Synthesis and evaluation of novel quinolinones as HIV-1 reverse transcriptase inhibitors

Article abstract of DOI:10.1016/S0960-894X(01)00331-6

A series of 4,4-disubstituted quinolinones was prepared and evaluated as HIV-1 reverse transcriptase inhibitors. The C-3 substituted compound 9h displayed improved antiviral activity against clinically significant single (K103N) and double (K103N/L100I) mutant viruses.

Full text of DOI:10.1016/S0960-894X(01)00331-6

Bioorganic & Medicinal Chemistry Letters 11 (2001) 1943–1945
Synthesis and Evaluation of Novel Quinolinones as HIV-1
Reverse Transcriptase Inhibitors
Mona Patel,* Robert J. McHugh, Jr., Beverly C. Cordova, Ronald M. Klabe,
Lee T. Bacheler, Susan Erickson-Viitanen and James D. Rodgers
DuPont Pharmaceuticals Company, Experimental Station, E500/4803, PO Box 80500, Wilmington, DE 19880-0500, USA
Received 17 April 2001; accepted 8 May 2001
Abstract—A series of 4,4-disubstituted quinolinones was prepared and evaluated as HIV-1 reverse transcriptase inhibitors. The C-3
substituted compound 9h displayed improved antiviral activity against clinically significant single (K103N) and double (K103N/
L100I) mutant viruses. # 2001 DuPont Pharmaceuticals Company. Published by Elsevier Science Ltd. All rights reserved.
Human immunodeficiency virus type -1 (HIV-1) is the
causative agent for the transmission and development of
the acquired immunodeficiency syndrome (AIDS).1
Current therapies target two sites of intervention in the
replication cycle of the virus. These sites are the inhibi-
tion of (a) HIV protease and (b) HIV reverse tran-
scriptase. Reverse transcriptase inhibitors are of two
types: nucleoside reverse transcriptase inhibitors
(NRTIs) such as AZT, 3TC, and DDI, and non-
nucleoside reverse transcriptase inhibitors (NNRTIs)
such as nevirapine, delavirdine and efavirenz.2 Non-
nucleoside reverse transcriptase inhibitors play a vital
role in combination therapy for the treatment of AIDS.
Efavirenz (Fig. 1),3 a potent NNRTI, is a significant
component of a very effective (protease sparing) regi-
men when coadministered with AZT and 3TC. One of
the difficulties encountered during antiretroviral therapy
has been the emergence of resistant mutant viral forms.
A subset of patients for reasons of poor compliance,
partial pre-existing resistance or poor bioavailability
often develops resistant viral strains. This situation is
compounded by the selection of some resistance muta-
tions which confer cross-class resistance such as single
mutation K103N and double mutation K103N/L100I.
Herein we describe a series of novel 4,4-disubstituted
quinolinones that were discovered as part of our con-
tinuing effort directed towards the development of sec-
ond generation NNRTIs possessing an improved
resistance profile.
Synthesis of the parent quinolinone is shown in Scheme 1.
Readily available 4-chloro-2-trifluoroacetylaniline 1 (an
intermediate in the synthesis of efavirenz)3 was acylated
with bromoacetyl bromide in tetrahydrofuran to pro-
vide 2 in quantitative yield. Due to the unstable nature
of this compound, it was used as is without further
purification. Treatment of 2 with two equivalents of the
sodium salt of benzenesulfinic acid resulted in the initial
displacement of the halogen followed by deprotonation
and ring closure to provide bicyclic compound 3 in
good yield. Introduction of the double bond through
an acylation–elimination pathway was accomplished by
treatment of 3 with acetic anhydride and DMAP in
dichloromethane, resulting in sulfone 4. Nucleophilic
addition of lithium cyclopropylacetylide to sulfone 4
followed by reductive desulfurization with aluminum
amalgam provided quinolinone 5 in good overall yield
(Scheme 1).4
Figure 1. Efavirenz (SustivaTM).
In order to introduce functionality at the C-3 position,
we had to first prepare the SEM protected quinolinone
using SEMCl, DIPEA in dichloromethane. Treatment
of the SEM protected quinolinone with LDA and tosyl
azide5 in tetrahydrofuran provided azido quinolinone 6
*Corresponding author at current address: The R. W. Johnson Phar-
maceutical Research Institute, 1000 Route 202, Building: PCC; Room:
PC110, Raritan, NJ 08869, USA. Tel.: +1-908-707-3558; fax: +1-
908-203-8109; e-mail: mpatel5@prius.jnj.com
0960-894X/01/$ - see front matter # 2001 DuPont Pharmaceuticals Company. Published by Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00331-6

