Design, synthesis and biological evaluation of novel desloratadine derivatives with anti-inflammatory and H1 antagonize activities

Article abstract of DOI:10.1016/j.bmcl.2019.126712

To improve the anti-inflammatory activity of desloratadine, we designed and synthesized a series of novel desloratadine derivatives. All compounds were evaluated for their anti-inflammatory and H₁ antagonistic activities. Among them, compound 2c showed the strongest H₁ antagonistic and anti-inflammatory activity. It also exhibited promising pharmacokinetic profiles and low toxicity. All these results suggest that compound 2c as a novel anti-allergic agent is worthy of further investigation.

Full text of DOI:10.1016/j.bmcl.2019.126712

Journal Pre-proofs
Design, Synthesis and Biological Evaluation of novel desloratadine derivatives
with anti-inflammatory and H1 antagonize activities
Feng Li, Qinlong Xu, Qihua Zhu, Zhaoxing Chu, Gaofeng Lin, Jiajia Mo, Yan
Zhao, Jiaming Li, Guangwei He, Yungen Xu
PII:
S0960-894X(19)30670-5
DOI:
https://doi.org/10.1016/j.bmcl.2019.126712
BMCL 126712
Reference:
Bioorganic & Medicinal Chemistry Letters
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Received Date:
Revised Date:
Accepted Date:
24 July 2019
7 September 2019
19 September 2019
Please cite this article as: Li, F., Xu, Q., Zhu, Q., Chu, Z., Lin, G., Mo, J., Zhao, Y., Li, J., He, G., Xu, Y., Design,
Synthesis and Biological Evaluation of novel desloratadine derivatives with anti-inflammatory and H1 antagonize
activities, Bioorganic & Medicinal Chemistry Letters (2019), doi: https://doi.org/10.1016/j.bmcl.2019.126712
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Design, Synthesis and Biological Evaluation of novel desloratadine derivatives with anti-
inflammatory and H1 antagonize activities
Feng Li a, c, Qinlong Xu c, d, Qihua Zhu a, b, Zhaoxing Chu a, c, Gaofeng Lin c, Jiajia Mo c, Yan
Zhao c, Jiaming Li d, Guangwei He c, Yungen Xu a, b,*
a Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009,
China
b Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical
University, Nanjing 21009, China
c Hefei Institute of Pharmaceutical Industry Co., Ltd., Hefei 230088, China
d Anhui University of Chinese Medicine, Hefei 230031, China
*Corresponding author: Yungen Xu
Email: xu_yungen@hotmail.com
1

Abstract
To improve the anti-inflammatory activity of desloratadine, we designed and synthesized a series
of novel desloratadine derivatives. All compounds were evaluated for their anti-inflammatory and
H1 antagonistic activities. Among them, compound 2c showed the strongest H1 antagonistic and
anti-inflammatory activity. It also exhibited promising pharmacokinetic profiles and low toxicity.
All these results suggest that compound 2c as a novel anti-allergic agent is worthy of further
investigation.
Keywords: anti-inflammatory; H1 antagonize; anti-allergic; desloratadine
Allergic diseases, such as acute and chronic urticaria, allergic rhinitis, allergic ophthalmia,
allergic skin disease etc., have severely influenced the quality of people’s life [1-2]. It has been
confirmed that the main effect of H1 antihistamines is related to the blockade of H1 receptors, thus
executing their antiallergic function [3]. Hence antihistamines, such as loratadine, desloratadine,
fexofenadine, cetirizine (shown in Fig 1) have been approved to treat allergic diseases. Although
they were efficacious and a lot of patients have benefited from these drugs, they still have some
side-effects such as sleepiness [4], nasal congestion, dry mouth and headache [5]. To avoid these
drawbacks, it is urgent to develop novel antihistamines drugs or new therapeutic strategies.
Cl
Cl
Cl
OH
N
N
OH
N
N
N
OH
O
N
N
H
O
O
O
COOH
loratadine
desloratadine
fexofenadine
cetirizine
Fig. 1. Structure of second-generation antihistamines commonly used in clinical practice
Allergy and inflammation are intertwined in many pathological processes. For instance,
chronic spontaneous urticaria (CSU) is characterized by the combined effects of allergy and chronic
inflammation, where patients benefit poorly from single anti-allergic or anti-inflammatory therapy.
Moreover, it has long been established that inflammation is a major consequence of allergic
reactions, hence the term “allergic inflammation” [6,7]. Unfortunately, despite their strong anti-
allergic potency, the new generation of H1 antihistamines have weak anti-inflammatory efficacy [8-
2

