Toward the back-up of Boceprevir (SCH 503034): Discovery of new extended P4-capped ketoamide inhibitors of hepatitis C virus NS3 serine protease with improved potency and pharmacokinetic profiles

Article abstract of DOI:10.1021/jm801632a

Hepatitis C is the most prevalent liver disease. Viral hepatitis C (HCV), a small (+)-RNA virus, infects chronically an estimated 300 million people worldwide. Results of Phase I clinical studies with our first generation HCV inhibitor Boceprevir, SCH 503034 (1), presented at the 56th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) were encouraging, and thus, additional human clinical studies are underway. In view of the positive data from our first generation compound, further work aimed at optimizing its overall profile was undertaken. Herein, we report that extension of our earlier inhibitor to the P₄ pocket and optimization of the P₁′ capping led to the discovery of new ketoamide inhibitors of the HCV NS3 serine protease with improved in vitro potency. In addition to being potent inhibitors of HCV subgenomic RNA replication, some of the new P₄-capped inhibitors were also found to have improved PK profile.

Full text of DOI:10.1021/jm801632a

J. Med. Chem. 2009, 52, 3679–3688
3679
Toward the Back-Up of Boceprevir (SCH 503034): Discovery of New Extended P4-Capped
Ketoamide Inhibitors of Hepatitis C Virus NS3 Serine Protease with Improved Potency and
Pharmacokinetic Profiles
Ste´phane L. Bogen,* Weidong Pan, Sumei Ruan, Latha G. Nair, Ashok Arasappan, Frank Bennett, Kevin X. Chen, Edwin Jao,
Srikanth Venkatraman, Bancha Vibulbhan, Rong Liu, Kuo-Chi Cheng, Zhuyan Guo, Xiao Tong, Anil K. Saksena,
Viyyoor Girijavallabhan, and F. George Njoroge
Schering Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, New Jersey 07033
ReceiVed December 22, 2008
Hepatitis C is the most prevalent liver disease. Viral hepatitis C (HCV), a small (+)-RNA virus, infects chronically
an estimated 300 million people worldwide. Results of Phase I clinical studies with our first generation HCV
inhibitor Boceprevir, SCH 503034 (1), presented at the 56th Annual Meeting of the American Association for
the Study of Liver Diseases (AASLD) were encouraging, and thus, additional human clinical studies are underway.
In view of the positive data from our first generation compound, further work aimed at optimizing its overall
profile was undertaken. Herein, we report that extension of our earlier inhibitor to the P4 pocket and optimization
of the P1′ capping led to the discovery of new ketoamide inhibitors of the HCV NS3 serine protease with improved
in vitro potency. In addition to being potent inhibitors of HCV subgenomic RNA replication, some of the new
P4-capped inhibitors were also found to have improved PK profile.
Introduction
Hepatitis C is the most prevalent liver disease. Viral hepatitis
C (HCVa), a small (+)-RNA virus, infects chronically an
estimated 300 million people worldwide. HCV displays genetic
heterogeneity with the genotype 1 being most common in the
U.S., Europe, and Japan, and the most challenging to eradicate.
Untreated HCV infections can progress to cirrhosis, hepatocel-
lular carcinoma, and liver failure, a primary cause for liver
transplantation.1 Subcutaneous and intramuscular injections of
R interferons (immune system booster) have been used since
Figure 1. Profile of 1 (SCH 503034).
the late 1980s in the treatment of chronic hepatitis C. Currently,
tive inhibitor of the HCV NS3 serine protease.6 Derivatives
PEGylated-interferon in combination with antiviral drug rib-
containing an R-ketoamide electrophilic trap have been reported
by our group7 and others8 to be potent inhibitors of HCV NS3
serine protease. Recently, we published our work that led to
the identification of our first generation clinical candidate
Boceprevir, (1R,5S)-N-[3-amino-1-(cyclobutylmethyl)-2-3-di-
oxopropyl]-3-[2(S)-[[[(1,1-dimethylethyl)-amino]carbonyl]amino]-
3,3-dimethyl-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]hexane-
2(S)-carboxamide (SCH 503034), 1 (Figure 1).9 Clinical
candidates (1S,3aR,6aS)-2-((S)-2-((S)-2-cyclohexyl-2-(pyrazine-
2-carboxamido)acetamido)-3,3-dimethylbutanoyl)-N-((S)-1-(cy-
clopropylamino)-1,2-dioxohexan-3-yl)octahydrocyclopenta[c]pyr-
role-1-carboxamide (VX950) and 1 belonging to the R-ketoamide
series established proof-of-concept in the aforementioned stud-
ies.10 Recently, several other NS3 protease inhibitors have been
advanced to clinical trial.11 Results of phase I clinical studies
with 1, presented at the 56th Annual Meeting of the American
Association for the Study of Liver Diseases (AASLD) in
November 2005, were encouraging.12 The drug was rapidly
absorbed, well tolerated, and demonstrated potent antiviral
activity, both as monotherapy and in combination with peginter-
feron R-2b. Phase II clinical studies of 1 are still underway,
and phase III trials have been initiated. Consequently, further
work aimed at optimizing the overall profile of our first
generation inhibitor was undertaken.
avirin has brought the rate of sustained virological response to
approximately 50% in patients infected with the genotype 1.2
Although the use of R interferons is an integral component in
the management of chronic hepatitis C infection, major adverse
events can occur and subsequently result in dose reduction or
discontinuation of treatment. Thus, several research groups have
been working toward development of a more effective, conve-
nient, and tolerable treatment.3
Upon entering a liver cell, the hepatitis C virus dissociates,
liberating the viral RNA genome. The HCV genome serves as a
template for cap-independent translation through an internal ribo-
some entry (IRES) located in the 5′ untranslated region. The
resulting polyprotein undergoes both co- and post-translational
proteolytic maturation by host and virally encoded proteases. The
NS3 serine protease, a pivotal enzyme required for maturation of
hepatitis C virons, assists in processing of the HCV polyprotein
by cleaving four downstream sites. Because of its central role in
viral replication,4 inhibition of HCV NS3 serine protease has been
actively pursued as target for antiviral therapy.5
The Boehringer Ingelheim group was the first one to report
phase Ib clinical antiviral efficacy with BILN 2061, a competi-
* To whom correspondence should be addressed. Phone: 908-740-4642.
Fax: 908-740-7152. E-mail: stephane.bogen@spcorp.com.
a Abbreviations: HCV, hepatitis C virus; DM periodinane, Dess-Martin’s
periodinane; Cys159, cysteine159; C6h, liver concentration at 6 h.
While investigating the P3 capping SAR that led to the
discovery of 1, we noticed that incorporation of the larger
10.1021/jm801632a CCC: $40.75
2009 American Chemical Society
Published on Web 05/20/2009

3680 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12
Bogen et al.
Table 1a
Figure 2. Profile of 2.
hydrophobic moiety in 2 (Figure 2) achieved improvement both
in enzyme and in cellular activity compared to 1.
Exploring the scope of the 1-substituted-cyclohexyl ureas
series, we discovered that incorporation of a benzyl ester moiety
provided a dramatic improvement of the cell potency (Table 1,
compound 20, EC90 ) 20 nM) compared to 1. Herein, we report
our finding that led to the discovery of new P4 extended
ketoamide inhibitors of the HCV NS3 serine protease with
improved potency and DMPK properties.
Chemistry. Synthesis of the inhibitors was generally carried
out as depicted in Scheme 1. The gem-dimethylcyclopropylproline
P2 core 3 was known to be essential for potency and was used to
prepare the Boc-protected P3 amino acid, dipeptide 4 according
previously described protocols.9b With the goal of exploring the
P4 area, we identified 6 as a key intermediate. Thus, acid 4 was
coupled with the appropriate P1 hydroxyamides 5 following
standard HATU coupling methodology. Oxidation of primary
hydroxyamide and secondary hydroxyamide moieties was ac-
complished using Moffatt and Dess-Martin conditions, respec-
tively.13 After Boc removal, intermediate 6 was reacted with
isocyanates of type
7 to efficiently deliver targets of
type 8.
The various capping moieties were prepared according to the
general procedures outlined in Scheme 2. Esterification of
protected amino acid 9 bearing the desired functionality R4
proceeded smoothly using EDCI and 4-DMAP to yield struc-
tures of type 10. Standard HATU coupling delivered corre-
sponding amides of type 11. Ketones of type 12 were prepared
by reacting various Grignard or organolithium reagents with
the appropriate Weinreb amide. Finally, Boc removal from
intermediates 10-12 and subsequent treatment of the amine salts
with phosgene in aqueous sodium bicarbonate led to the
corresponding isocyanates of type 7 that were needed for P4
capping exploration.
