Synthesis and antimicrobial activity of imidazo- and pyrimido[2,1-f]- theophyllines

Article abstract of DOI:10.1007/s00706-008-0854-z

Heating of 8-aminotheophylline with methyl (Z)-2-benzoylamino-3- (dimethylamino)propenoate in acetic acid afforded in a one-pot synthesis a new pyrimido[2,1-f]theophylline derivative. Methylation of this by using CH ₃I/NaH furnished in good yield the double methylated derivative. Furthermore, glycosidation of the former with 1-α-bromo-2,3,4,6-tetra-O- acetyl-d-glucose gave the β-glucoside derivative. Reaction of 8-aminotheophylline with [bis(methylthio)methylene]malonitrile, ethyl[bis(methylthio)methylene]cyanoacetate, 1,3-diphenylprop-2-en-1-one, 2-cyano-1,3-diphenylprop-2-en-1-one, 1-(4-nitrophenyl)-3-(dimethylamino)prop-2- ennitrile, 1-phenyl-3-(dimethylamino)prop-2-en-1-one, 2-substituted 3-aryl or heteroarylprop-2-ennitrile and ethyl(arylmethylene)cyanoacetate in N,N-dimethylformamide in the presence of anhydrous potassium carbonate afforded also the corresponding new derivatives of pyrimido-[2,1-f]theophylline. However, 8-aminotheophylline reacted in similar manner with 3-chloropentan-2,4-dione and 2-bromo-1-phenylethanone to give the corresponding imidazo[2,1-f]theophyllines. Furthermore, azo-coupling of one of these with 4-methylphenyldiazonium chloride was performed. The antimicrobial activity of the products has been evaluated. The structures of all new compounds obtained were established by their spectral analyses.

Full text of DOI:10.1007/s00706-008-0854-z

Monatsh Chem 139, 825–834 (2008)
DOI 10.1007/s00706-008-0854-z
Printed in The Netherlands
Synthesis and antimicrobial activity of imidazo- and pyrimido[2,1-f]-
theophyllines
Mosselhi A. N. Mosselhi1, Elham S. Darwish1, Klaus Peseke2
1
Department of Chemistry, Faculty of Science, Cairo University, Cairo, Egypt
2
Department of Chemistry, Faculty of Science, Rostock University, Rostock, Germany
Received 12 July 2007; Accepted 12 November 2007; Published online 11 April 2008
# Springer-Verlag 2008
Abstract Heating of 8-aminotheophylline with methyl
(Z)-2-benzoylamino-3-(dimethylamino)propenoate in
acetic acid afforded in a one-pot synthesis a new
pyrimido[2,1-f]theophylline derivative. Methylation
of this by using CH3I=NaH furnished in good yield
the double methylated derivative. Furthermore, glyco-
sidation of the former with 1-ꢀ-bromo-2,3,4,6-tetra-
O-acetyl-D-glucose gave the ꢁ-glucoside derivative.
Reaction of 8-aminotheophylline with [bis(methyl-
thio)methylene]malonitrile, ethyl[bis(methylthio)-
methylene]cyanoacetate, 1,3-diphenylprop-2-en-1-one,
2-cyano-1,3-diphenylprop-2-en-1-one, 1-(4-nitrophe-
nyl)-3-(dimethylamino)prop-2-ennitrile, 1-phenyl-3-
(dimethylamino)prop-2-en-1-one, 2-substituted 3-aryl
or heteroarylprop-2-ennitrile and ethyl(arylmethyl-
ene)cyanoacetate in N,N-dimethylformamide in the
presence of anhydrous potassium carbonate afforded
also the corresponding new derivatives of pyrimido-
[2,1-f]theophylline. However, 8-aminotheophylline
reacted in similar manner with 3-chloropentan-2,4-
dione and 2-bromo-1-phenylethanone to give the cor-
responding imidazo[2,1-f]theophyllines. Furthermore,
azo-coupling of one of these with 4-methylphenyldia-
zonium chloride was performed. The antimicrobial
activity of the products has been evaluated. The struc-
tures of all new compounds obtained were established
by their spectral analyses.
Keywords Theophylline; Fused purines; Methylxanthines;
Glycoside; Antimicrobial activity.
Introduction
Among new alkylxanthines, 7- and 8-substituted de-
rivatives were investigated in respect of their bron-
chospasmolytic [1–4], anticancer [5], and circulatory
blood system activity [6]. A large amount of work
has been performed on the fused systems derived
from theophylline, including synthetic procedures
and structure determination [7–15] but only few of
the synthesized new heterocyclic derivatives were
pharmacologically tested, which revealed antiin-
flammatory [16], anti P-388 leukemia [17], and vas-
cular relaxing agents [18]. Recently, it has been
found that anellation of a six or seven membered ring
at the 7,8-positions of theophylline changed the pro-
file of its CNS activity [19, 20].
In literature several examples of [f]-fused pu-
rines have been reported including pyrrolo[2,1-f]
[21], oxazolo[2,3-f] [22, 23], imidazo[2,1-f] [24–
26], pyrido[2,1-f] [21], pyrimido[2,1-f] [21, 27–32,
36], oxazino[2,3-f] [33], pyrazino[2,1-f] [21], diaze-
pino[2,1-f] [20, 3], 2,4-benzodiazepino[3,2-f] [34],
1,2,4-triazino[3,2-f] [35–37], and 1,2,4-triazepino-
[3,2-f] [35] purines. As part of our studies of new
fused purine compounds as potential antimicrobial
agents, we wish to report the synthesis of new de-
rivatives of imidazo and pyrimido[2,1-f]purine via
Correspondence: Mosselhi A. N. Mosselhi, Department of
Chemistry, Faculty of Science, Cairo University, Cairo,
Egypt. E-mail: mosselhi@hotmail.com

826
M. A. N. Mosselhi et al.
reaction of 8-aminotheophylline with ketene, thioa-
cetal, propenenitrile, and haloketone derivatives.
