2-Alkylthio-4-oxo-3-quinazolineacetonitriles and analogous thieno[3,2-d]pyrimidineacetonitriles: Reaction with thiols via trapped thioimidates

Full text of DOI:10.1021/jo010045y

J . Org. Chem. 2001, 66, 4723-4727
4723
Notes
Sch em e 1
2-Alk ylth io-4-oxo-3-qu in a zolin ea ceton itr iles
a n d An a logou s
Th ien o[3,2-d ]p yr im id in ea ceton itr iles:
Rea ction w ith Th iols via Tr a p p ed
Th ioim id a tes
Michael Gu¨tschow*,† and J ames C. Powers‡
Pharmaceutical Institute, Poppelsdorf, University of Bonn,
D-53115 Bonn, Germany, and School of Chemistry and
Biochemistry, Georgia Institute of Technology,
Atlanta, Georgia 30332-0400
guetschow@uni-bonn.de
Received J anuary 16, 2001
In tr od u ction
Cysteine proteases, a group of proteolytic enzymes,
play important roles in a multitude of physiological as
well as pathological processes including lysosomal func-
tion, bone resorption, hormone biosynthesis and inactiva-
tion, apoptosis, and certain viral and protozoal infections.
Therefore, cysteine proteases constitute prime targets for
the design of specific inhibitors1 to block the activity of
cathepsins, calpains,2 caspases,3 and viral cysteine pro-
teases.4 A characteristic feature of cysteine proteases is
the nucleophilic deprotonated active-site cysteine.1,5 Since
cysteine and serine proteases show similarities in their
catalytic mode of action, the development of inhibitors
specific for cysteine proteases presents a serious problem1a
and, thus, a special challenge in designing inhibitors.1,5,6
Amino acid and dipeptide-derived nitriles have been
reported to inactivate papain, cathepsin C, and cathepsin
B.6-9 Papain, a prototype cysteine protease, reacts re-
versibly with hippuronitrile 1 to form a thioimidate
covalent intermediate 2 (Scheme 1).7,10,11 Dipeptide-
derived nitriles, such as N-(N-acetyl-L-phenylalanyl)-
aminoacetonitrile are stronger transition-state analogue
inhibitors toward papain.6 The reversible formation of a
covalent thioimidate intermediate was demonstrated by
NMR studies and binding kinetics.8,11,12 Notably, amino
acid or peptide-derived nitriles did show some selectivity
for cysteine over serine proteases.1a,6,8 Conceptually, an
ideal nitrile inhibitor would prevent release of the active-
site thiol and dissociation of the enzyme-inhibitor com-
plex after formation of the intermediate thioimidate
enzyme-inhibitor adduct. The goal of the present work
was the design of compounds that contain an additional
nucleofuge situated at a favorable distance from the
nitrile function. Such nitriles could react with the active-
site cysteine residue of a cysteine protease to yield a
thioimidate that might be trapped by an adjacent elec-
trophilic carbon. Since heterocyclic alkylthio substituents
are excellent leaving groups, the 2-alkylthiopyrimidinone
structure was chosen. The lead structure 4 resembles the
papain inhibitor hippuronitrile 1, and the possible reac-
tion course with a cysteine protease, in principle, is
outlined in Scheme 1.
† University of Bonn.
‡ Georgia Institute of Technology.
In this paper, we report the reaction of a series of
2-alkylthio-4-oxo-3-quinazolineacetonitriles and analo-
gous thieno[3,2-d]pyrimidine-3-acetonitriles with thio-
lates. This mechanistic study was performed in order to
investigate whether such compounds react via thioimi-
dates and undergo a subsequent trapping reaction to
form imidazoquinazolines and imidazothienopyrimidines,
respectively.
(1) For reviews, see: (a) Leung, D.; Abbenante, G.; Fairlie, D. P. J .
Med. Chem. 2000, 43, 305. (b) Otto, H.-H.; Schirmeister, T. Chem. Rev.
1997, 97, 133 (c) Babine, R. E.; Bender, S. L. Chem. Rev. 1998, 97,
1359.
(2) (a) Wang, K. K.; Yueng, P. W. Trends Pharmacol. Sci. 1994, 15,
412. (b) Li, Z.; Ortega-Vilain, A.- C.; Patil, G. S.; Chu, D.-L.; Foreman,
J . E.; Eveleth, D. D.; Powers, J . C. J . Med. Chem. 1996, 39, 4089.
(3) (a) Thornberry, N. A. Chem. Biol. 1998, 5, R97-103. (b) Talanian,
R. V.; Allen, H. J . Annu. Rep. Med. Chem. 1998, 33, 273.
(4) Parick, A. K.; Potts, E. K. Clin. Microbiol. Rev. 1998, 11, 614.
(5) (a) Krantz, A.; Copp, L. J .; Coles, P. J .; Smith, R. A.; Heard, S.
