Toward the development of chemoprevention agents (III): Synthesis and anti-inflammatory activities of a new class of 5-glycylamino-2-substituted-phenyl-1,3-dioxacycloalkanes

Article abstract of DOI:10.1016/j.bmc.2007.11.017

A new series of 5-glycylamino-2-substituted-phenyl-1,3-dioxacycloalkanes were designed and synthesized. The anti-inflammatory activities of these compounds were tested using the xylene-induced mouse ear edema model. Sixteen of these new compounds exhibited comparable or better anti-inflammatory activities than aspirin suggesting that they can be further developed as potential anti-inflammatory drug leads. In addition, treatment with these anti-inflammatory agents did not prolong tail bleeding time in mice. The structure/activity relationships were also analyzed among these compounds. Considering their good efficacy and safety profiles, some 5-glycylamino-2-substituted-phenyl-1,3-dioxacycloalkanes are worthy to be explored further in assessing the possible link between anti-inflammation and cancer prevention.

Full text of DOI:10.1016/j.bmc.2007.11.017

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 1764–1774
Toward the development of chemoprevention agents (III):
Synthesis and anti-inflammatory activities of a new class of
5-glycylamino-2-substituted-phenyl-1,3-dioxacycloalkanes
a
b
c,
a,
*
Lanrong Bi,a Ming Zhao,a,* Keli Gu, Chao Wang, Jingfang Ju and Shiqi Peng
*
aCollege of Pharmaceutical Sciences, Capital Medical University, Beijing 100069, PR China
bCollege of Pharmaceutical Sciences, Peking University, Beijing 100083, PR China
cUSA Mitchell Cancer Institute, Cancer Research Institute, USA, 307 N. University Blvd, Mobile, AL 36688-0002, USA
Received 25 September 2007; revised 4 November 2007; accepted 5 November 2007
Available online 12 November 2007
Abstract—A new series of 5-glycylamino-2-substituted-phenyl-1,3-dioxacycloalkanes were designed and synthesized. The anti-
inflammatory activities of these compounds were tested using the xylene-induced mouse ear edema model. Sixteen of these new com-
pounds exhibited comparable or better anti-inflammatory activities than aspirin suggesting that they can be further developed as
potential anti-inflammatory drug leads. In addition, treatment with these anti-inflammatory agents did not prolong tail bleeding
time in mice. The structure/activity relationships were also analyzed among these compounds. Considering their good efficacy
and safety profiles, some 5-glycylamino-2-substituted-phenyl-1,3-dioxacycloalkanes are worthy to be explored further in assessing
the possible link between anti-inflammation and cancer prevention.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
Agents with potent anti-inflammatory activity will be
considered as candidate chemopreventive drugs. Long-
term use of non-steroidal anti-inflammatory drugs
(NSAIDs) has been associated with a substantially re-
duced risk of developing colorectal as well as other types
of cancer. This further supports the use of anti-inflam-
matory drugs as a chemopreventive strategy for cancer
prevention.5–8 Toward one of the related stages of colo-
rectal tumorigenesis, including reducing angiogenesis
and inducing cell cycle arrest and apoptosis, NSAIDs
can be offered as individual chemopreventive agents.5
Traditional NSAIDs, such as aspirin, usually target
both COX-1 and COX-2 and exhibit chemopreventive
properties. However, epidemiological studies associate
the use of NSAIDs with side effects such as gastric
bleeding. Having a low toxicity and being effective at
low doses and devoid of side effects are clearly needs
for the long-term use of chemopreventive agents.9–12
Chronic injury or irritation by infectious or non-infec-
tious processes may result in original inflammation,
and an inflammatory response may subsequently lead
to the recruitment of mast cells and leukocytes to the site
of inflammation with release of free radicals, including
reactive oxygen species (ROS).1 Free radicals are known
to be associated with cellular and genomic damage, in
particular through acting on lipids and DNA, and thus
contribute to tumorigenesis.2–4 As a critical area in can-
cer chemoprevention, the use of non-toxic substances to
delay, reverse or suppress multistage carcinogenesis of-
fers a unique scope to intervene at different stages of
tumorigenesis by a wide variety of substances of either
natural or synthetic origins.1,2
Inflammation is a well-established cancer risk factor clo-
sely associated with tumorigenesis in many tumor types.
1,3-Dioxanes have been reported as having anti-inflam-
matory, anti-cancer, and reperfusion injury protection
effects through their anti-proliferative and anti-inflam-
matory activities in human neutrophils and tumor
cells.13–16 Over the past decade, we have developed a ser-
ies of new anti-inflammatory agents based on a 1,3-diox-
ane scaffold. Considering their anti-inflammatory
Keywords: Chemoprevention; 5-Glycylamino-2-substituted-phenyl-1,
3-dioxacycloalkanes; Anti-inflammatory activity; Structure–activity
relationship.
*
Corresponding authors. Tel.: +1 251 460 7393; fax: +1 251 460 6994
(J.J.); tel./fax: +86 10 8391 1528 (S.P.); e-mail addresses:
jju@usouthal.edu; sqpeng@bjmu.edu.cn
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.11.017

L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
1765
potencies, basic properties, and lack of gastric bleeding
2. Results and discussion
risk, we have recently paid special attention to develop-
ing chemopreventive agents based on chemical struc-
tures with good anti-inflammatory activities, that is,
2-substitutedphenyl-5-amino-1,3-dioxacycloalkanes. Our
previous structure–activity relationship studies indicated
that the 5-amino group is responsible for the enhanced
anti-inflammatory activities of these compounds.17–20
It has been suggested that in 5-alkyl-substituted 1,3-
dioxanes, the 5-substituent has a much smaller prefer-
ence for the equatorial position than in cyclohexane
derivatives.21 In particular, with certain non-alkyl sub-
stituents (e.g., F, NO2, SOCH3, NMe3, etc.), the axial
position is preferred.16,22 In addition, the formation of
hydrogen bonds between the protons of the 5-amino
group and the 1,3-dioxygens further forces the 5-amino
group to assume the axial orientation. However, the
formed hydrogen bonds render the 5-amino functionally
less flexible, which may affect its further interaction with
the target. Toward this, our strategy is to introduce a
small Gly residue to 5-amino group, thereby increasing
molecular flexibility to further facilitate its interaction
with the target (Fig. 1). Our preliminary studies suggest
that these newly synthesized 2-substitutedphenyl-5-gly-
cylamino-1,3-dioxanes not only fulfill the stereochemical
requirements, but also have better biological activities
compared to their parental compounds. Based on these
preliminary findings, herein, we report the design, synthe-
sis, and biological studies of this new series of 2-sub-
stitutedphenyl-5-glycylamino-1,3-dioxacycloalkanes. The
in vivo anti-inflammatory activities of these compounds
were evaluated using the xylene-induced mouse ear ede-
ma model. In addition, the bleeding risks of these newly
synthesized compounds were also evaluated.
2.1. Preparation of amino-diols 3a–c via the reduction of
methylesters of L-Ser, L-Thr, L-Asp, and L-Glu
The synthesis of the precursors, amino-diols 3a–c, was
straightforward. The synthetic route is presented in
Scheme 1. Briefly, starting from L-amino acid, in the pres-
ence of SOCl2 and methanol, L-Ser (1a), L-Thr (1b), and L-
Asp (1c) were easily converted into their corresponding
methylesters (2a–c) with 95% yield and subsequently sub-
jected to reduction. The typical nucleophilic reactivity of
SOCl2 resulted in no chlorination of the primary hydroxyl
groups of 1a,b. After the treatment of 2a–c with potassium
borohydride, the 2-amino-1,3-diols (3a,b) and 2-amino-
1,4-diol (3c) were obtained with 39–62% yields (Scheme
1). These amino-diols (3a–c) are important building blocks
for the construction of the target compounds.
2.2. Preparation of 5-glycylamino-1,3-dioxanes via the
stereospecific acetalization of amino-diols 3a,b and
substituted benzaldehydes 4a–e
In our previous report, we have demonstrated that the
anti-inflammatory activities of 2-phenyl-5-amino-1,3-
dioxanes are stereochemically independent.23 Based on
this, we selected the thermodynamically stable (cis)-2-
phenyl-5-amino-1,3-dioxanes 5a–e and (2S,4R,5R)-2-
phenyl-4-methyl-5-amino-1,3-dioxanes 5f–j as the model
compounds to perform the coupling reaction. The re-
lated reactions are presented in Scheme 2.
The preparation of (cis)-2-phenyl-5-amino-1,3-dioxanes
5a–e was slightly modified based on our previously
A
O
H
H
H
N
N
N
C
H N CH
2
2
H
H
O
O
O
R
H
H
R
H
O
O
O
H
H
B
a
b
c
Figure 1. (A) The formed hydrogen bonds render the 5-amino functionally less flexible, which may affect its further interaction with the target. (B)
The comparison of the energy minimized 3D structure: (a) energy minimized 3D structure of 5-amino-1,3-dioxacycloalkanes; (b) energy minimized
3D structure of 2-substitutedphenyl-5-amino-1,3-dioxane; (c) energy minimized 3D structure of 2-substitutedphenyl-5-glycylamino-1,3-dioxane.
