Cyclopeptide Smac mimetics as antagonists of IAP proteins

Article abstract of DOI:10.1016/j.bmcl.2010.03.114

Two cyclopeptidic Smac mimetics, 2 and 3, were designed and synthesized. These two compounds bind to XIAP and cIAP-1/2 with low nanomolar affinities, and restore the activities of caspase-9 and caspase-3/-7 inhibited by XIAP. Compound 2 potently inhibits

Full text of DOI:10.1016/j.bmcl.2010.03.114

Bioorganic & Medicinal Chemistry Letters 20 (2010) 3043–3046
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Cyclopeptide Smac mimetics as antagonists of IAP proteins
*
Haiying Sun, Liu Liu, Jianfeng Lu, Su Qiu, Chao-Yie Yang, Han Yi, Shaomeng Wang
Comprehensive Cancer Center and Departments of Internal Medicine, Pharmacology and Medicinal Chemistry, University of Michigan,
1500 E. Medical Center Drive, Ann Arbor, MI 48109, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Two cyclopeptidic Smac mimetics, 2 and 3, were designed and synthesized. These two compounds bind
to XIAP and cIAP-1/2 with low nanomolar affinities, and restore the activities of caspase-9 and caspase-
3/-7 inhibited by XIAP. Compound 2 potently inhibits cancer cell growth and is 5–8 times more potent
than the initial lead compound.
Received 5 February 2010
Revised 30 March 2010
Accepted 31 March 2010
Available online 3 April 2010
Ó 2010 Published by Elsevier Ltd.
Keywords:
Smac mimetics
IAP antagonists
Apoptosis inducers
New anticancer agents
Apoptosis, or programmed cell death, is a cell suicide process
essential for normal development, host defense and suppression
of oncogenesis.1 Dysfunction of apoptosis machinery is a hallmark
of cancer, and targeting key apoptosis regulators has emerged as an
attractive strategy for the development of new approaches to hu-
man cancer treatment.1
Inhibitors of apoptosis proteins (IAPs) are a class of key regula-
tors of apoptosis characterized by containing one to three bacul-
oviral IAP repeat domains (BIRs).2 Eight members of IAPs have
been discovered. Of these, cIAP-1 and cIAP-2 inhibit tumor necrosis
factor mediated apoptosis,3 and XIAP binds to and inhibits the
activity of three caspases, an initiator caspase-9 and two effectors,
caspase-3 and -7, thus blocking both the intrinsic and extrinsic
apoptotic pathways.4 XIAP, cIAP-1 and cIAP-2 have three BIR do-
mains. While the BIR3 domain of XIAP binds to initiator caspase-
9, its BIR2 domain, together with the linker preceding it, binds to
the effectors caspase-3 and -7.5 Although the BIR3 domain of
cIAP-1 and -2 can also bind to caspase-9, biological studies indicate
that they do not inhibit the activity of this caspase.
Smac (second mitochondria-derived activator of caspase) is a
potent and direct endogenous inhibitor of IAPs.6 Structural and
biological studies have shown that the interaction between Smac
and the IAPs is mediated by the BIR domain(s) in IAPs and the four
amino acid residues, AVPI, at the N-terminus of Smac.7 On one
hand, Smac antagonizes cIAP-1 and cIAP-2 by direct binding, fol-
lowed by induction of their rapid degradation. On the other hand,
Smac blocks XIAP by concurrently binding to its BIR2 and BIR3 do-
mains as a homodimer, thus removing the ability of XIAP to inhibit
caspases.8 Using Smac AVPI peptide as a lead compound, a number
of groups have designed and synthesized many peptidic and non-
peptidic Smac mimetics.9 In addition, a series of bivalent Smac
mimetics which mimic the interaction of dimeric Smac proteins
with XIAP have been designed and synthesized.10
PSmac-21 (1, Fig. 1) is a cyclopeptidic Smac mimetic previously
designed by our group. Previous studies indicated that (N–
Me)AKPF binds to XIAP BIR3 more effectively than the Smac tetra-
peptide, AVPI.11 In compound 1, two (N–Me)AKPF tetrapeptides
are cyclized through two amide bonds formed between the two
Lys side chain amino groups and the carboxylic acid groups in
the two C-terminal Phe residues. The crystal structure of 1 in com-
plex with recombinant XIAP BIR3 protein has been determined11
and it was found that two XIAP BIR3 protein molecules form a
homodimmer with one molecule of 1. Because the dimerization
of XIAP BIR3 was not observed under a ligand free condition, we
proposed that it was induced by the binding of 1. Interestingly,
while 1 can bind simultaneously to two recombinant XIAP BIR3
protein molecules, it can also bind to both the BIR2 and BIR3 do-
mains of recombinant XIAP, making it a very high-affinity inhibitor
against XIAP. Compound 1 is cell-permeable and effective in inhi-
bition of cancer cell growth.11 These data indicate that 1 is a prom-
ising lead compound for further optimization.
