Azaindole hydroxamic acids are potent HIV-1 integrase inhibitors

Article abstract of DOI:10.1021/jm900862n

HIV-1 integrase (IN) is one of three enzymes encoded by the HIV genome and is essential for viral replication. Recently, HIV-1 IN inhibitors have emerged as a new promising class of therapeutics. Herein, we report the discovery of azaindole carboxylic aci

Full text of DOI:10.1021/jm900862n

J. Med. Chem. 2009, 52, 7211–7219 7211
DOI: 10.1021/jm900862n
Azaindole Hydroxamic Acids are Potent HIV-1 Integrase Inhibitors
Michael B. Plewe,*,† Scott L. Butler,‡ Klaus R. Dress,† Qiyue Hu,† Ted W. Johnson,† Jon E. Kuehler,†,¥ Atsuo Kuki,†
Hieu Lam,† Wen Liu,†,§ Dawn Nowlin,† Qinghai Peng,† Sadayappan V. Rahavendran,† Steven P. Tanis,† Khanh T. Tran,†
†,
Hai Wang,† Anle Yang,† and Junhu Zhang
†Pfizer Global Research and Development, La Jolla Laboratories, 10770 Science Center Drive, San Diego, California 92121, and ‡Pfizer Global
Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, U.K. §Current address: Genentech, Inc., 1 DNA Way, MS 18B, South
San Francisco, CA 94080. ¥Current address: AMPAC Fine Chemicals, PO Box 1718, Rancho Cordova, CA 95741. Current address: Trius
Therapeutics, 6310 Nancy Ridge Drive, Ste 101, San Diego CA 92121.
Received June 12, 2009
HIV-1 integrase (IN) is one of three enzymes encoded by the HIV genome and is essential for viral
replication. Recently, HIV-1 IN inhibitors have emerged as a new promising class of therapeutics.
Herein, we report the discovery of azaindole carboxylic acids and azaindole hydroxamic acids as potent
inhibitors of the HIV-1 IN enzyme and their structure-activity relationships. Several 4-fluorobenzyl
substituted azaindole hydroxamic acids showed potent antiviral activities in cell-based assays and
offered a structurally simple scaffold for the development of novel HIV-1 IN inhibitors.
Introduction
The catalytic core domain of IN contains two aspartate
(Asp64, Asp116) and one glutamate (Glu152) residues that are
critical for the catalytic activity of IN and are believed to bind
Mg2þ and Mn2þ ions.11 Recent data suggest that Mg2þ
is the biologically relevant divalent metal critical for IN activity.12
It is generally believed that IN inhibitors such as diketo acids
(DKA, A), or the dihydroxy pyrimidines carboxamide class (B)
bind these two metal ions in the active site while the hydrophobic
aryl group participates in a specific interaction with an adjacent
hydrophobic pocket or surface (Figure 1).13,14 Broad screening
of our internal compound collection lead to the identification of
azaindole carboxylic acids 1a-h with modest activity (IC50:
0.95-7.35 μM) and good ligand efficiencies LE15,16 (Δg >
0.35 kcal/mol) in the primary enzymatic assay (Table 1). As
hydroxamic acids are recognized for their metal binding proper-
ties.17 we reasoned that replacing the bidentate picolinic acid
(picA, C)18,19 moiety that only binds one Mg2þ by a picoline
hydroxamic acid (picHA, D) moiety (Figure 1) would greatly
facilitate binding of two Mg2þ ions, leading to improved in-
hibitory properties.20
Human immunodeficiency virus type 1 (HIV-1a), the causa-
tive pathogen of AIDS, replicates utilizing three essential en-
zymes encoded in the HIV pol gene: reverse transcriptase (RT),
protease (PR), and integrase (IN). Many anti-HIV agents target
either RT1 or PR.2 More recently, inhibitors of the host cor-
eceptor chemokine receptor 5 (CCR5)3,4 and the viral IN enzyme
have emerged as two new promising classes of therapeutics for
the treatment of AIDS5.6 Efforts to target HIV-1 IN in particular
have yielded the recent approval of raltegravir (MK-0518)7,8 and
encouraging phase II clinical trial with elvitegravir (GS-9137,
JTK 303).9 Several drivers remain however to discover new
chemical classes of HIV-1 IN inhibitors that might be developed
with complementary or improved properties regarding resis-
tance, dosing, and tolerability.10 Below, we present results from
our own HIV-1 IN program aimed at addressing those needs.
Results and Discussion
Replacing the carboxylic acid moiety in compounds 1b and
1c by a hydroxamic acid moiety (compounds 2b and 2c) lead
to a 40-fold increase in potency in the enzymatic assay,
providing excellent potencies in our antiviral cell protection
assay (EC50 < 10 nM) with no observed cytotoxicity up to the
*To whom correspondence should be addressed: Phone: þ858-526-
4653. Fax: þ858-678-8293. E-mail: michael.plewe@pfizer.com.
a Abbreviations: biolum Ames, bioluminescent reverse mutation
assay; CCR5, chemokine receptor 5; CC50, 50% cytotoxic concentra-
tion; CPE, cytopathic effect; DCM, dichloromethane; DIEA, diisopro-
pyl ethylamine; DKA, diketo acid; DMAP, dimethylamino pyridine;
DMF, dimethylformamide; DMF-DMA, dimethylformamide dimethy-
lacetal; DMSO, dimethylsulfoxide; EC50, 50% effective concentration;
ER, extraction ratio; HIV, human immunodeficiency virus; HATU,
2-(7-aza-1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluor-
ophosphate; HTS, high-throughput screening; hHEP, human hepato-
cyte; hLM, human liver microsome; HPLC, high-performance liquid
chromatography; IC50, 50% inhibitory concentration; IN, integrase;
LC-MS, liquid chromatography-mass spectrometry; LE, ligand effi-
ciency; NADPH, reduced nicotineamide adenine dinucleotide phos-
phate; PicA, picolinic acid; PicHA, picoline hydroxamic acid; PR,
protease; RT, reverse transcriptase; SPA, scintillation proximity assay;
TFA, trifluoroacetic acid; THF, tetrahydrofuran; TLC, thin-layer
chromatography.
highest concentration tested (2b: CC50 > 320 μM; 2c: CC50
>
1 μM). We explored a number of different aryl groups and
concluded that compounds containing at least one (g1)
fluorine atom, with one fluorine required to be in the para
position (2b: IC50 84 nM, EC50 8 nM; 2c: IC50 137 nM, EC50
9
Figure 1. Metal binding of DKA (A), dihydroxypyrimidine car-
boxamide (B), PicA (C), and PicHA (D).
r
2009 American Chemical Society
Published on Web 10/29/2009
pubs.acs.org/jmc

7212 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22
Plewe et al.
nM) provided the best combination of potency in both
biochemical and cell-based assays (Table 2), and the best
ligand efficiencies LE (Δg).10
our bioluminescent reverse mutation assay (biolum Ames)26
using Salmonella tester strains TA98 and TA100 and found it
to be nonmutagenic in the presence and absence of activating
enzymes (S9 fraction), whereas the unsubstituted hydroxamic
acid 9 and the O-methylated analogue 4b gave a positive result
in both strains with and without metabolic activation by S9
fraction. Both O-methylated compounds 4b (extraction ratio
(ER) = 0.68) and 5b (ER = 1) were rapidly cleared in our
human liver P450 microsome (hLM) lability assay in the
presence of NADPH. The N-methylated compound 3b (ER
< 0.36) showed low turnover in hLM against oxidative
metabolism, however it was rapidly cleared in human hepa-
tocytes (hHEP) due to glucuronidation of the free OH, a well-
known drug metabolism pathway for hydroxamic acids.27,28
We investigated if metabolism could be attenuated with bulkier
R1 groups. Increasing the size of R1 (Table 4) did not modify
turnover rate in human hepatocytes and resulted in a rapid
drop in both biochemical and cell-based antiviral assays.
Through metabolic activation, hydroxamic acids can un-
dergo a Lossen rearrangement to form potentially mutagenic
isocyanates.21-23 It has been noted that the presence of the
NH function is essential for mutagenicity of hydroxamic
acids.24 For the Lossen rearrangement to occur, the OH needs
to be converted to a leaving group and then formation of the
nitrene and rearrangement leads to the undesired isocya-
nate.25 We reasoned that alkylation of either the NH or the
OH would circumvent Lossen rearrangement. Methylation of
eitherthe NHorOHincompound2bprovidedcompounds 3b
(EC50: 32 nM) and 4b (EC50: 21 nM), leading to a small loss of
cell-based antiviral activity. Methylation of both heteroatoms
(compound 5b, EC50 > 10 μM) resulted in complete loss of
enzymatic activity (Table 3). We evaluated compound 3b in
Table 1. Enzymatic Activities and Ligand Efficiencies of Azaindole
Carboxylic Acids from High-Throughput Screening (HTS)
Synthesis
The chemistry used for formation of azaindole esters19a-b
and final products 2-11 is depicted in Scheme 1. Hydroxy-
pyridine 12 was converted to the corresponding bromide 13
using POBr3. Reaction of 13 with zinc cyanide29 in the
presence of a catalytic amounts of Pd(PPh3)4 provided nitrile
14, which was converted to esters 15 (R = Me) and 16 (R =
Et) under acidic Pinner conditions. Reaction of 15 and 16 with
dimethylformamide dimethyl acetal (DMF-DMA) followed
by reduction as described by Leimgruber-Batcho30 provided
azaindole esters 17 and 18,31,32 which were alkylated using
benzyl halides and sodium hydride to provide esters 19 (R =
Me) and 20 (R = Et). Saponification of esters 20a-h with
NaOH provided acids 1a-h.
compd
Ar
2-F-Ph
2,4-F-Ph
IC50a (μM)
LE (Δg)b (kcal/mol)
1a
1b
1c
1d
1e
1f
>50
<0.29
0.353
0.351
0.336
0.390
0.366
0.341
0.393
3.50 ( 0.90
7.35 ( 4.45(2)
3.69 ( 0.41
0.95 ( 0.36
1.19 ( 0.93
5.42 ( 2.2
3.20 ( 0.14
4-F-Ph
2,3,4-F-Ph
2-F, 3-Cl-Ph
2,6-F-3-Cl-Ph
2,3-Cl-Ph
Hydroxamic acids 2-11 were prepared either by treatment
of esters 19 and 20 with hydroxyl amines in the presence of
NaOH,33 or by coupling acids 1a-h with hydroxyl amines in
the presence of HATU. N-Alkylated hydroxylamines 23a-c
1g
1h
4-Cl-thiophene
a Strand transfer scintillation proximity assay. b Ligand efficiency
(LE), Δg = ΔG/Nnon-hydrogenatoms; ΔG = -RT ln(IC50); T = 300 K.
