Synthesis and antitumor activity of novel C-7 paclitaxel ethers: Discovery of BMS-184476

Article abstract of DOI:10.1021/jm0102607

The preparation of C-7 paclitaxel ethers is described. Various substituted ethers were prepared via activation of the corresponding methylthiomethyl ether followed by alcohol addition. Variation of the C-7 ether group as well the 3′ side chain position le

Full text of DOI:10.1021/jm0102607

J . Med. Chem. 2001, 44, 4577-4583
4577
Syn th esis a n d An titu m or Activity of Novel C-7 P a clita xel Eth er s: Discover y of
BMS-184476
Thomas J . Altstadt,† Craig R. Fairchild,‡ J erzy Golik,† Kathy A. J ohnston,‡ J ohn F. Kadow,† Francis Y. Lee,‡
Byron H. Long,‡ William C. Rose,‡ Dolatrai M. Vyas,† Henry Wong,† Mu-J en Wu,† and Mark D. Wittman*,†
Discovery Chemistry, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway, P.O. Box 5100,
Wallingford, Connecticut 06492-7660, and Oncology Drug Discovery, Bristol-Myers Squibb Pharmaceutical Research Institute,
P.O. Box 4000, Princeton, New J ersey 08543-4000
Received J une 12, 2001
The preparation of C-7 paclitaxel ethers is described. Various substituted ethers were prepared
via activation of the corresponding methylthiomethyl ether followed by alcohol addition.
Variation of the C-7 ether group as well the 3′ side chain position led to the discovery of a
novel taxane, BMS-184476 (4), with preclinical antitumor activity superior to paclitaxel.
Paclitaxel 1, the diterpenoid natural product isolated
from Taxus brevifolia in 1971 by Wani and Wall1 and
the active constituent of the antitumor drug TAXOL,
continues to have a major impact on the treatment of
ovarian and breast cancer. TAXOL has been approved
for first line treatment of refractory ovarian and breast
cancer as well as Kaposi’s sarcoma. Ongoing clinical
research is demonstrating the usefulness of TAXOL for
the treatment of cancers of the head, neck, and lung
(SCLC and NSCLC). Encouraging phase III results have
elevated TAXOL/platinum combinations to standard
therapy for advanced disease. As the clinical potential
of TAXOL continues to unfold, significant advances in
cancer treatment could be realized by the discovery and
development of novel taxanes with improved efficacy,
reduced toxicity, and an expanded spectrum of activity.
The search for novel taxane analogues has focused on
regions directly interacting with tubulin, principally the
side chain, the C-2 benzoate, and the C-4 acetate, as
well as on the nontubulin binding C-7 and C-10 region.2-4
Despite these efforts, identifying agents that have
superior preclinical efficacy to TAXOL has proved
extremely challenging. Herein, we describe the synthe-
sis and biological activity of C-7 paclitaxel ethers that
ultimately led to the identification of a novel taxane
clinical candidate with superior preclinical antitumor
activity to TAXOL.
Our focus on C-7 paclitaxel ethers was driven by
following observations. First, the C-7 to C-10 region
of paclitaxel does not interact directly with tubulin,
but it has been postulated that changes in this region
of the molecule may affect the specific binding of
paclitaxel to P-glycoprotein. Disruption of binding
to P-glycoprotein resulting in reduced P-glycoprotein
mediated efflux, believed to be responsible for the
MDR phenotype, could provide activity in tumors that
are resistant or unresponsive to TAXOL treatment or
become resistant as a result of treatment. It has been
proposed that the ability of C-10 taxane derivatives
to overcome MDR in vitro is the result of reduced
binding affinity for P-gp.5 Evidence for the proximity
of C-7 to the P-glycoprotein binding site of paclitaxel
was suggested by the fact that attachment of a photo-
affinity label to the C-7 hydroxyl group of paclitaxel
successfully labeled P-glycoprotein.6 Second, C-7 deriva-
tives may provide metabolical stability due to increased
steric bulk around C-6, a major site of metabolism7 as
well as removing the possibility for retro-aldol at C-7.8
The altered pharmacokinetics of C-7 paclitaxel ethers
relative to paclitaxel itself may also provide an efficacy
advantage over paclitaxel.
Ch em istr y
Entry into C-7 paclitaxel ethers started from pacli-
taxel 1 itself. Protection of the 2′ hydroxyl group as the
TES ether 2 followed by methythiomethyl ether9 forma-
tion provided intermediate 3. The TES ether could be
cleaved to provide MTM ether (4). Modification of the
side chain was accomplished by reductive cleavage of
the paclitaxel side chain using the Kingston10 procedure
to afford 7-methylthiomethyl baccatin III, 5. Side chain
analogues were then prepared by coupling 5 with a
series of azetidinones11-14 to provide derivatives 6a -f.
Ethers 7a -d , f-i, k -m were prepared from the
corresponding methythiomethyl ether using NIS activa-
tion under TESOTf 15 catalysis followed by addition of
the corresponding alcohols. The methyl ethers 7e
and 7j were prepared from the corresponding methyl-
thiomethyl ethers following desulfurization with Raney
Nickel16 (see Scheme 1).
Resu lts a n d Discu ssion
The initial goal was to identify compounds that could
overcome MDR-mediated resistance in vitro and test
these compounds in paclitaxel-resistant tumor models.
Compounds were evaluated in vitro in a tubulin polym-
erization assay17 and for cytotoxicity against both a
paclitaxel-sensitive cell line (HCT-116 human colon
tumor) and paclitaxel-resistant cell line (HCT-116/ MDR
resistant) (see Table 1). The potency differential in the
MDR resistant cell line vs the sensitive cell line is
expressed as a ratio (R/S ratio).18
* To whom correspondence should be addressed.
† Discovery Chemistry, Bristol-Myers Squibb Pharmaceutical Re-
search Institute.
‡ Oncology Drug Discovery, Bristol-Myers Squibb Pharmaceutical
Research Institute.
10.1021/jm0102607 CCC: $20.00 © 2001 American Chemical Society
Published on Web 11/16/2001

4578 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 26
Altstadt et al.
Sch em e 1a
a
Reagents and conditions: (a) TESCl, imidazole, CH2Cl2; (b) CH3SCH3, Bz2O2, CH3CN, 0 °C; (c) 1 N HCl, CH3CN, 0 °C; (d) Bu4NBH4,
CH2Cl2, MeOH (cat); (e) LiHMDS, -78 °C, lactam, -78 to 0 °C; Bu4NF, THF; (f) NIS, TESOTf, ROH, CH2Cl2 (7a -d , f-i, k -m );
(g) Raney Nickel, EtOAc, H2 (7e, j).
Ta ble 1. In Vitro and In Vivo Profile for C-7 Paclitaxel Ethers that Overcome MDR
R1
R2
R3
tubulina
HCT-116b (nM)
R/S ratioc
M109d
paclitaxel (1)
4
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
2-furyl
2-furyl
2-furyl
2-furyl
i-butenyl
phenyl
phenyl
phenyl
H
1.0
1.1
0.5
3.3
0.2
0.7
1.6
0.4
0.4
0.3
1.1
1.5-3.5
2.1
1.4
0.6
1.1
1.1
1.7
1.3
1.3
100-200
10.5
10
1.7
2
0.7
1
5.6
1.7
4.1
3.3
159-259 (40-60)
NTe
MTM
MOM
MTM
MOM
CH2O(CH2)2OH
MTM
MOM
Me
CH2O(CH2)2OH
MTM
7a
6a
7f
7g
6d
7i
7j
7k
6f
192 (50)/217
143 (12)/200
118 (5)/168
136 (25)/164
104 (3)/200
118 (0.32)/159
121 (2)/200
158 (2)/200
109 (4)/259
t-butoxy
t-butoxy
t-butoxy
t-butoxy
t-butoxy
t-butoxy
t-butoxy
t-butoxy
1.7
0.7
a
b
Concentration of test compound to give a change of 0.01 OD/h expressed as a ratio to the concentration of paclitaxel. IC50 human
colon tumor cell line sensitive to paclitaxel. c Ratio of IC50 for HCT-116 MDR resistant cell line /IC50 for HCT-116 sensitive cell line.
d
Madison Murine Lung Carcinoma. M109 tumors implanted ip and the drug given ip on days 5 and 8 post implantation. Values are
%T/C analogue (maximum tolerated dose)/% T/C for paclitaxel at a historically determined efficacious dose but does not represent the
MTD. %T/C values of greater than 125% are considered active. e Not tested in the ip model but taken directly into the SC M109 model,
see Table 2.
The initial observation that C-7 paclitaxel ethers 4
and 7a had in vitro potency against both the sensitive
and the MDR-resistant cell lines (R/S ratio of 10, see
Table 1) served to focus our synthetic efforts on iden-
tifying other C-7 ethers that would possess antitumor
efficacy against paclitaxel-resistant tumors. Toward this
end, other C-7 ether modifications in combination with
side chain changes were explored with the goal of
identifying agents active against MDR-resistant tumors.
