4-Substituted-7-azaindoles bearing a ureidobenzofuranone moiety as potent and selective, ATP-competitive inhibitors of the mammalian target of rapamycin (mTOR)

Article abstract of DOI:10.1016/j.bmcl.2010.02.012

A series of 5-ureidobenzofuranones was discovered as potent and selective inhibitors of mTOR with good cellular activity. Molecular modeling studies revealed several hydrogen bond interactions of the ureido group with the enzyme at the ATP-binding site. Furthermore, modeling showed that the ureido group is best situated at C-5 of the benzofuranone. Syntheses of 4-ureido and 5-ureidobenzofuranones are presented.

Full text of DOI:10.1016/j.bmcl.2010.02.012

Bioorganic & Medicinal Chemistry Letters 20 (2010) 2259–2263
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
4-Substituted-7-azaindoles bearing a ureidobenzofuranone moiety as potent
and selective, ATP-competitive inhibitors of the mammalian target
of rapamycin (mTOR)
a
a
a
a
Hwei-Ru Tsou a, , Gloria MacEwan , Gary Birnberg , Nan Zhang , Natasja Brooijmans ,
*
Lourdes Toral-Barza b, Irwin Hollander b, Semiramis Ayral-Kaloustian a, Ker Yu b
a Chemical Sciences, Wyeth Research, 401 N. Middletown Road, Pearl River, NY 10965, United States
b Oncology Research, Wyeth Research, 401 N. Middletown Road, Pearl River, NY 10965, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 5-ureidobenzofuranones was discovered as potent and selective inhibitors of mTOR with good
cellular activity. Molecular modeling studies revealed several hydrogen bond interactions of the ureido
group with the enzyme at the ATP-binding site. Furthermore, modeling showed that the ureido group
is best situated at C-5 of the benzofuranone. Syntheses of 4-ureido and 5-ureidobenzofuranones are
presented.
Received 5 January 2010
Revised 29 January 2010
Accepted 2 February 2010
Available online 6 February 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
mTOR
PI3K
Cancer
Serine/threonine kinase
The mammalian target of rapamycin (mTOR) is frequently
hyperactivated in human cancers,1–3 making it an attractive target
for treating cancer.4–6 mTOR belongs to a family of unconventional
high molecular mass serine/threonine protein kinases and is a key
component of the phosphoinositide 3-kinase (PI3K) signaling path-
way that plays an important role in regulating cell growth, metab-
olism and angiogenesis.7,8 mTOR is a clinically proven drug target
for cancer as demonstrated by rapamycin analogs.9 However, rap-
amycin analogs are allosteric inhibitors, only inhibiting mTORC
complex 1 (mTORC1), but not mTORC complex 2 (mTORC2).10,11
Inhibition of mTORC1 alone can block a desirable negative feed-
back mechanism, thereby causing an increase of PI3K–Akt signal-
ing and reducing the effectiveness of the inhibitors.2 This
negative feedback mechanism can be restored by inhibiting
mTORC2. This finding has led the cancer research community to
search for small molecule ATP-competitive inhibitors of mTOR. In
the PI3K/Akt/mTOR signaling pathway, mTOR and PI3K share high
sequence similarity (68%) at their ATP-binding sites, making the
search for selective mTOR inhibitors more challenging. Indeed,
many reported mTOR inhibitors are dual inhibitors that also inhibit
4-hydroxybenzofuran-3(2H)-ones as potent and selective ATP-
competitive inhibitors of mTOR.25 Through our analoging efforts,
we were able to prepare compounds that demonstrated subn-
anomolar inhibitory activity against mTOR kinase and were selec-
tive over PI3K
groups. Since there is no available crystal structure of mTOR, the
closely related protein, PI3K , was used for co-crystallization stud-
ies with our inhibitors. X-ray co-crystallographic structures of
inhibitor 1a with PI3K showed the importance of the two pheno-
a. Initially our lead contained two phenolic hydroxyl
c
c
lic hydroxyl groups for hydrogen bond interactions with Asp2195
and Lys2187 of the enzyme. In an effort to minimize the metabolic
liability of the phenolic groups, we eliminated one of the two hy-
droxyl groups. We now report the replacement of both hydroxyl
groups with a ureido group, to completely eliminate the potential
liabilities associated with glucuronidation of the phenolic hydroxyl
groups, and thus enhance metabolic stability.
