Green approach towards the facile synthesis of dihydropyrano(c)chromene and pyrano[2,3-d]pyrimidine derivatives and their biological evaluation

Article abstract of DOI:10.1007/s00044-012-0288-3

A simple and efficient one-pot synthesis of heteroaryl-substituted dihydropyrano(c)chromenes and pyrano[2,3-d]pyrimidines has been developed. Reaction proceeds via initial Knoevenagel, subsequent Michael and final heterocyclization reactions of heteroaryl aldehyde, malononitrile, and barbituric acid/dimedone. Triethylammonium acetate acts as a green catalyst as well as reusable solvents for this reaction. Short reaction time, environment friendly procedure, reusability, and excellent yields are the main advantages of this procedure. All synthesized compounds have shown good antibacterial activity against different microbial stains but not active against cancer cell lines.

Full text of DOI:10.1007/s00044-012-0288-3

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-012-0288-3
ORIGINAL RESEARCH
Green approach towards the facile synthesis
of dihydropyrano(c)chromene and pyrano[2,3-d]pyrimidine
derivatives and their biological evaluation
•
Pradeep K. Paliwal Srinivasa Rao Jetti
•
Shubha Jain
Received: 8 April 2012 / Accepted: 20 October 2012
Ó Springer Science+Business Media New York 2012
Abstract A simple and efficient one-pot synthesis
of heteroaryl-substituted dihydropyrano(c)chromenes and
pyrano[2,3-d]pyrimidines has been developed. Reaction
proceeds via initial Knoevenagel, subsequent Michael and
final heterocyclization reactions of heteroaryl aldehyde,
malononitrile, and barbituric acid/dimedone. Triethylam-
monium acetate acts as a green catalyst as well as reusable
solvents for this reaction. Short reaction time, environment
friendly procedure, reusability, and excellent yields are the
main advantages of this procedure. All synthesized com-
pounds have shown good antibacterial activity against
different microbial stains but not active against cancer cell
lines.
derivatives are of considerable interest as they possess a
wide range of biological properties such as spasmolytic,
diuretic, antiallergic, anticoagulant, anticancer, and anti-
anaphylactic activity, etc. (Zhang et al., 1982; Atwal et al.,
1992; Hiroshi et al., 1993). Polyfuctionalized pyran deriva-
tives are common structural subunits in variety of important
natural products (Katritzky et al., 1984; Bonsignore et al.,
1993). In addition, they can be used as cognitive enhancers,
for the treatment of neurodegenerative diseases (Riley and
Rankin, 1976). A number of 2-amino-2H pyrans are useful as
photoactive substances also (Armesto et al., 1989).
There are some methods reported in the literature for the
synthesis of polyfuctionalized pyran derivatives (Wang
et al., 2003; Singh et al., 1996). Unfortunately, many of
these processes suffer from limitations such as long reaction
times, hazardous by-products, microwave irradiations, use
of stoichiometric, or even excess amount of base, and use of
metal triflates (Abd El-Rahman et al., 2007; Mobinikhaledi
et al., 2010; Balalaie et al., 2009). The search for a non-
volatile and recyclable alternative is thus holding a key role
in this field of research. The development of cleaner tech-
nologies is a major emphasis in green chemistry. Among the
several aspects of green chemistry, the reduction/replace-
ment of volatile organic solvents from the reaction medium
is of utmost importance. So we tried to explore the new
catalyst that has certain properties such as good thermal and
mechanical stabilities of supported reagents, easy to handle,
of low toxicity, non-corrosive, easy to separate from reac-
tion mixture through filtration, and feasible for reuse.
