Synthesis and antitumor activity of 5,6-dihydro-17-hydroxy icogenin analogs

Article abstract of DOI:10.1016/j.ejmech.2012.02.043

Four 5,6-dihydro-17-hydroxy icogenin analogs were designed and synthesized. Their in vitro antitumor activities were tested by the standard MTT assay. Compound 22 (IC₅₀ = 3.38-8.30 μM) and compound 23 (IC₅₀ = 1.90-9.69 μM) showed pot

Full text of DOI:10.1016/j.ejmech.2012.02.043

European Journal of Medicinal Chemistry 51 (2012) 200e205
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and antitumor activity of 5,6-dihydro-17-hydroxy icogenin analogs
,
Yu-yao Guan a, Dan Zheng a, Zheng Yan b, Nan Wang b, Ping-sheng Lei a
*
a Department of Medicinal Chemistry, State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Beijing City Key Laboratory of Active Substances Discovery
and Drugability Evaluation, Institute of Materia Medica, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100050, PR China
b Department of Pharmacology, Institute of Materia Medica, Peking Union Medical College & Chinese Academy of Medical Sciences, Beijing 100050, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Four 5,6-dihydro-17-hydroxy icogenin analogs were designed and synthesized. Their in vitro antitumor
Received 11 January 2012
Received in revised form
20 February 2012
Accepted 21 February 2012
Available online 2 March 2012
activities were tested by the standard MTT assay. Compound 22 (IC50 ¼ 3.38e8.30
mM) and compound 23
M) showed potential antitumor activities against the entire tested seven cancer cell
(IC50 ¼ 1.90e9.69
m
lines. The SAR (structure activity relationship) research showed that the introduction of 17-hydroxy
lowered the antitumor activity to an extent.
Ó 2012 Elsevier Masson SAS. All rights reserved.
Keywords:
Icogenin analog
Saponin
Antitumor activity
Synthesis
1. Introduction
fold loss of activity, in addition, future work is needed to define
the role of the 17-hydroxy heteroatom [3]. Zheng et al. synthesized
Natural products are well known as an excellent source of
chemical structures with a broad range of promising pharmaceu-
tical properties, including antitumor activity [1]. Moreover, natural
products have been an important source of clinically useful agents,
for instance, useful anticancer agents [2]. Steroids and saponins
have attracted extreme interest of many research groups all over
the world owing to the potential anticancer activity, for example,
cephalostatin 1 [3] and OSW-1 (Fig. 1) [4].
a series of cholestane saponins without 17-hydroxy as mimics of
OSW-1. Since the compounds still displayed excellent antitumor
activity, they came to a conclusion that 17-hydroxy was not
essential for OSW-1’s antitumor activity [8]. Due to this contrast we
are curious about the impact of 17-hydroxy to icogenin, so we
planned to introduce 17-hydroxy into the structures of icogenin
mimics. In addition, the SAR of OSW-1 [9] and cephalostatin 1 [3]
showed that 5,6-double bond might not be of importance for
antitumor activity. Moreover, the natural furostan saponin tim-
osaponin BII [10] with 5,6-saturated single bond also showed
Icogenin (Fig. 2), a typical furostan saponin isolated from
Dracaena draco, exposed significant cytotoxic activity on the growth
of HL-60 with an IC50 of 2.6 ꢀ 0.9
synthesized icogenin [6]. Wang et al. further developed the SAR of
icogeninwith the simplified disaccharide [ -Rhap-(1 /2)e(
Glcp] displacing the trisaccharide [ -Rhap-(1 / 2)e -Glcp-
(1 / 3)e -Glcp] [7]. The cytotoxicity of the synthesized icogenin
and analogs were tested by MTT assay which showed that they have
similar activity ranging from 0.66 M to 7.8 M against SW1990,
m
M [5]. Hou in our lab first
potent activity on the growth of HL-60 with IC50 of 15.5 mg/mL. We
designed and synthesized the 5,6-dihydro-17-hydroxy icogenin
analogs with the aim to survey the impact of 17-hydroxy and enrich
the structural kinds of the furostan saponin family for finding more
promising antitumor compounds.
a-L
a)b-D-
a-
L
b-D
b-D
m
m
2. Results and discussion
BxPC3, Capan2, PANC1, A549, Bel-7402, A2780, HCT-8, MCF-7 [6,7].
A 17-hydroxy function exits in the structure of natural anti-
tumor product cephalostatin 1 and OSW-1. Fuchs et al. disclosed
that 17-hydroxy was beneficial to improve cephalostatin 1’s in vitro
antitumor activity and removal of 17-hydroxy resulted in 10e100
2.1. Chemistry
The aglycone was synthesized as shown in Scheme 1. The
starting material 1 was prepared from tigogenin, which was
reported in our previous article [11]. The 22-ketone in 1 was pro-
tected by ethylene glycol ketal group to produce 2 (81% yield)
which was deprotected by 1.5 M MeONa/MeOH to give 3 in a yield
of 92%. 3,26-diol 3 was selectively protected as 26-pivalyl 4 [12] in
* Corresponding author. Tel.: þ86 10 63162006; fax: þ86 10 63017757.
