Syntheses and biological evaluation of C-30-N-acyl modified taxane analogues from 1-deoxybaccatin-VI

Article abstract of DOI:10.1016/j.ejmech.2015.09.019

A series of side-chain modified taxane analogues were synthesized and their in vitro anticancer activities against four human cancer cell lines: MDA-MB-231 (human breast cancer), PC-3 (human prostatic cancer), HepG2 and H460 (human hepatoma) were studied.

Full text of DOI:10.1016/j.ejmech.2015.09.019

European Journal of Medicinal Chemistry 104 (2015) 97e105
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
0
Syntheses and biological evaluation of C-3 -N-acyl modified taxane
analogues from 1-deoxybaccatin-VI
*
Qing-Feng Li, Hai-Xia Lin , Yong-Mei Cui, Pei-Pei Xu
Department of Chemistry, College of Sciences, Shanghai University, 99 Shangda Road, Baoshan District, Shanghai 200444, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 November 2014
Received in revised form
A series of side-chain modified taxane analogues were synthesized and their in vitro anticancer activities
against four human cancer cell lines: MDA-MB-231 (human breast cancer), PC-3 (human prostatic
cancer), HepG2 and H460 (human hepatoma) were studied. The three hydroxyl groups at C-7, C-9 and C-
10 September 2015
10 enable the behavior of these compounds to be evidently distinct from other similar compounds. The
Accepted 12 September 2015
Available online 28 September 2015
strong cytotoxicity in the four cell lines showed by the newly synthesized taxane analogues 13a and 13d
indicated them as potential lead compounds for anticancer drug design.
©
2015 Elsevier Masson SAS. All rights reserved.
Keywords:
Paclitaxel
Taxane analogues
In vitro anticancer activity
MDA-MB-231
PC-3 and HepG2 and H460 cell lines
1
. Introduction
[14,15], Kingston synthesized several 1-deoxybaccatin-VI ana-
logues and reported that compound 4 (Fig. 1) (IC50 ¼ 0.0315 M)
had an IC50 value 11-fold greater than that of paclitaxel
M) in the HCT116 cell line evaluated [16]. In our
previous study, we also presented the detailed design and synthesis
of 1-deoxypaclitaxel [17]; in the A549 cell line evaluated by us 1-
m
Paclitaxel 1 (Fig. 1), a diterpenoid natural compound was iso-
lated from the stem bark of Taxus brevifolia, has preeminent anti-
tumor activities against a range of cancers, including breast,
ovarian, germ cell, lung and esophageal cancers [1e5]. The activity
is believed to be related to its binding to polymerize tubulin, to
promote microtubule assembly and to stabilize microtubule by
bundle formation [6]. Numerous structure-activity-relationship
studies (SARs) indicated that the C-13 side chain is an indispens-
able part for its antitumor activity, Ojima et al. synthesized a variety
of C-3 -N-acyl modified paclitaxel analogues by employing
tam four-membered ring which can be coupled to baccatin III
through coupling reaction as a side chain precursor to produce
paclitaxel analogues. Respectively, these C-3 -N-acyl (2-furyl, 2-
thienyl, p-fluorophrnyl and p-methoxyphenyl) modified pacli-
taxel analogues exhibited similar or lower IC50 comparing with
paclitaxel against J774.1 and J7.DEF3 [7e9]. The structure-activity-
relationship studies (SARs) also showed that the 1-hydroxyl
group is not crucial for the tubulin assembly activities of pacli-
taxel [10e13].
(IC50 ¼ 0.0028
m
deoxypaclitaxel 5 (Fig. 1) (IC50 ¼ 0.062
m
M) had an IC50 value 10-
fold greater than that of paclitaxel (IC50 ¼ 0.0063
m
M). According
to the two studies, both of the two compounds indicated a signif-
icant loss in cytotoxicity. However, in our further investigation of 1-
deoxypaclitaxel analogues [18], we discovered that compound 6
(Fig. 1) (IC50 ¼ 0.11 ng/mL) had the same IC50 value as that of
paclitaxel (IC50 ¼ 0.13 ng/mL) in the A2780 cell line evaluated,
while this compound (IC50 ¼ 0.18 ng/mL) even had an IC50 value
1.6-fold lower than that of paclitaxel (IC50 ¼ 0.29 ng/mL) in the
A549 cell line evaluated. Compared to the compound 4 and 1-
deoxypaclitaxel 5, compound 6 is structurally distinctive due to
the three hydroxyls at the C-7, C-9 and C-10 positions.
0
b-lac-
0
As an ongoing part of our research on 1-deoxypaclitaxel ana-
logues [17,18], we have become interested in developing the syn-
theses and biological activities of a series of 1-deoxypaclitaxel
0
Starting from 1-deoxybaccatin-VI 3 (Fig. 1), which is readily
available from Taxus chinensis, Rehd. Var. mairei in good yield
analogues bearing different substituted groups at the C-3 -N-Acyl
position and three hydroxyls at the C-7, C-9 and C-10 positions from
1-deoxybaccatin VI. The activities of these newly synthesized
compounds against four cancer cell lines and cell survival data are
reported in this paper.
*
Corresponding author.
E-mail address: haixialin@staff.shu.edu.cn (H.-X. Lin).
http://dx.doi.org/10.1016/j.ejmech.2015.09.019
223-5234/© 2015 Elsevier Masson SAS. All rights reserved.
0

98
Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
dimethoxypropane gave compound 8, in which only two hy-
droxyls remained at the C-7 and C-13 positions after deprotection.
However, the C-13 hydroxyl group is more active compared with
the C-7 hydroxyl group due to the huge stereo-hindrance effect on
the C-7 hydroxyl group caused by the acetal protection at the C-9
and C-10 positions. Therefore, the corresponding carboxylic acid
can be immediately coupled with compound 8 by the DDC-DMAP
method in toluene.
The key step is the synthesis of the corresponding carboxylic
acid, starting from commercially available material (2R,3S)-3-
Phenylisoserine
9 with natural configuration as outlined in
Scheme 1. Compound 9 was first transformed into 10a-f after
protection of the amine moiety by the acyl chloride and formation
of the methyl ester. The next cyclic protection used 4-methoxy
benzaldehyde dimethyl acetal in the presence of a catalytic
amount of pyridinium p-toluenesulfonate (PPTS), yielding com-
pounds 11a-f. Compounds 11a-f, after saponification to the corre-
sponding carboxylic acid without further purification, were then
coupled with compound 8 in the present of DCC and DMAP to
smoothly provide the corresponding cyclic ester intermediates
12a-f with good to excellent yield (80e91%). After hydrolysis of the
Fig. 1. Paclitaxel and 1-deoxybaccatin III analogues.
two acetonide protecting groups under strongly acidic conditions,
the final products 13a-f were afforded (Scheme 2).
2
. Results and discussion
Further investigation of the modification of the side chain
revealed it is difficult to modify the C-3-N’-acyl position using the
corresponding alkanoic acid, such as n-hexylic and n-butyric acid,
through the DDC-DMAP coupling method. However, the novel
2.1. Chemistry
0
As previously reported, paclitaxel side chains were synthesized
taxoid bearing a n-hexane group at the C-3-N -Acyl position was
by different methods [19e26]. In this study, we applied the method
which was recently described by Yoshio Hayashi et al. [25,26] to
synthesize the oxazoline side chain precursor by using (2R,3S)-3-
Phenylisoserine 9 with natural configuration (Scheme 1).
The synthesis of compounds 13a-f is shown in Scheme 1. The
starting material 1-deoxybaccatin VI 3 was selectively deacetylated
at the C-7, C-9, C-10 and C-13 acetoxyl groups without concomitant
deacylation of the C-2 and C-4 acyloxy groups. Subsequent
protection of the C-9 and C-10 hydroxyl groups using 2,2-
reported to exhibit excellent antitumor activities [27], which
interested us in the design and synthesis of n-hexanoyl-modified 1-
deoxypaclitaxel analogues via a
b-lactam four-membered ring-
opening coupling protocol [28e32]. The synthesis of the compound
18 is illustrated in Scheme 2. Starting from the commercially
available
the hydroxyl group of
thylsilyl (TES) ether afforded 3-OTES-
b
-lactam 14 with high enantiomeric purity, protection of
-lactam 14 at low temperature as a trie-
-lactam 15 in 76% yield.
b
b
Treatment of 3-OTES-
b-lactam 15 with n-hexanoyl chloride in
ꢀ
Scheme 1. Reagents and conditions: (a) NH
2
NH
2
$H
2
O, EtOH, rt, 82%; (b) 2,2-dimethoxypropane, montmorillonite K10, CH
2
Cl
2
, rt, 97%; (c) SOCl
2
, MeOH, 0 C to rt, overnight; (d)
ꢀ
ꢀ
ꢀ
carbonyl chloride, THF, sat. NaHCO
3
, 0 C to rt, 3 h; (e) 4-methoxybenzaldehyde dimethyl acetal, PPTS, toluene, 110 C, 90%; (f) (1) KOH, MeOH, rt, 2 h; (2) DCC, DMAP, CH
2
Cl
2
, 50 C,
2
h; (g) PTS, MeOH, rt, 5 h, 20e30%.

Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
99
ꢀ
, 0 ꢀC to rt, 65%; (c) 16, NaHMDS, THF, ꢁ30 ꢀC; then 0.04 N HCl, CH
Scheme 2. Reagents and conditions: (a) TESCl, imidazole, CH
2
Cl
2
, 0 C to rt, 87%; (b) NEt
3
, RCOCl, CH
2
Cl
2
3
OH, rt,
ꢀ
50%; (d) 0.04 N HCl, CH
3
OH, 60 C, 92%.
dichloromethane for 2 h at room temperature afforded N-hex-
anoyl- -lactam 16. The coupling of compound 8 with N-hexanoyl-
-lactam 16 was carried out under standard conditions using
inhibitory activity with IC50 values in the range of 0.004e0.09
except for compounds 13e, 17 and 20c.
m
M
b
0
b
The notable compound 18 with alkyl substituents at the C-3 -N
also showed potent cytotoxicity against the two human cancer cell
lines. In comparison with the compound 17, compound 18 has the
three hydroxyl groups at the C-7, C-9 and C-10 positions instead of
the acetal group of compound 17. In the two cell lines evaluated by
us, compound 18 had IC50 values that were, on average, 0.1-fold and
0.05-fold lower than that of compound 17. Interestingly, compound
20 in general had an IC50 values 270-fold and 30-fold greater than
that of compound 18 in the MDA-MB-231 cell line and the PC-3 cell
line evaluated, respectively. The results are consistent with our
previous report and Kingston's investigations [13e15]. As illus-
trated by the results above, it was evident that these 1-
dexoypaclitaxel analogues with three hydroxyls at the C-7, C-9
and C-10 positions have an obvious advantage in cytotoxicity.
