Structure-activity studies on 1,3-dioxane-2-carboxylic acid derivatives, a novel class of subtype-selective peroxisome proliferator-activated receptor α (PPARα) agonists

Article abstract of DOI:10.1016/j.bmc.2007.10.007

A series of 1,3-dioxane carboxylic acid derivatives was synthesized and evaluated for human PPAR transactivation activity. Structure-activity relationships on the phenyloxazole moiety of the lead compound 3 revealed that the introduction of small hydropho

Full text of DOI:10.1016/j.bmc.2007.10.007

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 981–994
Structure–activity studies on 1,3-dioxane-2-carboxylic acid
derivatives, a novel class of subtype-selective peroxisome
proliferator-activated receptor a (PPARa) agonists
Tetsuo Asaki,* Tomiyoshi Aoki, Taisuke Hamamoto, Yukiteru Sugiyama, Shinji Ohmachi,
Kenji Kuwabara, Kohji Murakami and Makoto Todo
Discovery Research Laboratories, Nippon Shinyaku Co., Ltd, 14 Nishinosho-Monguchi-Cho, Kisshoin, Minami-ku,
Kyoto 601-8550, Japan
Received 8 August 2007; revised 3 October 2007; accepted 4 October 2007
Available online 9 October 2007
Abstract—A series of 1,3-dioxane carboxylic acid derivatives was synthesized and evaluated for human PPAR transactivation activ-
ity. Structure–activity relationships on the phenyloxazole moiety of the lead compound 3 revealed that the introduction of small
hydrophobic substituents at the 4-position of the terminal phenyl ring increased the PPARa agonist activity, and that the oxazole
heterocycle was essential to the maintenance of both potency and PPARa subtype-selectivity. This investigation led to the identi-
fication of 14d (NS-220) and 14i as highly potent and selective human PPARa agonists. In KK-Ay type 2 diabetic mice, these com-
pounds significantly lowered plasma triglyceride and very-low-density plus low-density lipoprotein cholesterol levels while
simultaneously raising HDL cholesterol levels. Our results suggest that highly potent and subtype-selective PPARa agonists will
be promising drugs for the treatment of metabolic disorders in type 2 diabetes.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
tissues, such as liver, heart, kidney, and skeletal muscle,
and it plays a central role in the oxidation of fatty acids
and in lipoprotein metabolism.6 Although fibrates con-
stitute an important class of PPARa ligands, a recent
molecular-pharmacological study reveals that they have
relatively weak affinity for PPARa and poor subtype-
selectivity,4b so that fibrates must be used at high doses
to achieve useful clinical effects in humans. More-potent
and subtype-selective PPARa agonists are expected to
be promising drugs for the treatment of metabolic syn-
drome and atherosclerosis.
Hypolipidemic fibrate drugs (fibrates), such as bezafi-
brate 1 and fenofibrate 2 (Fig. 1), lower serum triglycer-
ide levels and moderately raise high-density lipoprotein
(HDL) cholesterol levels in patients with hyperlipidemia
or type 2 diabetes1 and prevent coronary heart disease
and stroke.2 Fibrates were originally developed without
knowledge of their molecular target, and in 1990 they
were identified as agonists of peroxisome proliferator-
activated receptor a (PPARa).3 Peroxisome prolifera-
tor-activated receptors (PPARs) are members of the thy-
roid/steroid hormone nuclear receptor superfamily and
ligand-activated transcription factors that form func-
tionally active heterodimers with another nuclear recep-
tor, the 9-cis-retinoic acid receptor (RXR).4 To date,
three distinct PPAR subtypes, a, c, and d, have been
identified in various species, including humans.4,5
PPARa is expressed at high levels in metabolically active
Although some groups have already disclosed potent
and subtype-selective PPARa agonists,7–10 these com-
pounds are not on the market. In another paper,11 we
describe the discovery of 2-methyl-c-5-{4-[5-methyl-2-
phenyl-1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic
acid 3 (Fig. 1) as a potent and subtype-selective human
PPARa agonist. This representative compound exhibits
superior hypolipidemic activity in type 2 diabetic KK-
Ay mice. (KK-Ay mice display severe hyperglycemia,
hyperinsulinemia, hypertriglyceridemia, and obesity,
the typical symptoms of type 2 diabetes, and are widely
used as animal models of type 2 diabetes.12) Structure–
activity studies on the linker and the dioxane moiety
Keywords: Selective PPARa agonist; 1,3-Dioxane carboxylic acid;
Metabolic disorder.
*
Corresponding author. Tel.: +81 75 321 9168; fax: +81 75 321
9039; e-mail: t.asaki@po.nippon-shinyaku.co.jp
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.10.007

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T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
O
O
CO2H
Cl
O
O
O
N
H
O
Cl
1: bezafibrate
2: fenofibrate
O
N
O
CO2H
O
3
Figure 1. Chemical structures of fibrates 1, 2, and 3.
of 1,3-dioxane-2-carboxylic acid derivatives reveal that
both the biological activity and the PPARa subtype-
selectivity are sensitive to linker length and the geomet-
rical configuration of the 1,3-dioxane ring.11 These
observations encouraged us to further optimize the hu-
man PPARa agonist activity by investigating various
1,3-dioxane-2-carboxylic acid derivatives. In the present
report, we highlight the effects of structural variations
associated with the phenyloxazole moiety of 3. The
objectives of this study were to explore the role of the
phenyl ring and the oxazole heterocycle in the expres-
sion of PPARa agonism and to develop a more potent
and subtype-selective PPARa agonist. Compounds of
this series which were identified by their PPARa agonist
activity were evaluated for their in vivo hypolipidemic
and hypoglycemic effects to establish their potential ben-
efit in the treatment of hyperlipidemia and metabolic
disorders in type 2 diabetes.
2. Chemistry
Compounds 14a–j were prepared according to Schemes
1 and 2. For this purpose, we designed a convergent syn-
thesis which was more efficient than the linear one de-
scribed previously.11 The 1,3-dioxane derivative 8 was
chosen as a common intermediate in this method, and
it was synthesized by the following simple method
(Scheme 1). Alkylation of diethyl malonate with 1-bro-
mo-4-chlorobutane 4 provided the diester 5. Reduction
b, c
a
Cl
I
d
e
Cl
CO2Et
CO2Et
Cl
O
O
Br
CO2Me
CO2Me
O
O
4
5
6
8
Cl
O
OH
O
7
Scheme 1. Reagents: (a) CH2(CO2Et)2, NaH, 1,3-dimethyl-2-imidazolidinone; (b) LiAlH4, Et2O; (c) MeCOCO2Me, BF3ÆOEt2, CH3CN; (d) NaI,
acetone; (e) LiAlH4, THF.
O
O
O
O
O
a or b
c
d
X
N
N
N
O
H
H
OH
O
H
CO2Me
R1
R3
R1
R3
R1
R3
R1
R3
O
R2
R2
R2
R2
X = Cl, OH 9a-j
10a-j
11a-j
12a-j
O
R1
e
N
O
R2
R3
CO2R
O
13a-j R = Me
R = H
f
14a-j
Scheme 2. Reagents: (a) 1-amino-2-propanol, Et3N, toluene; (b) 1-amino-2-propanol, EDC hydrochloride, HOBt, Et3N, DMF; (c) PCC, CH2Cl2; (d)
i—NaH, DMF; ii—8; (e) POCl3, toluene; (f) aq NaOH, MeOH.

T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
983
of 5 with lithium aluminum hydride followed by dioxane
ring formation brought about by methyl pyruvate gave
the 1,3-dioxane derivative 6. Formation of the dioxane
ring from the diol intermediate on refluxing with boron
trifluoride in CH3CN yielded a mixture of geometrical
isomers. This mixture was resolved by chromatography
on a column of silica gel to give the pure cis-isomer 6,
which has a chemical-shift pattern identical to that of
other cis-derivatives.11 The cis-configuration of 6 was
also confirmed by an NOE experiment on the corre-
sponding alcohol 7, which has protons that allow deter-
mination of the configuration of the dioxane ring
moiety. Compound 7 was synthesized by LiAlH4 reduc-
tion of 6 free of trans-isomer. a-Protons at the 4- and 6-
positions were clearly distinguished from the b-protons
by the observed NOE correlation between the 5-a- and
4-a(6-a)-protons. The strong NOE from the 4,6-b-pro-
tons assigned above to the 2-hydroxymethyl protons
shows conclusively that the configuration is cis
(Fig. 2). Sequential iodination of 6 with sodium iodide
in acetone was accomplished quantitatively to give the
key intermediate 8. Condensation of the various acid
chlorides or carboxylic acids 9a–j with 1-amino-2-
propanol and subsequent oxidation with pyridinium
chlorochromate gave the benzamides 11a–j. Coupling13
of 11a–j with 8 by using sodium hydride as a base gave
12a–j, which were converted to the oxazoles 13a–j by
treatment with phosphorus oxychloride. Hydrolysis of
13a–j with aqueous sodium hydroxide in methanol then
yielded the target products 14a–j.
The synthesis of the 5-ethyloxazole derivative 16 is
shown in Scheme 3. This compound was prepared from
9d and 1-amino-2-butanol in a manner similar to that
shown in Scheme 2.
The synthesis of the 5-trifluoromethyloxazole derivative
22 is shown in Scheme 4. The alcohol 17 was readily pre-
pared from N-(4-methylbenzoyl)proline by a known
method.14 Tosylation of 17 followed by cyanation gave
the corresponding nitrile, which was converted to the
methyl ester 18 by treatment with methanol–hydrogen
chloride and then with water. Reduction of 18 with
LiAlH4 and subsequent bromination with carbon tetra-
bromide/triphenylphosphine gave the bromide 19. Con-
version of 19 into the 1,3-dioxane derivative 21 was
accomplished in a manner similar to that shown in
Scheme 1, after which alkaline hydrolysis of 21 gave
the desired product 22.
The preparation of the thiazole derivative 24 and the
imidazole derivative 26 is shown in Scheme 5. The thia-
zole skeleton of 24 was constructed by a previously re-
ported procedure.13 Compound 12d mentioned above
was cyclized by treatment with Davy Reagent Methyl15
(2,4-bis(methylthio)-1,3-dithia-2,4-diphosphetane-2,4-
disulfide) to provide the thiazole 23, which was hydro-
lyzed in the usual manner to give the desired thiazole
24. The construction of the imidazole skeleton was
accomplished by cyclization of 12d with methylamine
in a mixture of acetic acid and xylene at reflux to give
the imidazole 25, which was then converted to the target
product 26 by alkaline hydrolysis.
H
H
OH
Hβ
Hβ
6
2
Hα
CH3
O
Cl(CH2)4
O
4
5
Hα
H
7
Figure 2. Interpretation of NOE experiment on 7, which has a 1,3-
dioxane ring system.
O
O
O
N
b, c, d, e
a
N
Cl
H
OH
O
CO2H
O
9d
15
16
Scheme 3. Reagents: (a) 1-amino-2-butanol, Et3N, THF; (b) PCC, CH2Cl2; (c) i—NaH, DMF; ii—8; (d) POCl3, toluene; (e) aq NaOH, MeOH.
CF3
CF3
CF3
O
N
O
O
N
a, b, c
d, e
f, g
OH
CO2Me
N
Br
17
18
19
CF3
CF3
O
N
O
N
h
OH
OH
O
CO2R
21 R = Me
22 R = H
O
i
20
Scheme 4. Reagents: (a) TsCl, Et3N, DMAP, THF; (b) NaCN, DMSO; (c) i—HCl, MeOH; ii—H2O; (d) LiAlH4, THF; (e) PPh3, CBr4, CH2Cl2; (f)
CH2(CO2Et)2, NaH, THF, DMF; (g) LiAlH4, THF; (h) MeCOCO2Me, BF3ÆOEt2, MeCN; (i) aq NaOH, MeOH.

