Novel synthesis and anti-inflammatory activities of 2,5-disubstituted- dioxacycloalkanes

Article abstract of DOI:10.1016/j.bmc.2005.05.032

A novel stereospecific synthetic route to obtain a series of 2,5-disubstituted-dioxacycloalkanes is reported. Using an in vivo inhibition assay by monitoring xylene-induced ear edema in mice, the structure-activity relationship of the dioxacycloalkane com

Full text of DOI:10.1016/j.bmc.2005.05.032

Bioorganic & Medicinal Chemistry 13 (2005) 5640–5646
Novel synthesis and anti-inflammatory activities
of 2,5-disubstituted-dioxacycloalkanes
Lanrong Bi,a Yue Zhang,b Ming Zhao,b,* Chao Wang,b Priscilla Chan,c
Jeffrey B.-H. Tokc,* and Shiqi Penga,*
aCollege of Pharmaceutical Sciences, Capital University of Medical Sciences, Beijing 100054, PR China
bCollege of Pharmaceutical Sciences, Peking University, Beijing 100054, PR China
cChemistry & Materials Science Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue,
Livermore, CA 94551, USA
Received 5 March 2005; revised 11 May 2005; accepted 18 May 2005
Available online 5 July 2005
Abstract—A novel stereospecific synthetic route to obtain a series of 2,5-disubstituted-dioxacycloalkanes is reported. Using an
in vivo inhibition assay by monitoring xylene-induced ear edema in mice, the structure–activity relationship of the dioxacycloalkane
compounds was studied, and compounds possessing high anti-inflammatory activity were identified.
ꢀ 2005 Elsevier Ltd. All rights reserved.
1. Introduction
minary observations indicate that certain 1,3-dioxacycle
compounds possess anti-inflammatory activities.12
Encouraged by these finding, a novel series of 2,5-disub-
stituted-1,3-dioxacycloalkanes were subsequently pre-
There has been a long-standing interest in identifying
novel targets for the rational development of anti-in-
flammatory drugs. Inhibitors that target proteins in-
volved in signaling pathways have been developed and
preliminary preclinical data suggest that they exhibit
anti-inflammatory activity. Recent studies implicate
protein kinase C (PKC) as another new target for the
treatment of inflammatory disorders.1–9 Some PKC
inhibitors such as Stausporine, GF 1092203X, and Bal-
anol analogs were confirmed to reduce a number of
inflammatory processes that resulted from PKC activa-
tion by the topical application of phorbol myristate ace-
tate to mouse ears.1,6,7 In addition, 1,3-dioxane
derivatives have been reported to possess PKC inhibito-
ry activity and exert anti-inflammatory, anti-cancer, and
reperfusion injury protection effects through their anti-
proliferative and anti-inflammatory activities in human
neutrophils and tumor cells.9
pared.
Their
corresponding
structure–activity
relationships were also characterized in the hope of
obtaining additional compounds possessing better anti-
inflammatory activities. During the preparation of 1,3-
dioxacycle derivatives, the diol transacetalation process
with 1,1,3,3-tetramethoxypropane was realized to afford
a complex mixture of monocyclic and bicyclic ace-
tals.10,11 Consequently, to avert the tedious separation
process for these isomeric mixtures, new methodologies
have to be developed to prepare the 2,5-disubstituted-
dioxacycloalkane compounds. Herein, we report a
convenient and efficient method for the preparation of
2,5-substituted-dioxacycloalkanes via transacetalation
using 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TAB-
CO)13 as catalyst under mild reaction conditions. With
this improved synthetic approach, sufficient quantities
of the 2,5-substituted-dioxacycloalkane compounds
were readily prepared for animal testing, which subse-
quently enabled a more precise elucidation of their
structure–activity relationship.
We had previously described 1,3-dioxacycle derivatives
that can be prepared through the transacetalation of
1,1,3,3-tetramethoxypropane and diols.10,11 Our preli-
Keywords: Acetalization; 2,5-Disubstituted-dioxacycloalkanes; Anti-
inflammatory activity.
2. Results and discussion
*
Corresponding authors. Tel./fax: +86 10 5137 6716 (S.P.); tel./fax:
+86 10 8280 2482 (M.Z.); tel./fax: +1 925 423 1549 (J.B.T.); e-mail
addresses: tok2@llnl.gov; sqpeng@mail.bjmu.edu.cn
Our previous results have demonstrated that it is possi-
ble to obtain 2,5-disubstituted-dioxacycloalkanes with
0968-0896/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.05.032

L. Bi et al. / Bioorg. Med. Chem. 13 (2005) 5640–5646
5641
stereoselectivity through thermodynamic or kinetic con-
trol of the transacetalation.10,11 Additionally, the stereo-
chemistry of the ring formed in the transacetalation is
also dependent on the structure of the amino-diol com-
pounds.10 Herein, we report an improved synthetic
methodology toward the 2,5-disubstituted-diox-
acycloalkanes. The amino-diols 4a–d, which are key
intermediates for the synthesis of 2,5-disubstituted-diox-
acycloalkanes, were prepared according to previously
reported methods.10 Treatment of 4a–d with 3,3-dimeth-
oxypropanal using TABCO as catalyst provided the cor-
responding cyclic acetals 5a–d in good to excellent
yields. Compounds 5a–d were then subjected to partial
hydrolysis to afford cyclic aldehydes 6a–d in quantitative
yields. Further acetalizations were carried out with
cyclic aldehydes as starting materials to provide stereo-
specific 2,5-disubstituted-dioxacycloalkanes 7a–d (syn-
thetic routes shown in Schemes 1–3). Upon comparing
the anti-inflammatory effect of 2-(2,2-dimethoxyethyl)-
5-benzoylamino-1,3-dioxane and 2-(2,2-dimethoxyeth-
yl)-5-phenylacetamino-1,3-dioxane, it was observed that
the latter exhibited better anti-inflammatory activity.12
Therefore, the benzoylamide functionality was subse-
quently replaced with a phenylacetamide functionality.
Using a previously described synthetic method,10 the
transacetalation of phenylacetaminodiols and equal
amount of the 1,1,3,3-tetramethoxypropane gave a com-
plex mixture of products comprised of both cis- and
trans-2,5-disubstituted-1,3-dioxamonocycloalkane, and
both cis- and trans-2,5-disubstituted-1,3-diox-
abiscycloalkane. To enable stereospecific products, dif-
ferent reaction conditions and catalysts were
investigated. It was observed that targeted stereospecific
products could exclusively be achieved by using TABCO
or trifluoroacetic acid (TFA) as catalyst under carefully
chosen thermodynamic or kinetic control conditions.