We chose to focus on compounds with R/S ratios of
less than 5. Small ethers (R3) such as MTM (6a , 6d ,
and 6f), MOM (7f and 7i), methoxy-2-hydroxyethyl (7g
and 7k ), and Me (7j) C-7 ethers gave good in vitro
potency against the MDR resistant cell lines. In general,
the replacement of the 3′-N-benzamide with an N-Boc
group provided compounds with the greatest potency
against the resistant cell line (lower R/S ratios). Re-
placement of the C-3′ phenyl with a 2-furyl (6d , 7i-k )

Antitumor Activity of Novel C-7 Paclitaxel Ethers
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 26 4579
Ta ble 2. In Vitro and In Vivo Activity of C-7 Paclitaxel Ethers
R1
R2
R3
tubulina
HCT-116b (nM)
M109d
Sc M109e
0.9-2.3
paclitaxel (1)
4
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
2-furyl
2-furyl
2-furyl
2-furyl
2-furyl
2-furyl
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
n-butoxy
i-propoxy
benzyloxy
t-butoxy
t-butoxy
t-butoxy
i-propoxy
phenyl
H
1.0
1.1
0.5
1.1
0.6
1
1.5-3.5
2.1
1.4
0.9
2.2
1.1
2.3
1.2
1.7
1.4
1.7
1.3
1.7
0.9
0.6
2.1
159-259 (40-60)
NT
MTM
MOM
MEM
1.0 (13,24)/0.9
1.8 (16)/2.3
7a
7b
7c
7d
7e
6b
6c
7h
6d
7i
192 (50)/217
132 (200)/232
132 (100)/232
238 (200)/217
121 (100)/194
177 (8)/259
191 (8,16)/259
139 (200)/243
104 (3)/200
118 (0.32)/159
158 (2)/200
145 (25)/164
191 (6)/259
CH2OCH2CH3
CH2O(CH2)2OH
Me
0.9 (25)/0.9
1
MTM
MTM
MOM
MTM
0.6
1.6
0.6
1.6
0.4
0.3
0.3
1
0.2 (10)/1.2
0.5 (4)/0.9
MOM
7k
7l
6e
7m
CH2O(CH2)2OH
CH2O(CH2)2OH
MTM
0.6 (1.0)/0.9
1.1 (4.5)/1.4
phenyl
MOM
2.3
115 (50)/223
a
b
Concentration of test compound to give a change of 0.01 OD/h expressed as a ratio to the concentration of paclitaxel. IC50 human
colon tumor cell line sensitive to paclitaxel. c Ratio of IC50 for HCT-116 MDR resistant cell line /IC50 for HCT-116 sensitive cell line.
d
Madison Murine Lung Carcinoma. M109 tumors implanted ip and the drug given ip on days 5 and 8 post implantation. Values are
%T/C analogue (maximum tolerated dose)/% T/C for paclitaxel at a historically determined efficacious dose but does not represent the
MTD. %T/C values of greater than 125% are considered active. e M109 tumors implanted subcutaneously and the drug administered iv
every day ×5 beginning 4 days post implant. Activity is expressed as LCK of analogue (maximum tolerated dose)/LCK for paclitaxel at
a historically determined efficacious dose but does not represent the MTD. An LCK of 1 is considered an active result.
or iso-butenyl moiety (6f) was also effective in combina-
tion with a 3′-N-Boc group at providing improved
potency against the sensitive and MDR-resistant HCT-
116 cell line. Potency in the tubulin assay was equiva-
lent or better than paclitaxel for these taxanes.
Ip model possessed the 3′-phenyl group of the natural
product, while three 2-furyl derivatives (7k , 7l, 6e) gave
active results. These compounds were subsequently
tested in the distal model, and the C-3′ phenyl deriva-
tives 4, 7a , 7d gave activity, while the only 2-furyl
derivative to show activity was 6e. Compound 6e was
5-fold more potent in vitro and had a significantly lower
MTD in the distal site model as compared with the
related C-3′ phenyl derivative 4. Our experience with
potent in vivo actives (see Table 1) coupled with the lack
of activity for other analogues with this side chain in
the A2780 human ovarian tumor xenograft model24
indicated that better efficacy could best be achieved with
compounds that had in vitro and in vivo potency similar
to paclitaxel. For this reason, we chose to focus on C-3′
phenyl derivatives.
Modification of the 3′-N substituent revealed that
three compounds (7a , 7d , 6e) out of the eight compounds
active in the Ip model were benzamide derivatives. The
remaining five compounds active in the Ip model were
carbamate derivatives (two iso-propoxylcarbamates 6c,
7l; one Boc derivative 7j; one n-butyoxycarbamate 6b;
and one benzylcarbamate 7h ). The benzylcarbamate 7h
was not tested in the distal model due to its high MTD
and marginal activity in the Ip model. In the Sc M109
model, only the benzamides 4, 7a , 7d , and 6e gave
active results.
Analysis of the SAR indicated a combination of a C-7
ether with the paclitaxel side chain was optimal for
achieving distal site antitumor activity (4, 7a , 7d ).
Compound 7d was clearly inferior to the MTM ether
4 and MOM ether 7a in the A2780 xenograft model24
and was dropped from further consideration. Both 4 and
7a were dosed intravenously to rats and plasma samples
analyzed to determine the stability of the parent
compounds in vivo. Plasma samples indicated that 32%
of the dose of the MOM ether 7a was converted to
paclitaxel, while no paclitaxel was detected after dosing
BMS-184476 (4). Because the MOM ether 7a was
functioning in vivo as a partial prodrug for paclitaxel,
it was not considered for further development.25 BMS-
184476 (4) was then directly compared with paclitaxel
Compounds with R/S ratios less than 5 were then
evaluated for in vivo activity in the paclitaxel-sensitive
Ip M109 Madison murine lung carcinoma model.19 Only
compounds 6a , 7g, and 7k achieved an active result (T/C
of greater than 125%). The two most active C-7 pacli-
taxel ethers 6a and 7k were then evaluated in the
HCT/VM46 MDR resistant distal tumor model.20 The
3′-N-Boc-7-MTM ether 6a did achieve an active result
of 1 LCK21 in this experiment, but paclitaxel also
achieved an equivalent result in this experiment. The
C-3′-furyl-3′-N-Boc-7-methoxy-2-hydroxyethyl ether 7k
failed to show efficacy in the HCT/VM46 tumor model.
The general lack of antitumor efficacy (T/C > 125%) in
the Ip M109 tumor model for most of the compounds in
Table 1 appears to stem from their low therapeutic
index. All the compounds, with the exception of 6a and
7g, which were active in the Ip model, had MTDs22
ranging from the extremely potent 0.32 mg/kg for 7i to
5 mg/kg for 7f. These MTDs were significantly lower
than the 40-60 mg/kg MTDs necessary to achieve anti-
tumor efficacy for paclitaxel (1) and 7a . These results
show that while the side chain modifications provided
improved in vitro potency, this potency corresponded to
a reduction in antitumor efficacy. Therefore, our goal
shifted to identifying C-7 paclitaxel ethers with an
efficacy advantage relative to paclitaxel.
To optimize for in vivo efficacy, the Ip M109 model19
was used to develop the SAR. Active compounds were
then evaluated in a distal Sc M109 model23 (see Table
2). C-7 MTM, MOM, and methoxy-2-hydroxyethyl ethers
showed activity in the Ip M109. Three of the eight
compounds active in the Ip model were MTM derivatives
(6b, 6c, 6e) along with three methoxy-2-hydroxyethyl
derivatives (7d , 7k , 7l), and two MOM derivatives (7a ,
7h ).
The SAR at the C-3′ position revealed that five (7a ,
7d , 6b, 6c, 7h ) out of the eight compounds active in the

4580 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 26
Altstadt et al.
Ta ble 3. Activity of BMS-184476 (4) in Human Tumor
Xenografts
our most paclitaxel-resistant ovarian carcinoma model
derived from TAXOL-treated and unresponsive patients.
In this model, BMS-184476 (4) showed superior activity
to paclitaxel. On the basis of the impressive antitumor
activity observed for BMS-184476 relative to pacli-
taxel,28 this analogue was selected for clinical develop-
ment.
BMS-184476 (4)
paclitaxel (1)
tumor
A2780
(Ovarian ca.)
L2987
(Lung ca.)
HCT/pk
(Colon ca.)
