Identification of 2-((2,3-dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-phenylpropanamides as a novel class of potent DprE1 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2020.127192

The identification of a novel series of DprE1 inhibitors based on a 2-((2,3-dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-phenylpropanamide scaffold is described herein. SAR exploration around the HTS hit 1 led to the identification of multiple analogues with potent DprE1 inhibition and good whole-cell antimycobacterial activity.

Full text of DOI:10.1016/j.bmcl.2020.127192

Journal Pre-proofs
Identification of 2-((2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-phenyl‐
propanamides as a novel class of potent DprE1 Inhibitors
Benjamin C. Whitehurst, Robert J. Young, Glenn A. Burley, Monica Cacho,
Pedro Torres, Laura Vela-Gonzalez del Peral
PII:
S0960-894X(20)30291-2
DOI:
Reference:
https://doi.org/10.1016/j.bmcl.2020.127192
BMCL 127192
To appear in:
Bioorganic & Medicinal Chemistry Letters
Received Date:
Revised Date:
Accepted Date:
28 January 2020
5 April 2020
11 April 2020
Please cite this article as: Whitehurst, B.C., Young, R.J., Burley, G.A., Cacho, M., Torres, P., Vela-Gonzalez del
Peral, L., Identification of 2-((2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-phenylpropanamides as a novel
class of potent DprE1 Inhibitors, Bioorganic & Medicinal Chemistry Letters (2020), doi: https://doi.org/10.1016/
j.bmcl.2020.127192
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Bioorganic & Medicinal Chemistry Letters
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Identification of 2-((2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-
phenylpropanamides as a novel class of potent DprE1 Inhibitors
Benjamin C. Whitehursta,b*, Robert J. Younga*, Glenn A. Burleyb, Monica Cachoc, Pedro Torresc, Laura
Vela-Gonzalez del Peralc
a GlaxoSmithKline, Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, U.K
b Department of Pure and Applied Chemistry, WestCHEM, University of Strathclyde, Glasgow, G1 1XL, U.K
c Global Health R&D, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, 28760 Madrid, Spain
ARTICLE INFO
ABSTRACT
Article history:
Received
Revised
The identification of
a
novel series of DprE1 inhibitors based on
a
2-((2,3-
dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-phenylpropanamide scaffold is described herein.
SAR exploration around the HTS hit 1 led to the identification of multiple analogues with potent
DprE1 inhibition and good whole-cell antimycobacterial activity.
Accepted
Available online
2009 Elsevier Ltd. All rights reserved.
Keywords:
Tuberculosis
DprE1
Inhibitor
2,3-dihydrobenzo[b][1,4]dioxine
Minimum inhibitory concentration
Tuberculosis (TB) is a highly contagious airborne disease caused
by the pathogenic organism Mycobacterium tuberculosis (M.tb).
The World Health Organization (WHO) estimated that in 2018 10
million people were infected with TB and 1.5 million perished
from the disease1. The current standard of care for TB is a 6-month
regimen of four “front-line” antibiotics, however, due to the
emergence of multi-drug resistant (MDR) strains of M.tb,
treatment for drug-susceptible TB is becoming increasingly
ineffective.2 Treatment for MDR-TB requires at least two years of
medication with less effective “second-line” antibiotics.3
Furthermore, extensively drug-resistant (XDR) TB cases are
becoming increasingly prevalent, where additional resistance to
the main second-line drug classes is observed.4 Encouragingly,
three new drugs have recently been approved by the FDA for the
treatment of MDR and XDR-TB: delamanid, bedaquiline and
pretomanid.5 All three compounds however, are associated with
serious adverse events.
component arabinan.6 Whilst there is evidence for redundancy of
the
DprE2-catalysed
reduction
(in
Corynebacterium
glutamicum),7 DprE1 is an essential8,9 enzyme; inhibition of DprE1
prevents cell wall metabolism and M.tb growth.10
DprE1 was identified through the action of a series of
nitroaromatic benzothiazinones (BTZs, e.g. BTZ-043, Figure 1), a
class of suicide inhibitors shown to bind covalently to the
enzyme.11,12 Since this discovery a diverse array of structurally
disparate covalent/ irreversible and noncovalent DprE1 inhibitors
have been identified.13–18 Furthermore, four advanced compounds
are currently being progressed through clinical trials: BTZ-043,10
PBTZ-169,19 TBA-737120 and OPC-16783217 (Figure 1). As such
DprE1 is a highly validated target, and inhibitors represent
potentially transformational medicines for the treatment of TB.