For example, the transacetalation of 4a–d and 3,3-
dimethoxypropanal at 50 ꢁC using TABCO as catalyst
exclusively gave the corresponding 5a–d.
To ensure correct structural assignment to compounds
5a–d and 7a–d, nuclear Overhauser effect (NOE) differ-
ence experiments were performed. For each of these
compounds analyzed, 5a,c,d and 7a,b, positive NOE ef-
fect were observed between the NH at the 5-position and
the CH2 at the 2-position, indicating that substitutions
at both the 2- and 5-positions of these compounds are
in a syn-arrangement. Similarly, a positive NOE effect
was observed between the CH3 at the 4-position and
the CH2 at the 2-position of compound 5b, indicating
that 2-dimethoxyethyl, 4-methyl and 5-phenylacetamino
of 5b are also in a syn-arrangement. For compound 7c,
two positive NOE signals were observed between the
CH3 at the 4-position and the CH2 at the 2-position,
and the NH at the 5-position, implying that the respec-
tive substitutions at 2-, 4- and 5-positions of 7c on its
Scheme 1. Synthetic route to compounds 4a–d. Reagents and conditions: (i) SOCl2/MeOH, 0 ꢁC to rt; (ii) phenylacetyl chloride, pH 8–9, rt; (iii)
NaBH4/THF, rt. In 1a: L-Ser, R1 = CH2OH; 1b: L-Thr, R1 = CH (CH3)OH; 1c: L-Asp, R1 = CH2COOH; 1d: L-Glu, R1 = CH2CH2COOH. In 2a
and 3a: R1 = CH2OH; 2b and 3b: R1 = CH (CH3)OH; 2c and 3c: R1 = CH2COOCH3; 2d and 3d: R1 = CH2CH2COOCH3. In 4a: R2 = CH2OH;
4b: R2 = CH(CH3)OH; 4c: R2 = CH2CH2OH; 4d: R2 = CH2CH2CH2OH.
Scheme 2. Synthetic route to compounds 5a–d and 5a0. Reagents and conditions: (iv): 6% orthophosphoric acid, rt; (v) For 5a–d: TABCO (cat), diol
4a–d, and (EtO)3CH, 50 ꢁC; for 5a0: diol 4a, TFA/CHCl3, 15 ꢁC, 4 h. In 5a: X = CH2, R1 = CH2CH(OCH3)2, R2 = H; 5a0: X = CH2, R1 = H,
R2 = CH2CH(OCH3)2; 5b: X = (S)-CHCH3, R1 = CH2CH(OCH3)2, R2 = H; 5c: X = CH2CH2, R1 = CH2CH(OCH3)2, R2 = H; 5d:
X = CH2CH2CH2, R1 = CH2CH(OCH3)2, R2 = H.
Scheme 3. Synthetic route to compounds 7a–d. Reagents and conditions: (vi) oxalic acid, silica gel, CHCl3, rt; (vii) TFA/CHCl3, 50 ꢁC. In 5a and 6a:
X = CH2; 5b and 6b: X = (S)-CHCH3; 5c and 6c: X = CH2CH2; 5d and 6d: X = CH2CH2CH2. In 7a: X = CH2, R = CH2CH(OCH3)OC2H5;
7b: X = CH2, R = 1,3-dioxapentan-2-yl-methylene; 7c: X = (S)-CHCH3, R = (2S,4S,5S)-4-methyl-5-phenylacetamino-1,3-dioxan-2-yl-methylene;
7d: X = CH2CH2, R = (2S,5S)-5-phenylacetamino-1,3-dioxacyclooctan-2-yl-methylene.

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L. Bi et al. / Bioorg. Med. Chem. 13 (2005) 5640–5646
Table 1. Anti-inflammatory activity of 1,3-dioxane derivatives against
xylene-induced ear edema in mice
two rings are in a syn-arrangement. On the basis of NOE
experiment, 7d was assigned as the syn-arrangement for
the respective substitutions of 2-, 4- and 5-position on its
hexacyclic ring and the syn-arrangement was also ob-
served for both substitutions of 2- and 5-position on
its heptacyclic ring. On the other hand, it was observed
that 4a was converted to 5a0 upon treatment with equal
amount of 3,3-dimethoxypropanal using TFA as cata-
lyst at 15 ꢁC for 4 h. Under similar conditions, the ace-
talization of both 6b and 4b afforded 7c0 as the sole
product. The NOE difference experiment showed that
substitutions of 2- and 5-positions of 5a0 and 7c0 are in
an anti-arrangement, because no NOE was observed
between the NH at the 5-position and the CH2 at the
2-position.
Agents
Anti-inflammatory activity
Edema weight (X SD mg) Inhibition (%)
CMC
Aspirin
DMPA
4a
7.76 1.55
4.17 1.80a
8.30 1.87
7.99 2.09
8.02 2.04
6.97 1.99
7.03 1.78
1.32 1.13a,d,e
2.12 1.34a,d,e
2.76 1.21a,d,e
4.31 1.46a
4.10 1.49a
5.80 1.56b
5.86 1.65b
5.55 1.98
5.90 1.75c
3.41 1.86a,f
3.73 1.33a,f
5.23 1.69b
5.11 1.23b
5.95 1.95c
N
46.3
N
N
4b
4c
N
10.2
9.4
4d
5a
5a0
83.0
72.7
64.4
44.5
47.2
25.3
24.5
28.5
24.0
56.0
51.9
32.6
34.1
23.3
5b
5c
5d
6a
To further confirm the stereochemical assignment of
these compounds, configuration conversion experiment
was carried out. When concentrated hydrochloric acid
was employed as catalyst at 50 ꢁC for 12 h, both 5a0
and 7c0 were converted to 5a and 7c, respectively. With
these configuration conversions, 5a0 and 7c0 were con-
firmed to be kinetically controlled products, whereas
5a and 7c were thermodynamically stable products.
This is an interesting example which shows the possi-
bility for isomer conversion from the thermodynami-
cally less stable compounds to the more stable ones.
These results enable us to tune and acquire the desired
stereospecificity by changing the experimental condi-
tions, for example, reaction time, temperature, and
catalyst.
6b
6c
6d
7a
7b
7c
7c0
7d
Dose = 20 mg/kg. DMPA = 3,3-dimethoxypropanal.
a Compared to CMC, DMPA, and 4a–d, p < 0.001.
b Compared to CMC, p < 0.01.
c Compared to CMC, p < 0.05.
d Compared to Aspirin, p < 0.05.
e Compared to 5c,d and 6a–d and 7c,d, p < 0.05.
f Compared to 7c,c0,d, p < 0.01.
