Highly Enantioselective Synthesis and Anticancer Activities of Chiral Conjugated Diynols

Article abstract of DOI:10.1002/cbic.201800458

A chiral amino alcohol based ligand was found to promote the highly enantioselective addition of terminal conjugated diynes to aromatic and aliphatic aldehydes. The combination of easily available C₂-symmetric (R)- and (S)-BINOL with Ti(OiPr)

Full text of DOI:10.1002/cbic.201800458

Accepted Article
Title: Highly Enantioselective Synthesis and Anticancer Activities of
Chiral Conjugated Diynols
Authors: Ke Zhang, Chun Zhang, Zhong-Hong He, Jian Huang, Xi Du,
Li Wang, Si-Ping Wei, Lin Pu, and Qin Wang
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10.1002/cbic.201800458
ChemBioChem
FULL PAPER
Highly Enantioselective Synthesis and Anticancer Activities of
Chiral Conjugated Diynols
[a]‡
[a]‡
[a]
[a]
[a]
[a]
Ke Zhang,[a] Chun Zhang, Zhong-Hong He, Jian Huang, Xi Du, Li Wang, Si-Ping Wei, Lin
‡
Pu*[a][b] and Qin Wang*[a][b]
‡.These authors contributed equally to this work.
Abstract: A chiral amino alcohol-based ligand is found to promote
the highly enantioselective addition of terminal conjugated diynes to
aromatic and aliphatic aldehydes. The easily available C2 symmetric
(R)- and (S)-BINOL in combination with Ti(OiPr)4, Zn powder and EtI
are also found to catalyze the asymmetric 1,3-diyne addition to
aldehydes under mild reaction conditions, which allows the
preparation of both enantiomers of the chiral conjugated diynols with
high enantioselectivity. The resulting optically active conjugated
diynols are found to have potential anticancer activities with
significant differences against HepG2 and HeLa cancer cells, and
remarkable enantioselective cytotoxicity is observed for the first time.
requires enantioselective 1,3-diyne addition to aldehydes to
generate the chiral diynols in a single chemical procedure. A
number of catalytic systems have been reported for the
asymmetric addition of alkynes to aldehydes in the past few
years 11; however the enantioselective addition of diynes as well
as the substrate scope is very limited because of the higher
conjugative stability of the diyne nucleophiles than that of simple
alkynes12-14
.
Chiral amino alcohol and 1,1’-binaphth-2-ol (BINOL)-based
reaction systems have been developed for the enantioselective
addition of diynes. For example, Carreira et al reported the
addition of a diyne to aliphatic aldehydes by using Zn(OTf)2 and
(+)-N-methylephedrine, but it needed a large excess of the chiral
amino alcohol with only moderate enantioselectivity12a. After the
initial report by Carreira, Jiang et al studied the use of several
analogues of (+)-N-methylephedrine15, but little work was done
on developing conditions directly applicable to the diyne addition.
Trost et al demonstrated a catalytic enantioselective diyne
addition to aldehydes by using another chiral amino alcohol
named as (S, S)-ProPhenol in the presence of ZnMe2 and
triphenylphosphine oxide13, but moderate enantioselectivity was
obtained for the addition of buta-1,3-diynyltriisopropylsilane, a
diyne substituted with a triisopropylsilyl (TIPS), to aliphatic
aldehydes with linear or secondary alkyl groups and no result
was reported for the reaction of substituted aromatic aldehydes.