R
R
C
R
C
R
C
I
III
II
C
H
CH2OH
H N
p-CH3-C6H4-SO H¡¤
H2N
CO2H
1a-c
H2N
CO2CH3
2a-c
2
CH2OH
3a-c
3
H2N
Tosylate of 3a-c
H
H
H
Scheme 1. Preparation of the aminodiols 3a–c. Reagents: (I) SOCl2 and methanol; (II) potassium borohydride; (III) p-CH3–C6H4–SO3HIn 1a–3a
R = CH2OH; 1b–3b R = CH(CH3)OH; 1c R = CH2CO2H; 2c R = CH2CO2CH3; 3c R = CH2CH2OH.

1766
L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
NH2
F3CCO-Gly-NH
R
R
O
O
ii
R'
H
R'
H
O
O
5a-j
6a-j
H
H
iii
H-Gly-NH
H
i
R
O
R'
CHO
O
7a-j
R'
4a-e
H
Scheme 2. The preparation of the target compounds 7a–j. Reagents: (i) tosylate of 3c and 3b; (ii) DCC, HOBt, and anhydrous THF; (iii) solution of
NaOH in alcohol. In 4a R0 = H; 4b R0 = 4-CH3, 4c R0 = 4-Cl, 4d R0 = 4-NO2, 4e R0 = 3-NO2; 5a–7a R = R0 = H; 5b–7b R0 = 4-CH3, R = H; 5c–7c
R0 = 4-Cl, R = H; 5d–7d R0 = 4-NO2, R = H; 5e–7e R0 = 3-NO2, R = H; 5f–7f R0 = 4-CH3, R = CH3; 5g–7g R0 = 4-Cl, R = CH3; 5h–7h R0 = 4-NO2,
R = CH3; 5i–7i R0 = 4-NO2, R = CH3; 5j–7j R0 = 3-NO2, R = CH3; the definitions of 3a,b are the same as that of Scheme 1.
reported procedure.23 The acetalization of the tosylate
of 2-amido-1,3-diols 3a,b and the substituted benzalde-
hydes 4a–e stereospecifically provided 5a–j with 88–
96% yields. The stereospecificity of the acetalization is
most likely due to the thermodynamic stability of the
resulting acetalization products 5a–j, and the stereospec-
ificity favors the hydrogen bond formation between the
5-amino protons and the 1,3-dioxygens on the ring. It
seems obvious that the equatorial orientation is a favor-
able conformation for the bulky 2-substitutedphenyl
(Fig. 1).
2.3. Preparation of 5-glycylamino-1,3-dioxaheptanes via
the acetalization of amino-diol 3c and substituted benz-
aldehydes 4a–e
We have demonstrated previously good anti-inflamma-
tory activities with 1,3-dioxanes > 1,3-dioxacycloalhep-
tanes > 1,3-dioxacyclooctanes.23 In order to further
explore the stereochemical effect on biological activity
after introducing the Gly residue, we selected (2S,5S)-2-
substitutedphenyl-5-amino-1,3-dioxaheptanes 8c–e and
(2R,5S)-2-substitutedphenyl-5-amino-1,3-dioxaheptanes
80c–e as the model compounds to couple with H-Gly-OH.
The related reactions are presented in Scheme 3.
In the presence of 1-hydroxybenzotriazole hydrate
(HOBt) and N,N0-dicyclohexylcarbodiimide (DCC),
F3CCO-Gly-OH was coupled with 5a–e to provide the
intermediates (cis)-2-substitutedphenyl-5-trifluoroacetyl-
glycyl-amino-1,3-dioxanes 6a–e, which were then directly
treated with a solution of NaOH in 10 mL of ethanol
(80%) to remove the trifluoroacetyl groups. (cis)-2-Phe-
nyl-5-glycylamino-1,3-dioxanes 7a–e were then readily
obtained with yields ranging from 85% to 90%.
The preparation of (2S,5S)-2-substitutedphenyl-5-ami-
no-1,3-dioxaheptanes 8c–e and (2R,5S)-2-substituted-
phenyl-5-amino-1,3-dioxaheptanes
80c–e
directly
followed our previously reported procedure.23 The ace-
talization of 2-amino-1,4-diol 3c and substituted benzal-
dehydes 4c–e stereoselectively provided (2S,5S)-isomers
8c–e with 23–32% yield and (2R,5S)-isomers 80c–e with
15–22% yield. Compared with the six-membered ring,
the seven-membered ring has higher molecular flexibil-
ity. The energy difference between the cis-isomers 8c–e
and the trans-isomers 80c–e was thereby minimized. It
is worthwhile to mention that we attempted to carry
out the acetalizations of 2-amino-1,4-diol 3c and the
substituted benzaldehydes 4a,b under various condi-
tions. However, no desired product was observed.
It seems that not only the steric accessibility of the
Similarly, F3CCO-Gly-OH was coupled with 5f–j to
give the intermediates (2S,4R,5R)-2-substitutedphenyl-
4-methyl-5-trifluoroacetylglycyl-amino-1,3-dioxanes 6f–
j, which were also directly treated with a solution of
NaOH in 10 mL of ethanol (80%) to remove the trifluoro-
acetyl groups. (2S,4R,5R)-2-Phenyl-4-methyl-5-glycyla-
mino-1,3-dioxanes 7f–j were easily obtained, and the
yields ranged from 82% to 91%.
NH2
NH-Gly-COCF3
O
NH-Gly-H
ii
O
H
iii
O
O
H
H
H
O
9'c-e
H
8'c-e
O
H
i
CHO
H
10'c-e
+
R
4c-e
NH2
R
NH-Gly-COCF3
O
R
ii
O
NH-Gly-H
R
iii
R
O
O
H
R
H
O
9c-e
R
8c-e
O
H
10c-e
H
H
Scheme 3. Preparation of 2-substitutedphenyl-5-glycylamino-1,3-dioxaheptanes 10 and 100c–e. Reagents: (i) tosylate of 3c and 3b; (ii) DCC, HOBt,
and anhydrous THF; (iii) NaOH solution in alcohol. In 4c R = 4-Cl, 4d R = 4-NO2, 4e R = 3-NO2; 8–10 and 80–100c R = 4-Cl; 8–10 and 80–100d
R = 4-NO2; 8–10 and 80–100e R = 3-NO2; the definition of 3c is the same as that of Scheme 1.

L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
1767
5-amino group of amino-diol and carbonyl of benzalde-
hyde is one of the key factors, but the stability of the
resulting products is also critical for the acetalizations
of 3c and 4a,b. The electron densities of the phenyls in
4a,b are relatively lower than that of the phenyls in
4c–e, and thereby the stability of seven-membered rings
is relatively lower than that of their corresponding six-
membered rings. Thus, there was no product produced
from the acetalizations of 3c and 4a,b.
ity against xylene-induced inflammation in mice as com-
pared with the CMC group, indicating that these
compounds possess potent anti-inflammatory activities.
2.4.1. The introduction of a Gly residue at the 5-amino
group led to enhanced anti-inflammatory activities in 2-
substitutedphenyl-5-amino-1,3-dioxanes. The anti-inflam-
matory activities of 2-substitutedphenyl-5-glycylamino-
1,3-dioxanes 7a–j were tested using xylene-induced ear
edema model. From Table 1, it was observed that the
anti-inflammatory activities of all of the compounds
7a–j (55–84%) were significantly higher (P < 0.01) than
that of CMC. In order to investigate the impact of
Gly residue on their anti-inflammatory activities, we
compared the anti-inflammatory activities of 2-substi-
tutedphenyl-5-amino-1,3-dioxanes 5a–j (41–78%) with
those of 7a–j. It was noticed that the introduction of a
Gly residue at the 5-amino group of 5a–j indeed led to
improved anti-inflammatory activities. In some cases,
this tendency was significant, that is, when a Gly residue
was introduced at the 5-amino group of 5c, the anti-
inflammatory activity was improved from 64% (5c) to
81% (7c) (P < 0.01). Similarly, in the case of 5h, the
anti-inflammatory activity was increased from 66%
(5h) to 84% (7h) (P < 0.01).
Next, in the presence of HOBt and DCC, F3CCO-Gly-
OH was coupled with 8 and 80c–e to provide the inter-
mediates (2S,5S)- and (2R,5S)-5-trifluoroacetyl-glycyla-
mino-2-substitutedphenyl-1,3-dioxa-heptanes 9 and 90c–
e, which were then directly treated with a solution of
NaOH in 10 mL of ethanol (80%) to remove the trifluo-
roacetyl groups. (2S,5S)- And (2R,5S)-5-glycylamino-2-
substitutedphenyl-1,3-dioxaheptanes 10 and 100c–e were
obtained, and the yields ranged from 68% to 85%.