All the 2,5-disubstituted-dioxacycloalkanes synthesized
were evaluated for their anti-inflammatory activity by
using a xylene-induced ear edema model assay.14 Briefly,
the in vivo assay involves the test compounds being
administrated orally in 0.5% carboxymethyl cellulose
(CMC) suspension. Each compound was initially tested
at a concentration of 20 mg/kg. It was observed that se-
ven of the tested compounds showed significant inhibi-
tion against xylene-induced inflammation in mice as
compared with the control (Table 1), indicating that
these compounds possess potent anti-inflammatory
activity. It was especially noted that the most potent
compound, 5a, exhibited an even higher anti-inflamma-
tory activity than the standard reference drug Aspirin.
Subsequently, compounds with significant activity
(namely 5a, 5b, 7a, 7b) were administrated in a series
of lower concentration doses to enable a detailed phar-
macological activity profile (Table 2).
Table 2. Anti-inflammatory activity of 5a,b and 7a,b at different doses
against xylene-induced ear edema in mice
Agents
Dose (mg/kg)
Edema weight (X SD mg)
5a
5b
7a
7b
5a
5b
7a
7b
5a
5b
7a
7b
20
20
20
20
4
2.32 1.13a
2.76 1.21a
3.41 1.86a
3.73 1.33b
4.62 1.09c
4.95 1.17d
5.69 1.21d
5.44 1.14d
6.62 1.21
6.77 1.19
7.03 1.26
7.15 1.33
4
4
4
0.8
0.8
0.8
0.8
a Compared to 4.0 mg/kg group, p < 0.001.
b Compared to 4.0 mg/kg group, p < 0.01.
c Compared to 0.8 mg/kg group, p < 0.001.
d Compared to 0.8 mg/kg group, p < 0.01.
Structure–activity relationship studies were also per-
formed on a series of phenylacetaminodiols compounds
to assess whether the presence of 1,3-dioxacycle rings is
required for anti-inflammatory activity. Observations
that both diol and 3,3-dimethoxypropanal were ineffec-
tive as anti-inflammatory compounds suggested that
the rigid 1,3-dioxacycle ring should be retained. To
examine the importance of the spatial disposition, two
pairs of cyclic acetals with different stereochemistries
were evaluated. Comparing compound 5a with 5a0 and
7c with 7c0, their comparable anti-inflammatory activi-
ties indicated that stereochemical constraints of these
2,5-disubstituted-dioxacycloalkanes exhibited little or
no effect toward their anti-inflammatory activities.
To investigate the effect of heterocyclic ring sizes, the
anti-inflammatory activities of compounds 5a–d and
7a,b were compared. It was observed that the potencies
of 5a,b and 7a,b are significantly higher than those of
5c,d and 7c. These observations indicate that the anti-in-
flammatory activity of 1,3-dioxane is more potent than
either 1,3-dioxacycloheptane or 1,3-dioxacyclooctane,

L. Bi et al. / Bioorg. Med. Chem. 13 (2005) 5640–5646
5643
suggesting that 2,5-disubstituted-1,3-dioxacycloalkane
cannot be further maximized. In addition, based on
the observations that 6a–d exhibited a loss in their in
vivo anti-inflammatory activity, we hypothesized the
cyclic acetals 5a–d do not exert their in vivo anti-inflam-
matory activities through hydrolytic conversion from
5a–d to 6a–d.
(3 · 30 mL). The chloroform phase was dried with
Na2SO4. After filtration and evaporation, 4a–d were
obtained as colorless crystals in 91–98% yields.
3.1.2. N-[2-Hydroxy-1-(hydroxymethyl)ethyl]phenylaceta-
mide (4a). Mp 135–136 ꢁC. IR (KBr, cmꢀ1) m: 3452,
3343, 3028, 3004, 2962, 2834, 1638, 1604, 1573, 1505,
1452, 721, 662. 1H NMR (DMSO-d6 d): 3.53 (d,
J = 5.7 Hz, 4H), 3.62 (s, 2H), 3.95 (m, J = 6.0 Hz, 1H),
4.64 (br, 2H), 7.43 (d, J = 8.1 Hz, 2H), 7.54 (t,
J = 7.2 Hz, 1H), 7.64 (d, J = 7.5 Hz, 2H), 8.11 (d,
J = 7.6 Hz, 1H). FAB-MS m/z (%): 210 [M+H]+. Anal.
Calcd for C11H15NO3: C, 63.12, H, 7.23, N, 6.70.
Found: C, 63.35; H, 7.06; N, 6.59.
Compound 5a also showed anti-inflammatory activity in
the PMA (phorbol–myristate–acetate) induced mouse
ear edema model,12,15 which is a model of PKC-medi-
ated acute inflammation. The in vivo anti-inflammatory
effect of 2,5-disubstituted-dioxacycloalkanes most likely
occurs via the inhibition of certain key enzymes involved
in inflammation and/or cell signaling pathways, in which
PKC is most likely the target protein. Experiments are
currently underway to ascertain the protein target(s) of
the dioxacycloalkane compounds, in which other possi-
ble protein targets may also include cyclooxygenase and
lipoxygenase, and phosphoinositide 3-kinase. Identifica-
tion and understanding the mechanism underlying the
enzyme inhibition processes should prove beneficial for
future treatment of inflammatory conditions.
3.1.3. (1S,2R)-N-[2-Hydroxy-1-(hydroxymethyl)propyl]-
)
phenylacetamide (4b). Mp 125–127 ꢁC. IR (KBr, cmꢀ1
m: 3451, 3362, 3033, 3005, 2965, 2862, 1643, 1608,
1
1592, 1505, 1482, 712, 651. H NMR (DMSO-d6, d):
1.22 (d, J = 6.9 Hz, 3H), 3.53 (s, 2H), 3.64 (s, 2H),
3.85 (d, J = 6.6 Hz, 2H), 3.96 (m, J = 6.4 Hz, 1H), 4.24
(q, J = 6.0 Hz, 1H), 7.19 (d, J = 7.8 Hz, 1H), 7.35 (t,
J = 7.6 Hz, 2H), 7.54 (d, J = 7.8 Hz, 2H), 8.04 (d,
20
D
J = 7.5 Hz, 1H). FAB-MS m/z (%): 224 [M+H]+. ½aꢁ
In summary, a precise and efficient stereochemically
controlled synthetic route to enable a series of 2,5-disub-
stituted-dioxacycloalkane compounds is presented. The
dioxacycloalkane compounds possess dose-dependent
in vivo anti-inflammatory properties, and it was found
that both their ring sizes and substitutions at the 2-posi-
tion have significant effects on their inhibitory
properties.
