Design and synthesis of novel macrocyclic 2-amino-6-arylpyrimidine Hsp90 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2011.11.100

Macrocyclic compounds bearing a 2-amino-6-arylpyrimidine moiety were identified as potent heat shock protein 90 (Hsp90) inhibitors by modification of 2-amino-6-aryltriazine derivative (CH5015765). We employed a macrocyclic structure as a skeleton of new i

Full text of DOI:10.1016/j.bmcl.2011.11.100

Bioorganic & Medicinal Chemistry Letters 22 (2012) 1136–1141
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design and synthesis of novel macrocyclic 2-amino-6-arylpyrimidine
Hsp90 inhibitors
⇑
Atsushi Suda , Hiroshi Koyano, Tadakatsu Hayase, Kihito Hada, Ken-ichi Kawasaki, Susumu Komiyama,
Kiyoshi Hasegawa, Takaaki A. Fukami, Shigeo Sato, Takaaki Miura, Naomi Ono, Toshikazu Yamazaki,
Ryoichi Saitoh, Nobuo Shimma, Yasuhiko Shiratori, Takuo Tsukuda
Kamakura Laboratories, Research Division, Chugai Pharmaceutical Co., Ltd, 200 Kajiwara, Kamakura, Kanagawa 247-8530, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Macrocyclic compounds bearing a 2-amino-6-arylpyrimidine moiety were identified as potent heat shock
protein 90 (Hsp90) inhibitors by modification of 2-amino-6-aryltriazine derivative (CH5015765). We
employed a macrocyclic structure as a skeleton of new inhibitors to mimic the geldanamycin-Hsp90
interactions. Among the identified inhibitors, CH5164840 showed high binding affinity for N-terminal
Received 11 October 2011
Revised 17 November 2011
Accepted 24 November 2011
Available online 1 December 2011
Hsp90
IC50 = 0.15
a
(Kd = 0.52 nM) and strong anti-proliferative activity against human cancer cell lines (HCT116
M, NCI-N87 IC50 = 0.066 M). CH5164840 displayed high oral bioavailability in mice
l
l
Keywords:
(F = 70.8%) and potent antitumor efficacy in a HCT116 human colorectal cancer xenograft model (tumor
growth inhibition = 83%).
Structure-based drug design
Lead optimization
Macrocyclic molecule
Antitumor agent
Ó 2011 Elsevier Ltd. All rights reserved.
Hsp90 inhibitor
Heat shock protein 90 (Hsp90) is an ATP-dependent molecular
chaperon which is constitutively and ubiquitously expressed in
mammalian cells. It governs the conformational maturation, stabil-
ity and function of these substrate proteins, called client proteins.1
Because client proteins are known to play an important role in con-
trolling proliferation, survival, invasion, metastasis, and angiogen-
esis, Hsp90 inhibitors could cause potent inhibition of tumor
growth and progression by simultaneous degradation of client pro-
teins.2–4 Indeed, it has been reported that the ansamycin antibiotic
geldanamycin (GM, 1a)5 and the macrocyclic lactone antibiotic
radicicol (RD, 2)6 demonstrated anti-proliferative activity against
tumor cells by inhibiting Hsp90 (Fig. 1). The selective effect of
these inhibitors to tumor cells and not to normal cells might stem
from the fact that Hsp90 exists in an activated state in tumor cells
by forming a complex with a series of co-chaperones.7–10 Conse-
quently, Hsp90 is believed to be an attractive molecular target
for anticancer agents.2–4 Actually, several Hsp90 inhibitors such
as semi-synthetic analogs of GM, 17-allylamino-17-demethoxy-
geldanamycin (17-AAG, 1b)11 and 17-(2-dimethylaminoethylami-
no)-17-demethoxygeldanamycin (17-DMAG, 1c)12 along with
synthetic small molecules such as CNF-2024 (3),13 NVP-AUY922
(4)14 and AT13387 (5)15 are being evaluated in clinical trials
(Fig. 1).
