Synthesis, isomerization, and antimicrobial evaluation of some pyrazolopyranotriazolopyrimidine derivatives

Article abstract of DOI:10.1002/ardp.200700007

6-Amino-5-imino-pyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidine derivative 4 and pyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidin-5- ylhydrazine derivative 5 were prepared starting from 6-amino-3-methyl-4-(p- nitrophenyl)-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitri

Full text of DOI:10.1002/ardp.200700007

Arch. Pharm. Chem. Life Sci. 2007, 340, 345–351
A. H. Shamroukh et al.
345
Full Paper
Synthesis, Isomerization, and Antimicrobial Evaluation of
Some Pyrazolopyranotriazolopyrimidine Derivatives
Ahmed H. Shamroukh, Magdi E. A. Zaki, Eman M. H. Morsy, Faiza M. Abdel-Motti, and
Farouk M. E. Abdel-Megeid
Photochemistry Department, National Research Centre, Dokki, Cairo, Egypt
6-Amino-5-imino-pyrazolo[49,39:5,6]pyrano[2,3-d]pyrimidine
derivative
4
and
pyrazolo-
[49,39:5,6]pyrano[2,3-d]pyrimidin-5-ylhydrazine derivative 5 were prepared starting from 6-amino-
3-methyl-4-(p-nitrophenyl)-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile 1. The synthesis and
structure characterization of 9,11-dihydropyrazolo[49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[4,3-c]pyri-
midine derivatives 7 and 9 and their isomerization to 9,11-dihydropyrazolo[49,39:5,6]pyrano[3,2-e]
[1,2,4]triazolo[1,5-c]pyrimidine derivatives 6 and 8, respectively, under different suitable reaction
conditions are reported. Moreover, the synthesis of 9,11-dihydropyrazolo[49,39:5,6]pyrano[3,2-e]
tetrazolo[1,5-c]pyrimidine derivative 14 and N9-acyclic nucleoside 15 are described. Some of the
prepared products showed potent antimicrobial activity.
Keywords: Acyclic nucleosides / Antimicrobial activities / Pyranopyrazoles / Pyrazolopyranopyrimidines / Pyrazolopyr-
anotriazolopyrimidines /
Received: January 17, 2007; accepted: May 16, 2007
DOI 10.1002/ardp.200700007
dines and pyrazolopyranotriazolo[1,5-c]pyrimidines not
only to study their isomerization, but also to obtain new
compounds which are expected to possess notable chem-
ical and biological activities.
Introduction
The synthesis of triazolopyrimidines fused to other heter-
ocyclic moieties has been described by many investiga-
tors; the compounds proved to have pronounced biologi-
cal activities [1–5]. Previous observations revealed that
the [1,2,4]triazolo[4,3-c]pyrimidine derivatives can iso-
merize under different suitable reaction conditions to
the thermodynamically more stable [1,2,4]triazolo[1,5-
c]pyrimidines [6–11]. This isomerization was reported
earlier by Miller and Rose [12, 13], when they treated
[1,2,4]triazolo[4,3-c]pyrimidine derivatives with acid,
base, or thermally. Nevertheless, this pattern of isomer-
ization appears to have been overlooked by a number of
workers [4, 5, 14, 15]. In continuation of our previous
work on pyrano[2,3-c]pyrazoles [16], fused pyrimidines
[11, 17–19] and pyrazolopyranopyrimidines [20], we
aimed to synthesize pyrazolopyranotriazolo[4,3-c]pyrimi-
Results and discussion
Chemistry
5-Amino-2,4-dihydro-3-methyl-4-(p-nitrophenyl)pyrano-
[2,3-c]pyrazole-5-carbonitrile 1 [16, 20], as the key com-
pound for this study and for further syntheses of other
fused heterocyclic compounds, was heated at reflux tem-
perature with an equimolar amount of triethyl orthoace-
tate in the presence of acetic anhydride to give a major
product which could be assigned the structure of ethyl N-
[2-acetyl-5-cyano-3-methyl-4-(p-nitrophenyl)-2,4-dihydro-
pyrano[2,3-c]pyrazol-6-yl]ethanimidate
2
(Scheme 1).
Inspection of the 1H-NMR spectra of the reaction product
2 revealed the absence of the signal characteristic for the
NH protons of the pyrazole moiety. The acetylation was
assigned to take place at N2 position which is in agree-
ment with the acetylation reported in one of our recent
publications [20]. Deacetylation of compound 2 was car-
Correspondence: Ahmed H. Shamroukh, Photochemistry Department,
National Research Centre, Dokki, Cairo 12622, Egypt.
E-mail: ahshamroukh@yahoo.com
Fax: +20 2 337-0931
i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

346
A. H. Shamroukh et al.
Arch. Pharm. Chem. Life Sci. 2007, 340, 345–351
Scheme 1. Deacetylation of compound 2.
ried out under mild conditions by treatment with ammo-
nium hydroxide solution to give ethyl N-[5-cyano-3-
methyl-4-(p-nitrophenyl)-2,4-dihydropyrano[2,3-c]pyrazol-
6-yl]ethanimidate 3 (Scheme 1).
On the other hand, when a solution of compound 2, in
dry benzene, was stirred with hydrazine hydrate, it
afforded 6-amino-3,7-dimethyl-5-imino-4-(p-nitrophenyl)-
2,4,5,6-tetrahydropyrazolo[49,39:5,6]pyrano[2,3-d]pyrimi-
1
dine 4 (Scheme 1). The H-NMR spectrum of the latter
compound revealed the absence of signals of the acetyl
protons and the ethoxy group protons and showed sig-
nals for NH2 and 2 times NH (D2O exchangeable).
Scheme 2. Synthesis route of compound 4–10.