Derivatization of ketone 13 was accomplished according to
Scheme 3. The alkene analogue 14 was prepared from 13 using
a Peterson olefination.14 Sodium borohydride reduction in
MeOH generated the benzylic alcohol 15 that was further
hydrogenated to 16 using Pd/C. Phenyl ketone 13 was reacted
with O-methylhydroxylamine in pyridine to provide oximes 17
as a mixture of isomers. Isocyanates 18 were prepared from
their corresponding HCl or TFA salt following the aforemen-
tioned conditions.
a Ki* value represents binding for a mixture of diastereomers at P1 and
within 2-fold for 95% confidence limit; Replicon (genotype 1) EC90 value
is within 3-fold for 95% confidence (single assay) and within 2-fold for
95% confidence (multiple assays). b P1 cyclobutylalanine.
Discussion
Inhibitors listed in Tables 1,3-5 were tested in continuous
assay using the NS4A-tethered single chain NS3 serine pro-
tease.15 HCV replicon inhibitory activity for the targets syn-
thesized was obtained using previously reported assay.16 As a
general trend, compounds listed in Tables 1,3-5 had GAPDH
CC50 > 5 µM when tested in counter screen measuring cellular
toxicity and maintained good selectivity vs HNE similar to
previously reported inhibitors.9b We evaluated our initial set of
P4 extended inhibitors 19-32 listed in Table 1 by varying the
R1 moieties. The P1 was kept constant as a cyclopropyl or
cyclobutyl alanine residue. as these two motifs previously
provided similar binding potencies. The tert-Leucine moiety,
which was previously optimized as a P3 surrogates, was used
during that entire study.9b As reported earlier, the nature of P3
capping could greatly influence the enzyme activity. While
investigating newer substitutions, we observed that the use of

Toward the Back-Up of BocepreVir (SCH 503034)
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12 3681
Scheme 3a
Table 2. Full Rat and Monkey Pharmacokinetic Properties of Inhibitor
20a
rat
monkey
AUC (PO)
AUC (IV)
t1/2 (IV)
Cl
Vd(ss)
F (PO)
0
0.05
3.4
3.1
43
1.7
3
9.3
2.9
28
3.5
0
a AUC(µM·h); t1/2 (h); Cl(mL/min/kg); Vd(ss) (L/kg); F (%); rat PO and
IV were dosed at 10 mpk, 3 animals; monkey PO and IV were dosed at 3
mpk, 3 animals; vehicle: rat IV (40%HPBCD); monkey IV (20%HPBCD);
rat and monkey PO (0.4%MC).
a Reaction conditions: (a) (i) TMSCH2MgCl, THF, 0 °C; (ii) KHMDS,
THF, 0 °C; (iii) 4 M HCl p-dioxane, RT. (b) (i) NaBH4, MeOH, 0 °C (R
) OH); (ii) H2, MeOH, 10%Pd/C, RT (R ) H); (iii) 4 M HCl p-dioxane,
RT. (c) (i) MeONH2.HCl, pyridine, 50 °C; (ii) 50% TFA in CH2Cl2, RT.
(d) Phosgene, NaHCO3, H2O /CH2Cl2, 0 °C.
Scheme 1a
of the improved cell potency, we quickly explored the SAR of
this new series and we identified additional esters that showed
low EC90 in the replicon assay (Table 1, compound 21-23).
Aromatic moieties seemed essential for improvement in potency,
whereas alkyl esters were less potent (Table 1, compound 24,
25). Modification of the benzyl ester moiety to a benzyl ether
26 and benzoyl ester 27 resulted in a significant loss in cellular
activity. Although the carbonyl group seemed to be required
for potency, phenyl ketone 28 (Ki* ) 100 nM) showed weak
enzyme activity and cell potency. Benzyl amide 29 was also
found to be less active. The rat and monkey pharmacokinetic
properties of inhibitor 20 were investigated, and the data is
summarized in Table 2. Clearance values reported for compound
20 indicated moderate metabolic stability in rat but low in
monkey (rat Cl ) 28 mL/min/kg, monkey Cl ) 43 mL/min/
kg). Cynomolgus monkeys (n ) 2) were dosed at 2 mg/kg PO
with the 14C ketoamide of 20. There was no observed radioac-
tivity for the plasma sample. The (0-24 h) recovery of
radioactivity (% of oral dose) was 4.3% in bile and 0.8% in
urine. Furthermore, the major response in bile was generated
by the ester hydrolysis metabolite 30. Unfortunately, while
retaining good enzyme potency (Ki* ) 9 nM), the carboxylic
acid 30 completely lacked activity in cell assay (EC90 ) 5 µM),
conceivably due to poor cell penetration. Carboxylic acid
isostere 31 was prepared, but the acid sulfonamide showed weak
enzyme potency and poor activity in cell (Ki* ) 110 nM, EC90
) 5 µM). Hindered ester 32 (Ki* ) 80 nM, EC90 ) 600 nM)
was synthesized in an attempt to improve pharmacokinetics
properties. Unfortunately, introduction of steric bulk at the
benzylic position, primarily architectured to prevent hydrolysis,
led to a decrease in both enzyme and cell potency.
a Reaction conditions: (a) (i) Boc-t-leucine, EDC, HOOBt; DMF/CH2Cl2,
iPr2NEt, 0 °C; (ii) LiOH, THF ·MeOH/H2O, 0 °C; (b) (i) HATU, DMF,
DIPEA, -20 °C; (ii) Cl2CO2H, EDCI ·HCl, DMSO, 0 °C (R′ ) H);
Dess-Martin periodinane, RT (R′ ) alkyls); (iii) 4 M HCl; p-dioxane, RT;
(c) CH2Cl2, iPr2NEt, 0 °C.
Scheme 2a
The improved cellular activity demonstrated by compound
20 in comparison to 1 prompted us to further investigate the
SAR of various P4 residues. Compounds prepared to evaluate
this effect are outlined in Table 3. Regarding spirocycloalkyl
series, compounds with the larger ring sizes such as compounds
20 and 33 had optimal potency, whereas those with smaller ring
sizes such as spirocyclopropyl analogue 34 (Ki* ) 170 nM and
EC90 ) 1000 nM) lost potency. Incorporation of 2-aminoisobu-
tyric acid as the P4 residue resulted in compound 35 with Ki*
) 210 nM, a similar activity to derivative 34. Inhibitors 36 (Ki*
) 290 nM) and 37 (Ki* ) 44 nM) having D and L R methyl
valine were used to establish which stereochemistry at P4 was
required for activity. Further evaluation of the P4 residues
was done by using various L amino acids; incorporation of
L-valine provided 38 (Ki* ) 13 nM and EC90 ) 35 nM), a
potent inhibitor in both enzyme and replicon assay. The
a Reaction conditions: (a) EDCI, 4-DMAP, ROH, 0 °C; (b) HATU, DMF,
DIPEA, R’NH2, -20 °C. (c) (i) EDCI, NMM, HCl ·HN(OMe)Me, CH2Cl2,
0 °C; (ii) R′′MgBr or R′′MgCl or R′′Li, Et2O or THF, -78 °C. (d) (i) 4 M
HCl p-dioxane, RT; (ii) phosgene, NaHCO3, H2O /CH2Cl2, 0 °C.
1-methyl-cyclohexyl urea as a P3 capping group in inhibitor 19
boosted further the enzyme and replicon activity by 2-fold
compared to 1. While exploring the scope of the 1-substituted-
cyclohexyl ureas, we discovered that the incorporation of a
benzyl ester moiety provided inhibitor 20 with a dramatic 10-
fold improvement in cell potency (EC90 ) 20 nM) compared
to 19. Inhibitor 20 was the first of its class to show such
enhanced activity in the replicon assay. PAMPA permeability
of similar analogues was recently disclosed in a communication
and seemed to correlate well with cellular activity.17 Because

3682 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12
Bogen et al.
Table 3a
Table 4a
a Ki* value represents binding for a mixture of diastereomers at P1 and
within 2-fold for 95% confidence limit; Replicon (genotype 1) EC90 value
is within 3-fold for 95% confidence (single assay) and within 2-fold for
95% confidence (multiple assays). b Not tested (nt).
a Ki* value represents binding for a mixture of diastereomers at P1 and
within 2-fold for 95% confidence limit; replicon (genotype 1) EC90 value
is within 3-fold for 95% confidence (single assay) and within 2-fold for
95% confidence (multiple assays). b Not tested (nt).
bulkier tert-butyl group in inhibitor 39 (Ki* ) 67 nM) was
detrimental to the enzyme activity. We further probed the
P4 region, and we discovered that small L-cycloakyls amino
acids were well tolerated. Thus, incorporation of cyclopropyl,
cyclopentyl, and cyclohexyl glycine resulted in inhibitors 40,
41, and 42, respectively, with improved enzyme and cell
potency. In summary, SAR studies of P4 groups identified
L-valine and L-cycloakyls amino acids as optimal substituent
that provided improved enzyme binding as well as cellular
activity. Commercially available L-valine and L-cyclohexyl
glycine were used to further investigate SAR, and the results
are outlined in Tables 4 and 5.