In summary, by use of these simple synthetic proce-
dures, we have developed a new series of 2-substituted-
phenyl-5-glycylamino-1,3-dioxacycloalkanes with good
yields and high purities. This method can be easily
scaled up to yield gram scale quantity of this new class
of compounds, which could be advantageously applied
to the preparation of amino acid-heterocyclic hybrids.
Effective receptor interaction is dependent on the confor-
mation assumed by the drug. The enhanced anti-inflam-
matory activity observed here might partially be due to
the contribution of molecular flexibility resulting from
the introduction of the Gly residue at the 5-amino group
thereby leading to a favorable conformation assumed by
2-substitutedphenyl-5-glycylamino-1,3-dioxanes.
2.4. In vivo anti-inflammatory assays of 2-substituted-
phenyl-5-glycylamino-1,3-dioxacycloalkanes
To investigate the impact of Gly residue at the 5-
amino group of 2-substitutedphenyl-5-amino-1,3-diox-
acycloalk-anes on their in vivo biological activities,
(cis)-2-substitutedphenyl-5-glycylamino-1,3-dioxanes (7a–j),
(2S,5S)-2-substitutedphenyl-5-glycylamino-1,3-dioxahep-
tanes (10c–e), and (2R,5S)-2-substitutedphenyl-5-glycyla-
mino-1,3-dioxaheptanes (100c–e) were evaluated using a
xylene-induced ear edema model assay. The test com-
pounds were administer orally by gavage in 0.5% carboxy-
methyl cellulose (CMC) suspension. Each compound was
tested at a dose of 20 mg/kg. It was observed that all of
thetestedcompoundsexhibitedsignificantinhibitionactiv-
2.4.2. The introduction of a Gly residue at the 5-amino
group led to significantly increased anti-inflammatory
activities in 2-substitutedphenyl-5-amino-1,3-dioxahep-
tane. The anti-inflammatory activities of 2-substituted-
phenyl-5-glycylamino-1,3-dioxanes 10c–e and 100c–e
were tested using xylene-induced ear edema model. From
Table 2, it was observed that the inflammation inhibitions
of 10c–e (45–50%) and 100c–e (46–49%) are significantly
(P < 0.01) higher than that of CMC. In addition, by com-
Table 1. Anti-inflammatory activities of 2-substitutedphenyl-5-glycylamino-1,3-dioxanes (7a–j) and 2-substitutedphenyl-5-amino-1,3-dioxanes (5a–j)
against xylene-induced ear edema in mice
Agents
Edema weight (X SD mg)
Inhibition (%)
Agents
Edema weight (X SD mg)
Inhibition (%)
CMCa
7a
7b
7c
3.12 0.55
1.45 0.42b
1.41 0.33b
0.58 0.21e
1.11 0.57c
1.24 0.43c
1.40 0.44b
1.35 0.40b
0.51 0.20e
0.56 0.31e
1.16 0.38c
Aspirin
5a
5b
1.85 0.72b
1.51 0.53b
1.56 0.21b
1.12 0.57c
1.84 0.73b
1.35 0.50b
1.47 0.50b
1.42 0.35b
1.04 0.29d
0.67 0.52d
1.20 0.42c
40.7
51.6
50.0
64.1
41.0
57.7
52.9
54.5
66.7
78.5
61.5
55.1
54.8
81.4
64.4
60.3
55.1
56.7
83.7
82.1
62.8
5c
5d
7d
7e
5e
7f
5f
5g
7g
7h
7i
5h
5i
7j
5j
a
CMC = vehicle, dose of 5a–j and 7a–j = 20 mg/kg, dose of aspirin = 30 mg/kg, n = 11.
b Compare to CMC P < 0.01.
c Compare to CMC P < 0.01, to aspirin P < 0.05.
d Compare to CMC and aspirin P < 0.01.
e Compare to CMC, aspirin, and 5a–h,j P < 0.01.

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L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
Table 2. Anti-inflammatory activities of 2-substitutedphenyl-5-glycylamino-1,3-dioxaheptanes (10 and 100c–e) and 2-substitutedphenyl-5-amino-1,3-
dioxaheptanes (8 and 80c–e) against xylene-induced ear edema in micea
Agents
Edema weight (X SD mg)
Inhibition (%)
Agents (X SD mg)
Edema weight
Inhibition (%)
CMC
10c
10d
3.12 0.55
1.60 0.55c
1.56 0.54c
1.71 0.40c
1.58 0.56c
1.59 0.51c
1.69 0.53c
Aspirin
8c
8d
1.85 0.72b
2.12 0.56b
2.44 0.53b
2.35 0.52b
2.15 0.53b
2.40 0.55b
2.38 0.55b
48.7
50.0
45.2
49.3
49.0
45.8
32.1
21.8
24.7
31.1
23.1
23.7
10e
8e
80c
80d
80e
100c
100d
100e
a CMC = vehicle, dose of 8 and 80c–e and 10 and 100e–e = 20 mg/kg, dose of aspirin = 30 mg/kg, n = 11.
b Compare to CMC P < 0.01.
c Compare to CMC P < 0.01, compare to aspirin P < 0.05.
parison of the anti-inflammatory activities between 10
and 100c–e and 8 and 80c–e, it was noticed that the intro-
duction of a Gly residue at the 5-amino group of 8 and
80c–e resulted in a significant increase in anti-inflamma-
tory activities. For instance, when a Gly residue was intro-
duced into the 5-amino group, the inflammatory
inhibition was increased from 8c–e (22–32%) and 80c–e
(24–31%) to 10c–e (45–50%) and 100c–e (46–49%)
(P < 0.05), respectively. Similarly, the enhanced anti-
inflammatory activity observed here might also be par-
tially due to the contribution of molecular flexibility
resulting from the introduction of the Gly residue at the
5-amino group.
2.5. Tail bleeding time measurement
Conventional use of NSAIDs is usually associated with a
number of significant adverse events, including gastroin-
testinal bleeding, impaired platelet function, and pro-
longed bleeding time. Clinical effects of NSAID-induced
platelet dysfunction consist of increased bleeding, pro-
longed surgical bleeding and an additive risk of significant
or life-threatening bleeding in patients. To develop safer
anti-inflammatory agents, it is critical to evaluate these
new synthetic agents for possible deleterious effects on
normal hemostasis leading to bleeding complications.
The cutaneous bleeding time model is the most common
method used in animal experiments to deduce bleeding
potential in humans.24–32
2.4.3. Dose-dependent anti-inflammatory activities. It was
observed that the oral administration of compounds
7c,h,i, and 10 and 100c at doses of 5.0, 10.0, and
20.0 mg/kg presents a dose-dependent anti-inflammatory
response in the xylene-induced mouse ear edema test. At
doses of 5.0, 10.0, and 20.0 mg/kg, the inflammatory inhi-
bitions of 7c,h,i were 31–35%, 61–64%, and 81–84%,
respectively. The anti-inflammatory activities were signif-
icantly enhanced with the concentration increase. In the
case of 10 and 100c, at doses of 5.0, 10.0, and 20.0 mg/
kg, the inflammatory inhibition was about 16%, 32%,
and 50%, respectively. A significant enhancement in their
anti-inflammatory activities in compounds 10 and 100c
with doses above 5.0 mg/kg was also observed. In com-
parison, the inflammatory inhibition of aspirin was 41%
at a dose of 30 mg/kg. Furthermore, compounds 7c,h,i
exhibited higher anti-inflammatory activity than aspirin
at a dose of 10.0 mg/kg. Clearly, compounds 7c,h,i, and
10 and 100c exhibited a dose-dependent anti-inflamma-
tory action (Table 3).
2-Substitutedphenyl-5-glycylamino-1,3-dioxanes 7a–j
and -1,3-dioxaheptanes 10 and 100c–e were orally
administered at a 200 mg/kg dose to male mice (body
weight 18–22 g). After 30, 45, 60, and 90 min, the mouse
was placed in a tube holder with its tail protruding, and
a 2-mm cut was made on the tail. Flowing blood was
gently wiped away with a tissue every 30 s until bleeding
ceased, and the time was recorded.
2.5.1.
5-Glycylamino-2-substitutedphenyl-1,3-dioxanes
exhibited no bleeding effect. To explore the anti-inflam-
matory mechanism of these novel 5-glycylamino-2-sub-
stitutedphenyl-1,3-dioxanes, the tail bleeding time
assays of 7a–j were performed on mice using a literature
method.23 The observed bleeding time in mice at all time
points tested (5–60 min) fell into a range of 118.8 8.1–
122.6 9.0 s, which was equal to before administration
(118.8 7.7–122.0 8.4 s) (Table 4). In each case, the
Table 3. Anti-inflammatory activities of 7c,h,i, 10d, and 100d at different doses against xylene-induced ear edema in micea
Compound
Edema weight
(X SD mg)
Inhibition (%)
Edema weight
(X SD mg)
Inhibition (%)
Edema weight
(X SD mg)
Inhibition (%)
Dose
7c
7h
5 mg/kg
10 mg/kg
20 mg/kg
2.15 0.55
1.95 0.52
2.02 0.54
2.62 0.55
2.62 0.54
31.0
37.5
35.2
16.0
16.0
1.20 0.22d
1.11 0.20d
1.22 0.26d
2.11 0.54e
2.12 0.53e
61.5
64.4
60.9
32.4
32.0
0.58 0.21b
0.51 0.20b
0.56 0.31b
1.56 0.54c
1.59 0.51c
81.4
83.7
82.1
50.0
49.0
7i
10c
100c
a N = 11. Compare to 10 mg/kg group of the same compound P < 0.01.
b Compare to 10 mg/kg group of the same compound P < 0.05.
c Compare to 5 mg/kg group of the same compound P < 0.01.
d Compare to 5 mg/kg group of the same compound P < 0.05.

