Structure-activity relationships of 3,4-dihydro-1H-quinazolin-2-one derivatives as potential CDK5 inhibitors

Article abstract of DOI:10.1016/j.bmc.2007.07.005

Cyclin-dependent kinase 5 (CDK5) is a serine/threonine kinase that plays a critical role in the early development of the nervous system. Deregulation of CDK5 is believed to contribute to the abnormal phosphorylation of various cellular substrates associated with neurodegenerative disorders such as Alzheimer's disease, amyotrophic lateral sclerosis, and ischemic stroke. Acyclic urea 3 was identified as a potent CDK5 inhibitor and co-crystallographic data of urea 3/CDK2 enzyme were used to design a novel series of 3,4-dihydroquinazolin-2(1H)-ones as CDK5 inhibitors. In this investigation we present our synthetic studies toward this series of compounds and discuss their biological relevance as CDK5 inhibitors.

Full text of DOI:10.1016/j.bmc.2007.07.005

Bioorganic & Medicinal Chemistry 15 (2007) 6574–6595
Structure–activity relationships of 3,4-dihydro-1H-
quinazolin-2-one derivatives as potential CDK5 inhibitors
Robert M. Rzasa,a,* Matthew R. Kaller,a Gang Liu,a Ella Magal,b Thomas T. Nguyen,a
Timothy D. Osslund,c David Powers,d Vincent J. Santora,a,ꢀ Vellarkad N. Viswanadhan,c
Hui-Ling Wang,a Xiaoling Xiong,d Wenge Zhonga and Mark H. Normana
aDepartment of Chemistry Research and Discovery, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320-1789, USA
bDepartment of Neuroscience, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320-1789, USA
cDepartment of Molecular Structure, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320-1789, USA
dDepartment of HTS and Molecular Pharmacology, Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320-1789, USA
Received 3 May 2007; revised 30 June 2007; accepted 9 July 2007
Available online 25 July 2007
Abstract—Cyclin-dependent kinase 5 (CDK5) is a serine/threonine kinase that plays a critical role in the early development of the
nervous system. Deregulation of CDK5 is believed to contribute to the abnormal phosphorylation of various cellular substrates
associated with neurodegenerative disorders such as Alzheimer’s disease, amyotrophic lateral sclerosis, and ischemic stroke. Acyclic
urea 3 was identified as a potent CDK5 inhibitor and co-crystallographic data of urea 3/CDK2 enzyme were used to design a novel
series of 3,4-dihydroquinazolin-2(1H)-ones as CDK5 inhibitors. In this investigation we present our synthetic studies toward this
series of compounds and discuss their biological relevance as CDK5 inhibitors.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
CDK5 in associative learning7,8 and regulation of dopa-
mine signaling in drug addiction.9–13
Cyclin-dependent kinase 5 (CDK5) is a serine/threonine
kinase that is expressed in most tissues, although its
enzymatic activity is predominantly detected in the cen-
tral nervous system.1,2 Similar to other CDKs, mono-
meric CDK5 has negligible enzymatic activity and
requires association with regulatory proteins for com-
plete activation. The two non-cyclin proteins, p35 and
p39, have been identified as CDK5 activators that are
localized to the cell membrane. Unlike other cyclin-
dependent kinases, CDK5 has no known involvement
in cell-cycle progression but is critical for the early devel-
opment of the central nervous system.3 Among its many
roles, CDK5 is involved in cellular processes such as
neuronal differentiation,4 cell adhesion,5 and axonal
guidance.6 In addition to its involvement in the develop-
ment of neurons, recent studies have suggested roles for
Deregulation of CDK5 from extracellular insults has
been implicated in the pathology of several neurodegen-
erative disorders.14–18 Extracellular insults, such as amy-
loid-b peptides, oxidative stress, and excitotoxicity,
result in the conversion of p35 to p25. As a consequence,
CDK5 becomes delocalized to the cytoplasm where it
hyperphosphorylates substrates such as tau, a constitu-
ent of neurofibrillary tangles commonly found in Alzhei-
mer’s diseased brains,19,20 and neurofilaments that
accumulate in neurons of patients with amyotrophic lat-
eral sclerosis.21 Recent animal studies have also impli-
cated CDK5 in Niemann–Pick type C,22 Parkinson’s
disease,23 and ischemic stroke.24–27 In the pursuit to
treat CDK-related diseases, several compound classes
have been identified as CDK5 inhibitors such as the
paullones,28 meridianins,29 indirubins,30,31 flavinols,32
pyrazolo-quinoxalines,33 purines,34 and thiazoles.35,36
In this report, we describe our investigation of 3,4-dihy-
dro-1H-quinazolin-2-ones as potential CDK5 inhibitors
for the treatment of neurodegenerative diseases.
Keywords: Neurodegenerative disorders; CDK5; Kinase inhibitor; 3,4-
Dihydro-1H-quinazolin-2-one.
*
Corresponding author. Tel.: +1 805 447 7963; fax: +1 805 480
3016; e-mail: rrzasa@amgen.com
Recently, X-ray crystal structure37,38 and molecular
modeling39–41 of CDK5 complexes have provided scien-
ꢀ
Present Address: Arena Pharmaceuticals, San Diego, CA 92121,
USA.
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2007.07.005

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6575
tists with useful tools in the design of selective CDK5
inhibitors. Prior to these most recent discoveries, we re-
lied on the screening of our internal compound collec-
tion to provide us with leads for further optimization.
Initial hits obtained from our screening collection were
a series of acyclic ureas 1–3 (Fig. 1).42 In our preliminary
SAR investigations we found that phenyl-urea 1 was 10-
fold less potent than the pyridyl-urea 2 (2990 vs 192 nM,
respectively) in the in vitro human CDK5 enzyme assay.
We hypothesized that an intramolecular hydrogen bond
between N1 and the N3-hydrogen placed the 2-amino-
pyridine ring and urea functionality of 2 in a planar
geometry within the active site of CDK5. This intramo-
lecular hydrogen bond hypothesis was supported by the
X-ray crystal structure of a piperazine substituted ana-
log urea 3 (CDK5 IC50 = 15 nM). Urea 3 was success-
fully co-crystallized with CDK2, a closely related
homolog of CDK5,43 and was also found to be a potent
CDK5 inhibitor (Fig. 2).44 In addition to reaffirming our
hypothesis of the presence of an intramolecular hydro-
gen bond between N1 and N3-hydrogen, this X-ray
crystal structure provided valuable information about
other key interactions between the inhibitor and the en-
zyme. For example, it was observed that the N2–NH
and the carbonyl oxygen of the urea were involved in
a donor–acceptor hydrogen bond network to the
Leu83 linker region of the CDK2 ATP binding site. Fur-
thermore, the thiazolo-pyridine extends through a
hydrophobic region (Ala31, Phe80, and Leu134) to form
a hydrogen bond with the Lys33-Asp145 salt bridge of
the ATP binding site.
Figure 2. X-ray co-crystal of compound 3/CDK2. Carbon atoms of
compound 3 are shown in green, carbon atoms of active site residues in
brown, nitrogen atoms are shown in blue, oxygen atoms are shown in
red,and sulfur atoms are shown in yellow. Hydrogen bonding is shown
in green and the backbone of the protein is traced with a solid brown
ribbon.
Using the CDK2/compound 3 co-crystallographic data
we developed a model of CDK5 that was used in the
design of inhibitors reported in this investigation
(Fig. 3). Figure 3 also illustrates the proposed binding
mode of 1, 2, and 20a (a cyclic urea derivative), to this
CDK5 homology model. The most notable difference
between the ATP binding pockets of CDK2 and
CDK5 is the linker region where the Leu83-His84 res-
idues of CDK2 are replaced with Cys83-Asp84 in
H
H
N
N2
O
O
Figure 3. Docked models of compounds 1, 2, and 20a in the active site
of CDK5. Nitrogen atoms are shown in blue, oxygen atoms are shown
in red, sulfur atoms are shown in yellow, and carbon atoms of active
site residues in brown. Carbon atoms of compounds 1, 2, and 20a are
shown in orange, cyan, and green, respectively. Ligand–protein H-
bonds are shown in green.
N1 N3
H
N
H
S
S
R
N
N
N
N
2 R = H
1
3 R = 4-methylpiperazino
CDK5. Homologous to CDK2, the binding pocket of
CDK5 conserves the key Phe80 residue of the hydro-
phobic pocket and maintains a Lys33-Asp144 salt
bridge. With our preliminary biological evaluation of
acyclic ureas 1 and 2, and the crystallographic data
of urea 3, we proposed that constrained cyclic ureas
with a general structure 4 would serve as effective
inhibitors of CDK5, consistent with our modeling ef-
forts. Herein, we describe the synthesis of 3,4-dihy-
H
N
B
U
R3
R2
O
Y
A
N
Z
C
R1
X
D
V
W
dro-1H-quinazolin-2-one
structure 4 along with the structure–activity relation-
analogs
with
general
4
Figure 1.
ships of this series of CDK5 inhibitors.

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R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
2. Chemistry
bromomalonate provided hydroxy-thiazole 10. Triflate
11 was obtained by the reaction of 10 with triflic
anhydride. Displacement of the triflate with 1,2-pheny-
lenediamine followed by cyclization with 1,10-carbon-
yldiimidazole (CDI) provided benzimidazolone 13.45
Hydrolysis of ester 13 gave acid 14 and subsequent
decarboxylation under acidic conditions provided the
desired benzimidazolone 15.
A variety of synthetic routes were employed to prepare
the conformationally constrained compounds required
for this investigation (Fig. 1, general structure 4). For
ease of discussion, these are divided into four main
areas: conformational constraints to the B-ring (U), sub-
stituents on the aromatic A-ring (R1–R3), alternative
aromatic C-rings (X, Y, and Z), and modifications to
the pyridine D-ring (W and V).
The majority of derivatives prepared in this study
were 6-membered dihydroquinazolinones 20a–p
(Fig. 1, U = CH2) and two general synthetic routes
were employed to prepare these compounds. The first
strategy involved a displacement of an activated ben-
zyl intermediate to introduce the substituted benzene
onto a thiazole-amine followed by cyclization to form
the urea (Scheme 3). Alternatively, these derivatives
were prepared by the addition of a benzylicamine to
a thiazole triflate followed by subsequent urea forma-
tion (Scheme 4). Both methods proved to be useful in
providing the appropriately substituted derivatives,
and the synthetic route used was dictated mainly by
the availability of the starting materials. The first
method employed is outlined in Scheme 3. Acids 7a
and 7b underwent Curtius rearrangements46 using
DPPA in refluxing toluene followed by treatment with
allyl alcohol to afford carbamates 16a and 16b, respec-
tively. Alkylation with the appropriate benzyl bro-
mides 17b–k vide supra under basic conditions
provided carbamates 18b–k and 18p. Deprotection of
The initial focus of this study was the examination of
conformationally restricting linking groups, and there-
fore, three different ring systems were prepared: a qui-
nazoline-2,4-dione (U = carbonyl), a benzimidazolone
(U = a single bond), and
a dihydroquinazolinone
(U = CH2). Quinazolinedione 9a was synthesized in
three steps as shown in Scheme 1. Reaction of commer-
cially available thioisonicotinamide 5a with ethyl
bromopyruvate followed by hydrolysis provided acid
7a. Acid 7a was converted to the acid chloride followed
by treatment with sodium azide to give the correspond-
ing acylazide 8a. Quinazolinedione 9a was obtained by a
Curtius rearrangement of azide 8a and trapping of the
resulting isocyanate intermediate with methyl 2-
aminobenzoate.
The 5-membered benzimidazolone derivative 15 (Fig. 1,
U = a single bond) was prepared as outlined in Scheme
2. Treatment of thioisonicotinamide 5a with diethyl
H
R
S
N
O
N
S
N
H2N
a
d
N
S
O
N
N
5a
9a
6a, R = CO2Et
7a, R = CO2H
8a, R = CON3
N
b
c
Scheme 1. Synthesis of quinazolinedione 9a. Reagents and conditions: (a) ethyl bromopyruvate, EtOH, 80 ꢁC, 68%; (b) NaOH, EtOH, 80 ꢁC, 73%;
(c) oxalyl chloride, NaN3, THF; (d) methyl 2-aminobenzoate, toluene, 95 ꢁC, 42%.
H
CO2Et
CO2Et
H2N
CO2Et
S
N
O
H
N
a
S
N
c
d
S
N
HO
b
TfO
R
S
N
5a
N
N
N
N
11
10
12
N
N
13 R = CO2Et
14 R = CO2H
15 R = H
e
f
Scheme 2. Synthesis of 5-membered benzimidazolone 15. Reagents and conditions: (a) diethyl bromomalonate, pyridine, EtOH, 80 ꢁC, 44%; (b)
(CF3SO2)2O, pyridine, CH2Cl2, 0 ꢁC–rt, 55%; (c) 1,2-phenylenediamine, dioxane, reflux, 72%; (d) NaH, CDI, DMF, room temperature, 74%; (e) 1 N
NaOH, MeOH, rt, 85%; (f) concd H3PO4, 120 ꢁC, 96%.

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6577
the Alloc group under palladium-mediated conditions
and reduction of the nitro moiety with iron dust
and ammonium chloride in refluxing aqueous ethanol
provided the corresponding anilines 19b–k and 19p.
Cyclization of anilines 19b–k and 19p with CDI or
p-nitrophenyl chloroformate afforded urea derivatives
20b–k and 20p.
ester hydrolysis followed by acidic decarboxylation pro-
vided the desired ureas 20a and 20l–o.
Several of the key intermediates needed for the synthesis
of the compounds prepared in this study were substi-
tuted benzyl derivatives such as bromides 17b–k
(Scheme 5) and benzyl amines 27, 30, 32, and 34
(Scheme 6). Intermediates 17b–k were easily accessible
from the corresponding 2-nitrotoluene compounds
23b–d, 23f, 23g, 23i–k or benzyl alcohols 24e, 24h. The
bromides 17b–d, 17f, 17g, and 17i–k were prepared
under radical conditions by reacting 23b–d, 23f, 23g,
and 23i–k with AIBN and NBS in carbon tetrachloride.
Alternatively, benzyl alcohols 24e and 24h were treated
with phosphorus tribromide to provide bromides 17e
and 17h. Amines 27 and 30 were readily obtained in
two steps from the corresponding benzyl bromides 25
An alternate route that involved the displacement of a
thiazolo-triflate with an appropriate benzylamine
(Scheme 4) was utilized to prepare dihydroquinazoli-
none 20a and analogs possessing a basic amine attached
to the A-ring (20l–o). Treatment of triflate 11 with the
appropriate benzylamines vide supra afforded thiazole
esters 21a and 21l–o. The cyclic ureas 22a and 22l–o
were obtained by reacting anilines 21a and 21l–o with
sodium hydride and CDI in dimethylformamide. Basic
R3
R2
NO2
Br
R3
R2
NO2
Alloc
AllocHN
HO2C
S
S
R1
b,
N
N
a
17
N
S
R1
N
N
N
X
X
N
7a X = H
7b X = Et
X
16a X = H
16b X = Et
18b-k, p
H
R3
R2
NH2
R3
R2
N
O
N
H
e or f
N
c,d or d,c
N
S
S
R1
R1
N
N
N
20b-k, p
19b-k, p
X
X
Scheme 3. Synthesis of dihydroquinazolinones—route A. Reagents and conditions: (a) DPPA, Et3N, toluene then allyl alcohol, 80 ꢁC, 21–23%; (b)
NaH, DMF, 80 ꢁC, 39–94%; (c) morpholine, (Ph3P)4Pd, CH3CN, rt; (d) iron powder, NH4Cl, 70% aq EtOH, 80 ꢁC, 12–90% over two steps;
(e) p-nitrophenyl chloroformate, Et3N, toluene/THF, 80 ꢁC, 3–23%; (f) CDI, NaH, DMF, rt, 16–93%.
H
H
R3
R2
N
O
N
R3
R2
N
O
N
R3
R2
NH2
H
N
CO2Et
S
CO2Et
S
d
e
a or b,c
N
11
N
S
R1
20a, l-o
R1
21a, l-o
R1
22a, l-o
N
N
N
N
Scheme 4. Synthesis of dihydroquinazolinones—route B. Reagents and conditions: (a) 2-aminobenzylamine or 34, dioxane, reflux, 70–84%; (b) 27,
30 or 32 (see Scheme 6), dioxane 80 ꢁC; (c) iron dust, NH4Cl, aq EtOH, 30–41% over two steps; (d) NaH, CDI, DMF, room temperature, 18–74%; (e)
NaOH, MeOH, 50 ꢁC then H2SO4, 120 ꢁC, 10–48%.
R3
R2
NO2
OH
R3
R2
NO2
Me
R3
R2
NO2
Br
b
a
R1
R1
R1
23b-d, f-g, i-k
17b-k
24e, h
Scheme 5. Synthesis of substituted benzyl bromides 17b–k. Reagents: (a) AIBN, NBS, CCl4, 22–100%; (b) PBr3, CH2Cl2, 22–71%.

