Design and synthesis of dipeptidyl glutaminyl fluoromethyl ketones as potent severe acute respiratory syndrome coronovirus (SARS-CoV) inhibitors

Article abstract of DOI:10.1021/jm0507678

This paper describes the design and synthesis of dipeptidyl N,N-dimethyl glutaminyl fluoromethyl ketones (fmk) as severe acute respiratory syndrome coronovirus (SARS-CoV) inhibitors. The compounds were tested against SARS-CoV-induced cell death in Vero or

Full text of DOI:10.1021/jm0507678

1198
J. Med. Chem. 2006, 49, 1198-1201
Brief Articles
Design and Synthesis of Dipeptidyl Glutaminyl Fluoromethyl Ketones as Potent Severe Acute
Respiratory Syndrome Coronovirus (SARS-CoV) Inhibitors
Han-Zhong Zhang,† Hong Zhang,† William Kemnitzer,† Ben Tseng,† Jindrich Cinatl, Jr.,‡ Martin Michaelis,‡
Hans Wilhelm Doerr,‡ and Sui Xiong Cai*,†
Maxim Pharmaceuticals, 6650 Nancy Ridge DriVe, San Diego, California 92121, and Institute for Medical Virology,
Clinics of the Johann Wolfgang Goethe-UniVersity, Paul-Ehrlich-Strasse 40, 60596 Frankfurt, Germany
ReceiVed August 4, 2005
This paper describes the design and synthesis of dipeptidyl N,N-dimethyl glutaminyl fluoromethyl ketones
(fmk) as severe acute respiratory syndrome coronovirus (SARS-CoV) inhibitors. The compounds were tested
against SARS-CoV-induced cell death in Vero or CaCo2 cells as a measurement of the inhibiting effects of
the compounds on the replication of the virus. Z-Leu-Gln(NMe2)-fmk (6a) was found to be a potent inhibitor
with low toxicity in cells, protecting cells with an EC50 value of 2.5 µM and exhibiting a selectivity index
of >40.
Chart 1
Introduction
Through a collaborative international effort that was initiated
during the 2003 severe acute respiratory syndrome (SARS)
outbreak, the causative pathogen of SARS has been identified
as a novel coronavirus (SARS-CoV).1 Human coronaviruses
(HCoVs) were previously associated with predominantly mild
respiratory illnesses, occasionally causing serious infections of
the lower respiratory tract in children and adults. In contrast,
SARS is marked by an unusually high mortality rate, having
infected over 8000 individuals in 29 countries and leaving nearly
800 dead during its 2003 outbreak. The rapid spread of SARS
to developed countries within a few months of its origin in Asia
highlights the vulnerability of large, diverse, and geographically
distant populations to the disease. SARS-CoV is the first
coronavirus that is known to regularly cause severe disease in
humans.
Coronaviruses, including SARS-CoV, are known to encode
several viral proteases for the proteolytic processing of poly-
proteins to release the functional proteins. Coronavirus proteases
have been found to be cysteine proteases, including a chymo-
trypsin-like main protease, Mpro, which is analogous to the main
picornavirus protease, 3Cpro, and is essential for viral replica-
tion.2 The conservation of substrate specificities within the Mpro
protease family of coronaviruses has been reported with the
amino acid sequence L-Q-S or L-Q-A as the preferred P2-P1-
P1′ sequences.3 Mpro exhibits a similarity of cleavage site
specificity to that of 3Cpro of picornaviruses, a family of viruses
that also cause respiratory illnesses. The functional significance
of Mpro in the coronavirus life cycle, as well as its extremely
low sequence similarity to other cellular proteinases, makes it
an ideal target for the discovery and development of novel drugs
against SARS.
vaccines and immune therapies have been initiated and have
encountered some problems, including evasion of antibody
neutralization due to genetic diversity among SARS viruses.4
Therefore it is critical to discover and develop novel and
effective treatments for SARS in preparation for future out-
breaks.