E-mail address: lei@imm.ac.cn (P.-s. Lei).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.02.043

Y.-y. Guan et al. / European Journal of Medicinal Chemistry 51 (2012) 200e205
201
OH
O
O
OH
OH
O
11
7
17
OH
O
OH
11
7
17
N
N
O
1
AcO
1
3
O
O
HO
HO
3
OH
HO
OMBz
O
O
O
OSW-1
Cephalostatin 1
OH
Fig. 1. Structures of cephalostatin 1 and OSW-1.
a yield of 91%. The free 3-hydroxy in 4 was protected by TBS group
to give 5 in a yield of 92%. The introduction of cis-16,17-dihydroxy to
5 was referred to the synthesis of OSW-1 by using OsO4 [13], giving
the desired product 6. The oxidation of 16-OH adopted Swern
oxidation with DMSO and oxalyl chloride [13], meanwhile in one
pot the 22-cycloethyleneketal protecting group and 3-TBS group
were cleaved [9] to afford 7 in a yield of 67%. The 13C NMR spectrum
illustrated that the chemical shift of C-22 ketone and C-16 ketone in
2.2. Pharmacology
The in vitro antitumor activities of compounds 20e23 against
A2780, BEL-7402, HCT-8, KB, BGC-823, HELA and A549 were eval-
uated by the standard MTT assay using dioscin as a positive control.
The results were listed in Table 1. The IC50 values of dioscin against
these seven cell lines used in our assays are consistent with those
determined by others [16].
compound 7 appeared at
d
217.57 and
d
218.85 respectively,
The aglycone 20 and compound 21 bearing glucose at C3-OH
meanwhile, the signal (
disappeared in compound 7.
d
ꢁ4.65) of dimethyl of TBS in compound 6
were not biologically active. Compound 22 (IC50 ¼ 3.38e8.30
with disaccharide [ -Rhap-(1 / 2)e -Glcp] linking at C3-OH
showed potential activities against the seven cell lines.
Compound 23 (IC50 ¼ 1.90e9.69 M) with trisaccharide [ -Rhap-
(1 / 2)e -Rhap-(1 / 4)e -Glcp] linking at C3-OH also dis-
played potential activities against the seven cell lines. The disac-
charide [ -Rhap-(1 / 2)e -Glcp] fragment was essential to the
antitumor activities of 5,6-dihydro-17-hydroxy icogenin saponin
analogs. The antitumor activity of compounds 22, 23 were 2e10
times lower than icogenin against lung cancer cells etc. This
showed that the introduction of 17-hydroxy resulted in the minor
loss of antitumor activity.
mM)
a
-L
a-D
In order to synthesize the aglycone of 5,6-dihydro-17-hydroxy
icogenin analogs, the intermediate 9 (86% yield) was prepared
throughthedihydroxylationof16,17-enein2 to give 8 (66%yield) and
then regioselective Swern oxidation of 16-OH in 8 (see Scheme 2).
The sugar donors 10e12 (see Scheme 3) were prepared
according to the procedures developed by our research group and
other group [7,14].
Coupling of the aglycone 7 with the sugar trichloroacetimidates
10e12 in the presence of TMSOTf (0.10 equiv) respectively provided
the resulting saponins 13 (89% yield), 14 (90% yield) and 15 (95%
yield). The 1H NMR spectra of 13e15 showed the signals for the
m
a-D
a-L
a
-
L
a
-L
a-D
10-
anomeric proton at
proton at
of 13e15 showed the signals for the anomeric carbons at
96.46 and 96.75, respectively.
Preferential reduction of the C16-ketone in compounds 9, 13e15
a
-anomeric proton at
d
4.93 (d, 1H, J ¼ 8.1 Hz, H-10), 10-
b-
3. Conclusion
d
4.82 (br s, 1H, H-10) and 10-
b-anomeric
d
5.21 (br s, 1H, H-10), respectively. The 13C NMR spectra
100.14,
In a conclusion, four analogs of icogenin were designed and
synthesized. Compounds 22, 23 still retain potential activities
which were 2e10 times lower than icogenin. As a summary, we
disclosed that the introduction of 17-hydroxy lowered the anti-
tumor activity to an extent. Furthermore, this work enriched the
kinds of icogenin structure and might produce more choices for
clinical research. These active analogs are promising candidates for
further efficacy evaluation.
d
d
d
respectively with NaBH4 in i-PrOH were achieved by the following
the known procedure [15], and the newly generated secondary
alcohol concurrently cyclized to give the hemiketal 16 (50% yield),
17 (71% yield), 18 (65% yield) and 19 (75% yield). After the
methoxylation of C22-OH and deprotection of acyl groups, the
designed icogenin analogs 20 (94% yield), 21 (98% yield), 22 (99%
yield) and 23 (95% yield) were finally obtained efficiently (see
Scheme 4).
4. Experimental section
4.1. General chemistry methods
Melting points were obtained on Yanaco MP-500D melting
point apparatus and were uncorrected. Optical rotations were
measured on a PerkineElmer Polarimeter 341LC using 10 cm cells
and the sodium D line (589 nm) at 20 ꢂC and concentration indi-
cated. IR spectra were recorded on a Nicolet 5700 FT-IR microscope
instrument (FT-IR microscope transmission). All NMR spectra were
recorded on Mercury-300 or Mercury-500 or Mercury-600 spec-
trometers in CDCl3 or pyridine-d5 as solution. The chemical shifts
are reported impart per million (ppm) with tetramethylsilane
(TMS) as an internal standard. HRMS experiments were performed
using an Aglient 1100 series LC/MSD TOF. Analytical thin layer
chromatography (TLC) was carried out on TLC plates silica gel
HSGF254 percolated by Branch of Qingdao Haiyang Chemical Plant.
OMe
OH
17
O
11
7
1
HO
3
HO
HO
O
O
HO
O
O
O
HO
OH
O
HO
OH
HO
Fig. 2. Structure of icogenin.

