overlap,
H-1, 2, 11, 15, 16), 2.10 (3H, s, CH3-70), 2.15 (3H, s, CH3-21), 2.16
(2H, s, H-7), 2.37 (1H, m, H-40), 2.42 (2H, m, H-4), 2.85 (1H, m,
H-16), 4.41 (1H, m, H-12), 4.74 (1H, m, H-3), 5.41 (1H, s, H-6),
5.51 (1H, s, H-20), 6.04 (1H, d, J = 14.2 Hz, H-200), 7.13 (1H, d,
J = 13.4 Hz, H-700), 7.24 (1H, d, J = 13.4 Hz, H-800), 7.81 (1H, s, H-
500), 7.89 (1H, d, J = 14.2 Hz, H-300); 13C NMR (CDCl3, 100 MHz): d
9.5 (C-18), 16.5 (C-70), 18.3 (C-19), 20.8 (C-50), 20.9 (C-60), 24.1
(C-11), 26.9 (C-2), 27.2 (C-21), 31.7 (C-16), 33.3 (C-7), 34.3 (C-
15), 36.9 (C-10), 37.9 (C-1), 38.1 (C-40), 38.4 (C-4), 43.5 (C-9),
57.8 (C-13), 71.5 (C-12), 74.1 (C-3), 74.4 (C-8), 88.0 (C-14), 91.5
(C-17), 107.6 (C-200), 112.9 (C-20), 116.2 (C-800), 119.2 (C-6), 131.3
(C-700), 136.4 (C-500), 137.7 (C-300), 138.9 (C-5), 165.1 (C-30), 165.9
(C-100), 166.9 (C-10), 209.0 (C-20); ESIMS: m/z 633 [M+Na]+ HRE-
SIMS: calcd for C34H46N2O8Na [M+Na]+ 633.3151, found 633.3160.
4.2.1.2. 3-O-(Ethoxyacetyl)caudatin (2b).
power, yield 81.7% (after chromatography with petroleum ether/
acetone, 80:20); 1H NMR (CDCl3, 400 MHz):
1.06 (6H, d,
White amorphous
d
J = 6.8 Hz, CH3-50, 60), 1.16 (3H, s, CH3-19), 1.24 (3H, t, J = 7.0 Hz,
CH3CH2O), 1.39 (3H, s, CH3-18), 1.60 (1H, m, H-9), 1.82–1.97 (9H,
overlap, H-1, 2, 11, 15, 16), 2.13 (3H, s, CH3-70), 2.16 (3H, s, CH3-
21), 2.23 (2H, s, H-7), 2.37 (1H, m, H-40), 2.42 (2H, overlap, H-4),
2.84 (1H, m, H-16), 3.59 (2H, q, J = 7.0 Hz, CH3CH2O), 4.05 (2H, s,
CH2CO), 4.57 (1H, t, J = 6.8 Hz, H-12), 4.73 (1H, m, H-3), 5.42 (1H,
s, H-6), 5.53 (1H, s, H-20); 13C NMR (CDCl3, 100 MHz): d 9.3 (C-
18), 15.0 (C-400), 16.5 (C-70), 18.4 (C-19), 20.8 (C-60), 20.9 (C-50),
24.1 (C-11), 26.8 (C-2), 27.2 (C-21), 31.7 (C-16), 33.3 (C-7), 34.2
(C-15), 36.9 (C-10), 37.8 (C-1), 38.2 (C-40), 38.4 (C-4), 43.5 (C-9),
58.0 (C-13), 67.2 (C-300), 68.2 (C-200), 71.6 (C-12), 74.1 (C-3), 74.2
(C-8), 87.8 (C-14), 91.4 (C-17), 112.9 (C-20), 119.0 (C-6), 139.1 (C-
5), 166.0 (C-30), 167.1 (C-10), 169.9 (C-100), 208.8 (C-20); EIMS: m/
z 576, HREIMS: calcd for C32H48O9 576.3298, found 576.3283.
4.2.1.6. 3-O-(Indole-2-carbonyl)caudatin (2f).
White amor-
phous power, yield 79.4% (after chromatography with petroleum
ether/acetone, 80:20); 1H NMR (CDCl3, 400 MHz): d 1.07 (6H, d,
J = 6.8 Hz, CH3-50, 60), 1.22 (3H, s, CH3-19), 1.44 (3H, s, CH3-18),
1.66 (1H, m, H-9), 1.86–2.00 (9H, overlap, H-1, 2, 11, 15, 16),
2.14 (3H, s, CH3-70), 2.17 (3H, s, CH3-21), 2.22 (2H, s, H-7), 2.37
(1H, m, H-40), 2.55 (2H, overlap, H-4), 2.86 (1H, m, H-16), 4.66
(1H, dd, J = 5.8, 9.7 Hz, H-12), 4.92 (1H, m, H-3), 5.42 (1H, s, H-6),
5.56 (1H, s, H-20), 7.14 (1H, t, J = 7.5 Hz, H-700), 7.23 (1H, s, H-300),
7.31 (1H, t, J = 7.6 Hz, H-600), 7.45 (1H, d, J = 8.3 Hz, H-800), 7.68
(1H, d, J = 8.0 Hz, H-500), 9.47 (1H, s, 1000-NH); 13C NMR (CDCl3,
100 MHz): d 9.4 (C-18), 16.5 (C-70), 18.4 (C-19), 20.8 (C-50), 20.9
(C-60), 24.2 (C-11), 27.0 (C-2), 27.2 (C-21), 31.8 (C-16), 33.2 (C-7),
34.3 (C-15), 37.0 (C-10), 38.1 (C-1), 38.2 (C-40), 38.4 (C-4), 43.5
(C-9), 57.9 (C-13), 71.6 (C-12), 74.2 (C-8), 74.5 (C-3), 88.1 (C-14),
91.5 (C-17), 108.6 (C-800), 112.0 (C-300), 112.9 (C-20), 119.0 (C-6),
120.7 (C-600), 122.5 (C-500), 125.2 (C-700), 127.4 (C-200), 127.5 (C-400),
137.0 (C-900), 139.2 (C-5), 161.6 (C-100), 166.1 (C-30), 167.0 (C-10),
209.0 (C-20); ESIMS: m/z 656 [M+Na]+ HRESIMS: calcd for
4.2.1.3. 3-O-(Phenoxyacetyl)caudatin (2c).
White amorphous
power, yield 70.9% (after chromatography with petroleum ether/ace-
tone, 85:15); 1H NMR (CDCl3, 400 MHz): d 1.06 (6H, d, J = 6.8 Hz, CH3-
50, 60), 1.15 (3H, s, CH3-19), 1.39 (3H, s, CH3-18), 1.60 (1H, m, H-9),
1.82–1.96 (9H, overlap, H-1, 2, 11, 15, 16), 2.12 (3H, s, CH3-70), 2.16
(3H, s, CH3-21), 2.20 (2H, s, H-7), 2.30–2.43 (3H, overlap, H-40, 4),
2.86 (1H, m, H-16), 4.60 (2H, s, CH2CO–), 4.54 (1H, m, H-12), 4.76
(1H, m, H-3), 5.41 (1H, s, H-6), 5.52 (1H, s, H-20), 6.89 (2H, d,
J = 8.5 Hz, H-500, 900), 7.01 (1H, t, J = 10.0 Hz, H-700), 7.29 (2H, m, H-600,
13
800); C NMR (CDCl3, 100 MHz): d 9.4 (C-18), 16.5 (C-70), 18.4 (C-
C
37H47NO8Na [M+Na]+ 656.3199, found 656.3235.
19), 20.8 (C-50), 20.9 (C-60), 24.1 (C-11), 26.8 (C-2), 27.2 (C-21), 31.7
(C-16), 33.3 (C-7), 34.3 (C-15), 36.9 (C-10), 37.7 (C-1), 38.2 (C-40),
38.3 (C-4), 43.5 (C-9), 57.9 (C-13), 65.5 (C-200), 71.6 (C-12), 74.1 (C-
8), 74.8 (C-3), 87.9 (C-14), 91.4 (C-17), 112.9 (C-20), 114.6 (2C-500,
900), 119.2 (C-6), 121.7 (C-700), 129.5 (2C-600, 800), 138.9 (C-5), 157.8
(C-400), 166.0 (C-30), 167.0 (C-10), 168.4 (C-100), 208.9 (C-20); ESIMS:
m/z 623 [M-H]ꢂ, HRESIMS: calcd for C36H47O9 [M-H]ꢂ 623.3220,
found 623.3206.
4.2.1.7. 3-O-(Nicotinyl)caudatin (2g).
power, yield 45.4% (after chromatography with petroleum ether/
acetone, 85:15); 1H NMR (CDCl3, 400 MHz):
1.02 (6H, d,
White amorphous
d
J = 6.8 Hz, CH3-50, 60), 1.19 (3H, s, CH3-19), 1.40 (3H, s, CH3-18),
1.56 (1H, m, H-9), 1.80–1.98 (9H, overlap, H-1, 2, 11, 15, 16),
2.09 (3H, s, CH3-70), 2.14 (3H, s, CH3-21), 2.20 (2H, s, H-7), 2.32
(2H, m, 40), 2.50 (2H, m, 4), 2.84 (1H, m, H-16), 4.54 (1H, dd,
J = 4.9, 10.8 Hz, H-12), 4.87 (1H, m, H-3), 5.38 (1H, s, H-6), 5.49
(1H, s, H-20), 7.36 (1H, dd, J = 7.2, 7.6 Hz, H-500), 8.27 (1H, m, H-
400), 8.70 (1H, dd, J = 1.4, 4.7 Hz, H-600), 9.13 (1H, s, H-200); 13C
NMR (CDCl3, 100 MHz): d 9.4 (C-18), 16.4 (C-70), 18.2 (C-19), 20.7
(C-50), 20.8 (C-60), 24.1 (C-11), 26.9 (C-2), 27.0 (C-21), 31.7 (C-
16), 33.1 (C-7), 34.1 (C-15), 36.8 (C-10), 37.8 (C-1), 38.0 (C-40),
38.3 (C-4), 43.5 (C-9), 57.7 (C-13), 71.4 (C-12), 74.0 (C-8), 74.8
(C-3), 87.9 (C-14), 91.4 (C-17), 112.8 (C-20), 119.3 (C-6), 123.2 (C-
500), 126.3 (C-300), 137.1 (C-400), 138.7 (C-5), 150.5 (C-200), 152.9 (C-
600), 164.4 (C-100), 165.8 (C-30), 166.8 (C-10), 208.9 (C-20); EIMS:
m/z 595, HREIMS: calcd for C34H45NO8 595.3145, found 595.3135.