Recently, Zask et al.18 reported that in the pyrazolopyrimidine
series, a phenolic hydroxyl group was successfully replaced with
a ureido group, a known isostere, to give potent and selective
mTOR inhibitors. One of these inhibitors, 2 (Fig. 1), was co-crystal-
PI3Ka.
4,12,13 However, recently, quite a few selective mTOR inhibi-
lized with PI3Kc to show that the ureido group formed hydrogen
tors have been discovered.14–24 Our group has just reported on a
bond interactions with Asp841 and Lys833 of PI3Kc (Asp2195
series of 2-(4-substituted-pyrrolo[2,3-b]pyridin-3-yl)methylene-
and Lys2187 in mTOR).18 To determine the best site for a ureido
substituent as a 4-OH replacement on the benzofuranone ring,
we overlayed the X-ray co-crystal structures of PI3K
(PDB code 3LJ3) and 2 (PDB code 3IBE), as shown in Figure 1. The
c
with 1a25
* Corresponding author. Tel.: +1 845 602 4712; fax: +1 845 602 5561.
E-mail addresses: tsouh@wyeth.com, tsouh10@gmail.com (H.-R. Tsou).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.02.012

2260
H.-R. Tsou et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2259–2263
Figure 1. Overlay of two X-ray co-crystal structures of PI3K
c
(in dark gray ribbon and carbons) with 1a (in cyano carbons) and PI3K
c (in light gray ribbon and carbons) with 2
(in orange carbons). mTOR residue numbering is used in the figure, and the corresponding PI3K
c
numbering is Val882, Lys833, and Asp841.
overlay and subsequent docking studies suggested that a C-5 ure-
ido group on benzofuranone was best positioned to form hydrogen
bond interactions with Asp2195 and Lys2187 of mTOR, similar to
the interactions observed with a 4,6-dihydroxybenzofuranone, 1a
or the urea 2. However, a C-4 ureidobenzofuranone is not expected
to form these interactions with the enzyme.
Before we embarked our analoging efforts on 5-ureidobenzofur-
anaones, we prepared both 5-methylurea 3a and 4-methylurea 3b to
verify the preference for 5- versus 4-ureidobenzofuranones, as sug-
gested by crystallography and modeling. The synthesis of 3a is
shown in Scheme 1. The 4-bromide 4 was converted into the 4-phe-
nyl compound 5a, under Suzuki coupling conditions,25 followed by
condensation with 5-ureidobenzofuranone 11 where R is a methyl
group. Compound 11 was prepared from 2-hydroxyacetophenone
7. Alpha bromination of 7,26 followed by nitration27 gave 8, which
was readily cyclized under basic conditions to yield 9. After reduc-
tion of 9, the resulting amine 10 was treated with isocyanate to af-
ford 11. The preparation of 4-ureidobenzofuranone 3b started
from 2-hydroxy-6-pivalamidobenzoic acid 12,28 as shown in
Scheme 2. After esterification, the resulting intermediate 13 was re-
acted with sodium ethoxide and bromoacetate to yield 14, which
was then cyclized to 4-pivalamidobenzofuranone 15. Attempts to
deprotect the pivaloyl group of 15 resulted in decomposition. We
then coupled 15 directly with the 4-phenyl-7-azaindole core by
heating with HCl in dioxane. To our delight, the pivaloyl group was
also removed and the resulting amine 16 was further converted to
the corresponding isocyanate, followed by treatment with methyl-
amine to yield 3b. Clearly, 3a was 100-fold more potent than 3b in
inhibiting mTOR kinase, as shown in Table 1, confirming the model-
ing hypothesis. However, 3a was 10-fold less potent and fourfold

H.-R. Tsou et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2259–2263
2261
Table 1
O
H
H
Ureas versus hydroxyl derivatives
N
N
R
O
Br
N
R'
N
R'
N
O
O
O
O
OH
O
O
HN
N
H
i
ii
4
5
N
N
N
O
O
4
3a: R' = Ph, R = Me
6: R' = NR1R2
5a: R' = Ph
5b: R' = NR1R2
N
N
N
N
O
O
O
3a, 3b
1b
Br
NO2
NO2
iii,iv
v
a
a
Compd
Sub
IC50 (nM)
IC50 (lM)
O
HO
HO
mTOR
PI3Ka
Selb
LNCap
9
8
7
1b
3a
3b
3.5
37
3500
89
233
>10,000
25.4
6
>2.9
0.2
60
>60
5-
4-
O
O
H
H
N
N
NH2
vii
R
vi
a
Determinations were done in duplicate and repeat values agreed, on average,
with a mean twofold difference.
