Synthesis of polyhydroxylated aromatics having amidation of piperazine nitrogen as HIV-1 integrase inhibitor

Article abstract of DOI:10.1016/j.bmcl.2010.07.087

(E)-N-[3-(4-Cinnamoylpiperazin-1-yl)propyl]-3,4-dihydroxybenzamide and (E)-N-[3-(4-cinnamoylpiperazin-1-yl)propyl]-3,4,5-trihydroxybenzamide were designed and synthesized as potential HIV-1 integrase inhibitors and evaluated their inhibition to the strand

Full text of DOI:10.1016/j.bmcl.2010.07.087

Bioorganic & Medicinal Chemistry Letters 20 (2010) 5469–5471
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of polyhydroxylated aromatics having amidation of piperazine
nitrogen as HIV-1 integrase inhibitor
*
Leifu Yang, Xuemei Xu, Yali Huang, Bin Zhang, Chengchu Zeng, Hongqiu He, Cunxin Wang, Liming Hu
College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China
a r t i c l e i n f o
a b s t r a c t
Article history:
(E)-N-[3-(4-Cinnamoylpiperazin-1-yl)propyl]-3,4-dihydroxybenzamide and (E)-N-[3-(4-cinnamoylpi-
perazin-1-yl)propyl]-3,4,5-trihydroxybenzamide were designed and synthesized as potential HIV-1
integrase inhibitors and evaluated their inhibition to the strand transfer process of HIV-1 integrase.
The result indicates that 3,4,5-trihydroxylated aromatic derivatives exhibit good inhibition to HIV-1
integrase, however, corresponding 3,4-dihydroxylated aromatic derivatives appear little inhibition of
HIV-1 integrase.
Received 1 April 2010
Revised 27 June 2010
Accepted 21 July 2010
Available online 25 July 2010
Keywords:
HIV-1 integrase
Inhibitors
Ó 2010 Elsevier Ltd. All rights reserved.
Polyhydroxylated aromatics
Strand transfer
The human immunodeficiency virus type 1 (HIV-1) is the caus-
ative agent of the acquired immunodeficiency syndrome (AIDS).1
Highly active antiretroviral therapy (HAART) is now the common
treatment for HIV-1 patients, but the infection has been difficult
to cure because of drug resistance2,3 and immune response. In
the essential steps for viral replication, the viral enzyme integrase
mediated viral integration catalyzes the insertion of the proviral
DNA into the genome of host cells,4 therefore integrase is an attrac-
tive strategy for antiretroviral drug design.
essential for the enzyme inhibitory activity as a pharmacophore,
through the sequestration of the divalent cofactor in the IN active
core and then blocking the access of a host DNA to the integrase
enzyme. Full coplanarity of polyhydroxylated aromatics inhibitor
structure is not an absolute requirement for high activity, compu-
tational studies performed that certain IN inhibitors, such as
AG593, which linker segment is piperazine, cannot assume an en-
tirely coplanar conformation.7 Based on the nature and the length
of the linker between piperazine amide nitrogens, we have
Polyhydroxylated compound caffeic acid phenethyl ester dis-
play potent activities against HIV-1 integrase with weak cytotoxic-
ity.5 Being a pharmacophore of caffeic acid phenethyl ester, the
phenolic hydroxyl group is coordinated with metal ions, such as
Mg2+ or Mn2+, which block the 30-end processing (30-P) and the
strand transfer (ST) in the HIV-1 integrase catalytic core. Previous
studies have made great strides in the design and discovery of
integrase inhibitors, such as phenalenones isolated from fungal ex-
tracts,6 chalcone derivatives (1),7 caffeic acid phenethyl ester (2),
O
HO
HO
1
O
HO
caffeoylamino acid derivatives,8 sulfonamide (3),9,10
L-chicoric
O
acid11 and catechol-diketoacid hybrid,12 which show inhibitory
activity against HIV-1 integrase. The structure of inhibitors consists
of a hydrophobic subunit, a hydrophilic polyhydroxylated aromatic
domain and a linker segment (Fig. 1).13
HO
2
SO2NH
O
The linker and phenyl ring are responsible for the interaction
with the hydrophobic pocket and residues around the domain to
reinforce their affinity and selectivity to HIV-1 integrase.14 The
hydrophilic domain, being polyhydroxylated aromatic moiety, is
HO
N
H
HO
hydrophilic
OH
3
hydrophobic
* Corresponding author. Tel.: +86 10 6739 6211.
E-mail address: huliming@bjut.edu.cn (L. Hu).
Figure 1. Structural features of polyhydroxylated aromatics integrase inhibitors.
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.07.087