4.2.1.4.
(2d).
3-O-[(2-Methoxy-2-oxoethoxy)acetyl]caudatin
White amorphous power, yield 82.1% (after chromatog-
raphy with petroleum ether/acetone, 70:30); 1H NMR (CD3COCD3,
600 MHz): d 1.06 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.19 (3H, s, CH3-19),
1.52 (3H, s, CH3-18), 1.62–1.94 (10H, overlap, H-1, 2, 9, 11, 15, 16),
2.11 (3H, s, CH3-70), 2.18 (3H, s, CH3-21), 2.22 (2H, s, H-7), 2.364–
2.41 (3H, overlap, H-4, 40), 2.91 (1H, m, H-16), 3.69 (3H, s, CH3-
500), 4.21 (2H, s, H-300), 4.31 (2H, s, H-200), 4.48 (1H, dd, J = 4.3,
11.6 Hz, H-12), 4.65 (1H, m, H-3), 5.37 (1H, s, H-6), 5.56 (1H, s,
13
H-20); C NMR (CD3COCD, 150 MHz): d 10.4 (C-18), 16.4 (C-70),
18.3 (C-19), 21.2 (C-50), 21.3 (C-60), 25.0 (C-11), 27.3 (C-21), 27.9
(C-2), 30.4 (C-16), 32.8 (C-7), 33.9 (C-15), 35.0 (C-10), 37.7 (C-40),
38.7 (C-1), 38.9 (C-4), 44.4 (C-9), 51.9 (C-500), 58.1 (C-13), 68.2 (C-
200), 68.4 (C-300), 72.4 (C-12), 74.7 (C-8), 75.0 (C-3), 89.6 (C-14),
92.7 (C-17), 114.3 (C-20), 120.5 (C-6), 138.9 (C-5), 165.7 (C-30),
165.8 (C-10), 169.9 (C-100), 171.0 (C-400), 208.8 (C-20); EIMS: m/z
620, HREIMS: calcd for C33H48O11 620.3197, found 620.3212.
4.2.1.8. 3-O-(6-Fluoronicotinyl)caudatin (2h).
As white
amorphous power, yield 60.7% (after chromatography with petro-
leum ether/acetone, 80:20); 1H NMR (CDCl3, 500 MHz): d 1.02
(6H, d, J = 6.8 Hz, CH3-50, 60), 1.16 (3H, s, CH3-19), 1.40 (3H, s,
CH3-18), 1.54 (1H, m, H-9), 1.82–1.95 (9H, overlap, H-1, 2, 11, 15,
16), 1.95 (3H, s, CH3-70), 2.14 (3H, s, CH3-21), 2.19 (2H, s, H-7),

L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
2883
2.32 (1H, m, H-40), 2.44 (2H, m, H-4), 2.82 (1H, m, H-16), 4.54 (1H,
dd, J = 4.4, 10.9 Hz, H-12), 4.77 (1H, m, H-3), 5.39 (1H, s, H-6), 5.49
(1H, s, H-20), 6.53 (1H, d, J = 9.5 Hz, H-600), 7.97 (1H, dd, J = 1.9,
9.6 Hz, H-700), 8.19 (1H, s, H-300); 13C NMR (CDCl3, 125 MHz): d
9.4 (C-18), 16.4 (C-70), 18.2 (C-19), 20.7 (C-50), 20.8 (C-60), 24.1
(C-11), 26.9 (C-2), 27.1 (C-21), 31.7 (C-16), 33.2 (C-7), 34.2 (C-
15), 36.8 (C-10), 37.8 (C-1), 38.0 (C-40), 38.3 (C-4), 43.5 (C-9),
57.8 (C-13), 71.5 (C-12), 74.0 (C-8), 74.5 (C-3), 88.0 (C-14), 91.4
(C-17), 111.4 (C-600), 112.8 (C-20), 119.1 (C-6), 119.3 (C-200), 138.8
(C-5), 139.7 (C-700), 141.1 (C-300), 163.2 (C-100), 165.2 (C-400), 165.9
(C-30), 166.8 (C-10), 209.0 (C-20); EIMS: m/z 613, HREIMS: calcd
for C34H44NO8F 613.3051, found 613.3130.
(C-5), 143.6 (C-200), 144.4 (C-500), 146.2 (C-400), 147.5 (C-300), 163.2
(C-100), 165.9 (C-30), 166.9 (C-10), 208.9 (C-20); ESIMS: m/z 619
[M+Na]+ HRESIMS: calcd for C33H44N2O8Na [M+Na]+ 619.2995,
found 619.3004.
4.2.1.12.
(2l).
3-O
-(1-Methyl-1H-pyrazole-5-carbonyl)caudatin
As white amorphous power, yield 79.2% (after chroma-
tography with petroleum ether/acetone, 80:20); 1H NMR (CDCl3,
400 MHz): d 1.00 (6H, d, J = 6.4 Hz, CH3-50, 60), 1.02 (3H, s, CH3-
19), 1.39 (3H, s, CH3-18), 1.54 (1H, m, H-9), 1.75–1.96 (9H, overlap,
H-1, 2, 11, 15, 16), 2.08 (3H, s, CH3-70), 2.13 (3H, s, CH3-21), 2.18
(2H, s, H-7), 2.31 (1H, m, H-40), 2.47 (2H, m, H-4), 2.82 (1H, m,
H-16), 4.12 (1H, s, NCH3), 4.51 (1H, dd, J = 4.8, 10.9 Hz, H-12),
4.77 (1H, m, H-3), 5.39 (1H, s, H-6), 5.48 (1H, s, H-20), 6.78 (1H,
d, J = 5.2 Hz, H-300), 7.39 (1H, d, J = 5.2 Hz, H-400); 13C NMR (CDCl3,
100 MHz): d 9.5 (C-18), 16.5 (C-70), 18.3 (C-19), 20.8 (C-50), 20.9
(C-60), 24.1 (C-11), 26.9 (C-2), 27.1 (C-21), 31.8 (C-16), 33.2 (C-7),
34.2 (C-15), 36.9 (C-10), 37.9 (C-1), 38.1 (C-40), 38.4 (C-4), 39.5
(C-NCH3), 43.6 (C-9), 57.8 (C-13), 71.5 (C-12), 74.0 (C-8), 74.5
(C-3), 88.1 (C-14), 91.5 (C-17), 111.1 (C-300), 112.9 (C-20), 119.2
(C-6), 132.6 (C-200), 137.6 (C-400), 138.8 (C-5), 159.2 (C-100), 165.9
(C-30), 166.8 (C-10), 209.0 (C-20); EIMS: m/z 598, HREIMS: calcd
for C33H46N2O8 598.3254, found 598.3234.
4.2.1.9.
(2i).
3-O-(5-Bromo-pyridine-2-carbonyl)caudatin
White amorphous power, yield 93.3% (after chromatog-
raphy with petroleum ether/acetone, 85:15); 1H NMR (CDCl3,
400 MHz): d 1.00 (6H, d, J = 6.5 Hz, CH3-50, 60), 1.14 (3H, s, CH3-
19), 1.38 (3H, s, CH3-18), 1.54 (1H, m, H-9), 1.78–1.94 (9H, overlap,
H-1, 2, 11, 15, 16), 2.06 (3H, s, CH3-70), 2.12 (3H, s, CH3-21), 2.17
(2H, s, H-7), 2.30 (1H, m, H-40), 2.46 (2H, m, H-4), 2.82 (1H, m,
H-16), 4.51 (1H, dd, J = 4.7, 10.7 Hz, H-12), 4.89 (1H, m, H-3),
5.39 (1H, s, H-6), 5.47 (1H, s, H-20), 7.91–7.96 (2H, overlap, H-300,
400), 8.73 (1H, s, H-600); 13C NMR (CDCl3, 100 MHz): d 9.5 (C-18),
16.5 (C-70), 18.3 (C-19), 20.8 (C-50), 20.9 (C-60), 24.1 (C-11), 26.8
(C-2), 27.1 (C-21), 31.8 (C-16), 33.2 (C-7), 34.2 (C-15), 36.9 (C-
10), 37.7 (C-1), 38.1 (C-40), 38.4 (C-4), 43.5 (C-9), 57.8 (C-13),
71.5 (C-12), 74.1 (C-8), 75.6 (C-3), 88.1 (C-14), 91.5 (C-17), 112.9
(C-20), 119.2 (C-6), 124.9 (C-500), 126.3 (C-300), 138.9 (C-5), 139.6
(C-400), 146.6 (C-200), 160.0 (C-600), 163.9 (C-100), 165.9 (C-30), 166.8
(C-10), 209.0 (C-20); EIMS: m/z 673, HREIMS: calcd for C34H44BrNO8
673.2847, found 673.2837.
4.2.1.13.
(2m).