984
T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
S
N
O
a
O
CO2R
O
O
23 R = Me
24 R = H
c
N
O
H
CO2Me
O
12d
N
b
N
O
CO2R
O
R = Me
25
c
26 R = H
Scheme 5. Reagents: (a) Davy Reagent Methyl, THF; (b) 2 M MeNH2 in THF, AcOH, xylene; (c) aq NaOH, MeOH.
3. In vitro structure–activity relationship (SAR) studies
14e (EC50 = 0.01 lM) were 30-fold more effective than
3. Strikingly, the 4-methylated compound 14d activated
human PPARa with more than 1000-fold selectivity
over the human c and d subtypes, while the 4-ethyl ana-
logue 14e exhibited less subtype-selectivity than 14d
(300-fold selectivity over human PPARc). These obser-
vations suggest that the hydrophobic character and ste-
ric bulk of the substituent at the 4-position have
important effects on PPARa agonist activity and sub-
type-selectivity. Further modification was focused on
methyl substitution at other positions on the phenyl
ring. Though the activity of the 2-methyl analogue 14h
(EC50 = 0.3 lM) was not markedly different from that
of 3, the 3-methyl analogue 14g (EC50 = 0.03 lM)
showed 10-fold-enhanced potency compared to 3. Based
on these investigations, we synthesized the two dimethyl-
The newly synthesized compounds were screened for
activity at each of the human PPAR subtypes by using
an established cell-based transactivation assay in CV-1
cells.16 We investigated the effect of substitution at the
phenyl ring of 3 on the agonist activity at the human
PPARa subtype. PPARa agonist activity was remark-
ably sensitive to modification of the terminal phenyl ring
(Table 1). First, we tested the effect of substitution at the
4-position in compounds 14a–e. The introduction of a
chloro, trifluoromethyl or methoxy substituent at this
position (14a–c) resulted in a 10-fold improvement
(EC50 = 0.03 lM) in PPARa agonist activity compared
to 3 (EC50 = 0.3 lM). Unexpectedly, the 4-methyl ana-
logue 14d (EC50 = 0.01 lM) and the 4-ethyl analogue
Table 1. Effect of phenyl-ring substituents on the agonist activity of human PPAR subtypes
O
R1
N
O
R2
R2
R3
CO2H
O
Compound
R1
R3
Human PPARs (EC50, lM)a,b
a
c
d
3
H
Cl
H
H
0.3
100
(0%)c
(9%)
14a
14b
14c
14d
14e
14f
14g
14h
14i
14j
H
H
0.03
0.03
0.03
0.01d
0.01
0.01
0.03
0.3
(21%)
(41%)
(18%)
(31%)d
3
CF3
OMe
Me
Et
H
H
(34%)
(20%)
(7%)d
(0%)
H
H
H
H
H
H
Me
H
F
H
(45%)
(34%)
(23%)
(42%)
(35%)
(25%)
(16%)
(5%)
Me
H
H
H
Me
H
Me
Me
Me
H
0.003
0.03
(0%)
(16%)
Me
Fenofibric acid
Bezafibrate
30
30
>100
100
>100
30
a The agonist activity of each PPAR subtype was measured by the corresponding transactivation assay in transiently transfected CV-1 cells (n = 2).
b EC50 is the concentration of test compounds that gave 50% of the maximum transactivation activity of each positive control.
c Less than 50% of maximum activity at 10 lM. The percentage of maximum activation observed at 10 lM is shown in parentheses.
d The EC50 values of compound 14d for PPARa, PPARc, and PPARd were reported as 0.019 lM, 9.6 lM as a partial agonist for PPARc, and
>100 lM, respectively, in a previous article16 from different assay data.

T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
985
Table 2. Effects of substituents at the 5-position of the oxazole ring
and replacement of the oxazole ring on the agonist activity of human
PPAR subtypes
Table 3. In vitro activity of 3, 14d, 14f, and 14i at mouse PPAR
subtypes a and c
Compound
Mouse PPARs (EC50, lM)a,b
a
c
R4
X
3
1
(11%)c
5
14d
14f
14i
0.03
0.1
(45%)
10
(42%)
N
O
CO2H
0.03
O
See corresponding footnotes to Table 1.
Compound
X
R4
Human PPARs (EC50,
lM)a,b
Table 4. Hypolipidemic and hypoglycemic effects of 3, 14d, 14f, and
14i in diabetic KK-Ay mice
a
c
d
14d
16
22
24
26
O
Me
Et
0.01d
0.03
0.3
(31%)c,d
10
(7%)d
(3%)
(24%)
(0%)
(0%)
Compound Dose (mg/kg)
% Change
O
O
CF3
Me
Me
3
TG PG (V)LDL-C HDL-C
S
NMe
0.3
(6%)
(25%)
(0%)
3
1
1
1
1
ꢀ46 ꢀ12 ꢀ29
ꢀ71 ꢀ21 ꢀ50
ꢀ53 ꢀ12 ꢀ63
ꢀ89 ꢀ32 ꢀ92
36
34
21
21
14d
14f
14i
See corresponding footnotes to Table 1.
Fenofibrate 300
ꢀ40 ꢀ25 ꢀ31
17
ated compounds 14i and 14j. The 3,4-dimethyl deriva-
tive 14i (EC50 = 0.003 lM) exhibited the most potent
human PPARa agonist activity of all the compounds
listed in Table 3, and it also exhibited high subtype-
selectivity.
Compounds were orally administered to male KK-Ay mice (aged 10
weeks, n = 5) once a day for 4 days at the indicated dose. Each value
represents the percentage change of the mean value from the control
group; TG = plasma triglyceride; PG = plasma glucose; (V)LDL-
C = very-low-density plus low-density lipoprotein cholesterol; HDL-
C = high-density lipoprotein cholesterol.
Having optimized the structural features for the distal
phenyl ring, we then turned our attention to the oxazole
moiety. We investigated the effect of both the substitu-
ent at the 5-position of the oxazole ring and structural
variations in the oxazole ring itself (Table 2). We synthe-
sized the 14d-related 5-ethyl and 5-trifluoromethyl deriv-
atives 16 and 22. Replacement of the methyl group at
the 5-position reduced both the potency and the sub-
type-selectivity compared to 14d. This study revealed
that the methyl substituent at the 5-position of the oxa-
zole ring contributes to a potent PPARa agonist activity
and a high PPARa selectivity. We also explored replace-
ment of the oxazole ring in 14d by other heterocycles.
The thiazole derivative 24 (EC50 = 0.3 lM) was 30-fold
less potent than the prototype 14d. The basic imidazole
derivative 26 showed no activity at any of the three
PPAR subtypes. These structure–activity correlations
suggest that the role of the oxazole heterocycle is more
than that of a simple scaffold and that in fact the oxazole
heteroatoms play a role in the binding interaction with
PPARa.
compound was orally administered at 1 mg/kg to 10-
week-old male KK-Ay mice once a day for 4 days. All
compounds markedly lowered plasma triglyceride levels
(TG) and very-low-density plus low-density lipoprotein
cholesterol levels ((V)LDL-C), while they raised HDL
cholesterol levels (HDL-C). These compounds also de-
creased glucose levels. For purposes of comparison, in
this study fenofibrate 2 was orally administered at
300 mg/kg. Although 2 showed similar effects at
300 mg/kg, it was significantly less potent than our com-
pounds. The hypolipidemic effects of our compounds
were correlated with their PPARa agonist activities.
This result provides clear evidence that PPARa agonists
have superior efficacy in the treatment of hyperlipidemia
and hyperglycemia. The detailed pharmacological prop-
erties of 14d have been investigated and published
elsewhere.16
5. Conclusion
4. Animal experiments
To identify more-potent PPARa agonists, we investi-
gated the structure–activity relationships (SAR) for the
phenyloxazole moiety of 1,3-dioxane derivative 3. We
found that key roles are played by the methyl group at
the 4-position of the terminal phenyl ring, and by the
oxazole heterocycle itself, in determining the potency
and subtype-selectivity of the compound as a PPARa
agonist. Our investigation led to the identification of
14d (NS-220) and 14i as highly potent and selective hu-
man PPARa agonists. In addition, as we had predicted,
these compounds exhibited excellent hypolipidemic
activity in diabetic KK-Ay mice. Our results suggest that
the development of potent and selective PPARa agonists
To assess the potential utility of the optimized com-
pounds as PPARa agonists, we selected 14d, 14f, and
14i for further testing because of their superior PPARa
agonist activity and subtype-selectivity. These com-
pounds activated mouse PPARa 3- to 10-fold less po-
tently than human PPARa (Table 3). Nevertheless,
they had sufficient in vitro activity with high selectivity
for mouse PPARa over mouse PPARc to allow
in vivo evaluation of their potential benefit. We then
examined the pharmacological effects of 3, 14d, 14f,
and 14i in type 2 diabetic KK-Ay mice12 (Table 4). Each