O
O
O
b
11
Selectivity = (IC50 PI3Ka)/(IC50 mTOR).
10
Scheme 1. Reagents and conditions: (i) for 5a: 4,4,5,5-tetramethyl-2-phenyl-1,3,2-
dioxaborolane, PS-Pd(PPh3)4, Na2CO3, DME, heat; for 5b: NHR1R2, Pd2(dba)3, 20-
(dicyclohexylphosphino)-N,N-dimethylbiphenyl-2-amine, K2HPO4, dioxane or DME,
heat; (ii) 5-ureidobenzofuranone 11, EtOH, HCl, heat; (iii) CuBr2, EtOAc, CHCl3,
reflux; (iv) HNO3, HOAc; (v) Hunig base, EtOAc, room temperature; (vi) Fe, HOAc,
H2O, EtOAc, heat; (vii) R-NCO, CH2Cl2 or THF.
PI3Ka. However, ethylurea 6b was sixfold less potent against
mTOR compared to 6a. Surprisingly, dimethylaminoethylurea 6c
was as potent as 6a, but suffered a decrease in selectivity. Com-
pared to methylurea 6a, phenylurea 6d was 15-fold less potent.
However, 3-pyridylurea 6e was equipotent to 6a against mTOR,
with higher selectivity and 10-fold higher cellular potency
(IC50 = 15 nM). Introducing a morpholine substituent on the 3-pyr-
idyl ring gave 6f, which was as potent as 6e, however with signif-
icant loss in cellular activity. So we focused our analoging efforts
on 3-pyridylureas and further investigated the effect of 4-bridged
morpholines23 on mTOR potency. Compared to morpholine 6g,
bridged morpholines 6e, 6h, 6i showed enhanced mTOR potency
and cellular activity, as shown in Table 3. Among them, 2,6-bridged
morpholine 6e showed the highest selectivity (145-fold) over
less selective compared to the corresponding 4-OH derivative 1b.
We then prepared a new methylurea 6a, where a bridged morpho-
line was introducedat C-4 of the azaindole core instead of a 4-phenyl
substituent shown in 3a. To our delight, 6a showed enhanced po-
tency in mTOR and cells as well as selectivity, compared to 3a. There-
fore, we focused our optimization efforts on varying the 4-amino
substituent on the azaindole core and the 5-ureido substituent on
the benzofuranone of 6. Derivatives 6 were prepared by converting
the 4-bromide 4 to the 4-amino analogs 5b, under Buchwald cou-
pling conditions,25 followed by condensation with a variety of 5-ure-
idobenzofuranones 11, as depicted in Scheme 1.