In this Letter, we report the design, synthesis and evaluation of
two new cyclopeptidic Smac mimetics, 2 (SM-162) and 3 (SM-
163), in which two amide bonds in 1 were replaced with two tria-
zole structures, in an effort to reduce its peptidic characteristics.
The synthesis of compounds 2 and 3 is shown in Scheme 1. We
use a ‘click reaction’ as the key cyclization step instead of the
macro cyclo-amidation reaction, which is used more frequently
for large cyclopeptides.12 The chiral amines 4a and 4b were
* Corresponding author.
E-mail address: shaomeng@umich.edu (S. Wang).
0960-894X/$ - see front matter Ó 2010 Published by Elsevier Ltd.
doi:10.1016/j.bmcl.2010.03.114

3044
H. Sun et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3043–3046
H
N
O
H
N
O
NH
NH
N
H
N
N
N
H
N
N
O
H
N
N
O
R
Bn
O
O
O
O
O
O
Bn
O
N
H
R
O
N
N
N
H
N
H
N
N
N
HN
HN
N
H
O
N
H
1
O
2
3
R = Phenyl
R = Benzyl
Figure 1. Design of cyclic Smac mimetics 2 and 3.
BocHN
NH2
R
R
N
BocN
a
b
HO
R
N
H
N
H
O
O
O
4a R = Ph
4b R = Bn
5a R = Ph, 89%
5b R = Bn, 86%
6a R = Ph, 79% over two steps
6b R = Bn, 81% over two steps
BocHN
N
BocHN
c
d
N
COOBn
N
HO
N3
OBn
OBn
O
H
O
7
8
9
O
O
BocHN
BocHN
N
N
N
N
N
N
N
N
NH
OBn
O
O
R
O
O
e
g
f
O
O
R
R
O
O
N
N
H
H
OH
OH
N
N
NHBoc
NHBoc
10a R = Ph, 72%
10b R = Bn, 73%
11a R = Ph, 85% over two steps
11b R = Bn, 88% over two steps
BocHN
BocHN
N
N
N
N
N
N
N
N
NH
NH
O
O
R
R
O
O
h
i
2 or 3
O
O
R
R
O
O
N
N
N
N
H
H
N3
N
N
N
NHBoc
NHBoc
12a R = Ph, 76% over two steps
12b R = Bn, 74% over two steps
13a R = Ph, 38%
13b R = Bn, 35%
Scheme 1. Reagents and conditions: (a) N-Boc-
hydroxynorleucine, EDC, HOBt, N,N-diisopropylethylamine, CH2Cl2; (c) N-Boc-
N,N-diisopropylethylamine, CH2Cl2; (ii) NaN3, DMF, 82% over two steps; (e) 6a or 6b, CuSO4, (+)-sodium
or 4b, EDC, HOBt, N,N-diisopropylethylamine, CH2Cl2; (g) (i) MsCl, N,N-diisopropylethylamine, CH2Cl2; (ii) NaN3, DMF, 82% over two steps; (h) CuSO4, (+)-sodium
L
-proline, EDC, HOBt, N,N-diisopropylethylamine, CH2Cl2; (b) (i) 4 N HCl in 1,4-dioxane, MeOH; (ii) N-Boc-
-6-hydroxynorleucine, EDC, HOBt, N,N-diisopropylethylamine, CH2Cl2, 87%; (d) (i) MsCl,
-ascorbate, t-BuOH/H2O 1:1, 74%; (f) (i) H2, 10% Pd–C, MeOH; (ii) 4a
-ascorbate,
-alanine, EDC, HOBt, N,N-diisopropylethylamine, CH2Cl2; (iii) 4 N HCl in 1,4-dioxane, MeOH;
L-6-
L
L
L
t-BuOH/H2O 1:1; (i) (i) 4 N HCl in 1,4-dioxane, MeOH; (ii) N-methyl-N-Boc-
L
compound 2: 79% over three steps, compound 3: 72% over three steps.