Heating of compound 4 or 5 [20] with triethyl orthoace-
tate at reflux temperature, gave 2,5,10-trimethyl-11-(p-
nitrophenyl)-9,11-dihydropyrazolo[49,39:5,6]pyrano[3,2-
e][1,2,4]triazolo-[1,5-c]pyrimidine 6 or 3,5,10-trimethyl-11-
underwent a Dimroth-type rearrangement [9, 21] under
the conditions of the reaction. To prove this assumption,
compound 7 was converted into its corresponding
[1,2,4]triazolo[1,5-c]pyrimidine derivative 6, by heating in
presence of a base, which presumably involves a sequence
of ring opening and ring closure reactions as depicted in
Scheme 3. Likewise, when compound 4 was refluxed with
triethyl orthoformate, it gave 5,10-dimethyl-11-(p-nitro-
phenyl)-9,11-dihydropyrazolo[49,39:5,6]pyrano[3,2-e][1,2,4]
triazolo[1,5-c]pyrimidine 8 (Scheme 2). While heating of
compound 5 with triethyl orthoformate, gave two prod-
ucts to which the structures of: 5,10-dimethyl-11-(p-nitro-
phenyl)-9,11-dihydropyrazolo[49,39: 5,6] pyrano[3,2-e]
[1,2,4] triazolo[4,3-c]pyrimidine 9, as a major product, and
9,9-diethoxymethyl-5,10-dimethyl-11-(p-nitrophenyl)-
(p-nitrophenyl)-9,11-dihydropyrazolo[49,39:5,6]
pyr-
ano[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine 7, respectively
(Scheme 2). It was noticed that the two triazolopyrimi-
dine derivatives 6 and 7 showed no appreciable differ-
ence in the fragmentation pattern under electron impact
(see Experimental), however, the 1H-NMR spectra of tria-
zolo[4,3-c]pyrimidine derivative 7 revealed that the
methyl protons (C3-CH3 and C5-CH3), respectively,
appeared at a more downfield chemical shift when com-
pared with that of the [1,2,4]triazolo[1,5-c]pyrimidine
derivative 6 (Table 1); these data are in agreement with
the reported results of related compounds [6, 7, 11].
9,11-dihydro-pyrazole[49,39:5,6]
pyrano[3,2-e][1,2,4]tria-
This confirmed that the product obtained from the
reaction with hydrazino derivative 5 differs from those
obtained from the reaction with the imino derivative 4.
However, when compound 5washeated underreflux tem-
perature in acetic acid, it afforded compound 6 probably
via the intermediacy of its isomer [1,2,4]triazolo[4,3-c]pyri-
midine 7 which was not isolated in this reaction, but
zolo[4,3-c]pyrimidine 10, isolated as a side product in 37%
yield, could be assigned (Scheme 2). Triethyl orthofor-
mate is considered as an alkylating agent for the NH of the
pyrazole moiety, and compound 10 can be considered as a
new pyrazole N9-acyclonucleoside. The triazolopyrimi-
dine derivatives 8, 9, and 10 showed differences in the 1H-
NMR spectra, where the triazolo[4,3-c]pyrimidine deriv-
i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

Arch. Pharm. Chem. Life Sci. 2007, 340, 345–351
Pyrazolopyranotriazolopyrimidine Derivatives
347
Scheme 3. Conversion of compounds 8 and 9.
Table 1. Correlations of 1H-NMR spectra.
Compd. No d C5-CH3 d C3-H
d C2-H
d C3-CH3 d C2-CH3
6
7
8
2.36
2.82
2.79
2.85
2.83
2.38
2.99
2.27
–
–
–
9.45
9.34
–
–
–
–
–
8.41
–
–
–
–
2.93
–
–
–
–
–
–
2.81
–
–
–
–
–
–
2.73
9
10
11
14
15
–
–
atives 9 and 10 revealed that the protons (C3-H and C5-CH3),
respectively, appeared at a more downfield chemical shift
when compared with that of the [1,2,4]triazolo[1,5-c]pyri-
midine derivative 8 (Table 1). Also, when compound 5 was
refluxed with formic acid, it afforded compound 8 prob-
ably via the intermediacy of its isomer [1,2,4]triazolo[4,3-
c]pyrimidine 9; and to prove this assumption, compound
9 was converted into its corresponding [1,2,4]triazolo[1,5-
c]pyrimidine derivative 8, by heating in piperidine and
ethanol (Scheme 3).
Scheme 4. Synthesis route of compound 11–15.
Condensation of compound 5 with p-nitrobenzalde-
hyde, p-methoxybenzaldehyde in the presence of a few
drops of piperidine and also with aldohexose [22, 23],
namely D-glucose, in the presence of a catalytic amount
of glacial acetic acid took place by heating under reflux
in ethanol, where the corresponding hydrazones 12a-c
were produced. Attemps to cyclize the latter compounds
to their corresponding [1,2,4]triazolo[4,3-c]pyrimidine
derivatives by refluxing with bromine in glacial acetic
acid failed.