The doseeresponse curves for paclitaxel and compounds 13a-f,
17 and 18 are shown in Fig. 2. All exponentially growing human
tumor cell lines exposed for 72 h to paclitaxel and the compounds
formulated in DMSO solution (MTT method) exhibited character-
istic doseeresponse curves. In the two cell lines evaluated, the
maximal antiproliferative response to either paclitaxel or 18 was
40e50% inhibition of cell survival by 72 h; thus, the efficacy of both
compounds was equivalent. However, the maximal reduction in
cell survival elicited by other compounds (13a-f) in a 72 h incu-
bation was approximately 90e99%, as shown in Fig. 2.
ꢀ
LiHMDS in THF at ꢁ40 C, followed by deprotection with 0.3 N HCl/
CH
3
OH, to afford the corresponding new taxoid 17 (Scheme 2).
ꢀ
Finally, compound 17 was treated with 0.3 N HCl at 60 C for 6 h to
obtain product 18.
To compare with these compounds 13a-f, 17 and 18 with three
hydroxyl groups on the parent skeleton, we also became interested
in the synthesis of the compound 20, as presented in Scheme 3.
Starting from compound 19, which was reported in our previous
work [17], compound 20 was successfully synthesized by the b-
lactam four-membered ring-opening coupling protocol which is
illustrated in detail above.
2
2
.2. Cytotoxicity assay
.2.1. Cytotoxicity to MDA-MB-231 and PC-3 cell lines
The in vitro antitumor activities of the newly synthesized com-
pounds 13a-f, 17, 18 and 19 were evaluated in a cytotoxicity assay
employing MDA-MB-231 (human breast cancer cells) cell line and
PC-3 (human prostatic cancer cells) cell line by MTT method. The
inhibitory activities (IC50) are summarized in Table 1.
As reported in Table 1, it was observed that most of compounds
exhibited similar cytotoxicities against two human cancer cell lines
in comparison with paclitaxel. In particular, 1-dexoypaclitaxel an-
alogues 13d was about as active as paclitaxel in both cell lines with
In MDA-MB-231 cell lines, all of the compounds exhibited
greater inhibition of cell survival than paclitaxel when the con-
IC50 values in the range of 0.001e0.004 mM. Although most of the
newly synthesized compounds showed similar antitumor activities,
some compounds exhibited selectivity between the two human
cancer cell lines. For the MDA-MB-231 cell line, the 3 -N-
centration was 10e100
pounds exhibited better efficacy at this range of concentration
(10e100 M) than paclitaxel. Generally speaking, the newly syn-
thesized compounds can effectively inhibit the growth of MDA-MB-
231 tumor at this range of concentration (10e100 M); the inhi-
bition was similar in the PC-3 cell lines. Interestingly, most of the
mM. This implied that each of the com-
0
m
substituted 1-dexoypaclitaxel analogues 13a, 13b, 13d and 18 were
about as active as paclitaxel with IC50 values less than 0.001
mM. In
m
the PC-3 cell line, all the compounds displayed the similar
Scheme 3. Reagents and conditions: (a) 16, NaHMDS, THF, ꢁ30 ꢀC; 0.04 N HCl, CH
3
OH, rt.

100
Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
Table 1
Cytotoxicity (IC50a) values for paclitaxel and its analogues 13a-f, 17e18 and 21a-b.
plateau in survival at concentrations of above 0.001e1 mM; no
additional obvious cytotoxicity was observed in any of the cell lines
exposed to paclitaxel for 72 h in the concentrations range from
Compounds
MDA-MB-231b PC-3c
IC50 M) IC50 (mM)
0
.001 to 10
greater inhibition of cell survival even at low concentrations
0.001 M), especially in MDA-MB-231, as shown in Fig. 2(a). The
mM. It is notable that some compounds still exhibited
(m
1
1
1
1
1
1
1
1
2
3a
3b
3c
3d
3e
3f
7
<0.001
<0.001
0.03
<0.001
1.26
0.02
0.01
<0.001
0.27
0.01
0.02
0.09
0.004
1.63
0.07
0.21
0.01
0.33
(
m
three hydroxyl groups at the C-7, C-9 and C-10 positions are a
possible explanation of this phenomenon.
2.2.2. Cytotoxicity to HepG2 and H460 cell lines
As we known, though paclitaxel has been used to in treatment
8
0
against breast, ovarian, germ cell, lung and esophageal cancers
[1e5], few paclitaxel analogues have been used to against to he-
patic carcinoma. In our study, however, we found that the newly
synthesized taxane analogues also had good activity to against
hepatic carcinoma. As shown in Table 2, the cytotoxicity of pacli-
taxel and its analogues against hepatic carcinoma were evaluated
by CCK-8 method employing HepG2 and H460 cell lines. As re-
ported in Table 2, compounds 13a and 13d indicated more potent
cytotoxicity activities than that of paclitaxel in the assay, especially
compound 13a which exhibited excellent cytotoxicity activities in
both cell lines. This result, which has important implications for
curing other cancers such as liver cancer, indicated that the newly
synthesized taxane analogues 13a and 13d showed outstanding
cytotoxicity activities in MDA-MB-231 and PC-3 cell lines as well as
in hepatic carcinoma cell lines.
Paclitaxel
<0.001
<0.001
a
Cytotoxicity (IC50) was assayed by MTT method under growing human tumor
cell lines were exposed for 72 h.
b
Human breast cancer cell line.
Human prostatic cancer cell line.
c
compounds also exhibited greater inhibition of cell survival than
that of paclitaxel when the concentration was 100 mM and showed
similar inhibition of cell survival at lower concentrations
(
0.001e1 mM) in the two cell lines. This curve demonstrated a
3. Conclusion
In summary, a series of polyhydroxy taxane derivatives were
synthesized and their cytotoxicities were evaluated. The new tax-
0
oids bearing different substituted groups at the C-3 -N-Acyl posi-
tion showed degrees of cytotoxicity which differed significantly.
Most of the compounds exhibited potent cytotoxicity to the MDA-
MB-231 (human breast cancer cells) cell line and PC-3 (human
prostatic cancer cells) cell line and exhibited greater inhibition of
cell survival than paclitaxel when the concentration was
10e100 mM in the two cell lines. Compounds 13a, 13d and 18
exhibited excellent cytotoxicity in MDA-MB-231 and PC-3 cell lines
as well as hepatic carcinoma cell lines. The IC50 values of compound
20 and compound 18 illustrated obviously the advantage of three
hydroxyl groups at the C-7, C-9 and C-10 positions. Further modi-
fications of these and other lead structures with the aim of
improving the potency in vitro as well as the efficacy in vivo are in
progress.
4. Experimental section
4.1. General chemical procedures
Commercially available reagents were purchased and were used
1
without further purification unless otherwise mentioned. H NMR
Table 2
Cytotoxicity (IC50a) values for paclitaxel and its analogues 13a, 13d against hepatic
carcinoma.
Compounds
HepG2b
IC50 M)
H460c
IC50
(
m
(
m
M)
1
1
3a
3d
0.567
2.02
1.217
0.199
0.289
4.287
Paclitaxel
a
Cytotoxicity (IC50) was assayed by CCK-8 method under which growing human
tumor cell lines were exposed for 48 h.
Fig. 2. Survival of two human tumor cell lines after exposure to compounds and
paclitaxel for 72 h. (a) MDA-MB-231 (human breast cancer) cell line; (b) PC-3 (human
prostatic cancer) cell line.
b
HepG2 hepatoma cell lines.
c
H460 hepatoma cell lines.

Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
101
and 13C NMR spectra were recorded on a Bruker Avance (500 MHz)
spectrometer in CDCl or DMSO-d , unless otherwise noted.
pressure, resulting in an oil. To a solution of the resulting oil in a
mixture of THF (10 mL) and saturated NaHCO (10 mL), one of a
3
6
3
Chemical shifts are reported in parts per million (ppm) and
coupling constants (J) are reported in Hertz (Hz). Coupling patterns
are described by abbreviations: s (singlet), d (doublet), t (triplet), m
series of different carbonyl chlorides (3 mmol) was added drop-
wise at 0 C, respectively. The whole mixture was stirred vigor-
ously at room temperature for 3 h. The desired compound was
ꢀ
(
multiplet) and br (broad). Chemical shifts in CDCl
3
were reported
(7.26 ppm) for H NMR, and to CDCl
77.16 ppm) for 13C NMR, as internal references. The center line of
2 4
extracted with EtOAc. The organic solution was dried over Na SO
1
in the scale relative to CHCl
(
the multiplets of DMSO-d was defined as 2.50 for H NMR. Mass
6
spectra were recorded using an EI source (Agilent 5975N instru-
ment). Silica gel plate GF254 was used for thin layer chromatog-
raphy (TLC) and silica gel H or 300e400 mesh was used for flash
column chromatography. Yields are shown in terms of those of
isolated pure materials.
3
3
and the solvent was evaporated under reduced pressure, and the
resulting oil was purified by silica gel column chromatography
(EtOAc: hexane ¼ 1:3), yielding a product 10 (80e90%).
1
ꢀ
4.2.3.1. Compound 10a. White solid; m.p.: 141e146 C; Yield: 80%;
1
3
H NMR (500 MHz, CDCl ) d (ppm): 3.85 (s, 3H), 3.87 (s, 3H), 4.65 (s,
1H), 5.74 (d, J ¼ 9.3 Hz, 1H), 6.94 (d, J ¼ 8.0 Hz, 3H), 7.32 (t,
J ¼ 15.3 Hz, 1H), 7.38 (t, J ¼ 15.2 Hz, 2H), 7.47 (d, J ¼ 8.0 Hz, 2H), 7.76
1
3
(
d, J ¼ 8.0 Hz, 2H); C NMR (125 MHz, CDCl
3
) d (ppm): 29.70, 53.29,
4
4
.2. Synthetic procedures
54.81, 55.44, 73.31, 113.84, 126.27, 126.89, 127.91, 128.54, 128.75,
28.93, 138.86, 162.71, 166.38, 173.43.
1
.2.1. Synthesis of 7,9,10,13-tetradeacetyl-1-deoxybaccantin 7 [18]
Compound 3 (3 g, 1.0 mmol) was dissolved in 95% ethanol
ꢀ
4.2.3.2. Compound 10b. White solid; m.p.: 150e157 C; Yield: 85%;
ꢀ
1
(
40 mL) and treated with hydrazine hydrate (86 mL) at 26 C for
H NMR (500 MHz, CDCl
3
)
d
(ppm): 3.83 (s, 3H), 4.64 (d, J ¼ 2.2 Hz,
1
2 h. After careful neutralization (1 N HCl, pH ¼ 7), the mixture was
1H), 4.60 (s, 1H), 5.74 (dd, J ¼ 2.3 and 2.5 Hz, 1H), 7.08 (t, J ¼ 18.5 Hz,
extracted with EtOAc and worked up in the usual manner, then
recrystallized from a mixture of methanol and water to yield 7 (2 g,
7
3
1
2H), 7.31 (t, J ¼ 15.0 Hz, 1H), 7.37 (t, J ¼ 15.5 Hz, 2H), 7.45 (d,
1
3
J ¼ 8.0 Hz, 2H), 7.76e7.80 (m, 2H); C NMR (125 MHz, CDCl
3
)
1
8%) as a white solid. H NMR (500 MHz, CDCl
3
)
d
(ppm): 1.01 (s,
d (ppm): 53.23, 55.02, 73.25, 115.57, 126.91, 128.00, 128.76, 129.47,
H), 1.59 (s, 6H), 1.64e1.67 (m, 2H), 1.72 (dd, J ¼ 8.7 and 0.8 Hz, 1H),
129.54, 130.13, 130.15, 138.59, 163.88, 165.89, 166.01,173.39.