We recently reported the identification of a new class of orally
available Hsp90 inhibitor bound to the N-terminal ATP binding
site, CH5015765 (6), by a combination of fragment screening, vir-
tual screening, and structure-based drug design with the assis-
tance of X-ray cocrystal structures of ligand-Hsp90 complexes.16
O
R
O
Cl
O
HO
N
H
O
O
O
OH
O
OH
O
O
O
O
NH2
2, Radicicol
1a, Geldanamycin; R = OMe
1b, 17-AAG; R = NHCH2CH=CH2
1c, 17-DMAG; R = NHCH2CH2NMe2
N
O
NH2
N
N
N
N
N
H2N
N
HO
N
HO
H
N
N
O
OH
O
N
O
OH
O
5, AT13387
3, CNF-2024
4, NVP-AUY922
⇑
Corresponding author. Tel.: +81 467 47 6067; fax: +81 467 45 6824.
E-mail address: sudaats@chugai-pharm.co.jp (A. Suda).
Figure 1. Known Hsp90 inhibitors.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.11.100

A. Suda et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1136–1141
1137
a
b
Thr184
Met98
Leu48
Leu48
Thr184
Asp93
Gly97
Asp93
Val150
Phe138
Val150
Phe138
Gly97
Asn51
Asn51
Ile96
Gly137
Ile96
Met98
Tyr139
Tyr139
Lys58
Leu107
Lys112
Contour
Leu107
Gray: -2.8 kcal/mol
Cyan: -2.3 kcal/mol
Figure 2. X-ray structure analysis of small molecular Hsp90 inhibitors in complex with human N-terminal Hsp90a. The numbering of the residues corresponds to those in
the X-ray cocrystal structure (gray CHsp90 , green Cligand, red O, blue N, yellow S, purple Cl). Hydrogen bonds are indicated by dashes. (a) Detailed binding mode of compound 6
a
(PDB code: 3B28). Hydrophobic space was predicted by the Site Finder application in MOE and its location is shown in cyan (ꢁ2.3 kcal/mol) and gray (ꢁ2.8 kcal/mol). (b)
Detailed binding mode of GM (PDB code: 1YET).
Table 1
Chemical structure of 6 and its biological,16 physicochemical, and pharmacokinetic profiles
NH2
Cl
N
N
N
S
O
6, CH5015765
(a) Binding affinity, in vitro anti-proliferative activity, and physicochemical properties of 6
IC50 M)
(
l
LM CL (
Human
43
l
L/min/mg protein)
Kd (nM)a
HCT116
0.46
NCI-N87
0.57
PSA (Å2)b
Solubility (
l
M)c
Mouse
60
3.4
59.1
29
(b) Pharmacokinetic profiles of 6
Administration
Dose (mg/kg)
t1/2 (h)
tmax (h)
Cmax
(
lg/mL)
AUCinf
(l
gꢀh/mL)
CL or CL/F (mL/h/kg)
Fd (%)
iv
po
10
200
0.25
2.62
—
0.5
—
3.92
8.55
7.65
1170
26100
—
4.5
a
b
c
Values were measured by surface plasmon resonance (SPR) using human N-terminal Hsp90
Molecular polar surface area (PSA) was calculated by TPSA.
Solubility in FaSSIF. The use of FaSSIF may over-predict the solubility in physiological in vivo conditions.
Oral bioavailability.
a.
d
Compound
(Kd = 3.4 nM) and in vitro anti-proliferative activity against cell
lines such as KRAS mutant HCT116 (IC50 = 0.46 M) and HER2-
overexpressing NCI-N87 (IC50 = 0.57 M). In mice, however, it
showed several drawbacks such as limited oral bioavailability
(F = 4.5%) and moderate tumor growth inhibition (TGI = 54%)
against the xenografted NCI-N87 (po, 400 mg/kg). These draw-
backs probably came from the low liver microsomal (LM) stability
6
showed high affinity for N-terminal Hsp90
with hydrophobic side chains of Ile96 and Met98; (3) a hydropho-
bic part from the chloro group to benzylic methylene carbon of a 5-
chloro-1H,3H-benzo[de]isochromene moiety fills the proximal
hydrophobic space formed by hydrophobic side chains of Val150,
Leu107, and Phe138 (explicitly visualized by the Site Finder appli-
cation in Molecular Operating Environment17); (4) an etheric oxy-
gen of a 5-chloro-1H,3H-benzo[de]isochromene moiety forms a
hydrogen bond with a water molecule which is hydrogen-bound
to the backbone of Phe138 and the side chain of Asn51. On the
other hand, we analyzed the binding mode of GM (PDB code:
1YET) and identified important interactions such as one with the
side chain of Lys58 (Fig. 2b).16 In our molecular design of new
inhibitors, we maintained the interactions found between com-
pound 6-Hsp90 and tried to incorporate GM-Hsp90 interactions.