3-O-(3-Methoxyisoxazole-5-carbonyl)
As white amorphous power, yield 98.4% (after chroma-
caudatin
tography with petroleum ether/acetone, 85:15); 1H NMR (CDCl3,
400 MHz): d 1.00 (6H, d, J = 6.4 Hz, CH3-50, 60), 1.02 (3H, s, CH3-
19), 1.38 (3H, s, CH3-18), 1.53 (1H, m, H-9), 1.75–1.98 (9H,overlap,
H-1, 2, 11, 15, 16), 2.07 (3H, s, CH3-70), 2.12 (3H, s, CH3-21), 2.17
(2H, s, H-7), 2.31 (1H, m, H-40), 2.43 (2H, m, H-4), 2.82 (1H, m,
H-16), 3.96 (1H, s, OCH3), 4.50 (1H, dd, J = 4.6, 11.0 Hz, H-12),
4.83 (1H, m, H-3), 5.39 (1H, s, H-6), 5.52 (1H, s, H-20), 6.48 (1H, s,
4.2.1.10. 3-O-(2-Methoxynicotinyl)caudatin (2j).
As white
13
amorphous power, yield 80.8% (after chromatography with petro-
leum ether/acetone, 85:15); 1H NMR (CDCl3, 500 MHz): d 1.01
(6H, d, J = 6.8 Hz, CH3-50,60), 1.16 (3H, s, CH3-19), 1.39 (3H, s, CH3-
18), 1.55 (1H, m, H-9), 1.78–1.96 (9H, overlap, H-1, 2, 11, 15, 16),
2.08 (3H, s, CH3-70), 2.13 (3H, s, CH3-21), 2.19 (2H, s, H-7), 2.33
(1H, m, H-40), 2.47 (2H, m, H-4), 2.83 (1H, m, H-16), 3.94 (1H, s,
CH3-400), 4.52 (1H, dd, J = 3.8, 8.7 Hz, H-12), 4.80 (1H, m, H-3),
5.40 (1H, s, H-6), 5.48 (1H, s, H-20), 6.72 (1H, d, J = 6.9 Hz, H-600),
8.09 (1H, dd, J = 1.7, 6.9 Hz, H-700), 8.77 (1H, s, H-300); 13C NMR
(CDCl3, 125 MHz): d 9.4 (C-18), 16.4 (C-70), 18.3 (C-19), 20.7 (C-
50), 20.8 (C-60), 24.1 (C-11), 26.9 (C-2), 27.0 (C-21), 31.7 (C-16),
33.1 (C-7), 34.2 (C-15), 36.9 (C-10), 37.9 (C-1), 38.0 (C-40), 38.3
(C-4), 43.5 (C-9), 53.9 (C-CH3O), 57.7 (C-13), 71.5 (C-12), 74.0 (C-
8), 74.2 (C-3), 88.0 (C-14), 91.4 (C-17), 110.4 (C-600), 112.8 (C-20),
118.9 (C-6), 119.8 (C-200), 139.0 (C-5), 139.4 (C-700), 149.8 (C-300),
164.6 (C-100), 165.8 (C-30), 166.6 (C-10), 166.7 (C-400), 208.9 (C-20);
EIMS: m/z 625, HREIMS: calcd for C35H47NO9 625.3251, found
625.3222.
H-300); C NMR (CDCl3, 100 MHz): d 9.4 (C-18), 16.5 (C-70), 18.3
(C-19), 20.8 (C-50), 20.9 (C-60), 24.1 (C-11), 26.7 (C-2), 27.1 (C-
21), 31.8 (C-16), 33.2 (C-7), 34.2 (C-15), 36.9 (C-10), 37.6 (C-1),
38.1 (C-40), 38.3 (C-4), 43.5 (C-9), 57.4 (C-OCH3), 57.8 (C-13), 71.5
(C-12), 74.0 (C-8), 75.9 (C-3), 88.0 (C-14), 91.5 (C-17), 100.4 (C-
300), 112.9 (C-20), 119.5 (C-6), 138.5 (C-5), 156.0 (C-400), 160.7 (C-
200), 165.9 (C-30), 166.8 (C-10), 172.0 (C-100), 209.0 (C-20); EIMS:
m/z 615, HREIMS: calcd for C33H45NO10 615.3043, found 615.3050.
4.2.1.14. 3-O-(4-Pyridylacetyl) caudatin (2n).
As yellow
amorphous power, yield 69.4% (after chromatography with petro-
leum ether/acetone, 75:25); 1H NMR (CDCl3, 400 MHz): d 1.00 (6H,
d, J = 6.8 Hz, CH3-50, 60), 1.10 (3H, s, CH3-19), 1.39 (3H, s, CH3-18),
1.60 (1H, m, H-9), 1.75–1.92 (9H, overlap, H-1, 2, 11, 15, 16),
2.00 (3H, s, CH3-70), 2.12 (3H, s, CH3-21), 2.13 (2H, s, H-7), 2.28–
2.32 (3H, overlap, H-4, 40), 2.82 (1H, m, H-16), 3.56 (1H, s, H-200),
4.52 (1H, dd, J = 5.0, 10.7 Hz, H-12), 4.59 (1H, m, H-3), 5.32 (1H,
s, H-6), 5.48 (1H, s, H-20), 7.20 (2H, d, J = 4.5 Hz, H-400, 800), 8.45
(2H, d, J = 4.5 Hz, H-500, 700); 13C NMR (CDCl3, 100 MHz): d 9.6 (C-
18), 16.5 (C-70), 18.2 (C-19), 20.8 (C-50), 20.9 (C-60), 24.1 (C-11),
26.8 (C-2), 27.1 (C-21), 31.8 (C-16), 33.3 (C-7), 34.3 (C-15), 36.8
(C-10), 37.7 (C-1), 38.1 (C-40), 38.3 (C-4), 40.8 (C-200), 43.5 (C-9),
57.6 (C-13), 71.5 (C-12), 73.9 (C-8), 74.8 (C-3), 88.2 (C-14), 91.5
(C-17), 112.9 (C-20), 119.3 (C-6), 124.7 (2C-400, 800), 138.6 (C-5),
143.7 (C-300), 149.1 (2C-500, 700), 165.9 (C-30), 166.6 (C-10), 169.2
(C-100), 209.1 (C-20); ESIMS: m/z 610 [M+H]+ HRESIMS: calcd for
C35H48NO8 [M+H]+ 610.3379, found 610.3372.
4.2.1.11. 3-O-(2-Pyrazinecarbonyl)caudatin (2k).
As light
yellow amorphous power, yield 74.8% (after chromatography with
petroleum ether/acetone, 80:20); 1H NMR (CDCl3, 400 MHz): d 1.05
(6H, d, J = 6.8 Hz, CH3-50, 60), 1.17 (3H, s, CH3-19), 1.38 (3H, s, CH3-
18), 1.55 (1H, m, H-9), 1.80–1.96 (9H, overlap, H-1, 2, 11, 15, 16),
2.12 (3H, s, CH3-70), 2.13 (3H, s, CH3-21), 2.19 (2H, s, H-7), 2.31
(1H, m, H-40), 2.55 (2H, m, H-4), 2.82 (1H, m, H-16), 4.52 (1H, dd,
J = 5.0, 10.7 Hz, H-12), 4.96 (1H, m, H-3), 5.42 (1H, s, H-6), 5.48
(1H, s, H-20), 8.68–8.72 (2H, overlap, H-300, 400), 9.25 (1H, s, H-600);
13C NMR (CDCl3, 100 MHz): d 9.4 (C-18), 16.5 (C-70), 18.3 (C-19),
20.8 (C-50), 20.9 (C-60), 24.1 (C-11), 26.8 (C-2), 27.1 (C-21), 31.8
(C-16), 33.3 (C-7), 34.2 (C-15), 36.9 (C-10), 37.7 (C-1), 38.1 (C-40),
38.4 (C-4), 43.5 (C-9), 57.8 (C-13), 71.5 (C-12), 74.0 (C-8), 75.9
(C-3), 88.0 (C-14), 91.5 (C-17), 112.9 (C-20), 119.2 (C-6), 138.7
4.2.1.15. 3-O-(N -Acetyl-
L
-prolinyl)caudatin (2o).
As white
amorphous power, yield 72.0% (after chromatography with petro-
leum ether/acetone, 80:20); 1H NMR (CDCl3, 500 MHz): d 1.01
(6H, d, J = 6.8 Hz, CH3-50, 60), 1.11 (3H, s, CH3-19), 1.38 (3H, s,
CH3-18), 1.50 (1H, m, H-9), 1.76–1.95 (11H, overlap, H-1, 2, 11,

2884
L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
15, 16, 400), 2.08 (3H, s, CH3-70), 2.11–2.13 (8H, overlap, H-300, CH3-
21, 700), 2.22 (2H, s, H-7), 2.31–2.33 (3H, overlap, H-4, 40), 2.82 (1H,
m, H-16), 4.36 (1H, dd, J = 2.9, 6.9 Hz, H-200), 4.49 (1H, dd, J = 3.5,
12.4 Hz, H-12), 4.62 (1H, m, H-3), 5.36 (1H, s, H-6), 5.47 (1H, s,
4.2.1.19.
(2s).