.84 (s, 3H), 2.15 (s, 3H), 2.26e2.37 (m, 2H), 2.87 (d, J ¼ 5.3 Hz, 1H),
ꢀ
3
4
.95 (d, J ¼ 8.0 Hz, 1H), 4.01e4.08 (br, 1H), 4.15 (d, J ¼ 8.0 Hz, 1H),
4.2.3.3. Compound 10c. White solid; m.p.: 139e144 C; Yield: 90%;
1
.22 (t, J ¼ 8.2 and 8.4 Hz, 1H), 4.26e4.45 (m, 2H), 4.68 (d,
3
H NMR (500 MHz, CDCl ) (ppm): 3.84 (s, 3H), 4.60 (s, 1H), 4.65 (d,
J ¼ 10.4 Hz, 1H), 4.90 (d, J ¼ 9.1 Hz, 1H), 4.99 (d, J ¼ 4.6 Hz, 1H), 5.58
J ¼ 1.0 Hz, 1H), 5.75 (d, J ¼ 9.5 Hz, 1H), 7.13 (d, J ¼ 9.0 Hz, 1H), 7.3 (t,
(
dd, J ¼ 4.4 and 1.7 Hz, 1H), 6.08 (br, 1H), 6.27 (br, 1H), 7.58 (m, 2H),
J ¼ 14.4 Hz,1H), 7.38 (t, J ¼ 15.6 Hz, 2H), 7.45 (t, J ¼ 16.0 Hz, 4H), 7.77
13
13
7
d
4
.69 (m, 1H), 8.02 (d, J ¼ 7.4 Hz, 2H); C NMR (125 MHz, CDCl
3
)
(d, J ¼ 8.0 Hz, 2H); C NMR (125 MHz, CDCl
3
) d (ppm): 45.33, 53.27,
(ppm): 13.01, 15.53, 23.04, 27.07, 30.34, 32.13, 37.82, 38.14, 43.85,
4.22, 47.64, 65.66, 70.83, 72.22, 73.42, 76.24, 78.97, 81.03, 83.71,
54.98, 73.25, 126.91, 127.60, 128.00, 128.77, 133.93, 138.57, 141.16,
166.44, 173.38.
1
29.34, 129.73, 130.05, 134.03, 136.25, 138.42, 164.85, 169.57.
ꢀ
4
.2.3.4. Compound 10d. White solid; m.p.: 138e143 C; Yield: 82%;
1
4.2.2. Synthesis of compound 8 [18]
H NMR (500 MHz, CDCl
3
)
d
(ppm): 3.37 (d, J ¼ 3.3 Hz, 2H), 3.86 (s,
To a solution of 7 (265.3 mg, 0.5 mmol) in a mixture of CH
2
Cl
2
3H), 4.63 (br, 1H), 5.72 (dd, J ¼ 2.0 and 2.2 Hz, 1H), 6.51 (dd, J ¼ 2.0
(
3
20 mL) and CH OH (0.5 mL) were added 2,2-DMP (0.37 mL,
and 1.0 Hz, 1H), 7.12 (d, J ¼ 4.5 Hz, 2H), 7.19 (br, 1H), 7.32 (t,
13
3
mmol) followed by Montmorillonite K10 (40 mg), and the reac-
J ¼ 15.5 Hz,1H), 7.38 (t, J ¼ 15.0 Hz, 2H), 7.46e7.49 (m, 2H); C NMR
ꢀ
tion mixture was vigorously stirred for 4 h at 26 C. The solution
(125 MHz, CDCl
3
) d (ppm): 53.31, 55.08, 112.23, 114.89, 126.95,
was filtered and evaporated to a white residue, which was recrys-
128.00, 128.76, 138.62, 144.19, 147.43, 157.64, 173.26.
tallized from acetonitrile, affording compound 8 (276.8 mg, 97%).
1
ꢀ
4.2.3.5. Compound 10e. White solid; m.p.: 177e181 C; Yield: 85%;
H NMR (500 MHz,CDCl
3
)
d
(ppm): 1.09 (s, 3H), 1.52 (s, 6H),
1
1.54e1.57 (m, 1H),1.70 (s, 3H),1.75 (s, 3H),1.85e1.88 (m, 1H),1.91 (d,
H NMR (500 MHz, CDCl
3
)
d
(ppm): 3.35 (d, J ¼ 3.0 Hz, 2H), 3.74 (s,
J ¼ 8.7 Hz, 1H), 2.04 (s, 3H), 2.10 (d, J ¼ 7.6 Hz, 1H), 2.26 (s, 3H),
3H), 4.63 (br, 1H), 5.35 (dd, J ¼ 2.0 and 2.2 Hz, 1H), 6.21 (dd, J ¼ 2.5
2
4
.58e2.61 (m, 2H), 2.81 (d, J ¼ 5.4 Hz, 1H), 4.14 (d, J ¼ 8.3 Hz, 1H),
.31 (t, J ¼ 8.7 and 8.4 Hz, 1H), 4.36 (d, J ¼ 8.3 Hz, 1H), 4.54 (d,
and 1.0 Hz, 1H), 7.20 (d, J ¼ 4.0 Hz, 2H), 7.30 (br, 1H), 7.35 (t,
13
J ¼ 15.5 Hz,1H), 7.51 (t, J ¼ 15.3 Hz, 2H), 7.52e7.56 (m, 2H); C NMR
J ¼ 9.9 Hz, 1H), 4.63 (d, J ¼ 8.5 Hz, 1H), 4.92 (d, J ¼ 8.7 Hz, 1H), 5.03
3
(125 MHz, CDCl ) d (ppm): 29.71, 53.35, 54.83, 73.18, 126.92, 127.71,
(
d, J ¼ 9.9 Hz, 1H), 5.0 (s, 1H), 5.78 (dd, J ¼ 5.4 and 2.0 Hz, 1H), 7.48
128.00, 128.54, 128.77, 130.46, 138.24, 138.61, 161.28, 173.29.
(
2
2
t, J ¼ 7.7 Hz, 2H), 7.60 (t, J ¼ 7.4 Hz, 1H), 8.08 (dd, J ¼ 8.1 and 1.3 Hz,
1
3
ꢀ
H); C NMR (125 MHz, CDCl
3
)
d
(ppm): 12.94, 15.72, 22.94, 25.84,
4.2.3.6. Compound 10f. White solid; m.p.: 183e187 C; Yield: 87%;
1
6.97, 27.13, 30.52, 31.75, 36.81, 38.23, 41.75, 42.57, 47.65, 67.72,
1.64, 72.25, 74.86, 76.57, 81.81, 83.87, 84.68, 107.33, 128.67, 129.84,
32.75, 133.58, 143.23, 165.19, 171.56.
H NMR (500 MHz, CDCl
3
)
d
(ppm): 3.87 (s, 3H), 4.67 (d, J ¼ 2.0 Hz,
7
1
1H), 5.79 (d, J ¼ 9.5 Hz, 1H), 7.29e7.35 (m, 2H), 7.38e7.46 (m, 3H),
13
7.49e7.54 (m, 4H), 7.67 (d, J ¼ 8.0 Hz, 2H); C NMR (125 MHz,
CDCl (ppm): 30.33, 53.33, 54.36, 73.19, 111.15, 111.94, 122.74,
3
) d
4.2.3. General procedure for synthesis of compounds 10a-f
123.77, 127.01, 128.08, 128.80, 138.49, 148.09, 158.28, 173.19.
To solution of (2R,3S)-3-Phenylisoserine (100 mg,
a
9
0
0
.52 mmol) in anhydrous MeOH (3 mL), thionyl chloride (SOCl
.05 mL, 0.79 mmol) was added drop-wise at 0 C. The reaction
2
,
4.2.4. General procedure for synthesis of compounds 11a-f
ꢀ
The resulting solid 10 (1 mmol) and pyridinium p-toluenesul-
fonate (PPTS) (0.1 mmol) were dissolved in anhydrous toluene
(30 mL), and 4-methoxybenzaldehyde dimethyl acetal (1.5 mmol)
was subsequently added drop-wise under an argon atmosphere.
Following 40 min of heating at reflux, the reaction mixture was
mixture was stirred overnight at room temperature and the reac-
tion was monitored by TLC. After the completion of the reaction, the
reaction was quenched with NaHCO
under reduced pressure and diluted with H
extracted with EtOAc three times, the combined organic solution
was dried over Na SO and the solvent was removed under reduced
3
. The solution was evaporated
2
O. The water phase was
allowed to cool to ambient temperature and was diluted with Et
The organic layer was washed successively with water, saturated
2
O.
2
4

102
Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
NaHCO
3
, water and brine; the solution was dried over Na
2
SO
4
; and
in anhydrous toluene (6 mL), and the reaction mixture was stirred
for 2 h at room temperature. The reaction mixture was diluted with
solvents were removed under reduced pressure. The resulting oil
was purified by silica gel column chromatography (EtOAc:
hexane ¼ 1:4), yielding a product 11 (74e84%).
EtOAc and washed with saturated NH
4
Cl, water, saturated NaHCO
3
,
and brine. The organic layer was dried over Na
2
SO and the solvent
4
was removed under reduced pressure. The resulting oil was puri-
fied by silica gel column chromatography (EtOAc: hexane ¼ 1:3),
yielding 12 as a white solid (80e91%).
4
(
.2.4.1. Compound 11a. Slight yellow oil; Yield: 84%; 1H NMR
500 MHz, CDCl (ppm): 3.77 (s, 3H), 3.82 (s, 6H), 4.86 (d,
J ¼ 3.5 Hz), 5.47 (br, 1H), 6.72 (d, J ¼ 9.0 Hz, 2H), 6.87 (d, J ¼ 9.5 Hz,
3
) d
13
ꢀ
2
H), 6.94 (br, 1H), 7.29e7.35 (m, 6H), 7.48 (br, 2H); C NMR
4.2.5.1. Compound 12a. White solid; m.p.: 150e156 C; Yield: 91%;
1
(
125 MHz, CDCl (ppm): 14.43, 52.27, 55.29, 113.50, 127.03,
3
)
d
3
H NMR (500 MHz, CDCl ) d (ppm): 1.27 (s, 3H), 1.54 (s, 3H), 1.55 (s,
1
27.69, 128.01, 128.69, 128.73, 129.30, 130.08, 159.88, 161.61, 170.53.