As observed in the spirocyclohexyl P4 series, introduction of
steric bulk at the benzylic position in compound 43 led to a
17-fold decrease in cell potency compare with 38. The acid
sulfonamide 44 (Ki* ) 6 nM) was also prepared with L-valine
at P4 and provided 18-fold improvement in enzyme potency
compared to 31 (Ki* ) 110 nM), but cell potency remained
poor (EC90 ) 5 µM). Tetrazole analogue 45 was made but like
the other carboxylic acid isostere previously evaluated, it
exhibited excellent enzyme potency but weak replicon activity
(Ki* ) 10 nM, EC90 ) 1 µM). In contrast with the spirocyclo-
hexyl P4 series, incorporation of a phenyl ketone in the L-valine
series yielded inhibitor 46 with more than 20-fold improvement
in both enzyme and replicon activity when compared to
compound 28. In addition to good potency, inhibitor 46 also
showed some exposure after oral administration in rats (AUC
) 0.26 µM.hr). Simple modifications of the ketone moiety
demonstrated that this functional group was essential for activity
with compounds 47-51 exhibiting more than 10-fold loss in
enzyme potency. With this information in hand, we further
explored the ketone series by introducing various aromatic and
alkyl modifications. Incorporation of a pyridine group improved
the PK profile of analogue 52 but resulted in some decrease in
cell potency (EC90 ) 200 nM) as compared to 46 (EC90 ) 80
nM). The thiophene and thiazole analogues 53 and 54 were
almost equipotent to the phenyl ketone 46 but did not show
better oral PK in rat. We then looked at small cycloakyl and
alkyl substituents. Thus, cyclopropyl ketone 55, cyclobutyl
ketone 56, and cyclohexyl ketones 57 were prepared. The
smaller cyclopropyl group seemed optimal for both enzyme and
replicon potency with similar overall profile compared to the
original ketone 46. Small alkyls groups were also probed
(compounds 58-60) but did not provide any improvements over
previous compounds. As established earlier in the ester series,
incorporation of cyclohexyl glycine at P4 provided inhibitor 42
with better overall potency profile. With that information in

Toward the Back-Up of BocepreVir (SCH 503034)
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12 3683
Table 5a
a Ki* value represents binding for a mixture of diastereomers at P1 and within 2-fold for 95% confidence limit; replicon (genotype 1) EC90 value is within
3-fold for 95% confidence (single assay) and within 2-fold for 95% confidence (multiple assays).
hand, we prepared the 2-pirydine ketone analogue 61 with the
aim of enhancing the replicon potency of this series. Interest-
ingly, through this manipulation, we were able to improve the
cell potency of 61 to EC90 ) 90 nM and also obtain an inhibitor
with good oral exposure and liver concentration in rats (Table
6). Similar improvement of pharmacokinetics profile for the
cyclopropyl ketone 62 was observed when combined with the
cyclohexylglycine at P4.
During our earlier exploratory studies that led to the discovery
of 1, we observed that P1′ secondary amides, especially allyl
amides, when used in combination with norvaline at P1 provided
inhibitors with very good rat PK profile but weak enzyme and
replicon potency.9b With the improved potency of our P4-capped
inhibitors, we decided to introduce the allyl residue at the P1′
position with the goal of further improving the PK profile. Thus,
the nor-valine P1 and allyl amide P1′ combinations were used
to generate inhibitors 63 and 64 bearing the cyclopropyl ketone
moiety. Introduction of the allyl moiety at P1′ resulted in
compounds with poorer cellular activity compared to primary
amide derivatives 55 and 61, however, they exhibited excellent
rat PK with oral exposure improved by 40- to 200-fold,
respectively. In addition, concentration in the liver for inhibitor
64 was also very high (5.8 µM at 6 h). To further improve the
cellular activity of these inhibitors, we decided to explore the
effect of variation of P1 residue. From our previous experience
with the discovery of 1, we were aware of the fact that the P1
norvaline was not the optimal substitution.9b Cyclopropyl alanine
analogue 65 and norleucine analogues 66 were prepared but
provided similar weak replicon potency. However, from Table
5, it was clear that introduction of butynylglycine at P1 had a
profound effect on the cellular potency of compound 67 (Ki*
) 9 nM, EC90 ) 250 nM) compared to earlier inhibitors.
Furthermore, 67 exhibited very good rat oral exposure
(AUC(µM·h)0-6 h ) 24) and high concentration in the liver
(8.5 µM at 6 h) (Table 6). Because of the potential in vivo
liability of the allyl moiety, we turned our effort toward the
identification of a more desirable surrogates at P1′. Replacement
of the allyl group with cyclopropyl resulted in compound 68.
The cyclopropyl at P1′ was well tolerated and resulted in 5-fold
improvement in cell potency (EC90 ) 55 nM) compared to the
allyl amide analogue 67 (EC90 ) 250 nM). Similar potency
profile was achieved when the P1 butynylglycine and P1′
cyclopropyl amide combinations were used with L-valine at P4
to generate inhibitor 69 (EC90 ) 70 nM). However, as observed
earlier with 59 and 62, the cyclohexylglycine at P4 in inibitor
68 (AUC(µM · h)0-6 ) 11) provided better oral exposure
h
comparedtotheL-valineresidueasininibitor69(AUC(µM·h)0-6
h ) 4.8).

3684 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12
Table 6. Rapid Rat PK Data for Selected Compoundsa
Bogen et al.
were identified as moieties that, when used in combination,
provided compounds with excellent binding and much improved
cellular potencies over 1. Evaluation of these potent compounds
in rapid rats allowed us to identify inhibitor 68 with excellent
enzyme and replicon potency (Ki* ) 4 nM and EC90 ) 55 nM)
and with an improved oral exposure in rats (AUC ) 11 µM·h)
compared to 1.
compd
AUC (µM·h)0-6 h
liver conc (µM)6h
1
0.14
0.26
0.42
0.08
0.15
0.12
1.4
1.4
26
55
24
0.3b
ndc
nd
nd
nd
45
52
53
54
55
61
62
63
64
67
68
69
nd
0.8
2.7
nd
5.8
8.5
2.9
0.9
Experimental Section
1
NMR spectra were recorded at 300, 400, or 500 MHz for H
and at 75, 100, or 125 MHz for 13C on a Bruker or Varian
spectrometer with CDCl3 or DMSO-d6 as solvent, respectively. The
chemical shifts are given in ppm, referenced to the internal TMS
or deuterated solvent signal.
11
4.8
a Rat PO were dosed at 10 mpk (no IV arm). Number of animals used:
2. Vehicle: PO (40%HPBCD). b Rat liver concentration at 8 h. c Rat liver
concentration in was not determined (nd).
General experimental procedures were described in earlier
publications9 for the synthesis of P2 core, peptide coupling, Boc
group deprotection, hydrolysis of ester to carboxylic acid, and
Dess-Martin periodinane oxidation. The syntheses of ketones and
analogues were performed from various starting material according
to literature procedures with some minor modifications.
Purity of target compounds were determined using LC-MS
analysis. LC-MS analyses were performed using an Applied
Biosystems API-150 mass spectrometer and Shimadzu SCL-10A
LC system. Column: Phenomenex Gemini C18, 5 µm, 50 mm ×
4.6 mm i.d., gradient: from 90% water, 10% CH3CN, 0.05%TFA,
5 min to 5% water, 95% CH3CN, 0.05% TFA in 5 min, UV
detection: 254 nm. All targets compounds were >95% pure.
Molecular Modeling. To model compound 68 in the NS3/NS4A
protease active site, the crystal structure of compound 1 bound to
NS3/NS4A protease (PDB ID 2OBO) was used as a template upon
which the P1 and P4 side chains and terminal caps corresponding
to 68 were built. From the crystal structure, the backbone atoms
form a network of hydrogen bonds with the protein and therefore
predefine the backbone orientation of the compounds. The side chain
atoms was energy minimized for 500 steps, followed by another
500 steps of minimization of the whole inhibitor molecule. SYBYL
(Tripos, Inc.) molecular modeling package was used in model
building and optimization.
Figure 3. Model of compound 68 bound to the active site of HCV
NS3/NS4A protease domain. The inhibitor is shown as stick and the
protein as surface. The S1-S4 subsites and the residues that occupy
the S4 pocket are indicated.
