Synthesis of a tetra-deuterium-labeled derivative of potent and selective anticancer agent AA005

Article abstract of DOI:10.1016/j.tetlet.2005.03.123

Annonaceous acetogenins are a series of potent naturally occurring anticancer agents, which act as inhibitors of complex I in mitochondria. AA005, a mimicry of acetogenins, has been found as active as those natural products and to present high selectivities between cancer and normal cells. In order to investigate the further cell-based mechanism induced by AA005, a d ⁴-labeled derivative of AA005 (AA005-d⁴) was designed to detect the drug permeation ability into the membranes. In this letter, the synthesis is reported of this deuterium-labeled compound, wherein a ethylene-d⁴ glycol unit is incorporated efficiently into the molecule skeleton by simple etherifications.

Full text of DOI:10.1016/j.tetlet.2005.03.123

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 3525–3528
Synthesis of a tetra-deuterium-labeled derivative of potent
and selective anticancer agent AA005
Hai-Xia Liu and Zhu-Jun Yao*
State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354Fenglin Road, Shanghai 200032, China
Received 28 January 2005; revised 10 March 2005; accepted 14March 2005
Available online 6 April 2005
Abstract—Annonaceous acetogenins are a series of potent naturally occurring anticancer agents, which act as inhibitors of complex
I in mitochondria. AA005, a mimicry of acetogenins, has been found as active as those natural products and to present high
selectivities between cancer and normal cells. In order to investigate the further cell-based mechanism induced by AA005, a
4
4
d -labeled derivative of AA005 (AA005-d ) was designed to detect the drug permeation ability into the membranes. In this letter,
the synthesis is reported of this deuterium-labeled compound, wherein a ethylene-d glycol unit is incorporated efficiently into
4
the molecule skeleton by simple etherifications.
Ó 2005 Elsevier Ltd. All rights reserved.
1
. Introduction
be as potent as those active natural products, and some
of which even showed highly distinctive abilities to only
kill the cancer cells and not to affect the normal cells.
Among them, AA005 (1 in Fig. 1) is a representative
with IC50 ranges from 50 nM to 100 nM against a variety
Annonaceous acetogenins, a family of naturally occur-
ring polyketides, are well known for their cytotoxic
and anti-tumoral activities. They were considered to
be the most powerful inhibitors of complex I (NADH-
1
,2
5
of cancer cells. AA005 is significantly simplified from
3
ubiquinone oxidoreductase) in mitochondria. Because
one of natural acetogenins, bullatacin (Fig. 1), by delet-
ing four carbons from the THF region of its natural
counterpart. Recent biological evidences show that it
efficiently induces the cancer cells death in 48 h, and
of the lack of detailed structural information about
complex I, there is still no clear experimental evidence
to elucidate its binding sites. In our recent work, we fo-
cused on structural modifications on the basis of natural
structures and developed a series of annonaceous ace-
7
no action to the normal cells. Such selectivities caused
by AA005 are rarely reported, and therefore, the further
mechanism study is of great value for future drug
4
–9
togenin mimetics.
These mimics have been found to
OH
O
O
O
O
O
O
O
O
OH
OH
OH
OH
Bullatacin
AA005 (1)
Figure 1. Bullatacin and its typical mimicry AA005.
*
0
Corresponding author. Tel.: +86 21 54925133; fax: +86 21 64166128; e-mail: yaoz@mail.sioc.ac.cn
040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.03.123