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R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
R3
NO2
CN
R3
NO2
CN
R3
NO2
NH2
a
b
R1
R1
R1
25 R1 = CH2Br, R3 = H
28 R1 = H, R3 = CH2Br
26 R1 =
, R3= H
27 R1 =
, R3 = H
O
N
N
O
29 R1 = H, R3 =
30 R1 = H , R3 =
N
O
N
O
31 R1 =
N
NMe, R3 = H
32 R1 =
N
NMe, R3 = H
NH2
CN
NH2
b
NH2
N
N
N
N
33
34
Scheme 6. Synthesis of substituted benzylamines. Reagents and conditions: (a) morpholine, DMF, rt, 71–75%; (b) BH3ÆTHF, 0 ꢁC–rt, 58–89%.
and 28 (Scheme 6). Treatment of bromides 25 and 28
with morpholine followed by borane reduction provided
amines 27 and 30, respectively. Amines 32 and 34 were
prepared by a borane reduction of the known nitriles
3147 and 3348, respectively.
with p-nitrophenyl chloroformate afforded the desired
isomeric thiazoles 38a–c.
Oxadiazole 41 and thiadiazole 45 were prepared as sum-
marized in Scheme 8. Addition of 2-aminobenzylamine
to 5-trichlorooxadiazole 3950 afforded aniline 40. The
desired dihydroquinazoline 41 was obtained by cycliza-
tion with p-nitrophenyl chloroformate as previously
described. Analogously, 5-amino-3-(4-pyridyl)thiadiaz-
ole 42 was converted to dihydroquinazoline 45 in three
steps. The 5-amino-3-(4-pyridyl)thiadiazole 4251 was
converted to the chloro derivative 43 using sodium
nitrite and copper turnings in hydrochloric acid.52 Dis-
placement of the chloride with 2-aminobenzylamine
afforded aniline 44 and treatment of amino-aniline 44
with CDI provided dihydroquinazoline 45.
Several 5-membered aromatic heterocycles were pre-
pared to evaluate the biological importance of the cen-
tral thiazole C-ring such as the isomeric thiazole,
1,2,4-oxadiazole, 1,2,4-thiadiazole, and the 2,5-thio-
phene derivatives. To incorporate these modifications,
linear reaction sequences were necessary. The synthetic
route employed to prepare the isomeric thiazoles 38a–c
is shown in Scheme 7. Treatment of 2-nitrobenzylamine
with benzoyl isothiocyanate followed by hydrolysis
under basic conditions provided thiourea 35. Thiazoles
36a–c were obtained by heating 35 in the presence of
the appropriate bromoacetylpyridinium hydrobro-
mide49 in aqueous methanol. Reduction of the nitro
group with iron provided anilines 37a–c and cyclization
The final two C-ring analogs, thiophene 52 and phenyl
derivative 57, were prepared as shown in Schemes 9 and
10. A Suzuki coupling reaction between 4-pyridylboronic
NO2
NO2
NO2
a
b
H
H
N
S
N
S
NH2
HN
O
NH2
35
Ph
H
N
O
NO2
H
NH2
H
c
N
S
e
d
N
N
S
S
N
N
N
Z
Z
Z
Y
Y
Y
X
X
X
37a-c
38a-c
36a, X = N, Y = Z = CH
36b, Y = N, X = Z = CH
36c, Z = N, X = Y = CH
Scheme 7. Synthesis of isomeric thiazole derivatives: Reagents and conditions: (a) benzoyl isothiocyanate, CHCl3, 61 ꢁC; (b) K2CO3, aq MeOH,
reflux, 73% over two steps; (c) bromoacetylpyridinium hydrobromide, 50% aq MeOH, 45 ꢁC; (d) iron dust, NH4Cl, aq EtOH, 75 ꢁC;
(e) p-nitrophenyl chloroformate, Et3N, THF, reflux, 1–6% over three steps.

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6579
H
O
N
N
NH2
N
X
N
X
H
a
b
c or d
N
X
N
X
H2N
N
N
Y
N
N
N
N
N
39 X = O, Y = CCl3
43 X = S, Y = Cl
40 X = O
44 X = S
41 X = O
45 X = S
42 X = S
N
N
Scheme 8. Synthesis of oxadiazole and thiadiazole derivatives. Reagents and conditions: (a) NaNO2, AcOH, HCl, Cu turnings, H2O, <15 ꢁC, 56%;
(b) 2-aminobenzylamine, THF, 60 ꢁC, 11%; (c) p-nitrophenyl chloroformate, Et3N, THF, room temperature, 42%; (d) CDI, NaH, DMF, rt, 5% over
two steps.
c
a
N
Alloc
MeO2C
Br
N
S
S
N
S
X
H
48
46, X = CO2Me
47, X = CO2H
b
H
NO2
X
N
O
S
e
H
g
d
Alloc
N
N
N
S
S
49
52
N
N
N
50, X = NO2
51, X = NH2
f
Scheme 9. Synthesis of thiophene derivative 52. Reagents and conditions: (a) 4-Pyridineboronic acid, (Ph3)4Pd, Na2CO3, DME, reflux, 33%; (b) 1 N
NaOH, EtOH, rt, 90%; (c) DPPA, Et3N, allyl alcohol, toluene, 70 ꢁC, 55%; (d) NaH, 2-nitrobenzyl bromide, DMF, rt, 76%; (e) morpholine,
(Ph3P)4Pd, THF, rt, 88%; (f) iron dust, NH4Cl, aq EtOH, 78 ꢁC; (g) CDI, NaH, DMF, rt, 76% over two steps.
acid and methyl 5-bromothiophene-2-carboxylate53 pro-
vided ester 46. Hydrolysis of ester 46 was followed by Cur-
tius rearrangement in the presence of allyl alcohol yielded
carbamate 48. Intermediate 49 was obtained by N-alkyl-
ation of carbamate 48 with 2-nitrobenzyl bromide.
Deprotection of the alloc-protecting group under palla-
dium-mediated conditions provided intermediate 50 and
reduction of the nitro group afforded aniline 51. Treat-
ment of aniline 51 with CDI under basic conditions pro-
vided the desired quinazolinone 52. The phenyl
derivative 57 was prepared in four steps as shown in
Scheme 10. A Suzuki reaction of 4-bromopyridine hydro-
chloride with 3-aminobenzeneboronic acid gave aniline
54. Compound 56 was prepared by reacting aniline 54
with 2-nitrobenzyl bromide followed by hydrogenation
of the resulting nitrobenzene 55. Urea formation using
p-nitrophenyl chloroformate provided the desired phenyl
analog 57.
3. Results and discussion
The derivatives prepared in this study were evaluated for
their ability to inhibit purified human CDK5. Com-
H
N
O
X
H2N
Br
H
N
N
a
b
d
N
HCl
N
53
N
N
54
57
55, X = NO2
56, X = NH2
c
Scheme 10. Synthesis of phenyl derivative 57. Reagents and conditions: (a) Pd(PPh3)4, 3-aminobenzene boronic acid monohydrate, 2 M Na2CO3,
toluene/ EtOH, 80 ꢁC, 64%; (b) 2-nitrobenzyl bromide, K2CO3, CH3CN, 55 ꢁC, 15%; (c) Pd/C, H2, EtOH, room temperature, 72%; (d) p-nitrophenyl
chloroformate, Et3N, toluene/THF, 70 ꢁC, 23%.

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Table 2. SAR of C-ring modified compounds
pounds were screened in an HTRF human CDK5/p25
assay that was run in the presence of 25 lM ATP and
1 lM histone-H1.54 The IC50 values were determined
from dose–response curves and are reported in Tables
1–5 as the average of at least two replications. The fol-
lowing structure–activity tables examine each of the var-
ious structural modifications studied in this
investigation.
H
N
O
X
N
N
Compound
X
CDK5/p25 (IC50, nM)a
The first derivatives examined in this study were com-
pounds with various B-ring compositions as shown in
Table 1. The biological data for the acyclic urea 1 are in-
cluded in Table 1 for comparison. Quinazolinedione 9a
(U = carbonyl) displayed an inhibition of CDK5
(IC50 = >10,000 nM) and was >3-fold less potent than
compound 1. The decrease in inhibition may result from
a non-planar B–C ring system, a consequence of lone
pair repulsion between the carbonyl oxygen and thiazole
nitrogen. Constraining the B-ring to a 5-membered
benzimidazolone (i.e., 15) resulted in a slight improve-
ment in activity (IC50 = 1,160 nM); however, significant
improvement in activity was observed with dihydro-qui-
nazolinone 20a (U = CH2). This increase in activity (20a
vs 1) is attributable to better van der Waals contacts of
the A-ring (in 20a) with Gln85, Lys89, Asp86, and
Leu134. The puckering of the fused B ring also allows
for better positioning of the phenyl ring of 20a (relative
to 1) within the active site (Fig. 3).
S
20a
79 40
77 33
N
N
S
O
S
38a
41
N
N
>10,000
N
N
45
616 405
52
>10,000
S
57
>10,000
With a satisfactory B-ring identified, we continued our
SAR investigations on several aromatic C-ring analogs
of compound 20a. The enzymatic data for these deriv-
atives are reported in Table 2. Compounds 38a, 41, 45,
a At least two independent experiments were performed for each
compound to determine the IC50 values.
52, and 57 were designed to investigate what effect
altering the heteroatom positioning of the C-ring had
on CDK5 inhibition. In our investigation we found
the isomeric thiazole analog 38a to be equipotent
to the parent compound 20a. Despite this favorable
result, further aromatic modifications to the parent
compound were not well tolerated. For example, the
introduction of a third heteroatom into the heterocyclic
C-ring (i.e., oxadiazole 41 and thiadiazole 45) resulted
in a significant decrease in potency as compared to
20a; however, aromatic rings were devoid of nitrogens
(i.e., 52 and 57) and were also significantly less potent.
From examination of the X-ray crystal structure of 3
and the homology models of 20a, 52, and 57 (Fig. 4)
the dramatic differences in activity of C-ring modified
compounds reported in this study could be rational-
ized. Compounds 20a, 38a, and 45 preserve the geom-
etry necessary for maintaining favorable interactions
between the linker region, the Lys33-Asp144 salt bridge
and the ligand. To the contrary, compounds 52 and 57
do not preserve the optimal geometry necessary for
Table 1. SAR of modified B-ring compounds
R
S
N
N
Compound
R
CDK5/p25 (IC50, nM)a
H
N
O
O
1
2990
7
HN
H
N
9a
>10,000
N
O
H
N
15
1160 206
O
O
N
maintaining
a good interaction with the Lys33-
Asp144 salt bridge, and hence, were significantly less
potent.
H
N
20a
79 40
N
A major focus of our SAR investigation was to examine
the substitution pattern of A-ring analogs and the results
for these derivatives are summarized in Table 3. We first
a At least two independent experiments were performed for each
compound to determine the IC50 values.

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6581
substituents (20e and 20f) vs. 20a. In contrast to the re-
sults we obtained for R1 modifications, substitutions at
the R2 and R3 positions were well tolerated and the best
activity was obtained for analog 20i (R3 = F). Close
examination of modeling studies indicated the R2 and
R3 positions are exposed to solvent and can accommo-
date a variety of substituents. Specifically, the R3 region
is surrounded by the residues Gln85, Asp86, and Lys89,
which contribute to van der Waals contacts with R3 sub-
stituents. This trend of increased potency (R3 > R2 > R1)
with respect to the position of substitution was observed
in a number of analogs. For example, 20g and 20i were
>3-fold more potent compared to 20b (R1 = F). Like-
wise, bromo analog 20j (R3 = Br) was 6-fold more potent
than 20d (R1 = Br). Methyl substitution in the R2 posi-
tion was also preferred over the R1 position (20h vs
20e). Large aromatic substituents were also well toler-
ated in the R3 position (i.e., 20k).
Figure 4. Docked models of compounds 20a, 52, and 57 in the active
site of CDK5. Nitrogen atoms are shown in blue, oxygen atoms are
shown in red, sulfur atoms are shown in yellow, and carbon atoms of
active site residues are shown in brown. Carbon atoms of compounds
20a, 52, and 57 are shown in green, orange, and cyan, respectively.
Ligand–protein H-bonds is shown in green.
In general, addition of a tertiary amine substituent di-
rectly onto the A-ring resulted in a decrease in activity
(20l and 20m vs 20a). However, insertion of a methylene
spacer between the phenyl ring and the amine did
improve potency (20o vs 20a). Molecular modeling stud-
ies suggest the additional carbon atom helps to direct
the amine away from active site residues and toward
the solvent exposed region of the pocket.
examined the effect of substitution at the R1 position
and, in general, we observed a loss in activity when this
position was substituted. For example, the three equipo-
tent halogenated analogs 20b–d were 3-fold less active
than the unsubstituted compound. A significant loss in
activity was also observed with electron-donating
The results of D-ring modifications are reported in
Table 4. Enzyme inhibition correlated directly with the
Table 3. SAR of substituted 3-(2-pyridin-4-yl-thiazol-4-yl)-3,4-dihydro-1H-quinazolin-2-ones
H
R3
R2
N
O
N
N
S
R1
N
Compound
R1
R2
R3
CDK5/p25 (IC50, nM)a
20a
20b
20c
20d
20e
20f
20g
20h
20i
H
H
H
H
H
H
H
F
H
H
H
H
H
H
H
H
F
79 40
240 57
332 147
228 190
1260 907
362 145
72 21
F
Cl
Br
Me
OMe
H
H
Me
H
H
H
165 13
16 11
38 22
H
20j
20k
H
Br
Ph
H
113 57
N
20l
H
H
H
H
829 189
1165 251
284 85
N
N
20m
20n
20o
H
N
N
H
H
O
N
H
62 28
O
a At least two independent experiments were performed for each compound to determine the IC50 values.