5470
L. Yang et al. / Bioorg. Med. Chem. Lett. 20 (2010) 5469–5471
R3
O
O
O
R4
R2
N
N
N
HO
HO
H
N
N
CN
CN
N
H
HO
OH
OH
OH
O
R1
Designed integrase inhibitor
AG593
Figure 2. The structures of AG593 and designed integrase inhibitor.
O
O
O
H3CO
H3CO
H3CO
H3CO
H3CO
(ii)
(i)
N
H
Cl
Cl
OH
H3CO
R5
6a,b
R5
R5
5a,b
4a,b
O
H3CO
H3CO
(iii)
N
N
R6
H
NH
O
R4
R2
R5
H3CO
7a,b
(iv)
(v)
N
N
N
(4-7) a R5=H,
(4-7) b R5=OCH3
H
H3CO
O
R5
10(a-f) R5=H
R2
O
R2
O
11(a-f) R5=OCH3
(i) R6
R6
R4
R3
Cl
OH
O
R4
R2
R4
HO
HO
N
N
N
H
8(a-f)
9(a-f)
O
R1
a R2=H, R4=H, R6=H
b R2=H, R4=CH3, R6=H
c R2=H, R4=Cl, R6=H
d R2=Cl, R4=H, R6=H
12(a-d) R1=H, R3=H; 12f R1=H, R3=OH
13(a-e) R1=OH, R3=H; 13f R1=OH, R3=OH
e R2=NO2,
f R2=H,
R4=H, R6=H
R4=H,
R6=OCH3
Scheme 1. Reagents and conditions: (i) SOCl2, reflux; (ii) NH2CH2CH2CH2Cl, CH2Cl2, 0 °C–rt, overnight; (iii) piperazine, K2CO3/KI, CHCl3, reflux; (iv) CH2Cl2, 0 °C–rt; (v) (1)
BBr3,CH2Cl2, rt, then H2O.
designed and synthesized polyhydroxylated aromatics compounds
as integrase inhibitors (Fig. 2).
Depicted in Scheme 1 is our synthetic route developed to allow
for efficient introduction of aromatic substituent on the piperazine
nitrogen toward the end of the synthesis.
at 5-position of the caffeoyl in 12 gave 13 to improve IN inhibition
activities. The results indicate the significance of galloyl as a core
pharmacophore. In order to investigate the substituent effect on
the phenyl ring in cinnamoyl moiety, electron-donating and elec-
tron-withdrawing groups were utilized (13a–f). All these com-
pounds display significant potent inhibitory activities without
any marked fluctuation. This observation somewhat indicates that
such substitution has no notable impact on their activities. The
HIV-IN inhibitory effect of compound 13 is nearly as much as that
of the control compound L-708906.
In conclusion, a series of nitrogen-containing polyhydroxylated
aromatics with piperazine linker have been identified as HIV-1
integrase inhibitors. Based on the nature and the length of the lin-
ker piperazine between amide nitrogens, it cannot assume that
conformation of polyhydroxylated aromatics structure is entirely
coplanar. The current work appears that (E)-N-[3-(4-cinnamoylpi-
perazin-1-yl)propyl]-3,4-dihydroxybenzamide and (E)-N-[3-(4-
cinnamoylpiperazin-1-yl)propyl]-3,4,5-trihydroxybenzamide
were designed and synthesized for HIV-1 integrase inhibitors and
(E)-N-[3-(4-cinnamoylpiperazin-1-yl)propyl]-3,4,5-trihydroxyben-
zamide can inhibit replication of HIV-1 in vitro against integrase in
strand transfer at micromolar concentrations. We believe that the
oxygen atoms in phenolic hydroxyl groups are coordinated with
The synthesis of inhibitors 12 and 13 starts with treatment of
3,4,5-trimethoxy benzoic acid or 3,4-dimethoxy benzoic acid 4
with thionyl chloride, to give benzoyl chloride 5 in excellent yield,
which was treated with 3-chloropropen-1-amine to provide the
3-chloropropyl benzamide 6. Direct mono-amination of 6 with
piperazine in chloroform obtained intermediate 7 in a good yield.
Another intermediate 9 was obtained from cinnamic acid 8 react-
ing with thionyl chloride. Amidation between 7 and 9 was carried
out in dichloromethane to convert to N-[3-(4-cinnamoylpiperazin-
1-yl)propyl]benzamide 10 and 11. Finally, the methyl removal led
to our target compounds 12 and 13 using tribromoborane.
Compounds 12 and 13 were tested in vitro for strand transfer in
the enzyme inhibition assay according to a previous method.15 As
shown in Table 1, 3,4-dihydroxylated aromatics derivatives 12
show less activity towards strand transfer, but 3,4,5-trihydroxylat-
ed aromatics derivatives 13 exhibit activities at micromolar con-
centrations. In comparing the potencies of 12 and 13 in the
strand transfer assay, it was seen that introduction of a hydroxyl

L. Yang et al. / Bioorg. Med. Chem. Lett. 20 (2010) 5469–5471
5471
Table 1
2009CB930200) and Beijing Natural Science Foundation (No.
7102009).
Inhibition of HIV-1 integrase catalytic activities of compounds 12 and 13a
R3
Supplementary data
O
R4
R2
HO
HO
N
H
N
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.07.087.
N
O
R1
References and notes
b
Compds
R1
R2
R3
R4
IC50 (lM)
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12b
12c
12d
12f
13a
13b
13c
13d
13e
13f
H
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24.94
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31.31
15.41
0.77
CH3
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H
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H
H
OH
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Acknowledgements
The authors would like to acknowledge financial support from
the National Key Basic Research Program of China (No.