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T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
will be useful in the treatment of hyperlipidemia and
metabolic disorders in type 2 diabetes.
A
mixture of 6-chloro-2-hydroxymethyl-1-hexanol
(3.92 g, 24 mmol), methyl pyruvate (9.61 g, 94 mmol),
and boron trifluoride diethyl ether complex (13.36 g,
94 mmol) in CH3CN (60 mL) was heated at 60 ꢂC for
1.5 h. After cooling to room temperature, the reaction
mixture was poured into saturated aqueous NaHCO3
and extracted with EtOAc. The organic layer was dried
over MgSO4. After evaporation of the solvent, the resi-
due was purified by chromatography on silica gel with
hexane–EtOAc (7:1) as the eluent to give cis-isomer 6
(1.72 g, 29%) as a pale yellow oil and a mixture of 6
and its trans-isomer (2.70 g, cis:trans = ca. 1:1 by 1H
NMR analysis) as a pale yellow oil. Compound 6:
TLC Rf = 0.40 (hexane–EtOAc, 1:4) (trans-isomer:
Rf = 0.35). FAB-MS m/z 251 [MH]+. 1H NMR (CDCl3)
d: 0.96–1.13 (2H, m), 1.34–1.60 (2H, m), 1.51 (3H, s),
1.65–1.85 (2H, m), 1.90–2.15 (1H, m), 3.40 (2H, t,
J = 11.4 Hz), 3.52 (2H, t, J = 6.4 Hz), 3.83 (3H, s),
3.96 (2H, dd, J = 11.4, 4.8 Hz). Anal. Calcd for
C11H19ClO4Æ0.1H2O: C, 52.32; H, 7.66. Found: C,
52.20; H, 7.61.
6. Experimental
Reagents and solvents were used as obtained from the
supplier without further purification. Melting points
were determined on a Shibata melting point apparatus
and are uncorrected. Column chromatography was car-
ried out on a silica gel column (Wako Wakogelꢁ C-200
or Fuji Silysia PSQ-100B). TLC was carried out on
Merck TLC aluminum sheets silica gel 60 F254, and
spots were visualized under 254-nm UV light or spray-
ing with phosphomolybdic acid. Yields were not opti-
mized. 1H NMR spectra were recorded on a Varian
Gemini 2000 (200 MHz) or a Varian UnityPlus 300
(300 MHz) spectrometer. Chemical shifts (d) are given
in ppm relative to the internal standard, tetramethylsil-
ane, and coupling constants are given in Hertz (Hz).
Mass spectra were recorded on a JEOL JMS-700 mass
spectrometer and IR spectra were recorded on a Shima-
dzu FT IR-8100 spectrometer.
6.1.3. c-5-(4-Chlorobutyl)-r-2-hydroxymethyl-2-methyl-
1,3-dioxane (7). To an ice-cooled suspension of LiAlH4
(91 mg, 2.4 mmol) in THF (5 mL) was added dropwise
a solution of 6 (500 mg, 2.0 mmol) in THF (2 mL) over
5 min. The mixture was stirred with ice-cooling for 1 h.
After the reaction had been quenched with water
(1 mL), the insoluble precipitate was filtered off. The fil-
trate was diluted with EtOAc, washed with water, and
dried over MgSO4. Removal of the solvent by evapora-
tion gave 7 (400 mg, 90%) as a colorless oil. FAB-MS m/z
6.1. Preparation of 8
6.1.1. Diethyl 2-(4-chlorobutyl)malonate (5). To a pre-
cooled (7 ꢂC) suspension of NaH (60% dispersion in
oil; 140 g, 3.5 mol) in 1,3-dimethyl-2-imidazolidinone
(600 mL) was added dropwise diethyl malonate
(1121 g, 7.0 mol) below 20 ꢂC. After having been stirred
at room temperature for 1 h, the mixture was cooled on
an ice-bath and a solution of 4 (600 g, 0.87 mmol) was
added dropwise over 1 h. The resulting mixture was
stirred below 20 ꢂC for 3 h and then recooled on the
ice-bath. The reaction was quenched with a mixture of
concd HCl (53.2 g) and water (1.5 L). The organic layer
was washed with water (1 L) and purified by distillation
to afford 5 (477.3 g, 54%) as a colorless oil. Bp 120–
132 ꢂC (4 mm Hg). FAB-MS m/z 251 [MH]+. 1H
NMR (CDCl3) d: 1.27 (6H, t, J = 7.2 Hz), 1.41–1.59
(2H, m), 1.74–1.98 (4H, m), 3.33 (1H, t, J = 7.5 Hz),
3.54 (2H, t, J = 6.6 Hz), 4.20 (4H, q, J = 7.2 Hz). Anal.
Calcd for C11H19ClO4Æ0.2H2O: C, 51.95; H, 7.69.
Found: C, 51.85; H, 7.38.
223 [MH]+. H NMR (300 MHz) (C5D5N) d: 1.13–1.32
1
(4H, m), 1.58 (2H, m), 1.66 (1H, m, H-5a), 1.70 (3H, s),
3.47 (2H, t, J = 6.6 Hz), 3.68 (2H, dd, J = 11.7, 7.5 Hz,
H-4,6b), 3.96 (2H, dd, J = 11.7, 4.5 Hz, H-4,6a), 4.06
(2H, d, J = 3.3 Hz, 2b-CH2OH), 6.29 (1H, br). Anal.
Calcd for C10H19ClO3: C, 53.93; H, 8.60. Found: C,
53.57; H, 8.75.
6.1.4. Methyl c-5-(4-iodobutyl)-2-methyl-1,3-dioxane-r-2-
carboxylate (8). A mixture of 6 (1.65 g, 6.6 mmol) and
sodium iodide (2.97 g, 19.8 mmol) in acetone (12 mL)
was heated at reflux for 13 h. The mixture was then di-
luted with water and extracted with EtOAc. The organic
layer was washed successively with water and brine, and
dried over MgSO4. Removal of the solvent by evapora-
tion gave 8 (2.00 g, 89%) as a pale yellow oil. The prod-
uct was used for the next step without further
purification. FAB-MS m/z 343 [MH]+. 1H NMR
(CDCl3) d: 0.97–1.16 (2H, m), 1.30–1.45 (2H, m), 1.51
(3H, s), 1.69–1.89 (2H, m), 1.91–2.14 (1H, m), 3.16
(2H, t, J = 6.9 Hz), 3.40 (2H, t, J = 12.0 Hz), 3.83 (3H,
s), 3.96 (2H, dd, J = 12.0, 4.8 Hz). Anal. Calcd for
C11H19IO4: C, 38.61; H, 5.60. Found: C, 38.94; H, 5.47.
6.1.2. Methyl c-5-(4-chlorobutyl)-2-methyl-1,3-dioxane-r-
2-carboxylate (6). To an ice-cooled suspension of
LiAlH4 (3.84 g, 101 mmol) in Et2O (100 mL) was added
dropwise a solution of 5 (12.69 g, 51 mmol) in Et2O
(25 mL) over a period of 1 h at 4–15 ꢂC. The mixture
was stirred with ice-cooling for 2 h and the reaction
was quenched with water (3.8 mL), aqueous 15% NaOH
(3.8 mL), and water (11.4 mL), in that order. The mix-
ture was stirred at room temperature for 1 h. The insol-
uble precipitate was filtered off and the filtrate was
evaporated in vacuo. The residue was purified by chro-
matography on silica gel with hexane–EtOAc (1:3) as
the eluent to give 6-chloro-2-hydroxymethyl-1-hexanol
6.2. Preparation of 10a–j
6.2.1. General procedure for the synthesis of 10d, 10g,
10h: N-(2-hydroxypropyl)-4-methylbenzamide (10d). A
solution of p-toluoyl chloride (20.01 g, 0.129 mol) in tol-
uene (10 mL) was added dropwise over 10 min to an ice-
cooled solution of 1-amino-2-propanol (10.58 g,
1
(4.07 g, 48%) as a colorless oil. H NMR (CDCl3) d:
1.23–1.40 (2H, m), 1.40–1.58 (2H, m), 1.64–1.90 (3H,
m), 2.34 (2H, br), 3.55 (2H, t, J = 6.4 Hz), 3.68 (2H,
dd, J = 10.6, 6.8 Hz), 3.84 (2H, dd, J = 10.6, 3.6 Hz).

T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
987
0.141 mol) and triethylamine (14.49 g, 0.143 mol) in tol-
uene (70 mL). The reaction mixture was stirred at room
temperature for 2.5 h and diluted with water. The result-
ing precipitate was collected by filtration, washed suc-
cessively with water and toluene, and dried under
reduced pressure, to give 10d (17.64 g, 71%) as colorless
and dried in vacuo to give 10f (6.06 g, 88%) as colorless
1
crystals. Mp 140–141 ꢂC. FAB-MS m/z 212 [MH]+. H
NMR (CDCl3) d: 1.25 (3H, d, J = 6.4 Hz), 2.31 (3H,
d, J = 2.2 Hz), 2.72 (1H, br), 3.28 (1H, ddd, J = 13.8,
8.0, 5.2 Hz), 3.65 (1H, ddd, J = 13.8, 6.6, 3.0 Hz),
3.92–4.11 (1H, m), 6.68 (1H, br), 7.20 (1H, t,
J = 8.0 Hz), 7.44 (1H, d, J = 8.0 Hz), 7.45 (1H, d,
J = 10.2 Hz). Anal. Calcd for C11H14FNO2: C, 62.55;
H, 6.68; N, 6.63. Found: C, 62.55; H, 6.48; N, 6.70.
1
crystals. Mp 121–124 ꢂC. FAB-MS m/z 194 [MH]+. H
NMR (CDCl3) d: 1.24 (3H, d, J = 6.2 Hz), 2.34 (3H,
s), 2.93 (1H, br), 3.29 (1H, ddd, J = 13.8, 7.8, 5.2 Hz),
3.64 (1H, ddd, J = 13.8, 6.6, 3.0 Hz), 3.97–4.07 (1H,
m), 6.69 (1H, br), 7.22 (2H, d, J = 8.2 Hz), 7.68 (2H,
d, J = 8.2 Hz). Anal. Calcd for C11H15NO2Æ0.1H2O: C,
67.74; H, 7.85; N, 7.18. Found: C, 67.83; H, 7.78; N,
7.35.
6.2.5. 4-Chloro-N-(2-hydroxypropyl)benzamide (10a).
Compound 10a was prepared from 4-chlorobenzoic acid
in a manner similar to that described for 10f. Yield 85%,
colorless crystals. Mp 146–147 ꢂC. FAB-MS m/z 214
1
[MH]+. H NMR (CDCl3) d: 1.26 (3H, d, J = 6.2 Hz),
6.2.2. N-(2-Hydroxypropyl)-3-methylbenzamide (10g).
Compound 10g was prepared from 3-methylbenzoyl
chloride in a manner similar to that described for 10d.
Yield 35%, colorless crystals. Mp 92–93 ꢂC. FAB-MS
m/z 194 [MH]+. 1H NMR (CDCl3) d: 1.24 (3H, d,
J = 6.2 Hz), 2.38 (3H, s), 2.88 (1H, d, J = 4.8 Hz), 3.30
(1H, ddd, J = 14.0, 7.7, 5.0 Hz), 3.65 (1H, ddd,
J = 14.0, 6.6, 2.8 Hz), 3.97–4.10 (1H, m), 6.71 (1H, br),
7.27–7.40 (2H, m), 7.50–7.60 (2H, m). Anal. Calcd for
C11H15NO2: C, 68.37; H, 7.82; N, 7.25. Found: C,
68.19; H, 7.72; N, 7.43.
2.58 (1H, br), 3.28 (1H, ddd, J = 13.8, 7.6, 5.2 Hz),
3.67 (1H, ddd, J = 13.8, 6.6, 2.9 Hz), 3.90–4.10 (1H,
m), 6.67 (1H, br), 7.40 (2H, d, J = 8.4 Hz), 7.72 (2H,
d, J = 8.4 Hz). Anal. Calcd for C10H12ClNO2: C,
56.21; H, 5.66; N, 6.56. Found: C, 56.13; H, 5.69; N,
6.57.
6.2.6. N-(2-Hydroxypropyl)-4-trifluoromethylbenzamide
(10b). Compound 10b was prepared from 4-trifluoro-
methylbenzoic acid in a manner similar to that described
for 10f. Yield 91%, colorless crystals. Mp 163–166 ꢂC.
FAB-MS m/z 248 [MH]+. 1H NMR (CDCl3) d: 1.27
(3H, d, J = 6.2 Hz), 2.40 (1H, br), 3.30 (1H, ddd,
J = 14.0, 8.0, 5.2 Hz), 3.71 (1H, ddd, J = 14.0, 6.4,
3.2 Hz), 3.98–4.15 (1H, m), 6.71 (1H, br), 7.69 (2H, d,
J = 8.6 Hz), 7.90 (2H, d, J = 8.6 Hz). Anal. Calcd for
C11H12F3NO2: C, 53.44; H, 4.89; N, 5.67. Found: C,
53.30; H, 4.88; N, 5.65.
6.2.3. N-(2-Hydroxypropyl)-2-methylbenzamide (10h). A
solution of o-toluoyl chloride (2.00 g, 12.9 mmol) in tol-
uene (2 mL) was added dropwise over 10 min to an ice-
cooled solution of 1-amino-2-propanol (1.07 g,
14.2 mmol) and triethylamine (2.0 mL, 14.3 mmol) in
toluene (7 mL). The reaction mixture was stirred at
room temperature for 2 h, then it was diluted with water
and extracted twice with EtOAc. The organic layers
were combined and washed successively with 10% aque-
ous HCl and water, and dried over MgSO4. After evap-
oration of the solvent, the resulting solid was washed
with Et2O, collected by filtration, and dried in vacuo
to give 10h (1.21 g, 48%) as colorless crystals. Mp 83–
6.2.7. N-(2-Hydroxypropyl)-4-methoxybenzamide (10c).
Compound 10c was prepared from 4-methoxybenzoic
acid in a manner similar to that described for 10f. Yield
53%, colorless crystals. Mp 100–101 ꢂC. FAB-MS m/z
210 [MH]+. 1H NMR (CDCl3) d: 1.23 (3H, d,
J = 6.2 Hz), 3.04 (1H, br), 3.29 (1H, ddd, J = 14.0, 7.7,
5.1 Hz), 3.63 (1H, ddd, J = 14.0, 6.2, 3.0 Hz), 3.84
(3H, s), 3.90–4.10 (1H, m), 6.68 (1H, br), 6.90 (2H, d,
J = 9.0 Hz), 7.75 (2H, d, J = 9.0 Hz). Anal. Calcd for
C11H15NO3: C, 63.14; H, 7.23; N, 6.69. Found: C,
63.05; H, 7.22; N, 6.73.
1
84 ꢂC. FAB-MS m/z 194 [MH]+. H NMR (CDCl3) d:
1.24 (3H, d, J = 6.2 Hz), 2.44 (3H, s), 2.66 (1H, br),
3.27 (1H, ddd, J = 14.0, 7.6, 5.9 Hz), 3.62 (1H, ddd,
J = 14.0, 6.4, 3.2 Hz), 3.90–4.10 (1H, m), 6.30 (1H, br),
7.10–7.40 (4H, m). Anal. Calcd for C11H15NO2: C,
68.37; H, 7.82; N, 7.25. Found: C, 68.27; H, 7.93; N,
7.24.
6.2.8. 4-Ethyl-N-(2-hydroxypropyl)benzamide (10e). Com-
pound 10e was prepared from 4-ethylbenzoic acid in a
manner similar to that described for 10f. Yield 81%, color-
less crystals. Mp 83–85 ꢂC. FAB-MS m/z 208 [MH]+. 1H
NMR (CDCl3) d: 1.24 (3H, d, J = 6.2 Hz), 1.24 (3H, t,
J = 7.6 Hz), 2.68 (2H, q, J = 7.6 Hz), 2.94 (1H, d,
J = 4.4 Hz), 3.30 (1H, ddd, J = 13.9, 7.9, 5.3 Hz), 3.65
(1H, ddd, J = 13.9, 6.6, 2.8 Hz), 3.90–4.12 (1H, m), 6.71
(1H, br), 7.24 (2H, d, J = 8.4 Hz), 7.71 (2H, d,
J = 8.4 Hz). Anal. Calcd for C12H17NO2: C, 69.54; H,
8.27; N, 6.76. Found: C, 69.31; H, 8.33; N, 6.69.
6.2.4. General procedure for the synthesis of 10a–c, 10e,
10f, 10i, 10j: 3-fluoro-N-(2-hydroxypropyl)-4-methylbenz-
amide (10f). To a mixture of 3-fluoro-4-methylbenzoic
acid (5.00 g, 32 mmol), 1-amino-2-propanol (2.68 g,
36 mmol),
and
1-hydroxybenzotriazole
(4.81 g,
36 mmol) in DMF (30 mL) were added triethylamine
(6.8 mL, 49 mmol) and N-(3-dimethylaminopropyl)-N0-
ethylcarbodiimide hydrochloride (EDC hydrochloride)
(4.81 g, 36 mmol). The mixture was stirred at room tem-
perature for 6 h, then diluted with water and extracted
twice with EtOAc. The organic layers were combined
and washed successively with 10% aqueous HCl, water
and saturated aqueous NaHCO3, and dried over
MgSO4. After evaporation of the solvent, the resulting
solid was washed with Et2O, collected by filtration,
6.2.9. 3,4-Dimethyl-N-(2-hydroxypropyl)benzamide (10i).
Compound 10i was prepared from 3,4-dimethylbenzoic
acid in a manner similar to that described for 10f. Yield
53%, colorless crystals. Mp 80–82 ꢂC. FAB-MS m/z 208
1
[MH]+. H NMR (CDCl3) d: 1.24 (3H, d, J = 6.2 Hz),

