Synthesis and in vitro evaluation of 2-aminoquinazolin-4(3H)-one-based inhibitors for tRNA-guanine transglycosylase (TGT)

Article abstract of DOI:10.1002/hlca.200490122

tRNA-Guanine transglycosylase (TGT) plays a key role in the post-transcriptional modification of tRNA. It has been linked with the pathogenicity of shigellae, the causative agents of bacillary dysentery (shigellosis). Here, we report structure-activity re

Full text of DOI:10.1002/hlca.200490122

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Synthesis and In Vitro Evaluation of 2-Aminoquinazolin-4(3H)-one-Based
Inhibitors for tRNA-Guanine Transglycosylase (TGT)
by Emmanuel A. Meyer, Maya Furler, and FranÁois Diederich*
Laboratorium f¸r Organische Chemie der Eidgenˆssischen Technischen Hochschule, ETH-Hˆnggerberg, HCI,
CH-8093 Z¸rich (e-mail: diederich@org.chem.ethz.ch)
and Ruth Brenk and Gerhard Klebe*
Institut f¸r Pharmazeutische Chemie der Philipps-Universit‰t Marburg, Marbacher Weg 6, D-35032 Marburg
tRNA-Guanine transglycosylase (TGT) plays a key role in the post-transcriptional modification of tRNA.
It has been linked with the pathogenicity of shigellae, the causative agents of bacillary dysentery (shigellosis).
Here, we report structureÀactivity relationships (SARs) for a new series of 2-aminoquinazolin-4(3H)-one-
based inhibitors of TGT, resulting from structure-based design (Fig. 2). Versatile synthetic protocols allow
selective functionalization of the 2-aminoquinazolin-4(3H)-one core (Schemes 1 6) with H-bond-donor groups
in position 6 (for H-bonding to the C ˆ O group of Leu231) and lipophilic residues in position 8 for reaching into
a shallow, newly discovered lipophilic pocket lined by Val282, Val45, and Leu68. The binding mode of several of
these ligands in the active site of TGTwas established by crystal structure analyses (Figs. 4 and 6). A dramatic S
effect was observed, with the replacement of the S-atom in the (phenylsulfanyl)methyl residue in position 8 of
inhibitor 1c (Ki ˆ 100 nm) by the O-atom (in 1h, Ki ˆ 5.6 mm) or CH2 (in 1i, Ki ˆ 3.6 mm), resulting in a massive
loss of activity (Fig. 3). Crystal structure analysis showed that the lipophilic Me group points into a highly
polar region of the active site encompassed by the side chains of Asp280 and Asp102 and collides directly
(d(C ¥¥¥ O) ˆ 3.1 ä) with one of the O-atoms of the carboxylate of Asp102. Similarly, lipophilic linkers departing
from position 8 and orienting residues in the shallow hydrophobic pocket presumably encounter analogous
unfavorable contacts, accounting for the modest contribution to the binding free enthalpy upon introduction of
these residues. These findings provide a valuable starting point for future structure-based lead optimization
cycles leading to TGT inhibitors with increased in vitro potency.
1. Introduction. The bacterial infection shigellosis (bacillary dysentery) kills 1.1
million people and affects more than 150 millions each year [1]. Increased bacterial
resistance toward a panel of antimicrobial drugs has become a main threat in
healthcare, and this phenomenon is observed with the Shigella organisms as well [2];
moreover, the longstanding non-availability of vaccines demands the development of
novel therapeutic treatment [3].
tRNA-Guanine transglycosylase (TGT, EC 2.4.2.29) has been recognized as one of
the key enzymes in the regulation of bacterial virulence in S. flexneri [4]. In eukaryotes
and prokaryotes, TGT is involved in the biosynthesis of the highly modified nucleobase
queuine (Q) found in the anticodon loop of specific tRNAs (Fig. 1) [5][6]. Bacterial
TGT catalyzes the exchange of guanine by the modified nucleobase preQ1, whereas
eukaryotes use queuine as substrate. In archaebacteriae, the related preQ0 serves as
modified nucleobase, which is transformed in additional biosynthetic steps to
archeosine G* in tRNA [7][8].

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Fig. 1. Top: Modified nucleobases entered into the anticodon loop of tRNAs with the assistance of TGT. Bottom:
Synthetic inhibitors of TGT.
Recently, Xie et al. clarified the catalytic mechanism of TGT-mediated trans-
glycosylation by trapping the covalent intermediate formed by displacement of guanine
from bound tRNA [9]. Crystal-structure analysis of the covalent TGTÀtRNA adduct
surprisingly revealed that Asp2801) is the catalytically active nucleophile displacing
guanine, whereas Asp102, previously thought to be the active nucleophile [10], serves
as general acid/base.
The first crystal structure of TGT (originating from the prokaryotic organism
Zymomonas mobilis) was reported in 1996 by Romier et al., together with the structure
of the complex with its natural substrate preQ1 [11]. In addition, initial crystallographic
studies of TGT complexed with pyridazinediones (1,2,3,4-tetrahydrophthalazine-1,4-
dione derivatives) established TGT as a suitable target for the de novo design of drugs
against shigellosis [12]. Here, we describe the synthesis and in vitro evaluation of a new
series of TGT inhibitors with a 2-aminoquinazolin-4(3H)-one scaffold, resulting from
structure-based design, a strategy pursued in our laboratory in a variety of other
medicinal-chemistry projects [13 15] (for a preliminary communication of parts of this
work, see [16]; for a detailed crystallographic analysis of the complexes of 2-
aminoquinazolin-4(3H)-one-based inhibitors bound to TGT, see [17]).
2. Results and Discussion. 2.1. Design of the Lead Structure. Chemical-structure
intuition and careful analysis of the enzyme active site with the molecular-modeling
program MOLOC [18] led to the proposal of 2,6-diaminoquinazolin-4(3H)-one as a
promising lead structure for TGT inhibition. For the modeling, the crystal structure of
TGT from prokaryotic Z. mobilis was used; all the targeted amino acid residues located
in the binding pocket are highly conserved in TGT from Z. mobilis and S. flexneri, the
1
)
For clarity, Z. mobilis numbering will be used throughout this paper.

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only difference being the replacement of Tyr106 with Phe [19]. However, this change
does not alter the kinetic parameter of TGT [20]. The designed inhibitors, similar to the
natural substrates, feature the characteristic guanine-like H-bonding edge and should
specifically bind through several H-bonds to Gly230, Gln203, and Asp156 (Fig. 2). The
NH2 group at C(6) was introduced to specifically interact with the CˆO group of
Leu231, thereby mimicking the NH2CH2 group in preQ1. Furthermore, the aromatic
heterocycle is intercalated between the flexible phenolic side chain of Tyr106 and the
side chain of Met260 (for a review on sulfurÀaromatic interactions, see [21]). During
our analysis of the active-site environment, we discovered a shallow lipophilic pocket
defined by Val45, Leu68, and Val282 at the bottom of the site, quite remote from the
nucleobase binding pocket. Modeling suggested that apolar substituents could be
conveniently directed into this lipophilic site if attached by a linker to C(8) of the
quinazolinone scaffold.
Fig. 2. A quinazolinone-based inhibitor modeled into the active site of TGT at the design stage. The H-bonds are
represented as dotted lines.
2.2. Targeting the Remote Lipophilic Pocket. A small set of quinazolinone inhibitors
(1a 1i and control compound 2) were selected, bearing apolar substituents at C(8)
(aliphatic, alicyclic, aromatic, heterocyclic) for binding within the small lipophilic
pocket defined by Leu68, Val45, and Val282. In addition, a tertiary amine substituent
was also chosen in view of potentially favorable ion-pairing (in the protonated form)
with the (presumably) deprotonated carboxylate side chain of Asp280.
First-generation inhibitors were synthesized starting from commercially available 3-
methyl-2-nitrobenzoic acid that was esterified (HCl, MeOH) and subsequently

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hydrogenated (H2, Pd/C, MeOH) to give amino ester 3 (76%). Quinazolinone 4 was
formed by treatment of 3 with chloroformamidinium chloride (88%; Scheme 1) [22],
and the following nitration provided exclusively the desired C(6)-NO2 isomer 5 in good
yield (72%). The solubility of 5 in common organic solvents was dramatically increased
by introduction of the pivaloyl group at C(2)-NH2, which allowed the subsequent
benzylic bromination of 6 in CCl4. The BrCH2 derivative 7 was subjected to
substitution with various commercially available thiols affording 8a 8f (for R' in
Scheme 1, see Fig. 3) [23], while reaction with PhOH resulted in aryl ether 8h. [1,1'-
Biphenyl]-3-thiol for the synthesis of 8g was prepared from 3-bromo-1,1'-biphenyl and
sodium ethanethiolate [24]. In the substitution with 2-sulfanyl-1H-imidazole to give 8e,
N-alkylation of the 1H-imidazole moiety was prevented by using Cs2CO3 in THF.
Reduction of the NO2 group in 8a 8h to give amines 9a 9h was carried out with SnCl2
or Zn in AcOH/H2O, the latter condition being far more convenient for the isolation of
the product. Finally, removal of the pivaloyl group provided inhibitors 1a 1h (see
Fig. 3). Due to the increased H2O solubility of inhibitor 1d, its purification was carried
out by ion-exchange chromatography.
Scheme 1. Synthesis of Inhibitors 1a 1h
a) Chloroformamidinium chloride, dimethyl sulfone, 1508, 2 h; 88%. b) HNO3, H2SO4, r.t., 12 h; 72%. c) PivCl,
Py, DMA, 1108, 12 h; 82%. d) NBS, Bz2O2, CCl4, D, 12 h; 59 %.e) R'SH, BuLi, or Cs2CO3, THF, r.t., 3 4 h;
58 79%. f) PhOH, NaH, THF, 0 ! r.t., 4 h; 52%. g) SnCl2, EtOH, 708, 6 h; 25 51% (X ˆ S). h) Zn, AcOH,
H2O, r.t., 3 h; 50 74% (X ˆ S, O). i) HCl, EtOH, 708, 3 h; 40 94%. Bz ˆ benzoyl; DMA ˆ N,N-dimeth-
ylacetamide; NBS ˆ N-bromosuccinimide; Piv ˆ pivaloyl; Py ˆ pyridine. See Fig. 3 for R' in R'SH, 8a 8h,
9a 9h, and 1a 1h.
The 2-phenylethyl derivative 1i was prepared starting from 2-amino-5-nitrobenzoic
acid that was esterified (SOCl2, MeOH; 77%) and brominated (Br2, AcOH; 92%) to
give methyl 2-amino-3-bromo-5-nitrobenzoate 10 (Scheme 2). Ring closure with
guanidinium chloride provided 11 and N-protection gave 12. Sonogashira cross-
coupling [25] with phenylacetylene led to 13 that was transformed by hydrogenation
( ! 14) and deprotection into the desired ligand 1i.

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Scheme 2. Synthesis of Inhibitor 1i
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a) Br2, AcOH, r.t., 4 h; 92%. b) Guanidinium chloride, EtONa, EtOH, D, 60 h; 63%. c) PivCl, Py, DMA, 1108,
8 h; 71%. d) PhCꢀCH, [Pd(OAc)2], P(o-tol)3, CuI, Et3N, D, 15 h; 23%. e) H2, Pd/C (10%), EtOH, 708, 4 h;
46%. f) HCl, EtOH, 708, 4 h; 93%. tol ˆ toluyl.
2.3. Biological Activity and Crystallographic Studies. The in vitro activity of
compounds 1a 1i and 2 toward TGT (Z. mobilis) was determined in an assay based on
radiolabeled substrates (Fig. 3; for a description of the assay, see [12]). The high
activity of the most potent inhibitor, phenyl thioether 1c (Ki ˆ 100 nm), validated our
strategy to occupy the apolar binding pocket defined by Val45, Leu68, and Val282, with
lipophilic residues. However, the other inhibitors showed decreased activity (0.6
7.7 mm) with respect to the parent heterocyclic scaffold 2 (Ki ˆ 350 nm). The modest
binding affinity of 1d (3.5 mm) and 1e (1.4 mm) indicated that no significant H-bonding
interaction to Asp280 was achieved.
Unexpectedly at first, the replacement of the S-atom in the thioether inhibitor 1c
(Ki ˆ 100 nm) by the O-atom (in 1h; Ki ˆ 5.6 mm) or by a CH2 group (in 1i; Ki ˆ 3.6 mm)
Fig. 3. Biological activity (Ki values) of the first series of TGT inhibitors

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resulted in a substantial loss of activity. This observation can be rationalized by a
combination of hydrophobicity, conformational, and stereoelectronic effects, as
discussed in detail in [16]. The phenyl thioether residue is quite hydrophobic and
can reach deeper into the hydrophobic pocket, while maintaining an energetically
favorable conformation. Also noticeable is the large difference in binding affinity
between cyclohexyl (1b; Ki ˆ 5.4 mm) and phenyl (1c; Ki ˆ 100 nm) thioethers, which
suggests that the shallow lipophilic pocket is better filled with a flat aromatic rather
than a bulkier alicyclic residue. The limited size of this pocket is further evidenced by
the decreased binding affinity of the 3-bromophenyl thioether 1f (Ki ˆ 0.6 mm) and 1,1'-
biphenyl derivative 1g (Ki ˆ 1.5 mm). The latter results were actually rather surprising
since, according to the molecular modeling, Br and Ph substituents in meta-position of
the phenyl thioether residue were expected to undergo favorable Van der Waals
interactions in the surrounding of the hydrophobic pocket.
Several crystal structures of the inhibitors soaked into TGT crystals were solved,
confirming, in general, the binding mode proposed for the diaminoquinazolinone
scaffold. The pyrimidone ring forms H-bonds with Asp156, Gln203, and Gly230, the
amino group at C(6) interacts with the CˆO group of Leu231, and the bicyclic scaffold
is sandwiched between the side chains of Tyr106 and Met260 (Fig. 4) [16][17]. In
agreement with the modeling predictions, substituents at C(8) of the quinazolinone
scaffold are correctly oriented for reaching into the lipophilic pocket formed by Val45,
Leu68, and Val282. This is illustrated in Fig. 4,a, for the thiopropyl side chain of
inhibitor 1a (soaked at pH 8.5 into TGT crystals). Its imidazole-substituted counterpart
1e was soaked for solubility reasons at two different pH values, 8.5 and 5.5. This change
in pH induced a profound conformational reorganization of the carboxylate side chain
of Asp102. Whereas, in the structure at pH 8.5, this residue is pointing away from the
heterocyclic ligand that interacts with a bound H2O molecule (as also seen in Fig. 4,a),
the carboxylate side chain turns around at lower pH, displaces the previously present
H2O, and undergoes H-bonding with N(1) and C(2)ÀNH2 of the quinazolinone scaffold
(Fig. 4,b). Moreover, two distinct conformations of the imidazole substituent were
deduced from the location of the S-atom above and below the quinazolinone core.
Rotational flexibility accounts for the non-observable electron density of the imidazole
moiety; this is consistent with the lack of a dominant H-bond to Asp280. Finally, the
weak activity of 1d (Ki ˆ 3.5 mm) is readily rationalized based on the crystal-structure
analysis: the (presumably protonated) 2-(dimethylamino)ethyl group of 1d does not
reach into the hydrophobic pocket but is rather oriented toward bulk H2O (for a more
detailed discussion of the crystallographic analysis, see [17]).
2.4. Variation of the H-Bond Donor at C(6). Aromatic NH2 groups at C(6) of the
quinazolinone scaffold, as in 1a 1i, are only modest H-bond donors, and, therefore, we
decided to introduce different H-bond donors to interact with the CˆO group of
Leu231. In a series of inhibitors featuring the phenyl thioether substituent at C(8), we
first prepared ligand 15 lacking any H-bond donor at C(6), to confirm the importance
of the H-bond to Leu231, as previously demonstrated by Graedler et al. for
pyrazinediones [12]. The synthesis of 15 followed the one shown in Scheme 1, with
pivaloyl derivatives 16 and 17 as isolated intermediates (Scheme 3).
Changing the aromatic amino to the more acidic phenolic OH group (pKa of
aniline: 27 vs. phenol: 10) was expected to increase the strength of the H-bonding

