Tetracyclic indole inhibitors of hepatitis C virus NS5B-polymerase

Article abstract of DOI:10.1016/j.bmcl.2008.12.068

We report the evolutionary path from an open-chain series to conformationally constrained tetracyclic indole inhibitors of HCV NS5B-polymerase, where the C2 aromatic is tethered to the indole nitrogen. SAR studies led to the discovery of zwitterionic comp

Full text of DOI:10.1016/j.bmcl.2008.12.068

Bioorganic & Medicinal Chemistry Letters 19 (2009) 627–632
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Tetracyclic indole inhibitors of hepatitis C virus NS5B-polymerase
a
a
a
a
Ian Stansfield a, , Caterina Ercolani , Angela Mackay , Immacolata Conte , Marco Pompei ,
*
Uwe Koch b, Nadia Gennari c, Claudio Giuliano d, Michael Rowley a, Frank Narjes a
a Department of Medicinal Chemistry, Istituto di Ricerche di Biologia Molecolare ‘‘P. Angeletti” S.p.A., Merck Research Laboratories Rome, 00040 Pomezia, Italy
b Department of Computational Science, Istituto di Ricerche di Biologia Molecolare ‘‘P. Angeletti” S.p.A., Merck Research Laboratories Rome, 00040 Pomezia, Italy
c Department of Pharmacology, Istituto di Ricerche di Biologia Molecolare ‘‘P. Angeletti” S.p.A., Merck Research Laboratories Rome, 00040 Pomezia, Italy
d Department of Drug Metabolism Discovery and Development, Istituto di Ricerche di Biologia Molecolare ‘‘P. Angeletti” S.p.A., Merck Research Laboratories Rome, 00040 Pomezia, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
We report the evolutionary path from an open-chain series to conformationally constrained tetracyclic
indole inhibitors of HCV NS5B-polymerase, where the C2 aromatic is tethered to the indole nitrogen.
SAR studies led to the discovery of zwitterionic compounds endowed with good intrinsic enzyme affinity
and cell-based potency, as well as superior DMPK profiles to their acyclic counterparts, and ultimately to
the identification of a pre-clinical candidate with an excellent predicted human pharmacokinetic profile.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 10 November 2008
Revised 12 December 2008
Accepted 14 December 2008
Available online 24 December 2008
Keywords:
Hepatitis C virus
NS5B-polymerase
Allosteric inhibitors
Tetracyclic indoles
Pre-clinical candidate
HCV is a major human pathogen associated with chronic hepa-
titis and liver disease, cirrhosis, hepato-cellular carcinoma and li-
ver failure,1 with worldwide, an estimated 170 million chronic
In this report we describe an alternative evolutionary path, from
an open-chain series to tetracyclic indoles, 3, where the C2 aro-
matic is tethered to the indole nitrogen, leading to the discovery
of compounds endowed with good cell-based activity and superior
DMPK profiles to their acyclic counterparts.
carriers.2 Frontline therapies are based around interferon-
a, com-
monly dosed in conjunction with ribavirin. Despite progress,
including introduction of pegylated interferon,3 sustained viral re-
sponse (SVR) rates are still poor—particularly for genotype-1 infec-
tions that predominate in Europe, Japan, and the U.S.4 In addition,
therapy is often accompanied by significant adverse side effects5—
consequently, there is a pressing need for new and broadly effec-
tive therapeutics to combat HCV.3,6
HCV is a small, enveloped, single stranded positive RNA virus in
the Flaviviridae family. NS5B is the viral RNA-dependent RNA poly-
merase (RdRp) that is essential for viral replication.7 With no func-
tional equivalent in uninfected mammalian cells, it is an attractive
target for drug discovery.8 Inhibition of NS5B can be achieved
through interaction at the active site, or at one of several allosteric
inhibitor binding sites located distal to the catalytic centre.9 Re-
ports from our laboratories have documented the development of
N-acetamidoindoles, such as 1 and 2, as potent inhibitors interact-
ing at allosteric site A lying close to a conserved amino acid, proline
495, on the surface of the thumb domain of the polymerase10–12
(Fig. 1).