To identify proprietary DprE1 inhibitors, a high-throughput
screening (HTS) campaign was conducted at GlaxoSmithKline
(GSK). These efforts led to the identification of a novel series of
2-((2,3-dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-
phenylpropanamides, the structures of which are unrelated to
previously published inhibitors. Herein we disclose this new series
and the work performed to elaborate on the HTS cluster, focusing
on the relationships between ligand structure and both DprE1
inhibition and antimycobacterial activity. We also provide
evidence that this series effects inhibition of mycobacterial growth
through engagement of DprE1.
The discovery of new medicines to treat TB is clearly of great
importance. In particular, there is an impetus to develop drugs
acting via novel modes of action that are unlikely to show cross-
resistance with marketed compounds. One such potential
therapeutic
target
is
the
mycobacterial
enzyme
decaprenylphosphoryl-β-D-ribose 2´-epimerase (DprE1). DprE1
is a dehydrogenase, that in concert with a reductase DprE2
converts
decaprenylphosphoryl-β-D-ribose
into
decaprenylphosphoryl-β-D-arabinose, a key arabinose donor
required for the synthesis of the mycobacterial cell wall

Br
O
O
O
NO2
NO2
N
a
b
Br
Br
O
1
Cl
42
N
H
S
N
S
N
N
N
43
F3C
F3C
O
O
BTZ-043
PBTZ-169
Scheme 1. Reagents and conditions: (a) p-bromoaniline, NaHCO3, DCM,
o
o
0 C → r.t. (b) 2,3-Dihydrobenzo[b][1,4]dioxin-6-amine, NEt3, DMF, 80 C,
O
µwave.
O H
HO
N
To facilitate delineation of SAR, the structure of 1 was divided
into 3 components: the central alanine linker; the left-hand side
aminobenzodioxane; and the right-hand side C-terminal aniline
(Figure 2). Before new compounds were synthesized, analysis of
closely related analogues from the HTS cluster and from sub-
structure searching of the GSK compound collection afforded
some early SAR information. This data is included in the following
analyses where appropriate.
O
F
N
N
N
F
N
H
O
N
H
Cl
N
O
F
O H
TBA-7371
OPC-167832
We first sought to investigate modification of the racemic
alanine linker of 1. A selection of linker variants 2-13 were
prepared as described in Scheme 2. A Chan-Lam coupling
between boronic acid 44 and D- or L-alanine methyl ester
hydrochloride,24 followed by an aluminium-mediated aminolysis
of the intermediate esters 45 and 46 furnished single enantiomers
2 and 3. Interestingly, intermediate carboxylic acid 47 generated
by saponification of ester 45 was unstable to protonating
conditions and decomposed upon acidic work-up. Compounds 4-
10 were prepared from commercial α-bromo carboxylic acids or
acid halides 48 via sequential amide bond formation and α-
bromide displacement with the appropriate anilines or phenol (for
10). C-linked derivative 11 was prepared by aluminium-mediated
aminolysis25 of ester 50, itself accessible from aldehyde 49. γ-
Lactam 12 was prepared by alkylation of 2,3-
dihydrobenzo[b][1,4]dioxin-6-amine with intermediate 51.26 δ-
Lactam 13 was prepared in an analogous fashion from tosylate 53,
which was prepared from known alcohol 52.27
Figure 1. DprE1 inhibitors currently in clinical trials
HTS hit compound 1 (Figure 2) was of interest as it
demonstrated potent DprE1 inhibition (pIC50 = 7.2). Upon re-
synthesis (Scheme 1), 1 pleasingly maintained enzymatic potency