Table 2. Enzymatic and Antiviral Activity of Azaindole Hydroxamic Acids
compd
Ar
2,4-F-Ph
4-F-Ph
IC50a (nM)
EC50b (nM)
CC50b(μM)
LE (Δg)c (kcal /mol)
2b
2c
2e
2f
84 ( 38 (6)
137 ( 31
102 ( 1
131 ( 35
442 ( 175
8
9
>320
159
0.440
0.444
0.436
0.407
0.393
0.436
0.418
0.324
0.360
0.358
<0.29
0.333
0.352
0.341
<0.29
2-F, 3-Cl-Ph
2,6-F, 3-Cl-Ph
2,3-Cl-Ph
8
>320
>1
7
35
2g
2h
2i
>320
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
4-Cl-thiophene
2-pyridyl
387 ( 48
20
88
779 ( 217 (2)
5730 ( 290 (2)
812 ( 680 (2)
1620 ( 200 (2)
>10000
2j
3-HOCH2-2-pyridyl
2-CN, 4-F-Ph
3-CN-Ph
730
120
500
1200
55
2k
2l
2m
2n
2o
2p
2q
4-CN-Ph
2-CONH2, 4-F-Ph
3-CONH2, 4-F-Ph
3-CONH2-Ph
4-CONH2-Ph
1300 ( 40 (2)
608 ( 28 (2)
1720 ( 60 (2)
>10000
58
530
>10,00
a Strand transfer scintillation proximity assay. b HIV-1 cytopathic effect (CPE) inhibition assay; EC50, 50% effective concentration; CC50, 50%
cytotoxic concentration. c Ligand efficiency (LE), Δg = ΔG/Nnon-hydrogenatoms; ΔG = -RT ln(IC50); T = 300 K.

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22 7213
Table 3. Enzymatic and Antiviral Activity, Metabolic Stability, and Mutagenicity of N- and O-Methyl Hydroxamic Acids
compd
R1
R2
IC50a (nM)
EC50b (nM)
CC50b (μM)
ERc (hLM)
ERc (hHEP)
Biolum Amesd
2b
3b
4b
5b
H
H
84 ( 38 (6)
250 ( 91 (4)
356 ( 213 (4)
8
32
>320
135
<0.26
<0.36
0.68
0.9
1
positive
negative
positive
ND
CH3
H
H
CH3
CH3
21
>10000
>320
>10
1
CH3
>50000
1.00
1
a Strand transfer scintillation proximity assay. b HIV-1 cytopathic effect (CPE) inhibition assay; EC50, 50% effective concentration, CC50, 50%
cytotoxic concentration. c Metabolic stability in human liver microsomes (hLM) þ NADPH, and in human hepatocytes (hHEP); ER, extraction ratio
after 4 h. d Bioluminescent reverse mutation assay (Biolum Ames) in Salmonella tester strains TA98 and TA100 ( metabolizing enzymes (S9 fraction);
ND, not determined.
Table 4. Enzymatic and Antiviral Activity of N-Alkyl-Substituted
Hydroxamic Acids
terminal 6-histidine tag, and mutations described by Chen
et al.36 was expressed in Escherichia coli and purified following
standard methods. Double-stranded donor DNA (ds-DNA)
representing preprocessed ds-DNA derived from the LTR U5
sequence of the viral genome was synthesized (TriLink Bio-
Technologies, San Diego, CA) as a 50 biotinylated strand and a
CA base-pair overhang at the 50 end of the nonbiotinylated
strand. A 30 dideoxy derivative of the donor DNA was generated
as a control ds-DNA to test for nonspecific interactions. Target
ds-DNA was prepared as a [3H]-thymidine labeled product
(PerkinElmer Life Sciences Inc., Boston, MA) from enzymatic
extension of overhanging 30 ends of poly(dA) DNA. The final
product consists of 50-blunt end ds-DNA with six [3H]-thymi-
dine nucleotides at both 50 ends and specific activity of >900 Ci/
mmol. Biotinylated donor ds-DNA bound to streptavidin-
coated polyvinyltoluene SPA beads (Amersham Pharmacia,
Piscataway, NJ) was incubated with enzyme 15 min at 22 ꢀC
to form an integrase-donor DNA complex. The strand-transfer
reaction was initiated by addition of [3H]-thymidine labeled
target DNA. Final assay conditions were 2 pmol donor DNA,
246 nM integrase, and 50 nM target DNA in 22.5 mM MOPS
(pH 7.2), 20 mM NaCl, 4 mM CHAPS, 0.05% NP40, 4 mM
MgCl2, 1% DMSO, and 10 mM DTT. Reactions were for 50
min at 37 ꢀC, followed by addition of 150 mM EDTA, 90 mM
NaOH, and 6 M CsCl to stop the reaction and dissociate
integrase/DNA complexes. Compounds solvated and diluted
in 100% DMSO were transferred to the assay well in 10%
DMSO prior to addition of assay components. Activity was
measured in the TopCount plate-based scintillation counter
programmed with quench correction to normalize data for
potential color absorption of the compounds (PerkinElmer Life
Sciences Inc., Boston, MA). Compounds are tested as 2-3
replicates per concentration in 1 or more independent experi-
ments. The corrected percentage inhibition for a compound was
fit to a four-parameter logistic equation with variable Hill slope
using GraphPad Prism software (GraphPad Software, La Jolla,
CA). Acceptable criteria for a curve fit is a percent correlation
coefficient (R2) exceeding 92%. Data is reported as the mean
IC50 ( standard deviation (SD) and number (N) of independent
experiments. All other enzymatic data is IC50 ( standard error
(SE) of the curve fit parameter from replicate compound doses
in a single experiment.
ERc
(hHEP)
b
b
EC50
(nM)
CC50
(μM)
compd
R1
IC50a (nM)
2c
6c
H
methyl
137 ( 31
250 ( 14
618 ( 108
804 ( 127
1700 ( 200
8000 ( 3700
23000 ( 3370
9
39
>320
200
26
0.92
1.0
7c
8c
n-propyl
3-OH-propyl
iso-butyl
iso-propyl
benzyl
350
300
1400
3500
330
0.96
0.95
0.95
0.93
1
77
9c
102
36
10c
11c
>320
a Strand transfer scintillation proximity assay. b HIV-1 cytopathic
effect (CPE) inhibition assay; EC50, 50% effective concentration; CC50
,
50% cytotoxic concentration. c Metabolic stability in human hepato-
cytes (hHEP); ER, extraction ratio after 4 h.
(Scheme 2) were prepared by alkylation of the sodium salt of
ethyl 3-methyl-4-isoxazolecarboxylate34 21 with iodoalkanes,
followed by cleavage of 22a-c under acid conditions.
Conclusion
Azaindole hydroxamic acids 9-12 are potent HIV inte-
grase inhibitors with antiviral cell-based activities comparable
to the currently marketed HIV Integrase inhibitor raltegravir
(EC50: 10 nM).7 Unsubstituted hydroxamic acids are muta-
genic, while N-methylation leads to analogues (e.g., com-
pound 3b) that show a negative result in the Ames assay.
Both unsubstituted and N-alkyl substituted hydroxamic acids
are cleared through phase 2 glucuronidation pathways, and
further efforts toward attenuating glucuronidation will be
reported in a subsequent publication.
HIV-1 Cytopathic Effect (CPE) Inhibition Assay. The anti-
viral activities of potential modulator compounds (test
compounds) were determined as a function of their ability to
protect T-cells from the cytopathic effects of HIV-1 infection
using the XTT dye reduction method.37 CEM-SS cells seeded at
2 ꢀ 104 cells per well into 96-well plates were mock infected or
infected with HIV-1 RF virus at an MOI resulting in 90% cell
Experimental Section
Integrase Strand-Transfer Scintillation Proximity Assay
(SPA). A detailed description of the integrase strand-transfer
scintillation proximity assay is described35 and briefly summar-
ized here. Full-length HIV-1 IN constructed with an amino

7214 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22
Scheme 1. Synthesis of Hydroxamic Acids 2-11a
Plewe et al.
a Reagents and conditions: (a) POBr3/DCM, heat, 34 h (90%); (b) Zn(CN)2, Pd(PPh3)4, DMF, 80 ꢀC, 3 h (83%); (c) HCl, MeOH, H2O, or
H2SO4,EtOH, heat, 3 h (92%); (d) DMF-DMA, DMF, 90 ꢀC, 0.5 h; (e) Pd/C, MeOH, H2, 50 ꢀC, 3 d (70%, 2 steps); (f) ArCH2(Cl,Br), NaH, DMF or
THF (47-100%) (g) NaOH, MeOH, H2O (18-91%); (h) NaOH, NH2OH, MeOH (4-28%); (i) HATU, NEt3 or DIEA or DMAP, NHR1OR2
(7-87%).