202
Y.-y. Guan et al. / European Journal of Medicinal Chemistry 51 (2012) 200e205
O
O
O
O
O
OAc
OH
OAc
a
b
BzO
HO
BzO
3
1
2
c
O
O
O
O
O
O
OPiv
OPiv
OPiv
OH
OH
e
d
HO
TBSO
TBSO
4
5
6
f
O
OPiv
OH
O
HO
7
Scheme 1. Synthesis of compound 7. Reagents and conditions: a. HOCH2CH2OH, HC(OEt)3, PTSA, rt, 81%; b. 1.5
M MeONa/MeOH, CH2Cl2/MeOH, reflux, 92%;
c. 3-pivaloylthiazolidine-2-thione, NaH, THF, rt, 91%; d. TBDMSCl, imidazole, DMAP, DMF, rt, 92%; e. OsO4, Et2O, pyridine, ꢁ70 ꢂC to rt, 67%; f. DMSO, oxalyl chloride, CH2Cl2,
Et3N, ꢁ60 ꢂC to rt, 61%.
Chromatography was performed with silica gel H (HG/T2354-92) or
Sephadex LH-20. The major chemicals were purchased from Alfa
Aesar Chemical Corporation. All other chemicals were analytical
grade.
(1.016 g, 91.4%) as a yellowish oil; 1H NMR (CDCl3, 300 MHz):
5.62 (s, 1H, H-16), 3.95 (s, 4H, OCH2CH2O), 3.93e3.77 (m, 2H,
d
H-26), 3.61e3.54 (m, 1H, H-3), 2.41 (q, J ¼ 7.2 Hz, 1H, H-20), 1.19
(s, 9H), 1.01 (d, J ¼ 7.2 Hz, 3H), 0.89 (d, J ¼ 6.3 Hz, 3H), 0.82 (s, 3H),
0.76 (s, 3H); 13C NMR (CDCl3, 75 MHz):
d 178.57, 156.58, 124.08,
113.58, 71.27, 69.12, 65.84, 65.27, 57.23, 54.95, 47.64, 45.11, 39.17,
38.80, 38.21, 36.82, 35.68, 34.87, 34.27, 33.10, 32.82, 31.94, 31.49,
31.27, 28.67, 27.19(3C), 26.99, 21.09, 17.33, 16.78, 15.80, 12.28;
HRMS (ESI) m/z: calcd for C34H56O5Na 567.4020, found 567.3997
(M þ Naþ).
4.2. Synthesis of compound 4
To a solution of compound 3 (940.3 mg, 2.041 mmol) and
3-pivaloylthiazolidine-2-thione (746 mg, 3.674 mmol) in dry THF
(50 mL) was added sodium hydride (60% in oil, 163 mg,
4.082 mmol) at room temperature under argon atmosphere. The
solution was stirred for 12 h and then quenched with aqueous
saturated NaHCO3 solution. The mixture was extracted with
CH2Cl2 and the combined organic layer was washed with brine,
dried over anhydrous Na2SO4. After concentration, the residue
was purified by column chromatography to give compound 4
4.3. Synthesis of compound 6
To a solution of compound 5 (1.149 g, 1.745 mmol) in 35 mL of
diethyl ether and 1.5 mL of pyridine was added OsO4 (480 mg,
1.889 mmol) at ꢁ70 ꢂC. Then, the reaction mixture was warmed to
O
O
O
O
O
OAc
OAc
OAc
a
b
OH
OH
OH
O
BzO
BzO
BzO
8
9
2
Scheme 2. Synthesis of compound 9. Reagent and conditions: a. OsO4, Et2O, pyridine, ꢁ70 ꢂC to rt, 66%; b. DMSO, oxalyl chloride, CH2Cl2, Et3N, ꢁ60 ꢂC to rt, 86%.

Y.-y. Guan et al. / European Journal of Medicinal Chemistry 51 (2012) 200e205
203
O
OPiv
OH
O
BzO
O
BzO
BzO
BzO
BzO
OCNHCCl3
OCNHCCl3
OBz
O
O
BzO
O
10
OBz
13
O
OPiv
+
OH
O
AcO
AcO
OPiv
a
OH
O
O
O
AcO
AcO
AcO
O
AcO
HO
O
AcO
AcO
O
O
7
O
AcO
AcO
OAc
11
14
OAc
O
PivO
OPiv
O
OH
O
OCNHCCl3
O
PivO
PivO
O
O
BzO
BzO
O
O
O
OBz
BzO
PivO
O
O
BzO
BzO
O
OBz
BzO
O
OBz
BzO
15
OBz
12
BzO
Scheme 3. The coupling of the aglycone with the three kinds of sugar donors to give 13e15. Reagents and conditions: a. TMSOTf, CH2Cl2, 0 ꢂC, 89% for 13, 90% for 14 and 95% for 15.
