Syntheses and structure-activity relationships of the second-generation antitumor taxoids: Exceptional activity against drug-resistant cancer cells

Article abstract of DOI:10.1021/jm9604080

A series of new 3'-(2-methyl-1-propenyl) and 3'-(2-methylpropyl) taxoids with modifications at C-10 was synthesized by means of the β-lactam synthon method using 10-modified 7-(triethylsilyl)-10-deacetylbaccatin III derivatives. The new taxoids thus synth

Full text of DOI:10.1021/jm9604080

J . Med. Chem. 1996, 39, 3889 3896
3889
Syn th eses a n d Str u ctu r e Activity Rela tion sh ip s of th e Secon d -Gen er a tion
An titu m or Ta xoid s: Excep tion a l Activity a ga in st Dr u g-Resista n t Ca n cer Cells
Iwao Ojima,*,† J ohn C. Slater,† Evelyne Michaud,† Scott D. Kuduk,† Pierre-Yves Bounaud,† Patricia Vrignaud,‡
Marie-Christine Bissery,‡ J ean M. Veith,§ Paula Pera,§ and Ralph J . Bernacki§
Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, Rhone-Poulenc
Rorer, Centre de Recherches de Vitry-Alfortville, 94403 Vitry sur Seine, France, and Department of Experimental Therapeutics,
Grace Cancer Drug Center, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York 14263
Received J une 7, 1996X
A series of new 3′-(2-methyl-1-propenyl) and 3′-(2-methylpropyl) taxoids with modifications at
C-10 was synthesized by means of the â-lactam synthon method using 10-modified 7-(trieth-
ylsilyl)-10-deacetylbaccatin III derivatives. The new taxoids thus synthesized show excellent
cytotoxicity against human ovarian (A121), non-small-cell lung (A549), colon (HT-29), and breast
(MCF-7) cancer cell lines. All but one of these new taxoids possess better activity than paclitaxel
and docetaxel in the same assay, i.e., the IC50 values of almost all the taxoids are in the
subnanomolar level. It is found that a variety of modifications at C-10 is tolerated for the
activity against normal cancer cell lines, but the activity against a drug-resistant human breast
cancer cell line expressing MDR phenotype (MCF7-R) is highly dependent on the structure of
the C-10 modifier. A number of the new taxoids exhibit remarkable activity (IC50 2.1 9.1
nM) against MCF7-R. Among these, three new taxoids, SB-T-1213 (4a ), SB-T-1214 (4b), and
SB-T-1102 (5a ), are found to be exceptionally potent, possessing 2 orders of magnitude better
activity than paclitaxel and docetaxel. The observed exceptional activity of these taxoids may
well be ascribed to an effective inhibition of P-glycoprotein binding by the modified C-10
moieties. The new taxoid SB-T-1213 (4a ) shows an excellent activity (T/C
7.7 mg/kg/dose, log10 cell kill 2.3 and 2.0, respectively) against B16 melanoma in B6D2F1
mice via intravenous administration.
0% at 12.4 and
In tr od u ction
the course of our SAR study of paclitaxel and docetaxel
21
analogs,16
we have established that the 3′-phenyl
Taxol (paclitaxel), a structurally complex diterpenoid,1
and its semisynthetic analog Taxote`re (docetaxel)2 are
group is not an essential component for the potent
cytotoxicity and antitumor activity expressed by this
class of compounds.17 We have also reported a series
of analogs possessing either a 3′-alkenyl or 3′-alkyl
moiety in place of the 3′-phenyl group such as SB-T-
1101, -1102, -1211, -1212, and -1302, which possess
substantially better cytotoxicity than the parent com-
pounds, especially against a drug-resistant human
currently considered to be the most promising leads in
the fight against cancer.3
Both paclitaxel and doc-
7
etaxel, through their unique antimitotic mechanism of
action,8 10 exhibit significant antitumor activity against
various cancers which have not been effectively treated
by existing chemotherapeutic drugs.11,12 Paclitaxel was
approved by the FDA for the treatment of advanced
ovarian cancer in December 1992 and for the treatment
of breast cancer in April 1994. It is also undergoing
clinical trials for other cancers. Docetaxel was approved
by the FDA for the treatment of breast cancer in May
1996 and is currently undergoing phase II and III
clinical trials for breast and lung cancers worldwide.3,12
Although both paclitaxel and docetaxel possess potent
antitumor activity, recent reports have shown that
treatment with these drugs often results in a number
of undesired side effects as well as multidrug resistance
(MDR).12,13 Therefore, it has become essential to de-
velop new anticancer agents with fewer side effects,
superior pharmacological properties, and improved
activity against various classes of tumors.
breast cancer cell line.18 Two taxoids (SB-T-1101 and
SB-T-1211) were shown to possess highly potent in vivo
antitumor activity equivalent to docetaxel against B16
melanoma in B6D2F1 mice.18
The limited availability of these two drugs, as well
as the pursuit for improved analogs, has made them the
focus of many synthetic investigations and extensive
structure activity relationship (SAR) studies.3,14,15 In
In the SAR study of a series of 3′-alkyl and 3′-alkenyl
taxoids shown above and others, we recognized that 10-
† State University of New York at Stony Brook.
‡ Rhone-Poulenc Rorer.
acetyl (R
Ac) analogs exhibited 2 3 times better
cytotoxicity than 10-unmodified analogs (R H) against
the doxorubicin-resistant human breast cancer cell line
§ Roswell Park Cancer Institute.
X Abstract published in Advance ACS Abstracts, September 15, 1996.
S0022-2623(96)00408-6 CCC: $12.00 © 1996 American Chemical Society

3890 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 20
Ta ble 1. C-10 Modification of 7-TES-DAB
Ojima et al.
Sch em e 1
baccatin
R
yield (%)a
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
1r
CH3CH2-CO
cyclopropane-CO
(CH3)2N-CO
CH3O-CO
CH3
72
91
92
90
81
83
67 (89)
63 (79)
87
78
30
60 (91)
92
52
68
30
60
50
CH3(CH2)3-CO
CH3(CH2)4-CO
(CH3)2CHCH2-CO
(CH3)3CCH2-CO
cyclohexane-CO
(E)-CH3CHdCH-CO
(CH3CH2)2N-CO
morpholine-4-CO
CH3NH-CO
CH3CH2NH-CO
CH3CH2CH2NH-CO
(CH3)2CHNH-CO
CH2dCHCH2NH-CO
cyclohexyl-NH-CO
1s
80
a
Isolated yield. The value in parentheses indicates the conver-
sion yield.
MCF-7R (vide infra). This observation prompted us to
examine the effects of C-10 modification on the cyto-
toxicity of the 3′-alkyl and 3′-alkenyl taxoids and led
us to discover a new series of exceptionally potent
taxoids, the second-generation taxoids, that possess 2
orders of magnitude higher potency than paclitaxel and
docetaxel against the drug-resistant human breast
cancer cells MCF7-R. These results are very unexpected
since the previous SAR studies on the C-10-modified
paclitaxel and taxoids concluded that the modification
at C-10 brought about little effects on their cytotoxic-
ity.14,22 Thus, we would like to describe here the
syntheses and SAR study of the second-generation
taxoids, i.e., 10-modified 3′-(2-methyl-1-propenyl) and
3′-(2-methylpropyl) taxoids.
reaction with isocyanates was reported to have failed.30
Accordingly, we examined cuprous chloride as the
activator, following up a general procedure for the
reactions of isocyanates and alcohols reported by Dug-
gan and Imagire.31 This turned out to be a good choice,
and we obtained the desired 10-carbamoyl-DABs. How-
ever, this procedure yields a side product, an allopha-
nate, arising from the second addition of isocyanate to
the carbamate nitrogen. In order to minimize this side
reaction, a slow addition of isocyanates to 7-TES-DAB
was employed in the presence of CuCl (1.0 equiv) in dry
dichloromethane. Although the reaction conditions
were not fully optimized, we were able to obtain the
desired 10-carbamoyl-DABs 1n s in moderate to high
yields (eq 2). Results are listed in Table 1.