Scheme 2. Synthesis of N-Alkyl Hydroxylaminesa
(HPLC) or thin-layer chromatography (TLC) and terminated
as judged by the consumption of starting material. The TLC
plates were visualized by UV, phosphomolybdic acid stain, or
iodine stain. Microwave assisted reactions were run in a Smith-
Creator (Personal Chemistry). 1H NMR spectra were recorded
on a Bruker instrument operating at 300 MHz unless otherwise
indicated. NMR spectra are obtained as DMSO-d6 or CDCl3
solutions (reported in ppm), using chloroform as the reference
standard (7.25 ppm) or DMSO-d6 (2.50 ppm). Other NMR
a Reagents and conditions: (a) RI, DMF, 120 ꢀC, 1 h (13-34%);
solvents were used as needed. When peak multiplicities are
(b) HCl (quant).
reported, the following abbreviations are used: s = singlet, d =
doublet, t = triplet, m = multiplet, br = broadened, dd =
death after 6 days. Test compounds at two or more replicate
doublet of doublets, dt = doublet of triplets. Coupling constants,
wells per half-log dilution were added to the cells at the time of
when given, are reported in Hz. The mass spectra were obtained
using liquid chromatography mass spectrometry (LC-MS) on an
Agilent instrument using atmospheric pressure chemical ioniza-
seeding and prior to the mock or HIV-1 RF virus infection. On
day 6, 50 μL of XTT (1 mg/mL XTT tetrazolium and 0.02 nM
phenazine methosulfate) was added to the wells for additional 4
tion (APCI) or electrospray ionization (ESI). High resultion mass
h incubation. Cell viability, as determined by the amount of
measurement were carrried out on an Agilent TOF 6200 series
XTT formazan produced, was quantified spectrophotometri-
withESI. Alltestcompoundsshowedg95%purityasdetermined
by combustion analysis or by high-performance liquid chroma-
tography (HPLC). HPLC conditions were as follows: Eclipse
XDB C8, 4.6 mm ꢀ 150 mm, 5 μm, 5% f 95% CH3CN/H2O/
0.1%TFA, 10 min run, flow rate 1.5 mL/min, UV detection (λ =
254, 224 nm), or 5% f 95% CH3CN/H2O/0.1%TFA, 9 min run,
hold 95% CH3CN/H2O/0.1%TFA for 3 min, flow rate 1.5 mL/
min. Combustion analyses were performed by Atlantic Microlab,
Inc. (Norcross, GA).
Bromo-4-methyl-5-nitropyridine (13). A solution of 4-methyl-
5-nitropyridin-2-ol 12 (82 g, 0.53 mol) and POBr3 (229 g, 0.8
mol, 1.5 equiv) in dichloromethane (2 L) was heated under a
nitrogen atmosphere in a 3 L three-neck flask with overhead
stirrer for 24 h. The mixture cooled to room temperature and
then was chilled in an ice-water bath and filtered. The solid
consisted of a 1:1 mixture of desired product 13 and unreacted
starting material 12; the filtrate contained the desired product
and unreacted POBr3. The solid (46 g) and fresh POBr3 was
dissolved in dichloromethane and refluxed for 10 h. The liquid
was decanted and combined with the filtrate of the first reaction.
The combined solutions were concentrated to a volume of 1.5 L.
With stirring in an ice-water bath, ice (500 g) was added to
quench excess POBr3. The organic layer was separated, and the
aqueous layer was extracted with dichloromethane. The
cally by absorbance at 450 nm. Data from CPE assays were
expressed as the percent of formazan produced in compound-
treated cells compared to formazan produced in wells of unin-
fected, compound-free cells. The 50% effective concentration
(EC50) was calculated as the concentration of compound
that increased the percentage of formazan production in in-
fected, compound-treated cells to 50% of that produced by
uninfected, compound-free cells. The 50% cytotoxic concentra-
tion (CC50) was calculated as the concentration of compound
that decreased the percentage of formazan produced in unin-
fected, compound-treated cells compared to uninfected, com-
pound-free cells. Compounds were tested in one or more
independent experiments. Variability was typically less than
30% for replicate data.
General Synthetic. Starting materials and other reagents were
purchased from commercial suppliers and were used without
further purification, unless otherwise indicated. All reactions
were performed under a positive pressure of nitrogen, argon, or
with a drying tube, at ambient temperature (unless otherwise
stated), in anhydrous solvents, unless otherwise indicated. Ana-
lytical thin-layer chromatography was performed on glass-
backed silica gel 60 ꢀF 254 plates (Analtech (0.25 mm)) and
eluted with the appropriate solvent ratios (v/v). The reactions
were assayed by high-performance liquid chromotagraphy

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22 7215
combined organic extracts were dried (magnesium sulfate) and
concentrated. The product was recrystallized from hexane.
temperature inside of the reaction reached 45 ꢀC, the hydrogen
gas flow into the Parr bottle was stopped and the temperature
was allowed to cool down to 25 ꢀC for 30 min. The color of the
liquid of the suspension changed from purple-red to light-green
and then colorless in the first hour of the reduction, and about
30 psi H2 was consumed. The hydrogen pressure was brought to
50 psi, and the hydrogenation was continued at 50 ꢀC for 20 h.
After cooling the reaction mixture to 20 ꢀC, the solid mixture,
which contained Pd(10%)/C and product, was isolated
by filtration. The solid mixture was suspended in DMSO
(200 mL), and the suspension was heated on a hot plate to
80 ꢀC inside with stirring for 10 min. The hot suspension was
filtered and the Pd(10%)/C solid was washed with a small
portion of DMSO (50 mL). The DMSO filtrate and washing
were combined and poured into water (600 mL) and the mixture
was allowed to stir for 1 h. Solids were removed by filtration
through a cake of celite to afford a pale-yellow liquid, which
was concentrated in vacuo to provide the title compound as
1
Yield: 104 g (90%). H NMR (CDCl3) δ 8.95 (s, 1H), 7.52 (s,
1H), 2.63 (s, 3H). LC-MS (APCI, M - H-) m/z 215 and 217
(bromine isotope pattern).
4-Methyl-5-nitropyridine-2-carbonitrile (14). 2-Bromo-4-
methyl-5-nitropyridine 13 (104 g, 0.479 mol), Zn(CN)2 (79 g,
0.673 mol), 1.4 equiv), and Pd(PPh3)4 (27 g, 0.023 mol, 5 mol %)
were added to a round-bottom flask (NOTE: using catalyst
purchased from STREM resulted in shorter reaction times and
better yields). DMF (900 mL) was degassed for 10 min before
adding to the solid mixture. The mixture was heated in an oil
bath to an internal temperature of 80 ꢀC. The color changed
from light-yellow to light-brown as the internal temperature
reached 80 ꢀC. The mixture was stirred at the same temperature
for 3 h and monitored by TLC. The solvent was removed in
vacuo. The residue was cast into a mixture of dichloromethane:
water, and insoluble material was removed by filtration through
celite. The organic layer was separated and the aqueous layer
was extracted with dichloromethane. The combined organic
extracts were dried (magnesium sulfate) and concentrated.
The residue was purified by column chromatography starting
with 100% hexane to hexane/ethyl acetate 4:1. Recrystallization
1
an ivory solid (11.3 g, 86%). H NMR (DMSO-d6) δ 11.99 (s,
1H), 8.80 (s, 1H), 8.36 (s, 1H), 7.73 (d, J = 3.0 Hz, 1H), 6.68 (d,
J = 2.8 Hz, 1H), 3.84 (s, 3H). LC-MS (APCI, M - H-)
m/z 175.
Ethyl 1H-Pyrrolo[2,3-c]pyridine-5-carboxylate (18). A mix-
ture of 16 (39.5 g, 0.19 mol) and DMF-DMA (30.6 g, 0.26 mol,
1.35 equiv) in DMF (470 mL) was heated to 90 ꢀC for 30 min.
The solvent was removed in vacuo. The residue (78 g) was used
without further purification in the next step. A solution of crude
(E)-ethyl 4-(2-(dimethylamino)vinyl)-5-nitropicolinate (78 g) in
ethanol (350 mL) was degassed and Pd (10%)/C (12 g, 30 wt %)
was added. The mixture was shaken in a Parr shaker under
hydrogen (40 psi) for 16 h. The initial reaction was exothermic,
the temperature rose to 65 ꢀC within 2 h, the pressure dropped
by 30 psi, and the color changed from red to light-green. After
the solution reached room temperature, the flask was shaken
under hydrogen (50 psi) for 16 h. The reaction was monitored by
LC-MS; at this point the solution contained 30% of desired
product. After shaking under hydrogen (50 psi, 50 ꢀC) for
additional 2.5 days, the LC-MS showed 70% of the desired
product. The mixture was filtered through a pad of celite, and
the filter cake was extracted twice by refluxing in ethanol (2 ꢀ
1 L) and filtration of the hot solution. The combined filtrates
were concentrated, and the residue was recrystallized from
ethanol to give 20 g of pure product. The mother liquor contain-
ing the desired product and the intermediate was concentrated
and dissolved in ethanol (300 mL). The mixture was hydro-
genated at 50 ꢀC and 50 psi for 3 days using Pd (10%)/C (5 g),
and then was worked up as before to provide additional 3 g of
desired product for a total yield of 23 g (64%). 1H NMR
(DMSO-d6) δ 11.99 (s, 1H), 8.82 (s, 1H), 8.37 (s, 1H), 7.73
(s, 1H), 6.69 (s, 1H), 4.32 (q, J = 7.5 Hz, 2H), 1.34 (t, J = 7.5 Hz,
3H). LC-MS (APCI, M þ Hþ) m/z 191.