room temperature and stirred for 3 h. The reaction was quenched
with saturated aqueous NaHSO3 solution and the suspension was
stirred overnight. The mixture was extracted with ethyl acetate,
and the combined organic layer was washed with brine, dried over
anhydrous Na2SO4. After concentration, the residue was purified by
column chromatography to give compound 6 (808 mg, 66.9%) as
4.4. Synthesis of compound 7
After the solution of oxalyl chloride (0.32 mL) and DMSO
(0.47 mL) in 8 mL of dryCH2Cl2 was stirred at ꢁ60 ꢂC for 15 min under
argon atmosphere, a solution of compound 6 (771 mg,1.114 mmol) in
dry CH2Cl2 (15 mL) was added. The mixture was stirred at ꢁ60 ꢂC for
another 3 h and then 2.5 mL of triethylamine was added. After the
reaction mixture was warmed to room temperature slowly, the
product was extracted with ethyl acetate, and the combined organic
layer was washed with brine, dried over anhydrous Na2SO4. After
concentration, the residue was purified by column chromatography
to give compound 7 (537.1 mg, 61.0%) as a white solid; mp:
a white solid; 1H NMR (CDCl3, 300 MHz):
d
4.22 (d,1H, J ¼ 8.7 Hz, H-
16), 3.95e3.88 (m, 6H, OCH2CH2O, H-26), 3.56e3.49 (m, 1H, H-3),
3.07 (s, 1H), 1.18 (s, 9H), 1.09 (d, 3H, J ¼ 6.9 Hz), 0.91 (d, 3H,
J ¼ 6.9 Hz), 0.86 (s, 9H), 0.76 (s, 3H), 0.73 (s, 3H), 0.03 (s, 6H); 13C
NMR (CDCl3, 75 MHz):
d 178.41, 115.44, 82.26, 75.85, 72.07, 68.80,
65.75, 64.33, 53.66, 50.16, 47.64, 45.20, 44.82, 38.78, 38.56, 36.94,
35.33, 35.26, 33.16, 32.96, 32.79, 32.01, 31.85, 28.64, 27.16(3C),
25.89(3C), 25.63, 20.54, 18.19, 16.95, 14.43, 13.03, 12.25, ꢁ4.62(2C);
HRMS (ESI) m/z: calcd for C40H72O7SiNa 715.4940, found 715.4907
(M þ Naþ).
129e132 ꢂC; ½a 2D0
ꢃ
ꢁ80ꢂ (c 0.23, CH2Cl2); IR:
n
¼ 3390, 2932, 1738,
1703,1284,1146,1075,1040 cmꢁ1; 1H NMR (CDCl3, 300 MHz):
d
5.46
(s, 1H), 3.90 (d, 1H, J ¼ 5.7 Hz, H-26), 3.59e3.52 (m, 1H, H-3),
2.85e2.74 (m,1H), 2.67e2.48 (m, 2H), 2.32e2.13 (m, 2H),1.16 (s, 9H),
OMe
OH
OH
OR2
b
OH
OH
O
a
O
9, 13, 14, 15
R1O
RO
HO
HO
BzO
BzO
O
20:R=OH
21:R=
17:R1=
R2=Piv
O
16:R1=BzO, R2=Ac
HO
BzO
OH
OBz
AcO
AcO
HO
HO
HO
PivO
O
18:R1=
19:R1=
22:R=
O
O
23:R=
O
O
O
O
AcO
HO
HO
O
O
O
HO
PivO
O
O
BzO
BzO
HO
O
O
O
AcO
AcO
R2=Piv
HO
OH
HO
OBz
BzO
O
HO
OH
HO
OAc
OH
R2=Piv
OBz
BzO
Scheme 4. The cyclization of compounds 16e19 and deprotection of protecting groups to give 20e23. Reagents and conditions: a. NaBH4, i-PrOH/CH2Cl2, rt, 50% for 16, 71% for 17,
65% for 18 and 75% for 19; b. i) MeOH/CH2Cl2, reflux, 24h; ii) 1 M MeONa, MeOH, reflux, 24h, 94% for 20, 98% for 21, 99% for 22 and 95% for 23.

204
Y.-y. Guan et al. / European Journal of Medicinal Chemistry 51 (2012) 200e205
Table 1
20.58, 20.22, 17.38, 16.86, 13.97, 12.16, 11.56; HRMS (ESI) m/z: calcd
for C56H84O21Na 1115.5397, found 1115.5428 (M þ Naþ).
The in vitro cytotoxicities (IC50
, mM) of synthetic 5,6-dihydro-17-hydroxy icogenin
analogs and dioscin.a
Cell lines
20
21
22
23
Dioscin
4.5.3. Compound 15
Mp: 137e140 ꢂC; ½a D20
ꢃ
þ88.8ꢂ (c 0.32, CH2Cl2); IR:
n
¼ 3375,
A2780
BEL-7402
HCT-8
KB
BGC-823
HELA
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
7.96
8.30
3.38
5.97
4.29
7.80
3.68
8.21
9.69
6.05
5.24
7.97
8.31
1.90
0.87
0.81
0.34
0.53
1.08
0.50
0.81
2971, 1731, 1602, 1277, 1147, 1107, 1068 cmꢁ1 1H NMR (CDCl3,
;
300 MHz):
d
8.08 (t, J ¼ 6, 6.3 Hz, 4H), 7.98 (t, J ¼ 6.6, 6.9 Hz, 4H),
7.85 (d, J ¼ 7.5 Hz, 2H), 7.80 (d, J ¼ 7.2 Hz, 2H), 7.59 (d, J ¼ 6.9 Hz,
2H), 7.52 (d, J ¼ 7.5 Hz, 2H), 7.47 (d, J ¼ 7.2 Hz, 2H), 7.39 (t, J ¼ 7.2,
7.8 Hz, 4H), 7.27 (d, J ¼ 7.5 Hz, 2H), 7.1 (d, J ¼ 7.8 Hz, 2H), 5.83e5.52
(m, 6H), 5.21 (br s, 1H), 5.07 (s, 1H), 4.62 (d, J ¼ 12 Hz, 1H), 4.49 (dd,
J ¼ 3.3, 8.7 Hz, 1H), 4.38e4.31 (m, 2H), 4.25 (d, J ¼ 9 Hz, 1H), 3.96 (d,
J ¼ 5.7 Hz, 2H), 3.89 (t, J ¼ 9.3, 9.9 Hz, 1H), 3.63 (d, J ¼ 6.3 Hz, 2H),
1.29 (s, 9H), 1.28 (s, 9H), 1.21 (s, 9H), 1.14 (d, J ¼ 7.2 Hz, 3H), 0.98
(d, J ¼ 6.6 Hz, 3H), 0.96 (s, 3H), 0.79 (s, 3H); 13C NMR (CDCl3,
A549
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.
