4-Pyridone derivatives as new inhibitors of bacterial enoyl-ACP reductase FabI

Article abstract of DOI:10.1016/j.bmc.2006.10.012

Bacterial FAS provides essential fatty acids for use in the assembly of key cellular components. Among them, FabI is an enoyl-ACP reductase which catalyzes the final and rate-limiting step of bacterial FAS. It is a potential target for selective antibacterial action, because it shows low overall sequence homology with mammalian enzymes. Until today, various compounds have been reported as inhibitors of bacterial FabI-inhibitory compounds. To discover novel small-molecular FabI inhibitors, we initially screened our compound library for inhibitory activity toward FabI of Escherichia coli. And discovered 4-pyridone derivatives as a lead compound. Structure optimization studies yielded 4-pyridone derivatives 7n having strong FabI-inhibitory and antibacterial activities against Staphylococcus aureus. There have been no reports concerning 4-pyridone derivatives as FabI inhibitor.

Full text of DOI:10.1016/j.bmc.2006.10.012

Bioorganic & Medicinal Chemistry 15 (2007) 1106–1116
4-Pyridone derivatives as new inhibitors of bacterial
enoyl-ACP reductase FabI
Hideo Kitagawa,* Ko Kumura, Sho Takahata, Maiko Iida and Kunio Atsumi
Pharmaceutical Research Center, Meiji Seika Kaisha, Ltd, 760 Morooka-cho, Kohoku-ku, Yokohama 222-8567, Japan
Received 4 August 2006; revised 6 October 2006; accepted 11 October 2006
Available online 13 October 2006
Abstract—Bacterial FAS provides essential fatty acids for use in the assembly of key cellular components. Among them, FabI is an
enoyl-ACP reductase which catalyzes the final and rate-limiting step of bacterial FAS. It is a potential target for selective antibac-
terial action, because it shows low overall sequence homology with mammalian enzymes. Until today, various compounds have been
reported as inhibitors of bacterial FabI-inhibitory compounds. To discover novel small-molecular FabI inhibitors, we initially
screened our compound library for inhibitory activity toward FabI of Escherichia coli. And discovered 4-pyridone derivatives as
a lead compound. Structure optimization studies yielded 4-pyridone derivatives 7n having strong FabI-inhibitory and antibacterial
activities against Staphylococcus aureus. There have been no reports concerning 4-pyridone derivatives as FabI inhibitor.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
Various compounds, including isoniazid,7 diazabo-
rines,8 triclosan,9 indole naphthyridinones,10 and thio-
pyridine,11 have been reported as inhibitors of
bacterial enoyl-ACP reductase, and a FabI-targeting ap-
proach to antibacterial drug therapy appears feasible
(Fig. 1). To discover novel small-molecular FabI inhib-
itors, we initially screened our compound library for
inhibitory activity toward FabI of Escherichia coli.
Among the hits, compound 1 having 4-pyridone as the
basic structure was selected as a lead compound (Fig. 2).
The emergence of bacterial resistance to most of the
antibacterials currently in clinical use represents a major
medical challenge.1 In particular, the spread of multire-
sistant Gram-positive bacteria, such as methicillin-
resistant Staphylococcus aureus (MRSA)2 and
penicillin-resistant Streptococcus pneumoniae (PRSP),3
during the last two decades is of major concern in che-
motherapy, and consequently research to discover anti-
bacterial agents with novel mechanisms of action is very
important. However, very few novel classes of broad-
spectrum antibacterial agents have been marketed since
the mid-1970s.4 In this regard, bacterial fatty acid bio-
synthesis (FAS) is an attractive target.5 Bacterial FAS
provides essential fatty acids for use in the assembly of
key cellular components, such as the cell envelope, phos-
pholipids, lipoproteins, lipopolysaccharides, and mycol-
ic acids. FabI is an enoyl-ACP reductase which catalyzes
the final and rate-limiting step of bacterial FAS.6 It is a
potential target for selective antibacterial action, be-
cause it shows low overall sequence homology with
mammalian enzymes.
Structure optimization studies yielded 4-pyridone deriv-
atives with strong FabI-inhibitory activity. We also
found that compound 7n showed good antibacterial
activity against S. aureus. In this report, we present
our investigation of a series of 4-pyridone derivatives
as novel FabI inhibitors with potent antibacterial activ-
ity against S. aureus.
2. Chemistry
4-Pyridone derivatives substituted at the 3-position were
prepared as outlined in Schemes 1 and 2. The benzyl-
type derivatives were synthesized by method A in
Scheme 1. Commercially available 4-methoxypyridine
was treated with alkyl magnesium bromide and carbob-
enzyloxy chloride in THF at ꢀ78 °C to afford com-
pound 3. The reaction of 3 with aldehyde was carried
Keywords: Bacterial enoyl-acyl reductase; FabI; 4-Pyridone; Fatty acid
biosynthesis; Inhibitors.
*
Corresponding author. Tel.: +81 45 541 2521; fax: +81 45 541
0667; e-mail: hideo_kitagawa@meiji.co.jp
0968-0896/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.10.012

H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
1107
Figure 1. Structures of FabI inhibitors.
out in THF at ꢀ78 °C in the presence of a lithium hex-
amethyldisilazide and the corresponding aldol adduct 4
was obtained. The hydroxyl group of compound 4 was
converted into the methanesulfonate 5 by treatment
with methanesulfonyl chloride under ice cooling.
Elimination of the methanesulfonyloxy group, followed
by isomerization of the double bond with potassium
tert-butoxide, yielded the desired 4(1H)-pyridone 6.
Alkylation of 6 with alkyl halide in the presence of sodi-
um hydride afforded 1-alkyl 4-pyridone 7.12
The biaryl-type derivative 11 was obtained starting from
a commercially available natural product, maltol 8,
from which the triflate ester 10 was synthesized as a
key intermediate. Compound 10 was coupled with phen-
ylboronic acid (catalyzed by palladium) to give the de-
sired biaryl-type product 11 (Scheme 2, method B).
Compound 10 was coupled with tributylvinylstannane
to give 12. It was reacted with 3-bromopyridine in the
Figure 2. Our discovered FabI inhibitor.
Scheme 1. Synthesis of compound 7 (method A). Reagents: (a) BnOCOCl, R2MgBr, THF; (b) 3 N HCl; (c) R3CHO, HMDSLi, THF; (d) MsCl,
0
0
pyridine; (e) t-BuOK, THF (in the case of compound 7x (R3 ¼ n-Pr) and 7y (R3 ¼ cyclohexyl), DBU was used in stead of t-BuOK and then Pd/C,
H2, THF); (f) R1X, NaH, THF.
Scheme 2. Synthesis of 4-pyridone derivatives. Reagents and conditions: (a) BnNH2, EtOH/H2O (35%); (b) Tf2O, 2,6-lutidine, CH2Cl2, rt (74%); (c)
phenylboronic acid, Pd(PPh3)4, K2CO3, 1,4-dioxane, 60 °C (20%); (d) tributylvinylstannane, Pd(PPh3)4, LiCl, 1,4-dioxane, reflux (61%); (e)
3-bromopyridine, Pd2(dba)3, t-Bu3P, Cy2NMe, 1,4-dioxane, reflux (32%); (f) Pd/C, H2, CH3OH, rt (51%).

1108
H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
Scheme 3. Synthesis of compound 19. Reagents and conditions: (a) bromomethylcyclohexane, NaH, DMF; (b) BnOCOCl, R4MgBr, THF; (c) 3 N
HCl; (d) PhSeBr, HMDSLi, THF; (e) m-CPBA, CH2Cl2; (f) CH3OH, reflux.
presence of palladium catalyst to give 13. The double
bond of compound 13 was reduced with palladium on
activated carbon under a hydrogen atmosphere to give
14 (Scheme 2, method C).
was monitored at room temperature for 10 min by fol-
lowing the change in absorbance at 340 nm. The concen-
tration giving 50% reduction of the absorption was
determined as the IC50.
