Design, synthesis and biological evaluation of novel fluorinated docetaxel analogues

Article abstract of DOI:10.1016/j.ejmech.2008.04.004

A series of novel fluorinated docetaxel analogues have been synthesized and evaluated in vitro and in vivo. Incorporated one, two or three fluorine atom(s) either at both meta position on C-2 benzolate and 3′-N-tert-butyloxyl group or only at 3′-N-tert-butyloxyl group has resulted in potent analogues which have comparable or superior in vitro and in vivo cytotoxicity to docetaxel. Among them, compounds 14d and 14e have displayed more potent cytotoxicity than docetaxel both in human cancer cell line SK-OV-3 in vitro and in human non-small cell lung cancer A549 xenografts in vivo. Preliminary data show that compound 14a has reduced acute animal toxicity in mice compared with docetaxel.

Full text of DOI:10.1016/j.ejmech.2008.04.004

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 44 (2009) 482e491
http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis and biological evaluation of novel
fluorinated docetaxel analogues
b
c
a,b
Hong-Fu Lu a, Xun Sun a, , Liang Xu , Li-Guang Lou , Guo-Qiang Lin
*
a Department of Chemistry of Natural Drugs, School of Pharmacy, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
b Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
c Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
Received 26 January 2008; received in revised form 3 April 2008; accepted 8 April 2008
Available online 27 April 2008
Abstract
A series of novel fluorinated docetaxel analogues have been synthesized and evaluated in vitro and in vivo. Incorporated one, two or three
fluorine atom(s) either at both meta position on C-2 benzolate and 30-N-tert-butyloxyl group or only at 30-N-tert-butyloxyl group has resulted in
potent analogues which have comparable or superior in vitro and in vivo cytotoxicity to docetaxel. Among them, compounds 14d and 14e have
displayed more potent cytotoxicity than docetaxel both in human cancer cell line SK-OV-3 in vitro and in human non-small cell lung cancer
A549 xenografts in vivo. Preliminary data show that compound 14a has reduced acute animal toxicity in mice compared with docetaxel.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Docetaxel; Fluorinated docetaxel analogues; Cytotoxicity
1. Introduction
The fluorine substitution in drug design has been
extensively exploited due to its unique and predictable physi-
cochemical properties. It is well documented that fluorine
could be effectively used as the bioisosterism of hydrogen in
nearly any agents because of the complementarity between
the carbonehydrogen bond and the carbonefluorine bond
[4]. The replacement of hydrogen with fluorine does have
consequence on molecular dipole and will produce new
electrostatic interactions due to the strong electronegativity
of fluorine. This property can be advantageous for the design
of new bioactive molecules: (1) can alter both binding and
functional property; and (2) more resistant to both chemical
and metabolic degradation due to the high bond energy (CeF)
[5]. Previous investigation revealed that both paclitaxel and
docetaxel were metabolic liabilities for enzymes in the cy-
tochrome P450 family. Major metabolites of these compounds
arose from the positions of para-hydroxylation at the C-30
phenyl ring and meta-hydroxylation at the C-2 benzoate moi-
ety [6]. Thus, the blockage of these metabolic pathways of
these molecules could increase their stability and possibly en-
hance the potency. The pioneering work reported by Ojima
Paclitaxel (1), a complex natural diterpene first isolated
from the bark of Taxus brevifolia, and its semi-synthetic deriv-
ative docetaxel (2) (Fig. 1) are currently considered to be the
most important and exciting drugs used in cancer chemother-
apy due to their unique mode of action involving stabilization
of microtubules and inhabitation of tubulin depolymerization
[1,2]. Although both of paclitaxel and docetaxel possess potent
antitumor activity against various cancer cells, several major
problems such as low aqueous solubility, multi-drug resistance
(MDR), and low activity for oral administration have emerged
after extensive clinical application for the treatment of ovar-
ian, breast, and lung cancer in the recent decades [3]. To over-
come these problems, developing new paclitaxel analogues as
anticancer drugs with fewer side effects and improved activity
against various classes of tumors are still necessary.
* Corresponding author. Tel.: þ86 21 54237127; fax: þ86 21 54237607.
E-mail address: sunxunf@shmu.edu.cn (X. Sun).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.04.004

H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
483
R2O
O
For the syntheses of compounds 14def, 7B was chosen as
the starting material. The synthesis of 7B has been previously
reported [19]. We adopted this synthetic route with a minor
change to synthesize 7B in four steps (Scheme 2). Compound
3 was selectively protected with TESCl in the presence of
imidazole to afford 4 [20] which was converted to 5 [21] by
debenzylation with Red-Al. Then compound 5 was trans-
formed into 7 by coupling with 3-fluorobenzoic acid followed
by the deprotection of TES groups. With 7B in hand,
fluorinated docetaxel analogues (14def) were obtained with
70e74% overall yields by following the same procedures
described for the synthesis of 14aec (Scheme 1).
OH
7
19
H
10
O
11
9
18
6
12
17
R1
8
3
2
paclitaxel (1 : R1 = Ph, R2 = Ac)
docetaxel (2 : R1 = t-BuO, R2 = H)
NH
O
1'
5
16
4
15
13
O
2'
O
3'
1
20
14
HO
OBz OAc
OH
Fig. 1. Structures of paclitaxel (1) and docetaxel (2).
et al. [7] showed that the 30-trifluoromethyl-10-acetyl
analogues of docetaxel exhibit better cytotoxicity than
paclitaxel and possesses more than one order of magnitude
higher potency than paclitaxel and docetaxel against a drug
resistant human breast cancer cell line. Further systematical
studies by this group [8e10] demonstrated that incorporating
fluorine at the metabolism site in the paclitaxel molecules
did indeed block some of the metabolic pathways by enzymes
of P450 (CYP) family and increased their stability. More
interestingly, the 30-N-tert-butyloxyl group on the side chain
2.2. In vitro cytotoxic activity
The cytotoxic activity of fluorinated docetaxel analogues
(14aef) was evaluated against human ovarian cell line SK-
OV-3 and the results are listed in Table 1. As shown in Table
1, compound 14a, which incorporated one fluorine atom at 30-
N-tert-butyloxyl group on the side chain of docetaxel, only ex-
hibited similar activity as compared with its parent compound
(docetaxel). However, compounds 14bee, which bear two or
three fluorine atoms either at both meta position on C-2
benzolate and 30-N-tert-butyloxyl group or only at 30-
N-tert-butyloxyl group, showed at least 76-fold enhancement
in cytotoxicity relative to docetaxel. Interestingly, compound
14f, a trifluoromethyl substituted analogue, showed 10-fold
decrease of the cytotoxicity compared with docetaxel.
of
docetaxel
analogue,
2-(3-fluorobenzoyl)docetaxel,
undergoes the unusual enzymatic hydroxylation by CYP 3A.
However, no hydroxylation was observed for 2-(3-fluoroben-
zoyl)paclitaxel both at the phenyl ring of 2-(3-fluorobenzoyl)
and at the 30-phenyl ring. Possibly, this remarkable effect is
the direct influence from the outlying fluorine moiety upon
enzymeesubstrate recognition and action [4]. These remarkable
works lay a solid foundation that the fluorine replacement on
the paclitaxel/docetaxel is a viable tool to enhance the potency,
perhaps against multi-drug resistant (MDR) cancer cell lines.
Herein, we described the syntheses of a series of docetaxel
analogues incorporated fluorine(s) at 30-N-tert-butyloxyl group
(a potential metabolic position) and/or meta position on C-2
benzolate and their cytotoxic activity.
2.3. In vivo antitumor activity
Since five new fluorinated docetaxel analogues 14aee were
relatively similar to or much more cytotoxic than docetaxel,
they were selected for further in vivo evaluation against human
non-small cell lung cancer A549 xenografts in nude mice. The
results are shown in Table 2. It can be seen that the compounds
14a, 14d and 14e showed greater inhibition rate of tumor
growth than docetaxel in human non-small cell lung cancer
A549-bearing nude mice following the intravenous
administration.
2. Results and discussion
2.1. Chemistry
The commercially available 10-deacetylbaccatin III (10-
DAB, 3) [11] was selected as the starting material for the syn-
thesis of 14aec. Compound 3 reacted with TrocCl in pyridine
to give 7,10-di-Troc-DAB 8A in 91% yield (Scheme 1) [12].
In the presence of DCC and 4-dimethylaminopyridine
(DMAP), 8A coupled with enantiopure oxazolidine 9, which
was readily prepared according to a known literature proce-
dure [13], to provide the corresponding product 10A. Removal
of 30-N-Boc and acetonide protecting group of compound 10A
with 98% formic acid gave the amino alcohol compound 11A
[14,15]. Intermediates 13aec were prepared by acylation of
amino group of compound 11A with freshly prepared fluorine
containing acyl chlorides, which could be generated by reac-
tion of corresponding fluorinated tert-butyl alcohols [16,17]
with phosgene in ether at low temperature. After removing
the 7,10-Troc protecting groups on 13aec with zinc in acetic
acid, new fluorinated docetaxel derivatives (14aec) were
synthesized in desirable yields (61e85%). To the best of our
knowledge, the introduction of fluorine on the tert-butyl group
of docetaxel has not been reported before [18].