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Fig. 4. Four different crystal structures of TGTÀinhibitor complexes [16][17]. The green color denotes parts of
the residues departing from position 8 of the quinazolinone scaffold without detectable electron density, and the
transparent portion represents the alternative conformation taken by these substituents. a) 1a, red spheres are
isolated bound H2O molecules; PDB code: 1K4 H (soaking at pH 8.5; 1.8-ä resolution). b) 1e, PDB code: 1Q63
(soaking at pH 5.5; 1.85-ä solution). c) 1d, PDB-code: 1Q65 (soaking at pH 5.5, 2.1-ä resolution). d) 34, PDB
code: 1Q66 (soaking at pH 5.5, 1.75-ä resolution). The arrow marks a repulsive (C)ˆO ¥¥¥ CH2 contact (3.0 ä).
At pH 5.5 (Fig. 4,b d), Asp102 undergoes a conformational rearrangement and points toward the inhibitor,
thereby displacing a bound H2O molecule present at pH 8.5 (Fig. 4,a). Color coding: N: blue, O: red, S: yellow,
C: grey.
interaction with the CˆO group of Leu231. For this purpose, regioselective
bromination of methyl anthranilate 3 in AcOH afforded 18 in 93% yield (Scheme 4).
Cyclization to 19 and introduction of the pivaloyl group provided quinazolinone 20.
After radical bromination to 21, the phenyl and thiophenoxy substituents were
introduced as described in Scheme 1. Deprotection of 22a and 22b furnished the

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Scheme 3. Synthesis of Inhibitor 15
a) PivCl, Py, DMA, 1108, 3 h; 44%. b) NBS, AIBN, CCl4, D, 18 h; then PhSH, BuLi, THF, r.t., 4 h; 57%. c) HCl,
EtOH, 708, 4 h; 70%. AIBN ˆ Azobis[isobutyronitrile].
potential ligands 23a and 23b, respectively, bearing a Br substituent at C(6). Borylation
of 22a with 4,4,4',4',5,5,5',5'-octamethyl[2,2'-bi[1,3,2]dioxaborolanyl] (24) in the
presence of [PdCl2(dppf)] and subsequent oxidation of the crude boronic ester with
H2O2 led to 25 (80% over two steps) [26], and acidic deprotection yielded inhibitor 26.
Scheme 4. Synthesis of Inhibitors 23a, 23b, and 26
a) Br2, AcOH, 30 min, 108; 93%. b) Chloroformamidinium chloride, dimethyl sulfone, 1408, 1 h; 90%. c) PivCl,
NEt3, DMA, 1008, 3 h; 76%. d) NBS, AIBN, CCl4, 808, 18 h; 76%. e) PhOH, NaH, THF, 08 ! r.t., 3 h; 80%
(22a). f) PhSH, BuLi, THF, 0 ! r.t., 3 h; 87% (22b). g) HCl, EtOH, 758, 2 3 h; 67% (23a); 60% (23b). h)
[PdCl2(dppf)], AcOK, Me2SO, 808, 18 h. i) H2O2, AcOH, r.t., 6 h; 80% over 2 steps. j) HCl, EtOH, 758, 4 h;
40%. dppf ˆ 1,1'-Bis(diphenylphosphino)ferrocene.
As the phenylsulfanyl derivative 23b would not survive the oxidative cleavage of
the boronic ester, another route was pursued to produce phenol 27. Starting from
bromoquinazolinone 20, the OH group was introduced in good yield by borylation
followed by oxidation (Scheme 5). Protection of 28 with (t-Bu)Me2SiCl provided 29

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Scheme 5. Synthesis of Inhibitor 27
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a) 24, [PdCl2(dppf)], AcOK, Me2SO, 808, 18 h. b) H2O2, AcOH, r.t., 5 h; 84% over 2 steps. c) Me2(t-Bu)SiCl,
1H-imidazole, DMF, 08 ! r.t., 18 h; 88%. d) NBS, AIBN, CCl4, 808, 18 h. e) PhSH, BuLi, THF, 08 ! r.t., 3 h;
77% over 2 steps. f) HCl, EtOH, 758, 4 h; 80%.
(88%). Bromination and subsequent thioether formation furnished 30, which, upon
acidic cleavage of both protecting groups, yielded inhibitor 27 (80%).
We also introduced an NH2CH2 substituent at C(6) of the quinazolinone core, in
analogy to the natural substrate preQ1 (Fig. 1). We expected that, under the biological
testing conditions (pH 7.3), the primary NH2 group would be protonated and
experience favorable ionic H-bonding interactions with the neighboring CˆO groups
of Leu231 and Ala232. Starting from 20, Br! CN exchange was performed in good
yield with CuCN in refluxing DMF (Scheme 6) [27]. Bromination of carbonitrile 31 and
substitution with phenylsulfanyl group provided 32, which was deprotected to yield the
potential inhibitor 33. Finally, chemoselective reduction of the CN group with
Li[Et3BH] in THF furnished the target compound 34.
2.5. Biological Activity of the Second Inhibitor Series. The comparison between 1c
(Ki ˆ 0.1 mm) and 15 (Ki ˆ 1.1 mm) shows that the introduction of the NH2 group at C(6)
enhances the binding affinity by a factor of 10 (D(DG) ꢁ 1.4 kcal molÀ1), most
probably due to H-bonding to the CˆO group of Leu231 (Fig. 5). On the other hand,
the introduction of an HO substituent as a potentially better H-bond donor does not
have a beneficial effect on the biological activity (27; Ki ˆ 0.25 mm). Ligands with Br or
CN substituents, lacking H-bond donor capacity, expectedly are modest binders. The
large difference in binding affinity between phenyl ether 1h and phenyl thioether 1c
(factor of 56) was well reproduced in the series of inhibitors bearing either Br or OH
groups at C(6) (23a: Ki ˆ 11.9 mm vs. 23b: Ki ˆ 1.1 mm, and 26: Ki ˆ 4.6 mm vs. 27: Ki ˆ
0.25 nm).
Unexpectedly at first, the NH2CH2-substituted inhibitor 34 displayed a substantially
reduced activity (Ki ˆ 1.7 mm) with respect to the anilino derivative 1c. Later, the
crystal structure of 34 complexed with TGTrevealed that the (presumably) protonated

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Scheme 6. Synthesis of Inhibitor 34
a) CuCN, DMF, D, 20 h; 56%. b) NBS, AIBN, CCl4, 808, 18 h. c) PhSH, BuLi, THF, 08 ! r.t., 3 h; 40% over 2
steps. d) HCl, EtOH, 758, 4 h; 94%. e) Li[Et3BH], THF, À788 ! r.t., 4 h; 50%.
Fig. 5. Biological activities (Ki values) of the second series of TGT inhibitors
aminomethyl group is too distant from the CˆO group of Leu231 (d(N ¥¥¥ O) ˆ 3.3 ä)
to be engaged in an effective ionic H-bond (Fig. 4,d) [17]. Furthermore, the CH2 group
of the NH2CH2 residue forms a repulsive contact with this CˆO group (d(C ¥¥¥ O) ˆ
3.0 ä).
2.6. Two Simple Inhibitors with an 2-Aminoquinazolin-4(3H)-one Core: Crystal-
lography Studies. In the course of this work, two scarcely substituted 2-amino-
quinazolinones were tested for their TGT binding. Both lack a H-bond-donor group at
C(6), the synthetic intermediate 4 shows a Me group at C(8), whereas 35 is
unsubstituted at this position (Fig. 6) [12].
The crystal structures of both compounds bound to TGT were solved and revealed
marked differences of the active site environments in the two complexes. Me
Derivative 4 and unsubstituted 35 displayed the normal complexation mode with the

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Fig. 6. Unexpected conformational change of the peptidic backbone at Leu231/Ala232 upon a minimal change in
the inhibitor structure. a) Crystal structure of 4 complexed with TGT (1.81-ä resolution, PDB code 1S38). b)
Crystal structure of 35 complexed with TGT (1.95-ä resolution, PDB code 1S39). Crystals were soaked with
inhibitor at pH 5.5. Dotted lines: H-bonds; straight lines: other significant intermolecular contacts, red spheres:
H2O molecules.
Asp102 in the −turn-on× conformation (carboxylate group rotated toward inhibitor),
expected for soaking conditions at pH 5.5 [17]. For 4, the CˆO O-atom of Leu231 is
pointing toward the inhibitor (Fig. 6,a). In contrast, the complex with 35 revealed a ca.
1808 rotation of this CˆO group toward the outside of the active site, with the adjacent
NÀH residue now turned inwards (Fig. 6,b). This flip of the peptide-bond region at
Leu231ÀAla232, previously described for pyridazinediones and preQ0, allows TGT to
switch between presenting donor (NÀH) and acceptor (CˆO) functionality, thereby
modulating the recognition properties of the substrate binding site [20][28].
We assume that this backbone flip is ligand-induced depending on the properties of
the H-bond functionality presented by the ligand in this region. Both 4 and 35 lack such
functionality. Interestingly, they provoke different conformations of the Leu231
Ala232 peptide bond, which suggests that both protein conformers are rather close in
energy. Tiny differences in the binding modes of 4 and 35 stabilize this flip in either
orientation. The applied assay conditions reveal 4 to be of 7.0m affinity in agreement
with the lack of a H-bond donor at C(6).
Futhermore, the major contributor to the weaker binding of 4 clearly is the Me
group at C(8). This lipophilic substituent orients into a highly polar environment
formed by several H2O molecules as well as the two catalytic residues Asp280 and

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Asp102. In fact, the crystal structure shows a strongly repulsive contact between the Me
group of 4 and one of the O-atoms of the carboxylate side chain of Asp102 (d(C ¥¥¥
O) ˆ 3.1 ä)(Fig. 6,a; the −turn-on× conformation of Asp102 seen in the two co-crystal
structures is most likely occurring at the biological testing conditions (pH 7.3) as well).
A lipophilic group protruding into the solvation sphere of a carboxylate group clearly is
highly detrimental to binding affinity.
To our surprise, the binding assay suggested significantly stronger binding of 35 in
the submicromolar range (20 50 nm). Although quite speculative, this unexpectedly
low value is possibly pretended by the superimposed tRNA binding. In this discussion,
it has to be considered that binding affinities are determined in presence of tRNATyr
[12]. In the assay, the quinazolinone ligands inhibit the TGT-catalyzed exchange of
guanine (G)34 in the anticodon loop with [8-3H]G, leading to radiolabeled tRNATyr
[12]. The recently solved crystal structure of the complex of 9-deazaguanine with TGT
covalently bound to tRNA [9] indicates that a small ligand of a size similar to 9-
deazaguanine, such as 35, could still be accommodated at the binding site in presence of
covalently bound tRNA. This would imply rather different binding conditions for 35
compared to the other inhibitors exhibiting a side chain at C(8). Supposedly, via their
occupation of the remote lipophilic pocket formed by Val45, Leu68, and Val282, they
pretend or at least strongly interfere (e.g., for 4 via its Me group) with the binding of
tRNA. This substrate is also accommodated in this pocket by its ribose ring and the
adjacent phosphate group as demonstrated in the crystal structure of the ternary TGT
complex with 9-deazaguanine. We further assume that the currently used CH2X linkers,
departing from C(8), pay a large penalty while passing through the highly hydrophilic
environment encompassed by Asp280 and Asp102 (at 6.1 ä distance from each other)
to direct lipophilic residues (such as a Ph ring) into that pocket. Possibly, the observed
S-effect is also determined by the fact that a well-polarizable S-atom in the pivotal
position between the two carboxylate side chains of Asp102 and Asp280 is more
favorable than an O-atom. To better cope with the given local requirements for
interactions, in a next lead optimization cycle, we, therefore, intend to introduce more-
polar, possibly positively charged linkers to eliminate the unfavorable interactions seen
with the current generation of inhibitors.
3. Conclusions. This study establishes 2-aminoquinazolin-4(3H)-ones as promis-
ing inhibitors for tRNA-guanine transglycosylase, an enzymatic target against
shigellosis. Structure-based design (Fig. 2) and versatile synthetic protocols
(Schemes 1 5) afforded a series of potent inhibitors, with activities up to Ki ˆ
100 nm (1c; Figs. 3 and 5). The binding mode of several of these ligands in the active
site of TGTwas established by crystal-structure analyses (Figs. 4 and 6). The following
results were obtained, providing valuable guidelines for future lead optimization
cycles: i) The pyrimidone ring of the heterocyclic core undergoes H-bonding with
Asp156, Gln203, and Gly230, and the bicyclic scaffold is nicely sandwiched between the
side chains of Tyr106 and Met260. ii) A shallow lipophilic pocket formed by Val45,
Leu68, and Val282 was identified, and its occupancy by a phenylsulfanyl moiety was
shown to enhance binding affinity. However, to reach into this remote pocket, PhXCH2
linkers (X ˆ S, O, CH2) departing from C(8) of the quinazolinone scaffold need to pass
across a very hydrophilic region of the active site encompassed by the catalytic residues