The 4-pyridone derivatives substituted at the 6-position
were prepared as outlined in Scheme 3. Alkylation of the
pyridone 6a with bromomethylcyclohexane in the pres-
ence of sodium hydride in DMF afforded the O-alkyl-
ated pyridine 15 as a major product. Addition of
alkylmagnesium bromide to the 6-position of compound
15 in the presence of carbobenzoxy chloride afforded
compound 16. The dehydrogenation of 16 to 17 by
introduction of a phenylselenyl group, followed by
oxidation to a selenoxide with m-CPBA and eventual
syn-elimination, proceeded well. Deprotection of the
carbobenzoxy group gave the corresponding 4(1H)-
pyridone 18.
3.3. Antibacterial activity assay
Antibacterial activity was determined by the agar dilu-
tion method in Mueller–Hinton agar supplemented with
5% horse blood. S. aureus ATCC29213 was used as a
test strain. Approximately 104 CFU per spot was inocu-
lated onto agar plates containing twofold serial dilutions
of compounds. After incubation at 35 °C for 20 h, the
minimum inhibitory concentration (MIC) was deter-
mined as the lowest concentration of the test compound
that prevented visible growth.
4. Results and discussion
3. Biological methods
The synthesized compounds were evaluated for the
FabI-inhibitory and antibacterial activities against S.
aureus.
3.1. Preparation of His-tagged FabI
The fabI gene from E. coli DH5a was amplified by PCR
and cloned into pBAD/Myc-His B vector (Invitrogen).
The resulting plasmid was transformed into E. coli
TOP10. The expression of FabI protein fused with a
His-tag was induced with 0.2% arabinose. The cell pel-
lets were resuspended in lysis buffer (5 mM Tris–HCl,
pH 8.0, 0.3 M NaCl, containing 1 mg/ml of lysozyme)
and lysed by sonication. Cell lysates were applied to a
Ni–NTA agarose column (QIAGEN) and eluted with
250 mM imidazole. The solvent was exchanged to
20 mM Tris–HCl, pH 7.5, 10 mM EDTA, pH 8.0,
1 mM DTT by dialysis and the purified protein was
stored at ꢀ80 °C until use.
SAR of 1,2-substituted-3-(2,6-dichloro)benzyl-4-pyri-
done is shown in Table 1.
Lead compound 1 exhibited weak FabI-inhibitory activ-
ity of E. coli (IC50 = 1.9 lM). The compound 6a
(R1 = H) showed significantly decreased both activities.
These results indicate that some kind of functional
group is essential to 1-position. Compound 7a–7c hav-
ing an alkyl group at 1-position showed good FabI-in-
hibitory activity compared with 6a. In particular,
compound 7b (R1 = n-Bu) exhibited a potent antibacte-
rial activity. We speculate that the substituent R1 may
be directed toward the surface of the FabI enzyme in
the binding mode. Therefore, compound 7c having a
long alkyl chain seems to be tolerant for FabI-inhibitory
activity. However compound 7e having a carboxyl
group at the end of alkyl chain exhibited weak FabI-in-
hibitory activity.
3.2. Assay of FabI-inhibitory activity
Enzyme inhibition assays were carried out in half-area,
96-well microtiter plates. Compounds were evaluated
in 100 lL assay mixtures containing 100 mM sodium
phosphate (pH 7.4), 0.25 mM crotonoyl-CoA, 0.4 mM
NADH, and 50 lg/mL of His-tagged E. coli FabI, pre-
pared as described above. The consumption of NADH
Introduction of benzyl group into 1-position (7g) affor-
ded good FabI-inhibitory and antibacterial activities.
But introduction of various functional groups into the

H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
Table 1. Antibacterial activities of FabI inhibitors: effect of variation of R1 and R2
1109
Cl
O
N
R1
R2 Cl
Compounda
R1
R2
IC50 (lM) for
Escherichia coli FabI
MIC (lg/mL) for
Staphylococcus aureus
b
1
3-CF3–PhCH2SC(CH3)2CH2
H
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
1.9
64
6a
7a
7b
7c
120
11
>64
>128
2
n-Bu
CH3(CH2)9
HO(CH2)5
0.31
0.22
1.8
32
7d
7e
8
HO2C(CH2)4
Furan-2-yl-CH2
PhCH2
110
0.47
0.30
1.8
NTc
2
7f
7g
7h
7i
0.5
16
4-NO2–PhCH2
4-CO2CH3–PhCH2
4-CO2H–PhCH2
4-NH2–PhCH2
4-CONH2–PhCH2
2,6-Dichloro-PhCH2
Cyclohexyl-CH2
PhCH2
0.30
22
>128
>128
1
7j
7k
7l
0.29
2.5
32
32
7m
7n
7o
7p
Triclosan
8.4
0.22
0.78
4.5
0.25
8
CH3CH2
CH3(CH2)3
PhCH2
32
0.125
0.51
a Prepared by method A.
b Staphylococcus aureus ATCC29213.
c NT, not tested.
phenyl group (7h–7m) did not improve both activities.
Replacement of benzyl group with cyclohexylmethyl
group at 1-position (7n) improved FabI-inhibitory
(0.22 lM) and antibacterial activities (0.25 lg/mL).
We examined the effect of the R2 side chain (compounds
7o and 7p), but the FabI-inhibitory and antibacterial
activities were not improved. Therefore, we chose the
methyl group as the preferred R2 substituent.
0
Table 2. Antibacterial activities of FabI inhibitors: effect of variation of R3
O
R3'
N
Ph
0
Compound
Methoda
R3
IC50 (lM) for
Escherichia coli FabI
MIC (lg/mL) for
Staphylococcus aureusb
7q
7r
A
A
A
A
A
A
A
A
B
PhCH2
20
4.2
64
64
2-Chloro-PhCH2
2,6-Dichloro-PhCH2
2,4-Dichloro-PhCH2
2,4,6-Trichloro-PhCH2
2-Chloro-6-fluoro-PhCH2
2,6-Difluoro-PhCH2
2,6-Dimethyl-PhCH2
Ph
7g
7s
0.30
2.0
0.5
32
7t
1.5
8
7u
7v
7w
11
13
14
12
7x
7y
0.39
2.7
2
4
4.3
2.9
16
NTc
NTc
NTc
NTc
>128
32
C
C
C
A
A
(E)-2-(Pyridin-2-yl)vinyl
2-(Pyridin-2-yl)Et
Vinyl
>100
>100
>100
61
n-Bu
Cyclohexyl-CH2
0.40
a Method of synthesis.
b Staphylococcus aureus ATCC29213.
c NT, not tested.

1110
H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
Table 3. Antibacterial activities of FabI inhibitors: effect of variation of R4
Cl
Cl
O
R4
N
R1
Compound
R1
R4
IC50 (lM) for
Escherichia coli FabI
MIC (lg/mL) for
Staphylococcus aureusa
6a
H
H
n-Bu
120
>64
8
18a
18b
CO2CH2Ph
CO2CH2Ph
0.38
0.29
Cyclohexyl-CH2
2
a Staphylococcus aureus ATCC29213.
SAR of 1-benzyl-2-methyl-3-subsutituted-4-pyridone is
shown in Table 2. Compound 7q having a non-substitut-
6. Experimental
0
ed benzyl group as R3 showed drastically reduced
6.1. Chemistry
FabI-inhibitory and antibacterial activities compared
0
with 7g (R3 ¼ 2; 6-dichlorobenzyl). Compounds 7r–7w
possessing various subsutituted benzyl group at 3-
position showed reduced both activities compared with
7g.
Melting points were determined on a Yamato MP-21
apparatus and are uncorrected. IR spectra were mea-
sured with a JASCO FT/IR-410 spectrometer. 1H
NMR (400 MHz) spectra were recorded on a JEOL
lambda400 spectrometer. Chemical shifts were reported
in d value (ppm) with tetramethylsilane (TMS) as the
internal standard (NMR peak designations: s, singlet;
d, doublet; t, triplet; q, quartet; sep, septet; m, multiplet;
and br, broad peak). Mass spectra were recorded with a
JEOL JMS-700 spectrometer. High-resolution mass
spectra (HRMS) were obtained on a JMS-FABmate
spectrometer. Column chromatography was performed
with silicagel (Kanto Chemical: 60N spherical, neutral).
All the reagents and solvents were from commercial sup-
pliers and were used without further purification.
