Synthesis of three OSW-1 analogs with maltose side chains bearing different protection groups

Article abstract of DOI:10.1080/10286020.2013.863185

In order to simplify the synthesis of OSW-1's disaccharide side chain and explore the structure-activity relationship of OSW-1, three 16α-O-maltose OSW-1 analogs carrying three maltose side chains bearing different protections were designed and synthesized.

Full text of DOI:10.1080/10286020.2013.863185

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Synthesis of three OSW-1 analogs with
maltose side chains bearing different
protection groups
Yu-Yao Guanb, Chao Songb & Ping-Sheng Leia
a State Key Laboratory of Bioactive Substance and Function of
Natural Medicines, Institute of Materia Medica, Peking Union
Medical College & Chinese Academy of Medical Sciences, Peking,
100050, China
b Pharmacy Department, Traffic Hospital of Shandong Province,
Jinan, 250031, China
Published online: 06 Dec 2013.
To cite this article: Yu-Yao Guan, Chao Song & Ping-Sheng Lei (2014) Synthesis of three OSW-1
analogs with maltose side chains bearing different protection groups, Journal of Asian Natural
Products Research, 16:1, 43-52, DOI: 10.1080/10286020.2013.863185
To link to this article: http://dx.doi.org/10.1080/10286020.2013.863185
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Journal of Asian Natural Products Research, 2014
Vol. 16, No. 1, 43–52, http://dx.doi.org/10.1080/10286020.2013.863185
Synthesis of three OSW-1 analogs with maltose side chains bearing
different protection groups
Yu-Yao Guanb, Chao Songb and Ping-Sheng Leia*
aState Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of
Materia Medica, Peking Union Medical College & Chinese Academy of Medical Sciences,
Peking 100050, China; Pharmacy Department, Traffic Hospital of Shandong Province,
b
Jinan 250031, China
(Received 3 September 2013; final version received 4 November 2013)
In order to simplify the synthesis of OSW-1’s disaccharide side chain and explore the
structure–activity relationship of OSW-1, three 16a-O-maltose OSW-1 analogs
carrying three maltose side chains bearing different protections were designed and
synthesized.
Keywords: OSW-1; antitumor; synthesis; maltose
1. Introduction
mechanism of OSW-1. Fuchs and co-
workers [16] speculated that structurally
the 22-oxocarbenium ions might be the
active intermediate for the anticancer
activity. Yohda and co-workers [17]
indicated that the three-dimensional (3D)
structure of OSW-1 was related to its good
activity. The hydrophobic cluster con-
structed by the C20-C27 side chain and the
C20-acetyl, C200-p-MBz groups in disac-
charide was a biologically required func-
tionality as well as of the overall
conformation.
OSW-1 with considerable antitumor and
antiproliferative activities has a potential
for clinical use as a new antitumor drug
[1]. It was isolated from Ornithogalum
saundersiae bulbs in 1992 by Sashida and
co-workers [2] and found to possess a
cholestane aglycone and a disaccharide
moiety. In vitro assay showed that it was
considerably toxic to a broad spectrum of
malignant cancer cells with a mean IC50 of
0.7 nM [3]. Because of its excellent
antitumor activities and low toxicities to
normal cells, the synthesis of OSW-1 has
been studied by many groups [4–6]. In
addition, a series of analogs have been
synthesized and tested for antitumor
activities in recent years [7–15,24].
According to the previous structure–
activity relationship (SAR) work, it is
interesting to note the removal of the
acetyl (Ac) and the 4-methoxy benzoyl
(MBz) groups on the disaccharide moiety
which diminished the cytotoxicity signifi-
cantly (about 1000 times less potent).
The NIH (National Institutes of
Health) pointed out that the antiapoptosis
protein Bcl-2 was the target of the study
[18]. Zhou et al. [19] showed that OSW-1
can damage the membrane and cristae of
cancer cell’s mitochondria, which plays an
important role in mediating the anticancer
activities. Yu and co-workers [20] pointed
that the target was caspase-8 which caused
the cleavage of Bcl-2. Shair and co-
workers [21] made breakthrough progress
in finding the exact target. Shair revealed
that the target of OSW-1 was oxysterol-
binding protein (OSBP) and its closest
Many research groups worldwide have
made much effort to study the action
*Corresponding author. Email: lei@imm.ac.cn
q 2013 Taylor & Francis

44
Y.-Y. Guan et al.
paralog, OSBP-related protein 4L
(ORP4L). OSBP and ORP4L were much
more expressed in tumor cells than in
normal cells. The antiproliferative activity
of OSW-1 was mediated by OSBP. The
cytotoxicity was mediated by ORP4L
which caused apoptosis. Nevertheless, the
previous study about the target was
meaningful too. They were the subsequent
processes of the apoptosis resulted from
binding to ORP4L.
Figure 1. The conformation of the target
compound was similar to the 3D structure
of OSW-1 which has the hydrophobic
cluster constructed by the C20-C-27 side
chain and the C20-acetyl, C200-p-MBz
groups in disaccharide. OSW-1’s confor-
mation was believed to be important to the
anticancer activity of OSW-1 [24].