2.4. Acute toxicity studies in mice
The acute toxicity investigation showed that there was a reg-
ular dose-dependent increase in mortality in both sexes of
mice after i.p. administration and the death occurred after 7
days. In addition to death, the toxicities included hair-floppy,
inactivity and loss of weight. The histological examination
of the death mice indicated that the reason of death was
closely related to obviously spleen shrink. The fluorinated
docetaxel derivative 14a was further selected for acute toxicity
investigation and its LD50 value was calculated to be
118.8 mg/kg (95% confidence limits ¼ 84.4e167.10 mg/kg),
larger than the value of docetaxel (LD50 ¼ 74.10 mg/kg by
i.p.), indicating that 14a was 1.6-fold less toxic than docetaxel.

484
H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
TrocO
HO
O
OTroc
TrocO
O
HO
HO
O
CO2H
Ph
OTroc
OH
TrocCl, Pyridine
rt, 30min
BocN
O
O
9
Ph
O
O
O
H
O
H
R
H
HO
HO
OAc
OAc
O
8A R3=H
8B R3=F
OAc
O
HO
O
DCC, DMAP
O
BocN
O
O
O
toluene
R3
R3
R3
3 R3=H (10-DAB)
7B R3=F
10A R3=H
10B R3=F
TrocO
O
OTroc
R
R4 5 R6
5 R6
R4
TrocO
O
OTroc
O
O
NH2
O
98% HCOOH
O
O
Cl
NH
O
O
12
H
O
Ph
O
OAc
HO
H
O
O
OH
EtOAc/Sat. NaHCO3(1:1)
HO
O
OCOCH3
O
OH
13a-f
O
11A R3=H
11B R3=F
R3
R3
R
R4 5 R6
HO
O
OH
O
Zn / HOAc
CH3OH, 50 °C
O
NH
O
a R3=H, R4=F, R5=H, R6=H
b R3=H, R4=F, R5=F, R6=H
c R3=H, R4=F, R5=F, R6=F
d R3=F, R4=F, R5=H, R6=H
e R3=F, R4=F, R5=F, R6=H
f R3=F, R4=F, R5=F, R6=F
O
H
O
14a-f
HO
OH
O
OCOCH3
O
R3
Scheme 1. Synthesis of new fluorinated docetaxel derivatives (14aef).
3. Conclusions
pathways plays a pivotal role for the enhancement of the
cytotoxicity.
In conclusion, incorporated one, two or three fluorine
atom(s) either at both meta position on C-2 benzolate and
30-N-tert-butyloxyl group or only at 30-N-tert-butyloxyl group
resulted in a series of potent analogues which have comparable
or superior in vitro and in vivo cytotoxicity to docetaxel and
have reduced acute animal toxicity in mice. Further studies
with these fluorinated docetaxel derivatives are currently
underway to elucidate whether the blockage of the metabolic
4. Experimental section
4.1. Materials and physical measurements
Reagents were purchased from Aldrich and TCI Chemical
companies. All solvents are purified and dried in accordance
with standard procedures, unless otherwise indicated. Ether,
TESO
O
TESO
O
OTES
HO
O
OTES
OH
TESCl, imidazol
DMF, rt, 40h
Red-Al
O
THF, -10°C
O
O
H
H
TESO
HO
TESO
H
HO
OAc
OAc
HO
HO
OAc
HO
HO
F
OH
OBz
4
OBz
3 (10-DAB)
5
O
OH
TESO
HO
O
OTES
COOH
HF/Pyridine
rt, 40h
O
OAc
O
H
O
H
TESO
HO
O
OAc
DIC, DMAP
Toluene
O
O
7B
6
F
F
Scheme 2. Synthesis of 2-debenzoyl-2-(m-fluorobenzoyl)-10-deacetylbaccatin III 7B.

H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
485
Table 1
In vitro cytotoxicity of fluorinated docetaxel analogues 14aef against human cancer cell line SK-OV-3
Docetaxel
14a
14b
14c
14d
14e
14f
IC50 (mM)a
3.4 ꢁ 10ꢂ3
3.8 ꢁ 10ꢂ3
2.0 ꢁ 10ꢂ5
1.0 ꢁ 10ꢂ5
3.0 ꢁ 10ꢂ5
The concentration of compound which inhibits the proliferation of tumor cells by 50% (IC50) after 72 h drug exposure.
5.0 ꢁ 10ꢂ5
3.4 ꢁ 10ꢂ2
a
tetrahydrofuran and toluene were dried over sodium/benzo-
phenone; dichloromethane and pyridine were distilled from
calcium hydride; and DMF was distilled from calcium hydride
by reduced pressure. Oxygen-free and water-free operations
were carried out under argon atmosphere in dried glassware
unless otherwise noted. All reactions were monitored by
TLC with precoated silica gel plates GF254, 10e40 mm
(Yantai, China). The purity of the samples was determined
by column chromatography with the silica gel H 300e400
mesh (Yantai, China). Melting points (mp) were determined
using an X-4 microscope melting point apparatus and were
4.2. Chemistry
4.2.1. 7,10,13-Tris(triethylsilyl)-2-debenzoyl-2-(m-fluorobe-
nzoyl)-10-deacetylbaccatin III (6)
Compound 5 (2 g, 2.55 mmol), DIC (4.83 g, 38.30 mmol),
DMAP (30.50 mg, 0.25 mmol), and 3-fluorobenzoic acid
(5.37 g, 38.30 mmol) were dissolved in toluene (20 mL).
The resulting mixture was warmed to 60 ꢀC and stirred over-
night at this temperature. The reaction mixture was quenched
with saturated NaHCO3 (10 mL), and then extracted with
EtOAc (20 mL ꢁ 2). The combined organic layers were
washed with brine, dried over anhydrous MgSO4, filtered,
and concentrated in vacuo. The obtained residue was purified
by silica gel chromatography column (petroleum ether/ethyl
acetate 20/1) to give 6 (1.80 g, 78%) as a white solid; mp
1
uncorrected. All H NMR spectra were recorded on Varian
Mercury 300 (300 MHz) or Bruker DRX-400 (400 MHz)
spectrometer at room temperature and chemical shifts are
reported in parts per million (d) relative to TMS (0.00) as
internal standard; expressed in peak shape, the number of
hydrogen, and coupling constant in hertz. 13C NMR spectra
data were recorded on Bruker DRX-400 (100 MHz) or Bruker
DPX-300 (75 MHz) spectrometer at room temperature and
chemical shifts are reported in parts per million (d) relative
to d-substituted solvents (chloroform-d at 77.2 ppm, acetone-
d6 at 30.6 and 206.7 ppm) as internal standard. Mass spectra
ware performed at the testing and analysis center of Shanghai
Institute of Organic Chemistry: Low-resolution mass spectra
(ESI) were performed on Shimadzu LCMS-2010EV and
high-resolution mass spectra on IonSpec 4.7 Tesla FTMS
(MALDI) or Bruker Daltonics, Inc. APEXIII7.0 TESLA
FMS (ESI).
1
218e220 ꢀC. H NMR (300 MHz, CDCl3): d 0.63 (m, 18H),
1.00 (m, 27H), 1.13 (s, 3H), 1.19 (s, 3H), 1.65 (s, 3H), 1.98
(s, 3H), 2.16 (m, 2H), 2.29 (s, 3H), 1.88 and 2.53 (2m, 2H),
3.86 (d, 1H, J ¼ 6.9 Hz), 4.13 and 4.28 (2d, 2H, J ¼ 8.1 Hz),
4.41 (dd, 1H, J ¼ 10.5, 6.9 Hz), 4.92 (m, 1H), 4.96 (m, 1H),
5.19 (s, 1H), 5.59 (d, 1H, J ¼ 6.9 Hz), 7.30 (m, 1H), 7.46
(m, 1H), 7.78 (m, 1H), 7.88 (m, 1H) [22].
4.2.2. 2-Debenzoyl-2-(m-fluorobenzoyl)-10-deacetylbacca-
tin III (7B)
To a solution of 6 (1.45 g, 1.60 mmol) in dried THF (40 mL)
was added anhydrous pyridine (8.0 mL). The reaction mixture
was cooled to 0 ꢀC, and then HFepyridine (8.0 mL) was added.
Table 2
In vivo antitumor activity of fluorinated docetaxel derivatives 14aee against human non-small cell lung cancer A549 xenograft in nude micea
Groups
Dose (mg/kg)
No.of mice
d0b
Body wt changed (%)
T/C (%)
dnc
Control
14a
14a
12
6
6
6
6
6
6
5
5
5
5
6
12
6
6
6
6
6
6
5
5
5
5
6
0
12
16
12
18
12
18
12
18
12
18
12
ꢂ19.1
ꢂ22.0
0
41.5e
37.9e
91.5
14b
14b
ꢂ7.7
0
83.5
91.8
14c
14c
ꢂ9.7
ꢂ18.0
ꢂ31.3
ꢂ16.5
ꢂ26.7
ꢂ19.6
72.0
14d
14d
53.7e
30.2e
51.7e
24.4e
43.0e
14e
14e
Docetaxel
a
Nude mice were subcutaneously injected with A549 cells. When the tumor reached 80e150 mm3 in volume, animals were i.v. administered 14aee or
docetaxel.
b
c
d
e
d0: at day before the first treatment.
dn: the day when maximum effect was gained (at day 14 after the first treatment).