1944
M. Patel et al. / Bioorg. Med. Chem. Lett. 11 (2001) 1943–1945
in good yield. Reduction of the azide to the corre-
sponding amine followed by either alkylation or acyla-
tion and removal of the SEM protecting group provided
compounds 7a–c as a 1:1 mixture of diastereomers
(Scheme 2).4 The diastereomers were separated by col-
umn chromatography and the relative stereochemistry
assigned on the basis of NOE experiments prior to anti-
viral evaluation.
In a comparable manner, the introduction of a hydroxy
group at the C-3 position was carried out by the
treatment of SEM protected quinolinone with LDA and
MoOPH6 in tetrahydrofuran to provide quinolinone 8
in good yield. Alkylation of the hydroxy group in qui-
nolinone 8 resulted in compounds 9a–o as a 1:1 mixture
of diastereomers (Scheme 3).4 As in the C-3 amino sub-
stituted series, the diastereomers were separated by
column chromatography prior to antiviral evaluation.
Scheme 1. (a) BrCOCH2Br, K2CO3, THF, 25 ꢀC, 3 h, quantitative; (b)
NaSO2Ph, DMF, 25 ꢀC, 18 h, 89%; (c) Ac2O, DMAP, DCM, 25 ꢀC,
18 h, 94%; (d) nBuLi, cyclopropylacetylene, THF, À78 ꢀC to 25 ꢀC,
1 h, 75%; (e) Al/Hg, EtOH, reflux, 1 h, 77%.
The results of the enzyme inhibition and the anti-
infectivity assays have been summarized in Table 1. The
parent quinolinone 5 showed good activity in the anti-
viral assays. However, the activity against single muta-
tions (K103N and L100I) was rather poor. In an
attempt to improve upon the resistance profile, we
introduced substitutions at the C-3 position. As seen in
Table 1, introduction of a nitrogen containing group at
the C-3 position was detrimental to antiviral activity. As
a series, the 3-alkoxy substituted quinolinones (9a–o)
were more potent in both the enzyme inhibition and
whole cell based assays than the C-3 amino substituted
compounds. The O-alkyl substituted compounds (9b–d)
Table 1. Antiviral activity of quinolinones
Scheme 2. (a) PMBCl, K2CO3, DMF, 25 ꢀC, 14 h, 74%; (b) LDA,
ꢀ
ꢀ
.
TsN3, THF, 0 C to 25 C, 1 h, 93%; (c) SnCl2 H2O, MeOH/THF
(1:1), 25 ꢀC, 3 h, 83%; (d) BuBr, K2CO3, DMF, 25 ꢀC, 14 h, 50%; or
Ac2O, pyridine, DCM, 25 ꢀC, 3 h, 74%; or ClCO2Me, K2CO3, THF,
25 ꢀC, 2 h, 67%; (e) CAN, MeCN/H2O (9:1), 25 ꢀC, 0.5 h, 45–84%.
Compound
R
IC50 (nM)7a IC50 (nM)7b
Efavirenza
5
—
H
48
130
2
14
7a
7b
7c
9a
9b
9c
9d
9e
9f
9g
9h
9i
9j
9k
9l
N(H)Bn
N(H)CO2Me
N(H)Ac
OH
>2000
>2000
>2000
>2000
>2000
1434
1051
440
1572
438
129
1296
1776
899
1019
1455
412
218
212
917
637
>1000
130
62
O-3,3-Dimethylallyl
O-Cyclopropylmethyl
O-n-Propyl
OBn
71
140
20
O-2-Pyridylmethyl
O-3-Pyridylmethyl
O-4-Pyridylmethyl
O-2-Fluorobenzyl
O-3-Fluorobenzyl
O-4-Fluorobenzyl
O-2-Aminobenzyl
O-3-Aminobenzyl
O-4-Aminobenzyl
O-3-Fluoro-4-aminobenzyl
19
140
201
112
115
138
21
Scheme 3. (a) SEMCl, NaH, THF, 25 ꢀC, 14 h, 39%; (b) LDA,
MoOPH, THF, 0–25 ꢀC, 14 h, 68%; (c) RX, NaH, DMF, 25 ꢀC, 14 h,
18–73%; (d) nBu3P, NH4OH/THF (1:1), 25 ꢀC, 14 h, 16–55%; (e)
TFA/DCM (1:1), 25 ꢀC, 0.3 h; 15% aq NaOH/MeOH (1:1), 25 ꢀC, 0.1
h, 12–61%.
9m
9n
9o
241
26
aDenotes single enantiomer.