(S)-BINOL in combination with ZnEt2 and Ti(OiPr)4 was found to
catalyze the highly enantioselective addition of various 1,3-
diynes to aldehydes. In this catalytic system, biscyclohexylamine
(Cy2NH) was added to facilitate the deprotonation of a terminal
1,3-diyne to form a nucleophilic diynylzinc16, and this method
was very efficient for synthesizing chiral falcardiol analogues
from buta-1,3-diynyltriisopropylsilane in short steps17. However,
the use of ZnEt2 in this method limits its application in industrial
production due to its moist and air-sensitivity and pyrophoric
property. Recently, we improved this method by using the
BINOL-Ti(OiPr)4 complex to activate the reaction of Zn powder
with EtI, but only the enantioselective simple alkyne addition to
aromatic aldehydes was reported and the use of conjugated
diynes was not examined18. Herein, we report that the chiral
amino alcohol-based ligand, (1S, 2S)-2-N,N-dimethylamino-1-(p-
Introduction
Polyacetylenes are a large group of natural products occurring in
many medicinal and dietary plants1. Among the most biologically
active polyacetylenes, conjugated diacetylenes are important
building blocks because of the unique properties of the
consecutive triple bonds2. In addition, optically active propargyl
alcohols with a stereogenic hydroxyl group are of particular
interest due to the diverse biological activities of these diyne
carbinols3. The interesting bioactivities and therapeutic
potentials of these secondary metabolites from plants have been
increasingly recognized. For example, the chiral conjugated
diynes of the falcarinol type, isolated from Panax ginseng,
notoginseng, carrots, celery and parsley, have exhibited
potential anticancer activities in a mammalian in vivo model,
which may improve human health and well-being4-10. However,
the potentially different cytotoxic effect of the opposite
enantiomers of these conjugated chiral diynols is still unknown.
Using the conventional synthetic methods to prepare the
enantiomers of the chiral conjugated diynols has proved more
challenging2. Usually, they can be prepared by asymmetric
ynone reductions to form chiral propargyl alcohols, followed by
copper-catalyzed
Cadiot-Chodkiewicz
cross-coupling
to
introduce the second acetylene unit 8-9. A shorter pathway
[a]
[b]
Mr. K. Zhang, Dr. C. Zhang, Mr. Z.-H. He, Mr. J. Huang, Ms. X. Du,
Dr. L. Wang, Dr. S.-P. Wei, Prof. Dr. Q. Wang
Department of Medicinal Chemistry, Center for Pharmaceutical
Research and Development, School of Pharmacy
Southwest Medical University, Luzhou, Sichuan 646000, PRC
E-mail: wq_ring@hotmail.com
nitrophenyl)-3-(t-butyldimethyl-silyloxy)
propane-1-ol,
can
promote the highly enantioselective addition of terminal diynes
to aliphatic and aromatic aldehydes. The easily available C2
symmetric (R)- and (S)-BINOL in combination with Ti(OiPr)4, Zn
powder and EtI, can also catalyze the highly enantioselective
1,3-diyne addition to aldehydes under mild reaction conditions.
Moreover, the resulting optically active conjugated diynols are
found to have potential anti-proliferative activities with significant
differences against HepG2 and HeLa cancer cells, and
Prof. L. Pu
Department of Chemistry
University of Virginia, Charlottesville, VA 22904-4319, USA
E-Mail: lp6n@virginia.edu
Supporting information for this article is given via a link at the end of
the document.
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10.1002/cbic.201800458
ChemBioChem
FULL PAPER
remarkable enantioselective cytotoxicity is observed for the most
potent probe molecule.
ee and yield of 59% (Table 1, entry 3). However, further
increasing the amounts of Et3N and Zn(OTf)2 gave reduced
enantioselectivity, though the yield was high (Table 1, entries 4-
7). No obvious improvement in enantioselectivity and yield was
observed for the reaction by varying the reaction time (Entry 8-9)
and temperature (Table 1, entries 11-14) and by using metal
complexes other than Zn(OTf)2 (Table 1, entries 15-16). Thus,
the best results were obtained by using 1.0 equiv of Zn(OTf)2,
1.1 equiv of (1S,2S)-AA3, 1.2 equiv of diyne and 1.5 equiv of
Et3N in CH2Cl2. The configuration of product was determined to
be R by comparing the optical rotation and HPLC data with the
literature.13, 16
Results and Discussion
We first prepared buta-1,3-diynyltriisopropylsilane according to
our previous report (Scheme S1)16-17. In order to investigate the
use of chiral amino alcohols to promote the enantioselective
addition of the 1,3-diyne to aldehydes, we chose an inexpensive
chiral
amino
alcohol
AA1,
(1S,
2S)-2-amino-3-(p-
nitrophenyl)propane-1,3-diol, to synthesize a serials of chiral
ligands AA2-6 (Scheme 1).
