Synthesis and antimicrobial activity of 2-iminocoumarin-3-carboxylic acid amides

Full text of DOI:10.1023/A:1012747018793

Pharmaceutical Chemistry Journal
Vol. 35, No. 7, 2001
SYNTHESIS AND ANTIMICROBIAL ACTIVITY
OF 2-IMINOCOUMARIN-3-CARBOXYLIC ACID AMIDES
S. V. Ukhov,1 M. E. Kon’shin,1 and T. F. Odegova1
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 35, No. 7, pp. 17 – 18, July, 2001.
Original article submitted February 26, 2001.
As is known, coumarin derivatives exhibit biological ac-
tivity of various types [1]. Previously [2] we reported on the
synthesis of 2-iminocoumarin-3-carboxylic acid amides by
condensation of salicylaldehyde with cyanoacetic acid ami-
des.
Aimed at expanding these investigations and evaluating
the biological activity of compounds of this class, we studied
the reactions of 5-nitrosalicylaldehyde with cyanoacetic acid
arylamides and malonanilic acid ethylates.
(C=N), 1680 – 1690 (CO), 3330 – 3340 (=NH), and
3420 cm – 1 (CONH).
Under the action of acetic or propionic acid anhydrides,
compounds Id – If were readily acylated at the imino group
with the formation of the corresponding substituted amides
of 2-acyliminocoumarin-3-carboxylic acid (IIa – IIf). The
proposed structures of compounds IIa – IIf were confirmed
1
by the characteristics of their IR and H NMR spectra. The
IR spectra display bands at 1660 (CO), 1700 (CO), and
1
3170 cm – 1 (NH). The H NMR spectra exhibit a singlet at
O
R
C
R
CONHR'
NH
2.21 – 2.26 ppm (COCH3), a pair of signals at 1.12 and
CNCH2CONHR'
H
4.16 ppm (COC2H5),
a multiplet at 7.60 – 7.86 ppm
OH
O
(H arom), and a singlet at 10.66 – 11.03 ppm (NH).
Ià – Ig
H2O, H+
for Ig
The treatment of 2-iminocoumarin-3-carboxylic acid
4-anisidide (Ig) [2] with concentrated hydrochloric acid leads
to hydrolysis of the imino group with the formation of cou-
marin-3-carboxylic acid anisidide (III). The IR spectrum of
compound III contain absorption bands at 1670 (CO), 1720
(CO), and 3290 cm – 1 (NH). For comparison, compound III
was also obtained by direct synthesis, using the interaction of
salicylaldehyde with malonic acid monoethyl ether 4-anisidi-
de (IV) in slightly heated alcohol solutions in the presence of
a catalytic amount of piperidine. The products obtained by
both methods proved to be identical.
IV
(R"CO)2O
-4
CONHC6H4OCH3
O2N
CONHR'
NCOR"
O
O
III
O
IIà –IIf
I: R = NO2 (a – f), H (g); R¢ = C2H5 (a), 2-ClC6H4 (b), 4-CH3C6H4 (c),
CH2C6H5 (d), 2,4-(CH3)2C6H3 (e), 3-C2H5OC6H4 (f), 4-CH3OC6H4 (g);
II: R¢ = CH2C6H5 (a, d), 3-C2H5OC6H4 (b, e), 2,4-(CH3)2C6H3 (c, f);
R² = CH3 (a, b, c); C2H5 (d, e, f).
EXPERIMENTAL CHEMICAL PART
The IR spectra of the synthesized compounds were re-
corded with a UR-20 spectrophotometer (Germany) using
samples prepared as nujol mulls. The 1H NMR spectra were
measured on a RYa-2310 (60 MHz) spectrometer (Russia)
using 5% solutions in DMSO-d6 with HMDS as the internal
standard. The data of elemental analyses agreed with the re-
sults of calculations using the empirical formulas.
6-Nitro-2-iminocoumarin-3-carboxylic acid amides
(Ia – If). A mixture of 3 g (0.025 mole) of 5-nitrosalicylalde-
hyde, 0.025 mole of the corresponding cyanoacetic acid ami-
de, and 5 drops of piperidine in 15 ml of ethanol was boiled
The reaction of 5-nitrosalicylaldehyde with substituted
cyanoacetic acid amides proceeded upon boiling an alcohol
solution of the initial compounds in the presence of piperidi-
ne as the catalyst. The reactions yield substituted amides of
6-nitro-2-iminocoumarin-3-carboxylic acid (Ia – If), the pro-
perties of which are listed in Table 1. Amides Ia – If appear
as yellowish crystalline substances insoluble in water and so-
luble in dioxane. The IR spectra of these amides contain cha-
racteristic absorption bands in the region of 1610 – 1620
1
State Pharmaceutical Academy, Perm, Russia.
364
0091-150X/01/3507-0364$25.00 © 2001 Plenum Publishing Corporation