prepared by reported methods.13 Condensation of N-Boc-
with 4a or 4b gave two amides 5a and 5b. Removal of the Boc pro-
tecting group from these two amides followed by condensation of
L
-proline
of the mesylates with sodium azide furnished 12a and 12b. Macro-
cyclization of 12a and 12b using ‘click reaction’ furnished the
cyclopeptides 13a and 13b, removal of whose Boc protecting
groups followed by condensation of the ammonium salts with N-
the resulting ammonium salts with N-Boc-
yielded compounds 6a and 6b. Condensation of
ester hydrochloride (7) with N-Boc- -6-hydroxynorleucine affor-
L
-6-hydroxynorleucine
L-proline benzyl
methyl-N-Boc-L-alanine provided two amides. Finally, removal of
L
the Boc protecting groups gave compounds 2 and 3.14
ded amide 8. Mesylation of the hydroxyl group in 8 followed by
substitution of the mesylate with sodium azide furnished com-
pound 9. Cycloaddition of 6a or 6b with azide 9 yielded 10a and
10b, respectively. Hydrolysis of the benzyl esters group in 10a
and 10b followed by condensation of the resulting acids with 4a
and 4b, respectively, afforded compounds 11a and 11b. Mesylation
of the hydroxyl group in 11a and 11b and subsequent substitution
Compounds 2 and 3 were tested for their binding affinities to re-
combinant XIAP and cIAP-1/2 proteins in an FP-based binding assay
using Smac-1F as a tracer.11 The results are summarized in Table 1.
The binding curves of 1, 2 and 3 to XIAP protein containing linker-
BIR2–BIR3 (L-BIR2–BIR3) indicate that these compounds have two
binding sites or modes (Fig. 2). Compound 2 has IC50 values of 0.43
and 28 nM, respectively, for the two sites, whereas compound 3

H. Sun et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3043–3046
3045
Table 1
Binding affinities of compounds 1, 2 and 3 to XIAP L-BIR2–BIR3, L-BIR2, cIAP-1 BIR3 and cIAP-2 BIR3 proteins
Compounds
XIAP L-BIR2–BIR3 IC50 (nM)
XIAP L-BIR2 IC50
(
lM)
cIAP-1 BIR3 Ki (nM)
cIAP-2 BIR3 Ki (nM)
Site 1
Site 2
1
2
3
1.0
0.43
1.3
481.0
28.0
1106.0
53.9 20.9
3.2 1.6
40.5 9.2
84
11
161 20
9
2
292 41
24
393 69
5
120
100
80
60
40
20
0
100
80
60
40
20
0
1
2
3
1 (pSmac-21)
2 (SM-162)
3 (SM-163)
-20
-2
0
2
4
6
log [compounds] (nM)
0.15
0.5
1.5
5
15
50
Figure 2. Binding curves of compound 1, 2 and 3 to XIAP protein containing linker-
BIR2–BIR3.
(µM)
Figure 3. Functional antagonism of Smac mimetics to XIAP-LB2B3 inhibition of
caspase-9 activity. 500 nM of XIAP protein was used in the assay.
has IC50 values of 1.3 and 1106 nM, respectively. In comparison,
compound 1 has IC50 values of 1.0 and 481 nM, respectively, for
the two sites.
The weaker binding site may correspond to the BIR2 domain in
XIAP, so we also determined the binding affinities of 1, 2 and 3 to
XIAP protein containing only linker-BIR2 (Table 1). In this assay,
80
1
2
3
60
40
20
0
compounds 1, 2 and 3 have IC50 values of 53.9, 3.2, and 40.5 lM,
respectively. Hence, these data showed that the weaker binding
site for these compounds is not simply due to their interaction to
XIAP BIR2. Further investigations are needed to define precisely
how these compounds interact with XIAP linker-BIR2–BIR3
protein.
These three compounds also potently bind to cIAP-1 and cIAP-2
proteins (Table 1). Compounds 1, 2 and 3 bind to cIAP-1 BIR3 pro-
tein with Ki values of 84, 11 and 161 nM, respectively, and to cIAP-
2 with Ki values of 292, 24 and 393 nM, respectively.
6
20
60
(nM)
200
600
Taken together, our binding data thus showed that compound 2
in which R is a phenyl group is much more potent than compound
3, in which R is a benzyl group. In fact, compound 2 also binds
more potently than compound 1 to all the three IAP proteins.
