Bioisosteric modification of PETT-HIV-1 RT-Inhibitors: Synthesis and biological evaluation

Article abstract of DOI:10.1016/S0960-894X(99)00675-7

Bioisosteric substitution of the thiourea (3, 5, 7, 9) and urea (10) moiety of PETT compounds with sulfamide (1), cyanoguanidine (2, 4) and guanidine (6, 8) functionalities, and replacement of the phenetyl group with benzolethyl group (compounds 11-20) ha

Full text of DOI:10.1016/S0960-894X(99)00675-7

Bioorganic & Medicinal Chemistry Letters 10 (2000) 265±268
Bioisosteric Modi®cation of PETT-HIV-1 RT-Inhibitors:
Synthesis and Biological Evaluation
Marita Ho
È
gberg,* Per Engelhardt, Lotta Vrang and Hong Zhang
Medivir AB, Lunastigen 7, S-141 44 Huddinge, Sweden
Received 3 September 1999; accepted 25 November 1999
AbstractÐBioisosteric substitution of the thiourea (3, 5, 7, 9) and urea (10) moiety of PETT compounds with sulfamide (1),
cyanoguanidine (2, 4) and guanidine (6, 8) functionalities, and replacement of the phenethyl group with benzoylethyl group (com-
pounds 11±20) have been studied. Synthesis and antiviral activities are described. # 2000 Elsevier Science Ltd. All rights reserved.
1
PETT (phenylethylthiazolethiourea) compounds as
2
with SO Cl and a catalytic amount of SbCl in aceto-
2 2 5
±4
delavirdine, efavirenz,6 HBY-
97, loviridine and tivirapine belong to the family
of non-nucleoside reverse transcriptase inhibitors
NNRTIs) which inhibit the viral reverse transcriptase
5
well as nevirapine,
8
nitrile at re¯ux to a€ord amidosulfonyl chloride. This
was then coupled with an anion of 2-amino-5-chloro-
pyridine which was generated by the reaction of 2-
7
9
0
ꢀ
(
by binding to it non-competitively.
amino-5-chloropyridine with NaH at � 10 C in THF to
9
give compound 1.
As earlier reported, thiourea10,11 and urea12,13 deriva-
tives in the PETT series are potent HIV-1 RT inhibitors
both at the enzyme level and in cell culture assays. As
with other NNRTIs, they bind to an allosteric site of
HIV-1 RT. The three-dimensional structure of com-
plexes between HIV-1 RT and some PETT derivatives
have been determined. To explore the e€ect of a bio-
isosteric replacement for the thiourea and urea moieties,
sulfamide, cyanoguanidine and guanidine functional-
ities (Table 1) were selected as synthetic targets. Addi-
tionally, a series of benzoylethyl analogues to the
phenylethyl, pyridylethyl and phenylcyclopropyl moi-
eties of PETT compounds, was synthesized (Table 2).
The antiviral activity was determined both at the RT
level and in cell culture against HIV-1 wild type virus.
Two di€erent methods to prepare cyanoguanidine deri-
vatives are described in Scheme 2. (i) Thiourea deriva-
tive 5 can be directly converted to the corresponding
cyanoguanidine by treatment with PbNCN in acetonitrile-
DMF at re¯ux to a€ord compound 4.15 (ii) Compound 2
1
1
was prepared from 4-chloro-2-pyridylisothiocyanate by
16
1
3
the procedure of Atwal. Isothiocyanate was treated
with NaHNCN in EtOH at room temperature to give
an intermediate thiourea compound which was reacted
with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide
hydrochloride and phenethylamine in a one pot reaction
to give compound 2.
A direct conversion of a thiourea compound 7 into
guanidine was achieved by reacting 7 with AgSO CF ,
2
3
ꢀ
described in Scheme 3. Compound 8 was synthesized
according to the same procedure.
in NH /CH Cl at � 30 C to give compound 6 as
3
2
2
Chemistry
The synthesis of the thiourea and urea compounds 3, 5,
1
The synthesis of the benzoylethyl derivative 11 is
described in Scheme 4 and this general methodology
was also used for the preparation of compounds 12±14,
16±20. Compound 15 was synthesized from compound
0±12
7
, 9 and 10 is described in our previous papers.
The
sulfamide derivative, compound 1, was synthesized
1
4
from phenethylamine hydrochloride as shown in
Scheme 1. Phenethylamine hydrochloride was treated
12 by converting it to the urea analogue by a procedure
2,13
described earlier.1
Benzoylethylamine was prepared
by a Mannich reaction where formaldehyde was con-
densed with ammonium chloride and acetophenone to
give an amine which was coupled with an intermediate
*Corresponding author. Fax: +46-8-608-31-99; e-mail: marita.
hogberg@medivir.se
1
1
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(99)00675-7