Body weight was measured at the end of the experiment.
p < 0.01 versus control.

486
H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
The resulting mixture was allowed to warm to room tempera-
ture, and stirred for 40 h. The reaction mixture was diluted
with EtOAc (200 mL), and the organic layer was washed with
sodium bicarbonate, brine, dried over Na2SO4, and concentrated
invacuo. The obtained residuewas purified by silica gel chroma-
tography column (CH2Cl2/CH3OH 40/1) to afford 7B (800 mg,
d 1.11 (s, 9H), 1.18 (s, 3H), 1.25 (s, 3H), 1.77 (s, 3H), 1.82 (s,
6H), 1.89 (s, 3H), 2.04 (s, 3H), 2.17 (m, 2H), 2.04 and 2.60
(2m, 2H), 3.89 (d, 1H, J ¼ 7.2 Hz), 4.10 and 4.28 (2d, 2H,
J ¼ 8.4 Hz), 4.48 (d, 1H, J ¼ 6.9 Hz), 4.60 and 4.91 (2d, 2H,
J ¼ 12.0 Hz), 4.78 (s, 2H), 4.91 (d, 1H, J ¼ 12.0 Hz), 5.07 (br
s, 1H), 5.57 (dd, 1H, J ¼ 10.8, 6.9 Hz), 5.64 (d, 1H,
J ¼ 7.2 Hz), 6.24 (s, 1H), 6.28 (t, 1H, J ¼ 9.6 Hz), 7.32e7.39
(m, 6H), 7.50 (m, 1H), 7.71 (d, 1H, J ¼ 8.1 Hz), 7.85 (d, 1H,
J ¼ 8.1 Hz); 13C NMR (100 MHz, CDCl3): d 10.5, 14.5, 20.8,
21.2, 26.1, 26.4, 27.8 (three overlapping peaks), 29.5, 33.0,
35.2, 42.9, 44.8, 46.7, 55.9, 64.2, 70.9, 74.6, 75.9, 76.1, 77.0,
77.3, 78.8, 78.9, 80.2, 80.4, 80.8, 83.5, 94.0, 96.8, 116.6,
120.8, 125.8, 126.2 (two overlapping peaks), 127.8, 128.6
(two overlapping peaks), 130.2, 130.3, 131.1, 131.7, 142.6,
151.4, 153.0, 153.0, 162.4 (d, JCeF ¼ 246.4 Hz), 165.5, 169.7,
170.0, 200.4; ESIMS m/z 1236.2 [M þ Naþ]; HRMS (MALDI)
m/z calcd for C52H58NO18FCl6Naþ [M þ Naþ]: 1236.1625,
found: 1236.16614.
1
89%) as a white solid; mp 227e229 ꢀC. H NMR (300 MHz,
CDCl3): d 1.08 (s, 3H), 1.10 (s, 3H), 1.72 (s, 3H), 2.06 (s, 3H),
2.26 (s, 3H), 2.39 (m, 2H), 1.82 and 2.47 (2m, 2H), 3.60 (s,
1H), 4.04 (d, 1H, J ¼ 7.2 Hz), 4.16 (s, 2H), 4.17 (d, 1H,
J ¼ 6.0 Hz), 4.24 (d, 1H, J ¼ 2.1 Hz), 4.34 (m, 1H), 4.59 (d,
1H, J ¼ 4.5 Hz), 4.91 (m, 1H), 4.98 (d, 1H, J ¼ 9.3 Hz), 5.27
(d, 1H, J ¼ 1.8 Hz), 5.63 (d, 1H, J ¼ 7.5 Hz), 7.45 (m, 1H),
7.62 (m, 1H), 7.78 (d, 1H, J ¼ 8.1 Hz), 7.94 (d, 1H,
J ¼ 7.8 Hz) [23].
4.2.3. 7,10-Di(2,2,2-trichloroethyloxycarbonyl)-2-deben-
zoyl-2-(m-fluorobenzoyl)-10-deacetylbaccatin III (8B)
To a solution of 7B (1.03 g, 1.84 mmol) in anhydrous
pyridine (20 mL) was added 2,2,2-trichloroethyl chloroformate
(0.85 mL, 6.17 mmol) dropwise at 0 ꢀC. Then the reaction
mixture was warmed to room temperature and further stirred
for 30 min. The reaction mixture was then quenched with
water and the solvent was removed under reduced pressure.
The residue was dissolved in CH2Cl2, and washed with diluted
HCl and brine. Then the organic layer was dried with
anhydrous Na2SO4, filtered, and concentrated in vacuo. The
crude residue was purified by flash chromatography column (pe-
troleum ether/ethyl acetate 2/1) to give8B (1.58 g, 94% yield) as
4.2.5. N-De-tert-butoxycarbonyl-7,10-di(2,2,2-trichloroe-
thyloxycarbonyl)-2-debenzoyl-2-(m-fluorobenzoyl)docetaxel
(11B)
To a round-bottomed flask (10 mL) were added 10B
(800 mg, 0.66 mmol) and HCOOH (>98%, 20 mL). The
reaction mixture was stirred at room temperature for 2 h.
Then the resulting solution was neutralized by addition of sat-
urated NaHCO3. The water phase was extracted with EtOAc,
dried over Na2SO4, filtered, and concentrated in vacuo. The
obtained residue was purified by silica gel flash chromatogra-
phy column (acetone/petroleum ether 1/3) to afford 11B
1
a white solid; mp 222e224 ꢀC. H NMR (300 MHz, CDCl3):
1
d 1.12 (s, 3H), 1.15 (s, 3H), 1.85 (s, 3H), 2.17 (s, 3H), 2.30
(m, 2H), 2.31 (s, 3H), 2.05 and 2.65 (2m, 2H), 3.98 (d, 1H,
J ¼ 6.6 Hz), 4.14 and 4.33 (2d, 2H, J ¼ 8.4 Hz), 4.61 and 4.92
(2d, 2H, J ¼ 12.0 Hz), 4.78 (d, 2H, J ¼ 12.0 Hz), 4.90 (m,
1H), 5.00 (d, 1H, J ¼ 7.8 Hz), 5.59 (m, 1H), 5.62 (d, 1H,
J ¼ 7.5 Hz), 6.27 (s, 1H), 7.33 (m, 1H), 7.48 (m, 1H), 7.79 (m,
1H), 7.90 (d, 1H, J ¼ 7.5 Hz); 13C NMR (100 MHz, CDCl3):
d 10.6, 15.4, 20.1, 22.5, 26.6, 33.3, 38.4, 42.6, 47.4, 56.3,
67.8, 74.6, 76.2, 76.6, 77.1, 77.4, 78.7, 79.7, 80.4, 83.7, 94.2,
94.3, 116.9, 120.9, 125.9, 130.4, 130.8, 131.4, 146.6, 153.2,
153.3, 162.6 (d, JCeF ¼ 246.4 Hz), 165.7, 170.8, 201.1; ESIMS
m/z 933.0 [M þ Naþ]; HRMS (MALDI) m/z calcd for
C35H37O14FCl6Naþ [M þ Naþ]: 933.0215, found: 933.01908.
(700 mg, 99%) as a white solid; mp 155e158 ꢀC. H NMR
(300 MHz, CDCl3): d 1.17 (s, 3H), 1.24 (s, 3H), 1.82 (s,
3H), 2.00 (s, 3H), 2.27 (s, 3H), 2.14 (m, 2H), 2.02 and 2.60
(2m, 2H), 3.85 (d, 1H, J ¼ 6.6 Hz), 4.11 and 4.28 (2d, 2H,
J ¼ 8.4 Hz), 4.31 (m, 1H), 4.35 (br s, 1H), 4.60 and 4.91
(2d, 2H, J ¼ 11.7 Hz), 4.77 (s, 2H), 4.90 (d, 1H, J ¼ 6.6 Hz),
5.54 (dd, 1H, J ¼ 10.5, 7.5 Hz), 5.64 (d, 1H, J ¼ 6.6 Hz),
6.22 (t, 1H, J ¼ 8.7 Hz), 6.22 (s, 1H), 7.36e7.43 (m, 6H),
7.51 (m, 1H), 7.71 (m, 1H), 7.86 (d, 1H, J ¼ 7.5 Hz); 13C
NMR (100 MHz, CDCl3): d 10.7, 14.6, 21.1, 21.2, 26.2,
26.8, 27.8, 33.1, 35.2, 43.0, 46.7, 55.9, 66.8, 70.6, 74.6,
76.0, 76.2, 77.3, 79.0, 80.2, 82.0, 83.6, 94.1, 98.8, 116.6,
121.0, 126.0, 126.8 (two overlapping peaks), 128.6, 129.1
(two overlapping peaks), 130.4, 131.2, 131.5, 137.9, 143.1,
153.1, 153.2, 162.5 (d, JCeF ¼ 246.2 Hz), 165.6, 170.2,
172.3, 200.6; ESIMS m/z 1096.1 [M þ Naþ]; HRMS
(MALDI) m/z calcd for C44H46NO16FCl6Naþ [M þ Naþ]:
1096.0810, found: 1096.08241.