indicated by TLC analysis of the crude product. The
structure of the isolated product was established on
the basis of its spectral (MS, IR, and 1H NMR) anal-
yses. The mass spectrum of the product isolated
revealed a molecular ion peak (m=z) at 366.34 of
C17H14N6O4. Its infrared spectrum revealed one ab-
sorption band of NH at ꢂꢀ¼ 3409 cmꢀ1 and no band
Results and discussion
The starting 8-aminotheophylline (1) was prepared as
previously reported [38]. Refluxing of 1 with methyl
(Z)-2-benzoylamino-3-(dimethylamino)propenoate
(2) in acetic acid for 15 h gave a single product as
1
of NH2. Also the H NMR spectrum showed 2NH
signals at ꢃ ¼ 9.8 and 13.8 ppm. Furthermore, the
Scheme 1

Imidazo- and pyrimido[2,1-f]theophyllines
827
13C NMR spectrum of the obtained product revealed
15 carbon signals. Since the chemical shift of the
carbonyl carbon at position 6 of product 3 (168.8)
is similar to that of the reported carbonyl carbon at
position 6 (169) of 7-benzoylamino-1,3-diphenyl-py-
rido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5,6(1H,8H)-
dione [39], these spectral data were in full agreement
with the expected structure of the product obtained
to resemble that of pyrimido[2,1-f]theophylline de-
rivative 3A and not the isomer 3B (Scheme 1).
Formation of 3A might occur via initial electrophilic
substitution of the 8-amino group of 1 in acidic
medium [39, 47], to give 1A as an intermediate
which undergoes cyclization to the final product 3
(Scheme 1). The assignment of the structure 3A is
also substantiated by investigation of its methylation
and glycosidation reactions. Thus, methylation of
3A by using methyl iodide in the presence of sodium
hydride yielded the double methylation product 4.
tyl-D-glucose (5) afforded the glucoside derivative 6
(Scheme 1). The 1H NMR spectrum of 6 showed the
anomeric proton as a doublet at ꢃ ¼ 6.2 ppm with a
spin–spin coupling constant (J) of 10.5 Hz corre-
sponding to a diaxial orientation of H-10 and H-20
protons indicating the ꢁ-glucoside [45].
The reaction of 1 with a molar equivalent of
2-(bis-methylthiomethylene) malonitrile (7) and
ethyl[bis(methylthio)methylene]cyanoacetate (9) in
refluxing N,N-dimethylformamide (DMF) containing
equivalent amounts of anhydrous potassium carbonate
for 15 h (evidenced by TLC) afforded the correspond-
ing cyclized products, pyrimido[2,1-f]theophylline de-
rivatives 8 and 10 (Scheme 2). The structures of 8
and 10 we confirmed by spectral data. The 1H NMR
of the product 8 showed a signal for SCH3 protons at
ꢃ ¼ 2.6 and two signals of NH at ꢃ ¼ 8.0 and 9.6 ppm
and no signal of NH2 was observed. This finding
indicates that the structure of the latter product 8
1
1
The H NMR spectrum of the latter product 4 re-
exists in imine form. The H NMR of the product
vealed two signals of new CH3 groups at ꢃ ¼ 3.1
(PhCON–CH3) and 3.15 (N9-CH3) ppm. However,
glycosidation of 3 with 1-ꢀ-bromo-2,3,4,6-tetraace-
10 showed one NH signal at ꢃ ¼ 9.6 ppm and no
signal of NH2. Moreover, the IR spectra of 8 and
10 revealed bands characteristic for a CN group.
Scheme 2

828
M. A. N. Mosselhi et al.
As reported in literature [21, 40], the formation
of 8 and 10 may proceed via initial alkylation of
the ring nitrogen in 1 to give II and III, respectively
as intermediates which undergo cyclization to the
final products 8 and 10. The synthetic approach
pointed out here was extended to enable the syn-
thesis of other functionally substituted pyrimido-
[2,1-f]theophyllines for their biological evaluation.
When 8-aminotheophylline 1 was reacted with 1,3-
diphenylprop-2-en-1-one (11a), 2-cyano-1,3-diphe-
Scheme 3

Imidazo- and pyrimido[2,1-f]theophyllines
829
nylprop-2-en-1-one (11b), 1-(4-nitrophenyl)-3-di-
methylaminoprop-2-ennitrile (13), and 1-phenyl-3-
dimethylaminoprop-2-en-1-one (15) in refluxing DMF
containing equivalent amounts of anhydrous po-
tassium carbonate for 10 h (TLC), the corresponding
pyrimido[2,1-f]theophylline derivatives 12a, 12b, 14,
and 16 were obtained (Scheme 3).
The structures of 12, 14, and 16 were established
on the basis of their spectral data (MS, H NMR,
and IR). For example, the 1H NMR spectrum of 12a
1
Chart 1
Scheme 4

830
M. A. N. Mosselhi et al.
showed a characteristic signal at ꢃ ¼ 6.99 ppm of the
proton at position 7 and that of 14 revealed a signal
at ꢃ ¼ 8.39 ppm for the proton at position 6. Also
in the 1H NMR spectrum of product 16, two doublet
signals at ꢃ ¼ 7.54 and 8.26 ppm with a coupling
constant J ¼ 7.5 Hz corresponding to CH¼CH group
of positions 6 and 7 are observed [19].
two absorption bands at lmax 267 and 461 nm. These
findings suggest that the isolated product 26 may be
a mixture of hydrazone 26A and azo tautomeric
form 26B, whereas the tautomeric form 26C does
not seem to play a role.