We considered that a macrocyclic structure like GM would offer
more chances to make effective interactions. In general, macrocy-
clic compounds are more conformationally restricted than their
acyclic analogs, which potentially give higher target bindings and
selectivities and improve oral bioavailabilities.18,19 We chose
pyrimidine instead of triazine as a core structure since a nitrogen
l
l
(mouse LM clearance (CL) = 60
solubility (solubility in fasted state simulated intestinal fluid (FaS-
SIF) = 29 M). In this work, compound 6 was chosen as a lead com-
lL/min/mg protein) and low water
l
pound for further optimization, and biological,16 physicochemical,
and pharmacokinetic profiles of 6 are summarized in Table 1.
In an X-ray cocrystal structure of 6 with human Hsp90 (PDB
code: 3B28), we observed the following effective interactions, as
depicted in Figure 2a: (1) an amino group on the 2-position of tri-
azine forms multiple hydrogen bonds with the carboxylic side
chain of Asp93 and a water molecule which is conserved in the
cocrystal structures of all Hsp90 ATP site binders; (2) a methylthio
group on the 4-position of triazine forms a hydrophobic interaction

1138
A. Suda et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1136–1141
NH2
N
NH2
NH2
N
SH
N
N
N
B(OR)2
N
+
+
S
S
Y
Cl
Cl
X
X
Y
Scheme 1. Synthetic route of macrocyclic derivatives.
Table 2
First, we designed and synthesized 7, 8 and 9 as prototypes of
macrocyclic derivatives. A phenyl group was connected to sulfur
atom at the 4-position of the core structure to increase a hydro-
phobic interaction to Ile96 and Met98. The two phenyl groups
were linked by 3, 4 and 5 of methylene carbons via etheric oxygen
atoms. The binding affinities and in vitro anti-proliferative activi-
ties of these derivatives are summarized in Table 2. The binding
affinity of 8 was the highest in the three compounds, but it was
ten times weaker than that of 6 (Table 1). An X-ray cocrystal struc-
ture of 8 and Hsp90 (PDB code: 3VHA, 1.4 Å resolution) revealed
that the etheric oxygen at the 5’-position of a phenyl ring did not
form the hydrogen bond (d(OꢀꢀꢀOwater) = 3.9 Å) with the water mol-
ecule which itself forms hydrogen bonds with the backbone of
Phe138 and the side chain of Asn51, although a carbon atom at
the 10-position of a phenyl ring formed aryl–alkyl interactions
(d(CꢀꢀꢀCIle96) = 4.1 Å) with the 3-methyl group of Ile96 and
(d(CꢀꢀꢀCMet98) = 3.9 Å) with the 4-methylene group of Met98
(Fig. 3a). (For a detailed discussion of noncovalent interactions,
see Bissantz et al.)20
Binding affinity and in vitro anti-proliferative activity of ether linkage derivatives
NH2
N
N
S
O
n O
)
(
IC50
HCT116
(l
M)
a
Compd
n
Ring size
Kd (nM)
NCI-N87
7
8
9
3
4
5
15
16
17
120
40
84
10.3
5.5
3.7
11.3
3.8
2.9
a
Values were measured by SPR using human N-terminal Hsp90a.
atom at the 5-position of 6 does not interact with the protein. In
addition, an o-tolyl moiety was employed instead of a 5-chloro-
1H,3H-benzo[de]isochromene moiety as a minimum structural
requirement for the necessary hydrophobic interactions. The selec-
tion of these moieties enables the general synthetic route depicted
in Scheme 1. Thus, Suzuki–Miyaura cross-coupling of the o-tolyl
moiety bearing an appropriate functional group (X) to pyrimidine
core and nucleophilic introduction of a sulfanyl moiety bearing a
counterpart (Y) followed by cyclization with X and Y gives
macrocyclic derivatives.