Table 1. Optimizing the conditions for the reaction of buta-1,3-
diynyltriisopropylsilane with benzaldehyde promoted by (1S,2S)-AA3[a]
OH
TBDMSC
OTBDMS
OH
OH
N
HCHO
HCOOH
O2N
OH
OH
(1S,2S)-AA3
diyne/aldehyde
(mmol)
Et3N/Zn(OTf)2
(equiv)
Temp
(oC)
Yield
(%)
ee
(%)[g]
Ph
Ph
Ph
N
NH2
Entry
OH
reflux
Ph
Ph
Ph
O2N
O2N
Cl
O
N
(1S,2S)-AA1
n-Butyl Bromide
OH
(1S,2S)-AA2
1
2
1.0/0.5
1.5/0.5
0.6/0.5
0.6/0.5
0.6/0.5
0.6/0.5
0.6/0.5
0.6/0.5
0.6/0.5
1.2/1.0
1.2/1.0
1.2/1.0
1.2/1.0
1.2/1.0
0.6/0.5
0.6/0.5
1.1/1.0
1.1/1.0
1.5/1.0
2.0/3.0
3.0/4.5
4.0/6.0
2.0/3.0
1.1/1.0
1.1/1.0
1.5/1.0
1.5/1.0
2.0/1.0
3.0/1.0
4.0/1.0
1.5/1.0
1.5/1.0
rt
rt
36
25
95
95
95
67
43
36
92
95
95
95
80
70
59
-
O2N
OH
(1S,2S)-AA4
TBDMSC
OTBDMS
OH
3
rt
rt
59
N
N
O2N
O2N
4
80
5
rt
73
(1S,2S)-AA5
(1S,2S)-AA6
6
rt
73
7[b]
8[c]
9[d]
10
11
12
13
14
15[e]
16[f]
rt
72
Scheme 1. Synthesis of chiral amino alcohol ligands (1S, 2S)-AA2-6
rt
20
rt
17
rt
52
We tested the use of these amino alcohol ligands (1S, 2S)-
AA1-6 (1.1 equiv) to promote the reaction of buta-1,3-
diynyltriisopropylsilane (1.2 equiv) with benzaldehyde (0.5 mmol)
in the presence of 1.0 equiv of Zn(OTf)2 and 1.1 equiv of
triethylamine on the basis of the reaction conditions reported
earlier by Jiang et al (Table S1 in SI)15. (1S,2S)-AA3 gave the
corresponding diynol product with an enantiomeric excess (ee)
of 93%, but a poor yield of 21%. Through the screening of
various solvents and Lewis bases (Table S2-3 in SI),
dichloromethane and triethylamine were found to be the most
favourable ones for the reaction promoted by (1S, 2S)-AA3
(Scheme 2).
50
50
50
50
rt
67
19
12
trace
NR
NR
-
rt
-
[a] (1S,2S)-AA3/Zn(OTf)2/Et3N/1,3-Diyne/Benzaldehyde = 1.1/1.0/1.5/1.2/1.0,
DCM (1mL). [b] 2.2 equiv (1S,2S)-AA3. [c] Aldehyde was added after 24h. [d]
Aldehyde was added after 48h. [e] Cu(OTf)2 was used. [f] Co(OTf)2 was used.
[g] Determined by chiral HPLC analysis.
The optimized conditions were applied to the reaction of
diynes with a variety of aromatic and aliphatic aldehydes, and
the results are summarized in Table 2. As shown in Table 2, the
reactions of TIPS-substituted 1,3-diyne with ortho- or meta-
substituted benzaldehydes containing electron-withdrawing or
electron-donating substituents gave the corresponding chiral
conjugated diynols with excellent enantioselectivity (Table 2,
entries 1-4). Especially the optically active conjugated diynols
with halogenated phenyl group at the 2-position were obtained
for the first time with high enantioselectivity and yield (Table 2,
entries 1-3). We tried to synthesize the conjugated diynols with
electron-withdrawing group at the 3-position and 4-position of
Scheme 2. Enantioselective addition of buta-1,3-diynyltriisopropylsilane to
benzaldehyde promoted by (1S, 2S)-AA3
Table 1 summarizes our further optimization of the reaction
conditions promoted by (1S,2S)-AA3, It was found that the
ratios of the diyne versus aldehyde and Et3N versus Zn(OTf)2
were also crucial for the reaction as shown in Entry 1-10.