1.08 (d, 3H, J ¼ 6.9 Hz), 0.93 (d, 3H, J ¼ 6.9 Hz), 0.78 (s, 3H), 0.71
75 MHz): d 218.81, 217.48, 178.50, 177.90, 176.53, 165.69, 165.52,
(s, 3H); 13C NMR (CDCl3, 75 MHz):
d
218.85, 217.57, 178.56, 85.89,
165.49, 165.30, 165.19, 164.82, 133.41(2C), 133.26(2C), 133.03(2C),
132.83(2C), 129.76(2C), 129.65(2C), 129.33(4C), 129.21(4C),
128.49(2C), 128.33(4C), 128.17 (4C), 128.08(2C), 127.78(2C), 99.88,
98.18, 96.75, 85.91, 80.11, 78.96, 77.76, 77.20, 71.68, 71.50, 71.09,
70.33, 69.59, 68.39, 68.05, 68.02, 67.06, 62.34, 53.46, 45.46, 44.90,
44.84, 42.94, 40.36, 38.88, 38.78, 36.75, 35.91, 35.55, 35.26, 34.41,
31.97, 30.23, 28.41, 28.06, 27.18, 27.11(8C), 26.18; HRMS (ESI) m/z:
calcd for C102H123O27 1779.8246, found 1779.8188 (M þ Hþ).
70.97, 68.43, 53.43, 45.45, 44.82, 44.59, 42.91, 40.35, 38.89, 37.89,
36.55, 35.42, 35.26, 34.41, 31.95, 31.22, 30.24, 28.35, 27.11(3C), 26.17,
20.22, 16.83, 13.96, 12.16, 11.53; HRMS (ESI) m/z: calcd for C32H53O6
533.3837, found 533.3829 (M þ Hþ).
4.5. General procedure for synthesis of compounds 13e15
A solution of aglycone 7, sugar donor (1.8 eq) and dry 4 Å MS
powder in dry CH2Cl2 was stirred at 0 ꢂC for 15 min under argon
atmosphere. TMSOTf (5% in CH2Cl2, 0.1 eq) was added. The reaction
was stirred at 0 ꢂC for 2 h and was quenched with Et3N. The solid
was filtered off and the filtrate was concentrated. The residue was
purified by column chromatography to afford the resulting
compounds. The yields of this reaction were 89% for 13, 90% for 14
and 95% for 15, respectively.
4.6. General procedure for synthesis of compounds 16e19
To a solution of reactant in isopropyl alcohol/CH2Cl2 (1/4) was
added NaBH4 (10 eq) at room temperature. The mixture was stirred
for 24 h. Then it was diluted with CH2Cl2 and washed by H2O and
brine, dried over anhydrous Na2SO4, filtered and evaporated under
reduced pressure. The residue was purified by column chroma-
tography deactivated by Et3N to afford the desired compound. The
yields of this reaction were 50% for 16, 71% for 17, 65% for 18 and
75% for 19, respectively.
4.5.1. Compound 13
Mp: 97e99 ꢂC; ½a 2D0
ꢃ
ꢁ30.6ꢂ (c 0.15, CH2Cl2); IR:
¼ 3373, 2938,
n
1731, 1602, 1266, 1175, 1095, 1069 cmꢁ1; 1H NMR (CDCl3, 300 MHz):
d
8.01 (d, J ¼ 7.2 Hz, 2H), 7.95 (d, J ¼ 7.5 Hz, 2H), 7.83 (d, J ¼ 7.5 Hz,
4.6.1. Compound 16
2H), 7.57e7.43 (m, 3H), 7.42e7.27 (m, 9H), 5.89 (t, J ¼ 9.6, 9.9 Hz,
1H), 5.51 (s, 1H), 5.48 (t, J ¼ 9, 9.6 Hz, 1H), 4.93 (d, 1H, J ¼ 8.1 Hz,
H-10), 4.61 (dd, J ¼ 3.3, 12 Hz, 1H), 4.53 (dd, J ¼ 6, 12 Hz, 1H),
4.22e4.12 (m, 1H), 3.94 (d, J ¼ 6 Hz, 2H), 3.63e3.56 (m, 1H), 1.20
(s, 9H), 1.12 (d, J ¼ 6.9 Hz, 3H), 0.97 (d, J ¼ 6.9 Hz, 3H), 0.72 (s, 3H),
1H NMR (C5D5N, 300 MHz):
d
8.25 (d, J ¼ 7.2 Hz, 2H), 7.53 (d,
J ¼ 6.9, 7.5 Hz, 2H), 5.20e4.90 (m, 1H, H-3), 4.75 (t, J ¼ 6.9, 7.2 Hz,
1H, H-16), 4.15e3.92 (m, 2H, H-26), 1.96 (s, 3H), 1.02 (s, 3H), 0.92 (d,
J ¼ 6.6 Hz, 3H), 0.81 (s, 3H); 13C NMR (C5D5N, 75 MHz): 170.78,
166.02, 133.21, 131.53, 129.89 (2C), 128.84 (2C), 111.10, 90.68, 90.51,
74.50, 69.37, 54.11, 52.69, 45.44, 44.69, 43.56, 36.76, 35.72, 35.63,
34.39, 33.24, 32.41, 32.16, 31.76, 28.73, 27.87, 26.80, 21.19, 20.73,
17.52, 16.99, 16.12, 15.26, 12.32, 10.44; HRMS (ESI) m/z: calcd for
C36H52O7Na 619.3605, found 619.3586 (M þ Naþ).