6582
R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
Table 4. In vitro inhibition of human CDK5 for 3-(2-aryl-thiazol-4-yl)-3,4-dihydro-1H-quinazolin-2-ones
H
N
O
N
N
Y
X
R
Compound
X
S
Y
R
CDK5 inhibition IC50 (nM)a
79 40
20a
CH
N
N
38a
38b
38c
20p
CH
CH
CH
S
S
77 33
399 20
S
N
S
7,360 976
746 267
N
Et
CH
N
a At least two independent experiments were performed for each compound to determine the IC50 values.
Table 5. In vitro inhibition of human CDK5 and CDK2 for 3-(2-aryl-thiazol-4-yl)-3,4-dihydro-1H-quinazolin-2-onesa
Compound
CDK5 inhibition
IC50 (nM)
CDK2 inhibition
IC50 (nM)
p38a inhibition
IC50 (nM)
JNK2 inhibition
IC50 (nM)
Erk1 inhibition
IC50 (nM)
PKA inhibition
IC50 (nM)
20a
20i
79 40
16 11
62 28
142 81
52 17
529b
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
20o
a At least two independent experiments were performed for each compound to determine the IC50 values.
b One experiment was performed to determine the IC50 value.
position of the nitrogen atom within the D-ring. The
importance of H-bonding between the inhibitor D-ring
and the Asp144 salt bridge is clearly demonstrated in
the diminished activity of the 2- and 3-pyridyl analogs
(38b and 38c vs. 38a). Introduction of alkyl substitution
on the pyridine ring results in unfavorable repulsive
interactions and interference with the salt bridge. This
accounts for a 10-fold decrease in potency of 20p relative
to 20a.
a series of 3,4-dihydro-1H-quinazolin-2-ones as potent
CDK5 inhibitors. From our studies, we were able to
generate structure activity relationships for the 3,4-dihy-
dro-1H-quinazolin-2-one core. In comparison to the
acyclic urea 1, the constrained 6,6-bicyclic AB ring sys-
tem showed a 10-fold improvement in activity. In gen-
eral, substitution on the A-ring was well tolerated with
a clear preference for substitution in the R3 position.
Although the isomeric thiazole 38a was an acceptable
replacement for the C-ring, other aromatic linking
groups (i.e., benzene, thiadiazole, oxadiazole, or thio-
phene) were not well tolerated. The 4-pyridyl moiety
proved to be the optimal D-ring moiety and illustrated
the importance of H-bonding to the Asp145-Lys33 salt
bridge to the inhibition of CDK5. Although compounds
prepared in this study were potent inhibitors of both
CDK5 and CDK2, only compounds 20i and 20o dis-
played moderate selectivity for CDK5. From this inves-
tigation we gained a better understanding of the
structural requirements and limitations necessary for
the preparation of selective CDK5 inhibitors. The com-
pounds in this study may serve as molecular probes to
better understand CDK5’s role in the treatment of neu-
rodegenerative disorders.
The compounds prepared for this study were evaluated
for kinase selectivity by screening the most potent ana-
logs against several serine/threonine kinases (Table 5).
In general, most compounds were potent inhibitors for
both CDK5 and CDK2 and significant CDK selectivity
was not observed. However, good selectivity over sev-
eral serine/threonine kinases was observed in a few rep-
resentative examples.
4. Conclusions
Using crystallographic data from the acyclic urea 3/
CDK2 complex, we rationally designed and synthesized

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6583
5. Experimental
5.2.2. 2-(2-Ethyl-4-pyridyl)-1,3-thiazole-4-carboxylic acid
1
(7b). Yield 77% for two steps; H NMR (DMSO-d6): d
1.28 (t, 3, J = 7.5 Hz), 2.85 (q, 2, J = 7.5 Hz), 7.74 (dd,
2, J = 5.1, 1.5 Hz), 8.79 (s, 1), 8.63–8.65 (m, 2).
5.1. General
Unless otherwise noted, all materials were obtained
from commercial suppliers and used without further
purification. Anhydrous solvents such as dichlorometh-
ane (CH2Cl2), dimethylformamide (DMF), dioxane,
tetrahydrofuran (THF), ethylene glycol dimethyl ether
(DME), and toluene were obtained from Aldrich
Chemical Co. in Sure/Seal bottles. All reactions involv-
ing air- or moisture-sensitive reagents were performed
under a nitrogen or argon atmosphere. Flash chroma-
tography was performed using EM Science silica gel 60
(230–400 mesh ASTM) or prepacked silica gel car-
tridges (Biotage). Thin-layer chromatography (TLC)
was performed with Analtech silica gel GF TLC plates
(250 lm). Melting points were determined on a Tho-
mas Hoover capillary melting point apparatus or a Bu-
chi-545 melting point apparatus and are uncorrected.
1H NMR spectra were obtained on a Bruker DRX-
400 NMR (400 MHz) spectrometer. Chemical shifts
are expressed in ppm (d) downfield from internal tetra-
5.3. Azido(2-(pyridin-4-yl)thiazol-4-yl)methanone (8a)
To a suspension of acid 7a (6.0 g, 29.1 mmol) in 150 mL of
MeOHwasaddedNaOH(1.28 g,32.0 mmol)atroomtem-
perature. After 45 min the reaction mixture was concen-
trated in vacuo and dried under high vacuum for 60 h.
The crude salt was suspended in 150 mL of CH2Cl2 and
cooled in an ice bath. Oxalyl chloride (2.8 mL) was added
slowly to the suspension followed by a catalytic amount of
DMF (0.2 mL). The mixture was stirred for 2 h and
warmed to room temperature. The reaction was cooled
in an ice bath and a solution of NaN3 (2.27 g) in 90 mL
of water was added. After 3 h the reaction mixture was di-
luted with 90 mL of water and extracted with CH2Cl2
(3 · 75 mL). The combined organic layers were filtered
through Celiteꢂ, washedwithbrine (90 mL) and dried over
MgSO4. Concentration in vacuo afforded 8a as a light
brown solid. MS (ESI, positive ion) m/z 204 (M+HꢀN2).
1
methylsilane. Significant H NMR data are reported in
the following order: multiplicity (s, singlet; d, doublet;
t, triplet; q, quartet; m, multiplet), number of protons,
and coupling constants. Low-resolution mass spectra
were determined on a Perkin-Elmer-SCIEX API 165
mass spectrometer using ES ionization modes (positive
or negative). High-resolution mass spectra were deter-
mined on an Agilent G1969A TOF spectrometer
[M+H]+ and are within 5 ppm error. Combustion
analyses were performed by Atlantic Microlab Inc.
Norcross, GA.
5.4. 3-(2-Pyridin-4-yl-thiazol-4-yl)-1H-quinazoline-2,4-
dione (9a)
A mixture of azide 8a (79 mg, 0.3 mmol) and methyl
anthranilate (204 mg, 1.4 mmol) in 11 mL of toluene
was heated at 95 ꢁC. After 3 h the reaction mixture
was allowed to cool to room temperature overnight.
The precipitate was filtered, washed with toluene,
and dried in vacuo. The crude material was added
to a solution of KOH (107 mg, 1.9 mmol) in 15 mL
of EtOH and the reaction mixture was heated to
75 ꢁC. After 3 h the reaction mixture was allowed to
cool to room temperature and the solvent was
removed in vacuo. The residue was diluted with
H2O and extracted with EtOAc. The organic solution
was dried over MgSO4 and concentrated to dryness to
give 50 mg (42%) of the title compound. 1H NMR
(CDCl3): d 7.25–7.30 (m, 2), 7.75 (t, 1, J = 7.0 Hz),
7.90 (t, 2, J = 4.5 Hz), 7.97 (d, 1, J = 8.2 Hz), 8.05
(s, 1), 8.73 (d, 2, J = 4.5 Hz), 11.76 (s, 1). MS (ESI,
positive ion) m/z 323 (M+1). HRMS calcd for
C16H10N4O2S [M+H]+ 323.0603, found 323.0599.
5.2. Representative procedure for the synthesis of 2-(2-
substituted-4-pyridyl)-1,3-thiazole-4-carboxylic acids 7a and 7b
5.2.1. 2-(4-Pyridyl)-1,3-thiazole-4-carboxylic acid (7a). A
mixture of thioisonicotinamide 5a (20.0 g, 144.7 mmol)
and ethyl bromopyruvate (19.0 mL, 151.4 mmol) in
250 mL of EtOH was heated at 80 ꢁC overnight. The
reaction mixture was allowed to cool to room temper-
ature and the solid was filtered. The filtrate was con-
centrated in vacuo and the solid was dried in vacuo
to give 23.1 g (68%) of 6a as a yellow solid. 1H
NMR (DMSO-d6): d 1.35 (t, 3, J = 7.1 Hz), 4.39 (q,
2, J = 7.1 Hz), 8.36 (d, 2, J = 5.1 Hz), 8.87 (s, 1), 8.96
(d, 2, J = 5.1 Hz). MS (ESI, positive ion) m/z 235
(M+1).
5.5. Ethyl 4-hydroxy-2-(4-pyridyl)-1,3-thiazole-5-carbox-
ylate (10)
To
a solution of thioisonicotinamide 5a (16.0 g,
A solution of NaOH (9.6 g, 240 mmol) in 75 mL H2O
was slowly added to a solution of ester 6a (23.1 g,
98.5 mmol) in 250 mL of EtOH and the reaction mixture
was heated at 80 ꢁC overnight. The reaction mixture was
allowed to cool to room temperature and then concen-
trated in vacuo. The residue was dissolved in H2O
(50 mL) and acidified with 1 N HCl. The resulting pre-
cipitate was filtered and dried to give 14.8 g (73%) of
7a as a gray-brown solid. 1H NMR (DMSO-d6): d
7.94 (d, 2, J = 4.9 Hz), 8.66 (s, 1), 8.76 (d, 2,
J = 4.5 Hz), 13.25 (br s, 1). MS (ESI, positive ion) m/z
207 (M+1).
115.9 mmol) in 300 mL of EtOH were added diethyl
bromomalonate (19.8 mL, 116.1 mmol) and pyridine
(37.5 mL, 463.7 mmol). The reaction mixture was heated
at 80 ꢁC overnight. The reaction mixture was allowed to
cool to room temperature and then filtered. The filtrate
was concentrated to approximately half its volume and
filtered again. The combined solids were allowed to
air-dry to give 12.8 g (44%) of the title compound as a
yellow solid. 1H NMR (CDCl3):
d 1.41 (t, 3,
J = 7.2 Hz), 4.44 (q, 2, J = 7.1 Hz), 7.83 (dd, 2, J = 4.5,
1.6 Hz), 8.77 (dd, 2, J = 4.8, 1.3 Hz), 9.94 (br s, 1). MS
(ESI, positive ion) m/z 251 (M+1).

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R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
5.6. Ethyl 2-(4-pyridyl)-4-[(trifluoromethyl)sulfonyloxy]-
1,3-thiazole-5-carboxylate (11)
5.10. 1-(2-Pyridin-4-yl-thiazol-4-yl)-1,3-dihydro-benzo-
imidazol-2-one (15)
Trifluoromethanesulfonic anhydride (20 g, 70.9 mmol)
was added slowly to a cooled solution (0 ꢁC) of compound
10 (12.7 g, 50.8 mmol) and pyridine (12.5 mL,
154.6 mmol) in 200 mL of anhydrous CH2Cl2. The reac-
tion mixture was allowed to warm to room temperature
and stirred overnight. The reaction mixture was concen-
trated in vacuo and purified by flash chromatography
on silica gel using hexane:EtOAc (2:1–6:4) as the eluant
A mixture of acid 14 (157 mg, 0.4 mmol) and concen-
trated H3PO4 (2.5 mL) was heated to 120 ꢁC. After 4 h
the reaction mixture was cooled to 0 ꢁC and quenched
with ice H2O. The solution was basified with concentrated
NH4OH to pH 10 and the resulting precipitate was fil-
tered, washed with H2O, and dried in vacuo to give
108 mg (96%) of a yellow solid. 1H NMR (DMSO-d6): d
7.11–7.17 (m, 4), 8.00 (m, 2), 8.16 (s, 2), 8.77 (dd, 2,
J = 4.5, 1.6 Hz), 11.38 (br s, 1). MS (ESI, positive ion)
m/z 295 (M+1). Anal. Calcd for C15H10N4OS: C, 61.21;
H, 3.42; N, 19.04. Found: C, 61.76; H, 3.74; N, 18.58.
1
to give 10.7 g (55%) of a light-yellow solid. H NMR
(CDCl3): d 1.43 (t, 3, J = 7.2 Hz), 4.47 (q, 2, J = 7.1 Hz),
7.80 (dd, 2, J = 4.5, 1.6 Hz), 8.82 (dd, 2, J = 4.6, 1.6 Hz),
9.94 (br s, 1). MS (ESI, positive ion) m/z 383 (M+1).
5.11. Representative procedure for the synthesis of
compounds 16a and 16b
5.7. 4-(2-Amino-phenylamino)-2-pyridin-4-yl-thiazole-5-
carboxylic acid ethyl ester (12)
5.11.1. N-[2-(4-pyridyl)(1,3-thiazol-4-yl)]prop-2-enyloxy-
carboxamide (16a). To a suspension of acid 7a (14.8 g,
71.9 mmol) in 250 mL of toluene was added Et3N
(10.2 mL, 73.2 mmol) and the mixture was allowed to
stir at room temperature for 1 h. Diphenylphosphoryl
azide (23.5 mL, 108.9 mmol) was added and the reaction
mixture was allowed to stir at room temperature for an
additional 1 h. The reaction mixture was heated at 80 ꢁC
for 1 h and then the mixture was treated with allyl alco-
hol (49 mL, 721 mmol). After heating overnight the
reaction mixture was allowed to cool to room tempera-
ture and was concentrated in vacuo. The residue was
dissolved in CH2Cl2 and ether was added until a yellow
solid precipitated from the solution. The precipitate was
filtered and the filtrate was concentrated in vacuo. The
filtrate residue was again dissolved in CH2Cl2 and ether
was added until a yellow solid precipitated from the
solution. The precipitate was filtered and the combined
yellow solids were dried in vacuo to give 7.5 g (40%)
of the title compound. The filtrate was concentrated in
vacuo and purified by flash chromatography on silica
gel using CH2Cl2:EtOAc (6:4) as the eluant to afford an-
other 4.0 g (21%) of the title compound. 1H NMR
(CDCl3): d 4.73 (s, 2), 5.31 (d, 1, J = 10.5 Hz), 5.41 (d,
1, J = 17.2 Hz), 5.97 (m, 1), 7.44 (br s, 1), 7.63 (br s,
1), 7.74 (d, 2, J = 4.5 Hz), 8.71 (d, 2, J = 4.5 Hz). MS
(ESI, positive ion) m/z 262 (M+1).
A
solution
of
1,2-phenylenediamine
(1.71 g,
15.8 mmol) and triflate 11 (2.01 g, 5.26 mmol) in
11 mL of dioxane was heated at reflux for 48 h.
The solvent was removed in vacuo and the crude
material was purified by flash chromatography on sil-
ica gel eluting with 2 M NH3 in MeOH/CH2Cl2
(1:50) to give a brown solid. The material was recrys-
tallized from MeOH to give 1.29 g (72%) of a yellow
crystalline solid. 1H NMR (DMSO-d6): d 1.53 (q, 3,
J = 7.1 Hz), 4.54 (t, 2, J = 7.1 Hz), 5.04 (br s, 2),
6.88–6.92 (m, 1), 7.03–7.12 (m, 2), 7.38 (dd, 1,
J = 7.9, 1.1 Hz), 8.08 (dd, 2, J = 4.5, 1.1 Hz), 8.79
(s, 1), 8.95 (dd, 2 , J = 4.5, 1.7 Hz). MS (ESI, posi-
tive ion) m/z 341 (M+1).
5.8. 4-(2-Oxo-2,3-dihydro-benzoimidazol-1-yl)-2-pyridin-
4-yl-thiazole-5-carboxylic acid ethyl ester (13)
Aniline 12 (1.29 g, 3.79 mmol) and 1,10-carbonyldiimi-
dazole (1.84 g, 11.4 mmol) were dissolved in 38 mL of
DMF and the solution was cooled to 0 ꢁC. To the mix-
ture was slowly added 95% NaH (335 mg, 13.3 mmol)
and the mixture was allowed to warm to room temper-
ature. After 3 days the reaction mixture was quenched
with H2O at 0 ꢁC. The precipitate was filtered, washed
with H2O, and dried in vacuo to give 1.02 g (74%) of a
yellow solid. 1H NMR (DMSO-d6): d 0.95 (q, 3,
J = 7.1 Hz), 4.01 (t, 2, J = 7.1 Hz), 6.81–6.92 (m, 4),
7.79 (dd, 2, J = 4.5, 1.7 Hz), 8.59 (dd, 2, J = 4.5,
1.7 Hz), 11.06 (s, 1). MS (ESI, positive ion) m/z 367
(M+1).
5.11.2. N-[2-(2-Ethyl(4-pyridyl))(1,3-thiazol-4-yl)]prop-2-
enyloxycarboxamide (16b). Yield: 23% of a yellow solid.
1H NMR (CDCl3): d 1.36 (t, 3, J = 7.6 Hz), 2.89 (q, 2,
J = 7.6 Hz), 4.72 (d, 2, J = 5.5 Hz), 5.29–5.40 (m, 2),
5.94–5.98 (m, 1), 7.41 (br s, 1), 7.53 (d, 1, J = 5.0 Hz),
7.61–7.64 (m, 2), 8.60 (d, 1, J = 5.2 Hz). MS (ESI, posi-
tive ion) m/z 290 (M+1).
5.9. 4-(2-Oxo-2,3-dihydro-benzoimidazol-1-yl)-2-pyridin-
4-yl-thiazole-5-carboxylic acid (14)
To a suspension of ester 13 (822 mg, 2.24 mmol) in
5 mL of MeOH was added 1 N NaOH (5 mL,
5.0 mmol) at room temperature. After 1 h the reac-
tion mixture was quenched with 10% HCl and the
resulting precipitate was filtered to give 787 mg
(85%) of a yellow solid. 1H NMR (DMSO-d6): d
7.07 (m, 4), 8.04 (m, 2), 8.82 (m, 2), 11.21 (br s,
1). MS (ESI, positive ion) m/z 339 (M+1); (ESI, neg-
ative ion) m/z 337 (Mꢀ1).
5.12. Representative procedure for the synthesis of substi-
tuted benzyl bromides 17b–d, 17f, 17g, 17i–k, 25, and 28
5.12.1. 3-Bromo-2-(bromomethyl)-1-nitrobenzene (17d).
To a heated (80 ꢁC) solution of 2-bromo-6-nitrotolu-
ene (3.33 g, 15.4 mmol) in 20 mL of CCl4 were added
N-bromosuccinimide (3.38 g, 19.0 mmol) and 2,20-azo-
bis(2-methylpropionitrile) (296 mg, 1.80 mmol). After
stirring overnight the reaction mixture was allowed