HOC79, ip
(Ovarian ca.)
schedule ODa LCKb (c/t) ODa LCK (c/t)
q2d×5; 8d 30c (8/8)
q2d×5; 26 22c 2.6 (0/7)
q2d×5; 10 24c (6/8)
2c 6.1 (0/8)
30c 1.3 (0/8)
40c 2.8 (1/8)
Con clu sion
The synthesis and biological activity of C-7 ethers of
paclitaxel has been described. Variation of the C-7 ether
group as well the 3′ position led to the discovery of
BMS-184476, which demonstrated preclinical antitumor
activity superior to paclitaxel and is presently being
evaluated in clinical trials.
q2d×5; 12 20c 321%e (1/7) 30c 273e (0/8)
a
OD, optimal dose (i.e., the next highest dose was excessively
b
toxic). All injections iv except where otherwise indicated. LCK,
gross log cell kill, with cures/total (c/t) shown in parentheses.
d
c MTD (maximum tolerated dose) probably reached. q2d×5 ) test
compound administered every other day ×5. The number after
the semicolon refers to the day treatment was initiated relative
to tumor implantation. e Data shown are median survival times
% T/C values. Numbers in parentheses following median survival
times refer to the number of animals surviving.
Exp er im en ta l Section
1H NMR spectra were recorded on a Bruker AC-300 spec-
trometer and chemical shifts reported in ppm downfield from
a TMS standard. 13C NMR spectra were recorded on the same
instrument at 75.5 MHz. High-resolution mass spectral analy-
sis was performed on a Kratos MS50RF spectrometer in the
FAB mode using m-nitrobenzyl alcohol as the matrix. Column
chromatography was performed using silica gel 60 (200-400
mesh). Unless otherwise noted, materials were obtained from
commercial sources and used without further purification. The
â-lactams used in this paper were prepared according to the
procedures outlined in the patent literature.13,14
2′-Tr ieth ylsilyl P a clita xel (2). To a solution of paclitaxel
(8.1 g, 9.49 mmol) in 40 mL of pyridine and 40 mL of
methylene chloride at 0 °C was added TESCl (6.3 mL, 37.8
mmol). The solution was stirred at 0 °C for 1 h and then diluted
with EtOAc and washed with water and brine. The organic
fraction was dried over MgSO4 and concentrated, and the
residue was chromatographed over silica gel (3:1 hexane/
EtOAc, then 2:1, and finally with 1:1 hexane/EtOAc) to give
9.34 g of 2′-triethylsilyl paclitaxel (95%).
2′-Tr ieth ylsilyl-7-m eth ylth iom eth ylp a clita xel (3). To a
solution of 2′-triethylsilyl paclitaxel (20.1 g, 20.8 mmol) in 200
mL of acetonitrile was added dimethyl sulfide (16 mL, 216
mmol), and the solution was cooled to 0 °C. At 0 °C, benzoyl
peroxide (20.2 g, 83.5 mmol) was added, and the solution was
stirred for 90 min. The reaction mixture was diluted with
EtOAc and washed with saturated NaHCO3 and then brine.
The solution was dried over MgSO4 and concentrated, and the
residue was chromatographed over silica gel (2:1 hexane/
EtOAc) to give 20.4 g of product (95%). FABMS (NOBA) M+Na
calcd for C55H69NSiSO14: 1050. Found: 1050. IR (KBr) 3442,
F igu r e 1. Optimal antitumor effects of BMS-184476 and
paclitaxel (1) vs staged A2780. The optimal dose is reported
(i.e., the next highest tested dose was excessively toxic).
Compound was administered at the indicated doses by the
intravenous route, every other day for a total of 5 doses
starting 8 days after tumor implantation (q2dx5;d.8, iv). The
incidence of cured mice/total is reported next to the graph
corresponding to each compound.
1
1724, 1242, 1066 cm-1. H NMR (CDCl3, 300 MHz) δ 8.11 (d,
in several human tumor xenograft models of varying
responsiveness or resistance to paclitaxel to gauge the
clinically potential of this novel taxane (see Table 3).
In A2780, a human ovarian tumor xenograft model
that demonstrated excellent sensitivity to paclitaxel,
BMS-184476 (4) was curative as compared with pacli-
taxel which achieved a very active 6.1 LCK but with no
cures (see Figure 1). In the L2987 human lung carci-
noma model, BMS-184476 (4) was also more efficacious
(greater than 1 LCK) than paclitaxel.
J ) 6.9 Hz, 2H), 7.73 (d, J ) 6.9 Hz, 2H), 7.60-7.23 (m, 11H),
7.11 (d, J ) 8.7 Hz, 1H), 6.54 (s, 1H), 6.22 (t, J ) 9.3 Hz, 1H),
5.69 (d, J ) 7.5 Hz, 2H), 4.95 (d, J ) 8.1 Hz, 1H), 4.68 (d, J )
2.0 Hz, 1H), 4.65 (s, 1H), 4.27 (m, 3H), 3.88 (d, J ) 6.9 Hz,
1H), 2.80 (m, 1H), 2.52 (s, 3H), 2.39 (m, 1H), 2.16 (s, 3H), 2.10
(s, 3H), 2.04 (s, 3H), 1.85 (m, 2H), 1.75 (s, 3H), 1.19 (s, 3H),
1.17 (s, 3H), 0.80 (t, J ) 7.8 Hz, 9H), 0.43 (m, 6H).
7-Meth ylth iom eth ylp a clita xel (4). To a solution of the
2′-triethylsilyl-7-methylthiomethyl paclitaxel (3.9 g, 3.79 mmol)
in 100 mL of acetonitrile at 0 °C was added 1 N HCl (7.6 mL,
7.6 mmol) and stirred 1 h. The solution was diluted with
EtOAc and washed with saturated NaHCO3 solution and brine
and dried over MgSO4. The solution was concentrated and
chromatographed over silica gel (1:1 hexane/EtOAc) to give
3.3 g of product (95%). ESIMS M+H calcd for C49H55NO14S:
914. Found: 914. IR (KBr) 3441, 1739, 1724, 1242, 1066, 710
Against HCT/pk,26 BMS-184476 (4) was active with
6 of 8 cures as compared to a 2.8 LCK with 1 cure for
paclitaxel. HCT/pk is an experimentally derived tumor
model developed by exposing HCT-116 human colon
tumor cells to concentrations of paclitaxel equivalent to
plasma concentrations that can be achieved clinically
for paclitaxel. HCT/pk expresses resistance to paclitaxel
as compared to the parental line and is characterized
by the MDR phenotype.
1
cm-1. H NMR (CDCl3, 300 MHz) δ 8.11 (d, J ) 7.4 Hz, 2H),
7.75 (d, J ) 7.4 Hz, 2H), 7.63-7.31 (m, 11H), 7.04 (d, J ) 9
Hz, 1H), 6.50 (s, 3H), 6.19 (t, J ) 7.8 Hz, 1H), 5.79 (dd, J ) 9,
2.4 Hz, 1H), 5.67 (d, J ) 6.9 Hz, 1H), 4.93 (d, J ) 7.8 Hz, 1H),
4.79 (d, J ) 2.4 Hz, 1H), 4.66 (s, 2H), 4.28 (m, 2H), 4.18 (d, J
) 8.4 Hz, 1H), 3.85 (d, J ) 6.9 Hz, 1H), 2.80 (m, 1H), 2.38 (s,
3H), 2.31 (d, J ) 9 Hz, 2H), 2.17 (s, 3H), 2.11 (s, 3H), 1.93 (s,
BMS-184476 (4) was also tested in HOC79,27 a clin-
ically derived ovarian carcinoma model. This model was

Antitumor Activity of Novel C-7 Paclitaxel Ethers
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 26 4581
3H), 1.93-1.56 (m, 1H), 1.76 (s, 3H), 1.21 (s, 3H), 1.21 (s, 3H),
1.18 (s, 3H). Anal. Calcd. For C49H55NO14S; C, 64.39; H, 6.06;
N, 1.53. Found: C, 64.35; H, 6.24; N, 1.37.
57.5, 56.5, 47.2, 43.2, 35.4, 26.6, 22.6, 21.5, 21.0, 18.9, 15.1,
14.7, 13.7, 10.9. Anal. Calcd. for C46H59NSO15; C, 62.03; H, 6.53;
N, 1.54. Found: C, 62.16; H, 6.45; N, 1.57.