Antimicrobial activity
Similarly, by the reaction of 1 with 2-substituted
3-aryl or heteroarylprop-2-ennitrile 17 and ethyl-
(arylmethylene)cyanoacetate 19 in refluxing DMF
containing equivalent amounts of anhydrous potas-
sium carbonate for 12 h, the corresponding pyr-
imido[2,1-f]theophylline derivatives 18 and 20 were
obtained (Scheme 3). Elemental analyses and spec-
tral data were consistent with the proposed structures
of 18 and 19. In the light of the foregoing results of
all new pyrimidotheophylline derivatives 3, 8, 10,
12, 14, 16, 18, and 20 obtained, it is proposed that
all isolated products are consistent with a pyrimi-
do[f]theophylline ring system and not the other iso-
meric pyrimido[e]theophylline (Chart 1) [19, 21,
46]. This is due to the steric hindrance caused by
the proximity of the N1–CH3 and substituents in
The compounds 3, 4, 8, 10, 12a, 12b, 16, 18c,
18d, and 26 were evaluated for their antifungal and
antibacterial activities against four fungal species
namely Aspergillus fumigatus (AF), Penicillium
italicum (PI), Syncephalastrum racemosum (SR),
and Candida albicans (CA) as well as four bacteria
species namely Staphylococcus aureus (SA), Pseu-
domonas aeruginosa (PA), Bacillus subtilis (BS),
and Escherichia coli (EC).
The organisms were tested against the activity of
solutions in a concentration of 1.0 ꢄg=cm3 of each
compound and using inhibition zone diameter in cm
(IZD) as a criterion for its antimicrobial activity.
Terbinafin as an antifungal agent and chloram-
phenicol as an antibacterial agent were used as
references to evaluate the potency of the tested com-
pounds under the same conditions. The results are
depicted in Table 1. The results revealed that some
compounds, such as 12a, 12b, 16, 18c, 18d, and 26
have no activities against the tested organisms PA,
BS, and EC, while compounds 12a, 16, and 26 exhib-
ited the highest degree of inhibition against the test-
ed organisms SA and PI.
1
the pyrimidine ring fused. In addition the H NMR
spectra of all isolated products revealed the signal of
the N1–CH3 protons at ꢃ ¼ 3.42–3.65 ppm. This val-
ue is very close to that of N3–CH3 of theophylline
(ꢃ ¼ 3.59 ppm) (Chart 1).
Attempts to prepare the ring system imidazo[2,1-
f]theophylline were made by reacting 8-aminotheo-
phylline (1) with 3-chloropentan-2,4-dione (21) and
2-bromo-1-phenylethanone (23) in refluxing DMF
containing equivalent amounts of anhydrous po-
tassium carbonate for 10 h. The corresponding imi-
dazo-[2,1-f]theophyllines 22 and 24 were isolated,
respectively (Scheme 4). The constitutions of the
products 22 and 24 were confirmed by elemental
Table 1 Antimicrobial activity of the products 3, 4, 8, 10,
ꢂ
12a, 12b, 16, 18c, 18d, and 26
Compound no. AF PI
SR CA SA PA BS EC
3
4
8
10
12a
12b
16
18c
18d
26
0
0
0
0
0
þþ
þ
þ
0
0
þþ
0
0
0
þ
þ
0
0
0
0
þ
0
0
0
0
0
0
0
0
0
0
0
þ
0
þ
þ
0
0
0
0
0
0
0
þ
0
0
0
0
0
0
0
1
and spectral analyses. In the H NMR spectrum of
þ
þ
24, a signal of aromatic CH at ꢃ ¼ 8.15 ppm was
observed. Treatment of 24 with 4-methylphenyl dia-
zonium chloride (25) in ethanol containing sodium
acetate at 0–5ꢁC for 3 h afforded a single product 26
according to TLC. The structure of the latter product
was elucidated by elemental analysis and spectral
data. The IR spectrum revealed absorption bands of
NH at ꢂꢀ¼ 3451 (NH) and two absorption bands of
2 CO at 1696 and 1643 cmꢀ1; its 1H NMR showed a
signal of NH proton at ꢃ ¼ 8.35 ppm (D2O exchange-
able) and no signal of CH proton. Also the UV
absorption spectrum of 26 in methanol revealed
0
0
þ
þ
þ
þ
þþ
0
0
0
0
0
0
0
0
0
0
0
þ
þ
0
0
0
þ
0
þ
0
50 cm3 of solution in DMF whose concentration was
ꢂ
1.0 ꢄg=cm3 was tested; chloramphenicol as standard antibac-
terial agent (IZD 1.0 cm); terbinfin as standard antifungal
agent (IZD 1.0 cm); þþ IZD 0.6–1.0 cm; þ IZD 0.1–0.5 cm;
0 no inhibition detected.

Imidazo- and pyrimido[2,1-f]theophyllines
831
50), 366 (15), 289 (80), 261 (5), 233 (5), 204 (10), 176 (15),
135 (15), 106 (25), 96 (15), 77 (100), 67 (30), 51 (28), 42 (40).
Experimental
IR spectra were determined on a KBr disc using a Perkin-
Elmer 1650 (FT-IR) spectrophotometer, 1H-NMR spectra
were recorded on a Bruker AC 250 MHz and on a Varian
Gemini 200 MHz NMR spectrometer using TMS as the inter-
nal reference; the mass spectra were recorded on a GC-MS
spectrometer, the ionizing voltage was 70 eV. Thin layer chro-
matography was performed on silica gel sheets F 1550 LS 254
of Schleicher & Schu¨ll. UV absorption spectra were recorded
on a Perkin-Elmer Lambda 40 spectrophotometer. Melting
points were measured on a Gallenkamp melting point appara-
tus. Elemental analyses were carried out at the Microanalytical
Center of Cairo University and were within 0.4% of the theo-
retical values.