Syn th eses of New Ta xoid s
A series of new 3′-(2-methyl-1-propenyl) and 3′-(2-
methylpropyl) taxoids with modifications at C-10 was
synthesized by means of the â-lactam synthon
21,23 28
method14,17
using 10-modified 7-(triethylsilyl)-
10-deacetylbaccatin III derivatives. Initial protection
at the C-7 position of 10-deacetylbaccatin III (DAB)29
with a triethylsilyl (TES) group and subsequent modi-
fication at the C-10 position with acyl, alkoxycarbonyl,
N,N-dialkylcarbamoyl, and alkyl halides using LiHMDS
as the base22 proceeded uneventfully to give the corre-
sponding 10-modified 7-TES-DABs 1a m in good yields
(eq 1). Results are summarized in Table 1.
The coupling reactions of the baccatins 1a s with
enantiomerically pure (3R,4S)-1-t-Boc-3-TIPSO-4-(2-
methyl-1-propenyl)azetidin-2-one (2)18 were carried out
based on the Ojima Holton protocol24 27,32,33 to give 2′-
TIPS-7-TES taxoids 3a s in fair to good yields (Scheme
1, Table 2). Treatment of 3a s with HF/pyridine (70:
30) afforded the taxoids 4a s in good to excellent yields
(Scheme 1). Results are summarized in Table 2.
The observed lower yields in the coupling of 10-
carbamoylbaccatins 1n p ,r are ascribed to the side
reaction causing the loss of the 10-carbamoyl group
through a rather unexpected retro-addition process
caused by the deprotonation of the carbamoyl NH by
LiHMDS and/or a lithium amide base generated upon
coupling of 1 with the â-lactam 2. This side reaction is
not serious in the case of 1 with bulky C-10 carbamoyl
groups, i.e., 1q,s.
The C-10 modification with N-alkyl and N-allyl iso-
cyanates under the same conditions resulted in the
formation of a mixture of C-10 (minor) and C-13 (major)
carbamoyl-DABs. The attempted introduction of a
carbamoyl group at C-7 by Chen et al. through the
10-Modified 3′-(2-methylpropyl) taxoids 5 were syn-
thesized in quantitative yields simply by hydrogenating
the 3′-(2-methyl-1-propenyl) group of selected 4 on 10%

Syntheses of Second-Generation Antitumor Taxoids
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 20 3891
Ta ble 4. Cytotoxicity (IC50, nM)a of Taxoids 4 and 5
Ta ble 2. Syntheses of C-10-Modified 3′-(2-Methyl-1-propenyl)
Taxoids 4
A121
A549
HT-29
MCF-7 MCF7-R
3
4
taxoid
(ovarian) (NSCL) (colon) (breast) (breast)
7-TES-baccatin
R
yield (%)a
yield (%)a
paclitaxel
docetaxel
SB-T-1102
SB-T-1212
4a
4b
4c
4d
4e
6.3
1.2
3.8
3.6
1.0
3.6
1.2
3.2
0.63
0.31
0.36
0.5
1.7
1.0
4.0
299
235
36
12
2.2
2.1
4.9
5.3
123
30
17.3
8.5
10.5
22.3
3.4
9.1
12.5
20
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
1r
CH3CH2-CO
cyclopropane-CO
(CH3)2N-CO
3a 75
3b 87
3c 74
3d 76
3e 66
3f 88
3g 80
3h 89
3i 89
3j 88
4a 69
4b 70
4c 70
4d 61
4e 69
4f 82
4g 39 (60)
4h 84
4i 87
0.98
0.27
0.29
0.57
0.60
0.32
0.90
0.60
0.57
0.40
0.50
0.75
1.70
0.20
0.22
0.7
0.15
0.22
0.36
0.35
0.20
0.53
1.1
0.46
0.12
0.26
0.30
0.23
0.70
0.60
0.50
0.60
0.34
0.50
0.45
0.17
0.09
1.2
0.29
0.34
0.34
0.44
0.28
0.41
0.51
0.40
0.18
0.70
5.0
0.55
0.18
0.20
0.13
0.14
0.37
0.50
0.40
0.40
0.40
0.46
0.26
0.20
0.09
0.4
0.31
0.36
0.46
0.44
0.33
0.35
0.51
0.36
0.28
0.33
1.6
CH3O-CO
CH3
CH3(CH2)3-CO
CH3(CH2)4-CO
(CH3)2CHCH2-CO
(CH3)3CCH2-CO
cyclohexane-CO
0.30
0.90
0.60
0.90
0.60
0.50
1.05
0.60
0.40
0.18
1.2
0.41
0.55
0.52
0.53
0.46
0.53
0.78
0.60
0.44
0.60
5.0
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
5a
5b
5c
5d
5e
4j 46 (58)
4k 63
4l 85
(E)-CH3CHdCH-CO 3k 75
(CH3CH2)2N-CO
morpholine-4-CO
CH3NH-CO
3l 84
3m 68 (78) 4m 88
3n 43
3o 27
4n 80
4o 83
4p 62
4q 98
4r 70
4s 98
CH3CH2NH-CO
CH3CH2CH2NH-CO 3p 38
(CH3)2CHNH-CO 3q 88
CH2dCHCH2NH-CO 3r 35
cyclohexyl-NH-CO 3s 67
162
87
65
76
48
1s
a
Isolated yield (conversion yield).
Ta ble 3. Syntheses of 3′-(2-Methylpropyl) Taxoids 5
2.8
4.3
5.8
6.4
214
33
taxoid 5
R
yielda (%)
0.50
0.35
0.60
3.7
5a
5b
5c
5d
5e
5s
CH3CH2-CO
cyclopropane-CO
(CH3)2N-CO
CH3O-CO
100
100
100
100
100
100
5s
a
The concentration of compound which inhibits 50% (IC50, nM)
of the growth of human tumor cell line after 72 h drug exposure.34
CH3
cyclohexyl-NH-CO
a
Isolated yield.
T-1213), 4b (SB-T-1214), and 5a (SB-T-1102), are
exceptionally potent, possessing 2 orders of magnitude
better activity than paclitaxel and docetaxel. It is
noteworthy that the observed exceptional activity is
clearly ascribed to the modification at C-10 in compari-
son with the activity of the corresponding 10-acetyl
taxoids SB-T-1212 (12 nM) and SB-T-1102 (36 nM). This
fact forms a sharp contrast to the result reported for
the SAR study of paclitaxel.14,22
Pd C at ambient temperature and hydrogen pressure
in ethyl acetate (eq 3). Results are listed in Table 3.