3′-N-Isop r op oxyca r ba m oyl-7-m eth ylth iom eth yl P a cli-
7-Meth ylth iom eth yl Ba cca tin III (5). To a solution of
7-methylthiomethyl paclitaxel (1.9 g, 2.08 mmol) in 20 mL of
dichloromethane was added tetrabutylammonium borohydride
(936 mg, 3.63 mmol), and the sample was stirred for 16 h. The
solution was diluted with dichloromethane and washed with
water, saturated bicarbonate, and brine. The organic fraction
was then dried over MgSO4 and concentrated. The residue was
chromatographed over silica gel (1:1 hexane/EtOAc) to give
980 mg of 7-MTM baccatin III (72%). HRFABMS (NOBA)
M+H calcd for C33H43SO11: 647.2526. Found: 647.2551. IR
(KBr) 3474, 1746, 1724, 1712, 1270, 1240, 1070 cm-1. 1H NMR
(CDCl3, 300 MHz) δ 8.08 (d, J ) 7.1 Hz, 2H), 7.58 (t, J ) 7.5
Hz, 1H), 7.45 (t, J ) 7.8 Hz, 2H), 6.55 (s, 1H), 4.94 (d, J ) 8.1
Hz, 1H), 4.83 (br q, J ) 5.1 Hz, 1H), 4.66 (ABq, J ) 14.7, 12.3
Hz, 2H), 4.30 (m, 2H), 4.13 (d, J ) 8.4 Hz, 1H), 3.91 (d, J )
6.6 Hz, 1H), 2.79 (m, 1H), 2.27 (s, 3H), 2.25 (m, 2H), 2.19 (s,
3H), 2.16 (s, 3H), 2.10 (s, 4H), 1.81 (m, 1H), 1.72 (s, 3H), 1.61
(m, 2H), 1.16 (s, 3H), 1.03 (s, 3H). 13C NMR (CDCl3, 75.5 Hz)
δ 202.3, 170.8, 169.3, 167.0, 144.2, 132.6, 132.1, 130.1, 129.4,
128.6, 83.9, 80.9, 78.7, 75.7, 74.5, 73.9, 67.9, 57.6, 47.6, 42.7,
38.3, 26.7, 22.6, 21.0, 20.1, 15.2, 15.0, 10.8.
ta xel (6c) (84%). FABMS (NOBA) M+Na calcd for C46H57
-
NO15SNa: 918. Found: 918. IR (KBr) 3460, 1720, 1266, 1244,
1
1230 cm-1. H NMR (CDCl3, 300 MHz) δ 8.07 (d, J ) 7.2 Hz,
2H), 7.59 (t, J ) 7.2 Hz, 1H), 7.47 (t, J ) 7.5 Hz, 2H), 7.32 (m,
5H), 6.51 (s, 1H), 6.18 (t, J ) 8.7 Hz, 1H), 5.65 (d, J ) 6.6 Hz,
1H), 5.50 (d, J ) 9.3 Hz, 1H), 5.28 (d, J ) 8.4 Hz, 1H), 4.91 (d,
J ) 8.1 Hz, 1H), 4.77 (m, 1H), 4.64 (br s, 3H), 4.26 (m, 2H),
4.15 (d, J ) 8.4 Hz, 1H), 3.83 (d, J ) 6.9 Hz, 1H), 3.44 (d, J )
5.1 Hz, 1H), 2.78 (m, 1H), 2.34 (s, 3H), 2.25 (d, J ) 9 Hz, 2H),
2.17 (s, 3H), 2.14 (s, 1H), 2.10 (s, 3H), 1.96 (s, 3H), 1.83 (m,
1H), 1.73 (s, 3H), 1.15 (m, 12H). 13C NMR (CDCl3, 75.5 Hz) δ
201.8, 170.4, 169.2, 167.0, 156.3, 140.1, 138.3, 133.7, 133.3,
130.2, 129.1, 128.8, 128.6, 128.1, 126.8, 83.8, 81.4, 78.7, 76.0,
75.5, 74.5, 74.0, 73.6, 72.2, 68.9, 57.5, 56.4, 47.1, 43.2, 35.3,
32.9, 26.6, 22.6, 22.0, 21.9, 20.9, 15.1, 14.6, 10.9. Anal. Calcd.
For C46H57NSO15; C, 61.66; H, 6.41; N, 1.56. Found: C, 61.63;
H, 6.36; N, 1.68.
3′-F u r yl-3′-N-Boc-7-m eth ylth iom eth yl P a clita xel (6d )
(88%). FABMS (NOBA) M+H calcd for C45H58NO16S: 900.
1
Found: 900. IR (film) 3442, 1720, 1242, 1066, 1026 cm-1. H
NMR (CDCl3, 300 MHz) δ 8.07 (d, J ) 7.3 Hz, 2H), 7.57 (t,
J ) 7.3 Hz, 1H), 7.45 (t, J ) 7.8 Hz, 2H), 7.38 (s, 1H), 6.53 (s,
1H), 6.34 (d, J ) 3.2 Hz, 1H), 6.29 (d, J ) 3.2 Hz, 1H), 6.17 (t,
J ) 8.1 Hz, 1H), 5.65 (d, J ) 6.9 Hz, 1H), 5.29 (m, 2H), 4.92
(d, J ) 8.0 Hz, 1H), 4.70 (m, 1H), 4.64 (d, J ) 4.6 Hz, 2H),
4.29 (m, 2H), 4.14 (d, J ) 8.3 Hz, 1H), 3.86 (d, J ) 6.8 Hz,
1H), 3.37 (d, J ) 5.8 Hz, 1H), 2.77 (m, 1H), 2.38 (s, 3H), 2.32
(m, 2H), 2.16 (s, 3H), 2.10 (s, 3H), 2.02 (s, 3H), 1.75 (m, 6H),
1.33 (s, 9H), 1.17 (s, 3H), 1.12 (s, 3H). 13C NMR (CDCl3, 75.5
Hz) δ 202.0, 172.6, 170.3, 169.2, 167.0, 155.2, 151.3, 142.4,
140.4, 133.7, 133.2, 130.2, 129.1, 128.7, 110.7, 107.4, 83.9, 81.2,
80.5, 78.6, 76.5, 76.1, 75.4, 74.6, 74.0, 72.5, 71.8, 57.4, 51.7,
47.2, 43.2, 35.2, 32.8, 28.1, 26.4, 22.6, 20.9, 15.2, 14.6, 10.9,
8.3.
Rep r esen tive Cou p lin g P r oced u r e. To a solution of
hexamethyldisilazane (HMDS) (0.275 mL, 1.30 mmol) in 8 mL
of THF was added a solution of n-BuLi (0.48 mL, 2.5 M in
hexanes, 1.20 mmol) and stirred 5 min at -55 °C. To this
solution was added 7-MTM baccatin III (639 mg, 0.99 mmol)
in 8 mL of THF and stirred for 10 min before addition of an 8
mL solution of azetidinone (575 mg, 1.52 mmol) in THF. The
cold bath was removed and replaced with a 0 °C bath, and
the reaction was stirred for 30 min. The solution was diluted
with EtOAc and washed with saturated NH4Cl solution, dried
over MgSO4, and concentrated. The residue was chromato-
graphed over silica gel. To a solution of the silyl ether obtained
above (269 mg, 0.26 mmol) in 6 mL of THF was added
tetrabutylammonium fluoride (0.3 mL, 1.0 M in THF, 0.3
mmol) and stirred 10 min. The solution was diluted with
EtOAc and washed with brine, dried over MgSO4, and con-
centrated, and the residue was chromatographed over silica
gel (1:1 hexane/EtOAc) to give the title compound.
3′-F u r yl-7-m et h ylt h iom et h yl P a clit a xel (6e) (95%).
FABMS (NOBA) M+ calcd for C47H53NO15S: 903. Found: 903.
IR (film) 3432, 1722, 1240, 1066 cm-1 1H NMR (CDCl3,
.
300 MHz) δ 8.10 (d, J ) 7.2 Hz, 2H), 7.73 (d, J ) 7.2 Hz,
2H), 7.61-7.36 (m, 7H), 6.91 (d, J ) 9 Hz, 1H), 6.51 (s, 1H),
6.38 (s, 2H), 6.19 (t, J ) 7.8 Hz, 1H), 5.87 (dd, J ) 9, 2.4 Hz,
1H), 5.67 (d, J ) 6.9 Hz, 1H), 4.93 (d, J ) 8.1 Hz, 1H), 4.80
(m, 1H), 4.65 (ABq, J ) 14.7, 2.4 Hz, 2H), 4.28 (m, 2H), 4.17
(d, J ) 8.4 Hz, 1H), 3.86 (d, J ) 6.9 Hz, 1H), 3.56 (d, J )
5.4 Hz, 1H), 2.78 (m, 1H), 2.41 (s, 3H), 2.33 (m, 2H), 2.16 (s,
3H), 2.10 (s, 3H), 1.99 (s, 3H), 1.83 (m, 1H), 1.77 (s, 1H),
3′-N-Boc-7-m et h ylt h iom et h yl P a clit a xel (6a ) (95%).
FABMS (NOBA) M+Na calcd for
C47H59NO15SNa: 932.