988
T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
2.29 (6H, s), 2.90 (1H, br), 3.30 (1H, ddd, J = 14.0, 7.3,
5.1 Hz), 3.64 (1H, ddd, J = 14.0, 6.5, 2.9 Hz), 3.90–4.10
(1H, m), 6.66 (1H, br), 7.16 (1H, d, J = 7.8 Hz), 7.49
(1H, dd, J = 7.8, 1.7 Hz), 7.57 (1H, d, J = 1.7 Hz). Anal.
Calcd for C12H17NO2Æ0.1H2O: C, 68.94; H, 8.29; N,
6.70. Found: C, 68.76; H, 8.14; N, 6.77.
J = 4.4 Hz), 6.85 (1H, br), 6.94 (2H, d, J = 8.8 Hz),
7.79 (2H, d, J = 8.8 Hz). Anal. Calcd for C11H13NO3:
C, 63.76; H, 6.32; N, 6.76. Found: C, 63.80; H, 6.21;
N, 6.80.
6.3.5. N-Acetonyl-4-ethylbenzamide (11e). Compound
11e was prepared from 10e in a manner similar to that
described for 11d. Yield 72%, colorless crystals. Mp
6.2.10. 2,4-Dimethyl-N-(2-hydroxypropyl)benzamide
(10j). Compound 10j was prepared from 2,4-dimethyl-
benzoic acid in a manner similar to that described for
10f. Yield 32%, colorless crystals. Mp 89–90 ꢂC. FAB-
1
57–59 ꢂC. FAB-MS m/z 206 [MH]+. H NMR (CDCl3)
d: 1.25 (3H, t, J = 7.7 Hz), 2.27 (3H, s), 2.70 (2H, q,
J = 7.7 Hz), 4.36 (2H, d, J = 4.4 Hz), 6.92 (1H, br),
7.27 (2H, d, J = 8.2 Hz), 7.75 (2H, d, J = 8.2 Hz). Anal.
Calcd for C12H15NO2: C, 70.22; H, 7.37; N, 6.82.
Found: C, 70.22; H, 7.38; N, 6.85.
1
MS m/z 208 [MH]+. H NMR (CDCl3) d: 1.23 (3H, d,
J = 6.2 Hz), 2.32 (3H, s), 2.41 (3H, s), 2.77 (1H, br),
3.26 (1H, ddd, J = 13.8, 7.4, 5.2 Hz), 3.60 (1H, ddd,
J = 13.8, 6.6, 3.2 Hz), 3.90–4.07 (1H, m), 6.30 (1H, br),
6.98 (1H, d, J = 8.2 Hz), 7.02 (1H, s), 7.27 (1H, d,
J = 8.2 Hz). Anal. Calcd for C12H17NO2: C, 69.54; H,
8.27; N, 6.76. Found: C, 69.27; H, 8.27; N, 6.78.
6.3.6. N-Acetonyl-3-fluoro-4-methylbenzamide (11f).
Compound 11f was prepared from 10f in a manner sim-
ilar to that described for 11d. Yield 63%, colorless crys-
tals. Mp 103–105 ꢂC. FAB-MS m/z 210 [MH]+. 1H
NMR (CDCl3) d: 2.28 (3H, s), 2.32 (3H, d,
J = 1.8 Hz), 4.35 (2H, d, J = 4.4 Hz), 6.89 (1H, br),
7.25 (1H, t, J = 7.8 Hz), 7.48 (1H, d, J = 7.8 Hz), 7.49
(1H, d, J = 10.6 Hz). Anal. Calcd for C11H12FNO2: C,
63.15; H, 5.78; N, 6.69. Found: C, 63.04; H, 5.73; N,
6.67.
6.3. Preparation of 11a–j
6.3.1. General procedure for the synthesis of 11a–j: N-
acetonyl-4-methylbenzamide (11d). Celite (11.15 g) and
finely powdered pyridinium chlorochromate (11.15 g,
52 mmol) were added to a solution of 10d (5.00 g,
26 mmol) in CH2Cl2 (100 mL). The reaction mixture
was stirred at room temperature for 6 h and then di-
luted with Et2O (200 mL). The mixture was filtered
through a pad of Celite and the filtrate was concen-
trated in vacuo. The residue was subjected to silica
gel column chromatography with hexane–EtOAc (1:3)
as the eluent to give 11d (3.53 g, 71%) as colorless crys-
6.3.7. N-Acetonyl-3-methylbenzamide (11g). Compound
11g was prepared from 10g in a manner similar to that
described for 11d. Yield 76%, colorless oil. FAB-MS
m/z 192 [MH]+. 1H NMR (CDCl3) d: 2.28 (3H, s),
2.41 (3H, s), 4.36 (2H, d, J = 4.4 Hz), 6.93 (1H, br),
7.20–7.40 (2H, m), 7.55–7.70 (2H, m). Anal. Calcd for
C11H13NO2Æ0.35H2O: C, 66.88; H, 6.99; N, 7.09. Found:
C, 66.48; H, 6.60; N, 7.13.
1
tals. Mp 90–92 ꢂC. FAB-MS m/z 192 [MH]+. H NMR
(CDCl3) d: 2.27 (3H, s), 2.40 (3H, s), 4.36 (2H, d,
J = 4.4 Hz), 6.91 (1H, br), 7.25 (2H, d, J = 8.2 Hz),
7.72 (2H, d, J = 8.2 Hz). Anal. Calcd for C11H13NO2:
C, 69.09; H, 6.85; N, 7.32. Found: C, 69.02; H, 6.76;
N, 7.42.
6.3.8. N-Acetonyl-2-methylbenzamide (11h). Compound
11h was prepared from 10h in a manner similar to that
described for 11d. Yield 66%, colorless crystals. Mp
65.5–66 ꢂC. FAB-MS m/z 192 [MH]+. 1H NMR
(CDCl3) d: 2.27 (3H, s), 2.46 (3H, s), 4.35 (2H, d,
J = 4.8 Hz), 6.54 (1H, br), 7.18–7.45 (4H, m). Anal.
Calcd for C11H13NO2: C, 69.09; H, 6.85; N, 7.32.
Found: C, 68.99; H, 6.81; N, 7.41.
6.3.2. N-Acetonyl-4-chlorobenzamide (11a). Compound
11a was prepared from 10a in a manner similar to that
described for 11d. Yield 70%, colorless crystals. Mp
133–135 ꢂC. FAB-MS m/z 212 [MH]+. 1H NMR
(CDCl3) d: 2.29 (3H, s), 4.36 (2H, d, J = 4.2 Hz), 6.91
(1H, br), 7.43 (2H, d, J = 8.6 Hz), 7.77 (2H, d,
J = 8.6 Hz). Anal. Calcd for C10H10ClNO2: C, 56.75;
H, 4.76; N, 6.62. Found: C, 56.74; H, 4.57; N, 6.68.
6.3.9. N-Acetonyl-3,4-dimethylbenzamide (11i). Com-
pound 11i was prepared from 10i in a manner similar
to that described for 11d. Yield 63%, colorless crystals.
Mp 99–100 ꢂC. FAB-MS m/z 206 [MH]+. 1H NMR
(CDCl3) d: 2.27 (3H, s), 2.31 (6H, s), 4.36 (2H, d,
J = 4.4 Hz), 6.91 (1H, br), 7.19 (1H, d, J = 7.7 Hz),
7.54 (1H, d, J = 7.7 Hz), 7.60 (1H, s). Anal. Calcd for
C12H15NO2: C, 70.22; H, 7.37; N, 6.82. Found: C,
70.09; H, 7.30; N, 6.83.
6.3.3. N-Acetonyl-4-trifluoromethylbenzamide (11b).
Compound 11b was prepared from 10b in a manner sim-
ilar to that described for 11d. Yield 50%, colorless crys-
tals. Mp 139–141 ꢂC. FAB-MS m/z 246 [MH]+. 1H
NMR (CDCl3) d: 2.30 (3H, s), 4.39 (2H, d,
J = 4.4 Hz), 6.98 (1H, br), 7.72 (2H, d, J = 8.4 Hz),
7.94 (2H, d, J = 8.4 Hz). Anal. Calcd for C11H10F3NO2:
C, 53.88; H, 4.11; N, 5.71. Found: C, 53.72; H, 4.10; N,
5.71.
6.3.10. N-Acetonyl-2,4-dimethylbenzamide (11j). Com-
pound 11j was prepared from 10j in a manner similar
to that described for 11d. Yield 66%, colorless crystals.
Mp 73–75 ꢂC. FAB-MS m/z 206 [MH]+. 1H NMR
(CDCl3) d: 2.25 (3H, s), 2.33 (3H, s), 2.43 (3H, s), 4.32
(2H, d, J = 4.4 Hz), 6.56 (1H, br), 7.01 (1H, d,
J = 7.6 Hz), 7.04 (1H, s), 7.33 (1H, d, J = 7.6 Hz). Anal.
Calcd for C12H15NO2: C, 70.22; H, 7.37; N, 6.82.
Found: C, 70.13; H, 7.34; N, 6.84.
6.3.4. N-Acetonyl-4-methoxybenzamide (11c). Com-
pound 11c was prepared from 10c in a manner similar
to that described for 11d. Yield 47%, colorless crystals.
Mp 80–82 ꢂC. FAB-MS m/z 208 [MH]+. 1H NMR
(CDCl3) d: 2.27 (3H, s), 3.86 (3H, s), 4.35 (2H, d,