9]. Therefore, development of drugs with dual antihistamine and anti-inflammatory functionalities
could represent a viable approach towards the treatment of allergy-related disease where
inflammation also plays a critical role [10]. The aim of this study was to design, synthesize and
evaluate novel desloratadine analogs for their H1 antagonistic activity and anti-inflammatory
potential.
Some studies found that guaiacol has anti-inflammation effect [11-12]. For example, natural
product extract containing guaiacol inhibits NF-κB and MAPK in lipopolysaccharide-stimulated
RAW264.7 cells and reduces cellular inflammatory response [13]. Based on the above studies, two
compounds (1c-2c) were initially designed by combining the structures of desloratadine and
guaiacol through a linker, as shown in Fig 2. Then, based on their activities, compound 2c was
chosen as the lead compound for further modification. Compounds 3c-15c were subsequently
designed and synthesized in the search for more potent compounds and to establish a structure-
activity relationship (Fig 2).
N
NH
desloratadine
N
N
Cl
OH
R1
R
OCH3
N
O
R2
R3
N
O
OH
Cl
Cl
1c: R = H;
2c: R = OH;
OCH3
3c-15c
guaiacol
Fig. 2. Design of target compounds
The synthesis of target compound 1c is described in scheme 1. Reaction of guaiacol (1a) with
1,3-dibromopropane afforded intermediate 1b that was then condensed with desloratadine to afford
the target compound 1c.
The preparation of compounds 2c-15c is described in Scheme 2. Reaction of
(chloromethyl)oxirane with corresponding compounds 2a-15a in NaOH aqueous afforded
intermediates 2b-15b that were condensed with desloratadine to afford the target compounds 2c-
15c.
The preparation of chiral isomers 16c and 17c is described in scheme 3. Guaiacol 1a reacted
with R- or S-(chloromethyl) oxirane to give the intermediates 16b or 17b that were condensed with
desloratadine respectively to give the target compounds 16c and 17c.
3

N
O
OH
O
Br
O
Br
Br
desloratadine
ii
O
i
N
O
1a
1b
Cl
1c
Scheme 1. Reagents and conditions: (i) DMF, K2CO3, r t, 2 h; (ii) DMF, K2CO3, 60℃, 6 h。
OH
R2
N
R1
R2
O
R1
R3
Cl
OH
R1
desloratadine
ii
N
O
R2
R3
O
i
R3
2a-15a
O
Cl
2b-15b
2c-15c
2a, 2b, 2c: R1 = OCH3,
3a, 3b, 3c: R1 = R2 = R3 = H;
4a, 4b, 4c: R1 = OCH2CH3, R2 = R3 = H;
R2 = R3 = H;
9a, 9b, 9c:
R1 = Br,
R2 = R3 = H;
R2 = R3 = H;
R2 = R3 = H;
R2 = R3 = H;
R1 = R3 = H;
R1 = R2 = H;
R2 = R3 = F;
10a, 10b, 10c: R1 = NO2,
11a, 11b, 11c: R1 = CF3,
12a, 12b, 12c: R1= COCH3,
13a, 13b, 13c: R2 = OCH3,
14a, 14b, 14c: R3 = OCH3,
15a, 15b, 15c: R1 = OCH3,
5a, 5b, 5c: R1 = CH3,
6a, 6b, 6c: R1 = OCF3,
7a, 7b, 7c: R1 = F,
R2 = R3 = H;
R1 = R3 = H;
R2 = R3 = H;
R2 = R3 = H;
8a, 8b, 8c: R1 = Cl,
Scheme 2. Reagents and conditions: (i) NaOH, 50℃, 6 h; (ii) isopropanol, 90℃, 6 h;
N
O
desloratadine
ii
OH
O
O
N
O
O
Cl
O
Cl
16a
16b
16c
O
i
OH
O
O
N
i
Cl
O
1a
desloratadine
ii
OH
O
17a
O
N
O
17b
Cl
17c
Scheme 3. Reagents and conditions: (i) NaOH, 50℃, 6 h; (ii) isopropanol, 90℃, 6 h.
1c and 2c were firstly designed to assess whether a three-carbon linker is appropriate. H1
antagonistic activities of both 1c and 2c were maintained (IC50 values of 9.28 nM and 2.95 nM,
respectively) suggesting incorporating this linker does not damp ligand binding to H1 receptor.
Moreover, 2c is more potent than 1c, indicating a hydroxyl group on the linker is beneficial. Next,
effects of the substituents on the distal benzene ring were examined. The results showed that neither
4