With respect to the SAR of new taxoids 4 and 5
against MCF7-R, the bulkiness of the C-10 modifier has
a considerable effect on activity. It appears that the
n-propanoyl and cyclopropanecarbonyl groups are more
or less optimal as demonstrated by the exceptionally
high potency of 4a (SB-T-1213), 4b (SB-T-1214), and 5a
(SB-T-1102). As the size of the C-10 modifier increases,
the activity shows a fairly steady decline as exemplified
by the comparison of the dimethylcarbamoyl analog 4c
(4.9 nM) with the diethylcarbamoyl analog 4l (9.1 nM)
as well as the n-hexanoyl analog 4g (17.3 nM) with the
cyclohexanecarbonyl analog 4j (22.3 nM). However, it
is worthy of note that the electronic and conformational
factors also exert substantial influence on the activity
as observed in the comparison of the cyclohexanecar-
bonyl analog 4j (22.3 nM) with the morpholine-N-
carbonyl analog 4m (12.5 nM). It should also be pointed
out that the activity of 4m against MCF7-R is not
among the most potent analogs, although its activity
against normal cancer cell lines is the highest of the
new taxoids assayed (vide supra). The C-10 methyl
analogs 4e (123 nM) and 5e (214 nM) resulted in 2
orders of magnitude decrease in activity. This result
implies the importance of a carbonyl functionality at this
position for exceptionally high activity. Although the
N,N-dialkylcarbamoyl analogs 4c,l show nanomolar
Cytotoxicity of New Ta xoid s
The in vitro cytotoxicity of these new taxoids thus
synthesized was evaluated against several human tu-
mor cell lines, A121 (ovarian carcinoma), A549 (non-
small-cell lung carcinoma), HT-29 (colon carcinoma),
and MCF-7 (mammary carcinoma) as well as the drug-
resistant cell line MCF7-R (mammalian carcinoma 180-
fold resistant to doxorubicin) using the method devel-
oped by Skehan et al.34 Results are summarized in
Table 4 with the values of paclitaxel, docetaxel, SB-T-
1102,18 and SB-T-121218 shown for comparison.
As Table 4 shows, the new taxoids 4 and 5 possess
excellent activity against human cancer cell lines, which
are better than paclitaxel and docetaxel except for 5s.
A number of the new taxoids 4 and 5 show 1 order of
magnitude stronger activity than paclitaxel and doc-
etaxel, and the most cytotoxic taxoid against normal
human cancer cell lines is 4m (SB-T-12162) that exhib-
its the IC50 value of 0.09 nM against ovarian (A121) and
breast (MCF7) cancer cell lines. The most significant
result, however, is the remarkable activity (IC50 2.1
9.1 nM) against the doxorubicin-resistant breast cancer
cell line MCF7-R expressed by a number of new taxoids
4 and 5. Among these, the three new taxoids, 4a (SB-

3892 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 20
Ojima et al.
An titu m or Activity of 4a (SB-T-1213) in Vivo
Ta ble 5. Cytotoxicities of Selected Antitumor Agents against
Ovarian and Drug-Resistant Ovarian Cancer Cell Lines
The in vivo antitumor activity of 4a (SB-T-1213) was
evaluated against B16 melanoma implanted subcutane-
ously in B6D2F1 mice.37 Taxoid 4a (0.4 mL/mouse) was
administered intravenously (iv) on days 5, 7, and 9.
Results are as follows: T/C (tumor growth inhibition)
0% (12.4 mg/kg/day), T C (tumor growth delay)
A2780-WTa A2780-DX5b A2780-C25c A2780-CP3d
cisplatin
450
5
2.7
1.2
0.4
280
357
547
122
1600
63
9000
56
doxorubicin
paclitaxel
docetaxel
SB-T-1212
3.4
1.0
0.3
4.1
1.4
5.7
0.36
10.9 days, log10 cell kill
day), T 9.3 days, log10 cell kill
(4.8 mg/kg/day), T
(For detailed explanation about T/C, T C, and log10 cell
kill values, see the Experimental Section. A T/C value
of 10% is considered excellent antitumor activity by
the National Cancer Institute; a larger number for T C
as well as for log cell kill values indicates higher
activity.) Under the same conditions, docetaxel showed
the following activity: T/C 0% (20 mg/kg/day, optimal
2.3; T/C
0% (7.7 mg/kg/
a
b
A2780-WT, human ovarian carcinoma. A2780-DX5, doxoru-
bicin-resistant ovarian carcinoma. c A2780-C25, oxaliplatin-resis-
C
2.0; T/C
34%
0.6.
d
tant ovarian carcinoma. A2780-CP3, cisplatin-resistant ovarian
carcinoma.
C
3.0 days, log10 cell kill
level IC50 values, the analogs bearing N-monoalkyl and
N-monoallyl groups, 4n s and 5s, show, uniformly, a
substantial decrease in activity (20 162 nM). It should
be noted that cyclohexylcarbamoyl, a bulky carbamoyl
group, brings about better activity than small size
carbamoyl groups as exemplified by the comparison of
4s (20 nM) or 5s (33 nM) with 4n (R CH3NHCO, 162
nM).
It is worth mentioning that the activity against MCF7-
R, a drug-resistant cell line expressing MDR phenotype,
is very sensitive to the structure of the C-10 modifier,
while this structural variation has little effects, in
general, on the activity against the normal cancer cell
lines, i.e., there is no apparent correlation between the
activity against the normal cancer cell lines and that
against the drug-resistant cell line.
It has been shown that multidrug resistance, i.e., the
cross-resistance to various structurally different cyto-
toxic agents, is caused by increased outward transport
of these agents through the plasma membrane by the
action of P-glycoprotein.35 The photoaffinity label of
P-glycoprotein with tritiated photoreactive paclitaxel
analog has recently been reported.36 Accordingly, it is
reasonable to assume that the observed SAR that is
unique to the drug-resistant cell line MCF7-R is related,
at least in part, to the binding ability of these new
taxoids to P-glycoprotein. All the new taxoids 4 and 5,
except 5s, possess subnanomolar level IC50 values
against the normal cancer cell lines (as an average value
for four cell lines). This means that most of the C-10
modifications we made are tolerated for cytotoxicity. On
the contrary, the binding of these taxoids to P-glyco-
protein is strongly affected by the structure of the C-10
modifier, i.e., it appears that the C-10 position is crucial
for P-glycoprotein to recognize and bind taxoid antitu-
mor agents.
In order to certify the relevance of using MCF7-R as
the probe cell line to evaluate activity against various
drug-resistant cancer cell lines, we looked at the activity
of SB-T-1212 against doxorubicin-resistant (A2780-
DX5), oxaliplatin-resistant (A2780-C25), and cisplatin-
resistant (A2780-CP3) ovarian cancer cell lines. Results
are listed in Table 5. As Table 5 clearly shows, taxane
antitumor agents, paclitaxel, docetaxel, and SB-T-1212,
maintain their excellent activity against the oxaliplatin-
and cisplatin-resistant cancer cells. However, paclitaxel
and docetaxel suffer from a substantial (100 200 times)
cross-resistance against the doxorubicin-resistant cancer
cell. In stark contrast to these two drugs, SB-T-1212
keeps excellent activity (IC50 5.7 nM). These results
clearly indicate the validity of the use of MCF7-R assay
for the evaluation of the cytotoxicity of the new taxoids
4 and 5 against drug-resistant cancer cells expressing
MDR phenotype.
dose), T
(12.4 mg/kg/day), T
T/C 8% (7.7 mg/kg/day), T
C
15.2 days, log10 cell kill 3.3; T/C 7%
7.1 days, log10 cell kill 1.5;
4.3 days, log10 cell
C
C
kill 0.9. The results clearly indicate that 4a (SB-T-
1213) is extremely active in vivo against this tumor.