The compounds described herein were assessed for activity
(IC50) against the purified
DC21 NS5B enzyme in the presence of
heterogenic template RNA. Inhibition of replication of subgenomic
HCV RNA was measured in HUH-7 cells using a modification of the
procedure of Bartenschlager13 (the so-called replicon assay). Un-
less otherwise stated, cell-based data (EC50) were measured in
the presence of 10% fetal calf serum.
The tetracyclic indoles reported herein were prepared as out-
lined in Schemes 1 and 2. Thus, for the most part the synthetic
strategy used standard chemistry,14 starting from methyl 2-bro-
mo-3-cyclohexylindole-6-carboxylate substrates 4 and 15,10 to af-
ford the cyclization pre-cursors 5, 17 and 21: alkylation to install
the appropriate side chain on the indole nitrogen, Suzuki cross-
coupling and, where necessary, manipulation of the ortho-func-
tionality. In the case of 5, following acetal deprotection, the
resultant reactive intermediate was not isolated. Dilution with
MeOH, adjusting the pH and reduction afforded the cyclic amine.
Conversion to the desired product 6 was by simple ester hydroly-
sis. Alternatively, isolation of the intermediate following deprotec-
tion of 5 allowed a Strecker reaction to give the cyclic
a-amino
nitrile. Nitrile reduction to the primary amine, reductive amination
and ester hydrolysis yielded 7. Of particular note is the chemistry
* Corresponding author. Tel.: +39 06 91093286; fax: +39 06 91093654.
E-mail address: ian_stansfield@merck.com (I. Stansfield).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.12.068

628
I. Stansfield et al. / Bioorg. Med. Chem. Lett. 19 (2009) 627–632
to assemble the tetracyclic cores 10 and 13. Following Suzuki cou-
pling and deprotection to yield ortho-aniline 9, reaction with
straints in the 7-membered system) prior to ester hydrolysis led
to cyclic amines 24.
a-
chloro methyl acrylate afforded solely indolobenzo-diazepinedi-
carboxylate regio-isomer 10—presumably via a selective conjugate
addition–cyclization cascade. Instead, triphenylphosphine cata-
The binding mode at allosteric site A of the indole (and related
benzimidazole) class has been well documented11,16 and is illus-
trated in Figure 2. Salient features include the C3 cyclohexyl ring
buried deep in a lipophilic pocket, the C2 phenyl rotated out of
the indole plane and occupying a lipophilic channel and a key elec-
trostatic interaction between the carboxylic acid and arginine 503.
The substituent on the indole nitrogen is oriented towards solvent
and as such offers a suitable handle for modulating physicochem-
ical properties. Similarly, whilst one ortho position on the C2 phe-
nyl moiety in (1) faces the lipophilic surface of the polymerase, the
other projects to solvent.
lyzed a a-acry-
-addition15 of indole 8 to methyl propiolate yielded
late 12, which, after Boc deprotection, could be induced to
participate in a conjugate addition to afford tetracyclic regio-iso-
mer 13 under the same conditions employed in the cascade reac-
tion above. In both cases, reductive amination to methylate the
anilinic nitrogen, side chain manipulation to install the basic
amine, and ester hydrolysis gave the final compounds 11 and 14.