The starting materials such as 8-aminotheophylline [38]
(1), methyl (Z)-2-benzoylamino-3-dimethylaminopropeno-
ate [41] (2), [bis(methylthio)methylene]malonitrile [42]
(7), ethyl[bis(methylthio)methylene]cyanoacetate [42] (9),
1,3-diphenylprop-2-en-1-one [43] (11a), 2-cyano-1,3-diphe-
nylprop-2-en-1-one [43] (11b), 1-(4-nitrophenyl)-3-dimeth-
ylaminoprop-2-enenitrile [44] (13), 1-phenyl-3-dimethyl-
aminoprop-2-en-1-one [44] (15), 2-substituted 3-aryl- or
-heteroarylprop-2-enenitrile [43] (17), and ethyl (arylmethy-
lene)cyanoacetate [43] (19) were prepared by literature
methods. 3-Chloropentan-2,4-dione (21) and 2-bromo-1-
phenylethanone (23) were bought from Aldrich.
7-Benzoylamino-1,3-dimethyl-9-(2,3,4,6-tetra-O-acetyl-ꢁ-D-
glucopyranosyl)pyrimido[2,1-f]purine-1,2,3,4,6,9-
hexahydro-2,4,6-trione (6, C31H32N6O13)
To a solution of 3.7 g (0.01 mol) 3 in 0.01mol aqueous potas-
sium hydroxide in 6 cm3 distilled water, a solution of 4.15g
(0.011mol) 5 was added. The mixture was stirred at room
temperature until the reaction was judged complete by TLC
[using CHCl3=CH3OH (90=10, v=v) as eluent, 15 h]. The mix-
ture was evaporated under reduced pressure at 40ꢁC and the
residue was washed with distilled water to remove KBr. The
product was filtered off, dried, and crystallized from dioxane.
Yield 5.6 g (80%); Rf ¼ 0.42; mp 280–282ꢁC; IR: ꢂꢀ¼ 3240
(NH), 1750, 1710, 1666, 1590 (4CO) cmꢀ1; 1H NMR (DMSO-
d6, 200 MHz): ꢃ ¼ 1.90–2.02 (4s, 12H, 4COCH3), 3.35 (s, 3H,
N3–CH3), 3.65 (s, 3H, N1–CH3), 4.05 (m, 2H, 60, 600–CH2),
4.36 (m, 1H, 50-H), 5.10 (t, 1H, 40-H), 5.30 (t, J ¼ 9 Hz, 1H, 20-
0
H), 5.70 (t, 1H, 30-H), 6.20 (d, 1H, J1 ,2 ¼ 10.5Hz, 1 -H), 7.2–
0
0
7.5 (m, 5Harom), 8.4 (s, 1H, ¼CH), 9.2 (s, 1H, NH) ppm.
1,3-Dimethylpyrimido[2,1-f]purine-1,2,3,4-tetrahydro-2,4-
dione derivatives (general procedure)
Compound 1 (0.2g, 0.001mol) was dissolved in 50cm3 dry
DMF by heating, 1.4g (0.015 mol) anhydrous potassium car-
bonate were added, followed by addition of 0.001 mol 7, 9,
11a, 11b, 15, 17, 19, 21, or 23. After being stirred under reflux
for 10–15h (TLC using ethyl acetate as eluent), the reaction
mixture was concentrated in vacuo, poured into ice water, and
neutralized with dilute HCl. The solid product precipitated,
which was collected by filtration and recrystallized from the
appropriate solvent.
7-Benzoylamino-1,3-dimethyl-pyrimido[2,1-f]purine-
1,2,3,4,6,9-hexahydro 2,4,6-triones (3, C17H14N6O4)
A mixture of 3.90 g (0.02 mol) 1 and 4.96 g (0.02 mol) 2 in
50cm3 glacial acetic acid was heated under reflux for 15h.
The reaction was followed by TLC using CHCl3=CH3OH
(90=10, v=v) as eluent. The reaction solvent was evaporated
in vacuo and the residue was recrystallized from DMF.
Yield 5.13 g (70%); Rf ¼ 0.22; mp>300ꢁC; IR: ꢂꢀ¼ 3409
8-Amino-1,3-dimethyl-6-(methylthio)-2,4-dioxo-1,2,3,4,8,9-
hexahydropyrimido[2,1-f]purine-7-carbonitrile
(NH), 1710, 1671, 1653, 1597 (4CO) cmꢀ1
;
1H NMR
(8, C12H11N7O2S)
(DMSO-d6, 200 MHz): ꢃ ¼ 3.2 (s, 3H, N3–CH3), 3.41 (s, 3H,
N1–CH3), 7.50–8.01 (m, 5Harom), 8.3 (s, 1H, ¼CH), 9.8 (s, 1H,
NH), 13.8 (s, 1H, NH) ppm; MS: m=z (%) ¼ 366 (Mþ, 30), 349
(5), 232 (5), 176 (3), 149 (35), 105 (100), 77 (40), 44 (25).
Reflux 15h; yield 0.22g (70%); Rf ¼ 0.19; mp>300ꢁC
(DMF); IR: ꢂꢀ¼ 3364, 3274 (2NH), 2225 (CN), 1697, 1639
(2CO) cmꢀ1; 1H NMR (DMSO-d6, 200 MHz): ꢃ ¼ 2.6 (s, 3H,
SCH3), 3.25 (s, 3H, N3–CH3), 3.45 (s, 3H, N1–CH3), 8.0 (s,
1H, NH), 9.6 (s, 1H, NH) ppm; MS: m=z (%) ¼ 317 (Mþ,
100), 300 (10), 284 (10), 231 (20), 205 (5), 180 (3), 165
(30), 109 (25), 94 (10), 82 (35), 67 (35), 42 (35).