Ionic liquids as new reaction media and catalyst have
been experimentally and theoretically recognized and
accepted (Holbrey et al., 2000). A great deal of attention
has been given to imidazolium ionic liquid in the past
several years (Martyn and Kenneth, 2000; Louie and
Meade, 1999). However, industrial application of these
Keywords Multi-component ꢀ Green ꢀ
Triethylammonium acetate (TEAA) ꢀ
Dihydropyrano(c)chromene ꢀ Pyrano[2,3-d]pyrimidine ꢀ
Antibacterial and anticancer activity
Introduction
Multi-component reactions (MCRs) have attracted consid-
erable interest because of their exceptional synthetic and
¨
practical efficiency (Domling, 2000). MCRs involve three or
more starting materials reacting in a single flask to form a
new product, where basically all the atoms contribute to the
newly formed product. Chromenes, pyridines, and pyri-
midinones, etc., are some examples of multi-component
synthesis (Sharanin and Klokol, 1984; Jin et al., 2005). Pyran
P. K. Paliwal (&) ꢀ S. R. Jetti ꢀ S. Jain
School of Studies in Chemistry & Biochemistry,
Vikram University, Ujjain 456010, MP, India
e-mail: paliwalchemi@gmail.com
123

Med Chem Res
ionic liquids is limiting because of the high price imi-
dazolium ionic liquids and also due to low reusability
(Namboodiri and Varma, 2002). Triethylammonium ace-
tate (TEAA) is an inexpensive and easily synthesized ionic
liquid that can be used in laboratory without special pre-
cautions, and it has not been used much in heterocyclic
synthesis, only a few reports are there in the literature
(Wang et al., 2006; Balaskar et al., 2010; Sandhu, 2009;
Da-Zhen et al., 2010). Therefore, in this article, we wish to
report triethylammonium ionic liquid-mediated one-pot
synthesis of heteroaryl-substituted pyran derivatives. The
antibacterial and anticancer activities were also tested.
d6): d = 1.18 (t, 9H, CH3), 2.10 (s, 3H, CH3), 3.10 (m, 6H,
CH2), 9.0 (s, 1H, NH) ppm.
General procedure for the synthesis of heteroaryl-
substituted pyrano(c)chromene/pyrano[2,3-d] pyrimidine:
5-Memberd heteroaryl aldehyde (2 mmol), malononitrile
(2 mmol), 5,50-dimethyl-cyclohexane-1,3-dione/barbituric
acid (2 mmol), and TEAA (5 mL) were added to a round
bottom flask. The reaction mixture was stirred at room
temperature for appropriate time (Scheme 1; Table 1). The
completion of the reaction was monitored by TLC. After
completion of the reaction, water (5–10 mL) was added in
reaction mixture, precipitation of product is occurred. The
pure product (6/7) was obtained by recrystallization from
ethanol:water (9:1). Products (6/7) thus obtained were in
high yields.
Experimental
Melting points were determined by open capillary method
and are uncorrected. 1H NMR and 13C NMR analysis were
carried out on a Bruker AM-400 spectrometer in CDCl3/
DMSO-d6. Chemical shift values are reported as d values
(in ppm) relative to tetramethylsilane (TMS) as an internal
standard. IR spectra were recorded on a Perkin-Elmer 298
spectrophotometer. Reactions were monitored by thin layer
chromatography on 0.2 mm silica gel F-252 (Merck)
plates. All chemicals were obtained from Aldrich Chemical
Co. and CDH Chemical Co. and were used without further
purification. Antibacterial activity was tested by the disk
diffusion assay and anticancer activity by using sulforho-
damine B assay against human breast cancer, prostate
cancer, and ovarian cancer cell lines (Grivsky et al., 1980;
Midolo et al., 1995; Drew et al., 1972; Monks et al., 1990).
Procedure of triethylammonium ionic liquid TEAA
synthesis (Wang et al., 2006; Weng et al., 2006): The
synthesis of ionic liquid was carried out in a 250-mL
round-bottomed flask, which was immersed in a water-bath
and fitted with a reflux condenser. Acetic acid (1.5 mol,
90.1 g, and 86.03 mL) was dropped into 101.2 g triethyl-
amine (1 mol, 139.4 mL) at 70 °C within 1 h. After the
addition, the reaction mixture was stirred for 2 h at 80 °C
to ensure that the reaction had proceeded to completion.
The reaction mixture was then dried at 80 °C in high
vacuum (5 mmHg) until the weight of the residue remained
constant. The yield of TEAA was 98 %. 1H NMR (DMSO-
Antimicrobial activity measurements
All test micro organisms were obtained from Microbiology
Department, Lokmanya Tilak College Ujjain and were as
follows: Citrobactor freundii, Klebsiella pneumoniae,
Bacillus megaterium, Escherichia coli, Pseudomonas aeru-
ginosa, and Salmonella typhi. Antibacterial activity of the
prepared compounds 6a–6f and 7a–7f was tested by the disk
diffusion method. Whatman No. 1 filter paper disks were
sterilized by autoclaving for 1 h at 140 °C. All the synthe-
sized compounds were dissolved in DMSO for dilution to
prepare stock solutions of 20 mg/mL for antimicrobial assay.