For the benzylic cyclic amides, following deprotection of 17,
cyclization under standard amide bond forming conditions (or base
mediated for R2 = Me) and methyl ester cleavage with BBr3 affor-
ded the endocyclic amides 19. Reduction of 18 was an alternative
to give the corresponding cyclic amine, and for R = H afforded the
secondary amine suitable for accessing exocyclic amides 20. The
anilinic tetracycles were prepared in similar fashion from 21. Inter-
estingly, deprotection of 21 led to spontaneous ring closure afford-
ing 22 in the case of the 7-membered ring, whilst peptide coupling
conditions were required for the 8-membered homolog. N-Alkyl-
ation and ester cleavage gave cyclic amides 23. Facile reduction
of the cyclic amide (presumably aided by conformational con-
Thus, we and others17,18 have reasoned that it ought to be pos-
sible to improve intrinsic affinity for the binding site on the en-
zyme by constraining the C2 aromatic in the bound conformation
via tethering from the ortho position to the indole nitrogen. Our
analysis suggested that tethering to form either an 8- or a 7-mem-
bered ring would be suitable, and pleasingly (as illustrated by 25)
the entropic gain from tethering gave a 6-fold boost in biochemical
potency (Table 1). Activity in the cell-based assay, however, dete-
riorated by an order of magnitude. In this instance the reduced cel-
lular potency could likely be ascribed to raised affinity of 25 for
serum protein (human plasma protein binding (hPPB) 99.7%) with
NEt2
Chx = cyclohexyl
IC50 0.048 µM
EC50 0.18 µM
IC50 0.43 µM
N
N
N
EC50 1.54 µM
tether
O
O
HO2C
HO2C
HO2C
N
N
Cl
2
1
3
Chx
Chx
Chx
Figure 1. Acyclic N-acetamide and tethered indole inhibitors of HCV NS5B-polymerase.
NR
Ar
HO2C
N
OMe
N
6
NHR
Ar
MeO
d, e, f
Chx
H
N
MeO2C
MeO2C
Me2N
a, b, c
l
Br
NR
Ar
d, g, h, j, f
5
HO2C
4
N
Chx
Chx
7
Chx
k
R1=Boc
8
R1=H
9
m
CO2Me
NH
Me2N
j, n, o, p, f
NHR1
NMe
H
N
MeO2C
HO2C
MeO2C
MeO2C
N
N
10
11
Chx
Chx
Chx
q
MeO2C
MeO2C
Me2N
NHBoc
NH
NMe
MeO2C
l, r
HO2C
j, n, o, p, f
N
N
N
12
13
14
Chx
Chx
Chx
Scheme 1. Reagents and conditions: (a) NaH, BrCH2CH(OMe)2, KI (cat), DMF, 60 °C, 79%; (b) Pd(PPh3)2Cl2, Na2CO3 (aq), (2-formylaryl)boronic acid, 1,4-dioxane, reflux, 85–
95%; (c) i—H2NR, AcOH (cat), THF; ii—NaBH4, MeOH, 85–100%; (d) 3 N HCl (aq), THF, 60 °C; (e) pH 5–6; NaBH4, MeOH; (f) i—NaOH (aq), MeOH, 60 °C; ii—RP-HPLC, 20–50%; (g)
KCN, H2O, MeCN, pH 5, 65%; (h) PtO2, H2, 50 psi, AcOH (1 equiv), EtOH, 75%; (j) CH2O, NaBH(OAc)3, DCE, 72–80%; (k) Pd(PPh3)2Cl2, Na2CO3 (aq), tert-butyl [2-(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-carbamate, 1,4-dioxane, reflux, 95%; (l) CF3CO2H, CH2Cl2, H2O, 57–70%; (m) methyl a-chloro acrylate, K2CO3, BnEt3NCl, MeCN,
60 °C, 75%; (n) LiOH (aq), THF, MeOH, 81%; (o) TBTU, iPr2NEt, HNMe2, CH2Cl2, 70–80%; (p) BH3ÁDMS, THF, 70–80%; (q) PPh3, methyl propiolate, CH2Cl2, 80%; (r) K2CO3,
BnEt3NCl, MeCN, 60 °C, 53%.