Several compounds have been reported as inhibitors of SARS-
CoV.5 Through the screening of a library of >10000 compounds
to inhibit viral replication, a peptide inhibitor of HIV protease
was found to inhibit SARS-CoV Mpro with a Ki value of 0.6
µM and showed protective effect in the cell based viral
replication assay at a concentration of 10 µM.6 Another group
screened 50240 small molecules in the cell based viral replica-
tion assay. One of the active compounds was identified as an
inhibitor of SARS-CoV Mpro with an IC50 value of 2.5 µM in
the enzyme assay and an EC50 value of 7 µM in the cell
protection assay.7 Through the screening of 50000 compounds
in a quenched fluorescence resonance energy transfer assay
against SARS-CoV Mpro, followed by additional studies, five
novel small molecules that show inhibitory activity (IC50
)
0.5-7 µM) against SARS-CoV Mpro were identified.8 A series
of keto-glutamines with a phthalhydrazido group in the R-posi-
tion were synthesized based on the enzyme recognizing peptide
substrates sequence as inhibitors of SARS-CoV Mpro. These
tetrapeptide based molecules were found to have IC50 values
ranging from 0.60 to 70 µM in the enzyme assays.9 In addition,
glycyrrhizin (GL) has been reported to inhibit SARS-CoV
replication in vitro with an EC50 value of 365 µM, and several
more active analogues of GL have also been discovered.10
We have been studying the design and synthesis of inhibitors
of caspases, which are a class of cysteine proteases that play a
critical role in apoptosis. Our dipeptide based caspase inhibitors,
such as 7 (MX1013, Z-Val-Asp-fmk, Chart 1), are active in
The rapid emergence and spread of the SARS-CoV caught
public health agencies off guard, and currently there is no
effective treatment for SARS. Major efforts to develop SARS
* Tel: 858-202-4006. Fax: 858-202-4000. E-mail: scai@maxim.com.
† Maxim Pharmaceuticals.
‡ Clinics of the Johann Wolfgang Goethe-University.
10.1021/jm0507678 CCC: $33.50 © 2006 American Chemical Society
Published on Web 01/10/2006

Brief Articles
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 3 1199
Table 1. Effect of SARS-CoV Inhibitors on FFM1 or 6109 SARS-CoV
Replication in Vero and CaCo2 Cells
Scheme 1
Scheme 2
inhibiting apoptosis in cell culture models (IC50 < 500 nM)
and are highly efficacious in animal models, including mouse
acute liver failure model and mouse and rat models of brain
ischemia/reperfusion injury and acute myocardial infarction.11
Since SARS-CoV Mpro is also a cysteine protease, we sought
to apply our knowledge from the studies of caspase inhibitors
toward the discovery of potential SARS-CoV inhibitors. Herein
we report the design and synthesis of a series of dipeptidyl
glutaminyl fluoromethyl ketones as novel inhibitors of SARS-
CoV.
a Concentration of compound inhibiting cytopathic effect to 50% of
untreated cells. Values represent the mean ( SD from three independent
experiments. b Incubation of confluent CaCo2 or Vero cell layers with
different concentrations of all the dipeptides for 3 days did not reveal any
toxic effects at concentrations up to 100 µM. c Ratio of CC50 to EC50 in
Vero cells with strain 6109.
measurement of the inhibiting effects of compounds on the
replication of SARS-CoV. Antiviral activity assessed by CPE
inhibition in SARS-CoV infected Vero cultures revealed that
compounds 6a-6c were effective inhibitors of both FFM1 and
6109 strains of SARS-CoV replication (Table 1). Compound
6a has an EC50 value of 2.5 µM in the Vero cells infected with
strain 6109. In the toxicity assay, incubation of confluent CaCo2
or Vero cell layers with different concentrations of the dipeptides
for 3 days did not reveal any toxic effects at concentrations up
to 100 µM, indicating that the toxicity CC50 values for all
compounds are >100 µM. This provides a selectivity index (SI)
value of >40 for compound 6a. Compound 6a was about 2-fold
more potent than compounds 6b and 6c. This is consistent with
the substrate specificity of SARS-CoV Mpro that leucine is the
dominant P2 amino acid (>75%). Valine and phenylalanine also
can be the P2 amino acid,12 suggesting a preference for a
hydrophobic side chain at the P2 position. Compounds 6d and
6e with glycine and alanine as the P2 amino acid did not inhibit
virus replication at concentrations up to 100 µM (maximum
concentration tested), confirming that a hydrophobic side chain
in the P2 position such as those in leucine, isoleucine, and valine
is important for activity. Compound 7, a potent caspase inhibitor
with an aspartic acid as P1, did not inhibit virus replication up
to 100 µM. This is in agreement with the specificity of SARS-
CoV Mpro substrate that glutamine is essential in the P1 position.