PI3Ka, whereas 3,6-bridged morpholine 6h was the most potent
one in inhibiting mTOR kinase (IC50 = 7.5 nM) and cellular prolifer-
ation (IC50 = 1.8 nM). Other 4-substituted analogs carrying 4-pipe-
A variety of substituted ureas, 6a–6f, were prepared and evalu-
ated for mTOR potency as shown in Table 2. Methylurea 6a showed
good potency (mTOR IC50 = 9.5 nM) with 61-fold selectivity over
Table 2
Substituted ureas
O
N
O
O
H
H
O
N
N
R
O
HN
O
HN
O
O
ii
HO
HO
i
EtO
HO
N
N
13
12
a
a
O
O
Compd
R
IC50 (nM)
PI3K
IC50 (lM)
mTOR
a
Selb
LNCap
O
O
HN
HN
O
iv
6a
6b
9.5
580
311
61
0.14
2.8
CH3
iii
EtO
EtO
57.0
5.5
CH2CH3
N
O
O
15
14
6c
5.6
24
4
0.06
0.28
O
HN
N
NH2
6d
145.0
498
3.4
O
O
H
6e
6f
14.3
29.0
2080
2220
145
0.015
>60
O
O
N
N
v
N
O
N
N
76.6
N
N
3b
16
a
Determinations were done in duplicate and repeat values agreed, on average,
with a mean twofold difference.
Scheme 2. Reagents and conditions: (i) SOCl2, EtOH; (ii) NaOEt, BrCH2CO2Et; (iii)
NaH, toluene, then NaOH, followed by HCl; (iv) 5a, HCl, dioxane; (v) triphosgene,
Et3N, THF, followed by MeNH2.
b
Selectivity = (IC50 PI3Ka)/(IC50 mTOR).

2262
H.-R. Tsou et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2259–2263
Table 3
Table 4
Morpholine versus bridged morpholines
Piperidinylamides
O
NR1R2
O
H
N
H
N
O
NR1R2
O
H
H
O
N
N
N
N
N
O
O
N
N
N
N
Compd
NR1R2
IC50 (nM)
IC50 (lM)
a
a
NR1R2
IC50 (nM)
PI3K
IC50 (lM)
a
a
mTOR
14.3
PI3Ka
Selb
145
LNCap
0.015
Compd
mTOR
a
Selb
LNCap
6e
6g
6h
6i
2080
275
249
128
N
N
N
N
O
6j
10.5
2030
308
193
2.7
0.08
0.05
NMe2
NEt2
71.0
7.5
4
33
3
0.05
O
O
O
6k
115.0
6l
18.0
17.0
5.4
2660
1677
3477
4598
909
148
3.2
N
N
N
N
N
N
O
O
O
N
0.0018
0.006
6m
6n
6o
6p
6q
98.6
0.09
0.2
42.0
a
Determinations were done in duplicate and repeat values agreed, on average,
with a mean twofold difference.
644
b
Selectivity = (IC50 PI3Ka)/(IC50 mTOR).
70.0
8.2
65.7
111
12.6
0.33
0.012
0.018
ridinylamides, were also prepared as mTOR kinase inhibitors
(Table 4). Their synthesis began with Buchwald coupling of 4 and
4-piperidinyl ester. The resulting ester was hydrolyzed and con-
densed with a variety of amines via mixed anhydride method25
to yield amides. Final coupling of the amides with ureidobenzof-
uranone 11 yield 6j–6y. Dimethylamide 6j showed good mTOR
potency and 193-fold selectivity. However, diethylamide 6k lost
10-fold in mTOR potency, compared to 6j, and was not selective.
The morpholinylamides 6l–6n were all potent and selective mTOR
inhibitors, with 6n showing the highest selectivity (644-fold).
Compared to morpholinylamide 6l, N-Me-piperazinylamide 6o
and piperidinylamide 6q showed reduced mTOR potency and
selectivity, but enhanced cellular activity. Pyrrolidinylamide 6p
was superior to piperidinylamide 6q in terms of mTOR potency
and selectivity. To enhance the water solubility of 6p, dimethyl-
amino and ethoxy groups were introduced on the pyrrole ring
(6r and 6s, respectively). Although both 6r and 6s were as potent
as 6p, and more selective, they exhibited much reduced cellular
activity. 3-Pyridylmethylaminoamide 6t was found to be a potent
(IC50 = 9 nM) and selective (450-fold) mTOR inhibitor; unfortu-
nately, it lacked cellular activity. This prompted us to prepare three
isomers of N-methyl-(3-pyridylmethyl)aminoamides 6u–6w.