2. Results and discussion
In order to simplify the synthesis of
OSW-1’s disaccharide side chain and
explore the SAR of OSW-1, we designed
and synthesized 16a-O-maltose OSW-1
analogs carrying three maltose side chains
bearing different protections including
[40,60-O-benzylidene-6-O-benzyl-a-D-mal-
tose], [40,60-O-benzylidene-6-O-benzoyl-a-
D-maltose], and [2,3,20,30-tetra-O-acetyl-a-
D-maltose]. The synthesis of the original
b-D-Xylp-(1-3)-a-L-Arap disaccharide was
complicated in 14 steps [4]. The synthesis of
the chosen protected maltose chain was
simple with eight steps [22]. The protected
maltose glycoside showed a potent anti-
proliferative activity against smooth muscle
cells with an IC50 of 0.023–0.001 mM [22].
According to Shair’s work, OSBP was the
target which mediated the antiproliferative
activity of OSW-1 and recognized steroids.
Therefore, the coupling of aglycone of
OSW-1 to the maltose was hoped to be
recognized by OSBP and shows antiproli-
ferative activity against the tumor cell. The
protected maltose has similar polarity
distribution to the disaccharide of OSW-1.
One side of the disaccharide was distributed
by lipophilic groups, and the other side was
distributed by the hydrophilic hydroxyl
groups. The lipophilic groups in maltose
might form the biologically required hydro-
phobic cluster.
Three 16a-O-maltose-OSW-1 analogs 11,
22, and 23 were synthesized in a facile
way. The key intermediate 4 was syn-
thesized from the starting material (D)-
maltose through four-step reactions with
an overall yield of 64.4% (Scheme 1).
After 4 in hand, we prepared three
different protected maltose donors 8, 15,
and 19 through relative protection strategy
(Schemes 1–3). Aglycone 9 (Scheme 4)
was prepared according to the procedures
developed by our research group [23].
Coupling aglycone 9 and thioglycoside 8
in the presence of NIS/AgOTf (N-iodo-
succinimide/silver triflate) provided the
desired glycoside 10 (Scheme 4). The
resulting saponin bearing acetyl protec-
tions was removed by 1 M MeONa/
MeOH, providing the expected target
1
compound 11 (Scheme 4). The H NMR
spectrum of 11 showed the signal for the
10-b-anomeric proton at d 5.17 (d, 1H,
J ¼ 3.6 Hz, H-10). The 13C NMR spectrum
of 11 showed the signal for the anomeric
carbon at d 98.21. The glycosylation of
aglycone 9 with the maltose trichloroace-
timidates (15 and 19) in the presence of
trimethylsilyl trifluoromethanesulfonate
(TMSOTf) (0.10 equiv.) provided the
desired glycosides (20 and 21) (Scheme
5). The resulting saponin 20 bearing TES
(triethylsilyl) protections was deprotected
using HF·pyridine in pyridine, providing
the desired product 22 (Scheme 5). The
resulting saponin 21 bearing silyl and
benzylidene protection groups was depro-
tected using HF·pyridine in pyridine and
followed by NaHSO4·SiO2 in CH2Cl2/
Structural superimposition analysis
was implemented in our study with
Accelrys Discovery Studio program pack-
age. The minimum energy conformation
of one of the target compounds was
calculated and aligned as shown in

Journal of Asian Natural Products Research
45
Figure 1. The minimum energy conformation of the target compound 11.
MeOH, providing the desired product 23
(Scheme 5). The 1H NMR spectrum of 22
showed the signal for the 10-b-anomeric
proton at d 5.12 (d, 1H, J ¼ 3.6 Hz, H-10).
The 13C NMR spectrum of 22 showed the
signal for the anomeric carbon at d 94.26.
The IC50 values of dioscin against these
seven cell lines used in our assays are
consistent with those determined by others
[24].
The bioassay results showed that the
16a-O-maltose OSW-1 analogs showed
no cytotoxicity against the seven tested
tumor cells. The consequences proved that
the introduction of protected maltose did
not improve the cytotoxicities of the whole
molecule. However, the antitumor activity
of OSW-1 was not only cytotoxic but also
antiproliferative, mediated by target
ORP4L and OSBP, respectively. There-
fore, we planned to test the antiprolifera-
tive activity of compounds 11, 22, and 23
and the interaction between OSBP and
1
The H NMR spectrum of 23 showed the
signal for the 10-b-anomeric proton at d
5.32 (d, 1H, J ¼ 3.3 Hz, H-10). The 13C
NMR spectrum of 23 showed the signal for
the anomeric carbon at d 94.5.
The in vitro antitumor activities of
compounds 11, 22, and 23 against A2780,
BEL-7402, HCT-8, KB, BGC-823, HeLa,
and A549 were evaluated by the standard
MTT assay using dioscin as a positive
control. The results are listed in Table 1.