4.2.4. 7,10-Di(2,2,2-trichloroethyloxycarbonyl)-2-deben-
zoyl-2-(m-fluorobenzoyl)-10-deacetylbaccatin
III-13-O-
[(4S,5R)-4-phenyl-3-(tert-butoxycarbonyl)-2,2-dimethyl-
1,3-oxazolidine-5-carboxylate] (10B)
To a solution of anhydrous toluene (20 mL) were added 8B
(0.91 g, 1.00 mmol), 9 (0.96 g, 3.00 mmol), DCC (0.62 g,
3.00 mmol) and DMAP (12.2 mg, 0.10 mmol). The resulting
mixture was stirred at 85 ꢀC for 1 h. After the completion, the
reaction mixture was washed with water (10 mL ꢁ 3), dried
over Na2SO4, filtered and concentrated in vacuo. The obtained
residue was purified by silica gel flash chromatography column
(petroleum ether/ethyl acetate 4/1) to afford 10B (1.13 g, 93%)
as a white solid; mp 221e223 ꢀC. 1H NMR (300 MHz, CDCl3):
4.2.6. General procedure for the preparation of 12
To a dried round bottom flask were added ethyl fluoro-
substituted acetate (0.1 mol), benzyl alcohol (0.3 mol) and
boron trifluoride etherate (0.01 mol) under nitrogen
atmosphere. The resulting mixture was stirred overnight at
75 ꢀC. The reaction mixture was extracted with ethyl acetate
(100 mL ꢁ 3) and the organic layer was washed with saturated
NaHCO3 solution, brine, dried over anhydrous MgSO4, and

H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
487
evacuated in vacuo. The residue was purified by silica gel
column chromatography (petroleum ether/ethyl acetate 20/1)
to give the colorless liquid product benzyl fluoro-substituted
acetate (60% yield). The obtained benzyl fluoro-substituted
acetate in ether (20 mL) was added to a solution of methyl-
magnesium bromide (3 M, 36.7 mL). The mixture was stirred
at 0e5 ꢀC for 20 min and quenched with ice water and
hydrochloric acid. The ethereal layer was separated, washed
with diluted NaHCO3 solution, dried over anhydrous
MgSO4, and distilled. The fractions with b.p. 96e98 ꢀC
were collected (21.7% yield). Then pyridine (11 mmol) in
ether (8 mL) was added dropwise to a mixture of above
obtained alcohol (10 mmol) and triphosgene (3.33 mmol) in
ether (10 mL) at ꢂ30 ꢀC. The mixture was stirred for 2 h at
this temperature, slowly warmed to room temperature, and
further stirred for 10 h. The resulting solution was used
directly for the next step without further purification.
(300 MHz, CDCl3): d 1.20 (s, 3H), 1.27 (s, 3H), 1.39 (s, 6H),
1.86 (s, 3H), 1.94 (s, 3H), 2.29 (m, 2H), 2.39 (s, 3H), 2.07 and
2.62 (2m, 2H), 3.41 (d, 1H, J ¼ 3.9 Hz), 3.90 (d, 1H,
J ¼ 6.6 Hz), 4.18 and 4.34 (2d, 2H, J ¼ 8.4 Hz), 4.60 and
4.91 (2d, 2H, J ¼ 11.7 Hz), 4.66 (m, 1H), 4.78 (s, 2H), 4.95
(d, 1H, J ¼ 10.8 Hz), 5.26 (d, 1H, J ¼ 8.1 Hz), 5.54 (dd, 1H,
J ¼ 10.5, 7.2 Hz), 5.67 (d, 1H, J ¼ 2.7 Hz), 5.70 (s, 1H),
6.00 (t, 1H, J ¼ 57.0 Hz), 6.23 (s, 1H), 6.23 (m, 1H), 7.35e
7.45 (m, 5H), 7.50 (t, 2H, J ¼ 7.5 Hz), 7.63 (t, 1H,
J ¼ 7.2 Hz), 8.10 (d, 2H, J ¼ 7.5 Hz); 13C NMR (100 MHz,
CDCl3): d 10.7, 14.6, 19.8 (two overlapping peaks), 20.9,
22.5, 26.3, 33.2, 35.3, 43.1, 46.9, 56.2, 56.4, 72.2, 73.3,
74.1, 76.3, 76.4, 77.1, 77.4, 78.6, 79.1, 79.8 (t, JCeF
¼
27.1 Hz), 80.9, 83.6, 94.1 (two overlapping peaks), 114.8 (t,
JCeF ¼ 246.9 Hz), 126.7 (two overlapping peaks), 128.3,
128.7 (two overlapping peaks), 128.9 (two overlapping peaks),
129.7, 130.1 (two overlapping peaks), 132.2, 133.8, 137.8,
142.2, 153.2, 153.2, 154.2, 166.8, 170.4, 172.4, 200.6; ESIMS
m/z 1214.1 [M þ Naþ]; HRMS (MALDI) m/z calcd for
C49H53NO18F2Cl6Naþ [M þ Naþ]: 1214.1230, found:
1214.12541.
4.2.7. General procedure for the preparation of 13aef
To a solution of 11A (2.00 g, 1.89 mmol) or 11B (2.03 g,
1.89 mmol) in EtOAc/H2O (1/1, 120 mL) was dropwise added
excessive 12 at 0 ꢀC. The resulting mixture was stirred at room
temperature for 2 h. The reaction mixture was extracted with
ethyl acetate (20 mL ꢁ 3) and the combined organic layer
was washed with brine, dried over Na2SO4, filtered, and
concentrated in vacuo. The obtained residue was purified by
silica gel flash chromatography column (petroleum ether/ethyl
acetate 1/1) to afford 13aef as a white solid, which would be
used directly for the next step.
4.2.7.3.
N-De-tert-butoxycarbonyl-N-[2-(1,1,1-trifluoro-2-
methyl)propyloxycarbonyl]-7,10-di(2,2,2-trichloroethyloxycar-
bonyl)docetaxel (13c). Yield 46%; mp 170e173 ꢀC; 1H NMR
(300 MHz, CDCl3): d 1.20 (s, 3H), 1.27 (s, 3H), 1.54 (s, 3H),
1.58 (s, 3H), 1.85 (s, 3H), 1.93 (s, 3H), 2.29 (m, 2H), 2.37 (s,
3H), 2.06 and 2.58 (2m, 2H), 3.46 (br s, 1H), 3.90 (d, 1H,
J ¼ 6.6 Hz), 4.17 and 4.31 (2d, 2H, J ¼ 8.4 Hz), 4.64 (m,
1H), 4.60 and 4.91 (2d, 2H, J ¼ 11.7 Hz), 4.78 (s, 2H), 4.95
(d, 1H, J ¼ 10.2 Hz), 5.25 (d, 1H, J ¼ 7.8 Hz), 5.53 (dd, 1H,
J ¼ 9.9, 7.5 Hz), 5.69 (d, 1H, J ¼ 6.6 Hz), 5.75 (d, 1H,
J ¼ 9.3 Hz), 6.20 (t, 1H, J ¼ 8.1 Hz), 6.23 (s, 1H), 7.33e
7.45 (m, 5H), 7.51 (t, 2H, J ¼ 7.5 Hz), 7.64 (t, 1H,
J ¼ 7.5 Hz), 8.10 (d, 2H, J ¼ 7.5 Hz); 13C NMR (100 MHz,
CDCl3): d 10.7, 14.6, 19.3, 19.6, 20.8, 22.4, 26.3, 33.2, 35.2,
43.1, 46.9, 56.2, 56.4, 60.4, 72.2, 73.3, 74.1, 76.3, 77.1,
77.4, 78.6, 78.6, 79.1, 80.9, 83.6, 94.1 (two overlapping
peaks), 126.2, 126.8 (two overlapping peaks), 128.3, 128.7
(two overlapping peaks), 128.9 (two overlapping peaks),
129.7, 130.1 (two overlapping peaks), 132.2, 133.8, 137.7,
142.2, 153.1, 153.2, 153.5, 166.9, 170.3, 172.4, 200.6; ESIMS
m/z 1232.1 [M þ Naþ]; HRMS (MALDI) m/z calcd for
C49H52NO18F3Cl6Naþ [M þ Naþ]: 1232.1176, found:
1232.11599.