ꢀ32.5ꢁ (c 0.02, CH3OH). Anal. Calcd for C12H17NO3:
C, 64.50; H, 7.67; N, 6.27. Found: C, 64.62; H 7.56;
N, 6.39.
3.1.4.
phenylacetamide (4c). Mp 132–134 ꢁC. IR (KBr, cmꢀ1
(1S)-N-[3-Hydroxy-1-(hydroxymethyl)propyl]-
)
m: 3415, 3344, 3023, 3006, 2964, 2833, 1632, 1602,
1
1585, 1506, 1463, 715, 651. H NMR (DMSO-d6, d):
1.63 (dt, J = 5.6 Hz, J = 3.3 Hz, 1H), 1.76 (dt,
J = 4.7 Hz, J = 2.7 Hz, 1H), 3.40 (t, J = 3.9 Hz, 1H),
3.43 (t, J = 3.9 Hz, 1H), 3.49 (s, 2H), 3.66 (s, 2H), 4.06
(dq, J = 3.7 Hz, J = 2.5 Hz, 1H), 4.44 (t, J = 3.9 Hz,
1H), 4.75 (t, J = 3.9 Hz, 1H), 7.16 (t, J = 4.5 Hz, 1H),
7.32 (t, J = 7.5 Hz, 2H), 7.64 (t, J = 7.5 Hz, 2H), 8.03
3. Materials and methods
3.1. Experimental section
All reactions were carried out under nitrogen (1 bar). 1H
NMR spectra were recorded at 300 MHz on a VXR-300
instrument or at 500 MHz on an ARX-500 instrument
in CDCl3 with tetramethylsilane as the internal stan-
dard. IR spectra were recorded with a Perkin-Elmer
983 instrument and mass spectra with a ZAB-MS
(70 eV) spectrometer. Chromatography was performed
with Qingdao silica gel H. Optical rotations were deter-
mined on a Schmidt and Haensch Polartronic D instru-
ment at 20 ꢁC.
(d, J = 5.5 Hz, 1H). FAB-MS m/z (%): 224 [M+H]+.
20
D
½aꢁ
ꢀ28.4ꢁ (c 0.02, CH3OH). Anal. Calcd for
C11H15NO3: C, 64.50; H, 7.67; N, 6.27. Found: C,
64.32; H, 7.52; N, 6.43.
3.1.5. (1S)-N-[4-Hydroxy-1-(hydroxymethyl)butyl]phenyl-
acetamide (4d). Mp 102–104 ꢁC. IR (KBr, cmꢀ1) m: 3425,
3345, 3033, 3004, 2952, 2841, 1636, 1604, 1587, 1505,
1442, 723 662. 1H NMR (DMSO-d6, d): 1.45 (q,
J = 3.6 Hz, 2H), 1.49 (m, J = 4.5 Hz, 1H), 1.68 (m,
J = 4.8 Hz, 1H), 3.35 (t, J = 6.6 Hz, 1H), 3.38 (s, 2H),
3.43 (t, J = 6.6 Hz, 1H), 3.66 (s, 2H), 3.96 (dq,
J = 3.9 Hz, J = 2.4 Hz, 1H), 4.41 (t, J = 3.8 Hz, 1H),
4.67 (t, J = 3.9 Hz, 1H), 7.15 (t, J = 7.5 Hz, 1H), 7.31
3.1.1. General procedure for phenylacetaminodiols 4a–d.
L–Ser, L-Thr, L-Asp, or L-Glu were esterified to 2a–d by
methanol in 96–98 % yield and treated with phenylacetyl
chloride to give 3a–d in 75–81% yield.10,11
(t, J = 7.4 Hz, 1H), 7.36 (d, J = 7.6 Hz, 2H), 8.06 (d,
20
D
J = 4.9 Hz, 1H). FAB-MS m/z (%): 238 [M+H]+. ½aꢁ
A solution of 3a–d (4.5 mmol) in tetrahydrofuran (THF)
(10 mL) was slowly added to a suspension of sodium
borohydride (5.6 mmol) in THF (10 mL). The reaction
mixture was stirred at room temperature for 24 h until
thin-layer of chromatography (TLC) (CHCl3/CH3OH,
30:1) indicated complete disappearance of 3a–d. The
reaction mixture was adjusted to pH 7 with hydrochloric
acid (3%). After evaporation, the residue was dissolved
in 50 mL of chloroform and washed with water
ꢀ23.3ꢁ (c 0.02, CH3OH). Anal. Calcd for C13H19NO3:
C, 65.80; H, 8.07; N, 5.90. Found: C, 65.92; H, 8.26; N,
6.11.
3.1.6. 3,3-Dimethoxypropanal. Aqueous orthophos-
phoric acid (1 mL, 6%) was added to 1,1,3,3-tetrameth-
oxypropane (2.0 g, 12.2 mmol), and the mixture
was stirred at rt for 40 h until TLC (petroleum ether/
ether, 2:1) indicated the complete consumption of 1,1,3,

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L. Bi et al. / Bioorg. Med. Chem. 13 (2005) 5640–5646
3-tetramethoxypropane. Ether (30 ml) was added to the
above mixture, and the solution neutralized with sodium
carbonate and filtered. The filtrate was subsequently
concentrated and the residue was purified with flash
chromatography (petroleum ether/ether, 2:1) to give
850 mg (60%) of the title compound as a colorless syrup.
IR (KBr, cmꢀ1) m: 3000, 2944, 2839, 1735, 1622, 1453,
1391, 1144, 935. 1H NMR (DMSO-d6, d): 2.76 (dd,
J = 7.6 and 7.3 Hz, 2H), 3.42 (s, 6H), 4.69 (t, J = 7.3
Hz, 1H), 9.75 (t, J = 7.6 Hz, 1H).
J = 6.75.0 Hz, 2H), 3.66 (s, 2H), 3.94 (d, J = 7.2 Hz,
1H), 4.08 (d, J = 7.2 Hz, 1 H), 4.32 (dt, J = 5.8 2.7 Hz,
1H), 4.55 (t, J = 5.6 Hz, 1H), 4.85 (t, J = 4.3 Hz, 1 H),
6.91 (d, J = 5.5 Hz, 1H), 7.17 (t, J = 7.4 Hz, 2H), 7.36
(t, J = 7.6 Hz, 1H), 7.50 (d, J = 7.4 Hz, 2H). FAB-MS
20
m/z (%): 324 [M+H]+. ½aꢁ ꢀ11.0ꢁ (c 0.02, CH3OH).