2
66
M. HoÈgberg et al. / Bioorg. Med. Chem. Lett. 10 (2000) 265±268
Table 1.
Table 2.
Compound
HIV-1 RT
rCdG),
IC50, mM
HIV-1
MT-4 cells,
ED50, mM
(
a
b
>10
>100
Compound
Ar
Y
X
HIV-1 RT
rCdG),
IC50, mM
HIV-1
MT-4 cells,
(
a
ED50,
b
mM
>10
>100
1
1
1
1
1
1
1
1
1
2
1
2
3
4
5
6
7
8
9
0
Phenyl
S
S
S
S
O
S
S
S
S
S
Br
Br
Br
Br
Br
Br
Br
Br
Cl
Br
<0.027
0.004
0.010
0.003
0.054
0.080
0.047
<0.025
0.006
0.003
0.036
0.009
0.100
0.076
0.201
0.911
0.300
0.067
0.028
0.050
0.010
2-¯uorophenyl
2-chlorophenyl
2-methoxyphenyl
2-¯uorophenyl
3-methoxyphenyl
4-¯uorophenyl
2,5-di¯uorophenyl
2,6-di¯uorophenyl
2,6-di¯uorophenyl
0
.003
0.03
0.001
>
10
>100
a,bSee footnote a and b, Table 1.
0
0
.04
.18
0.4
1.2
0
derived from 2-amino-5-bromopyridine and 1,1 -thio-
carbonyldiimidazole to a€ord compound 11.
Biological Results and Discussion
0
0
.008
.4
0.02
1.0
All compounds in this study were tested in an HIV-1
RT wild-type enzyme assay and in a cell culture assay
using MT-4 cells and wild-type virus. The IC50 and
ED50 values from these assays are presented in Tables 1
and 2. The replacement of the thiourea moiety of
compound 3 with a sulfamide functionality, compound
1
, caused complete loss of activity as well as did the
replacement of the thiourea moiety of compounds 3 and
with the cyanoguanidine moiety, compounds 2 and 4
5
0
0
.012
.004
0.007
0.05
(Table 1). The replacement of the thiourea moiety of
compounds 7 and 9 or the urea moiety of compound 10
with a guanidine functionality, compounds 6 and 8,
caused a decrease in activity, but the compounds
retained an IC50 of 0.18±0.4 mM and ED50 of 1.0±1.2
mM. The role of thiourea and urea moiety of PETT
compounds thus appears essential for optimal anti-HIV
activity. The size of guanidine moiety is close to that of
thiourea and urea, whereas the sulfamide and cyano-
guanidine moieties are somewhat larger which may
explain their respective activities. Benzoylethyl deriva-
tives 11±20 in Table 2 were quite potent inhibitors of
wild-type HIV-1 RT and HIV-1 virus in cell culture.
aThe HIV-1 RT assay which used (poly)rC.(oligo)dG as the template/
primer is described in ref 17.
Anti HIV activity assay: MT4 cells (human T cell line) grown in
RPMI 1640 medium supplemented with 10% fetal calf serum, peni-
2
,6-Di¯uorobenzoyl compound 20 showed a three fold
b
loss of activity at the HIV-1 RT level and a ®ve fold loss
in cell culture against HIV-1 wild type virus compared
4
cillin and streptomycin were seeded into 96 well microplates (2Â10
1
1
cells/well) and infected with 10±20 TCID50 of HIV-1, IIIb per well.
Test compounds in di€erent concentrations were added. The cultures
to the corresponding phenethyl compound 21. The
structure±activity relationships followed the same
substitution pattern as we have described earlier for
phenethyl thiourea compounds.11 The change of a ¯uo-
ro substituent from the 2-position of the phenyl ring,
ꢀ
were incubated at 37 C in CO
2
atmosphere and the viability of cells
18
was determined at day ®ve or six with XTT vital dye. The anti HIV-1
activity was measured as the reduction in cytopathic e€ect caused by
the virus.

M. HoÈgberg et al. / Bioorg. Med. Chem. Lett. 10 (2000) 265±268
267
Scheme 1.
Scheme 2.
Scheme 3.
Scheme 4.
compound 12, to 4-position of the phenyl ring, com-
pound 17, decreased the activity on wild type virus from
ED50 of 0.009 mM to ED50 of 0.3 mM. When benzoyl-
ethyl compounds were tested on mutant HIV-1 RT and
virus they di€ered from the phenethyl compounds by
losing much more activity. The ED50 on mutant virus
for benzoylethyl compound 20 was >260 mM compared
to 5.7 mM for phenethyl compound 21. Activities on
Acknowledgements
Ê
Ê
We thank C. Rydegard and C. Ahgren for technical
assistance with the biological assays.
References and Notes
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