Found: 932. IR (film) 3440, 1720, 1370, 1242, 1170, 1108, 1066,
1
756 cm-1. H NMR (CDCl3, 300 MHz) δ 8.06 (d, J ) 7.2 Hz,
2H), 7.57 (t, J ) 7.2 Hz, 1H), 7.46 (t, J ) 7.8 Hz, 2H), 7.35 (m,
5H), 6.52 (s, 1H), 6.16 (t, J ) 8.7 Hz,1H), 5.64 (d, J ) 6.9 Hz,
1H), 5.43 (br d, J ) 9.3 Hz, 1H), 5.24 (br d, J ) 8.1 Hz, 1H),
4.91 (d, J ) 8.1 Hz, 1H), 4.63 (m, 3H), 4.26 (m, 2H), 4.14 (d, J
) 8.4 Hz, 1H), 3.83 (d, J ) 6.9 Hz, 1H), 3.46 (d, J ) 5.4 Hz,
1H), 2.77 (m, 1H), 2.34 (s, 3H), 2.27 (m, 1H), 2.16 (s, 3H), 2.09
(s, 3H), 1.97 (s, 3H), 1.79 (m, 2H), 1.72 (s, 3H), 1.32 (s, 9H),
1.19 (s, 3H), 1.18 (s, 3H). 13C NMR (CDCl3, 75.5 Hz) δ 202.0,
172.7, 170.3, 169.2, 167.0, 155.3, 140.3, 138.4, 133.7, 133.2,
130.2, 129.1, 128.8, 128.7, 128.0, 126.7, 83.9, 81.3, 80.2, 78.6,
76.5, 76.1, 75.4, 74.6, 74.0, 73.6, 72.3, 57.4, 56.1, 47.1, 43.2,
35.3, 32.8, 28.2, 26.5, 22.6, 21.0, 15.1, 14.6, 10.9.
1.74 (s, 3H), 1.20 (s, 3H), 1.17 (s, 3H). Anal. Calcd. For C47H53
-
NSO15; C, 62.45; H, 5.91; N, 1.55. Found: C, 62.18; H, 6.02;
N, 1.59.
3′-Isobu ten yl-3′-N-Boc-7-m eth ylth iom eth yl P a clita xel
(6f) (78%). FABMS (NOBA) M+ calcd for C45H61NO15S: 888.
Found: 888. IR (KBr) 3452, 1724, 1242, 710 cm-1 1H NMR
.
(CDCl3, 300 MHz) δ 8.07 (d, J ) 7.2 Hz, 2H), 7.59 (t, J ) 7.5
Hz, 1H), 7.45 (t, J ) 7.8 Hz, 2H), 6.54 (s, 1H), 6.11 (t, J ) 9
Hz, 1H), 5.65 (d, J ) 6.9 Hz, 1H), 5.29 (br d, J ) 8.4 Hz, 1H),
4.94 (d, J ) 7.8 Hz, 1H), 4.81-4.69 (m, 3H), 4.65 (Abq, J )
15, 2.7 Hz, 2H), 4.30-4.14 (m, 4H), 3.86 (d, J ) 6 Hz, 1H),
3.37 (br s, 1H), 2.79 (m, 1H), 2.34 (s, 4H), 2.17 (s, 3H), 2.10 (s,
3H), 2.04 (s, 3H), 1.82 (m, 1H), 1.74 (s, 9H), 1.39 (s, 9H), 1.23
(d, J ) 3 Hz, 1H), 1.20 (s, 3H), 1.18 (s, 3H). Anal. Calcd. For
3′-N-Bu toxyca r ba m oyl-7-m eth ylth iom eth yl P a clita xel
(6b) (77%). FABMS (NOBA) M+H calcd for C47H60NO15S: 910.
Found: 910. IR (KBr) 3444, 1722, 1372, 1242, 1108, 1066,
1
1026, 988 cm-1. H NMR (CDCl3, 300 MHz) δ 8.08 (d, J ) 7.5
Hz, 2H), 7.59 (t, J ) 7.5 Hz, 1H), 7.47 (t, J ) 7.2 Hz, 2H),
7.39-7.11 (m, 5H), 6.51 (s, 1H), 6.20 (t, J ) 8.7 Hz, 1H), 5.65
(d, J ) 6.9 Hz, 1H), 5.56 (d, J ) 9.3 Hz, 1H), 5.29 (d, J ) 8.4
Hz, 1H), 4.91 (d, J ) 8.1 Hz, 1H), 4.65 (br s, 3H), 4.27 (m,
2H), 4.15 (d, J ) 8.4 Hz, 1H), 3.97 (m, 2H), 3.84 (d, J ) 6.9
Hz, 1H), 3.45 (d, J ) 4.8 Hz, 1H), 2.78 (m, 1H), 2.33 (s, 6H),
2.25 (d, J ) 8.7 Hz, 2H), 2.17 (s, 3H), 2.10 (s, 3H), 1.96 (s,
3H), 1.83 (m, 1H), 1.74 (s, 3H), 1.62 (s, 1H), 1.48 (m, 2H), 1.19
(m, 5H), 0.83 (t, J ) 7.2 Hz, 3H). 13C NMR (CDCl3, 75.5 Hz) δ
201.9, 172.3, 170.5, 169.2, 167.0, 156.3, 140.1, 138.4, 133.8,
133.4, 130.2, 129.2, 129.0, 128.9, 128.7, 128.2, 126.8, 125.3,
83.9, 81.4, 78.8, 77.3, 76.0, 75.6, 74.6, 74.1, 73.7, 72.2, 65.4,
C
45H61NSO15; C, 60.86; H, 6.92; N, 1.58. Found: C, 60.25; H,
6.36; N, 1.51.
Rep r esen ta tive P r oced u r e for Con ver sion of Meth yl-
th iom eth yl Eth er to Meth oxya lk oxy Eth er s. To a solution
of the 7-methylthiomethyl paclitaxel (48 mg, 0.047 mmol) in
1 mL of dichloromethane was added alcohol (20 mg, 0.6 mmol)
and the solution cooled to 0 °C. Then NIS (13 mg, 0.058 mmol)
and triethylsilyltriflate (1 µL, 0.004 mmol) were added and
the dark red solution stirred 30 min and then warmed to
25 °C for 30 min. The solution was diluted with EtOAc and
washed with 10% NaS2O8 and bicarbonate, dried (MgSO4), and

4582 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 26
Altstadt et al.
concentrated. The residue was chromatographed over silica gel
(1:1 hexane/EtOAc) to give the desired ether.
Hz, 2H), 7.58 (t, J ) 7.2 Hz, 1H), 7.46 (t, J ) 7.8 Hz, 2H), 7.31
(m, 5H), 6.35 (s, 1H), 6.15 (t, J ) 8.7 Hz, 1H) 5.63 (d, J ) 6.9
Hz, 1H), 5.44 (br d, J ) 9.2, 1H), 5.24 (br s, 1H), 4.90 (d, J )
8.4 Hz, 1H), 4.74 (s, 2H), 4.59 (br s, 1H), 4.27 (d, J ) 8.4 Hz,
1H), 4.11 (m, 2H), 3.81 (d, J ) 6.8 Hz, 1H), 3.66 (m, 3H), 3.48
(m, 2H), 2.75 (m, 1H), 2.33 (s, 3H), 2.26 (m, 2H), 2.18 (s, 3H),
1.90 (m, 2H), 1.87 (s, 3H), 1.78 (m, 1H), 1.72 (s, 3H), 1.32 (s,
9H), 1.19 (s, 3H), 1.18 (s, 3H). 13C NMR (CDCl3, 75.5 Hz) δ
202.1, 172.8, 170.3, 169.6, 167.0, 155.3, 140.2, 138.3, 133.7,
133.3, 130.2, 129.1, 128.8, 128.7, 128.0. 126.8, 96.8. 84.1, 81.2,
80.2, 79.4, 78.6, 76.5, 75.2, 74.5, 73.6, 72.3, 70.0, 61.8, 57.3,
56.2, 46.9, 43.2, 35.3, 35.0, 28.2, 26.5, 22.6, 21.0, 20.9, 14.6,
10.6.
7-Meth oxym eth yl P a clita xel (7a ) (72%). ESIMS M+H
calcd for C49H56NO15: 898. Found: 898. IR(KBr) 3436, 1724,
1
1242, 1106, 1026 cm-1. H NMR (CDCl3, 300 MHz) δ 8.09 (d,
J ) 7.2 Hz, 2H), 7.75 (d, J ) 7.2 Hz, 2H), 7.62-7.30 (m, 11H),
7.06 (d, J ) 8.5 Hz, 1H), 6.30 (s, 1H), 6.16 (t, J ) 8.7 Hz, 1H),
5.78 (d, J ) 9.0 Hz, 1H), 5.64 (d, J ) 6.9 Hz, 1H), 4.90 (d, J )
8.1 Hz, 1H), 4.77 (m, 1H), 4.65 (ABq, J ) 15.6, 7.8 Hz, 2H),
4.28 (d, J ) 8.2 Hz, 1H), 4.16 (d, J ) 8.2 Hz, 1H), 4.08 (m 1H),
3.81 (d, J ) 6.9 Hz, 1H), 3.63 (d, J ) 4.8 Hz, 1H), 3.28 (s, 3H),
2.77 (m, 1H), 2.34 (s, 3H), 2.29 (d, J ) 8.4 Hz, 2H), 2.21 (s,
3H), 1.94 (m, 1H), 1.79 (s, 3H), 1.74 (s, 3H), 1.17 (s, 6H). Anal.