D
Anal. Calcd for C17H25NO5: C, 63.14; H, 7.79; N,
4.33. Found: C, 63.01; H, 7.66; N, 4.49.
3.1.10. [(2R,5S)-N-2-(2,2-Dimethoxyethyl)-1,3-dioxacy-
clooctan-5-yl]phenylacetamide (5d). A similar procedure
was used as that for the preparation of 5a, starting from
4d (119 mg, 0.5 mmol), the title compound (123 mg,
yield 76%) was obtained as a colorless powder. Mp
125–127 ꢁC. IR (KBr, cmꢀ1) m: 3460, 3051, 2952, 2891,
2822, 1651, 1602, 1593, 1508, 1455, 1372, 1192, 1085,
3.1.7.
(cis)-N-[2-(2,2-Dimethoxyethyl)-1,3-dioxan-5-
yl]phenylacetamide (5a). To a solution of 3,3-dimethoxy-
propanal (94 mg, 0.5 mmol), triethyl orthoformate
(0.5 mmol) and 4a (105 mg, 0.5 mmol) in acetonitrile
(10 mL),
2,4,4,6-tetrabromo-2,5-cyclohexadienone
1
(TABCO) (0.005 mmol) was added. The reaction mix-
ture was stirred at 50 ꢁC until TLC indicated the com-
pletion of the reaction, and then neutralized with
sodium carbonate. The product was extracted with ethyl
acetate (3 · 10 mL). The organic layer was separated,
dried over anhydrous Na2SO4, and concentrated, puri-
fied with flash chromatography (CHCl3/CH3OH, 30:1)
to give 135 mg (yield 86%) of the title compound as a
colorless powder. Mp 139–141 ꢁC. IR (KBr, cmꢀ1) m:
3264, 3060, 2920, 2852, 1620, 1601, 1569, 1540, 1446,
762, 688. H NMR (DMSO-d6, d): 1.78 (m, J = 5.2 Hz,
4H), 1.93 (dd, J = 6.2 Hz, J = 4.9 Hz, 2H), 3.30 (s,
3H), 3.32 (s, 3H), 3.52 (d, J = 7.2 Hz, 1H), 3.65 (s,
2H), 3.88 (d, J = 7.2 Hz, 1H), 4.31 (dt, J = 5.6 Hz,
J = 2.4 Hz, 1H), 4.48 (t, J = 6.1 Hz, 1H), 4.55 (m,
J = 4.8 Hz, 2H), 6.64 (t, J = 9.3 Hz, 1H), 7.19 (t,
J = 7.6 Hz, 2H), 7.48 (t, J = 7.6 Hz, 1H), 7.70
(d, J = 7.2 Hz, 2 H). FAB-MS m/z (%): 338 [M+H]+.
20
D
½aꢁ
ꢀ14.5ꢁ (c 0.02, CH3OH). Anal. Calcd for
C18H27NO5: C, 64.07; H, 8.07 N, 4.15. Found: C,
63.98; H, 7.99; N, 4.26.
1
1380, 1360, 1189, 1074, 721, 696. H NMR (DMSO-d6,
d): 1.96 (t, J = 7.9 Hz, 2H), 3.36 (s, 6H), 3.64 (s, 2H),
4.06 (d, J = 12.4 Hz, 4H), 4.12 (m, J = 9.5 Hz, 1H), 4.55
(t, J = 6.3 Hz, 1H), 4.77 (d, J = 6.3 Hz, 1H), 7.08
(d, J = 9.4 Hz, 1H), 7.23 (t, J = 9.1 Hz, 2H), 7.51
(d, J = 9.1 Hz, 1H), 7.70 (d, J = 9.1 Hz, 2H). FAB-MS
m/z (%) 310 [M+H]+. Anal. Calcd for C16H23NO5:
C, 62.12; H, 7.49; N, 4.53. Found: C, 62.30; H, 7.30; N,
4.62.
3.1.11. (trans)-N-[2-(2,2-Dimethoxyethyl)-1,3-dioxan-5-
yl]phenylamide (5a0). To a solution of 4a (105 mg,
0.5 mmol)
and
3,3-dimethoxypropanal
(94 mg,
0.5 mmol) in 10 mL of chloroform, 20 mg of trifluoro-
acetic acid was added. The reaction mixture was stirred
at 15 ꢁC for 4 h, and then neutralized with sodium car-
bonate. The residue was purified by flash chromato-
graphy (CH3Cl/CH3OH, 30:1) to give 143 mg (yield
92%) of the title compound as colorless powder. Mp.
122–124 ꢁC. IR (KBr, cmꢀ1) m: 3287, 3055, 2962, 2931,
2852, 1638, 1604, 1549, 1456, 1405, 1382, 1191, 1086,
3.1.8. [(2S,4R,5R)-N-2-(2,2-Dimethoxyethyl)-4-methyl-
1,3-dioxan-5-yl]phenylacetamide (5b). A similar proce-
dure was used as that for the preparation of 5a, starting
from 4b (112 mg, 0.5 mmol), the title compound
(130 mg, yield 80%) was obtained as colorless syrup.
IR (KBr, cmꢀ1) m: 3432, 3051, 2970, 2930, 2865, 1660,
1593, 1570, 1475, 1406, 1375, 1355 1178, 1065, 710,
1
707, 682. H NMR (DMSO-d6, d): 1.96 (t, J = 5.3 Hz,
2H), 3.37 (s, 6H), 3.45 (d, J = 11.2 Hz, 4H), 3.65 (s,
2H), 4.45 (m, J = 3.9 Hz, 1H), 4.53 (t, J = 7.8 Hz,
1H), 4.56 (t, J = 7.8 Hz, 1H), 5.64 (d, J = 7.8 Hz, 1H),
5.72 (d, J = 7.8 Hz, 1H), 7.19 (t, J = 9.1 Hz, 2H), 7.43
1
690. H NMR (DMSO-d6, d): 1.21 (d, J = 8.1 Hz, 3H),
1.98 (t, J = 5.1 Hz, 2H), 3.35 (s, 6 H), 3.66 (s, 2H),
3.96 (d, J = 9.7 Hz, 1H), 3.99 (q, J = 5.4 Hz, 1H), 4.04
(d, J = 14.1 Hz, 1H), 4.14 (dt, J = 5.5 Hz, J = 1.5 Hz,
1H), 4.62 (t, J = 5.3 Hz, 1H), 4.75 (d, J = 5.3 Hz, 1H),
6.82 (d, J = 10.1 Hz, 1H), 7.15 (t, J = 7.4 Hz, 2H), 7.53
(d, J = 9.1 Hz, 1H), 7.71 (d, J = 9.1 Hz, 2H). FAB-MS
20
m/z (%): 310 [M+H]+. ½aꢁ ꢀ16.4ꢁ (c 0.02, CH3OH).