3H), 1.65e1.69 (m, 1H), 1.71 (s, 3H), 1.83 (s, 3H), 1.85e1.88 (m, 1H),
.98 (s, 3H), 2.03 (s, 3H), 2.30 (s, 3H), 2.45e2.53 (m, 1H), 2.59e2.66
1
4
.2.4.2. Compound 11b. Slight yellow oil; Yield: 75%; 1H NMR
(ppm): 3.82 (s, 3H), 3.84 (s, 3H), 4.89 (br, 1H),
.45 (br, 1H), 6.87 (d, J ¼ 8.5 Hz, 2H), 6.92 (t, J ¼ 17.5 Hz, 2H),
(m, 1H), 2.76 (d, J ¼ 6.5 Hz, 1H), 3.76 (s, 3H), 3.84 (s, 3H), 4.09e4.15
(m, 2H), 4.32e4.37 (m, 2H), 4.60 (d, J ¼ 11.2 Hz, 1H), 4.91 (d,
J ¼ 9.5 Hz, 2H), 4.94 (br, 1H), 5.07 (d, J ¼ 12.3 Hz, 2H), 5.61 (br, 1H),
5.8 (dd, J ¼ 1.3 Hz, J ¼ 2.0 Hz, 1H), 6.17 (t, J ¼ 18.5 Hz, 1H), 6.72 (d,
J ¼ 9.4 Hz, 2H), 6.89 (d, J ¼ 8.0 Hz, 2H), 7.01 (br, H), 7.29e7.35 (m,
(
3
500 MHz, CDCl ) d
5
13
7
d
1
.25e7.36 (m, 7H), 7.43 (br, 2H); C NMR (125 MHz, CDCl
(ppm): 52.78, 55.27, 113.58, 115.46, 127.04, 128.76, 128.78, 129.43,
29.50, 129.65, 131.77, 160.01, 170.41; HR-MS: calcd for C25 22FNO
3
)
H
5
6H), 7.44e7.49 (m, 3H), 7.59 (t, J ¼ 15.5 Hz, 1H), 8.05 (d, J ¼ 6.6 Hz,
þ
13
(
[MþH] ), 436.1380; found, 436.1554.
2H); C NMR (125 MHz, CDCl
3
)
d
(ppm): 13.02, 14.19, 15.60, 21.45,
22.03, 24.95, 26.52, 26.78, 26.90, 27.11, 31.96, 36.71, 38.64, 41.88,
4
.2.4.3. Compound 11c. Slight yellow oil; Yield: 78%; 1H NMR
(ppm): 3.79 (s, 3H), 3.82 (s, 3H), 4.50 (s, 2H),
.89 (br, 1H), 5.42 (br, 1H), 6.85 (s, 2H), 7.18e7.36 (m, 9H), 7.43 (br,
42.36, 47.82, 55.30, 60.38, 71.70, 72.09, 74.38, 76.36, 81.13, 83.77,
84.553, 107.42, 113.48, 113.54, 127.17, 127.61, 128.17, 128.63, 128.79,
128.87, 129.32, 129.54, 129.79, 130.02, 133.61, 133.65, 138.81, 159.91,
161.53, 161.58, 165.05, 169.33, 170.87.
(
3
500 MHz, CDCl ) d
4
2
5
13
3
H); C NMR (125 MHz, CDCl ) d (ppm): 14.20, 21.02, 45.39, 52.75,
5.26, 60.36, 113.55, 127.41, 128.14, 128.42, 128.79, 135.64, 159.98,
þ
ꢀ
170.39; HR-MS: calcd for C26
H24ClNO
5
([M þ H] ), 466.1241; found,
4.2.5.2. Compound 12b. White solid; m.p.: 102e107 C; Yield: 90%;
H NMR (500 MHz, CDCl
1
4
66.1415.
3
) d (ppm): 1.28 (s, 3H), 1.55 (s, 3H), 1.56 (s,
3
H), 1.66e1.70 (m, 1H), 1.71 (s, 3H), 1.84 (s, 3H), 1.85e1.88 (m, 1H),
4
.2.4.4. Compound 11d. Slight yellow oil; Yield: 80%; 1H NMR
1.99 (s, 3H), 2.01 (s, 3H), 2.45e2.53 (m, 1H), 2.59e2.66 (m, 1H), 2.76
(d, J ¼ 6.5 Hz, 1H), 3.83 (s, 3H), 4.09e4.15 (m, 3H), 4.32e4.37 (m,
2H), 4.61 (d, J ¼ 11.5 Hz, 1H), 4.90 (d, J ¼ 10.3 Hz, 1H), 4.94 (br, 1H),
5.07 (d, J ¼ 12.5 Hz, 2H), 5.58 (br, 1H), 5.04 (dd, J ¼ 3.5 and 2.4 Hz,
1H), 6.87e6.93 (m, 4H), 7.28e7.38 (m, 6H), 7.47 (t, J ¼ 16.5 Hz, 3H),
(
3
500 MHz, CDCl ) d (ppm): 3.80 (s, 3H), 3.84 (s, 3H), 4.95 (br, 1H),
5
6
.84 (br, 1H), 6.37 (dd, J ¼ and 1.0 Hz, 1H), 6.88 (d, J ¼ 10.5 Hz, 2H),
.94 (d, J ¼ 2.4 Hz, 2H), 7.02 (s, 1H), 7.29e7.37 (m, 6H), 7.50 (d,
13
J ¼ 8.5 Hz, 2H); C NMR (125 MHz, CDCl
3
) d (ppm): 14.20, 21.03,
13
5
2.82, 55.26, 60.38, 63.90, 64.02, 111.67, 113.48, 117.57, 127.95,
7.60 (t, J ¼ 14.5 Hz, 1H), 8.05 (d, J ¼ 8.0 Hz, 2H); C NMR (125 MHz,
128.57, 128.79, 128.97, 129.72, 144.98, 147.01, 158.91, 159.97, 170.42.
CDCl
3
) d (ppm): 13.01, 14.20, 15.55, 21.04, 22.07, 26.50, 26.77, 26.90,
2
7.11, 31.95, 36.73, 38.66, 41.90, 42.37, 47.79, 60.38, 71.66, 71.75,
4
(
.2.4.5. Compound 11e. Slight yellow oil; Yield: 75%; 1H NMR
500 MHz, CDCl (ppm): 3.8 (s, 3H), 3.84 (s, 3H), 4.96 (d,
72.12, 74.37, 81.19, 83.76, 88.51, 107.52, 113.64, 115.26, 115.44,
128.39, 128.63, 128.88, 128.90, 129.44, 129.52, 129.56, 129.80,
3
) d
J ¼ 2.5 Hz, 1H), 5.76 (d, J ¼ 2.3 Hz, 1H), 6.85 (t, J ¼ 9.8 Hz, 1H), 6.90
133.63, 133.83, 160.06, 165.04, 169.33, 170.68; HR-MS: calcd for
þ
(
(
(
d, J ¼ 16.0 Hz, 2H), 6.99 (s, 1H), 7.05 (d, J ¼ 4.0 Hz, 1H), 7.34e7.39
C
56
H60FNO13 ([M þ Na] ), 996.3938; found, 996.3941.
13
m, 5H), 7.43 (d, J ¼ 5.5 Hz, 1H), 7.55 (d, J ¼ 8.5 Hz, 2H); C NMR
125 MHz, CDCl (ppm): 52.88, 55.29, 64.91, 91.81, 113.52, 126.92,
ꢀ
3
)
d
4.2.5.3. Compound 12c. White solid; m.p.: 136e143 C; Yield: 80%;
1
1
27.49, 128.26, 128.88, 129.15, 129.52, 129.93, 131.22, 138.37, 139.02,
3
H NMR (500 MHz, CDCl ) d (ppm): 1.28 (s, 3H), 1.33e1.45 (m, 1H),
þ
160.07, 163.90, 170.39; HR-MS: calcd for C23
H21NO
5
S ([M þ H] ),
1.55 (s, 3H), 1.56 (s, 3H), 1.65e7.71 (m, 1H), 1.72 (s, 3H), 1.84 (s, 3H),
1.99 (s, 3H), 2.01 (s, 3H), 2.46e2.67 (m, 2H), 2.76 (d, J ¼ 2.3 Hz, 1H),
4
24.1038; found, 424.1212.
3.83 (s, 3H), 4.11e4.26 (m, 1H), 4.32e4.36 (m, 2H), 4.52 (t,
4
.2.4.6. Compound 11f. Slight yellow oil; Yield: 82%; 1H NMR
(ppm): 3.80 (s, 3H), 3.85 (s, 3H), 5.01 (s, 1H),
.95 (br, 1H), 6.90 (d, J ¼ 8.5 Hz, 2H), 7.13 (br, 1H), 7.20e7.24 (m, 2H),
J ¼ 17.3 Hz, 3H), 4.61 (d, J ¼ 1.0 Hz, 1H), 4.90 (d, J ¼ 1.2 Hz, 1H), 4.97
(br, 1H), 5.07 (s, 1H), 6.17 (t, J ¼ 16.3 Hz, 1H), 6.89 (br, 2H), 7.22e7.36
(m, 10H), 7.47 (t, J ¼ 15.3 Hz, 3H), 7.60 (t, J ¼ 16.5 Hz, 1H), 8.05 (d, t,
(
3
500 MHz, CDCl ) d
5
1
3
7
.30e7.39 (m, 4H), 7.45 (d, J ¼ 7.4 Hz, 2H), 7.55 (d, J ¼ 8.0 Hz, 2H);
J ¼ 7.3 Hz, 2H); C NMR (125 MHz, CDCl
3
) d (ppm): 13.02, 15.56,
1
3
C NMR (125 MHz, CDCl
3
)
d
(ppm): 14.22, 21.03, 52.84, 55.25,
22.09, 24.95, 26.50, 26.91, 27.12, 31.96, 33.92, 36.74, 38.66, 41.89,
42.37, 45.39, 47.79, 55.30, 71.66, 72.12, 74.38, 76.37, 81.18, 83.76,
84.51, 107.50, 113.53, 113.63, 127.45, 128.39, 128.64, 128.86, 128.93,
6
0.37, 64.35, 91.78, 111.88, 113.34, 113.56, 122.62, 123.72, 126.69,
1
27.12, 128.06, 128.64, 129.03, 147.85, 154.87, 160.06, 170.36; HR-
þ
MS: calcd for C27
H23NO
6
([M þ H] ), 458.1423; found, 458.1597.
129.52, 129.80, 133.81, 135.54, 138.64, 165.05, 169.33, 170.67; HR-
þ
MS: calcd for C57
1026.3802.