Helvetica Chimica Acta Vol. 87 (2004)
1345
Asp280 and Asp102. During this passage, unfavorable contacts of the linker, protruding
in the solvation sphere of the carboxylate of Asp102, are difficult to avoid. We intend
using more-polar and even positively charged linkers in future generations of inhibitors
to avoid these unfavorable contacts. iii) A dramatic S-effect was observed, with the
replacement of the S-atom in phenylsulfanyl inhibitor 1c (Ki ˆ 100 nm) by the O-atom
(in 1h; Ki ˆ 5.6 mm) or CH2 (in 1i; Ki ˆ 3.6 mm), resulting in a substantial loss of activity.
The phenylsulfanyl residue is quite hydrophobic and can reach deeper into the
hydrophobic pocket, while maintaining an energetically favorable conformation. iv)
The free enthalpy increment of the H-bond between an NH2 group at C(6) and the
CˆO group of neighboring Leu231 was quantified as D(DG) ꢂ 1.4 kcal ¥ molÀ1. v)
Flexibility in two regions of the active site was observed in the crystal structures,
namely the rotation of the Asp102 toward the inhibitor upon changing the pH from 8.5
to 5.5 during the soaking of TGT crystals with the inhibitor, and a flip of the peptidic
backbone at Ala232/Leu231.
We are grateful to the ETH Research Council and the Fonds der Chemischen Industrie for support of the
work done at the ETH. Work at the University of Marburg was supported by the Deutsche Forschungsgemein-
schaft (DFG Grant KL-1204/1). We thank Mr. Bernhard Stengl (Univ. of Marburg) for assistance with the
biological assays.
Experimental Part
General. Solvents and reagents were reagent-grade, purchased from commercial suppliers, and used
without further purification unless otherwise stated. The following compounds were prepared according to
literature procedures: chloroformamidinium chloride [29], 2 [30], and 35 [31]. THF was freshly distilled from
sodium benzophenone ketyl. Evaporation in vacuo was conducted at H2O aspirator pressure. All products were
dried under high vacuum (h.v., 10À2 Torr) before anal. characterization. Column chromatography (CC): SiO2 60
(40 63 mm) from Fluka, 0 0.3 bar pressure. TLC: SiO2 60 F245, Merck, visualization by UV light at 254/356 nm.
M.p.: B¸chi B540 melting-point apparatus; uncorrected. IR spectra [cmÀ1]: Perkin-Elmer 1600-FT spectrometer.
NMR spectra (1H, 13C): Varian Gemini-200, Varian Gemini-300, or Bruker AMX-500; spectra were recorded at
r.t. with solvent peak as reference. MS (m/z (%)): EI-MS: VG-TRIBRID spectrometer at 70 eV; ESI-MS:
Perkin-Elmer Sciex API III spectrometer; HR-MALDI-MS: IonSpec Ultima (2,5-dihydroxybenzoic acid
(DHB) matrix or 2-[(2E)-3-[4-(tert-butyl)phenyl]-2-methylprop-2-enylidene]malonitrile, (DTCB)). Elemental
analyses were performed by the Mikrolabor at the Laboratorium f¸r Organische Chemie, ETH-Z¸rich. The
nomenclature was generated with the computer program ACD-Name (ACD/Labs) [32].
Crystallization and Soaking. TGTwas crystallized and soaked with inhibitors at pH 8.5 or 5.5 as described in
[17][28]. The new structures of TGT ¥ 4 and TGT¥ 35 have been deposited in the Protein Data Bank (PDB) with
codes 1S38 and 1S39, resp. The crystal data of these structures are summarized in the Table.
Determination of Apparent Inhibition Constants. The apparent Ki values were measured as described by
Graedler et al. [12]. The error given amounts to the standard deviation of two independent measurements with
different substrate concentrations. Due to the elaborate determination of the Ki values, the actual error is
assumed to be ꢁÆ 20 30%.
Cyclization with Chloroformamidinium Chloride: General Procedure A (GP A). A mixture of the
anthranilate (1 equiv.), chloroformamidinium chloride (1.5 equiv.), and dimethyl sulfone (50 equiv.) was heated
to 1508 for 2 3 h. After addition of conc. aq. NH4OH soln. (2 ml), the mixture was diluted with H2O and
filtered. The residue was washed with H2O, MeOH, acetone, and CHCl3. The crude product was precipitated
from hot DMF and H2O and dried under h.v. at 808.
Thioether Formation: General Procedure B (GP B). To a soln. of BuLi (1.6m in hexane; 2.5 equiv.) in abs.
THF, the thiol (3.0 equiv.) was added dropwise at 08. The soln. was allowed to warm to r.t. for 15 min, after which
a soln. of the benzyl bromide (1.0 equiv.) in abs. THF was added. After stirring at r.t. for 3 h, the mixture was
concentrated in vacuo. The residue was taken up in sat. aq. NaHCO3 soln. and extracted with CH2Cl2 (3Â). The
combined org. phases were washed with sat. aq. NaCl soln. (1Â), dried (MgSO4), and evaporated in vacuo.

1346
Helvetica Chimica Acta Vol. 87 (2004)
Table. Crystal-Structure Data for the Complexes of TGT with Inhibitors 4 and 35
TGT ¥ 4
Crystal data
TGT ¥ 35
pH
5.5
5.5
Space group
Cell constants
a [ä]
C2
C2
90.60
89.71
b [ä]
65.48
64.72
c [ä]
70.43
70.66
b [deg.]
96.53
95.76
Resolution [ä]
Total No. of refl.
No. of unique refl.
20 1.81
20 1.95
70,409
29,337
99.7 (93.8)
7.2 (51.5)
24.2
85,968
35,820
95.7 (94.7)
8.8 (46.0)
22.2
Completeness of all data [%] (outer shell)
Rsymm for all data [%] (outer shell)a)
Rfree [%]b)
R Factor [%]b)
19.7
20.9
r.m.s. dev., angle [deg.]
r.m.s. dev., bond [ä]
1.4
0.006
1.2
0.006
a) Rsymm ˆ S j I À hIi j /SI, where I is the observed intensity and hIi is the average intensity for multiple
measurements. b) Rfree [33] was calculated from a random selection of reflections constituting 10% of the data;
the R-factor was calculated with the remaining intensities.
Reduction with SnCl2: General Procedure C (GP C). To a soln. of the NO2 derivative (1.0 equiv.) in EtOH,
SnCl2 ¥ 2 H2O (4.0 eq) was added, and the mixture was heated to 708 for 6 h. After removal of the solvent in
vacuo, the residue was taken up in sat. aq. NaHCO3 soln./CH2Cl2. The suspension was filtered, and the filtrate
was extracted with CH2Cl2 (3Â). The combined org. phases were washed with sat. aq. NaCl soln. (1Â), dried
(MgSO4), and evaporated in vacuo.
Reduction with Zn: General Procedure D (GP D). To a suspension of the NO2 derivative (1.0 equiv.) in
AcOH and H2O, Zn powder (10.0 equiv.) was added portionwise at r.t. The mixture was stirred for 1 3 h at r.t.,
filtered, and the solvent was evaporated in vacuo. A 2m aq. NH3 soln. was added to the residue, and the aq. phase
was extracted with CH2Cl2 (3Â). The combined org. phases were washed with sat. aq. NaCl soln. (1Â), dried
(MgSO4), and evaporated in vacuo.
Removal of the Pivaloyl Protecting Group: General Procedure E (GP E). The pivaloyl-protected derivative
was taken up at r.t. in ethanolic HCl soln. (EtOH/conc. aq. HCl 10 :1), and the mixture was heated to 708 for 3
4 h. The mixture was adjusted to pH 8 with 1n NaOH and sat. aq. Na2CO3 soln. The precipitate formed was
filtered, washed with H2O, acetone, and CHCl3, and dried several hours under h.v. at 708.
2-Amino-8-methylquinazolin-4(3H)-one (4). GP A with 3 (2 g, 12.1 mmol) and chloroformamidinium
chloride (2 g, 17.4 mmol). Precipitation from Me2SO/H2O yielded 4 (1.86 g, 88%). White woolly solid. M.p. 3008.
IR (KBr): 3379s, 3134s, 2922m, 1650s, 1605s, 1561s, 1519m. 1H-NMR (300 MHz, (CD3)2SO): 11.39(br. s, 1 H);
7.74 (d, J ˆ 7.4, 1 H); 7.46 (d, J ˆ 7.4, 1 H); 7.04 (t, J ˆ 7.4, 1 H); 6.76 (br. s, 2 H); 2.34 (s, 3 H). 13C-NMR (50 MHz,
‡
(CD3)2SO): 160.5; 149.9; 143.8; 133.4; 127.9; 122.3; 120.4; 114.8; 15.6. HR-MALDI-MS (DHB): 176.0818 (MH ,
‡
C9H10N3O ; calc. 176.0824). Anal. calc. for C9H9N3O (175.19): C 61.70, H 5.18, N 23.99, O 9.13; found: C 61.54,
H 5.09, N 23.83, O 9.37.
2-Amino-8-methyl-6-nitroquinazolin-4(3H)-one (5). Conc. H2SO4 (15 ml) was poured into 65% HNO3
(15 ml) at 08, and 4 (1.0 g, 5.7 mmol) was added portionwise in a way to keep Tꢂ 108. The ice bath was removed,
and the mixture was allowed to stir overnight at r.t. The mixture was poured on to ice and treated with conc. aq.
NH4OH soln. The precipitate formed was collected by filtration, washed with H2O, and dried under h.v.: 0.9g
(72%) of 5. Yellow solid. M.p. > 3258. IR (KBr): 3410m, 3141m, 1689m, 1657m, 1595s, 1493s, 1336s. 1H-NMR
(200 MHz, (CD3)2SO): 11.39(br. s, 1 H); 8.52 (d, J ˆ 2.3, 1 H); 8.23 (d, J ˆ 2.3, 1 H); 7.04 (br. s, 2 H); 2.43 (s,
3 H). 13C-NMR (75 MHz, (CD3)2SO): 161.8; 155.6; 153.9; 140.1; 134.0; 127.7; 120.4; 115.9; 17.5. HR-MALDI-
MS (DTCB): 219.0526 ([M À H]À, C9H7N4OÀ3 ; calc. 219.0518).

Helvetica Chimica Acta Vol. 87 (2004)
1347
N-(3,4-Dihydro-8-methyl-6-nitro-4-oxoquinazolin-2-yl)-2,2-dimethylpropanamide (6). To a suspension of
5 (500 mg, 2.27 mmol) in DMA (12 ml), pyridine (0.36 ml, 4.54 mmol) and 2,2-dimethylpropanoyl chloride
(0.36 ml, 2.95 mmol) were sequentially added at r.t., and the mixture was heated to 1108 overnight. After cooling
to r.t., the mixture was poured into H2O (200 ml), and the precipitate formed was collected by filtration. CC
(SiO2; CH2Cl2/MeOH 99 :1) provided 6 (570 mg, 82%). Yellow solid. M.p. 207 2088 (CHCl3/hexane). IR
(CHCl3): 3426w, 3196w, 3035w, 1685s, 1626s, 1587s, 1441w, 1340s. 1H-NMR (200 MHz, CDCl3): 12.12 (br. s, 1 H);
8.92 (d, J ˆ 3.0, 1 H); 8.33 (dd, J ˆ 3.0, 0.9, 1 H); 8.20 (br. s, 1 H); 2.55 (s, 3 H); 1.39 (s, 9 H). 13C-NMR
(125 MHz, CDCl3): 180.5; 160.1; 151.9; 147.8; 143.8; 136.7; 128.6; 121.0; 120.0; 40.5; 27.9; 17.7. HR-MALDI-MS
‡
‡
(DHB): 305.1245 (MH , C14H17N4O4 ; calc. 305.1250). Anal. calc. for C14H16N4O4 (304.30): C 55.26, H 5.30,
N 18.41; found: C 55.21, H 5.47, N 18.51.
N-[8-(Bromomethyl)-3,4-dihydro-6-nitro-4-oxoquinazolin-2-yl]-2,2-dimethylpropanamide (7). To a sus-
pension of 6 (9.30 g, 30.6 mmol) and NBS (5.44 g, 30.6 mmol) in CCl4 (700 ml), a cat. amount of Bz2O2 was
added, and the mixture was heated to reflux overnight. After removal of the solvent in vacuo, the residue was
washed with hot H2O. CC (SiO2; hexane/AcOEt 7:3) provided 7 (5.9g, 50%). White solid. M.p. 201 202 8. IR
(neat): 3214w, 3086w, 2986w, 1660s, 1620s, 1581s, 1496s, 1341s, 1247s. 1H-NMR (200 MHz, CDCl3): 12.22 (br. s,
1 H); 9.04 (d, J ˆ 2.7, 1 H); 8.58 (d, J ˆ 2.7, 1 H); 8.29(br. s, 1 H); 4.84 (s, 2 H); 1.40 (s, 9 H). 13C-NMR
(100 MHz, CDCl3): 180.8; 159.6; 151.2; 148.8; 143.8; 135.3; 129.6; 123.6; 120.8; 40.6; 27.1; 27.0. HR-MALDI-MS
‡
‡
(DHB): 383.0352 (MH , C14H16N4O4 ; calc. 383.0355).
N-{3,4-Dihydro-6-nitro-4-oxo-8-[(propylsulfanyl)methyl]-2,2-dimethylquinazolin-2-yl}-2,2-dimethylpropan-
amide (8a). GP B with BuLi (1.6m in hexane; 4.06 ml, 6.5 mmol) in abs. THF (10 ml), PrSH (0.71 ml, 7.8 mmol),
7 (1.0 g, 2.6 mmol) in abs. THF (10 ml). CC (SiO2; CH2Cl2 ! CH2Cl2/MeOH 99 :1) provided 8a (750 mg, 76%).
Yellow solid. M.p. 153 1558. IR (KBr): 3211w, 3000w, 2923m, 1665s, 1627s, 1604s, 1583s, 1521m, 1468m, 1436m,
1339s, 1247s, 1137s. 1H-NMR (200 MHz, CDCl3): 12.19(br. s, 1 H); 8.99 (d, J ˆ 2.6, 1 H); 8.47 (d, J ˆ 2.6, 1 H);
8.29( s, 1 H); 4.04 (s, 2 H); 2.50 (t, J ˆ 7.3, 2 H); 1.57 1.72 (m, 2 H); 1.40 (s, 9H); 1.01 ( t, J ˆ 7.3, 3 H). 13C-NMR
(50 MHz, CDCl3): 178.4; 157.6; 149.1; 146.0; 141.6; 134.8; 126.0; 119.8; 118.4; 38.1; 31.7; 28.5; 24.6; 20.2; 11.0.
‡
‡
HR-MALDI-MS (DHB): 379.1434 (MH , C17H23N4O4S ; calc. 379.1440).
N-{8-[(Cyclohexylsulfanyl)methyl]-3,4-dihydro-6-nitro-4-oxoquinazolin-2-yl}-2,2-dimethylpropanamide
(8b). GP B with BuLi (1.6m in hexane; 4.06 ml, 6.5 mmol) in abs. THF (10 ml), cyclohexanethiol (0.96 ml,
7.8 mmol), 7 (1.0 g, 2.6 mmol) in abs. THF (10 ml). CC (SiO2; CH2Cl2 ! CH2Cl2/MeOH 99 :1) provided 8b
(800 mg, 74%). Yellow solid. M.p. 97 1028. IR (KBr): 3177w, 2922m, 2844w, 1674s, 1602s, 1516w, 1388s, 1250m.
1H-NMR (300 MHz, CDCl3): 12.16 (br. s, 1 H); 8.90 (d, J ˆ 2.6, 1 H); 8.50 (d, J ˆ 2.6, 1 H); 8.42 (s, 1 H); 4.00 (s,
2 H); 2.52 2.68 (m, 1 H); 1.87 2.03 (m, 2 H); 1.66 1.70 (m, 2 H); 1.52 1.65 (m, 1 H); 1.36 (s, 9H); 1.13 1.37
(m, 5 H). 13C-NMR (75 MHz, CDCl3): 181.0; 160.3; 151.6; 148.5; 144.2; 137.9; 128.6; 122.2; 120.8; 43.9; 40.6;
‡
‡
33.5; 29.2; 27.0; 26.0; 25.8. HR-MALDI-MS (DHB): 419.1748 (MH , C20H27N4O4S ; calc. 419.1753).
N-{3,4-Dihydro-6-nitro-4-oxo-8-[(phenylsulfanyl)methyl]quinazolin-2-yl}-2,2-dimethylpropanamide (8c).
GP B with BuLi (1.6m in hexane; 4.06 ml, 6.5 mmol) in abs. THF (10 ml), PhSH (0.8 ml, 7.8 mmol), 7 (1.0 g,
2.6 mmol) in abs. THF (10 ml). CC (SiO2; CH2Cl2 then CH2Cl2/MeOH 99 :1) provided 8c (850 mg, 79%).
Yellow solid. M.p. 148 1508. IR (KBr): 3272m, 3077w, 2966w, 1664s, 1624s, 1583s, 1522s, 1433s, 1339s, 1245s,
1139s. 1H-NMR (200 MHz, CDCl3): 12.17 (br. s, 1 H); 8.9 6 (d, J ˆ 2.8, 1 H); 8.20 (d, J ˆ 2.8, 1 H); 8.19( s, 1 H);
7.23 7.33 (m, 5 H); 4.40 (s, 2 H); 1.33 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 180.7; 159.9; 151.3; 148.3; 143.6;
‡
135.8; 135.1; 131.1; 129.1; 128.5; 127.3; 122.3; 120.5; 40.5; 34.2; 27.0. HR-MALDI-MS (DHB): 413.1277 (MH ,
‡
C20H21N4O4S ; calc. 413.1284).
N-[8-({[(2-Dimethylamino)ethyl]sulfanyl}methyl)-3,4-dihydro-6-nitro-4-oxo-quinazolin-2-yl]-2,2-dimeth-
ylpropanamide (8d). GP B with BuLi (1.6m in hexane; 8.12 ml, 13.0 mmol) in abs. THF (10 ml), 2-
(dimethylamino)ethanethiol hydrochloride (1.21 g, 8.58 mmol), 7 (1.0 g, 2.6 mmol) in abs. THF (10 ml). CC
(SiO2; CH2Cl2/MeOH/NEt3 98 :1 :1) provided 8d (740 mg, 74%). Yellow solid. M.p. 161 1638. IR (KBr):
3211w, 2995w, 2923m, 1662s, 1625s, 1600s, 1521m, 1468m, 1435m, 1353s, 1240s. 1H-NMR (200 MHz, CDCl3): 9.65
(br. s, 2 H); 8.9 0 (d, J ˆ 2.6, 1 H); 8.43 (d, J ˆ 2.6, 1 H); 4.00 (s, 2 H); 2.46 2.66 (m, 4 H); 2.22 (s, 6 H); 1.36 (s,
9H). 13C-NMR (75 MHz, CDCl3): 181.2; 160.4; 151.7; 148.9; 144.0; 137.3; 128.6; 122.4; 120.8; 59.0; 45.4; 40.6;
‡
‡
31.2; 30.3; 27.0. HR-MALDI-MS (DHB): 408.1712 (MH , C18H26N5O4S ; calc. 408.1705).
N-{3,4-Dihydro-8-[(1H-imidazol-2-ylsulfanyl)methyl]-6-nitro-4-oxoquinazolin-2-yl}-2,2-dimethylpropan
(8e). To a soln. of 2-sulfanyl-1H-imidazole (104 mg, 1.04 mmol) in abs. THF (10 ml), Cs2CO3 (338 mg,
1.04 mmol) was added at r.t. To the resulting suspension, 7 (200 mg, 0.52 mmol) in abs. THF (10 ml) was added,
and the mixture was stirred at r.t. for 4 h. After removal of the solvent in vacuo, the residue was taken up in
CH2Cl2/sat. aq. Na2CO3 soln. and extracted with CH2Cl2 (3Â). The combined org. phases were washed with sat.
aq. NaCl soln., dried (MgSO4), and evaporated in vacuo. CC (SiO2; CH2Cl2/MeOH 98.5 :1.5) provided 8e