L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
1769
Table 4. Effect of 5-glycylamino-2-substitutedphenyl-1,3-dioxanes on the tail bleeding time ( SDs) of mice
Compound
Before administration
After administration
5 min
15 min
30 min
60 min
7a
7b
7c
7d
7e
7f
119.5 8.1
120.0 8.2
118.8 7.7
119.7 8.3
122.0 8.4
120.1 7.7
121.0 8.0
121.5 8.3
118.8 7.3
119.7 7.5
120.0 8.0
120.0 8.2
120.8 8.3
120.9 8.0
120.1 8.2
121.1 8.4
119.9 8.3
122.5 8.7
120.0 7.6
120.4 8.3
120.2 7.7
120.3 7.4
120.6 8.5
120.4 7.7
120.2 8.4
119.8 8.2
122.6 9.0
120.5 8.3
121.0 8.4
120.8 8.1
120.9 8.2
119.1 8.1
120.3 7.7
122.5 8.3
122.2 8.4
120.7 8.2
121.4 8.3
120.1 8.0
118.8 8.1
119.0 8.3
120.5 8.4
120.3 8.5
120.0 8.1
121.0 8.0
121.2 8.0
121.8 8.5
120.3 8.3
120.4 8.1
120.5 8.3
119.9 8.4
7g
7h
7i
7j
Dose = 200 mg/kg, n = 10; NS (normal saline) = vehicle.
Table 5. Effect of 5-glycylamino-2-substitutedphenyl-1,3-dioxaheptanes on the tail bleeding time ( SDs) of mice
Compound
Before administration
After administration
5 min
15 min
30 min
60 min
10c
10d
119.3 8.8
119.6 7.4
118.6 7.5
119.8 7.8
118.5 7.6
119.4 7.8
119.5 8.2
120.3 7.6
119.5 7.7
121.1 8.2
120.4 7.9
121.0 8.2
120.4 8.8
123.0 8.0
119.5 7.9
119.1 8.6
120.7 8.7
119.8 8.4
120.8 8.1
120.1 8.7
123.1 8.8
120.0 7.8
120.1 7.5
120.2 8.1
120.1 7.5
119.3 7.8
119.6 7.9
119.4 7.5
119.2 7.0
120.9 8.3
10e
100c
100d
100e
Dose = 200 mg/kg, n = 10; NS (normal saline) = vehicle.
dose was 200 mg/kg body weight. This observation im-
plied that at 10-fold anti-inflammatory dose the bleeding
time of 7a–j receiving mice was kept at a normal level
and the introduction of Gly residue onto the 5-amino
group of 5a–j resulted in no bleeding risk.
efficacy and safety profiles, it would be worthwhile to
work further in detail with these newly synthesized com-
pounds in assessing the possible link between inflamma-
tory inhibition and cancer prevention.
2.5.2. 5-Glycylamino-2-substitutedphenyl-1,3-dioxahep-
tanes exhibited no bleeding effect. To explore the anti-
inflammatory mechanism of these novel 5-glycylamino-
2-substitutedphenyl-1,3-dioxaheptanes, the tail bleeding
time assays of 10 and 100c–e were also performed on
mice using a literature method.23 The observed bleeding
time in mice at all time points tested (5–60 min) fell into
a range of 119.2 7.0–123.1 8.8 s, which was equal to
before administration (118.5 7.6–119.8 7.8 s) (Table
5). In each case, the dose was 200 mg/kg body weight.
This observation implied that, at 10-fold anti-inflamma-
tory dose the bleeding time of 10 and 100c–e receiving
mice was kept at a normal level and the introduction
of Gly residue onto the 5-amino group of 8 and 80c–e re-
sulted in no bleeding risk.
4. Experimental
Unless otherwise stated, all reactions were performed
under a nitrogen atmosphere (1 bar). Melting points
are uncorrected. The agents used in this work were pur-
chased from Sigma Chemical Co. (USA). Chromatogra-
phy was performed on Qingdao silica gel H (Qingdao of
China). The purities of the intermediates and the prod-
ucts were confirmed by TLC (Merck silica gel plates of
type 60 F254, 0.25 mm layer thickness, Germany) and
HPLC (Waters, C18 column 4.6 · 150 mm, USA).
NMR spectra were recorded at 300 MHz on a VXR-
300 instrument or at 500 MHz on a Bruker Am-500
instrument in CDCl3 with tetramethylsilane as internal
standard. EI-MS was determined by Trace MS System
(Thermo Finnigan, USA). Optical rotations were deter-
mined with a Schmidt+Haensch Polartromic D instru-
ment (Germany). The statistical analysis of all the
biological data was carried out by use of ANOVA test,
P < 0.05 is considered significant.
3. Conclusion
In this study, we have developed a series of new 2-sub-
stitutedphenyl-5-glycylamino-1,3-dioxacycloalkanes as
potent anti-inflammatory agents. Sixteen of the newly
synthesized compounds exhibit improved in vivo anti-
inflammatory activities. In addition, these compounds
did not prolong tail bleeding time even at high doses
(200 mg/kg). Taken together, these newly synthesized
compounds display a favorable pharmacological profile
relative to the reference drug aspirin. Considering their
4.1. Preparation of amino acid methylesters (2a–c)
According to our previously reported procedure,23 at
0 ꢁC, to 50 mL of anhydrous methanol, 3.75 mL
(47.5 mmol) of thionyl chloride was added dropwise.
The solution was stirred at 0 ꢁC for 30 min and then
47.6 mmol of L-Ser-OH, L-Thr-OH or L-Asp-OH was

1770
L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
added. The reaction mixture was stirred at room tem-
perature for 24 h and TLC (CH3Cl/CH3OH, 9:1) indi-
cated complete disappearance of L-Ser-OH, L-Thr-OH
or L-Asp-OH. The reaction mixture was concentrated
under reduced pressure and the residue was triturated
with petroleum ether repeatedly to provide 7304 mg
(99%) of HClÆL-Ser-OCH3 (2a, colorless powder, mp
161–162 ꢁC), 7867 mg (98%) of HClÆL-Thr-OCH3 (2b,
colorless powder, mp 140–142 ꢁC) or HClÆL-Asp-
(OCH3)2 (2c, colorless powder, mp 149–151 ꢁC).
4.4.2. (cis)-[2-(40-Methylphenyl)-1,3-dioxan-5-yl]amine
(5b). 328 mg (85%), colorless powder, mp 55–56 ꢁC.
4.4.3.
(cis)-[2-(40-Chlorophenyl)-1,3-dioxan-5-yl]amine
(5c). 409 mg (96%), colorless powder, mp 76–78 ꢁC.
4.4.4. (cis)-2-[40-Nitrophenyl]-1,3-dioxan-5-yl]amine (5d).
419 mg (93%), colorless powder, mp 113–114 ꢁC.
4.4.5. (cis)-2-[30-Nitrophenyl]-1,3-dioxan-5-yl]amine (5e).
403 mg (93%), colorless powder, mp 50–52 ꢁC.
4.2. Preparation of aminodiols (3a–c)
4.5. Preparation of (2S,4R,5R)-(2-substitutedphenyl-4-
methyl-1,3-dioxan-5-yl)amine (5f–j)
According to the literature,23 to the suspension of
200 mg (5.6 mmol) of KBH4 in 10 mL of THF, the solu-
tion of 1.0 mmol of HClÆL-Ser-OCH3, HClÆL-Thr-OCH3
or HClÆL-Asp-(OCH3)2 in 20 mL of THF was added.