3-O-(2-Cyano-3-methylbut-2-enoyl)caudatin
Derivatives 2s was obtained from compound 2r by chro-
matography using a silica gel column with petroleum ether and
acetone, as white amorphous power, yield 86.3% (after chromatog-
raphy with petroleum ether/acetone, 85:15); 1H NMR (CDCl3,
500 MHz): d 1.03 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.15 (3H, s, CH3-
19), 1.39 (3H, s, CH3-18), 1.60 (1H, m, H-9), 1.79–1.96 (9H, overlap,
H-1, 2, 11, 15, 16), 2.09 (3H, s, CH3-70), 2.14 (3H, s, CH3-21), 2.18
(2H, s, H-7), 2.27 (3H, s, H-600), 2.33 (2H, m, 4), 2.37 (3H, s, H-500),
2.42 (2H, m, 40), 2.83 (1H, m, H-16), 4.52 (1H, dd, J = 3.8, 8.7 Hz,
H-12), 4.68 (1H, m, H-3), 5.39 (1H, s, H-6), 5.49 (1H, s, H-20); 13C
NMR (CDCl3, 125 MHz): d 9.4 (C-18), 16.4 (C-70), 18.3 (C-19), 20.7
(C-50), 20.8 (C-60), 22.7 (C-600), 24.1 (C-11), 26.7 (C-2), 27.1 (C-21),
27.3 (C-500), 31.7 (C-16), 33.2 (C-7), 34.2 (C-15), 36.9 (C-10), 37.6
(C-1), 38.1 (C-40), 38.3 (C-4), 43.5 (C-9), 57.8 (C-13), 71.4 (C-12),
74.0 (C-8), 75.2 (C-3), 87.9 (C-14), 91.4 (C-17), 105.1 (C-200), 112.8
(C-20), 115.5 (C-300), 119.0 (C-6), 138.9 (C-5), 161.1 (C-400), 165.9
(C-30), 166.8 (C-10), 173.7 (C-100), 208.8 (C-20); EIMS: m/z 597, HRE-
IMS: calcd for C34H47NO8 597.3302, found 597.3297.
13
H-20); C NMR (CDCl3, 125 MHz): d 9.4 (C-18), 16.4 (C-70), 18.2
(C-19), 20.7 (C-50), 20.8 (C-60), 22.1 (C-700), 24.0 (C-11), 24.6 (C-
400), 26.6 (C-2), 27.0 (C-21), 29.3 (C-300), 31.7 (C-16), 33.1 (C-7),
34.2 (C-15), 36.8 (C-10), 37.6 (C-1), 38.0 (C-40), 38.2 (C-4), 43.4
(C-9), 47.7 (C-500), 57.6 (C-13), 58.7 (C-200), 71.4 (C-12), 74.0 (C-8),
74.4 (C-3), 88.1 (C-14), 91.4 (C-17), 112.8 (C-20), 118.9 (C-6),
138.9 (C-5), 165.8 (C-30), 166.5 (C-10), 169.5 (C-100), 171.5 (C-600),
208.9 (C-20); EIMS: m/z 629, HREIMS: calcd for
C35H51NO9
629.3564, found 629.3546.
4.2.1.16.
(2p).
3-O-(1-Acetyl-4-piperidinecarbonyl)caudatin
As white amorphous power, yield 71.1% (after chroma-
tography with petroleum ether/acetone, 70:30); 1H NMR (CDCl3,
400 MHz): d 1.00 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.11 (3H, s, CH3-
19), 1.38 (3H, s, CH3-18), 1.60 (1H, m, H-9), 1.75–1.92 (13H, over-
lap, H-1, 2, 11, 15, 16, 300), 2.04 (1H, s, H-600), 2.07 (3H, s, CH3-70),
2.12 (3H, s, CH3-21), 2.14 (2H, s, H-7), 2.30–2.32 (3H, overlap, H-
4, 40), 2.80–2.84 (2H, overlap, H-16, 200), 3.98–4.02 (4H, overlap,
H-400), 4.50 (1H, dd, J = 4.5, 10.9 Hz, H-12), 4.58 (1H, m, H-3), 5.34
(1H, s, H-6), 5.47 (1H, s, H-20); 13C NMR (CDCl3, 100 MHz): d 9.5
(C-18), 16.5 (C-70), 18.2 (C-19), 20.8 (C-50), 20.9 (C-60), 21.3 (C-
600), 24.1 (C-11), 26.8 (C-2), 27.1 (C-21), 29.2 (2C-300), 31.8 (C-16),
33.3 (C-7), 34.2 (C-15), 36.9 (C-10), 37.8 (C-1), 38.1 (C-40), 38.3
(C-4), 40.9 (C-200), 43.5 (C-9), 57.7 (C-13), 64.3 (2C-400), 71.5 (C-
12), 73.9 (C-8), 74.0 (C-3), 88.1 (C-14), 91.5 (C-17), 112.9 (C-20),
119.1 (C-6), 138.8 (C-5), 165.9 (C-30), 166.6 (C-10), 169.0 (C-500),
173.4 (C-100), 209.0 (C-20); ESIMS: m/z 666 [M+Na]+ HRESIMS:
calcd for C36H53NO9Na [M+Na]+ 666.3618, found 666.3617.
4.2.2. General procedure for preparation of compounds 2t, 2u
and 3
A
mixture of caudatin (0.2 mmol), appropriate anhydride
(1.2 equiv) and DMAP (0.2 equiv) was heated in anhydrous pyri-
dine (5.0 mL) overnight under reflux until the starting material
was not observed by TLC check. The reaction mixture was diluted
with 20 mL of EtOAc and washed three times with 60 mL of 5%
HCl solution. The organic layer was dried over anhydrous Na2SO4
and concentrated under reduced pressure. The residue was chro-
matographed using a silica gel column to afford the pure target
products.
4.2.2.1. 3-O-Diglycolylcaudatin (2t).
As white amorphous
4.2.1.17. 3-O-(N,N-Dimethylglycinyl)caudatin (2q).
As white
power, yield 64.3% (after chromatography with petroleum ether/
acetone, 70:30); 1H NMR (CD3COCD3, 400 MHz): d 1.06 (6H, d,
J = 6.8 Hz, CH3-50, 60), 1.19 (3H, s, CH3-19), 1.42 (3H, s, CH3-18),
1.60 (1H, m, H-9), 1.80–1.98 (9H, overlap, H-1, 2, 11, 15, 16),
2.13 (3H, s, CH3-70), 2.16 (3H, s, CH3-21), 2.21 (2H, s, H-7), 2.44–
2.49 (3H, overlap, H-4, 40), 2.84 (1H, m, H-16), 4.31 (2H, s, H-300),
4.32 (2H, s, H-200), 4.45 (1H, dd, J = 4.1, 11.4 Hz, H-12), 4.76 (1H,
m, H-3), 5.43 (1H, s, H-6), 5.52 (1H, s, H-20); 13C NMR (CD3COCD,
100 MHz): d 10.3 (C-18), 16.3 (C-70), 18.3 (C-19), 21.1 (C-50), 21.2
(C-60), 24.9 (C-11), 27.2 (C-21), 27.7 (C-2), 30.4 (C-16), 32.7 (C-7),
33.8 (C-15), 34.9 (C-10), 37.5 (C-1), 38.5 (C-40), 38.8 (C-4), 44.3
(C-9), 58.0 (C-13), 68.5 (2C-200, 300), 72.3 (C-12), 74.5 (C-8), 75.2
(C-3), 89.5 (C-14), 92.5 (C-17), 114.2(C-20), 120.4 (C-6), 138.7 (C-
5), 165.6 (C-30), 165.8 (C-10), 171.9 (C-100), 170.4 (C-400), 208.8 (C-
20); EIMS: m/z 606, HREIMS: calcd for C32H46O11 606.3040, found
606.3019.
amorphous power, yield 64.8% (after chromatography with petro-
leum ether/acetone, 80:20); 1H NMR (CDCl3, 400 MHz): d 1.05 (6H,
d, J = 6.8 Hz, CH3-50, 60), 1.15 (3H, s, CH3-19), 1.40 (3H, s, CH3-18),
1.54 (1H, m, H-9), 1.80–1.98 (9H, overlap, H-1, 2, 11, 15, 16),
2.12 (3H, s, CH3-70), 2.16 (3H, s, CH3-21), 2.20 (2H, s, H-7), 2.33–
2.44 (9H, overlap, H-4, 40, 300), 2.86 (1H, m, H-16), 3.13 (1H, s, H-
200), 4.55 (1H, dd, J = 5.2, 10.5 Hz, H-12), 4.71 (1H, m, H-3), 5.36
(1H, s, H-6), 5.52 (1H, s, H-20); 13C NMR (CDCl3, 100 MHz): d 9.4
(C-18), 16.5 (C-70), 18.3 (C-19), 20.8 (C-50), 20.9 (C-60), 24.1 (C-
11), 26.9 (C-2), 27.1 (C-21), 31.8 (C-16), 33.2 (C-7), 34.2 (C-15),
36.9 (C-10), 37.8 (C-1), 38.1 (C-40), 38.4 (C-4), 43.5 (C-9), 45.3
(2C-300, 400), 57.8 (C-13), 60.6 (C-200), 71.5 (C-12), 73.9 (C-3), 74.1
(C-8), 88.0 (C-14), 91.4 (C-17), 112.9 (C-20), 118.9 (C-6), 139.1 (C-
5), 165.9 (C-30), 166.8 (C-10), 169.9 (C-100), 208.9 (C-20); EIMS: m/
z 575, HREIMS: calcd for C32H49NO8 575.3458, found 575.3455.
4.2.1.18. 3-O-(Cyanoacetyl)caudatin (2r).
As white amor-
4.2.2.2. 3-O-Glutarylcaudatin (2u).