We evaluated these three compounds for their ability to restore
the activity of caspase-9 and -3 inhibited by XIAP in cell-free cas-
pase functional assays. A Caspase-Glo 9 assay kit (Promega) was
used in the caspase-9 assay and caspase-3 Fluorescent Assay kit
(BD Bioscience) in the caspase-3 assay. In the caspase-9 functional
assay, XIAP protein containing linker-BIR2–BIR3 dose dependently
inhibits the activity of caspase-9, achieving 80% inhibition at con-
centrations of 500 nM. Each of the three compounds can dose
dependently restore the activity of caspase-9 (Fig. 3). While com-
pounds 1 and 2 are equally potent, compound 3 is less potent. At
Figure 4. Functional antagonism of Smac mimetics to inhibition of caspase-3
activity by XIAP-linker-BIR2–BIR3 protein. 20 nM of XIAP protein was used in the
assay.
activity. These compounds were evaluated together for their activ-
ity in inhibition of cell growth in the MDA-MB-231 breast cancer
and SK-OV-3 ovarian cancer cell lines, which are sensitive to Smac
mimetics as single agents. Although 3 is weaker than 1, compound
2 is 5–8 times more potent than 1 in inhibition of cell growth in
both cancer cell lines (Fig. 5). Compound 2 has IC50 values of 1.0
and 2.1
lM, respectively, in the MDA-MB-231 and SK-OV-3 cancer
cell lines.
In summary, we designed two cyclopeptidic Smac mimetics, 2
and 3, from our previous lead compound 1 by replacing two amide
bonds with two triazole structures and efficiently synthesized
these using ‘click reaction’ as a key step for macrocyclization.
Compound 2 is more potent than compound 1 in binding to XIAP,
cIAP-1 and cIAP-2 and in antagonizing XIAP in cell-free caspase
functional assays. Importantly, compound 2 is 5–8 times more
potent than compound 1 in inhibition of cell growth in two cancer
cell lines. Taken together, our data indicate that compound 2 rep-
resents a promising new lead compound for further optimization
500 nM and 1.5 lM, compounds 1 and 2 can restore the caspase-
9 activity by 40% and 60%, respectively. In a caspase-3 functional
assay, 20 nM of XIAP protein containing linker-BIR2–BIR3 can inhi-
bit 90% of the enzymatic activity of caspase-3 (Fig. 4). Compound 2
is the most potent compound in antagonizing XIAP and restoring
the activity of caspase-3. Compound 2 at 60 nM restores the activ-
ity of caspase-3 by 50% (Fig. 4). These functional data show that
compound 2 is a potent XIAP antagonist.
One major goal in the design of compounds 2 and 3 is to reduce
the peptidic nature of compound 1 and to improve the cellular

3046
H. Sun et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3043–3046
6. (a) Du, C.; Fang, M.; Li, Y.; Li, L.; Wang, X. Cell 2000, 102, 33; (b) Verhagen, A. M.;
MDA-MB-231 Cancer Cell Line
A
B
Ekert, P. G.; Pakusch, M.; Silke, J.; Connolly, L. M.; Reid, G. E.; Moritz, R. L.;
Simpson, R. J.; Vaux, D. L. Cell 2000, 102, 43.
1, IC50 4.6 µM
2, IC50 1.0 µM
3, IC50 25.9 µM
7. (a) Wu, G.; Chai, J.; Suber, T. L.; Wu, J. W.; Du, C.; Wang, X.; Shi, Y. Nature 2000,
408, 1008; (b) Liu, Z.; Sun, C.; Olejniczak, E. T.; Meadows, R.; Betz, S. F.; Oost, T.;
Herrmann, J.; Wu, J. C.; Fesik, S. W. Nature 2000, 408, 1004; (c) Srinivasula, S.
M.; Hegde, R.; Saleh, A.; Datta, P.; Shiozaki, E.; Chai, J.; Lee, R. A.; Robbins, P. D.;
Fernandes-Alnemri, T.; Shi, Y.; Alnemri, E. S. Nature 2001, 410, 112; (d)
Shiozaki, E. N.; Chai, J.; Rigotti, D. J.; Riedl, S. J.; Li, P.; Srinivasula, S. M.; Alnemri,
E. S.; Fairman, R.; Shi, Y. Mol. Cell 2003, 11, 519.
100
75
50
25
0
8. (a) Samuel, T.; Welsh, K.; Lober, T.; Togo, S. H.; Zapata, J. M.; Reed, J. C. J.
Biol. Chem. 2006, 281, 1080; (b) Yang, Q. H.; Du, C. J. Biol. Chem. 2004, 279,
16963; (c) Varfolomeev, E.; Blankenship, J. W.; Wayson, S. M.; Fedorova, A.