Increasing the amounts of Et3N and Zn(OTf)2 to 1.5 and 1.0
equiv and maintaining the ratio of the diyne versus aldehyde
each at 0.6/0.5 mmol gave improved enantioselectivity of 95%
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10.1002/cbic.201800458
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FULL PAPER
phenyl ring in the presence of the chiral amino alcohol ligand,
but only low yields of the products were observed. High
enantioselectivity and high yield were also observed for the
alkyne addition to -branched aliphatic aldehydes (Table 2,
entries 5-7). We investigated the catalytic asymmetric addition of
another diyne containing a linear alkyl group to aldehydes
(Table2, entries 8-14). Excellent enantioselectivities were also
achieved for the linear diyne addition to the - and -branched
aliphatic aldehydes (Table 2, entries 8-12), as well as the
substituted benzaldehydes (Table 2, entries 13-14).
the primary structure-activity relationship showed that the
observed inhibitions in cancer cells were influenced mostly by
hydroxyl groups of the conjugated diynols.6 Thus, with the
synthetically optically active diynols in hand, we evaluated their
antiproliferative effects on HepG2 and HeLa cancer cells. Since
the natural falcarinol exhibited no cytotoxicity toward HepG2
cancer cells with an undetectable IC50 value, 9 we selected 5-
fluorouracil (5-FU) as a positive control (Table S4-5), which
currently is widely used in clinical therapeutics as an anticancer
drug.
Table 2. Addition of diynes to various aldehydes in the presence of the amino
alcohol ligand (1S,2S)-AA3, Zn(OTf)2 and Et3N[a]
Table 3. Anticancer activities (HepG2 and HeLa Cell) of the Enantiomers 1-
14 obtained from the 1,3-diyne addition to aldehydes by using (1S,2S)-AA3[a]
ee(%)[b]
96
Entry
20[c]
IC50 of HepG2
(uM) [b]
IC50 of HeLa
(uM) [b]
Entry
1
Yield(%)
99
Aldehyde
1,3-diyne
[]D
Enantiomer
-18.9
1
2
3
4
165.6±1.1
110.9±1.0
118.3±1.0
290.9±1.0
115.8±1.1
94.7±1.0
92.2±1.0
136.3±1.0
1S
2S
3S
4R
2
3
82
80
92
93
-63.8
-67.6
4
5
60
93
98
97
5.5
-17.0
5
6
340.7±1.0
282.2±1.0
165.0±1.1
166.2±1.0
6
98
93
-6.0(R)
5R
6R
7
8
94
94
97
98
-5.5(R)
5.7
7
8
291.8±1.0
474.1±1.0
461.6±1.0
>500
240.4±1.0
332.5±1.0
330.2±1.0
465.1±1.0
431.3±1.0
9
87
96
5.2
7R
8R
10
11
75
79
92
96
-2.4
9
-12.8
9R
-
10
11
12
87
93
10R
12.7(R)
342.4±1.0
13
14
64
80
93
94
3.1
11R
11.1
12
378.1±1.0
382.4±1.0
12R
13R
14R
13
14
201.8±1.0
103.0±1.1
130.2±1.0
109.7±1.0
[a] (1S, 2S)-AA3 / Zn(OTf)2 / Et3N / Diyne / Aldehyde = 1.0/1.0/1.5/1.2/1.0 in
CH2Cl2 (1mL). [b] Determined by chiral HPLC analysis. [c] The product
configuration in parentheses was determined by comparison with results
reported in the references 12, 13 and 16.
[a] Four replicate wells were tested per assay which was repeated three
times. [b] The average IC50 value of 5-fluorouracil was 128.2±1.1 uM in
HepG2 cells and 19.5±1.2 uM in HeLa cells.