Following this, a 20,40-disubstitued derivative was designed in
order to achieve enhanced hydrophobic interactions by further
occupation of the hydrophobic space formed by Val150, Leu107,
and Phe138. As expected, 2’,4’-dichloro derivative 10 showed
about four times stronger binding affinity than 8. A 20,4’-di-
methyl-5’-benzamide derivative 11, with a Kd value of 1.3 nM,
achieved both the hydrophobic interaction and the hydrogen bond
formation with the water molecule which forms hydrogen bonds
a
b
Thr184
Asp93
Asp93
Leu48
Leu48
Val150
Val150
Gly97
Phe138
Gly97
Phe138
Ile96
Ile96
Asn51
Asn51
4.1
4.3
3.9
3.8
Met98
Met98
3.9
2.8
Leu107
Tyr139
Tyr139
Lys58
Lys58
Leu107
c
Thr184
Asp93
Gly97
Leu48
Val150
Phe138
Asn51
Ile96
3.9
3.7
Met98
Tyr139
Lys58
Leu107
Figure 3. X-ray structures of N-terminal Hsp90
a
in complex with identified compounds. The numbering of the residues corresponds to those in the X-ray cocrystal structure
(gray CHsp90 , green Cligand, red O, blue N, yellow S). Distances are given in Å. Noncovalent interactions are indicated by dashes (black: hydrogen bonds, magenta: hydrophobic
a
interactions). Detailed binding modes of (a) compound 8 (PDB code: 3VHA), (b) compound 11 (PDB code: 3VHC), (c) compound 16 (PDB code: 3VHD).

A. Suda et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1136–1141
1139
Table 3
Binding affinity, in vitro anti-proliferative activity and water solubility of amide linkage derivatives having an aromatic side chain on the S atom
NH2
R1
L1
N
N
S
R2
n O
)
(
IC50
HCT116
(l
M)
NCI-N87
a
Compd
R1
R2
L1
n
Ring size
Kd (nM)b
PSA (Å2)c
Solubility (l
M)d
8
10
11
12
13
14
15
Me
Cl
H
Cl
O
O
4
4
3
4
5
3
3
16
16
16
17
18
16
16
40
11
5.5
1.5
0.78
2.5
3.1
4.0
4.1
3.8
1.1
0.94
3.3
3.0
4.2
4.3
56.3
55.4
71.0
71.1
72.1
78.5
78.3
18
<7
79
69
39
Me
Me
Me
Me
Me
Me
Me
Me
MeO
EtO
–CONH–
–CONH–
–CONH–
–CONH–
–CONH–
1.3
7.4
6.2
5.8
10
260
186
a
b
c
Element order as seen left to right in a formula.
Values were measured by SPR using human N-terminal Hsp90
PSA was calculated by TPSA.
a.
d
Solubility in FaSSIF.
Table 4
Binding affinity, in vitro anti-proliferative activity, and physicochemical properties of amide linkage derivatives having an aliphatic side chain on the S atom
NH2
N
N
S
L3
H
N
L2
O
(
)
n
IC50
(l
M)
LM CL (lL/min/mg protein)
a
Compd
n
L2
O
L3
Ring size
Kd (nM)b
HCT116
NCI-N87
Solubility (l
M)c
Human
Mouse
11
3
3
4
5
2
3
2
2
–1,3-C6H4–
–(CH2)2–
–(CH2)2–
–(CH2)2–
–(CH2)3–
–(CH2)2–
–(CH2)2–
–(CH2)2–
16
16
17
18
16
16
16
16
1.3
0.78
0.15
0.13
0.21
0.29
0.25
0.13
0.13
0.94
0.066
0.092
0.091
0.18
0.15
0.1
79
125
553
169
106
117
911
111
56
93
16, CH5164840
–NHCO–
–NHCO–
–NHCO–
–NHCO–
–CONH–
–OCONH–
–NHCOO–
0.52
0.38
0.25
0.61
0.65
0.7
0.28
5.1
1.7
5.4
1
2.3
3.5
1.8
3.6
15
17
18
19
20
21
22
3.5
9.3
7.3
21
0.8
0.17
a
b
c
Element order as seen left to right in a formula.