V.; Kayagaki, N.; Garg, P.; Zobel, K.; Dynek, J. N.; Elliott, L. O.; Wallweber, H.
J.; Flygare, J. A.; Fairbrother, W. J.; Deshayes, K.; Dixit, V. M.; Vucic, D. Cell
2007, 131, 669; (d) Vince, J. E.; Wong, W. W.; Khan, N.; Feltham, R.; Chau,
D.; Ahmed, A. U.; Benetatos, C. A.; Chunduru, S. K.; Condon, S. M.; McKinlay,
M.; Brink, R.; Leverkus, M.; Tergaonkar, V.; Schneider, P.; Callus, B. A.;
Koentgen, F.; Vaux, D. L.; Silke, J. Cell 2007, 131, 682; (e) Petersen, S. L.;
Wang, L.; Yalcin-Chin, A.; Li, L.; Peyton, M.; Minna, J.; Harran, P.; Wang, X.
Cancer Cell 2007, 12, 445.
0.1
1
10
100
[Compounds] (µM)
SK-OV-3 Cancer Cell Line
1, IC50 15.9 µM
2, IC50 2.1 µM
3, IC50 31.5 µM
100
75
50
25
0
9. (a) Sun, H.; Nikolovska-Coleska, Z.; Yang, C.-Y.; Xu, L.; Liu, M.; Tomita, Y.; Pan,
H.; Yoshioka, Y.; Krajewski, K.; Roller, P. P.; Wang, S. J. Am. Chem. Soc. 2004, 126,
16686; (b) Oost, T. K.; Sun, C.; Armstrong, R. C.; Al-Assaad, A. S.; Betz, S. F.;
Deckwerth, T. L.; Ding, H.; Elmore, S. W.; Meadows, R. P.; Olejniczak, E. T.;
Oleksijew, A.; Oltersdorf, T.; Rosenberg, S. H.; Shoemaker, A. R.; Tomaselli, K. J.;
Zou, H.; Fesik, S. W. J. Med. Chem. 2004, 47, 4417; (c) Sun, H.; Nikolovska-
Coleska, Z.; Lu, J.; Qiu, S.; Yang, C.-Y.; Gao, W.; Meagher, J.; Stuckey, J.; Wang, S.
J. Med. Chem. 2006, 49, 7916; (d) Zobel, K.; Wang, L.; Varfolomeev, E.; Franklin,
M. C.; Elliott, L. O.; Wallweber, H. J.; Okawa, D. C.; Flygare, J. A.; Vucic, D.;
Fairbrother, W. J.; Deshayes, K. ACS Chem. Biol. 2006, 1, 525; (e) Sun, H.;
Nikolovska-Coleska, Z.; Lu, J.; Meagher, J. L.; Yang, C.-Y.; Qiu, S.; Tomita, Y.;
Ueda, Y.; Jiang, S.; Krajewski, K.; Roller, P. P.; Stuckey, J. A. J. Am. Chem. Soc.
2007, 129, 15279; (f) Sun, H.; Stuckey, J. A.; Nikolovska-Coleska, Z.; Qin, D.;
Meagher, J. L.; Qiu, S.; Lu, J.; Yang, C. Y.; Saito, N. G.; Wang, S. J. Med. Chem. 2008,
51, 7169.
0.1
1
10
100
[Compounds] (µM)
Figure 5. Cell growth inhibition of compounds 1, 2 and 3 in (A) MDA-MB-231 and
(B) SK-OV-3 cancer cell lines. Cells were treated for 4 days and cell growth was
determined using a standard WST-8 assay.
10. (a) Li, L.; Thomas, R. M.; Suzuki, H.; De Brabander, J. K.; Wang, X.; Harran, P. G.
A. Science 2004, 305, 1471; (b) Sun, H.; Nikolovska-Coleska, Z.; Lu, J.; Meagher,
J. L.; Yang, C.-Y.; Qiu, S.; Tomita, Y.; Ueda, Y.; Jiang, S.; Krajewski, K.; Roller, P.
P.; Stuckey, J. A.; Wang, S. J. Am. Chem. Soc. 2007, 129, 15279.
toward the development of a new class of anticancer agents by tar-
geting multiple IAP proteins.
11. Nikolovska-Coleska, Z.; Meagher, J. L.; Jiang, S.; Yang, C. Y.; Qiu, S.; Roller, P. P.;
Stuckey, J. A.; Wang, S. Biochemistry 2008, 47, 9811.