As white amorphous
phouspower, yield74.9%(afterchromatographywithCHCl3/CH3OH,
100:1); 1H NMR (CDCl3, 500 MHz): d 1.03 (6H, d, J = 6.8 Hz, CH3-50,
60), 1.13 (3H, s, CH3-19), 1.38 (3H, s, CH3-18), 1.51 (1H, m, H-9),
1.78–1.96 (9H, overlap, H-1, 2, 11, 15, 16), 2.09 (3H, s, CH3-70), 2.13
(3H, s, CH3-21), 2.17 (2H, s, H-7), 2.33 (2H, m, 4), 2.41 (2H, m, 40),
2.84 (1H, m, H-16), 3.44 (2H, s, H-200), 4.51 (1H, dd, 4.4, 11.2 Hz, H-
12), 4.68 (1H, m, H-3), 5.39 (1H, s, H-6), 5.48 (1H, s, H-20); 13C NMR
(CDCl3, 125 MHz): d 9.5 (C-18), 16.5 (C-70), 18.2 (C-19), 20.8 (C-50),
20.9 (C-60), 24.1 (C-11), 25.0 (C-200), 26.6 (C-2), 27.1 (C-21), 31.8 (C-
16), 33.2 (C-7), 34.3 (C-15), 36.8 (C-10), 37.5 (C-1), 38.1 (C-40), 38.2
(C-4), 43.5 (C-9), 57.8 (C-13), 71.5 (C-12), 74.0 (C-8), 76.6 (C-3),
88.0 (C-14), 91.5 (C-17), 112.9 (C-20), 113.2 (C-300), 119.6 (C-6),
138.4 (C-5), 162.3 (C-100), 165.9 (C-30), 166.9 (C-10), 209.0 (C-20);
ESIMS: m/z 592 [M+Cl]ꢂ, HRESIMS: calcd for C31H43NO8Cl [M+Cl]ꢂ
592.2677, found 592.2667.
power, yield 77.1% (after chromatography with petroleum ether/
acetone, 70:30); 1H NMR (CD3COCD3, 400 MHz): d 1.05 (6H, d,
J = 6.4 Hz, CH3-50, 60), 1.18 (3H, s, CH3-19), 1.51 (3H, s, CH3-18),
1.63–2.08 (12H, overlap, H-1, 2, 9, 11, 15, 16, 300), 2.09 (3H, s,
CH3-70), 2.15 (3H, s, CH3-21), 2.21 (2H, s, H-7), 2.33–2.38 (7H, over-
lap, H-4, 40, 200, 400), 2.87 (1H, m, H-16), 4.45 (1H, dd, J = 4.3, 11.4 Hz,
H-12), 4.58 (1H, m, H-3), 5.35 (1H, s, H-6), 5.55 (1H, s, H-20); 13C
NMR (CD3COCD, 100 MHz): d 10.3 (C-18), 16.3 (C-70), 18.3 (C-19),
21.1 (C-50), 21.2 (C-60), 24.9 (C-11), 27.2 (C-2), 27.8 (C-21), 30.2
(C-16), 32.7 (C-7), 33.1 (C-300), 33.8 (C-15), 33.9 (C-200), 34.9 (C-
10), 37.6 (C-1), 38.5 (C-40), 38.7 (C-4), 39.0 (C-400), 44.3 (C-9), 58.0
(C-13), 72.3 (C-12), 74.3 (C-8), 74.5 (C-3), 89.4 (C-14), 92.5 (C-
17), 114.2(C-20), 120.1 (C-6), 139.0 (C-5), 165.6 (C-30), 165.7 (C-
10), 172.7 (C-100), 174.1 (C-500), 208.7 (C-20); EIMS: m/z 604, HRE-
IMS: calcd for C33H48O10 604.3247, found 604.3238.

L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
2885
4.2.2.3. 3-O-(2-Hydroxuacetyl)caudatin (3).
As white amor-
4.2.4. General procedure for preparation of compounds 4a–4f,
and 5
phous power, yield 2.6% (after chromatography with petroleum
ether/acetone, 70:30); 1H NMR (CDCl3, 600 MHz): d 1.05 (6H, d,
J = 6.8 Hz, CH3-50, 60), 1.16 (3H, s, CH3-19), 1.39 (3H, s, CH3-18),
1.50–1.99 (10H,overlap, H-1, 2, 9, 11, 15, 16), 2.10 (3H, s, CH3-70),
2.14 (3H, s, CH3-21), 2.20 (2H, s, H-7), 2.34–2.41 (3H, overlap, H-
4, 40), 2.83 (1H, m, H-16), 4.19 (2H, s, H-200), 4.55 (1H, dd, J = 5.4,
10.4 Hz, H-12), 4.72 (1H, m, H-3), 5.40 (1H, s, H-6), 5.50 (1H, s,
The derivatives (4a–4f, 5) were obtained by the reaction of
caudatin (0.2 mmol) with an excess of acids (5 equiv) and DCC
(5 equiv) in the presence of DMAP (0.8 equiv) was stirred in CH2Cl2
at room temperature, which had the similar treatment process to
preparation of compounds 2a–2r.
13
H-20); C NMR (CDCl3, 150 MHz): d 9.6 (C-18), 16.7 (C-70), 18.7
4.2.4.1. 3,17-O-Di(methoxyacetyl)caudatin (4a).
As white
(C-19), 21.1 (2C-50, 60), 24.3 (C-11), 27.1 (C-2), 27.5 (C-21), 31.9
(C-16), 33.5 (C-7), 34.5 (C-15), 37.1 (C-10), 38.0 (C-1), 38.4 (C-40),
38.6 (C-4), 43.7 (C-9), 58.2 (C-13), 68.5 (C-200), 71.8 (C-12), 74.3
(C-8), 74.8 (C-3), 88.0 (C-14), 91.6 (C-17), 113.1(C-20), 119.4 (C-
6), 139.2 (C-5), 166.3 (C-30), 167.5 (C-10), 169.4 (C-100), 209.2 (C-
20); ESIMS: m/z 571 [M+Na]+ HRESIMS: calcd for C30H44O9Na
[M+Na]+ 571.2878, found 571.2807.
amorphous power, yield 36.6% (after chromatography with petro-
leum ether/acetone, 85:15); 1H NMR (CDCl3, 500 MHz): d 1.05 (6H,
d, J = 6.8 Hz, CH3-50, 60), 1.16 (3H, s, CH3-19), 1.51 (3H, s, CH3-18),
1.60 (1H, m, H-9), 1.81–1.92 (9H, overlap, H-1, 2, 11, 15, 16),
2.03 (3H, s, CH3-70), 2.12 (3H, s, CH3-21), 2.17 (2H, s, H-7), 2.35–
2.42 (3H, overlap, H-40, 4), 3.06 (1H, m, H-16), 3.43 (3H, s, OCH3),
3.47 (3H, s, OCH3), 3.99 (2H, s, OCH2CO), 4.06 (2H, s, OCH2CO–),
4.55 (1H, dd, J = 4.0, 11.5 Hz, H-12), 4.74 (1H, m, H-3), 5.40 (1H,
s, H-6), 5.51 (1H, s, H-20); 13C NMR (CDCl3, 125 MHz): d 10.2 (C-
18), 16.6 (C-70), 18.2 (C-19), 20.8 (C-50), 20.9 (C-60), 23.8 (C-11),
26.9 (C-2), 29.3 (C-21), 30.3 (C-16), 33.8 (C-7), 34.6 (C-15), 36.8
(C-10), 37.8 (C-1), 38.1 (C-40), 38.3 (C-4), 43.4 (C-9), 58.2 (C-13),
59.3 (C-300), 59.6 (C-300), 70.0 (C-200), 70.4 (C-200), 71.0 (C-12), 74.2
(C-3), 74.3 (C-8), 87.8 (C-14), 98.6 (C-17), 112.7 (C-20), 119.4 (C-
6), 138.3 (C-5), 165.9 (C-30), 166.8 (C-10), 168.8 (C-100), 169.6 (C-
100), 202.1 (C-20); EIMS: m/z 634, HREIMS: calcd for C34H50O11
634.3353, found 634.3322.
4.2.3. General procedure for preparation of compounds 2v and
2w
The diphenylphosphoryl (dimethoxyphosphoryl) chloride
(1.5 equiv) was added the mixture of caudatin (0.2 mmol), pyridine
(2 mL) in CH2Cl2 (5 mL). The resulting mixture was stirred at room
temperature until the starting material was not observed by TLC.
CH2Cl2 (20 mL) was added, and the CH2Cl2 solution was washed
with 5% HCl (3 ꢁ 30 mL), saturated NaHCO3 (3 ꢁ 30 mL) and satu-
rated NaCl (3 ꢁ 30 mL), respectively. The organic layer was dried
over anhydrous Na2SO4 and concentrated to dryness under re-
duced pressure. The residue was chromatographed using a silica
gel column to yield the pure target compounds.
4.2.4.2. 3,17-O-Di(2-chlorocinnamoyl)caudatin (4b).
As
white amorphous power, yield 46.9% (after chromatography with
petroleum ether / acetone, 85:15), 1H NMR (CDCl3, 500 MHz): d
1.05 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.21 (3H, s, CH3-19), 1.34 (3H,
s, CH3-18), 1.86–2.61 (22H, overlap, H-1, 2, 4, 7, 9, 11, 15, 16, 40,
CH3-70, 21), 3.02 (1H, m, H-16), 4.65 (1H, dd, J = 4.8, 11.3 Hz, H-
12), 4.77 (1H, m, H-3), 5.37 (1H, s, H-6), 5.52 (1H, s, H-20), 6.38–
6.42 (2H, m, 200-H), 7.26–7.44 (6H, overlap, H- 700, 800, 900), 7.60
(2H, m, H-600), 8.07 (1H, d, J = 16.0 Hz, H-300), 8.16 (1H, d,
J = 16.0 Hz, H-300); 13C NMR (CDCl3, 125 MHz): d 10.2 (C-18), 16.5
(C-70), 18.5 (C-19), 20.8 (C-60), 20.9 (C-50), 24.5 (C-11), 27.0 (C-2),
27.3 (C-21), 27.9 (C-16), 33.3 (C-7), 36.6 (C-15), 37.0 (C-10), 37.8
(C-1), 38.1 (C-40), 38.6 (C-4), 45.9 (C-9), 57.5 (C-13), 70.8 (C-12),
73.8 (C-3), 89.9 (C-14), 90.5 (C-8), 91.4 (C-17), 112.8 (C-20), 117.2
(C-6), 120.2 (C-200), 121.1 (C-200), 127.0 (C-800), 127.1 (C-800), 127.6
(C-900), 127.8 (C-900), 130.1 (C-600), 130.2 (C-600), 130.3 (C-700), 130.9
(C-700), 131.4 (C-500), 131.6 (C-500), 134.9 (C-400), 135.3 (C-400), 138.8
(C-5), 140.4 (C-300), 142.6 (C-300), 165.6 (C-100), 165.7 (C-100), 166.5
(C-30), 169.3 (C-10), 209.3 (C-20); EIMS: m/z 818, HREIMS: calcd
for C46H52O9Cl2 818.2988, found 818.2971.