The values were measured by SPR using human N-terminal Hsp90
Solubility in FaSSIF.
a.
with the backbone of Phe138 and the side chain of Asn51. The ste-
ric bulkiness of the methyl group of 11 is similar to that of the
chloro group to achieve a hydrophobic interaction. This modifica-
tion significantly improved the binding affinity and in vitro anti-
proliferative activity (Table 3). An X-ray cocrystal structure of 11
and Hsp90 (PDB code: 3VHC, 1.4 Å resolution) revealed that the
amide oxygen of 11 formed a hydrogen bond (d(OꢀꢀꢀOwater) = 2.8 Å)
with the water, which was not observed in 8, and the 2040-dimeth-
ylphenyl group filled the hydrophobic space (Fig. 3b). In addition,
(Table 3). Therefore, R2 group should be a small hydrophobic group
such as a methyl or chloro group.
In an X-ray cocrystal structure of 11-Hsp90, we observed a lack of
the interaction of 11 to Lys58’s side chain NH which is present in
GM-Hsp90 complex (Fig. 3b). As a hydrogen bond acceptor, an
alkylamide or a carbamate group (L2) was introduced in between
the amide nitrogen and sulfur (Table 4). Based on the molecular
modeling analysis, we abandoned a phenylene group and used
methylene carbons as L3 to direct amide carbonyl oxygen toward
Lys58. Hydrophobic interactions of methylene carbons with Ile96
and Met98 may contribute to affinity. As expected, an X-ray cocrys-
tal structure of 16 and Hsp90 (PDB code: 3VHD, 1.3 Å resolution) re-
vealedthat the amideoxygen of 16 formeda hydrogen bond with the
side chain of Lys58, and the methylene carbonattached to the S atom
formed alkyl–alkyl interactions (d(CꢀꢀꢀCIle96) = 3.9 Å) with Ile96 and
(d(CꢀꢀꢀCMet98) = 3.7 Å) with Met98 (Fig. 3c). The alkylamide deriva-
tives (16–20) showed improved binding affinities, in vitro anti-
proliferative activity, solubility, and LM stability (Table 4). The
carbamate derivatives also showed improvement in these profiles.
Out of 16–22, 16 showed the highest LM stability.
11 had better water solubility (solubility in FaSSIF = 79 lM) than
the lead compound 6, presumably due to increased molecular po-
lar surface area (PSA, 71.0 Å2 as calculated by TPSA21).22 The ring
size enlargement to 17- and 18-membered rings (12 and 13,
respectively) by the addition of methylene carbons caused a reduc-
tion in binding affinity (Table 3). These results indicate that 16-
membered ring is also optimal in the case of the amide linkage
derivatives. When we tried keeping the amide linkage and 16-
membered ring and exchanging methyl to a methoxy or ethoxy
group at the R2 position (14 and 15, respectively), the water solu-
bility was improved, but it led to a reduction in binding affinity

1140
A. Suda et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1136–1141
HCT116
NCI-N87
y = 0.2769x0.8131
r ² = 0.8189
y = 0.3782x0.733
r²= 0.8487
a
b
10
1
10
1
0.1
0.1
0.01
0.01
0.1
1
10
Kd (nM)
100
1000
0.1
1
10
Kd (nM)
100
1000
Figure 4. Correlation between Kd value (determined by SPR) and in vitro anti-proliferative activity (IC50).
Table 5
PK parameters of 16 in nude mice
Administration
Dose (mg/kg)
t1/2 (h)
tmax (h)
Cmax
(
lg/mL)
AUCinf
(l
gꢀh/mL)
CL or CL/F (mL/h/kg)
Fa (%)
iv
po
3
3
1.66
2.64
—
0.5
—
2.93
9.07
6.42
337
468
—
70.8
a
Oral bioavailability.
plasma clearance, which is consistent with the low mouse LM
clearance (Table 5).