3526
H.-X. Liu, Z.-J. Yao / Tetrahedron Letters 46 (2005) 3525–3528
O
O
O
O
D
D
D
D
O
O
O
O
OH
OH
OH
OH
4
AA005-d (2)
AA005 (1)
D
D
D
D
HO
OH
4
Ethylene-d Glycol
Figure 2. Stable isotope labeled derivative of AA005.
design. In other words, AA005 is a valuable biological
tool to probe those related unknown or unclear mecha-
nisms, by which cancer cell death is induced in a selec-
tive way. Membrane selectivity between normal cells
and tumor cells by AA005 is the first question we want
to know. A direct shortcut for this question is to mea-
sure the concentration difference of AA005 inside differ-
ent cells. Considering the low abundance of AA005 in
cells, mass spectrometry-based methodology is chosen
to meet the sensitivity requirements. In order to acquire
the more clear and accurate information from complex
background in cell, a proper stable isotope labeled deriv-
ative of AA005 becomes a must.
D
D
D
D
O
O
O
7
5
OH
OH
O
4
AA005-d (2)
D
D
D
O
D
O
O
7
5
OMOM
OMOM
O
3
D
D
D
OH
D
D
O
O
O
1
3
15
18
Stable isotope labelings with C, N, O, or deute-
7
5
OMOM
OMOM
O
1
0
rium are used commonly in quantification in mass
spectrometry. In order to make the quantification of
AA005 in different cells possible, we design a stable iso-
tope labeled AA005 (heavy reagent), which will be
administrated with its light counterpart AA005, both
in cancer cells and normal cells in equal quantity. The
deuteriums in the deuterium-labeled molecule AA005-
4
D
D
D
O
O
O
O
7
5
OMOM
OMOM
O
5
6
4
d should be introduced by an easy way and located sta-
bly. Figure 2 shows our considerations for its synthesis.
4
A commercially available agent, ethylene-d glycol is
TMS
D
OTHP
COOEt
chosen as the labeled building block, which will be
incorporated into the chemically inert ether region of
AA005.
7
9
D
D
D
O
OMe
O
7
O
5
O
MOMO
8
10
2
. Results and discussion
4
Retrosynthetic analysis of AA005-d 2 is illustrated in
O
D
D
4
Figure 3. Successive O-alkylations of ethylene-d glycol
OH
OH
O
H
7
D
D
O
Cl
HO
OH
with (R)-(ꢀ)-epichlorohydrin 13 and 11, respectively,
are designed as the key steps to introduce the four deu-
teriums, and functionalize the middle region of AA005-
O
1
4
11
12
13
4
Figure 3. Retro synthetic analysis of AA005-d .
4
d in the mean time. Trimethylsilylacetylene 7 plays as a
two-directional C-alkylation reagent to link both epox-
ide-intermediates 8 and 6 together, constructing the
whole molecular skeleton of AA005-d . The starting chi-
ral materials 14, 13, and 9 are readily available or easy
to prepare.
4
Key intermediate 5 is synthesized as shown in Scheme 1.
Starting from chiral aldehyde 14, a three-step reaction
6
,11
sequence was applied to obtain the diol 10.
The resul-

H.-X. Liu, Z.-J. Yao / Tetrahedron Letters 46 (2005) 3525–3528
3527
5
+ 6
O
a
b, c
H
a
O
O
5
D
D
OH
O
O
4
D
D
O
15
1
7
3
OR2
MOMO
OMOM
O
D
D
D
O
D
4
f
5
OH
OR1
5
b
OMOM
1
2
D
D
1
0 R =R =H
18
D
D
O
d
1
2
7
3
1
6 R =MOM, R =H
MOMO
OMOM
O
e
1
2
3
1
7 R =MOM, R =Ms
O
c
D
D
g
D
O
D
O
h
D
D
D
D
O
5
O
OMOM
O
7
HO
5
8
OH
O
D
D
4
AA005-d (2)
D
O
D
O
5
Scheme 3. Reagents and conditions: (a) n-BuLi, BF
N, CH Cl
, NaOAc, DME, reflux; (ii) concd HCl, MeOH,
3
ÆEt
2
O, THF,
OMOM
OMOM
ꢀ
78 °C, 94%; (b) (i) MsCl, Et
3
2
2
, 0 °C ; (ii) DBU, THF, rt,
5
4
3%; (c) (i) TsNHNH
2
Scheme 1. Reagents and conditions: (a) C
0% Pd–C, H , CH OH; (c) 10% HCl, CH
d) (i) HC(OCH , D-10-CSA, CH Cl , (ii) DIBALH in toluene,
CH Cl N, CH Cl , 100%; (f)
, 0 °C, 90% over two-steps; (e) MsCl, Et
NaH, DMF, 130 °C, 57%; (g) NaOH, H O, Bu NHSO , (R)-epichlo-
rohydrin, 79%; (h) (i) n-BuLi, BF ÆEt O, THF, trimethylsilylacetylene,
78 °C; (ii) i-Pr NEt, MOMCl, CH Cl ; (iii) TBAF, THF, 0 °C, 76%
over three-steps.
8
H
17CH@PPh
3
, 90%; (b)
46% over two-steps.
1
2
3
3
OH, 88% over two-steps;
(
3
)
3
2
2
2
2
3
2
2
4
,15
involved a three-step sequence
previously developed
2
4
4
by us: (i) aldol reaction of 10 with freshly prepared
(2S)-O-tetrahydropyranyl lactal; (ii) acid-catalyzed THP
cleavage and in situ lactonization; and (iii) b-elimination
of hydroxyl in the presence of (CF CO) O and Et N.
3
2
ꢀ
2
2
2
3
2
3
Regioselective epoxidation of 19 was achieved by m-CPBA
to give 6 in 86% yield.
tant diol 10 was protected with MOMCl regioselectively
9
,12
to afford 16 (90%) by a two-step procedure.
remaining primary hydroxyl group was then masked
The
With both functionalized synthons 5 and 6 in hand, con-
struction of the whole skeleton was performed as fol-
lows (Scheme 3). Treatment of terminal alkyne 5 with
butyllithium followed by reaction with 6 in the presence
as a mesylate (17, 100% yield). The following reaction
of mesylate 17 with ethylene-d glycol 11 was carried
4
out in the presence of NaH in DMF, giving 18 in 57%
yield. Coupling of alcohol 18 with (R)-(ꢀ)-epichlorohy-
drin 13 was achieved in the presence of a phase-transfer
of BF etherate at ꢀ78 °C gave whole skeleton 4 in 70%
3
yield. Elimination of newly formed hydroxyl group in
the presence of MsCl–Et N and then DBU afforded 3.
1
3
catalyst and furnished 8 in 88% yield. The following
regioselective opening of epoxides 8 with trimethylsilyl
acetylene mono-lithium salt, MOM-protection, and
3
Selective reductions of triple and double bonds in the
middle region of 3 were carried out by diimide-based
1
4
TMS-deprotection elaborated the left part 5.
14b
reductions. Final deprotection of MOM ethers was
accomplished in MeOH with catalytic amount of con-
The right part 6 was synthesized as shown in Scheme 2.
Subsequent introduction of the butenolide unit to 8
4
centrated HCl, affording final product AA005-d 2. All
16
the physical data w4ere excellent agreement with the
structure of AA005-d .
OMe
a
b
O
5
3. Conclusion
5
O
O
1
0
19
4
In summary, AA005-d , a stable isotope-labeled deriva-
tive of anticancer agent AA005 was synthesized enantio-
selectively. This is the first example of annonaceous
acetogenin mimicry containing multiple deuteriums in
the designed location. The reported synthesis presents
advantages of high efficiency and use of readily available
reagents and materials. The cell membrane-penetration
studies using AA005 and AA005-d by mass spectro-
metry is currently underway, and result will be reported
in due course.
O
O
5
O
6
Scheme 2. Reagents and conditions: (a) (i) LDA, THF–HMPA, (S)-
O-tetrahydropyranyl lactal, ꢀ78 °C; (ii) 10% H SO , THF, rt; (iii)
CF CO) O, Et N, CH Cl , 60% over three-steps; (b) m-CPBA,
CH Cl
, 0 °C, 86%.
4
2
4
(
3
2
3
2
2
2
2