removal (3c) nor replacement (4c-12c) of the -OCH3 group on the benzene ring with other electron-
donating or electron-withdrawing groups led to an increase in H1 antagonistic activity. Only
compounds 3c (IC50 = 6.23 nM), 5c (IC50 = 8.90 nM) and 7c (IC50 = 4.74 nM) exhibited H1
antagonistic activities similar to 2c. These results indicated that -OCH3 is the optimal substituent at
this position. Moreover, H1 antagonistic activity slightly decreased when the -OCH3 group was
switched to meta- or para- position (13c-14c). It was also found that diflourine-substituted analogue
15c did not exhibit better activity.
N
R
R1
N
O
R2
R3
Cl
1c-15c
Table 1 Activities of the target compounds against H1 receptor
Compd.
R
R1
-OCH3
-OCH3
H
R2
H
R3
H
IC50 (nM)
9.28±1.86
2.95±0.79
6.23±0.84
17.65±2.28
8.90±1.51
36.71±6.38
4.74±1.01
28.41±2.41
40.22±2.00
52.85±4.96
81.78±5.55
20.98±2.64
8.14±1.06
11.97±2.26
27.88±3.66
1.84±0.19
1c
H
2c
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
H
H
3c
H
H
4c
-OCH2CH3
-CH3
-OCF3
-F
H
H
5c
H
H
6c
H
H
7c
H
H
8c
-Cl
H
H
9c
10c
-Br
H
H
-NO2
-CF3
H
H
11c
H
H
12c
-COCH3
H
H
H
13c
H
-OCH3
H
14c
H
-OCH3
-F
15c
-OCH3
-F
desloratadine
Based on the above results, compounds 1c-3c, 5c, 7c and 13c were chosen to evaluate their anti-
inflammatory activities in 2,4-dinitrofluorobenzene (DNFB)-induced mouse ear edema model. As
shown in Table 2, compared with the desloratadine (35.6%), all compounds exhibited higher
inhibitory activity (43-59.5%) at the dose of 5 mg/kg except compound 7c. This result indicates that
incorporating guaiacol structure into desloratadine could indeed enhance its anti-inflammatory
5

activity, which further supports our design rationale.
Table 2 Effect of DNFB-induced swelling and swelling inhibition of mouse ear (Mean±SD, n=8)
Compd.
Swelling（mg）
17.4±3.6
inhibition(%)@5mg/kg
model
-
Desloratadine
11.2±3.2△△
7.1±4.3△△#
7.1±2.4△△#
7.1±2.9△△#
7.1±2.9△△#
12.9±3.2△
35.6
59.5
59.2
59.1
59.1
26.0
43.1
1c
2c
3c
5c
7c
13c
9.9±3.0△△
△P<0.05 △△P<0.01 vs model group; #P<0.05, ##P<0.01 vs Desloratadine
As pro-inflammatory mediators (such as TNF-α) play a key role in inflammatory diseases, [14-
16] compounds 1c, 2c, 3c, 5c, 7c and 13c were selected to evaluate their inhibitory effects on TNF-
α via enzyme-linked immunosorbent assay (ELISA) at a dosage of 5 mg/kg in BALB/C mice (shown
in Figure 3). Compared with the model group, all compounds and desloratadine can significantly
inhibit the release of TNF-α (P<0.05). Among them, compounds 1c, 2c and 3c demonstrated higher
potency than desloratadine in TNF-α inhibition (P<0.05), suggesting that these compounds have
more pronounced immunosuppressive activity compared with desloratadine.
4
3
P<0.05 vs model
2
*
*
*
1
0
1c
2c
3c
5c
7c
13c
odel dine
ehicle m
v
slorata
De
Fig3. LPS induced inflammatory factor release in BALB/C mice (*P<0.05 vs desloratadine)
Since compound 2c showed both the strongest activity against H1 receptor and promising anti-
inflammatory effects, it was subjected to further study. Firstly, the R- and S-enantiomers (16c and
17c) were prepared individually and evaluated for their H1 antagonistic activity and anti-
6