1000
800
600
400
200
Compound 16 was further evaluated in a human HCT116 colo-
rectal cancer xenograft model in mice (Fig. 5). Mice bearing
HCT116 were orally treated with 16 once daily for 11 days at
3.13, 6.25, 12.5, and 25 mg/kg, and their body weight and tumor
volume were measured twice a week. Compound 16 showed po-
tent antitumor efficacy with TGI of 83% without significant loss
of body weight. In addition, 16 demonstrated potent antitumor
efficacy especially in HER2-overexpressing cancer xenograft mod-
els when administered alone or in combination with the HER2-tar-
geted agents such as trastuzumab and lapatinib.23
control
3.13 mg/kg
6.25 mg/kg
12.5 mg/kg
25 mg/kg
0
11
15
15
19
19
23
The preparation of 16 is shown in Scheme 2. Boronate ester 26
was prepared from commercial 2,4-dimethylbenzoic acid (23) via
selective idodination at the 4-position (75%), esterification (70%),
and Miyaura borylation (94%). This boronate 26 was coupled
with commercially available 2-amino-4,6-dichloropyrimidine by
Pd-catalyzed Suzuki-Miyaura cross-coupling to give 2-amino-6-
aryl-4-chloropyrimidine 27 (67%). Nucleophilic substitution with
3-mercaptopropionic acid gave 28 (75%) and following amide for-
mation gave a Boc-protected precursor of macrocyclization 29
(71%). Deprotection followed by amide formation under highly di-
luted condition (2 mM) gave 16 (21% in 2 steps). A synthetic route
amenable to scale-up preparation was established in our laborato-
ries and the work is due to be reported in a separate publication.
In summary, we identified novel macrocyclic 2-amino-6-aryl-
pyrimidines as Hsp90 inhibitors by modification of 2-amino-6-
aryltriazine derivative (CH5015765). We employed a macrocyclic
structure as a skeleton for the new inhibitors to mimic the GM-
Hsp90 interactions and to improve the metabolic stability. This
macrocyclic structure enabled us to introduce several functional
groups, such as a carbonyl moiety at the appropriate position, with
proper direction to interact with the key elements of the protein,
resulting in significant improvement of the binding affinity to-
gether with antiproliferative activity. Among the macrocycles,
compound 16 (CH5164840) showed low clearance and high solu-
bility. The compound demonstrated high oral bioavailability in
mice and potent antitumor efficacy in a human HCT116 colorectal
cancer xenograft model.
110
100
90
80
11
23
Days after inoculation
Figure 5. Growth inhibitory effect of 16 on HCT116 tumor xenograft model. SCID
mice bearing HCT116 were administered compound 16 orally once daily for 11
consecutive days (days 11–21) at 3.13 mg/kg (TGI = 48%), 6.25 mg/kg (TGI = 25%),
12.5 mg/kg (TGI = 66%), and 25 mg/kg (TGI = 83%).
Human Hsp90 exhibits weak ATPase activity in the absence of
co-chaperones.9 The conventional ATPase assay did not offer
sufficient information for the lead optimization because of its
inherent low sensitivity. Therefore, we used surface plasmon reso-
nance (SPR) to assess inhibitor binding affinity. Positive correlation
between Kd values and in vitro anti-proliferative activities (IC50
)
against two cell lines was found for 16 derivatives (compounds
7–22), which suggests that in vitro anti-proliferative activities
were derived from inhibitory activities against Hsp90 (Fig. 4).