The high potency of compounds 6a-6c also suggests that the
NH2 group of the glutamine side chain might not be important
for hydrogen bonding interactions with SARS-CoV Mpro. It has
been reported that for hepatitis A virus (HAV) 3C proteinase,
a class of protease having similar substrate specificity as that
of Mpro of coronavirus, the P1 glutamine can be replaced by
N,N-dimethylglutamine with no impact on substrate peptide
recognition or cleavage.17
Results and Discussion
Synthesis. It is known from the substrate cleavage site
specificity of SARS-CoV Mpro that glutamine is essential as
the P1 amino acid. Leucine is the preferred P2 amino acid, while
valine and phenylalanine are also allowed.12 We therefore
designed and synthesized a series of dipeptides, using N,N-
dimethyl-Gln-fmk as the P1 amino acid and warhead, in
combination with different P2 amino acids. These dipeptide-
fmk inhibitors were prepared in five steps as shown in Scheme
1 for Cbz-Val-N,N-dimethyl-Gln-fmk (6c). The intermediate
amino-alcohol 4 was prepared by conversion of the ester 1 to
the amide 2 by reaction with dimethylamine, followed by
reaction of amide 2 with the aldehyde intermediate that is
produced by Swern-oxidation of 2-fluoroethanol to produce the
nitro-alcohol 3, which was then reduced by hydrogenation.
Coupling of 4 with a Z-protected valine produced amide 5c,
which was oxidized by Dess-Martin reagent to produce 6c.
Dipeptides 6a, 6b, 6d, and 6e were prepared similarly by
replacing Z-valine with other Z-protected amino acids. We also
explored the synthesis of dipeptides with N-methyl-glutamine
and glutamine as the P1 amino acid. The N-methyl-glutamine
analogue was prepared by using MeNH2 instead of NHMe2,
and the glutamine analogue was prepared by using ammonia
instead of NHMe2. As expected, the NH2 of the glutamine side
chain in compound 9 was found to predominantly cyclize with
1
the carbonyl of the fmk group (Scheme 2), as observed by H
NMR in solution,13 similar to what has been reported for a
glutamine-aldehyde based inhibitor,14 whereas the N,N-dimethyl-
glutamine analogues 6a-6e could not form the cyclized
structure.15 The N-methyl-glutamine analogue 8 was found to
To show that drugs exert the antiviral activity independently
of cell type, effects of compounds 6a-6e on CPE were tested
in the human colon carcinoma cell line CaCo2 infected with
the FFM1 virus strain. The results were similar to those obtained
in Vero cells (Table 1). Compound 6a was 3- to 5-fold more
potent than compounds 6b and 6c, respectively. Compounds
6d and 6e were again not active up to 100 µM.
1
partially form the cyclized structure as observed by H NMR
in solution.16
Biological Results. The dipeptides were first tested against
SARS-CoV infected Vero cells as described previously.10 The
assays measure the protective effects of compounds against
SARS-CoV-induced cell death (cytopathic effect (CPE)) as a

1200 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 3
Brief Articles
hertz. Elemental analyses were performed by Numega Resonance
Labs, Inc. (San Diego, CA). For cell based antiviral assays, the
compounds were dissolved in DMSO at a concentration of 50 mM
and stored in aliquots at -20 °C.
It is known that picornaviruses, including human rhinoviruses
(HRV), also encode a viral 3C protease with specificity for
glutamine-glycine cleavage for the processing and releasing
of viral proteins that are essential for the replication of the
viruses.18 We therefore sought to test our compounds against
rhinoviruses. Interestingly, compounds 6a-6c were found to
be inactive against rhinovirus type-2 in a cell based assay,19
suggesting that compounds 6a-6c might be specific against
SARS-CoV and may not inhibit nonspecifically all the viruses
that encode a 3C protease. There are several possible reasons.
For example, the P1 N,N-dimethyl-glutamine might not be
preferred by rhinovirus 3C,20 or a tripeptide structure might be
important for inhibition of rhinovirus. Interestingly, rupintrivir
(AG7088), the novel HRV 3C protease inhibitor with broad-
spectrum antiviral activity against all HRV serotypes,21 has been
reported to be inactive against SARS-CoV (IC50 > 100 µM),22
suggesting that there might be significant differences between
N,N-Dimethyl-4-nitrobutyramide (2). To a solution of methyl-
4-nitrobutyrate (1.0 g, 6.8 mmol) in methanol (10 mL) was added
40% dimethylamine water solution (12.5 mL, 102 mmol). The
solution was stirred at room temperature for 48 h, concentrated by
vacuum, and diluted with ethyl acetate (20 mL). The organic layer
was dried and evaporated. The residue was purified by flash
chromatography over silica gel (hexane/EtOAc ) 1:1) to give 2
1
(0.99 g, 91%). H NMR (CDCl3): 4.53 (t, J ) 6.6, 2H), 3.02-
2.94 (m, 6H), 2.48-2.43 (m, 2H), 2.36-2.31 (m, 2H).