Heterocyclic azides, especially azidomethines, can
exist in equilibrium with their tetrazolo tautomers and
this equilibrium is affected by many factors: pH, temper-
ature, the nature of the substituents around the (C=N),
and the used solvent [24–26]. This equilibrium can be
shifted in either direction by controlling these factors,
and the IR spectroscopy is helpful in revealing which
form is predominant, since the azido structure can show
Similarly, when the hydrazino derivative 5 was re-
fluxed with 1-naphthylacetic acid in the presence of
phosphorus oxychloride, it afforded the polycyclic 5,10-
dimethyl-3-naphthalen-1-ylmethyl-11-(p-nitrophenyl)-
9,11-dihydropyrazolo[49,39:5,6]pyrano[3,2-e][1,2,4]tria-
zolo[1,5-c]pyrimidine 11 probably via a Dimroth-type
rearrangement of the [1,2,4]triazolo[4,3-c]pyrimidine
intermediate under the acidic conditions of the reaction
1
[6, 7]. That was judged from the H-NMR signal of the
methyl proton (C5-CH3) which appeared at d 2.38 ppm; if
the [1,2,4]triazolo[4,3-c] isomer was the product, the C5-
methyl group would have been expected to be more de-
shielded and to appear at a more downfield position
(Table 1); these data are in agreement with reported
results of related compounds [6, 7, 11].
a characteristic band in the region m 2100–2200 cm– 1
Thus, nitrosation of the hydrazino group of compound
5, afforded 5,10-dimethyl-11-(p-nitrophenyl)-9,11-dihy-
.
i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

348
A. H. Shamroukh et al.
Arch. Pharm. Chem. Life Sci. 2007, 340, 345–351
Table 2. Antimicrobial activity of some synthesized com-
dropyrazolo[49,39:5,6]pyrano[3,2-e]tetrazolo[1,5-c]pyrimi-
dine 14. Analytical and spectral data are in agreement
with the proposed structure (see Experimental). In partic-
ular, the IR spectrum of compound 14 did not show
absorption frequency indicative for the azido group. The
formation of the tetrazolo structure in compound 14
may be caused by the effect of an electron-donating
group (CH3), which stabilizes the tetrazolo structure.
The N9-acyclic nucleosides of pyrazolo[49,39:5,6]pyr-
ano[2,3-e][1,2,4]triazolo[1,5-c]pyrimidine derivatives are
still not known (to the best of our knowledge) in the liter-
ature. In continuation of our previous work in preparing
various cyclic and acyclic nucleosides of different hetero-
cyclic compounds[17, 18, 20, 22, 27], in this report, we
described the synthesis of N9-acyclic nucleoside related to
pyrazolo[49,39:5,6]pyrano[2,3-e][1,2,4]triazolo[1,5-c]pyrimi-
dine derivatives by treating the sodium salt of compound
7 (generated in situ, see Experimental) with 2-chloroethyl
methyl ether to afford the corresponding N9-acyclic
poundsa).
Disc diffusion test (mm) Microorganisms
Bacteria
Gram-
Gram-
Yeast
Fungi
negative
positive
Compound
Escherichia Bacillus
Candida
albicans
Aspergillus
niger
coli
subtillis
Streptomycinb) +++
+++
+++
+
1
4
5
6
7
8
9
11
12c
14
+
+
+
+
+
+
+
+
+
+
-
-
+
-
+
-
+
-
+
+
-
-
-
-
-
-
++
+
+++
-
++
-
++
++
++
-
+
-
-
-
a)
c = 2 lg/mL in DMSO.
c = 25 lg/mL in DMSO, (Lot. 30730, Bioanalyse Turkey).
nucleoside:
9-(2-methoxyethyl)-2,5,10-trimethyl-11-(p-
b)
nitrophenyl)-9,11-dihydropyrazolo[49,39:5,6]pyrano[2,3-e]
[1,2,4]triazolo[1,5-c]pyrimidine 15 (Scheme 4). The struc-
tural assignment and site of nucleosidation of compound
15 was assigned on the basis of the elemental and spec-
tral data (see Experimental).
+++ highly sensitive (14–16 mm).
++ fairly sensitive (12–14 mm).
+ slightly sensitive (10–12 mm); – not sensitive.
gal activity more effective than that of the isomeric
[1,2,4]triazolo[1,5-c]pyrimidine derivatives 6, 8, and 11.
On the other hand, the hydrazino, hydrazone, and tetra-
zolo[1,5-c]pyrimidine derivatives 5, 12c, and 14 revealed
antifungal activity more effective than that of the amino
imino derivative 4.
Biological evaluation
The antimicrobial activity of some newly synthesized
compounds 1, 4, 5, 6, 7, 8, 9, 11, 12c, and 14 were tested
and the results are shown in Table 2. Evaluation of the
new compounds established that compounds 5, 7, 9, 12c,
and 14 were slightly active against gram-positive and
gram-negative bacteria. On the other hand, it was found
that compounds 7 and 9 revealed more effective activity
against yeast than the other tested compounds while
compounds 5, 6, 7, 9, 12c, and 14 revealed a slight to
strong antifungal activities. In particular, compound 7
revealed higher antifungal activity than that of the other
tested compounds and the reference drug.
We are grateful to Dr. H. M. Awad, Department of Natural and
Microbial Products, National Research Centre, for his biologi-
cal evaluation.
Experimental
Chemistry
All melting points are uncorrected and measured using Electro-
thermal IA 9100 apparatus, (Shimadzu, Tokyo, Japan). IR spectra
were recorded as potassium bromide pellets on a Perkin-Elmer
1650 spectrophotometer (Perkin Elmer, Norwalk, CT, USA),
National Research Centre, Cairo, Egypt. 1H-NMR and 13C-NMR
spectra were determined on a Jeol-Ex-300 NMR spectrometer
(JEOL, Tokyo, Japan) and chemical shifts were expressed as part
per million; ppm (d values) against TMS as internal reference
(Faculty of Science, Cairo University, Cairo, Egypt). Mass spectra
were recorded on EI + Q1 MSLMR UPLR, National Research
Centre, Cairo, Egypt. Microanalyses were operated using Mario
El Mentar apparatus, Organic Microanalysis Unit, National
Research Centre, Cairo, Egypt and the results were within the
accepted range (l 0.40) of the calculated values. Column chroma-
Conclusion
Synthesis and structure characterization of pyrazo-
lo[49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine
derivatives 7 and 9 and their isomerization to pyrazo-
lo[49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine
derivatives 6 and 8, respectively, are reported. Moreover,
pyrazolo[49,39:5,6]pyrano[3,2-e]tetrazolo[1,5-c]pyrimidine
derivative 14 was obtained. Structure-activity correla-
tions of the obtained results revealed that the [1,2,4]tria-
zolo[4,3-c]pyrimidine derivatives 7 and 9 showed antifun-
i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

Arch. Pharm. Chem. Life Sci. 2007, 340, 345–351
Pyrazolopyranotriazolopyrimidine Derivatives
349
tography was performed on Silica gel 60 (particle size 0.06–
0.20 mm; Merck, Darmstadt, Germany). Compounds 1 and 5
were prepared according to a reported method [16].