0
Compound 11 having a phenyl group as R3 showed
moderate FabI-inhibitory activity. Replacement of ben-
zyl group with cyclohexylmethyl group at 3-position
(7y) improved FabI-inhibitory activity. However, com-
0
pounds 13 (R3 ¼ ðEÞ-2-ðpyridine-2-ylÞvinylÞ and 12
0
(R3 ¼ vinyl) did not show FabI-inhibitory activity.
From these results, we concluded that the 2,6-dichlorob-
enzyl moiety was favorable for both FabI-inhibitory and
antibacterial activities. We presumed that R3 should be
a lipophilic substituent which would conform to the sub-
strate-binding site of FabI.
6.1.1. 1-Benzyloxycarbonyl-2,3-dihydro-2-methyl-4-pyri-
done (3a).13. To a solution of methylmagnesium bromide
(178 mmol) and 4-methoxypyridine (16.1 g, 148 mmol)
in THF (300 ml) at ꢀ25 °C was added benzyl chlorofor-
mate over a period of 30 min. The resulting mixture was
stirred at ꢀ25 °C for 4 h and then poured into 3 N HCl
(300 ml). After stirring for 10 min at room temperature,
the mixture was extracted with ethyl acetate twice and
the combined organic extract was washed with 5% NaH-
CO3 aq, dried over Na2SO4, filtered, and concentrated
in vacuo. The residue was purified by column chroma-
tography on silica gel [hexane/AcOEt (3:1)] to afford
The effects of the 6-position derivatives on the
FabI-inhibitory and antibacterial activities were
examined (Table 3). Introduction of the substituent
into 6-position (18a, 18b) strengthened FabI-inhibi-
tory activity and antibacterial activity compared
with 6a. Therefore, we presume that the substituents
at 6-position act an important role for FabI-inhibi-
tory activity and antibacterial activity similar to 1-
substituents.
1
3a (34.1 g, 94%). H NMR (400 MHz, CDCl3) d 1.26
5. Conclusion
(3H, t, J = 6.8 Hz), 2.31 (1H, d, J = 16.6 Hz), 2.85
(1H, dd, J = 16.6, 6.8 Hz), 4.73 (1H, br), 5.22–5.40
(3H, m), 7.28–7.45 (5H, m), 7.74 (1H, d, J = 8.0 Hz);
MS (FAB+) m/z 246 (M+H)+.
We discovered the 4-pyridone derivative 7n as a novel
inhibitor of bacterial enoyl-ACP reductase (FabI). Com-
pound 7n exhibited both strong FabI-inhibitory activity
and good antibacterial activity. The present results sup-
port the idea that FabI is a valid antibacterial target,
and that small-molecular FabI inhibitors are candidate
drugs for the treatment of bacterial infections, and fur-
ther suggest that the 4-pyridone structure represents a
good lead structure. Further structural development
studies are in progress.
6.1.2. 1-Benzyloxycarbonyl-2,3-dihydro-2-ethyl-4-pyri-
done (3b). Yield (1.04 g, 81%). 1H NMR (400 MHz,
CDCl3) d 0.89 (3H, t, J = 7.5 Hz), 1.59–1.77 (2H, m),
2.47 (1H, d, J = 16.8 Hz), 2.80 (1H, dd, J = 16.8,
6.6 Hz), 4.52 (1H, br), 5.27 (2H, s), 5.31 (1H, br),
7.28–7.45 (5H, m), 7.78 (1H, br); MS (FAB+) m/z 260
(M+H)+.

H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
1111
6.1.3. 1-Benzyloxycarbonyl-2-butyl-2,3-dihydro-4-pyri-
done (3c). Yield (5.57 g, 99%). 1H NMR (400 MHz,
CDCl3) d 0.85 (3H, br), 1.10–1.45 (4H, br), 1.55–1.74
(2H, m), 2.45 (1H, d, J = 16.6 Hz), 2.80 (1H, dd,
J = 16.6, 6.6 Hz), 4.58 (1H, br), 5.21–5.40 (3H, m),
7.28–7.40 (5H, m), 7.76 (1H, br); MS (FAB+) m/z 288
(M+H)+.
The following compounds (6b–6k) were prepared from
3a or 3b or 3c and appropriate aldehydes by a similar
procedure to that described for 4a, 5a, and 6a.
6.1.7. 3-Benzyl-2-methyl-4-pyridone (6b). Yield (110 mg,
27%, 3 steps). IR (KBr) 3331, 1623, 1498, 1168, 841,
724, 549 cmꢀ1 1H NMR (400 MHz, CDCl3) d 2.19
.
(3H, s), 3.91 (2H, s), 6.27 (1H, d, J = 7.1 Hz), 7.06–
7.22 (6H, m), 12.4 (1H, br). 13C NMR (100 MHz,
CD3OD) d 17.5, 31.1, 115.9, 127.0, 128.3, 129.2, 129.4,
137.7, 141.3, 148.3, 180.6; HRMS (FAB+) m/z: calcd
for C13H14NO (M+H)+: 200.1075, found: 200.1074.
6.1.4. 1-Benzyloxycarbonyl-3-[(2,6-dichlorophenyl)(hydroxy)-
a
methyl]-2,3-dihydro-2-methyl-4-pyridone (4a). To
solution of 3a (5.0 g, 20.4 mmol) in THF (60 ml) at
ꢀ78 °C was added 1 M lithium bis(trimethylsilyl)amide
in THF (22.4 ml). The resulting mixture was stirred at
0 °C for 30 min and cooled to ꢀ78 °C. To this solution
6.1.8. 3-(2-Chlorobenzyl)-2-methyl-4-pyridone (6c). Yield
1
was
added
2,6-dichlorobenzaldehyde
(4.64 g,
(185 mg, 37%, 3 steps). H NMR (400 MHz, CDCl3) d
26.5 mmol). The resulting solution was stirred at
ꢀ78 °C for 1 h, then poured into saturated NH4Cl aq
(200 ml). The mixture was extracted with ethyl acetate
twice and the combined organic extract was washed with
brine, dried over Na2SO4, filtered, and concentrated in
vacuo. The crude product was purified by column chro-
matography on silica gel [hexane/AcOEt (3:1)] to afford
4a (8.4 g, 98%). 1H NMR (400 MHz, CDCl3) d 1.20
(3H, d, J = 6.8 Hz), 3.12 (1H, d, J = 9.0 Hz), 3.17–3.30
(1H, br), 3.90–4.15 (1H, br), 5.10–5.63 (4H, m), 7.05–
7.50 (8H, br), 7.70–8.00 (1H, br); MS (FAB+) m/z 420
(M+H)+.
2.08 (3H, s), 3.92 (2H, s), 6.30 (1H, d, J = 7.1 Hz),
6.80 (2H, dd, J = 5.6, 4.1 Hz), 7.01–7.09 (2H, m), 7.23
(1H, d, J = 7.1 Hz), 7.26–7.29 (1H, m); MS (FAB+) m/
z 234 (M+H)+.
6.1.9. 3-(2,4-Dichlorobenzyl)-2-methyl-4-pyridone (6d).
Yield (224 mg, 17%, 3 steps). 1H NMR (400 MHz,
CD3OD) d 2.22 (3H, s), 3.96 (2H, s), 6.43 (1H, d,
J = 7.3 Hz), 6.85 (1H, d, J = 8.5 Hz), 7.16 (1H, dd,
J = 8.5, 2.2 Hz), 7.67 (1H, d, J = 7.3 Hz); MS (FAB+)
m/z 268 (M+H)+.
6.1.10.
(6e). Yield (684 mg, 57%,
(400 MHz, DMSO-d6) d 2.15 (3H, s), 4.07 (2H, s), 6.01
(1H, d, J = 7.1 Hz), 7.39–7.56 (3H, m); MS (FAB+) m/
z 302 (M+H)+.
2-Methyl-3-(2,4,6-trichlorobenzyl)-4-pyridone
steps). 1H NMR
6.1.5. 1-Benzyloxycarbonyl-3-[(2,6-dichlorophenyl)(meth-
ylsulfonyloxy)methyl]-2,3-dihydro-2-methyl-4-pyridone (5a).