AcO
AcO
HO
HO
O
O
O
AcO
AcO
AcO
AcO
HO
HO
O
OAc
O
HO
HO
c
OAc
O
OH
O
OH
O
a
b
AcO
AcO
HO
O
HO
STol
O
O
OAc
STol
O
AcO
HO
AcO
OH
HO
OAc
OAc
OH
1
2
OH
3
Ph
O
O
Ph
Ph
O
O
O
OH
O
O
O
O
d
HO
e
OTs
O
OTs
O
f
HO
AcO
HO
O
STol
STol
HO
AcO
HO
O
O
STol
STol
HO
AcO
OH
4
5
6
OH
OAc
Ph
O
Ph
O
O
O
O
j
O
OH
O
h
OBn
AcO
AcO
AcO
AcO
O
O
O
STol
AcO
AcO
OAc
OAc
7
8
Scheme 1. Reagents and conditions: (a) Ac2O, AcONa, 1008C, 92%; (b) p-thiocresol, BF3·Et2O,
CH2Cl2, r.t., 73%; (c) 1 M MeONa/MeOH, CH2Cl2/MeOH, r.t., 99%; (d) PhCH (OMe)2,
NaHSO4·SiO2, DMF/CH3CN, r.t., 97%; (e) p-TsCl, pyridine/CH2Cl2, r.t., 64%; (f) Ac2O, Et3N,
DMAP, CH2Cl2, r.t., 94%; (j) HCOONa, AcOEt/MeOH, 708C, 75%; (h) BnBr, NaH, DMF, 08C,
50%.

46
Y.-Y. Guan et al.
Ph
O
Ph
O
Ph
O
O
O
O
O
O
O
OBz
O
c
OBz
O
a
d
OBz
O
b
HO
TESO
TESO
4
TESO
HO
TESO
O
O
O
STol
STol
OH
HO
TESO
TESO
OH
OTES
OTES
14
12
13
Ph
O
O
O
OBz
TESO
TESO
O
O
OCNHCCl3
TESO
OTES
15
Scheme 2. Reagents and conditions: (a) BzCl, CH2Cl2/pyridine, r.t., 60%; (b) TESOTf
(triethylsilyl trifluoromethanesulfonate), 2,6-lutidine, CH2Cl2, 08C, r.t., 80%; (c) NBS (N-
bromosuccinimide), TMSOTf, CH2Cl2/H2O, r.t., 80%; (d) CCl3CN, DBU (1,8-diazabicyclo[5.4.0]
undec-7-ene), CH2Cl2, r.t., 90%.
O
Ph
O
Ph
O
Ph
O
O
O
O
O
a
O
OTBDPS
OTBDPS
O
OTBDPS
O
c
b
AcO
AcO
HO
4
HO
16
AcO
AcO
O
O
O
O
STol
STol
OH
AcO
HO
AcO
OAc
OAc
OH
17
18
O
Ph
O
d
O
OTBDPS
O
AcO
AcO
O
AcO
OCNHCCl3
OAc
19
Scheme 3. Reagents and conditions: (a) TBDPSiCl, DMAP, pyridine (99%), r.t., 78%; (b) Ac2O,
Et3N, DMAP, CH2Cl2, r.t., 99%; (c) NIS, AgOTf, H2O, CH2Cl2, 2158C, r.t.; (d) CCl3CN, DBU,
CH2Cl2, r.t., 70% for two steps.
OTBS
a
8+
OH
O
OBn
O
OTBS
OH
O
AcO
10
OAc
AcO
O
O
TBSO
TBSO
O
Ph
9
OAc
b
O
OBn
O
O
HO
OH
HO
O
HO
O
Ph
O
11
OH
Scheme 4. Reagents and conditions: (a) NIS, AgOTf, CH2Cl2, 2508C, 45%; (b) (i) HF·pyridine,
pyridine (99%), r.t.; (ii) 1 M MeONa/MeOH, CH2Cl2/MeOH, reflux, 76% for two steps.

Journal of Asian Natural Products Research
47
OBz
OTBS
20 R=
21 R=
O
TESO
O
a
15
19
O
OR
TESO
O
+ 9
Ph
SETO
O
OTES
TBSO
OTBDPS
O
AcO
O
OAc
O
O
Ph
Ph
AcO
O
OAc
OH
OH
OBz
22 R=
23 R=
O
b
HO
O
20
21
OR
OH
O
O
b, c
HO
O
HO
OH
O
AcO
O
OAc
OH
OH
O
AcO
OAc
Scheme 5. Reagents and conditions: (a) TMSOTf, CH2Cl2, 2308C, 55% for 20, 56% for 82; (b)
HF·pyridine, pyridine (99%), r.t.; (c) NaHSO4·SiO2, CH2Cl2/MeOH, r.t.
target compounds. These bioactive results
and further synthesis of analogs with the
maltose bearing various protection groups
will be reported in future.