H
62ClNO
3
([M þ Na] ), 1026.3808; found,
4.2.5. General procedure for synthesis of compounds 12a-f
A solution of KOH (1.1 mmol) in water (4 mL) was added slowly
ꢀ
at room temperature to a stirred solution of 11 in MeOH (30 mL).
The reaction mixture was stirred for 2 h. After the completion of the
reaction, MeOH was evaporated under reduced pressure. The re-
sidual mixture successively was diluted with water, washed with
4.2.5.4. Compound 12d. White solid; m.p.: 140e147 C; Yield: 85%;
1
3
H NMR (500 MHz, CDCl ) d (ppm): 1.26 (s, 3H), 1.53 (s, 6H),
1.65e1.69 (m,1H),1.71 (s, 3H),1.83 (s, 3H),1.84e1.89 (m,1H),1.95 (s,
3H), 2.01 (s, 3H), 2.48e2.55 (m, 1H), 2.61e2.67 (m, 1H), 2.77 (d,
J ¼ 5.5 Hz, 2H), 3.82 (s, 3H), 4.32e4.37 (q, J ¼ 22.5 Hz, 2H), 4.60 (d,
J ¼ 10.6 Hz, 1H), 4.91 (d, J ¼ 9.7 Hz, 1H), 5.03e5.09 (m, 2H), 5.08 (s,
3H), 5.82 (d, J ¼ 6.5 Hz, 1H), 5.98 (s, 1H), 6.17 (t, J ¼ 17.6 Hz, 1H), 6.36
(dd, J ¼ 1.0 and 1.2 Hz, 1H), 6.87 (d, J ¼ 9.5 Hz, 2H), 6.95 (d,
Et
The organic phase was dried over Na
reduced pressure. The resulting solid (2.0 mmol), compound 8
1.0 mmol), DCC (2.0 mmol) and DMAP (1.0 mmol) were dissolved
2
O, acidified with 1 N HCl, and extracted with EtOAc successively.
2
SO and evaporated under
4
(

Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
103
J ¼ 3.4 Hz, 1H), 7.18 (s, 1H), 7.30e7.35 (m, 4H), 7.40e7.51 (m, 6H),
113.88, 125.93, 127.28, 127.94, 128.67, 128.94, 129.51, 129.75, 133.64,
13
7
.59 (t, J ¼ 15.5 Hz, 1H), 8.05 (d, J ¼ 8.2 Hz, 2H); C NMR (125 MHz,
CDCl (ppm): 13.01, 14.02, 15.48, 21.04, 22.03, 26.54, 26.85, 26.88,
7.10, 31.92, 36.74, 38.65, 41.89, 42.35, 47.85, 55.26, 60.37, 71.68,
1.92, 72.13, 74.35, 76.36, 81.14, 83.75, 84.52, 91.84, 107.44, 111.74,
28.63, 128.98, 129.53, 133.63, 133.70, 138.59, 145.02, 146.86,
59.98, 165.04,169.46.
133.91, 138.38, 138.54, 162.41, 165.04, 166.17, 171.17, 171.37; HR-MS:
þ
3
)
d
calcd for C46
H
53NO13 ([M þ H] ), 828.3595; found, 828.3574.
2
7
1
1
ꢀ
4.2.6.2. Compound 13b. White solid; m.p.: 186e191 C; Yield: 30%;
1
H NMR (500 MHz, CDCl
CH ), 1.71 (s, 3H, CH ), 1.85 (s, 3H, CH
m, 2H), 2.29 (s, 3H, CH ), 2.10e2.16 (m, 1H), 2.56e2.70 (m, 2H),
3
)
d
(ppm): 1.08 (s, 3H, CH
3
), 1.25 (s, 3H,
3
3
3
), 1.95 (s, 3H, CH
3
), 1.86e1.98
(
3
ꢀ
4
.2.5.5. Compound 12e. White solid; m.p.: 130e136 C; Yield: 87%;
3.86 (s, 1H), 3.96 (s, 1H), 4.05 (d, J ¼ 8.5 Hz, 1H), 4.19e4.27 (m, 2H),
4.42 (dd, J ¼ 8.3 Hz, 1H), 4.71 (d, J ¼ 2.2 Hz, 1H), 4.96 (d, J ¼ 2.5 Hz
1H), 4.77 (br, 1H), 4.83 (d, J ¼ 10.0 Hz, 2H), 4.92e4.97 (d, J ¼ 2.6 Hz,
1
H NMR (500 MHz, CDCl
H), 1.65e1.69 (m, 1H), 1.71 (s, 3H), 1.83 (s, 3H),1.84e1.89 (m, 1H),
.95 (s, 3H), 2.05 (s, 3H), 2.48e2.55 (m, 1H), 2.61e2.67 (m, 1H), 2.77
d, J ¼ 5.5 Hz, 2H), 3.84 (s, 3H), 4.09e4.15 (m, 3H), 4.32e4.37 (q,
J ¼ 26.6 Hz, 2H), 4.60 (d, J ¼ 10.5 Hz, 1H), 4.91 (d, J ¼ 9.5 Hz, 1H),
.03e5.09 (m, 3H), 5.82 (d, J ¼ 6.2 Hz, 1H), 5.91 (s, 1H), 6.18 (t,
3
) d (ppm): 1.26 (s, 3H), 1.53 (s, 3H), 1.55 (s,
3
1
(
2H), 5.3 (s, 3H, CH
3
), 5.74 (dd, J ¼ 5.5 and 1.5 Hz, 1H), 5.88 (dd,
J ¼ 9.5 and 2.5 Hz, 1H), 5.9e5.94 (m, 1H), 7.13e7.16 (t, 2H),
7.30e7.43 (m, 4H), 7.30e7.40 (m, 4H), 7.88 (m, 2H), 8.07 (d,
13
5
J ¼ 7.0 Hz, 2H). C NMR (125 MHz, CDCl
3
) d (ppm): 12.61, 14.12,
J ¼ 20.5 Hz, 1H), 6.86 (t, J ¼ 9.7 Hz, 1H), 6.91 (d, J ¼ 8.8 Hz, 2H), 7.04
14.19, 15.12, 19.16, 22.69, 26.45, 26.72, 29.36, 29.66, 29.70, 31.68,
31.92, 38.00, 43.95, 44.63, 47.15, 54.53, 60.43, 71.21, 71.26, 71.33,
73.83, 74.16, 76.86, 77.22, 78.98, 82.68, 83.82,126.61, 127.32, 128.14,
128.65, 128.70, 129.52, 129.76, 131.92, 132.63, 133.64, 133.81, 138.18,
(
8
1
3
7
1
d, J ¼ 3.5 Hz, 1H), 7.14 (s, 1H), 7.37e7.49 (m, 8H), 7.54e7.61 (m, 3H),
13
.05 (d, J ¼ 7.5 Hz, 2H); C NMR (125 MHz, CDCl
3
) d (ppm): 13.04,
4.20, 15.63, 21.04, 22.03, 26.55, 26.84, 26.90, 27.11, 31.96, 36.72,
8.65, 41.87, 42.37, 47.85, 55.29, 60.38, 65.35, 71.72, 71.95, 72.08,
4.36, 76.37, 81.14, 83.77, 84.56, 92.08, 107.44, 113.58, 127.07, 127.49,
28.37, 128.62, 128.93, 129.23, 129.55, 129.81, 130.00, 131.24, 133.61,
138.47, 165.61, 165.55, 171.19, 171.27; HR-MS: calcd for C45
([M þ Na] ), 838.3215; found, 838.3183.
H50FNO12
þ
ꢀ
1
33.70, 138.15, 138.64, 160.09, 163.46, 15.06, 169.41, 171.00; HR-MS:
4.2.6.3. Compound 13c. White solid; m.p.: 146e153 C; Yield: 25%;
þ
1
calcd for C54
H59NO13S ([M þ H] ), 984.3598; found, 984.3599.
H NMR (500 MHz, CDCl
3
)
d
(ppm): 1.16 (s, 3H, CH
), 1.71 (s, 2H), 1.41e1.71 (m, 2H), 1.76 (s, 3H, CH
), 1.84e1.95 (m, 2H), 2.28 (s, 3H, CH ), 2.52e2.67 (m, 4H), 2.83
3
), 1.56 (s, 3H,
CH
CH
3
3
), 1.80 (s, 3H,
ꢀ
4
.2.5.6. Compound 12f. White solid; m.p.: 145e150 C; Yield: 83%;
3
3
1
H NMR (500 MHz, CDCl
H), 1.65e1.69 (m, 1H), 1.71 (s, 3H), 1.84 (s, 3H), 1.87e1.94 (m, 1H),
.98 (s, 3H), 2.01 (s, 3H), 2.46e2.53 (m, 1H), 2.58e2.66 (m, 1H), 2.75
d, J ¼ 5.5 Hz, 2H), 3.83 (s, 3H), 4.32e4.36 (m, 2H), 4.60 (d,
J ¼ 10.2 Hz, 1H), 4.90 (d, J ¼ 8.2 Hz, 1H), 4.96 (br, 1H), 5.07 (s, 1H),
.82 (d, J ¼ 6.5 Hz, 1H), 6.17 (t, J ¼ 18.6 Hz, 1H), 6.89 (br, 2H), 7.14 (d,
J ¼ 4.5 Hz, 2H), 7.31e7.39 (m, 7H), 7.46 (t, J ¼ 15.4 Hz, 3H), 7.59 (t,
3
)
d
(ppm): 1.28 (s, 3H), 1.54 (s, 3H), 1.56 (s,
(t, 1H), 3.36 (br, 1H), 4.20 (d, J ¼ 8.5 Hz, 1H), 4.26e4.30 (m, 2H), 4.36
(d, J ¼ 8.0 Hz, 2H), 4.62 (s, 2H), 4.76 (d, J ¼ 2.5 Hz, 1H), 4.83 (d,
J ¼ 10.3 Hz,1H), 4.97 (t, J ¼ 15.6 Hz, 2H), 5.05 (d, J ¼ 3.6 Hz, 2H), 5.88
(dd, J ¼ 9.5 and 2.5 Hz, 1H), 5.91 (m, 2H), 7.31e7.41 (m, 3H),
3
1
(
13
7.46e7.65 (m, 6H), 7.82 (d, J ¼ 2.5 Hz, 2H), 8.07 (m, 3H). C NMR
5
3
(125 MHz, CDCl ) d (ppm): 12.65, 14.12, 15.08, 20.45, 21.47, 22.69,
25.60, 26.49, 29.69, 31.67, 31.92, 32.72, 37.89, 38.07, 43.92, 44.56,
47.19, 53.26, 54.50, 71.29, 73.29, 73.92, 74.04, 76.78, 77.03, 77.24,
77.29, 79.02, 82.62,83.91, 126.90, 127.05, 127.16, 127.29, 128.01,
128.65, 128.76, 128.82, 129.35, 129.55, 129.77,130.01, 130.86, 133.63,
13
J ¼ 15.5 Hz, 1H), 8.05 (d, J ¼ 8.4 Hz, 2H); C NMR (125 MHz, CDCl
3
)
d
3
(ppm): 13.01, 14.26, 15.55, 21.05, 22.09, 26.50, 26.76, 27.12, 30.95,
6.73, 38.66, 41.90, 42.37, 47.78, 55.31, 60.38, 71.64, 72.13, 74.37,
7
1
6.36, 76.87, 77.13, 77.38, 81.19, 83.76, 84.50, 107.51, 113.66, 128.42,
28.71, 128.96, 129.44, 129.52, 129.80, 133.47, 133.64, 133.86, 134.38,
133.93, 138.47, 142.42, 165.06, 166.65, 171.13, 171.38; HR-MS: calcd
þ
for C46H52ClNO12 ([M þ Na] ), 868.3076, found 868.3071.