and demonstrated good antimycobacterial whole-cell activity
(minimum inhibitory concentration, MIC = 8 µM). Whilst
compound 1 was one of the most potent molecules identified from
the HTS, similarity-based clustering of the HTS hits revealed a
range of analogues with moderate-to-good DprE1 inhibition,
which gave confidence to initiate hit-to-lead chemistry. However,
compound 1 contained 4 structural alerts21: two anilines, and
precursors to potential ortho quinone and para quinone imine
metabolites. Furthermore, physicochemical profiling highlighted
that 1 was rather lipophilic (Chrom LogD7.4 = 5.5) and had a high
PFI score (7.5). The Property Forecast Index (PFI = Chrom
LogD7.4 + # Aromatic rings) was used as a metric to assess
physicochemical quality: a PFI < 7 is indicative of likely
reasonable solubility and ADMET outcomes.22,23
alanine
linker
Br
O
H
N
O
O
N
H
(±) 1
amino-
benzodioxane
C-terminal
aniline
DprE1 pIC50[a] (IC50 / µM)
MIC / µM[b]
7.2 (0.063)
7.8
Chrom logD7.4 (PFI[c])
HepG2 IC50 / µM [d]
5.5 (7.5)
>100
Figure 2. Structure of HTS hit 1. [a] DprE1 pIC50 is the negative logarithm
of the IC50 concentration expressed in molar (M) obtained in the DprE1-
inhibition assay. [b] MIC against M.tb (H37Rv); isoniazid was used as reference
with MIC = 1.8 µM. [c] PFI = Property Forecast Index. [d] Cytotoxicity against
HepG2 human Caucasian hepatocyte carcinoma.

MIC (4.0 µM). Reversal of the alanine linker in 8 almost ablated
activity entirely, demonstrating the importance of the linker
orientation. Methylation of the amine afforded potent compound 9
with a low MIC (2.5 µM), whilst replacement with an oxygen in
ether-linked 10 was less well-tolerated. Exchange of this linking
atom with a carbon removed the aniline and aminophenol
structural alerts of 1, but unfortunately led to reduced potency for
11. Lactams 12 and 13 were only poorly active, demonstrating that
constrained linkages were not well tolerated.
B(OH)2
O
O
H
H
N
O
O
N
O
O
*
a
O
b
O H
O
O
45 = (R)
46 = (S)
47
44
c
Br
O
H
N
*
Table 1. Linker variation SAR
O
O
N
H
[a]
pIC50
Chrom logD7.4,
(PFI)
Linker
MIC / µM [b]
6.5
(IC50 / µM)
2 = (R)
3 = (S)
O
H
N
2
3
6.6 (0.251)
6.0 (1.00)
5.5 (7.5)
5.5 (7.5)
6.0 (8.0)
6.6 (8.6)
5.1 (7.1)
6.3 (8.3)
5.3 (7.3)
6.7 (8.7)
6.2 (8.2)
6.2 (8.2)
6.0 (8.0)
5.8 (7.8)
N
H
Br
O
O
O
O
H
N
Y
d, e
Br
N
13
62
X
N
H
R'
H
R
R
H
N
48 = Br, Cl or OH
4 - 10
N
H
4
5.4 (3.98)
Y = NH, NMe, O
O
H
N
O
N
H
5
4.4 (39.81)
6.7 (0.200)
6.9 (0.126)
4.2 (63.10)[c]
7.2 (0.063)
6.7 (0.200)
5.7 (2.00)
>125
16
O
O
O
f, g
OEt
O
O
O
H
N
O
6
N
H
49
50
H
N
h
7
4.0
N
H
H
N
Br
O
N
H
8
125
2.5
O
O
N
H
O
O
O
N
O
9
N
H
Br
11
O
O
Linker
O
X
O
10
11
12
13
12
H
N
N
H
O
i
N
Br
N
Br
O
O
O
( )
n
( )
O
n
110
>125
110
N
H
51 X = Br, n = 1
52 X = OH, n = 2
53 X = OTs, n = 2
12 n = 1
13 n = 2
j
4.5 (31.62)
4.2 (63.10)
N
N
Scheme 2. Reagents and conditions: (a) D-alanine methyl ester
hydrochloride or L-alanine methyl ester hydrochloride, Cu(OAc)2, NEt3, 4Å
MS, DCM, r.t. (b) 45, LiOH, THF, H2O, H+ workup (c) AlMe3, p-bromoaniline,
DCM then 45 or 46, r.t. (d) Acid bromide or acid chloride, NaHCO3,
p-bromoaniline, DCM, 0 oC→r.t. OR carboxylic acid, p-bromoaniline, DMAP,
[a] DprE1 pIC50 is the negative logarithm of the IC50 concentration expressed
[b]
in molar (M) obtained in the DprE1-inhibition assay.