Palo Alto, CA, USA) in CDCl3, dimethyl-
sulfoxide-d6 (DMSO-d6), or pyridine-d5 as
solution. The chemical shifts are reported in
parts per million (ppm) with tetramethylsi-
lane (TMS) as an internal standard. HR-MS
experiments were carried out using an
Agilent 1100 series LC/MSD TOF (Agi-
lent, Santa Clara, CA, USA). Analytical
thin layer chromatography (TLC) was
carried out on TLC plates coated with
silica gel HSGF254 (Marine Chemical
Group Co., Qingdao, China). Chromatog-
raphy was performed with silica gel H (HG/
T2354-92) (Marine Chemical Group Co.,
Qingdao, China). Dried solvents used as
reaction media were purified in the usual
way. The major chemicals were purchased
from Alfa Chemical Corporation (Massa-
chusetts, USA). All other chemicals were of
analytical grade.
3. Experimental
3.1 General experimental procedures
All NMR spectra were recorded on
Mercury-300 spectrometers (Varian Co.,
Table 1. The in vitro cytotoxicities (IC50,
mM) of synthetic 16a-O-maltose OSW-1
analogs and dioscin.a
Cell lines
A2780
BEL-7402 .10 .10 .10
11
22
23
Dioscin
.10 .10 .10
0.87
0.81
0.34
0.53
1.08
0.50
0.81
HCT-8
KB
.10 .10 .10
.10 .10 .10
.10 .10 .10
.10 .10 .10
.10 .10 .10
BGC-823
HeLa
A549
3.2 General procedures for the
synthetic compounds
a The in vitro cytotoxic activities against A2780
(ovarian cancer), BEL-7402 (liver cancer), HCT-8
(colon cancer), KB (nasopharyngeal carcinoma),
BGC-823 (stomach cancer), HeLa (cervical cancer),
and A549 (lung cancer) cell lines were evaluated by
the standard MTT assay using dioscin as a positive
control.
3.2.1 Synthesis of compound 4
Catalyst NaHSO4·SiO2:NaHSO4·H2O
(4.14 g), H2O (20 ml), and silica gel
(200–300 mesh, 10 g) were mixed
together and evaporated under reduced

48
Y.-Y. Guan et al.
pressure. The mixture was activated at
1058C in drying oven for 10 h.
7.40–7.30 (m, 5H), 7.18 (d, J ¼ 8.1 Hz,
2H), 7.11 (d, J ¼ 7.8 Hz, 2H), 5.49 (s, 1H),
5.37 (d, J ¼ 9.9 Hz, 1H), 5.32 (d,
J ¼ 3.9 Hz, 1H), 5.21 (t, J ¼ 8.7 Hz, 1H),
4.85 (dd, J ¼ 3.9 and 10.2 Hz, 1H), 4.68–
4.52 (m, 2H), 4.43 (d, J ¼ 5.4 Hz, 1H),
4.36 (d, J ¼ 11.4 Hz, 1H), 4.25 (dd,
J ¼ 3.6, 11.1 Hz, 1H), 3.93 (t,
J ¼ 9.3 Hz, 1H), 3.76–3.66 (m, 2H),
3.65–3.54 (m, 2H), 2.35 (s, H), 2.30
(s, 3H), 2.03 (s, 6H), 2.01 (s, 3H), and 1.96
(s, 3H); 13C NMR (DMSO-d6, 75 MHz):
d 145.0, 137.7, 136.7, 132.2, 131.5 (2C),
130.2 (2C), 129.6, 129.4 (2C), 128.9,
128.0 (2C), 127.5 (2C), 126.4 (2C), 101.6,
100.8, 86.5, 80.7, 79.6, 77.2, 74.9, 72.7,
71.5, 69.9, 69.5, 67.7, 63.4, 21.1, and 20.6;
LC-HR-ESI-MS: m/z 691.1903 [M þ H]þ
(calcd for C33H39O12S2 691.1877).
Compound 3 (290 mg, 0.647 mmol)
was dissolved in CH3CN (15 ml) and
dimethylformamide (DMF) (15 ml), fol-
lowed by the addition of NaHSO4·SiO2
(580 mg) and PhCH (OMe)2 (0.49 ml,
3.235 mmol) at room temperature. The
reaction mixture was stirred for 2 h and
quenched with Et3N. The solid was
filtered, and the solvent was removed.
The residue was purified by silica gel
column chromatography (CH2Cl2/MeOH
20:1, v/v) to afford the desired compound
4 (349 mg, 97%). 1H NMR (CDCl3,
300 MHz): d 7.50–7.42 (m, 2H), 7.39
(d, J ¼ 7.8 Hz, 2H), 7.35–7.25 (m, 3H),
7.06 (d, J ¼ 7.8 Hz, 2H), 5.43 (s, 1H), 5.08
(brs, 1H), 4.50 (d, J ¼ 4.0 Hz, 1H), 4.24–
4.14 (m, 1H), 4.01–3.90 (m, 1H), 3.88–
3.73 (m, 2H), 3.72–3.48 (m, 4H),
3.46–3.32 (m, 2H), 3.30–3.18 (m, 1H),
and 2.28 (s, 3H); 13C NMR (CDCl3,
75 MHz): d 138.1, 137.1, 132.6 (2C),
129.8 (2C), 19.2, 128.8, 128.3 (2C), 126.4
(2C), 102.0, 101.7, 87.9, 80.5, 79.7, 78.4,
73.2, 71.9, 70.8, 68.6, 63.7, 61.4, and 21.1.