Since 16 showed high binding affinity, strong in vitro anti-pro-
liferative activity, and sufficient in vitro metabolic stability, we
conducted in vivo profiling. The pharmacokinetic study in mice
demonstrated high oral bioavailability (F = 70.8%) and favorable

A. Suda et al. / Bioorg. Med. Chem. Lett. 22 (2012) 1136–1141
1141
O
B
I
I
a
b
c
d
O
O
OH
O
OH
Ot-Bu
O
O
26
Ot-Bu
N
23
24
25
NH2
N
NH2
N
NH2
N
N
N
S
e
f
Cl
S
HN
O
O
Ot-Bu
HO
O
O
Ot-Bu
O
Ot-Bu
27
28
BocNH
29
NH2
NH2
N
N
N
N
S
g
h
S
2TFA
O
HN
OH
O
HN
NH
O
O
H2N
30
16, CH5164840
Scheme 2. Synthesis of compound 16a. aReagents and conditions: (a) I2, NaIO4, Ac2O, H2SO4, AcOH, 105 °C, 6 h, 75%; (b) N,N-dimethylformamide di-tert-butyl acetal, toluene,
80 °C, 2 h, 70%; (c) B2pin2, Pd2Cl2(dppf)-CH2Cl2, AcOK, DMF, 80 °C, 18 h, 94%; (d) 2-amino-4,6-dichloropyrimidine, Pd2Cl2(dppf)-CH2Cl2, NaHCO3, 1,4-dioxane, H2O, 80 °C, 19 h,
67%; (e) 3-mercaptopropionic acid, Cs2CO3, DMF, 80 °C, 2 h, 75%; (f) EDC–HCl, HOBT, N-Boc-1,3-propanediamine, DIPEA, DMF, rt, 6 h, 71%; (g) TFA, CH2Cl2, anisol, 0 °C to rt,
3 h; (h) EDC–HCl, HOBT, DIPEA, DMF, THF, 2 mM, rt, 13 h, 21% in 2 steps.
10. Siligardi, G.; Panaretou, B.; Meyer, P.; Singh, S.; Woolfson, D. N.; Piper, P. W.;
Acknowledgments
Pearl, L. H.; Prodromou, C. J. Biol. Chem. 2002, 277, 20151.
11. Schulte, T. W.; Neckers, L. M. Cancer Chemother. Pharmacol. 1998, 42, 273.
We thank Yuko Aoki and Shige Nagahashi for their helpful sug-
gestions and comments. We also thank Masami Kohchi, Takehiro
Okada, Yoshiaki Isshiki, Toshihiko Fujii, Kiyoaki Sakata, Young-Jin
Na, Sung-Jin Kim, Dong-Oh Yoon, Young-Jin Kwon, Azusa Hoshino,
Shin-ichi Arai and all people who contributed to this work.
12. Egorin, M. J.; Lagattuta, T. F.; Hamburger, D. R.; Covey, J. M.; White, K. D.;
Musser, S. M.; Eiseman, J. L. Cancer Chemother. Pharmacol. 2002, 49, 7.
13. Lundgren, K.; Zhang, H.; Brekken, J.; Huser, N.; Powell, R. E.; Timple, N.; Busch,
D. J.; Neely, L.; Sensintaffar, J. L.; Yang, Y. C.; McKenzie, A.; Friedman, J.;
Scannevin, R.; Kamal, A.; Hong, K.; Kasibhatla, S. R.; Boehm, M. F.; Burrows, F. J.
Mol. Cancer Ther. 2009, 8, 921.
14. Brough, P. A.; Aherne, W.; Barril, X.; Borgognoni, J.; Boxall, K.; Cansfield, J. E.;
Cheung, K. M.; Collins, I.; Davies, N. G.; Drysdale, M. J.; Dymock, B.; Eccles, S. A.;
Finch, H.; Fink, A.; Hayes, A.; Howes, R.; Hubbard, R. E.; James, K.; Jordan, A. M.;
Lockie, A.; Martins, V.; Massey, A.; Matthews, T. P.; McDonald, E.; Northfield, C.
J.; Pearl, L. H.; Prodromou, C.; Ray, S.; Raynaud, F. I.; Roughley, S. D.; Sharp, S. Y.;
Surgenor, A.; Walmsley, D. L.; Webb, P.; Wood, M.; Workman, P.; Wright, L. J.
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Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2011.11.100.
15. Woodhead, A. J.; Angove, H.; Carr, M. G.; Chessari, G.; Congreve, M.; Coyle, J. E.;
Cosme, J.; Graham, B.; Day, P. J.; Downham, R.; Fazal, L.; Feltell, R.; Figueroa, E.;
Frederickson, M.; Lewis, J.; McMenamin, R.; Murray, C. W.; O’Brien, M. A.;
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