The reaction mixture was stirred at room temperature
for 24 h and TLC (C2H5OH/H2O, 7:1) indicated com-
plete disappearance of HClÆL-AA-OCH3. At 0 ꢁC, the
reaction mixture was adjusted to pH 10 with hydrochlo-
ric acid (2 mol/L) and concentrated under reduced pres-
sure. The residue was purified by chromatography
(CH3Cl/CH3OH, 19:1) to offer 74 mg (62%) 2-amino-
propane-1,3-diol hydrochloride (3a, colorless powder,
mp 55–58 ꢁC), 98 mg (58%) of (2R,3R)-2-aminobu-
According to the literature,23 a mixture of 2.0 mmol of
3b, 2.6 mmol of 4a–d or 4e, 30 mg of tolylsulfonylic acid,
100 mg of anhydrous NaSO4, 50 mL of chloroform, and
4 mL of THF was stirred at room temperature overnight
until TLC (CHCl3/CH3OH, 20:1) indicated complete
disappearance of aminodiol. The reaction mixture was
then adjusted to pH 7 with sodium carbonate and fil-
tered. The filtrate was concentrated under reduced pres-
sure, and the residue was purified by chromatography
on silica gel (CHCl3/CH3OH, 40:1) to provide the title
compounds.
tane-1,3-diol hydrochloride [3b, colorless powder, mp
20
D
(2S)-2-aminobutane-1,4-diol hydrochloride [3c, yellow
50–52 ꢁC, ½aꢀ ꢁ4.0 (c = 4, H2O)] or 55 mg (39%) of
20
4.5.1. (2S,4R,5R)-(2-Phenyl-4-methyl-1,3-dioxan-5-yl)a-
mine (5f). 309 mg (80%), colorless powder, mp 48–
20
D
oil, ½aꢀ ꢁ13.5 (c = 4.0, H2O)].
50 ꢁC, ½aꢀ ꢁ8.1 (c = 1.00, CHCl3).
D
4.3. F3CCO-Gly-OH
4.5.2.
(2S,4R,5R)-2-[(40-Methylphenyl)-4-methyl-1,3-
dioxan-5-yl]amine (5g). 311 mg (75%), colorless powder,
20
D
At 0 ꢁC, 15.0 g (0.07 mol) of trifluoroacetic anhydride
was added dropwise to the solution of 3.0 g (0.04 mol)
of H-Gly-OH in 75 mL of anhydrous THF for 30 min.
The reaction mixture was stirred at room temperature
for 45 min and TLC (CHCl3/MeOH, 10:1) indicated
complete disappearance of H-Gly-OH. The reaction
mixture was concentrated under reduced pressure and
the residue was refluxed in 60 mL of mixed solvent of
chloroform and petroleum (1:1) for 10 min, then cooled
to room temperature. By filtration, 6.0 g (66%) of the ti-
tle compound was obtained as a colorless powder, mp
117–118 ꢁC.
mp 63–64 ꢁC, ½aꢀ ꢁ8.0 (c = 1.00, CHCl3).
4.5.3.
(2S,4R,5R)-2-[(40-Chlorophenyl)-4-methyl-1,3-
dioxan-5-yl]amine (5h). 386 mg (85%), colorless powder,
20
D
mp 45–46 ꢁC, ½aꢀ ꢁ8.0 (c = 1.00, CHCl3).
4.5.4. (2S,4R,5R)-2-[(40-Nitrophenyl)-4-methyl-1,3-diox-
an-5-yl]amine (5i). 419 mg (88%), colorless powder, mp
80–82 ꢁC, ½aꢀ ꢁ8.3 (c = 1.00, CHCl3).
4.5.5. (2S,4R,5R)-2-[(30-Nitrophenyl)-4-methyl-1,3-diox-
an-5-yl]amine (5j). 433 mg (91%), colorless powder, mp
20
D
20
D
50–52 ꢁC, ½aꢀ ꢁ8.1 (c = 1.00, CHCl3).
4.4. Preparation of (cis)-5-amino-2-substitutedphenyl-1,3-
dioxanes (5a–e)
4.6. Preparation of (cis)-2-substitutedphenyl-5-glycyla-
mino-1,3-dioxanes (7a–e)
According to the literature,23 a mixture of 2.0 mmol of
3a, 2.6 mmol of 4a–d or 4e, 30 mg of tolylsulfonylic acid,
100 mg of anhydrous NaSO4, 50 mL of chloroform, and
4 mL of THF was stirred at room temperature overnight
until TLC (CHCl3/CH3OH, 20:1) indicated complete
disappearance of 4a–d or 4e. The reaction mixture was
then adjusted to pH 7 with sodium carbonate and then
filtered. The filtrate was concentrated under reduced
pressure, and the residue was purified by chromatogra-
phy on silica gel (CHCl3/CH3OH, 40:1) to provide the
title compounds.
To a solution of 0.25 mmol of 5a–d or 5e in 10 mL of
anhydrous THF at 0 ꢁC, 426 mg (0.25 mmol) of
F3CCO-Gly-OH, 38 mg (0.28 mmol) of 1-hydroxyben-
zotriazole hydrate (HOBt), and 52 mg (0.25 mmol) of
N,N0-dicyclohexylcarbodiimide (DCC ) were added.
The reaction mixture was stirred at 0 ꢁC for 2 h, at room
temperature for 10 h, and TLC (CHCl3/MeOH = 10:1)
indicated complete disappearance of 5a–d or 5e. Upon
concentration under reduced pressure, the residue was
dissolved in 20 mL of ethyl acetate. The solution was
washed successively with saturated sodium bicarbonate,
saturated sodium chloride, 5% kalium bisulfate, and
again with saturated sodium chloride, and the organic
4.4.1. (cis)-(2-Phenyl-1,3-dioxan-5-yl)amine (5a). 315 mg
(88%), colorless powder, mp 52–54 ꢁC.

L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
1771
phase was dried over anhydrous sodium sulfate. After
filtration and concentration under reduced pressure,
the product was purified by silica column chromatogra-
phy (CHCl3/CH3OH, 10:1) to provide the intermediates
(cis)-5-trifluoroacetylglycylamino-2-substitutedphenyl-1,3-
dioxanes 6a–d or 6e.
1584, 1520, 1500, 1455, 1350, 1046, 820. 1H NMR
(CDCl3): d/ppm = 8.204 (d, J = 5.62 Hz, 2H), 8.064 (s,
1H), 7.635 (d, J = 8.50 Hz, 2H), 5.581 (d, J = 7.39 Hz,
1H), 4.168 (d, J = 10.20 Hz, 2H), 4.045 (d, J = 9.90 Hz,
2H), 3.847 (d, J = 5.10 Hz, 1H), 3.731 (d, J = 5.10 Hz,
1H), 3.459 (s, 1H), 1.982 (s, 2H). 13C NMR (DMSO-d6):
d/ppm = 172.446, 148.241, 144.194, 127.068, 123.475,
100.011, 70.786, 44.660, 43.226. ESI-MS (m/e) 282
[M+H]+. Anal. Calcd for C12H15N3O5: C, 51.24; H,
5.38; N, 14.94. Found: C, 51.00; H, 5.50; N, 14.71.
To a solution of 50 mg of NaOH in 10 mL of ethanol
(80%), the obtained 6a–d or 6e was added. The reaction
mixture was stirred at room temperature for 12 h and
TLC (CHCl3/MeOH = 10:1) indicated complete disap-
pearance of 6a–d or 6e. Upon removal of ethanol, the
residue was mixed with 2 mL of water and the solution
was extracted with dichloromethane (3· 10 mL). The
dichloromethane phase was dried over anhydrous
Na2SO4 and then filtered. The filtrate was concentrated
under reduced pressure to provide (cis)-2-substituted-
phenyl-5-glycylamino-1,3-dioxanes 7a–e.
4.6.5. (cis)-2-(30-Nitrophenyl)-5-glycylamino-1,3-dioxane
(7e). Yield: 90%, light yellow solids, mp 95–97 ꢁC.
IR(KBr): t/cmꢁ1 = 3245, 3180, 1692, 1640, 1605, 1583,
1
1522, 1503, 1456, 1352, 1045, 862, 775, 704. H NMR
(CDCl3): d/ppm = 8.389 (s, 1H), 8.226 (d, J = 4.10 Hz,
2H), 7.826 (d, J = 7.80 Hz, 1H), 7.563 (t, J = 8.00 Hz,
1H), 5.635 (s, 1H), 4.184 (t, J = 12.60 Hz, 4H), 4.059
(d, J = 9.90 Hz, 2H), 3.476 (s, 1H), 2.418 (s, 2H). 13C
NMR (DMSO-d6): d/ppm = 172.018, 148.109, 139.744,
132.194, 129.293, 123.862, 121.307, 99.829, 70.670,
44.388, 43.267. ESI-MS (m/e) 282 [M+H]+. Anal. Calcd
for C12H15N3O5: C, 51.24; H, 5.38; N, 14.94. Found: C,
51.45; H, 5.22; N, 14.69.
4.6.1. (cis)-2-Phenyl-5-glycylamino-1,3-dioxane (7a).
Yield: 85%, colorless solids, mp 96–98 ꢁC. IR(KBr): t/
cmꢁ1 = 3249, 3183, 1692, 1644, 1632, 1605, 1576, 1504,
1
1455, 1053, 746, 695. H NMR (CDCl3): d/ppm = 8.209
(s,1H), 7.494 (d, J = 7.14 Hz, 2H), 7.390 (t, J = 7.51 Hz,
1H), 7.351 (t, J = 7.52 Hz, 2H), 5.579 (s, 1H), 4.165 (t,
J = 2.20 Hz, 2H), 4.113 (d, J = 1.51 Hz, 2H), 3.644 (d,
J = 4.80 Hz, 1H), 3.411 (s, 2H), 1.569 (s, 2H). 13C NMR
(DMSO-d6): d/ppm = 172.446, 137.848, 129.137,
128.345, 125.881, 101.774, 70.712, 44.742, 43.316. ESI-
MS (m/e) 237 [M+H]+. Anal. Calcd for C12H16N2O3: C,
61.00; H, 6.83; N, 11.86. Found: C, 60.80; H, 7.00; N,
12.10.