LC-HR-ESI-MS: m/z 537.1782 [M þ H]þ
(calcd for C26H33O10S, 537.1789).
3.2.3 Synthesis of compound 7
To a solution of compound 6 (1.5 g,
1.74 mmol) in EtOAc/MeOH (1:1, 60 ml)
was added HCOONa (0.356 g, 5.24 mmol).
The reaction mixture was stirred at 708C
for 24 h. It was then diluted with ethyl
acetate (100 ml), washed with aqueous
saturated NaHCO3 (15 ml £ 3), brine
(15 ml £ 3), dried over anhydrous
Na2SO4, filtered, and concentrated in
vacuo. The residue was purified by silica
gel column chromatography (petroleum
ether/EtOAc 5:1, v/v) to give compound
7 (917 mg, 75%). 1H NMR (CDCl3,
300 MHz): d 7.48–7.39 (m, 2H), 7.38–
7.30 (m, 5H), 7.07 (d, J ¼ 6.9 Hz, 2H),
5.72 (d, J ¼ 4.8 Hz, 1H), 5.56 (d,
J ¼ 3.9 Hz, 1H), 5.48 (s, 1H), 5.43 (d,
J ¼ 9.6 Hz, 1H), 4.97 (brs, 1H), 4.85 (dd,
J ¼ 3.3, 9.6 Hz, 1H), 4.31 (brs, 1H), 4.15
(dd, J ¼ 3.3, 9.9 Hz, 1H), 3.91–3.78 (m,
2H), 3.74 (dd, J ¼ 9.0, 10.5 Hz, 2H), 3.62
(dd, J ¼ 9.6, 9.9 Hz, 1H), 2.99 (dd,
J ¼ 6.9, 13.5 Hz, 1H), 2.35 (s, 3H), 2.08
3.2.2 Synthesis of compound 5
To a solution of compound 4 (1.85 g,
3.457 mmol) in anhydrous pyridine
(10 ml) was added p-toluenesulfonyl
chloride ( p-TsCl) (1.32 g, 6.915 mmol) in
CH2Cl2 (7 ml) at room temperature. The
reaction mixture was stirred for 2.5 h,
quenched with MeOH (20 ml), and diluted
with CH2Cl2 (200 ml). It was then washed
with 1 M HCl (30 ml £ 3), aqueous satu-
rated NaHCO3 (30 ml £ 3), brine (30 ml
£ 3), dried over anhydrous Na2SO4,
filtered, and concentrated in vacuo. The
residue was purified by silica gel column
chromatography (CH2Cl2/MeOH 40:1,
v/v) to give compound 5 (1.52 g, 64%).
1H NMR (DMSO-d6, 300 MHz): d 7.83
(d, J ¼ 8.1 Hz, 2H), 7.50–7.42 (m, 2H),
(s, 6H), 2.06 (s, 3H), and 1.60 (s, 3H); 13
C
NMR (CDCl3, 75 MHz): d 170.6, 169.7,
169.5, 137.0, 136.9, 131.2 (2C), 129.9
(2C), 129.0, 128.1 (2C), 126.1 (2C), 121.9,

Journal of Asian Natural Products Research
49
101.4, 96.9, 95.0, 78.8, 75.4, 72.4, 71.0,
68.8, 68.5, 67.8, 63.3, 50.9, 38.9, 20.9, 20.8
(2C), 20.7, and 19.6; LC-HR-ESI-MS: m/z
was stirred for 12 h and quenched with
aqueous saturated NaHCO3 (1 ml). It was
then extracted with CH2Cl2 (15 ml £ 3),
and the combined extracts were washed
with aqueous saturated NaHCO3 (5 ml
£ 3), brine (5 ml £ 3), dried over anhy-
drous Na2SO4, filtered, and concentrated
in vacuo. The crude product was dissolved
in CH2Cl2/MeOH (1:1, 2 ml), followed
by the addition of 10 equiv. 1 M MeONa/
MeOH. The reaction was refluxed for 12 h
and then cooled to room temperature. It
was neutralized by ion exchange resin
Amberlite IR-120(Hþ), filtered, and con-
centrated to give yellow oil, which was
purified by silica gel column chromatog-
raphy (CH2Cl2/MeOH 20:1, v/v) to afford
the desired compound 11 (3.2 mg, 76%).