Calcd. for C49H55NO15; C, 65.54; H, 6.17; N, 1.56. Found: C,
65.62; H, 6.24; N, 1.37.
3′-N-Ben zyloxycar bam oyl-7-m eth oxym eth yl P aclitaxel
(7h ) (78%). ESIMS M+H calcd for C50H58NO16: 928. Found:
928. IR (KBr) 3440, 1723, 1242, 1040, 700 cm-1 1H NMR
.
7-Met h oxy-(2-m et h oxyet h yl) P a clit a xel (7b ) (69%).
(CDCl3, 300 MHz) δ 8.10 (d, J ) 7.2 Hz, 2H), 7.63-7.22 (m,
13H), 6.33 (s, 1H), 6.17 (t, J ) 9 Hz, 1H), 5.71 (d, J ) 9.0 Hz,
1H), 5.64 (d, J ) 6.9 Hz, 1H), 5.36 (br d, J ) 9 Hz, 1H), 5.02
(ABq, J ) 31.2, 12.1 Hz, 2H), 4.90 (d, J ) 8.1 Hz, 1H), 4.66
(m, 2H), 4.23 (ABq, J ) 15.6, 7.5 Hz, 2H), 4.09 (dd, J ) 16.8,
6.6 Hz, 1H), 3.81 (d, J ) 6.9 Hz, 1H), 3.45 (br s, 1H), 3.29 (s,
3H), 2.78 (m, 1H), 2.34 (s, 3H), 2.27-1.91 (m, 4H), 2.20 (s, 3H),
1.83 (s, 3H), 1.75 (s, 3H), 1.26 (s, 3H), 1.19 (s, 6H). Anal. Calcd.
for C50H57NO16; C, 64.71; H, 6.19; N, 1.51. Found: C, 64.74;
H, 6.04; N, 1.56.
ESIMS M-H calcd for C51H58NO16: 940. Found: 940. IR (KBr)
3434, 1724, 1242, 1109, 1025, 710 cm-1 1H NMR (CDCl3) δ
.
8.10 (d, J ) 7.2 Hz, 2H), 7.76 (d, J ) 7.2 Hz, 2H), 7.63-7.31
(m, 11H), 7.08 (d, J ) 9 Hz, 1H), 6.28 (s, 1H), 6.16 (t, J ) 8.7
Hz, 1H), 5.79 (dd, J ) 9,2.4 Hz, 1H), 5.64 (d, J ) 6.9 Hz, 1H),
4.91 (d, J ) 8.7 Hz, 1H), 4.77 (m, 3H), 4.23 (Abq, J ) 37, 8.3
Hz, 2H), 4.10 (m, 1H), 3.82 (d, J ) 6.8 Hz, 1H), 3.74 (m, 1H),
3.67 (d, J ) 4.7 Hz, 1H), 3.49 (m, 3H), 3.35 (s, 3H), 2.86 (m,
1H), 2.35 (s, 3H), 2.29 (d, J ) 9 Hz, 2H), 2.18 (s, 3H), 1.95 (m,
1H), 1.77 (s, 3H), 1.74 (s, 3H), 1.61 (s, 1H), 1.18 (s, 6H). Anal.
Calcd. for C51H59NO16; C, 65.03; H, 6.31; N, 1.49. Found: C,
64.64; H, 6.08; N, 1.51.
3′-Fu r yl-3′-N-Boc-7-m eth oxym eth yl P aclitaxel (7i) (46%).
HRFABMS (NOBA) M+H calcd for C45H58NO17
: 884.3705.
7-Meth oxyeth yl P a clita xel (7c) (72%). ESIMS M+H
Found: 884.3732. IR (film) 3442, 1720, 1268, 1242, 1040, 1026,
1
calcd for C50H58NO15: 912. Found: 912. IR (KBr) 3434, 1725,
756 cm-1. H NMR (CDCl3, 300 MHz) δ 8.08 (d, J ) 7.2 Hz,
1242, 1109, 1025, 710 cm-1
.
1H NMR (CDCl3) δ 8.10 (d, J )
2H), 7.58 (t, J ) 7.3 Hz, 1H), 7.46 (t, J ) 7.8 Hz, 2H), 7.39 (s,
1H), 6.35 (m, 2H), 6.30 (d, J ) 3.2 Hz, 1H), 6.17 (t, J ) 8.2
Hz, 1H) 5.65 (d, J ) 6.9 Hz, 1H), 5.32 (d, J ) 9.6, 1H), 5.24 (d,
J ) 9.8 Hz, 1H), 4.91 (d, J ) 8.0 Hz, 1H), 4.69 (m, 2H), 4.62
(d, J ) 7.5 Hz, 1H), 4.29 (d, J ) 8.4 Hz, 1H), 4.10 (m, 2H),
3.84 (d, J ) 6.9 Hz, 1H), 3.33 (d, J ) 5.7 Hz, 1H), 3.27 (s, 3H),
2.77 (m, 1H), 2.37 (s, 3H), 2.31 (d, J ) 9.0 Hz, 2H), 2.18 (s,
3H), 1.93 (m, 4H), 1.73 (m, 5H), 1.34 (s, 9H), 1.19 (s, 6H). 13C
NMR (CDCl3, 75.5 Hz) δ 202.2, 172.6, 170.2, 169.4, 167.0,
155.2, 151.3, 142.5, 140.2, 133.7, 133.3, 130.2, 129.1, 128.7,
110.7, 107.5, 98.2, 84.3, 81.1, 80.5, 79.8, 78.6, 75.3, 74.6, 72.5,
71.7, 57.4, 55.8, 51.7, 46.9, 43.2, 35.4, 35.2, 28.1, 26.4, 22.6,
21.0, 20.9, 14.6, 10.7.
7.2 Hz, 2H), 7.76 (d, J ) 7.2 Hz, 2H), 7.63-7.30 (m, 11H), 7.08
(d, J ) 9 Hz, 1H), 6.30 (s, 1H), 6.17 (t, J ) 7.8 Hz, 1H), 5.79
(dd, J ) 9,2.4 Hz, 1H), 5.65 (d, J ) 6.9 Hz, 1H), 4.92 (d, J )
8.0 Hz, 1H), 4.78 (m, 1H), 4.71 (Abq, J ) 12.3, 8.1 Hz, 2H),
4.23 (Abq, J ) 37, 8.4 Hz, 2H) 4.08 (m, 1H), 3.82 (d, J ) 6.9
Hz, 1H), 3.66 (m, 2H), 3.41 (m, 1H), 2.83 (m, 1H), 2.35 (s, 3H),
2.32 (d, J ) 9 Hz, 2H), 2.19 (s, 3H), 1.99 (m, 1H), 1.79 (s, 3H),
1.75 (s, 4H), 1.89 (s, 6H), 1.41 (t, J ) 7.2 Hz, 3H). Anal. Calcd.
for C50H57NO15; C, 65.85; H, 6.30; N, 1.54. Found: C, 65.81;
H, 6.29; N, 1.55.
7-Meth oxy-(2-h yd r oxyeth yl) P a clita xel (7d ) (60%). IR
(KBr) 3434, 1724, 1242, 1026, 710 cm-1 1H NMR (CDCl3) δ
.
8.09 (d, J ) 7.2 Hz, 2H), 7.74 (d, J ) 7.2 Hz, 2H), 7.62-7.32
(m, 11H), 7.05 (d, J ) 9 Hz, 1H), 6.33 (s, 1H), 6.15 (t, J ) 9.3
Hz, 1H), 5.77 (dd, J ) 9, 2.4 Hz, 1H), 5.64 (d, J ) 6.9 Hz, 1H),
4.90 (d, J ) 8 Hz, 1H), 4.77 (m, 1H), 4.74 (s, 2H), 4.22 (Abq, J
) 39, 8.4 Hz, 2H), 3.81 (d, J ) 6.9 Hz, 1H), 3.65 (m, 3H), 3.50
(m, 1H), 2.77 (m, 1H), 2.35 (s, 3H), 2.29 (d, J ) 9 Hz, 2H),
2.18 (s, 4H), 1.92 (m, 1H), 1.80 (s, 3H), 1.73 (s, 3H), 1.29 (s,
3H), 1.18 (s, 6H). Anal. Calcd. for C50H57NO16; C, 64.71; H,
6.19; N, 1.51. Found: C, 64.64; H, 6.21; N, 1.50.