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6585
to cool to room temperature and was filtered. The fil-
trate was concentrated in vacuo to give 4.55 g of a
brown oil that was a mixture of starting mate-
rial:desired product (1:2). This mixture was used with-
out further purification. H NMR (CDCl3): d 4.89 (s,
2), 7.36 (t, 1, J = 8.1 Hz), 7.89 (d, 1, J = 3.1 Hz), 7.90
(d, 1, J = 3.1 Hz).
J = 8.0 Hz), 7.95 (d, 1, J = 7.8 Hz), 8.28 (d, 1,
J = 8.2 Hz).
5.12.10. 4-(Bromomethyl)-2-nitrobenzenecarbonitrile (28).
1
1
Yield: 64%; H NMR (CDCl3): d 4.55 (s, 2), 7.85 (d, 1,
J = 7.9 Hz), 7.92 (d, 1, J = 7.9 Hz), 8.36 (s, 1,).
5.13. Representative procedure for the synthesis of
substituted benzyl bromides 17e and 17h
5.12.2. 2-(Bromomethyl)-3-fluoro-1-nitrobenzene (17b).
Yield: 22%; H NMR (CDCl3): d 4.84 (s, 2), 7.40 (t, 1,
J = 8.6 Hz), 7.46–7.50 (m, 1), 7.87 (d, 1, J = 8.2 Hz).
1
5.13.1. 2-(Bromomethyl)-3-methyl-1-nitrobenzene (17h).
1
Yield: 64%; H NMR (CDCl3): d 2.38 (s, 3), 4.47 (s, 2),
7.28 (d, 1, J = 6.4 Hz), 7.35–7.38 (m, 2).
5.12.3. 2-(Bromomethyl)-3-chloro-1-nitrobenzene (17c).
1
Yield: 55%; H NMR (CDCl3): d 4.88 (s, 2), 7.44 (t, 1,
J = 8.2 Hz), 7.70 (d, 1, J = 8.1 Hz), 7.88 (d, 1, J = 8.2 Hz).
5.13.2. 2-(Bromomethyl)-4-methyl-1-nitrobenzene (17e).
5-Methyl-2-nitrobenzyl alcohol (2.16 g, 12.9 mmol) was
dissolved in 40 mL of dry CH2Cl2. Phosphorus tribro-
mide (1.25 mL, 13.3 mmol) was added dropwise. The
reaction mixture was stirred overnight. Saturated
NaHCO3 was cautiously added until pH 6. The reac-
tion mixture was partitioned and the aqueous layer
was extracted with CH2Cl2 (2·). The combined
CH2Cl2 layers were washed with brine, dried over
MgSO4, and concentrated in vacuo to provide 2.11 g
(71%) of the title compound as a yellow oil which
5.12.4. 2-(Bromomethyl)-3-methoxy-1-nitrobenzene (17f).
Yield: 100%; 1H NMR (CDCl3): d 3.98 (s, 3), 5.15 (s, 2),
7.61 (t, 1, J = 7.9 Hz), 7.97 (d, 1, J = 7.9 Hz), 8.10 (d, 1,
J = 7.9 Hz).
5.12.5. 2-(Bromomethyl)-4-fluoro-1-nitrobenzene (17g).
1
Yield: 36%; H NMR (CDCl3): d 4.83 (s, 2), 7.17 (td,
1, J = 6.6, 2.7 Hz), 7.33 (dd, 1, J = 8.7, 2.8 Hz), 8.16
(dd, 1, J = 9.1, 5.1 Hz).
1
crystallized upon standing. H NMR (CDCl3): d 2.45
(s, 3), 4.82 (s, 2), 7.28 (d, 1, J = 6.1 Hz), 7.35 (s, 1),
7.99 (d, 1, J = 8.3 Hz).
5.12.6. 1-(Bromomethyl)-4-fluoro-2-nitrobenzene (17i).
1
Yield: 41%; H NMR (CDCl3): d 4.81 (s, 2), 7.35 (td,
1, J = 8.3, 2.6 Hz), 7.60 (dd, 1, J = 8.6, 5.4 Hz), 7.80
(dd, 1, J = 8.2, 2.6 Hz).
5.14. Representative procedure for the synthesis of
compounds 18b–k and 18p
5.12.7. 4-Bromo-1-(bromomethyl)-2-nitrobenzene (17j).
1
Yield: 51%; H NMR (CDCl3): d 5.15 (s, 2), 7.61 (d,
1, J = 7.9 Hz), 7.97 (d, 1, J = 7.9 Hz), 8.10 (s, 1).
5.14.1. N-[(6-Bromo-2-nitrophenyl)methyl]prop-2-enyloxy-
N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18d). To a
solution of carboxamide 16a (1.02 g, 3.9 mmol) in 20 mL
of dry DMF was added 60% NaH in portions. The reac-
tion mixture was stirred for 45 min at room temperature
and a solution of bromide 17d (2.3 g, 5.14 mmol) in
5 mL of DMF was added dropwise. The reaction mixture
was heated at 80 ꢁC for 4 h. The reaction mixture was al-
lowed to cool to room temperature and partitioned be-
tween EtOAc/H2O. The aqueous layer was extracted
with EtOAc (3·) and the combined organic layers were
washed with H2O and brine, dried over MgSO4, and con-
centrated in vacuo. The crude oil was purified by flash
chromatography on silica gel using CH2Cl2:MeOH
(97:3) as the eluant to afford 940 mg (50%) of a brown
5.12.8. 1-(Bromomethyl)-2-nitro-4-phenylbenzene (17k).
To a mixture of bromobenzene (3.3 mL, 29.6 mmol),
3-nitro-4-methylbenzene boronic acid (5.11 g, 28.3 mmol),
and 2 M Na2CO3 (63 mL, 126.0 mmol) in 100 mL of
toluene/15 mL of EtOH was added tetrakis(triphenyl-
phosphine)palladium (0) (2.04 g, 1.8 mmol) and the
mixture was stirred at 80 ꢁC for 4 h. The reaction
was cooled to room temperature and partitioned be-
tween EtOAc:H2O. The aqueous layer was extracted
with EtOAc and the combined organic layers were
washed with brine, dried over MgSO4, and concen-
trated in vacuo. Purification by flash chromatography
on silica gel using hexane:EtOAc (98:2) as eluant
afforded 4.68 g (78%) of 1-methyl-2-nitro-4-phenylben-
1
oil. H NMR (CDCl3): d 4.68 (d, 2, J = 5.6 Hz), 5.20–
5.30 (m, 2), 5.68 (s, 2), 5.83–5.94 (m, 1), 7.15–7.30 (m,
2), 7.58 (d, 1, J = 7.8 Hz), 7.67–7.76 (m, 3), 8.70 (d, 2,
J = 5.5 Hz). MS (ESI, positive ion) m/z 476 (M+1).
1
zene as a light orange solid. H NMR (CDCl3)d 2.64
(s, 3), 7.38–7.42 (m, 2), 7.48 (t, 2, J = 7.8 Hz), 7.62
(d, 2, J = 7.7 Hz), 7.74 (dd, 1, J = 8.0, 1.8 Hz), 8.22
(s, 1).
5.14.2. N-[(6-Fluoro-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18b).
Analogous to the procedure described for compound 17d,
1-methyl-2-nitro-4-phenylbenzene (4.68 g, 22.0 mmol)
provided the title compound as a white solid (1.40 g,
22%). H NMR (CDCl3) d 4.88 (s, 2), 7.43–7.52 (m,
3), 7.60–7.65 (m, 3), 7.84 (dd, 1, J = 8.0, 1.9 Hz), 8.27
(d, 1, J = 1.8 Hz).
Yield: 82%; 1H NMR (CDCl3):
d 4.70 (d, 2,
J = 5.8 Hz), 5.22–5.31 (m, 2), 5.69 (s, 2), 5.86–5.95 (m,
1), 7.24 (t, 1, J = 9.4 Hz), 7.34–7.38 (m, 1), 7.60 (d, 1,
J = 8.1 Hz), 7.69 (d, 2, J = 5.6 Hz), 8.69 (br s, 2).
1
5.14.3. N-[(6-Chloro-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18c).
5.12.9. 6-(Bromomethyl)-2-nitrobenzenecarbonitrile (25).
Yield: 72%; 1H NMR (CDCl3):
J = 5.8 Hz), 5.20–5.29 (m, 2), 5.69 (s, 2), 5.81–5.92 (m,
d
4.68 (d, 2,
1
Yield: 66%; H NMR (CDCl3): d 4.76 (s, 2), 7.81 (t, 1,

6586
R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
1), 7.29 (t, 1, J = 8.1 Hz), 7.56 (d, 2, J = 8.2 Hz), 7.71
(dd, 2, J = 4.6, 1.5 Hz), 8.70 (dd, 2, J = 4.6, 1.5 Hz).
MS (ESI, positive ion) m/z 431 (M+1).
2.85 (q, 2, J = 7.6 Hz), 4.72 (d, 2, J = 5.5 Hz), 5.20–5.30
(m, 2), 5.70 (s, 2), 5.81–5.93 (m, 1), 7.30–7.41 (m, 4), 7.46
(s, 1), 7.53 (d, 1, J = 7.4 Hz), 8.06 (d, 1, J = 8.2 Hz), 8.55
(d, 1, J = 5.1 Hz). MS (ESI, positive ion) m/z 425 (M+1).
5.14.4. N-[(6-Methyl-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18e).
Yield: 75%; H NMR (CDCl3): d 2.37 (s, 3), 4.73 (d,
5.15. Representative procedure for the synthesis of
compounds 19b–f, 19h, 19i, 19k, and 19p
1
2, J = 5.6), 5.21–5.27 (m, 2), 5.36 (s, 2), 5.85–5.90 (m,
1), 7.18 (d, 2, J = 7.6 Hz), 7.29 (t, 1, J = 7.6 Hz), 7.70
(dd, 1, J = 4.6, 1.6 Hz), 8.68 (dd, 2, J = 4.5, 1.7 Hz).
5.15.1. [(2-Amino-6-bromophenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19d). To a solution of carboxamide
18d (936 mg, 2.0 mmol) in 20 mL of acetonitrile
were added morpholine (1.71 mL, 19.6 mmol) and
tetrakis(triphenylphosphine)palladium (0) (205 mg,
0.2 mmol) at room temperature. After stirring over-
night the reaction mixture was concentrated in vacuo
and the residue was dissolved in EtOAc and washed
with H2O. The aqueous layer was extracted with
EtOAc (2·) and the combined organic layers were
washed with brine, dried over MgSO4, and concen-
trated in vacuo. The crude oil was purified by flash
chromatography on silica gel using CH2Cl2:EtOAc
(6:4) as the eluant to afford 400 mg (52%) of a brown
oil. 1H NMR (CDCl3): d 4.81 (d, 2, J = 4.0 Hz), 5.0
(br s, 1), 6.0 (s, 1), 7.33 (td, 1, J = 8.1, 2.8 Hz), 7.72
(dd, 2, J = 4.5, 1.6 Hz), 7.79 (d, 1, J = 7.2 Hz), 7.87
(d, 1, J = 7.1 Hz), 8.66 (dd, 2, J = 4.5, 1.6 Hz). MS
(ESI, positive ion) m/z 392 (M+1).
5.14.5. N-[(6-Methoxy-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18f).
Yield: 83%; 1H NMR (DMSO-d6): d 3.98 (s, 3), 4.72 (d,
2, J = 4.8 Hz), 5.25 (dd, 2, J = 4.8, 10.5 Hz), 5.75 (s, 2),
5.95 (m, 1), 7.45 (d, 2, J = 7.8 Hz), 7.55 (t, 1, J = 7.8 Hz),
7.70 (d, 2, J = 4.8 Hz), 8.10 (d, 1, J = 7.8 Hz), 8.68 (d, 2,
J = 4.8 Hz).
5.14.6. N-[(5-Fluoro-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18g).
Yield: 58%; 1H NMR (CDCl3):
d 4.73 (d, 2,
J = 5.2 Hz), 5.23–5.28 (m, 2), 5.71 (s, 2), 5.83–5.93 (m,
1), 7.00–7.15 (m, 2), 7.61 (d, 2, J = 4.7 Hz), 7.67 (s, 1),
8.16–8.20 (m, 1), 8.66 (d, 2, J = 5.9 Hz). MS (ESI, posi-
tive ion) m/z 415 (M+1).
5.14.7. N-[(5-Methyl-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18h).
Yield: 88%; H NMR (CDCl3): d 2.34 (s, 3), 4.73 (d,
2, J = 5.6 Hz), 5.20–5.26 (m, 2), 5.70 (s, 2), 5.85–5.89
(m, 1), 7.16–7.19 (m, 2), 7.63 (d, 2, J = 4.8 Hz), 8.01
(d, 1, J = 8.3 Hz), 8.65 (d, 2, J = 5.0 Hz).
The amine from the previous step (400 mg, 1.0 mmol)
was dissolved in 35 mL of 70% aqueous EtOH. Iron
powder (255 mg, 4.6 mmol) and NH4Cl (28 mg,
0.5 mmol) were added and the reaction mixture was
heated at 80 ꢁC. After stirring for 3 h the reaction mix-
ture was filtered while hot through a pad of Celiteꢂ,
and the pad was rinsed liberally with EtOAc. The filtrate
was concentrated in vacuo and the residue was parti-
tioned between EtOAc/H2O. The aqueous layer was ex-
tracted with EtOAc (2·). The combined organic layers
were washed with brine, dried over MgSO4, and concen-
1
5.14.8. N-[(4-Fluoro-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18i).
Yield: 94%; 1H NMR (CDCl3): d 4.71 (d, 2, J = 5.6 Hz),
5.22–5.24 (m, 2), 5.66 (s, 2), 5.83–5.95 (m, 1), 7.29 (dd, 1,
J = 7.9, 2.6 Hz), 7.42 (br s, 1), 7.62 (dd, 2, J = 4.5,
1.5 Hz), 7.81 (dd, 1, J = 8.2, 2.6 Hz), 8.66 (dd, 2,
J = 4.6, 1.4 Hz). MS (ESI, positive ion) m/z 415 (M+1).
1
trated in vacuo to give 296 mg (80%) of a brown oil. H
NMR (CDCl3): d 4.60 (d, 2, J = 4.3 Hz), 6.08 (s, 1), 6.62
(d, 1, J = 6.8 Hz), 7.00 (m, 2), 7.73 (dd, 2, J = 4.6,
1.6 Hz), 8.68 (dd, 2, J = 4.6, 1.5 Hz). MS (ESI, positive
ion) m/z 362 (M+1).
5.14.9. N-[(4-Bromo-2-nitrophenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18j).
Yield: 39%; 1H NMR (DMSO-d6): d 4.55 (d, 2,
J = 4.8 Hz), 5.15 (dd, 2, J = 10.5, 4.8 Hz), 5.65 (s, 2),
5.95 (m, 1), 7.45 (s, 1), 7.71 (t, 1, J = 7.9 Hz), 7.72 (d,
2, J = 4.8 Hz), 7.85 (d, 1, J = 7.9 Hz), 7.95 (d, 2,
J = 7.9 Hz), 8.68 (d, 2, J = 4.8 Hz). MS (ESI, positive
ion) m/z 477 (M+1).
5.15.2. [(2-Amino-6-fluorophenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19b). Yield: 23%; 1H NMR (CDCl3):
d 4.42 (br s, 5), 6.08 (s, 1), 6.47–6.51 (m, 2), 7.07 (q, 1,
J = 6.5 Hz), 7.73 (dd, 2, J = 4.5, 1.5 Hz), 8.68 (dd, 2,
J = 4.7, 1.4 Hz).
5.14.10. N-[(2-Nitro-4-phenylphenyl)methyl]prop-2-enyl-
oxy-N-(2-(4-pyridyl)(1,3-thiazol-4-yl))carboxamide (18k).
Yield: 46%; H NMR (CDCl3; 400 MHz): d 4.74 (d, 2,
J = 5.5 Hz), 5.20–5.30 (m, 2), 5.74 (s, 2), 5.85–5.94 (m,
1), 7.40–7.49 (m, 4), 7.60 (d, 2, J = 7.7 Hz), 7.64 (dd,
2, J = 4.5, 1.5 Hz), 7.77 (dd, 1, J = 8.2, 1.8 Hz), 8.30
(d, 1, J = 1.8 Hz), 8.66 (dd, 2, J = 4.7, 1.5 Hz). MS
(ESI, positive ion) m/z 473 (M+1).
5.15.3. [(2-Amino-6-chlorophenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19c). Yield: 67%; 1H NMR
(CDCl3): d 4.46 (br s, 2), 4.53 (br s, 1), 4.58 (s, 2),
6.08 (s, 1), 6.61 (d, 1, J = 8.0 Hz), 6.83 (d, 1,
J = 7.9 Hz), 7.03 (t, 1, J = 8.0 Hz), 7.73 (dd, 2,
J = 4.6, 1.4 Hz), 8.68 (dd, 2, J = 4.6, 1.5 Hz). MS
(ESI, positive ion) m/z 317 (M+1).
1
5.15.4. [(2-Amino-6-methylphenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19e). Yield: 45%; H NMR (CDCl3):
d 2.21 (s, 3), 4.12 (br s, 2), 4.33 (d, 2, J = 4.1 Hz), 4.52
(br s, 1), 6.00 (s, 1), 6.70 (t, 1, J = 7.5 Hz), 7.08 (d, 2,
1
5.14.11. N-[2-(2-Ethyl(4-pyridyl))(1,3-thiazol-4-yl)]-N-
[(2-nitrophenyl)methyl]prop-2-enyloxycarboxamide (18p).
Yield: 85%; 1H NMR (CDCl3): d 1.32 (t, 3, J = 7.7 Hz),