1348
Helvetica Chimica Acta Vol. 87 (2004)
(132 mg, 63%). Yellow solid. M.p. 224 2268. IR (KBr): 2980m, 2888w, 1663s, 1628s, 1584s, 1529s, 1438m, 1343s,
1249s, 1137s. 1H-NMR (200 MHz, (CD3)2SO): 12.44 (br. s, 1 H); 11.78 (br. s, 2 H); 8.59( d, J ˆ 2.7, 1 H); 8.15 (d,
J ˆ 2.7, 1 H); 7.02 (s, 2 H); 4.56 (s, 2 H); 1.26 (s, 9 H). 13C-NMR (75 MHz, (CD3)2SO): 180.5; 158.1; 150.0; 148.2;
140.8; 136.0; 134.5; 126.1; 122.8; 119.3; 118.0; 30.9; 24.4; C of t-Bu hidden by (CD3)2SO peaks. HR-MALDI-MS
‡
‡
(DHB): 403.1198 (MH , C17H19N6O4S ; calc. 403.1188).
N-(8-{[(3-Bromophenyl)sulfanyl]methyl}-3,4-dihydro-6-nitro-4-oxoquinazolin-2-yl)-2,2-dimethylpropan-
amide (8f). GP B with BuLi (1.6m in hexane; 2.45 ml, 3.9mmol) in abs. THF (10 ml), 3-bromothiophenol
(0.5 ml, 4.3 mmol), 7 (0.5 g, 1.3 mmol) in abs. THF (10 ml). CC (SiO2; AcOEt/hexane 2 :8) provided 8f
(373 mg, 58%). Yellow oil. IR (CHCl3): 3428w, 3028w, 2969w, 1687s, 1624s, 1607s, 1586s, 1342s. 1H-NMR
(300 MHz, CDCl3): 12.22 (s, 1 H); 8.90 (d, J ˆ 2.5, 1 H); 8.49(br. s, 1 H); 8.30 (d, J ˆ 2.5, 1 H); 7.39( dd, J ˆ 1.5,
1.5, 1 H); 7.25 (ddd, J ˆ 7.8, 1.5, 1.5, 1 H); 7.12 (ddd, J ˆ 7.8, 1.5, 1.5, 1 H); 7.05 (t, J ˆ 7.8, 1 H); 4.36 (s, 2 H); 1.37
(s, 9 H). 13C-NMR (50 MHz, CDCl3): 180.7; 159.7; 151.3; 148.5; 143.6; 137.7; 135.2; 132.0; 130.2; 129.6; 128.6;
‡
‡
128.2; 122.7; 122.4; 120.4; 40.7; 31.1; 27.1. HR-MALDI-MS (DHB): 491.0392 (MH , C20H20BrN4O4S ; calc.
491.0389).
N-(8-{[([1,1'-Biphenyl]-3-yl)sulfanyl]methyl}-3,4-dihydro-6-nitro-4-oxoquinazolin-2-yl)-2,2-dimethylpro-
panamide (8g). GP B with BuLi (1.6m in hexane; 2.0 ml, 3.7 mmol) in abs. THF (10 ml), [1,1'-biphenyl]-3-thiol
(0.70 g, 3.7 mmol), 7 (0.64 g, 1.7 mmol) in abs. THF (7 ml). CC (SiO2; CH2Cl2/AcOEt 1 to 10%) provided 8g
(0.59g, 72%). Yellow solid. M.p. 84 85 8. IR (CHCl3): 3430w, 3153w, 2953w, 2252m, 1685s, 1624s, 1606s, 1585s,
1
1530m, 1503m, 1474m, 1441m, 1375w, 1341s, 1251m, 1209s, 1127m. H-NMR (300 MHz, CDCl3): 12.15 (br. s,
1 H); 8.92 (d, J ˆ 2.8, 1 H); 8.27 (d, J ˆ 2.8, 1 H); 8.18 (br. s, 1 H); 7.24 7.49( m, 9H); 4.42 ( s, 2 H); 1.32 (s, 9 H).
13C-NMR (75 MHz, CDCl3): 180.5; 159.7; 151.1; 148.3; 143.5; 142.0; 140.0; 135.6 (2Â); 129.2; 128.9; 128.8; 128.7;
‡
‡
128.5; 127.6; 126.9; 125.7; 122.2; 120.4; 40.5; 33.7; 27.0. HR-MALDI-MS (DHB): 489.1595 ( MH , C26H25N4O4S ;
calc. 489.1591).
N-[3,4-Dihydro-6-nitro-4-oxo-8-(phenoxymethyl)quinazolin-2-yl]-2,2-dimethylpropanamide (8h). To a
soln. of PhOH (610 mg, 6.5 mmol) in abs. THF (15 ml), NaH (60% in oil, 260 mg, 6.5 mmol) was added at
08, and the mixture was stirred for 15 min. Subsequently, 7 (1.0 g, 2.6 mmol) in abs. THF (7 ml) was added, and
the mixture was stirred for 4 h at r.t. After removal of the solvent in vacuo, the residue was taken up in H2O/
CH2Cl2 and extracted with CH2Cl2 (3Â). The combined org. phases were washed with sat. aq. NaCl soln., dried
(MgSO4), and evaporated in vacuo. CC (SiO2; CH2Cl2, then CH2Cl2/AcOEt 95 :5) provided 8h (500 mg, 52%).
White solid. M.p. 205 2068 (CH2Cl2/hexane). IR (CHCl3): 3425w, 3200w, 3015w, 1689s, 1625s, 1591s, 1533m,
1497m, 1411w, 1341s. 1H-NMR (300 MHz, CDCl3): 12.18 (br. s, 1 H); 9 .03 (d, J ˆ 2.7, 1 H); 8.72 (d, J ˆ 2.7, 1 H);
8.16 (br. s, 1 H); 7.30 7.36 (m, 2 H); 6.83 7.18 (m, 3 H); 5.38 (s, 2 H); 1.39 (s, 9 H). 13C-NMR (75 MHz,
CDCl3): 178.4; 157.4; 155.9; 148.0; 146.1; 142.0; 132.8; 127.3; 124.6; 120.1; 119.2; 117.9; 112.5; 62.5; 38.1; 24.5.
‡
‡
HR-MALDI-MS (DHB): 397.1503 (MH , C20H21N4O5 ; calc. 397.1512). Anal. calc. for C20H20N4O5 (396.40):
C 60.60, H 5.09, N 14.13; found: C 60.68, H 5.22, N 14.17.
N-{6-Amino-3,4-dihydro-4-oxo-8-[(propylsulfanyl)methyl]quinazolin-2-yl}-2,2-dimethylpropanamide
(9a). GP C with 8a (140 mg, 0.37 mmol), SnCl2 ¥ 2 H2O (333 mg, 1.48 mmol) in EtOH (25 ml). CC (SiO2;
CH2Cl2/MeOH/Et3N 98 :1 :1) provided 9a (65 mg, 50%). Yellow solid. M.p. 201 2038. IR (CHCl3): 3436w,
3231w, 2954m, 2913m, 2851w, 1667s, 1631s, 1451m, 1364w. 1H-NMR (200 MHz, CDCl3): 11.88 (br. s, 1 H); 8.09
(br. s, 1 H); 7.38 (d, J ˆ 2.6, 1 H); 7.10 (d, J ˆ 2.6, 1 H); 3.97 (s, 2 H); 3.92 (br. s, 2 H); 2.49( t, J ˆ 7.2, 2 H); 1.56
1.74 (m, 2 H); 1.35 (s, 9H); 0.99( t, J ˆ 7.3, 3 H). 13C-NMR (75 MHz, CDCl3): 180.2; 161.3; 144.1; 143.3; 139.4;
‡
136.2; 124.0; 122.0; 109.1; 40.2; 34.1; 30.9; 27.2; 22.8; 13.6. HR-MALDI-MS (DHB): 349.1690 (MH ,
‡
C17H25N4O2S ; calc. 349.1698).
N-{6-Amino-8-[(cyclohexylsulfanyl)methyl]-3,4-dihydro-4-oxoquinazolin-2-yl}-2,2-dimethylpropanamide
(9b). GP C with 8b (0.65 g, 1.55 mmol), SnCl2 ¥ 2 H2O (1.40 g, 6.2 mmol) in EtOH (25 ml). CC (SiO2; CH2Cl2/
MeOH 99 :1) provided 9b (150 mg, 27%). Yellow solid. M.p. 1798 (CH2Cl2/hexane). IR (CHCl3): 3436w, 3231w,
2944m, 2851w, 1669s, 1634s, 1450m. 1H-NMR (300 MHz, CDCl3): 11.85 (br. s, 1 H); 8.07 (br. s, 1 H); 7.35 (d, J ˆ
2.7, 1 H); 7.11 (d, J ˆ 2.7, 1 H); 3.98 (s, 2 H); 3.89( s, 2 H); 2.59 2.71 ( m, 1 H); 1.93 2.06 (m, 2 H); 1.50 1.82
(m, 2 H); 1.55 1.65 (m, 1 H); 1.33 (s, 9H); 1.19 1.42 ( m, 5 H). 13C-NMR (50 MHz, CDCl3): 177.5; 158.7; 141.6;
140.6; 137.8; 134.1; 121.4; 119.4; 106.5; 41.1; 37.7; 31.0; 26.7; 24.7; 23.6; 23.4. HR-MALDI-MS (DHB): 389.2007
‡
‡
(MH , C20H29N4O2S ; calc. 389.2011).
N-{6-Amino-3,4-dihydro-4-oxo-8-[(phenylsulfanyl)methyl]quinazolin-2-yl}-2,2-dimethylpropanamide
(9c). GP C with 8c (0.70 mg, 1.7 mmol), SnCl2 ¥ 2 H2O (1.53 g, 6.8 mmol) in EtOH (25 ml). CC (SiO2; CH2Cl2/
MeOH 99 :1) provided 9c (330 mg, 51%). Yellow solid. M.p. 234 2358 (CH2Cl2/hexane). IR (CHCl3): 3260w,
1
3010s, 2976m, 1667s, 1633s, 1552m, 1478m, 1420m, 1230s. H-NMR (300 MHz, CDCl3): 11.92 (s, 1 H); 7.9 8 (s,
1 H); 7.35 (d, J ˆ 2.8, 1 H); 7.16 7.35 (m, 5 H); 6.95 (d, J ˆ 2.8, 1 H); 4.37 (s, 2 H); 3.79( s, 2 H); 1.33 (s, 9 H).