Method C: A solution of compound 7 (0.37 g, 1 mmol) in etha-
nol (20 mL) in the presence of a few drops of piperidine was
heated under reflux temperature for 30 min. The solvent was
removed under reduced pressure leaving a solid product which
was recrystallized from dioxane to give a compound identical in
all aspects with compound 6 obtained before. Yield 62%, mp.
364–3668C. IR m 3225 (NH) cm– 1. 1H-NMR (DMSO-d6): d 1.90 (s, 3H,
C10-CH3), 2.36 (s, 3H, C5-CH3), 2.81 (s, 3H, C2-CH3), 5.72 (s, 1H,
pyran-H), 7.57 (d, J = 9 Hz, 2H, Ar-H), 8.11 (d, J = 8.4 Hz, 2H, Ar-H),
12.31 (s, 1H, NH, D2O exchangeable). 13C-NMR (DMSO-d6): d 9.8
(C10-CH3), 12.8 (C2-CH3), 19.9 (C5-CH3), 34.7 (C-11), 95.5 (C-11a),
97.3 (C-10a), 123, 129, 134.5, 136 (Ar-C), 144.5 (C-7a), 146.1 (C-10),
148.5 (C-11b), 149.5 (C-2), 150.5 (C-5), 151.2 (C-6a). MS m/z (%): 377
[M+] (18.01). Anal. calcd. for C18H15N7O3: C 57.29, H 4.01, N 25.98.
Found: C 57.40, H 3.98, N 25.90.
Ethyl-N-[2-acetyl-5-cyano-3-methyl-4-(p-nitrophenyl)-2,4-
dihydropyrano[2,3-c]pyrazol-6-yl]ethanimidate 2
A mixture of compound 1 (2.97 g, 10 mmol) in triethyl orthoace-
tate (5 mL) and acetic anhydride (5 mL) was refluxed for 5 h. The
reaction mixture was evaporated under reduced pressure and
the residue was filtered off, dried, and recrystallized from abso-
lute ethanol to give compound 2. Yield 85%, mp. 160–1628C. IR m
2220 (CN) and 1720 (CO) cm– 1. 1H-NMR (DMSO-d6): d 1.28 (t, J =
9 Hz, 3H, OCH2CH3), 2.13 (s, 3H, C3-CH3), 2.15 (s, 3H, N=C-CH3),
2.48 (s, 3H, O=C-CH3), 4.24 (q, J = 9 Hz, 2H, OCH2CH3), 5.20 (s, 1H,
pyran-H), 7.62 (d, J = 9 Hz, 2H, Ar-H), 8.24 (d, J = 9 Hz, 2H, Ar-H).
MS m/z (%): 409 [M+] (81.25). Anal. calcd. for C20H19N5O5: C 58.68, H
4.68, N 17.11. Found: C 58.61, H 4.63, N 17.23.
3,5,10-Trimethyl-11-(p-nitrophenyl)-9,11-
dihydropyrazolo[49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[4,3-
c]pyrimidine 7
Ethyl-N-[5-cyano-3-methyl-4-(p-nitrophenyl)-2,4-
Compound 5 (3.53 g, 10 mmol) was heated under reflux temper-
ature in triethyl orthoacetate (40 mL) for 5 h. The product which
separated on cooling was filtered off, dried, and recrystallized
from dioxane to give compound 7. Yield 80%, mp. 323–3258C. IR
m 3228 (NH) cm– 1. 1H-NMR (DMSO-d6): d 1.96 (s, 3H, C10-CH3), 2.82
(s, 3H, C5-CH3), 2.93 (s, 3H, C3-CH3), 5.67 (s, 1H, pyran-H), 7.58 (d, J
= 9 Hz, 2H, Ar-H), 8.10 (d, J = 8.4 Hz, 2H, Ar-H), 12.24 (s, 1H, NH,
D2O exchangeable). 13C-NMR (DMSO-d6): d 9.8 (C10-CH3), 13.6 (C3-
CH3), 21.8 (C5-CH3), 34.8 (C-11), 95.9 (C-11a), 97.4 (C-10a), 123,
128, 129, 136 (Ar-C), 144.5 (C-7a), 146.2 (C-10), 149.1 (C-11b), 150.5
(C-3), 151.2 (C-5), 151.6 (C-6a). MS m/z (%): 377 [M+] (29.98). Anal.
calcd. for C18H15N7O3: C 57.29, H 4.01, N 25.98. Found: C 57.33, H
4.11, N 25.84.
dihydropyrano[2,3-c]pyrazol-6-yl]ethanimidate 3
To a solution of compound 2 (2.45 g, 5 mmol) in absolute etha-
nol (20 mL), ammonium hydroxide solution (1 mL, 25%) was
added with stirring at room temperature for 1 h. The formed
precipitate was filtered off, dried, and recrystallized from abso-
lute ethanol to give compound 3. Yield 51%, mp. 238–2408C. IR
m 3279 (NH), 2215 (CN) cm– 1. 1H-NMR (DMSO-d6): d 1.28 (t, J = 9 Hz,
3H, OCH2CH3), 1.80 (s, 3H, C3-CH3), 2.12 (s, 3H, N=C-CH3), 4.23 (q, J
= 9 Hz, 2H, OCH2CH3), 5.08 (s, 1H, pyran-H), 7.56 (d, J = 9 Hz, 2H,
Ar-H), 8.23 (d, J = 9 Hz, 2H, Ar-H), 12.50 (s, 1H, NH, D2O exchange-
able). MS m/z (%): 367 [M+] (61.04). Anal. calcd. for C18H17N5O4: C
58.85, H 4.66, N 19.06. Found: C 58.91, H 4.67, N 18.99.