3′-Fu r yl-3′-N-Boc-7-(m eth oxy-2-h ydr oxyeth yl) P aclitaxel
(7k ) (66%). FABMS (NOBA) M+H calcd for C46H60NO18
914.3810. Found: 914.3781. IR (film) 3440, 1722, 1370, 1244,
1166, 1108, 1070, 1050, 1026 cm-1. 1H NMR (CDCl3, 300 MHz)
δ 8.07 (d, J ) 7.3 Hz, 2H), 7.58 (t, J ) 7.3 Hz, 1H), 7.46 (t, J
) 7.8 Hz, 2H), 7.39 (d, J ) 1.7 Hz, 1H), 6.37 (s, 1H), 6.35 (m,
1H), 6.30 (d, J ) 3.2 Hz, 1H), 6.16 (t, J ) 8.3 Hz, 1H), 5.64 (d,
J ) 6.9 Hz, 1H), 5.27 (m, 2H), 4.91 (d, J ) 8.0 Hz, 1H), 4.73
(m, 3H), 4.28 (d, J ) 8.3 Hz, 1H), 4.16 (m, 2H), 3.84 (d, J )
6.9 Hz, 1H), 3.65 (m, 3H), 3.46 (m, 2H), 2.77 (m, 1H), 2.37 (s,
3H), 2.32 (m, 3H), 2.18 (s, 3H), 1.93 (m, 4H), 1.72 (m, 4H),
1.33 (s, 9H), 1.19 (s, 6H). 13C NMR (CDCl3, 75.5 Hz) δ 202.1,
172.6, 170.4, 169.6, 167.0, 155.2, 151.3, 142.4, 140.2, 133.7,
133.4, 130.2, 129.1, 128.7, 110.7, 107.5, 96.7, 84.2, 81.1, 80.5,
79.4, 78.6, 76.5, 75.3, 74.5, 72.4, 71.7, 70.0, 61.8, 57.3, 51.7,
47.0, 43.3, 35.2, 35.0, 28.1, 26.4, 22.6, 21.1, 20.9, 14.6, 10.7.
3′-N-Boc-7-m eth oxym eth yl P a clita xel (7f) (76%). HR-
FABMS (NOBA) M+H calcd for
C47H60NO16: 894.3912.
Found: 894.3943. IR (film) 3440, 1722, 1370, 1242, 1106, 1068,
1
1026 cm-1. H NMR (CDCl3, 300 MHz) δ 8.07 (d, J ) 7.3 Hz,
2H), 7.59 (t, J ) 7.3 Hz, 1H), 7.46 (t, J ) 7.8 Hz, 2H), 7.36 (m,
5H), 6.33 (s, 1H), 6.16 (t, J ) 8.8 Hz, 1H), 5.64 (d, J ) 6.9 Hz,
1H), 5.40 (d, J ) 9.5 Hz, 1H), 5.24 (br d, J ) 8.1 Hz, 1H), 4.90
(d, J ) 7.9 Hz, 1H), 4.68 (d, J ) 7.6 Hz, 1H), 4.62 (d, J ) 7.6
Hz, 1H), 4.28 (d, J ) 8.4 Hz, 1H), 4.14 (d, J ) 8.2 Hz, 1H),
4.08 (m, 1H), 3.82 (d, J ) 6.8 Hz, 1H), 3.40 (d, J ) 5.2 Hz,
1H), 3.27 (s, 3H), 2.77(m, 1H), 2.33 (s, 3H), 2.27 (d, J ) 8.9
Hz, 2H), 2.19 (s, 3H), 1.94 (m, 1H), 1.86 (s, 3H), 1.73 (s, 3H),
1.72 (m, 1H), 1.63 (br s, 1H), 1.32 (s, 9H), 1.20 (s, 3H), 1.19 (s,
3H). 13C NMR (CDCl3, 75.5 Hz) δ 202.2, 172.7, 170.2, 169.4,
167.0, 155.3, 140.2, 138.3, 133.7, 133.3, 130.2, 129.1, 128.8,
128.7, 128.1, 126.8, 98.2, 84.3, 81.2, 80.2, 79.9, 78.6, 75.3, 74.5,
73.6, 72.3, 57.3, 56.1, 55.8, 46.9, 43.2, 35.4, 35.3, 28.2, 26.5,
22.6, 20.9, 14.7, 10.7.
3′-F u r yl-3′-N-isop r op oxyca r b a m oyl-7-(m et h oxy-2-h y-
d r oxyeth yl) P a clita xel (7l) (74%). HRFABMS (NOBA)
M+H calcd for C45H58NO18: 900.3654. Found: 900.3640. IR
(film) 3440, 1722, 1242 cm-1 1H NMR (CDCl3, 300 MHz) δ
.
8.07 (d, J ) 7.2 Hz, 2H), 7.56 (t, J ) 7.5 Hz, 1H), 7.46 (t, J )
7.8 Hz, 2H), 7.39 (s, 1H), 6.37 (s, 1H), 6.35 (m, 1H), 6.31 (m,
1H), 6.18 (t, J ) 7.8 Hz, 1H), 5.65 (d, J ) 6.9 Hz, 1H), 5.38
(m, 2H), 4.90 (d, J ) 7.8 Hz, 1H), 4.75 (m, 4H), 4.28 (d, J )
8.4 Hz, 1H), 4.16 (m, 2H), 3.83 (d, J ) 6.8 Hz, 1H), 3.66 (m,
3H), 3.50 (m, 2H), 2.77 (m, 1H), 2.37 (s, 3H), 2.29 (m, 2H),
2.18 (s, 3H), 1.91 (s, 4H), 1.75 (m, 2H), 1.72 (s, 4H), 1.20 (s,
3H), 1.18 (s, 3H), 1.16 (d, J ) 6.3 Hz, 3H), 1.11 (d, J ) 6.3 Hz,
3H). 13C NMR (CDCl3, 75.5 Hz) δ 202.0, 172.3, 170.5, 169.6,
166.9, 155.8, 151.2, 142.5, 140.0, 133.7, 133.5, 130.2, 129.1,
128.7, 110.7, 107.6, 96.7, 84.1, 81.2, 79.2. 78.6, 75.3, 74.6, 72.3,
3′-N-Boc-7-(m et h oxy-2-h yd r oxyet h yl) P a clit a xel (7g)
(46%). HRFABMS (NOBA) M+H calcd for
C48H62NO17:
924.4018. Found: 924.4009. IR (film) 3440, 1720, 1242, 1070,
1
1026, 756 cm-1. H NMR (CDCl3, 300 MHz) δ 8.06 (d, J ) 7.5

Antitumor Activity of Novel C-7 Paclitaxel Ethers
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 26 4583
(6) Ojima, I.; Kuduk, S. D.; Chakravarty, S. Adv. Med. Chem. 1999,
4, 69-124.
71.8, 70.0, 69.2, 61.8, 57.3, 52.0, 47.0, 43.3, 35.3, 35.0, 26.5,
22.5, 22.0, 21.9, 21.1, 20.9, 14.6, 10.7.
3′-F u r yl-7-m eth oxym eth yl P a clita xel (7m ) (47%). HR-
(7) Wittman, M. D.; Altstadt, T. J .; Fairchild, C.; Hansel, S.;
J ohnston, K.; Kadow, J . K.; Long, B. H.; Rose, W. C.; Vyas, D.
M.; Wu, M.-J .; Zoeckler, M. E. Bioorg. Med. Chem. Lett. 2001,
11, 809-810.
FABMS (NOBA) M+H calcd for
C47H54NO16: 888.3443.
Found: 888.3432. IR (KBr) 3450, 1750, 1722, 1712, 1268, 1244,
1
1024 cm-1. H NMR (CDCl3, 300 MHz) δ 8.09 (d, J ) 7.2 Hz,
(8) (a) McLaughlin, J . L.; Miller, R. W.; Powell, R. G.; Smith, J r.,
C. R. J . Nat. Prod. 1981, 44, 312. (b) Fang, W. S.; Fang, Q. C.;
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2H), 7.73 (d, J ) 7.2 Hz, 2H), 7.57 (m, 1H), 7.45 (m, 6H), 6.92
(d, J ) 9.2 Hz, 1H), 6.38 (s, 2H), 6.33 (s, 1H), 6.18 (t, J ) 8.1
Hz, 1H), 5.86 (dd, J ) 9.3, 2.4 Hz, 1H), 5.65 (d, J ) 6.9 Hz,
1H), 4.91 (d, J ) 8.4 Hz, 1H), 4.80 (m, 1H), 4.68 (d, J ) 7.5
Hz, 1H), 4.62 (d, J ) 7.5 Hz, 1H), 4.29 (d, J ) 8.4 Hz, 1H),
4.16 (d, J ) 8.4 Hz, 1H), 4.10 (dd, J ) 10.5, 3.6 Hz, 1H), 3.84
(d, J ) 6.9 Hz, 1H), 3.60 (d, J ) 5.4 Hz, 1H), 3.27 (s, 3H), 2.78
(m, 1H), 2.40 (s, 3H), 2.34 (d, J ) 8.7 Hz, 2H), 2.18 (s, 3H),
2.00 (m, 1H), 1.89 (s, 3H), 1.80 (s, 1H), 1.75 (s, 3H), 1.18 (s,
6H). 13C NMR (CDCl3, 75.5 Hz) δ 202.1, 172.2, 170.4, 169.4,
167.0, 166.9, 150.8, 142.7, 139.9, 133.7, 133.6, 133.4, 132.1,
130.2, 129.2, 128.7, 127.1, 110.8, 108.0, 98.2, 84.3, 81.2, 79.8,
78.5, 75.3, 74.5, 72.3, 71.7, 57.4, 55.8, 50.2, 46.9, 43.2, 35.4,
29.5, 26.6, 22.6, 21.0, 20.9, 14.7, 10.7.