Helvetica Chimica Acta Vol. 87 (2004)
1349
13C-NMR (50 MHz, CDCl3): 177.6; 158.6; 141.4; 140.8; 136.8; 134.4; 132.1; 127.5; 126.5; 124.0; 121.4; 119.4;
‡
‡
106.7; 37.7; 31.2; 24.7. HR-MALDI-MS (DHB): 383.1538 (MH , C20H23N4O2S ; calc. 383.1542).
N-[6-Amino-8-({[2-(dimethylamino)ethyl]sulfanyl}methyl)-3,4-dihydro-4-oxoquinazolin-2-yl]-2,2-di-
methylpropanamide (9d). GP D with 8d (600 mg, 1.45 mmol), Zn powder (958 mg, 14.7 mmol) in AcOH
(35 ml) and H2O (5 ml). CC (SiO2; CH2Cl2/MeOH/NH3 79:20 :1) provided 9d (372 mg, 67%). Yellow solid.
M.p. 168 1708. IR (KBr): 3682w, 3436w, 3220w, 1669s, 1633s, 1472m, 1456m, 1364w. 1H-NMR (200 MHz,
CDCl3): 11.65 (br. s, 1 H); 8.19(br. s, 1 H); 7.35 (d, J ˆ 2.7, 1 H); 7.08 (d, J ˆ 2.7, 1 H); 3.97 (s, 2 H); 3.88 (s, 2 H);
2.48 2.66 (m, 4 H); 2.23 (s, 6 H); 1.33 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 179.7; 160.7; 143.7; 142.8; 138.9;
‡
135.8; 123.6; 121.7; 108.8; 59.0; 45.4; 40.2; 31.0; 29.8; 27.1. HR-MALDI-MS (DHB): 378.1971 (MH ,
‡
C18H28N5O2S ; calc. 378.1964).
N-{6-Amino-3,4-dihydro-8-{[(1H-imidazol-2-yl)sulfanyl]methyl}-4-oxoquinazolin-2-yl}-2,2-dimethylpro-
panamide (9e). GP C with 8e (0.52 g, 1.23 mmol), SnCl2 ¥ 2 H2O (1.02 g, 5.17 mmol) in EtOH (25 ml). CC (SiO2;
CH2Cl2/MeOH 95 :5) provided 9e (120 mg, 25%). Yellow solid. M.p. 207 2108 (CH2Cl2/hexane). IR (KBr):
3433w, 3178w, 2968m, 1678s, 1625s, 1600s, 1578s, 1527m, 1491m, 1339s, 1244m, 1142s. 1H-NMR (200 MHz,
(CD3)2SO): 12.15 (br. s, 1 H); 12.01 (br. s, 1 H); 10.58 (br. s, 1 H); 7.11 (s, 1 H); 7.06 (d, J ˆ 2.6, 1 H); 6.94 (d, J ˆ
2.6, 1 H); 6.93 (s, 1 H); 5.41 (s, 2 H); 4.50 (s, 2 H); 1.23 (s, 9 H). 13C-NMR (75 MHz, (CD3)2SO): 180.9; 160.2;
145.9; 142.8; 139.0; 137.0; 134.1; 129.1; 122.7; 121.0; 118.2; 106.4; 39.7; 32.6; 26.4. HR-MALDI-MS (DHB):
‡
‡
373.1434 (MH , C17H21N6O2S ; calc. 373.1447).
N-(6-Amino-8-{[(3-bromophenyl)sulfanyl]methyl}-3,4-dihydro-4-oxoquinazolin-2-yl)-2,2-dimethylpropan-
amide (9f). GP D with 8f (0.25 g, 0.65 mmol), Zn powder (0.42 g, 6.5 mmol) in AcOH (20 ml) and H2O (10 ml).
CC (SiO2; CH2Cl2/MeOH 99 :1) provided 9f (160 mg, 53%). Yellow solid. M.p. 196 1968. IR (CHCl3): 3684w,
3240w, 3023w, 1669s, 1633s, 1573w, 1499w, 1476m, 1458m. 1H-NMR (300 MHz, CDCl3): 11.87 (br. s, 1 H); 7.96
(br. s, 1 H); 7.54 (dd, J ˆ 1.5, 1.5, 1 H); 7.37 (d, J ˆ 2.7, 1 H); 7.30 (ddd, J ˆ 7.8, 1.5, 1.5, 1 H); 7.19( ddd, J ˆ 7.8, 1.5,
1.5, 1 H); 7.11 (t, J ˆ 7.8, 1 H); 7.04 (d, J ˆ 2.7, 1 H); 4.40 (s, 2 H); 3.84 (br. s, 2 H); 1.36 (s, 9 H). 13C-NMR
(50 MHz, CDCl3): 179.6; 160.6; 143.7; 143.0; 139.0; 138.9; 133.7; 131.4; 129.9; 128.9; 127.5; 123.7; 122.5; 121.7;
‡
‡
109.3; 40.2; 33.0; 27.2. HR-MALDI-MS (DHB): 461.0640 (MH , C20H22BrN4O2S ; calc. 461.0647).
N-{6-Amino-8-{[([1,1'-biphenyl]-3-yl)sulfanyl]methyl}-3,4-dihydro-4-oxoquinazolin-2-yl}-2,2-dimethyl-
propanamide (9g). GP D with 8g (500 mg, 1.0 mmol), Zn powder (650 mg, 10.0 mmol) in AcOH (10 ml) and
H2O (30 ml). CC (SiO2; CH2Cl2/MeOH 99 :1) provided 9g (220 mg, 50%). Yellow solid. M.p. > 1058 (dec.). IR
(KBr): 3201m, 2360s, 1700m, 1684m, 1653s, 1635s, 1560m, 1473s, 1457s, 1399m, 1363w, 1256w, 1153m. 1H-NMR
(300 MHz, CDCl3): 11.91 (br. s, 1 H); 8.39(br. s, 1 H); 7.17 7.44 (m, 10 H); 7.01 (d, J ˆ 2.7, 1 H); 4.34 (s, 2 H);
4.01 (br. s, 2 H); 1.22 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 179.9; 160.8; 143.9; 143.2; 141.6; 140.3; 139.0; 137.3;
134.1; 129.1; 128.7; 127.5; 127.4; 127.2; 126.9; 124.7; 124.0; 121.6; 109.2; 40.2; 33.1; 27.1. HR-MALDI-MS (DHB):
‡
‡
459.1849 (MH , C26H27N4O2S ; calc. 459.1852). Anal. calc. for C26H26N4O2S ¥ 2 MeOH (522.66): C 64.34, H 6.56,
N 10.72; found: C 64.35, H 6.25, N 10.64.
N-[6-Amino-3,4-dihydro-4-oxo-8-(phenoxymethyl)quinazolin-2-yl]-2,2-dimethylpropanamide (9h). GP D
with 8h (500 mg, 1.26 mmol), Zn powder (817 mg, 12.60 mmol) in AcOH (75 ml) and H2O (15 ml). CC (SiO2;
CH2Cl2/AcOEt 8 :2) provided 9h (340 mg, 74%). Yellow foam. IR (CHCl3): 3245w, 3231w, 2927m, 2851w, 1672s,
1633s, 1595m, 1454m. 1H-NMR (200 MHz, CDCl3): 11.88 (br. s, 1 H); 7.98 (br. s, 1 H); 6.95 7.41 (m, 7 H); 5.35
(s, 2 H); 3.90 (br. s, 2 H); 1.35 (s, 9 H). 13C-NMR (50 MHz, CDCl3): 177.6; 158.5; 156.5; 141.8; 140.8; 136.0;
‡
131.6; 127.2; 119.7; 119.2; 118.7; 112.6; 106.7; 63.1; 37.4; 24.7. HR-MALDI-MS (DHB): 367.1764 (MH ,
‡
C20H23N4O3 ; calc. 367.1770).
2,6-Diamino-8-[(propylsulfanyl)methyl]quinazolin-4(3H)-one (1a). GP E with 9a (206 mg, 0.59mmol),
ethanolic HCl soln. (11 ml): 1a (132 mg, 84%). Yellow solid. M.p. 3008 (dec.). IR (KBr): 3418m, 3328s, 3199m,
3056w, 2922w, 1680s, 1632s, 1480s, 1437m, 1346s. 1H-NMR (300 MHz, (CD3)2SO): 10.66 (s, 1 H); 6.96 (d, J ˆ 2.7,
1 H); 6.92 (d, J ˆ 2.7, 1 H); 5.86 (s, 2 H); 4.98 (s, 2 H); 3.84 (s, 2 H); 2.39( t, J ˆ 7.2, 2 H); 1.47 1.59( m, 2 H); 0.88
(t, J ˆ 7.3, 3 H). 13C-NMR (75 MHz, (CD3)2SO): 162.1; 148.1; 142.9; 140.4; 133.2; 122.9; 117.9; 106.5; 33.0; 29.9;
‡
‡
22.2; 13.3. HR-MALDI-MS (DHB): 265.1117 (MH , C12H17N4OS ; calc. 265.1112).
2,6-Diamino-8-[(cyclohexylsulfanyl)methyl]quinazolin-4(3H)-one (1b). GP
E
with 9b (105 mg,
0.27 mmol), ethanolic HCl soln. (11 ml): 1b (54 mg, 66%). Yellow solid. M.p. 2838 (dec.). IR (KBr): 3411w,
3328m, 3189w, 2925m, 2844w, 1680m, 1633s, 1600s, 1480m, 1443m, 1343m. 1H-NMR (300 MHz, (CD3)2SO):
10.68 (br. s, 1 H); 6.96 (d, J ˆ 2.7, 1 H); 6.95 (d, J ˆ 2.7, 1 H); 5.88 (br. s, 2 H); 5.02 (br. s, 2 H); 3.90 (s, 2 H);
2.55 2.68 (m, 1 H); 1.85 2.00 (m, 2 H); 1.59 1.77 ( m, 2 H); 1.48 1.58 (m, 1 H); 1.32 1.40 (m, 5 H).
13C-NMR (125 MHz, (CD3)2SO): 162.1; 148.0; 143.0; 140.4; 133.6; 122.9; 117.9; 106.5; 42.6; 33.2; 28.4; 25.4; 25.4.
‡
‡
HR-MALDI-MS (DHB): 305.1433 (MH , C15H21N4OS ; calc. 305.1436).

1350
Helvetica Chimica Acta Vol. 87 (2004)
2,6-Diamino-8-[(phenylsulfanyl)methyl]quinazolin-4(3H)-one (1c). GP E with 9c (210 mg, 0.55 mmol),
ethanolic HCl soln. (11 ml): 1c (82 mg, 50%). Yellow solid. M.p. 3038 (dec.). IR (KBr): 3329m, 3156m, 2955w,
1
1672m, 1635s, 1561m, 1480s, 1441m, 1358m. H-NMR (300 MHz, (CD3)2SO): 11.00 (br. s, 1 H); 7.13 7.33 (m,
5 H); 6.99 (s, 2 H); 6.10 (s, 2 H); 4.99 (s, 2 H); 4.40 (s, 2 H). 13C-NMR (75 MHz, (CD3)2SO): 163.0; 149.3; 143.0;
‡
140.7; 137.7; 131.1; 129.1; 127.4; 125.4; 123.0; 118.3; 107.3; 31.5. HR-MALDI-MS (DHB): 299.0964 (MH ,
‡
C15H15N4OS ; calc. 299.0967).
2,6-Diamino-8-({[2-(dimethylamino)ethyl]sulfanyl}methyl)quinazolin-4(3H)-one (1d). Compound 9d
(206 mg, 0.59mmol) was dissolved in ethanolic HCl soln. (11 ml) and heated to 70 8 for 3 h. The pH of the
mixture was adjusted to 8 with 1n NaOH and sat. aq. Na2CO2 soln., and the solvent was removed in vacuo. The
¾
‡
residue was dissolved in 1n HCl and loaded onto a column of Dowex 50 Wx4, (NH4 , 1 cm  25 cm). Washing
with H2O (500 ml) and MeOH (200 ml), and elution with H2O with an added gradient of conc. aq. NH4OH (1
5%; 100-ml fractions), followed by removal of the solvent in vacuo, provided 1d (75 mg, 40%). Beige solid. M.p.
> 2508 (dec.). IR (KBr): 3410m, 3323s, 3198m, 2922w, 1678m, 1630s, 1610s, 1480m, 1344m. 1H-NMR (300 MHz,
(CD3)2SO): 10.70 (br. s, 1 H); 6.9 8 (d, J ˆ 2.4, 1 H); 6.95 (s, J ˆ 2.4, 1 H); 5.90 (s, 2 H); 5.03 (s, 2 H); 3.88 (s, 2 H);
2.34 2.53 (m, 4 H); 2.08 (s, 6 H). 13C-NMR (50 MHz, (CD3)2SO): 162.1; 148.1; 142.9; 140.4; 133.2; 122.9; 118.0;
‡
‡
106.7; 59.0; 44.9; 30.1; 28.8. HR-MALDI-MS (DHB): 294.1395 (MH , C13H20N5OS ; calc. 294.1389).
2,6-Diamino-8-{[(1H-imidazol-2-yl)sulfanyl]methyl}quinazolin-4(3H)-one (1e). GP E with 9e (80 mg,
0.21 mmol), ethanolic HCl soln. (5.5 ml): 1e (39mg, 63%). Yellow-beige solid. M.p. 266 8 (dec.). IR (KBr):
3300w, 3136s, 1689m, 1651s, 1611s, 1572m, 1483s, 1439m, 1361m, 1328m. 1H-NMR (200 MHz, (CD3)2SO): 10.74
(br. s, 1 H); 7.01 (s, 2 H); 6.97 (d, J ˆ 3.0, 1 H); 6.81 (d, J ˆ 3.0, 1 H); 5.99 (s, 2 H); 4.96 (s, 2 H); 4.37 (s, 2 H).
13C-NMR (125 MHz, (CD3)2SO): 162.1; 148.5; 142.9; 140.3; 139.6; 131.9; 128.5; 122.9; 118.1; 107.1; 32.9. HR-
‡
‡
MALDI-MS (DHB): 289.0866 (MH , C12H12N6OS ; calc. 289.0872).
2,6-Diamino-8-{[(3-bromophenyl)sulfanyl]methyl}quinazolin-4(3H)-one (1f). GP E with 9f (120 mg,
0.26 mmol), ethanolic HCl soln. (1m; 11 ml). Precipitation from Me2SO/H2O provided 1f (54 mg, 55%). White
solid. M.p. > 2508 (dec.). IR (KBr): 3415m, 3330m, 3201m, 2926w, 1680m, 1632s, 1599s, 1480m, 1343m.
1H-NMR (300 MHz, (CD3)2SO): 10.72 (br. s, 1 H); 7.50 (s, 1 H); 7.19 7.32 ( m, 3 H); 7.00 (s, 2 H); 5.9 7 (s, 2 H);
5.04 (s, 2 H); 4.42 (s, 2 H). 13C-NMR (50 MHz, CDCl3): 162.7; 149.1; 143.8 (2Â); 141.1; 131.5; 131.4; 129.4;
‡
‡
128.5; 126.5; 123.6; 122.8; 118.8; 108.0; 31.6. HR-MALDI-MS (DHB): 377.0073 (MH , C15H14BrN4OS ; calc.
377.0072).
2,6-Diamino-8-{[([1,1'-biphenyl]-3-yl)sulfanyl]methyl}quinazolin-4(3H)-one (1g). GP E with 9g (200 mg,
2.0 mmol), ethanolic HCl soln. (15 ml EtOH, 2 ml conc. HCl): 1g (150 mg, 94%). Yellow solid. M.p. > 2408
(dec.). IR (KBr) 3317s, 3167s, 1700m, 1675s, 1653s, 1635s, 1560s, 1507m, 1476m, 1448m, 1399m, 1363m. 1H-NMR
(300 MHz, (CD3)2SO): 7.28 7.58 (m, 9H); 7.11 ( s, 1 H); 7.06 (s, 1 H); 6.32 (br. s, 2 H); 4.50 (s, 2 H). 13C-NMR
(75 MHz, (CD3)2SO): 161.6; 148.9; 142.5; 140.7; 140.7; 139.4; 137.6; 130.4; 129.3; 128.8; 127.5; 126.6; 126.3;
‡
‡
125.0; 123.6; 123.1; 117.8; 108.0; 30.9. HR-MALDI-MS (DHB): 375.1277 (MH , C21H19N4OS ; calc. 375.1274).
2,6-Diamino-8-(phenoxymethyl)quinazolin-4(3H)-one (1h). GP E with 9h (120 mg, 0.33 mmol), ethanolic
HCl soln. (11 ml): 1h (67 mg, 72%). Yellow solid. M.p. > 3008 (dec.). IR (KBr): 3444m, 3333m, 3168m, 1648s,
1
1594m, 1487m, 1439m, 1223m. H-NMR (300 MHz, (CD3)2SO): 10.76 (br. s, 1 H); 7.28 (dd, J ˆ 8.4, 6.9, 2 H);
7.05 (m, 2 H); 6.96 (d, J ˆ 8.4, 2 H); 6.91 (t, J ˆ 6.9, 1 H); 6.00 (br. s, 2 H); 5.25 (s, 2 H); 5.01 (br. s, 2 H).
13C-NMR (50 MHz, (CD3)2SO): 160.4; 157.0; 146.9; 141.6; 138.3; 129.4; 127.9; 119.9; 118.8; 116.3; 112.9; 105.5;
‡
‡
63.4. HR-MALDI-MS (DHB): 283.1190 (MH , C15H15N4O2 ; calc. 283.1195).
Methyl 2-Amino-3-bromo-5-nitrobenzoate (10). Br2 (0.26 ml, 5.1 mmol) was added slowly at r.t. to a soln. of
methyl 2-amino-5-nitrobenzoate (1.0 g, 5.1 mmol) [34] in AcOH (120 ml). After stirring at r.t. for 4 h, H2O was
added, and the suspension was filtered. The residue was washed with H2O and dried under h.v. to yield 10 (1.29g,
92%). Golden-yellow platelets. M.p. 200 2028 (CH2Cl2/hexane). IR (CHCl3): 3483m, 3348m, 3020w, 2955w,
1701s, 1610s, 1550m, 1514m, 1333s, 1276s, 1226s. 1H-NMR (200 MHz, (CD3)2SO): 8.62 (d, J ˆ 2.6, 1 H); 8.48 (d,
J ˆ 2.6, 1 H); 7.84 (br. s, 2 H); 3.92 (s, 3 H). 13C-NMR (75 MHz, (CD3)2SO): 166.3; 152.3; 135.5; 131.9; 127.2;
‡
109.0; 52.7; signal of C(1) not visible or masked. ESI-MS: 275.1 (100, M ). Anal. calc. for C8H7BrN2O4 (275.06):
C 34.93, H 2.57, N 10.18, O 23.27, Br 29.05; found: C 35.13, H 2.70, N 10.07, O 23.14, Br 29.21.
2-Amino-8-bromo-6-nitroquinazolin-4(3H)-one (11). To
a soln of guanidinium chloride (17.36 g,
181.8 mmol) in EtOH (200 ml), EtONa (12.37 g, 181.8 mmol) and 10 (10.00 g, 36.4 mmol) were added, and
the yellow suspension was heated to reflux for 60 h. After evaporation in vacuo, H2O was added, and the mixture
was acidified (pH 5) with AcOH. The solid formed was isolated by filtration and recrystallized from DMF/H2O
to give 11 (6.68 g, 63%). Yellow solid. M.p. > 3008 (DMF/H2O). IR (KBr): 3401s, 3143s, 1700s, 1656s, 1589s,
1
1337s. H-NMR (300 MHz, (CD3)2SO): 11.57 (s, 1 H); 8.55 (d, J ˆ 2.8, 1 H); 8.53 (d, J ˆ 2.8, 1 H); 7.26 (br. s,