MIC against M.tb
(H37Rv); isoniazid was used as reference with MIC = 1.8 µM. [c] Compound
o
DIC, r.t. (e) Substituted aniline or phenol, K2CO3, MeCN, 90 C OR aniline,
tested as pIC50 < 4 in 2 out of 4 test occasions.
NaH, THF, r.t. (f) ethyl 2-(diethoxyphosphoryl)propanoate, NaH, THF, 0 oC,
then 49, 0 oC → r.t. (g) Pd/C, H2, EtOH, r.t. (h) p-bromoaniline, DABAl-Me3
THF, 50 oC then 50. (i) 2,3-Dihydrobenzo[b][1,4]dioxin-6-amine, K2CO3,
MeCN, 90 oC. (j) TsCl, DABCO, DCM, 0 oC → r.t.
We next sought to vary the left-hand side aminobenzodioxane
motif. Whilst compounds 14-15 and 17-18 were HTS hits,
compounds 16 and 19-25 were synthesized as described in Scheme
3. Alkylation of
a
variety of substituted anilines or
Biological and physicochemical data for compounds 2-13 are
shown in Table 1. Rather unexpectedly, the single enantiomers 2
and 3 were less potent than the racemate 1 in the DprE1 inhibition
assay. (R)-2 however, demonstrated an MIC two-fold more potent
than (S)-3. Lengthening the amino acid side chain diminished
DprE1 inhibition for α-ethylglycine 4 relative to (R)-2, whilst
increasing the steric demand for valine 5 reduced potency even
further. DprE1 inhibition was maintained with concomitant
reduction in lipophilicity when substitution was removed in
glycine 6, whilst addition of a second substituent in α-
methylalanine 7 led to similar DprE1 inhibition and a more potent
aminoheterocycles with intermediate 43 afforded compounds 16
and 19-23. Benzoxazines 24 and 25 were prepared similarly, but
the alkylation step was performed in the absence of base to achieve
the desired regiochemistry.

[a]
pIC50
Chrom
logD7.4, (PFI)
MIC / µM [b]
n.d.
Br
Br
R
O
O
(IC50 / µM)
H
N
Br
a
H
N
N
H
N
H
O
R
14[c]
15[c]
5.8 (1.59)
n.d.
n.d.
X
43
16, 19 - 23
X = CH, N
H
N
O
4.6 (25.12)
n.d.
O
O
Br
H
N
O
O
O
H
N
N H2
O
O
N
b
N
16
5.7 (2.00)
5.4 (3.98)
6.0 (1.00)
6.8 (0.158)
5.6 (2.51)
40
n.d.
n.d.
4.0
5.2 (7.2)
n.d.
O
H
H2N
54 = 6-NH2
55 = 7-NH2
56 = 6-NH2
57 = 7-NH2
H
N
17[c]
18[c]
19
Br
c
H
N
Br
H
N
O
O
O
n.d.