6-Fluoro-5-hydroxy-4-nitrohexanoic Acid Dimethylamide (3).
To a cooled (-78 °C) solution of oxalyl chloride (0.9 mL, 9.6
mmol) in anhydrous dichloromethane (5 mL) was added anhydrous
DMSO (1.4 mL, 19 mmol) dropwise, and the reaction mixture was
stirred for 15 min. A solution of 2-fluoroethanol (0.44 mL, 7.5
mmol) in dichloromethane (2 mL) was slowly added into the
reaction flask. The reaction mixture was stirred for 15 min; then it
was diluted with dichloromethane (60 mL), followed by addition
of dry Et3N (4.4 mL, 31 mmol). The reaction mixture was stirred
for 15 min, then warmed to 0 °C and stirred at 0 °C for 2 h. To the
reaction mixture was added a solution of N,N-dimethyl-4-nitro-
butyramide (0.99 g, 6.3 mmol) in CH2Cl2 (5 mL). The reaction
mixture was stirred at 0 °C for 3 h and then stirred at room-
temperature overnight. The mixture was concentrated and extracted
with ethyl acetate. The organic layer was dried and evaporated.
The residue was purified by silica gel (CH2Cl2/EtOAc ) 1:3) to
give 1.2 g (89%) of 3 as a colorless viscous oil. 1H NMR (CDCl3):
5.19 (bs) and 5.02 (bs, 1H), 4.80-4.40 (m, 3H), 4.25 (bs) and 4.20
(bs, 1H), 3.02-2.94 (m, 6H), 2.45-2.20 (m, 4H).
the structure of HRV 3C protease and SARS-CoV Mpro
.
The toxicity of compound 6c in mice was tested by IV
injection (5% dextrose/water solution) of a single dose at 25,
50, and 100 mg/kg, followed by observation for one week. No
weight loss or behavioral changes nor any gross pathology
change of the major organs was observed at the tested doses.
This is in agreement with the low toxicity observed in cell assay
for 6c (CC50 > 100 µM). It is expected that related analogues
of 6c should also have low toxicity.
In conclusion, we have designed and synthesized a group of
dipeptidyl glutaminyl fluoromethyl ketones as potential inhibi-
tors of SARS-CoV Mpro. The antiviral activity of these
compounds was assessed by CPE inhibition in SARS-CoV
infected Vero and CaCo2 cultures. Compound 6a was found to
have an EC50 value of 2.5 µM in the CPE inhibition assay with
a SI value of >40, presumably through the inhibition of SARS-
CoV Mpro. Preliminary SAR studies showed that glutamine is
important as the P1 amino acid and N,N-dimethyl-glutamine is
tolerated at P1. Leucine is the preferred P2 amino acid, which
can be replaced by isoleucine and valine. Compound 6c also
has been found to have low toxicity in mice, suggesting that
these SARS-CoV inhibitors should have a good safety profile
for animal efficacy studies.
In addition, picornaviruses, including several important human
and veterinary pathogens, such as poliovirus and coxsackievirus
(enterovirus), foot-and-mouth disease virus (aphthovirus), en-
cephalomyocarditis virus (cardiovirus), hepatitis A virus (hepa-
tovirus), and human rhinoviruses (rhinovirus), also encode a
viral 3C protease with specificity for glutamine-glycine cleav-
age for the processing and releasing of viral proteins that is
essential for the replication of the viruses.18 Therefore our
approach for the design and synthesis of protease inhibitors of
SARS-CoV could also be applied to the discovery of inhibitors
of picornaviral 3C proteases for the treatment of diseases that
are caused by picornaviruses. Additional studies, such as
incorporating other amino acids at P2, replacing the dipeptide
structure with a tripeptide, modifying the P1 glutamine side
chain, converting the dipeptide structure into a non-peptide
structure to improve oral bioavailability, and animal efficacy
studies, will be reported in the future.