Agar plates were uniformly surface inoculated with fresh
broth culture of C. freundii, K. pneumoniae, B. megaterium,
E. coli, P. aeruginosa, and S. typhi. The impregnated disks
were placed on the medium suitably spaced apart and the
plates were incubated at 30 °C for 1 h to permit good dif-
fusion andwere thentransferred toan incubator at37 2 °C
for 24 h. The zones of inhibition were measured on mm
scale. Streptomycin was used as standard antimicrobial
drug. Dimethylsulphoxide was used as solvent control.
Anticancer activity measurement
All test cancer cell lines were obtained from NCI, USA and
were as follows: human breast cancer cell line MDA-MB-435,
human prostate cancer cell line PC3, and human ovarian
O
H3C
CH3
HN
NH
O
O
O
NH2
CN
O
NH2
CN
O
O
HN
CN
CN
O
O
5
4
Ar-CHO +
H3C
H3C
TEAA, RT
N
H
O
TEAA, RT
Ar
1
2
7
6
Ar
Scheme 1 TEAA promoted synthesis of pyrano(c)chromene and pyrano[2,3-d]pyrimidine
123

Med Chem Res
Table 1 TEAA promoted
synthesis of pyrano(c)chromene
and pyrano[2,3-d]pyrimidine
Entry
Aldehyde
(2 mmol)
AMC (2 mmol)
Time
(min)
Product
Yielda
(%)
M.P. (°C)
1
1a
1b
1c
1d
1e
1f
Dimedone
40
40
50
40
50
40
30
30
50
40
50
50
6a
6b
6c
6d
6e
6f
90
94
84
95
95
97
92
94
86
95
96
97
216–218 [217–219]
205–207 [204–205]
178–180
2
Dimedone
3
Dimedone
4
Dimedone
208–210 [209–211]
214–215
5
Dimedone
6
Dimedone
217–219
7
1a
1b
1c
1d
1e
1f
Barbituric acid
Barbituric acid
Barbituric acid
Barbituric acid
Barbituric acid
Barbituric acid
7a
7b
7c
7d
7e
7f
280–282
8
284–286
9
191–193
10
11
12
274–275
AMC active methylene
compound
289–291
[320
a
Isolated yields
1
cancer cell line Ovkar-3. DMSO was used as vehicle for
anticancer activity and adriamycin (ADR) as a positive
control drug. GI50, TGI, and LC50 parameters were
studied using sulforhodamine B assay method.
cm-1; H NMR (DMSO-d6), d 0.99 (s, 3H, CH3), 1.08
(s, 3H, CH3), 2.22 (m, 2H), 2.42 (m, 2H), 4.31 (s, 1H), 5.21
(s, 1H, NH), 6.05 (s, 1H, Ar–H), 5.91 (s, Ar–H), 6.32
(s, Ar–H), 7.07 (s, 2H, NH2); EI-MS (m/z): 283 (M?)
C16H17N3O2 (283.33): calcd. C, 67.83; H, 6.05; N, 14.83.
Found: C, 67.88; H, 5.99; N, 14.84.
Spectroscopic data
2-Amino-7,7-dimethyl-4-(furan-2-yl)-5-oxo-5,6,7,8-
tetrahydro-4H-chromene-3-carbonitrile (6a)
2-Amino-7,7-dimethyl-4-(thiophen-2-yl)-5-oxo-5,6,7,8-
tetrahydro-4H-chromene-3-carbonitrile (6d)
White solid, m.p. 216–218 °C (lit. m.p. 217–219 °C, Bho-
sale et al., 2003). IR (KBr): 3355, 3208 (NH2), 2941 (C–H),
Yellow solid, m.p. 208–210 °C (lit. m.p. 209–211 °C, Tu
et al., 2002). IR (KBr) 3402, 3212 (NH2), 2977 (C–H),
;
2206 (CN), 1678 (C=O), 1662 (C=C) cm-1 1H NMR
2202 (CN), 1680 (C=O), 1652 (C=C) cm-1
;
1H NMR
(300 MHz, DMSO-d6), d 0.99 (s, 3H, CH3), 1.05 (s, 3H,
CH3), 2.17 (m, 2H, CH2), 2.48 (m, 2H, CH2), 4.33 (s, 1H,
CH), 6.05 (s, 1H), 6.32 (s, 1H), 7.07 (s, 2H), 7.48 (s, 1H)
ppm; EI-MS (m/z): 284 (M?). C16H16N2O3: % calcd. C,
67.59; H, 5.67; N, 9.85. Found: C, 67.88; H, 5.56; N, 9.63.