0.69 (s, 3H); 13C NMR (CDCl3, 75 MHz):
d 218.92, 217.53, 178.57,
166.04, 165.81, 165.23, 165.04, 133.39(2C), 133.09(2C), 129.81(2C),
129.70(4C), 129.47(2C), 128.85(2C), 128.78(2C), 128.37(2C),
128.28(4C), 128.81(2C), 100.14, 85.96, 79.96, 73.01, 72.11, 72.08,
70.07, 68.46, 63.38, 53.43, 45.49, 44.85, 44.50, 42.99, 40.42, 36.44,
35.48, 35.31, 34.38, 34.28, 32.04, 31.94, 30.32, 29.25, 28.29,
27.19(3C), 26.24, 22.63, 20.22, 16.90, 14.00, 12.08, 11.61; HRMS (ESI)
m/z: calcd for C66H78O15Na 1133.5233, found 1133.5154 (M þ Naþ).
4.6.2. Compound 17
1H NMR (C5D5N, 300 MHz):
d
8.24 (d, J ¼ 7.8 Hz, 2H), 8.19 (d,
J ¼ 7.8 Hz, 2H), 8.08 (d, J ¼ 7.5 Hz, 2H), 8.01 (d, J ¼ 7.5 Hz, 2H), 7.60e7.10
(m,12H), 6.56 (t, J ¼ 9.6, 9.6 Hz,1H), 6.22 (t, J ¼ 9.3, 9.9 Hz,1H), 6.11 (t,
J ¼ 8.7, 8.7 Hz, 1H), 5.50 (d, J ¼ 7.8 Hz, 1H), 5.10e4.86 (m, 2H),
4.78e4.66 (m, 2H), 4.17e3.99 (m, 2H), 3.90e3.76 (m, 1H),1.21 (s, 9H),
1.18 (d, J ¼ 6.3 Hz, 3H), 0.99 (s, 3H), 0.93 (d, J ¼ 6.9 Hz, 3H), 0.58 (s, 3H);
4.5.2. Compound 14
Mp: 87e89 ꢂC; ½a 2D0
ꢃ
ꢁ10.7ꢂ (c 0.14, CH2Cl2); IR:
¼ 3375, 2938,
n
1748, 1697, 1225, 1163, 1083, 1042 cmꢁ1; 1H NMR (CDCl3, 300 MHz):
d
5.40 (t, J ¼ 9.6, 9.9 Hz, 1H), 5.22 (dd, J ¼ 3.0,10.2 Hz, 1H), 5.05e4.85
13C NMR(C5D5N,75MHz):
d178.05,166.27(2C),165.78,165.66,133.90,
(m, 2H), 4.93 (t, J ¼ 9.3,9.9 Hz,1H), 4.82 (br s,1H), 4.27e4.19 (m,1H),
4.12e4.01 (m, 3H), 3.91 (d, J ¼ 5.4 Hz, 2H), 3.88e3.84 (m, 1H), 3.67
(dd, J ¼ 3.3, 9.9 Hz, 1H), 3.54e3.46 (m, 1H), 2.10 (s, 3H), 2.05 (s, 6H),
2.01 (s, 3H), 1.97 (s, 3H), 1.95 (s, 3H), 1.17 (s, 9H), 1.09 (d, J ¼ 7.2 Hz,
3H), 0.95 (d, J ¼ 6.6 Hz, 3H), 0.83 (s, 3H), 0.72 (s, 3H); 13C NMR
133.68(2C), 133.47, 130.41(2C), 130.08(6C), 129.94(2C), 129.51(2C),
128.87(6C),128.76(2C),111.10,100.31, 90.68, 90.50, 79.97, 74.30, 73.17,
72.46, 70.75, 69.10, 63.70, 54.25, 52.72, 45.43, 44.69, 43.44, 38.89,
37.20, 36.76, 35.64, 35.59, 35.18, 33.37, 32.48, 31.75, 29.90, 28.73,
27.28(3C), 21.17, 19.11, 17.51, 17.07, 12.17, 10.43; HRMS (ESI) m/z: calcd
for C66H78O15Na 1133.5233, found 1133.5184 (M þ Naþ).
(CDCl3, 75 MHz):
d 218.84, 217.42, 178.53, 170.55, 170.21, 169.98,
169.86, 169.74, 169.58, 99.02, 96.46, 85.91, 78.74, 74.90, 71.60, 71.27,
71.00, 69.84, 68.72, 68.44, 68.42, 67.35, 66.91, 62.08, 60.30, 60.02,
53.43, 45.46, 44.84, 44.82, 42.94, 40.38, 38.79, 36.53, 35.83, 35.54,
35.26, 34.39, 31.98, 30.24, 28.46, 27.71, 27.14(3C), 26.20, 20.80,
4.6.3. Compound 18
1H NMR (C5D5N, 600 MHz):
d
6.01 (t, J ¼ 9.6, 10.2 Hz, 1H), 5.73
(dd, J ¼ 3, 10.2 Hz, 1H), 5.62e5.58 (m, 2H), 5.46 (d, J ¼ 4.2 Hz, 1H),

Y.-y. Guan et al. / European Journal of Medicinal Chemistry 51 (2012) 200e205
205
5.42 (t, J ¼ 9.6, 9.6 Hz, 1H), 5.35 (s, 1H), 4.76 (t, J ¼ 7.2, 7.2 Hz, 1H),
4.53 (dd, J ¼ 4.8, 11.4 Hz, 1H), 4.46e4.35 (m, 3H), 4.13e4.09 (m, 2H),
4.03 (dd, J ¼ 6.6, 10.8 Hz, 1H), 3.73e3.68 (m, 1H), 2.53 (q, J ¼ 7.2 Hz,
1H), 2.22 (s, 3H), 2.10 (s, 3H), 2.09 (s, 3H), 2.07 (s, 3H), 2.02 (s, 3H),
1.95 (s, 3H), 1.44 (d, J ¼ 6.6 Hz, 3H), 1.38 (d, J ¼ 6.6 Hz, 3H), 1.21 (s,
9H), 1.05 (s, 3H), 0.94 (d, J ¼ 7.2 Hz, 3H), 0.80 (s, 3H); 13C NMR
J ¼ 7 Hz, 3H), 1.09 (d, J ¼ 6.5 Hz, 3H), 0.90 (s, 3H), 0.68 (s, 3H); 13C
NMR (C5D5N, 75 MHz):
d 113.47, 102.10, 90.41, 90.22, 78.62, 78.50,
77.11, 75.34, 71.77, 67.51, 62.90, 54.20, 52.68, 46.98, 45.70, 44.59,
43.03, 37.18, 36.98, 35.81, 35.38, 34.82, 32.45, 32.19, 31.54, 31.12,
29.95, 28.97, 28.07, 21.03, 17.34, 17.08, 12.30, 10.49; HRMS (ESI) m/z:
calcd for C34H58O10Na 649.3922, found 649.3944 (M þ Naþ).