7-(Benzoylmethylamino)-1,3,9-trimethylpyrimido[2,1-f]-
purine-1,2,3,4,6,9-hexahydro-2,4,6-trione (4, C19H18N6O4)
To a stirred suspension of 0.002 mol sodium hydride (60% oil)
in 5 cm3 DMF, a solution of 3.7 g (0.01 mol) 3 in 10cm3 DMF
was added. The reaction mixture was cooled to 0–5ꢁC and a
solution of 0.0012mol methyl iodide in 2 cm3 DMF was
added. The reaction mixture was stirred overnight and the
solvent was evaporated. The residue was treated with 10cm3
ice-water and 2 cm3 acetic acid and then stirred 2 h. The solid
product was collected, washed with water, and recrystallized
from dioxane=DMF (1=1, v=v) to give pure colourless powder
[TLC using CHCl3=CH3OH (90=10, v=v) as eluent].
1,3-Dimethyl-6-(methylthio)-2,4,8-trioxo-1,2,3,4,8,9-hexahy-
dropyrimido[2,1-f]purine-7-carbonitrile (10, C12H10N6O3S)
Reflux 15h; yield 0.21g (65%); Rf ¼ 0.23; mp>300ꢁC
(DMF); IR: ꢂꢀ¼ 3448 (OH), 2217 (CN), 1705, 1655 (2CO)
cmꢀ1; 1H NMR (DMSO-d6, 200 MHz): ꢃ ¼ 2.7 (s, 3H, SCH3)
3.20 (s, 3H, N3–CH3), 3.50 (s, 3H, N1–CH3), 9.6 (s, 1H, NH)
ppm; MS: m=z (%) ¼ 318 (Mþ, 40), 279 (10), 261 (15), 192
(10), 135 (5), 105 (15), 77 (20), 44 (100).
Yield 0.3 g (75%); Rf ¼ 0.30; mp>300ꢁC; IR: ꢂꢀ¼ 1715,
1680, 1650, 1600 (4CO) cmꢀ1
;
1H NMR (DMSO-d6,
1,3-Dimethyl-6,8-diphenylpyrimido[2,1-f]purine-
2,4(1H,3H)-dione (12a, C22H17N5O2)
200 MHz): ꢃ ¼ 3.1 (s, 3H, PhCON–CH3), 3.15 (s, 3H, N-9
CH3), 3.25 (s, 3H, N3–CH3), 3.65 (s, 3H, N1–CH3), 7.2–7.5
(m, 5Harom), 8.2 (s, 1H, ¼CH) ppm; MS: m=z (%) ¼ 394 (Mþ,
Reflux 10 h; yield 0.25 g (65%); Rf ¼ 0.22; mp>300ꢁC (EtOH);
IR: ꢂꢀ¼ 1702, 1663 (2CO) cmꢀ1
;
1H NMR (DMSO-d6,

832
M. A. N. Mosselhi et al.
200 MHz): ꢃ ¼ 3.25 (s, 3H, N3–CH3), 3.57 (s, 3H, N1–CH3),
6.99 (s, 1H, 7-CH¼), 7.47–8.37 (m, 10Harom) ppm; MS: m=z
(%) ¼ 384 (Mþ þ 1, 30), 383 (Mþ, 100), 325 (51), 248
(62), 297 (24), 221 (12), 216 (15), 142 (22), 105 (79), 77
(59), 56 (13).
8-Amino-6-(2-furyl)-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetra-
hydropyrimido[2,1-f]purine-7-carbonitrile (18c, C15H11N7O3)
Reflux 12h; yield 0.14g (42%); Rf ¼ 0.21; mp>300ꢁC
(DMF); IR: ꢂꢀ¼ 3396, 3210 (NH2), 2201 (CN), 1698, 1649
(2CO) cmꢀ1; 1H NMR (DMSO-d6, 200MHz): ꢃ ¼ 3.47 (s, 3H,
N3–CH3), 3.51 (s, 3H, N1–CH3), 7.10–7.70 (m, 3H, furan-H),
8.60 (br s, 2H, NH2) ppm; MS: m=z (%) ¼ 337 (Mþ,75), 256
(80), 249 (60), 210 (75), 199 (100), 140 (60), 128 (50), 121
(70), 110 (75), 108 (80), 86 (100), 83 (70), 68 (50), 56 (65).
1,3-Dimethyl-2,4-dioxo-6,8-diphenyl-1,2,3,4-tetrahydro-
pyrimido[2,1-f]purine-7-carbonitrile (12b, C23H16N6O2)
Reflux 10 h; yield 0.22g (55%); Rf ¼ 0.25; mp>300ꢁC
(EtOH); IR: ꢂꢀ¼ 2192 (CN), 1699, 1652 (2CO) cmꢀ1
;
1H
8-Amino-1,3-dimethyl-2,4-dioxo-6-(2-thienyl)-1,2,3,4-
tetrahydropyrimido[2,1-f]purine-7-carbonitrile
NMR (DMSO-d6, 200 MHz): ꢃ ¼ 3.38 (s, 3H, N3–CH3), 3.45
(s, 3H, N1–CH3), 7.52–8.07 (m, 10Harom) ppm; MS: m=z
(%) ¼ 408 (Mþ, 23), 301 (10), 300 (19), 299 (100), 82 (38),
68 (21), 55 (24).