(DMSO-d6), d 6.32–6.33 (dd, 1H, Ar–H), 6.15 (d, 1H,
Ar–H), 6.05 (d, 1H, Ar–H), 7.08 (s, 2H, NH2), 4.33 (s, 1H,
CH), 2.50 (m, 2H, CH2), 2.30 (m, 2H, CH2), 1.04 (s, 3H,
CH3), 0.99 (s, 3H, CH3); EI-MS (m/z): 300 (M?)
C16H16N2O2S (300.09): calcd. C, 63.98; H, 5.37; N, 9.33.
Found: C, 63.92; H, 5.34; N, 9.42.
2-Amino-7,7-dimethyl-4-(5-methyl-furan-2-yl)-5-oxo-
5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (6b)
2-Amino-7,7-dimethyl-4-(3-methyl-thiophen-2-yl)-5-oxo-
5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (6e)
Yellow solid, m.p. 205–207 (lit. m.p. 204–205 °C, Shest-
opalov et al., 2003). IR (KBr) cm-1 3396, 3210 (NH2),
Light yellow, m.p. 214–215 °C. IR (KBr) 3396, 3209
(NH2), 2966 (C–H), 2196 (CN), 1680 (C=O), 1660
2966 (C–H), 2196 (CN), 1680 (C=O), 1660 (C=C) cm-1
;
1H NMR (DMSO-d6), 2.17 (s, 3H, CH3), 6.32–6.33 (dd,
1H, Ar–H), 6.05 (d, 1H, Ar–H), 7.08 (s, 2H, NH2), 4.33
(s, 1H), 2.50 (s, 2H, CH2), 2.30 (d, 1H, CH2), 2.15 (d, 1H),
1.04 (s, 3H, CH3), 0.99 (s, 3H, CH3) ppm; EI-MS (m/z):
298 (M?) C17H18N2O3 (298.34): % calcd. C, 68.44; H,
6.08; N, 9.39. Found: C, 68.40; H, 6.10; N, 9.41.
(C=C) cm-1; H NMR (DMSO-d6), d 2.29 (s, 3H, CH3),
1
6.32–6.33 (dd, 1H, Ar–H), 6.05 (d, 1H, Ar–H), 7.08 (s, 2H,
NH2), 4.33 (s, 1H, CH), 2.50 (s, 2H, CH2), 2.35 (s, 2H,
CH2), 1.04 (s, 3H, CH3), 0.99 (s, 3H, CH3); EI-MS (m/z):
314 (M?) C17H18N2O2S (314.11): calcd. C, 64.94; H, 5.77;
N, 8.91. Found: C, 64.98; H, 5.73; N, 8.89.
2-Amino-7,7-dimethyl-5-oxo-4-(1H-pyrrol-2-yl)-5,6,7,8-
tetrahydro-4H-chromene-3-carbonitrile (6c)
2-Amino-7,7-dimethyl-4-(5-methyl-thiophen-2-yl)-5-oxo-
5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (6f)
White solid, m.p. 178–180 °C. IR (KBr): 3355, 3208
(NH2), 2941 (C–H), 2212 (CN), 1675 (C=O), 1658 (C=C)
Yellow solid, m.p. 217–219 °C. IR (KBr) 3386, 3219
(NH2), 2976 (C–H), 2189 (CN), 1679 (C=O), 1661 (C=C)
123

Med Chem Res
cm-1
;
1H NMR (DMSO-d6), d 2.19 (s, 3H, CH3),
(288.28): calcd. C, 50.00; H, 2.80; N, 19.43. Found:
C, 49.89; H, 2.84; N, 19.46.
6.32–6.33 (dd, Ar–H), 6.05 (d, Ar–H), 7.08 (s, 2H, NH2),
4.33 (s, CH), 2.50 (s, 2H, CH2), 2.30 (d, 2H, CH2), 1.04
(s, 3H, CH3), 0.99 (s, 3H, CH3); EI-MS (m/z): 314 (M?)
C17H18N2O2S (314.11): calcd. C, 64.94; H, 5.77; N, 8.91.
Found: C, 64.92; H, 5.75; N, 8.86.