Synthesis and Antimicrobial Activity of 2-Iminocoumarin-3-carboxylic Acid Amides
365
TABLE 1. Characteristics of the Synthesized Com-
TABLE 2. Antimicrobial Activity of Compounds
pounds
Ia – If and IIa – IIe
Com-
pound
Empirical for-
mula
MIC, mg/ml
St. aureus
Yield, %
M.p., °C
Compound
E. coli
Ia
Ib
Ic
Id
Ie
If
49.0
92.7
92.3
42.3
44.4
92.3
50.8
44.6
87.7
86.2
66.6
67.8
95.0
130 – 132
269 – 271
235 – 237
187 – 188
230 – 231
206 – 207
112 – 114
208 – 210
238 – 240
200 – 202
196 – 198
206 – 208
210 – 211
C12H11N3O4
C16H10ClN3O4
C17H13N3O4
C17H13N3O4
C18H15N3O4
C18H15N3O5
C19H15N3O5
C20H17N3O5
C20H17N3O5
C21H19N3O6
C21H19N3O6
C21H19N3O6
C17H13N3O4
Ia
500
62
125
62
Ib
Ic
500
500
1000
125
62
500
1000
1000
62
Id
Ie
If
IIa
IIb
IIc
IId
IIe
IIf
III
IIa
31
IIb
1000
500
1000
500
1000
500
1000
2000
IIc
IIe
Ethacridine
double serial dilutions in a beef-infusion broth [3]. A daily
grown culture washed by sterile physiological solution was
used to prepare the initial stock solution with a bacterial load
of 500 ´ 106 microbial cells/ml (according to bacterial stan-
dard). Then 0.1 ml of the bacterial stock solution was intro-
duced into 2 ml of the beef-infusion broth containing a given
dilution of the test compound. The final bacterial load was
250 ´ 103 microbial cells/ml. The results were assessed after
incubation of the test and control samples for 18 – 20 h in a
thermostat at 37°C. The activity was characterized by the mi-
for 1 h and cooled. The precipitate was separated by filtrati-
on, washed with ether, and crystallized from dioxane.
6-Nitro-2-acyliminocoumarin-3-carboxylic acid ami-
des (IIa – IIf). A solution (prepared on weak heating to
40°C) of 1 g (0.003 mole) of compound Id – If in 20 ml of
acetic or propionic acid anhydride was allowed to stand at
20°C for 12 h. Then the reaction mixture was diluted with
water and the precipitate was separated by filtration, washed
with water, and crystallized from dioxane.
Coumarin-3-carboxylic acid anisidide (III). M e t -
h o d A . To a cooled solution of 0.5 g (1 mmole) of anisidide
Ig [2] in 15 ml of DMF was added 15 ml of concentrated
hydrochloric acid and the mixture was allowed to stand for
two days at room temperature. The precipitate was separated
by filtration, washed with water until neutral reaction, and
crystallized from dioxane.
M e t h o d B . A mixture of 0.61 g (5 mmole) of salicy-
laldehyde, 1.18 g (5 mmole) of malonic acid monoethyl et-
her 4-anisidide (IV), 10 ml of ethanol, and 5 drops of piperi-
dine was heated for 1 h at 70°C and cooled. The precipitate
was separated by filtration, washed with ether, and crystalli-
zed from dioxane.
nimum inhibiting concentration (MIC, mg/ml) correspon-
ding to the maximum dilution leading to complete suppressi-
on of the test microbe growth. The test compounds were dis-
solved in DMF; the reference drug was ethacridine.
It was established that all the synthesized compounds po-
ssess antimicrobial properties (Table 2) with respect to both
St. aureus and E. coli. The most active substances (Ib, If, and
IIa) significantly exceed ethacridine in the bacteriostatic ef-
fect. Thus, the results of our experiments are indicative of
good prospects in the search for new antimicrobial agents in
the series of substituted 6-nitrocoumarin-3-carboxylic acid
amides.
REFERENCES
EXPERIMENTAL BIOLOGICAL PART
1. A. H. Bedar, J. Pract. Chem., 329(2), 359 – 364 (1987).
2. S. V. Ukhov, S. N. Nikulina, L. P. Drovosekova, et al., Dep.
VINITI, No. 4189-B88.
3. G. N. Pershin, Methods of Experimental Chemotherapy [in Rus-
sian], Meditsina, Moscow (1969), pp. 109 – 111, 546 – 460.
The antimicrobial properties of the compounds Ia – If
and IIa – IIf were studied with respect to standard strains of
Escherichia coli and Staphylococcus aureus. The bacterios-
tatic activity was determined by the conventional method of