I. Stansfield et al. / Bioorg. Med. Chem. Lett. 19 (2009) 627–632
629
tBuO2C
tBuO2C
tBuO2C
CHO
n NHBoc
n
n
MeO2C
MeO2C
MeO2C
N
N
N
a
j
Br
16
15
Chx
Chx
Chx
21
n=1; c
n=2; c, g
b
OR2
O
NHR
O
NH
n
n
MeO2C
MeO2C
N
N
a, l
X
4
X=F; R=Boc
Chx
O
Chx
22
17
R2=tBu R2=Me
R
c, d c, m
N
n
R3O2C
R3=Me
18
19
N
e
k, f, h
k, e
R3=H
X
Chx
O
NMe2
f, g, e
O
N
NR
NR
n
n
HO2C
N
HO2C
HO2C
N
N
X
20
23
24
Chx
Chx
Chx
Scheme 2. Reagents and conditions: (a) Pd(PPh3)2Cl2, Na2CO3 (aq), (aryl)boronic acid, 1,4-dioxane, reflux, 53–84%; (b) i—H2NR, AcOH (cat), THF; ii—NaBH3CN, MeOH, 88–
95%; (c) CF3CO2H, CH2Cl2, 53–100%; (d) HATU, iPr2NEt, CH2Cl2, 98%; (e) i—BBr3, CH2Cl2; ii—RP-HPLC, 20–50%; (f) BH3ÁDMS, THF, 80–83%; (g) TBTU, iPr2NEt, RCO2H, CH2Cl2, 70–
80%; (h) i—NaOH (aq), MeOH, 60 °C; ii—RP-HPLC, 20–50%; (j) Pd(PPh3)2Cl2, Na2CO3 (aq), tert-butyl [2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-carbamate, 1,4-
dioxane, reflux, 60–95%; (k) NaH, RX, DMF, 73–90%; (l) BrCH2CO2Me; K2CO3, DMSO, 60 °C, 70%; (m) NaOMe, MeOH, 100%.
Interestingly, exocyclic amide analog 29 is essentially equipo-
tent to 26. Considering calculated pKa values,19 this suggests that
a strongly basic amine is not required for cell-based activity.
Rather, a less basic centre will suffice so long as a significant per-
centage of the protonated species exists at physiological pH. Sub-
stitution of the C2 aromatic afforded incremental improvements
in intrinsic enzyme affinity and cell-based activity (e.g., 30).
Given the projection of the tether moiety itself into solvent, we
believed it ought to be possible to generate a zwitterionic species
and improve cell-based activity by moving from an amide (25) to
an amine linker (31). Pleasingly, combining the basic centre and
the conformational constraint in a single structural motif (form
and function) was not only tolerated with regard to enzyme affin-
ity, but afforded sub-lM cell-based activity (Table 2). Para-meth-
oxy substitution of the aryl at C2 (32), afforded a further 3-fold
boost in both intrinsic and replicon potency—providing, for the
first time, simplified structures with activity to rival 2 and 26.
Introduction of a distal amine to the aminotetracycle core (33,
36, 11, and 37) gave a further 6- to 7-fold potency boost and con-
solidated cell-based activity in the 100 nM range—with 33 offering
the advantage of not introducing a chiral branch point to the
tether. Substitution on the C2 aromatic in this class provided at
best incremental gains in replicon activity (e.g., 34). Consistent
with our earlier predictions and results, 33 and its counterpart in
the 7-membered ring series 36 are essentially equipotent. Interest-
ingly, data for hybrid anilinic 8-membered tetracycle 35 is more in
keeping with what has been reported elsewhere in the litera-
ture17—the compound losing potency with regard to 33 and 36.
In addition, 14 would suggest that branching alpha to the indole
nitrogen is not tolerated.
The PK properties for potent tetracyclic indoles (30, 32, and 33)
are summarized in Table 3, alongside acyclic N-acetamide 2 for
comparison. As mentioned above, the structural simplicity of 32
made it particularly attractive—indeed this simplicity may well
contribute to its excellent PK properties in pre-clinical species also.
Ultimately, however, cell-based potency focused attention on com-
pounds 30 and 33.
Figure 2. Superimposition of tetracyclic 25 and acyclic indole N-acetamide 1,
docked in the allosteric inhibitor binding site.
respect to 1 (hPPB 97.1%). Previously in the indole class, zwitter-
ionic species have been found to exhibit reduced PPB and im-
proved cell permeability over related non-zwitterionic systems—
enhancing cell-based activity. Accordingly, introduction in 26 of a
distal basic centre improved activity in the replicon assay by close
on 2 orders of magnitude. With in vitro and cell-based activity in
hand, the 7- and 9-membered cyclic analogs were prepared for
comparison. Modelling predicted the dihedral angle between the
plane of the indole and the C2 phenyl for the 7- and 8-membered
rings (Ucalc 48° and 56°, respectively) to be in line with the enzyme
bound conformation11
(U 51°), whilst the 9-membered ring di-
verges (Ucalc 73°). In agreement with the prediction, 28 shows sig-
nificantly reduced affinity on the isolated enzyme and 26, 27 both
show good (and equivalent) levels of activity. The observation that
these 8- and 7-membered tetracyclic amides are equipotent is in
contrast to what has been reported to date for tetracyclic in-
doles—where a clear preference for 7- over 8-membered systems
has been noted.17 Cell-based activity proved better for 26 and we
report here data primarily from the 8-membered ring class.