Phenylmethyl 1-[[[[1(S)-[[(1R,5S)-2(S)-[[[3-Amino-1-(cyclopro-
pylmethyl)-2,3-dioxopropyl]amino]carbonyl]-6,6-dimethyl-3-
azabicyclo[3.1.0]hex-3-yl]carbonyl]-2,2-dimethylpropyl]amino]car-
bonyl]amino]cyclohexan Carboxylate (20). The product was isolated
1
To understand the interactions, especially the P4 and P4 cap,
with the protein, compound 68 was modeled in the active site
of the NS3/NS4A protease domain (Figure 3). Similar to the
t-butyl glycine P3 cap of compound 1, the P4 cyclohexyl glycine
binds to the S4 subsite, which is a shallow hydrophobic pocket
consisting of residues Arg 123, Asp 168, Arg 155, Ala 156,
and Val 158. The cyclopropyl P4 cap sits on top of Val 158
side chain. The ketone oxygen points toward the solvent. The
favorable hydrophobic contacts of the P4 cyclopropyl cap with
the side chain of Val 158 may attribute to the enhancement in
enzyme potency of compound 68 compared with 1.
as a mixture of two diastereomers (∼1:1). H NMR (500 MHz,
DMSO-d6) δ 8.41 and 8.34 (d, J ) 6.93 and 7.56 Hz, 1H), 8.02 (d, J
) 7.88 Hz, 1H), 7.75 (bs, 1H), 7.35-7.30 (m, 5H), 6.47 (bs, 1H),
6.20 (dd, J ) 10.08 and 16.07 Hz, 1H), 5.12-5.08 (m, 1H), 5.06 (d,
J ) 12.92 Hz, 1H), 4.94 (dd, J ) 4.72 and 12.92 Hz, 1H), 4.33 (s,
1H), 4.18 (t, J ) 8.19 Hz, 1H), 3.88 (t, J ) 9.77 Hz, 1H), 3.78-3.73
(m, 1H),1.96 (d, J ) 11.03 Hz, 1H), 1.82 (d, J ) 12.29 Hz, 1H),
1.71-1.17 (m, 12H), 0.99 (d, J ) 11.35 Hz, 3H), 0.93-0.84 (m, 10H),
0.77 (d, J ) 12.92 Hz, 3H), 0.43-0.35 (m, 2H), 0.12-0.009 (m, 2H).
13C NMR (125 MHz, DMSO-d6) δ 198.47, 197.92, 175.47, 171.82,
171.55, 171.52, 171.32, 163.78, 163.49, 157.63, 157.57, 137.30,
129.11, 128.56, 128.31, 128.30, 128.28, 66.32, 60.20, 59.96, 58.09,
57.76, 57.68, 55.02, 48.34, 35.85, 35.16, 35.14, 33.94, 32.55, 31.56,
31.45, 27.67, 27.58, 27.13, 27.11, 26.97, 26.93, 25.69, 21.62, 21.52,
19.33, 19.30, 13.32, 13.24, 8.75, 8.55, 5.90, 5.21, 4.90. HRMS calcd
for C36H52N5O7, 666.3867 (M + H)+; found, 666.3844.
Conclusion
As we moved toward the back-up for 1, we discovered that P4-
capped inhibitors could provide enhanced enzyme and cellular
potency. Initially, we identified novel series of P4 ester derived
inhibitors that showed 18-fold improvements in cellular potency
(EC90) but lacked oral exposure in rat. Derivatization of the ester
and optimization of the P4 residue led to the identification of the
ketone series that provided compounds with excellent enzyme
potency, improved replicon activity, and modest oral exposure in
rat. Modification of the primary amide P1′ capping group to a
secondary allyl amide drastically improved rat oral exposure but
resulted in weak cell potency. By systematic optimization of the
P1 and the P1′ residues, P1 butynylglycine and P1′ cyclopropyl amide
3-Thienylmethyl 1-[[[[1(S)-[[(1R,5S)-2(S)-[[[3-Amino-1-(cyclo-
propylmethyl)-2,3-dioxopropyl]amino]carbonyl]-6,6-dimethyl-3-
azabicyclo[3.1.0]hex-3-yl]carbonyl]-2,2-dimethylpropyl]amino]car-
bonyl]amino]cyclohexanecarboxylate (21). The product was isolated
1
as a mixture of two diastereomers (∼1:1). H NMR (500 MHz,
DMSO-d6) δ 8.40 and 8.35 (d, J ) 6.62 and 7.25 Hz, 1H), 8.00 (d, J
) 8.51 Hz, 1H), 7.75 (bs, 1H), 7.49-7.44 (m, 2H), 7.05-7.04 (m,
1H), 6.46 (bs, 1H), 6.20 (dd, J ) 10.09 and 16.39 Hz, 1H), 5.15-5.02
(m, 2H), 4.96-4.95 and 4.93-4.92 (m, 1H), 4.33 (bs, 1H), 4.17 (t, J
) 9.45 Hz, 1H), 3.89-3.85 (m, 1H), 3.78-3.72 (m, 1H), 1.98-1.91
(m, 1H), 1.82-1.79 (m, 1H), 1.72-1.13 (m, 13H), 0.99-0.97 (m,
3H), 0.89 (bs, 9H), 0.77-0.75 (m, 3H), 0.39-0.38 (m, 2H), 0.10-0.01

Toward the Back-Up of BocepreVir (SCH 503034)
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12 3685
(m, 2H). 13C NMR (125 MHz, DMSO-d6) δ 198.47, 197.92, 175.41,
171.81, 171.51, 171.31, 163.78, 163.48, 157.65, 157.60, 138.20,
128.09, 127.26, 124.18, 62.08, 60.21, 59.97, 58.11, 57.77, 57.70, 55.02,
48.35, 35.87, 35.17, 33.88, 32.59, 31.57, 31.45, 27.69, 27.60, 27.12,
26.98, 26.93, 25.69, 21.63, 21.54, 19.34, 13.31, 13.23, 8.75, 8.54, 5.90,
5.23, 4.90. HRMS calcd for C34H50N5O7S, 672.3431 (M + H)+; found,
672.3437.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-1-oxo-2(S)-[[[[1-[[(phenylsulfonyl)amino]carbonyl]cy-
clohexyl]amino]carbonyl]amino]butyl]-6,6-dimethyl-3-azabicyclo-
[3.1.0]hexan-2(S)-carboxamide (31). The product was isolated as
a mixture of two diastereomers (∼1:1). 1H NMR (500 MHz,
DMSO-d6) δ 8.41 and 8.34 (d, J ) 7.25 and 7.56 Hz, 1H), 8.02
(d, J ) 11.35 Hz, 3H), 7.88 (bs, 1H), 7.79-7.74 (m, 2H), 7.59 (t,
J ) 10.40 Hz, 1H), 6.63-6.58 (m, 1H), 6.54 (s, 1H), 6.16 (s, 1H),
5.12-5.08 and 5.06-5.02 (m, 1H), 4.34 (bs, 1H), 4.25 (dd, J )
6.62, 9.77 Hz, 1H), 3.87-3.74 (m, 2H), 2.12-2.08 (m, 1H),
2.02-1.98 (m, 1H), 1.85-1.13 (m, 13H), 1.01 (d, J ) 10.71 Hz,
3H), 0.91 (s, 9H), 0.80 (d, J ) 11.66 Hz, 3H), 0.47-0.36 (m, 2H),
0.12-0.01 (m, 2H). HRMS calcd for C35H51N6O8S, 714.8880 (M
+ H)+; found, 714.8892.
(1R,5S)-N-[3-Amino-1-(cyclobutylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-1-oxo-2(S)-[[[[1-[(phenylmethoxy)methyl]cyclohexyl]-
amino]carbonyl]amino]butyl]-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexan-2(S)-Carboxamide (26). The product was isolated as a
mixture of two diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-
d6) δ 8.29 and 8.17 (d, J ) 7.25 and 7.25 Hz, 1H), 8.02 (d, J )
17.34 Hz, 1H), 7.76(bs, 1H), 7.35-7.27 (m, 5H), 6.15 (t, J ) 8.82
Hz, 1H), 5.79(bs, 1H), 4.99-4.95 and 4.88-4.84 (m, 1H), 4.43
(bs, 1H), 4.28 (d, J ) 5.04 Hz, 1H), 4.17 (t, J ) 6.62 Hz, 1H),
4.02-3.89 (m, 2H), 3.75 (d, J ) 12.29 Hz, 1H), 3.53 (d, J ) 8.82
Hz, 1H), 3.46 (d, J ) 9.14 Hz, 1H), 2.05-1.07 (m, 21H), 1.00 (d,
J ) 5.99 Hz, 3H), 0.91(s, 9H), 0.87(d, J ) 14.81 Hz, 3H). 13C
NMR (125 MHz, DMSO-d6) δ 198.65, 197.98, 173.72, 171.86,
171.80, 171.61, 171.60, 163.89, 163.69, 158.03, 157.94, 139.76,
132.43, 130.03, 129.55, 129.03, 129.09, 100.16, 75.93, 73.34, 72.01,
60.34, 60.26, 59.98, 57.62, 57.54, 55.17, 54.33, 52.97, 52.74, 48.28,
37.61, 37.55, 37..39, 35.05, 33.07, 33.00, 32.78, 32.08, 31.50, 31.41,
29.87, 28.80, 28.66, 28.49, 28.34, 28.27, 27.22, 26.98, 26.80, 26.26,
25.37, 22.86, 21.60, 21.52, 19.74, 19.35, 18.73, 18.60, 13.40, 13.34.