(C5D5N, 125 MHz):
d 178.10, 170.53, 170.38, 170.27, 169.97, 111.14,
99.65, 97.06, 90.73, 90.53, 79.14, 78.27, 71.90, 71.40, 70.53, 69.72,
69.43, 69.15, 68.27, 67.77, 62.90, 54.30, 52.78, 45.51, 45.01, 43.52,
38.93, 37.12, 36.83, 36.34, 35.80, 35.69, 33.41, 32.54, 31.83, 30.00,
29.01, 28.46, 27.88, 27.32(3C), 21.15, 20.74, 20.67, 20.58, 20.51, 17.76,
17.58, 17.09, 12.41, 10.50; HRMS (ESI) m/z: calcd for C56H86O21Na
1117.5554, found 1117.5558 (M þ Naþ).
4.7.3. Compound 22
Mp: 157e160 ꢂC; ½a D20
ꢃ
þ4.1ꢂ (c 0.11, MeOH); IR:
n
¼ 3415, 2928,
5.94 (s, 1H),
1057, 922, 838, 814 cmꢁ1; 1H NMR (C5D5N, 300 MHz):
d
5.58 (d, J ¼ 3.6 Hz,1H), 4.76 (d, J ¼ 1.5 Hz, 1H), 4.68 (t, J ¼ 9.3, 9.3 Hz,
1H), 4.59 (dd, J ¼ 3.3, 9.3 Hz, 1H), 4.55e4.38 (m, 3H), 4.37e4.25 (m,
2H), 4.24e4.11 (m, 2H), 3.83e3.70 (m, 3H), 3.20 (s, 3H), 1.71 (d,
J ¼ 6.3 Hz, 3H), 1.27 (d, J ¼ 6.6 Hz, 3H), 0.88 (s, 3H), 0.61 (s, 3H); 13C
4.6.4. Compound 19
NMR (C5D5N, 75 MHz): d 113.45, 104.13, 98.25, 90.41, 90.19, 78.89,
1H NMR (C5D5N, 500 MHz):
d
8.29 (d, J ¼ 7.5 Hz, 2H), 8.25 (d,
77.63, m74.25, 74.17, 73.94, 72.79, 72.56, 72.26, 70.18, 67.50, 62.98,
54.11, 52.66, 46.97, 45.93, 45.70, 45.00, 43.00, 36.98, 36.66, 32.39,
32.18, 31.50, 31.11, 29.93, 28.83, 28.40, 28.06, 21.03, 18.65, 17.29,
17.07, 12.20, 10.49; HRMS (ESI) m/z: calcd for C39H63O12 723.4314,
found 723.4300 (M þ Hþ).
J ¼ 7.5 Hz, 2H), 8.16 (d, J ¼ 7.5 Hz, 2H), 8.07 (d, J ¼ 7.5 Hz, 2H), 8.01 (d,
J ¼ 7.5 Hz, 2H), 7.98 (d, J ¼ 7.5 Hz, 2H), 7.54e7.34 (m, 10H), 7.31e7.22
(m, 4H), 7.10e7.05 (m, 4H), 6.39e6.30 (m, 4H), 6.23e6.21 (m, 2H),
6.17 (t, J ¼ 10.0, 10.0 Hz, 1H), 5.85 (br s, 1H), 5.65 (s, 2H), 5.15 (d,
J ¼ 11 Hz,1H), 4.80e4.75 (m, 4H), 4.46 (t, J ¼ 9.0, 9.6 Hz,1H), 4.30 (dd,
J ¼ 3.3, 9.9 Hz, 1H), 4.13e3.98 (m, 2H), 3.88e3.78 (m, 1H), 1.64 (d,
J ¼ 6 Hz, 3H),1.55 (d, J ¼ 6 Hz, 3H),1.50 (s, 9H),1.37 (s, 9H),1.21 (s, 9H),
1.04 (s, 3H), 0.93 (d, J ¼ 7 Hz, 3H), 0.85 (s, 3H); 13C NMR (C5D5N,
4.7.4. Compound 23
Mp: 179e182 ꢂC; ½a D20
ꢃ
ꢁ4.2ꢂ (c 0.16, MeOH); IR:
n
¼ 3385, 2929,
1049, 911, 837, 812 cmꢁ1 1H NMR (C5D5N, 600 MHz):
; d 6.61 (d,
125 MHz):
d
178.08, 177.94, 177.18, 166.09, 165.98, 165.80, 165.69,
J¼ 5.4 Hz,1H), 5.97 (s,1H), 5.87(s,1H), 5.52(d, J¼ 3.6 Hz,1H), 4.92(dd,
J ¼ 6.6, 9.6 Hz, 1H), 4.67e4.63 (m, 3H), 4.57 (dd, J ¼ 3, 9 Hz, 1H), 4.46
(dd, J ¼ 6.6, 9.6 Hz,1H), 4.42 (t, J ¼ 9.6, 9.6 Hz,1H), 4.38e4.26 (m, 6H),
4.19e4.16 (m, 2H), 3.81e3.72 (m, 3H), 3.23 (s, 3H), 1.73 (d, J ¼ 6 Hz,
3H), 1.68 (d, J ¼ 6.6 Hz, 3H), 1.30 (d, J ¼ 7.2 Hz, 3H), 1.12 (d, J ¼ 6.6 Hz,
165.51, 138.01, 135.91, 135.09, 134.03, 133.93, 133.81, 133.50, 130.10,
130.03(2C), 130.00(2C), 129.85, 129.78(2C), 129.75(2C), 129.70,
129.66, 129.39, 129.16, 129.10, 129.05, 128.96, 128.69, 128.66, 125.74,
125.62,123.88,123.06,111.11,100.58, 98.86, 97.30, 90.86, 90.46, 80.40,