1H NMR (CD3OD, 600 MHz): d 7.38 (d,
J ¼ 7.2 Hz, 2H), 7.30–7.24 (m, 6H), 6.99
(d, J ¼ 8.4 Hz, 2H), 5.62 (d, J ¼ 4.8 Hz,
1H), 5.28 (d, J ¼ 4.8 Hz, 1H), 5.17 (d,
J ¼ 3.6 Hz, 1H), 4.71 (d, J ¼ 12.0 Hz,
1H), 4.69 (d, J ¼ 11.4 Hz, 1H), 4.29 (dd,
J ¼ 3.6, 4.2 Hz, 1H), 4.09–4.05 (m, 2H),
4.03–4.02 (m, 1H), 3.85 (dd, J ¼ 3.0,
3.6 Hz, 1H), 3.80–3.67 (m, 1H), 3.72–
3.59 (m, 4H), 3.45–3.42 (m, 2H), 3.38 (dd,
J ¼ 5.4, 10.8 Hz, 1H), 3.35–3.25 (m, 1H,
H-3), 2.99 (dd, J ¼ 8.4, 13.8 Hz, 1H), 0.98
(s, 3H), 0.90 (d, J ¼ 6.6 Hz, 3H), 0.85 (d,
J ¼ 6.6 Hz, 3H), and 0.83 (s, 3H); 13C
NMR (CD3OD, 150 MHz): d 142.4, 139.7,
137.8, 129.9, 129.3 (2C), 129.1 (2C),
129.1 (2C), 128.6, 127.6 (2C), 122.3,
102.9, 98.7, 98.2, 82.6, 80.9, 79.6, 78.0,
73.9, 73.7, 72.4, 71.0, 70.7, 69.7, 68.7,
64.9, 62.6, 56.3, 51.7, 43.5, 43.0, 41.1,
39.3, 38.5, 37.7, 37.5, 36.9, 36.8, 34.8,
32.9, 32.3, 31.2, 25.5, 24.8, 21.9, 21.0,
19.9, 18.8, 17.3, and 13.4; LC-HR-ESI-
MS: m/z 921.5340 [M þ H]þ (calcd for
C53H77O13 921.5359).
705.2216
C34H41O14S 705.2212).
[M þ H]þ
(calcd
for
3.2.4 Synthesis of compound 10
A solution of compound 8 (18.6 mg,
0.0234 mmol), compound 9 (30.3 mg,
˚
0.0468 mmol), and dry 4 A MS powder
(about 20 mg) in dry CH2Cl2 (6 ml) was
stirred at 2508C for 15 min under argon.
TMSOTf (5% in CH2Cl2, v/v, 22 ml,
0.00585 mmol) was added. The reaction
mixture was stirred at 2508C for 1 h and
was quenched with 0.01 ml Et3N. The
solid was filtered, and the solvent was
removed. The residue was purified by
silica gel column chromatography (pet-
roleum ether/EtOAc 10:1, v/v) to afford
compound 10 (14 mg, 45%). 1H NMR
(CDCl3, 600 MHz): d 7.44–7.40 (m, 2H),
7.36–7.29 (m, 6H), 7.05 (d, J ¼ 7.8 Hz,
2H), 5.67 (d, J ¼ 5.4 Hz, 1H), 5.47 (d,
J ¼ 4.2 Hz, 1H), 5.43 (s, 1H), 5.40 (dd,
J ¼ 9.0, 10.2 Hz, 1H), 5.30 (d, J ¼ 4.8 Hz,
1H), 5.16 (d, J ¼ 2.4 Hz, 1H), 4.76 (d,
J ¼ 12.0 Hz, 1H), 4.60 (d, J ¼ 12.6 Hz,
1H), 4.38–4.32 (m, 1H), 4.31–4.27 (m,
1H), 4.14 (dd, J ¼ 4.8, 10.2 Hz, 1H),
4.05–4.00 (m, 1H), 3.95–3.90 (m, 1H),
3.84–3.78 (m, 2H), 3.66 (dd, J ¼ 10.2,
10.8 Hz, 1H), 3.61 (dd, J ¼ 3.6, 10.2 Hz,
1H), 3.52 (t, J ¼ 9.6 Hz, 1H), 3.50–3.41
(m, 2H), 3.38–3.30 (m, 2H), 3.00 (dd,
J ¼ 6.6, 13.8 Hz, 1H), 2.23 (s, 3H), 2.12 (s,
3H), 2.01 (s, 6H), 0.98 (d, J ¼ 6 Hz, 3H),
0.92 (d, J ¼ 6.6 Hz, 3H), 0.88 (s, 18H),
0.05 (s, 6H), 0.02 (s, 6H); LC-HR-ESI-
MS: m/z 1317.7550 [M þ H]þ (calcd for
C73H113O17Si2 1317.7511).
3.2.5 Synthesis of compound 11
3.2.6 Synthesis of compound 12
To a solution of compound 10 (6 mg,
0.00455 mmol) in dry pyridine (2 ml) was
added HF·pyridine (6.3 ml, 0.0455 mmol)
at room temperature. The reaction mixture
Benzoyl chloride (BzCl, 1.7 ml, 15 mmol,
10 equiv.) was added several times to a
stirred solution of compound 4 (833 mg,

50
Y.-Y. Guan et al.
1.553 mmol) in CH2Cl2/pyridine (3:1, v/v,
40 ml). The reaction mixture was stirred
for 48 h and quenched with MeOH (2 ml).