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6587
J = 7.4 Hz), 7.74 (dd, 2, J = 4.6, 1.5 Hz), 8.68 (dd, 2,
J = 4.6, 1.5 Hz). MS (ESI, positive ion) m/z 297 (M+1).
bined EtOAc layers were washed 1 N HCl (2·) and the
combined acidic layers were neutralized with 5N NaOH
and extracted with EtOAc (3·). The combined EtOAc
layers were washed with brine, dried over MgSO4, and
concentrated in vacuo to afford 610 mg (92%) of a light-
brown oil. 1H NMR (CDCl3): d 4.01 (br s, 2), 4.29 (d, 2,
J = 5.5), 4.58 (br s, 1), 5.98 (s, 1), 6.64–6.67 (m, 1), 6.87
(td, 1, J = 8.7, 2.6 Hz), 6.97 (dd, 1, J = 9.0, 2.7 Hz), 7.74
(d, 2, J = 6.0 Hz), 8.68 (d, 2, J = 6.1 Hz). MS (ESI, posi-
tive ion) m/z 301 (M+1).
5.15.5. [(2-Amino-6-methoxyphenyl)methyl](2-(4-pyr-
idyl)(1,3-thiazol-4-yl))amine (19f). Yield: 13%; 1H
NMR (DMSO-d6):
d
3.98 (s, 3), 4.21 (d, 2,
J = 4.8 Hz), 5.12 (s, 2), 6.15 (s, 1), 6.52 (t, 1,
J = 7.4 Hz), 6.62 (d, 1, J = 7.4 Hz), 6.72 (s, 1), 6.95 (t,
1, J = 7.4 Hz), 7.13 (d, 1, J = 7.4 Hz), 7.80 (d, 2,
J = 4.8 Hz), 8.72 (d, 2, J = 4.8 Hz).
5.15.6. [(2-Amino-5-methylphenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19h). Yield: 12%; H NMR (CDCl3):
5.16.2. [(2-Amino-4-bromophenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19j). Yield: 67%; H NMR (DMSO-
1
1
d 2.26 (s, 3), 4.28 (d, 2, J = 5.0 Hz), 5.99 (s, 1), 6.66 (d, 1,
J = 8.0 Hz), 6.96–7.01 (m, 3), 7.74 (d, 2, J = 6.1 Hz),
8.67 (d, 2, J = 6.1 Hz). MS (ESI, positive ion) m/z 297
(M+1).
d6): d 5.65 (s, 2), 7.45 (s, 1), 7.71 (t, 1, J = 7.9 Hz),
7.72 (d, 2, J = 4.8 Hz), 7.85 (d, 1, J = 7.9 Hz), 7.95 (d,
2, J = 7.9 Hz), 8.68 (d, 2, J = 4.8 Hz). MS (ESI, positive
ion) m/z 363 (M+1).
5.15.7. [(2-Amino-4-fluorophenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19i). Yield: 28%; H NMR (CDCl3):
5.17. Representative procedure for the synthesis of
compounds 20d–f, 20h and 20i
1
d 4.28 (d, 2, J = 5.0 Hz), 4.32 (br s, 2), 4.48 (br s, 1), 6.00
(s, 1), 6.42 (m, 2), 7.12 (t, 1, J = 7.4 Hz), 7.73 (dd, 2,
J = 4.6, 1.5 Hz), 8.68 (dd, 2, J = 4.6, 1.5 Hz). MS (ESI,
positive ion) m/z 301 (M+1).
5.17.1. 5-Bromo-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20d). Aniline 19d (296 mg,
0.8 mmol), p-nitrophenyl chloroformate (175 mg,
0.9 mmol), and Et3N (0.12 mL, 0.9 mmol) were dis-
solved in 10 mL of toluene/10 mL of THF and stirred
at room temperature for 1 h. After heating the reac-
tion at 80 ꢁC overnight the mixture was allowed to
cool to room temperature and was concentrated in
vacuo. The residue was dissolved in CH2Cl2 and
washed with H2O. The aqueous layer was extracted
with CH2Cl2 (2·) and the combined organic layers
were washed with brine, dried over MgSO4, and con-
centrated in vacuo. The crude solid was purified by
5.15.8. [(2-Amino-4-phenylphenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19k). Yield: 13%; MS (ESI, positive
ion) m/z 359 (M+1).
5.15.9. [(2-Aminophenyl)methyl][2-(2-ethyl(4-pyridyl))(1,3-
thiazol-4-yl)]amine (19p). Yield: 48%; 1H NMR (CDCl3): d
1.35 (t, 3, J = 7.6 Hz), 2.87 (q, 2, J = 7.6 Hz), 4.18 (br s, 2),
4.31 (s, 2), 4.53 (br s, 1), 5.98 (s, 1), 6.71–6.79 (m, 2), 7.13–
7.20 (m, 2), 7.68 (d, 1, J = 5.2 Hz), 7.61 (s, 1), 8.57 (d, 1,
J = 5.2 Hz). MS (ESI, positive ion) m/z 311 (M+1).
flash
CH2Cl2:MeOH (99:1 to 97:3) as the eluant to afford
chromatography
on
silica
gel
using
5.16. Representative procedure for the synthesis of
compounds 19g and 19j
40 mg (12%) of an off-white solid. Mp 283-284 ꢁC.
1H NMR (CDCl3):
d 5.38 (s, 2), 6.72 (d, 1,
J = 7.6 Hz), 7.13 (t, 1, J = 7.8 Hz), 7.13–7.30 (m, 2),
7.83–7.86 (m, 3), 8.74 (d, 2, J = 5.7 Hz). MS (ESI,
positive ion) m/z 388 (M+1). Anal. Calcd for
C16H11BrN4OS: C, 49.63; H, 2.86; N, 14.47. Found:
C, 49.61; H, 2.99; N, 14.26.
5.16.1. [(2-Amino-5-fluorophenyl)methyl](2-(4-pyridyl)(1,3-
thiazol-4-yl))amine (19g). A mixture of carboxamide 18 g
(949 mg, 2.3 mmol), iron powder (680 mg, 12.2 mmol),
and NH4Cl (79 mg, 1.5 mmol) was dissolved in 60 mL
of acetonitrile and 30 mL of H2O. The solution was
stirred at 80 ꢁC for 2 h and filtered while hot through
a bed of Celite. The filtrate was concentrated in vacuo
and the aqueous solution was extracted with EtOAc
(3·). The combined organic layers were washed with
brine, dried over MgSO4, and concentrated in vacuo
to afford 875 mg (98%) of a tan solid. 1H NMR
(CDCl3): d 4.16 (br s, 2), 4.74 (d, 2, J = 4.6 Hz), 5.15
(s, 2), 5.24–5.33 (m, 2), 5.91–5.95 (m, 1), 6.57–6.60
(m,1), 6.75–6.85 (m, 2), 7.34 (br s, 1), 7.76 (dd, 2,
J = 4.5, 1.5 Hz), 8.72 (dd, 2, J = 4.5, 1.5 Hz). MS
(ESI, positive ion) m/z 385 (M+1).
5.17.2. 5-Methyl-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20e). Yield: 3%; 1H NMR
(CDCl3): d 2.28 (s, 3), 5.78 (s, 2), 6.70 (br s, 1), 6.96 (t,
1, J = 7.5 Hz), 7.09–7.12 (m, 2), 7.84 (dd, 2, J = 4.4,
1.7 Hz), 8.73 (dd, 2, J = 4.6, 1.4 Hz). MS (ESI, positive
ion) m/z 323 (M+1). HRMS calcd for C17H15N4OS
[M+H]+ 323.0967, found 323.09655.
5.17.3. 5-Methoxy-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20f). Yield: 23%; 1H NMR
(DMSO-d6): d 3.98 (s, 3), 5.25 (s, 2), 6.95 (d, 1,
J = 7.4 Hz), 7.05 (t, 1, J = 7.4 Hz), 7.23 (t, 1,
J = 7.4 Hz), 7.35 (d, 1, J = 7.4 Hz), 8.05 (s, 1), 8.35 (d,
2, J = 4.8 Hz), 8.95 (d, 2, J = 4.8 Hz), 9.90 (s, 1). MS
(ESI, positive ion) m/z 339 (M+1).
The material (850 mg, 2.2 mmol) from the previous step,
morpholine (4 mL, 45.7 mmol), and tetrakis(triphenyl-
phosphine)palladium (0) (260 mg, 0.2 mmol) were dis-
solved in 30 mL of THF. The solution was stirred at
room temperature for 4 h and then concentrated in vacuo.
The residue was partitioned between EtOAc:H2O and the
aqueous layer was extracted with EtOAc (2·). The com-
5.17.4. 6-Methyl-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20h). Yield: 20%; mp 259–
261 ꢁC. 1H NMR (CDCl3): d 2.33 (s, 3), 5.31 (s, 2),

6588
R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6.66 (d, 1, J = 8.0 Hz), 6.75 (s, 1), 7.03–7.07 (m, 2), 7.82
(d, 2, J = 5.7 Hz), 7.83 (s, 1), 8.73 (d, 2, J = 6.1 Hz). MS
(ESI, positive ion) m/z 323 (M+1). Anal. Calcd for
C17H14N4OSÆ0.3H2O: C, 62.29; H, 4.53; N, 17.09.
Found: C, 62.49; H, 4.53; N, 16.50.
5.18.5. 7-Phenyl-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20k). Yield: 17%; mp 248–
250 ꢁC. H NMR (DMSO-d6): d 5.51 (s, 2), 7.38 (s,
1), 7.50 (d, 1, J = 7.8 Hz), 7.60–7.63 (m, 2), 7.70 (t, 2,
J = 7.7 Hz), 7.83 (d, 2, J = 7.9 Hz), 8.11 (s, 1), 8.17
(dd, 2, J = 4.4, 1.4 Hz), 8.96 (dd, 2, J = 4.6, 1.4 Hz),
10.12 (s, 1). MS (ESI, positive ion) m/z 385 (M+1).
Anal. Calcd for C22H16N4OS0Æ4H2O: C, 67.47; H,
4.32; N, 14.31. Found: C, 67.86; H, 4.71; N, 13.77.
1
5.17.5. 7-Fluoro-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20i). Yield: 22%; mp 285–
286 ꢁC. 1H NMR (CDCl3)d 5.31 (s, 2), 6.53 (dd, 1,
J = 9.1, 2.2 Hz), 6.75 (td, 1, J = 9.1, 2.2 Hz), 7.12 (br s,
1), 7.23 (t, 1, J = 6.0 Hz), 7.84 (m, 3), 8.74 (d, 2,
J = 6.0 Hz). MS (ESI, positive ion) m/z 327 (M+1).
Anal. Calcd for C16H11FN4OS: C, 58.89; H, 3.40; N,
17.17. Found: C, 58.90; H, 3.47; N, 16.88.
5.18.6. 3-[2-(2-Ethyl-4-pyridyl)-1,3-thiazol-4-yl]-1,3,4-tri-
hydroquinazolin-2-one (20p). Yield: 57%; mp 239–
240 ꢁC. 1H NMR (CDCl3): d 1.29 (t, 3, J = 7.6 Hz),
2.85 (q, 2, J = 7.6 Hz), 5.23 (s, 2), 6.92 (d, 1,
J = 8.0 Hz), 6.98 (t, 1, J = 7.5 Hz), 7.22 (t, 1,
J = 7.4 Hz), 7.32 (d, 1, J = 7.5 Hz), 7.74 (d, 1,
J = 5.1 Hz), 7.78 (s, 1), 7.85 (s, 1), 8.62 (d, 1,
J = 5.2 Hz). MS (ESI, positive ion) m/z 337 (M+1).
Anal. Calcd for C18H16N4OSÆ0.1H2O: C, 63.92; H,
4.83; N, 16.57. Found: C, 63.75; H, 4.81; N, 16.40.
5.18. Representative procedure for the synthesis of
compounds 20b, 20c, 20g, 20j, 20k, and 20p
5.18.1. 6-Fluoro-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20g). To a mixture of amine
19g (610 mg, 2.0 mmol) and 1,10-carbonyldiimidazole
(995 mg, 6.1 mmol) in 20 mL of anhydrous DMF was
added 60% NaH (290 mg, 7.3 mmol) in portions at
room temperature. After 4 h, the reaction mixture was
diluted with H2O and filtered. The precipitate was
washed with H2O (2· 10 mL) and stirred in a solution
of H2O:hexane (1:1) to remove any remaining mineral
oil. The precipitate was filtered and dried in vacuo at
60 ꢁC to afford 110 mg (17%) of a white solid. Mp
5.19. 6-(Morpholin-4-ylmethyl)-2-nitrobenzenecarbonitri-
le (26)
A solution of bromide 25 (126 mg, 0.5 mmol) in 7 mL
of DMF was treated with morpholine (0.21 mL,
2.4 mmol) resulting in an immediate color change from
a light-yellow to an orange-tan. The reaction mixture
was partitioned between EtOAc:H2O and the aqueous
layer was extracted with EtOAc (3·). The combined
EtOAc layers were washed with H2O and brine, dried
over MgSO4 and concentrated in vacuo to provide
97 mg (75%) of the title compound as a yellow solid.
1H NMR (CDCl3): d 2.53–2.56 (m, 4), 3.72–3.75 (m,
4), 3.83 (s, 2), 7.77 (t, 1, J = 7.9 Hz), 7.99 (d, 1,
J = 7.7 Hz), 8.22 (d, 1, J = 8.2 Hz). MS (ESI, positive
ion) m/z 248 (M+1).
1
290–291 ꢁC. H NMR (DMSO-d6): d 5.24 (s, 2), 6.89–
6.93 (m, 1), 7.08 (td, 1, J = 8.8, 2.8 Hz), 7.25 (dd, 1,
J = 9.0, 2.6 Hz), 7.86 (s, 1), 7.93 (dd, 2, J = 4.5,
1.5 Hz), 8.74 (dd, 2, J = 4.5, 1.5 Hz), 9.84 (br s, 1) MS
(ESI, positive ion) m/z 327 (M+1). Anal. Calcd for
C16H11FN4OSÆ0.1H2O: C, 58.56; H, 3.44; N, 17.07.
Found: C, 58.31; H, 3.56; N, 16.82.
5.18.2. 5-Fluoro-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20b). Yield: 77%; mp 247–
249 ꢁC. H NMR (DMSO-d6): d 5.27 (s, 2), 6.76 (d, 1,
5.20. 4-(Morpholin-4-ylmethyl)-2-nitrobenzenecarbonitri-
le (29)
1
J = 8.0 Hz), 6.83 (t, 1, J = 8.7 Hz), 7.27 (q, 1,
J = 6.5 Hz), 7.90–7.92 (m, 3), 8.74 (dd, 2, J = 4.5,
1.4 Hz), 10.05 (br s, 1). MS (ESI, positive ion) m/z 327
(M + 1). Anal. Calcd for C16H11FN4OS: C, 58.89; H,
3.40; N, 17.17. Found: C, 59.35; H, 3.58; N, 16.90.
To a solution of bromide 28 (1.92 g, 7.9 mmol) in 40 mL
of CH3CN was added morpholine (1.0 mL, 11.4 mmol)
and the reaction mixture changed immediately from a
light-yellow to a orange-tan color. The reaction mixture
was concentrated in vacuo. The crude residue was puri-
fied by flash chromatography on silica gel using
CH2Cl2:MeOH (1:0–96:4) as the eluant provided the ti-
5.18.3. 5-Chloro-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20c). Yield: 16%; mp 292–
1
1
293 ꢁC. H NMR (DMSO-d6): d 5.29 (s, 2), 6.89 (d, 1,
tle compound as 1.4 g (71%) of a light-brown oil. H
J = 7.9 Hz), 7.09 (d, 1, J = 7.9 Hz), 7.25 (t, 1,
J = 8.0 Hz), 7.90 (dd, 2, J = 4.6, 1.5 Hz), 7.92 (s, 1),
8.75 (dd, 2, J = 4.6, 1.4 Hz), 10.04 (s, 1). MS (ESI, posi-
tive ion) m/z 343 (M+1). Anal. Calcd for
C16H11ClN4OS0.2H2O: C, 55.48; H, 3.32; N, 16.17.
Found: C, 55.24; H, 3.47; N, 15.90.
NMR (CDCl3): d 2.47–2.49 (m, 4), 3.65 (s, 2), 3.73–
3.75 (m, 4), 7.82 (d, 1, J = 7.9 Hz), 7.88 (d, 1,
J = 7.9 Hz), 8.35 (s, 1). MS (ESI, positive ion) m/z 248
(M+1).
5.21. Representative procedure for the synthesis of
substituted benzylamines 27, 30, and 32
5.18.4. 7-Bromo-3-(2-(4-pyridyl)(1,3-thiazol-4-yl))-1,3,4-
trihydroquinazolin-2-one (20j). Yield: 93%; 1H NMR
(DMSO-d6): d 5.25 (s, 2), 6.95 (d, 1, J = 7.4), 7.05 (d,
1, J = 7.4), 7.23 (d, 1, J = 7.4), 7.75 (s, 1), 7.87 (d, 2,
J = 4.8), 8.75 (d, 2, J = 4.8), 9.93 (s, 1). HRMS
calcd for C16H12BrN4OS [M+H]+ 386.9915, found
386.9909.
5.21.1. [6-(Morpholin-4-ylmethyl)-2-nitrophenyl]methyl-
amine (27). Nitrile 26 (1.59 g, 6.4 mmol) was added as a
solid to 35 mL of 1 M BH3THF (35 mmol) at 0 ꢁC. The
solution was allowed to warm to room temperature and
stirred overnight. The reaction mixture was concentrated
to half its volume, carefully poured into 40 mL of 10% aq