M. Patel et al. / Bioorg. Med. Chem. Lett. 11 (2001) 1943–1945
1945
Table 2. Resistance profile of 9h
References and Notes
Compound
K103N
IC90 (nM)
L100I
IC90 (nM)
K103N/L100II
C90 (nM)
1. Levy, J. A. Microbiol. Rev. 1993, 57, 183.
2. (a) Jonckheere, H.; Anne, J.; De Clercq, E. Med. Res. Rev.
2000, 20, 129. (b) Hajos, G.; Riedl, Z.; Molnar, J.; Szabo, D.
Drugs Future 2000, 25, 47.
Efavirenza
5
9h
9n
64 (Æ24)b
1770
50
77 (Æ18)b
7300 (Æ5000)b
992
23
nd
4830
3848
3. Young, S. D.; Britcher, S. F.; Tran, L. O.; Payne, L. S.;
Lumma, W. C.; Lyle, T. A.; Huff, J. R.; Andersen, P. S.;
Olsen, D. B.; Carroll, S. S.; Pettibone, D. J.; O’Brien, J. A.;
Ball, R. G.; Balani, S. K.; Lin, J. H.; Chen, I-W.; Scheif, W. A.;
Sardana, V. V.; Long, W. J.; Brynes, V. W.; Emini, E. A.
Antimicrob. Agents Chemother. 1995, 39, 2602.
4. All compounds provided satisfactory spectral data (1H
NMR, 19F NMR, CI-MS/ESI-MS, and HR-MS/peak match)
and were homogeneous by TLC.
5. Tosyl azide was prepared as follows: To a solution of tosyl
chloride (20 g, 105 mmol) in water (40 mL) at room tem-
perature was added sodium azide (8.6 g, 132 mmol) and the
resulting reaction mixture was allowed to stir at room tem-
perature for 2 h. The reaction mixture was diluted with water
(500 mL) and extracted with ether (3Â100 mL). The com-
bined ether extracts were dried over anhydrous sodium sul-
fate and concentrated in vacuo to provide 19.73 g of tosyl
azide (20.63 g theoretical, 96% yield). Tosyl azide can be
purchased from Esprit Chemical Company, Sarasota, FL,
USA.
1082
49
nd=not determined.
aDenotes single enantiomer.
bValues are means of two experiments, standard deviation is given in
parentheses.
were unimpressive as antivirals. The introduction of
aryloxy substitutions at the C-3 position improved the
antiviral activity profile. Of particular interest were the
pyridylmethyl (9f–h) and the aminobenzyl (9m–o) sub-
stituted compounds for they exhibit low nanomolar
activity in the whole cell assay. The most potent com-
pound 9h was selected for further testing against resistant
mutant strains (Table 2).
Although the activity of 9h as a racemic mixture against
wild type is 5-fold worse than efavirenz, the activity
against the two important singles (K103N and L100I)
was improved. Unfortunately, there was no significant
improvement against the K103N/L100I double muta-
tion (Table 2).
6. For the preparation of MoOPH see: Vedejs, E.; Larsen, S.
In Organic Syntheses; Freeman, J. P., Ed.; John Wiley & Sons:
New York, 1990; Coll. Vol. 7, pp 277–282.
7. (a) All compounds were assayed for enzyme inhibitory
activity (IC50) according to the protocol described in: Sardana,
V. V.; Emini, E. A.; Gotlib, L.; Graham, D. J.; Lineberger,
D. W.; Long, D. W.; Schlabach, A. J.; Wolfgang, J. A.; Con-
dra, J. H. J. Biol. Chem. 1992, 267, 17526, using a template
primer poly (rA) oligo (dT)12À18. (b) All compounds were
assayed for whole cell based antiviral activity (IC90) according
to the protocol described in: Bacheler, L. T.; Paul, M.; Jadhav,
P. K.; Otto, M.; Miller, J. Antiviral Chem. Chemother. 1994, 5,
111.
In summary, we have described the preparation and
evaluation of quinolinones as novel non-nucleoside
reverse transcriptase inhibitors. Although compound 9h
showed an improved resistance profile as compared to
efavirenz against single mutations, there was not
enough improvement against the K103N/L100I double
mutation to warrant further investigation.