Although docetaxel shows a higher log cell kill value at
optimal dosage, 4a is more potent than docetaxel on a
mg/kg basis, reflecting the exceptional activity of this
agent in the in vitro cell line assay (vide supra). These
observations warrant further investigation on 4a and
other exceptionally potent new taxoids such as 4b (SB-
T-1214) and 5a (SB-T-1102). Accordingly, we are cur-
rently preparing for in vivo assay against a series of
drug-resistant tumors (human cancer xenografts) in
nude mice. Results will be reported in due course.
Con clu sion s
We have found that the proper modifications at the
C-10 position of 3′-(2-methyl-1-propenyl) and 3′-(2-
methylpropyl) taxoids result in significant increase in
their cytotoxicity, particularly against drug-resistant
human breast cancer cell line MCF7-R expressing MDR
phenotype. New taxoids possessing exceptionally high
potency against MCF7-R, which is 2 orders of magnitude
better than those of paclitaxel and docetaxel, have been
developed. The observed exceptional activity against
the drug-resistant cancer cells appears to be ascribed
to the blocking of P-glycoprotein binding to these C-10-
modified analogs. A variety of C-10 acyl groups is
tolerated in terms of the cytotoxicity against normal
cancer cells, although there is a limitation toward the
optimal size of the acyl group. On the contrary, the
structure of the C-10 modifier is very sensitive to the
activity against the drug-resistant cancer cells. One of
the most active new taxoids thus developed, SB-T-1213
(4a ), shows extremely strong in vivo antitumor activity
against B16 melanoma in nude mice. Further studies
on the development of the second-generation taxoids
that possess strong activity against drug-resistant
tumors are actively underway in these laboratories.
Exp er im en ta l Section
Gen er a l Meth od s. Melting points were measured with a
Thomas Hoover capillary melting point apparatus and are
uncorrected. Infrared spectra were recorded on a Perkin-
Elmer Model 1600 FT-IR spectrophotometer with neat samples.
1H,13C, and 2D nuclear magnetic resonance (NMR) spectra
were measured using a General Electric QE-300 or a Bruker
AC-250 spectrometer using tetramethylsilane as the internal

Syntheses of Second-Generation Antitumor Taxoids
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 20 3893
standard. Optical rotations were measured with a Perkin-
Elmer Model 241 polarimeter. Thin layer chromatography
was performed on Merck DC-alufolien with Kieselgel 60F-254.
Column chromatography was carried out on silica gel 60 (230
400 mesh ASTM; Merck). Elemental analyses were performed
at M-H-W Laboratories, Phoenix, AZ, and Supersun Technol-
ogy Analytical Laboratory, Stony Brook, NY. FAB HRMS
were performed at UCR Mass Spectrometry Facility, Riverside,
CA.
Ma ter ia ls. The chemicals were purchased from Aldrich Co.
and Sigma and purified before use by standard methods. THF
was freshly distilled over sodium and benzophenone. 7-(Tri-
ethylsilyl)-10-deacetylbacctain III (7-TES-DAB) was prepared
by the literature method.26,38 (3R,4S)-3-[(Triisopropylsilyl)-
oxy]-4-isobutenyl-1-(tert-butoxycarbonyl)azetidin-2-one (2) was
prepared by the literature procedure.18
Gen er a l P r oced u r es for th e Syn th esis of a C-10-
Mod ified 7-(Tr iet h ylsilyl)-10-d ea cet ylb a cca t in III (1).
Meth od A: To a solution of 7-TES-DAB in THF (0.055 M) was
added 1.1 1.3 equiv of LiHMDS at 40 °C. After the reaction
mixture was stirred for 10 min, 1.0 1.2 equiv of an alkanoyl
chloride, an N,N-dialkylcarbamoyl chloride, or methyl iodide
(freshly distilled) was added dropwise at 40 °C. The mixture
was warmed to 0 °C over a period of 30 60 min and then
concentrated in vacuo. Purification of the crude product by
silica gel chromatography (hexane/EtOAc 4:1 1:1) afforded
the 10-modified 7-TES-baccatin III 1a m as a white solid.
Meth od B: To a solution of 7-TES-DAB (0.10 M) in dry
dichloromethane was added 1.0 equiv of copper(I) chloride with
stirring. A freshly distilled isocyanate (1.5 3.0 equiv) was
added dropwise to the resulting green-yellow suspension, and
the mixture was stirred at room temperature for 22 72 h. The
reaction was quenched with saturated NH4Cl and the mixture
extracted with dichloromethane. The organic layer was dried
over MgSO4, filtered, and concentrated in vacuo. The crude
product was purified by silica gel chromatography with dichlo-
romethane/methanol (98:2 96:4) as the eluant to give the 10-
modified 7-TES-baccatin III 1n s as a white solid. Identifi-
cation data for these 10-modified baccatin III derivatives are
given in the Supporting Information.
(c 0.76, CHCl3); 1H NMR (300 MHz, CDCl3) δ 1.15 (s, 3 H),
1.26 (s, 3 H), 1.36 (s, 9 H), 1.68 (s, 3 H), 1.77 (br s, 6 H), 1.90
(br s, 4 H), 2.25 (s, 3 H), 2.36 (s, 3 H), 2.39 (br s, 1 H), 2.53 (m,
2 H), 3.44 (d, J
6.7 Hz, 1 H), 3.82 (d, J
7.0 Hz, 1 H), 4.20
(d, J 8.5 Hz, 1 H), 4.24 (m, 1 H), 4.31 (d, J
8.5 Hz, 1 H),
4.43 (m, 1 H), 4.78 (dq, J
4.96 (d, J
8.5, 2.6 Hz, 1 H), 4.83 (br s, 1 H),
8.1 Hz, 1 H), 5.32 (d, J
8.3 Hz, 1 H), 5.67 (d, J
7.0 Hz, 1 H), 6.17 (t, J
8.6 Hz, 1 H), 6.31 (s, 1 H), 7.45 (d,
2 H), 7.60 (t, 1 H), 8.10 (d, 2 H); 13C NMR (63 MHz, CDCl3) δ
9.6, 14.9, 18.5, 20.8, 22.4, 25.7, 26.6, 28.2, 35.6, 43.2, 45.7, 51.6,
58.5, 72.1, 72.2, 73.8, 75.1, 75.6, 76.4, 79.1, 79.9, 81.0, 84.4,
120.7, 128.6, 129.3, 130.1, 132.8, 133.6, 137.7, 145.6, 155.5,
166.9, 170.1, 171.2, 173.7, 203.7. Anal. Calcd for C43H55
-
NO15: C, 62.38; H, 6.94; N, 1.69. Found: C, 62.47; H, 6.71;
N, 1.60.