B. Biochemistry 1991, 30, 4678. (b) Magrath, J .; Abeles, R. H. J . Med.
Chem. 1992, 35, 4279.
(6) Thompson, S. A.; Andrews, R. R.; Hanzlik, R. P. J . Med. Chem.
1986, 29, 104.
(7) Lewis, C. A.; Wolfenden, E. Biochemistry 1977, 16, 4890.
(8) Liang, T.-C.; Abeles, R. H. Arch. Biochem. Biophys. 1987, 252,
626.
(9) Picken, P. P.; Guthrie, D. J . S.; Walker, B. Biochem. Soc. Trans.
1990, 18, 316.
(10) Brisson, J .-R.; Carey, P. R.; Storer, A. C. J . Biol. Chem. 1986,
261, 9087.
Resu lts a n d Discu ssion
The synthesis of quinazolineacetonitriles 4 and thieno-
[3,2-d]pyrimidineacetonitriles 7 is shown in Scheme 2.
Compounds 4a ,b and 7a ,b were prepared in good yields
by base-catalyzed treatment of 3 or 6 with 1-bromopro-
pane and benzyl chloride, respectively, in aqueous ac-
(11) Hanzlik, R. P.; Zygmunt, J .; Moon, J . B. Biochim. Biophys. Acta
1990, 1035, 62.
(12) Moon, J . B.; Coleman, R. S.; Hanzlik, R. P. J . Am. Chem. Soc.
1986, 108, 1350.
10.1021/jo010045y CCC: $20.00 © 2001 American Chemical Society
Published on Web 05/25/2001

4724 J . Org. Chem., Vol. 66, No. 13, 2001
Notes
Sch em e 2
Sch em e 3
a
Reactions and conditions: (a) aminoacetonitrile bisulfate,
pyridine, rt, 24 h; (b) 0.5 M NaOH, acetone, rt, 15 h; (c) RX, 1 M
NaOH, acetone, rt (a , b), or ClCH2CO2H, KI, Na2CO3, DMF, 100
°C, 90 min (c); (d) 1 M NaOH, 0 °C, 10 min.
imidazo[2,1-b]quinazolin-5-ones 5c-e were obtained as
pure compounds in excellent yields. In an analogous
manner, treatment of the carboxyalkylthio thienopyri-
midinones 7c-e with mercaptoacids readily provided the
imidazo[1,2-a][3,2-d]pyrimidin-9-ones 8c-e.
a
Reactions and conditions: (a) RX, 1 M NaOH, acetone, rt (a ,
When the reactions of 4a (with propyl mercaptan) or
4b (with benzyl mercaptan) in a solution of sodium
hydroxide in 50% acetone at room temperature were
performed, they were found to be much slower compared
to those of the carboxyalkylthio derivatives described
above.14 The resulting product mixtures were analyzed
by TLC using the reference substances 10,16 12a , and
12b. The preparation of these reference substances is
shown in Scheme 3. When 4a was treated with propyl
mercaptan in aqueous acetone in the presence of sodium
hydroxide at room temperature over 5 days, the reaction
mixture contained the quinazolineacetamide 12a , to-
gether with starting material and 5a . Similarly, 4b and
benzyl mercaptan gave a mixture of the amide 12b,
starting material, and 5b. However, the quinazolinedione
10, which would result from hydrolysis at the C(2) carbon
of 4a and 4b, was not detected. This showed that the
nitrile group is more reactive than the C(2) electrophile
under basic aqueous conditions.
b); or RCl, KI, Na2CO3, DMF, 100 °C, 90 min (c-e); (b) RSH,
t-BuOH, t-BuOK, rt, 24 h (a , b); or RSH, 1 M NaOH, 0 °C, 10 min
(c, d ); or HSCH2CH2CO2H, 1 M NaOH, rt, 4 h (e).
etone at room temperature. To obtain the thienopyrim-
idines 7, a one-pot reaction involving S-alkylation and
cyclocondensation was employed.13 However, these condi-
tions were not suitable for the preparation of the car-
boxyalkyl substituted compounds 4c-e and 7c-e, and
their preparation was accomplished in moderate yields
using the respective chloroacetic or chloropropionic acid
under conditions of the Finkelstein reaction (KI, DMF).
The base-catalyzed reaction of compounds 4 and 7 with
thiols was studied in order to prove the concept of
trapping thioimidates by an adjacent electrophilic site.
We chose to utilize those thiols that had already been
incorporated into the alkylthio function of each of the
starting compounds. All reactions were performed using
a 1:10:5 ratio (nitrile/thiol/base).