4-Amino-6-fluoro-5-hydroxyhexanoic Acid Dimethylamide
(4). To a solution of 6-fluoro-5-hydroxy-4-nitrohexanoic acid
dimethylamide (1.2 g, 5.5 mmol) in MeOH (20 mL) was added
Ranny Ni (about 500 mg), and the mixture was hydrogenated under
40-45 psi H2 at room temperature for 6 h. The catalyst was
removed. The MeOH solution was evaporated, and the residue oil
(0.92 g, yield 87%) was used without further purification. 1H NMR
(CDCl3): 4.70-4.40 (m, 2H), 3.80-3.50 (m, 1H), 3.20-2.80 (m,
8H), 2.60-2.40 (m, 2H), 2.00-1.65 (m, 2H).
4-(Z-Val-amido)-6-fluoro-5-hydroxyhexanoic Acid Dimethyl-
amide (5c). To a solution of Z-valine (1.2 g, 5.0 mmol) in THF
(30 mL) was added 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide
hydrochloride (EDCI; 0.95 g, 5.0 mmol), 1-hydroxybenzotriazole
(HOBT; 0.67 g, 5.0 mmol), and 4-dimethylaminopyridine (DMAP)
(0.30 g, 2.5 mmol). The resulting mixture was stirred for 10 min;
then a solution of 4-amino-6-fluoro-5-hydroxyhexanoic acid dim-
ethylamide (0.95 g, 5.0 mmol) in THF (2 mL) was added, and the
mixture was stirred at room temperature overnight. The solvent
was evaporated, and the residue was diluted with ethyl acetate (100
mL). The solution was washed with brine (10 mL), and the organic
layer was dried and evaporated. The residue was purified by
chromatography over silica gel (hexane/EtOAc ) 1:1 to EtOAc/
MeOH ) 3:1) to give 1.2 g (58%) of 5c as a white solid. 1H NMR
(acetone-d6): 7.40-7.30 (m, 5H), 7.10 (m, 1H), 6.40 (m, 1H), 5.05
(s, 2H), 4.60-4.15 (m, 3), 4.05-3.80 (m, 3H), 3.00-2.85 (m, 6H),
2.40 (m, 2H), 2.20-2.09 (m, 1H), 2.00-1.75 (m, 2H), 1.00-0.90
(m, 6H).
4-(Z-Val-amido)-6-fluoro-5-oxohexanoic Acid Dimethylamide
(6c). To a solution of 4-(Z-Val-amido)-6-fluoro-5-hydroxyhexanoic
acid dimethylamide (0.90 g, 2.1 mmol) in CH2Cl2 (60 mL) at 0 °C
was added Dess-Martin periodinane (2.7 g, 6.0 mmol). The
resulting mixture was stirred at room temperature for 4 h, the solvent
was evaporated, and the residue was diluted with ethyl acetate (80
mL). It was washed with brine (30 mL), and the organic layer was
dried and concentrated. The residue was purified by column
chromatography (EtOAc/MeOH ) 8:1) to give 6c (0.87 g, 97%)
Experimental Section
General Methods and Materials. Commercial-grade reagents
and solvents were obtained from Aldrich; Z-amino acids were
obtained from Advanced ChemTech and were used without further
purification. The 1H NMR spectra were recorded at 300 MHz.
Chemical shifts are reported in parts per million (ppm) downfield
from TMS (0.00 ppm), and J coupling constants are reported in
1
as a solid. H NMR (acetone-d6): 7.95 (bs, 1H), 7.38-7.29 (m,
5H), 6.43 (bs, 1H), 5.30-5.20 (m, 1H), 5.14-5.05 (m, 3H), 4.55-
4.51 (m, 1H), 4.09-4.00 (m, 1H), 2.98-2.82 (m, 6H), 2.50-2.46

Brief Articles
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 3 1201
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(m, 2H), 2.17-2.09 (m, 2H), 2.00-1.88 (m, 1H), 0.99-0.92 (m,
6H). Anal. (C21H30FN3O5‚0.7H2O) C, H, N.
The following compounds were prepared from the corresponding
Z protected amino acid and 4 in two steps by a procedure similar
to that described for the preparation of compounds 5c and 6c.