1
from hexane yielded 65.8 g (83%) of the desired product. H
NMR (CDCl3) δ 9.20 (s, 1H), 7.73 (s, 1H), 2.71 (s, 1H). LC-MS
(APCI, M - H-) m/z 162.
Methyl 4-Methyl-5-nitropyridine-2-carboxylate (15). HCl gas
was bubbled into the solution of 14 (30 g, 0.185 mol) in methanol
(200 mL) with cooling in a ice-water bath for 5 min. Then
3.3 mL water (1 equiv) was added to the flask. The resulting
solution was heated to reflux for 3 h. The desired product
precipitated as HCl salt (white crystals). The mixture was cooled
to room temperature, and the precipitate was collected by
vacuum filtration. The solid was transferred to a 1 L separation
funnel, neutralized with satd aq NaHCO3 (400 mL), and
extracted with dichloromethane (400 mL). The organic layer
was dried over Na2SO4, concentrated, and dried in vacuo to give
1
a white solid (33 g, 92% yield). H NMR (DMSO-d6) δ 9.19
(s, 1H), 8.21 (s, 1H), 3.91 (s, 3H), 2.63 (s, 3H). LC-MS (APCI,
M þ Hþ) m/z 197.0.
Ethyl 4-Methyl-5-nitropyridine-2-carboxylate (16). Concen-
trated sulfuric acid (768 mL) was added slowly to ethanol (1.6 L)
with cooling. 14 (62.4 g, 0.38 mol) was added to the cold
solution, and the solution was then warmed to reflux under
nitrogen for 2 h. The majority of the solvent was removed in
vacuo, and the remaining thick solution was poured onto ice
(1 kg). After stirring for 15 min, the mixture was extracted with
ether (2 ꢀ 1 L) and multiple times with dichloromethane.
(NOTE: the organic layer is the TOP layer due to lower density
than water/sulfuric acid 1:1). As the extraction continued, the
organic layer changed from top layer to bottom layer due to
change in density as less ethanol was extracted. The combined
organic extracts were dried (magnesium sulfate) and concen-
trated. Recrystallization from hexane yielded 44.4 g (56%) of
the desired product. 1H NMR (CDCl3) δ 9.22 (s, 1 H), 8.13 (s,
1H), 4.51 (q, J = 7.5 Hz, 2H), 2.71 (s, 3 H), 1.46 (t, J = 7.5 Hz,
3 H). LC-MS: (APCI, M þ Hþ) m/z 209.
General Procedure A. Methyl 1-(4-Fluorobenzyl)-1H-
pyrrolo[2,3-c]pyridine-5-carboxylate (19c). To a stirred solution
of 17 (15.0 g, 85.1 mmol) in DMF (120 mL) at 10 ꢀC under a
nitrogen atmosphere was added sodium hydride (3.75 g, 60% in
mineral oil, 93.7 mmol, 1.1 equiv) in three portions over 5 min.
The slurry gradually became a homogeneous solution after
stirring for 130 min, and then 4-fluorobenzyl bromide (0.60 g,
2.89 mmol) was added at such a rate that the temperature did not
exceed 15 ꢀC. The resulting mixture was allowed to warm to
room temperature and was stirred for 2.5 h at ambient tempera-
ture. The mixture was carefully poured into water (120 mL) and
extracted with ethyl acetate (3 ꢀ 30 mL). The combined organic
extracts were washed with water (2 ꢀ 30 mL), dried over sodium
sulfate, and concentrated in vacuo to provide the crude product
as a sticky yellow solid. The crude material was purified by flash
chromatography (hexane:ethyl acetate 2:1), to provide the title
compound as a white solid (21.3 g, 88% yield). 1H NMR
(DMSO-d6) δ 8.97 (s, 1H), 8.30 (s, 1H), 7.87 (d, J = 2.8 Hz,
1H), 7.34 (dd, J = 8.3, 5.7 Hz, 2H), 7.15 (t, J = 8.9 Hz, 2H), 6.73
Methyl 1H-Pyrrolo[2,3-c]pyridine-5-carboxylate (17). A mix-
ture of 15 (3.5 g, 17.8 mmol) and dimethylformamide dimethy-
lacetal (DMF-DMA) (3.6 mL, 1.5 equiv) in acetonitrile (35 mL)
was heated in a microwave at 140 ꢀC for 20 min. The solvent was
removed, and the residue (5.1 g) was carried onto the next step
without further purification. To a 500 mL Parr bottle was added
crude (E)-methyl 4-(2-(dimethylamino)vinyl)-5-nitropicolinate
(18.9 g, 75.2 mmol) and anhydrous methanol (200 mL). The
mixture was purged with nitrogen gas for 10 min. To this
suspension was added Pd/C (1.90 g, 10% w/w), and the suspen-
sion was degassed for 5 more min. The hydrogenation began
with 43 psi H2, and an exotherm was noted (about 2-3 ꢀC per
min) inside the Parr bottle (monitored internally). As the

7216 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22
Plewe et al.
(d, J = 2.8 Hz, 1H), 5.59 (s, 2H), 3.84 (s, 3H). LC-MS (APCI,
M þ Hþ) m/z 285.3.
benzyl bromide (180 mg, 0.81 mmol) as described by general
procedure A. Yield: 250 mg (95%). H NMR (CDCl3) δ 9.05
(s, 1H), 8.50 (s, 1H), 7.55 (d, J = 3.0 Hz, 1H), 7.40 (m, 1H), 7.00
(m, 2H), 6.80 (d, J = 3.0 Hz, 1H), 5.55 (s, 2H), 4.50 (q, J = 7.0
Hz, 2H), 1.50 (t, J = 7.0 Hz, 3H). LC-MS (ESI, M þ Hþ) m/z
333.0.
1
Methyl 1-(2,4-Difluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-
carboxylate (19b). Prepared from 17 (976 mg, 5.5 mmol) using
2,4-difluorobenzylbromide (1.13 g, 5.5 mmol) as described by
general procedure A to provide 1.32 g (82%) colorless needles.
1H NMR (400 MHz, DMSO-d6) δ 8.98 (s, 1H), 8.36 (s, 1H), 7.79
(d, J = 3.03 Hz, 1H), 7.32 (dd, J = 8.97, 6.69 Hz, 2H), 7.32 (m,
1H), 7.07 (td, J = 8.53, 1.89 Hz, 1H), 6.75 (d, J = 3.03 Hz, 1H),
5.65 (s, 2H), 3.85 (s, 3H). LC-MS (APCI, M þ Hþ) m/z 303.0.
Methyl 1-(2-Cyano-4-fluorobenzyl)-1H-pyrrolo[2,3-c]pyridi-
ne-5-carboxylate (19k). Prepared according to general proce-
dure A using THF as solvent to provide the crude product (750
mg, 82%), which was used in the next step without further
Ethyl 1-(3-Chloro-2,6-difluorobenzyl)-1H-pyrrolo[2,3-c]pyri-
dine-5-carboxylate (20f). Prepared from 18 and 3-chloro-2,6-
difluoro-benzyl bromide (210 mg, 0.87 mmol) as described by
general procedure A. Yield: 130 mg (47%). 1H NMR (CD3OD)
δ 8.96 (s, 1H), 8.47 (s, 1H), 7.71 (d, J = 3.0 Hz, 1H), 7.55
(m, 1H), 7.05 (m, 1H), 6.75 (d, J = 3.0 Hz, 1H), 5.72 (s, 2H), 4.52
(q, J = 7.3 Hz, 2H), 1.45 (t, J = 7.3 Hz, 3H). LC-MS (ESI,
M þ Hþ) m/z 351.0.