It might be assumed that the treatment of compounds
4 and 7 with thiols could occur by an initial attack of
the thiolate at the C(2) carbon. In the case of the parent
compounds 4 and 7, reaction at the C(2) rather than at
the nitrile group would give starting material, and the
products 5 and 8 could be formed subsequently. To test
the reactivity of the C(2) electrophilic site, the acetamide
12c was reacted with thiolactic acid (Scheme 3). The
reaction was performed under the same conditions that
have been applied for the conversion of the nitriles 4c
and 4d into the corresponding imidazo compounds 5c and
The reactions of the propylthio- and benzylthio-
substituted heterocycles (4a ,b and 7a ,b) with propyl
mercaptan and benzyl mercaptan, respectively, were
performed in tert-butyl alcohol with potassium tert-
butoxide at room temperature. The desired imidazo
derivates 5a ,b and 8a ,b were obtained in low yields after
column chromatography.
The reaction of the carboxyalkylthio quinazolinones
4c-e with mercaptoacetic acid, thiolactic acid, and
3-mercaptopropionic acid, respectively, in aqueous alkali
afforded the carboxyalkylthio imidazoquinazolinones 5c-
e. The reaction to produce 5e was carried out at room
temperature, whereas the reactions of 4c with mercap-
toacetic acid and 4d with thiolactic acid occurred rapidly
and were completed after 10 min at 0 °C. The resulting
(14) The greater nucleophilicity of mercaptoalkylcarboxylate dian-
ions compared to simple thiolate anions is the likely explanation for
this difference; see ref 15.
(15) Friedman, M.; Cavins, J . F.; Wall, J . S. J . Am. Chem. Soc. 1965,
87, 3672.
(16) For the reaction of N-(sulfonyloxy)phthalimides with nucleo-
philes, see ref 17 and references therein.
(13) Gu¨tschow, M.; Powers, J . C. J . Heterocycl. Chem., in press.

Notes
J . Org. Chem., Vol. 66, No. 13, 2001 4725
Sch em e 4
ible ring closure upon treatment with thiols via thioimi-
date intermediates. Thioimidates were trapped by attack
of the thioimidate nitrogen at an adjacent electrophilic
site contained within the heterocyclic structure. To the
best of our knowledge, the synthesis of 5 and 8 is the
first report of an in situ cyclization of thioimidates to form
fused nitrogen heterocycles. This “trapped thioimidate”
cyclization should also be applicable to other types of
heterocyclic compounds. Furthermore, the trapped thio-
imidate strategy might be useful in the design of new
inhibitors of cysteine proteases. For such an approach,
the heterocyclic structure should be utilized as a scaffold
onto which amino acid or peptidic moieties could be
introduced to provide specific recognition in the active
site of the targeted cysteine protease.
Exp er im en ta l Section
Melting points are not corrected. 1H NMR spectra (300 MHz)
were recorded in DMSO-d6. Mass spectra were performed using
electron impact ionization (EI, 70 eV), unless otherwise stated.
Thin-layer chromatography was performed on Merck aluminum
sheets, silica gel 60 F254. The solvent systems used for TLC were
toluene/ethyl acetate (2:1, 1:1) and 1-propanol/30% NH3 (10:1).
Column chromatography was performed on silica gel (32-63 µm)
using ethyl acetate/hexane (1:1). Elemental analyses were
performed by Atlanta Microlab Inc., Norcross, GA.
1,4-Dihydro-4-oxo-2-thioxo-3(2H)-quinazolineacetonitrile (3)
and methyl 3-[3-(cyanomethyl)thioureido]thiophene-2-carboxy-
late (6) were prepared as reported.13 2-(Propylthio)-4-oxo-3(4H)-
quinazolineacetonitrile (4a )13 was prepared from 3 and 1-bro-
mopropane in 88% yield. 2-(Benzylthio)-4-oxo-3(4H)-quinazo-
lineacetonitrile (4b)13 was prepared from 3 and benzyl chloride
in 92% yield. 2-(Propylthio)-4-oxothieno[3,2-d]pyrimidine-3(4H)-
acetonitrile (7a )13 was prepared from 6 and 1-bromopropane in
91% yield. 2-(Benzylthio)-4-oxothieno[3,2-d]pyrimidine-3(4H)-
acetonitrile (7b)13 was prepared from 6 and benzyl chloride in
71% yield.
Gen er a l P r oced u r e for th e P r ep a r a tion of Ca r boxy-
a lk ylth io Der iva tives 4c-e a n d 7c-e. A mixture of compound
3 or 6 (5 mmol), Na2CO3 (2.12 g, 20 mmol), KI (1.66 g, 10 mmol),
DMF (25 mL), and the appropriate chloro-substituted acid (10
mmol) was stirred at 100 °C for 90 min and poured into H2O
(200 mL). The pH was adjusted to 7.5, and the solution was
extracted with ethyl acetate (200 mL), followed by hexane (150
mL). The aqueous layer was acidified with 1 M HCl, and the
mixture was cooled. The precipitate that formed was collected
by filtration, dried, and recrystallized from acetonitrile after
charcoal treatment.