4.2.7.1. N-De-tert-butoxycarbonyl-N-[2-(1-fluoro-2-methyl)-
propyloxycarbonyl]-7,10-di(2,2,2-trichloroethyloxycarbonyl)-
docetaxel (13a). Yield 27%; mp 176e179 ꢀC; 1H NMR
(300 MHz, CDCl3): d 1.20 (s, 3H), 1.27 (s, 3H), 1.35 (s,
6H), 1.86 (s, 3H), 1.95 (s, 3H), 2.32 (m, 2H), 2.41 (s, 3H),
2.07 and 2.62 (2m, 2H), 3.91 (d, 1H, J ¼ 6.9 Hz), 4.18 and
4.34 (2d, 2H, J ¼ 8.1 Hz), 4.34 and 4.46 (m, 2H), 4.60 and
4.91 (2d, 2H, J ¼ 12.0 Hz), 4.66 (m, 1H), 4.78 (s, 2H), 4.95
(d, 1H, J ¼ 11.4 Hz), 5.28 (m, 1H), 5.55 (m, 1H), 5.57 (d,
1H, J ¼ 9.3 Hz), 5.70 (d, 1H, J ¼ 6.9 Hz), 6.24 (s, 1H), 6.24
(t, 1H, J ¼ 7.5 Hz), 7.34e7.44 (m, 5H), 7.50 (t, 2H,
J ¼ 7.5 Hz), 7.63 (t, 1H, J ¼ 7.5 Hz), 8.11 (d, 2H,
J ¼ 7.5 Hz); 13C NMR (100 MHz, CDCl3): d 10.7, 14.6,
18.8, 21.0, 22.3, 22.3, 22.5, 26.3, 33.3, 35.4, 43.2, 46.9,
56.3, 69.6, 72.3, 73.5, 74.2, 76.4, 77.2, 77.4, 78.7, 79.1, 79.9
(d, JCeF ¼ 18.8 Hz), 80.9, 83.7, 86.8 (d, JCeF ¼ 176.1 Hz),
94.2 (two overlapping peaks), 126.7 (two overlapping peaks),
128.2, 128.7 (two overlapping peaks), 128.9 (two overlapping
peaks), 129.1, 130.2 (two overlapping peaks), 132.1, 133.8,
138.0, 142.3, 153.2, 153.2, 154.8, 166.8, 170.4, 172.6,
200.7; ESIMS m/z 1196.1 [M þ Naþ]; HRMS (MALDI) m/z
calcd for C49H54NO18FCl6Naþ [M þ Naþ]: 1196.1373, found:
1196.13484.
4.2.7.4. N-De-tert-butoxycarbonyl-N-[2-(1-fluoro-2-methyl)-
propyloxycarbonyl]-7,10-di(2,2,2-trichloroethyloxycarbonyl)-
2-debenzoyl-2-(m-fluorobenzoyl)docetaxel (13d). Yield 20%;
mp 164e167 ꢀC; 1H NMR (300 MHz, CDCl3): d 1.17 (s,
3H), 1.20 (s, 3H), 1.28 (s, 6H), 1.86 (s, 3H), 1.94 (s, 3H),
2.25 (m, 2H), 2.37 (s, 3H), 2.06 and 2.63 (2m, 2H), 3.45 (d,
1H, J ¼ 5.1 Hz), 3.90 (d, 1H, J ¼ 6.9 Hz), 4.05 (dd, 2H,
J ¼ 14.1, 7.2 Hz), 4.20 and 4.31 (2d, 2H, J ¼ 8.4 Hz), 4.61
and 4.92 (2d, 2H, J ¼ 12.0 Hz), 4.65 (m, 1H), 4.78 (s, 2H),
4.95 (d, 1H, J ¼ 10.8 Hz), 5.29 (br d, 1H, J ¼ 8.7 Hz), 5.55
(m, 1H), 5.56 (m, 1H), 5.66 (d, 1H, J ¼ 6.9 Hz), 6.23 (s,
4.2.7.2.
N-De-tert-butoxycarbonyl-N-[2-(1,1-difluoro-2-
methyl)propyloxycarbonyl]-7,10-di(2,2,2-trichloroethyloxycar-
bonyl)docetaxel (13b). Yield 76%; mp 166e169 ꢀC; 1H NMR

488
H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
1H), 6.23 (t, 1H, J ¼ 9.0 Hz), 7.24e7.41 (m, 6H), 7.50 (m,
1H), 7.78 (d, 1H, J ¼ 8.7 Hz), 7.91 (d, 1H, J ¼ 7.8 Hz).
distillation gave a white solid. The obtained solid was then dis-
solved in 60 ml ethyl acetate, which was washed with satu-
rated NaHCO3 and brine, dried over Na2SO4, and
concentrated in vacuo. The obtained residue was purified by
silica gel flash chromatography column (CH2Cl2/MeOH 40/
1) to give 14aef as a white solid.
4.2.7.5. N-De-tert-butoxycarbonyl-N-[2-(1,1-difluoro-2-meth-
yl)propyloxycarbonyl]-7,10-di(2,2,2-trichloroethyloxycarbonyl)-
2-debenzoyl-2-(m-fluorobenzoyl)docetaxel (13e). Yield 75%;
mp 144e146 ꢀC; 1H NMR (300 MHz, CDCl3): d 1.20
(s, 3H), 1.28 (s, 3H), 1.39 (s, 6H), 1.86 (s, 3H), 1.94 (s, 3H),
2.27 (m, 2H), 2.38 (s, 3H), 2.07 and 2.63 (2m, 2H), 3.32 (d,
1H, J ¼ 5.4 Hz), 3.90 (d, 1H, J ¼ 6.9 Hz), 4.17 and 4.33 (2d,
2H, J ¼ 8.4 Hz), 4.60 and 4.91 (2d, 2H, J ¼ 11.7 Hz), 4.66
(m, 1H), 4.78 (s, 2H), 4.96 (d, 1H, J ¼ 8.1 Hz), 5.25 (d, 1H,
J ¼ 11.1 Hz), 5.54 (m, 1H), 5.61 (d, 1H, J ¼ 7.8 Hz), 5.66 (d,
1H, J ¼ 6.9 Hz), 6.01 (t, 1H, J ¼ 57.0 Hz), 6.20 (m, 1H), 6.23
(s, 1H), 7.31e7.46 (m, 6H), 7.51 (m, 1H), 7.78 (m, 1H), 7.90
(d, 1H, J ¼ 7.5 Hz); 13C NMR (100 MHz, CDCl3): d 10.7,
14.7, 19.8 (two overlapping peaks), 20.9, 22.4, 26.3, 33.3,
35.2, 43.1, 46.9, 56.2, 56.5, 68.2, 72.2, 73.4, 74.6, 76.2, 76.3,
77.2, 78.8, 79.1, 79.8 (t, JCeF ¼ 27.1 Hz), 80.9, 83.6, 94.2
(two overlapping peaks), 115.0 (t, JCeF ¼ 244.5 Hz), 116.9,
121.0, 126.0, 126.7 (two overlapping peaks), 128.8, 129.0
(two overlapping peaks), 130.5, 131.2, 132.1, 138.0, 142.3,
153.2, 153.2, 154.3, 163.7 (d, JCeF ¼ 243.7 Hz), 165.7, 170.4,
172.5, 200.5; ESIMS m/z 1232.1 [M þ Naþ]; HRMS (MALDI)
m/z calcd for C49H52NO18F3Cl6Naþ [M þ Naþ]: 1232.1139,
found: 1232.11599.
4.2.8.1. N-De-tert-butoxycarbonyl-N-[2-(1-fluoro-2-methyl)-
propyloxycarbonyl]docetaxel (14a). Yield 81%; mp 164e
166 ꢀC; 1H NMR (400 MHz, CDCl3): d 1.13 (s, 3H,
17-CH3), 1.24 (s, 3H, 16-CH3), 1.35 (s, 6H, eOeC(CH3)2e),
1.76 (s, 3H, 19-CH3), 1.85 (s, 3H, 18-CH3), 2.23 (m, 2H, 14-
CH2), 2.38 (s, 3H, OAc), 1.85 and 2.58 (2m, 2H, 6-CH2), 3.38
(d, 1H, J ¼ 5.1 Hz, 20-OH), 3.92 (d, 1H, J ¼ 7.3 Hz, 3-CH),
4.20 and 4.31 (2d, 2H, J ¼ 8.6 Hz, 20-CH2), 4.23 (m, 1H, 7-
CH), 4.23e4.45 (m, 2H, FeCH2e), 4.63 (br s, 1H, 20-CH),
4.94 (d, 1H, J ¼ 7.7 Hz, 5-CH), 5.20 (s, 1H, 10-CH), 5.27
(br d, 1H, J ¼ 8.9 Hz, 30-CH), 5.60 (d, 1H, J ¼ 9.5 Hz,
eCONHe), 5.68 (d, 1H, J ¼ 7.1 Hz, 2-CH), 6.24 (t, 1H,
J ¼ 8.6 Hz, 13-CH), 7.38 (m, 5H, 30-Ph), 7.49 (t, 2H,
J ¼ 7.5 Hz, m-OBz), 7.61 (t, 1H, J ¼ 7.4 Hz, p-OBz), 8.11
(d, 2H, J ¼ 7.5 Hz, o-OBz); 13C NMR (100 MHz, CDCl3):
d 9.9 (C-19), 14.3 (C-18), 20.7 (C-17), 22.3 (OAc), 22.5
(two overlapping peaks, eOeC(CH3)2e), 26.4 (C-16), 35.7
(C-14), 36.8 (C-6), 43.1 (C-15), 46.5 (C-3), 56.2 (C-30), 57.7
(C-8), 71.9 (C-7), 72.4 (C-13), 73.6 (C-20), 74.5 (C-10),
74.9 (C-2), 76.6 (C-20), 78.8 (C-1), 79.8 (d, JCeF ¼ 16.5 Hz,
4.2.7.6.