Helvetica Chimica Acta Vol. 87 (2004)
1351
‡
2 H). 13C-NMR (75 MHz, (CD3)2SO): 161.1; 154.7; 154.4; 140.1; 131.2; 122.0; 118.6; 117.0. EI-MS: 284.0 (M ).
Anal. calc. for C8H5BrN4O3 (283.97): C 33.71, H 1.77, N 19.65; found: C 33.98, H 1.99, N 19.54.
N-(8-Bromo-3,4-dihydro-6-nitro-4-oxoquinazolin-2-yl)-2,2-dimethylpropanamide (12). To a suspension of
11 (2.0 g, 7.0 mmol) in DMA (50 ml), pyridine (1.13 ml, 14.0 mmol) and pivaloyl chloride (1.73 ml, 14.0 mmol)
were added, and the mixture was stirred for 1 h at r.t., then for 8 h at 1108. The mixture was poured into H2O
(400 ml), and the formed precipitate was isolated by filtration, and washed with H2O and a small amount of
EtOH. CC (SiO2; CH2Cl2/MeOH 99 :1) gave 12 (1.83 g, 71%). Colorless solid. M.p. 237 2388. IR (CHCl3):
3180w, 3036w, 1691s, 1623s, 1604s, 1529m, 1433m, 1342s. 1H-NMR (200 MHz, CDCl3): 12.37 (br. s, 1 H); 9.05 (d,
J ˆ 2.6, 1 H); 8.79( d, J ˆ 2.6, 1 H); 8.62 (br. s, 1 H); 1.40 (s, 9 H). 13C-NMR (125 MHz, (CD3)2SO): 181.6; 159.6;
‡
151.4; 150.1; 144.1; 132.5; 122.9; 121.5; 121.0; 40.8; 26.9. HR-MALDI-MS (DHB): 369.0185 (MH ,
‡
C13H14BrN4O4 ; calc. 369.0198). Anal. calc. for C13H13BrN4O4 (369.17): C 42.30, H 3.55, N 15.18; found:
C 42.10, H 3.50, N 15.21.
N-[3,4-Dihydro-6-nitro-4-oxo-8-(phenylethinyl)quinazolin-2-yl]-2,2-dimethylpropanamide (13). To a mix-
ture of 12 (250 mg, 0.68 mmol), [Pd(OAc)2] (19mg, 0.08 mmol), P( o-tol)3 (43 mg, 0.14 mmol), CuI (16 mg,
0.08 mmol), and Et3N (0.95 ml) in MeCN (10 ml), phenylacetylene (83 ml, 0.76 mmol) was added. The mixture
turned black and was heated to reflux for 15 h. After evaporation in vacuo, CC (SiO2; hexane/AcOEt 9:1, then
SiO2; CH2Cl2) afforded 13 (60 mg, 23%). Yellow solid. M.p. 203 2058. IR (CHCl3): 3155w, 2253s, 1724m,
1625m, 1593s, 1476m, 1337s. 1H-NMR (300 MHz, CDCl3): 12.63 (br. s, 1 H); 8.90 (d, J ˆ 2.0, 1 H); 8.79( d, J ˆ
2.0, 1 H); 7.47 7.59( m, 5 H); 6.89( s, 1 H); 0.81 (s, 9 H). 13C-NMR (125 MHz, CDCl3): 194.2; 158.3; 147.6;
145.7; 144.5; 139.3; 131.4; 129.6; 129.2; 128.2; 128.1; 122.3; 118.4; 113.7; 111.3; 42.4; 26.4. HR-MALDI-MS
‡
‡
(DHB): 413.1224 ([M ‡ Na] , C21H18N4O4Na ; calc. 413.1226).
N-[6-Amino-3,4-dihydro-4-oxo-8-(2-phenylethyl)quinazolin-2-yl]-2,2-dimethylpropanamide (14). To
a
soln. of 13 (670 mg, 1.716 mmol) in AcOEt/MeOH (90 ml, 1:2), Pd/C (10%, 600 mg) was added, and
hydrogenation was performed for 3 h under H2 (760 Torr) at r.t. Filtration over Celite and washing the plug with
MeOH provided a soln. that was evaporated in vacuo. CC (SiO2; CH2Cl2/MeOH 99 :1) and recrystallization
(CHCl3/hexane) gave 14 (320 mg, 51%). Yellowish solid. M.p. 170 1728. IR (KBr): 3367m, 3220m, 2970w,
1634s, 1475m, 1349w, 1254w, 1164m. 1H-NMR (200 MHz, CDCl3): 11.85 (br. s, 1 H); 8.03 (br. s, 1 H); 7.34 (d, J ˆ
2.6, 1 H); 7.16 7.33 (m, 5 H); 6.87 (d, J ˆ 2.6, 1 H); 3.87 (br. s, 2 H); 3.15, 2.94 (AA'BB', J ˆ 10.6, 8.6, 4 H); 1.35
(s, 9 H). 13C-NMR (50 MHz, CDCl3): 180.1; 161.5; 144.1; 142.9; 142.3; 139.6; 139.4; 128.7; 128.5; 126.2; 123.8;
‡
‡
121.8; 108.0; 40.2; 36.7; 32.6; 27.2. HR-MALDI-MS (DHB): 365.1979 (MH , C21H25N4O2 ; calc. 365.1978).
2,6-Diamino-8-(2-phenylethyl)quinazolin-4(3H)-one (1i). GP E with 14 (280 mg, 0.77 mmol), ethanolic
HCl soln. (1m; 22 ml): 1i (170 mg, 79%). Yellow solid. M.p. 3028 (Me2SO/H2O; dec.). IR (KBr): 3414m, 3327s,
3198m, 3068w, 2922w, 1679m, 1633s, 1600s, 1480m, 1445m, 1344m. 1H-NMR (300 MHz, (CD3)2SO): 10.6 (br. s,
1 H); 7.14 7.32 (m, 5 H); 6.9 4 (d, J ˆ 2.0, 1 H); 6.82 (d, J ˆ 2.0, 1 H); 5.90 (s, 2 H); 4.97 (br. s, 2 H); 2.80 3.02
(m, 4 H). 13C-NMR (50 MHz, (CD3)2SO): 162.8; 148.4; 143.2; 142.4; 140.8; 136.3; 128.5; 128.4; 125.8; 122.8;
‡
‡
‡
118.1; 105.8; 35.8; 32.8. ESI-MS: 281.3 (100, M ). HR-MALDI-MS (DHB): 281.1399 (MH , C16H17N4O ; calc.
281.1402).
N-(3,4-Dihydro-8-methyl-4-oxoquinazolin-2-yl)-2,2-dimethylpropanamide (16). To a suspension of
4
(663 mg, 3.79mmol) in DMA (15 ml), Et 3N (1.19ml, 8.53 mmol) was added at r.t., and the resulting soln.
was heated to 1108. Pivaloyl chloride (1.16 ml, 9.47 mmol) was added, and the mixture heated for 3 h at 1108.
After cooling to r.t., H2O (500 ml) was added, and the precipitate formed was isolated by filtration. The residue
was washed with H2O, taken up in sat. aq. NaHCO3/CH2Cl2, and extracted with CH2Cl2 (3Â). The combined
org. layers were dried (MgSO4) and evaporated in vacuo. Recrystallization (hexane/CH2Cl2) provided 16
(430 mg, 44%). Colorless solid. M.p. 183 1848. IR (neat): 3189w, 2973w, 1659s, 1627s, 1576m, 1296m, 1457s,
1231s, 1148s. 1H-NMR (300 MHz, CDCl3): 11.93 (br. s, 1 H); 8.28 (br. s, 1 H); 8.06 (d, J ˆ 7.8, 1 H); 7.64 (t, J ˆ
7.8, 1 H); 7.52 (d, J ˆ 7.8, 1 H); 2.47 (s, 3 H); 1.35 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 179.9; 161.2; 146.9; 145.1;
‡
‡
135.2; 134.1; 124.7; 124.5; 120.2; 40.3; 27.2; 17.7. HR-MALDI-MS (DHB): 260.1390 (MH , C14H18N3O2 ; calc.
260.1399).
N-{3,4-Dihydro-4-oxo-8-[(phenylsulfanyl)methyl]quinazolin-2-yl}-2,2-dimethylpropanamide (17). To a
suspension of 16 (400 mg, 1.54 mmol) and NBS (288 mg, 1.62 mmol) in CCl4 (20 ml), a cat. amount of AIBN
was added, and the mixture was heated to reflux for 18 h. After removal of the solvent in vacuo, the residue was
washed with hot H2O (300 ml) and taken up in CH2Cl2. Drying (MgSO4) and evaporation in vacuo left a crude
product that was used without further purification in the next step. GP B with BuLi (1.6m in hexane; 2.77 ml) in
abs. THF (10 ml), PhSH (0.45 ml, 4.43 mmol), crude benzyl bromide (500 mg) in abs. THF (10 ml). CC (SiO2;
AcOEt/hexane 2 :8) provided 17 (320 mg, 57%). White solid. M.p. 1568. IR (neat): 3157w, 2974w, 1649s, 1633s,
1603s, 1576m, 1497m, 1453s, 1236s, 1156s. 1H-NMR (300 MHz, CDCl3): 11.94 (br. s, 1 H); 8.13 (dd, J ˆ 7.8, 1.5,