4.7. Preparation of (2S,4R,5R)-2-substitutedphenyl-4-
methyl-5-glycylamino-1,3-dioxanes (7f–j)
To a solution of 0.25 mmol of 5f–i or 5j in 10 mL of
anhydrous THF at 0 ꢁC, 426 mg (0.25 mmol) of
F3CCO-Gly-OH, 38 mg (0.28 mmol) of 1-hydroxyben-
zotriazole hydrate (HOBt), and 52 mg (0.25 mmol) of
N,N0-dicyclohexylcarbodiimide (DCC) were added.
The reaction mixture was stirred at 0 ꢁC for 2 h, at room
temperature for 10 h, and TLC (CHCl3/MeOH = 10:1)
indicated complete disappearance of 5f–i or 5j. Upon
concentration under reduced pressure, the residue was
dissolved in 20 mL of ethyl acetate. The solution was
washed successively with saturated sodium bicarbonate,
saturated sodium chloride, 5% kalium bisulfate, and sat-
urated sodium chloride, and the organic phase was dried
over anhydrous sodium sulfate. After filtration and con-
centration under reduced pressure, the product was
purified by silica gel column chromatography (CHCl3/
CH3OH, 10:1) to provide the intermediates (cis)-5-triflu-
oroacetylglycylamino-2-substitutedphenyl-1,3-dioxanes
6f–i or 6j.
4.6.2. (cis)-2-(40-Methylphenyl)-5-glycylamino-1,3-diox-
ane (7b). Yield: 90%, colorless solids, mp 105–108 ꢁC.
IR(KBr): t/cmꢁ1 = 3244, 3186, 1693, 1643, 1632, 1600,
1583, 1506, 1462, 1380, 1044, 820. 1H NMR (CDCl3): d/
ppm = 8.184 (s, 1H), 7.382 (d, J = 8.10 Hz, 2H), 7.191
(d, J = 7.80 Hz, 2H), 5.544 (s, 1H), 4.141 (d,
J = 9.60 Hz, 2H), 4.030 (t, J = 6.00 Hz, 2H), 3.900 (s,
1H), 3.738 (d, J = 10.80 Hz, 1H), 3.407 (s, 1H), 2.354 (s,
3H), 1.614 (s, 2H). 13C NMR (DMSO-d6): d/
ppm = 172.455, 138.961, 135.071, 128.988, 125.744,
101.914, 70.679, 44.767, 43.341, 21.262. ESI-MS (m/e)
251 [M+H]+. Anal. Calcd for C13H18N2O3: C, 62.38; H,
7.25; N, 11.19. Found: C, 62.14; H, 7.11; N, 11.44.
4.6.3. (cis)-2-(40-Chlorophenyl)-5-glycylamino-1,3-diox-
ane (7c). Yield: 89%, colorless solids, mp 99–102 ꢁC.
IR(KBr): t/cmꢁ1 = 3254, 3186, 1690, 1639, 1603, 1584,
1505, 1383, 1455, 1047, 820. 1H NMR (CDCl3): d/
ppm = 8.188 (s, 1H), 7.427 (t, J = 7.40 Hz, 2H), 7.362 (t,
J = 7.01 Hz, 2H), 5.550 (s, 1H), 4.153 (t, J = 6.50 Hz,
2H), 4.033 (d, J = 10.50 Hz, 2H), 3.898 (d, J = 5.10 Hz,
1H), 3.416 (s, 2H), 1.623 (s, 2H). 13C NMR (DMSO-d6):
d/ppm = 172.438, 136.364, 134.914, 128.494, 127.365,
100.925, 70.687, 44.709, 43.226. ESI-MS (m/e) 271
[M+H]+. Anal. Calcd for C12H15ClN2O3: C, 53.24; H,
5.58; N, 10.35. Found: C, 53.00; H, 5.69; N, 10.11.
To a solution of 50 mg of NaOH in 10 mL of ethanol
(80%), the obtained 6f–i or 6j was added. The reaction
mixture was stirred at room temperature for 12 h and
TLC (CHCl3/MeOH = 10:1) indicated complete disap-
pearance of 6–i or 6j. Upon removal of ethanol, the res-
idue was mixed with 2 mL of water and the solution was
extracted with dichloromethane (3· 10 mL). The dichlo-
romethane phase was dried over anhydrous Na2SO4 and
then filtered. The filtrate was concentrated under re-
duced pressure to provide (cis)-2-substitutedphenyl-5-
glycylamino-1,3-dioxanes 7f–j.
4.6.4. (cis)-2-(40-Nitrophenyl)-5-glycylamino-1,3-dioxane
(7d). Yield: 85%, light yellow solids, Mp128–131 ꢁC.
IR(KBr): t/cmꢁ1 = 3252, 3189, 1695, 1648, 1633, 1606,
4.7.1. (2S,4R,5R)-2-Phenyl-4-methyl-5-glycylamino-1,3-
dioxane (7f). Yield: 91%, light yellow oil. IR(KBr): t/
cmꢁ1 = 3249, 3183, 1690, 1642, 1634, 1605, 1580, 1504,

1772
L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
1452, 1385, 1044, 744, 696. 1H NMR (CDCl3): d/
ppm = 7.945 (s, 1H), 7.513 (q, J = 7.72 Hz, 2H), 7.386
(m, J = 7.68 Hz, 1H), 7.334 (t, J = 7.67 Hz, 2H), 5.573
(s, 1H), 4.167 (m, J = 4.70 Hz, 1H), 4.097 (t,
J = 1.80 Hz, 2H), 3.927 (q, J = 11.60 Hz, 1H), 3.483 (s,
2H), 2.765 (s, 2H), 1.221 (d, J = 6.60 Hz, 3H). 13C
NMR (DMSO-d6): d/ppm = 172.282, 137.914, 129.062,
699. 1H NMR (CDCl3): d/ppm = 8.396 (s, 1H), 8.220 (d,
J = 7.50 Hz, 1H), 7.990 (d, J = 9.60 Hz, 1H), 7.842 (q,
J = 7.80 Hz, 1H), 7.549 (q, J = 7.60 Hz, 1H), 5.671 (s,
1H), 4.224 (t, J = 6.90 Hz, 1H), 4.070 (m, J = 5.20 Hz,
2H), 3.941 (d, J = 5.40 Hz, 1H), 3.494 (s, 2H), 2.330 (s,
2H), 1.256 (d, J = 6.30 Hz, 3H). 13C NMR (DMSO-d6):
d/ppm = 172.858, 148.150, 139.851, 132.260, 129.293,
128.321, 126.038, 101.725, 75.088, 71.503, 46.481,
123.845, 121.389, 99.854, 75.393, 71.659, 46.201, 44.643,
20
D
20
D
44.207, 17.685. ESI-MS (m/e) 251 [M+H]+. ½aꢀ ꢁ42.0
17.611. ESI-MS (m/e) 296 [M+H]+. ½aꢀ
ꢁ34.1
(c = 1.00, CHCl3). Anal. Calcd for C13H18N2O3: C,
62.38; H, 7.25; N, 11.19. Found: C, 62.59; H, 7.40; N,
11.43.
(c = 1.00, CHCl3). Anal. Calcd for C13H17N3O5: C,
52.88; H, 5.80; N, 14.23. Found: C, 52.67; H, 5.93; N,
14.51.
4.7.2. (2S,4R,5R)-2-(40-Methylphenyl)-4-methyl-5-gly-
cylamino-1,3-dioxane (7g). Yield: 89%, light yellow oil.
t/cmꢁ1 = 3253, 3186, 1691, 1644, 1637, 1605, 1580,
1504, 1452, 1385, 1044, 820. 1H NMR (CDCl3): d/
ppm = 7.959 (s, 1H), 7.338 (q, J = 8.10 Hz, 2H), 7.183
(d, J = 8.10 Hz, 2H), 5.552 (s, 1H), 4.146 (m,
J = 4.00 Hz, 1H), 3.970 (d, J = 1.20 Hz, 2H), 3.938 (m,
J = 1.50 Hz, 1H), 3.426 (s, 2H), 2.343 (s, 3H), 2.041 (s,
2H), 1.212 (d, J = 6.30 Hz, 3H). 13C NMR (DMSO-d6):
d/ppm = 172.545, 138.804, 135.087, 128.906, 125.823,
4.8. Preparation of (2S,5S)- and (2R,5S)-(2-substituted-
phenyl-1,3-dioxaheptan-5-yl)-amine (8c–e) and (80c–e)
According to the literature,23 the suspension of 102 mg
(0.72 mmol) of 3c (tosylate), 0.72 mmol of 4c, 4d or 4e,
10 mg of tolylsulfonylic acid, 30 mg of anhydrous
NaSO4, 20 mL of chloroform, and 4 mL of THF was
stirred at 50 ꢁC for 12 h and TLC (CHCl3/CH3OH,
20:1) indicated complete disappearance of 3c. The reac-
tion mixture was cooled to 20 ꢁC and adjusted to pH 7
with sodium carbonate. The reaction mixture was fil-
tered and the filtrate was concentrated under reduced
pressure. The residue was purified by chromatography
on silica gel to provide the title compound.