To a solution of 4a (1.61 g, 3.83 mmol) in pyridine
(10 ml) at 0 °C was added mesyl chloride (0.445 ml,
5.75 mmol). The resulting mixture was stirred at room
temperature for 3 h, then poured into water (150 ml).
The mixture was extracted with ethyl acetate (150 ml)
and the organic extract was washed with water, dried
over Na2SO4, filtered, and concentrated in vacuo. The
crude product was purified by column chromatography
on silica gel [hexane/AcOEt (3:1)] to afford 5a (1.79 g,
94%). 1H NMR (400 MHz, CDCl3) d 1.22 (3H, d,
J = 6.8 Hz), 2.89 (3H, s), 3.40–3.61 (1H, br), 3.91–4.15
(1H, br), 5.02–5.59 (3H, m), 6.40 (1H, d, J = 10.7 Hz),
7.05–7.52 (8H, br), 7.80–8.05 (1H, br); MS (FAB+) m/
z 498 (M+H)+.
3
6.1.11. 3-(2-Chloro-6-fluorobenzyl)-2-methyl-4-pyridone
3
(6f). Yield (131 mg, 19%,
steps). 1H NMR
(400 MHz, CDCl3) d 2.21 (3H, s), 4.06 (2H, s), 6.23
(1H, d, J = 7.1 Hz), 6.79–6.87 (1H, m), 6.99–7.11 (1H,
m), 7.30 (1H, d, J = 7.1 Hz); MS (FAB+) m/z 252
(M+H)+.
6.1.12. 3-(2,6-Difluorobenzyl)-2-methyl-4-pyridone (6g).
Yield (240 mg, 9%, 3 steps). 1H NMR (400 MHz,
CD3OD) d 2.30 (3H, s), 3.95 (2H, s), 6.34 (1H, d,
J = 7.1 Hz), 6.81–6.91 (2H, m), 7.15–7.24 (1H, m), 7.57
(1H, d, J = 7.1 Hz); MS (FAB+) m/z 236 (M+H)+.
6.1.6. 3-(2,6-Dichlorobenzyl)-2-methyl-4-pyridone (6a).
To a solution of a (1.00 g, 2.01 mmol) in THF (35 ml)
was added potassium tert-butoxide (1.13 g 10.0 mmol).
The resulting solution was stirred at room temperature
for 10 min, then poured into 5% NH4Cl aq (100 ml).
The mixture was extracted with chloroform/i-propanol
(5:1, 100 ml) twice and the combined organic phase
was dried over Na2SO4, filtered, and concentrated in
vacuo. The residue was purified by column chromatog-
raphy on silica gel [CHCl3/MeOH (9:1)] to afford 6a
(469 mg, 87%). IR (KBr) 3333, 1624, 1503, 1159, 842,
6.1.13. 3-(2,6-Dimethylbenzyl)-2-methyl-4-pyridone (6h).
Yield (171 mg, 37%, 3 steps). 1H NMR (400 MHz,
CDCl3) d 1.93 (3H, s), 2.20 (6H, s), 4.00 (2H, s), 6.28
(1H, d, J = 7.1 Hz), 6.88–7.00 (3H, m), 7.37 (1H, d,
J = 7.1 Hz); MS (FAB+) m/z 228 (M+H)+.
6.1.14. 3-(2,6-Dichlorobenzyl)-2-ethyl-4-pyridone (6i).
Yield (61.1 mg, 23%, 3 steps). 1H NMR (400 MHz,
CDCl3) d 0.80 (3H, t, J = 7.6 Hz), 2.49 (2H, q,
J = 7.6 Hz), 4.30 (2H, s), 6.33 (1H, d, J = 7.1 Hz), 7.18
(1H, t, J = 7.8 Hz), 7.33 (2H, d, J = 7.8 Hz), 7.59 (1H,
d, J = 7.1 Hz); MS (FAB+) m/z 282 (M+H)+.
768, 543 cmꢀ1 1H NMR (400 MHz, CDCl3) d 2.10
.
(3H, s), 4.24 (2H, s), 6.23 (1H, d, J = 7.1 Hz), 7.05
(1H, t, J = 8.1 Hz), 7.22 (2H, d, J = 8.1 Hz), 7.26 (1H,
br). 13C NMR (100 MHz, CD3OD) d 17.5, 28.0, 115.3,
126.4, 129.3, 129.7, 137.2, 137.57, 137.63, 147.2, 180.4;
HRMS (FAB+) m/z: calcd for C13H12Cl2NO (M+H)+:
268.0296, found: 268.0294.
6.1.15. 2-Butyl-3-(2,6-dichlorobenzyl)-4-pyridone (6j).
Yield (92 mg, 50%, 3 steps). 1H NMR (400 MHz,
CD3OD) d 0.76 (3H, t, J = 7.1 Hz), 1.03–1.39 (4H, m),
2.53 (2H, br), 4.29 (2H, s), 6.27 (1H, d, J = 7.1 Hz),

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H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
7.05 (1H, t, J = 7.8 Hz), 7.21–7.26 (2H, m), 7.45 (1H, d,
J = 7.1 Hz); MS (FAB+) m/z 310 (M+H)+.
The following compounds (7a–7d, 7f–7j, 7m–7w, and
7x–7y) were similarly obtained.
6.1.16. 3-Butyl-2-methyl-4-pyridone (6k). To a solution
of 1-benzyloxycarbonyl-3-[1-(methylsulfonyloxy)butyl]-
2,3-dihydro-2-methyl-4-pyridone (prepared in the same
manner as 4a and 5a (112 mg, 0.354 mmol) in THF
(2 ml) was added DBU (0.079 ml, 0.531 mmol)). The
resulting solution was stirred at room temperature over-
night, then diluted with ethyl acetate and washed with
5% NaHCO3 aq and brine. The organic phase was dried
over Na2SO4, filtered, and concentrated in vacuo. The
residue was purified by column chromatography on sil-
ica gel [hexane/AcOEt (4:1)] to afford1-benzyloxycar-
bonyl-3-butylidene-2,3-dihidro-2-methyl-4-pyridone
6.1.19. 3-(2,6-Dichlorobenzyl)-1,2-dimethyl-4-pyridone
(7a). Yield (45 mg, 86%). H NMR (400 MHz, CDCl3)
d 2.08 (3H, s), 3.53 (3H, s), 4.37 (2H, s), 6.30 (1H, d,
J = 7.6 Hz), 7.06 (1H, t, J = 8.0 Hz), 7.21 (1H, d,
J = 7.6 Hz), 7.25 (2H, d, J = 8.0 Hz); MS (FAB+) m/z
282 (M+H)+.
1
6.1.20. 1-Butyl-3-(2,6-dichlorobenzyl)-2-methyl-4-pyri-
done (7b). Yield (49 mg, 81%). 1H NMR (400 MHz,
CDCl3) d 0.93 (3H, t, J = 7.6 Hz), 1.34 (2H, tq,
J = 7.6 Hz), 1.58–1.74 (2H, m), 2.09 (3H, s), 3.74 (2H,
t, J = 7.6 Hz), 4.36 (2H, s), 6.31 (1H, d, J = 7.6 Hz),
7.05 (1H, t, J = 8.0 Hz), 7.21 (1H, d, J = 7.6 Hz), 7.25
(2H, d, J = 8.0 Hz); MS (FAB+) m/z 324 (M+H)+.
1
(90 mg, 85%, E: Z = 2:8). H NMR (400 MHz, CDCl3)
d 0.88–1.00 (3H, m), 122–1.36 (3H, m), 1.37–1.57 (4H,
m), 2.02–2.28 (1.6H, br), 4.78–5.06 (0.2H, br), 5.20–
5.65 (3.8H, br), 5.78–5.95 (0.2H, br), 6.69 (0.8H, t,
J = 6.7 Hz), 7.32–7.45 (5H, br), 7.50–7.80 (1H, br);
HRMS (FAB+) m/z: calcd for C18H22NO3 (M+H)+:
300.1600, found: 300.1596.