D
Anal. Calcd for C16H23NO5: C, 62.12; H, 7.49; N,
4.53. Found: C, 62.01; H, 7.55; N, 4.40.
(t, J = 7.5 Hz, 1H), 7.73 (d, J = 8.0 Hz, 2H). FAB-MS
3.1.12.
[(cis)-N-(2-Carbonylmethyl-1,3-dioxan-5-yl)]-
20
m/z (%): 324 [M+H]+. ½aꢁ ꢀ23.0ꢁ (c 0.02, CH3OH).
phenylamide (6a). To a mixture of 5a (309 mg, 1.0 mmol)
and 30 mg of silica gel in chloroform (20 mL), 30 mg of
oxalic acid was added. The reaction mixture was stirred
at 45 ꢁC for 40 h, and then neutralized with sodium car-
bonate, filtered, and concentrated. The crude product
was purified with flash chromatography (CHCl3/
CH3OH, 50:1) to give 225 mg (yield 85%) of the title
compound as colorless syrup. IR (KBr, cmꢀ1) m: 3304,
3021, 2961, 2922, 2855, 1762, 1631, 1604, 1570, 1543,
D
Anal. Calcd for C17H25NO5: C, 63.14; H, 7.79; N,
4.33. Found: C, 63.32; H, 7.96; N, 4.13.
3.1.9. [(2R,5S)-N-2-(2,2-Dimethoxyethyl)-1,3-dioxacy-
cloheptan-5-yl]phenylacetamide (5c). A similar procedure
was used as that for the preparation of 5a, starting from
4c (112 mg, 0.5 mmol), the title compound (138 mg,
yield 85%) was obtained as a colorless powder. Mp
117–119 ꢁC. IR (KBr, cmꢀ1) m: 3308, 3052, 2970, 2929,
2858, 1642, 1602, 1565, 1451, 1380, 1189, 1084,
1
1448, 1200, 1067, 727, 692. H NMR (DMSO-d6, d):
2.77 (d, J = 3.8 Hz, 2H), 3.64 (s, 2H), 4.28 (d,
J = 5.6 Hz, 2H), 4.33 (d, J = 6.5 Hz, 2H), 4.46 (m,
J = 3.8 Hz, 1H), 4.95 (t, J = 4.8 Hz, 1 H), 5.98 (d,
1
722, 692. H NMR (DMSO-d6, d): 1.90 (q, J = 5.2 Hz,
2H), 1.94 (t, J = 5.3 Hz, 2H), 3.37 (s, 6H), 3.63 (dd,

L. Bi et al. / Bioorg. Med. Chem. 13 (2005) 5640–5646
5645
J = 7.5 Hz, 1H), 7.36 (t, J = 7.2 Hz, 2H), 7.50 (d,
J = 7.2 Hz, 1H), 7.72 (d, J = 7.2 Hz, 2H), 9.81 (t, J =
2.5 Hz, 1H). FAB-MS m/z (%): 264 [M+H]+. Anal.
Calcd for C14H17NO4: C, 63.87; H, 6.51; N, 5.32.
Found: C, 63.99; H, 6.70; N, 5.50.
10 mL of chloroform was added. The reaction mixture
was stirred at 50 ꢁC for 8 h, and then neutralized with
sodium carbonate, filtered, concentrated. The residue
was purified by flash chromatography (CHCl3/CH3OH,
30:1) to give 289 mg (yield 89%) of the title compound as
colorless powder. Mp 136–138 ꢁC. IR (KBr, cmꢀ1) m:
3262, 3058, 2918, 2850, 1622, 1603, 1564, 1542, 1443,
3.1.13. (2S,4S,5R)-[N-(2-Carbonylmethyl)-4-methyl-1,3-
dioxan-5-yl]phenylacetamide (6b). Similar procedure
was used as that for the preparation of 6a. Starting from
5b (323 mg, 1.0 mmol), 227 mg (yield 82%) of the title
compound was obtained as colorless syrup. IR (KBr,
cmꢀ1) m: 3442, 3059, 2968, 2939, 2862, 1758, 1648,
1
1384, 1361, 1187, 1070, 722, 694. H NMR (DMSO-d6,
d): 1.76 (t, J = 4.9 Hz, 2 H), 1.99 (t, J = 7.8 Hz, 2H),
3.33 (q, J = 4.9 Hz, 2H), 3.36 (s, 3H), 3.66 (s, 2H), 4.03
(d, J = 12.1 Hz, 4H), 4.14 (m, J = 9.2 Hz, 1H), 4.53
(t, J = 6.5 Hz, 1H), 4.75 (d, J = 6.5 Hz, 1H), 7.05 (d,
J = 8.6 Hz, 1H), 7.21 (t, J = 9.0 Hz, 2H), 7.49 (d,
J = 9.0 Hz, 1H), 7.73 (d, J = 9.0 Hz, 2H). FAB-MS m/z
(%): 324 [M+H]+. Anal. Calcd for C17H25NO5: C,
63.14; H, 7.79; N, 4.33. Found: C, 63.01; H, 7.66; N,
4.51.
1
1602, 1573, 1480, 1415, 1381, 1174, 1062, 716, 694. H
NMR (DMSO-d6, d): 1.28 (d, J = 6.1 Hz, 3H), 2.82 (d,
J = 3.7 Hz, 2H), 3.66 (s, 2H), 4.03 (d, J = 10.4 Hz,
1H), 4.07 (d, J = 10.4 Hz, 1H), 4.14 (m, J = 10.7 Hz,
1H), 4.15 (t, J = 8.5 Hz, 1H), 5.25 (t, J = 7.8 Hz, 1H),
6.82 (d, J = 6.5 Hz, 2H), 7.37 (t, J = 7.5 Hz, 1H), 7.54
(t, J = 7.4 Hz, 2H), 9.84 (t, J = 2.6 Hz, 1H). FAB-MS
3.1.17. (cis)-[N-2-(1,3-Dioxolan-2-yl)methyl-1,3-dioxan-
5-yl]phenylacetamide (7b). A similar procedure was used
as that for the preparation of 7a. Starting from 6b
(263 mg, 1.0 mmol) and glycol (62 mg, 1.0 mmol),
268 mg (yield 87%) of the title compound was obtained
as colorless powder. Mp 127–129 ꢁC. IR (KBr, cmꢀ1) m:
3320, 3038, 2948, 2841, 1636, 1601, 1504, 1447, 1459,
20
D
m/z (%): 278 [M+H]+. ½aꢁ ꢀ26.2ꢁ (c 0.02, CH3OH).