101.708, 74.973, 71.445, 46.341, 44.511, 21.179, 17.644.
20
ESI-MS (m/e) 265 [M+H]+. ½aꢀ ꢁ34.0 (c = 1.00, CHCl3).
D
Anal. Calcd for C14H20N2O3: C, 63.62; H, 7.63; N, 10.60.
Found: C, 63.40; H, 7.52; N, 10.83.
4.7.3.
(2S,4R,5R)-2-(40-Chlorophenyl)-4-methyl-5-gly-
4.8.1.
(2S,5S)-2-(40-Chlorophenyl-1,3-dioxaheptan-5-
yl)amine (8c). 49 mg (30%), colorless powder, mp 48–
cylamino-1,3-dioxane (7h). Yield: 82%, light yellow oil.
IR(KBr): t/cmꢁ1 = 3255, 3186, 1690, 1644, 1633, 1604,
1580, 1505, 1386, 1454, 1045, 820. 1H NMR (CDCl3): d/
ppm = 7.905 (d, J = 9.30 Hz, 1H), 7.389 (m,
J = 10.10 Hz, 2H), 7.324 (m, J = 8.01 Hz, 2H), 5.502 (s,
1H), 4.095 (q, J = 11.10 Hz, 1H), 4.022 (q, J = 11.70 Hz,
2H), 3.923 (d, J = 11.9 Hz, 1H), 3.604 (s, 2H), 1.210 (s,
2H), 1.144 (d, J = 6.30 Hz, 3H). 13C NMR (DMSO-d6):
d/ppm = 170.831, 136.422, 134.832, 128.469, 127.661,
20
D
49 ꢁC, ½aꢀ 8.0 (c = 1.00, CHCl3).
4.8.2.
(2R,5S)-2-(40-Chlorophenyl-1,3-dioxaheptan-5-
yl)amine (80c). 35 mg (21%), colorless powder, mp 56–
20
D
57 ꢁC, ½aꢀ ꢁ6.0 (c = 1.00, CHCl3).
4.8.3. (2S,5S)-2-(40-Nitrophenyl-1,3-dioxaheptan-5-yl)a-
mine (8d). 39 mg (23%), colorless powder, mp 76–
78 ꢁC, ½aꢀ 8.0 (c = 1.00, CHCl3).
20
D
100.909, 75.137, 71.445, 46.547, 44.605, 17.636. ESI-MS
20
D
(m/e) 285 [M+H]+. ½aꢀ ꢁ36.0 (c = 1.00, CHCl3). Anal.
Calcd for C13H17ClN2O3: C, 54.84; H, 6.02; N, 9.84.
Found: C, 54.62; H, 6.19; N, 9.57.
4.8.4. (2R,5S)-2-(40-Nitrophenyl-1,3-dioxaheptan-5-yl)a-
mine (80d). 26 mg (15%), colorless powder, mp 61–63 ꢁC,
20
½aꢀ ꢁ16.0 (c = 1.00, CHCl3).
D
4.7.4. (2S,4R,5R)-2-(40-Nitrophenyl)-4-methyl-5-glycyla-
mino-1,3-dioxane (7i). Yield: 82%, light yellow solids, mp
136–140 ꢁC. IR(KBr): t/cmꢁ1 = 3252, 3184, 1691, 1645,
1634, 1604, 1585, 1527, 1502, 1454, 1386, 1354, 1044,
4.8.5.
(2S,5S)-[2-(30-Nitrophenyl)-1,3-dioxaheptan-5-
yl]amine (8e). 55 mg (32%), colorless powder, mp 68–
20
D
70 ꢁC, ½aꢀ 12.0 (c = 1.00, CHCl3).
1
820. H NMR (CDCl3): d/ppm = 8.205 (d, J = 8.70 Hz,
2H), 7.939 (d, J = 9.00 Hz, 1H), 7.646 (q, J = 7.30 Hz,
2H), 6.117 (s, 1H), 4.197 (m, J = 3.90 Hz, 1H), 4.024 (q,
J = 10.50 Hz, 2H), 3.894 (d, J = 4.50 Hz, 2H), 3.470 (s,
1H), 2.331 (s, 2H), 1.223 (d, J = 6.30 Hz, 3H). 13C
NMR (DMSO-d6): d/ppm = 172.282, 148.208, 144.268,
4.8.6.
(2R,5S)-[2-(30-Nitrophenyl)-1,3-dioxaheptan-5-
yl]amine (80e). 38 mg (22%), colorless powder, mp 65–
20
D
67 ꢁC, ½aꢀ ꢁ6.0 (c = 1.00, CHCl3).
4.9. Preparation of (2S,5S)- and (2R,5S)-2-substitutedphe-
nyl-5-glycylamino-1,3-dioxa-heptanes (10) and (100c–e)
127.192, 123.475, 100.019, 75.401, 71.668, 46.267,
20
D
44.363, 17.611. ESI-MS (m/e) 296 [M+H]+. ½aꢀ ꢁ34.0
(c = 1.00, CHCl3). Anal. Calcd for C13H17N3O5: C,
52.88; H, 5.80; N, 14.23. Found: C, 52.65; H, 5.99; N,
14.46.
To a solution of 0.25 mmol of 8c and 80c, 8d and 80d or
8e and 80e in 10 mL of anhydrous THF at 0 ꢁC, 426 mg
(0.25 mmol) of F3CCO-Gly-OH, 38 mg (0.28 mmol) of
HOBt, and 52 mg (0.25 mmol) of DCC were added.
The reaction mixture was stirred at 0 ꢁC for 2 h, at room
temperature for 10 h, and TLC (CHCl3/MeOH = 10:1)
indicated complete disappearance of 8c and 80c, 8d
and 80d or 8e and 80e. Upon concentration under
4.7.5. (2S,4R,5R)-2-(30-Nitrophenyl)-4-methyl-5-glycyla-
mino-1,3-dioxane (7j). Yield: 85%, light yellow solids, mp
78–81 ꢁC. IR(KBr): t/cmꢁ1 = 3249, 3186, 1645, 1637,
1601, 1582, 1522, 1502, 1458, 1381, 1351, 1048, 743,

L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
1773
reduced pressure, the residue was dissolved in 20 mL of
ethyl acetate. The solution was washed successively with
saturated sodium bicarbonate, saturated sodium chlo-
ride, 5% kalium bisulfate, and saturated sodium chlo-
ride, and the organic phase was dried over anhydrous
sodium sulfate. After filtration and concentration under
reduced pressure, the product was purified by silica gel
column chromatography (CHCl3/CH3OH, 10:1) to pro-
vide the intermediates (2S,5S)- and (2R,5S)-2-substitut-
edphenyl-5-trifluoroacetyl-glycylamino-1,3-dioxa-hep-
tanes 9c and 90c, 9d and 90d or 9e and 90e.
ppm = 8.227 (d, J = 9.00 Hz, 2H), 7.882 (d, J = 7.50 Hz,
1H), 7.681 (d, J = 8.50 Hz, 2H), 5.819 (s, 1H), 4.202 (q,
J = 4.00 Hz, 1H), 3.991 (m, J = 4.00 Hz, 2H), 3.875 (m,
J = 5.10 Hz, 1H), 3.610 (m, J = 2.60 Hz, 1H), 3.403 (s,
2H), 1.976 (m, J = 4.70 Hz, 1H), 1.883 (m, J = 2.40 Hz,
1H), 1.557 (s, 2H). 13C NMR (CDCl3): d/
ppm = 172.063, 147.979, 145.927, 127.480, 123.406,
99.124, 64.924, 62.589, 46.904, 44.821, 35.438. ESI-MS
20
(m/e) 296 [M+H]+. ½aꢀ 35.0 (c = 1.00, CHCl3). Anal.
D
Calcd for C13H17N3O5: C, 52.88; H, 5.80; N, 14.23.
Found: C, 52.65; H, 5.94; N, 14.00.
To a solution of 50 mg of NaOH in 10 mL of ethanol
(80%), the obtained 9c and 90c, 9d and 90d or 9e and
90e were added. The reaction mixture was stirred at
room temperature for 12 h and TLC (CHCl3/
MeOH = 10:1) indicated complete disappearance of 9c
and 90c, 9d and 90d or 9e and 90e. Upon removal of eth-
anol, the residue was mixed with 2 mL of water and the
solution was extracted with dichloromethane (3·
10 mL). The dichloromethane phase was dried over
anhydrous Na2SO4 and then filtered. The filtrate was
concentrated under reduced pressure to provide
(2S,5S)- and (2R,5S)-2-substitutedphenyl-5-glycylami-
no-1,3-dioxaheptanes 10 and 100c–e.