1
purification. H NMR (400 MHz, DMSO-d6) δ 8.94 (s, 1H),
Ethyl
1-(2,3-Dichlorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-
8.39 (s, 1H), 7.95 (dd, J = 8.5, 2.7 Hz, 1H), 7.79 (d, J = 3.2 Hz,
1H), 7.54 (td, J = 8.9, 2.7 Hz, 1H), 7.08 (dd, J = 8.9, 5.5 Hz,
1H), 6.81 (d, J = 3.0 Hz, 1H), 5.84 (s, 2H), 3.86 (s, 3H). LC-MS
(ESI, M þ Hþ) m/z 311.2.
carboxylate (20g). Prepared from 18 and 2,3-dichlorobenzyl
chloride (170 mg, 0.87 mmol) as described by general procedure
A. Yield: 240 mg (84%). 1H NMR (DMSO-d6) δ 9.15 (s, 1H),
8.63 (s, 1H), 8.04 (d, J = 3.0 Hz, 1H), 7.85 (d, J = 8.1 Hz, 1H),
7.52 (t, J = 7.9 Hz, 1H), 7.04 (d, J = 3.0 Hz, 1H), 6.91 (d, J =
7.9 Hz, 1H), 6.01 (s, 2H), 4.56 (q, J = 7.2 Hz, 2H), 1.57 (t, J =
7.0 Hz, 3H). LC-MS (ESI, M þ Hþ): 349.0, 351.0, 353.0 (10:6:1).
Ethyl 1-(5-Chloro-thiophen-2-ylmethyl)-1H-pyrrolo[2,3-c]py-
ridine-5-carboxylate (20h). Prepared from 19b and 2-chloro-
5-(chloromethyl)thiophene (150 mg, 0.90 mmol) as described
by general procedure A. Yield: 280 mg (87%). 1H NMR
(CD3OD) δ 8.89 (s, 1H), 8.48 (s, 1H), 7.72 (d, J = 3.2 Hz,
1H), 6.99 (d, J = 3.8 Hz, 1H), 6.87 (d, J = 4.8 Hz, 1H), 6.75(d,
J = 3.2 Hz, 1H), 5.73 (s, 2H), 4.46 (q, J = 7.2 Hz, 2H), 1.46
(t, J = 7.2 Hz, 3H). LC-MS (ESI, M þ Hþ) m/z 321.0.
Methyl 1-(3-Cyanobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-car-
boxylate (19l). Prepared from 17 and 3-cyano-benzylbromide
(870 mg) as described by general procedure A using THF as
1
solvent. Yield: 100%. H NMR (400 MHz, DMSO-d6) δ 8.99
(s, 1H), 8.37 (s, 1H), 7.92 (d, J = 3.2 Hz, 1H), 7.83 (bs, 1H), 7.78
(m, 1H), 7.57 (s, 1H), 7.56 (m, 1H), 6.77 (d, J = 3.2 Hz, 1H), 5.68
(s, 2H), 3.86 (s, 3H). LC-MS (ESI, M þ Hþ) m/z 292.
Methyl 1-(4-Cyanobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-car-
boxylate (19m). Prepared from 17 and 4-cyano-benzylbromide
(300 mg) as described by general procedure A using THF as
solvent. Yield: 73%. 1H NMR (400 MHz, DMSO-d6) δ 8.92 (s,
1H), 8.37 (s, 1H), 7.90 (d, J = 3.2 Hz, 1H), 7.81 (d, J = 8.1 Hz,
2H), 7.39 (d, J = 8.1 Hz, 2H), 6.79 (d, J = 3.2 Hz, 1H), 5.74 (s,
2H), 3.85 (s, 3H). LC-MS (ESI, M þ Hþ) m/z 292.
General Procedure B. 1-(2,4-Difluorobenzyl)-1H-pyrrolo[2,3-
c]pyridine-5-carboxylic Acid (1b). To 19b (0.30 g, 1.58 mmol) in
methanol (3 mL) was added sodium hydroxide (0.076 g, 3.16
mmol) in water (0.5 mL). The reaction was heated in a Smith-
Creator (microwave reactor from Personal Chemistry) to 100 ꢀC
for 5 min. The solution was poured into water (30 mL) and the
pH was adjusted to 2-3 by addition of citric acid. The pre-
cipitate that formed was collected by filtration and dried in
vacuo to provide 1b as a white powder (0.15 g, 55% yield). 1H
NMR (DMSO-d6) δ 8.97 (s, 1H), 8.35 (s, 1H), 7.82 (d, J = 3.2
Hz, 1H), 7.33 (m, 2H), 7.09 (t, J = 8.4 Hz, 1H), 6.76 (d, J = 3.2
Hz, 1H), 5.67 (s, 2H). LC-MS (ESI, M þ Hþ): 289.1. HRMS
Methyl 1-(Pyridin-2-ylmethyl)-1H-pyrrolo[2,3-c]pyridine-5-
carboxylate (19i). Prepared from 17 and 2-(bromo-
methyl)pyridine hydrobromide salt (340 mg) as described by
general procedure A using THF as solvent and an additional
equivalent of NaH to free base the aforementioned salt. Yield:
90%. LC-MS (ESI, M þ Hþ) m/z 268. Used as crude material in
the next step.
Methyl 1-((6-(Hydroxymethyl)pyridin-2-yl)methyl)-1H-pyr-
rolo[2,3-c]pyridine-5-carboxylate (19j). Prepared from 17 and
(6-(bromomethyl)pyridin-2-yl)methanol (170 mg) as described by
general procedure A using THF as solvent. Yield: 40%. LC-MS
(ESI, M þ Hþ) m/z 298. Used as crude material in the next step.
Ethyl 1-(2,4-Difluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-car-
boxylate (20b). Prepared from 18 and 2,4-difluorobenzyl bro-
mide (0.60 g, 2.89 mmol) as described by general procedure A.
Yield: 0.40 g (48%). 1H NMR (DMSO-d6) δ 8.98 (s, 1H), 8.37
(s, 1H), 7.80 (d, J = 3.0 Hz, 1H), 7.38-7.27 (m, 2H), 7.11 (dd,
J = J0 = 6.2 Hz, 1H), 6.76 (d, J = 3.2 Hz, 1H), 5.66 (s, 2H), 4.33
(q, 7.1 Hz, 2H), 1.34 (t, J = 7.1 Hz, 3H). LC-MS (ESI, M þ Hþ)
m/z 317.0.
calcd for C15H11F2N2O2 [M
289.077457.
þ
Hþ] 289.07831; found
1-(4-Fluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carboxylic Acid
(1c). Prepared from 19c (110 mg, 0.37 mmol) as described by
general procedure B. Yield: 40 mg (40%). 1H NMR (DMSO-d6)
δ 8.97 (s, 1H), 8.35 (s, 1H), 7.90 (d, J = 3.0 Hz, 1H), 7.35 (m,
2H), 7.15 (m, 2H), 6.76 (d, J = 3.0 Hz, 1H), 5.67 (s, 2H). LC-MS
(ESI, M þ Hþ) m/z 271.1.
1-(2,3,4-Trifluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carbox-
ylic Acid (1d). Prepared from 20d (100 mg, 0.3 mmol) as
described by general procedure B. Yield: 87 mg (91%). 1H
NMR (DMSO-d6) δ 8.99 (s, 1H), 8.36 (s, 1H), 7.83 (d, J =
2.64 Hz, 1H), 7.30 (q, J = 7.93 Hz, 1H), 7.08 (m, 1H), 6.77 (d,
J = 3.02 Hz, 1H), 5.73 (s, 2H). LC-MS (ESI, M þ Hþ) m/z
307.0. HRMS calcd for C15H19F3N2O2 (M þ Hþ) 307.0694;
found 307.0705.
Ethyl 1-(4-Fluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carbox-
ylate (20c). Prepared from 18 and 4-fluorobenzyl bromide (220
mg, 1.18 mmol) as described by general procedure A. Yield: 110
mg (47%). 1H NMR (CD3OD) δ 8.91 (s, 1H), 8.62 (s, 1H), 7.90
(d, J = 3.0 Hz, 1H), 7.42 (m, 2H), 7.20 (m, 2H), 6.90 (d, J = 3.0
Hz, 1H), 5.75 (s, 2H), 4.60 (q, J = 7.0 Hz, 2H), 1.60 (t, J = 7.0
Hz, 3H). LC-MS (ESI, M þ Hþ) m/z 299.1.
1-(3-Chloro-2-fluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-car-
boxylic Acid (1e). Prepared from 20e (250 mg, 0.75 mmol) as
described by general procedure B. Yield: 40 mg (18%). 1H NMR
(DMSO-d6) δ 8.96 (s, 1H), 8.35 (s, 1H), 7.84 (d, J = 3.0 Hz, 1H),
7.56 (t, J = 7.4 Hz, 1H), 7.19 (t, J = 7.9 Hz, 1H), 7.09 (t, J = 7.3
Hz, 1H), 5.75 (s, 2H). LC-MS (ESI, M þ Hþ) m/z 305.0.
1-(3-Chloro-2,6-difluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-
carboxylic Acid (1f). Prepared from 20f (130 mg, 0.37 mmol) as
described by general procedure B. Yield: 86 mg (72%). 1H NMR
(DMSO-d6) δ 8.95 (s, 1H), 8.34 (s, 1H), 7.75 (d, J = 3.2 Hz, 1H),
7.69 (m, 1H), 7.28 (m, 1H), 6.75 (d, J = 3.2 Hz, 1H), 5.75 (s, 2H).
LC-MS (ESI, M þ Hþ) m/z 323.0.
Ethyl 1-(2,3,4-Trifluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-
carboxylate (20d). Prepared from 18 and 2,3,4-trifluorobenzyl
bromide (177 mg, 0.79 mmol) as described by general procedure
1
A. Yield: 101 mg (38%). H NMR (CDCl3) δ 8.84 (brs., 1H),
8.50 (brs, 1H), 7.38 (d, J = 2.6 Hz, 1H), 7.26 (s, 1H), 6.89 (t, J =
7.9 Hz, 1H), 6.75 (d, J = 7.9 Hz,1H), 6.71 (d, J = 2.6 Hz, 1H),
5.48 (s, 2H), 4.49 (q, J = 7.1 Hz, 2H), 4.49 (q, J = 7.1 Hz, 2H),
1.46 (t, J = 7.1 Hz, 3H). LC-MS (ESI, M þ Hþ) m/z 335.0.