Benzyl 2-(3-((2S)-1-((1R,2S,5S)-2-(4-Amino-1-cyclopropyl-3,4-
dioxobutan-2-yl)carbamoyl)-6,6-dimethyl-3-azabicyclo[3.1.0]hexan-
3-yl)-3,3-dimethyl-1-oxobutan-2-yl)ureido)-2-methylpropanoate (33).
The product was isolated as a mixture of two diastereomers (∼1:
1
1). H NMR (300 MHz, CDCl3) δ 7.72 -7.60 (m, 1H), 7.05 (s,
1H), 6.95 (s, 1H), 5.85 (d, J ) 9.85 Hz, 1H), 5.62-5.56 (m, 1H),
5.17-5.02 (m, 3H), 4.46-4.37 (m, 2H), 4.13-4.00 (m, 2H),
3.84-3.74 (m, 1H), 2.48 (s, 1H), 1.89-1.64 (m, 2H), 1.58-1.37
(m, 5H), 1.27-1.20 (m, 1H), 1.01-0.78 (m, 20H), 0.75-0.64 (m,
1H), 0.40 (t, J ) 7.07 Hz, 2H), 0.13-0.05 (m, 2H). LCMS for
C33H47N5O7: 626.10 (M + H)+, purity 98.7%.
(2R)-Benzyl 2-(3-((2S)-1-((1R,2S,5S)-2-(4-Amino-1-cyclopropyl-
3,4-dioxobutan-2-yl)carbamoyl)-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexan-3-yl)-3,3-dimethyl-1-oxobutan-2-yl)ureido)-2,3-dimethylbu-
tanoate (36). The product was isolated as a mixture of two diastere-
2-Furanylmethyl 1-[[[[1(S)-[[(1R,5S)-2(S)-[[[3-Amino-1-(cyclo-
propylmethyl)-2,3-dioxopropyl]amino]carbonyl]-6,6-dimethyl-3-
azabicyclo[3.1.0]hex-3-yl]carbonyl]-2,2-dimethylpropyl]amino]car-
bonyl]amino]cyclohexanecarboxylate (28). The product was isolated
1
omers (∼1:1). H NMR (300 MHz, CDCl3) δ 7.34 (s, 5H), 6.96 (s,
1
as a mixture of two diastereomers (∼1:1). H NMR (500 MHz,
1H), 6.89 (s, 1H), 6.81 (s, 1H), 5.51-5.33 (m, 1H), 5.23 (s, 2H), 5.15
(d, J ) 12.64 Hz, 1H), 5.03 (d, J ) 12.64 Hz, 1H), 4.44-4.34 (m,
2H), 4.05-3.97 (m, 1H), 3.83-3.73 (m, 1H), 3.82-3.67 (m, 2H),
3.66-3.60 (m, 1H), 2.19-2.07 (m, 1H), 1.97-1.78 (m, 1H), 1.70-1.54
(m, 2H), 1.52-1.43 (m, 2H), 1.05-0.85 (m, 17H), 0.84-0.63 (m,
3H), 0.49-0.37 (m, 2H), 0.17-0.07 (m, 2H). LCMS for C35H52N5O7:
654.50 (M + H)+, purity 98.9%.
DMSO-d6) δ 8.40 and 8.32 (d, J ) 6.62 and 7.25 Hz, 1H), 8.01 (d, J
) 7.88 Hz, 1H), 7.74(bs, 1H), 7.62 (bs, 1H), 6.44 (d, J ) 6.93 Hz,
2H), 6.16 (dd, J ) 10.08, 16.39 Hz, 1H), 5.11-5.07 and 5.06-5.02
(m, 1H), 4.96-4.87(m, 2H), 4.32 (s, 1H), 4.15 (t, J ) 8.82 Hz, 1H),
3.86 (t, J ) 10.71 Hz, 1H), 3.77-3.71 (m, 2H), 1.90-1.74 (m, 1H),
1.71-1.15 (m, 14H), 1.00 (d, J ) 9.77 Hz, 3H), 0.88 (bs, 9H), 0.80
(d, J ) 13.24 Hz, 3H), 0.41-0.37 (m, 2H), 0.12-0.01 (m, 2H). 13
C
(2S)-Benzyl 2-(3-((2S)-1-((1R,2S,5S)-2-(4-Amino-1-cyclopropyl-
3,4-dioxobutan-2-yl)carbamoyl)-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexan-3-yl)-3,3-dimethyl-1-oxobutan-2-yl)ureido)-2,3-dimethylbu-
tanoate (37). The product was isolated as a mixture of two
diastereomers (∼1:1). 1H NMR (300 MHz, CDCl3) δ 7.62 (d, J )
5.09 Hz, 1H), 7.32 (s, 5H), 6.93 (s, 1H), 6.79 (s, 1H), 6.23 (s, 1H),
5.33 (d, J ) 6.72 Hz, 1H), 5.13 (s, 2H), 4.44 (d, J ) 12.11 Hz,
2H), 4.11 (d, J ) 10.35 Hz, 1H), 3.83-3.73 (m, 1H), 3.69 (s, 1H),
2.21-2.03 (m, 1H), 1.89-1.66 (m, 2H), 1.61-1.40 (m, 5H), 1.25
(s, 1H), 1.04-0.68 (m, 20H), 0.43 (d, J ) 8.22 Hz, 2H), 0.14-0.02
(m, 2H). LCMS for C35H51N5O7: 654.20 (M + H)+, purity 96.5%.
NMR (125 MHz, DMSO-d6) δ 198.47, 197.90, 175.18, 171.82, 171.53,
171.49, 171.27, 163.77, 163.48, 157.53, 157.46, 150.31, 144.29,
111.48, 111.14, 60.20, 59.95, 58.65, 58.11, 57.64, 57.56, 55.01, 54.98,
48.32, 35.85, 35.11, 35.16, 33.88, 32.57, 32.53, 31.55, 31.44, 27.65,
27.55, 27.08, 27.07, 26.98, 26.82, 25.64, 21.59, 21.49, 19.33, 19.30,
13.30, 13.22, 8.73, 8.53, 5.89, 5.21, 4.90.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyll)-2,3-dioxopropyl]-3-
[3,3-dimethyl-1-oxo-2(S)-[[[[1-[[(phenylmethyl)amino]carbonyl]-
cyclohexyl]amino]carbonyl]amino]butyl]-6,6-dimethyl-3-azabi-
cyclo[3.1.0]hexan-2(S)-carboxamide (29). The product was isolated
1
as a mixture of two diastereomers (∼1:1). H NMR (500 MHz,
DMSO-d6) δ 8.40 and 8.33 (d, J ) 6.62 and 10.71 Hz, 1H), 8.02
(d, J ) 9.14 Hz, 1H), 7.93 (bs, 1H), 7.74 (s, 1H), 7.24 (m, 5H),
6.54-.6.45 (m, 1H), 6.20 (s, 1H), 5.11-5.06 and 5.05-5.01 (m,
1H), 4.31 (s, 1H), 4.29 (d, J ) 6.62 Hz, 1H), 4.24 (t, J ) 9.14 Hz,
1H), 4.20-4.13 (m, 1H), 3.91-3.74 (m, 2H), 2.05 (d, J ) 14.50
Hz, 1H), 1.86 (d, J ) 9.45 Hz, 1H), 1.71-1.14 (m, 12H), 0.97-0.88
(m, 13H), 0.74 (d, J ) 12.61 Hz, 3H), 0.43-0.36 (m, 2H),
0.17-0.02 (m, 2H).