(18d, C15H11N7O2S)
Reflux 12h; yield 0.14g (40%); Rf ¼ 0.20; mp>300ꢁC
(DMF); IR: ꢂꢀ¼ 3326, 3205 (NH2), 2210 (CN), 1700, 1646
(2CO) cmꢀ1; 1H NMR (DMSO-d6, 200MHz): ꢃ ¼ 3.37 (s, 3H,
N3–CH3), 3.43 (s, 3H, N1–CH3), 7.00–7.40 (m, 3H, thio-
phene-H), 8.00 (br s, 2H, NH2) ppm; MS: m=z (%) ¼ 354
(Mþ+1, 9), 353 (Mþ, 5), 325 (30), 215 (7), 121 (7), 95
(11), 94 (100), 83 (10), 73 (9), 66 (10).
8-Amino-1,3-dimethyl-7-(4-nitrophenyl)pyrimido[2,1-f]-
purine-2,4(1H,3H)-dione (14, C16H13N7O4)
Reflux 10 h; yield 0.26 g (70%); Rf ¼ 0.21; mp>300ꢁC
(Dioxane=DMF); IR: ꢂꢀ¼ 3360, 3341 (2 NH), 1703, 1640
(2CO) cmꢀ1
;
1H NMR (DMSO-d6, 200 MHz): ꢃ ¼ 3.48 (s,
3H, N3–CH3), 3.52 (s, 3H, N1–CH3), 7.35–8.35 (m,
5Harom), 8.39 (s, 1H, 6-CH¼), 9.2, 11 (s, 2H, NH2) ppm;
MS: m=z (%) ¼ 367 (Mþ, 29), 366 (17), 306 (22), 234 (15),
194 (13), 179 (15), 152 (18), 127 (22), 104 (17), 99 (28), 82
(20), 59 (44).
1,3-Dimethyl-2,4,8-trioxo-6-phenyl-1,2,3,4,8,9-hexahydro-
pyrimido[2,1-f]purine-7-carbonitrile (20, C17H12N6O3)
Reflux 12h; yield 0.14g (40%); Rf ¼ 0.25; mp>300ꢁC
(EtOH); IR: ꢂꢀ¼ 3334 (NH), 2203 (CN), 1703, 1654 (2CO)
1
cmꢀ1; H NMR (DMSO-d6, 200MHz): ꢃ ¼ 3.34 (s, 3H, N3–
CH3), 3.45 (s, 3H, N1–CH3), 7.16–8.00 (m, 5Harom), 8.10 (s,
1H, NH) ppm; MS: m=z (%) ¼ 348 (Mþ, 23), 275 (25), 195
(84), 176 (4), 138 (14), 105 (24), 91 (23), 82 (20), 77 (19), 68
(15), 52 (8).
1,3-Dimethyl-8-phenylpyrimido[2,1-f]purine-2,4(1H,3H)-
dione (16, C16H13N5O2)
Reflux 10 h; yield 0.18g (60%); Rf ¼ 0.26; mp>300ꢁC
1
(EtOH); IR: ꢂꢀ¼ 1703, 1659 (2CO) cmꢀ1; H NMR (DMSO-
d6, 200 MHz): ꢃ ¼ 3.24 (s, 3H, N3–CH3), 3.44 (s, 3H, N1–
CH3), 7.54 (d, J ¼ 7 Hz, 1H, 7-CH¼), 7.57–7.87 (m, 5Harom),
8.26 (d, J ¼ 7 Hz, 1H, 6-CH¼) ppm; MS: m=z (%) ¼ 307 (Mþ,
66), 183 (33), 147 (33), 121 (53), 104 (100), 90 (53), 67 (35).
6-Acetyl-1,3,7-trimethyl-1H-imidazo[2,1-f]purine-
2,4(3H,8H)-dione (22, C12H13 N5O3)
Reflux 10 h; yield 0.18 g (65%); Rf ¼ 0.29; mp>300ꢁC
(DMF); IR: ꢂꢀ¼ 3419 (NH), 1700, 1652 (2CO) cmꢀ1
;
1H
NMR (DMSO-d6, 200 MHz): ꢃ ¼ 2.27 (s, 3H, CH3), 2.44 (s,
3H, COCH3), 3.17 (s, 3H, N3–CH3), 3.47 (s, 3H, N1–CH3),
8.71 (s, 1H, NH) ppm; MS: m=z (%) ¼ 275 (Mþ, 92), 255
(52), 201 (68), 190 (48), 167 (60), 150 (72), 112 (60), 109
(60), 100 (44), 90 (80), 80 (48), 67 (100), 60 (60).
8-Amino-1,3-dimethyl-2,4-dioxo-6-phenyl-1,2,3,4-tetrahydro-
pyrimido[2,1-f]purine-7-carbonitrile (18a, C17H13N7O2)
Reflux 12 h; yield 0.19g (55%); Rf ¼ 0.19; mp>300ꢁC
(EtOH); IR: ꢂꢀ¼ 3319, 3260 (NH2), 1704, 1637 (2CO)
1
cmꢀ1; H NMR (DMSO-d6, 200 MHz): ꢃ ¼ 3.38 (s, 3H, N3–
CH3), 3.57 (s, 3H, N1–CH3), 7.50–7.89 (m, 5Harom), 8.36 (br,
2H, NH2) ppm; MS: m=z (%) ¼ 347 (Mþ, 25), 323 (32), 281
(33), 261 (29), 206 (62), 195 (49), 180 (18), 153 (27), 141 (8),
127 (32), 105 (11), 103 (23), 93 (30), 77 (78), 67 (67), 6 (31),
53 (49).