It was then concentrated in vacuo and
diluted with CH2Cl2 (100 ml), then washed
with 1 M HCl (10 ml £ 3), aqueous satu-
rated NaHCO3 (10 ml £ 3), brine (10 ml
£ 3), dried over anhydrous Na2SO4,
filtered, and concentrated in vacuo. The
residue was purified by silica gel column
chromatography (CH2Cl2/MeOH 40:1,
v/v) to give compound 12 (596 mg,
60%). 1H NMR (CDCl3, 400 MHz): d
8.02 (d, J ¼ 7.6 Hz, 2H), 7.57 (t,
J ¼ 7.2 Hz, 1H), 7.49–7.40 (m, 4H), 7.38
(d, J ¼ 7.6 Hz, 2H), 7.32–7.26 (m, 3H),
6.89 (d, J ¼ 8.0 Hz, 2H), 5.42 (s, 1H), 4.98
(d, J ¼ 2.8 Hz, 1H), 4.68 (d, J ¼ 12.0 Hz,
1H), 4.43 (d, J ¼ 9.6 Hz, 1H), 4.34–4.28
(m, 2H), 3.96 (dd, J ¼ 9.2, 9.6 Hz, 1H),
3.92–3.84 (m, 1H), 3.73 (dd, J ¼ 8.4,
8.8 Hz, 1H), 3.63–3.42 (m, 4H), 3.35 (t,
J ¼ 9.2 Hz, 1H), and 2.27 (s, 3H); 13C
NMR (CDCl3, 100 MHz): d 166.1, 138.0,
137.0, 133.0, 133.0 (2C), 129.9, 129.7
(2C), 129.6 (2C), 129.2, 128.4 (2C), 128.3
(2C), 128.2, 126.4 (2C), 102.5, 101.8,
87.5, 81.2, 80.5, 77.4, 76.2, 73.2, 71.5,
70.9, 68.5, 63.7, and 21.1; LC-HR-ESI-
MS: m/z 641.2052 [M þ H]þ (calcd for
C33H37O11S 641.2051).
(CDCl3, 300 MHz): d 7.81 (d, J ¼ 6.9 Hz,
2H), 7.73 (d, J ¼ 6.9 Hz, 2H), 7.49–7.41
(m, 4H), 7.40–7.31 (m, 5H), 7.30–7.22
(m, 4H), 6.98 (d, J ¼ 7.5 Hz, 2H), 5.43 (s,
1H), 5.05 (d, J ¼ 3.0 Hz, 1H), 5.39 (d,
J ¼ 3.9 Hz, 1H), 4.42 (t, J ¼ 9.6 Hz, 1H),
4.20–4.16 (m, 1H), 3.96–3.84 (m, 2H),
3.83–3.75 (m, 2H), 3.74–3.60 (m, 2H),
3.59–3.44 (m, 2H), 3.43–3.30 (m, 2H),
3.29–3.20 (m, 2H), 2.26 (s, 3H), and 1.04
(s, 3H); 13C NMR (CDCl3, 75MHz): d
137.9, 137.1, 135.9 (2C), 135.7 (2C),
133.4, 132.9, 132.7 (2C), 129.7 (4C),
129.2, 128.7, 128.3 (2C), 127.6 (4C),
126.4 (2C), 102.3, 101.8, 87.8, 80.6, 80.5,
79.2, 73.7, 71.7, 71.0, 68.6, 63.6, 62.4,
26.78 (3C), 21.07, and 19.21; LC-HR-ESI-
MS: m/z 775.2964 [M þ H]þ (calcd for
C42H51IO10SSi 775.2967).
3.2.8 Synthesis of compound 22
To a solution of compound 20 (11 mg,
0.010 mmol) in pyridine, HF·pyridine
(9.0 ml, 0.100 mmol) was added at room
temperature. The mixture was stirred for
12 h and quenched with aqueous saturated
NaHCO3 and then extracted with CH2Cl2
(15 ml £ 3). The combined extracts were
washed with aqueous saturated NaHCO3
(5 ml £ 3), brine (5 ml £ 3), dried over
anhydrous Na2SO4, filtered, and concen-
trated in vacuo. The residue was purified
by silica gel column chromatography
(petroleum ether/EtOAc 5:1, v/v) to give
compound 22 (5.4 mg, 58%). 1H NMR
(CDCl3, 600 MHz): d 8.03 (d, J ¼ 7.8 Hz,
2H), 7.57 (t, J ¼ 7.2 Hz, 2H), 7.46 (d,
J ¼ 6.0 Hz, 2H), 7.43 (d, J ¼ 6.6 Hz, 2H),
7.34 (d, J ¼ 6.0 Hz, 3H), 5.49 (s, 1H), 5.32
(d, J ¼ 3.6 Hz, 1H), 5.12 (d, J ¼ 3.6 Hz,
2H), 5.01 (t, J ¼ 3.6 Hz, 1H), 4.64 (d,
J ¼ 12.0 Hz, 1H), 4.48–4.38 (m, 2H), 4.33
(dd, J ¼ 4.2, 10.2 Hz, 1H), 4.02–3.94 (m,
2H), 3.93–3.85 (m, 2H), 3.68 (dd, J ¼ 3.9,
9.9 Hz, 1H), 3.66–3.58 (m, 2H), 3.56–
3.47 (m, 1H), 3.44 (dd, J ¼ 9.0, 9.6 Hz,
1H), 3.40 (dd, J ¼ 6.0, 10.2 Hz, 1H), 3.28
(dd, J ¼ 6.0, 10.2 Hz, 1H), and 0.96 (d,
3.2.7 Synthesis of compound 16
Compound 4 (302mg, 0.563 mmol) was
dissolved in dry pyridine (5 ml), followed