7-Amino-5-(3-methyl-thiophen-2-yl)-2,4-dioxo-1,3,4,5-
tetrahydro-2H-pyrano[2,3-d] pyrimidine-6-
carbonitrile (7e)
7-Amino-5-furan-2-yl-2,4-dioxo-1,3,4,5-tetrahydro-2H-
pyrano[2,3-d]pyrimidine-6-carbonitrile (7a)
m.p. 289–291 °C. IR (KBr): 3399, 3281 (NH2), 3174 (NH),
2981 (C–H), 2200 (CN), 1707 (C=O), 1463 (C=C) cm-1
;
1H NMR (DMSO-d6) dH: 3.99 (1H, s, CH), 7.26 (2H, br s,
NH2), 2.20 (3H, s, CH3), 6.62 (1H, m, H–Ar), 6.48 (1H, d,
H–Ar), 11.02 (1H, br s, NH), 12.04 (1H, br s, NH); EI-MS
(m/z): 302 (M?) C13H10N4O3S (302.5): calcd. C, 51.65;
H, 3.33; N, 18.53. Found: C, 51.62; H, 3.36; N, 18.57.
Dark yellow solid, m.p. 280–282 °C. IR (KBr): 3391, 3302
(NH2), 3188 (NH), 3072 (C–H), 2197 (CN), 1718 (C=O),
1665 (C=C) cm-1; 1H NMR (DMSO-d6) dH: 4.26 (s, CH),
7.20 (br s, 2H, NH2), 7.22 (1H, d, H–Ar), 6.59 (1H, m,
H–Ar), 6.51 (1H, d, H–Ar), 11.12 (1H, br s, NH), 12.14
(1H, br s, NH); EI-MS (m/z): 272 (M?); C12H8N4O4
(272.22): calcd. C, 52.95; H, 2.96; N, 20.58. Found: C,
52.94; H, 2.93; N, 20.47.
7-Amino-5-(5-methyl-thiophen-2-yl)-2,4-dioxo-1,3,4,5-
tetrahydro-2H-pyrano[2,3-d] pyrimidine-6-
carbonitrile (7f)
7-Amino-5-(5-methyl-furan-2-yl)-2,4-dioxo-1,3,4,5-
tetrahydro-2H-pyrano[2,3-d] pyrimidine-6-
carbonitrile (7b)
m.p. [320 °C. IR (KBr): 3402, 3299 (NH2), 3178 (NH),
2989 (C–H), 2202 (CN), 1715 (C=O), 1460 (C=C) cm-1
;
1H NMR (DMSO-d6) dH: 4.02 (1H, s, CH), 7.16 (2H, br s,
NH2), 2.26 (3H, s, CH3), 6.59 (1H, m, H–Ar), 6.51 (1H, d,
H–Ar), 11.12 (1H, br s, NH), 12.14 (1H, br s, NH); EI-MS
(m/z): 302 (M?) C13H10N4O3S (302.05): calcd. C, 51.65;
H, 3.33; N, 18.53. Found: C, 51.62; H, 3.38; N, 18.51.
Dark yellow solid, m.p. 284–286 °C. IR (KBr): 3402, 3299
(NH2), 3178 (NH), 2989 (C–H), 2202 (CN), 1715 (C=O),
1
1460 (C=C) cm-1; H NMR (DMSO-d6) dH: 4.12 (1H, s,
CH), 7.16 (2H, br s, NH2), 2.15 (3H, s, CH3), 6.59 (1H, m,
H–Ar), 6.51 (1H, d, H–Ar), 11.12 (1H, br s, NH), 12.14
(1H, br s, NH); EI-MS (m/z): 286 (M?) C13H10N4O4
(286.24): calcd. C, 54.55; H, 3.52; N, 19.57. Found:
C, 54.46; H, 3.56; N, 19.59.
Results and discussion
We found TEAA as an efficient organic catalyst as well as
reaction medium for one-pot multi-component synthesis
with high yields. TEAA is air and water stable ionic liquid
which is easy to synthesize by just neutralizing triethyl-
amine and acetic acid, which are relatively inexpensive. It is
needless to say that the synthesis of this unconventional
triethylammonium ionic liquid is direct, simple, and eco-
friendly. This method offers an alternative route for the
synthesis of dihydropyrano(c)chromenes and pyrano[2,3-d]
pyrimidines in reasonable yields. Structures of the products
6 and 7 have been deduced from their spectral data and
melting points. It is expected that the synthesis of 6/7 fol-
lows initial arylidinemalonontrile formation followed by
Michael addition of 4/5–3 which on heterocyclization with
4/5 gives intermediate 8. Intermediate 8 on tautomerization
(proton transfer) gives 6 or 7 (Scheme 2). This mechanism
has been supported by synthesizing 3 in separate single step.