1,3-Dimethyl-7-phenyl-1H-imidazo[2,1-f]purine-
2,4(3H,8H)-dione (24 C15H13N5O2)
Reflux 10 h; yield 0.18 g (60%); Rf ¼ 0.25; mp>300ꢁC
(EtOH); IR: ꢂꢀ¼ 3395 (NH), 1698, 1644 (2CO) cmꢀ1
;
1H
NMR (DMSO-d6, 200 MHz): ꢃ ¼ 3.40 (s, 3H, N3–CH3),
3.46 (s, 3H, N1–CH3), 7.31–8.08 (m, 5Harom), 8.15 (s, 1H,
CH¼), 12.03 (s, 1H, NH) ppm; MS: m=z (%) ¼ 295 (Mþ,18),
295 (9), 238 (4), 209 (4), 105 (100), 77 (61), 67 (5), 51 (20).
6-(4-Chlorophenyl)-1,3-dimethyl-2,4,8-trioxo-1,2,3,4,8,9-
hexahydropyrimido[2,1-f]purine-7-carbonitrile
(18b, C17H12ClN7O2)
Reflux 12 h; yield 0.19g (50%); Rf ¼ 0.18; mp>300ꢁC; IR:
1
ꢂꢀ¼ 3320, 3250 (NH2), 1700, 1640 (2CO) cmꢀ1; H NMR
(6E)-1,3-Dimethyl-7-phenyl-1H-imidazo[2,1-f]purine-
2,4,6(3H)-trione 6-[(4-methylphenyl)hydrazone]
(26, C22H19N7O2)
A solution of 2.95 g (0.01 mol) 24 in 50cm3 ethanol was
stirred with 1.4 g (0.01 mol) sodium acetate trihydrate for
15min. The mixture was chilled in an ice bath at 0ꢁC.
While the solution was cooling, the 4-methylbenzene diazoni-
(DMSO-d6, 200 MHz): ꢃ ¼ 3.37 (s, 3H, N3–CH3), 3.42 (s,
3H, N1–CH3), 7.50–7.88 (m, 4Harom), 8.30 (br s, 2H, NH2)
ppm; MS: m=z (%) ¼ 383 (Mþ+1, 29), 382 (Mþ, 41), 344
(41), 258 (79), 238 (73), 237 (85), 186 (41), 177 (38), 161
(100), 141 (52), 139 (47), 138 (61), 114 (38), 108 (35), 84
(67), 69 (61), 52 (44).

Imidazo- and pyrimido[2,1-f]theophyllines
833
um chloride was prepared by the diazotization of 1.1 g
(0.01 mol) p-toluidine in 6 cm3 6 M hydrochloric acid with
10cm3 cold 1 M sodium nitrite solution in the usual way
keeping the temperature below 5ꢁC. The diazonium chloride
solution was added to the reaction solution dropwise under
stirring. The reaction mixture was left for 3 h in a refrigerator.
The precipitated solid was filtered off, washed with water and
ethanol, and dried. The product was recrystallized from
1,4-dioxane to give 26 as pure pale yellow crysrtals (TLC
using ethyl acetate as eluent). Yield 0.29 g (70%); Rf ¼ 0.19;
mp>300ꢁC; IR: ꢂꢀ¼ 3451 (NH), 1696, 1643 (2CO) cmꢀ1; 1H
NMR (DMSO-d6, 200 MHz): ꢃ ¼ 2.60 (s, 3H, CH3), 3.43 (s,
3H, N3–CH3), 3.50 (s, 3H, N1–CH3), 7.30–8.15 (m, 9Harom),
8.35 (br s, 1H, NH) ppm; MS: m=z (%) ¼ 414 (Mþ, 80), 413
(100), 307 (11), 282 (35), 234 (3), 207 (3), 195 (3), 106 (26),
94 (10), 77 (25), 67 (45), 53 (9); UV (methanol): lmax(") ¼
267 (18200), 461 (9800) nm (molꢀ1 cmꢀ1).
8. Hesek D, Tegza M, Rybar A, Povazanec F (1989)
Synthesis:681
9. Dreier A, Haller R (1987) Arch Pharm (Weinheim)
320:1004
10. Nanavyan IM, Kuzmenko VV, Pozharskii AF, Klyuev AN
(1987) Khim Geterotsikl Soedin 10:1398; (1988) Hetero-
cyclic Compounds 206:97
11. Karczmarzyk Z, Karolak-Wojciechowska J, Pawlowski
M (1991) Acta Cryst 47:1902
12. Karolak-Wojciechowska J, Pawlowski M (1990) J Crys-
tallograph Spectrosc Res 20:477
13. Pawlowski M (1987) Pharmazie 42:371
14. Pawlowski M, Buschauer A, Schunack W (1989) Arch
Pharm (Weinheim) 322:447
15. Jin RH, Nisshjkubo T (1992) Tetrahedron Lett 33:6307
16. Blythin DJ, Kamiinski JJ, Domalski MS, Spitler J,
Solomon DM, Conn DJ, Shing-Chun W, Lehman LV,
Bober LA, Chiu PJS, Watnick AS, Siegel MI, Hibert JM,
Mc Phail AT (1986) J Med Chem 29:1099
17. Conn DJ, Kamiinski JJ, Solomon DM, Mc Phail AT
(1988) J Org Chem 53:3265
18. Solomon DM, Kamiinski JJ (1989) USPat 4,816,458;
Chem Abstr 111:153833j
19. Pawlowski M, Katlabi J, Rys B, Szneler E (1997)
Pharmazie 52:279
20. Pawlowski M, Katlabi J, Drabrzynska A, Duszynska B,
Charakchieva-Minol S, Deren-Wesolek A, Tatarczynska
E, Chojnacka-Wojcik E, Mokrosz MJ, Bojarski AJ (1999)
Eur J Med Chem 34:167
21. Gatta F, Del Giudice MR, Borioni A, Mustazza C, (1994)
J Heterocycl Chem 31:81
22. Harsanyi VK, Szebeni R, Korbonits D (1975) J Prakt
Chem 317:745
23. Jin RH, Nishikubo T (1992) Tetrahedron Lett 33:6307
24. Lefebvro A, Rips R, Martine A, Lespagnol C (1985)
J Heterocycl Chem 22:105
25. Priimenko BA, Samura BA, Skulskaya EA, Troshin DA,
Garmash SN, Milonova NP (1984) Khim Farm Zh
18:1456; (1985) Chem Abstr 103:22539e
26. Nosachenko VI, Kochergin PM, Steblyuk PN (1976)
Khim Geterotsikl Soedin:1132; (1977) Chem Abstr
86:5414y
Antimicrobial assay
Cultures of four fungal species namely Aspergillus fumigatus
(AF), Penicillium italicum (PI), Syncephalastrum racemosum
(SR), and Candida albicans (CA) as well as four bacterial
species namely Staphylococcus aureus (SA), Pseudomonas
aeruginosa (PA), Bacillus subtilis (BS), and Escherichia coli
(EC) were used to investigate the antimicrobial activity of the
compounds 3, 4, 8, 10, 12a, 12b, 16, 18c, 18d, and 26. The
antimicrobial activity was assayed biologically using the dif-
fusion plate technique. The latter technique was carried out by
pouring a spore suspension of the fungal species (1cm3 of
sterile water contains approximately 108 conidia) or spreading
bacterial suspension over a solidified malt agar medium.