[[3-(Cya n om et h yl)-3,4-d ih yd r o-4-oxo-2-q u in a zolin yl]-
th io]a cetic Acid (4c). Treatment of compound 3 with chloro-
acetic acid gave 4c as white crystals in 70% yield: mp 191-192
°C; 1H NMR δ 4.16 (s, 2H), 5.20 (s, 2H), 7.48-7.54 (m, 2H), 7.81-
7.87 (m, 1H); EIMS (m/z) 275 (M+, 51), 231 (M+ - CO2, 50), 191
(100). Anal. Calcd for C12H9N3O3S: C, 52.36; H, 3.30; N, 15.26.
Found: C, 52.40; H, 3.32; N, 15.16.
(R,S)-2-[[3-(Cya n om eth yl)-3,4-dih yd r o-4-oxo-2-qu in a zoli-
n yl]th io]p r op ion ic Acid (4d ). Compound 3 was reacted with
2-chloropropionic acid to obtain 4d as a white solid in 43%
yield: mp 175-176 °C; 1H NMR δ 1.62 (d, J ) 7.3 Hz, 3H), 4.60
(q, J ) 7.3 Hz, 1H), 5.16 (s, 2H), 7.48-7.53 (m, 2H), 7.82-7.88
(m, 1H), 8.09-8.12 (m, 1H); EIMS (m/z) 289 (M+, 57), 245 (M+
- CO2), 162 (C6H4(CO)NCS, 100). Anal. Calcd for C13H11N3O3S:
C, 53.97; H, 3.83; N, 14.52. Found: C, 54.19; H, 3.89; N, 14.76.
3-[[3-(Cya n om eth yl)-3,4-d ih yd r o-4-oxo-2-qu in a zolin yl]-
th io]p r op ion ic Acid (4e). Compound 3 was reacted with
3-chloropropionic acid to obtain 4e as white crystals in 58%
yield: mp 159-160 °C; 1H NMR δ 2.80 (t, J ) 6.7 Hz, 2H), 3.49
(t, J ) 6.7 Hz, 2H), 5.13 (s, 2H), 6.47-7.59 (m, 2H), 7.81-7.87
(m, 1H), 8.08-8.11 (m, 1H); EIMS (m/z) 289 (M+, 14), 217 (100),
162 (C6H4(CO)NCS, 44). Anal. Calcd for C13H11N3O3S: C, 53.97;
H, 3.83; N, 14.52. Found: C, 54.06; H, 3.80; N,14.58.
5d . However, no formation of the C(2) reaction product
12d was observed. Instead, pure starting material 12c
was obtained in quantitative yield. This indicated that
the thiolate prefers to attack at the nitrile function and
not at the electrophilic site at C(2) of 4 and 7.
The structures 5 and 8 were established by elemental
1
analyses and spectral data. In particular, the H NMR
spectra of 5 and 8 showed a sharp singlet in the range of
7.50-7.60 ppm for the CH of the imidazole.18 Mass
spectra of 5 and 8 were characterized by a typical
fragmentation pattern.19
As shown for the quinazoline series in Scheme 4, the
formation of the tricyclic compounds 5 involves the attack
of the thiolate anion at the nitrile function of 4 followed
by rapid protonation to give the neutral thioimidates 13.
Thioimidates are known to undergo a base-catalyzed
decomposition;12,20 an equilibrium between nitriles 4 and
thioimidates 13 is therefore assumed. However, attack
of the thioimidate nitrogen at the C(2) carbon followed
by displacement of the alkylthio leaving group affords
15. Tautomeric rearrangement to the more stable21
ketene-S,N-acetals 5 probably occurs in a subsequent
step. However, we cannot exclude the rearrangement to
14 prior to cyclization.
In summary, it was demonstrated that fused 2-alkyl-
thio-4-oxopyrimidine-3-acetonitriles undergo an irrevers-
(17) Gu¨tschow, M. J . Org. Chem. 1999, 64, 5109.
(18) Compounds 5 and 8 showed signals for S-CH2 methylene at
0.33-0.39 ppm upfield compared to the S-CH2 protons of the corre-
sponding bicyclic compounds 4 and 7. Similarly, the methine signals
of 5d and 8d were upfield 0.60-0.63 ppm compared to 4d and 7d .
(19) MS fragmentation of compounds of 5 (X ) -CHdCH-) and 8
(X ) S, m/z values in parentheses) is shown below. Relative intensities
are noted in the Experimental Section. Additionally, carboxyalkyl
derivatives 5c-e and 8c-e underwent an initial loss of H2O.
(20) Chatuvedi, R. K.; MacMahon, A. E.; Schmir, G. L. J . Am. Chem.
Soc. 1967, 89, 6984.
(21) Hino, T.; Nakagawa, M.; Yamaji, N.; Miwa, Y.; Tsuneoka, K.;
Akaboshi, S. Tetrahedron 1971, 27, 775.