4.9.4. (2R,5S)-2-(40-Nitrophenyl)-5-glycylamino-1,3-dioxa-
heptanes (100d). Yield: 79%, light yellow oil. IR(KBr): t/
cmꢁ1 = 3332, 3034, 2961, 2913, 2845, 1690, 1641, 1602,
1
1526, 1455, 1372, 1352, 1164, 1045, 824, 743, 695. H
NMR (CDCl3): d/ppm = 8.234 (d, J = 9.00 Hz, 2H),
7.805 (d, J = 6.54 Hz, 1H), 7.700 (d, J = 9.00 Hz, 2H),
5.796 (s, 1H), 4.307 (m, J = 2.20 Hz, 1H), 3.994 (m,
J = 4.70 Hz, 1H), 3.924 (m, J = 2.40 Hz, 1H), 3.785 (m,
J = 4.40 Hz, 2H), 3.354 (d, J = 3.50 Hz, 2H), 2.054 (m,
J = 4.40 Hz, 1H), 1.848 (m, J = 2.60 Hz, 1H), 1.552 (s,
2H). 13C NMR (CDCl3): d/ppm = 172.017, 147.979,
146.064, 127.427, 123.437, 99.650, 68.562, 60.972, 47.240,
20
44.699, 35.217. ESI-MS (m/e) 296 [M+H]+. ½aꢀ ꢁ39.0
D
(c = 1.00, CHCl3). Anal. Calcd for C13H17N3O5: C,
52.88;H,5.80;N,14.23.Found:C, 53.11;H,5.68;N,14.46.
4.9.1. (2S,5S)-2-(40-Chlorophenyl)-5-glycylamino-1,3-
dioxaheptanes (10c). Yield: 73%, light yellow solids, mp
120–124ꢁC. IR(KBr): t/cmꢁ1 = 3342, 3041, 2964, 2911,
2841, 1692, 1641, 1602, 1554, 1460, 1372, 1171, 1055,
823, 745, 694. 1H NMR (CDCl3): d/ppm = 7.850 (s,
1H), 7.424 (d, J = 8.01 Hz, 2H), 7.338 (d, J = 8.01 Hz,
2H), 5.744 (s, 1H), 4.202 (s, 1H), 3.966 (d, J = 12.00 Hz,
1H), 3.843 (d, J = 11.50 Hz, 2H), 3.541 (t, J = 5.80 Hz,
1H), 3.393 (s, 2H), 1.951 (t, J = 12.00 Hz, 1H), 1.855 (d,
J = 14.50 Hz, 1H), 1.548 (s, 2H). 13C NMR (CDCl3): d/
ppm = 172.017, 137.604, 134.285, 128.357, 127.801,
4.9.5. (2S,5S)-2-(30-Nitrophenyl)-5-glycylamino-1,3-dioxa-
heptanes (10e). Yield: 79%, light yellow oil. IR(KBr): t/
cmꢁ1 = 3324, 3043, 2960, 2921, 2852, 1693, 1640, 1616,
1554, 1523, 1460, 1366, 1355, 1162, 1054, 862, 770, 745,
1
693. H NMR (CDCl3): d/ppm = 8.364 (s, 1H), 8.192
(d, J = 7.50 Hz, 1H), 7.927 (d, J = 8.50 Hz, 1H), 7.829
(t, J = 7.50 Hz, 1H), 7.550 (d, J = 8.30 Hz, 1H), 5.819
(s, 1H), 4.203 (q, J = 3.80 Hz, 1H), 3.997 (m,
J = 3.90 Hz, 1H), 3.897 (t, J = 10.30 Hz, 1H), 3.839 (d,
J = 3.50 Hz, 1H), 3.619 (t, J = 3.50 Hz, 1H), 3.450
(s, 2H), 2.140 (s, 2H), 1.977 (m, J = 5.00 Hz, 1H), 1.888
(d, J = 14.50 Hz, 1H). 13C NMR (CDCl3): d/
ppm = 172.025, 148.261, 141.326, 132.561, 129.242,
99.597, 64.420, 62.383, 46.942, 44.860, 35.537. ESI-MS
20
(m/e) 285 [M+H]+. ½aꢀ 36.0 (c = 1.00, CHCl3). Anal.
D
Calcd for C13H17ClN2O3: C, 54.84; H, 6.02; N, 9.84.
Found: C, 54.60; H, 6.14; N, 9.61.
123.399, 121.713, 98.933, 64.771, 62.620, 46.912, 44.814,
20
D
4.9.2. (2R,5S)-2-(40-Chlorophenyl)-5-glycylamino-1,3-
dioxaheptanes (100c). Yield: 75%, colorless solids, mp
107–109ꢁC. IR(KBr): t/cmꢁ1 = 3340, 3042, 2965, 2913,
2843, 1690, 1643, 1605, 1552, 1461, 1373, 1172, 1053,
825, 742, 691. 1H NMR (CDCl3): d/ppm = 7.791 (d,
J = 6.00, 1H), 7.450 (d, J = 8.50 Hz, 2H), 7.347 (d,
J = 8.00 Hz, 2H), 5.720 (s, 1H), 4.299 (m, J = 2.90 Hz,
1H), 3.932 (m, J = 6.70 Hz, 2H), 3.718 (m, J = 4.70 Hz,
2H), 3.350 (d, J = 2.50 Hz, 2H), 2.026 (m, J = 4.60 Hz,
1H), 1.820 (q, J = 4.70 Hz, 1 H), 1.482 (s, 2H). 13C
NMR (CDCl3): d/ppm = 171.956, 137.726, 134.163,
35.430. ESI-MS (m/e) 296 [M+H]+. ½aꢀ 20.0 (c = 1.00,
CHCl3). Anal. Calcd for C13H17N3O5: C, 52.88; H,
5.80; N, 14.23. Found: C, 52.67; H, 5.91; N, 14.01.
4.9.6. (2R,5S)-2-(30-Nitrophenyl)-5-glycylamino-1,3-dioxa-
heptanes (100e). Yield: 85%, light yellow oil. IR(KBr):
t/cmꢁ1 = 3322, 3031, 2966, 2914, 2842, 1690, 1643,
1604, 1556, 1520, 1456, 1374, 1355, 1163, 1052, 864,
770, 735, 696. 1H NMR (CDCl3): d/ppm = 8.409 (s,
1H), 8.190 (d, J = 7.42 Hz, 1H), 7.905 (d, J = 8.50 Hz,
1H), 7.824 (d, J = 7.50 Hz, 1H), 7.556 (t, J = 8.00 Hz,
1H), 5.879 (s, 1H), 4.301 (d, J = 3.50 Hz, 1H), 3.952
(m, J = 5.90 Hz, 2H), 3.759 (m, J = 4.10 Hz, 2H),
3.408 (d, J = 4.00 Hz, 2H), 2.354 (s, 2H), 2.042 (m,
J = 4.50 Hz, 1H), 1.850 (t, J = 6.80 Hz, 1H). 13C NMR
(CDCl3): d/ppm = 171.529, 148.238, 141.388, 132.675,
129.281, 123.406, 121.560, 99.436, 68.379, 60.918,
128.304, 127.686, 100.054, 68.204, 60.445, 47.232,
20
44.692, 35.209. ESI-MS (m/e) 285 [M+H]+. ½aꢀ ꢁ38.0
D
(c = 1.00, CHCl3). Anal. Calcd for C13H17ClN2O3: C,
54.84; H, 6.02; N, 9.84. Found: C, 54.63; H, 6.12; N, 9.60.
4.9.3. (2S,5S)-2-(40-Nitrophenyl)-5-glycylamino-1,3-dioxa-
heptanes (10d). Yield: 68%, light yellow solids, mp 135–
138 ꢁC. IR(KBr): t/cmꢁ1 = 3343, 3045, 2972, 2915,
2853, 1690, 1645, 1603, 1563, 1524, 1460, 1370, 1354,
1173, 1054, 825, 744, 691. 1H NMR (CDCl3): d/
47.408, 44.371, 35.079. ESI-MS (m/e) 296 [M+H]+.
20
D
½aꢀ
ꢁ24.0 (c = 1.00, CHCl3). Anal. Calcd for
C13H17N3O5: C, 52.88; H, 5.80; N, 14.23. Found: C,
52.64; H, 5.93; N, 14.48.

1774
L. Bi et al. / Bioorg. Med. Chem. 16 (2008) 1764–1774
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Acknowledgments
We appreciate the critical reviews from Paul Howell.
This work was supported by Beijing Area Major Labo-
ratory of Peptide and Small Molecular Drugs, the 973
Project of China (2006CB708501) and Beijing Municipal
Commission of Education (KZ 200510025015).
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