4.2.3.1. 3-O-(Diphenylphosphoryl)caudatin (2v).
White
amorphous power, yield 89.3% (after chromatography with petro-
leum ether/acetone, 70:30); 1H NMR (CDCl3, 400 MHz): d 1.05 (6H,
d, J = 6.8 Hz, CH3-50, 60), 1.14 (3H, s, CH3-19), 1.39 (3H, s, CH3-18),
1.50 (1H, m, H-9), 1.76–1.96 (9H, overlap, H-1, 2, 11, 15, 16),
2.11 (3H, s, CH3-70), 2.16 (3H, s, CH3-21), 2.18 (2H, s, H-7), 2.35
(1H, m, H-40), 2.49 (2H, m, H-4), 2.84 (1H, m, H-16), 3.74 (6H,
OCH3), 4.19 (1H, m, H-3), 4.54 (1H, dd, J = 4.8, 10.9 Hz, H-12),
5.41 (1H, s, H-6), 5.51 (1H, s, H-20); 13C NMR (CDCl3, 100 MHz): d
9.4 (C-18), 16.5 (C-70), 18.3 (C-19), 20.8 (C-60), 20.9 (C-50), 24.1
(C-11), 27.2 (C-21), 28.6 (C-2), 31.7 (C-16), 33.3 (C-7), 34.2 (C-
15), 36.7 (C-10), 38.1 (C-1), 38.2 (C-40), 39.6 (C-4), 43.5 (C-9),
54.2 (2C-OCH3), 57.8 (C-13), 71.5 (C-12), 74.0 (C-8), 78.1 (C-3),
88.0 (C-14), 91.4 (C-17), 112.9 (C-20), 119.4 (C-6), 138.7 (C-5),
166.0 (C-30), 166.9 (C-10), 208.9 (C-20); ESIMS: m/z 633 [M+Cl]ꢂ,
HRESIMS: calcd for
633.2596.
C
30H47O10PCl [M+Cl]ꢂ 633.2595, found
4.2.3.2. 3-O-(Dimethoxyphosphoryl)caudatin (2w).
White
4.2.4.3.
(4c).
3,17-O-Di[3,4-(methylenedioxy)cinnamoyl]caudatin
As white amorphous power, yield 40.3% (after chroma-
amorphous power, yield 88.7% (after chromatography with petro-
leum ether/acetone, 70:30); 1H NMR (CDCl3, 400 MHz): d 1.06 (6H,
d, J = 6.8 Hz, CH3-50, 60), 1.13 (3H, s, CH3-19), 1.38 (3H, s, CH3-18),
1.50 (1H, m, H-9), 1.78–1.96 (9H, overlap, H-1, 2, 11, 15, 16),
2.11 (3H, s, CH3-70), 2.15 (3H, s, CH3-21), 2.16 (2H, s, H-7), 2.34
(1H, m, H-40), 2.47 (2H, m, H-4), 2.82 (1H, m, H-16), 4.42 (1H, m,
H-3), 4.54 (1H, dd, J = 3.5, 8.8 Hz, H-12), 5.36 (1H, s, H-6), 5.51
(1H, s, H-20), 7.17–7.21 (6H, overlap, H-200, 400, 600), 7.33 (4H, m, H-
tography with petroleum ether/acetone, 85:15), 1H NMR (CDCl3,
400 MHz): d 1.06 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.18 (3H, s, CH3-
19), 1.25 (3H, s, CH3-18), 1.52–2.48 (21H, overlap, H-1, 2, 4, 7, 9,
11, 15, 16, 40, CH3-70, 21), 3.17 (1H, m, H-16), 4.60 (1H, m, H-12),
4.76 (1H, m, H-3), 5.44 (1H, s, H-6), 5.44 (1H, s, H-20), 6.00 (2H, s,
OCH2O), 6.03 (2H, s, OCH2O), 6.21–6.31 (2H, overlap, 200-H), 6.78–
6.84 (2H, m, 800-H), 6.99–7.05 (4H, overlap, H-500, 900), 7.56–7.65
(2H, m, 300-H); 13C NMR (CDCl3, 100 MHz): d 10.6 (C-18), 16.6 (C-
70), 18.3 (C-19), 20.8 (C-60), 20.9 (C-50), 24.0 (C-11), 27.1 (C-2),
29.2 (C-21), 29.7 (C-16), 33.9 (C-7), 34.6 (C-15), 36.9 (C-10), 38.0
(C-1), 38.1 (C-40), 38.5 (C-4), 43.4 (C-9), 58.1 (C-13), 70.9 (C-12),
73.7 (C-3), 74.3 (C-8), 88.2 (C-14), 97.9 (C-17), 101.5 (C-OCH2O),
101.7 (C-OCH2O), 106.4 (C-500), 106.5 (C-500), 108.5 (C-800), 108.6
(C-800), 112.8 (C-20), 114.8 (C-200), 116.4 (C-200), 119.0 (C-6), 124.4
(C-900), 125.1 (C-900), 128.8 (C-400), 128.9 (C-400), 138.9 (C-5), 144.3
(C-300), 146.5 (C-300), 148.3 (C-700), 148.5 (C-700), 149.5 (C-600), 150.2
13
300, 500); C NMR (CDCl3, 100 MHz): d 9.4 (C-18), 16.5 (C-70), 18.3
(C-19), 20.8 (C-60), 20.9 (C-50), 24.1 (C-11), 27.2 (C-21), 28.6 (C-
2), 31.7 (C-16), 33.3 (C-7), 34.3 (C-15), 36.7 (C-10), 38.1 (C-1),
38.2 (C-40), 39.5 (C-4), 43.5 (C-9), 57.9 (C-13), 71.5 (C-12), 74.0
(C-8), 80.0 (C-3), 87.9 (C-14), 91.4 (C-17), 112.9 (C-20), 119.6 (C-
6), 120.0 (4C-200, 600), 125.3 (2C-400), 129.7 (4C-300, 500), 138.5 (C-5),
150.5 (2C-100), 166.0 (C-30), 167.0 (C-10), 208.9 (C-20); ESIMS: m/z
757 [M+Cl]ꢂ, HRESIMS: calcd for C40H52O10PCl [M+Cl]ꢂ 757.2908,
found 757.2919.

2886
L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
(C-600), 165.7 (C-30), 166.5 (2C-100), 166.9 (C-10), 202.9 (C-20); EIMS:
m/z 838, HREIMS: calcd for C48H54O13 838.3564, found 838.3589.
acetone, 85:15); 1H NMR (CDCl3, 400 MHz):
d 1.07 (6H, d,
J = 6.8 Hz, CH3-50, 60), 1.20 (3H, s, CH3-19), 1.32 (3H, s, CH3-18),
1.85–2.47 (22H, overlap, H-1, 2, 4, 7, 9, 11, 15, 16, 40, CH3-70, 21),
3.00 (1H, m, H-16), 4.69 (1H, dd, J = 4.5, 10.7 Hz, H-12), 4.92 (1H,
m, H-3), 5.30 (1H, s, H-6), 5.60 (1H, s, H-20), 7.50–7.56 (2H, m, H-
500), 8.32–8.47 (2H, m, H-400), 8.83 (2H, m, H-600), 9.22 (2H, s, H-
4.2.4.4. 3,17-O-Di(3,5-difluorocinnamoyl)caudatin (4d).
As
white amorphous power, yield 39.8% (after chromatography with
petroleum ether/acetone, 85:15), 1H NMR (CDCl3, 400 MHz): d
1.05 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.21 (3H, s, CH3-19), 1.62 (3H,
s, CH3-18), 1.72–2.49 (21H, overlap, H-1, 2, 4, 7, 9, 11, 15, 16, 40,
CH3-70, 21), 3.20 (1H, m, H-16), 4.61 (1H, dd, J = 4.3, 11.2 Hz, H-
12), 4.76 (1H, m, H-3), 5.45 (1H, s, H-6), 5.55 (1H, s, H-20), 6.38–
6.49 (2H, overlap, H-200), 6.86 (2H, m, H-700), 7.02–7.07(4H, overlap,
H-500, 900), 7.54–7.64 (2H, overlap, H-300); 13C NMR (CDCl3,
100 MHz): d 10.5 (C-18), 16.6 (C-70), 18.3 (C-19), 20.8 (C-60), 20.9
(C-50), 24.0 (C-11), 26.9 (C-2), 30.1 (C-21), 32.2 (C-16), 33.8 (C-7),
34.6 (C-15), 37.0 (C-10), 37.9 (C-1), 38.1 (C-40), 38.4 (C-4), 43.4
(C-9), 58.3 (C-13), 70.8 (C-12), 74.2 (C-3), 74.4 (C-8), 87.9 (C-14),
98.1 (C-17), 105.3 (C-700), 105.9 (C-700), 110.5 (C-500), 110.6 (C-500),
110.7 (C-900), 110.8 (C-900), 112.8 (C-20), 119.0 (C-6), 120.1 (C-200),
121.2 (C-200), 137.0 (C-400), 137.6 (C-400), 138.9 (C-5), 142.0 (C-300),
143.9 (C-300), 161.9 (C-800), 162.0 (C-800), 164.3 (C-600), 164.4 (C-600),
165.0 (C-100), 165.5 (C-100), 166.5 (C-30), 167.1 (C-10), 202.3 (C-20);
ESIMS: m/z 857 [M+Cl]ꢂ, HRESIMS: calcd for C46H50O9F4Cl
[M+Cl]ꢂ 857.3079, found 857.3074.