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-2(S)-[[[[2-methyl-1(S)-[[(phenylsulfonyl)amino]car-
bonyl]propyl]amino]carbonyl]amino]butyl]-6,6-dimethyl-3-
azabicyclo[3.1.0]hexan-2(S)-carboxamide (44). The product was
1
isolated as a mixture of two diastereomers (∼1:1). H NMR (500
MHz, DMSO-d6) δ 8.40 and 8.34 (d, J ) 6.62 and 7.56 Hz, 1H),
8.01(d, J ) 10.40 Hz, 1H), 7.86 (d, J ) 7.56 Hz, 3H), 7.74 (bs,
1H), 7.61 (bs, 1H),7.55 (d, J ) 6.93 Hz, 2H), 6.30 (dd, J ) 10.40,
13.87 Hz, 1H), 6.23 (d, J ) 8.52 Hz, 1H), 5.10-5.06 and 5.04-5.00
(m, 1H), 4.29 (s, 1H), 4.12 (t, J ) 9.14 Hz, 1H), 3.99 (bs, 1H),
3.86 (t, J ) 10.40 Hz, 1H), 3.76-3.71 (m, 1H), 1.88-1.82 (m,
1H), 1.70-1.52 (m, 1H), 1.44-1.23 (m, 4H), 1.00 (d, J ) 10.40
Hz, 3H), 0.83 (s, 9H), 0.79 (d, J ) 13.24 Hz, 3H), 0.66 (d, J )
5.35 Hz, 3H), 0.54 (d, J ) 6.62 Hz, 3H), 0.39-0.36 (m, 2H),
0.12-0.005 (m, 2H). 13C NMR (125 MHz, DMSO-d6) δ 198.47,
197.89, 171.87, 171.59, 171.47, 171.27, 163.81, 163.50, 158.41,
158.39, 129.43, 128.09, 60.23, 59.99, 59.23, 58.20, 58.09, 54.98,
54.96, 48.28, 35.83, 35.07, 35.05, 31.86, 31.56, 31.45, 27.78, 27.69,
27.22, 27.19, 26.99, 26.95, 19.86, 19.36, 19.34, 17.75, 13.46, 13.41,
8.74, 8.53, 5.90, 5.21, 4.90. HRMS calcd for C33H49N6O8S,
689.8500 (M + H)+; found, 689.8591.
1-[[[[1(S)-[[(1R,5S)-2(S)-[[[3-Amino-1-(cyclopropylmethyl)-2,3-
dioxopropyl]amino]carbonyl]-6,6-dimethyl-3-azabicyclo[3.1.0]hex-
3-yl]carbonyl]-2,2-dimethylpropyl]amino]carbonyl]amino]cyclo-
hexanecarboxylate (30). The product was isolated as a mixture of
two diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-d6) δ 8.39
and 8.32 (d, J ) 6.62 and 7.25 Hz, 1H), 8.01 (d, J ) 7.25 Hz,
1H), 7.75(bs, 1H), 6.30 (d, J ) 4.09 Hz, 2H), 6.20 (d, J ) 10.08
Hz, 1H), 5.11-5.08 and 5.07-5.03 (m, 1H), 4.33 (s, 1H),
4.24-4.15 (m, 1H), 3.91-3.84 (m, 1H), 3.80-3.71 (m, 1H),
1.96-1.93 (m, 1H), 1.81 (d, J ) 12.61 Hz, 1H), 1.70-1.11 (m,
12H), 1.01-0.99 (m, 3H), 0.95-0.85 (m, 10H), 0.81-0.77 (m, 3H),
0.47-0.35 (m, 2H), 0.14-0.02 (m, 2H). HRMS calcd for
C29H46N5O7, 576.3397 (M + H)+; found, 576.3403.

3686 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12
Bogen et al.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[2(S)-[[[(1(S)-benzoyl-2-methylpropyl)amino]carbonyl]amino]-3,3-
dimethyl-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]hexan-2(S)-
carboxamide (46). The product was isolated as a mixture of two
diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-d6) δ 8.42 and
8.36 (d, J ) 6.93 and 7.25 Hz, 1H), 8.02 (d, J ) 9.77 Hz, 1H),
7.97 (d, J ) 8.19 Hz, 2H), 7.75(bs, 1H), 7.64 (t, J ) 7.56 Hz, 1H),
7.52 (t, J ) 7.88 Hz, 2H), 6.58 (d, J ) 8.82 Hz, 1H), 6.39 (J )
9.77 and 13.55 Hz, 1H), 5.17 (dd, J ) 5.04 and 8.82 Hz, 1H),
5.13-5.09 and 5.07-5.03 (m, 1H), 4.35 (s, 1H), 4.21 (d, J ) 8.19
Hz, 1H), 3.90 (t, J ) 10.40 Hz, 1H), 3.80-3.74 (m, 1H), 2.04-1.99
(m, 1H), 1.72-1.56 (m, 1H), 1.47-1.31 (m, 3H), 1.01 (d, J )
9.77 Hz, 3H), 0.90-0.83 (m, 16H), 0.70 (d, J ) 9.14 Hz, 3H),
0.42-0.36 (m, 2H), 0.11-0.006 (m, 2H). 13C NMR (125 MHz,
DMSO-d6) δ 201.00, 198.48, 197.90, 171.83, 171.55, 171.44,
171.24, 163.79, 163.50, 158.55, 158.53, 136.57, 134.23, 129.27,
129.05, 60.25, 60.02, 59.28, 58.17, 58.07, 55.01, 54.98, 48.32,
35.89, 35.17, 35.16, 31.58, 31.47, 31.25, 31.22, 27.77, 27.67, 27.16,
27.13, 26.99, 26.95, 20.49, 19.35, 19.33, 17.66, 13.48, 13.41, 8.74,
8.54, 5.90, 5.21, 4.90. HRMS calcd for C33H48N5O6, 611.3672 (M
+ H)+; found, 611.3674.
19.33, 18.10, 13.47, 13.43, 8.76, 8.55, 5.91, 5.21, 4.90. HRMS calcd
for C33H48N5O6S, 616.3169 (M + H)+; found, 616.3170.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-2(S)-[[[[2-methyl-1(S)-(2-thiazolylcarbonyl)propyl]-
amino]carbonyl]amino]-1-oxobutyl]-6,6-dimethyl-3-azabicyclo-
[3.1.0]hexan-2(S)-carboxamide (54). The product was isolated
1
as a mixture of two diastereomers (∼1:1). H NMR (500 MHz,
DMSO-d6) δ 8.42 and 8.36 (d, J ) 6.62 and 7.25 Hz, 1H), 8.27 (d, J
) 2.87 Hz, 1H), 8.20 (d, J ) 2.83 Hz, 1H), 8.02 (d, J ) 9.45 Hz,
1H), 7.75 (bs, 1H), 6.62 (d, J ) 8.82 Hz, 1H), 6.42 (dd, J ) 9.77 and
13.55 Hz, 1H), 5.32-5.30 (m, 1H), 5.12-5.08 and 5.06-5.02 (m,
1H), 4.34 (d, J ) 3.15 Hz, 1H), 4.15 (t, J ) 9.14 Hz, 1H), 3.85 (t, J
) 10.71 Hz, 1H), 3.77-3.72 (m, 1H), 2.29-2.25 (m, 1H), 1.72-1.53
(m, 1H), 1.47-1.30 (m, 3H), 1.01 (d, J ) 9.77 Hz, 3H), 0.94-0.79
(m, 16H), 0.74 (d, J ) 6.62 Hz, 3H), 0.43-0.35 (m, 2H), 0.12-0.008
(m, 2H). 13C NMR (125 MHz, DMSO-d6) δ 198.50, 197.94, 193.98,
171.83, 171.55, 171.38, 171.18, 165.91, 163.81, 163.49, 158.52,
158.51, 146.22, 129.31, 60.51, 60.21, 60.02, 58.18, 58.10, 55.00, 54.98,
48.30, 35.86, 35.15, 31.58, 31.49, 31.20, 31.18, 27.75, 27.66, 27.18,
27.16, 27.00, 26.96, 20.60, 19.38, 19.35, 17.58, 13.45, 13.38, 8.76,
8.55, 5.91, 5.21, 4.90. HRMS calcd for C30H45N6O6S, 617.3121 (M
+ H)+; found, 617.3134.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-2(S)-[[[[2-methyl-1(R)-([phenylmethyl)propyl]ami-
no]carbonyl]amino]-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexan-2(S)-carboxamide (48). The product was isolated as a mixture
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[2(S)-[[[[1(S)-(cyclopropylcarbonyl)-2-methylpropyl]amino]carbo-
nyl]amino]-3,3-dimethyl-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexan-2(S)-carboxamide (55). The product was isolated as a mixture
of two diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-d6) δ 8.41
and 8.35 (d, J ) 6.62 and 7.25 Hz, 1H), 8.00 (d, J ) 9.77 Hz, 1H),
7.75 (bs, 1H), 6.44 (d, J ) 8.83 Hz, 1H), 6.34 (dd, J ) 10.08 and
14.18 Hz, 1H), 5.12-5.08 and 5.06-5.02 (m, 1H), 4.36-4.32 (m,
2H), 4.19 (t, J ) 9.45 Hz, 1H), 3.90-3.83 (m, 1H), 3.79-3.73 (m,
1H), 2.24-2.11 (m, 2H), 1.73-1.65 (m, 1H), 1.63-1.52 (m, 1H),
1.49-1.39 (m, 2H), 1.36-1.29 (m, 1H), 1.00 (d, J ) 10.4 Hz, 3H),
0.90-0.72 (m, 18H), 0.70-0.69 (m, 4H), 0.45-0.29 (m, 2H),
0.15-0.01 (m, 2H). 13C NMR (125 MHz, DMSO-d6) δ 210.83, 198.46,
197.88, 171.85, 171.56, 171.48, 171.27, 163.8, 163.48, 158.56, 64.61,
60.24, 60.02, 58.13, 58.04, 54.97, 48.30, 35.86, 35.17, 31.56, 31.45,
30.23, 30.21, 27.76, 27.67, 27.17, 26.98, 20.35, 19.36, 18.81, 17.79,
13.44, 11.78, 11.20, 8.73, 8.53, 5.89, 5.20, 4.89. HRMS calcd for
C30H48N5O6, 574.3604 (M + H)+; found, 574.3616.