Acknowledgments
12. Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B. Angew. Chem., Int. Ed.
2002, 41, 2596.
ThefinancialsupportfromtheNationalCancerInstitute, National
Institutes of Health, USA (R01CA127551 and R01CA109025), Susan
G. Komen Foundation and the Breast Cancer Research Foundation
is greatly appreciated.
13. Messina, F.; Botta, M.; Corelli, F.; Schneider, M. P.; Fazio, F. J. Org. Chem. 1999,
64, 3767.
14. (a) Chemical data for compound 2: 1H NMR (300 M Hz, D2O) d 7.75 (s, 2H),
7.39–7.25 (m, 6H), 7.21–7.10 (m, 4H), 6.22 (s, 2H), 4.79 (m, 2H), 4.58 (m, 2H),
4.45–4.19 (m, 6H), 3.82 (m, 2H), 3.78 (m, 2H), 3.49 (m, 2H), 2.62 (s, 6H), 2.31
(m, 2H), 2.05–1.85 (m, 6H), 1.84–1.73 (m, 4H), 1.68–1.50 (m, 4H), 1.41 (d,
J = 7.0 Hz, 6H), 1.32–1.13 (m, 4H); 13C NMR (75 MHz, D2O)
d
172.83Â2,
References and notes
172.07Â2, 170.02Â2, 148.31Â2, 139.78Â2, 129.49Â2, 128.73Â2, 127.68Â2Â2,
124.67Â2, 61.61Â2, 57.45Â2, 52.18Â2, 50.98Â2, 49.89Â2, 48.75Â2, 31.59Â2,
30.65Â2, 30.05Â2, 29.51Â2, 25.40Â2, 21.94Â2, 15.96Â2; ESI MS: m/z 957.5
(M+Na)+. (b) Selected chemical data for compound 3: 1H NMR (300 M Hz, D2O)
1. (a) Thompson, C. B. Science 1995, 267, 1456; (b) Nicholson, D. W. Nature 2000,
407, 810; (c) Reed, J. C. Nat. Rev. Drug Disc. 2002, 1, 111.
2. (a) Deveraux, Q. L.; Reed, J. C. Genes Dev. 1999, 1, 239; (b) Salvesen, G. S.;
Duckett, C. S. Nat. Rev. Mol. Cell Biol. 2002, 3, 401.
d
1H NMR (300 M Hz, D2O) d 7.70 (s, 2H), 7.30–7.08 (m, 10H), 5.33 (t, J = 7.8 Hz,
3. (a) Fotin-Mleczek, M.; Henkler, F.; Samel, D.; Reichwein, M.; Hausser, A.;
Parmryd, I.; Scheurich, P.; Schmid, J. A.; Wajant, H. J. Cell Sci. 2002, 115, 2757;
(b) Deng, Y.; Ren, X.; Yang, L.; Lin, Y.; Wu, X. Cell 2003, 115, 61.
2H), 4.62 (m, 2H), 4.40–4.31 (m, 4H), 4.07 (m, 2H), 3.81 (m, 2H), 3.68–3.52 (m,
4H), 3.25–3.12 (m, 4H), 2.57 (s, 6H), 2.06–1.65 (m, 14H), 1.48–1.27 (m, 4H),
1.26 (d, J = 7.2 Hz, 6H), 1.05 (m, 2H); 13C NMR (75 MHz, D2O) d 173.50Â2,
172.40Â2, 170.09Â2, 148.25Â2, 137.81Â2, 129.88Â2, 129.17Â2, 127.52Â2,
123.88Â2, 62.11Â2, 57.45Â2, 51.35Â2, 50.32Â2, 48.60Â2, 47.25Â2, 39.72Â2,
31.70Â2, 30.72Â2, 29.81Â2, 29.63Â2, 25.01Â2, 21.43Â2, 16.31Â2; ESI MS: m/z
985.5 (M+Na)+.
4. Holcik, M.; Gibson, H.; Korneluk, R. G. Apoptosis 2001, 6, 253.
5. (a) Riedl, S. J.; Shi, Y. Nat. Rev. Mol. Cell Biol. 2004, 5, 897; (b) LaCasse, E. C.;
Baird, S.; Korneluk, R. G.; MacKenzie, A. E. Oncogene 1998, 17, 3247; (c) Huang,
Y.; Park, Y. C.; Rich, R. L.; Segal, D.; Myszka, D. G.; Wu, H. Cell 2001, 104, 781.