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6589
HCl, and stirred at reflux for 3 h. The reaction mixture
was allowed to cool to room temperature and concen-
trated in vacuo to remove any remaining THF. The result-
ing aqueous solution was washed with benzene (2·) and
neutralized with 1 N NaOH. The aqueous solution was
then extracted with CH2Cl2 (2·) and the combined organ-
ic layers were washed with brine, dried over MgSO4, and
concentrated in vacuo to provide 975 mg (60%) of the title
J = 7.1), 2.35 (s, 3), 2.55 (m, 4), 3.10 (m, 4), 4.15 (s, 2),
4.35 (q, 2, J = 7.1), 4.78 (d, 2, J = 6.0), 6.70 (m, 2),
6.95 (t, 1, J = 6.0), 7.05 (d, 1, J = 8.7), 7.82 (d, 2,
J = 5.3), 8.75 (d, 2, J = 5.3). MS (ESI, positive ion) m/z
453 (M+1).
5.24. Representative procedure for the synthesis of
compounds 21l, 21n and 21o
1
compound as a light-brown oil. H NMR (CDCl3): d
2.48–2.51 (m, 4), 3.61 (s, 2), 3.67–3.70 (m, 4), 3.88 (s, 2),
7.34 (t, 1, J = 7.7 Hz), 7.49 (d, 1, J = 7.5 Hz), 7.77 (d, 1,
J = 8.1 Hz). MS (ESI, positive ion) m/z 252 (M+1).
5.24.1. Ethyl-4-({[2-amino-6-(morpholin-4-ylmethyl)
phenyl]methyl}amino)-2-(4-pyridyl)-1,3-thiazole-5-car-
boxylate (21n). A mixture of triflate 11 (1.49 g,
3.9 mmol) and amine 27 (975 mg, 3.9 mmol) in
25 mL of dioxane was heated at 80 ꢁC for 6 h. The
reaction mixture was cooled to room temperature
and the reaction mixture was concentrated in vacuo.
The residue was purified by flash chromatography
on silica gel using CH2Cl2:EtOAc (7:3 to 1:1) as
the eluant to afford 660 mg of an orange-yellow solid.
1H NMR (CDCl3): d 1.34 (t, 3, J = 7.1 Hz), 2.46–2.49
(m, 4), 3.71–3.76 (m, 6), 4.30 (q, 2, J = 7.1 Hz), 5.16
(d, 2, J = 6.3 Hz), 7.38 (t, 1, J = 7.8 Hz), 7.48 (br s,
1), 7.55 (d, 1, J = 7.7 Hz), 7.75–7.79 (m, 3), 8.75
(dd, 2, J = 6.0, 1.5 Hz). MS (ESI, positive ion) m/z
484 (M+1).
5.21.2. [4-(Morpholin-4-ylmethyl)-2-nitrophenyl]methyl-
1
amine (30). Yield: 60%; H NMR (CDCl3): d 2.44–2.49
(m, 4), 3.55 (s, 2), 3.71–3.73 (m, 4), 4.09 (s, 2), 7.55 (d,
1, J = 7.9 Hz), 7.60 (d, 1, J = 7.9 Hz), 7.98 (s, 1). MS
(ESI, positive ion) m/z 252 (M+1).
5.21.3. (2-(4-Methylpiperazin-1-yl)-6-nitrophenyl)meth-
anamine (32). Yield: 89%; 1H NMR (CDCl3): d 2.38
(s, 3), 2.52–2.60 (m, 4), 3.00–3.10 (m, 4), 4.04 (s, 2),
7.30–7.40 (m, 2), 7.56 (dd, 1, J = 2.4, 7.2 Hz). MS
(ESI, positive ion) m/z 251 (M+1).
5.22. 2-(Aminomethyl)-4-(4-methylpiperazinyl)phenyla-
mine (34)
The material from the previous step was dissolved in
30 mL of acetonitrile/15 mL of H2O. Iron powder
(460 mg, 8.2 mmol) and NH4Cl (90 mg, 1.7 mmol)
were added and the solution was heated at 80 ꢁC
for 2 h. The reaction mixture was filtered while hot
and concentrated to an aqueous solution. The aque-
ous solution was extracted with EtOAc (3·) and
the combined organic layers were washed with brine,
dried over MgSO4, and concentrated in vacuo to pro-
vide 530 mg (30%) of the title compound as a light-
To a stirred solution of nitrile 33 (1.7 g, 7.86 mmol) in
dry THF (15 mL) was added a solution of 1 M BH3THF
(27.5 mL, 27.5 mmol) dropwise. After stirring for 2 h at
room temperature the mixture was allowed to cool to
0 ꢁC and quenched slowly with 10% aqueous HCl. The
resulting mixture was heated at reflux for 2 h then
cooled to room temperature. The mixture was washed
with ether and the aqueous layer was neutralized with
5 N NaOH. The aqueous solution was extracted with
CH2Cl2 (3·) and the combined organic layers were dried
over MgSO4 to provide the title compound as a light-
yellow oil (1.0 g, 58%). NMR (CDCl3): d 2.35 (s, 3),
2.55 (m, 4), 3.10 (m, 4), 3.58 (s, 2), 3.87 (s, 2), 6.70 (d,
1, J = 8.7 Hz), 6.81 (m, 3).
brown oil. 1H NMR (CDCl3):
d
1.32 (t, 3,
J = 7.1 Hz), 2.46–2.50 (m, 4), 3.53 (s, 2), 3.87–3.90
(m, 4), 4.29 (q, 2, J = 7.1 Hz), 4.63 (br s, 2), 4.86
(d, 2, J = 6.6 Hz), 6.63–6.66 (m, 2), 7.56 (br s, 1),
7.80 (d, 2, J = 6.0 Hz), 8.76 (d, 2, J = 4.7 Hz). MS
(ESI, positive ion) m/z 454 (M+1).
5.23. Representative procedure for the synthesis of compounds
21a and 21m
5.24.2. Ethyl-4-(2-amino-6-(4-methylpiperazin-1-yl)ben-
zylamino)-2-(pyridin-4-yl)thiazole-5-carboxylate
(21l).
1.33 (t, 3,
Yield: 41%; 1H NMR (CDCl3):
d
5.23.1.
Ethyl-4-{[(2-aminophenyl)methyl]amino}-2-(4-
J = 7.2 Hz), 2.39 (s, 3), 2.66 (br s, 4), 2.94–2.99 (m, 4),
4.27 (q, 2, J = 7.2 Hz), 4.36 (br s, 2), 4.88 (d, 2,
J = 6.4 Hz), 6.50 (d, 1, J = 8.0 Hz), 6.68 (d, 1,
J = 7.2 Hz), 7.07 (t, 1, J = 8.0 Hz), 7.16 (br s, 1), 7.79
(dd, 2, J = 4.8, 1.6 Hz), 8.75 (dd, 2, J = 4.8, 1.6 Hz).
MS (ESI, positive ion) m/z 453 (M+1).
pyridyl)-1,3-thiazole-5-carboxylate (21a). A mixture of
triflate 11 (2.17 g, 5.68 mmol) and 2-aminobenzylamine
(2.08 g, 17.03 mmol) in 12 mL of dioxane was heated
at reflux for 16 h. The reaction mixture was cooled to
room temperature and the resulting precipitate was col-
lected by filtration to give 1.69 g (84%) of a bright-yel-
low solid. 1H NMR (DMSO-d6):
d
1.32 (t, 3,
5.24.3. Ethyl-4-({[2-amino-4-(morpholin-4-ylmethyl)phenyl]
methyl}amino)-2-(4-pyridyl)-1,3-thiazole-5-carboxylate
(21o). Yield: 38%; 1H NMR (CDCl3): d 1.34 (t, 3,
J = 7.1 Hz), 2.46–2.51 (m, 4), 3.45 (br s, 2), 3.67–
3.72 (m, 4), 4.15 (br s, 2), 4.30 (q, 2, J = 7.1 Hz),
4.76 (d, 2, J = 6.1 Hz), 6.68–6.6.74 (m, 2), 6.95 (br s,
1), 7.14 (d, 1, J = 7.6 Hz), 7.81 (dd, 2, J = 4.5,
1.5 Hz), 8.75 (dd, 2, J = 4.6, 1.5 Hz). MS (ESI, posi-
tive ion) m/z 454 (M+1).
J = 7.1 Hz), 4.12 (d, 2, J = 6.3 Hz), 4.27 (q, 2,
J = 7.1 Hz), 4.76 (d, 2, J = 6.3 Hz), 6.68–6.77 (m, 2),
6.96 (br s, 1), 7.09–7.20 (m, 2), 7.79 (m, 2), 8.73 (m,
2). MS (ESI, positive ion) m/z 355 (M+1).
5.23.2. Ethyl-4-({[2-amino-5-(4-methylpiperazinyl)phenyl]
methyl}amino)-2-(4-pyridyl)-1,3-thiazole-5-carboxylate
(21m). Yield: 70%; 1H NMR (CDCl3): d 1.35 (t, 3,

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R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
5.25. Representative procedure for the synthesis of Ethyl-
4-(substituted-2-oxo(1,3,4-trihydroquinazolin-3-yl))-2-(4-
pyridyl)-1,3-thiazole-5-carboxylates 22a and 22l–o
was added 6 mL of 1 N NaOH. The reaction mixture
was heated at 50 ꢁC for 30 min and cooled to room
temperature. The reaction mixture was acidified to
pH 2 with 10% aqueous HCl solution and the precip-
itate was collected by filtration to give 1.02 g (99%)
of the corresponding acid as a yellow solid. 1H
5.25.1. Ethyl-4-(2-oxo(1,3,4-trihydroquinazolin-3-yl))-2-
(4-pyridyl)-1,3-thiazole-5-carboxylate (22a). To a mix-
ture of amine 21a (1.69 g, 4.76 mmol) and 1,10-carbon-
yldiimidazole (2.30 g, 14.28 mmol) in 50 mL of DMF
was added 95% NaH (361 mg, 14.28 mmol) slowly at
room temperature. After 18 h the reaction mixture was
quenched with water and the resulting precipitate was
filtered, washed with water, and dried in vacuo to give
1.12 g (61%) of the title compound as a yellow solid.
1H NMR (DMSO-d6): d 1.21 (t, 3, J = 7.1 Hz), 4.22
(q, 2, J = 7.1 Hz), 4.97 (s, 2), 6.96 (m, 2), 7.23 (m, 2),
7.96 (dd, 2, J = 4.6, 1.3 Hz), 8.79 (dd, 2, J = 4.6,
1.3 Hz), 9.93 (s, 1). MS (ESI, positive ion) m/z 381
(M+1).
NMR (DMSO-d6):
d
4.93 (s, 2), 6.90 (d, 1,
J = 8.4 Hz), 6.96 (t, 1, J = 7.5 Hz), 7.22 (t, 2,
J = 7.0 Hz), 7.96 (dd, 2, J = 4.6, 1.5 Hz), 8.77 (dd,
2, J = 4.6, 1.5 Hz), 9.83 (s, 1). MS (ESI, positive
ion) m/z 353 (M+1). The acid (89 mg, 0.25 mmol)
was dissolved in 2 mL of H2SO4 and heated at
120 ꢁC. After 4 h the reaction mixture was cooled
to 0 ꢁC and quenched with ice water. The mixture
was basified to pH 10 and the resultant precipitate
was purified by flash chromatography using 2 M
NH3 in MeOH:CH2Cl2 (1:60) as eluant to afford
34 mg (44%) of the title compound as a white solid.
1H NMR (DMSO-d6): d 5.24 (s, 2), 6.91 (d, 1,
J = 7.7 Hz), 6.98 (t, 1, J = 7.5 Hz), 7.22 (t, 1,
J = 7.5 Hz), 7.31 (d, 1, J = 7.7 Hz), 7.87 (s, 1), 7.93
(dd, 2, J = 4.6, 1.3 Hz), 8.73 (dd, 2, J = 4.6, 1.3 Hz),
9.81 (s, 1). MS (ESI, positive ion) m/z 309 (M+1).
Anal. Calcd for C16H12 N4OS: C, 62.32; H, 3.92;
N, 18.17. Found: C, 62.44; H, 4.15; N, 17.90.
5.25.2. Ethyl-4-(5-(4-methylpiperazin-1-yl)-2-oxo-1,2-
dihydroquinazolin-3(4H)-yl)-2-(pyridin-4-yl)thiazole-5-
1
carboxylate (22l). Yield: 50%; H NMR (DMSO-d6): d
1.19 (t, 3, J = 7.2 Hz), 2.19 (s, 3), 2.35–2.55 (m, 4),
2.80–2.85 (m, 4), 4.20 (q, 2, J = 7.2 Hz), 4.86 (s, 2),
6.68 (d, 1, J = 8.0 Hz), 6.76 (d, 1, J = 8.0 Hz), 7.20 (t,
1, J = 8.0 Hz), 7.97 (dd, 2, J = 4.4 1.6 Hz), 8.80 (dd, 2,
J = 4.4, 1.6 Hz), 9.94 (s, 1). MS (ESI, positive ion) m/z
479 (M+1).
5.26.2. 5-(4-Methylpiperazin-1-yl)-3-(2-(pyridin-4-yl)thia-
zol-4-yl)-3,4-dihydroquinazolin-2(1H)-one (20l). Yield:
40%; 1H NMR (DMSO-d6): d 2.30 (s, 3), 2.50–2.65
(m, 4), 2.85–2.93 (m, 4), 5.22 (s, 2), 6.66 (d, 1,
J = 7.6 Hz), 6.73 (d, 1, J = 7.6 Hz), 7.18 (t, 1,
J = 8.0 Hz), 7.86 (s, 1), 7.89 (dd, 2, J = 4.6, 1.6 Hz),
8.74 (dd, 2, J = 4.6, 1.6 Hz), 9.80 (s, 1). MS (ESI, posi-
tive ion) m/z 407 (M+1). HRMS calcd for C21H23N6OS
[M+H]+ 407.1654, found 407.1648.
5.25.3. Ethyl-4-[6-(4-methylpiperazinyl)-2-oxo(1,3,4-tri-
hydroquinazolin-3-yl)]-2-(4-pyridyl)-1,3-thiazole-5-carbox-
ylate (22m). Yield: 18%; 1H NMR (CDCl3): d 1.35 (t, 3,
J = 7.1 Hz), 2.35 (s, 3), 3.50 (m, 4), 3.72 (m, 4), 4.25 (q,
2, J = 7.1 Hz), 5.05 (s, 2), 6.71 (d, 1, J = 8.6 Hz), 6.82 (d,
1, J = 8.6 Hz), 6.87 (s, 1), 7.85 (s, 1), 8.13 (d, 2,
J = 5.3 Hz), 8.75 (d, 2, J = 5.3 Hz), 10.75 (s, 1). MS
(ESI, positive ion) m/z 479 (M+1).
5.26.3. 6-(4-Methylpiperazinyl)-3-(2-(4-pyridyl)(1,3-thia-
zol-4-yl))-1,3,4-trihydro-quinazolin-2-one (20m). Yield:
1
5.25.4. Ethyl-4-[5-(morpholin-4-ylmethyl)-2-oxo(1,3,4-tri-
hydroquinazolin-3-yl)]-2-(4-pyridyl)-1,3-thiazole-5-carbox-
ylate (22n). Yield: 59%; mp 115–117 ꢁC. 1H NMR
(CDCl3): d 1.31 (t, 3, J = 7.1 Hz), 2.38-2.41 (m, 4),
3.45 (s, 2), 3.63-3.67 (m, 4), 4.34 (q, 2, J = 7.1 Hz),
5.12 (s, 2), 6.70 (d, 1, J = 7.8 Hz), 6.94 (d, 1,
J = 7.5 Hz), 7.16 (t, 1, J = 7.8 Hz), 7.22 (s, 1), 7.84 (dd,
2, J = 4.6, 1.6 Hz), 8.79 (dd, 2, J = 4.5, 1.6 Hz). MS
(ESI, positive ion) m/z 480 (M+1).
25%; H NMR (DMSO-d6): d 2.35 (s, 3), 3.50 (m, 4),
3.72 (m, 4), 5.05 (s, 2), 6.71 (d, 1, J = 8.6 Hz), 6.82 (d,
1, J = 8.6 Hz), 6.87 (s, 1), 7.85 (s, 1), 8.13 (d, 2,
J = 5.3 Hz), 8.75 (d, 2, J = 5.3 Hz), 9.45 (s, 1). MS
(ESI, positive ion) m/z 407 (M+1). HRMS calcd for
C21H23N6OS [M+H]+ 407.1654, found 407.1657.
5.26.4. 5-(Morpholin-4-ylmethyl)-3-(2-(4-pyridyl)(1,3-
thiazol-4-yl))-1,3,4-trihydroquinazolin-2-one Hydrochlo-
ride Dihydrate (20n). The free base was dissolved in
CH2Cl2 (15 mL) and of MeOH (6 mL), and 1 N ethe-
real HCl (0.36 mL, 0.4 mmol) was added. After stir-
ring for 2 h, the reaction mixture was concentrated
in vacuo. The resulting residue was stirred in ether
and the resulting precipitate was filtered and washed
with ether to give 140 mg (48%) of an orange solid.
Mp 261–263 ꢁC. 1H NMR (CDCl3): d 3.26–3.31 (m,
4), 3.63–3.71 (m, 2), 3.84–3.88 (m, 2), 4.37 (s, 2),
5.29 (s, 2), 6.96 (d, 1, J = 7.7 Hz), 7.23 (d, 1,
J = 7.7 Hz), 7.27 (t, 1, J = 7.7 Hz), 7.85 (s, 1), 8.02
(d, 2, J = 4.5 Hz), 8.72 (d, 2, J = 4.5 Hz), 9.97 (s, 1),
10.36 (br s, 1). MS (ESI, positive ion) m/z 408
(M+1). Anal. Calcd for C21H21N5O2S1.0HCl2H2O:
C, 52.55; H, 5.46; N, 14.59. Found: C, 52.52; H
5.30; N, 14.42.
5.25.5. Ethyl-4-[7-(morpholin-4-ylmethyl)-2-oxo(1,3,4-tri-
hydroquinazolin-3-yl)]-2-(4-pyridyl)-1,3-thiazole-5-carbox-
1
ylate (22o). Yield: 74%; H NMR (CDCl3): d 1.30 (t, 3,
J = 7.1 Hz), 2.44–2.49 (m, 4), 3.46 (s, 2), 3.67-3.72 (m,
4), 4.34 (q, 2, J = 7.1 Hz), 5.00 (s, 2), 6.79 (s, 1), 6.98
(d, 1, J = 7.7 Hz), 7.03-7.09 (m, 1), 7.34 (s, 1), 7.84
(dd, 2, J = 4.5, 1.3 Hz), 8.78 (dd, 2, J = 4.5, 1.4 Hz).
MS (ESI, positive ion) m/z 480 (M+1).
5.26. Representative procedure for the synthesis of
compounds 20a and 20l–o
5.26.1. 3-(2-(Pyridin-4-yl)thiazol-4-yl)-3,4-dihydroquinaz-
olin-2(1H)-one (20a). To a solution of ester 22a (1.10 g,
2.89 mmol) in 6.0 mL of MeOH at room temperature