13
200); C NMR (CDCl3, 100 MHz): d 10.5 (C-18), 16.6 (C-70), 18.7
(C-19), 20.8 (C-50), 20.9 (C-60), 24.7 (C-11), 26.9 (C-2), 27.3 (C-
21), 28.2 (C-16), 33.1 (C-7), 36.8 (C-15), 37.0 (C-10), 37.6 (C-1),
38.2 (C-40), 38.3 (C-4), 46.2 (C-9), 57.6 (C-13), 70.6 (C-12), 75.5
(C-3), 90.4 (C-14), 91.1 (C-17), 91.3 (C-8), 112.6 (C-20), 117.8 (C-
6), 124.0 (C-500), 124.7 (C-500), 126.3 (2C-300), 138.4 (C-400), 138.6
(C-400), 140.5 (C-5), 149.7 (2C-200), 152.5 (2C-600), 162.9 (C-100),
167.4 (C-100), 165.7 (C-30), 166.9 (C-10), 209.2 (C-20); EIMS: m/z
700, HREIMS: calcd for C40H48N2O9 700.3360, found 700.3333.
4.2.5. General procedure for preparation of compounds 4g and
4h
Compound 1 (0.2 mmol) with excess anhydride (5 equiv) and
DMAP (0.8 equiv) was refluxed in dry pyridine to obtain the
3,17-O-disubsituted derivatives 4g and 4h. The similar treatment
process preparation of compounds 2t, 2u and 3 was used.
4.2.5.1. 3,17-O -Di(succinyl)caudatin (4g).
As white amor-
4.2.4.5.
(4e).
3,17-O-Di(3-phthalimidopropianyl)caudatin
As white amorphous power, yield 42.1% (after chroma-
phous power, yield 41.2% (after chromatography with petroleum
ether/acetone, 70:30); 1H NMR (CD3COCD3, 400 MHz): d 1.05
(6H, d, J = 6.8 Hz, CH3-50, 60), 1.21 (3H, s, CH3-19), 1.57 (3H, s,
CH3-18), 1.74–2.18 (19H,overlap, H-1, 2, 7, 9, 11, 15, 16, CH3-70,
21), 2.32–2.43 (3H, overlap, H-4, 40), 2.55–2.58 (4H, m, H-200),
2.67 (4H, m, H-300), 2.96 (1H, m, H-16), 4.49 (1H, m, H-12), 4.57
(1H, m, H-3), 5.33 (1H, s, H-6), 5.58 (1H, s, H-20); 13C NMR
(CD3COCD3, 100 MHz): d 11.2 (C-18), 16.4 (C-70), 18.3 (C-19),
21.0 (C-50), 21.2 (C-60), 24.7 (C-11), 27.3 (C-21), 27.8 (C-2), 29.0
(2C-300), 29.1 (2C-200), 31.8 (C-16), 34.4 (C-7), 35.4 (2C-10, 15),
37.6 (C-1), 38.6 (C-40), 38.9 (C-4), 44.0 (C-9), 59.2 (C-13), 71.9 (C-
12), 74.5 (C-3), 75.0 (C-8), 88.5 (C-14), 98.2 (C-17), 114.2 (C-20),
120.3 (C-6), 138.7 (C-5), 165.4 (C-30), 166.0 (C-10), 172.2 (C-100),
172.6 (C-100), 173.6 (C-400), 174.0 (C-400), 204.1 (C-20); EIMS: m/z
690, HREIMS: calcd for C36H50O13 690.3251, found 690.3258.
tography with petroleum ether/acetone, 70:30), 1H NMR (CDCl3,
500 MHz): d 1.03 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.11 (3H, s, CH3-
19), 1.49 (3H, s, CH3-18), 1.77–1.86 (9H, overlap, H-1, 2, 11, 15,
16), 2.00 (3H, s, CH3-70), 2.11 (3H, s, CH3-21), 2.15 (2H, s, H-7),
2.31–2.33 (3H, overlap, H-40, 4), 2.68–2.71 (4H, m, H-200), 3.05
(1H, m, H-16), 3.95–4.07 (4H, m, H-300), 4.51 (1H, m, H-12), 4.60
(1H, m, H-3), 5.36 (1H, s, H-6), 5.50 (1H, s, H-20), 7.70 (4H, m, H-
600, 900), 7.82 (4H, m, H-700, 800); 13C NMR (CDCl3, 100 MHz): d 10.5
(C-18), 16.6 (C-70), 18.1 (C-19), 20.8 (C-60), 20.9 (C-50), 23.9 (C-
11), 26.8 (C-2), 29.2 (C-21), 29.5 (C-16), 33.2 (C-7), 33.7 (C-200),
33.8 (C-200), 33.9 (C-300), 34.2 (C-300), 34.7 (C-15), 36.8 (C-10), 36.9
(C-1), 38.1 (C-40), 38.4 (C-4), 43.3 (C-9), 58.6 (C-13), 70.9 (C-12),
74.2 (C-3), 74.4 (C-8), 87.7 (C-14), 98.2 (C-17), 112.8 (C-20), 119.1
(C-6), 123.3 (2C-600, 900), 123.5 (2C-600, 900), 131.7 (2C-500, 1000),
132.0 (2C-500, 1000), 134.0 (2C-700, 800), 134.3 (2C-700, 800), 168.0 (2C-
400, 1100), 168.1 (2C-400, 1100), 138.6 (C-5), 165.3 (C-30), 167.0 (C-10),
169.7 (C-100), 170.1 (C-100), 203.0 (C-20); EIMS: m/z 892, HREIMS:
calcd for C50H56N2O13 892.3782, found 892.3784.
4.2.5.2. 3,17-O-Di(glutaryl)caudatin (4h).
As white amor-
phous power, yield 37.1% (after chromatography with petroleum
ether/acetone, 70:30); 1H NMR (CD3COCD3, 400 MHz): d 1.06
(6H, d, J = 6.8 Hz, CH3-50, 60), 1.19 (3H, s, CH3-19), 1.57 (3H, s,
CH3-18), 1.63–1.88 (11H, overlap, H-1, 2, 9, 11, 15, 16), 2.01 (3H,
s, CH3-70), 2.06 (4H, m, H-300), 2.09 (3H, s, CH3-21), 2.18 (2H, s, H-
7), 2.33–2.52 (7H, overlap, H-4, 40, 200, 400), 2.98 (1H, m, H-16),
4.50 (1H, dd, J = 4.2, 11.4 Hz, H-12), 4.59 (1H, m, H-3), 5.34 (1H,
s, H-6), 5.59 (1H, s, H-20); 13C NMR (CD3COCD3, 100 MHz): d 11.2
(C-18), 16.4 (C-70), 18.3 (C-19), 20.7 (2C-300), 21.1 (C-50), 21.2 (C-
60), 24.7 (C-11), 27.3 (C-21), 27.8 (C-2), 31.0 (C-16), 33.1 (C-7),
33.2 (C-15), 33.9(C-200), 34.3 (C-200), 34.5 (C-10), 35.4 (C-400), 37.6
(C-1), 38.6 (C-40), 38.7 (C-4), 38.9 (C-400), 44.0 (C-9), 59.3 (C-13),
72.1 (C-12), 74.3 (C-8), 75.0 (C-3), 88.4 (C-14), 97.8 (C-17), 114.2
(C-20), 120.3 (C-6), 138.9 (C-5), 165.5 (C-30), 166.2 (C-10), 172.7
(C-100), 173.1 (C-100), 174.3 (2C-500), 204.0 (C-20); EIMS: m/z 718,
HREIMS: calcd for C38H54O13 718.3564, found 718.3587.
4.2.4.6. 3,17-O-Di(nicotinyl)caudatin (4f).
As white amor-
phous power, yield 34.9% (after chromatography with petroleum
ether/acetone, 85:15); 1H NMR (CDCl3, 400 MHz): d 1.04 (6H, d,
J = 6.8 Hz, CH3-50, 60), 1.23 (3H, s, CH3-19), 1.68 (3H, s, CH3-18),
1.86–2.61 (22H, overlap, H-1, 2, 4, 7, 9, 11, 15, 16, 40, CH3-70, 21),
3.20 (1H, m, H-16), 4.63 (1H, dd, J = 4.5, 11.3 Hz, H-12), 4.90 (1H,
m, H-3), 5.41 (1H, s, H-6), 5.54 (1H, s, H-20), 7.37–7.43 (2H, m, H-
500), 8.28–8.34 (2H, m, H-400), 8.73–8.79 (2H, m, H-600), 9.18 (1H, s,
H-200), 9.30 (1H, s, H-200); 13C NMR (CDCl3, 100 MHz): d 10.7 (C-
18), 16.6 (C-70), 18.4 (C-19), 20.8 (C-50), 20.9 (C-60), 24.0 (C-11),
26.9 (C-2), 29.2 (C-21), 30.6 (C-16), 33.6 (C-7), 34.5 (C-15), 37.0
(C-10), 37.8 (C-1), 38.1 (C-40), 38.4 (C-4), 43.5 (C-9), 58.9 (C-13),
70.9 (C-12), 74.6 (C-3), 74.9 (C-8), 87.5 (C-14), 98.1 (C-17), 112.8
(C-20), 119.2 (C-6), 123.3 (C-500), 123.5 (C-500), 126.3 (C-300), 126.4
(C-300), 137.2 (C-400), 137.3 (C-400), 139.0 (C-5), 150.7 (C-200), 150.9
(C-200), 153.1 (C-600), 153.7 (C-600), 164.5 (2C-100), 165.3 (C-30),
167.2 (C-10), 203.4 (C-20); EIMS: m/z 700, HREIMS: calcd for
4.2.6. 8,14-Dihydroxylisopropylidenylcaudatin (6)
To a solution of caudatin (0.4 mmol) in acetone (8 mL) was
added BF3ꢀOEt2 (50
lL) at 0 °C. The resulting mixture was stirred
at room temperature until the material was not determined, and
then poured into aqueous saturated NaHCO3. The solution was ex-
tracted with ethyl acetate (3 ꢁ 20 mL). The organic layer was
washed with brine, dried over anhydrous Na2SO4, and concen-
trated under reduced pressure. The residue was purified by silica
C40H48N2O9 700.3360, found 700.3334.