3528
H.-X. Liu, Z.-J. Yao / Tetrahedron Letters 46 (2005) 3525–3528
Jos e´ , R.; Tormo, T.; Gallardo, R.; Arag o´ n, D.; Cortes, E.
E. Chem. Biol. Interact. 1999, 122, 171–183.
Acknowledgements
4
. (a) Yao, Z.-J.; Wu, H.-P.; Wu, Y.-L. J. Med. Chem. 2000,
This work was financially supported by the Major
State Basic Research and Development Program
4
3, 2484–2487; (b) Jiang, S.; Wu, Y.-L.; Yao, Z.-J. Chin. J.
Chem. 2002, 20, 1393–1400.
(
2
G2000077500), NSFC (30271531, 20425205, and
0321202), the Chinese Academy of Sciences (KGCX2-
5
. Zeng, B.-B.; Wu, Y.; Jiang, S.; Yu, Q.; Yao, Z.-J.; Liu, Z.-
H.; Li, H.-Y.; Li, Y.; Chen, X.-G.; Wu, Y.-L. Chem. Eur.
J. 2003, 9, 282–290.
. Zeng, B.-B.; Wu, Y.; Yu, Q.; Wu, Y.-L.; Li, Y.; Chen,
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. Huang, G.; Jiang, S.; Wu, Y.-L.; Yao, Z.-J.; Wu, J.-R.
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SW-209) and Shanghai Municipal Commission of
Science and Technology (04DZ14901).
6
7
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16. Physical data for AA005-d (2): ½aꢁD +7.22 (c 0.64,
1
CHCl3). H NMR (CDCl , 300 MHz): 0.88 (3H, t,
3
J = 6.6 Hz), 1.10–1.60 (40H, m), 1.41 (3H, d,
J = 6.6 Hz), 2.27 (2H, t, J = 7.8 Hz), 2.99 (2H, br) 3.16
(t, 2H, J = 5.7 Hz), 3.53 (2H, d, J = 6.9 Hz), 3.78 (2H, m),
1621–1636; (l) Makabe, H.; Hattori, Y.; Tanaka, A., et al.
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references cited therein.
. (a) Landolt, J. L.; Ahammadsahib, K. I.; Hollingworth, R.
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McLaughlin, J. L. Chem. Biol. Interact. 1995, 98, 1–13; (b)
1
3
5.00 (1H, qd, J = 6.9, 1.5 Hz), 7.00 (1H, s) ppm. C NMR
(100 MHz, CDCl ): 173.9, 148.9, 134.3, 76.6, 75.8, 70.3,
3
33.0, 31.9, 29.7, 29.6, 29.6, 29.5, 29.3, 29.3, 29.2, 27.4, 25.6,
25.2, 22.7, 19.2, 14.1 ppm. IR (film): 3491, 2914, 2849,
ꢀ
1
3
1749, 1474, 1314, 1124 cm
.
(M +Na). HRMS (ESI) calcd for C H D O Na
MS (ESI, m/z): 581
+
3
3
58
4
6
+
[M +Na]: 581.4689. Found 581.4703.