3′-Dep h en yl-3′-(2-m eth yl-2-p r op en yl)-10-n -p r op a n oyl-
d oceta xel (4a ): 69% yield; [ ]D 40.0° (c 1.00, CHCl3); 1H
NMR (300 MHz, CDCl3) δ 1.08 (s, 3 H), 1.13 1.18 (m, 6 H),
1.28 (s, 9 H), 1.60 (s, 3 H), 1.69 (br s, 6 H), 1.72 (m, 1 H), 1.83
(s, 3 H), 2.29 (s, 3 H), 2.31 (s, 2 H), 2.44 (m, 3 H), 3.38 (br s, 1
H), 3.74 (d, J
s, 1 H), 4.22 (d, J
H), 4.67 (m, 2 H), 4.88 (d, J
6.9 Hz, 1 H), 4.10 (d, J
8.1 Hz, 1 H), 4.13 (br
8.1 Hz, 1 H), 4.33 (dd, J 10.1, 7.5 Hz, 1
9.3 Hz, 1 H), 5.23 (d, J 8.4
Hz, 1 H), 5.59 (d, J
6.9 Hz, 1 H), 6.06 (m, 1 H), 6.24 (s, 1 H),
7.37 (t, 2 H), 7.51 (t, 1 H), 8.01 (d, 2 H); 13C NMR (63 MHz,
CDCl3) δ 9.0, 9.5, 14.9, 18.5, 21.8, 22.3, 25.7, 26.6, 27.5, 28.2,
35.5, 43.1, 45.6, 51.6, 55.5, 58.5, 72.1, 72.3, 73.7, 75.0, 75.4,
76.4, 76.5, 77.0, 77.5, 79.1, 79.9, 81.0, 84.3, 120.6, 128.6, 129.2,
130.1, 132.9, 133.6, 137.8, 142.4, 155.4, 166.9, 170.1, 173.0,
174.6, 203.8; HRMS (FAB, DCM/NBA) m/ z calcd for C44H59O15-
NH 842.3962, found 842.4007.
10-(Cyclop r op ylca r bon yl)-3′-d ep h en yl-3′-(2-m eth yl-2-
p r op en yl)d oceta xel (4b): 70% yield; [ ]D 160° (c 1.00,
CHCl3); 1H NMR (250 MHz, CDCl3) δ 1.10 (m, 2 H), 1.14 (s, 3
H), 1.25 (s, 3 H), 1.34 (s, 9 H), 1.65 (s, 3 H), 1.71 (s, 2 H), 1.75
(br s, 6 H), 1.84 (m, 1 H), 1.88 (s, 3 H), 2.34 (s, 3 H), 2.37 (s, 2
H), 2.46 (m, 1 H), 2.56 (d, J
3.3 Hz, 1 H), 3.36 (m, 1 H), 3.78
(d, J
6.9 Hz, 1 H), 4.13 (d, J 8.4 Hz, 1 H), 4.18 (br s, 1 H),
4.27 (d, J
8.4 Hz, 1 H), 4.40 (m, 1 H), 4.72 (m, 2 H), 4.93 (d,
J
8.6 Hz, 1 H), 5.28 (d, J 7.6 Hz, 1 H), 5.64 (d, J 6.9 Hz,
Gen er a l P r oced u r e for th e Syn th eses of Ta xoid s 4 a n d
SB-T-1212. To a solution of a baccatin 1 (0.02 M) and 1.3
1.5 equiv of 4-isobutenyl-1-(tert-butoxycarbonyl)-3-[(triisopro-
pylsilyl)oxy]azetidin-2-one (2) in dry THF was added dropwise
1.0 1.5 equiv of LiHMDS (1.0 M in THF) at 40 °C. The
reaction mixture was allowed to warm to 15 ° to 10 °C and
stirred for 30 60 min. Then, the reaction was quenched with
saturated NH4Cl. The mixture was extracted with ethyl
acetate and the organic layers were washed with saturated
NH4Cl and brine, dried over MgSO4, and concentrated in
vacuo. Purification of the crude product by silica gel chroma-
1 H), 6.16 (m, 1 H), 6.28 (s, 1 H), 7.43 (t, 2 H), 7.56 (t, 1 H),
8.07 (d, 2 H); 13C NMR (63 MHz, CDCl3) δ 9.1, 9.4, 9.5, 13.0,
14.9, 18.5, 21.9, 22.4, 25.7, 26.7, 28.2, 35.5, 35.6, 43.2, 45.6,
51.6, 58.5, 72.2, 72.3, 73.7, 75.0, 75.4, 76.5, 77.0, 77.5, 79.2,
79.7, 81.0, 84.4, 120.6, 128.6, 129.2, 130.1, 132.9, 133.6, 137.9,
142.6, 155.4, 166.9, 170.1, 175.1, 203.9; IR (neat, cm
1) ν 3368,
2989, 2915, 1786, 1754, 1725, 1709, 1641, 1630, 1355, 1315,
1109; HRMS (FAB, DCM/NBA/NaCl) m/ z calcd for C45H59O15
-
NNa 876.3784, found 876.3782.
3′-Dep h en yl-10-(N,N-d im eth ylca r ba m oyl)-3′-(2-m eth yl-
2-p r op en yl)d oceta xel (4c): 70% yield; [ ]D 50.0° (c 2.00,
1
tography (hexane/EtOAc
4:1) afforded the corresponding
CHCl3); H NMR (250 MHz, CDCl3) δ 1.13 (s, 3 H), 1.23 (s, 3
taxoid 3 with protecting groups as a white solid. The depro-
tection was carried out using the following two methods.
Meth od A: To a solution of 3 (0.015 M) in a 1:1 mixture of
pyridine and acetonitrile was added HF/pyridine (70:30) (0.1
mL/10 mg of starting material) at 0 °C. After the reaction
mixture was warmed to 30 °C for 4 5 h, the reaction was
quenched with water and the mixture extracted with ethyl
acetate. The combined organic layers were washed with brine,
dried over MgSO4, and concentrated in vacuo. Purification of
the crude product by silica gel chromatography (hexane/EtOAc
1:1) afforded the corresponding taxoid 4a e as well as SB-
T-1212 as a white solid.
Meth od B: To a solution of 3 (0.015 M) in a 1:1 mixture of
pyridine and acetonitrile was added HF/pyridine: (70:30) (0.1
mL/10 mg of starting material) at 0 °C. After the reaction
mixture was allowed to warm to room temperature and stir
for 12 16 h, the reaction was quenched with water and the
mixture extracted with ethyl acetate. The combined organic
layers were washed with brine, dried over MgSO4, and
concentrated in vacuo. Purification of the crude product by
silica gel chromatography (hexane/EtOAc 1:1) afforded the
corresponding taxoid 4f s as a white solid.
H), 1.33 (s, 9 H), 1.64 (s, 3 H), 1.74 (br s, 6 H), 1.85 (m, 1 H),
1.89 (s, 3 H), 2.33 (s, 3 H), 2.36 (s, 2 H), 2.45 (m, 1 H), 2.93 (s,
3 H), 3.02 (s, 3 H), 3.20 (br s, 1 H), 3.45 (m, 1 H), 3.78 (d, J
6.9 Hz, 1 H), 4.14 (d, J
8.4 Hz, 1 H), 4.18 (br s, 1 H), 4.26 (d,
8.4 Hz, 1 H), 4.40 (dd, J 10.2, 6.7 Hz, 1 H), 4.69 (m, 1
8.6 Hz, 1 H), 5.27 (d, J 7.6 Hz,
J
H), 4.80 (s, 1 H), 4.93 (d, J
1 H), 5.62 (d, J
6.9 Hz, 1 H), 6.12 (m, 1 H), 6.23 (s, 1 H),
7.41 (t, 2 H), 7.55 (t, 1 H), 8.06 (d, 2 H); 13C NMR (63 MHz,
CDCl3) δ 9.3, 15.0, 18.5, 22.2, 22.3, 25.7, 26.8, 28.2, 35.3, 35.6,
36.0, 36.6, 43.1, 45.6, 51.6, 58.4, 72.3, 72.4, 73.7, 75.2, 76.2,
76.4, 76.5, 77.0, 77.5, 79.2, 81.0, 84.6, 128.6, 129.2, 130.1, 133.1,
133.6, 137.8, 142.9, 155.4, 156.1, 166.9, 170.0, 173.0, 205.6;
HRMS (FAB, DCM/NBA) m/ z calcd for C44H60O15N2Na
879.3891, found 879.3870.