1352
Helvetica Chimica Acta Vol. 87 (2004)
1 H); 8.08 (br. s, 1 H); 7.52 (d, J ˆ 7.8, 1.5, 1 H); 7.19 7.34 ( m, 6 H); 4.43 (s, 2 H); 1.36 (s, 9 H). 13C-NMR
(75 MHz, CDCl3): 180.3; 161.3; 146.9; 145.9; 136.7; 135.3; 133.5; 130.3; 129.0; 126.7; 126.4; 125.0; 121.0; 40.5;
‡
‡
34.2; 27.3. HR-MALDI-MS (DHB): 368.1424 (MH , C20H22N3O2S ; calc. 368.1433).
2-Amino-8-[(phenylsulfanyl)methyl]quinazolin-4(3H)-one (15). GP E with 17 (270 mg, 0.73 mmol),
ethanolic HCl soln. (11 ml): 15 (146 mg, 70%). White solid. M.p. > 2508 (DMF/H2O, dec.). IR (neat) 3052w,
2900w, 1717s, 1698m, 1652s, 1621s, 1568m, 1520s, 1483m, 1438s, 1334m. 1H-NMR (300 MHz, (CD3)2SO): 11.97
(br. s, 1 H); 7.83 (d, J ˆ 7.2, 1 H); 7.51 (d, J ˆ 7.2, 1 H); 7.12 7.36 (m, 7 H); 7.01 (t, J ˆ 7.2, 1 H); 4.46 (s, 2 H).
13C-NMR (75 MHz, (CD3)2SO): 160.6; 151.4; 135.5; 135.1; 129.0 (2Â); 128.7; 127.9; 126.0; 125.5; 122.3; 116.6;
‡
‡
32.3. HR-MALDI-MS (DHB): 284.0853 (MH , C15H14N3OS ; calc. 284.0858). Anal. calc. for C15H13N3OS ¥ H2O
(301.37): C 59.78, H 5.02, N 13.94; found: C 59.76, H 4.90, N 13.85.
Methyl 2-Amino-5-bromo-3-methylbenzoate (18). To a soln. of 3 (10 g, 60 mmol) in AcOH (200 ml), Br2
(3.1 ml, 60 mmol) in AcOH (100 ml) was slowly added at 108. After stirring for 30 min at r.t., the solvent was
evaporated in vacuo. The residue was taken up in sat. aq. Na2CO3 soln. and extracted with CH2Cl2 (3Â). The
combined org. phases were dried (Na2SO4) and evaporated in vacuo. Recrystallization from hexane yielded 18
(13.7 g, 93%). Yellow solid. M.p. 57 588. IR (CHCl3): 3511s, 3380s, 2953m, 1694s, 1609s, 1297s, 1233m, 1203m.
1H-NMR (300 MHz, CDCl3): 7.88 (d, J ˆ 2.4, 1 H); 7.28 (d, J ˆ 2.4, 1 H); 5.83 (br. s, 2 H); 3.86 (s, 3 H); 2.14 (s,
3 H). 13C-NMR (75 MHz, CDCl3): 168.3; 148.3; 137.4; 131.5; 125.5; 111.7; 107.1; 51.9; 17.2. ESI-MS: 245.0 (100,
‡
M ). Anal. calc. for C9H10BrNO2 (244.08): C 44.29, H 4.13, N 5.74; found: C 44.23, H 4.21, N 5.70.
2-Amino-6-bromo-8-methylquinazolin-4(3H)-one (19). GP A with 18 (23.0 g, 94 mmol), chloroformami-
dinium chloride (14.1 g, 122 mmol), and dimethyl sulfone (80 g). Precipitation from Me2SO/H2O yielded 19
(21.5 g, 90%). Yellowish solid. M.p. > 3008. IR (KBr): 3311w, 3155w, 2922m, 2777m, 1682s, 1644s, 1611m,
1544m, 1494m, 1455s, 1338m, 1200m. 1H-NMR (300 MHz, (CD3)2SO): 11.06 (br. s, 1 H); 7.76 (d, J ˆ 2.4, 1); 7.56
(d, J ˆ 2.4, 1 H); 6.44 (br. s, 2 H); 2.31 (s, 3 H). 13C-NMR (75 MHz, (CD3)2SO): 161.5; 151.5; 148.5; 136.4; 134.5;
‡
‡
125.3; 118.2; 112.5; 17.1. HR-MALDI-MS (DHB): 253.9922 (MH , C9H9BrN3O ; calc. 253.9929).
N-(6-Bromo-3,4-dihydro-8-methyl-4-oxoquinazolin-2-yl)-2,2-dimethylpropanamide (20). To a suspension
of 19 (9g, 35.4 mmol) in DMA (250 ml), Et 3N (11.1 ml, 79.7 mmol) was added at r.t., and the resulting soln. was
heated to 1008. Pivaloyl chloride (10.9ml, 88.6 mmol) was added, and the mixture was heated to 100 8 for 3 h.
After cooling to r.t., H2O (500 ml) was added, and the precipitate formed was isolated by filtration, washed with
H2O, and recrystallized from EtOH to yield 20 (9.1 g, 76%). Yellow solid. M.p. 1998. IR (CHCl3): 3431m, 3226w,
2971m, 1677s, 1629s, 1489m, 1435m, 1254m. 1H-NMR (200 MHz, CDCl3): 11.98 (br. s, 1 H); 8.19( d, J ˆ 2.3,
1 H); 8.13 (br. s, 1 H); 7.64 (dd, J ˆ 2.3, 0.8, 1 H); 2.47 (s, 3 H); 1.36 (s, 9 H). 13C-NMR (50 MHz, CDCl3): 178.1;
‡
157.9; 143.8; 143.3; 135.7; 134.4; 124.7; 119.3; 115.8; 37.9; 24.6; 14.9. HR-MALDI-MS (DHB): 338.0501 ( MH ,
‡
C14H17BrN3O2 ; calc. 338.0704).
N-[6-Bromo-3,4-dihydro-8-(bromomethyl)-4-oxoquinazolin-2-yl]-2,2-dimethylpropanamide (21). To a sus-
pension of 20 (4 g, 11.8 mmol) and NBS (2.1 g, 11.8 mmol) in CCl4 (130 ml), a cat. amount of AIBN was added
at 08, and the mixture was heated to reflux for 18 h. After removal of the solvent in vacuo, the residue was
washed with hot H2O to yield crude 21 (3.79g, 76%) that was used without further purification in the next step.
For anal. purposes, a small amount was purified by CC (SiO2; CH2Cl2). Yellow foam. M.p. 187 1888 (THF). IR
(CHCl3): 3429w, 3222w, 2971w, 1679s, 1627s, 1489m, 1436m, 1328w, 1285m, 1252m, 1221w, 1138m. 1H-NMR
(200 MHz, CDCl3): 12.08 (br. s, 1 H); 8.30 (br. s, 1 H); 8.28 (d, J ˆ 2.6, 1 H); 7.84 (d, J ˆ 2.6, 1 H); 4.75 (s, 2 H);
1.36 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 180.7; 159.9; 146.6; 145.8; 139.0; 135.8; 130.3; 122.6; 118.3; 40.5; 34.0;
‡
‡
27.1. HR-MALDI-MS (DHB): 415.9587 (MH , C14H16Br2N3O2 ; calc. 415.9589). Anal. calc. for C14H15Br2N3O2
(417.09): C 40.31, H 3.62, N 10.07; found: C 40.38, H 3.77, N 9.98.
N-[6-Bromo-3,4-dihydro-4-oxo-8-(phenoxymethyl)quinazolin-2-yl]-2,2-dimethylpropanamide (22a). To a
soln. of PhOH (1.13 g, 12.0 mmol) in abs. THF (20 ml), NaH (60% in oil, 0.29g, 12.0 mmol) was added at 0 8, and
the mixture was stirred for 20 min. Compound 21 (1.40 g, 3.36 mmol) in abs. THF (20 ml) was added at 08, and
the mixture was stirred at r.t. for 24 h. After removal of the solvent in vacuo, the residue was taken up in sat. aq.
Na2CO3/CH2Cl2 and extracted with CH2Cl2 (3Â). The combined org. phases were dried (MgSO4) and
evaporated in vacuo. CC (SiO2; CH2Cl2, then CH2Cl2/AcOEt 4 :1) provided 22a (1.15 g, 80%). White solid. M.p.
1858 (CHCl3/hexane). IR (CHCl3): 3245w, 3220w, 3015w, 1679s, 1629s, 1595m, 1496m, 1247w. 1H-NMR
(300 MHz, CDCl3): 12.06 (br. s, 1 H); 8.33 (d, J ˆ 2.4, 1 H); 8.16 (br. s, 1 H); 8.02 (d, J ˆ 2.4, 1 H); 6.98 7.40 (m,
5 H); 5.35 (s, 2 H); 1.38 (s, 9 H). 13C-NMR (50 MHz, CDCl3): 178.0; 157.4; 156.3; 143.8; 142.5; 133.8; 132.2;
‡
127.2; 126.4; 119.4; 118.9; 116.3; 112.6; 62.6; 37.9; 24.6. HR-MALDI-MS (DHB): 430.0765 ( MH ,
‡
C20H21BrN3O3 ; calc. 430.0766). Anal. calc. for C20H20BrN3O3 (430.30): C 55.83, H 4.68, N 9.77; found:
C 55.67, H 5.06, N 9.67.

Helvetica Chimica Acta Vol. 87 (2004)
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N-{6-Bromo-3,4-dihydro-4-oxo-8-[(phenylsulfanyl)methyl]quinazolin-2-yl}-2,2-dimethylpropanamide
(22b). GP B with BuLi (1.6m in hexane; 6.27 ml, 10.0 mmol) in abs. THF (15 ml), PhSH (1.23 ml, 12.0 mmol), 21
(1.67 g, 4.0 mmol) in abs. THF (10 ml). CC (SiO2; AcOEt/hexane 3 :7) provided 22b (1.56 g, 87%). Yellow
solid. M.p. 128 1298. IR (CHCl3): 3430w, 3222w, 3018s, 2400w, 1677s, 1628s, 1482m, 1438s, 1214s, 1139w, 1046m.
1H-NMR (200 MHz, CDCl3): 12.01 (br. s, 1 H); 8.03 (br. s, 1 H); 8.24 (d, J ˆ 2.4, 1 H); 7.54 (d, J ˆ 2.4, 1 H);
7.20 7.34 (m, 5 H); 4.35 (s, 2 H); 1.36 (s, 9 H). 13C-NMR (50 MHz, CDCl3): 178.1; 157.6; 143.7; 143.3; 135.4;
‡
133.5; 130.4; 128.2; 126.6; 126.1; 124.5; 119.7; 115.6; 37.9; 31.2; 24.6. HR-MALDI-MS (DHB): 446.0537 (MH ,
‡
C20H21BrN3O2S ; calc. 446.0517). Anal. calc. for C20H20BrN3O2S (446.36): C 53.82, H 4.52, N 9.41; found:
C 53.80, H 4.80, N 9.49.
2-Amino-6-bromo-8-(phenoxymethyl)quinazolin-4(3H)-one (23a). GP E with 22a (130 mg, 0.38 mmol),
ethanolic HCl soln. (11 ml). Recrystallization from MeOH and drying at 808 provided 23a (70 mg, 67%). White
solid. M.p. > 2508 (dec.). IR (KBr): 3334m, 3155m, 1617s, 1594s, 1551m, 1495s, 1455s, 1239s. 1H-NMR
(300 MHz, (CD3)2SO): 11.18 (br. s, 1 H); 7.89( d, J ˆ 2.6, 1 H); 7.73 (d, J ˆ 2.6, 1 H); 7.28 (d, J ˆ 7.5, 2 H); 6.98 (d,
J ˆ 7.5, 2 H); 6.92 (t, J ˆ 7.5, 1 H); 6.58 (br. s, 2 H); 5.27 (s, 2 H). 13C-NMR (50 MHz, (CD3)2SO): 161.8; 158.1;
152.6; 148.3; 134.5; 133.0; 129.5; 127.2; 120.7; 118.6; 114.5; 112.2; 64.4. HR-MALDI-MS (DHB): 346.0182
‡
‡
(MH , C15H13BrN3O2 ; calc. 346.0191).
2-Amino-6-bromo-8-[(phenylsulfanyl)methyl]quinazolin-4(3H)-one (23b). GP E with 22b (150 mg,
0.33 mmol), ethanolic HCl soln. (10 ml). Recrystallization from MeOH and drying at 808 provided 23b
(70 mg, 60%). Yellowish solid. M.p. 270 2728 (MeOH). IR (CHCl3): 3361w, 3139w, 2918s, 2849m, 1687m,
1649s, 1616m, 1537m, 1513w, 1462m, 1405w, 1338m, 1262w, 1087w, 1020w. 1H-NMR (200 MHz, (CD3)2SO): 11.20
(br. s, 1 H); 7.86 (d, J ˆ 2.7, 1 H); 7.60 (d, J ˆ 2.7, 1 H); 7.20 7.40 (m, 5 H); 6.61 (br. s, 2 H); 4.44 (s, 2 H).
13C-NMR (75 MHz, (CD3)2SO): 160.9; 151.6; 148.6; 136.2; 133.9; 130.9; 129.0; 128.3; 126.8; 125.8; 118.7; 112.1;
‡
‡
31.3. HR-MALDI-MS (DHB): 361.9960 (MH , C15H13BrN3OS ; calc. 361.9963). Anal. calc. for C15H12BrN3O-
S ¥ H2O (380.26): C 47.38, H 3.71, N 11.05; found: C 47.15, H 3.71, N 10.92.
N-[3,4-Dihydro-6-hydroxy-4-oxo-8-(phenoxymethyl)quinazolin-2-yl]-2,2-dimethylpropanamide (25). To
degassed abs. Me2SO (8 ml), 22a (400 mg, 0.93 mmol), [PdCl2(dppf)] (68 mg, 0.09mmol), AcOK (273 mg,
2.70 mmol), and 24 (354 mg, 1.40 mmol) were added, and the mixture was heated to 808 for 18 h. After cooling
to r.t., H2O was added, and the aq. phase was extracted with CH2Cl2 (3Â). The combined org. layers were
washed with H2O (2Â), dried (Na2SO4), filtered over Celite, and evaporated in vacuo. To a soln. of the crude
boronic ester in THF (4 ml), AcOH (0.11 ml, 1.80 mmol) and 15% aq. H2O2 soln. (0.4 ml, 1.80 mmol) were
added with stirring at ca. 108. After 1 and 2 h, respectively, the same amounts of reagents were added again. The
mixture was stirred at r.t. for 6 h, then H2O was added. The aq. phase was extracted with CH2Cl2 (3Â). The
combined org. layers were dried (MgSO4) and evaporated in vacuo. CC (SiO2; AcOEt/hexane 1:1) and
recrystallization from MeOH provided 25 (273 mg, 80%). White solid. M.p. 217 2188. IR (CHCl3): 3425w,
3233w, 2971w, 1669s, 1634s, 1598m, 1498m, 1450m, 1367w, 1262w, 1223s, 1208s, 1143w, 1017m. 1H-NMR
(200 MHz, (CD3)2SO): 12.22 (br. s, 1 H); 10.73 (br. s, 1 H); 9.97 (br. s, 1 H); 7.36 (s, 2 H); 7.32 (d, J ˆ 8.2, 2 H);
7.03 (d, J ˆ 8.2, 2 H); 6.97 (t, J ˆ 7.0, 1 H); 5.46 (s, 2 H); 1.28 (s, 9 H). 13C-NMR (75 MHz, (CD3)2SO): 181.1;
160.0; 158.1; 154.4; 144.5; 139.1; 134.3; 129.5; 122.6; 120.8; 120.6; 114.6; 108.7; 64.5; 39.8; 26.3. HR-MALDI-MS
‡
‡
(DHB): 368.1605 (MH , C20H22N3O4 ; calc. 368.1610). Anal. calc. for C20H21N3O4 ¥ MeOH (399.44): C 63.14,
H 6.31, N 10.52; found: C 63.06, H 6.24, N 10.46.
2-Amino-6-hydroxy-8-(phenoxymethyl)quinazolin-4-(3H)-one (26). GP E with 25 (100 mg, 0.27 mol),
ethanolic HCl soln. (11 ml). Precipitation from DMF provided 26 (30 mg, 40%). Beige solid. M.p. 2788 (dec.).
IR (KBr): 3478s, 3344s, 3144s, 2344w, 1688w, 1644s, 1600s, 1566s, 1494m, 1455m, 1433m, 1366m, 1289w, 1233m,
1189w, 1133m, 1039w. 1H-NMR (300 MHz, (CD3)2SO): 10.86 (br. s, 1 H); 9.37 (br. s, 1 H); 6.84 7.30 (m, 7 H);
6.11 (br. s, 2 H); 5.26 (s, 2 H). 13C-NMR (75 MHz, (CD3)2SO): 161.7; 151.6; 149.4; 146.8; 141.9; 131.9; 129.5;
‡
‡
122.0; 120.3; 117.7; 114.5; 108.5; 64.8. HR-MALDI-MS (DHB): 284.1030 (MH , C15H14N3O3 ; calc. 284.1035).
N-(3,4-Dihydro-6-hydroxy-8-methyl-4-oxoquinazolin-2-yl)-2,2-dimethylpropanamide (28). To 20 (2 g,
5.92 mmol), [PdCl2(dppf)] (433 mg, 0.59mmol), AcOK (1.74 g, 17.7 mmol), and 24 (2.25 g, 8.87 mmol),
degassed abs. Me2SO (40 ml) was added, and the mixture was heated to 808 for 18 h. After cooling to r.t., H2O
was added, and the aq. phase was extracted with CH2Cl2 (3Â). The combined org. layers were washed with H2O
(2Â), dried (Na2SO4), filtered over Celite, and evaporated in vacuo. To a soln. of the crude boronic ester in THF
(20 ml), AcOH (0.7 ml, 12 mmol) and 15% aq. H2O2 soln. (2.4 ml, 12 mmol) were added under stirring at ca.
108. After 1 and 2 h, respectively, the same amounts of AcOH and H2O2 were added. After stirring r.t. for 5 h,
H2O was added and the aq. phase extracted with CH2Cl2 (3Â). The combined org. layers were dried (MgSO4)
and evaporated in vacuo. CC (SiO2; AcOEt/hexane 1 :1) and recrystallization from MeOH provided 28 (1.37 g,
84%). White solid. M.p. 206 2078 (CHCl3/hexane). IR (CHCl3): 3425w, 3232w, 2974w, 1667s, 1633s, 1476m,