[[3-(Cya n om et h yl)-3,4-d ih yd r o-4-oxot h ien o[3,2-d ]p yr i-
m id in -2-yl]th io]a cetic Acid (7c). Treatment of compound 6

4726 J . Org. Chem., Vol. 66, No. 13, 2001
Notes
with chloroacetic acid gave 7c as white crystals in 47% yield:
mp 180-181 °C; 1H NMR δ 4.16 (s, 2H), 5.22 (s, 2H), 7.29 (d, J
) 5.2 Hz, 1H), 8.25 (d, J ) 5.2 Hz, 1H); EIMS (m/z) 281 (M+,
46), 237 (M+ - CO2, 40), 168 (C4H2S(CO)NCS, 100). Anal. Calcd
for C10H7N3O3S2: C, 42.70; H, 2.51; N, 14.94. Found: C, 42.62;
H, 2.46; N, 14.85.
[(1,5-Dih yd r o-5-oxoim id a zo[2,1-b]qu in a zolin -2-yl)th io]-
a cetic Acid (5c). Compound 4c was reacted with mercaptoace-
tic acid to give 5c as white crystals in 86% yield: mp >265 °C
1
dec; H NMR δ 3.83 (s, 2H), 7.24-7.30 (m, 1H), 7.40-7.44 (m,
1H), 7.53 (s, 1H), 7.73-7.78 (m, 1H), 8.11-8.14 (m, 1H); EIMS
(m/z)19 275 (M+, 10), 257 (M+ - H2O, 100), 216 (18), 145 (23).
(R,S)-2-[[3-(Cya n om eth yl)-3,4-d ih yd r o-4-oxoth ien o[3,2-
d ]p yr im id in -2-yl]th io]p r op ion ic Acid (7d ). Compound 6 was
reacted with 2-chloropropionic acid to obtain 7d as colorless
Anal. Calcd for C12H9N3O3S: C, 52.36; H, 3.30; N, 15.26.
Found: C, 51.99; H, 3.28; N, 14.91.
(R,S)-2-[(1,5-Dih yd r o-5-oxoim id a zo[2,1-b]q u in a zolin -2-
yl)th io]p r op ion ic Acid (5d ). Compound 4d was treated with
thiolactic acid to afford 5d in 84% yield as a white solid: mp
255-257 °C; 1H NMR δ 1.44 (d, J ) 7.1 Hz, 3H), 3.97 (q, J )
7.1 Hz, 1H), 7.23-7.30 (m, 1H), 7.40-7.44 (m, 1H), 7.63 (s, 1H),
7.73-7.79 (m, 1H), 8.11-8.15 (m, 1H); EIMS (m/z)19 289 (M+,
4), 271 (M+ - H2O, 100), 216 (17), 145 (37). Anal. Calcd for
C13H11N3O3S: C, 53.97; H, 3.83; N, 14.52. Found: C, 53.93; H,
3.86; N, 14.39.
[(5,9-Dih ydr o-9-oxoim idazo[1,2-a ]th ien o[3,2-d]pyr im idin -
6-yl)th io]a cetic Acid (8c). Compound 7c was treated with
mercaptoacetic acid to obtain 8c as a white solid in 82% yield:
mp 242-245 °C; 1H NMR δ 3.84 (s, 2H), 7.18 (d, J ) 5.4 Hz,
1H), 7.60 (s, 1H), 8.16 (d, J ) 5.4 Hz, 1H); EIMS (m/z)19 281
(M+, 9), 263 (M+ - H2O, 100), 222 (7), 151 (12). Anal. Calcd for
C10H7N3O3S2: C, 42.70; H, 2.51; N, 14.94. Found: C, 42.46; H,
2.55; N, 14.66.
1
crystals in 41% yield: mp 127-128 °C; H NMR δ 1.61(d, J )
7.3 Hz, 3H), 4.58 (q, J ) 7.3 Hz, 1H), 5.19 (s, 2H), 7.30 (d, J )
5.4 Hz, 1H), 8.26 (d, J ) 5.4 Hz, 1H); EIMS (m/z) 295 (M+, 31),
223 (100), 168 (C4H2S(CO)NCS, 73). Anal. Calcd for
C11H9N3O3S2: C, 44.74; H, 3.07; N, 14.23. Found: C, 44.45; H,
3.01; N, 14.06.
3-[[3-(Cya n om eth yl)-3,4-d ih yd r o-4-oxoth ien o[3,2-d ]p yr i-
m id in -2-yl]th io]p r op ion ic Acid (7e). Compound 6 was re-
acted with 3-chloropropionic acid to obtain 7e as a slightly yellow
1
solid in 57% yield: mp 172-173 °C; H NMR δ 2.78 (t, J ) 6.7
Hz, 2H), 3.46 (t, J ) 6.7 Hz, 2H), 5.16 (s, 2H), 7.36 (d, J ) 5.3
Hz, 1H), 8.25 (d, J ) 5.3 Hz, 1H); EIMS (m/z) 295 (M+, 34), 251
(M+ - CO2, 14), 168 (C4H2S(CO)NCS, 100). Anal. Calcd for
C
11H9N3O3S2: C, 44.74; H, 3.07; N, 14.23. Found: C, 44.91; H,
3.11; N, 14.23.