6.1.21. 1-Decyl-3-(2,6-dichlorobenzyl)-2-methyl-4-pyri-
done (7c). Yield (49 mg, 62%). 1H NMR (400 MHz,
CDCl3) d 0.88 (3H, t, J = 6.8 Hz), 1.25 (14H, br), 1.68
(2H, br), 2.08 (3H, s), 3.73 (2H, t, J = 7.6 Hz), 4.37
(2H, s), 6.31 (1H, d, J = 7.6 Hz), 7.05 (1H, t,
J = 8.0 Hz), 7.21 (2H, d, J = 7.6 Hz), 7.26 (2H, d,
J = 8.0 Hz); MS (FAB+) m/z 408 (M+H)+.
To a solution of afford1-benzyloxycarbonyl-3-butyli-
dene-2,3-dihidro-2-methyl-4-pyridone(64 mg, 0.214 mmol)
in methanol (1 ml) was added 10% Pd/C (15 mg). The mix-
ture was stirred under a hydrogen atmosphere at room
temperature for 10 min, filtered through Celite, and con-
centrated in vacuo. The residue was purified by column
chromatography on silica gel [CHCl3/MeOH (9:1)] to af-
ford 6l (33 mg, 93%). 1H NMR (400 MHz, CDCl3) d
0.90 (3H, t, J = 7.1 Hz), 1.28–1.50 (4H, m), 2.39 (3H, s),
2.53 (2H, t, J = 7.8 Hz), 6.28 (1H, d, J = 6.8 Hz), 7.43
(1H, d, J = 6.8 Hz), 13.1 (1H, br). 13C NMR (100 MHz,
CDCl3) d 14.1, 17.2, 23.0, 25.3, 30.8, 114.3, 128.5, 136.0,
145.5, 178.6; HRMS (FAB+) m/z: calcd for C10H16NO
(M+H)+: 166.1232, found: 166.1236.
6.1.22.
3-(2,6-Dichlorobenzyl)-1-(5-hydroxypentyl)-2-
1
methyl-4-pyridone (7d). Yield (89 mg, 21%). H NMR
(400 MHz, CDCl3) d 1.35–1.47 (2H, m), 1.50–1.81
(4H, m), 2.10 (3H, s), 3.65 (2H, t, J = 6.2 Hz), 3.77
(2H, t, J = 7.5 Hz), 4.35 (2H, s), 6.31 (1H, d,
J = 7.3 Hz), 7.06 (1H, t, J = 8.0 Hz), 7.20–7.26 (2H,
m); MS (FAB+) m/z 354 (M+H)+.
6.1.23. 3-(2,6-Dichlorobenzyl)-1-furfuryl-2-methyl-4-pyri-
done (7f). Yield (61 mg, 47%). 1H NMR (400 MHz,
CDCl3) d 2.15 (3H, s), 4.35 (2H, s), 4.90 (2H, s), 6.15–
6.21 (1H, m), 6.29–6.39 (2H, m), 7.05 (1H, t,
J = 8.0 Hz), 7.24 (2H, d, J = 8.0 Hz), 7.31 (1H, d,
J = 7.6 Hz), 7.37–7.43 (1H, m); HRMS (FAB+) m/z:
calcd for C18H16Cl2NO2 (M+H)+: 348.0558, found:
348.0561.
6.1.17. 3-Cyclohexylmethyl-2-methyl-4-pyridone (6l). The
title compound was prepared from 3a by means of a
similar procedure to that described for 6k, (59 mg,
57%, 4 steps). 1H NMR (400 MHz, CDCl3) d 0.85–
1.01 (2H, br), 1.05–1.20 (3H, br), 1.45–1.68 (6H, br),
2.25 (3H, s), 2.32 (2H, d, J = 7.1 Hz), 6.23 (1H, d,
J = 7.1 Hz), 7.46 (1H, d, J = 7.1 Hz); MS (FAB+) m/z
206 (M+H)+.
6.1.24. 3-(2,6-Dichlorobenzyl)-1-(4-nitrobenzyl)-2-meth-
yl-4- pyridone (7h). Yield (16 mg, 86%). 1H NMR
(400 MHz, CD3OD) d 1.96 (3H, s), 4.37 (2H, s), 5.11
(2H, s), 6.41 (1H, d, J = 7.6 Hz), 7.05 (1H, t,
J = 8.0 Hz), 7.16 (2H, d, J = 8.8 Hz), 7.24 (2H, d,
J = 8.0 Hz), 7.30 (1H, d, J = 7.6 Hz), 8.23 (2H, d,
J = 8.8 Hz); MS (FAB+) m/z 403 (M+H)+.
6.1.18. 1-Benzyl-3-(2,6-dichlorobenzyl)-2-methyl-4-pyri-
done (7g). To a solution of 6a (100 mg, 0.373 mmol)
in THF (3 ml) were added sodium hydride (19.4 mg,
0.485 mmol as a 60% dispersion in mineral oil) and
benzyl bromide (0.0577 ml, 0.485 mmol). The reaction
mixture was stirred at room temperature for 3 h, then
diluted with ethyl acetate and washed with 5% NaCl
aq. The extract was dried over Na2SO4, filtered, and
concentrated in vacuo. The residue was purified by
column chromatography on silica gel [CHCl3/MeOH
(20:1)] to afford 7g (123 mg, 92%). 1H NMR
(400 MHz, CDCl3) d 1.98 (3H, s), 4.36 (2H, s),
5.01 (2H, s), 6.38 (1H, d, J = 7.6 Hz), 6.96–7.06
(3H, m), 7.21–7.39 (6H, m); HRMS (FAB+) m/z:
calcd for C20H18Cl2NO (M+H)+: 358.0765, found:
358.0775.
6.1.25. Methyl 4-[3-(2,6-dichlorobenzyl)-2-methyl-4-pyri-
don-1-yl]methylbenzoate (7i). Yield (294 mg, 40%). 1H
NMR (400 MHz, CD3OD) d 2.29 (3H, s), 3.90 (3H, s),
4.43 (2H, s), 5.61 (2H, s), 6.88 (1H, d, J = 7.2 Hz),
7.15–7.22 (3H, m), 7.34 (2H, d, J = 7.8 Hz), 8.03 (2H,
d, J = 7.8 Hz), 8.30 (1H, d, J = 7.2 Hz); MS (FAB+)
m/z 416 (M+H)+.
6.1.26. 1,3-Bis(2,6-dichlorobenzyl)-2-methyl-4-pyridone
(7m). Yield (57 mg, 72%). 1H NMR (400 MHz,
CDCl3) d 2.25 (3H, s), 4.41 (2H, s), 5.20 (2H, s),
6.22 (1H, d, J = 7.8 Hz), 6.86 (1H, d, J = 7.8 Hz),

H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
1113
7.06 (1H, t, J = 8.3 Hz), 7.24–7.29 (2H, br), 7.30–7.47
(1H, m), 7.42 (2H, d, J = 8.3 Hz); MS (FAB+) m/z
426 (M+H)+.
6.1.35. 1-Benzyl-3-(2,6-difluorobenzyl)-2-methyl-4-pyri-
done (7v). Yield (37 mg, 53%). 1H NMR (400 MHz,
CDCl3) d 2.16 (3H, s), 2.50 (2H, s), 5.02 (2H, s), 6.40
(1H, d, J = 7.6 Hz), 6.74–6.82 (2H, m), 6.97–7.02 (2H,
m), 7.04–7.13 (1H, m), 7.28–7.39 (4H, m); HRMS
(FAB+) m/z: calcd for C20H18F2NO (M+H)+:
326.1356, found: 326.1362.
6.1.27.
1-Cyclohexylmethyl-3-(2,6-dichlorobenzyl)-2-
1
methyl-4-pyridone (7n). Yield (30 mg, 44%). H NMR
(400 MHz, CDCl3) d 0.85–1.00 (2H, m), 1.08–1.28
(3H, m), 1.50–1.82 (6H, m), 2.08 (3H, s), 3.58 (2H, d,
J = 7.1 Hz), 4.37 (2H, s), 6.29 (1H, d, J = 7.6 Hz), 7.05
(1H, t, J = 8.0 Hz), 7.16 (1H, d, J = 7.6 Hz), 7.25 (2H,
d, J = 8.0 Hz); HRMS (FAB+) m/z: calcd for
C20H24Cl2NO (M+H)+: 364.1235, found: 364.1230.