630
I. Stansfield et al. / Bioorg. Med. Chem. Lett. 19 (2009) 627–632
Table 1
Table 2
Tetracyclic indole amides versus acyclic indole 1
Aminotetracycle indole inhibitors of HCV polymerase
a
a
Compound Structure
IC50/EC50
M)
Amine
pKa calc
Compound Structure
IC50/EC50
M)
Amine
pKa calc
19
19
(
l
(l
NMe
NMe
O
NMe2
N
O
O
HO
31
0.17/0.89
0.055/0.29
0.027/0.14
8.0
8.1
1
0.43/1.54
0.08/18.9
0.11/0.26
0.13/0.41
0.86/1.44
0.13/0.22
0.06/0.17
—
N
HO
Chx
Chx
O
O
N
HO
32
NMe
O
OMe
Chx
25
26
27
28
29
30
N
—
HO
NMe2
N
N
O
Chx
33
9.2/9.5c
N
HO
NMe2
O
Chx
N
O
O
NMe2
OMe
8.9
8.9
8.9
7.8
7.8
N
HO
HO
O
N
34
35
0.035/0.10
0.077/0.54
9.2
HO
HO
Chx
Chx
O
NMe2
N
O
O
N
NMe2
N
N
8.8
Chx
Chx
O
N
NMe2
NMe2
N
O
N
N
HO
HO
36
0.028/0.13
1.92/13.5
0.043/0.16
0.035/0.14
8.8
9.0
9.0
8.9
HO
Chx
Chx
O
N
NMe2
Me2N
O
O
O
NMe
O
O
14b
N
N
HO
HO
Chx
Chx
Me2N
O
N
NMe2
NMe
NMe
11b
N
HO
HO
N
Chx
F
Chx
IC50/EC50 values are the mean from at least two experiments, standard
Me2N
a
deviation 20%.
37b
N
Chx
IC50/EC50 values are the mean from at least two experiments, standard
In general, compounds in this class have been found to be
cleared mainly by metabolism, with only minimal biliary and renal
excretion of intact drug. Thus, it was judged reasonable to extrap-
olate human PK predictions based on data from pre-clinical species
and relative intrinsic metabolic stability in vitro. The relative rank
order across species of intrinsic clearance (Clint) was seen as a more
reliable means of comparing compounds than absolute Clint values,
as it is known that compounds from this class are highly bound to
microsomal protein.20 This carries a number of provisos, not least
that for a given compound there is a similar significant percentage
a
deviation 20%.
b
Racemic mixture.
Measured value.
c
unbound to plasma protein across species. In this regard, ca. 2% 30
is unbound in PPB (rat, dog, human), whilst values for 33 are 3–4%
(dog, human) and 7% in rat.

I. Stansfield et al. / Bioorg. Med. Chem. Lett. 19 (2009) 627–632
631
Table 3
In vivo and in vitro pharmacokinetic properties for indole inhibitors of the HCV NS5B-polymerase
Compound
Speciesa
Fb (%)
AUCdose (mpk)
(
l
M h)
Clpc (ml/min/kg)
44
Clintd (ml/min/kg)
r, d, rh, h
2
32
30
33
a
Rat
10
0.23
Rat
Dog
83
67
2.93
18.72
32
2.9
43, 6, 16, 7
16, 8, 42, 13
100, 26, 51, 5
Rat
Dog
48
83
4.03
17.62
12
3.0
Rat
Dog
Rhesus
31
74
57
4.215
232
2.02
61
2.5
22
Compounds were dosed as HCl or trifluoroacetate salts; n = 3. Vehicle iv 20% DMSO/60% PEG400/20% H2O; po PEG400.