We investigated the reusability of the ionic liquid TEAA
without any catalyst. For this purpose, after the completion
of the reaction TEAA was separated from the reaction
mixture, washed with water and dried at high vacuum. As
shown in Fig. 1 TEAA could be reused for six times
without apparent loss of catalytic activity.
7-Amino-2,4-dioxo-5-(1H-pyrrol-2-yl)-1,3,4,5-tetrahydro-
2H-pyrano[2,3-d]pyrimidine-6-carbonitrile (7c)
Pale-yellow solid, m.p. 191–193 °C. IR (KBr): 3402, 3299
(NH2), 3168 (NH), 2989 (C–H), 2202 (CN), 1708 (C=O),
1
1460 (C=C) cm-1; H NMR (DMSO-d6) dH: 4.19 (1H, s,
CH), 7.10 (2H, br s, NH2), 6.97 (1H, d, H–Ar), 6.59 (1H,
m, H–Ar), 6.51 (1H, d, H–Ar), 11.12 (1H, br s, NH), 12.14
(1H, br s, NH); EI-MS (m/z): 271 (M?) C12H9N5O3
(271.23): calcd. C, 53.14; H, 3.34; N, 25.82. Found:
C, 53.07; H, 3.28; N, 25.89.
7-Amino-5-(thiophen-2-yl)-2,4-dioxo-1,3,4,5-tetrahydro-
2H-pyrano[2,3-d]pyrimidine-6-carbonitrile (7d)
Dark yellow solid, m.p. 274–275 °C. IR (KBr): 3390, 3306
(NH2), 3188 (NH), 3072 (C–H), 2197 (CN), 1708 (C=O),
1459 (C=C) cm-1; 1H NMR (DMSO-d6) dH: 4.21 (1H, s),
7.38 (2H, br s, NH2), 7.02 (1H, d, H–Ar), 6.57 (1H, m,
H–Ar), 6.49 (1H, d, H–Ar), 11.42 (1H, br s, NH), 12.09
(1H, br s, NH); EI-MS (m/z): 288 (M?) C12H8N4O3S
123

Med Chem Res
A
A
O
O
3
O
O
CN
CN
4
8
4
3
2
5
5
HN
6
7
H3C
H3C
6'
8
6a
2
O
NH2
O
N
H
O
NH2
7a
The IR spectrum of 2-amino-3-cyano-4-(furan-2-yl)-7,
7-dimethyl-5-oxo-4H-5,6,7,8-tetrahydrobenzo-[b]pyran has
a series of stretching absorption bands of the amino group
(3,355 and 3,208) and a bending band of this group
(1,675–1,650 cm-1). The high intensity of the absorption
band at 2,202 and 1,680 cm-1 confirm the presence of the
1
Fig. 1 Reusability of ionic liquid TEAA
cyano and carbonyl group, respectively, and in H NMR
presence of new signal at d: 0.99 (s, 3H, H70), 1.05 (s, 3H,
H700), 2.17 (m, 2H, H6), 2.48 (m, 2H, H60), 4.33 (s, 1H, H5),
7.07 (s, 2H) confirms the structure 6a.
calcd. C, 67.59; H, 5.67; N, 9.85. Found: C, 67.88; H, 5.56;
N, 9.63. C12H8N4O4 (272.22) 7a: calcd. C, 52.95; H, 2.96;
N, 20.58. Found: C, 52.94; H, 2.93; N, 20.47.
The IR spectrum of 7-amino-5-furan-2-yl-2,4-dioxo-
1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-6-carbonitr
-ile has a series of stretching absorption bands of the –NH
at (3,188), amino group (3,391 and 3,302), and a bending
band of this group (1,675–1,650 cm-1). The high intensity
of the absorption band at 2,197 and 1,718 cm-1 confirm
the presence of the cyano and carbonyl group, respectively,
and in 1H NMR presence of new peak at d: 11.12 (1H, br s,
NH), 12.14 (1H, br s, NH, 4.26 (s, 1H, H5), 7.20 (s, 2H,
NH2) confirms the structure 7a.