T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
989
6.4. Preparation of 12a–j
6.4.5. Methyl c-5-[5-(4-ethylbenzoylamino)-6-oxoheptyl]-
2-methyl-1,3-dioxane-r-2-carboxylate (12e). Compound
12e was prepared from 11e in a manner similar to that
6.4.1. General procedure for the synthesis of 12a–j: methyl
c-5-[5-(4-methylbenzoylamino)-6-oxoheptyl]-2-methyl-1,3-
dioxane-r-2-carboxylate (12d). Compound 12d was pre-
pared from 11d and 8 in a manner similar to that de-
scribed previously.13 To a stirred suspension of NaH
(60% dispersion in oil, 0.31 g, 7.8 mmol) in DMF
(10 mL) was added dropwise a solution of 11d (1.50 g,
7.8 mmol) in DMF (4 mL) at ꢀ25 to ꢀ20 ꢂC under ar-
gon. The mixture was stirred for 1 h, and then a solution
of 8 (2.68 g, 7.8 mmol) in DMF (4 mL) was added drop-
wise at the same temperature and the mixture was stirred
for 0.5 h. The temperature was allowed to rise to 0 ꢂC
within 0.5 h, and then the reaction mixture was poured
into water and extracted twice with Et2O. The combined
extracts were washed successively with water and brine,
and dried over MgSO4. After evaporation of the solvent,
the residue was subjected to silica gel column chroma-
tography with hexane–EtOAc (1:1) as the eluent to give
12d (2.35 g, 74%) as a colorless oil. FAB-MS m/z 406
1
described for 12d. Yield 81%, colorless oil. H NMR
(CDCl3) d: 0.85–1.10 (2H, m), 1.10–1.43 (4H, m), 1.25
(3H, t, J = 7.4 Hz), 1.50 (3H, s), 1.52–1.80 (1H, m),
1.85–2.20 (2H, m), 2.27 (3H, s), 2.70 (2H, q, J = 7.4
Hz), 3.36 (2H, t, J = 11.9 Hz), 3.82 (3H, s), 3.92 (2H,
dd, J = 11.9, 4.8 Hz), 4.85 (1H, td, J = 6.6, 4.8 Hz),
6.89 (1H, d, J = 6.6 Hz), 7.27 (2H, d, J = 8.3 Hz), 7.73
(2H, d, J = 8.3 Hz).
6.4.6. Methyl c-5-[5-(3-fluoro-4-methylbenzoylamino)-6-
oxoheptyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12f).
Compound 12f was prepared from 11f in a manner sim-
ilar to that described for 12d. Yield 45%, pale yellow oil.
1H NMR (CDCl3) d: 0.90–1.07 (2H, m), 1.10–1.42 (4H,
m), 1.50 (3H, s), 1.55–1.80 (1H, m), 1.85–2.20 (2H, m),
2.27 (3H, s), 2.32 (3H, s), 3.37 (2H, t, J = 11.9 Hz),
3.82 (3H, s), 3.92 (2H, dd, J = 11.9, 4.7 Hz), 4.83 (1H,
td, J = 6.8, 4.4 Hz), 6.92 (1H, d, J = 6.8 Hz), 7.25 (1H,
t, J = 8.0 Hz), 7.47 (2H, d, J = 9.6 Hz).
1
[MH]+. H NMR (CDCl3) d: 0.82–1.05 (2H, m), 1.10–
1.45 (4H, m), 1.50 (3H, s), 1.52–1.80 (1H, m), 1.84–
2.20 (2H, m), 2.27 (3H, s), 2.40 (3H, s), 3.37 (2H, t,
J = 11.9 Hz), 3.82 (3H, s), 3.92 (2H, dd, J = 11.9, 4.7
Hz), 4.84 (1H, td, J = 7.0, 4.8 Hz), 6.90 (1H, d,
J = 7.0 Hz), 7.25 (2H, d, J = 8.4 Hz), 7.71 (2H, d,
J = 8.4 Hz). Anal. Calcd for C22H31NO6Æ0.5EtOAcÆ0.3-
H2O: C, 63.36; H, 7.89; N, 3.08. Found: C, 63.03; H,
7.72; N, 3.29.
6.4.7. Methyl c-5-[5-(3-methylbenzoylamino)-6-oxohep-
tyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12g). Com-
pound 12g was prepared from 11g in a manner similar
1
to that described for 12d. Yield 51%, colorless oil. H
NMR (CDCl3) d: 0.90–1.10 (2H, m), 1.10–1.45 (4H,
m), 1.50 (3H, s), 1.53–1.85 (1H, m), 1.85–2.20 (2H, m),
2.27 (3H, s), 2.41 (3H, s), 3.37 (2H, t, J = 11.8 Hz),
3.82 (3H, s), 3.92 (2H, dd, J = 11.8, 4.8 Hz), 4.85 (1H,
td, J = 6.7, 4.8 Hz), 6.91 (1H, d, J = 6.7 Hz), 7.32–7.40
(2H, m), 7.56–7.61 (2H, m).
6.4.2. Methyl c-5-[5-(4-chlorobenzoylamino)-6-oxohep-
tyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12a). Com-
pound 12a was prepared from 11a in a manner similar
1
to that described for 12d. Yield 62%, colorless oil. H
6.4.8. Methyl c-5-[5-(2-methylbenzoylamino)-6-oxohep-
tyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12h). Com-
pound 12h was prepared from 11h in a manner similar
NMR (CDCl3) d: 0.90–1.10 (2H, m), 1.10–1.45 (4H,
m), 1.50 (3H, s), 1.55–1.80 (1H, m), 1.84–2.20 (2H, m),
2.27 (3H, s), 3.37 (2H, t, J = 11.9 Hz), 3.82 (3H, s),
3.92 (2H, dd, J = 11.9, 4.7 Hz), 4.85 (1H, td, J = 6.7,
4.8 Hz), 6.91 (1H, d, J = 6.7 Hz), 7.42 (2H, d,
J = 8.7 Hz), 7.75 (2H, d, J = 8.7 Hz).
1
to that described for 12d. Yield 53%, colorless oil. H
NMR (CDCl3) d: 0.93–1.15 (2H, m), 1.17–1.46 (4H, m),
1.51 (3H, s), 1.53–1.80 (1H, m), 1.89–2.20 (2H, m), 2.29
(3H, s), 2.44 (3H, s), 3.39 (2H, t, J = 11.9 Hz), 3.83 (3H,
s), 3.94 (2H, dd, J = 11.9, 4.8 Hz), 4.84 (1H, td, J = 7.2,
4.8 Hz), 6.49 (1H, d, J = 7.2 Hz), 7.15–7.45 (4H, m).
6.4.3. Methyl c-5-[5-(4-trifluoromethylbenzoylamino)-6-
oxoheptyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12b).
Compound 12b was prepared from 11b in a manner sim-
ilar to that described for 12d. Yield 60%, pale yellow oil.
1H NMR (CDCl3) d: 0.75–1.10 (2H, m), 1.10–1.45 (4H,
m), 1.50 (3H, s), 1.52–1.82 (1H, m), 1.82–2.20 (2H, m),
2.29 (3H, s), 3.37 (2H, t, J = 11.8 Hz), 3.82 (3H, s),
3.92 (2H, dd, J = 11.8, 4.8 Hz), 4.86 (1H, td, J = 6.8,
5.2 Hz), 7.00 (1H, d, J = 6.8 Hz), 7.72 (2H, d,
J = 8.4 Hz), 7.92 (2H, d, J = 8.4 Hz).
6.4.9. Methyl c-5-[5-(3,4-dimethylbenzoylamino)-6-oxo-
heptyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12i). Com-
pound 12i was prepared from 11i in a manner similar to
that described for 12d. Yield 29%, colorless oil. 1H
NMR (CDCl3) d: 0.90–1.10 (2H, m), 1.10–1.46 (4H,
m), 1.50 (3H, s), 1.55–1.80 (1H, m), 1.85–2.20 (2H, m),
2.27 (3H, s), 2.31 (6H, s), 3.36 (2H, t, J = 11.9 Hz),
3.82 (3H, s), 3.92 (2H, dd, J = 11.9, 4.8 Hz), 4.84 (1H,
td, J = 7.0, 4.8 Hz), 6.88 (1H, d, J = 7.0 Hz), 7.20 (1H,
d, J = 8.3 Hz), 7.53 (1H, d, J = 8.3 Hz), 7.58 (1H, s).
6.4.4. Methyl c-5-[5-(4-methoxybenzoylamino)-6-oxohep-
tyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12c). Com-
pound 12c was prepared from 11c in a manner similar
6.4.10. Methyl c-5-[5-(2,4-dimethylbenzoylamino)-6-oxo-
heptyl]-2-methyl-1,3-dioxane-r-2-carboxylate (12j). Com-
pound 12j was prepared from 11j in a manner similar to
that described for 12d. Yield 91%, colorless oil. 1H
NMR (CDCl3) d: 0.80–1.10 (2H, m), 1.10–1.46 (4H,
m), 1.51 (3H, s), 1.53–1.80 (1H, m), 1.89–2.20 (2H, m),
2.27 (3H, s), 2.33 (3H, s), 2.42 (3H, s), 3.38 (2H, t,
J = 12.0 Hz), 3.83 (3H, s), 3.93 (2H, dd, J = 12.0,
1
to that described for 12d. Yield 37%, colorless oil. H
NMR (CDCl3) d: 0.90–1.08 (2H, m), 1.10–1.45 (4H,
m), 1.50 (3H, s), 1.56–1.80 (1H, m), 1.85–2.20 (2H, m),
2.27 (3H, s), 3.37 (2H, t, J = 11.8 Hz), 3.82 (3H, s),
3.86 (3H, s), 3.92 (2H, dd, J = 11.8, 4.8 Hz), 4.84 (1H,
td, J = 7.0, 4.6 Hz), 6.84 (1H, d, J = 7.0 Hz), 6.94 (2H,
d, J = 8.7 Hz), 7.78 (2H, d, J = 8.7 Hz).