Gen er a l P r oced u r e for th e P r ep a r a tion of Alk ylth io
Im id a zo[2,1-b]qu in a zolin on es a n d Im id a zo[1,2-a ]th ien o-
[3,2-d ]p yr im id in on es 5a ,b a n d 8a ,b. Potassium tert-butoxide
(560 mg, 5 mmol) was added to a mixture of compound 4 or 7 (1
mmol), t-BuOH (80 mL), and the appropriate thiol (10 mmol).
The reaction mixture was stirred at room temperature for 24 h,
diluted with brine (400 mL), and extracted with ethyl acetate
(2 × 100 mL). The organic layer was washed with H2O (400 mL)
and dried (Na2SO4). The solvent was evaporated under reduced
pressure, and the residue was washed with cold hexane (40 mL)
and purified by column chromatography.
(R,S)-2-[(5,9-Dih yd r o-9-oxoim id a zo[1,2-a ]th ien o[3,2-d ]-
p yr im id in -6-yl)th io]p r op ion ic Acid (8d ). Compound 7d was
reacted with thiolactic acid to give 8d as a white solid in 86%
yield. An analytic sample was obtained by washing the product
1
with hot i-PrOH: mp 262-266 °C; H NMR δ 1.41 (d, J ) 7.1
Hz, 3H), 3.89 (q, J ) 7.1 Hz, 1H), 7.19 (d, J ) 5.4 Hz, 1H), 7.70
(s, 1H), 8.16 (d, J ) 5.4 Hz, 1H); EIMS (m/z)19 295 (M+, 2), 277
(M+ - H2O, 100), 223 (10), 151 (21). Anal. Calcd for C11H9N3O3S2‚
0.5 H2O: C, 43.41; H, 3.31; N, 13.81. Found: C, 43.25; H, 2.99;
N, 13.50.
2-(P r op ylth io)im id a zo[2,1-b]qu in a zolin -5(1H)-on e (5a ).
Compound 4a was reacted with 1-propanethiol to give 5a in 36%
Gen er a l P r oced u r e for th e P r ep a r a tion of Ca r boxyeth -
ylth io Der iva tives 5e a n d 8e. A mixture of compound 4e or
7e (2 mmol), 3-mercaptopropionic acid (2.12 g, 20 mmol), and 1
M NaOH (30 mL) was stirred at room temperature for 4 h. The
mixture was acidified with 1 M HCl (45 mL) and cooled. The
precipitate was collected by filtration and washed with cold H2O
to obtain pure products.
1
yield as a light brown solid: mp >164 °C dec; H NMR δ 0.97
(t, 3H), 1.64 (sextet, 2H), 2.59 (t, 2H), 7.24-7.30 (m, 1H), 7.40-
7.44 (m, 1H), 7.53 (s, 1H), 7.72-7.78 (m, 1H), 8.12-8.15 (m, 1H);
EIMS (m/z)19 259 (M+, 62), 217 (100), 145 (26). Anal. Calcd for
C
13H13N3OS: C, 60.21; H, 5.05; N, 16.20; S, 12.36. Found: C,
60.47; H, 5.28; N, 16.11; S, 12.28.
3-[(1,5-Dih yd r o-5-oxoim id a zo[2,1-b]qu in a zolin -2-yl)th io]-
p r op ion ic Acid (5e). Compound 5e was obtained from com-
pound 4e in 91% yield. Recrystallization from i-PrOH afforded
2-(Ben zylth io)im id a zo[2,1-b]qu in a zolin -5(1H)-on e (5b).
Compound 5b was obtained from 4b and benzyl mercaptan in
41% yield as slightly yellow crystals: mp 242-243 °C; 1H NMR
δ 4.26 (s, 2H), 7.22-7.45 (m, 7H), 7.50 (s, 1H), 7.73-7.79 (m,
1H), 8.10-8.14 (m, 1H); EIMS (m/z)19 307 (M+, 37), 216 (15),
145 (22), 91 (C7H7+, 100). Anal. Calcd for C17H13N3OS: C, 66.43;
H, 4.26; N, 13.67. Found: C, 66.27; H, 4.21; N, 13.59.