These three isomers were as potent as 6t, however, with reduced
selectivity. Analogs 6v and 6w showed good cellular activity. Inter-
estingly, replacement of the pyridyl group of 6u with a phenyl gave
6x that showed 10-fold reduction of mTOR potency. However, re-
moval of the methylene bridge between the pyridine ring and N
from 6u did not affect the mTOR potency of the resulting derivative
6y and provided 4-fold and 10-fold enhancement in selectivity and
cellular activity, respectively, as shown in Table 4.
47.5
600
N
6r
6s
N
N
11.0
8.2
>10,000
2310
>909
282
2.3
O
0.19
H
N
6t
9.0
10.9
9.3
4040
1030
450
94
60
N
6u
6v
6w
6x
6y
3.2
N
N
N
N
1230
132
187
>98
380
0.023
0.04
0.020
0.3
N
8.4
1570
N
102.5
13.0
>10,000
4960
N
N
N
a
Determinations were done in duplicate and repeat values agreed, on average,
with a mean twofold difference.
b
Selectivity = (IC50 PI3Ka)/(IC50 mTOR).
specific hydrogen bond interaction, it is not surprising to see that
6d showed 10-fold reduction of mTOR potency compared to the
corresponding 3-pyridyl urea 6e (Table 2). Furthermore, Gln2167
An mTOR homology model was built based on the X-ray crystal
in mTOR is Lys776 in PI3K
with solvent, rather than the inhibitor. This may lead to the high
selectivity (145-fold) of 6e over PI3K . The bridged morpholines
a. The lysine likely prefers to interact
structure of PI3K
c
.
The X-ray structure of our 4,6-
was used
dihydroxybenzofuranone inhibitor 1a bound to PI3K
c
a
as the basis for docking studies in the mTOR homology model.
Binding studies of urea 6h with this homology model showed a
hydrogen bond between N-7 and Val2240 in the hinge region of
the ATP-binding domain of the enzyme as shown in Figure 2. Fur-
thermore, the urea group forms three hydrogen bonds with the en-
zyme, namely the two NHs with Asp2195 and the carbonyl with
Lys2187, consistent with what was predicted from the overlay
studies shown in Figure 1. The homology model also showed an
additional hydrogen bond between the 3-pyridyl nitrogen and
Gln2167. Since the phenyl urea 6d is not expected to form this
at C-4 of the azaindole core sit below the glycine-rich loop and
the pocket in this region is quite large, especially compared to
the region directly adjacent to the hinge region. It is likely that
the bridged morpholines are able to fill more space in this area,
resulting in increased potency (Table 3). However, the resolution
of the homology model is not sufficiently high to help explain
selectivity for groups (i.e., C-4 substituents) away from the hinge
region. It is clear from the model that the amide substituent
NR1R2 (Table 4) at C-4 point towards solvent, providing opportu-
nity for future design of inhibitors.

H.-R. Tsou et al. / Bioorg. Med. Chem. Lett. 20 (2010) 2259–2263
2263
References and notes
1. Yuan, T. L.; Cantley, L. C. Oncogene 2008, 27, 5497.
2. Carracedo, A.; Pandolfi, P. P. Oncogene 2008, 27, 5527.
3. Inoki, K.; Corradetti, M. N.; Guan, K. L. Nat. Genet. 2005, 37, 19.
4. Verheijen, J.; Yu, K.; Zask, A. Annu. Rep. Med. Chem. 2008, 43, 189.
5. Strimpakos, A. S.; Karapanagiotou, E. M.; Saif, M. W.; Syrigos, K. N. Cancer Treat.
Rev. 2009, 35, 148.