Ethyl 1-(3-Chloro-2-fluorobenzyl)-1H-pyrrolo[2,3-c]pyridine-
5-carboxylate (20e). Prepared from 18 and 3-chloro-2-fluoro-

Article
1-(2,3-Dichlorobenzyl)-1H-pyrrolo[2,3-c]pyridine-5-carboxy-
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22 7217
7.81 (d, J = 8.4 Hz, 1H), 7.10 (d, J = 3.0 Hz, 1H), 6.99 (d, J =
2.8 Hz, 1H), 6.70 (d, J = 3.0 Hz, 1H), 5.76 (s, 2H). LC-MS (ESI,
M þ Hþ) m/z 308.0. HRMS calcd for C13H11ClN3O2S (M þ
Hþ) 308.0261; found 308.0265. Anal. (C13H10ClN3O2S) C, H, N
General Procedure D. 1-(2-Carbamoyl-4-fluorobenzyl)-N-hy-
droxy-1H-pyrrolo[2,3-c]pyridine-5-carboxamide (2n) and 1-(2-
Cyano-4-fluorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]pyridine-5-
carboxamide (2k). To a solution of 19k (688 mg, 2.22 mmol) in
methanol (22 mL) was added hydroxyl amine (50% solution in
water, 0.722 mL, 11.1 mmol) and 1 N sodium hydroxide (4.44
mL, 11.1 mmol). The solution was stirred at ambient tempera-
ture for 16 h. The reaction mixture was adjusted to pH 7 by
addition of 1 N HCl,to provide a white precipitate. The solid was
collected by filtration, washed with water and ethyl acetate, and
dried in vacuo. Purification by reversed-phase preparative
HPLC (acetonitrile:water:TFA) provided 2k (190 mg, 28%)
and the nitrile hydrolysis product 2n (25 mg, 4%). Data for
2n: 1H NMR (400 MHz, DMSO-d6) δ 11.11 (bs, 1H), 8.91 (bs,
1H), 8.75 (s, 1H), 8.21 (s, 1H), 8.07 (s, 1H), 7.74 (d, J = 3.0 Hz,
1H), 7.70 (s, 1H), 7.36 (dd, J = 9.4, 2.8 Hz, 1H), 7.22 (td, J =
8.5, 2.8 Hz, 1H), 7.00 (dd, J = 8.5, 5.6 Hz, 1H), 6.70 (d, J = 2.8
Hz, 1H), 5.75 (s, 2H). LC-MS (ESI, M þ Hþ) m/z 329.2. Data
for 2k: 1H NMR (400 MHz, DMSO-d6) δ 11.16 (bs, 1H), 8.91
(bs, 1H), 8.82 (s, 1H), 8.25 (s, 1H), 7.95 (dd, J = 8.6, 2.5 Hz, 1H),
7.77 (d, J = 3.0 Hz, 1H), 7.55 (td, J = 8.6, 3.0 Hz, 1H), 7.10 (dd,
J = 8.6, 5.3 Hz, 1H), 6.77 (d, J = 3.0 Hz, 1H), 5.82 (s, 2H). LC-
MS (ESI, M þ Hþ) m/z 311.2.
lic Acid (1g). Prepared from 20g (240 mg, 0.69 mmol) as
described by general procedure B except that the mixture was
heated to 60 ꢀC for 16 h. Yield: 160 mg (67%). 1H NMR
(DMSO-d6) δ 8.92 (s, 1H), 8.40 (s, 1H), 7.83 (d, J = 3.0 Hz,
1H), 7.62 (d, J = 7.4 Hz, 1H), 7.30 (t, J = 7.8 Hz, 1H), 6.83 (d,
J = 3.0 Hz, 1H), 6.68 (d, J = 7.9 Hz, 1H), 5.79 (s, 2H). LC-MS
(ESI, M þ Hþ) m/z 320.9, 323.0, 325.0 (10:6:1). HRMS calcd for
C15H11Cl2N2O2 [M þ Hþ] 321.0204; found 321.0198.
1-(5-Chloro-thiophen-2-ylmethyl)-1H-pyrrolo[2,3-c]pyridine-
5-carboxylic Acid (1h). Prepared from 20h (240 mg, 0.75 mmol)
as described by general procedure B. Yield: 150 mg (68%). 1H
NMR (DMSO-d6) δ 9.05 (s, 1H), 8.34 (s, 1H), 7.88 (d, J = 3.0
Hz, 1H), 7.12 (d, J = 3.8 Hz, 1H), 7.01 (d, J = 4.0 Hz, 1H), 6.75
(d, J = 3.0 Hz, 1H), 5.78 (s, 2H). LC-MS (ESI, M þ Hþ) m/z
293.0.
General Procedure C. (1-(2,4-Difluorobenzyl)-N-hydroxy-1H-
pyrrolo[2,3-c]pyridine-5-carboxamide (2b). To a solution of 1b
(0.15 g, 0.52 mmol) in DMF (10 mL) were added HATU (0.20 g,
0.52 mmol), triethylamine (0.15 mL, 1.05 mmol), and hydro-
xylamine hydrochloride (0.036 g, 0.52 mmol). The resulting
mixture was stirred for 16 h at ambient temperature. The
mixture was cast into water (30 mL) and extracted with ethyl
acetate (3 ꢀ 30 mL). The combined organic extracts were
washed with water (2 ꢀ 30 mL), dried over sodium sulfate,
concentrated in vacuo, and purified by preparative HPLC to
1
provide 1b as a white powder (0.075 g, 48% yield). H NMR
(DMSO-d6) δ 11.14 (s, 1H), 8.92 (s, 1H), 8.85 (s, 1H), 8.21 (s,
1H), 7.78 (s, 1H), 7.26-7.38 (m, 2H), 7.08 (t, J = 8.3 Hz, 1H),
6.71 (d, J = 3.0 Hz, 1H), 5.64 (s, 2H). LC-MS (ESI, M þ Hþ) m/
z 304.1. HRMS calcd for C15H12F2N3O2 (M þ H) 304.0898;
found 304.0886. Anal. (C15H11F2N3O2) C, H, N.
1-(4-Fluorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]pyridine-5-car-
boxamide (2c). Prepared from 1c (150 mg, 0.56 mmol) as described
by general procedure C. Yield: 60 mg (29%). 1H NMR (DMSO-
d6) δ 11.12 (s, 1H), 8.90 (s, 1H), 8.83 (s, 1H), 8.21 (s, 1H), 7.85 (d,
J = 3.0 Hz, 1H), 7.36 (d, J = 8.4 Hz, 2H), 7.17 (d, J = 8.4 Hz,
2H), 6.71 (d, J = 3.0Hz, 1H), 5.59 (s, 2H). LC-MS (ESI, M þ Hþ)
m/z 286.1. HRMS calcd for C15H13FN3O2 (M þ H) 286.0992;
found 286.0978.
1-(3-Carbamoyl-4-fluorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]-
pyridine-5-carboxamide (2o). Prepared from 19o as described by
general procedure D to provide 33 mg (8%). H NMR (400
1
MHz, DMSO-d6) δ 11.52 (s, 1H), 9.09 (s, 1H), 8.34 (s, 1H), 8.13
(s, 1H), 7.68 (s, 2H), 7.67 (s, 1H), 7.47 (m, 1H), 7.26 (dd, J =
10.1, 8.8 Hz, 1H), 6.89 (s, 1H), 5.69 (s, 2H). LC-MS (ESI, M þ
Hþ) m/z 329.2.
N-Hydroxy-1-(pyridin-2-ylmethyl)-1H-pyrrolo[2,3-c]pyridine-
5-carboxamide (2i). Prepared from crude 19i as described by
general procedure D to provide 63 mg (23%). H NMR (400
1
MHz, DMSO-d6) δ 11.12 (s, 1H), 8.90 (s, 1H), 8.80 (s, 1H), 8.52
(d, J = 5.7 Hz, 1H), 8.21 (s, 1H), 7.83 (d, J = 3.0 Hz, 1H), 7.76
(td, J = 7.7, 1.7 Hz, 1H), 7.30 (dd, J = 4.9, 1.1 Hz, 1H), 7.21 (d,
J = 7.7 Hz, 1H), 6.71 (d, J = 3.0 Hz, 1H), 5.69 (s, 2H). LC-MS
(ESI, M þ Hþ) m/z 269.2.
1-(3-Chloro-2-fluorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]pyri-
dine-5-carboxamide (2e). Prepared from 1e (190 mg, 0.62 mmol)
as described by general procedure C. Yield: 120 mg (60%). 1H
NMR (DMSO-d6) δ 11.16 (s, 1H), 8.95 (s, 1H), 8.85 (s, 1H), 8.23
(s, 1H), 7.79 (d, J = 2.8 Hz, 1H), 7.55 (t, J = 7.5 Hz, 1H), 7.19 (t,
J = 7.5 Hz, 1H), 7.10 (t, J = 7.5 Hz, 1H), 6.73 (d, J = 3.0 Hz,
1H), 5.74 (s, 2H). LC-MS (ESI, M þ Hþ) m/z 320.0. HRMS
1-(3-Carbamoylbenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]pyridine-
5-carboxamide (2p) and 1-(3-Cyanobenzyl)-N-hydroxy-1H-
pyrrolo[2,3-c]pyridine-5-carboxamide (2l). Prepared from 19l as
described by general procedure D to provide 2p (16 mg, 9%) and
1
2l (23 mg, 14%). Data for 2p: H NMR (400 MHz, CD3OD)
calcd for C15H12ClFN3O2 (M
320.06045.