4.2.4.7.3,8-O-Di(nicotinyl)caudatin (5).
power, yield 11.7% (after chromatography with petroleum ether/
As white amorphous

L.-J. Wang et al. / Bioorg. Med. Chem. 20 (2012) 2877–2888
2887
gel column chromatography (petroleum ether/acetone, 15:1) to af-
ford compound 6. Yield 59.6%; 1H NMR (CD3COCD3, 400 MHz): d
1.06 (6H, d, J = 6.4 Hz, CH3-50, 60), 1.13 (3H, s, CH3-19), 1.26 (6H,
s, CH3-200), 1.41 (3H, s, CH3-18), 1.51–2.01 (10H, overlap, H-1, 2,
9, 11, 15, 16), 2.13 (3H, s, CH3-70), 2.17 (3H, s, CH3-21), 2.20 (2H,
s, H-7), 2.28–2.38 (3H, overlap, H-4, 40), 2.85 (1H, m, H-16), 3.49
(1H, m, H-12), 4.56 (1H, m, H-3), 5.37 (1H, s, H-6), 5.52 (1H, s, H-
the 3% HCl was added dropwise, and the mixture was extracted
with EtOAc (2 ꢁ 30 mL). The EtOAc solution was washed with sat-
urated NaHCO3 (3 ꢁ 30 mL) and saturated NaCl (3 ꢁ 30 mL),
respectively. The organic layer was dried over anhydrous Na2SO4
and concentrated under reduced pressure to give a residue which
was purified by silica gel column chromatography (CHCl3/CH3OH,
97:3) to afford compound 9. Yield 72.0%; 1H NMR (CDCl3,
400 MHz): d 1.09 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.11 (3H, s, CH3-
19), 1.18 (3H, s, CH3-21),1.49 (3H, s, CH3-18), 1.54 (1H, m, H-9),
1.76–1.96 (10H, overlap, H-1, 2, 11, 15, 16), 2.17 (3H, s, CH3-70),
2.33–2.42 (5H, overlap, H-4, 7, 40), 3.50–3.62 (2H, overlap, H-3,
20), 4.65 (1H, dd, J = 3.8, 11.3 Hz, H-12), 5.37 (1H, s, H-6), 5.69
(1H, s, H-20); 13C NMR (CDCl3, 100 MHz): d 11.4 (C-18), 16.4 (C-
70), 17.0 (C-21), 18.1 (C-19), 20.7 (C-60), 20.8 (C-50), 24.6 (C-11),
30.8 (C-2), 31.6 (C-16), 33.4 (C-7), 34.5 (C-15), 36.7 (C-10), 38.3
(C-1), 38.7 (C-40), 42.0 (C-4), 43.4 (C-9), 55.8 (C-13), 71.5 (C-20),
71.8 (C-3), 73.4 (C-12), 73.7 (C-8), 87.9 (2C-14, 17), 112.6 (C-20),
118.4 (C-6), 139.3 (C-5), 166.0 (C-10), 168.6 (C-30); EIMS: m/z 492,
HREIMS: calcd for C28H44O7 492.3087, found 492.3086.
13
20); C NMR (CD3COCD3, 100 MHz): d 9.4 (C-18), 16.5 (C-70), 18.6
(C-19), 20.8 (C-50), 20.9 (C-60), 24.2 (C-11), 27.1 (2C-CH3), 27.6
(C-21), 30.7 (C-2), 31.8 (C-16), 33.1 (C-7), 34.2 (C-15), 36.9 (C-
10), 38.1 (C-40), 38.7 (C-1), 41.9 (C-4), 43.6 (C-9), 57.9 (C-13),
71.5 (C-12), 71.8 (C-3), 74.3 (C-8), 88.0 (C-14), 91.5 (C-17), 112.9
(C-20), 117.7 (C-6), 124.1 (C-100), 140.6 (C-5), 165.9 (C-30), 166.8
(C-10), 208.9 (C-20); EIMS: m/z 530, HREIMS: calcd for C31H46O7
530.3244, found 530.3244.
4.2.7. Caudatin-3,7-dione (7)
A CH2Cl2 solution of caudatin (0.2 mmol) and pyridininm chlo-
rochromate (1.2 mmol) was stirred for 3 h at room temperature.
When TLC showed no start material, the mixture was poured into
H2O and extracted with chloroform. The organic layer was succes-
sively washed with H2O, saturated aqueous NaHCO3, once again
with H2O, and then dried over Na2SO4. The solution was evapo-
rated under reduced pressure, loaded onto a silica gel column,
and eluted with petroleum ether/acetone (70:30) to afford com-
pound 7 as a white amorphous powder. Yield 47.1%; 1H NMR
(CDCl3, 400 MHz): d 1.06 (6H, d, J = 6.4 Hz, CH3-50, 60), 1.30 (3H, s,
CH3-19), 1.36 (3H, s, CH3-18), 1.97–2.03 (7H,overlap, H-1, 9, 11,
15), 2.11 (3H, s, CH3-70), 2.13 (3H, s, CH3-21), 2.21–2.76 (7H, over-
lap, H-2, 12, 16, 40), 3.04–3.24 (2H, s, H-4), 4.66 (1H, m, H-12), 5.55
(1H, s, H-20), 6.12 (1H, s, H-6); 13C NMR (CDCl3, 100 MHz): d 9.3 (C-
18), 16.5 (C-70), 20.2 (C-19), 20.8 (2C-50, 60), 23.3 (C-11), 27.2 (C-
21), 30.9 (C-16), 33.6 (C-15), 34.1 (C-1), 37.4 (C-2), 38.3 (C-40),
40.1 (C-10), 44.6 (C-9), 49.3 (C-4), 58.4 (C-13), 71.8 (C-12), 77.3
(C-8), 86.1 (C-14), 90.8 (C-17), 112.6 (C-20), 125.5 (C-6), 166.2 (C-
30), 161.4 (C-10), 168.5 (C-5), 199.3 (C-7), 200.8 (C-3), 208.7 (C-
20); ESIMS: m/z 537 [M+Cl]ꢂ, HRESIMS: calcd for C28H38O8Cl
[M+Cl]ꢂ 537.2255, found 537.2266.
4.3. In vitro anti-HBV assay
Inhibitory activity against HBV was determined according to
our previous description.6 The anti-HBV activities and cytotoxicity
of compounds were evaluated on the Hep G 2.2.15 cell line. The
anti-HBV antigen secretion activities were assayed by enzyme-
linked immunosorbent assay (ELISA; Autobio Diagnostics Co., Ltd,
China). A real-time PCR assay was used to detect the inhibiting
HBV DNA replication of the derivatives. Cytotoxicity was assayed
with a modified 3-(4,5-dimethylthiazole-2-yl)-2, 5-diphenyltet-
razolium bromide (MTT) method (Gibco Invitrogen, Carlsbad, CA,
USA).
Acknowledgment
The work was supported by the National Natural Science Foun-
dation of China for Distinguished Young Scholars (No. 81025023).
References and notes
4.2.8. 5a,6a-Epoxycaudatin (8)
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To a solution of caudatin (0.4 mmol) in CH2Cl2 was added m-
CPBA (1.2 equiv) at 0 °C. The resulting mixture was stirred at room
temperature until the starting material was not observed by TLC.
Then the saturated NaHCO3 and Na2S2O3 were added dropwise,
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NMR (CDCl3, 400 MHz): d 1.07 (6H, d, J = 6.8 Hz, CH3-50, 60), 1.12
(3H, s, CH3-19), 1.43 (3H, s, CH3-18), 1.47 (1H, m, H-9), 1.74–1.89
(14H, overlap, H-1, 2, 4, 7, 11, 15, 16), 1.89 (3H, s, CH3-70), 2.15
(3H, s, CH3-21), 2.40 (1H, m, H-40), 2.94 (1H, d, J = 4.0 Hz, H-6),
3.42 (1H, m, H-3), 4.44 (1H, m, H-12), 5.51 (1H, s, H-20); 13C NMR
(CDCl3, 100 MHz): d 9.8 (C-18), 16.6 (C-70), 17.4 (C-19), 20.8 (C-
60), 21.0 (C-50), 24.8 (C-11), 27.1 (C-21), 30.2 (C-2), 30.6 (C-16),
31.6 (C-15), 32.6 (C-7), 35.7 (C-10), 38.1 (C-40), 38.2 (C-1), 41.1
(C-4), 44.4 (C-9), 57.4 (C-13), 64.4 (C-5), 65.1 (C-6), 69.1 (C-12),
70.9 (C-3), 75.3 (C-8), 87.9 (C-14), 91.7 (C-17), 112.8 (C-20), 165.8
(C-10), 166.5 (C-30), 209.1 (C-20); EIMS: m/z 506, HREIMS: calcd
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