990
T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
4.6 Hz), 4.83 (1H, td, J = 7.2, 4.4 Hz), 6.46 (1H, d,
J = 7.2 Hz), 7.02 (1H, d, J = 7.8 Hz), 7.04 (1H, s), 7.31
(1H, d, J = 7.8 Hz).
6.5.3.
2-Methyl-c-5-{4-[5-methyl-2-(4-trifluoromethyl-
phenyl)-1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic
acid (14b). Compound 14b was prepared from 12b in a
manner similar to that described for 14d. Yield 34% (in
two steps), colorless crystals. Mp 132–134 ꢂC. FAB-MS
m/z 428 [MH]+. IR (KBr): 2924, 1725, 1321, 1258, 1067,
6.5. Preparation of 14a–j
1
6.5.1. General procedure for the synthesis of 14a–j: 2-
methyl-c-5-{4-[5-methyl-2-(4-methylphenyl)-1,3-oxazol-4-
yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14d)
847, 760 cmꢀ1. H NMR (CDCl3) d: 1.00–1.15 (2H, m),
1.20–1.45 (2H, m), 1.50–1.75 (2H, m), 1.57 (3H, s),
1.90–2.20 (1H, m), 2.34 (3H, s), 2.52 (2H, t, J = 7.5 Hz),
3.48 (2H, t, J = 11.8 Hz), 3.99 (2H, dd, J = 11.8,
4.8 Hz), 6.30 (1H, br), 7.69 (2H, d, J = 8.0 Hz), 8.10
(2H, d, J = 8.0 Hz). Anal. Calcd for C21H24F3NO5: C,
59.01; H, 5.66; N, 3.28. Found: C, 59.14; H, 5.83; N, 3.29.
6.5.1.1. Step 1: methyl 2-methyl-c-5-{4-[5-methyl-2-(4-
methylphenyl)-1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-car-
boxylate (13d). A mixture of 12d (1.85 g, 4.6 mmol) and
phosphorus oxychloride (1.40 g, 9.1 mmol) in toluene
(37 mL) was heated at reflux for 2 h. The resulting mix-
ture was poured into ice water and extracted with
EtOAc. The extract was washed with saturated aqueous
NaHCO3 and brine, and dried over MgSO4. After evap-
oration of the solvent, the residue was purified by chro-
matography on silica gel with hexane–EtOAc (5:1) as the
eluent to give 13d (1.23 g, 69%) as colorless crystals. Mp
93.5–94.5 ꢂC. FAB-MS m/z 388 [MH]+. 1H NMR
(CDCl3) d: 1.00–1.15 (2H, m), 1.20–1.42 (2H, m), 1.51
(3H, s), 1.51–1.70 (2H, m), 1.89–2.15 (1H, m), 2.29
(3H, s), 2.38 (3H, s), 2.44 (2H, t, J = 7.5 Hz), 3.39
(2H, t, J = 11.9 Hz), 3.83 (3H, s), 3.95 (2H, dd,
J = 11.9, 4.4 Hz), 7.22 (2H, d, J = 8.5 Hz), 7.86 (2H, d,
J = 8.5 Hz). Anal. Calcd for C22H29NO5: C, 68.20; H,
7.54; N, 3.61. Found: C, 68.15; H, 7.47; N, 3.91.
6.5.4. 2-Methyl-c-5-{4-[2-(4-methoxyphenyl)-5-methyl-
1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14c).
Compound 14c was prepared from 12c in a manner similar
to that described for 14d. Yield 64% (in two steps), color-
less crystals. Mp 157–158 ꢂC. FAB-MS m/z 390 [MH]+. IR
(KBr): 2926, 1717, 1615, 1505, 1260, 1169, 1034, 835,
762 cmꢀ1. H NMR (CDCl3) d: 1.00–1.15 (2H, m), 1.26–
1
1.47 (2H, m), 1.50–1.75 (2H, m), 1.57 (3H, s), 1.90–2.15
(1H, m), 2.30 (3H, s), 2.52 (2H, t, J = 7.7 Hz), 3.51 (2H,
t, J = 11.9 Hz), 3.84 (3H, s), 3.99 (2H, dd, J = 11.9,
4.4 Hz), 6.94 (2H, d, J = 8.8 Hz), 7.92 (2H, d,
J = 8.8 Hz), 8.90 (1H, br). Anal. Calcd for C21H27NO6:
C, 64.77; H, 6.99; N, 3.60. Found: C, 64.80; H, 7.13; N,
3.57.
6.5.1.2. Step 2: 2-methyl-c-5-{4-[5-methyl-2-(4-meth-
ylphenyl)-1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carbox-
ylic acid (14d). To a stirred suspension of 13d (1.01 g,
2.6 mmol) in MeOH (10 mL) was added 1 N NaOH
(5.2 mL), and the mixture was heated at reflux for 1 h.
After the reaction mixture was evaporated in vacuo,
the residue was diluted with water, neutralized with
1 N HCl, and extracted with EtOAc. The extract was
dried over MgSO4 and evaporated in vacuo. The resid-
ual solid was recrystallized from EtOAc–hexane to give
14d (0.90 g, 93%) as colorless crystals. Mp 150–152 ꢂC.
FAB-MS m/z 374 [MH]+. IR (KBr): 2998, 1729, 1503,
6.5.5. 2-Methyl-c-5-{4-[2-(4-ethylphenyl)-5-methyl-1,3-
oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14e).
Compound 14e was prepared from 12e in a manner sim-
ilar to that described for 14d. Yield 20% (in two steps),
colorless crystals. Mp 147 ꢂC. FAB-MS m/z 387 [MH]+.
1
IR (KBr): 2969, 1732, 1499, 1165, 839, 752 cmꢀ1. H
NMR (CDCl3) d: 1.00–1.15 (2H, m), 1.25 (3H, t,
J = 7.6 Hz), 1.25–1.45 (2H, m), 1.50–1.72 (2H, m), 1.57
(3H, s), 1.90–2.20 (1H, m), 2.31 (3H, s), 2.52 (2H, t,
J = 7.9 Hz), 2.68 (2H, q, J = 7.6 Hz), 3.50 (2H, t,
J = 11.9 Hz), 3.99 (2H, dd, J = 11.9, 4.4 Hz), 6.32 (1H,
br), 7.25 (2H, d, J = 8.4 Hz), 7.89 (2H, d, J = 8.4 Hz).
Anal. Calcd for C22H29NO5: C, 68.20; H, 7.54; N,
3.61. Found: C, 67.99; H, 7.50; N, 3.76.
1152, 828, 754 cmꢀ1 1H NMR (CDCl3) d: 0.99–1.15
.
(2H, m), 1.27–1.46 (2H, m), 1.50–1.75 (2H, m), 1.58
(3H, s), 1.90–2.16 (1H, m), 2.31 (3H, s), 2.38 (3H, s),
2.53 (2H, t, J = 7.7 Hz), 3.50 (2H, t, J = 11.7 Hz), 3.99
(2H, dd, J = 11.7, 4.4 Hz), 7.23 (2H, d, J = 8.0 Hz),
7.86 (2H, d, J = 8.0 Hz), 11.40 (1H, br). Anal. Calcd
for C21H27NO5: C, 67.54; H, 7.29; N, 3.75. Found: C,
67.48; H, 7.20; N, 3.78.
6.5.6.
2-Methyl-c-5-{4-[2-(3-fluoro-4-methylphenyl)-5-
methyl-1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic
acid (14f). Compound 14f was prepared from 12f in a
manner similar to that described for 14d. Yield 32% (in
two steps), colorless crystals. Mp 139–140 ꢂC. FAB-MS
m/z 391 [MH]+. IR (KBr): 2924, 1730, 1646, 1505, 1169,
6.5.2. 2-Methyl-c-5-{4-[2-(4-chlorophenyl)-5-methyl-1,3-
oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14a).
Compound 14a was prepared from 12a in a manner sim-
ilar to that described for 14d. Yield 39% (in two steps),
colorless crystals. Mp 145–146 ꢂC. FAB-MS m/z 393
1144, 889, 760 cmꢀ1 1H NMR (CDCl3) d: 1.00–1.15
.
(2H, m), 1.25–1.47 (2H, m), 1.50–1.70 (2H, m), 1.58
(3H, s), 1.90–2.20 (1H, m), 2.30 (3H,s), 2.31 (3H, s), 2.51
(2H, t, J = 7.7 Hz), 3.49 (2H, t, J = 11.6 Hz), 3.99 (2H,
dd, J = 12.2, 4.8 Hz), 5.80 (1H, br), 7.21 (1H, t,
J = 7.8 Hz), 7.60 (1H, dd, J = 13.2, 1.8 Hz), 7.66 (1H,
dd, J = 7.8, 1.8 Hz). Anal. Calcd for C21H26FNO5: C,
64.44; H, 6.69; N, 3.58. Found: C, 64.49; H, 6.68; N, 3.90.
[MH]+. IR (KBr): 2940, 1721, 1213, 1171, 758 cmꢀ1
.
1H NMR (CDCl3) d: 1.00–1.15 (2H, m), 1.26–1.43
(2H, m), 1.50–1.73 (2H, m), 1.57 (3H, s), 1.90–2.12
(1H, m), 2.31 (3H, s), 2.50 (2H, t, J = 7.7 Hz), 3.48
(2H, t, J = 11.8 Hz), 3.99 (2H, dd, J = 11.8, 4.6 Hz),
5.10 (1H, br), 7.40 (2H, d, J = 8.8 Hz), 7.91 (2H, d,
J = 8.8 Hz). Anal. Calcd for C20H24NO5Cl: C, 60.99;
H, 6.14; N, 3.56. Found: C, 60.75; H, 6.25; N, 3.36.
6.5.7. 2-Methyl-c-5-{4-[5-methyl-2-(3-methylphenyl)-1,3-
oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14g).
Compound 14g was prepared from 12g in a manner sim-
ilar to that described for 14d. Yield 55% (in two steps),

T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
991
colorless crystals. Mp 168–168.5 ꢂC. FAB-MS m/z 373
(3H, s), 2.90 (1H, br), 3.31 (1H, ddd, J = 14.1, 8.2,
5.4 Hz), 3.63–3.80 (2H, m), 6.69 (1H, br), 7.22 (2H, d,
J = 8.2 Hz), 7.68 (2H, d, J = 8.2 Hz). Anal. Calcd for
C12H17NO2Æ0.5H2O: C, 66.64; H, 8.39; N, 6.48. Found:
C, 66.44; H, 8.23; N, 6.88.
[MH]+. IR (KBr): 2990, 2822, 1717, 1649, 1551, 1213,
887, 760, 725 cmꢀ1 1H NMR (CDCl3) d: 1.00–1.15
.
(2H, m), 1.25–1.45 (2H, m), 1.53–1.75 (2H, m), 1.57
(3H, s), 1.90–2.20 (1H, m), 2.32 (3H, s), 2.39 (3H, s),
2.52 (2H, t, J = 7.7 Hz), 3.50 (2H, t, J = 11.9 Hz), 3.99
(2H, dd, J = 11.9, 4.4 Hz), 7.23 (1H, d, J = 7.6 Hz),
7.32 (1H, t, J = 7.6 Hz), 7.77 (1H, d, J = 7.6 Hz), 7.81
(1H, s). Anal. Calcd for C21H27NO5: C, 67.54; H,
7.29; N, 3.75. Found: C, 67.57; H, 7.22; N, 3.80.
6.6.2. 2-Methyl-c-5-{4-[5-ethyl-2-(4-methylphenyl)-1,3-
oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (16).
N-(2-Oxobutyl)-4-methylbenzamide was prepared from
15 in a manner similar to that described for 11d. Yield
66%, colorless crystals. Mp 80–81 ꢂC. FAB-MS m/z
206 [MH]+. 1H NMR (CDCl3) d: 1.16 (3H, t,
J = 7.5 Hz), 2.40 (3H, s), 2.55 (2H, q, J = 7.5 Hz), 4.35
(2H, d, J = 4.4 Hz), 6.95 (1H, br), 7.25 (2H, d,
J = 8.0 Hz), 7.72 (2H, d, J = 8.0 Hz). Anal. Calcd for
C12H15NO2: C, 70.22; H, 7.37; N, 6.82. Found: C,
70.09; H, 7.17; N, 6.88.
6.5.8. 2-Methyl-c-5-{4-[5-methyl-2-(2-methylphenyl)-1,3-
oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14h).
Compound 14h was prepared from 12h in a manner sim-
ilar to that described for 14d. Yield 32% (in two steps),
colorless crystals. Mp 121–122 ꢂC. FAB-MS m/z 373
[MH]+. IR (KBr): 2971, 1734, 1647, 1215, 1142, 752,
729 cmꢀ1 1H NMR (CDCl3) d: 1.00–1.15 (2H, m),
.
1.25–1.45 (2H, m), 1.51 (3H, s), 1.55–1.75 (2H, m),
1.90–2.20 (1H, m), 2.32 (3H, s), 2.52 (2H, t,
J = 7.6 Hz), 2.59 (3H, s), 3.46 (2H, t, J = 11.8 Hz),
3.97 (2H, dd, J = 11.8, 4.8 Hz), 7.19–7.35 (3H, m),
7.85 (1H, dd, J = 7.8, 1.8 Hz). Anal. Calcd for
C21H27NO5: C, 67.54; H, 7.29; N, 3.75. Found: C,
67.47; H, 7.29; N, 3.71.
Methyl c-5-[5-(4-methylbenzoylamino)-6-oxooctyl]-2-
methyl-1,3-dioxane-r-2-carboxylate was prepared from
N-(2-oxobutyl)-4-methylbenzamide and 8 in a manner
similar to that described for 12d. Yield 73%, colorless
crystals. Mp 87–89 ꢂC. FAB-MS m/z 420 [MH]+. 1H
NMR (CDCl3) d: 0.90–1.42 (6H, m), 1.12 (3H, t,
J = 7.3 Hz), 1.50 (3H, s), 1.51–1.75 (1H, m), 1.80–2.13
(2H, m), 2.40 (3H, s), 2.46–2.70 (2H, m), 3.36 (2H, t,
J = 12.0 Hz), 3.82 (3H, s), 3.92 (2H, dd, J = 12.0,
4.8 Hz), 4.85 (1H, td, J = 7.4, 4.8 Hz), 6.90 (1H, d,
J = 7.4 Hz), 7.25 (2H, d, J = 8.4 Hz), 7.70 (2H, d,
J = 8.4 Hz). Anal. Calcd for C23H33NO6: C, 65.85; H,
7.93; N, 3.34. Found: C, 65.75; H, 7.87; N, 3.34.
6.5.9. 2-Methyl-c-5-{4-[2-(3,4-dimethylphenyl)-5-methyl-
1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14i).
Compound 14i was prepared from 12i in a manner similar
to that described for 14d. Yield 65% (in two steps), color-
less crystals. Mp 169.5–170 ꢂC. FAB-MS m/z 387 [MH]+.
IR (KBr): 2950, 1730, 1651, 1489, 1169, 1047, 887, 760,
733 cmꢀ1
.
1H NMR (CDCl3) d: 1.00–1.15 (2H, m),
Compound 16 was prepared from methyl c-5-[5-(4-
methylbenzoylamino)-6-oxooctyl]-2-methyl-1,3-diox-
ane-r-2-carboxylate in a manner similar to that de-
scribed for 14d. Yield 63% (in two steps), colorless
crystals. Mp 160–161 ꢂC. FAB-MS m/z 388 [MH]+. IR
1.25–1.45 (2H, m), 1.50–1.72 (2H, m), 1.58 (3H, s), 1.90–
2.15 (1H, m), 2.29 (6H, s), 2.30 (3H, s), 2.51 (2H, t,
J = 7.7 Hz), 3.50 (2H, t, J = 11.9 Hz), 3.99 (2H, dd,
J = 11.9, 4.8 Hz), 7.18 (1H, d, J = 8.0 Hz), 7.69 (1H, dd,
J = 8.0, 1.4 Hz), 7.76 (1H, d, J = 1.4 Hz). Anal. Calcd
for C22H29NO5: C, 68.20; H, 7.54; N, 3.61. Found: C,
68.31; H, 7.53; N, 3.65.
(KBr): 2939, 1717, 1501, 1156, 766 cmꢀ1 1H NMR
.
(CDCl3) d: 1.00–1.15 (2H, m), 1.20–1.47 (2H, m), 1.27
(3H, t, J = 7.5 Hz), 1.50–1.80 (2H, m), 1.57 (3H, s),
1.90–2.20 (1H, m), 2.38 (3H, s), 2.53 (2H, t,
J = 7.7 Hz), 2.67 (2H, q, J = 7.5 Hz), 3.50 (2H, t,
J = 11.9 Hz), 3.99 (2H, dd, J = 11.9, 4.6 Hz), 7.23 (2H,
d, J = 8.0 Hz), 7.40 (1H, br), 7.87 (2H, d, J = 8.0 Hz).
Anal. Calcd for C22H29NO5: C, 68.20; H, 7.54; N,
3.61. Found: C, 68.25; H, 7.53; N, 3.65.
6.5.10. 2-Methyl-c-5-{4-[2-(2,4-dimethylphenyl)-5-methyl-
1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (14j).
Compound 14j was prepared from 12j in a manner similar to
that described for 14d. Yield 20% (in two steps), colorless
crystals. Mp 130–131 ꢂC. FAB-MS m/z 387 [MH]+. IR
1
(KBr): 2910, 1732, 1485, 1150, 1061, 758 cmꢀ1. H NMR
(CDCl3) d: 1.00–1.15 (2H, m), 1.25–1.45 (2H, m), 1.51
(3H, s), 1.52–1.75 (2H, m), 1.90–2.15 (1H, m), 2.31 (3H, s),
2.33 (3H, s), 2.51 (2H, t, J = 8.0 Hz), 2.54 (3H, s), 3.46
(2H, t, J = 11.9 Hz), 3.97 (2H, dd, J = 11.9, 4.8 Hz), 7.04
(1H, d, J = 7.9 Hz), 7.06 (1H, s), 7.73 (1H, d, J = 7.9 Hz),
8.65 (1H, br). Anal. Calcd for C22H29NO5: C, 68.20; H,
7.54; N, 3.61. Found: C, 68.25; H, 7.53; N, 3.65.
6.7. Preparation of 22
6.7.1. 3-[2-(4-Methylphenyl)-5-trifluoromethyloxazol-4-
yl]-1-propanol (17). Compound 17 was prepared in 67%
yield from N-(4-methylbenzoyl)proline according to a
known method.14 Mp 87–89 ꢂC. FAB-MS m/z 286
1
[MH]+. H NMR (CDCl3) d: 1.98 (2H, qn, J = 6.4 Hz),
2.30 (1H, br), 2.42 (3H, s), 2.82 (2H, td, J = 6.4, 1.6 Hz),
3.74 (2H, t, J = 6.4 Hz), 7.28 (2H, d, J = 8.0 Hz), 7.93
(2H, d, J = 8.0 Hz). Anal. Calcd for C14H14F3NO2: C,
58.95; H, 4.95; N, 4.91. Found: C, 58.96; H, 4.87; N, 4.89.
6.6. Preparation of 16
6.6.1. N-(2-Hydroxybutyl)-4-methylbenzamide (15).
Compound 15 was prepared from 3-methylbenzoyl chlo-
ride and 1-amino-2-butanol in a manner similar to that
described for 10d. Yield 93%, colorless crystals. Mp 80–
6.7.2. Methyl 4-[2-(4-methylphenyl)-5-trifluoromethyl-
oxazol-4-yl]butyrate (18). To a stirred solution of 17
(6.40 g, 22 mmol), triethylamine (4.7 mL, 34 mmol), and
4-dimethylaminopyridine (0.29 g, 2.4 mmol) in CH2Cl2
83 ꢂC. FAB-MS m/z 208 [MH]+. H NMR (CDCl3) d:
1
0.99 (3H, t, J = 7.5 Hz), 1.55 (2H, qn, J = 7.5 Hz), 2.39