H
N
O
N
H
O
H
O
N
5.7 (7.7)
4.8 (6.8)
24 = 6-NH2
25 = 7-NH2
O
H
H
N
N
20
>125
Scheme 3. Reagents and conditions: (a) substituted aniline or
aminoheterocycle, K2CO3, MeCN, 90 oC (a) 43, K2CO3, MeCN, 90 oC. (c)
EtOH, 43, 90 oC.
O
H
N
H
N
21
22
5.9 (1.26)
125
16
6.0 (8.0)
7.7 (9.7)
The data for compounds 14-25 are displayed in Table 2.
Compounds 14-17 demonstrate that removal or deconstruction of
the dioxane ring was not favourable. Increasing the saturated ring
size was tolerated, as benzodioxepane 19 remained potent at
DprE1 (pIC50 = 6.8) and demonstrated a low MIC (4.0 µM). The
smaller benzodioxole 18 however, exhibited reduced DprE1
inhibition relative to 1 (pIC50 = 6.0). Modification or removal of
the heteroatoms in the saturated ring was also detrimental to
activity: nitrogen analogues 20 and 21, and tetrahydronaphthalene
22 were less potent than dioxane 1. Finally, efforts to reduce
lipophilicity of 1 through incorporation of heteroatoms were
ineffective, demonstrated by moderately active pyridine analogue
23 and inactive benzoxazines 24-25.
H
N
6.2 (0.631)
H
N
O
O
23
24
5.7 (2.00)
<4 (>100)
62
4.0 (6.0)
4.2 (6.2)
N
H
N
H
N
O
O
n.d.
O
O
H
N
25
<4 (>100)
n.d.
3.9 (5.9)
N
H
Shifting focus to the right-hand side of 1, we sought to
investigate how modification of this aniline would affect DprE1
inhibition. Compound design focused on replacement with alkyl
groups and saturated ring systems, as well as reduction of
lipophilicity through incorporation of heteroatoms into the aniline
and replacement of the para-bromine substitution. Analysis of the
HTS data revealed that para substitution of this aniline was
preferred, whilst ortho and meta substitution were detrimental to
DprE1 inhibition (data not shown), so only para substituents were
considered.
[a] DprE1 pIC50 is the negative logarithm of the IC50 concentration expressed
[b]
in molar (M) obtained in the DprE1-inhibition assay.
MIC against M.tb
(H37Rv); isoniazid was used as reference with MIC = 1.8 µM. [c] Compound
was HTS hit. n.d. = not determined.
Data for the varied amides 26-41 are displayed in Table 3. It is
apparent from N-methyl amides 26 and 27 that truncation of 1 led
to a large drop in DprE1 potency (pIC50 4.4-4.5). Interestingly, N-
cyclohexyl 28 and unsubstituted aniline 29 displayed similar weak
activity, as did toluidine 32, but 1, p-Cl 30 and p-CF3 31 were all
at least 100-fold more potent (pIC50 ≥ 6.4), suggesting a preference
for lipophilic substitution at this para position. Accordingly,
amide 33 was inactive, but we were surprised to see that polar
nitrile 34 (Chrom logD7.4 = 4.2) demonstrated modest DprE1
potency (pIC50 = 5.7) and had a moderate MIC (31 µM). This result
encouraged us to investigate incorporation of para-heterocycles
and fused heterobicyclic systems. Whilst pyridyl 35 and oxazolyl
36 were inactive, fused bicycles 37-39 retained DprE1 activity,
albeit diminished relative to 1. Finally, replacement of p-
bromoaniline with the two pyridine congeners in 40 and 41 was
similarly deleterious.
Syntheses of compounds designed to modify the right-hand
aniline are described in Scheme 4. Ester 59 was prepared via
alkylation of 2,3-dihydrobenzo[b][1,4]dioxin-6-amine with ethyl
2-bromopropanoate 58. Use of the air-stable DABCO adduct of
trimethyl aluminum (DABAL-Me3)25 facilitated high throughput
aminolyses of common intermediate 59 to furnish compounds 26-
30, 32-34, 37-38, and 40-41. AlMe3 itself, however, was required
for the synthesis of benzimidazole 39 as DABAL-Me3 did not
promote amide bond formation in this instance. Compounds 35-36
were prepared via Suzuki reactions between 1 and the appropriate
boronic acid.