6-Amino-3,7-dimethyl-5-imino-4-(p-nitrophenyl)-2,4,5,6-
5,10-Dimethyl-11-(p-nitrophenyl)-9,11-
tetrahydropyrazolo[49,39:5,6]pyrano[2,3-d]pyrimidine 4
To a solution of compound 2 (0.40 g, 1 mmol) in dry benzene
(30 mL), hydrazine hydrate (4 mL, 99%) was added with stirring
at 08C for 1 h. The obtained product was filtered off, dried, and
recrystallized from ethanol to give compound 4. Yield 40%, mp.
282–2848C. IR m 3240–3160 (NH2, NH) cm– 1. 1H-NMR (DMSO-d6):
d 1.93 (s, 3H, C3-CH3), 2.41 (s, 3H, C7-CH3), 5.21 (s, 1H, pyran-H),
5.67 (brs, 2H, NH2, D2O exchangeable), 6.45 (s, 1H, NH, D2O
exchangeable), 7.56 (d, J = 9 Hz, 2H, Ar-H), 8.12 (d, J = 8.4 Hz, 2H,
Ar-H), 12.06 (s, 1H, NH, D2O exchangeable). MS m/z (%): 353 [M+]
(19.6). Anal. calcd. for C16H15N7O3: C 54.39, H 4.28, N 27.75.
Found: C 54.45, H 4.33, N 27.64.
dihydropyrazolo[49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[1,5-
c]pyrimidine 8
Method A: A mixture of compound 4 (0.35 g, 1 mmol) and
triethyl orthoformate (30 mL) was refluxed for 10 h. On cooling
a precipitate formed which was filtered off, dried, and recrystal-
lized from dioxane to give compound 8. Yield 80%, mp. 357–
3598C.
Method B: Compound 5 (3.53 g, 1 mmol) was heated under
reflux temperature in formic acid (40 mL, 85%) for 10 h. The
reaction mixture was cooled and poured into water. The formed
solid was filtered off, dried, and recrystallized from dioxane to
give a product identical in all aspects with compound 8 obtained
before. Yield 77%, mp. 357–3598C.
2,5,10-Trimethyl-11-(p-nitrophenyl)-9,11-
Method C: A solution of compound 9 (0.39 g, 1 mmol) in etha-
nol (20 mL) in a presence of a few drops of piperidine was heated
under reflux temperature for 1 h. The reaction mixture was
evaporated to dryness and the remaining solid was recrystal-
lized from dioxane to give a compound identical in all aspects
with compound 8 obtained before. Yield 50%, mp. 357–3598C. IR
m 3224 (NH) cm– 1. 1H-NMR (DMSO-d6): d 1.96 (s, 3H, C10-CH3), 2.79
(s, 3H, C5-CH3), 5.77 (s, 1H, pyran-H), 7.58 (d, J = 9 Hz, 2H, Ar-H),
8.10 (d, J = 8.4 Hz, 2H, Ar-H), 8.41 (s, 1H, C2-H), 12.34 (s, 1H, NH,
D2O exchangeable). 13C-NMR (DMSO-d6): d 9.8 (C10-CH3), 19.8 (C5-
CH3), 35 (C-11), 95 (C-11a), 97.3 (C-10a), 123, 129, 135, 136 (Ar-C),
146 (C-7a), 147.5 (C-10), 148.3 (C-2), 150 (C-11b), 151.5 (C-5), 154.8
(C-6a). MS m/z (%): 363 [M+] (19.33). Anal. calcd. for C17H13N7O3: C
56.20, H 3.61, N 26.99. Found: C 56.31, H 3.58, N 26.91.
dihydropyrazolo[49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[1,5-
c]pyrimidine 6
Method A: A mixture of compound 4 (0.18 g, 0.5 mmol) and
triethyl orthoacetate (30 mL) was refluxed for 10 h. The reaction
mixture was evaporated to dryness and the remaining solid was
recrystallized from dioxane to give compound 6. Yield 70%, mp.
364–3658C.
Method B: Compound 5 (3.53 g, 1 mmol) was heated under
reflux temperature in acetic acid (30 mL) for 8 h. The reaction
mixture was cooled and poured into water. The formed solid
was filtered off, dried, and recrystallized from dioxane to give a
product identical in all aspects with compound 6 obtained
before. Yield 77%, mp. 364–3658C.
i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

350
A. H. Shamroukh et al.
Arch. Pharm. Chem. Life Sci. 2007, 340, 345–351
Synthesis of compounds 9 and 10
N-{3,7-Dimethyl-4-(p-nitrophenyl)-2,4-
Compound 5 (3.53 g, 10 mmol) was heated under reflux temper-
ature in triethyl orthoformate (40 mL) for 5 h. The reaction mix-
ture was kept at room temperature overnight, then the solvent
was evaporated to dryness and the remaining solid was purified
on TLC plate using chloroform: methanol (9 : 1) as an eluent to
separate two products, 9 as a major product and 10 as a minor
product.