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6591
5.26.5. 7-(Morpholin-4-ylmethyl)-3-(2-(4-pyridyl)(1,3-
thiazol-4-yl))-1,3,4-trihydroquinazolin-2-one (20o). Yield:
10%; mp 249–250 ꢁC. H NMR (CDCl3): d 2.43–2.49
(m, 4), 3.47 (s, 2), 3.70–3.76 (m, 4), 5.33 (s, 2), 6.79 (s,
2), 7.01 (d, 1, J = 7.7 Hz), 7.21 (d, 1, J = 7.7 Hz), 7.84
(m, 3), 8.73 (dd, 2, J = 4.6, 1.5 Hz). MS (ESI, positive
ion) m/z 408 (M+1). Anal. Calcd for C21H21
N5O2S0.4H2O: C, 60.82; H, 5.30; N, 16.89. Found C,
60.81; H, 5.24; N, 16.67.
The reaction mixture was heated at reflux for 9 h and
was allowed to cool to room temperature. Purification
by flash chromatography on silica gel using hex-
anes:EtOAc (4:1) followed by CH2Cl2:MeOH (9:1) as
eluant gave 34 mg (12%) of a white solid. Mp
1
1
>267 ꢁC. H NMR (DMSO-d6): d 5.38 (s, 1), 6.94 (d,
1, J = 7.5 Hz), 7.02 (t, 1, J = 7.5 Hz), 7.23 (t, 1,
J = 7.5 Hz), 7.35 (d, 1, J = 7.5 Hz), 7.92 (d, 2,
J = 6.1 Hz), 7.96 (s, 1), 8.61 (d, 2, J = 6.1 Hz). MS
(ESI, positive ion) m/z 309 (M+1), (ESI negative ion)
307 (Mꢀ1). Anal. Calcd for C16H12 N4OS0.06 MeOH:
C, 62.16; H, 3.98; N, 18.06. Found: C, 62.21; H, 4.05;
N, 18.04. HRMS calcd for C16H13N4OS [M+H]+
309.0810, found 309.0816.
5.27. Amino{[(2-nitrophenyl)methyl]amino}methane-1-
thione (35)
To a solution of 2-nitrobenzylamine hydrochloride
(4.93 g, 26.1 mmol) and Et3N (10 mL, 71.8 mmol) in
300 mL of CHCl3 was added benzoyl isothiocyanate
(3.4 mL, 25.3 mmol) and the resulting yellow solution
was heated at 61 ꢁC. After 1.5 h the solvent was
removed in vacuo and the residue was dissolved in
70% aqueous MeOH. To the solution was added
K2CO3 (4.06 g, 29.4 mmol) and the reaction mixture
was heated at reflux for 30 min. The yellow-orange mix-
ture was cooled to room temperature and the crude
material was purified by flash chromatography on silica
gel with hexanes:EtOAc (4:1–1:3) as eluant to afford
4.05 g (73%) of the title compound as a purple solid.
1H NMR (CD3OD): d 5.03 (br s, 2), 5.89 (br s, 2),
6.98 (br s, 1), 7.42–7.57 (m, 1), 7.60–7.73 (m, 1), 7.87
(br s, 1), 8.08 (d, 1, J = 8.0 Hz). MS (ESI, positive ion)
m/z : 212 (M+1).
5.30. 3-(4-(3-Pyridyl)-1,3-thiazol-2-yl)-1,3,4-trihydroqui-
nazolin-2-one (38b)
To a heated (45 ꢁC) slurry of thiourea 35 (1.03 g,
4.87 mmol) in 50 mL of 50% aqueous MeOH was
added 3-(bromoacetyl)pyridine hydrobromide (1.37 g,
4.87 mmol). After 2 h the mixture was allowed to cool
to room temperature and the solvent was removed in
vacuo to give 36 b as a yellow solid. 1H NMR
(DMSO-d6): d 1.72 (s, 6), 3.83 (s, 4), 6.69 (br s, 1),
7.25 (t, 1, J = 3.9 Hz), 7.69 (br s, 1), 7.75 (br s, 1),
8.30 (s, 1), 11.34 (s, 1). MS (ESI, positive ion) m/z
313 (M+1).
A mixture of crude 36b, iron dust (1.39 g, 24.9 mmol),
and NH4Cl (198 mg, 3.7 mmol) in 50 mL of 50% EtOH
was heated at reflux. After 1 h the reaction mixture was
cooled to room temperature and the solvent was re-
moved in vacuo to give compound 37b. MS (ESI, posi-
tive ion) m/z 283 (M+1).
5.28. [(2-Nitrophenyl)methyl](4-(4-pyridyl)(1,3-thiazol-2-
yl))amine (36a)
To a heated (45 ꢁC) slurry of thiourea 35 (841 mg,
4.0 mmol) in 50 mL of 50% aqueous MeOH was added
4-(bromoacetyl)pyridine
hydrobromide
(1.16 g,
The crude 37b was dissolved in 20 mL of THF and to this
solution were added p-nitrophenyl chloroformate
(860 mg, 4.2 mmol) and Et3N (0.85 mL, 6.1 mmol). The
reaction mixture was heated at reflux for 1 h and cooled
to room temperature overnight. The solvent was removed
in vacuo and the residue was purified by flash chromatog-
raphy on silica gel with hexanes:EtOAc (1:1) followed by
CHCl3:MeOH (19:1) as eluant to give 84 mg (6%, three
steps) of the title compound as an off-white solid. Mp
269–272 ꢁC. 1H NMR (DMSO-d6): d 5.39 (s, 2), 6.94 (d,
1, J = 7.9 Hz), 7.03 (t, 1, J = 7.6 Hz), 7.24 (t, 1,
J = 7.6 Hz), 7.39 (d, 1, J = 7.6 Hz), 7.48 (dd, 1, J = 7.9,
4.7 Hz), 7.86 (s, 1), 8.33 (d, 2, J = 9.0 Hz), 8.53 (d, 1,
J = 4.7 Hz) 9.22 (s, 1), 10.26 (s, 1). MS (ESI, positive
ion) m/z 309 (M+1). HRMS calcd for C16H13N4OS
[M+H]+ 309.0810, found 309.0817.
4.1 mmol) and the reaction mixture was stirred at
45 ꢁC for 1.5 h. The reaction mixture was cooled to
room temperature and the solids were filtered and
washed with water. Drying in vacuo over P2O5 over-
1
night gave 1.08 g (86%) of a pale yellow powder. H
NMR (DMSO-d6): d 4.84 (d, 2, J = 5.7 Hz), 7.47 (s,
1), 7.50–7.58 (m, 1), 7.65–7.77 (m, 2), 7.69 (d, 2,
J = 5.6 Hz), 8.04 (d, 1, J = 8.1 Hz), 8.41 (t, 1,
J = 5.7 Hz), 8.53 (d, 1, J = 5.6 Hz). MS (ESI, positive
ion) m/z 313 (M+1), (ESI, negative ion) 311 (Mꢀ1).
5.29. 3-(4-(4-Pyridyl)-1,3-thiazol-2-yl)-1,3,4-trihydroqui-
nazolin-2-one (38a)
A slurry of compound 36a (924 mg, 3.0 mmol), iron
dust (872 mg, 15.6 mmol), and NH4Cl (119 mg,
2.2 mmol) in 30 mL of 50% aqueous EtOH was heated
at 75 ꢁC. After 1.5 h the reaction mixture was cooled to
room temperature and the EtOH removed in vacuo.
The aqueous solution was extracted sequentially with
EtOAc and CH2Cl2, and the combined organics were
washed with brine and dried over Na2SO4. Concentra-
tion in vacuo gave 264 mg (32%) of aniline 37a as a so-
lid. Crude 37a was dissolved in 10 mL of THF and to
this solution were added p-nitrophenyl chloroformate
(398 mg, 2.0 mmol) and Et3N (0.4 mL, 2.9 mmol).
5.31. 3-(4-(2-Pyridyl)-1,3-thiazol-2-yl)-1,3,4-trihydroqui-
nazolin-2-one (38c)
To a heated (45 ꢁC) slurry of thiourea 35 (1.04 g,
4.9 mmol) in 10 mL of 50% aqueous MeOH was added
an aqueous solution of 2-(bromoacetyl)pyridine hyd-
robromide (1.34 g, 4.9 mmol). After 2 h the reaction
mixture was allowed to cool to room temperature and
the solvent was removed in vacuo to give compound
36 c. MS (ESI, positive ion) m/z 313 (M+1).