Table 2. Left-hand side variation SAR
Br
O
R
N
H

Table 3. Right-hand side variation SAR.
O
O
H
Br
O
O
N
a
O
H
OEt
OEt
O
O
N
R
58
59
[a]
pIC50
Chrom
logD7.4, (PFI)
b
R
MIC / µM [b]
>125
(IC50 / µM)
26
27
-NHMe
-NMe2
4.5 (31.62)
1.6 (2.6)
2.2 (3.2)
O
H
N
O
O
NR1R2
4.4 (39.81)
4.4 (39.81)
>125
28
29
30
>125
>125
8.0
4.4 (5.4)
4.3 (6.3)
5.2 (7.2)
26 - 30, 32 - 34, 37 - 38, 40 - 41
N
H
O
O
N
H
N
H
N
4.2 (63.10)
6.4 (0.398)
6.9 (0.126)
4.8 (15.85)
c
N
H
O
O
O
N
H
OEt
N
H
Cl
O
59
39
N
H
Het
CF3
O
H
N
31[c]
32
n.d.
125
n.d.
O
O
d
N
H
N
H
1
35 - 36
4.8 (6.8)
N
H
Scheme 4. Reagents and conditions: (a) 2,3-Dihydrobenzo[b][1,4]dioxin-
6-amine, K2CO3, MeCN, 90 oC (b) amine or aniline, DABAL-Me3, THF, 50 oC,
then 59. (c) AlMe3, 2-aminobenzimidazole, toluene, 50 oC, then 59. (d)
Pd(Ph3P)2Cl2 (5 mol%), K2CO3, aryl boronic acid, 1,4-dioxane, water, 100 oC.
O
N
H
33
34
35
<4 (>100)
5.7 (2.00)
<4 (>100)
n.d.
31
2.4 (4.4)
4.2 (6.2)
4.2 (7.2)
N
H
N
Collectively, the above SAR demonstrates that it was a
substantial challenge to improve upon 1, however a selection of
compounds was identified that demonstrated equal or improved
MICs over the HTS hit: 2, 7, 9 and 19. Whilst MICs did generally
track with DprE1 inhibition (see Supplementary Information,
Figure S1), we sought to gain confirmation that cellular activity
was indeed driven by engagement of DprE1. Pleasingly, an 8-fold
shift in MIC was observed for 1 against a strain of M.tb engineered
to overexpress DprE128 when compared to wild type MIC (Table
4), further validating this series as whole-cell active DprE1
inhibitors.
N
H
N
n.d.
N
H
N
O
36
<4 (>100)
n.d.
3.7 (6.7)
N
H
At this point we could not address the potential risks indicated
by the structural alerts present in 1, as both anilines and in
particular the 2,3-dihydrobenzo[b][1,4]dioxin-6-amine motif were
required for potent DprE1 inhibition. Whilst not all structural
alerts translate to in vivo toxicity,21 further analyses would be
required to assess the risk associated with compound 1, for
example investigating the mutagenicity of the anilines.29 A second
aim of this work was to reduce the PFI of 1 through attenuation of
lipophilicity, but the only beneficial modification to the alanine
linker was methylation of the amine, and neither aniline tolerated
incorporation of heteroatoms. Furthermore, lipophilic para
substitution of the right-hand side aniline was crucial for enhanced
DprE1 potency. An analysis of the SAR data (Figure 3) illustrates
a clear relationship between lipophilicity and DprE1 potency.