6.1.36. 1-Benzyl-3-(2,6-dimethylbenzyl)-2-methyl-4-pyri-
done (7w). Yield (35 mg, 62%). 1H NMR (400 MHz,
CDCl3) d 1.81 (3H, s), 2.23 (6H, s), 4.14 (2H, s), 4.97
(2H, s), 6.44 (1H, d, J = 7.3 Hz), 6.89–7.02 (5H, m),
7.28–7.48 (4H, m); MS (FAB+) m/z 318 (M+H)+.
6.1.28.
1-Benzyl-3-(2,6-dichlorobenzyl)-2-ethyl-4-pyri-
done (7o). Yield (13 mg, 49%). 1H NMR (400 MHz,
CDCl3) d 0.77 (3H, t, J = 7.6 Hz), 2.48 (2H, q,
J = 7.6 Hz), 4.39 (2H, s), 5.02 (2H, s), 6.37 (1H, d,
J = 7.5 Hz), 6.97 (2H, d, J = 7.1 Hz), 7.03 (1H, t,
J = 8.0 Hz), 7.24–7.38 (6H, m); MS (FAB+) m/z 372
(M+H)+.
6.1.37. 1-Benzyl-3-butyl-2-methyl-4-pyridone (7x). Yield
(5.0 mg, 44%). 1H NMR (400 MHz, CDCl3) d 0.91
(3H, t, J = 7.1 Hz), 1.24 (4H, br), 2.22 (3H, s), 2.59
(2H, t, J = 7.3 Hz), 5.05 (2H, s), 6.37 (1H, d,
J = 7.6 Hz), 7.02 (2H, d, J = 7.6 Hz), 7.26–7.43 (4H,
m); MS (FAB+) m/z 256 (M+H)+.
6.1.29.
1-Benzyl-2-butyl-3-(2,6-dichlorobenzyl)-4-pyri-
6.1.38. 3-Cyclohexylmethyl-1-benzyl-2-methyl-4-pyridone
(7y). Yield (13.5 mg, 22%). 1H NMR (400 MHz, CDCl3)
d 0.95–1.25 (5H, m), 1.45–1.78 (6H, m), 2.21 (3H, s),
2.49 (2H, d, J = 7.3 Hz), 5.05 (2H, s), 6.36 (1H, d,
J = 7.5 Hz), 7.01 (2H, d, J = 7.1 Hz), 7.27–7.40 (4 H,
m); MS (FAB+) m/z 296 (M+H)+.
done (7p). Yield (21 mg, 48%). 1H NMR (400 MHz,
CDCl3) d 0.73 (3H, t, J = 7.3 Hz), 0.96–1.22 (4H, m),
2.40 (2H, br), 4.39 (2H, s), 4.99 (2H, s), 6.36 (1H, d,
J = 7.5 Hz), 6.98 (2H, d, J = 7.1 Hz), 7.05 (1H, t,
J = 7.8 Hz), 7.24–7.45 (6H, m); MS (FAB+) m/z 400
(M+H)+.
6.1.39. 5-[3-(2,6-Dichlorobenzyl)-2-methyl-4-pyridon-1-
yl]pentanoic acid (7e). To a solution of 7d (10.9 mg,
0.031 mmol) in acetone (0.11 ml) at 0 °C was added an
aqueous solution of chromium(VI) oxide and sulfuric
acid (2.2 mg 0.022 mmol). The mixture was stirred at
room temperature for 70 min, then methanol (0.1 ml)
was added. The mixture was diluted with ethyl acetate
and washed with brine. The extract was dried over
Na2SO4, filtered, and concentrated in vacuo. The resi-
due was purified by preparative TLC [CHCl3/MeOH
6.1.30. 1,3-Dibenzyl-2-methyl-4-pyridone (7q). Yield
(58 mg, 50%). 1H NMR (400 MHz, CDCl3) d 2.15
(3H, s), 4.03 (2H, s), 5.03 (2H, s), 6.48 (1H, d,
J = 7.3 Hz), 7.02 (2H, d, J = 6.8 Hz), 7.10–7.16 (1H,
m), 7.18–7.23 (4H, m), 7.32–7.41 (4H, m); MS (FAB+)
m/z 290 (M+H)+.
6.1.31. 1-Benzyl-3-(2-chlorobenzyl)-2-methyl-4-pyridone
(7r). Yield (20 mg, 33%). H NMR (400 MHz, CDCl3)
1
1
d 2.07 (3H, s), 3.95 (2H, s), 5.09 (2H, s), 6.49 (1H, d,
J = 7.5 Hz), 6.90–6.17 (5H, m), 7.27–7.95 (5H, m); MS
(FAB+) m/z 324 (M+H)+.
(8:1)] to give 7e (2.5 mg, 25%). H NMR (400 MHz,
CDCl3) d 1.50–1.80 (6H, m), 2.13 (3H, s), 3.83 (2H,
br), 4.36 (2H, br), 6.52 (1H, d, J = 7.5 Hz), 7.06 (1H,
t, J = 8.1 Hz), 7.22–7.26 (2H, m), 7.35 (1H, d,
J = 7.5 Hz); MS (FAB+) m/z 368 (M+H)+.
6.1.32. 1-Benzyl-3-(2,4-dichlorobenzyl)-2-methyl-4-pyri-
done (7s). Yield (39 mg, 45%). 1H NMR (400 MHz,
CDCl3) d 2.07 (3H, s), 4.06 (2H, s), 5.06 (2H, s), 6.49
(1H, d, J = 7.6 Hz), 6.94 (1H, d, J = 8.3 Hz), 7.02 (2H,
d, J = 6.8 Hz), 7.06 (1H, dd, J = 8.3, 2.2 Hz), 7.31–7.43
(5H, m); MS (FAB+) m/z 358 (M+H)+.
6.1.40. 4-[3-(2,6-Dichlorobenzyl)-2-methyl-4-pyridone-1-
yl]methylbenzoic acid (7j). To a solution of 7i (100 mg,
0.240 mmol) in 1,4-dioxane (1 ml) was added 1 N NaOH
(1 ml). The mixture was stirred at room temperature for
30 min. The solution was acidified with 1 N HCl,
extracted with chloroform/i-propanol (5:1) three times,
and washed with brine. The organic phase was dried
over Na2SO4, filtered, and concentrated in vacuo to give
6.1.33.
1-Benzyl-2-methyl-3-(2,4,6-trichlorobenzyl)-4-
pyridone (7t). Yield (50 mg, 77%). 1H NMR
(400 MHz, CDCl3) d 2.02 (3H, s), 4.38 (2H, s), 5.03
(2H, s), 6.38 (1H, d, J = 7.6 Hz), 6.98 (2H, d,
J = 7.3 Hz), 7.17–7.25 (2H, m), 7.29–7.41 (4H, m); MS
(FAB+) m/z 392 (M+H)+.
1
7j (75.1 mg, 78%). H NMR (400 MHz, DMSO-d6) d
2.40 (3H, s), 4.30 (2H, s), 5.76 (2H, s), 7.14 (1H, d,
J = 7.2 Hz), 7.18 (2H, d, J = 8.3 Hz), 7.26 (1H, t,
J = 8.3 Hz), 7.41 (2H, d, J = 7.8 Hz), 7.94 (2H, d,
J = 7.8 Hz), 8.57 (1H, d, J = 7.2 Hz); MS (FAB+) m/z
402 (M+H)+.
6.1.34. 1-Benzyl-3-(2-chloro-6-fluorobenzyl)-2-methyl-4-
pyridone (7u). Yield (103 mg, 76%). 1H NMR
(400 MHz, CDCl3) d 2.08 (3H, s), 4.20 (2H, s), 5.02
(2H,s), 6.40 (1H, d, J = 7.3 Hz), 6.84–6.92 (1H, m),
6.99 (2H, d, J = 6.8 Hz), 7.02–7.14 (2H, m), 7.28–7.39
(4H, m); HRMS (FAB+) m/z: calcd for C20H18ClFNO
(M+H)+: 342.1061, found: 362.1067.