N-De-tert-butoxycarbonyl-N-[2-(1,1,1-trifluoro-2-
eOeC(CH3)2), 81.1 (C-4), 84.2 (C-5), 86.9 (d, JCeF
¼
methyl)propyloxycarbonyl]-7,10-di(2,2,2-trichloroethyloxycar-
175.0 Hz, FeCH2e), 126.7 (two overlapping peaks, o-Ph),
128.0 ( p-Ph), 128.7 (two overlapping peaks, m-OBz), 128.8
(two overlapping peaks, m-Ph), 129.3 (C-1, OBz), 130.2
(two overlapping peaks, o-OBz), 133.7 ( p-OBz), 136.0 (C-11),
138.2 (C-12), 138.4 (C-1, Ph), 154.9 (eNHCOe), 166.9
(C]O in OBz), 170.3 (OAc), 172.6 (C-10), 211.2 (C-9);
ESIMS m/zþ848.4 [M þ Naþ]; HRMS (ESI) m/z calcd for
C43H53FNO14 [M þ Hþ]: 826.3423, found: 826.3450.
bonyl)-2-debenzoyl-2-(m-fluorobenzoyl)docetaxel (13f). Yield
1
35%; mp 158e161 ꢀC; H NMR (300 MHz, CDCl3): d 1.20
(s, 3H), 1.27 (s, 3H), 1.56 (s, 3H), 1.58 (s, 3H), 1.86 (s,
3H), 1.93 (s, 3H), 2.27 (m, 2H), 2.36 (s, 3H), 2.07 and 2.63
(2m, 2H), 3.35 (d, 1H, J ¼ 5.1 Hz), 3.90 (d, 1H, J ¼ 6.9 Hz),
4.16 and 4.33 (2d, 2H, J ¼ 8.1 Hz), 4.60 and 4.91 (2d, 2H,
J ¼ 11.7 Hz), 4.62 (m, 1H), 4.78 (s, 2H), 4.96 (d, 1H,
J ¼ 11.7 Hz), 5.24 (br d, 1H, J ¼ 9.6 Hz), 5.53 (m, 1H), 5.66
(d, 1H, J ¼ 7.2 Hz), 5.66 (m, 1H), 6.20 (t, 1H, J ¼ 10.5 Hz),
6.23 (s, 1H), 7.33e7.46 (m, 6H), 7.51 (m, 1H), 7.78 (d, 1H,
J ¼ 8.4 Hz), 7.90 (d, 1H, J ¼ 7.8 Hz); 13C NMR (100 MHz,
CDCl3): d 10.6, 14.6, 19.4, 19.6, 20.8, 22.4, 26.3, 33.2, 35.1,
43.1, 46.9, 56.2, 56.5, 68.1, 72.1, 73.4, 74.5, 76.2, 76.3,
77.1, 77.4, 78.7, 79.1, 80.8, 83.6, 94.1 (two overlapping
peaks), 109.7, 116.9, 121.0, 126.0, 126.8 (two overlapping
peaks), 128.4, 129.0 (two overlapping peaks), 130.4, 131.2,
4.2.8.2. N-De-tert-butoxycarbonyl-N-[2-(1,1-difluoro-2-meth-
yl)propyloxycarbonyl]docetaxel (14b). Yield 61%; mp 166e
168 ꢀC; 1H NMR (300 MHz, CDCl3): d 1.12 (s, 3H, 17-CH3),
1.23 (s, 3H, 16-CH3), 1.36 (s, 6H, eOeC(CH3)2e), 1.73
(s, 3H, 19-CH3), 1.83 (s, 3H, 18-CH3), 2.22 (m, 2H, 14-
CH2), 2.36 (s, 3H, OAc), 1.83 and 2.55 (2m, 2H, 6-CH2),
3.39 (m, 1H, 20-OH), 3.88 (d, 1H, J ¼ 6.9 Hz, 3-CH), 4.18
and 4.31 (2d, 2H, J ¼ 8.1 Hz, 20-CH2), 4.24 (m, 1H, 7-CH),
4.65 (br s, 1H, 20-CH), 4.94 (d, 1H, J ¼ 9.0 Hz, 5-CH), 5.25
(s, H, 10-CH), 5.25 (m, 1H, 30-CH), 5.65 (d, 1H, J ¼ 7.2 Hz,
2-CH), 5.88 (d, 1H, J ¼ 7.5 Hz, eCONHe), 5.97 (t, 1H,
J ¼ 57.0 Hz, F2eCHe), 6.22 (t, 1H, J ¼ 8.1 Hz, 13-CH),
7.33e7.40 (m, 5H, 30-Ph), 7.49 (t, 2H, J ¼ 7.5 Hz, m-OBz),
7.62 (t, 1H, J ¼ 7.5 Hz, p-OBz), 8.10 (d, 2H, J ¼ 7.5 Hz, o-
OBz); 13C NMR (CD3COCD3, 75 MHz): d 10.3 (C-19), 14.3
(C-18), 20.0 (C-17), 21.3 (OAc), 23.0 (two overlapping peaks,
eOeC(CH3)2e), 27.0 (C-16), 36.7 (C-14), 37.4 (C-6), 44.0
(C-15), 47.4 (C-3), 58.3 (C-30), 58.5 (C-8), 72.0 (C-7), 72.2
(C-13), 74.9 (C-20), 75.0 (C-10), 75.9 (C-2), 76.8 (C-20),
78.5 (C-1), 79.2 (d, JCeF ¼ 27.1 Hz, eOeC(CH3)2), 81.7
132.1, 138.0, 142.3, 153.2, 153.2, 154.3, 162.6 (d, JCeF
246.2 Hz), 165.7, 170.3, 172.4, 200.5; ESIMS m/z 1250.1
¼
[M þ Naþ];
HRMS
(MALDI)
m/z
calcd
for
C49H51NO18F4Cl6Naþ [M þ Naþ]: 1250.1056, found:
1250.10657.
4.2.8. General procedure for the preparation of 14aef
To a solution of 13aef (0.53 mmol) in methanol (20 mL)
were added glacial acetic acid (3 mL) and zinc powder
(1.14 g, 17.54 mmol). The resulting mixture was stirred at
50 ꢀC for 0.5 h. The reaction mixture was filtered to remove
the zinc and solid formed. Removal of the solvent by

H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
489
(C-4), 85.0 (C-5), 116.3 (t, JCeF ¼ 244.1 Hz, F2eCHe), 128.0
(two overlapping peaks, o-Ph), 128.4 ( p-Ph), 129.2 (two over-
lapping peaks, m-OBz), 129.4 (two overlapping peaks, m-Ph),
130.7 (two overlapping peaks, o-OBz), 131.2 (C-1, OBz),
134.1 ( p-OBz), 137.5 (C-11), 138.4 (C-12), 140.1 (C-1, Ph),
155.2 (eNHCOe), 166.6 (C]O in OBz), 171.0 (OAþc),
173.5 (C-10), 211.3 (C-9); ESIMS m/z 866.4 [M þ Na ];
HRMS (ESI) m/z calcd for C43H51F2NO14Naþ [M þ Naþ]:
866.31653, found: 866.31698.
100 MHz): d 10.7 (C-19), 14.7 (C-18), 19.5 (C-17), 21.7
(OAc), 22.9 (eOeC(CH3)2e), 23.3 (eOeC(CH3)2e), 27.4
(C-16), 37.1 (C-14), 37.8 (C-6), 44.4 (C-15), 47.7 (C-3),
58.5 (C-30), 58.9 (C-8), 72.3 (C-7), 72.6 (C-13), 75.4 (C-20),
75.5 (C-10), 76.9 (C-2), 77.2 (C-20), 78.9 (C-1), 80.8 (d,
JCeF ¼ 16.5 Hz, eOeC(CH3)2), 82.1 (C-4), 85.4 (C-5), 88.2
(d, JCeF ¼ 173.7 Hz, FeCH2e), 117.6 (C-2, OBz), 121.4 (C-
4, OBz), 127.2 (C-6, OBz), 128.4 (two overlapping peaks, o-
Ph), 128.8 ( p-Ph), 129.6 (two overlapping peaks, m-Ph),
131.9 (C-5, OBz), 133.9 (C-1, OBz), 137.8 (C-11), 138.9
(C-12), 140.7 (C-1, Ph), 156.3 (eNHCOe), 163.7 (d, JCe
4.2.8.3.