1
of two diastereomers (∼1:1). H NMR (500 MHz, DMSO-d6) δ
8.39 and 8.31 (d, J ) 6.62 and 7.25 Hz, 1H), 8.01 (d, J ) 9.14 Hz,
1H), 7.47 (s, 1H), 7.23-7.12 (m, 5H), 5.99-5.94 (m, 2H),
5.11-5.07 and 5.05-5.01 (m, 1H), 4.31 (s, 1H), 4.13 (t, J ) 6.93
Hz, 1H), 3.87 (t, J ) 10.08 Hz, 1H), 3.76-3.70 (m, 1H), 3.68-3.63
(m, 1H), 2.67 (dd, J ) 4.72 and 13.87 Hz, 2H), 1.71-1.54 (m,
2H), 1.46-1.23 (m, 3H), 1.00 (d, J ) 10.40 Hz, 3H), 0.83 (s, 9H),
0.81-0.76 (m, 10H), 0.43-0.36 (m, 2H), 0.12-0.01 (m, 2H). 13
C
NMR (125 MHz, DMSO-d6) δ 198.47, 197.92, 171.85, 171.72,
171.56, 171.52, 163.78, 163.48, 158.54, 158.49, 140.52, 129.83,
128.82, 126.55, 60.17, 59.91, 57.78, 57.70, 55.87, 55.86, 54.99,
54.96, 48.26, 48.23, 39.45, 39.43, 35.85, 35.13, 35.11, 31.92, 31.55,
31.45, 27.68, 27.58, 27.14, 27.12, 26.99, 26.94, 20.39, 19.32, 19.29,
17.66, 13.38, 13.32, 8.74, 8.54, 5.90, 5.21, 4.90. HRMS calcd for
C33H49NaN5O5, 618.3631 (M + Na)+; found, 618.3655.
(1R,5S)-N-[3-Amino1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-1-oxo-2(S)-[[[[1(S)-(2-pyridinylcarbonyl)-2-methyl-
propyl]amino]carbonyl]amino]butyl]-6,6-dimethyl-3-azabicyclo-
[3.1.0]hexan-2(S)-carboxamide (52). The product was isolated
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-2(S)-[[[[3-methyl-1(S)-(1-methylethyl)-2-oxobutyl]amino]car-
bonyl]amino]-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]hexan-
2(S)-carboxamide (59). The product was isolated as a mixture of two
diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-d6) 8.40 and 8.34
(d, J ) 6.62 and 7.25 Hz, 1H), 8.01 (d, J ) 9.14 Hz, 1H), 7.74 (bs,
1H), 6.41 (d, J ) 9.14 Hz, 1H), 6.30 (dd, J ) 9.77 and 14.18 Hz,
1H), 5.12-5.08 and 5.06-5.02 (m, 1H), 4.33 (d, J ) 2.83 Hz, 1H),
4.27 (q, J ) 5.35 and 9.14 Hz, 1H), 4.19 (t, J ) 9.45 Hz, 1H), 3.88
(d, J ) 10.71 Hz, 1H), 3.79-3.73 (m, 1H), 2.82 (p, J ) 6.90 Hz,
1H), 2.07-2.00 (m, 1H), 1.71-1.52 (m, 1H), 1.47-1.40 (m, 2H),
1.35-1.30 (m, 1H), 1.01-0.98 (m, 6H), 0.95-0.87 (m, 13H),
0.82-0.79 (m, 6H), 0.69 (d, J ) 6.93 Hz, 3H), 0.42-0.36 (m, 2H),
0.14-0.01 (m, 2H). 13C NMR (125 MHz, DMSO-d6) δ 214.96, 198.47,
197.92, 171.84, 171.55, 171.44, 171.24, 163.80, 163.49, 158.54,
158.52, 62.34, 60.22, 59.99, 58.10, 58.02, 55.00, 54.98, 48.31, 37.84,
35.85, 35.18, 35.17, 29.86, 29.84, 28.53, 27.73, 27.63, 27.16, 27.13,
26.99, 26.95, 20.49, 19.44, 19.35, 19.33, 18.55, 17.90, 13.41, 13.35,
8.76, 8.55, 5.90, 5.21, 4.90. HRMS calcd for C33H59N5O5, 576.3761
(M + H)+; found, 576.3738.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[2(S)-[[[[1(S)-cyclohexyl-2-oxo-2-(2-pyridinyl)ethyl]amino]carbonyl]-
amino]-3,3-dimethyl-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexane-2(S)-carboxamide (61). The product was isolated as a
mixture of two diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-
d6) δ 8.77 (d, J ) 5.04 Hz, 1H), 8.41 and 8.35 (d, J ) 6.93 and
7.56 Hz, 1H), 8.04-7.96 (m, 3H), 7.75 (bs, 1H), 7.70-7.67 (m,
1H), 6.56 (d, J ) 9.14 Hz, 1H), 6.44-6.39 (m, 1H), 5.68-5.65
(m, 1H), 5.12-5.08 and 5.07-5.03 (m, 1H), 4.34 (bs, 1H), 4.16
(t, J ) 9.45 Hz, 1H), 3.89(t, J ) 10.71 Hz, 1H), 3.78-3.72 (m,
1H), 1.80-1.75 (m, 1H), 1.66-1.30 (m, 8H), 1.13-0.83 (m, 22H),
1
as a mixture of two diastereomers (∼1:1). H NMR (500 MHz,
DMSO-d6) δ 8.76 (t, J ) 4.72 Hz, 1H), 8.03 (d, J ) 7.56 Hz, 2H),
7.98 (t, J ) 9.14 Hz, 1H), 7.75-7.68 (m, 2H), 6.55-6.52 (m, 2H),
5.67-5.64 (m, 1H), 5.11-5.08 and 5.06-5.03 (m, 1H), 4.33 (d, J
) 3.15 Hz, 1H), 4.16 (t, J ) 9.14 Hz, 1H), 3.88 (d, J ) 9.45 Hz,
1H), 3.78-3.72 (m, 2H), 2.21-2.14 (m, 1H), 1.73-1.15 (m, 5H),
1.02 (d, J ) 9.77 Hz, 3H), 0.92-0.71 (m, 15H), 0.66 (d, J ) 6.62
Hz, 3H), 0.41-0.35 (m, 2H), 0.11-0.02 (m, 2H). HRMS calcd
for C32H47N6O6, 611.3479 (M + H)+; found, 611.3522.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[3,3-dimethyl-2(S)-[[[[2-methyl-1(S)-(2-thienylcarbonyl)propyl]ami-
no]carbonyl]amino]-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexan-2(S)-carboxamide (53). The product was isolated as a mixture
1
of two diastereomers (∼1:1). H NMR (500 MHz, DMSO-d6) δ
8.42 and 8.37 (d, J ) 6.62 and 7.56 Hz, 1H), 8.03 (t, J ) 4.72 Hz,
3H), 7.75 (bs, 1H),7.26 (t, J ) 4.72 Hz, 1H), 6.60 (d, J ) 8.51 Hz,
1H), 6.36 (dd, J ) 10.08 and 13.87 Hz, 1H), 5.12-5.08 and
5.06-5.02 (m, 1H), 4.93-4.90 (m, 1H), 4.34 (d, J ) 3.15 Hz,
1H), 4.18 (t, J ) 9.14 Hz, 1H), 3.87 (t, J ) 11.35 Hz, 1H),
3.81-3.73 (m, 1H), 2.08-2.03 (m, 1H), 1.72-1.52 (m, 1H),
1.47-1.23 (m, 4H), 1.02 (d, J ) 10.40 Hz, 3H), 0.89-0.81 (m,
15H), 0.77 (d, J ) 6.93 Hz, 3H), 0.42-0.37 (m, 2H), 0.12-0.01
(m, 2H). 13C NMR (125 MHz, DMSO-d6) δ 198.51, 197.89, 193.82,
173.66, 171.82, 171.54, 171.36, 171.19, 163.79, 163.49, 158.42,
158.40, 143.31, 136.23, 134.45, 129.73, 60.65, 60.40, 60.22, 60.01,
58.12, 58.03, 54.98, 48.31, 35.86, 35.22, 35.16, 31.79, 31.75, 31.58,
31.48, 27.73, 27.64, 27.11, 27.05, 27.00, 26.96, 26.88, 20.47, 19.36,

Toward the Back-Up of BocepreVir (SCH 503034)
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 12 3687
0.41-0.36 (m, 2H), 0.11-0.01 (m, 2H). 13C NMR (125 MHz,
DMSO-d6) δ 201.69, 198.49, 197.92, 171.85, 171.57, 171.54,
171.32, 163.82, 163.52, 158.51, 158.49, 152.81, 150.12, 138.67,
128.82, 123.00, 60.23, 60.00, 58.40, 58.39, 58.15, 58.05, 55.01,
54.98, 48.28, 35.88, 35.13, 35.11, 31.59, 31.50, 30.69, 27.82, 27.76,
27.69, 27.20, 27.17, 27.02, 26.98, 26.64, 26.56, 26.44, 19.35, 19.33,
13.38, 13.32, 8.74, 8.54, 5.90, 5.21, 4.91. HRMS calcd for
C35H51N6O6, 651.3870 (M + H)+; found, 651.3872.