6.1.41. 1-(4-Aminobenzyl)-3-(2,6-dichlorobenzyl)-2-meth-
yl-4-pyridone (7k). To a solution of 7h (348 mg,
0.348 mmol) in methanol (3 ml) was added 10% Pd/C
(35 mg). The mixture was stirred under a hydrogen

1114
H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
atmosphere at room temperature for 1 h, filtered
through Celite, and concentrated in vacuo. The residue
was purified by column chromatography on silica gel
[CHCl3/MeOH (30:1)] to give 7k (85 mg, 26%). 1H
NMR (400 MHz, CDCl3) d 2.00 (3H, s), 3.76 (2H, br),
4.35 (2H, s), 4.88 (2H, s), 6.35 (1H, d, J = 7.6 Hz),
6.64 (2H, d, J = 8.3 Hz), 6.78 (2H, d, J = 8.3 Hz), 7.03
(1H, t, J = 8.0 Hz), 7.23 (2H, d, J = 8.0 Hz), 7.32 (2H,
d, J = 7.6 Hz); MS (FAB+) m/z 373 (M+H)+.
6.1.46. 1-Benzyl-2-methyl-3-vinyl-4-pyridone (12). To a
solution of 10 (300 mg, 0.864 mmol) in 1,4-dioxane
(4 ml) were added lithium chloride (73.2 mg,
1.73 mmol),
tetrakis(triphenylphosphine)palladium
(99.8 mg, 10 mol%), and tributyl(vinyl)tin (0.327 ml,
1.12 mmol). The mixture was stirred under reflux for
3 h then cooled and diluted with CHCl3. The mixture
was washed with brine, dried over Na2SO4, filtered,
and concentrated in vacuo. The residue was purified
by column chromatography on silica gel [AcOEt/MeOH
(20:1)] to afford 12 (118 mg, 61%). 1H NMR (400 MHz,
CDCl3) d 1.26 (3H,s), 5.08 (2H, s), 5.57 (1H, dd,
J = 11.7, 2.2 Hz), 5.75 (1H, dd, J = 17.8, 2.2 Hz), 6.44
(1H, d, J = 7.3 Hz), 6.67 (1H, dd, J = 17.8, 11.7 Hz),
7.05 (2H, d, J = 7.1 Hz), 7.24–7.43 (4H, m); MS
(FAB+) m/z 226 (M+H)+.
6.1.42. 4-[3-(2,6-Dichlorobenzyl)-2-methyl-4-pyridon-1-
yl]methylbenzamide (7l). A solution of 7i (50 mg,
0.120 mmol) in 7 M NH3 in methanol (4 ml) was sealed
and stirred at 60 °C for 3 h. The mixture was concentrat-
ed in vacuo and the residue was purified by column
chromatography on silica gel [CHCl3/MeOH (30:1)] to
1
give 7l (20 mg, 42%). H NMR (400 MHz, CD3OD) d
2.02 (3H, s), 4.35 (2H, s), 5.32 (2H, s), 6.44 (1H, d,
J = 7.4 Hz), 7.08–7.16 (3H, m), 7.29 (2H, d,
J = 8.0 Hz), 7.81 (1H, d, J = 7.4 Hz), 7.86 (2H, d,
J = 8.3 Hz); MS (FAB+) m/z 401 (M+H)+.
6.1.47. (E)-1-Benzyl-2-methyl-3-[2-(pyridin-3-yl)vinyl]-4-
pyridone (13). To a solution of 12 (30 mg, 0.133 mmol)
in 1,4-dioxane (1 ml) were added 3-bromopyridine
(31.6 mg,
0.200 mmol),
dicyclohexylmethylamine
(0.057 ml, 0.266 mmol), tris(dibenzylideneacetone)dipal-
ladium (18.3 mg, 15 mol%), and tri-tert-butylphosphine
(0.011 ml, 30 mol%). The mixture was stirred overnight
at room temperature, then concentrated in vacuo. The
residue was purified by preparative TLC [CHCl3/MeOH
(9:1)] to give 13 (13 mg, 32%). 1H NMR (400 MHz,
CDCl3) d 2.41 (3H, s), 5.12 (2H, s), 6.46 (1H, d,
J = 7.6 Hz), 7.07 (2H, d, J = 7.8 Hz), 7.10 (1H, d,
J = 16.3 Hz), 7.22–7.30 (1H, m), 7.31–7.46 (4H, m),
7.64 (1H, d, J = 16.3 Hz), 7.81 (1H, d, J = 8.0 Hz),
8.45 (1H, d, J = 4.6 Hz), 8.69 (1H, s); MS (FAB+) m/z
303 (M+H)+.
6.1.43. 1-Benzyl-3-hydroxy-2-methyl-4-pyridone (9). To a
solution of maltol (25 g, 198 mmol) in EtOH/H2O (3:1,
100 ml) at room temperature was added benzylamine
(108 ml, 991 mmol). The mixture was stirred overnight
at 50 °C. The mixture was concentrated in vacuo, neu-
tralized with 1 N HCl, and then extracted with CHCl3.
The extract was dried over Na2SO4, filtered, and concen-
trated in vacuo. The resulting crystals were collected by
filtration and washed with ethyl acetate to afford 9
(15.5 g, 36%); mp 195–198 °C. 1H NMR (400 MHz,
CDCl3) d 2.28 (3H, s), 5.13 (2H, s), 6.45 (1H, d,
J = 7.3 Hz), 7.02 (2H, d, J = 6.8 Hz), 7.27–7.42 (4H,
m); MS (FAB+) m/z 216 (M+H)+.
6.1.48. 1-Benzyl-2-methyl-3-[2-(pyridin-3-yl)ethyl]-4-pyri-
done (14). To a solution of 13 (5 mg, 0.016 mmol) in
MeOH (0.5 ml) was added 10% Pd/C (1 mg). The mix-
ture was stirred under a hydrogen atmosphere at room
temperature for 3 h, then filtered through Celite and
concentrated in vacuo. The residue was purified by pre-
parative TLC [CHCl3/MeOH (9:1)] to give 14 (2.5 mg,
51%). 1H NMR (400 MHz, CDCl3) d 1.90 (3H, s),
2.80–2.94 (4H, m), 4.99 (2H, s), 6.42 (1H, d,
J = 7.6 Hz), 6.97 (2H, d, J = 7.3 Hz), 7.12 (1H, dd,
J = 7.8, 4.7 Hz), 7.30–7.43 (4H, m), 7.50 (1H, d,
J = 7.8 Hz), 8.36–8.43 (2H, m); MS (FAB+) m/z 305
(M+H)+.
6.1.44. 1-Benzyl-2-methyl-4-pyridon-3-yl trifluorome-
thanesulfonate (10). To a solution of 9 (1.0 g, 4.65 mmol)
in CH2Cl2 (20 ml) at 0 °C were added 2,6-lutidine
(0.813 ml, 6.98 mmol) and trifluoromethanesulfonic
anhydride (0.616 ml, 5.11 mmol). The mixture was stir-
red at 0 °C for 2 h, then diluted with CHCl3 and washed
with 5% NaCl aq. The extract was dried over Na2SO4,
filtered, and concentrated in vacuo. The residue was
purified by column chromatography on silica gel
[CHCl3/MeOH (30:1)] to afford 10 (1.20 g, 74%). 1H
NMR (400 MHz, CDCl3) d 2.33 (3H, s), 5.10 (2H, s),
6.56 (1H, d, J = 7.8 Hz), 7.06 (2H, d, J = 6.8 Hz),
7.34–7.48 (4H, m); MS (FAB+) m/z 348 (M+H)+.
6.1.49. 4-Cyclohexylmethoxy-3-(2,6-dichlorobenzyl)-2-
methylpyridine (15). To a solution of 6a (150 mg,
0.559 mmol) in DMF (3 ml) were added sodium hydride
(29 mg 0.727 mmol as a 60% dispersion in mineral oil)
and cyclohexylmethyl bromide (128 mg, 0.727 mmol).