3′-Dep h en yl-10-(m eth oxyca r bon yl)-3′-(2-m eth yl-2-p r o-
p en yl)d oceta xel (4d ): 61% yield; [ ]D 15.0° (c 2.00, CHCl3);
1H NMR (250 MHz, CDCl3) δ 1.14 (s, 3 H), 1.23 (s, 3 H), 1.33
(s, 9 H), 1.68 (s, 3 H), 1.71 (br s, 6 H), 1.87 (m, 1 H), 1.92 (s, 3
H), 2.34 (s, 3 H), 2.47 (m, 2 H), 2.55 (m, 1 H), 3.40 (br s, 1 H),
3.76 (d, J
6.9 Hz, 1 H), 3.85 (s, 3 H), 4.15 (d, J
8.3 Hz, 1
H), 4.19 (br s, 1 H), 4.28 (d, J
4.72 (m, 2 H), 4.93 (d, J
8.3 Hz, 1 H), 4.38 (m, 1 H),
8.6 Hz, 1 H), 5.29 (d, J
7.8 Hz, 1
10-Acet yl-3′-d ep h en yl-3′-(2-m et h yl-2-p r op en yl)d oce-
ta xel (SB-T-1212): 90% yield; mp 157 160 °C; [ ]D 76.3°
H), 5.64 (d, J
6.9 Hz, 1 H), 6.11 (s, 1 H), 6.15 (s, 1 H), 7.43
(t, 2 H), 7.56 (t, 1 H), 8.07 (d, 2 H); 13C NMR (75 MHz, CDCl3)

3894 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 20
Ojima et al.
δ 9.4, 15.0, 18.5, 21.7, 22.3, 25.7, 26.5, 28.2, 35.5, 43.1, 45.6,
51.6, 55.5, 58.6, 72.0, 72.2, 73.7, 75.0, 76.4, 76.5, 77.0, 77.2,
77.4, 78.3, 79.1, 79.9, 81.0, 84.3, 120.6, 128.6, 129.2, 130.1,
132.5, 133.6, 137.9, 143.4, 155.4, 155.7, 166.9, 170.1, 172.9,
8.8 Hz, 1 H), 6.31 (s, 1 H), 7.48 (t, 2 H), 7.61 (t, 1 H), 8.12 (d,
2 H); 13C NMR (63 MHz, CDCl3) δ 9.6, 14.9, 20.8, 21.9, 22.5,
23.2, 24.7, 26.6, 27.9, 28.2, 35.6, 41.3, 43.2, 45.6, 51.4, 58.6,
72.2, 73.0, 75.1, 75.6, 76.5, 77.2, 79.2, 79.7, 81.1, 84.4, 128.6,
129.3, 130.2, 132.9, 133.6, 142.6, 155.5, 167.0, 170.0, 171.2,
174.0, 203.7. Anal. Calcd for C43H57NO15: C, 62.23; H, 7.17;
N, 1.69. Found: C, 62.18; H, 6.82; N, 1.51.
3′-Dep h en yl-3′-(2-m eth ylp r op yl)-10-n -p r op a n oyld oce-
ta xel (5a ): 100% yield; [ ]D 30.0° (c 1.00, CHCl3); 1H NMR
(250 MHz, CDCl3) δ 0.96 (m, 6 H), 1.13 (s, 3 H), 1.22 1.27 (m,
6 H), 1.30 (s, 9 H), 1.63 (s, 3 H), 1.73 (s, 2 H), 1.82 (m, 1 H),
1.88 (s, 3 H), 2.36 (s, 3 H), 2.40 (s, 2 H), 2.46 (m, 1 H), 2.49 (m,
203.9; HRMS (FAB, DCM/NBA/PPG) m/ z calcd for C43H57O16
-
NH 844.3710, found 844.3755.
3′-Dep h en yl-10-m et h yl-3′-(2-m et h yl-2-p r op en yl)d oce-
1
ta xel (4e): 69% yield; [ ]D 16.7° (c 3.00, CHCl3); H NMR
(300 MHz, CDCl3) δ 1.08 (s, 3 H), 1.13 (s, 3 H), 1.18 (s, 3 H),
1.28 (s, 9 H), 1.60 (s, 3 H), 1.69 (br s, 6 H), 1.72 (m, 1 H), 1.83
(s, 3 H), 2.29 (s, 3 H), 2.31 (s, 2 H), 2.44 (m, 3 H), 3.38 (br s, 1
H), 3.74 (d, J
s, 1 H), 4.22 (d, J
4.88 (d, J 9.3 Hz, 1 H), 5.23 (d, J
6.9 Hz, 1 H), 4.10 (d, J
8.1 Hz, 1 H), 4.33 (m, 1 H), 4.67 (m, 2 H),
8.4 Hz, 1 H), 5.59 (d, J
8.1 Hz, 1 H), 4.13 (br
2 H), 3.25 (br s, 1 H), 3.79 (d, J
Hz, 1 H), 4.16 (br s, 1 H), 4.27 (d, J
7.0 Hz, 1 H), 4.09 (d, J
8.3
8.3 Hz, 1 H), 4.38 (dd,
9.5 Hz, 1 H), 4.94 (d, J
6.9 Hz, 1 H), 6.06 (m, 1 H), 6.24 (s, 1 H), 7.37 (t, 2 H), 7.51
(t, 1 H), 8.01 (d, 2 H); 13C NMR (75 MHz, CDCl3) δ 9.7, 14.6,
18.5, 20.8, 22.4, 25.7, 26.3, 28.2, 35.4, 37.0, 43.1, 46.7, 51.5,
56.8, 57.8, 71.9, 72.3, 73.7, 74.9, 76.5, 77.0, 77.2, 77.5, 78.8,
79.9, 81.2, 82.6, 84.2, 120.6, 128.6, 129.2, 130.1, 133.6, 134.9,
139.5, 155.4, 166.9, 170.1, 172.9, 206.7; HRMS (FAB, DCM/
NBA) m/ z calcd for C42H57O14NNa 822.3676, found 822.3705.