37
38
6.1 (0.794)
5.4 (3.98)
32
31
4.0 (7.0)
3.0 (6.0)
N
H
N
H
N
N
N
H
H
N
39
5.4 (3.98)
62
3.7 (6.7)
N
H
N
H
Br
40
41
5.8 (1.59)
5.2 (6.31)
32
80
4.2 (6.2)
5.4 (7.4)
N
N
H
Br
In
conclusion,
a
novel
series
of
2-((2,3-
N
H
N
dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-phenylpropanamide
DprE1 inhibitors has been identified. Whilst further work is
required to develop this new structure into a viable lead series,
several examples have been identified that demonstrate potent
DprE1 inhibition and good whole-cell antimycobacterial activity.
These compounds 1, 2, 7, 9 and 19 represent potential probe
molecules30 which could be used to further investigate DprE1
inhibition in the context of M.tb growth and survival.
[a] DprE1 pIC50 is the negative logarithm of the IC50 concentration expressed
[b]
in molar (M) obtained in the DprE1-inhibition assay.
(H37Rv); isoniazid was used as reference with MIC = 1.8 µM. [c] Compound
MIC against M.tb
was HTS hit. n.d. = not determined.
Table 4. MIC against M.tb overexpressing DprE1.

[a]
6.
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pIC50
MICWT
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/
MICOE
/ µM [c]
OE
Compound
(IC50 / µM)
shift [d]
1
7.2 (0.063)
7.8
62.5
8x
7.
8.
9.
[a] DprE1 pIC50 is the negative logarithm of the IC50 concentration expressed
[b]
in molar (M) obtained in the DprE1-inhibition assay.
(H37Rv). [c] MIC against M.tb overexpressing DprE1. [d] MICOE/ MICWT
MIC against M.tb
.
Figure 3. Analysis of DprE1 inhibition vs. lipophilicity. HTS hit 1 is
highlighted in blue. The orange dotted line indicates the targeted PFI of 7 (for
#Ar = 2, appropriate for 80% of the compounds 1-41).
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The DprE1 enzymatic inhibition assay, the DprE1-overexpressing
strain, the MIC determination assay, and syntheses and
characterization data of key compounds 1, 2, 7, 9 and 19 are
presented in the Supplementary Information.
Acknowledgments
We thank the GlaxoSmithKline/University of Strathclyde
Industrial PhD program for funding this work. We also thank
Global Alliance for TB Drug Development for helpful discussions
and financial support, and all the staff at GSK who have
contributed to this work.
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Author Information (Current addresses for corresponding
authors)
Benjamin C. Whitehurst Medicinal Chemistry, Discovery
Sciences, Biopharmaceuticals R&D, AstraZeneca, Cambridge,
United Kingdom. e-mail: ben.whitehurst@astrazeneca.com
Robert J. Young Blue Burgundy Ltd, Ampthill, Bedfordshire,
MK45 2AD, UK. e-mail: Rob@blue-burgundy.co.uk
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Selby, M.; Reuberson, J.; Atienzar, F.; Gerets, H.; Kenyon, M. O.;
Dobo, K. L.; Walter, M. W.; Jolly, R. A.; Amberg, A.; Spirkl, H.
P.; Muster, W.; van Gompel, J.; Comput. Toxicol.; 2018, 7, 27–35.
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References and notes
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Declaration of interests
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Dorman, S. E.; Chaisson, R. E.; Nat. Med., 2007, 13, 295–298.
Bahuguna, A. ; Rawat, D. S.; Med. Res. Rev., 2019, 1-30.

☒ The authors declare that they have no known
competing financial interests or personal
relationships that could have appeared to influence
the work reported in this paper.
☐The authors declare the following financial
interests/personal relationships which may be
considered as potential competing interests:
Identification of 2-((2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)amino)-N-phenylpropanamides as a
novel class of potent DprE1 Inhibitors
Benjamin C. Whitehurst, Robert J. Young, Glenn A. Burley, Monica Cacho, Pedro Torres, Laura Vela-
Gonzalez del Peral
Br
O
H
N
O
O
N
H
1
DprE1 pIC50 (IC50 / µM)
MIC / µM
7.2 (0.063)
7.8
Chrom logD 7.4 (PFI)
5.5 ( 7.5)
HepG2 IC50 / µM
>100