The layer is allowed to set for 30 min. A solution of the test
compounds (1.0g=cm3) in DMF was placed onto sterile 5 mm
filter paper discs and allowed to dry, then the discs were
placed on the centre of the malt agar plate and incubated at
optimum incubation temperature 28 ꢃ 2ꢁC. The fungicide
Terbinfin and the bactericide chloramphenicol were used as
standards under the same conditions. Measurements were con-
sidered after 72h for fungi and 24 h for bacteria. The results
are summarized in Table 1.
27. Hesek D, Tegza M, Rybar A, Povazanec F (1989)
Synthesis:681
References
28. Pawlowski M, Drabczynska A, Gorczyca M, Malecand
D, Modzelewski J (1995) Pharmazie 50:453
29. Ueda T, Oh R, Nagai SI, Sakakibara J (1998) J Heterocycl
Chem 35:135
30. Da Settimo A, Da Settimo F, Marini AM, Primofiore G,
Salerno S, Viola G, Via L, Magna SM (1998) Eur J Med
Chem 33:685
1. Corsano S, Scapiochi R, Strappaghetii G (1994) Arch
Pharm (Weinheim) 327:411
2. Baziard-Mouysset G, Rached A, Younes S, Tournaire C,
Stigliani JL, Payard M, Yavo JC, Advenier C (1995) Eur J
Med Chem 30:253
3. Sandoz AG (1992) Israeli IL 83:659; (1992) Chem Abstr
117:7957k
31. Eckstein M, Loson W (1968) Diss Pharm Pharmacol 20:
35; Abstract 69:43891h
4. Gajewczyk L, Zejc A (1992) Acta Pol Pharm 49:61
5. Parrick J, Mehta LK (1993) J Heterocyclic Chem
30:323
6. Bovy PR, Collins JT, Chamberlain TS, Gheng BK (1992)
PCT Int ppl WO 92 07 852; Chem Abstr 117:131218j
7. Kuzmenko VV, Pozharskii AF, Chemyshev AJ, Nanavyan
IM (1987) Khim Geterotsikl Soedin 11:1551; (1988)
Heterocyclic Compounds 240:94
32. Hino K, Irie A, Uno H (1975) Chem Pharm Bull 23:1696
33. Dreier A, Haller R (1986) Arch Pharm 320:999
34. Da-Sellimo A, Prinofiore G, Marini AM, Dasetlimo F,
La Motta C, Salerno S (1999) J Heterocycl Chem 36:639
35. Ueda T, Adachi T, Nagai S, Sakakibara J, Murata M
(1988) J Heterocycl Chem 25:791

834
M. A. N. Mosselhi et al.
36. Gatta F, Del Giudice MR, Borioni A, Borea PA, Dionisotti
S, Ongini E (1993) Eur J Med Chem 28:569
37. Le Brun A (1971) Fr-Demande 2; 157:726; (1973)
Abstract 79:126529d
38. a) Mosselhi MAN (1990) PhD Thesis, Konstanz Univer-
sity, Germany; b) Jones JW, Robins RK (1960) J Am
Chem Soc 82:3773
43. a) Brunskill JSA, De A, Ewing DF (1978) J Chem Soc
Perkin Trans I:629; b) Freemann F (1980) Chem Rev
80:329; c) Tornetta B, Scapini G, Guerrera F, Bernardini
A (1970) Boll Seduta Accad Gioenia Sci Nat Catania
10:353; (1973) Chem Abstr 78:620n
44. Tseng SS, Epstein JW, Brabander HJ, Francisco G (1987)
J Heterocyclic Chem 24:837
39. Mosselhi MAN (2002) Monatsh Chemie 133:1297
40. Zahran AM, El-Sharief AMS, El-Gaby MSA, Ammar
YA, El-Said UH (2001) IL Farmaco 56:277
41. Stanovnik B, Svete J, Tisler M, Zorz L, Hvala A, Simonic
I (1980) Heterocycles 27:903
45. Elgemeie GEH, Attia AME, Fathy NM (1997) Nucleo-
sides Nucleotides 16:485
46. Shawali AS, Mosselhi MAN, Tawfik NM (2001) J Org
Chem 66:4055
47. Kralj L, Hvala A, Svete J, Golic L, Stanovnik B (1997)
J Heterocycl Chem 34:247
42. Gompper R, Topfl W (1962) Chem Ber 95:2861