dihydropyrazolo[49,39:5,6]pyrano[2,3-d]pyrimidin-5-yl}-N9-
(p-nitrobenzylidene)hydrazine 12a
Yield (90%, ethanol), mp. 333–3358C. IR m 3163 (NH), 3113 (NH)
1
cm– 1. H-NMR (DMSO-d6): d 1.96 (s, 3H, C3-CH3), 2.45 (s, 3H, C7-
CH3), 6.05 (s, 1H, pyran-H), 7.41 (d, J = 8.1 Hz, 2H, Ar-H), 7.94 (d, J =
9 Hz, 2H, Ar-H), 8.07 (d, J = 9 Hz, 2 H, Ar-H), 8.16 (s, 1H, N=CH),
8.30 (d, J = 8.4 Hz, 2H, Ar-H), 11.05 (s, 1H, NH, D2O exchangeable),
12.24 (s, 1 H, NH, D2O exchangeable). 13C-NMR (DMSO-d6): d 10.0
(C3-CH3), 25.2 (C7-CH3), 33.3 (C-4), 94.7 (C-4a), 98.0 (C-3a), 124-146
(Ar-C), 151 (C-3), 154.7 (C-9a), 159 (C-8a), 159.1 (N=CH), 164.4 (C-7),
165.9 (C-5). MS m/z (%): 486 [M+] (16.36). Anal. calcd. for
C23H18N8O5: C 56.79, H 3.73, N 23.03. Found: C 56.85, H 3.70, N
23.00.
5,10-Dimethyl-11-(p-nitrophenyl)-9,11-
dihydropyrazolo[49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[4,3-
c]pyrimidine 9
Yield 49%, mp. 390–3928C. IR m 3225 (NH) cm– 1. 1H-NMR (DMSO-
d6): d 1.96 (s, 3H, C10-CH3), 2.85 (s, 3H, C5-CH3), 5.75(s, 1H, pyran-H),
7.60 (d, J = 9 Hz, 2H, Ar-H), 8.15 (d, J = 9 Hz, 2H, Ar-H), 9.45 (s, 1 H,
C3-H), 12.35 (s, 1H, NH, D2O exchangeable). 13C-NMR (DMSO-d6): d
9.9 (C10-CH3), 20.5 (C5-CH3), 35 (C-11), 95.5 (C-11a), 97.3 (C-10a),
123, 129, 135, 136.5 (Ar-C), 146 (C-7a), 148 (C-10), 149 (C-3), 151 (C-
11b), 152 (C-5), 155 (C-6a). MS m/z (%): 363 [M+] (50.74). Anal. calcd.
for C17H13N7O3: C 56.20, H 3.61, N 26.99. Found: C 56.34, H 3.63, N
26.83.
N-[3,7-Dimethyl-4-(p-nitrophenyl)-2,4-
dihydropyrazolo[49,39:5,6]pyrano[2,3-d]pyrimidin-5-yl]-N9-
(p-methoxybenzylidene)hydrazine 12b
Yield (92%, ethanol), mp. 283–2858C. 1H-NMR (DMSO-d6): d 2.06
(s, 3H, C3-CH3), 2.41 (s, 3H, C7-CH3), 3.80 (s, 3H, OCH3), 6.04 (s, 1H,
pyran-H), 7.02 (d, J = 9 Hz, 2H, Ar-H), 7.42 (d, J = 9 Hz, 2H, Ar-H),
7.63 (d, J = 9 Hz, 2H, Ar-H), 8.02 (s, 1H, N=CH), 8.08 (d, J = 9 Hz, 2H,
Ar-H), 10.53 (s, 1H, NH, D2O exchangeable), 12.21 (s, 1H, NH, D2O
exchangeable). 13C-NMR (DMSO-d6): d 9.9 (C3-CH3), 25.2 (C7-CH3),
33.2 (C-4), 55 (OCH3), 94.7 (C-4a), 98 (C-3a), 123–146 (Ar-C), 152 (C-
3), 155 (C-9a), 159 (C-8a), 160 (N=CH), 164 (C-7), 165 (C-5). MS m/z
(%): 471 [M+] (17.77). Anal. calcd. for C24H21N7O4: C 61.14, H 4.49, N
20.80. Found: C 61.30, H 4.50, N 20.58.
9,9-Diethoxymethyl-5,10-dimethyl-11-(p-nitrophenyl)-
9,11-dihydropyrazolo[49,39:5,6]pyrano [3,2-e]
[1,2,4]triazolo[4,3-c]pyrimidine 10
Yield 37%, mp. 215–2188C. 1H-NMR (DMSO-d6): d 1.05 (t, J = 9 Hz,
3H, OCH2CH3), 1.20 (t, J = 9 Hz, 3H, OCH2CH3), 1.96 (s, 3H, C10-CH3),
2.83 (s, 3H, C5-CH3), 4.12 (q, J = 9 Hz, 2H, CH2 CH3), 4.4 (q, J = 9Hz,
2H, CH2CH3), 5.76 (s, 1H, pyran-H), 6.09 (s, 1H, CH(OC2H5)2), 7.60
(d, J = 9 Hz, 2H, Ar-H), 8.13 (d, J = 9 Hz, 2H, Ar-H), 9.34 (s, 1H, C3-H).
MS m/z (%): 465 [M+] (11.40), 420 [M+-OC2H5] (2.91), 363 [(M++H)-
CH(OC2H5)2] (8.8), 103 [+CH(OC2H5)2] (100). Anal. calcd. for
C22H23N7O5: C 56.77, H 4.98, N 21.06. Found: C 56.90, H 4.90, N
21.01.