160.09, 163.03, 169.34, 170.63; HR-MS: calcd for C54
H
59NO13
S
þ
ꢀ
(
[M þ Na] ), 1018.3947; found, 1018.3984.
4.2.6.4. Compound 13d. White solid; m.p.: 155e161 C; Yield: 27%;
1
H NMR (500 MHz, CDCl
CH ), 1.46e1.73 (m, 2H), 1.75 (s, 3H, CH
1.92e1.98 (m, 2H), 2.27 (s, 3H, CH ), 2.4e2.6 (m, 2H), 3.44 (br, 1H),
3
)
d
(ppm): 1.15 (s, 3H, CH
3
), 1.61 (s, 3H,
4
.2.6. General procedure for synthesis of compounds 13a-f
The resulting solid 12 (1.0 mmol) was dissolved in MeOH (5 mL)
and p-toluenesulfonic acid (0.7 mmol) was added. After stirring for
h at room temperature, the reaction mixture was diluted with
EtOAc and washed three times with saturated NaHCO and brine.
The organic layer was dried over Na SO and the solvent was
3
3
), 1.80 (s, 3H, CH
3
),
3
3.84 (m, 1H), 4.22 (d, J ¼ 8.5 Hz, 1H), 4.26e4.30 (m, 2H), 4.36 (d,
J ¼ 8.0 Hz, 1H), 4.68 (br, 1H), 4.74 (d, J ¼ 2.5 Hz, 1H), 4.83 (d,
J ¼ 10.5 Hz, 1H), 4.85 (d, J ¼ 2.7 Hz, 2H), 4.97 (d, J ¼ 2.5 Hz, 1H), 5.06
(br, 1H), 5.79 (dd, J ¼ 5.5 and 1.5 Hz,1H), 5.90e5.94 (m,1H), 6.51 (m,
1H), 7.13 (d, 2H), 7.30e7.39 (m, 3H), 7.46e7.52 (m, 4H), 7.64 (t,
5
3
2
4
removed under reduced pressure. The resulting oil was purified by
silica gel column chromatography (EtOAc: hexane ¼ 2:3), and the
unreacted minor diastereomer was discarded, yielding 13 as a
white powder (20e30%).
13
J ¼ 10.6 Hz, 1H), 8.07 (d, J ¼ 7.0 Hz, 2H). C NMR (125 MHz, CDCl
(ppm): 12.64, 14.12, 15.11, 21.02, 22.65, 26.41, 26.75, 31.68, 37.98,
43.98, 44.65, 47.15, 53.81, 60.46, 71.14, 71.27, 71.33, 74.07, 76.88,
7.24, 79.05, 82.78, 83.88,112.38, 115.08, 127.34, 128.0, 128.65,
3
)
d
7
ꢀ
4
.2.6.1. Compound 13a. White solid; m.p.: 159e163 C; Yield: 20%;
129.35, 129.76, 133.68, 133.98, 138.38, 138.42, 144.38, 147.47, 157.68,
1
þ
H NMR (500 MHz, CDCl
CH ), 1.41e1.71 (m, 1H), 1.75 (s, 3H, CH
m, 2H), 2.27 (s, 3H, CH ), 2.51e2.63 (m, 2H), 3.46 (br, 1H), 3.80 (s,
3
)
d
(ppm): 1.15 (s, 3H, CH
3
), 1.57 (s, 3H,
165.04, 170.97,171.25; HR-MS: calcd for C43
810.3102, found 810.3070.
H
49NO13 ([M þ Na] ),
3
3
), 1.77 (s, 3H, CH
3
), 1.92e1.95
(
3
ꢀ
3
1
4
5
H), 4.20 (d, J ¼ 8.0 Hz, 1H), 4.26e4.30 (m, 2H), 4.36 (d, J ¼ 8.0 Hz,
4.2.6.5. Compound 13e. White solid; m.p.: 148e153 C; Yield: 27%;
1
H), 4.65 (br, 1H), 4.76 (d, J ¼ 2.5 Hz, 1H), 4.83 (d, J ¼ 10.5 Hz, 2H),
.95 (d, J ¼ 2.5 Hz, 2H), 5.07 (br, 3H), 5.74 (dd, J ¼ 5.5 and 1.5 Hz,1H),
.88 (dd, J ¼ 9.5 and 2.5 Hz, 1H), 5.90e5.94 (m, 1H), 6.92 (d,
H NMR (500 MHz, CDCl
CH ), 1.54e1.70 (m,1H), 1.76 (s, 3H, CH
(m, 2H), 2.27 (s, 3H, CH
3
)
d
(ppm): 1.16 (s, 3H, CH
), 1.81 (s, 3H, CH
), 2.4e2.6 (m, 2H), 2.85 (d, J ¼ 2.5 Hz, 1H),
3
), 1.62 (s, 3H,
3
3
3
), 1.86e1.97
3
J ¼ 3.3 Hz, 2H), 7.30e7.43 (m, 4H), 7.30e7.40 (m, 3H), 7.64 (t,
3.36 (br, 1H), 4.20 (d, J ¼ 8.5 Hz, 1H), 4.26e4.30 (m, 2H), 4.36 (d,
J ¼ 8.6 Hz, 1H), 4.66e4.77 (m, 3H), 4.83 (d, J ¼ 10.5 Hz, 1H), 4.97 (d,
J ¼ 2.2 Hz, 2H), 5.76 (dd, J ¼ 5.5 and 1.5 Hz, 1H), 5.83 (dd, J ¼ 9.5 and
2.5 Hz, 1H), 5.9e5.94 (m, 1H), 7.08 (t, J ¼ 10.7 Hz, 1H), 7.31e7.40 (d,
J ¼ 3 Hz, 4H), 7.46e7.53 (m, 4H), 7.56e7.64 (m, 2H), 8.07 (d,
13
J ¼ 7.3 Hz, 1H), 7.70 (d, J ¼ 7.5 Hz, 2H), 8.07 (d, J ¼ 7.2 Hz, 2H).
NMR (125 MHz, CDCl (ppm): 12.62, 14.11, 16.12, 21.10, 22.67,
6.45, 26.72, 29.32, 37.84, 37.91, 43.92, 44.52, 47.11, 54.40, 55.41,
0.44, 71.35, 71.31, 73.94, 74.07, 76.85, 77.24, 79.07, 82.65, 83.87,
C
3
) d
2
6

104
Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
J ¼ 7.9 Hz, 2H). 13C NMR (125 MHz, CDCl
to bring the pH of the mixture to 7. The solvent was removed under
reduced pressure, the resulting mixture was extracted with EtOAc,
3
) d (ppm): 12.64, 15.33,
2.62, 26.45, 29.7,31.74, 31.85, 38.16, 43.98, 44.63, 47.27, 54.57,
2
71.29, 71.32, 73.90, 74.14, 76.81, 77.27, 79.07, 82.77,83.97, 127.31,
2 4
the solution was dried over Na SO , and the resulting oil was pu-
1
27.70, 128.17, 128.63,128.74, 129.54, 129.75, 130.58, 133.64, 133.97,
rified by silica gel column chromatography (EtOAc: hexane ¼ 1:1),
ꢀ
1
138.21, 138.48, 138.57, 161.14, 165.08, 171.08, 171.60; HR-MS: calcd
yielding 17 as a white solid (100 mg, 50%); m.p.: 155e163 C;
NMR (500 MHz, CDCl
(ppm): 0.87 (t, J ¼ 6.9 Hz, 3H), 1.18 (s, 3H),
.22e1.31 (m, 4H), 1.53 (s, 6H), 1.53e1.62 (m, 3H), 1.65 (s, 3H), 1.69
H
þ
for C43
H
49SO12 ([M þ H] ), 804.3053, found 804.3060.
3
) d
1
ꢀ
4
.2.6.6. Compound 13f. white solid; m.p.: 160e166 C; yield: 23%;
(s, 3H), 1.78 (s, 3H), 1.84 (dd, J ¼ 15.3 and 9.2 Hz, 1H), 1.99 (d,
J ¼ 8.7 Hz, 1H), 2.18e2.23 (m, 2H), 2.24 (s, 3H), 2.55e2.64 (m, 2H),
2.68 (d, J ¼ 5.5 Hz,1H), 4.14 (d, J ¼ 8.8 Hz,1H), 4.21 (t, J ¼ 8.5 Hz,1H),
4.34 (d, J ¼ 8.4 Hz, 1H), 4.53 (d, J ¼ 9.8 Hz, 1H), 4.66 (d, J ¼ 2.3 Hz,
1H), 4.92 (d, J ¼ 8.7 Hz, 1H), 4.96 (d, J ¼ 9.8 Hz, 2H), 5.62 (dd, J ¼ 9.3
and 8.0 Hz, 1H), 5.79 (dd, J ¼ 5.4 and 1.7 Hz, 1H),5.9 (t, J ¼ 8.5 Hz,
1H), 6.57 (d, J ¼ 9.3 Hz, 1H), 7.29 (t, J ¼ 7.2 Hz, 1H), 7.36 (t, J ¼ 7.5 Hz,
2H), 7.43 (d, J ¼ 7.3 Hz, 2H), 7.47 (t, J ¼ 7.8 Hz, 2H), 7.61 (t, J ¼ 7.4 Hz,
1
H NMR (500 MHz, CDCl
3
)
d
(ppm): 1.14 (s, 3H, CH
), 1.71 (s, 2H), 1.41e1.71 (m, 1H), 1.76 (s, 3H, CH
), 1.84e1.95 (m, 2H), 2.28 (s, 3H, CH
3
), 1.65 (s, 3H,
), 1.81 (s, 3H,
), 2.4 (s, 3H, CH ), 2.4e2.6
3
CH
CH
3
3
3
3
(
4
m, 2H), 2.83 (d, J ¼ 2.4 Hz 1H), 3.36 (br, 1H), 4.20 (d, J ¼ 8.5 Hz, 1H),
.26e4.30 (m, 2H), 4.36 (d, J ¼ 8.0 Hz, 1H), 4.6 (br, 1H), 4.76 (d,
J ¼ 2.5 Hz,1H), 4.83 (d, J ¼ 10.0 Hz,1H), 4.92e4.97 (d, J ¼ 2.7 Hz, 2H),
5
.3 (s, 3H, CH
3
), 5.74 (dd, J ¼ 5.5 and 1.5 Hz,1H), 5.88 (dd, J ¼ 9.5 and
1
3
2
.5 Hz, 1H), 5.90e5.94 (m, 1H), 7.31e7.52 (m, 7H), 7.55 (d, d,
1H), 8.06 (d, J ¼ 7.2 Hz, 2H); C NMR (125 MHz, CDCl
3
) d (ppm):
J ¼ 9.8.0 Hz, 2H), 7.60e7.69 (m, 3H), 7.85 (d, J ¼ 2.5 Hz, 1H), 8.07 (d,
13.12, 14.00, 15.62, 22.34, 22.77, 25.41, 26.07, 26.95, 27.00, 27.10,
29.81, 31.50, 31.95, 36.67, 36.82, 36.84, 38.64, 41.80, 42.55, 47.67,
54.14, 54.55, 71.38, 71.64, 72.27, 73.60, 74.57, 76.55, 82.25, 83.74,
84.47, 107.56, 127.08, 127.38, 127.90, 128.04, 128.87, 128.70, 128.81,
13
J ¼ 5.6 Hz, 2H); C NMR (125 MHz, CDCl
3.10, 25.55, 31.65, 37.8,8 38.04, 43.97, 44.65, 47.14, 54.15, 71.15,
1.20, 76.85, 77.14, 79.06, 82.65, 83.88, 111.10, 111.80, 122.74, 123.87,
26.97, 127.37, 127.57, 128.14, 128.67, 129.57, 129.78, 133.68, 133.91,
3
) d (ppm): 12.54, 14.11,
2
7
1
129.54, 129.91, 133.81, 134.24, 138.67, 138.64, 165.40, 170.87, 171.64,
þ
138.14, 138.47, 148.17, 154.72, 158.12, 165.08, 170.87, 171.14; HR-MS:
172.74; HR-MS: calcd for C47
832.4253.