It was reported that certain polyacetylenes from medicinal and
dietary plants have showed potential anti-proliferation activity
against certain cancer cell lines such as human hepatocellular
carcinoma HepG2 and cervical cancer HeLa cell lines6-9. Recent
toxicological and pharmacological studies have demonstrated
that these polyacetylenes can alkylate cysteine (Cys) residue of
the active site in certain targeted proteins of cancer cells via
direct thiol addition to the conjugated triple bond.4-5 Furthermore,
As shown in Table 3, the 14 enantiomers exhibited various
degree of antiproliferative effects on HepG2 and HeLa cancer
cells at the adopted concentrations (1-500 μM), and only the
enantiomer 10R was not observed to inhibit the HepG2 cancer
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10.1002/cbic.201800458
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FULL PAPER
cell growth (Table 3, entry 10). Generally, the enantiomers 1-3
(Table 3, entries 1-3) of the TIPS-substituted diynols containing
the electron-withdrawing halogen substituents displayed higher
activity against HepG2 and HeLa cancer cells than the
enantiomers 4-7 (Table 3, entries 4-7) of the other TIPS-
substituted diynols and the enantiomers 8-13 (Table 3, entries 8-
13) of the linear alkyl diynols. In HepG2 cells, the enantiomer 2S
(Table 3, entry 2) of the TIPS-substituted diynols showed an
IC50 value of 110 uM which is comparable with the other
substrates containing halogen-substituted aromatic rings, while
the enantiomer 14R (Table 3, entry 14) with an IC50 value of
103 uM possessed better anti-cancer activity than all the other
linear alkyl diynols. In comparison with the average IC50 value
of 5-fluorouracil (128 uM, Table S4 in SI) in HepG2 cells, the
enantiomers 2S, 3S and 14R may be used as promising
compounds for further investigation. In HeLa cells, although anti-
proliferation activity of the enantiomers 2S, 3S and 14R (Table
3, entries 2, 3 and 14) gave a low IC50 value of 94 uM, 92 uM
and 109 uM respectively, 5-fluorouracil exhibited better cytotoxic
activity with a relatively constant IC50 value of 19 uM (Table S4
in SI).
proliferation effect on HepG2 cells than its enantiomer 14R
(Table 3, entry 14) with IC50 value of 103 uM, and the cytotoxic
activity against HeLa cells of compound 3R (Table 4, entry 3)
was less than that of its enantiomer 3S (Table 3, entry 3). These
results demonstrate that one enantiomer of the chiral diynols is
more potent than the other. This is the first investigation on the
enantioselective cytotoxicity of the chiral conjugated diynols
toward HepG2 and HeLa cells.
Table 4 Highly enantioselective synthesis of chiral conjugated diynols by using
BINOL and Ti(OiPr)4 in combination with Zn and EtI and their anticancer
activities
IC50 (uM) [c]
20
Entry
Product[a]
ee(%)[b]
[]D
HepG2
HeLa
1
2
91
93
+25.5
+60.9
365.9±1.0
290.4±1.0
1R
2R
232.4±1.0
326.5±1.0
Besides the amino alcohol-based compound (1S,2S)-AA3, we
also studied the use of the (R)- and (S)-BINOL-based catalyst
system for the enantioselective addition of 1,3-diynes to
aldehydes to prepare both enantiomers of the chiral diynols
(Scheme 3).19 The optimized conditions for this reaction
includes the use of 5.1 mmol Zn powder, 10.2 mmol EtI, 0.34
mmol (R)-BINOL, 0.85 mmol Ti(OiPr)4, 1 mmol alkyne and 0.5
mmol aldehyde in THF and diethyl ether.
3
4
91
94
+68.0
-10.4
177.0±1.0
234.6±1.1
138.1±1.0
188.5±1.0
3R
14S
[a] (R)-BINOL was used. [b] Determined by chiral HPLC analysis. [c] Four
replicate wells were tested per assay which was repeated three times, the
average IC50 value of 5-fluorouracil was 135.2±1.1 uM in HepG2 cells and
18.7±1.3 uM in HeLa cells.
We also studied the anticancer activity against HepG2 and
HeLa cells by using the conjugated diynols with various
enantiomeric compositions. In the experiments, the (S)- and (R)-
isomers of a conjugated diynol were mixed at certain ratios, and
the toxicity of the resulting mixtures including a racemic mixture
toward HepG2 and HeLa cells was evaluated separately. As
shown in Figure 1a and 1b, a linear relationship between the
IC50 value and the enantiomeric composition of the conjugated
diynols 14 and 3 was obtained for the anticancer activity against
HepG2 and HeLa cells respectively. The observed linear
relationship suggests that the chiral propargyl alcohol might
dominate the stereo-selective inhibition presumably by binding
to a Cys residue of the active site to form a diastereomeric vinyl
sulphide. These results can provide clues to further design and
optimize the conjugated diynols for the desired anticancer
activity.