Anal. Calcd for C15H19NO4: C, 64.97; H, 6.91; N,
5.05. Found: C, 64.78; H, 6.82; N 5.20.
3.1.14. (2R,5S)-[N-(2-Carbonylmethyl)-1,3-dioxacyclo-
heptan-5-yl]phenylacetamide (6c). Similar procedure
was used as that for the preparation of 6a. Starting from
5c (323 mg, 1.0 mmol), 209 mg (yield 75%) of the title
compound was obtained as colorless syrup. IR (KBr,
cmꢀ1) m: 3441, 3056, 2969, 2941, 2860, 1761, 1644,
1605, 1575, 1482, 1418, 1380, 1172, 1064, 717, 692 .
1H NMR (DMSO-d6, d): 1.87 (q, J = 5.5 Hz, 2H), 1.94
(t, J = 5.5 Hz, 2H), 3.61 (dd, J = 6.5 5.2 Hz, 2H), 3.65
(s, 2H), 3.96 (d, J = 7.4 Hz, 1H), 4.11 (d, J = 7.5 Hz,
1H), 4.34 (dt, J = 5.9 2.5 Hz, 1 H), 4.57 (t, J = 5.8 Hz,
1H), 6.03 (d, J = 7.6 Hz, 1H), 6.87 (t, J = 4.5 Hz, 1H),
7.19 (t, J = 7.5 Hz, 2H), 7.38 (t, J = 7.4 Hz, 1H), 7.53
1
1189, 1078, 737, 699. H NMR (DMSO-d6, d): 2.07 (t,
J = 6.1 Hz, 2H), 3.66 (s, 2H), 3.86 (t, J = 5.9 Hz, 2H),
4.01 (t, J = 6.0 Hz, 2H), 4.08 (d, J = 8.1 Hz, 4H), 4.10
(m, J = 8.0 Hz, 1H), 4.83 (t, J = 6.3 Hz, 1H), 5.00 (t,
J = 6.3 Hz, 1H), 7.11 (d, J = 8.0 Hz, 1H), 7.43 (t, J =
7.9 Hz, 2H), 7.55 (d, J = 7.9 Hz, 1H), 7.81 (d,
J = 7.3 Hz, 2H). FAB-MS m/z (%): 308 [M+H]+. Anal.
Calcd for C16H21NO5: C, 62.53; H, 6.89; N, 4.56.
Found: C, 62.70; H, 6.99; N, 4.72.
3.1.18.
N,N0-Methylenebis[(2S,4R,5R)/(2R,4S,5S)-4-
(d, J = 7.5 Hz, 2H), 9.81 (t, J = 2.7 Hz, 1 H). FAB-MS
methyl-1,3-dioxan-2,5-diyl]bisphenyl-acetamide (7c). A
similar procedure was used as that for the preparation
of 7a. Starting from 6b (277 mg, 1.0 mmol) and 4b
(223 mg, 1.0 mmol), 398 mg (yield 85%) of the title com-
pound was obtained as colorless powder. Mp 122–
124 ꢁC. IR (KBr, cmꢀ1) m: 3545, 3409, 3060, 2969, 2920,
2852, 1648, 1625, 1597, 1526, 1481, 1417, 1380, 1354,
20
m/z (%): 278 [M+H]+. ½aꢁ ꢀ14.5ꢁ (c 0.02, CH3OH).
D
Anal. Calcd for C15H19NO4: C, 64.97; H, 6.91; N,
5.05. Found: C, 65.12; H, 7.10; N, 4.98.
3.1.15. (2R,5S)-[N-(2-Carbonylmethyl)-1,3-dioxacyclooc-
tan-5-yl]phenylacetamide (6d). Similar procedure was
used as that for the preparation of 6a. Starting from
5d (337 mg, 1.0 mmol), 207 mg (yield 71%) of the title
compound was obtained as a colorless syrup. IR (KBr,
cmꢀ1) m: 3444, 3058, 2966, 2942, 2865, 1760, 1641,
1
1180, 1063, 719, 691. H NMR (DMSO-d6, d): 1.25 (d,
J = 6.7 Hz, 6H), 2.07 (t, J = 6.1 Hz, 4H), 3.65 (s, 2H),
3.94 (d, J = 7.2 Hz, 2H), 4.09 (d, J = 12.0 Hz, 2H), 4.42
(q, J = 7.2 Hz, 2H), 4.11 (dt, J = 8.8 Hz, J = 2.5 Hz,
2H), 4.84 (t, J = 6.2 Hz, 2H), 6.78 (d, J = 6.1 Hz, 2H),
7.44 (t, J = 8.9 Hz, 4H), 7.51 (t, J = 8.3 Hz, 2H), 7.81 (d,
J = 8.4 Hz, 4 H). FAB-MS m/z (%): 469 [M+H]+. Anal.
Calcd for C26H32N2O6: C, 66.65; H, 6.88; N, 5.98. Found:
C, 66.67; H, 6.70; N, 5.79.
1
1602, 1577, 1480, 1415, 1382, 1170, 1062, 715, 690. H
NMR (DMSO-d6, d): 1.82 (m, J = 5.4 Hz, 4H), 1.94
(dd, J = 6.4 4.5 Hz, 2H), 3.54 (d, J = 7.4 Hz, 1H), 3.64
(s, 2H), 3.92 (d, J = 7.4 Hz, 1H), 4.33 (dt, J = 5.8 2.7
Hz, 1H), 4.46 (t, J = 6.2 Hz, 1H), 4.56 (m, J = 4.9 Hz,
2H), 6.65 (d, J = 7.4 Hz, 1H), 7.22 (t, J = 7.6 Hz, 2H),
7.39 (t, J = 7.5 Hz, 1H), 7.68 (d, J = 7.5 Hz, 2H), 9.77
3.1.19. N,N0-Methylene[(2S,4R,5R)-4-methyl-1,3-dioxan-
2,5-diyl]-[(20S,50R)-1,3-dioxacyclo-octan-2,5-diyl]bisphenyl-
acetamide (7d). A similar procedure was used as that for
the preparation of 7a. Starting from 6c (277 mg,
1.0 mmol) and 4c (223 mg, 1.0 mmol), 393 mg (yield
84%) of the title compound was obtained as a colorless
powder. Mp 132–134 ꢁC. IR (KBr, cmꢀ1) m: 3552, 3448,
3058, 2973, 2908, 2849, 1652, 1628, 1602, 1527, 1478,
(t, J = 2.8 Hz, 1H). FAB-MS m/z (%): 292 [M+H]+.