(2R,3R,4R,5S)-6-{[3,7-Dimethyl-4-(p-nitrophenyl)-2,4-
dihydropyrazolo [49,39:5,6]pyrano[2,3-d]pyrimidin-5-yl]-
hydrazono}hexane-1,2,3,4,5-pentaol 12c
Yield (95%, dioxane), mp. 133–1358C. IR m 3411–3310 (broad
1
NH, OH) cm– 1. H-NMR (DMSO-d6): d 1.88 (s, 3H, C3-CH3), 2.33 (s,
3H, C7-CH3), 2.99–3.63 (some of the alditol protons congregated
with water signals), 3.65–3.90 (m, 2H, CH2OH), 4.20–4.70 (m,
2H, 2OH, D2O exchangeable), 5.0 (m, 1H, OH, D2O exchangeable),
5.30 (d, 1H, OH, D2O exchangeable), 5.60 (s, 1H, pyran-H), 5.92 (d,
1H, OH, D2O exchangeable), 7.33–7.59 (m, 3H, 2Ar-H + N=CH),
8.10 (d, J = 9 Hz, 2H, Ar-H), 10.40 (s, 1H, NH, D2O exchangeable),
12.13 (s, 1H, NH, D2O exchangeable). MS m/z (%): 454 [M+-(CH2OH
+ CHOH)] (14.45). Anal. calcd. for C22H25N7O8: C 51.26, H 4.89, N
19.02. Found: C 51.31, H 4.90, N 18.96.
The attempted cyclization of compounds 12a-c to their corre-
sponding pyrazolo [49,39:5,6]pyrano[3,2-e][1,2,4]triazolo[4,3-c]pyr-
imidine derivatives 13a–c by refluxing with bromine in glacial
acetic acid did not succeed, however, unidentified products
were isolated.
5,10-Dimethyl-3-naphthalen-1-ylmethyl-11-(p-
nitrophenyl)-9,11-dihydropyrazolo[49,39:5,6]pyrano[3,2-e]
[1,2,4]triazolo[1,5-c]pyrimidine 11
A mixture of compound 5 (3.53 g, 10 mmol) in phosphorus oxy-
chloride (40 mL) and 1-naphthylacetic acid (1.86 g, 10 mmol)
was heated under reflux temperature for 5 h. The reaction mix-
ture was poured onto crushed ice, and then the obtained solid
was filtered off, dried, and recrystallized from dioxane to give
compound 11. Yield 81%, mp. 222–2238C. IR m 3220 (NH) cm– 1
.
1H-NMR (DMSO-d6): d 1.9 (s, 3H, C10-CH3), 2.38 (s, 3H, C5-CH3), 4.0 (s,
2H, CH2), 5.7 (s, 1H, pyran-H), 7.37–8.14 (m, 11H, Ar-H), 12.3 (s,
1H, NH, D2O exchangeable). MS m/z (%): 503 [M+] (13.02). Anal.
calcd. for C28H21N7O3: C 66.79, H 4.20, N 19.47. Found: C 66.84, H
4.17, N 19.45.
5,10-Dimethyl-11-(p-nitrophenyl)-9,11-dihydropyrazolo-
Synthesis of compounds 12a–c
[49,39:5,6]pyrano[3,2-e]tetrazolo[1,5-c]pyrimidine 14
General procedure: A solution of compound 5 (3.53 g, 10 mmol)
in ethanol (50 mL), p-nitrobenzaldehyde (1.51 g, 10 mmol), p-
methoxybenzaldehyde (0.12 mL, 10 mmol) in the presence of a
few drops of piperidine or D-glucose (1.8 g, 10 mmol) in the pres-
ence a catalytic amount of acetic acid was heated at 808C for 1 h.
On cooling, a precipitate formed which was filtered off, dried,
and recrystallized from appropriate solvent to give compounds
12a–c, respectively.
A cooled solution of compound 5 (3.53 g, 10 mmol) in diluted
HCl (20 mL) was treated drop wise with a cooled solution of
sodium nitrite (prepared from 1 g sodium nitrite dissolved in
15 mL water), then stirred at room temperature for 2 h. The sep-
arated solid was filtered off, dried, and recrystallized from etha-
nol to give compound 14. Yield 87%, mp. 255–2578C. IR m 3219
(NH) cm– 1. 1H-NMR (DMSO-d6): d 1.96 (s, 3H, C10-CH3), 2.99 (s, 3H,
C5-CH3), 5.89 (s, 1 H, pyran-H), 7.63 (d, J = 9 Hz, 2 H, Ar-H), 8.15 (d, J
i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

Arch. Pharm. Chem. Life Sci. 2007, 340, 345–351
Pyrazolopyranotriazolopyrimidine Derivatives
351
= 9 Hz, 2 H, Ar-H), 12.45 (s, 1 H, NH, D2O exchangeable). MS m/z
(%): 364 [M+] (28). Anal. calcd. for C16H12N8O3: C 52.75, H 3.32, N
30.76. Found: C 52.64, H 3.21, N 30.98.
[5] S. A. Swelam, O. I. Abdel-Salam, M. E. A. Zaki, J. Serb.
Chem. Soc. 1999, 64, 655–662.
[6] C. J. Shishoo, M. B. Devani, G. V. Ullas, S. Ananthan, V. S.
Bhadti, J. Heterocycl. Chem. 1981, 18, 43–46.
9-(2-Methoxyethyl)-2,5,10-trimethyl-11-(p-nitrophenyl)-
9,11-dihydropyrazolo[49,39:5,6]pyrano [2,3-e]
[7] C. J. Shishoo, M. B. Devani, G. V. Ullas, S. Ananthan, V. S.
Bhadti, J. Heterocycl. Chem. 1985, 22, 825–830.
[1,2,4]triazolo[1,5-c]pyrimidine 15
[8] C. J. Shishoo, M. B. Devani, G. V. Ullas, S. Ananthan, V. S.