Scheme 3. Asymmetric synthesis of chiral conjugated diynols by 1,3-diyne (2
eq) addition to aldehydes (1 eq) in the presence of Zn (10.2 eq), EtI (20.4 eq),
(R) or (S)-BINOL (0.34 eq) and Ti(OiPr)4 (1.7 eq)
Using (R)-BINOL allowed us to obtain compounds 1R, 2R, 3R
and 14S with high enantiomeric purity as shown in Table 4.
These compounds are the opposite enantiomers of the products
obtained by using (1S,2S)-AA3. Recently, Sieber et al reported
that a falcarinol-based probe molecule can be used as a
selective tool to target a specific protein in cancer cells, in which
a conserved preference of a chiral propargyl alcohol by
irreversibly binding to Cys of the active site was observed with
sterically selective catalytic inhibition.9 In order to investigate
whether there is stereo-selective cytotoxic activity against
HepG2 and HeLa cancer cells, we studied the anticancer activity
of the enantiomers 1R, 2R, 3R and 14S against HepG2 and
HeLa cells (Table 4, entries 1-4 and Table S5 in SI). It was
found that these newly prepared chiral diynols showed much
greater IC50 values than those of their opposite enantiomers
respectively (Table 4). For example, compound 14S (Table 4,
entry 4) with an IC50 value of 234 uM had weaker anti-
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10.1002/cbic.201800458
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fetal bovine serum, 100 U/mL penicillin and 100 mg/mL streptomycin.
Cells were maintained in a humidified 5% CO2 incubator at 37 oC.
Typical procedure for asymmetric diyne addition into
aldehydes by using amino alcohol ligand (1S, 2S)-AA3
Under argon atmosphere, zinc trifluoromethanesulfonate (0.5 mmol, 1
equiv.) was added to a 25 mL round-bottom flask equipped with magnetic
stirrer. Then ligand (1S, 2S)-AA3 (0.55 mmol, 1.1 equiv.), triethylamine
(0.75 mmol, 1.5 equiv.) and an alkyne (0.60 mmol, 1.2 equiv.) were
added to the flask via syringe in portions. After the mixture was dissolved
in CH2Cl2 (1 mL) and stirred at rt for 0.5 h, an aldehyde was added (0.5
mmol, 1 equiv.). After stirred for 24 h, the reaction solution was quenched
with aqueous saturated ammonium chloride (1 mL). Then, the solution
was extracted with CH2Cl2 (2 × 25 mL), dried over Na2SO4, filtered and
concentrated in vacuum. The crude product was purified by column
chromatography on silica gel.
Figure 1. The anticancer activity against a) HepG2 cells for the conjugated
diynol 14 and b) HeLa cell for the conjugated diynol
3 with various
enantiomeric compositions [ee = (R − S)/(R + S), and red lines are linear
fitting].
Conclusions
Typical procedure for asymmetric diyne addition into
aldehydes by using ligand (R)- and (S)-BINOL
In conclusion, we have developed highly enantioselective
syntheses of chiral conjugated diynols by using the chiral amino
alcohol as well as the BINOL ligand systems to promote the
asymmetric 1,3-diyne addition to aldehydes under very mild
reaction conditions. These optically active conjugated diynols
have exhibited potential anticancer activities against HepG2 and
HeLa cancer cells. The enantioselective cytotoxicity effect on
HepG2 and HeLa cells for the (R)- and (S)-enantiomers was
observed for the first time, and the observed linear relationship
between the IC50 values and the enantiomeric composition
should be helpful in designing new chiral conjugated diynols for
anticancer activity.
Under argon atmosphere, Zn powder (5.1 mmol, 10.2 equiv.) and (R)- or
(S)-BINOL (0.34 mmol, 0.68 equiv.) were added to a 25 mL flask
equipped with a mechanical stirrer. Then EtI (10.2 mmol, 20.4 equiv.),
Ti(OiPr)4 (0.85 mmol,1.70 equiv.) and an alkyne (1 mmol, 2 equiv.) were
added dropwise via syringe. After 5 min, THF (1 mL) was added and the
mixture was stirred at rt for 24 h. Then diethyl ether (15 mL) was added,
followed by the addition of an aldehyde (0.5 mmol, 1equiv.). The reaction
mixture was stirred for 12 h, and then it was quenched with aqueous
saturated NH4Cl (5 mL). The solution was extracted with methylene
chloride (4 × 50 mL), and the combined organic phase was dried over
Na2SO4, filtered and concentrated under reduce pressure. The crude
residue was purified by column chromatography on silica gel to afford the
corresponding compound.