The mixture was stirred at 50 °C for 6 h, then diluted with
ethyl acetate and washed with 5% NaCl aq. The extract
was dried over Na2SO4, filtered, and concentrated in vac-
uo. The residue was purified by column chromatography
on silica gel [CHCl3/MeOH (30:1)] to afford 15 (146 mg,
72%). 1H NMR (400 MHz, CDCl3) d 0.79–0.93 (2H, m),
1.06–1.30 (4H, m), 1.51–1.77 (5H, m), 2.48 (3H, s), 3.65
(2H, d, J = 6.1 Hz), 6.58 (1H, d, J = 5.6 Hz), 7.06 (1H, t,
J = 8.0 Hz), 7.25 (2H, d, J = 8.0 Hz), 8.23 (1H, d,
J = 5.6 Hz); MS (FAB+) m/z 364 (M+H)+.
6.1.45. 1-Benzyl-2-methyl-3-phenyl-4-pyridone (11). To a
solution of 10 (50 mg, 0.144 mmol) in 1,4-dioxane (1 ml)
were added potassium carbonate (39.8 mg, 0.288 mmol),
tetrakis(triphenylphosphine)palladium
10 mol%), and phenylboronic
(16.6 mg,
(26.3 mg,
acid
0.216 mmol). The mixture was stirred overnight at
60 °C, then concentrated in vacuo. The resulting residue
was purified by preparative TLC [CHCl3/MeOH (9:1)]
1
to give 11 (8 mg, 20%). H NMR (400 MHz, CDCl3) d
2.09 (3H, s), 5.09 (2H, s), 6.51 (1H, d, J = 7.6 Hz),
7.10 (2H, d, J = 7.3 Hz), 7.18–7.46 (9H, m); HRMS
(FAB+) m/z: calcd for C19H18NO (M+H)+: 276.1388,
found: 276.1387.

H. Kitagawa et al. / Bioorg. Med. Chem. 15 (2007) 1106–1116
1115
6.1.50. 1-Benzyloxycarbonyl-6-butyl-3-(2,6-dichloroben-
zyl)-5,6-dihydro-2-methyl-4-pyridone (16a). To a solution
of 15 (100 mg, 0.279 mmol) in THF (2 ml) at 0 °C were
added butylmagnesium bromide (0.335 mmol as a 0.9 M
THF solution) and benzylchloroformate (0.0397 ml,
0.279 mmol). The solution was stirred for 3 h at room
temperature, then poured into 3 N HCl (15 ml) and stir-
red at room temperature for 1 h. The mixture was
extracted with ethyl acetate, and the extract was washed
with 5% NaHCO3 aq, dried over Na2SO4, filtered, and
concentrated in vacuo. The residue was purified by col-
umn chromatography on silica gel [hexane/AcOEt (5:1)]
to afford 16a (72 mg, 56%). 1H NMR (400 MHz,
CDCl3) d 0.85 (3H, t, J = 6.8 Hz), 1.10–1.32 (4H, m),
1.39–1.52 (1H, m), 1.73–1.89 (1H, m), 2.12 (3H, s),
2.36 (1H, dd, J = 17.3, 1.4 Hz), 2.81 (1H, dd, J = 17.3,
6.1 Hz), 3.93 (1H, d, J = 15.9 Hz), 4.03 (1H, d,
J = 15.9 Hz), 4.77–4.86 (1H, m), 5.20 (2H, s), 7.07
(1H, t, J = 8.0 Hz), 7.26 (2H, d, J = 8.0 Hz), 7.30–7.41
(5H, m); MS (FAB+) m/z 460 (M+H)+.
7.05 (1H, t, J = 8.0 Hz), 7.25 (2H, d, J = 8.0 Hz), 7.38–
7.47 (5H, m); MS (FAB+) m/z 498 (M+H)+.
6.1.54. 6-Butyl-3-(2,6-dichlorobenzyl)-2-methyl-4-pyri-
done (18a). A solution of 17a (19 mg, 0.041 mmol) in
methanol (3 ml) was refluxed for 15 h. The mixture
was concentrated in vacuo and resulting residue was
purified by column chromatography on silica gel
[CHCl3/MeOH (20:1)] to give 18a (10 mg, 75%). 1H
NMR (400 MHz, CDCl3) d 0.85 (3H, t, J = 7.3 Hz),
1.26 (2H, tq, J = 7.3 Hz), 1.55 (2H, m), 2.08 (3H, s),
2.44 (2H, t, J = 7.6 Hz), 4.21 (2H, s), 6.06 (1H, s), 7.00
(1H, t, J = 8.0 Hz), 7.18 (2H, d, J = 8.0 Hz), 11.26
(1H, br); HRMS (FAB+) m/z: calcd for C17H20Cl2NO
(M+H)+: 324.0922, found: 324.0927.
6.1.55.
6-Cyclohexylmethyl-3-(2,6-dichlorobenzyl)-2-
methyl-4-pyridone (18b). The title compound was pre-
pared from 17b by means of a similar procedure to that
described for 18b (46% yield). 1H NMR (400 MHz,
CDCl3) d 0.85–0.96 (2H, m), 1.07–1.28 (3H, m), 1.48–
1.74 (6H, m), 2.03 (3H, s), 2.29 (2H, d, J = 7.3 Hz), 4.25
(2H, s), 6.09 (1H, s), 7.04 (1H, t, J = 8.0 Hz), 7.23 (2H,
d, J = 8.0 Hz), 8.70 (1H, br); HRMS (FAB+) m/z: calcd
for C20H24Cl2NO (M+H)+: 364.1235, found: 364.1227.
6.1.51. 1-Benzyloxycarbonyl-6-cyclohexylmethyl-3-(2,6-
dichlorobenzyl)-5,6-dihydro-2-methyl-4-pyridone (16b).
The title compound was prepared from 15 by means of
a similar procedure to that described for 16b (68% yield).
1H NMR (400 MHz, CDCl3) d 0.76–0.94 (2H, m), 1.05–
1.23 (4H, m), 1.24–1.37 (1H, m), 1.49–1.84 (6H, m), 2.11
(3H, s), 2.32 (1H, dd, J = 17.3, 1.4 Hz), 2.81 (1H, dd,
J = 17.3, 6.1 Hz), 3.92 (1H, d, J = 15.8 Hz), 4.03 (1H, d,
J = 15.8 Hz), 4.76–4.84 (1H, m), 5.17–5.23 (2H, m), 7.06
(1H, t, J = 8.0 Hz), 7.26 (2H, d, J = 8.0 Hz), 7.30–7.41
(5H, m); MS (FAB+)m/z 500 (M+H)+.
Acknowledgments
The authors thank Ms Sigeko Miki, Mrs Takako Miy-
ara, Mrs Kazue Sasaki, and Mr Tetsuya Matsusima of
Meiji Seika Kaisha, Ltd (http://www.meiji.co.jp/
home.html) for their help with mass spectrometric
analysis.
6.1.52. 1-Benzyloxycarbonyl-6-butyl-3-(2,6-dichloroben-
zyl)-2-methyl-4-pyridone (17a). To a solution of 16a
(56 mg, 0.122 mmol) in THF (1 ml) at ꢀ78 °C was add-
ed 1 M lithium hexamethyldisilazide in THF
(0.134 mmol). The mixture was stirred at 0 °C for
30 min, then cooled to ꢀ78 °C. To the resulting mix-
ture was added phenylselenyl bromide (37 mg,
0.158 mmol), and the whole was stirred at ꢀ78 °C
for 1 h, then poured into 1 N HCl. The mixture was
extracted with ethyl acetate and washed with brine
and 5% NaHCO3 aq. The organic phase was dried
over Na2SO4, filtered, concentrated in vacuo, and dis-
solved in CH2Cl2 (1 ml). To this solution was added
m-chloroperbenzoic acid (17.8 mg, 0.129 mmol). The
mixture was stirred at room temperature for 1 h and
purified by preparative TLC [CHCl3/MeOH (9:1)] to
give 17a (22 mg, 39%). 1H NMR (400 MHz, CDCl3)
d 0.84 (3H, t, J = 7.3 Hz), 1.26 (2H, tq, J = 7.3 Hz),
1.47 (2H, m), 1.95 (3H, s), 2.29 (2H, t, J = 7.5 Hz),
4.26 (2H, s), 5.36 (2H, s), 6.13 (1H, s), 7.06 (1H, t,
J = 8.0 Hz), 7.22–7.27 (2H, m), 7.42 (5H, br); MS
(FAB+) m/z 458 (M+H)+.
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