H
61NO12 ([M þ H] ), 832.4272, found
þ
calcd for C47
H
51NO13 ([M þ Na] ), 860.3258, found 860.3244.
4
.2.7. Synthesis of compound 15 [33,34]
Compound 14 (100 mg, 0.6 mmol), triethylsilane (142 mg,
.23 mmol) and 1H-imidazole (125 mg, 1.84 mmol) were dissolved
4.2.10. Synthesis of compound 18
Compound 17 (40 mg, 0.048 mmol) was dissolved in MeOH
(6 mL) and 0.04 N HCl was slowly added to the mixture until pH of
1
ꢀ
ꢀ
in dry CH
mosphere for 0.5 h, the reaction was quenched by with saturated
NH Cl, the solvent was removed under reduced pressure. The water
layer was extracted with EtOAc, the organic layer was dried over
Na SO and the solvent was removed under reduced pressure. The
resulting oil was purified by silica gel column chromatography
EtOAc: hexane ¼ 1: 15), yielding 15 as a colorless oil (150 mg, 87%).
2
Cl
2
(6 mL) under 0 C. After stirring under nitrogen at-
the mixture measured 3e4. After stirring at 60 C for 6 h, saturated
NaHCO
solvent was removed under reduced pressure, the products
extracted with EtOAc and dried over Na SO , and the resulting oil
3
solution was added to bring the pH of the mixture to 7. The
4
2
4
2
4
was purified by silica gel column chromatography (EtOAc:
hexane ¼ 2:1), yielding 18 as a white powder (35 mg, 92%); m.p.:
ꢀ
1
(
171e176 C; H NMR (500 MHz, CDCl
3
)
d
(ppm): 0.82 (t, J ¼ 7.1 Hz,
1
H NMR (500 MHz, CDCl
3
)
d
(ppm): 0.35e0.48 (m, 6H), 0.76 (t,
3H), 1.18 (s, 3H), 1.23e1.31 (m, 4H), 1.52e1.58 (m, 2H), 1.58e1.64 (m,
1H), 1.66 (s, 3H), 1.74 (s, 3H), 1.75 (s, 3H), 1.93 (dd, J ¼ 14.6 and
10.6 Hz, 1H), 1.99 (d, J ¼ 8.8 Hz, 1H), 2.12 (t, J ¼ 7.0 Hz, 2H), 2.26 (s,
J ¼ 7.9 Hz, 9H), 4.78 (d, J ¼ 4.7 Hz, 1H), 5.07 (dd, J ¼ 4.7 and 2.7 Hz,
1
H), 6.44 (s, 1H), 7.28e7.36 (m, 5H).
3
H), 2.40e2.50 (m, 1H), 2.51e2.60 (m, 1H), 2.83 (d, J ¼ 5.7 Hz, 1H),
4
.2.8. Synthesis of compound 16 [33,34]
Compound 15 (150 mg, 0.6 mmol), triethylsilane (109 mg,
3.77 (s,1H), 4.16 (d, J ¼ 8.4 Hz,1H), 4.27 (dd, J ¼ 21.2 and 9.7 Hz, 2H),
4.34 (d, J ¼ 8.4 Hz, 1H), 4.71 (s, 1H), 4.85 (s, 1H), 4.89e4.95 (m, 2H),
5.39 (s, 1H), 5.62 (dd, J ¼ 9.4 and 1.4 Hz, 1H), 5.72 (dd, J ¼ 5.7 and
1.4 Hz, 1H), 5.90 (t, J ¼ 8.0 Hz, 1H), 6.7 (d, J ¼ 9.4 Hz, 1H), 7.28 (t,
J ¼ 7.2 Hz, 1H), 7.34 (t, J ¼ 7.4 Hz, 2H), 7.40 (d, J ¼ 7.4 Hz, 2H), 7.46 (t,
1.08 mmol), and DMAP (66.5 mg, 0.54 mmol) were dissolved in dry
CH
2
Cl
2
(6 mL), and hexanoyl chloride (24.39 mg, 0.81 mmol) was
ꢀ
slowly added to the mixture at 0 C. After stirring under nitrogen
atmosphere for 2 h, the reaction was quenched with water and the
solvent was removed under reduced pressure. The water layer was
13
J ¼ 7.8 Hz, 2H), 7.59 (t, J ¼ 7.4 Hz, 1H), 8.04 (d, J ¼ 7.2 Hz, 2H);
C
3
NMR (125 MHz, CDCl ) d (ppm): 12.64, 14.11, 14.32, 15.22, 21.31,
extracted with EtOAc, the organic layer was dried over Na
the solvent was removed under reduced pressure. The resulting oil
was purified by silica gel column chromatography (EtOAc:
2
SO
4
, and
22.44, 22.70, 25.41, 26.45, 26.94, 29.47, 29.95, 31.55, 31.74, 36.67,
37.94, 38.45, 44.27, 44.50, 47.34, 53.94, 71.65, 71.54, 71.74, 73.50,
74.14, 79.04, 82.47, 84.18, 127.17, 128.04, 128.88, 128.67, 129.67,
1
hexane ¼ 1:8), yielding 16 as a colorless oil (130 mg, 65%). H NMR
129.94, 133.61, 134.57, 138.17, 138.67, 165.0, 170.61, 172.87; HR-MS:
þ
(
500 MHz, CDCl
3
)
d
(ppm): 0.37e0.51 (m, 6H), 0.77 (t, J ¼ 7.9 Hz,
calcd for C44
H
57NO12 ([M þ H] ), 792.3959, found 792.3949.
9
2
5
H), 0.89 (t, J ¼ 7.0 Hz, 3H), 1.33 (q, J ¼ 7.2, 3.6 Hz, 4H), 1.64e1.69 (m,
H), 2.68e2.76 (m, 1H), 2.76e2.84 (m, 1H), 5.09 (d, J ¼ 5.9 Hz, 1H),
.14 (d, J ¼ 5.9 Hz, 1H), 7.22e7.23 (m, 2H), 7.28e7.34 (m, 3H).
4.2.11. Synthesis of compound 20
Compound 19 (30 mg, 0.049 mmol) and compound 16 (27.7 mg,
0.074 mmol) were dissolved in dry THF (2 mL), and sodium bis(-
4
.2.9. Synthesis of compound 17
Compound 16 (130 mg, 0.6 mmol) and compound 8 (131 mg,
.23 mmol) were dissolved in dry THF (6 mL), and sodium bis(-
trimethylsilyl) amide (0.04 mL, 0.074 mmol) was slowly added to
the mixture at 0 C. After stirring under nitrogen atmosphere for
ꢀ
0
2 h, the reaction was quenched with saturated NH
solvent was removed under reduced pressure. The water layer was
4
extracted with EtOAc and the organic layer was dried over Na SO .
4
Cl, and the
trimethylsilyl) amide (63.47 mg, 0.35 mmol) was slowly added to
the mixture at 0 C. After stirring under nitrogen atmosphere for
ꢀ
2
2
h, the reaction was quenched with saturated NH
vent was removed under reduced pressure. The water layer was
extracted with EtOAc and the organic layer was dried over Na SO
4
Cl and the sol-
The resulting intermediate was dissolved in 2 mL MeOH, and 0.04 N
HCl was slowly added until the pH of the mixture measured 3e4.
ꢀ
2
4
.
After stirring at 40 C for 3 h, saturated NaHCO
3
solution was added
The resulting intermediate was dissolved in 2 mL MeOH and 0.04 N
to bring the pH of the mixture to 7. The solvent was removed under
reduced pressure, the resulting mixture was extracted with EtOAc,
the solution was dried over Na SO , and the resulting oil was
2 4
HCl was slowly added until the pH of the mixture measured 3e4.
ꢀ
After stirring at 40 C for 3 h, saturated NaHCO
3
solution was added

Q.-F. Li et al. / European Journal of Medicinal Chemistry 104 (2015) 97e105
160e167.
105
purified by silica gel column chromatography (EtOAc:
1
[11] K.C. Nicolaou, W.M. Dai, R.K. Guy, Chemistry and biology of taxol, Angew.
hexane ¼ 1:1), yielding 20 as a white solid (20.1 mg, 47%). H NMR
Chem. Int. Ed. Engl. 33 (1994) 15e44.
(
500 MHz, CDCl
3
):
d
ppm 0.82 (t, J ¼ 6.9 Hz, 3H), 1.15 (s, 3H),
[
12] O.N. Zefirova1, E.V. Nurieva1, A.N. Ryzhov, N.V. Zyk1, N.S. Zefirov1, Taxol:
synthesis, bioactive conformations, and structure-activity relationships in its
analogs, Russ. J. Org. Chem. 41 (2005) 315e351.