6-(P r op ylt h io)im id a zo[1,2-a ]t h ie n o[3,2-d ]p yr im id in -
9(5H)-on e (8a ). Compound 7a was treated with 1-propanethiol
to obtain 8a in 23% yield as yellow crystals: mp >150 °C dec;
1H NMR δ 0.95 (t, 3H), 1.59 (sextet, 2H), 2.94 (t, 2H), 7.19 (d, J
) 5.4 Hz, 1H), 7.62 (s, 1H), 8.14 (d, J ) 5.4 Hz, 1H); EIMS (m/
z)19 265 (M+, 75), 223 (100), 151 (56). Anal. Calcd for C11H11N3-
OS2‚0.5 H2O: C, 48.16; H, 4.41; N, 15.32. Found: C, 48.10; H,
4.02; N 15.36.
1
slightly yellow crystals: mp >235 °C dec; H NMR δ 2.63 (t, J
) 7.0 Hz, 2H), 3.13 (t, J ) 7.0 Hz, 2H), 7.24-7.30 (m, 1H), 7.40-
7.44 (m, 1H), 7.59 (s, 1H), 7.72-7.79 (m, 1H), 8.11-8.15 (m, 1H);
EIMS (m/z)19 289 (M+, 28), 271 (M+ - H2O, 50), 216 (100), 145
(20). Anal. Calcd for C13H11N3O3S: C, 53.97; H, 3.83; N, 14.52.
Found: C, 53.97; H, 3.93; N, 14.41.
3-[(5,9-Dih yd r o-9-oxoim id a zo[1,2-a ]th ien o[3,2-d ]p yr im i-
d in -6-yl)th io]p r op ion ic Acid (8e). Compound 8e was obtained
from compound 7e in 89% yield. Recrystallization from i-PrOH
1
afforded colorless crystals: mp 229-230 °C; H NMR δ 2.59 (t,
J ) 7.0 Hz, 2H), 3.11 (t, J ) 7.0 Hz, 2H), 7.19 (d, J ) 5.4 Hz,
1H), 7.65 (s, 1H), 8.14 (d, J ) 5.4 Hz, 1H); EIMS (m/z)19 295
(M+, 6), 277 (M+ - H2O, 73), 223 (100), 151 (19). Anal. Calcd for
6-(Be n zylt h io)im id a zo[1,2-a ]t h ie n o[3,2-d ]p yr im id in -
9(5H)-on e (8b). Compound 7b was reacted with benzyl mer-
captan to give 8b in 27% yield as yellow crystals: mp >170 °C
dec; 1H NMR δ 4.24 (s, 2H), 7.19 (d, J ) 5.4 Hz, 1H), 7.23-7.33
(m, 5H), 7.50 (s, 1H), 8.14 (d, J ) 5.4 Hz, 1H); EIMS (m/z)19 313
(M+, 65), 222 (14), 151 (25), 91 (C7H7+, 100). Anal. Calcd for
C
11H9N3O3S2: C, 44.74; H, 3.07; N, 14.23. Found: C, 44.51; H,
3.19; N, 14.00.
1,4-Dih ydr o-2,4-dioxo-3(2H)-qu in azolin eaceton itr ile (10).
Compound 922 (2.42 g, 10 mmol), aminoacetonitrile bisulfate
(1.74 g, 11.3 mmol), and pyridine (50 mL) were stirred at room
temperature for 24 h. The precipitate that formed was separated,
and the filtrate was evaporated under reduced pressure to obtain
a yellow oil. Ice-water (150 mL) was added, and the precipitate
was collected by filtration to give 10 (1.63 g, 81%). Recrystalli-
zation from EtOH/H2O afforded colorless crystals: mp 250-251
°C; 1H NMR δ 4.89 (s, 2H), 7.19-7.28 (m, 2H), 7.68-7.74 (m,
1H), 7.95-7.99 (m, 1H), 11.76 (s, 1H); EIMS (m/z) 201 (M+, 100).
Anal. Calcd for C10H7N3O2: C, 59.70; H, 3.51; N, 20.89. Found:
C, 59.84; H, 3.58; N, 20.93.
C
15H11N3OS2‚0.5 AcOEt: C, 57.12; H, 4.23; N, 11.76. Found: C,
57.15; H, 4.26; N, 11.71.
Gen er a l P r oced u r e for th e P r ep a r a tion of Ca r boxy-
a lk ylth io Im id a zo[2,1-b]qu in a zolin on es a n d Im id a zo[1,2-
a ]th ien o[3,2-d ]p yr im id in on es 5c,d a n d 8c,d . A mixture of
compound 4 or 7 (2 mmol) and mercaptoacetic acid (1.84 g, 20
mmol) or thiolactic acid (2.12 g, 20 mmol) was cooled to 0 °C
and 1 M NaOH (30 mL, previously cooled to 0 °C) was added.
The mixture was stirred for 10 min in an ice-bath and then
acidified with 1 M HCl (45 mL). After the mixture was cooled
for 6 h, the precipitate was collected by filtration and washed
with i-PrOH to obtain pure products. Analytical samples were
obtained by recrystallization from i-PrOH.