3′-Dep h en yl-3′-(2-m eth yl-2-p r op en yl)-10-n -p en ta n oyl-
J
10.2, 6.7 Hz, 1 H), 4.57 (d, J
8.0 Hz, 1 H), 5.64 (d, J
7.0 Hz, 1 H), 6.13 (m, 1 H), 6.30 (s,
1 H), 7.43 (t, 2 H), 7.56 (t, 1 H), 8.08 (d, 2 H); 13C NMR (63
MHz, CDCl3) δ 9.0, 9.5, 14.9, 21.8, 21.9, 22.5, 23.2, 24.6, 26.5,
27.5, 28.1, 29.6, 35.5, 41.2, 43.1, 45.6, 51.3, 58.5, 72.1, 72.6,
73.0, 75.1, 75.4, 76.4, 76.5, 77.0, 77.5, 79.1, 79.7, 81.0, 84.4,
128.6, 129.2, 130.1, 132.9, 133.6, 142.4, 155.5, 166.9, 169.9,
173.9, 174.6, 203.8; HRMS (FAB, DCM/NBA) m/ z calcd for
C44H61O15NH 844.4119, found 844.4157.
d oceta xel (4f): 82% yield; mp 130 133°C; [ ]D 78.8° (c 0.33,
1
CHCl3); H NMR (250 MHz, CDCl3) δ 0.93 (t, J
7.3 Hz, 3
10-(Cyclop r op ylca r bon yl)-3′-d eph en yl-3′-(2-m eth ylp r o-
p yl)d oceta xel (5b): 100% yield; [ ]D 30.0° (c 1.00, CHCl3);
1H NMR (250 MHz, CDCl3) δ 0.96 (m, 6 H), 1.09 (m, 2 H),
1.14 (s, 3 H), 1.24 (s, 3 H), 1.30 (s, 9 H), 1.62 1.70 (m, 4 H),
1.66 (s, 3 H), 1.73 (m, 1 H), 1.88 (s, 3 H), 2.36 (s, 3 H), 2.39 (s,
1 H), 2.48 (m, 1 H), 2.50 (m, 1 H), 3.20 (m, 1 H), 3.78 (d, J
H), 1.13 (s, 3 H), 1.24 (s, 3 H), 1.33 1.48 (m, 11 H), 1.63 1.82
(m, 9 H), 1.85 1.90 (m, 4 H), 2.37 (br s, 4 H), 2.43 2.59 (m, 3
H), 3.40 (d, J
4.21 (m, 2 H), 4.29 (d, J
4.68 4.81 (m, 2 H), 4.95 (d, J
6.4 Hz, 1 H), 3.80 (d, J
7.0 Hz, 1 H), 4.14
8.4 Hz, 1 H), 4.38 4.44 (m, 1 H),
8.1 Hz, 1 H), 5.30 (d, J
7.8
Hz, 1 H), 5.65 (d, J
7.0 Hz, 1 H), 6.15 (t, J
8.9 Hz, 1 H),
7.4 Hz, 1
6.9 Hz, 1 H), 4.16 (d, J
8.3 Hz, 1 H), 4.20 (br s, 1 H), 4.27 (d,
6.29 (s, 1 H), 7.46 (t, J
7.4 Hz, 2 H), 7.60 (t, J
J
8.3 Hz, 1 H), 4.40 (m, 1 H), 4.55 (m, 1 H), 4.93 (d, J
8.1
H), 8.09 (d, J
7.4 Hz, 2 H); 13C NMR (63 MHz, CDCl3) δ
Hz, 1 H), 5.64 (d, J
7.0 Hz, 1 H), 6.14 (m, 1 H), 6.29 (s, 1 H),
9.56, 13.74, 14.98, 18.59, 21.90, 22.23, 22.41, 25.75, 26.65,
26.90, 28.23, 33.91, 35.57, 43.16, 45.63, 51.59, 58.56, 72.22,
72.36, 73.76, 75.03, 75.39, 79.15, 80.00, 81.04, 84.45, 120.61,
128.65, 129.19, 130.16, 132.94, 133.71, 137.94, 142.51, 155.45,
166.95, 170.10, 171.19, 173.10, 174.07, 203.81. Anal. Calcd
for C46H63NO15: C, 63.51; H, 7.30; N, 1.61. Found: C, 63.74;
H, 7.13; N, 1.63.
7.43 (t, 2 H), 7.56 (t, 1 H), 8.09 (d, 2 H); 13C NMR (63 MHz,
CDCl3) δ 9.1, 9.4, 9.5, 13.0, 14.9, 21.9, 22.0, 22.5, 23.2, 24.7,
26.6, 28.1, 35.4, 35.5, 41.2, 43.1, 45.6, 51.3, 58.5, 72.2, 72.7,
72.9, 75.1, 75.4, 76.5, 77.0, 77.5, 79.2, 79.7, 81.0, 84.4, 128.6,
129.2, 130.2, 132.9, 133.6, 142.6, 155.5, 166.9, 169.9, 173.9,
175.1, 203.9; HRMS (FAB, DCM/NBC/NaCl) m/ z calcd for
C45H61O15NNa 878.3938, found 878.3926.
3′-Dep h en yl-10-n -h exa n oyl-3′-(2-m et h yl-2-p r op en yl)-
d oceta xel (4g): 39% yield (60% conversion yield); mp 126
128°C; [ ]D 72.0° (c 0.50, CHCl3); 1H NMR (250 MHz, CDCl3)
3′-Dep h en yl-10-(N,N-d im eth ylca r ba m oyl)-3′-(2-m eth yl-
p r op yl)d oceta xel (5c): 100% yield; [ ]D 80.0° (c 2.00,
CHCl3); 1H NMR (250 MHz, CDCl3) δ 0.95 (m, 6 H), 1.14 (s, 3
H), 1.23 (s, 3 H), 1.29 (s, 9 H), 1.66 (s, 3 H), 1.68 (m, 2 H), 1.82
(m, 1 H), 1.90 (s, 3 H), 2.36 (s, 3 H), 2.39 (s, 2 H), 2.50 (m, 1
δ 0.90 (t, J
6.8 Hz, 3 H), 1.13 (s, 3 H), 1.24 (s, 3 H), 1.34 (br
s, 13 H), 1.65 1.92 (m, 16 H), 2.34 2.39 (m, 4 H), 2.42 2.61
(m, 3 H), 3.42 (d, J
6.1 Hz, 1 H), 3.79 (d, J
7.0 Hz, 1 H),
8.4 Hz, 1 H), 4.36 4.46 (m, 1
8.1 Hz, 1 H), 5.30 (d, J
H), 2.95 (s, 3 H), 3.03 (s, 3 H), 3.22 (m, 1 H), 3.78 (d, J
7.0
4.09 4.21 (m, 2 H), 4.29 (d, J
H), 4.67 4.83 (m, 2 H), 4.94 (d, J
8.4 Hz, 1 H), 5.65 (d, J
Hz, 1 H), 4.10 (d, J
8.3 Hz, 1 H), 4.16 (br s, 1 H), 4.27 (d, J
8.3 Hz, 1 H), 4.41 (dd, J
10.2, 6.5 Hz, 1 H), 4.56 (m, 1 H),
7.0 Hz, 1 H), 6.15 (t, J
8.7 Hz, 1
4.95 (d, J
8.1 Hz, 1 H), 5.63 (d, J 7.0 Hz, 1 H), 6.14 (m, 1
H), 6.24 (s, 1 H), 7.42 (t, 2 H), 7.56 (t, 1 H), 8.08 (d, 2 H); 13C
NMR (75 MHz, CDCl3) δ 9.8, 15.3, 22.3, 22.7, 22.9, 23.6, 25.1,
27.2, 28.5, 35.8, 36.0, 36.4, 37.0, 41.6, 43.6, 46.0, 51.7, 58.9,
72.8, 73.1, 75.7, 76.6, 76.8, 76.9, 77.1, 77.4, 77.6, 77.8, 79.6,
80.0, 81.5, 85.0, 128.7, 129.0, 129.7, 130.6, 133.6, 133.9, 143.3,
155.9, 156.5, 167.3, 170.3, 174.3, 206.0; HRMS (FAB) m/ z
calcd for C44H62O15N2Na 881.4074, found 881.4047.