N-De-tert-butoxycarbonyl-N-[2-(1,1,1-trifluoro-2-
methyl)propyloxycarbonyl]docetaxel (14c). Yield 85%; mp
178e180 ꢀC; 1H NMR (300 MHz, CDCl3): d 1.13 (s, 3H,
17-CH3), 1.25 (s, 3H, 16-CH3), 1.53 (s, 3H, 1 CH3 of eOe
C(CH3)2e), 1.57 (s, 3H, 1CH3 of eOeC(CH3)2e), 1.75 (s,
3H, 19-CH3), 1.82 (s, 3H, 18-CH3), 2.23 (m, 2H, 14-CH2),
2.36 (s, 3H, OAc), 1.82 and 2.59 (2m, 2H, 6-CH2), 3.45 (br
s, 1H, 20-OH), 3.90 (d, 1H, J ¼ 6.3 Hz, 3-CH), 4.18 and 4.32
(2d, 2H, J ¼ 8.1 Hz, 20-CH2), 4.24 (m, 1H, 7-CH), 4.24 (br
s, 1H, 10-OH), 4.62 (br s, 1H, 20-CH), 4.94 (d, 1H,
J ¼ 8.1 Hz, 5-CH), 5.21 (s, 1H, 10-CH), 5.26 (br s, 1H, 30-
CH), 5.67 (d, 1H, J ¼ 6.9 Hz, 2-CH), 5.78 (d, 1H,
J ¼ 9.0 Hz, eCONHe), 6.21 (t, 1H, J ¼ 8.7 Hz, 13-CH),
7.34e7.45 (m, 5H, 30-Ph), 7.50 (t, 2H, J ¼ 7.5 Hz, m-OBz),
7.63 (t, 1H, J ¼ 7.5 Hz, p-OBz), 8.10 (d, 2H, J ¼ 7.5 Hz, m-
OBz); 13C NMR (75 MHz, CDCl3): d 9.8 (C-19), 14.3
(C-18), 19.3 (eOeC(CH3)2e), 19.6 (eOeC(CH3)2e), 20.5
(C-17), 22.5 (OAc), 26.5 (C-16), 35.6 (C-14), 36.9 (C-6),
43.1 (C-15), 46.5 (C-3), 56.4 (C-30), 57.5 (C-8), 71.9 (C-7),
72.4 (C-13), 73.5 (C-20), 74.5 (C-10), 74.8 (C-2), 76.6
(C-20), 77.2 (eOeC(CH3)2), 78.8 (C-1), 81.2 (C-4), 84.2
(C-5), 126.0 (F3eCe), 126.7 (two overlapping peaks, o-Ph),
128.3 ( p-Ph), 128.7 (two overlapping peaks, m-OBz), 128.9
(two overlapping peaks, m-Ph), 129.2 (C-1, OBz), 130.1 (two
overlapping peaks, o-OBz), 133.7 ( p-OBz), 136.1 (C-11),
137.8 (C-12), 138.2 (C-1, Ph), 153.4 (eNHCOe), 167.0
(C]O in OBz), 170.3 (OAc), 172.3 (C-10), 211.2 (C-9);
ESIMS m/z 884.4 [M þ Naþ]; HRMS (MALDI) m/z calcd
for C43H50NO14F3Naþ [M þ Naþ]: 884.3085, found:
884.30756.
¼ 243.9 Hz, C-3, OBz), 165.9 (C]O in OBz), 171.4
F
(OAc), 174.0 (C-10), 211.6 (C-9); ESIMS m/z 848.4
[M þ Hþ], 866.3 [M þ Naþ]; HRMS (MALDI) m/z calcd for
C43H51NO14F2Naþ [M þ Naþ]: 866.3184, found: 866.31699.
4.2.8.5. N-De-tert-butoxycarbonyl-N-[2-(1,1-difluoro-2-meth-
yl)propyloxycarbonyl]-2-debenzoyl-2-(m-fluorobenzoyl)doce-
taxel (14e). Yield 73%; mp 156e158 ꢀC; 1H NMR (400 MHz,
CD3COCD3): d 1.13 (s, 3H, 17-CH3), 1.19 (s, 3H, 16-CH3),
1.35 (s, 6H, eOeC(CH3)2e), 1.71 (s, 3H, 19-CH3), 1.89 (s,
3H, 18-CH3), 2.21 (m, 2H, 14-CH2), 2.37 (s, 3H, OAc), 1.83
and 2.46 (2m, 2H, 6-CH2), 3.29 (s, 1H, 20-OH), 3.91 (d, 1H,
J ¼ 7.1 Hz, 3-CH), 4.16 (s, 2H, 20-CH2), 4.27 (m, 1H, 7-
CH), 4.63 (d, 1H, J ¼ 4.2 Hz, 20-CH), 4.97 (d, 1H,
J ¼ 8.5 Hz, 5-CH), 5.18 (m, 1H, 30-CH), 5.24 (s, 1H, 10-
CH), 5.64 (d, 1H, J ¼ 7.2 Hz, 2-CH), 6.13 (t, 1H,
J ¼ 57.0 Hz, F2eCHe), 6.15 (t, 1H, J ¼ 8.9 Hz, 13-CH),
7.27 (t, 1H, J ¼ 7.3 Hz, p-Ph), 7.39 (t, 2H, J ¼ 7.6 Hz, o-Ph),
7.46 (m, 2H, m-Ph), 7.46 (m, 1H, 5-CH in OBz), 7.63 (m,
1H, 4-CH in OBz), 7.76 (d, 1H, J ¼ 9.3 Hz, 2-CH in OBz),
7.93 (d, 1H, J ¼ 7.7 Hz, 6-CH in OBz); 13C NMR
(100 MHz, CD3COCD3): d 10.7 (C-19), 14.7 (C-18), 20.4
(C-17), 20.5 (OAc), 21.7 (eOeC(CH3)2e), 23.3 (eOe
C(CH3)2e), 27.3 (C-16), 37.1 (C-14), 37.8 (C-6), 44.4
(C-15), 47.7 (C-3), 58.7 (C-30), 58.9 (C-8), 72.3 (C-7), 72.6
(C-13), 75.3 (C-20), 75.4 (C-10), 76.9 (C-2), 77.1 (C-20),
78.9 (C-1), 79.9 (t, JCeF ¼ 22.9 Hz, eOeC(CH3)2), 82.1 (C-
4), 85.4 (C-5), 116.7 (t, JCeF ¼ 244.5 Hz, F2eCHe), 117.6
(C-2, OBz), 121.4 (C-4, OBz), 127.2 (C-6, OBz), 128.4 (two
overlapping peaks, o-Ph), 128.9 ( p-Ph), 129.6 (two overlap-
ping peaks, m-Ph), 131.9 (C-5, OBz), 133.9 (C-1, OBz),
137.5 (C-11), 138.9 (C-12), 140.4 (C-1, Ph), 155.8
(eNHCOe), 163.7 (d, JCeF ¼ 243.7 Hz, C-3, OBz), 165.9
(C]O in OBz), 171.4 (OAc), 173.9 (C-10), 211.6 (C-9);
ESIMS m/z 884.3 [M þ Naþ]; HRMS (MALDI) m/z calcd
for C43H50NO14F3Naþ [M þ Naþ]: 884.3092, found:
884.30756.
4.2.8.4. N-De-tert-butoxycarbonyl-N-[2-(1-fluoro-2-methyl)-
propyloxycarbonyl]-2-debenzoyl-2-(m-fluorobenzoyl)docetaxel
(14d). Yield 70%; mp 152e155 ꢀC; 1H NMR (400 MHz,
CD3COCD3): d 1.13 (s, 3H, 17-CH3), 1.19 (s, 3H, 16-CH3),
1.36 (s, 6H, eOeC(CH3)2e), 1.71 (s, 3H, 19-CH3), 1.89 (s,
3H, 18-CH3), 2.21 (m, 2H, 14-CH2), 2.38 (s, 3H, OAc), 1.83
and 2.45 (2m, 2H, 6-CH2), 3.91 (1H, d, J ¼ 7.3 Hz, 3-CH),
4.16 (s, 2H, 20-CH2), 4.27 (m, 1H, 7-CH), 4.35e4.48 (m,
2H, FeCH2e), 4.62 (m, 1H, 20-CH), 4.97 (d, 1H,
J ¼ 9.7 Hz, 5-CH), 5.18 (br s, 1H, 30-CH), 5.24 (s, 1H, 10-
CH), 5.59 (s, 1H, eCONHe), 5.65 (d, 1H, J ¼ 7.2 Hz, 2-
CH), 6.16 (t, 1H, J ¼ 9.0 Hz, 13-CH), 7.26 (t, 1H,
J ¼ 7.3 Hz, p-Ph), 7.39 (t, 2H, J ¼ 7.5 Hz, o-Ph), 7.46 (m,
2H, m-Ph), 7.46 (m, 1H, 5-CH in OBz), 7.63 (m, 1H, 4-CH
in OBz), 7.77 (d, 1H, J ¼ 9.5 Hz, 2-CH in OBz), 7.93 (d,
1H, J ¼ 7.7 Hz, 6-CH in OBz); 13C NMR (CD3COCD3,
4.2.8.6.
N-De-tert-butoxycarbonyl-N-[2-(1,1,1-trifluoro-2-
methyl)propyloxycarbonyl]-2-debenzoyl-2-(m-fluorobenzoyl)-
docetaxel (14f). Yield 74%; mp 161e164 ꢀC; 1H NMR
(300 MHz, CDCl3): d 1.13 (s, 3H, 17-CH3), 1.23 (s, 3H, 16-
CH3), 1.54 (s, 3H, 1CH3 of eOeC(CH3)2e), 1.57 (s, 3H,
1CH3 of eOeC(CH3)2e), 1.75 (s, 3H, 19-CH3), 1.82 (s,
3H, 18-CH3), 2.21 (m, 2H, 14-CH2), 2.34 (s, 3H, OAc), 1.82
and 2.59 (2m, 2H, 6-CH2), 3.42 (br s, 1H, 20-OH), 3.90 (d,

490
H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
1H, J ¼ 6.9 Hz, 3-CH), 4.16 and 4.31 (2d, 2H, J ¼ 8.7 Hz, 20-
CH2), 4.23 (m, 1H, 7-CH), 4.23 (br s, 1H, 10-OH), 4.61 (br s,
1H, 20-CH), 4.95 (d, 1H, J ¼ 8.1 Hz, 5-CH), 5.21 (s, 1H, 10-
CH), 5.23 (m, 1H, 30-CH), 5.64 (d, 1H, J ¼ 7.2 Hz, 2-CH),
5.75 (d, 1H, J ¼ 9.3 Hz, eCONHe), 6.20 (t, 1H, J ¼ 8.5 Hz,
13-CH), 7.31e7.46 (m, 5H, 30-Ph), 7.46 (m, 1H, 5-CH in
OBz), 7.50 (m, 1H, 4-CH in OBz), 7.78 (d, 1H, J ¼ 9.0 Hz,
2-CH in OBz), 7.90 (d, 1H, J ¼ 7.8 Hz, 6-CH in OBz); 13C
3 times each week. Data were expressed as T/C (%), where the
T/C value has been calculated as follows: (mean tumor volume
of the treated group/mean tumor volume of the control
group) ꢁ 100.