A mixture of compound 6 (0.38 g, 1 mmol) and 50% oil-
immersed sodium hydride (0.05 g, 0.2 mmol) in dry dimethylfor-
mamide (30 mL) was stirred at 708C for 1 h, then cooled to room
temperature. 2-Chloroethylmethyl ether (1 mmol) was added,
and stirred at 908C for 8 h. The mixture was evaporated under
reduced pressure and chromatographed on a silica gel column
with a chloroform : methanol mixture (9 : 1) as an eluent to give
compound 15. Yield 54%, oil. 1H-NMR (DMSO-d6): d 2.08 (s, 3H, C10-
CH3), 2.27 (s, 3H, C5-CH3), 2.73 (s, 3H, C2-CH3), 3.24 (s, 3H, OCH3),
3.33–3.41 (m, 4H, CH2CH2), 5.40 (s, 1H, pyran-H), 7.04 (d, J = 9 Hz,
2H, Ar-H), 7.86 (d, J = 8.4 Hz, 2H, Ar-H). Anal. calcd. for C21H21N7O4:
C 57.93, H 4.86, N 22.52. Found: C 58.01, H 4.81, N 22.49.
Bhadti, J. Heterocycl. Chem. 1985, 22, 831–833.
[9] V. Nair, A. G. Lyons, D. F. Purdy, Tetrahedron 1991, 47,
89498968.
[10] A. A. Moneer, M. M. Ismail, A. N. Osman, B. Abdel-Fattah,
K. M. Ghoniem, Egypt. J. Pharm. Sci. 1993, 34, 623–641.
[11] A. E. Rashad, O. A. Heikal, A. H. El-Nezhawy, F. M. E.
Abdel-Megeid, Heteroatom Chem. 2005, 16, 226–234.
[12] G. W. Miller, F. L. Rose, J. Chem. Soc. 1964, 5642–5644.
[13] G. W. Miller, F. L. Rose, J. Chem. Soc. 1965, 3369–3372.
[14] M. Robba, J. M. Lecomte, M. Cugnon de Sevricourt, C. R.
Acad. Sci. Paris, Ser. C 1968, 266, 128–130; Chem. Abstr.
1968, 69, 27365j.
Antimicrobial activity of the newly synthesized
[15] F. M. Abdel Razek, H. A. Ead, J. Prakt. Chem. 1988, 330,
compounds
585–589.
The in-vitro antimicrobial activity of the synthesized compounds
was tested against several pathogenic representatives: Escheri-
chia coli, Bacillus subtilis, Candida albicans, and Aspergillus niger.
All microorganisms used were obtained from the Department of
Chemistry of Natural and Microbial Products, National Research
Centre, Cairo, Egypt. Disc-diffusion sensitivity testing was done
in the manner identical to that described by Bauer et al. [28].
Media for disc-sensitivity tests were nutrient agar and Mꢀller–
Hinton agar (MHA), purchased from Difco, USA. The non sterile
powder of the tested compounds was dissolved in sterile DMSO
to yield 2 lgmL– 1 passed through 0.2 lm membrane filter (Milli-
pore Corp., USA). The filtrates were dispensed as 2 mL samples
into sterile, small screw-capped vials and kept stored at –158C.
DMSO as a solvent showed no inhibition zones. The results were
compared to Streptomycin as a reference drug.
[16] M. E. A. Zaki, E. M. Morsy, F. M. Abdel-Motti, F. M. E.
Abdel–Megeid, Heterocycl. Comm. 2004, 10, 97–102.
[17] A. H. Shamroukh, A. E. Rashad, H. H. Sayed, Phosphorus,
Sulfur, Silicon 2005, 180, 2347–2360.
[18] F. M. E. Abdel-Megeid, N. A. Hassan, M. A, Zahran, A. E.
Rashad, Sulfur Lett. 1998, 21, 269–284.
[19] A. E. Rashad, H. H. Sayed, A. H. Shamroukh, H. M. Awad,
Phosphorus, Sulfur, Silicon Relat Elem 2005, 180, 2767–
2777.
[20] A. H. Shamroukh, M. E. A. Zaki, E. M. H. Morsy, F. M.
Abdel-Motti, F. M. E. Abdel-Megeid, Arch. Pharm. 2007,
340, 236–243.
[21] G. G. Danagulyan, L. G. Saakyan, M. G. Zalinyan, Khim.
Geterotsikl. Soedin, 1992, 2, 225–227; Chem. Abstr. 1992,
117, 233226c.
[22] A. E. Rashad, M. M. Mohamed, M. E. A. Zaki, S. S. Fata-
References
hala, Arch. Pharm. 2006, 339, 664–669.
[23] M. T. Abdel-Aal, W. A. El-Sayed, E. H. El-Ashry, Arch.
Pharm. 2006, 339, 656–663.
[1] A. Konnecke, R. Dorre, E. Lippmann, Tetrahedron Lett.
1978, 19, 2071–2074.
[24] H. Reimlinger, Chem. Ber. 1970, 103, 1900–1907.
[25] M. Tisler, Synthesis 1973, 123–136.
[2] P. G. Baraldi, B. Cacciari, G. Spalluto, M. J. Pineda de las
Infantas, et al., Farmaco 1996, 51, 297–300.
[26] C. J. Shishoo, K. S. Jain, J. Heterocycl. Chem. 1992, 29, 883–
[3] P. G. Baraldi, B. Cacciari, M. Viziano, S. Dionisotti, E.
Ongini, PCT Int. Appl. WO 9705, 138 (Cl. CO7D 487/14)
13 Feb. 1997, IT Appl. 95/ MI 1, 671, 28 Jul. 1995; Chem.
Abstr. 1997, 126, 212155z.
893.
[27] A. E. Rashad, A. H. Shamroukh, M. A. Ali, F. M. Abdel-
Motti, Heteroatom Chem. 2007, 18, 214–282.
[4] G. Biagi, I. Giorgi, O. Livi, C. Manera, V. Scartoni, J. Hetero-
cycl. Chem. 1999, 36, 1195–1198.
[28] A. W. Bauer, M. M. Kirby, J. C. Sherris, M. Turck, Am. J.
Clin. Pathol. 1996, 45, 493–496.
i 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com