þ
Hþ) 320.0602; found
δ 11.52 (bs, 1H), 9.06 (s, 1H), 8.36 (s, 1H), 8.13 (s, 1H), 7.97
(s, 1H), 7.84 (s, 1H), 7.79 (m, 1H), 7.42 (d, J = 5.1 Hz, 2H), 7.38
(s, 1H), 6.90 (s, 1H), 5.73 (s, 2H). LC-MS (ESI, M þ Hþ) m/z
311.2. Data for 2l: 1H NMR (400 MHz, DMSO-d6) δ 11.10 (bs,
1H), 8.9 (bs, 1H), 8.86 (s, 1H), 8.22 (s, 1H), 7.89 (d, J = 3.0 Hz,
1H), 7.84 (s, 1H), 7.57 (dt, J = 6.8, 1.8 Hz, 1H), 7.56 (s, 1H), 7.55
(m, 1H), 6.73 (d, J = 3.0 Hz, 1H), 5.66 (s, 2H). LC-MS (ESI, M
þ Hþ) m/z 293.2.
1-(3-Chloro-2,6-difluorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]-
pyridine-5-carboxamide (2f). Prepared from 1f (210 mg, 0.65
mmol) as described by general procedure C. Yield: 75 mg
(34%). 1H NMR (DMSO-d6) δ 11.17 (s, 1H), 8.89 (s, 1H), 8.81
(s, 1H), 8.18 (s, 1H), 7.69-7.70 (m, 2H), 7.25 (m, 1H), 6.68
(s, 1H), 5.70 (s, 2H). LC-MS (APCI, M þ Hþ) m/z 338.0. HRMS
(M þ Hþ) calcd for C15H11ClF2N3O2 (M þ Hþ) 338.0508; found
338.0511.
N-Hydroxy-1-{[6-(hydroxymethyl)pyridin-2-yl]methyl}-1H-
pyrrolo[2,3-c]pyridine-5-carboxamide (2j). Prepared from 19j
as described by general procedure D to provide 69 mg (51%).
1H NMR (400 MHz, DMSO-d6) δ 11.76 (bs, 1H), 9.18 (s, 1H),
8.43 (s, 1H), 8.23 (s, 1H), 7.79 (dd, J = J0 = 8.0 Hz, 1H), 7.40
(d, J = 8.0 Hz, 1H), 7.10 (d, J = 8.0 Hz, 1H), 6.98 (s, 1H), 5.79
(s, 2H), 4.49 (s, 2H). LC-MS (ESI, M þ Hþ) m/z 299.2.
1-(4-Carbamoylbenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]pyridine-
5-carboxamide (2q) and 1-(4-Cyanobenzyl)-N-hydroxy-1H-
pyrrolo[2,3-c]pyridine-5-carboxamide (2m). Prepared from 19m
as described by general procedure D to provide 2q (43 mg, 6%)
and 2m (50 mg, 6%). Data for 2m: 1H NMR (400 MHz,
CD3OD) δ 11.50 (bs, 1H), 9.02 (s, 1H), 8.35 (s, 1H), 8.12
(s, 1H), 7.93 (s, 1H), 7.82 (d, J = 8.1 Hz, 1H), 7.36 (s, 1H),
7.32 (d, J = 8.1 Hz, 1H), 6.90 (s, 1H), 5.74 (s, 2H). LC-MS (ESI,
(1-(2,3-Dichlorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]pyridine-
5-carboxamide (2g). Prepared from 1g (160 mg, 0.50 mmol) as
described by general procedure C. Yield: 36.4 mg (22%). H
1
NMR (DMSO-d6) δ 11.15 (s, 1H), 8.91 (s, 1H), 8.78 (s, 1H), 8.24
(s, 1H), 7.76 (d, J = 3.2 Hz, 1H), 7.60 (d, J = 8.1 Hz, 1H), 7.28 (t,
J = 8.1 Hz, 1H), 6.76 (d, J = 3.2 Hz, 1H), 6.67 (d, J = 8.1 Hz,
1H), 5.75 (s, 2H). LC-MS (ESI, M þ Hþ) m/z 336.0, 338.0, 340.0
(10:6:1). HRMS calcd for C15H12Cl2N3O2 (M þ Hþ) 336.0303;
found 336.0300.
1-(5-Chloro-thiophen-2-ylmethyl)-N-hydroxy-1H-pyrrolo[2,3-c]-
pyridine-5-carboxamide (2h). Prepared from 1h (150 mg, 0.51
mmol) as described by general procedure C. Yield: 33 mg (21%).
1H NMR (DMSO-d6) δ 11.15 (s, 1H), 8.93 (s, 2H), 8.21 (s, 1H),

7218 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22
Plewe et al.
1
M þ H): 311.2. Data for 2q: 1H NMR (400 MHz, DMSO-d6) δ
11.11 (bs, 1H), 8.91 (bs, 1H), 8.79 (s, 1H), 8.23 (s, 1H), 7.87 (d, J
= 3.0 Hz, 1H), 7.81 (d, J = 8.2 Hz, 2H), 7.39 (d, J = 8.2 Hz,
2H), 6.74 (d, J = 3.0 Hz, 1H), 5.72 (s, 2H). LC-MS (ESI, M þ
Hþ) m/z 293.2.
1-(2,4-Difluorobenzyl)-N-hydroxy-N-methyl-1H-pyrrolo[2,3-
c]pyridine-5-carboxamide (3b). Prepared from 1b (200 mg, 0.69
mmol), N-methyl hydroxylamine hydrochloride (60 mg, 0.72
mmol), triethylamine (0.20 mL, 1.43 mmol), and HATU (270
mg, 0.71 mmol) as described by general procedure C. Yield: 120
mg (55%). 1H NMR (DMSO-d6) δ 11.10 (br, 1H), 8.92 (s, 1H),
8.04 (s, 1H), 7.82 (s, 1H), 7.26-7.38 (m, 2H), 7.07-7.08 (m, 1H),
6.72 (s, 1H), 5.64 (s, 2H), 3.33 (s, 3H). LC-MS (ESI, M þ Hþ) m/
z 318.0. HRMS calcd for C16H14F2N3O2 (M þ Hþ) 318.1054;
found 318.1037. Anal. (C16H13F2N3O2) C, H, N.
1-(2,4-Difluorobenzyl)-N-methoxy-1H-pyrrolo[2,3-c]pyridine-
5-carboxamide (4b). Prepared from 1b, O-methyl hydroxyla-
mine hydrochloride (200 mg, 0.69 mmol), triethylamine (0.20
mL, 1.43 mmol), and HATU (262 mg, 0.69 mmol) as described
by general procedure C. Yield: 190 mg (87%). 1H NMR
(CD3OD) δ 8.80 (s, 1H), 8.33 (s, 1H), 7.64 (d, J = 3.0 Hz,
1H), 7.26 (m, 1H), 6.96-7.08 (m, 2H), 6.74 (d, J = 3.0 Hz, 1H),
5.62 (s, 2H) 3.85 (s, 3H). LC-MS (ESI, M þ Hþ) m/z 318.0.
HRMS calcd for C16H14F2N3O2 (M þ H) 318.1054; found
318.1045.
procedure C. Yield: 67.4 mg (35%). H NMR (DMSO-d6) δ
12.00 (bs, 1H), 8.83 (s, 1H), 7.95 (s, 1H), 7.84 (d, J = 3.0 Hz, 1H),
7.29 (m, 2H), 7.10 (d, J = 8.8 Hz, 2H), 6.64 (d, J = 3.0 Hz, 1H),
5.51 (s, 2H), 3.50 (d, J = 7.2 Hz, 2H), 1.98-2.05 (m, 1H), 0.80 (s,
6H). LC-MS (ESI, M þ Hþ) m/z 342.1. HRMS calcd for
C19H21FN3O2 (M þ Hþ) 342.1613; found 342.1608.
1-(4-Fluorobenzyl)-N-hydroxy-N-isopropyl-1H-pyrrolo[2,3-c]-
pyridine-5-carboxamide (10c). Prepared from 1c (160 mg, 0.59
mmol), N-isopropylhydroxylamine hydrochloride (114 mg, 1.22
mmol), DMAP (290 mg, 2.73 mmol), and HATU (230 mg, 0.60
mmol) as described by general procedure C. Yield: 23 mg (7%).
1H NMR (CDCl3) δ 8.59 (s, 1H), 8.46 (s, 1H), 7.39 (s, 1H), 7.10
(m, 2H), 7.02 (d, J = 8.6 Hz, 2H), 6.73 (s, 1H), 5.41 (s, 2H), 5.08
(m, 1H), 1.33 (d, J = 6.6 Hz, 6H). LC-MS (APCI, M þ Hþ) m/z
328.1. HRMS calcd for C18H18FN3O2 (M þ Hþ) 328.1456;
found 328.1456.
N-Benzyl-1-(4-fluorobenzyl)-N-hydroxy-1H-pyrrolo[2,3-c]py-
ridine-5-carboxamide (11c). Prepared from 1c (150 mg, 0.56
mmol), N-benzylhydroxylamine hydrochloride (90 mg, 0.56
mmol), triethylamine (0.16 mL, 1.15 mmol), and HATU (210
mg, 0.55 mmol) as described by general procedure C. Yield: 60
1
mg (29%). H NMR (DMSO-d6) δ 8.92 (s, 1H), 8.11 (s, 1H),
7.91 (d, J = 2.8 Hz, 1H), 7.26-7.38 (m, 7H), 7.16 (d, J = 8.5 Hz,
2H), 6.72 (d, J = 2.8 Hz, 1H), 5.58 (s, 2H), 4.97 (s, 2H). LC-MS
(ESI, M þ Hþ) m/z 376.1. HRMS calcd for C22H19FN3O2 (M þ
Hþ) 376.1461; found 376.1448. Anal. (C22H18FN3O2) C, H, N.