6592
R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
A mixture of crude 36c, iron dust (1.41 g, 25.2 mmol),
and NH4Cl (190 mg, 3.5 mmol) in 50 mL of 50% EtOH
was heated at reflux. After 1 h the reaction mixture was
cooled to room temperature and the solvent was re-
moved in vacuo to give compound 37 c. MS (ESI, posi-
tive ion) m/z 283 (M+1).
5.34. 5-Chloro-3-(4-pyridyl)-1,2,4-thiadiazole (43)
To a cooled (<15 ꢁC) suspension of thiadiazole 42
(765 mg, 4.3 mmol) in 13 mL of glacial acetic acid
and 3 mL of concentrated HCl were added copper
turnings (81 mg, 1.3 mmol). To this suspension was
added a solution of NaNO2 (312 mg, 4.5 mmol) in
1 mL of H2O dropwise over a period of 30 min. After
4 h, a second portion of NaNO2 (312 mg, 4.5 mmol)
in 1 mL of H2O was added while maintaining an
internal temperature at <15 ꢁC. After 1 h, the reaction
mixture was poured into 40 mL of H2O and extracted
with CHCl3. The combined organic layers were
washed with saturated NaHCO3, dried over Na2SO4,
and concentrated in vacuo to give 477 mg (56%) of
a white powder. 1H NMR (CDCl3): d 8.79 (d, 2,
J = 6.0 Hz), 8.11 (d, 2, J = 6.0 Hz). MS (ESI, positive
ion) m/z 198 (M+1).
The residue from the previous step was dissolved in
20 mL of THF and to this solution were added p-nitro-
phenyl chloroformate (1.17 g, 5.8 mmol) and Et3N
(1 mL, 7.2 mmol). The reaction mixture was heated at
reflux for 3 h and was allowed to cool to room temper-
ature. The solvent was removed in vacuo and the crude
material was purified by flash chromatography on silica
gel with hexanes:EtOAc (4:1–0:1) as eluant to give
13 mg (1%, three steps) of a tan solid. Mp >275 ꢁC.
1H NMR (DMSO-d6): d 5.39 (s, 2), 6.94 (d, 1,
J = 7.9 Hz), 7.03 (t, 1, J = 7.6 Hz), 7.24 (t, 1,
J = 7.6 Hz), 7.31–7.36 (m, 1), 7.38 (d, 1, J = 7.6 Hz),
7.86 (s, 1), 7.92 (t, 1, J = 7.6 Hz), 8.13 (d, 1,
J = 7.9 Hz), 8.61 (d, 1, J = 4.3 Hz), 10.25 (s, 1). MS
(ESI, positive ion) m/z 309 (M+1); (ESI negative ion)
m/z 307 (Mꢀ1). Anal. Calcd for C16H12 N4OS0.5H2O:
C, 60.55; H, 4.13; N, 17.65. Found: C, 60.20; H, 4.17;
N, 16.92.
5.35. 3-(3-(4-Pyridyl)-1,2,4-thiadiazol-5-yl)-1,3,4-trihy-
droquinazolin-2-one (45)
To a solution of thiadiazole 43 (202 mg, 1.0 mmol) in
10 mL of THF was added 2-aminobenzylamine
(122 mg, 1.0 mmol) at room temperature. After 2 h,
the reaction mixture was heated at 60 ꢁC. After 15 h,
the reaction mixture was allowed to cool to room tem-
perature and the solvent was removed in vacuo to give
aniline 44.
5.32. [(2-Aminophenyl)methyl](3-(4-pyridyl)(1,2,4-oxa-
diazol-5-yl))amine (40)
A flask charged with oxadiazole 39 (528 mg, 2.0 mmol)
and 2-aminobenzylamine (224 mg, 1.8 mmol) was
heated at 60 ꢁC. After 9 h the reaction mixture was al-
lowed to cool to room temperature and the solids
were washed with MeOH, filtered, and dried in vacuo
to give 51 mg (11%) of a beige powder. 1H NMR
(DMSO-d6): d 4.37 (d, 2, J = 5.6 Hz), 5.08 (s, 2),
6.54 (t, 1, J = 7.5 Hz), 6.66 (d, 1, J = 7.5 Hz), 6.99 (t,
1, J = 7.5 Hz), 7.07 (d, 1, J = 7.5 Hz), 7.81 (d, 2,
J = 5.3 Hz), 8.74 (d, 2, J = 5.3 Hz), 8.97 (br t, 1,
J = 5.6 Hz). MS (ESI, positive ion) m/z 268 (M+1),
(ESI, negative ion) m/z 266 (Mꢀ1).
The crude residue from the previous step was dissolved
in 10 mL of DMF and 1,10-carbonyldiimidazole
(352 mg, 2.2 mmol) was added followed by 95% NaH
(58 mg, 2.4 mmol) at room temperature. After 18 h,
20 mL of H2O was added and the white precipitate
was washed sequentially with H2O, MeOH, and
CH2Cl2. The crude material was purified by flash chro-
matography with CH2Cl2:MeOH (39:1–19:1) as eluant
to give 18 mg (5%) as a white amorphous solid. Mp
1
>290. H NMR (DMSO-d6): d 5.43 (s, 2) 6.97 (d, 1,
J = 7.8 Hz), 7.07 (t, 1, J = 7.4 Hz), 7.27 (t, 1,
J = 7.4 Hz), 7.39 (d, 1, J = 7.2 Hz), 8.12 (d, 2,
J = 6.0 Hz), 8.77 (d, 2, J = 6.0 Hz), 10.75 (br s, 1,). MS
(ESI, positive ion) m/z 310 (M+1), (ESI negative ion)
308 (Mꢀ1). HRMS calcd for C15H11N5OS [M+H]+
310.0763. Found: 310.0764.
5.33. 3-(3-(4-Pyridyl)-1,2,4-oxadiazol-5-yl)-1,3,4-trihy-
droquinazolin-2-one (41)
To a solution of aniline 40 (51 mg, 0.2 mmol) in 2 mL of
THF were added p-nitrophenyl chloroformate (82 mg,
0.4 mmol) and Et3N (0.050 mL, 0.4 mmol) at room tem-
perature. After 3 h the solvent was removed in vacuo
and the residue was partitioned between H2O/CH2Cl2.
The aqueous layer was extracted consecutively with
CHCl3 and EtOAc, and the combined organic layers
were dried over Na2SO4. The solvent was removed in va-
cuo and the residue was washed with EtOAc, filtered,
and dried in vacuo to give 25 mg (42%) of an off-white
5.36. Methyl-5-(4-pyridyl)thiophene-2-carboxylate (46)
Toasolutionof5-bromothiophene-2-carboxylate(4.02 g,
18 mmol) and 4-pyridine boronic acid (2.0 g, 16 mmol) in
150 mL of DME was added PdCl2dppfCH2Cl2 (1.27 g,
1.7 mmol) followed by 12 mL of 2 M Na2CO3 solution.
The reaction mixture was heated to reflux for 16 h and
cooled to room temperature. The solvent was removed
in vacuo, partitioned between EtOAc/H2O, and filtered.
The organic layer was extracted with 1 N HCl (3·
50 mL) and the combined acidic layers were neutralized
with 1 N NaOH. The resulting precipitate was extracted
with EtOAc (3· 50 mL) and the combined organic ex-
tracts were concentrated in vacuo to give 1.18 g (33%) of
1
powder. Mp 264–267 ꢁC. H NMR (DMSO-d6): d 5.23
(s, 2), 6.95 (d, 1, J = 7.8 Hz), 7.04 (t, 1, J = 7.5 Hz),
7.27 (t, 1, J = 7.8 Hz), 7.35 (d, 1, J = 7.5 Hz), 7.93 (d,
1, J = 6.1 Hz), 8.82 (d, 1, J = 6.1 Hz), 10.47 (s, 1). MS
(ESI, positive ion) m/z 294 (M+1); (ESI negative ion)
292 (Mꢀ1). Anal. Calcd for C15H11 N5O2: C,
61.43; H, 3.78; N, 23.88. Found: C, 61.20; H, 3.77; N,
23.75.
1
a pale-green powder. H NMR (CDCl3): d 3.93 (s, 3),
7.47 (d, 1, J = 3.9 Hz), 7.51 (d, 2, J = 6.1 Hz), 7.80 (d, 1,

R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
6593
J = 3.9 Hz), 8.66 (d, 2, J = 6.1 Hz). MS (ESI, positive ion)
m/z 220 (M+1).
was added tetrakis(triphenylphosphine)palladium (0)
(128 mg, 0.1 mmol) at room temperature. After 16.5 h
the reaction mixture was concentrated in vacuo and
purified by flash chromatography with hexanes:EtOAc
(3:1–1:4) as eluant to give 535 mg (88%) as a red foam.
1H NMR (CDCl3): d 8.45 (d, 2, J = 6.1 Hz), 8.10 (d, 1,
J = 8.1 Hz), 7.68 (d, 1, J = 7.8 Hz), 7.63 (t, 1,
J = 7.4 Hz), 7.48 (t, 1, J = 7.7 Hz), 7.25 (d, 2,
J = 6.1 Hz), 7.17 (d, 1, J = 4.0 Hz), 6.00 (d, 1,
J = 4.0 Hz), 4.95 (br t, 1, J = 6.0 Hz), 4.73 (d, 2,
J = 6.0 Hz). MS (ESI, positive ion) m/z 312 (M+1);
(ESI, negative ion) m/z 310 (Mꢀ1).
5.37. 5-(4-Pyridyl)thiophene-2-carboxylic acid (47)
To a solution of ester 46 (2.44 g, 11.1 mmol) in 130 mL
EtOH was added 30 mL of 1 N NaOH at room temper-
ature. After 2 h the solvent was removed in vacuo.
The residue was dissolved in 100 mL of H2O, and acid-
ified with 1 N HCl to pH 5. The resulting white precip-
itate was filtered, washed with H2O and dried in vacuo
1
to give 2.06 g (90%) of an off-white powder. H NMR
(DMSO-d6/CF3CO2D): d 8.94 (d, 2, J = 6.4 Hz), 8.40
(d, 2, J = 6.4 Hz), 8.22 (d, 1, J = 3.6 Hz), 7.88 (d, 1,
J = 3.6 Hz). MS (ESI, positive ion) m/z 206 (M+1);
(ESI negative ion) 204 (Mꢀ1).
5.41. 3-(5-(4-Pyridyl)-2-thienyl)-1,3,4-trihydroquinazolin-
2-one (52)
To a solution of amine 50 (535 mg, 1.7 mmol) and
NH4Cl (95 mg, 1.8 mmol) in 20 mL of 70% aqueous
EtOH was added iron dust (482 mg, 8.6 mmol) and
the reaction mixture was heated at 78 ꢁC. After 1 h the
reaction mixture was filtered through a pad of Celiteꢂ
and the pad was washed with hot EtOH. The filtrate
was concentrated in vacuo and the residue was azeotr-
oped twice with benzene. The crude 51 was dissolved
in 20 mL of DMF and to this solution were added
1,10-carbonyldiimidazole (754 mg, 4.6 mmol) and 95%
NaH (132 mg, 5.5 mmol) at room temperature, resulting
in gas evolution. After 16 h, 40 mL of H2O was carefully
added and the precipitate was filtered, washed sequen-
tially with H2O and MeOH, and dried in vacuo to give
400 mg (76%) of an off-white amorphous solid. Mp 301–
5.38. Prop-2-enyloxy-N-(5-(4-pyridyl)(2-thienyl))carbox-
amide (48)
To a suspension of acid 47 (1.21 g, 6.0 mmol) in 50 mL
of toluene was added Et3N (1.0 mL, 7.2 mmol) at
room temperature. After 1 h diphenylphosphoryl azide
(2.1 mL, 9.7 mmol) was added and after an additional
hour the reaction mixture was heated to 80 ꢁC. After
1 h, allyl alcohol (4.0 mL, 62 mmol) was added and
the reaction mixture was allowed to cool to 70 ꢁC. After
15 h, the reaction mixture was cooled to room tempera-
ture, concentrated in vacuo and purified by flash chro-
matography with hexanes:EtOAc: CH2Cl2:MeOH
(3:1:0:0–0:0:99:1) as eluant to give 860 mg (55%) as a
pale-yellow amorphous solid. 1H NMR (CDCl3): d
8.54 (d, 2, J = 6.2 Hz), 7.41 (d, 2, J = 6.2 Hz), 6.59 (d,
1, J = 4.0 Hz), 5.90–6.01 (m, 1), 5.39 (d, 1, J =
17.2 Hz), 5.30 (d, 1, J = 10.5 Hz), 4.73 (d, 2, J =
5.8 Hz), 3.50 (d, 1, J = 4.0 Hz). MS (ESI, positive ion)
m/z 261 (M+1); (ESI, negative ion) m/z 259 (Mꢀ1).
1
305 ꢁC. H NMR (DMSO-d6): d 5.07 (s, 2), 6.83 (d, 1,
J = 4.1 Hz), 6.90 (d, 1, J = 7.5 Hz), 7.00 (t, 1,
J = 7.5 Hz), 7.22 (t, 1, J = 7.5 Hz), 7.26 (d, 1,
J = 7.5 Hz), 7.57 (d, 2, J = 5.5 Hz), 7.66 (d, 1,
J = 4.1 Hz), 8.49 (d, 2, J = 5.5 Hz), 10.06 (s, 1). MS
(ESI, positive ion) m/z 308 (M+1); (ESI, negative ion)
m/z 306 (Mꢀ1). Anal. Calcd for C17H13N3OSÆ0.1H2O:
C, 66.04; H, 4.30; N, 13.59. Found: C, 66.21; H, 4.50;
N, 13.55.
5.39. N-[(2-Nitrophenyl)methyl]prop-2-enyloxy-N-(5-(4-
pyridyl)(2-thienyl))carboxamide (49)
To a room temperature slurry of 95% NaH (101 mg,
4.2 mmol) in 20 mL of DMF was added a solution
of carboxamide 48 (882 mg, 3.4 mmol) in 15 mL of
DMF. After 1 h a solution of 2-nitrobenzyl bromide
(814 mg, 3.8 mmol) in 10 mL of DMF was added.
After 17 h the reaction mixture was concentrated in
vacuo and purified by flash chromatography with hex-
anes:EtOAc (3:1) followed by CH2Cl2:MeOH (19:1) as
eluant to give 1.01 g (76%) as a pale-yellow amor-
5.42. 3-(Pyridin-4-yl)benzenamine (54)
To
a mixture of 4-bromopyridine hydrochloride
(4.50 g, 23.2 mmol) and 3-aminobenzene boronic acid
monohydrate (4.00 g, 25.9 mmol) in 55 mL of 8:3 tol-
uene/EtOH were added 2 M Na2CO3 (50 mL,
100 mmol) and tetrakis(triphenylphosphine)palladium
(0) (1.017 g, 0.88 mmol) and the mixture was heated
at 80 ꢁC overnight. The reaction mixture was allowed
to cool to room temperature and partitioned between
EtOAc/H2O. The aqueous layer was extracted with
EtOAc (2·) and the combined organic layers were
washed with 2% aqueous HCl (2· 25 mL). The acidic
aqueous layers were combined, neutralized with 1 N
NaOH, and extracted with EtOAc (3 · 50 mL). The
combined organic layers were washed with brine, dried
over MgSO4, and concentrated in vacuo to afford
2.52 g (64%) of an orange solid. 1H NMR (CDCl3):
d 3.81 (br s, 2), 6.77 (d, 1, J = 7.9 Hz), 6.94 (br s,
1), 7.04 (d, 1, J = 7.6 Hz), 7.27 (t, 1, J = 7.8 Hz),
7.48 (d, 2, J = 4.6 Hz), 8.64 (d, 2, J = 4.6 Hz). MS
(ESI, positive ion) m/z 171 (M+1).
phous solid. 1H NMR (CDCl3):
d 8.54 (d, 2,
J = 6.0 Hz), 8.19 (m, 1), 7.62 (t, 1, J = 7.6 Hz), 7.49
(t, 1, J = 7.6 Hz), 7.30–7.43 (m, 3), 7.19 (d, 1,
J = 4.0 Hz), 6.38 (br s, 1), 5.87 (br s, 1), 5.50 (br s,
2), 5.24 (d, 2, J = 10.4 Hz), 4.75 (d, 2, J = 5.6 Hz).
MS (ESI, positive ion) m/z 396 (M+1); (ESI, negative
ion) m/z 394 (Mꢀ1).
5.40. [(2-Nitrophenyl)methyl](5-(4-pyridyl)(2-thienyl))-
amine (50)
To a solution of carboxamide 49 (776 mg, 2.0 mmol)
and morpholine (1.8 mL, 21 mmol) in 20 mL of THF

6594
R. M. Rzasa et al. / Bioorg. Med. Chem. 15 (2007) 6574–6595
5.43. N-(2-Nitrobenzyl)-3-(pyridin-4-yl)benzenamine (55)
as the starting point. Ab initio (Gaussian 98) calcula-
tions (energy minimizations) using Density Functional
Theory as implemented in Gaussian 9856 software, uti-
lizing the B3LYP hybrid density functional and the
6-31G* basis set at B3LYP/6-31G* level were carried
out on these molecules. These were aligned using In-
sight II, Transform/Superimpose options. Solvation
free energies were calculated57 using the Polarizable
Continuum Model (PCM) implemented in Gaussian
98 software.
A mixture of compound 54 (1.02 g, 6.00 mmol), 2-
nitrobenzyl bromide (1.32 g, 6.09 mmol), and K2CO3
(1.04 g, 7.51 mmol) in 20 mL of CH3CN was heated at
55 ꢁC. After 4 days the reaction mixture was cooled to
25 ꢁC and partitioned between EtOAc/H2O. The aque-
ous layer was extracted with EtOAc (2·) and the com-
bined organics were washed with brine and dried over
MgSO4. The crude residue was purified by flash chroma-
tography on silica gel using CH2Cl2:EtOAc (8:2) as the
eluant to afford 280 mg (15%) of a light-orange solid.
1H NMR (DMSO-d6): d 4.65 (d, 2, J = 6.1 Hz), 6.53
(t, 1, J = 3.9 Hz), 6.66 (d, 1, J = 5.9 Hz), 6.96 (m, 2),
7.20 (t, 1, J = 7.8 Hz), 7.56 (d, 2, J = 4.5 Hz), 7.65–
7.72 (m, 2), 8.08 (d, 1, J = 8.2 Hz), 8.59 (d, 2,
J = 4.5 Hz). MS (ESI, positive ion) m/z 306 (M+1).
Acknowledgment
The authors thank members of the Small Molecule Ana-
lytical group at Amgen, particularly Yining Zhao and
Jen Wilson, for compound analysis.
5.44. N-(2-Aminobenzyl)-3-(pyridin-4-yl)benzenamine
(56)
References and notes
A mixture of compound 55 (280 mg, 0.92 mmol) and 10%
palladium on carbon (84 mg) in 20 mL of EtOH was stir-
red under 1 atm of H2 at room temperature overnight.
The reaction mixture was filtered through a pad of Celiteꢂ
and the filtrate was concentrated to dryness to provide
182 mg (72%) of a light-brown solid. 1H NMR (DMSO-
d6): d 4.22 (d, 2, J = 4.8 Hz), 5.04 (br s, 2), 6.24 (br s, 1),
6.59 (t, 1, J = 7.4 Hz), 6.71–6.77 (m, 2), 6.97–7.03 (m, 3),
7.19 (d, 1, J = 7.4 Hz), 7.25 (t, 1, J = 7.8 Hz), 7.63 (d, 2,
J = 4.5 Hz), 8.65 (d, 2, J = 4.5 Hz).
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1
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