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Helvetica Chimica Acta Vol. 87 (2004)
1
1453m, 1364w, 1272w, 1220s. H-NMR (200 MHz, (CD3)2SO): 12.12 (br. s, 1 H); 10.62 (br. s, 1 H); 9.78 (br. s,
1 H); 7.23 (d, J ˆ 3.0, 1 H); 7.13 (d, J ˆ 3.0, 1 H); 2.47 (s, 3 H); 1.28 (s, 9 H). 13C-NMR (50 MHz, (CD3)2SO):
179.4; 158.9; 152.6; 142.1; 138.8; 134.4; 122.9; 119.1; 105.2; 38.59; 24.7; 15.6. HR-MALDI-MS (DHB): 276.1343
‡
‡
(MH , C14H18N3O3 ; calc. 276.1348). Anal. calc. for C14H17N3O3 (275.30): C 61.08, H 6.22, N 15.26; found:
C 60.84, H 6.50, N 15.09.
N-(6-{[(tert-Butyl)dimethylsilyl]oxy}-3,4-dihydro-8-methyl-4-oxoquinazolin-2-yl)-2,2-dimethylpropan-
amide (29). 1H-Imidazole (0.74 g, 10.9mmol), 28 (1 g, 3.63 mmol), and (t-Bu)Me2SiCl (0.67 g, 4.36 mmol) were
dissolved at 08 in DMF (20 ml). After stirring at r.t. for 16 h, (t-Bu)Me2SiCl (0.42 g, 2.73 mmol) was added again,
and the mixture was stirred for 2 h at r.t. The mixture was diluted with H2O and extracted with CH2Cl2 (3Â).
The combined org. layers were washed with sat. aq. NH4Cl and sat. aq. NaCl solns., dried (MgSO4), and
evaporated in vacuo. CC (SiO2; AcOEt/hexane 3 :7) provided 29 (1.38 g, 88%). White solid. M.p. 145 1468
(CHCl3/hexane). IR (CHCl3): 3433w, 3237w, 2960m, 2855w, 1671s, 1633s, 1459m, 1351m, 1260s, 1209w, 1131m,
1
1018s. H-NMR (200 MHz, CDCl3): 11.87 (br. s, 1 H); 8.09(br. s, 1 H); 7.47 (d, J ˆ 2.8, 1 H); 7.08 (d, J ˆ 2.8,
1 H); 2.45 (s, 3 H); 1.36 (s, 9H); 0.99( s, 9H); 0.23 ( s, 6 H). 13C-NMR (50 MHz, CDCl3): 177.7; 170.8; 158.9;
150.5; 141.4; 133.7; 126.8; 118.9; 110.7; 37.8; 24.6; 23.2; 15.7; 15.0; À7.0. HR-MALDI-MS (DHB): 390.2207
‡
‡
(MH , C20H32N3O3Si ; calc. 390.2213).
N-{6-{[(tert-Butyl)dimethylsilyl]oxy}-3,4-dihydro-4-oxo-8-[(phenylsulfanyl)methyl]quinazolin-2-yl}-2,2-
dimethylpropanamide (30). To a suspension of 29 (1.38 g, 3.54 mmol) and NBS (0.63 g, 3.54 mmol) in CCl4
(25 ml), a cat. amount of AIBN was added at 08, and the mixture was heated to reflux overnight. A second
portion of NBS was added (0.12 g, 0.71 mmol), and, after 2 h at reflux temp., the solvent was evaporated in
vacuo. The residue was washed with hot H2O (300 ml) and taken up in CH2Cl2. The soln. was dried (MgSO4)
and evaporated in vacuo, and the crude BrCH2 derivative (1.7 g) was used without further purification in the
next step. GP B with BuLi (1.6m in hexane; 5.54 ml, 8.86 mmol) in abs. THF (15 ml), PhOH (1.09ml,
10.6 mmol), benzyl bromide (1.66 g) in abs. THF (10 ml). CC (SiO2; AcOEt/hexane 2 :8) provided 30 (1.36 g,
77%). White foam. M.p. 160 1628 (hexane). IR (CHCl3): 3432w, 3234w, 2960m, 2844w, 1672s, 1633s, 1447s,
1350m, 1257m, 1143w, 1119m, 1009m. 1H-NMR (200 MHz, CDCl3): 11.89(br. s, 1 H); 8.03 (br. s, 1 H); 7.52 (d,
J ˆ 3.0, 1 H); 7.19 7.53 ( m, 5 H); 7.08 (d, J ˆ 3.0, 1 H); 4.39( s, 2 H); 1.36 (s, 9H); 0.95 ( s, 9H); 0.15 ( s, 6 H).
13C-NMR (50 MHz, CDCl3): 180.2; 161.0; 153.0; 144.3; 141.4, 136.6; 135.2; 130.4; 129.1; 128.8; 127.9; 121.9;
‡
‡
115.0; 40.3; 33.8; 27.2; 25.7; 18.2; À4.5. HR-MALDI-MS (DHB): 498.2241 (MH , C26H36N3O3SSi ; calc.
498.2247). Anal. calc. for C26H35N3O3SSi (497.73): C 62.74, H 7.09, N 8.44; found: C 62.91, H 7.11, N 8.41.
2-Amino-6-hydroxy-8-[(phenylsulfanyl)methyl]quinazolin-4(3H)-one (27). GP
E with 30 (100 mg,
0.2 mmol), ethanolic HCl soln. (11 ml): 27 (40 mg, 80%). Yellow solid. M.p. 2508 (dec.). IR (KBr): 3350s,
3144s, 1646s, 1616s, 1567s, 1505m, 1479m, 1428m, 1361m, 1267w, 1233w, 1194w, 1133m, 1061w. 1H-NMR
(300 MHz, (CD3)2SO): 10.84 (br. s, 1 H); 9.32 (br. s, 1 H); 7.13 7.31 (m, 5 H); 7.11 (d, J ˆ 3.0, 1 H); 7.05 (d, J ˆ
3.0, 1 H); 6.09(br. s, 2 H); 4.39( s, 2 H). 13C-NMR (75 MHz, (CD3)2SO): 162.2; 151.6; 149.6; 142.7; 137.2; 132.5;
‡
‡
129.1; 127.9; 125.6; 123.7; 118.1; 108.7; 31.5. HR-MALDI-MS (DHB): 300.0801 (MH , C15H14N3O2S ; calc.
300.0807).
N-(6-Cyano-3,4-dihydro-8-methyl-4-oxoquinazolin-2-yl)-2,2-dimethylpropanamide (31). A suspension of
20 (6.0 g, 17 mmol) and CuCN (6.36 g, 71 mmol) in degassed abs. DMF (60 ml) was heated to reflux for 20 h.
After removal of the solvent in vacuo, the residue was taken up in CH2Cl2, and the mixture was filtered. The
filtrate was washed with H2O (2Â) and sat. aq. LiCl soln. (1Â). The aq. phases were extracted with CH2Cl2, and
the combined org. phases were dried (MgSO4) and evaporated in vacuo. CC (SiO2; CH2Cl2/AcOEt 95 :5)
provided 31 (2.71 g, 56%). White solid. M.p. 255 2568. IR (CHCl3): 3428w, 3217w, 2973w, 2233m, 1686s, 1628s,
1605s, 1478m, 1441m, 1283m, 1247m, 1220s, 1129m. 1H-NMR (300 MHz, CDCl3): 12.06 (br. s, 1 H); 8.35 (d, J ˆ
1.8, 1 H); 8.13 (br. s, 1 H); 7.68 (d, J ˆ 1.8, 1 H); 2.48 (s, 3 H); 1.36 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 180.2;
159.7; 150.3; 147.2; 136.4; 136.2; 129.7; 120.4; 118.3; 107.8; 40.5; 27.1; 17.6. HR-MALDI-MS (DHB): 285.1348
‡
‡
(MH , C15H17N4O2 ; calc. 285.1346). Anal. calc. for C15H16N4O2 (285.31): C 63.37, H 5.67, N 19.71; found:
C 63.39, H 5.78, N 19.78.
N-{6-Cyano-3,4-dihydro-4-oxo-8-[(phenylsulfanyl)methyl]quinazolin-2-yl}-2,2-dimethylpropanamide
(32). To a suspension of 31 (2.50 g, 8.79mmol) and NBS (1.72 g, 9.67 mmol) in CCl 4 (100 ml), a cat. amount of
AIBN was added, and the mixture was heated to reflux for 6 h. After a second addition of NBS (0.33 g,
1.86 mmol), the mixture was heated to reflux for additional 12 h. After removal of the solvent in vacuo, the
residue was washed with hot H2O (300 ml) and taken up in CH2Cl2. The soln. was dried (MgSO4) and
evaporated in vacuo, and the crude benzyl bromide was used without further purification in the next step. GP B
with BuLi (1.6m in hexane; 6.44 ml, 10.30 mmol) in abs. THF (20 ml), PhSH (1.05 ml, 10.3 mmol), crude benzyl
bromide (2.5 g, 6.87 mmol) in abs. THF (20 ml). CC (SiO2; AcOEt/hexane 3 :7) provided 32 (690 mg, 40%).

Helvetica Chimica Acta Vol. 87 (2004)
1355
Yellowish solid. M.p. 125 1268. IR (CHCl3): 3427w, 3202w, 2980w, 2230m, 1683s, 1628s, 1602s, 1478m, 1444m,
1371w, 1251m, 1218m, 1134m. 1H-NMR (300 MHz, CDCl3): 12.08 (br. s, 1 H); 8.37 (d, J ˆ 1.8, 1 H); 8.08 (br. s,
1 H); 7.52 (d, J ˆ 1.8, 1 H); 7.24 7.26 (m, 5 H); 4.32 (s, 2 H); 1.34 (s, 9 H). 13C-NMR (75 MHz, CDCl3): 180.4;
159.4; 149.7; 147.8; 136.1; 135.4; 135.0; 130.9; 130.6; 128.9; 127.0; 120.8; 117.9; 107.6; 40.5; 33.8; 27.0. HR-
‡
‡
MALDI-MS (DHB): 393.1384 (MH , C21H21N4O2S ; calc. 393.1380).
2-Amino-3,4-dihydro-4-oxo-8-[(phenylsulfanyl)methyl]quinazoline-6-carbonitrile (33). GP E with 32
(800 mg, 2.0 mmol), ethanolic HCl soln. (66 ml): 33 (591 mg, 94%). White solid. M.p. > 2608 (DMF/H2O,
dec.). IR (KBr): 3166s, 2227m, 1889w, 1723s, 1659s, 1613s, 1560s, 1476s, 1437s, 1346s. 1H-NMR (300 MHz,
(CD3)2SO): 8.13 (d, J ˆ 2.4, 1 H); 7.69( d, J ˆ 2.4, 1 H); 7.19 7.34 ( m, 5 H); 4.41 (s, 2 H); 4.16 (br. s, 2 H).
13C-NMR (75 MHz, (CD3)2SO): 159.9; 153.0; 136.2; 135.1; 131.0; 130.4; 129.5; 128.9; 126.4; 126.4; 118.3; 117.3;
‡
‡
103.2; 32.1. HR-MALDI-MS (DHB): 309.0811 (MH , C16H13N4OS ; calc. 309.0810).
2-Amino-6-(aminomethyl)-8-[(phenylsulfanyl)methyl]quinazolin-4(3H)-one (34). To a suspension of 33
(100 mg, 0.32 mmol) in abs. THF (11 ml), 1m LiEt3BH soln. (1.3 ml, 1.30 mmol) in THF (11 ml) was added
dropwise at À788, and the mixture was allowed to warm to r.t. After stirring for 4 h at r.t., 1n HCl (10 ml) was
added, and the mixture was stirred for 20 min. THF was removed in vacuo, and the aq. phase was washed with
AcOEt (3Â). The pH of the aq. phase was adjusted to 8 with 1n NaOH, and the precipitate formed was isolated
by filtration. The solid was washed with H2O, CHCl3, and cold MeOH. Recrystallization from MeOH provided
34 (50 mg, 50%). Light-orange solid. M.p. 179 182 8. IR (KBr): 3133s, 2360m, 1700m, 1653s, 1609s, 1506m,
1479s, 1437m, 1349m. 1H-NMR (300 MHz, (CD3)2SO): 7.77 (s, 1 H); 7.50 (s, 1 H); 7.14 7.35 (m, 5 H); 6.39( s,
2 H); 4.43 (s, 2 H); 3.65 (s, 2 H). 13C-NMR (125 MHz, (CD3)2SO): 162.3; 151.1; 137.2; 136.3; 133.9; 130.3; 128.9;
‡
‡
128.9; 127.9; 125.5; 123.1; 116.9; 44.9; 32.0. HR-MALDI-MS (DHB): 313.1121 ( MH , C16H17N4OS ; calc.
313.1118).
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Received January 16, 2004