inflammatory activity. As shown in Table 3, compare with 2c, enantiomers 16c and 17c showed
nearly identical H1 antagonistic activity with IC50 values of 3.67 nM and 4.56 nM, respectively. No
deviation is anti-inflammation activity was observed either, which means there is no significant
biological discrepancy between the two enantiomers.
Table 3 H1 antagonize and anti-inflammatory activity of 2c and its optical isomer
H1 antagonize
compound
Stereo configuration
TNF-α (ng/mL, n=10)
activity IC50 (nM)
Racemate
2.95
3.67
4.56
1.14±0.32
1.21±0.33
1.18±0.28
2c
R
S
16c
17c
Next, the pharmacokinetics of 2c was studied and the results showed that 2c has longer half-life
in rats (iv. 2 mg/kg) (T1/2=0.9 h) than in mice (iv. 2.5 mg/kg) (T1/2=0.47 h). Meanwhile, good plasma
exposure was observed in rats after oral administration (10 mg/kg) and the oral bioavailability of 2c
in rats is 18% (see Supporting Information Table 1). The metabolic stability and the potential
metabolites of 2c were investigated by incubating it with microsomes from different species (human,
mouse, rat, dog and monkey) for 6 h and the major metabolites were identified by LC/MS (see
Supporting Information Table 2). The results showed that compound 2c exhibited the greatest
stability in dog liver microsomes (DLM). The major metabolic pathway for 2c was the N-
dealkylation of the piperidinyl moiety leading to the formation of desloratadine (M-1, 24%). As, O-
dealkylation constitutes the second major metabolic pathway, leading to M-2 (9.2%). Similar to
desloratadine, the tricyclic structure is readily hydroxylated leading to the hydroxylated product (M-
3, 3.5%). (see Supporting Information Figure 1).
To further evaluate the safety profile of 2c, additional maximum tolerated dose (MTD)
determination test was conducted. The results showed that compound 2c exhibited significantly low
toxicity with MTD values over 750 mg/kg, which is significantly higher than desloratadine (LD50 =
250 mg/kg).
In this study, a series of novel derivatives were designed and synthesized to optimize the anti-
inflammatory activity of desloratadine. All compounds were evaluated for their H1 antagonize and
some compounds with single-digit nanomole IC50 values were evaluated for their anti-inflammatory
7

activities. Among them, racemate 2c exhibited the most promising anti-inflammatory and H1
antagonistic activities. Moreover, pharmacokinetic profiling of 2c demonstrated that it possesses
high stability in vivo and satisfying oral bioavailability and low toxicity. Currently, compound 2c is
undergoing further investigation in our lab.
Acknowledgements
This work was supported by Outstanding Scientific and Technological Innovation Team Projects
of Jiangsu Province, China（2015）
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Graphical Table of Contents
Graphical Abstract
8

N
N
NH
Cl
OH
OCH3
desloratadine
OH
N
O
Cl
2c
H1 antagonize: IC50=2.95nM
Swelling inhibition:59.2% @5mg/kg
LPS-induced release of TNF- 1.14 0.32ng/mL
OCH3
guaiacol
α:
±
To improve the anti-inflammatory activity of desloratadine, we designed and synthesized a
series of novel desloratadine derivatives. All compounds were evaluated for their anti-inflammatory
and H1 antagonistic activities. Among them, compound 2c showed the strongest H1 antagonistic
and anti-inflammatory activity. It also exhibited promising pharmacokinetic profiles and low
toxicity. All these results suggest that compound 2c as a novel anti-allergic agent is worthy of further
investigation.
9