Experimental Section
Anticancer activities of chiral conjugated diynols
Preparation of 1,3-diynes, synthetic procedures for chiral amino alcohol
ligands, optimization of conditions for the reaction of 1,3-diynes with
aldehydes, and supplementary schemes, tables and figures can be found
in the Supporting Information.
The viability of cells was measured by a colorimetric CCK8 assay.
Cultured cells were counted and suspended in DMEM and RPMI1640
medium. 96-well plates were seeded at concentrations of 7000 and 5000
cells/well (180 L medium) for HepG2 and Hela cell lines respectively
and then preincubated for 24 h. Each compound was dissolved in DMSO
to produce a 0.2 mol/L stock solution. Serial dilutions were performed
(with the addition of DMEM and RPMI1640 medium for HepG2 and Hela
cell lines respectively) to produce final ligand concentrations ranging from
300-500 µmol/L. Compounds diluents were added at 20 µL per well ,
followed by incubation for 48 h at 37 oC in a humidified atmosphere of 5%
CO2. Then, the medium was removed and replaced with 100 µL 10%
CCK8 (V/V) per well, followed by 30 min incubation at 37 °C. The
absorbance was recorded at 450 nm using Thermo Multiskan Spectrum
microplate reader. The results were expressed as ratio of absorbance
between treatments and control cells (solvent vehicle set at 100%). Four
replicate wells were tested per assay which was repeated three times.
IC50 values (concentration resulting in 50% inhibition) were calculated
using GraphPad Prism (San Diego, CA).
General procedure and materials
All reactions are performed under inert gas conditions unless otherwise
specified. The chemicals we used are commercially available and can be
used directly without purification. Methylene chloride, tetrahydrofuran and
diethyl ether are purified by Mbraun SPS-800-Systems, other solvents
are dried by the standard methods prior to use. The NMR data we
obtained were recorded on a Bruker TM400 NMR spectrometer. HPLC
analyses were operated on the Waters 1525 by using Diacel Chiralcel
OD, Chiracel AD-H and Chiralcel AS columns, and were detected at
254nm or 220nm by the Waters 2487. Optical rotations were obtained
using a Hanon P810/P850 automatic polarimeter with a sodium 589.3 nm
filter. For anticancer activities of chiral conjugated diynols, DMSO,
Penicillin, Streptomycin was purchased from Sigma-Aldrich. DMEM
medium with high glucose and RPMI1640 medium were purchased from
Gibco. Human hepatocellular liver cell lines (HepG2) and human cervical
carcinoma cell lines (HeLa) were obtained from the Institute of Cell
Biology, Academic Sinica (Shanghai, China). HepG2 Cells were cultured
using DMEM medium with high glucose supplemented with 10% fetal
bovine serum, 100 U/mL penicillin and 100 mg/mL streptomycin. Hela
cells were cultured using RPMI1640 medium supplemented with 10%
Acknowledgements
This project is supported by the National Natural Science
Foundation of China (No. 21072088), the Program for New
Century Excellent Talents in University (NCET-10-0945), the
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10.1002/cbic.201800458
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Keywords: enantioselective synthesis; anticancer activities;
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10.1002/cbic.201800458
ChemBioChem
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Entry for the Table of Contents (Please choose one layout)
Text
Highly enantioselective syntheses of chiral conjugated diynols are developed by using chiral amino alcohols and BINOL to
promote the asymmetric 1,3-diyne addition to aldehydes. The resulting conjugated diynols are found to have potential
anticancer activities against HepG2 and HeLa cancer cells, and remarkable enantioselective cytotoxicity is observed for the
first time.
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FULL PAPER
Ke Zhang, Chun Zhang, Zhong-Hong
He, Jian Huang, Xi Du, Li Wang, Si-Ping
Wei, Lin Pu* and Qin Wang*
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Highly Enantioselective Synthesis
and Anticancer Activities of Chiral
Conjugated Diynols
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