992
T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
(35 mL) was added p-toluenesulfonyl chloride (5.13 g,
27 mmol) and stirring was continued for 3 h at room tem-
perature. The reaction mixture was poured into ice water
and extracted with EtOAc. The organic layer was washed
successively with 10% aqueous HCl, water, and saturated
aqueous NaHCO3, and dried over MgSO4. Removal of
the solvent by evaporation gave 3-[2-(4-methylphenyl)-
5-trifluoromethyloxazol-4-yl]propyl p-toluenesulfonate
(10.08 g, quant) as pale brown crystals. Mp 57–58 ꢂC.
FAB-MS m/z 440 [MH]+. 1H NMR (CDCl3) d: 1.98
(2H, qn, J = 6.4 Hz), 2.42 (6H, s), 2.82 (2H, td, J = 6.4,
1.4 Hz), 4.14 (2H, t, J = 6.4 Hz), 7.28 (2H, d, J =
6.8 Hz), 7.31 (2H, d, J = 8.4 Hz), 7.79 (2H, d, J =
8.4 Hz), 7.89 (2H, d, J = 6.8 Hz). Anal. Calcd for
C21H20F3NO4SÆ0.6H2O: C, 56.02; H, 4.75; N, 3.11.
Found: C, 56.04; H, 4.75; N, 3.21.
purified by chromatography on silica gel with hexane–
EtOAc (2:1) as the eluent to give crude 4-[2-(4-methyl-
phenyl)-5-trifluoromethyloxazol-4-yl]-1-butanol (5.17 g)
as a wet, colorless solid. To a solution of this crude
product in CH2Cl2 (90 mL) were added triphenylphos-
phine (4.98 g, 19 mmol) and carbon tetrabromide
(6.30 g, 19 mmol). The mixture was stirred at room tem-
perature for 1 h. After evaporation of the solvent, the
residue was purified by chromatography on silica gel
with hexane–EtOAc (10:1) as the eluent to give 19
1
(0.97 g, 16% in two steps) as a colorless oil. H NMR
(CDCl3) d: 1.80–2.05 (4H, m), 2.42 (3H, s), 2.72 (2H,
t, J = 6.2 Hz), 3.44 (2H, t, J = 6.2 Hz), 7.28 (2H, d,
J = 8.6 Hz), 7.94 (2H, d, J = 8.6 Hz).
6.7.4. 2-Hydroxymethyl-6-[2-(4-methylphenyl)-5-tri-
fluoromethyloxazol-4-yl]-1-hexanol (20). To an ice-
cooled suspension of NaH (60% dispersion in oil,
0.22 g, 5.5 mmol) in THF (10 mL) and DMF (5 mL)
was added dropwise diethyl malonate (1.06 g,
6.6 mmol). The mixture was stirred with ice-cooling
for 15 min, after which a solution of 19 (0.96 g,
2.7 mmol) was added dropwise. The resulting mixture
was stirred at 100 ꢂC for 15 h and then diluted with ice
water and extracted with Et2O. The extract was washed
with water and dried over MgSO4. After the solvent was
evaporated, the crude product was purified by silica gel
column chromatography with hexane–EtOAc (10:1) as
the eluent to give crude diethyl 2-{4-[2-(4-methyl-
phenyl)-5-trifluoromethyloxazol-4-yl]butyl}malonate
(1.21 g), including diethyl malonate, as a pale yellow oil.
Compound 20 was prepared by reduction of crude
diethyl 2-{4-[2-(4-methylphenyl)-5-trifluoromethyloxazol-
4-yl]butyl}malonate with LiAlH4 in a manner similar to
that described for 6. Yield 54% (in two steps), colorless
crystals. Mp 95–97 ꢂC. FAB-MS m/z 358 [MH]+. 1H
NMR (CDCl3) d: 1.20–1.50 (4H, m), 1.61–1.82 (3H,
m), 2.35 (2H, br), 2.42 (3H, s), 2.71 (2H, td, J = 7.4,
1.2 Hz), 3.67 (2H, dd, J = 10.6, 7.4 Hz), 3.82 (2H, dd,
J = 10.6, 3.6 Hz), 7.29 (2H, d, J = 8.4 Hz), 7.95 (2H, d,
J = 8.4 Hz). Anal. Calcd for C18H22F3NO3Æ1H2O: C,
57.59; H, 6.44; N, 3.73. Found: C, 57.65; H, 6.33; N,
3.66.
A mixture of this compound and sodium cyanide (1.16 g,
24 mmol) in DMSO (40 mL) was heated at 90 ꢂC for 2 h.
The mixture was diluted with water and extracted with
Et2O, and the extract was washed with water and dried
over MgSO4. Removal of the solvent by evaporation gave
4-[2-(4-methylphenyl)-5-trifluoromethyloxazol-4-yl]butyro-
nitrile (6.35 g, 96%) as pale brown crystals. Mp 41–42.5 ꢂC.
FAB-MSm/z 295[MH]+.1HNMR(CDCl3)d:2.12(2H,qn,
J = 7.0 Hz), 2.42 (3H, s), 2.47 (2H, t, J = 7.0 Hz), 2.86 (2H,
td, J = 7.0, 1.4 Hz), 7.29 (2H, d, J = 8.2 Hz), 7.94 (2H, d,
J = 8.2 Hz). Anal. Calcd for C15H13F3N2O: C, 61.22; H,
4.15; N, 9.52. Found: C, 61.12; H, 4.45; N, 9.32.
HCl gas was passed through an ice-cooled solution of 4-
[2-(4-methylphenyl)-5-trifluoromethyloxazol-4-yl]butyro-
nitrile (5.28 g, 18 mmol) in dry MeOH (42 mL) until the
solution was saturated with HCl gas. The mixture was
stirred at room temperature for 30 min, and after water
(5.3 mL, 294 mmol) was added, the mixture was allowed
to stand at room temperature for 16 h. The reaction mix-
ture was diluted with water and then extracted twice with
EtOAc. The organic extracts were combined and washed
with saturated aqueous NaHCO3 and dried over MgSO4.
After evaporation of solvent, the residue was subjected to
chromatography on silica gel with hexane–EtOAc (4:1)
as the eluent to give 18 (5.63 g, 96%) as colorless crystals.
Mp 44.5–45 ꢂC. FAB-MS m/z 328 [MH]+. 1H NMR
(CDCl3) d: 1.95–2.14 (2H, m), 2.40 (2H, t, J = 7.4 Hz),
2.42 (3H, s), 2.75 (2H, td, J = 7.4, 1.2 Hz), 3.68 (3H, s),
7.28 (2H, d, J = 8.0 Hz), 7.94 (2H, d, J = 8.0 Hz). Anal.
Calcd for C16H16F3NO3: C, 58.71; H, 4.93; N, 4.28.
Found: C, 58.64; H, 4.88; N, 4.30.
6.7.5. Methyl 2-methyl-c-5-{4-[2-(4-methylphenyl)-5-tri-
fluoromethyl-1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-car-
boxylate (21). Compound 21 was prepared from 20 in a
manner similar to that described for 6. Yield 38%, color-
less crystals. Mp 58.5–60 ꢂC. FAB-MS m/z 442 [MH]+.
1H NMR (CDCl3) d: 1.04–1.15 (2H, m), 1.20–1.42
(2H, m), 1.51 (3H, s), 1.60–1.75 (2H, m), 1.90–2.20
(1H, m), 2.42 (3H, s), 2.66 (2H, t, J = 6.5 Hz), 3.40
(2H, t, J = 11.8 Hz), 3.83 (3H, s), 3.95 (2H, dd,
J = 11.8, 4.4 Hz), 7.28 (2H, d, J = 7.4 Hz), 7.94 (2H, d,
J = 8.4 Hz). Anal. Calcd for C22H26F3NO5: C, 59.86;
H, 5.94; N, 3.17. Found: C, 60.05; H, 5.92; N, 3.19.
6.7.3. 4-(4-Bromobutyl)-2-(4-methylphenyl)-5-trifluoro-
methyloxazole (19). To an ice-cooled suspension of
LiAlH4 (0.76 g, 20 mmol) in THF (40 mL) was added
dropwise a solution of 17 (5.47 g, 17 mmol) in THF
(20 mL) at 4–13 ꢂC. The mixture was stirred at room
temperature for 1 h and then recooled in an ice-bath.
The reaction was quenched with water (0.75 mL), aque-
ous 15% NaOH (0.75 mL), and water (2.2 mL), in that
order. The mixture was stirred at room temperature
for 1 h. The insoluble precipitate was filtered off and
the filtrate was evaporated in vacuo. The residue was
dissolved in EtOAc and the solution was dried over
MgSO4 and concentrated in vacuo. The residue was
6.7.6.
2-Methyl-c-5-{4-[2-(4-methylphenyl)-5-trifluoro-
methyl-1,3-oxazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic
acid (22). Compound 22 was prepared from 21 by alka-
line hydrolysis by a method similar to that described for
14d. Yield 80%, colorless crystals. Mp 130–131 ꢂC.
FAB-MS m/z 428 [MH]+. IR (KBr): 2925, 1738, 1501,