Oral bioavailability.
Plasma clearance.
b
c
d
Intrinsic clearance in liver microsomes from rat (r), dog (d), rhesus (rh), human (h), incubated in the presence of NADPH.
Figure 3. HPLC-radiochromatograms of [3H]-33 after 4 h incubation with human and dog hepatocytes.
Compounds 30 and 33 have moderate to good oral bioavailabil-
protein in the presence of NADPH and no propensity to prolong
the QT interval in anesthetized dogs (escalating dose up to
10 mpk).
ity in the rat, with good systemic exposure attainable. Although
clearance of 33 in rat was relatively high, the compound was found
to be dose proportional. Furthermore, elevated compound concen-
trations (liver/plasma ratio = 16 for 33; 8 for 30) were found in rat
liver 6 h after oral administration (encouraging when considering
liver is the target organ for an anti-HCV agent). In dog, both 30
and 33 showed excellent PK profiles with low clearance, high oral
bioavailability and systemic exposure, and a plasma half-life of
over 5 h. Discriminating on the basis of relative metabolic stability
singled out 33 for further profiling. Human PK for 33 would be ex-
pected to be even better than that seen in dog, whilst 30 would be
predicted to be worse. Stability in hepatocytes supported relative
Clint data, with 33 showing the same rank order of stability across
species and proving appreciably more stable in human prepara-
tions (Fig. 3).
In summary, we have described the development of tetracyclic
indoles, where the C2 aromatic is tethered to the indole nitrogen as
part of an 8-membered ring, that are potent allosteric inhibitors of
the HCV NS5B enzyme. Optimization furnished zwitterionic inhib-
itors that show potency in the blockade of subgenomic HCV RNA
replication in HUH-7 cells. PK profiling of potent analogs from
three diverse classes (30, 32 and 33) showed good to excellent
PK properties in pre-clinical species. Compound 33 was advanced
on the basis of a superior predicted human PK profile. Further char-
acterization showed 33 to be clean in an extensive panel of count-
erscreening assays. On the basis of these data, 33 progressed as a
pre-clinical candidate.
Significantly, following oral dosing, 33 was cleared mainly by
metabolism, with only minimal excretion of intact drug (rat urine
1%, bile 4%; dog urine <1%). The main oxidative metabolic path-
ways for 33 were found to be cyclohexyl hydroxylation (CYP3A4
mediated), N-demethylation (CYP3A4, 2D6 mediated). Taken as a
whole, these data lead to an excellent predicted human PK profile
for 33 that is similar or, more probably, superior to that deter-
mined in dog.
Acknowledgments
We thank Fabrizio Fiore for PK data and Marina Taliani for PPB
determinations; Renzo Bazzo, Silvia Pesci, Fabio Bonelli for analyt-
ical work and Sergio Altamura, Monica Bisbocci, Ottavia Cecchetti
and Sue Ellen Vignetti for biological testing. This work was funded
in part by a grant from the MIUR.