1
1
2
(
.21e1.26 (m, 7H), 1.50e1.61 (m, 2H), 1.69 (dd, J ¼ 15.1, 8.8 Hz, 1H),
.78 (s, 3H), 1.82 (dd, J ¼ 14.3, 12.0 Hz, 1H), 1.87 (s, 3H), 2.02 (s, 3H),
.05 (d, J ¼ 9.4 Hz, 1H), 2.13e2.20 (m, 5H), 2.33 (s, 3H), 2.50e2.63
m, 2H), 3.73 (d, J ¼ 6.7 Hz, 1H), 3.76 (d, J ¼ 4.4 Hz, 1H), 4.13 (d,
J ¼ 8.5 Hz,1H), 4.37 (d, J ¼ 8.6 Hz,1H), 4.68 (s,1H), 4.97 (d, J ¼ 9.1 Hz,
H), 5.53e5.60 (m, 2H), 5.63 (dd, J ¼ 6.7, 2.8 Hz, 1H), 5.93 (t,
J ¼ 8.9 Hz,1H), 6.20 (s, 1H), 6.45 (d, J ¼ 9.1 Hz, 1H), 7.29 (t, J ¼ 6.9 Hz,
H), 7.37 (td, J ¼ 15.2, 7.4 Hz, 4H), 7.48 (t, J ¼ 7.7 Hz, 2H), 7.60 (t,
[
13] I. Ojima, C.P. Borella, X.Y. Wu, P.Y. Bounaud, C.F. Oderda, M. Sturm, M.L. Miller,
S. Chakravarty, J. Chen, Q. Huang, P. Pera, T.A. Brooks, M.R. Baer, R.J. Bernacki,
Design, synthesis and structure-activity relationships of novel taxane-based
multidrug resistance reversal agents, J. Med. Chem. 48 (2005) 2218e2228.
14] H.X. Lin, M. Li, J.M. Chen, M.Q. Chen, Isolation and structure of 1-
deoxybaccatin VI from the root of taxus chinensis, rehd. var. mairei, Chin. J.
Chem. 22 (2004) 751e756.
[
1
[
[
[
[
15] H.X. Lin, N. Han, J.M. Chen, T.H. Yuan, Synthesis and crystal structure of 7,9-
dideacetyl-1-deoxybaccatinVI, J. Chem. Crystallogr. 36 (2006) 337e341.
16] D.G.I. Kingston, M.D. Chordia, P.G. Jagtap, Synthesis and biological evaluation
of 1-deoxypaclitaxel analogues, J. Org. Chem. 64 (1999) 1814e1822.
17] D.H. Jin, Y.M. Cui, H.X. Lin, Semi-synthesis of 1-deoxypaclitaxel and its ana-
logues from 1-deoxybaccatin VI, Med. Chem. 8 (2012) 789e798.
18] T.H. Yuan, Y. Jiang, X.H. Wang, D.L. Wang, A. Bannerjee, S. Bane, J.P. Snyder,
H.X. Lin, Synthesis, biological activity and tubulin binding poses of 1-deoxy-9-
(R)-dihydrotaxane analogs, Bioorg. Med. Chem. Lett. 19 (2009) 1148e1151.
19] J.N. Denis, A.E. Greene, Highly efficient, practical approach to natural taxol,
J. Am. Chem. Soc. 110 (1988) 5917e5919.
1
13
J ¼ 7.4 Hz, 1H), 8.05 (d, J ¼ 7.3 Hz, 2H); C NMR (125 Hz, CDCl
3
)
d
2
7
1
ppm: 13.99, 14.74, 20.85, 21.20, 22.42, 22.62, 25.49, 25.66, 26.38,
9.87, 31.41, 33.60, 36.67, 38.50, 45.00, 54.43, 56.46, 60.52, 71.46,
1.84, 72.02, 73.22, 75.67, 76.67, 81.10, 83.93, 127.13, 128.19, 128.81,
28.93, 129.40, 129.94, 132.70,133.77, 138.39, 138.94, 165.08, 169.14,
70.27, 170.63, 172.69, 173.05, 202.68; ESI Full MS m/z: [M þ Na]
þ
1
[
[
8
96, 595.
20] D.G.I. Kingston, A.G. Chaudhary, A.A.L. Gunatilaka, M.L. Middleton, Synthesis
of taxol from baccatin III via an oxazoline intermediate, Tetrahedron Lett. 35
Acknowledgments
(1994) 4483e4484.
0
[
21] B. Ke, Y. Qin, F. Zhao, Y. Qu, Synthesis and biological evaluation of novel 3 -N-
tert-butylsulfonyl analogues of docetaxel, Bioorg. Med. Chem. Lett. 18 (2008)
4783e4785.
22] H.F. Lu, X. Sun, L. Xu, L.G. Lou, G.Q. Lin, Design, synthesis and biological
evaluation of novel fluorinated docetaxel analogues of docetaxel, Eur. J. Med.
Chem. 44 (2009) 482e491.
The authors are grateful for support from the National Natural
Science Foundation of China (Project Nos. 21272154, 81202402 and
0672506). The authors also thank Dr. H. Deng and The Instru-
[
3
mental Analysis & Research Center of Shanghai University for
structural analysis.
[23] R.A. Holton, EP-A400971, 1990.
[
[
24] R.A. Holton, US-5274124, 1993.
25] Y. Hayashi, M. Skwarczynski, Y. Hamada, Y. Sohma, T. Kimura, Y. Kiso, A novel
approach of water-soluble paclitaxel prodrug with no auxiliary and no
byproduct: design and synthesis of isotaxel, J. Med. Chem. 46 (2003)
Appendix A. Supplementary data
3
782e3784.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2015.09.019.
[
[
[
[
26] Y. Hayashi, Y. Kiso, M. Skwarczynski, et al., No auxiliary, no byproduct strategy
for water-soluble prodrugs of taxoids: scope and limitation of OeN intra-
molecular acyl and acyloxy migration reactions, J. Med. Chem. 48 (2005)
2655e2666.
27] W.W. Ma, G.L. Park, G.A. Gomez, M.H. Nieder, T.L. Adams, J.S. Aynsley,
O.P. Sahai, R.J. Smith, R.W. Stahlhut, P.J. Hylands, F. Bitsch, C. Shackleton, New
bioactive taxoids from cell cultures of Taxus baccata, J. Nat. Prod. 57 (1994)
References
[
1] M.C. Wani, H.L. Taylor, M.E. Wall, P. Coggon, A.T. McPhail, Plant antitumor
agents. VI. Isolation and structure of taxol, a novel antileukemic and antitumor
agent from Taxus brevifolia, J. Am. Chem. Soc. 93 (1971) 2325e2327.
116e122.
28] I. Ojima, I. Habus, M. Zhao, M. Zucco, Y.H. Park, C.M. Sun, T. Brigaud, New and
[
2] R.M. Cusid oꢀ , J. Palaz oꢀ n, M. Bonfill, A. Navia-Osorio, C. Morales, M.T. Pinol,
efficient approaches to the semisynthesis of taxol and its C-13 side chain
Improved paclitaxel and baccatin III production in suspension cultures of
Taxus media, Biotechnol. Prog. 18 (2002) 418e423.
analogs by means of
985e7012.
b-lactam synthon method, Tetrahedron 48 (1992)
6
[
[
3] M. Suffness, Taxol: Science and Applications, CRC Press, New York, 1995.
4] A. Al-Farsi, P.M. Ellis, Treatment paradigms for patients with metastatic non-
small cell lung cancer, squamous lung cancer: first, second, and third-line,
Front. Oncol. 4 (2014) 157e162.
29] H. Mastalerz, D. Cook, C.R. Fairchild, S. Hansel, W. Johnson, J.F. Kadow,
B.H. Long, W.C. Rose, J. Tarrant, M.J. Wu, M.Q. Xue, G. Zhang, M. Zoeckler,
D.M. Vyas, The discovery of BMS-275183: an orally efficacious novel taxane,
Bioorg. Med. Chem. 11 (2003) 4315e4323.
[
[
[
5] S.M. Lichtman, How I treat ovarian cancer in older women, J. Geritr. Oncol. 5
[
[
30] H. Ge, J.T. Spletstoser, Y. Yang, M. Kayser, G.I. Georg, Synthesis of docetaxel
(
2014) 223e229.
and butitaxel analogues through kinetic resolution of racemic
-O-triethylsilylbaccatin III, J. Org. Chem. 72 (2007) 756e759.
b-lactams with
6] P.B. Sciff, J. Fant, S.B. Horwitz, Promotion of microtubule assembly in vitro by
taxol, Nature 277 (1979) 665e667.
7] T. Kirikae, I. Ojima, F. Kirikae, Z. Ma, S.D. Kuduk, J.C. Slater, et al., Structural
requirements of taxoids for nitric oxide and tumor necrosis factor production
by murine macrophages, Biochem. Biophys. Res. Commun. 227 (1996)
7
31] L. Sun, X.D. Geng, R. Geney, Y. Li, C. Simmerling, Z. Li, J.W. Lauher, S.J. Xia,
S.B. Horwitz, J.M. Veith, P. Pera, R.J. Bernacki, I. Ojima, Design, synthesis, and
0
biological evaluation of novel C14-C3 Bz-N-linked macrocyclic taxoids, J. Org.
Chem. 73 (2008) 9584e9593.
32] I. Paterson, G.J. Naylor, T. Fujita, E. Guzman, A.E. Wright, Total synthesis of a
library of designed hybrids of the microtubule-stabilising anticancer agents
taxol, discodermolide and dictyostatin, Chem. Commun. 46 (2010) 261e263.
33] E.J. Roh, D. Kim, J.Y. Choi, B.S. Lee, C.O. Lee, C.E. Song, Synthesis, biological
activity and receptor-based 3-D QSAR study of 3 -N-substituted-3 -N-deben-
zoylpaclitaxel analogues, Bioorg. Med. Chem. 10 (2002) 3135e3143.
34] E.J. Roh, D. Kim, J.Y. Choi, S.U. Choi, C.E. Song, Structure-activity relationship
227e235.
[
[
[
[
8] T. Kirikae, I. Ojima, Z. Ma, F. Kirikae, Y. Hirai, M. Nakano, Structural significance
0
of the benzoyl groups at C-3 -N position of paclitaxel for nitric oxide and
tumor necrosis factor production by murine macrophages, Biochem. Biophys.
Res. Commun. 245 (1998) 698e704.
0
0
[
9] I. Ojima, C.L. Fumero-Oderma, S.D. Kuduk, Z. Ma, F. Kirikae, T. Kirikae, Struc-
ture-activity relationship study of taxoids for their ability to activate murine
macrophages as well as inhibit the growth of macrophages cells, Bioorg. Med.
Chem. 11 (2003) 2867e2888.
0
study at the 3 -N-position of paclitaxel: synthesis and biological evaluation of
3
0
-N-acyl-paclitaxel analogues, Bioorg. Med. Chem. 10 (2002) 3145e3151.
[10] D. Guenard, F. Gueritte-Voegelein, P.A. Potier, Taxol and taxotere: discovery,
chemistry, and structure-activity relationships, Chem. Res. 26 (1993)