(1R,5S)-N-[3-Amino-1-(cyclopropylmethyl)-2,3-dioxopropyl]-3-
[2(S)-[[[(1(S)-cyclohexyl-2-cyclopropyl-2-oxoethyl)amino]carbonyl]-
amino]-3,3-dimethyl-1-oxobutyl]-6,6-dimethyl-3-azabicyclo[3.1.0]-
hexane-2(S)-carboxamide (62). The product was isolated as a
mixture of two diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-
d6) δ 8.41 and 8.36 (d, J ) 6.62 and 7.25 Hz, 1H), 8.02 (t, J )
8.82 Hz, 1H), 7.75 (bs, 1H), 6.46 (d, J ) 8.82 Hz, 1H), 6.32 (dd,
J ) 10.08 and 14.50 Hz, 1H), 5.11-5.08 and 5.06-5.02 (m, 1H),
4.33-4.30 (m, 2H), 4.23-4.15 (m, 1H), 3.88 (t, J ) 10.71 Hz,
1H), 3.80-3.73 (m, 1H), 2.17-2.10 (m, 1H), 1.83-1.75 (m, 1H),
1.71-1.11 (m, 11H), 1.02-0.97 (m, 5H), 0.94-0.85 (m, 13H),
0.83-0.81 (m, 3H), 0.80-0.75 (m, 2H), 0.47-0.31 (m, 2H),
0.14-0.03 (m, 2H). 13C NMR (125 MHz, DMSO-d6) δ 210.78,
198.51, 197.90, 171.82, 171.54, 171.46, 171.26, 163.77, 163.50,
158.45, 158.43, 130.23, 115.66, 110.47, 94.63, 64.37, 60.12, 59.93,
58.06, 57.98, 55.01, 48.31, 35.85, 35.24, 35.17, 31.60, 30.41, 28.07,
27.77, 27.63, 27.17, 27.15, 27.09, 27.00, 26.97, 26.62, 26.53, 19.36,
19.32, 18.95, 13.37, 13.32, 13.00, 11.74, 11.34, 8.75, 8.55, 5.91,
5.21, 4.90. HRMS calcd for C33H52N5O6, 614.3839 (M + H)+;
found, 614.3845.
(1R,5S)-3-[2(S)-[[[[1(S)-(Cyclopropylcarbonyl)-2-methylpropyl]-
amino]carbonyl]amino]-3,3-dimethyl-1-oxobutyl]-N-[1-[1,2-dioxo-
2-(propenylamino)ethyl]butyl]-6,6-dimethyl-3-azabicyclo[3.1.0]hexan-
2(S)-carboxamide (63). The product was isolated as a mixture of
two diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-d6) δ 8.87
and 8.81 (t, J ) 6.0 Hz, 1H), 8.39 and 8.34 (d, J ) 6.93 and 7.25
Hz, 1H), 6.44 (d, J ) 8.82 Hz, 1H), 6.33 (t, J ) 10.08 Hz, 1H),
5.83-5.75 (m, 1H), 5.12 (d, J ) 1.57 Hz, 1H), 5.09-5.04 (m,
1H), 5.00-4.96 and 4.89-4.85 (m, 1H), 4.35 (q, J ) 4.72 and
8.82 Hz, 1H), 4.30 (d, J ) 6.93 Hz, 1H), 4.22-4.16 (m, 1H), 3.87
(d, J ) 10.08 Hz, 1H), 3.79-3.68 (m, 3H), 2.18-2.15 (m, 2H),
1.74-1.65 (m, 1H), 1.55-1.23 (m, 5H), 1.01 (d, J ) 9.45 Hz,
3H), 0.93-0.75 (m, 22H), 0.71 (d, J ) 6.93 Hz, 3H). 13C NMR
(125 MHz, DMSO-d6) δ 210.82, 198.22, 197.60, 171.88, 171.79,
171.40, 171.24, 162.02, 161.64, 158.59, 158.56, 135.05, 135.00,
116.46, 116.36, 64.61, 60.23, 59.98, 58.07, 54.37, 48.29, 41.70,
35.16, 32.51, 32.47, 31.58, 31.55, 30.23, 30.21, 27.83, 27.75, 27.18,
26.99, 26.96, 20.59, 20.37, 19.57, 19.43, 19.36, 18.81, 17.81, 17.58,
14.45, 14.33, 13.44, 13.38, 11.76, 11.19. HRMS calcd for
C32H52N5O6, 602.3918 (M + H)+; found, 602.3940.
(1R,5S)-3-[2(S)-[[[(1(S)-Cyclohexyl-2-cyclopropyl-2-oxoethyl)ami-
no]carbonyl]amino]-3,3-dimethyl-1-oxobutyl]-N-[1-[1,2-dioxo-2-(2-
propenylamino)ethyl]butyl]-6,6-dimethyl-3-azabicyclo[3.1.0]hexane-
2(S)-carboxamide (64). The product was isolated as a mixture of
two diastereomers (∼1:1). 1H NMR (500 MHz, DMSO-d6) δ 8.88
and 8.82 (t, J ) 5.99 Hz, 1H), 8.40 and 8.35 (d, J ) 6.62 and 7.25
Hz, 1H), 6.46 (d, J ) 8.50 Hz, 1H), 6.31 (t, J ) 10.40 Hz, 1H),
5.83-5.76 (m, 1H), 5.12-5.04 (m, 2H), 5.01-4.96 and 4.89-4.85
(m, 1H), 4.33-4.29 (m, 2H), 4.19-4.16 (m, 1H), 3.87 (t, J ) 10.08
Hz, 1H), 3.79-3.71 (m, 3H), 2.17-2.12 (m, 1H), 1.84-1.76 (m,
1H), 1.73-1.03 (m, 16H), 1.07-0.97 (m, 5H), 0.94-0.75 (m, 17H).
13C NMR (125 MHz, DMSO-d6) δ 210.77, 198.22, 197.61, 171.96,
171.79, 171.41, 171.25, 162.02, 161.64, 158.46, 158.43, 135.05,
135.00, 116.46, 116.36, 64.37, 60.22, 59.96, 58.00, 54.37, 48.28,
41.70, 35.17, 32.52, 32.47, 31.58, 31.55, 30.41, 28.08, 27.83, 27.74,
27.16, 27.00, 26.97, 26.63, 26.54, 19.57, 19.44, 19.35, 18.95, 14.45,
13.35, 13.29, 11.71, 11.32. HRMS calcd for C35H55N5NaO6,
664.4050 (M + Na)+; found, 664.4059.
(d, J ) 5.13 Hz, 1H), 8.44(d, J ) 7.32 Hz, 1H), 6.46-6.41 (m,
2H), 6.31-6.24 (m, 2H), 5.00-4.92 (m, 1H), 4.33-4.26 (m, 2H),
4.25 (s, 1H), 4.23-4.18 (m, 1H), 4.14 (d, J ) 9.52 Hz, 2H), 3.84
(d, J ) 10.25 Hz, 2H), 3.81-3.69 (m, 2H), 2.78 (s, 1H), 2.76-2.68
(m, 1H), 2.34-2.18 (m, 2H), 2.17-2.08 (m, 2H), 2.00-1.90 (m,
1H), 1.83-1.73 (m, 2H), 1.71-1.48 (m, 4H), 1.44-1.38 (m, 1H),
1.36-1.27 (m, 1H), 1.25-1.05 (m, 2H), 1.03-0.92 (m, 4H), 0.88
(s, 9H), 0.82-078 (m, 4H), 0.66-0.60 (m, 2H), 0.58-0.51 (m,
2H). 13C NMR (125 MHz, DMSO-d6) δ 210.77, 197.40, 172.07,
171,27, 162.92, 158.45, 84.15, 72.73, 60.06, 57.99, 54.18, 48.27,
40.99, 40.82, 40.65, 35.16, 31.50, 30.41, 29.96, 28.08, 27.88, 27.20,
26.98, 26.63, 26.54, 23.33, 20.42, 19.39, 18.95, 15.58, 13.34, 11.73,
11.34, 6.26. LCMS for C36H54N5O3: 652.3 (M + H)+, purity 96.5%.
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