T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
993
1
1391, 1130, 1100, 752 cmꢀ1. H NMR (CDCl3) d: 1.00–
6.9.2. c-5-{4-[1,5-Dimethyl-2-(4-methylphenyl)imidazol-
4-yl]butyl}-2-methyl-1,3-dioxane-r-2-carboxylic acid
1.15 (2H, m), 1.25–1.45 (2H, m), 1.57 (3H, s), 1.62–1.77
(2H, m), 1.90–2.20 (1H, m), 2.42 (3H, s), 2.68 (2H, t,
J = 6.7 Hz), 3.47 (2H, t, J = 11.9 Hz), 3.99 (2H, dd,
J = 11.9, 4.4 Hz), 7.28 (2H, d, J = 8.4 Hz), 7.94 (2H, d,
J = 8.4 Hz). Anal. Calcd for C21H24F3NO5: C, 59.01;
H, 5.66; N, 3.28. Found: C, 59.11; H, 5.67; N, 3.16.
(26). To a stirred solution of 25 (572 mg, 1.4 mmol) in
MeOH (8 mL) was added 1 N NaOH (2 mL), and the
mixture was heated at reflux for 2 h. After evaporation
of the solvent, the residue was dissolved in water and
washed with Et2O. The aqueous layer was separated,
neutralized with 1 N HCl (2 mL), and extracted with
CHCl3 (6 · 30 mL). The organic extracts were dried
over MgSO4 and evaporated in vacuo. The residual so-
lid was washed with Et2O and filtered to give 26
(309 mg, 56%) as colorless crystals. Mp 192–194 ꢂC
(dec). FAB-MS m/z 386 [MH]+. IR (KBr): 2937, 2361,
1169, 1140, 885, 791 cmꢀ1. 1H NMR (D2O) d: 0.80–1.40
(4H, m), 1.28 (3H, s), 1.40–1.60 (2H, m), 1.65–1.95 (1H,
m), 2.16 (3H, s), 2.32 (3H, s), 2.55 (2H, t, J = 7.0 Hz),
3.32 (2H, t, J = 11.7 Hz), 3.76 (2H, dd, J = 11.7,
4.6 Hz), 7.35 (2H, d, J = 8.4 Hz), 7.40 (2H, d,
J = 8.4 Hz). Anal. Calcd for C22H30N2O4Æ1H2O: C,
65.32; H, 7.97; N, 6.93. Found: C, 65.36; H, 7.58; N, 6.75.
6.8. Preparation of 24
6.8.1. Methyl 2-methyl-c-5-{4-[5-methyl-2-(4-methylphenyl)-
1,3-thiazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylate (23). A
mixture of 12d (2.02 g, 5 mmol)and DavyReagentMethyl15
(2.84 g, 10 mmol) in THF (20 mL) was stirred for 3 h at
55 ꢂC and then for further 3 h at 75 ꢂC. After dilution with
EtOAc, the reaction mixture was successively washed with
10% aqueous HCl, water, and saturated aqueous NaHCO3,
and dried over MgSO4. After evaporation of the solvent, the
residue was purified by chromatography on silica gel with
hexane–EtOAc (4:1) as the eluent to give 23 (0.38 g, 19%)
1
as a pale yellow oil. H NMR (CDCl3) d: 1.00–1.15 (2H,
m), 1.23–1.40 (2H, m), 1.51 (3H, s), 1.60–1.77 (2H, m),
1.92–2.14 (1H, m), 2.37 (6H, s), 2.66 (2H, t, J = 7.5 Hz),
3.39 (2H, t, J = 11.9 Hz), 3.83 (3H, s), 3.95 (2H, dd,
J = 11.9, 4.8 Hz), 7.20 (2H, d, J = 8.0 Hz), 7.75 (2H, d,
J = 8.0 Hz).
6.10. Biological procedures
6.10.1. PPAR transactivation assays. Agonist activity at
each PPAR subtype was determined by cell-based trans-
activation assay as described previously.16 Briefly, CV-1
cells (ATCC, Manassas, VA) were cultured in Dul-
becco’s modified Eagle’s minimal essential medium con-
taining 10% fetal bovine serum, 100 U/mL penicillin G,
and 100 lg/mL streptomycin sulfate under humidified
5% CO2 and 95% air at 37 ꢂC. Three kinds of expression
vectors were cotransfected into CV-1 cells using Tfx-20
transfection reagent (Promega, Madison, WI) according
to the manufacturer’s instructions: (1) pSG5 (Strata-
gene, La Jolla, CA), containing a full-length cDNA
clone of each PPAR subtype (an expression vector);
(2) pGL3 (Promega) containing three copies of a perox-
isome proliferator response element derived from the
promoter region of the rat acyl-CoA oxidase gene and
a thymidine kinase promoter sequence (a reporter vec-
tor); and (3) phRL-TK (Promega), a Renilla luciferase
reporter vector for use as an internal standard. All com-
pounds were dissolved in DMSO, and the final concen-
tration of DMSO in the medium was 0.1% (v/v). Cells
were treated with DMSO or compound for 48 h, and
the luciferase activity of the cell lysate was measured
with a Wallac 1420 ARVOsx multilabel counter (Per-
kin-Elmer Inc., Wellesley, MA) by means of a dual lucif-
erase assay system (Promega). The half-maximum
effective concentration (EC50) for each PPAR agonist
activity was estimated from the concentration–activity
curves as the concentration giving 50% of the maximum
activity gained by the relevant positive control. The
approximate EC50 values were given as the closest con-
centration in a geometric progression of agonist concen-
trations with a common ratio of three.
6.8.2. 2-Methyl-c-5-{4-[5-methyl-2-(4-methylphenyl)-1,3-
thiazol-4-yl]butyl}-1,3-dioxane-r-2-carboxylic acid (24).
Compound 24 was prepared from 23 by alkaline hydroly-
sis by a method similar to that described for 14d. Yield
84%, colorless crystals. Mp 172–172.5 ꢂC. FAB-MS m/z
390 [MH]+. IR (KBr): 2923, 1728, 1557, 1246, 1210,
1
1165, 1144, 812 cmꢀ1. H NMR (CDCl3) d: 1.02–1.13
(2H, m), 1.26–1.44 (2H, m), 1.54 (3H, s), 1.60–1.72 (2H,
m), 1.90–2.15 (1H, m), 2.37 (3H, s), 2.38 (3H, s), 2.70
(2H, t, J = 7.7 Hz), 3.47 (2H, t, J = 11.8 Hz), 3.98 (2H,
dd, J = 11.8, 4.6 Hz), 7.20 (2H, d, J = 8.4 Hz), 7.75 (2H,
d, J = 8.4 Hz). Anal. Calcd for C21H27NO4S: C, 64.76;
H, 6.99; N, 3.60. Found: C, 64.68; H, 6.97; N, 3.64.
6.9. Preparation of 26
6.9.1. Methyl c-5-{4-[1,5-dimethyl-2-(4-methylphenyl)imi-
dazol-4-yl]butyl}-2-methyl-1,3-dioxane-r-2-carboxylate
(25). Compound 25 was prepared in a manner similar to
that previously described.17 Acetic acid (0.84 mL,
15 mmol) and a solution of 2 M methylamine in THF
(1.5 mL, 3 mmol) were added to a solution of 12d
(0.80 g, 2 mmol) in xylene (20 mL). The mixture was re-
fluxed for 2 h with azeotropic removal of water. After
cooling, the reaction mixture was poured into saturated
aqueous NaHCO3 and the organic layer was dried over
MgSO4. After evaporation of the solvent, the residue
was purified by chromatography on silica gel with
CHCl3–MeOH (100:1) as the eluent to give 25 (0.63 g,
1
80%) as a pale yellow oil. H NMR (CDCl3) d: 0.97–
1.10 (2H, m), 1.20–1.40 (2H, m), 1.50 (3H, s), 1.54–
1.70 (2H, m), 1.90–2.15 (1H, m), 2.18 (3H, s), 2.38
(3H, s), 2.51 (2H, t, J = 7.5 Hz), 3.38 (2H, t,
J = 12.0 Hz), 3.53 (3H, s), 3.83 (3H, s), 3.95 (2H, dd,
J = 12.0, 4.5 Hz), 7.23 (2H, d, J = 8.2 Hz), 7.45 (2H, d,
J = 8.2 Hz).
6.10.2. Animal experiments. KK-Ay mice, 8 weeks old,
were purchased from Clea Japan, Inc. (Tokyo, Japan).
The mice were housed in a room maintained at
23 2 ꢂC under a 12/12 h light/dark cycle. They had free
access to laboratory chow (CE-2, Clea Japan) and tap
water, and were used for experiments at 10 weeks of

994
T. Asaki et al. / Bioorg. Med. Chem. 16 (2008) 981–994
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for measuring plasma TG and glucose levels. In the after-
noon, blood samples were taken from the inferior vena
cava of nonfasted animals under sodium pentobarbital
anesthesia for measuring plasma lipoprotein cholesterol
levels. The plasma TG and glucose levels were determined
enzymatically by means of the commercial diagnostic kits
Triglyceride E-test Wako and Glucose CII-test Wako
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automated Tosoh Lipoprotein Analytical System (Tosoh
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resolved by HPLC on a TSKgel Lipopropak column
(Tosoh Co., 7.5 mm id · 300 mm) with TSK eluent LP-
1 (Tosoh Co.) as the elution buffer. Each 5-lL sample of
plasma was applied to the column and the cholesterol
was detected by an on-line enzymatic reaction by mixing
the effluent from the column with a liquid reagent from
a commercial kit, Determiner L TC (Kyowa Medex
Co., Tokyo, Japan). All animal procedures were ap-
proved by the Committee for the Institutional Care and
Use of Animals at Nippon Shinyaku Co.
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Acknowledgments
11. Aoki, T.; Asaki, T.; Hamamoto, T.; Sugiyama, Y.;
Ohmachi, S.; Kuwabara, K.; Murakami, K.; Todo, M.
Bioorg. Med. Chem. Lett., submitted for publication.
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We thank Mr. Shoichi Chokai, Mr. Shinichi Tada, and
Mr. Tetsuji Harabe for practical guidance, and Dr.
Akira Matsuura, Mr. Masayuki Hattori, and Dr. Ger-
ald E. Smyth for helpful suggestions during the prepara-
tion of the manuscript.
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