79.08, 78.23, 72.77, 72.45, 72.05, 71.58, 70.96, 70.87, 69.11, 69.03,
68.68, 67.65, 63.46, 54.33, 52.74, 45.90, 45.49, 45.17, 43.46, 39.33,
39.15, 38.90, 37.37, 36.80, 36.39, 35.84, 35.70, 33.37, 33.15, 32.57,
32.45, 31.78, 29.96, 28.91, 28.57, 27.84, 27.50 (3C), 27.40 (3C), 27.28
(3C), 27.25, 27.10, 18.00, 17.67, 17.57, 17.06, 12.52, 10.47; HRMS (ESI)
m/z: calcd for C102H125O27 1781.8403, found 1781.8394 (M þ Hþ).
3H), 0.92 (s, 3H), 0.65 (s, 3H); 13C NMR (C5D5N, 150 MHz):
d 113.44,
104.07, 102.92, 98.07, 90.39, 90.16, 79.58, 79.33, 78.01, 73.83, 72.80,
72.66, 72.58, 72.20, 70.40, 70.21, 67.47, 61.48, 54.08, 52.61, 49.59,
46.94, 45.67, 44.97, 42.95, 36.94, 36.57, 35.64, 32.37, 32.15, 31.47, 31.06,
29.90, 28.82, 28.38, 28.02, 20.99,18.61,17.26,17.03,12.15,10.46; HRMS
(ESI) m/z: calcd for C46H78O18Na 941.5080, found 941.5085 (M þ Naþ).
4.7. General procedure for synthesis of compounds 20e23
Acknowledgment
The glycoside was dissolved in dry CH2Cl2/MeOH (1/1). The
mixture was heated to 80 ꢂC and stirred for 24 h. TLC disclosed the
starting material was completely transformed to a lower polar
product. Then 1 M MeONa/MeOH (20 eq) added to the reaction
solution. After refluxing for about 24 h, the solution was neutralized
with ion exchange resin (Hþ), filtered, and concentrated to give
yellow oil, which was purified by Sephadex LH-20 column to afford
the desired compound. The yields of this reaction were 94% for 20,
98% for 21, 99% for 22 and 95% for 23, respectively.
National Program of New Drug Innovation and Production
(2009ZX09301-003) is gratefully acknowledged by authors.
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4.7.1. Compound 20
Mp: 106e109 ꢂC; ½a D20
ꢃ
ꢁ23.9ꢂ (c 0.12, MeOH); IR:
n
¼ 3372, 2927,
1044, 901 cmꢁ1 1H NMR (C5D5N, 300 MHz):
; d
4.32 (t, J ¼ 6.0,
6.6 Hz, 1H, H-16), 4.01e3.87 (m, 1H, H-3), 3.86e3.66 (m, 2H, H-26),
3.20 (s, 3H), 1.26 (d, J ¼ 7.5 Hz, 3H), 1.09 (d, J ¼ 6.6 Hz, 3H), 0.92 (s,
3H), 0.81 (s, 3H); 13C NMR (C5D5N, 75 MHz):
d 113.16, 90.12, 89.93,
70.24, 67.21, 54.00, 52.43, 46.66, 45.94, 45.44, 44.88, 42.71, 38.98,
37.18, 36.69, 35.53, 32.25, 31.95, 31.21, 30.82, 29.64, 28.79, 27.77,
20.82, 17.08, 16.78, 12.18, 10.20; HRMS (ESI) m/z: calcd for
C28H48O5Na 487.3394, found 487.3383 (M þ Naþ).
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4.7.2. Compound 21
Mp: 258e260 ꢂC; ½a D20
ꢃ
ꢁ45.9ꢂ (c 0.11, MeOH); IR:
n
¼ 3402, 2929,
1067, 894, 817 cmꢁ1; 1H NMR (C5D5N, 300 MHz):
d
5.01 (d, J ¼ 8 Hz,
1H), 4.88 (br s, 1H), 4.57 (dd, J ¼ 2, 11.5 Hz, 1H), 4.39 (dd, J ¼ 5,
11.5 Hz, 1H), 4.33e4.21 (m, 3H), 4.05e3.97 (m, 2H), 3.96e3.87 (m,
1H), 3.78e3.71 (m, 2H), 3.21 (s, 3H), 2.56 (q, J ¼ 6.5 Hz, 3H), 1.25 (d,
(b) J. Cai, M.J. Liu, Z. Wang, Y. Ju, Biol. Pharm. Bull. 25 (2002) 193e196.