6. Baldo, P.; Cecco, S.; Giacomin, E.; Lazzarini, R.; Ros, B.; Marastoni, S. Curr. Cancer
Drug Targets 2008, 8, 647.
7. Guertin, D. A.; Sabatini, D. M. Cancer Cell 2007, 12, 9.
8. Chiang, G. G.; Abraham, R. T. Trends Mol. Med. 2007, 13, 433.
9. Fasolo, A.; Sessa, C. Expert Opin. Investig. Drugs 2008, 17, 1717.
10. Choi, J.; Chen, J.; Schreiber, S. L.; Clardy, J. Science 1996, 273, 239.
11. Liang, J.; Choi, J.; Clardy, J. Acta Crystallogr., Sect. D 1999, 55, 736.
12. Maira, S.-M.; Staffer, F.; Brueggen, J.; Furet, P.; Schnell, C.; Fritsch, C.;
Brachmann, S.; Chene, P.; De Pover, A.; Schoemaker, K.; Fabbro, D.; Gabriel,
D.; Simonen, M.; Murphy, L.; Finan, P.; Sellers, W.; Garcia-Echeverria, C. Mol.
Cancer Ther. 2008, 7, 1851.
13. Folkes, A. J.; Ahmadi, K.; Alderton, W. K.; Alix, S.; Baker, S. J.; Box, G.;
Chuckowree, I. S.; Clarke, P. A.; Depledge, P.; Eccles, S. A.; Friedman, L. S.; Hayes,
A.; Hancox, T. C.; Kugendradas, A.; Lensun, L.; Moore, P.; Olivero, A. G.; Pang, J.;
Patel, S.; Pergl-Wilson, G. H.; Raynaud, F. I.; Robson, A.; Saghir, N.; Salphati, N.
C.; Wiesmann, C.; Workman, P.; Zhyvoloup, A.; Zvelebil, M. J.; Shuttleworth, S.
J. J. Med. Chem. 2008, 51, 5522.
14. Feldman, M. E.; Apsel, B.; Uotila, A.; Loewith, R.; Knight, Z. A.; Ruggero, D.;
Shokat, K. M. PLoS Biol. 2009, 7, 371.
15. Garcia-Martinez, J. M.; Moran, J.; Clarke, R. G.; Gray, A.; Cosulich, S. C.; Chresta,
C. M.; Alessi, D. R. Biochem. J. 2009, 421, 29.
Figure 2. Docking of 6h (in orange carbons) in an mTOR homology model based on
the PI3K crystal structure. Hydrogen bonds are shown with black dashed lines and
residue numbers are indicated for hydrogen bonding partners.
c
16. Thoreen, C. C.; Kang, S. A.; Chang, J. W.; Liu, Q.; Zhang, J.; Gao, Y.; Reichling, L. J.;
Sim, T.; Sabatini, D. M.; Gray, N. S. J. Biol. Chem. 2009, 284, 8023.
17. Yu, K.; Toral-Barza, L.; Shi, C.; Zhang, W.-G.; Lucas, J.; Shor, B.; Kim, J.;
Verheijen, J.; Curran, K.; Malwitz, D. J.; Cole, D. C.; Ellingboe, J.; Ayral-
Kaloustian, S.; Mansour, T. S.; Gibbons, J. J.; Abraham, R. T.; Nowak, P.; Zask, A.
Cancer Res. 2009, 69, 6232.
18. Zask, A.; Verheijen, J. C.; Curran, K.; Kaplan, J.; Richard, D. J.; Nowak, P.;
Malwitz, D. J.; Brooijmans, N.; Bard, J.; Svenson, K.; Lucas, J.; Toral-Barza, L.;
Zhang, W.-G.; Hollander, I.; Gibbons, J. J.; Abraham, R. T.; Ayral-Kaloustian, S.;
Mansour, T. S.; Yu, K. J. Med. Chem. 2009, 52, 5013.