by the addition of 4-dimethylaminopyri-
dine (DMAP; 13.7mg, 0.112 mmol) and
tert-butyldiphenylchlorosilane (TBDPSiCl)
(0.57 ml, 2.253 mmol) at room tempera-
ture. The mixture was stirred for 5 h and
diluted with EtOAc (50 ml). Then it was
washed with aqueous saturated NaHCO3
(5ml £ 3), brine (5 ml £ 3), dried over
anhydrous Na2SO4, filtered, and concen-
trated in vacuo. The residue was purified
by silica gel column chromatography
(petroleum ether/EtOAc 5:1, v/v) to give
compound 16 (340mg, 78%). 1H NMR

Journal of Asian Natural Products Research
51
J ¼ 6.6 Hz, 3H); 13C NMR (CDCl3,
150 MHz): d 166.2, 140.8, 136.9, 135.2,
133.1, 129.6 (2C), 128.4 (2C), 128.3 (2C),
126.2 (2C), 125.0, 121.3, 102.5, 101.7,
94.3, 81.8, 80.8, 75.5, 74.6, 73.4, 71.8,
70.7, 70.8, 69.6, 68.6, 68.0, 63.9, 63.6,
61.1, 54.2, 49.9, 42.3, 37.1, 36.4, 35.4,
33.3, 32.4, 32.2, 31.6, 31.4, 30.2, 29.7,
26.4, 23.9, 23.4, 20.7, 19.4, 18.1, 16.3, and
13.2; LC-HR-ESI-MS: m/z 935.5162
[M þ H]þ (calcd for C53H75O14
935.5151).
20.7, 20.6, 19.3, 18.2, 15.8, 14.1, and 10.9;
LC-HR-ESI-MS: m/z 911.4989 [M þ H]þ
(calcd for C47H75O17 911.4999).
Supplementary data
The synthetic procedure, 1H NMR, 13C
NMR, HR-MS data of compounds 1–3, 6,
8–9, 13–15, 17–19, and 21, and exper-
imental procedures of these compounds
are available online in supporting
information.
Acknowledgments
3.2.9 Synthesis of compound 23
Financial support of this research by the
National Natural Science Foundation of China
(NNSFC 30772632) and the National Program
of New Drug Innovation and Production
(2009ZX09301-003-9-1) is gratefully acknowl-
edged by the authors.
To a solution of compound 21 (15 mg,
0.0102 mmol) in pyridine, HF·pyridine
(9.2 ml, 0.102 mmol) was added at room
temperature. The mixture was stirred for
12 h and quenched with aqueous saturated
NaHCO3 and then extracted with CH2Cl2
(15 ml £ 3). The combined extracts were
washed with aqueous saturated NaHCO3
(5 ml £ 3), brine (5 ml £ 3), dried over
anhydrous Na2SO4, filtered, and concen-
trated in vacuo. The residue was resolved
in CH2Cl2/MeOH (2:1, v/v, 5 ml), fol-
lowed by the addition of NaHSO4·SiO2
(30 mg) at room temperature. The mixture
was stirred for 12 h and concentrated in
vacuo. The residue was purified by silica
gel column chromatography (petroleum
ether/EtOAc 5:1, v/v) to give compound
23 (6 mg, 64.6%). 1H NMR (CDCl3,
300 MHz): d 5.41 (d, J ¼ 3.6 Hz, 1H),
5.32 (d, J ¼ 3.3 Hz, 1H), 5.20 (d,
J ¼ 9.9 Hz, 1H), 5.18–5.07 (m, 1H), 4.95
(d, J ¼ 3.3 Hz, 1H), 4.78 (dd, J ¼ 3.9,
10.2 Hz, 1H), 4.46–4.34 (m, 1H), 4.10–
3.92 (m, 3H), 3.90–3.66 (m, 4H), 3.62–
3.38 (m, 5H), 2.10 (s, 3H), 2.08 (s, 6H),
2.04 (s, 3H), 0.89 (d, J ¼ 6.9 Hz, 3H), and
0.85 (s, 3H); 13C NMR (CDCl3, 150 MHz):
d 171.8, 171.6, 170.6, 170.4, 140.9, 121.2,
95.8, 94.5, 75.99, 75.67, 72.92, 72.65,
71.71, 71.45, 71.37, 70.39, 70.20, 68.20,
62.57, 61.06, 60.73, 49.97, 42.3, 39.7, 37.2,
36.5, 36.3, 34.8, 32.8, 32.2, 31.9, 31.6,
31.5, 30.2, 29.7, 23.4, 23.1, 21.3, 20.9,
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