Compound 33 was characterized further and showed no activity
References and notes
(at 10
thermore, there was no significant inhibition of CYP3A4, 2D6 and
2C9 up to 100 M and no evidence of time dependent inhibition
of CYP3A4 in human liver microsomes. Overall, this suggests 33
has little potential to cause drug–drug interactions or autoinduc-
tion of metabolism in humans. The compound also showed no
inhibition of human DNA polymerases and no significant off-target
activities in extensive counterscreening efforts.21 Lastly, 33 had
low potential for covalent binding to rat and human microsomal
lM) in human PXR-dependent reporter gene assays. Fur-
1. Wong, T.; Lee, S. S. CMAJ 2006, 174, 649.
2. WHO. Hepatitis C Fact Sheet No. 164. Rev. October, 2000.
3. Hayashi, N.; Takehara, T. J. Gastroenterology 2006, 41, 17.
4. Dymock, B. W. Emerg. Drugs 2001, 6, 13.
l
5. Fried, M. W. Hepatology 2002, 36, S237.
6. Davis, G. L.; Lindsay, K. L. Lancet Infect. Dis. 2005, 5, 524.
7. Appel, N.; Schaller, T.; Penin, F.; Bartenschlager, R. J. Biol. Chem. 2006, 281, 9833.
8. Walker, M. P.; Hong, Z. Curr. Opin. Pharmacol. 2002, 2, 534.
9. (a) Koch, U.; Narjes, F. Curr. Top. Med. Chem. 2007, 7, 1302; (b) Kwong, A. D.;
McNair, L.; Jacobsen, I.; George, S. Curr. Opin. Pharmacol. 2008, 8, 522; (c)
Beaulieu, P. L. Curr. Opin. Investig. Drugs 2007, 8, 614.

632
I. Stansfield et al. / Bioorg. Med. Chem. Lett. 19 (2009) 627–632
10. Harper, S.; Pacini, B.; Avolio, S.; Di Filippo, M.; Migliaccio, G.; Laufer, R.; De
Francesco, R.; Rowley, M.; Narjes, F. J. Med. Chem. 2005, 48, 1314.
11. Harper, S.; Avolio, S.; Pacini, B.; Di Filippo, M.; Altamura, S.; Tomei, L.; Paonessa,
G.; Di Marco, S.; Carfi, A.; Giuliano, C.; Padron, J.; Bonelli, F.; Migliaccio, G.; De
Francesco, R.; Laufer, R.; Rowley, M.; Narjes, F. J. Med. Chem. 2005, 48, 4547.
12. Concomitant studies on allosteric N-acetamido-indole inhibitors have been
described: Beaulieu, P. L.; Gillard, J.; Bykowski, D.; Brochu, C.; Dansereau, N.;
Duceppe, J.-S.; Hache, B.; Jakalian, A.; Lagace, L.; LaPlante, S.; McKercher, G.;
Moreau, E.; Perreault, S.; Stammers, T.; Thauvette, L.; Warrington, J.; Kukolj, G.
Bioorg. Med. Chem. Lett. 2006, 16, 4987.
15. Yavari, I.; Norouzi-Arasi, H. Phosphorus, Sulfur Silicon 2002, 177, 87.
16. LaPlante, S.; Jakalian, A.; Aubry, N.; Bousquet, Y.; Ferland, J.-M.; Gillard, J.;
Lefebvre, S.; Poirier, M.; Tsantrizos, Y. S.; Kukolj, G.; Beaulieu, P. L. Angew.
Chem., Int. Ed. 2004, 43, 4306.
17. Ikegashira, K.; Oka, T.; Hirashima, S.; Noji, S.; Yamahaka, H.; Hara, Y.; Adachi,
T.; Tsuruha, J.-I.; Doi, S.; Hase, Y.; Noguchi, T.; Ando, I.; Ogura, N.; Ikeda, S.;
Hashimoto, H. J. Med. Chem. 2006, 49, 6950.
18. Hirashima, S.; Oka, T.; Ikegashira, K.; Noji, S.; Yamanaka, H.; Hara, Y.; Goto, H.;
Mizojiri, R.; Nima, Y.; Noguchi, T.; Ando, I.; Ikeda, S.; Hashimoto, H. Bioorg. Med.
Chem. Lett. 2007, 17, 3181.
13. Lohmann, V.; Korner, F.; Koch, J.; Herian, U.; Theilmann, L.; Bartenschlager, R.
Science 1999, 285, 110.
14. See: Ercolani, C.; Habermann, J.; Narjes, F.; Ponzi, S.; Rowley, M.; Stansfield, I.
WO2006/046039. Conte, I.; Ercolani, C.; Narjes, F.; Pompei, M.; Rowley, M.;
Stansfield, I. WO2006/046030.
19. pKa calc for most basic centre calculated using ACDlabs 8.0.
20. Giuliano, C.; Jairaj, M.; Zafiu, C.; Laufer, R. Drug Metab. Dispos. 2005, 33, 1319.
21. MDS Pharma Services Taiwan Ltd, Pharmacology Labs, 158 Li-The Road, Peitou,
Taipei, Taiwan 112, ROC.