19. Menear, K. A.; Gomez, S.; Malagu, K.; Bailey, C.; Blakburn, K.; Cockroft, X.-L.;
Ewen, S.; Fundo, A.; Le Gall, A.; Hermann, G.; Sebastian, L.; Sunose, M.; Presnot,
T.; Torode, E.; Hickson, I.; Martin, N. M. B.; Smith, G. C. M.; Pike, K. G. Bioorg.
Med. Chem. Lett. 2009, 19, 5898.
20. Richard, D. J.; Verheijen, J. C.; Curran, K.; Kaplan, J.; Toral-Barza, L.; Hollander,
I.; Lucas, J.; Yu, K.; Zask, A. Bioorg. Med. Chem. Lett. 2009, 19, 6830.
21. Nowak, P.; Cole, D. C.; Brooijmans, N.; Bursavich, M. G.; Curran, K. J.; Ellingboe,
J. W.; Gibbons, J. J.; Hollander, I.; Hu, Y.; Kaplan, J.; Malwitz, D. J.; Toral-Barza,
L.; Verheijen, J. C.; Zask, A.; Zhang, W.-G.; Yu, K. J. Med. Chem. 2009, 52, 7081.
22. Verheijen, J.; Richard, D. J.; Curran, K.; Kaplan, J.; Lefever, M.; Nowak, P.;
Malwitz, D. J.; Brooijmans, N.; Toral-Barza, L.; Zhang, W.-G.; Lucas, J.;
Hollander, I.; Ayral-Kaloustian, S.; Mansour, T.; Yu, K.; Zask, A. J. Med. Chem.
2009, 52, 8010.
In conclusion, we have shown that 5-ureidobenzofuranones are
attractive replacements for 4-hydroxybenzofuranones. Overlays of
co-crystal structures of PI3Kc with 4,6-dihydroxylbenzofuranone
1a and pyrazolopyrimidine 2 suggested a ureido replacement for
the 4,6-dihydroxy groups would be optimal at the 5-position.
Molecular modeling studies of 6h suggested that potentially three
hydrogen bonds can be formed between the urea group and the en-
zyme, and that these interactions were best achieved with the urea
appendage on the 5-position. An additional hydrogen bond inter-
action between the pyridyl nitrogen and the enzyme appears to
provide further enhancement of potency with 3-pyridylurea. Opti-
mization of the C-4 substituents on the azaindole led to discovery
of potent (low nanomolar) and selective (up to 132-fold) inhibitors
of mTOR, with good cellular activity (IC50 = 1.8–23 nM).
Acknowledgments
The authors thank Dr. Arie Zask for providing bridged morphol-
ines. We thank Drs. Tarek Mansour and Robert Abraham for sup-
porting this project. We are grateful to members of the Wyeth
Chemical Technologies group for analytical support.
23. Zask, A.; Kaplan, J.; Verheijen, J. C.; Richard, D. J.; Curran, K.; Brooijmans, N.;
Bennett, E. M.; Toral-Barza, L.; Hollander, I.; Ayral-Kaloustian, S.; Yu, K. J. Med.
Chem. 2009, 52, 7942.
24. Kaplan, J.; Verheijen, J. C.; Brooijmans, N.; Toral-Barza, L.; Hollander, I.; Yu, K.;
Zask, A. Bioorg. Med. Chem. Lett. 2009, 20, 640.
25. Tsou, H.-R.; MacEwan, G.; Birnberg, G.; Grosu, G.; Bursavich, M. G.; Bard, J.;
Brooijmans, N.; Toral-Barza, L.; Hollander, I.; Mansour, T. S.; Ayral-Kaloustian,
S.; Yu, K. Bioorg. Med. Chem. Lett., 2010, doi:10.1016/j.bmcl.2010.01.135.
26. King, L. C.; Ostrum, G. K. J. Org. Chem. 1964, 29, 3459.
Supplementary data
27. Joshi, S. S.; Singh, H. J. Am. Chem. Soc. 1954, 76, 4993.
28. Hillis, L. R.; Gould, S. J. J. Org. Chem. 1985, 50, 718.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.02.012.