4-(Z-Leu-amido)-6-fluoro-5-oxohexanoic Acid Dimethylamide
1
(6a). Colorless solid. H NMR (acetone-d6): 8.00-7.94 (m, 1H),
7.38-7.30 (m, 5H), 6.57 (m, 1H), 5.29-5.18 (m, 1H), 5.13-5.09
(m, 3H), 4.50-4.47 (m, 1H), 4.22-4.14 (m, 1H), 2.99-2.80 (m,
6H), 2.49-2.44 (m, 2H), 2.15-2.11 (m, 1H), 1.96-1.89 (m, 1H),
1.79-1.70 (m, 1H), 1.64-1.59 (m, 2H), 0.95-0.91 (m, 6H). Anal.
(C22H32FN3O5‚0.5H2O) C, H, N.
4-(Z-Ile-amido)-6-fluoro-5-oxohexanoic Acid Dimethylamide
1
(6b). Oil. H NMR (acetone-d6): 7.95-7.93 (m, 1H), 7.38-7.29
(m, 5H), 6.43 (m, 1H), 5.30-5.20 (m, 1H), 5.14-5.04 (m, 3H),
4.54-4.48 (m, 1H), 4.09-4.00 (m, 1H), 2.99-2.80 (m, 6H), 2.50-
2.46 (m, 2H), 2.16-2.11 (m, 1H), 1.97-1.88 (m, 2H), 1.61-1.52
(m, 1H), 1.30-1.17 (m, 1H), 0.96-0.86 (m, 6H). Anal. (C22H32-
FN3O5) C, H, N.
(13) In anti-SARS-CoV screening studies done by the National Institute
of Allergy and Infectious Diseases (NIAID) and managed by Southern
Research Institute (SRI), compound 9 was found to be >200-fold
less active than the corresponding N,N-dimethyl-glutamine analogue
6a (personal communication from Dr. Joseph A. Maddry of SRI).
The low activity of compound 9 most probably is due to the dominant
cyclized form, which is not expected to interact effectively with the
SARS-CoV Mpro enzyme.
4-(Z-Gly-amido)-6-fluoro-5-oxohexanoic Acid Dimethylamide
(6d). Oil. 1H NMR (acetone-d6): 7.90 (bs, 1H), 7.83-7.25 (m, 5H),
6.70 (bs, 1H), 5.40-5.20 (m, 1H), 5.13-5.04 (m, 3H), 4.55 (bs,
1H), 3.83 (d, J ) 6.3, 2H), 2.98-2.85 (m, 6H), 2.45 (m, 2H), 2.16-
2.07 (m, 1H), 1.98-1.85 (m, 1H). Anal. (C18H24FN3O5‚0.8H2O)
C, H, N.
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compound 8 was found to have an EC50 value of 1.2 µM against the
cytopathic effect (personal communication from Dr. Joseph A.
Maddry of SRI). Therefore there might be advantage of N-methyl-
glutamine over N,N-dimethyl-glutamine due to potential hydrogen
bonding of the NH group with the SARS-CoV Mpro enzyme.
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Patick, A. K.; Zalman, L. S.; Hendrickson, T. F.; Love, R. A.; Prins,
T. J.; Marakovits, J. T.; Zhou, R.; Tikhe, J.; Ford, C. E.; Meador, J.
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4-(Z-Ala-amido)-6-fluoro-5-oxohexanoic Acid Dimethylamide
(6e). Oil. H NMR (CDCl3): 7.85-7.78 (m, 1H), 7.30-7.20 (m,
5H), 5.40 (m, 1H), 5.15 (m, 3H), 4.98 (bs, 1H), 4.65 (bs, 1H),
4.25 (m, 1H), 2.98 (s, 3H), 2.95 (s, 3H), 2.60-2.25 (m, 2H), 2.25-
2.00 (m, 2H), 1.40 (m, 3H). Anal. (C19H26FN3O5‚H2O) C, H, N.
1
Acknowledgment. We would like to thank National Institute
of Allergy and Infectious Diseases, Dr. Joseph A. Maddry of
Southern Research Institute, and Professors Dale L. Barnard
and Robert W. Sidwell of Utah State University (NIAID
Contract NO1-AI-30048) for the initial testing of our SARS-
CoV inhibitors in a cell based screening assay. The authors also
thank Gabriele Bauer for technical assistance.
Supporting Information Available: Antiviral assay, animal
studies, and table of elemental analysis data for the targeted
compounds 6a-6e. This material is available free of charge via
the Internet at http://pubs.acs.org.
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