20
D
½aꢁ
ꢀ17.1ꢁ (c 0.02, CH3OH). Anal. Calcd for
C16H21NO4: C, 65.96; H, 7.27; N, 4.81. Found C,
65.87; H, 7.40; N, 4.96.
3.1.16. (cis)-[N-2-(2-Ethoxy-2-methoxyethyl)-1,3-dioxan-
5-yl]phenylacetamide (7a). To a solution of 6a (263 mg,
1.0 mmol) in methanol (32 mg, 1.0 mmol) and ethanol
(46 mg, 1.0 mmol), 20 mg of trifluoroacetic acid in
1
1401, 1373, 1178, 1060, 728, 685. H NMR (DMSO-
d6, d): 1.24 (d, J = 6.5 Hz, 3H), 1.98 (m, J = 5.5 Hz,

5646
L. Bi et al. / Bioorg. Med. Chem. 13 (2005) 5640–5646
2H), 2.05 (t, J = 7.5 Hz, 2H), 3.65 (s, 2H), 3.95 (d,
J = 12.5 Hz, J = 3.2 Hz, 2H), 3.75 (d, 1H), 3.92 (d,
J = 8.2 Hz, 2H), 3.95 (d, J = 12.5 3.2 Hz, 2H), 4.15 (d,
J = 10.5 Hz, 2H), 4.27 (m, J = 5.9 Hz, 1H), 4.47 (m,
J = 5.9 Hz, 1H), 4.84 (t, J = 4.8 Hz, 1H), 4.97 (t,
J = 9.2 Hz, 1H), 6.78 (d, J = 6.7 Hz, 1H), 6.83 (d,
J = 6.6 Hz, 1H), 7.44 (t, J = 7.3 Hz, 2H), 7.48 (t,
J = 7.3 Hz, 2H), 7.78 (d, J = 7.4 Hz, 2H), 7.83 (d,
in weight caused by the irritant was measured through
subtracting the weight of the untreated left ear section
from that of the treated right ear section. The statistical
analysis of the data was carried out by use of ANOVA
test, p < 0.05 is considered significant. Inhibition
percentage was expressed as a reduction in weight with
respect to the control group.
J = 7.3 Hz, 2H). FAB-MS: m/z (%) = 469 [M+H]+.
20
D
Acknowledgments
½aꢁ
ꢀ17.2ꢁ (c 0.02, CH3OH). Anal. Calcd for
C26H32N2O6: C, 66.65; H, 6.88; N, 5.98. Found: C,
66.46; H, 6.99; N, 6.11.
P.S. wishes to thank National Key-Basic Project of
China (2003CCA04400), National Natural Science
Foundation of China (20232020 and 30372433), and Sci-
entific Foundation Guangzhou City of China for finan-
cial support. Work performed in LLNL is carried out
under the auspices of the U.S. Department of Energy
by the University of California under Contract No.
W-7405-Eng-48.
3.1.20.
N,N0-Methylenebis[(2S,4R,5R)/(2S,4S,5S)-4-
methyl-1,3-dioxan-2,5-diyl]bisphenyl-acetamide (7c0). To
a solution of 6b (277 mg, 1.0 mmol), and 4b (223 mg,
1.0 mmol) in 10 mL of chloroform, 20 mg of trifluoroace-
tic acid was added. The reaction mixture was stirred at
15 ꢁC for 4 h, and then neutralized with sodium carbon-
ate, filtered, concentrated. The residue was subjected to
flash chromatography (CHCl3/CH3OH, 30:1) to give
389 mg (yield 83%) of the title compound as colorless
powder. Mp 158–160 ꢁC. IR (KBr, cmꢀ1) m: 3551, 3406,
3052, 2974, 2907, 2862, 1652, 1632, 1601, 1533, 1484,
1402, 1371, 1366, 1185, 1058, 728, 702. 1H NMR
(DMSO-d6, d): 1.23 (d, J = 6.5 Hz, 3H), 1.28 (d,
J = 6.7 Hz, 3H), 2.07 (t, J = 6.1 Hz, 2H), 3.66 (s, 2H),
3.98 (d, J = 7.2 Hz, 2 H), 4.06 (d, J = 12.0 Hz, 2H), 4.09
(dt, J = 8.2 2.4 Hz, 2H), 4.44 (q, J = 7.2 Hz, 2H), 4.80 (t,
J = 6.0 Hz, 2H), 4.82 (t, J = 6.0 Hz, 2H), 6.76 (d,
J = 6.1 Hz, 2H), 7.45 (t, J = 7.5 Hz, 4H), 7.52 (t,
J = 7.6 Hz, 2H), 7.84 (d, J = 7.4 Hz, 4H). FAB-MS
m/z (%): 469 [M+H]+. Anal. Calcd for C26H32N2O6: C,
66.65; H, 6.88; N, 5.98. Found: C, 66.80; H, 6.99; N, 5.81.
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12. Zhao, M.; Wang, C.; Peng, S.; Unpublished results.
13. Firouzabadi, H.; Iranpoor, N.; Shaterian, H. R. Bull.
Chem. Soc. Jpn. 2002, 75, 2195–2205.
3.2. In vivo anti-inflammatory assay
3.2.1. Animals. Male Kunming mice (about 25 g) were
inbred and grown in the animal room at the College
of Pharmacy, Peking University. The animal room was
maintained at 23 2 ꢁC with a 12 h light/dark cycle.
Food and tap water were supplied ad libitum. The eth-
ical guidelines described in the NIH guide for care and
use of laboratory animals was followed throughout the
experiments.
3.2.2. Xylene-induced ear edema.14 Male Kunming mice
were randomly divided into three groups of 12 mice,
namely the test group, vehicle control group, and posi-
tive control group. The mice in vehicle control group
were administrated orally a suspension of Aspirin in
CMC at a dosage of 20 mg/kg, and a concentration of
0.3 mg/ml, while the mice in the test group were orally
administrated a suspension of 1,3-dioxacycloalkane in
CMC at a dosage of 20, 4.0, and 0.8 mg/kg, and a con-
centration of 2.0, 0.4, and 0.08 mg/ml. Thirty minutes la-
ter, 0.03 mL of xylene was applied to both the anterior
and posterior surfaces of the right ear. The left ear
was considered as control. Two hours after xylene appli-
cation, the mice were killed and both ears were removed.
Using a cork borer with a diameter of 7 mm, several
circular sections were taken and weighed. The increase
14. Romay, C.; Ledon, N.; Gonzalez, R. Inflamm. Res. 1998,
47, 334–338.
15. Griswold, D. E.; Martin, L. D.; Badger, A. M.; Breton, J.;
Chabot-Fletcher, M. Inflamm. Res. 1998, 47, 56–61.