The EI-MS gave M? at m/z 284 (100) for 6a, and at
m/z 272 (100) for 7a which were consistent with the
molecular formula to be C16H16N2O3 for 6a and
C12H8N4O4 for 7a requiring structure. C16H16N2O3 6a: %
Antimicrobial activity measurements
Antimicrobial activity: the antimicrobial strains reveal
that the heteroaryl-substituted products (6 and 7) showed
differential activities (Fig. 1). The presence of heteroaryl
ring and cyano and amino groups on pyran ring make
these more basic which increases its penetrating power on
bacterial cell wall (protein) and the compounds becomes
more active. In these cases, heteroaryl part is associated
with the bacterial cell wall which makes them more active.
The comparative antibacterial activities of the products
are summarized in Tables 2 and 3.
Scheme 2 A plausible
CN
TEAA, RT
mechanism for the synthesis
of pyrano(c)chromene and
pyrano[2,3-d] pyrimidine
CN
O
10-20 min.
CN
+
X
3
X
2
CN
O
1
A
A= CH2 or NH
B= CH3 or B,B= O
X = O, NH, S
B
B
A
O
4 or 5
N
NC
C
NC
CN
O
O
A
A
A
X
H
B
X
B
O
A
8
B
O
B
NH2
NC
NH
C
NC
O
A
H
H- Transfer
H
O
A
A
A
X
B
X
B
6 or 7
O
B
O
B
B= CH3 or B,B= O
A= CH2 or NH
123

Med Chem Res
Table 2 Comparative
antibacterial activity of
dihydropyrano(c)chromenes
(lg)
S. no.
Bacteria
Diameter of zone of inhibition in mm
6a
6b
6c
6d
6e
6f
1.
2.
3.
4.
5.
6.
Citrobacter freundii ATCC 8090
Klebsiella pneumoniae ATCC 15380
Bacillus megaterium ATCC 12872
Escherichia coli ATCC 25922
10
15
12
16
15
14
10
15
12
17
16
15
10
19
12
20
22
20
10
19
10
20
22
20
10
20
12
21
19
22
10
21
10
22
19
22
Salmonella typhi ATCC 19430
MIC value is 10 lg for each
bacterial species
Pseudomonas aeruginosa ATCC 27853
Table 3 Comparative
antibacterial activity of
pyrano[2,3-d]pyrimidines (lg)
S. no.
Bacteria
Diameter of zone of inhibition in mm
7a
7b
7c
7d
7e
7f
1.
2.
3.
4.
5.
6.
Citrobacter freundii ATCC 8090
Klebsiella pneumoniae ATCC 15380
Bacillus megaterium ATCC 12872
Escherichia coli ATCC 25922
10
16
14
12
18
14
10
17
14
12
18
15
12
20
12
14
22
18
12
20
12
15
22
18
12
22
10
16
21
20
12
22
10
16
20
22
Salmonella typhi ATCC 19430
MIC value is 10 lg for each
bacterial species
Pseudomonas aeruginosa ATCC 27853
biological activities. Compounds 6a and 7a were also
tested for anticancer activity test by using SRB assay
method. But, both the compounds did not give the satis-
factory results in between 10-7 and 10-4 molar concen-
trations in comparison with ADR (doxorubicin) as a
positive control drugs (Table 4).
Table 4 Anticancer activity of dihydropyrano(c)chromenes and
pyrano[2,3-d] pyrimidines
S. no. Cell lines
Compounda/ 6a
parameters
7a
ADRb
1.
2.
3.
Breast cancer cell
line MDA-MB-435
LC50
TGI
[100 [100 91.8
[100 [100 5.5
[100 [100 \0.1
[100 [100 [100
[100 [100 76.7
[100 98.8 \0.1
[100 [100 [100
[100 [100 56.3
[100 [100 \0.1
Acknowledgments Author is thankful to SAIF-CDRI, Lucknow for
providing spectral and elemental analysis data and Mr. Kapilesh
Jadhav, Lok Manya Tilak College, Ujjain for providing microbio-
logical facilities and Tata Memorial Centre ACTREC for carrying out
cancer activity test.
GI50
LC50
TGI
Prostate cancer cell
line PC-3
GI50
LC50
TGI
Ovarian cancer cell
line Ovkar-3
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