(9) Golik, J .; Wong, H. S. L.; Chen, S. H.; Doyle, T. W.; Wright, J .
J . K.; Knipe, J .; Rose, W. C.; Casazza, A. M.; Vyas, D. M. Bioorg.
Med. Chem. Lett. 1996, 6, 1837-1842.
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Org. Chem. 1986, 51, 3239-3242.
(11) Holton, R. A. Method for Preparation of Taxol Using Beta
Lactam, U.S. Patent 5,175,315, 1990.
(12) Holton, R. A. Metal Alkoxides. U.S. Patent 5,229,526, 1986.
(13) Wong, H. S. Wittman. M. D. 7-O-Ethers of Taxane Derivatives,
U.S. Patent 6,201,140, 2001.
(14) Golik, J .; Vyas, D.; Wright, J . J .; Wong, H.; Kadow, J . F.;
Thottathil, J . K.; Li, W.-S.; Kaplan, M. A.; Perrone, R. K.;
Wittman, M. D. Phophonoxymethyl or Methylthiomethyl ethers
of Taxane Derivatives As Antitumor Agents. U.S. Patent
5,646,176, 1997.
Gen er a l P r oced u r e for th e Con ver sion of Meth ylth io-
m eth yl Eth er s to th e Meth yl Eth er . Raney nickel (∼0.5 g)
was added to a solution of 7-methylthiomethyl paclitaxel (73
mg, 0.0799 mmol) in 20 mL of EtOAc. This solution was
hydrogenated on a Parr apparatus at 50 psi and ambient
temperature for 6 h. Filtration through Celite, concentration
in vacuo, and purification by flash chromatography over silica
gel using 1:2 EtOAc:hexane as eluent provided 45 mg (65%)
of the methyl ether.
(15) Konradsson, P.; Udodong, U. E.; Fraser-Reid, B. Tetrahedron
Lett. 1990, 31, 4313-16.
(16) Pojer, P. M.; Angyal, S. J . Aust. J . Chem. 1978, 31, 1031-1040.
(17) Schiff, P. B.; Fant, J .; Horwitz, S. B. Nature 1979, 277, 665-
667. An EC0.01 was determined for each analogue and expressed
as a ratio relative to paclitaxel.
(18) HCT-116 is a human colon tumor cell line. The resistant HCT-
116 cell line was established by exposing cells to VM-26 and
establishing a cell line resistant to these drugs. The resistance
is characterized by an MDR (multi-drug-resistance) phenotype.
R/S ratio is defined as the IC50 in the HCT-116 MDR resistant
cell line divided by the IC50 in the HCT-116 sensitive cell line.
The R/S ratio for paclitaxel is approximately 300.
(19) Rose, W. Cancer Treat. Rep. 1981, 65, 299-312. In the Ip model,
both the drug and tumor are delivered intraperitoneally (ip).
%T/C refers to the median lifespan of the drug treated group/
lifespan of the control group × 100. %T/C values of greater than
125% are considered active.
(20) A distal tumor model refers to a model in which the tumor
is implanted at a site distal to the site of administration of
the drug. In the HCT/VM46 MDR tumor model, the tumor is
implanted subcutaneously and the drug is administered intra-
venously every other day ×5. HCT/VM46 is a cell line in which
resistance has been induced with VM-46 (topo II active agent).
Resistance is characterized by an MDR phenotype.
(21) log cell kill (LCK) is defined as LCK ) (T - C/TVDT) ÷ 3.32.
T - C refers to the difference in days for the for the tumor to
reach target size for the treated vs the control group. TVDT is
the tumor volume doubling time which varies between in vivo
models.
(22) MTD refers to the maximum tolerated dose that a given agent
can be administered before undue toxicity is observed.
(23) Sc M109 refers to a distal tumor model in which the M109
murine tumor is implanted subcutaneously and the drug is
administered intravenously.
(24) A2780 is a paclitaxel sensitive model that was used to further
evaluate analogues of interest, unpublished results.
(25) Both 4 and 7a were dosed IV to rats (three per group; 10 mg/
kg; in 10:10:80 cremophor/ethanol/water by volume). Plasma
samples were taken at 0, 15, 30 min, 1, 2, 4, 6, and 24 h and
plasma samples analyzed by HPLC (UV or MS/MS detection).
(26) HCT/pk was established by exposing parental HCT-116 cells to
concentrations of paclitaxel that mimic clinically achievable
plasma levels. This resulted in a multidrug resistant tumor
model that expressed elevated levels of P-glycoprotein, was cross
resistant to a number of natural product anticancer agents, and
was resistant to paclitaxel in vivo.
7-Meth oxy P a clita xel (7e) (65%). HRFABMS (NOBA)
M+H calcd for C48H53NO14: 868.3544. Found 868.3511. IR
(KBr) 3424, 3064, 2928, 1724, 1652, 1602, 1580, 1486, 1316,
1270, 1244, 1178 cm-1 1H NMR (CDCl3) δ 1.203 (s, 6H),
.
1.203-2.353 (obscured multiplets, 4H), 1749 (s, 3H), 1794 (s,
3H), 2.190 (s, 3H), 2.353 (s, 3H), 2.667 (m, 3H), 3.336 (s, 3H),
3.796 (d, 1H), 4.134 (d, 1H, 4.276 (d, 1H), 4.765 d, 1H), 4.875
(d, 1H), 5.630 (d, 1H), 5.768 (d, 1H), 6.155 (t, 1H), 6.333 (s,
1H), 7.096 (d, 1H), 7.348-8.150 (m, 15H).
3′-F u r yl-3′-N-Boc-7-m eth oxy P a clita xel (7j). Using a
procedure similar as described above (16%). HRFABMS (NOBA)
M+H calcd for C44H56NO16: 854.3599. Found: 854.3608. IR
1
(film) 3440, 1722, 1268, 1244, 1170, 1106, 756 cm-1. H NMR
(CDCl3, 300 MHz) δ 8.07 (t, J ) 7.2 Hz, 2H), 7.58 (t, J ) 7.3,
1H), 7.46 (t, J ) 7.7 Hz, 2H), 7.39 (m, 1H), 6.42 (s, 1H), 6.35
(m, 1H), 6.30 (m, 1H), 6.18 (t, J ) 7.6 Hz, 1H), 5.64 (d, J ) 7.0
Hz, 1H), 5.28 (m, 2H), 4.95 (d, J ) 7.8 Hz, 1H), 4.69 (dd, J )
5.8, 2.1 Hz, 1H), 4.28 (d, J ) 8.3 Hz, 1H), 4.13 (d, J ) 8.3 Hz,
1H), 3.86 (m, 2H), 3.36 (d, J ) 5.6 Hz, 1H), 3.32 (s, 3H), 2.70
(m, 1H), 2.38 (s, 3H), 2.32 (d, J ) 8.9 Hz, 2H), 2.20 (s, 3H),
1.94 (s, 3H), 1.76 (m, 1H), 1.76 (m, 2H), 1.69 (m, 3H), 1.34 (s,
9H), 1.20 (s, 3H), 1.19 (s, 3H). 13C NMR (CDCl3, 75.5 Hz) δ
202.2, 172.6, 170.4, 169.4, 167.1, 155.2, 151.3, 142.4, 140.0,
133.7, 130.2, 129.1, 128.7, 110.7, 107.5, 84.1, 81.5, 80.4, 78.6,
76.5, 74.7, 74.5, 72.5, 71.8, 57.6. 57.2, 51.7, 47.2, 43.3, 35.2,
32.3, 28.1, 26.5, 22.6, 21.1, 20.9, 14.6, 10.3.
Refer en ces
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(27) The HOC79 tumor model was developed from a clinical sample
of ovarian carcinoma cells derived from a woman whose tumor
had relapsed following therapy with cisplatin, doxorubicin, and
cytoxan and finally this tumor progressed in the face of paclitaxel
therapy. As compared to other similar clinical specimens of
ovarian carcinoma adapted to grow in nude mice, we consider
HOC79 as the most resistant to paclitaxel treatment.
(28) For a more detailed discussion of the antitumor activity of
BMS-184476, see: Rose, W. C.; Fairchild, C.; Lee, F. Y. F. Cancer
Chemother. Pharmacol. 2001, 47, 97-105.
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J M0102607