General Procedure E. Ethyl 3-Methyl-5-oxo-2-propyl-2,5-di-
hydroisoxazole-4-carboxylate (22a). To a stirred solution of ethyl
3-methyl-5-oxo-2,5-dihydroisoxazole-4-carboxylate sodium salt
(21)32 in DMF (20 mL) was added 1-iodopropane (1.70 g, 18.1
mmol). The resulting mixture was heated to 120 ꢀC for 1 h. The
cold solution was poured into ice-water (30 mL), and extracted
withdichloromethane(2 ꢀ 50 mL). The organic layer was washed
with water (2 ꢀ 50 mL), dried over sodium sulfate, concentrated,
and purified by flash chromatography with ethyl acetate/hexane
(2,4-Difluorobenzyl)-N-methyl-N-methoxy-1H-pyrrolo[2,3-c]-
pyridine-5-carboxamide (5b). Prepared from 1b (190 mg, 0.66
mmol), N,O-dimethyl hydroxylamine hydrochloride (77 mg,
0.79 mmol), diisopropylethylamine (0.46 mL, 2.64 mmol), and
HATU (301 mg, 0.79 mmol) as described by general procedure
1
C. Yield: 88 mg (39%). H NMR (DMSO-d6) δ 8.88 (s, 1 H),
7.86 (s, 1 H), 7.75 (d, J = 3.0 Hz, 1H), 7.23-7.40 (m, 2H), 6.66
(d, J = 3.0 Hz, 1 H), 5.62 (s, 2 H), 3.69 (s, 3 H), 3.29 (s, 3 H). LC-
MS (APCI, M þ Hþ) m/z 332.2.
1-(4-Fluorobenzyl)-N-hydroxy-N-methyl-1H-pyrrolo[2,3-c]py-
ridine-5-carboxamide (6c). Prepared from 1c (87 mg, 0.232
mmol), N-methyl hydroxylamine hydrochloride (32 mg, 0.38
mmol), diisopropylethylamine (0.224 mL, 1.29 mmol), and
HATU (147 mg, 0.38 mmol as described by general procedure
C. Yield: 76.0 mg (79%). 1H NMR (DMSO-d6) δ 12.00 (bs, 1H),
8.91 (s, 1H), 8.03 (s, 1H), 7.91 (d, J = 2.8 Hz, 1H), 7.38 (dd, J =
5.7 Hz, 8.5 Hz, 2H), 7.12 (d, J = 8.5 Hz, 2H), 6.71 (d, J = 3.0 Hz,
1H), 5.59 (s, 2H), 3.33 (s, 3H). LC-MS (ESI, M þ Hþ) m/z 301.1.
HRMS calcd for C16H15FN3O2 (M þ Hþ) 300.1148; found
300.1138. Anal. (C16H14FN3O2) C, H, N.
1
(1/1) to provide a solid product (0.52 g, 13% yield). H NMR
(CDCl3) δ 4.33 (q, J = 7.1 Hz, 2H), 3.86 (t, J = 6.8 Hz, 2H), 2.57
(s, 3H), 1.81-1.88 (m, 2H), 1.37 (t, J = 7.1 Hz, 3H), 0.98 (t, J =
7.6 Hz, 3H). LC-MS (APCI, M þ Hþ) m/z 214.1.
Ethyl 3-Methyl-5-oxo-2-[(3-tert-butyldimethylsilanoxyl)pro-
pyl]-2,5-dihydroisoxazole-4-carboxylate (22b). Prepared by alky-
lation of 21 (3.08 g, 15.54 mmol) with (3-bromopropoxy)(tert-
butyl)dimethylsilane (7.2 mL, 31.08 mmol) as described by general
procedure E. Yield: 1.8 g (34%). 1H NMR (CDCl3) δ 4.30 (q, J =
7.2 Hz, 2H), 4.00 (t, J = 6.4 Hz, 2H), 3.58 (t, J = 5.5 Hz, 2H), 2.55
(s, 3H), 1.93-1.96 (m, 2H), 1.34 (t, J = 7.0 Hz, 3H), 0.88 (s, 9H),
0.04 (s, 6H). LC-MS (APCI, M þ Hþ) m/z 344.1.
1-(4-Fluorobenzyl)-N-hydroxy-N-propyl-1H-pyrrolo[2,3-c]pyri-
dine-5-carboxamide (7c). Prepared from 1c (150 mg, 0.56 mmol),
N-propyl hydroxylamine hydrochloride 23a (124 mg, 1.11
mmol), dimethylaminopyridine (DMAP, 270 mg, 2.2 mmol),
and HATU (230 mg, 0.60 mmol) as described by general
procedure C. Yield: 37 mg (20%). 1H NMR (DMSO-d6) δ
11.93 (bs, 1H), 8.88 (s, 1H), 7.99 (s, 1H), 7.88 (d, J = 3.0 Hz,
1H), 7.34 (m, 2H), 7.15 (d, J = 8.8 Hz, 2H), 6.69 (d, J = 3.0 Hz,
1H), 5.56 (s, 2H), 3.66 (t, J = 7.1 Hz, 2H), 1.64 (m, 2H), 0.83 (s,
3H). LC-MS (ESI, M þ Hþ) m/z 328.1. HRMS calcd for
C18H19FN3O2 (M þ Hþ) 328.1456; found 328.1458.
Ethyl 3-Methyl-5-oxo-2-isobutyl-2,5-dihydroisoxazole-4-car-
boxylate (22c). Prepared by alkylation of 21 (2.0 g, 10.36 mmol)
with 1-iodo-3-methylbutane (2.4 mL, 20.73 mmol) as described
by general procedure E. Yield: 510 mg (22%). 1H NMR (CDCl3)
δ 4.12 (q, J = 7.1 Hz, 2H), 3.47 (t, J = 6.8 Hz, 2H), 2.35 (s, 3H),
2.02 (m, 1H), 1.16 (t, J = 7.1 Hz, 3H), 0.77 (d, J = 6.8 Hz, 6H).
LC-MS (APCI, M þ Hþ) m/z 228.2.
General Procedure F. N-Propylhydroxylamine Hydrochloride
(23a). To a stirred solution of 22a (0.52 g, 2.44 mmol) in water
(10 mL) were added acetic acid (10 mL) and hydrochloric acid (1
mL, 37%). The resulting solution was heated reflux for 8 h, and
solvents were removed in vacuo to provide a glue-like liquid
(0.30 g, quant), which was used without further purification. 1H
NMR (CDCl3) δ 10.94 (s, 2H), 3.24 (s, 2H), 2.77 (m, 2H), 1.89
(m, 2H), 1.03 (t, J = 7.5 Hz, 3H).
1-(4-Fluorobenzyl)-N-hydroxy-N-(3-hydroxypropyl)-1H-pyr-
rolo[2,3-c]pyridine-5-carboxamide (8c). Prepared from 1c (190
mg, 0.70 mmol), 23b (180 mg, 1.41 mmol), DMAP (350 mg, 2.87
mmol), and HATU (263 mg, 0.69 mmol) as described by general
procedure C. Yield: 34.2 mg (14%). 1H NMR (CD3OD) δ 8.71
(s, 1H), 8.20 (s, 1H), 7.71 (d, J = 3.0 Hz, 1H), 7.26 (m, 2H), 7.05
(d, J = 8.9 Hz, 2H), 6.75 (d, J = 3.0 Hz, 1H), 5.55 (s, 2H), 3.90
(m, 2H), 3.65 (t, J = 6.0 Hz, 2H), 1.94-2.00 (m, 2H). LC-MS
(ESI, M þ Hþ) m/z 344.1. HRMS calcd for C18H19FN3O3 (M þ
Hþ) 344.1405; found 344.1402. Anal. (C18H18FN3O3) C, H, N.
1-4-(Fluorobenzyl)-N-hydroxy-N-isobutyl-1H-pyrrolo[2,3-c]-
pyridine-5-carboxamide (9c). Prepared from 1c (150 mg, 0.56
mmol), 23c (140 mg, 1.12 mmol), DMAP (270 mg, 2.21 mmol),
and HATU (230 mg, 0.60 mmol) as described by general
N-(3-Hydroxypropyl)hydroxylamine Hydrochloride (43b).
Prepared from 22b (1.8 g, 5.25 mmol) as described by general
1
procedure F. Yield: 760 mg (quant). H NMR (DMSO-d6) δ
11.32 (s, 3H), 10.80 (s, 1H), 3.47 (d, J = 6.1 Hz, 2H), 3.10-3.17
(m, 2H), 1.17-1.78 (m, 2H).
N-Isobutylhydroxylamine Hydrochloride (23c). Prepared
from 22c (510 mg, 2.25 mmol) as described by general procedure
F. Yield: 280 mg (99%). 1H NMR (DMSO-d6) δ 11.22 (s, 2H),

Article
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 22 7219
10.78 (s, 1H), 2.95 (d, J = 7.0 Hz, 2H), 2.01-2.06 (m, 1H), 0.95
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Acknowledgment. We thank Drs. Martin Edwards, Peter
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thank Michael Lee and Leo Lee for evaluation of compounds
in the bioluminescent Ames test.
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