1,4-Dih yd r o-4-oxo-2-t h ioxo-3(2H )-q u in a zolin e a ce t a -
m id e (11). Compound 3 (870 mg, 4 mmol) was dissolved in a
(22) Ku¨hle, E.; Wegler, R. Liebigs Ann. Chem. 1958, 616, 183.

Notes
J . Org. Chem., Vol. 66, No. 13, 2001 4727
mixture of 0.5 M NaOH (16 mL) and acetone (8 mL), stirred at
room temperature for 15 h, and poured into 0.5 M HCl (20 mL).
The precipitate was collected by filtration to afford 11 (605 mg,
64%). Recrystallization from acetic acid gave colorless crystals:
mp >280 °C dec; 1H NMR δ 4.99 (s, 2H), 7.10 (s, br, 1H), 7.32-
7.45 (m, 2H), 7.58 (s, br, 1H), 7.73-7.79 (m, 1H), 7.93-7.97 (m,
1H); EIMS (m/z) 235 (M+, 50), 218 (100). Anal. Calcd for
C10H9N3O2S: C, 51.05; H, 3.86; N, 17.86. Found: C, 51.22; H,
3.83; N, 17.64.
2-(P r op ylth io)-4-oxo-3(4H)-qu in a zolin ea ceta m id e (12a ).
1-Bromopropane (615 mg, 5 mmol) and 1 M NaOH (4.4 mL) were
added to a mixture of compound 11 (940 mg, 4 mmol) and
acetone (10 mL). This was stirred at room temperature for 24
h, diluted with H2O, and cooled. The precipitate was collected
to obtain 12a (895 mg, 81%): mp 216-217 °C (acetone/H2O);
1H NMR δ 0.99 (t, 3H), 1.72 (sextet, 2H), 3.24 (t, 2H), 4.67 (s,
2H), 7.30 (s, br, 1H), 7.41-7.48 (m, 1H), 7.53-7.57 (m, 1H), 7.72
(s, br, 1H), 7.76-7.83 (m, 1H), 8.30-8.80 (m, 1H); EIMS (m/z)
277 (M+, 17), 260 (M+ - OH, 22), 218 (M+ - OH - C3H6, 100).
Anal. Calcd for C13H15N3O2S: C, 56.30; H, 5.45; N, 15.15.
Found: C, 56.46; H, 5.36; N, 15.15.
collected to afford 12b (1.09 g, 84%): mp 228-229 °C (ethyl
acetate/cyclohexane); 1H NMR δ 4.54 (s, 2H), 4.65 (s, 2H), 7.26-
7.35 (m, 4H), 7.47-7.52 (m, 3H), 7.63-7.66 (m, 1H), 7.72 (s, br,
1H), 7.80-7.85 (m, 1H), 8.05-8.08 (m, 1H); EIMS (m/z) 325 (M+,
+
19), 308 (M+
C
-
OH), 91 (C7H7
,
100). Anal. Calcd for
17H15N3O2S: C, 62.75; H, 4.65; N, 12.91. Found: C, 62.54; H,
4.67; N, 13.01.
[[3-(Car bam oylm eth yl)-3,4-dih ydr o-4-oxo-2-qu in azolin yl]-
th io]a cetic Acid (12c). A mixture of compound 11 (1.18 g, 5
mmol), Na2CO3 (2.12 g, 20 mmol), KI (1.66 g, 10 mmol), DMF
(25 mL), and chloroacetic acid (945 mg, 10 mmol) was stirred at
100 °C for 90 min and poured into H2O (200 mL). The pH was
adjusted to 7.5 and the solution was extracted with ethyl acetate
(200 mL), followed by hexane (150 mL). The aqueous layer was
acidified with 1 M HCl, and the mixture was cooled. The
precipitate that formed was collected by filtration, dried, and
recrystallized from acetic acid to give 12c (760 mg, 52%): mp
227-228 °C; 1H NMR δ 4.07 (s, 2H), 4.69 (s, 2H), 7.35 (s, br,
1H), 7.43-7.50 (m, 2H), 7.76-7.83 (m, 2H), 8.04-8.07 (m, 1H);
MS (FAB) 294 (MH+). Anal. Calcd for C12H11N3O4S: C, 49.14;
H, 3.78; N, 14.33. Found: C, 49.21; H, 3.76; N, 14.33.
2-(Ben zylth io)-4-oxo-3(4H)-qu in a zolin ea ceta m id e (12b).
Benzyl chloride (633 mg, 5 mmol) and 1 M NaOH (4.4 mL) were
added to a mixture of compound 11 (940 mg, 4 mmol) and
acetone (10 mL). The mixture was stirred at room temperature
for 24 h, diluted with H2O, and cooled. The precipitate was
Ack n ow led gm en t. We thank BASF Biotechnology
Corp., for financial support.
J O010045Y