H), 6.29 (s, 1 H), 7.46 (t, J
1 H), 8.09 (d, J
7.4 Hz, 2 H), 7.60 (t, J 7.4 Hz,
7.4 Hz, 2 H); 13C NMR (63 MHz, CDCl3) δ
9.56, 13.92, 14.96, 18.57, 21.89, 22.29, 22.41, 24.51, 25.73,
26.66, 28.02, 28.23, 31.21, 34.15, 35.55, 35.60, 43.18, 45.64,
51.61, 58.56, 72.20, 72.34, 73.76, 75.39, 76.46, 79.14, 79.98,
81.06, 84.45, 120.64, 128.64, 129.22, 130.16, 132.96, 133.68,
137.90, 142.48, 155.46, 166.94, 170.10, 173.09, 174.07, 203.76.
Anal. Calcd for C47H65NO15
: C, 63.86; H, 7.41; N, 1.58.
Identification data for taxoids 5d ,e,s are given in the
Supporting Information.
Found: C, 63.63; H, 7.31; N, 1.64.
Identification data for taxoids 4h
Supporting Information.
Cytotoxicity Assa y in Vitr o.39 Tumor cell growth inhibi-
tion was determined according to the method established by
Skehan et al.34 Human tumor cells (A121a, ovarian carcinoma,
HT-29, colon carcinoma; A549, non-small-cell lung carcinoma;
MCF-7, breast carcinoma) were plated at a density of 400 cells/
well in 96-well plates and allowed to attach overnight. These
cell lines were maintained in RPMI-1640 medium (Roswell
Park Memorial Institute growth medium) supplemented with
5% fetal bovine serum and 5% Nu serum (Collaborative
Biomedical Product, MA). Taxanes were solubilized in DMSO
and further diluted with RPMI-1640 medium. Triplicate wells
were exposed to various treatments. After 72 h incubation,
100 µL of ice-cold 50% trichloroacetic acid (TCA) was added
to each well, and the samples were incubated for 1 h at 4 °C.
Plates were then washed five times with water to remove TCA
and serum proteins, and 50 µL of 0.4% sulforhodamine B (SRB)
was added to each well. Following a 5 min incubation, plates
were rinsed five times with 0.1% acetic acid and air-dried. The
dye was then solubilized with 10 mM Tris base (pH 10.5) for
s
are given in the
Gen er a l P r oced u r e for th e Syn th eses of 3′-(2-Meth yl-
p r op yl) Ta xoid s 5 a n d SB-T-1102. A solution of a 3′-(2-
methyl-1-propenyl) taxoid 4 in ethyl acetate (0.01M) was
subjected to hydrogenation in the presence of 10% Pd C (30
50% by weight of starting material) at ambient temperature
and pressure for 24 h. The solution was filtered through silica
gel to remove the catalyst and concentrated in vacuo to afford
the corresponding 3′-(2-methylpropyl) taxoid 5 or SB-T-1102
as a white solid.
10-Acet yl-3′-d ep h en yl-3′-(2-m et h ylp r op yl)d ocet a xel
(SB-T-1102): 85% yield; [ ]D 81.2° (c 1.00, CHCl3); 1H NMR
(250 MHz, CDCl3) δ 0.98 (s, 3 H), 1.01 (s, 3 H), 1.16 (s, 3 H),
1.26 (s, 3 H), 1.32 (s, 9 H), 1.30 1.34 (m, 1 H), 1.65 2.05 (m,
3 H), 1.70 (s, 3 H), 1.90 (s, 3 H), 2.38 (s, 3 H), 2.42 (m, 2 H),
2.56 (m, 1 H), 3.82 (d, J
7.0 Hz, 1 H), 4.10 4.25 (m, 3 H),
4.31 (d, J
(d, J
8.4 Hz, 1 H), 4.41 (dd, J 10.7, 7.2 Hz, 1 H), 4.97
8.0 Hz, 1 H), 5.67 (d, J
7.0 Hz, 1 H), 6.19 (br t, J

Syntheses of Second-Generation Antitumor Taxoids
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 20 3895
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5 min on a gyratory shaker. Optical density was measured
at 570 nm. The IC50 values were then calculated by fitting
the concentration effect curve data with the sigmoid-Emax
model using nonlinear regression, weighted by the reciprocal
of the square of the predicted effect.40
An titu m or Activity Assa y in Vivo.37,41 Tumor fragments
of B16 melanoma (1 mm3, 30 60 mg) were grafted subcutane-
ously (sc) on day 0 in B6D2F1 mice (5 mice/group). Taxoid
SB-T-1213 was first dissolved in ethanol, then polysorbate 80
was added, and the final dilution was made with 5% glucose
in water (5/5/90, v/v/v). The pH of the final solution was 5.
Taxoid SB-T-1213 (0.4 mL/mouse) was administered intrave-
nously (i.v.) on days 5, 7, and 9. Animals were observed for
toxicity and tumor growth. Tumors were measured with a
caliper. Tumor weights were calculated from 2-dimensional
measurements: tumor weight (mg) (l × w2)/2, where l and
w are the tumor length and width (mm), respectively. Anti-
tumor activity was expressed by the tumor growth inhibition
(T/C) value obtained at the maximal tolerated dose (no
lethality, body weight loss
20%), wherein T is the median
tumor weight of treated animals and C is the median tumor
weight of control animals. A T/C value of 42% or less is
considered significant antitumor activity and 10% or less is
regarded as excellent by the National Cancer Institute. The
other end point used was the tumor growth delay (T C), where
T and C are the median time in days required for the
treatment group (T) and the control group (C) to reach 750
mg, respectively. The log cell kill values are derived from the
T
C value using the formula: log cell kill
T C (in days)/
3.32 × Td, where Td is the tumor doubling time in days (1.4
(19) Ojima, I.; Fenoglio, I.; Park, Y. H.; Pera, P.; Bernaki, R. J .
Synthesis and Biological Activity of 14â-Hydroxydocetaxel.
Bioorg. Med. Chem. Lett. 1994, 4, 1571 1576.
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S. D.; Zucco, M.; Appendino, G.; Pera, P.; Veith, J . M.; Bernacki,
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Ack n ow led gm en t. This research was supported by
grants from the National Institutes of Health (GM417980
to I.O.), the Center for Biotechnology at Stony Brook
which is sponsored by the New York State Science &
Technology Foundation (I.O.), and the National Cancer
Institute (CA13038 to R.J .B.). Generous support from
Rhone-Poulenc Rorer (I. O.) is gratefully acknowledged.
The authors would like to thank Dr. Ezio Bombardelli,
Indena, SpA, for the generous gift of 10-DAB. Two of
the authors (J .C.S. and S.D.K.) thank the U.S. Depart-
ment of Education for GAANN fellowships.
(22) (a) Kant, J .; O’Keeffe, W. S.; Chen, S.-H.; Farina, V.; Fairchild,
C.; J ohnston, K.; Kadow, J . F.; Long, B. H.; Vyas, D.
A
Chemoselective Approach to Functionalize the C-10 Position of
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Ordering information is given on any current masthead page.
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