4.5. Acute toxicity study in mice
Healthy Kunming mice of both sexes, weighing 18e22 g,
were divided into 7 groups of 10 animals matched for weight
and size. The fluorinated docetaxel derivative (14a) was i.p.
administered at the dose of 92.0, 115.0, 143.0, 179.0, 224.0,
280.0, 350.0 mg/kg body weight. Behavior and changes in
the weight of mice were monitored and the death was recorded
within 14 days. The LD50 values were calculated using Bliss
method.
NMR (100 MHz, CDCl3):
d
9.8 (C-19), 14.3
(C-18), 19.3 (eOeC(CH3)2e), 19.5 (C-17), 20.4 (eOe
C(CH3)2e), 22.4 (OAc), 26.4 (C-16), 35.6 (C-14), 37.0
(C-6), 43.0 (C-15), 46.5 (C-3), 56.4 (C-30), 57.6 (C-8), 72.0
(C-7), 72.3 (C-13), 73.5 (C-20), 74.5 (C-10), 75.2 (C-2), 76.5
(C-20), 78.9 (C-1), 80.0 (q, eOeC(CH3)2), 81.1 (C-4), 84.1
(C-5), 116.9 (C-2, OBz), 120.8 (C-4, OBz), 124.8 (q, JCeF
¼
280.4 Hz, F3eCe), 125.9 (C-6, OBz), 126.8 (two overlapping
peaks, o-Ph), 128.3 ( p-Ph), 128.9 (two overlapping peaks, m-
Ph), 130.4 (C-5, OBz), 131.4 (C-1, OBz), 136.0 (C-11), 137.8
Acknowledgements
(C-12), 138.2 (C-1, Ph), 153.4 (eNHCOe), 162.6 (d, JCeF
¼
Financial support by the National Natural Science Founda-
tion of China (No: 20772017) and the Shanghai Municipal
Committee of Science and Technology (No: 07DZ19713)
are acknowledged.
246.1 Hz, C-3, OBz), 165.8 (C]O in OBz), 170.2 (OAþc),
172.3 (C-10), 211.1 (C-9); ESIMS m/z 902.3 [M þ Na ];
HRMS (MALDI) m/z calcd for C43H49NO14F4Naþ
[M þ Naþ]: 902.3000, found: 902.29814.
4.3. In vitro cytotoxicity
References
Potential cytotoxicity was evaluated against human ovarian
cell line SK-OV-3. The compounds were pre-dissolved in
DMSO and diluted with cell culture medium to at least five
required concentrations. The content of DMSO in the final
concentrations did not exceed 0.1%. At this content, DMSO
was found to be nontoxic to the cells tested. All cells were
cultured in RPMI 1640 supplemented with 10% fetal bovine
serum, at 37 ꢀC in a humidified atmosphere of 5% CO2. The
cells were seeded at a density of 0.4e1.0 ꢁ 104 cells per
well in 96-well microplates. After 24 h, the cells were treated
with 10 times diluted concentration test compound. The cells
were exposed to drugs for 72 h. Cell growth was assayed using
sulforhodamine B (SRB). The optical density (OD) was read
at 520 nm. All cytotoxicity tests were performed 3 times in
quadruplicate. The IC50 values were calculated from curves
constructed by plotting cell survival (%) versus compound
concentration (in nM).
[1] P.B. Schiff, J. Fant, S.B. Horwitz, Nature 277 (1979) 665e667.
´
´
[2] F. Gueritte-Voegelein, D. Guenard, F. Lavelle, M.-T. Le Goff,
L. Mangatal, P. Potier, J. Med. Chem. 34 (1991) 992e998.
[3] E.K. Rowinsky, R.C. Donehower, N. Engl. J. Med. 332 (1995) 1004e1014.
[4] C.J. Thomas, Curr. Top. Med. Chem. 6 (2006) 1529e1543.
[5] B.K. Park, N.R. Kitteringham, P.M. O’Neill, Annu. Rev. Pharmacol.
Toxicol. 41 (2001) 443e470.
´
´
´
[6] B. Monsarrat, E. Mariel, S. Cros, M. Gares, D. Guenard, F. Gueritte-Voe-
gelein, M. Wright, Drug Metab. Dispos. 18 (1990) 895e901.
[7] I. Ojima, S.D. Kuduk, J.C. Slater, R.H. Gimi, C.M. Sun, S. Chakravarty,
´
´
´
M. Ourevitch, A. Abouabdellah, D. Bonnet-Delpon, J.P. Begue, P. Pera,
J.M. Veith, R.J. Bernacki, in: I. Ojima, J.R. MaCarthy, J.T. Welch (Eds.),
Biomedical Frontiers of Fluorine Chemistry, ACS Symposium Series,
vol. 639, American Chemical Society, Washington, DC, 1996 (Chapter
17), pp. 228e243.
[8] I. Ojima, S.D. Kuduk, J.C. Slater, R.H. Gimi, C.M. Sun, Tetrahedron 52
(1996) 209e224.
[9] I. Ojima, T. Inoue, J.C. Slater, S. Lin, S.C. Kuduk, S. Chakravarty,
J.J. Walsh, L. Gilchrist, A.E. McDermott, T. Cresteil, B. Monsarrat,
P. Pera, R.J. Bernacki, in: P.V. Ramachandran (Ed.), Asymmetric Fluo-
roorganic Chemistry: Synthesis, Application, and Future Directions,
ACS Symposium Series, vol. 746, American Chemical Society, Washing-
ton, DC, 1999 (Chapter 12), pp. 158e181.
4.4. Antitumor activity
[10] I. Ojima, T. Inoue, S. Chakravarty, J. Fluorine Chem. 97 (1999) 3e10.
[11] Jiangsu Heng-Rui Medicine Co. Ltd, No. 145 East Renmin Road, Lia-
nyungang, Jiangsu, China.
A549 human NSCLC cells were injected subcutaneous onto
BALB/cA-nude mice (18 ꢃ 3 g body weight, 6 animals per
group). After 2e3 passages, A549 human NSCLC tumors
were grafted subcutaneously onto the right oxter of the nude
mice. The volume of tumor masses was measured with cali-
pers. When the tumor was palpable (about 100e300 mm3),
the nude mice were divided randomly into non-treated group,
positive control (docetaxel) group and treated group. The dos-
age used in this study is shown in Table 2. The treatment
started at day. All the drugs were administered intravenously.
The tumor volumes and mice body weights were measured 2e
´
[12] F. Gueritte-Voegelein, V. Senilh, B. David, D. Guenard, P. Potier, Tetra-
´
´
hedron 42 (1986) 4451e4460.
[13] A. Commercon, D. Bezard, F. Bernard, J.D. Bourzat, Tetrahedron Lett.
33 (1992) 5185e5188.
[14] N. Harada, T. Hashiyama, K. Ozaki, T. Yamaguchi, A. Ando,
K. Tsujihara, Heterocycles 44 (1997) 305e318.
´
´
[15] L. Mangatal, M.T. Adeline, D. Guenard, F. Gueritte-Voegelein, P. Potier,
Tetrahedron 45 (1989) 4177e4190.
[16] E.D. Bergmann, S. Cohen, J. Chem. Soc. (1958) 2259e2262.
[17] R.S. Corley, S.G. Cohen, M.S. Simon, H.T. Wolosinski, J. Am. Chem.
Soc. 78 (1956) 2608e2610.

H.-F. Lu et al. / European Journal of Medicinal Chemistry 44 (2009) 482e491
491
[18] G.Q. Lin, L. Xu, X. Sun, X.W. Yang. PCT Int. Appl. ZL 2005 1
0027537.8, 2007.
[21] I. Ojima, C.L. Fumero-Oderda, S.D. Kuduk, Z.P. Ma, F. Kirikaeb,
T. Kirikae, Bioorg. Med. Chem. 11 (2003) 2867e2888.
[22] I. Ojima, S.D. Kuduk, P. Pera, J.M. Veith, R.J. Bernacki, J. Med. Chem.
40 (1997) 279e285.
[19] I. Ojima, T. Wang, M.L. Miller, S. Lin, C.P. Borella, X.D. Geng, P. Pera,
R.J. Bernacki, Bioorg. Med. Chem. Lett. 9 (1999) 3423e3428.
´
[20] R. Marder-Karsenti, J. Dubois, L. Bricard, D. Guenard, F. Gueritte-Voe-
´
[23] C.H. Liu, J.K. Schilling, R. Ravindra, S. Bane, D.G.I. Kingston, Bioorg.
Med. Chem. 12 (2004) 6147e6161.
gelein, J. Org. Chem. 62 (1997) 6631e6637.