Synthesis and antimicrobial properties of 1-(3,4-dichlorophenyl)cycloalkyl-1-penicillins and cephalosporins

Full text of DOI:10.1023/A:1013728105186

Pharmaceutical Chemistry Journal
Vol. 35, No. 8, 2001
SYNTHESIS AND ANTIMICROBIAL PROPERTIES
OF 1-(3,4-DICHLOROPHENYL)CYCLOALKYL-1-PENICILLINS
AND CEPHALOSPORINS
S. G. Akopyan,1 A. O. Martirosyan,1 Sh. L. Mndzhoyan,1 Yu. Z. Ter-Zakharyan,1 É. V. Kazaryan,1
and M. V. Aleksanyan1
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 35, No. 8, pp. 17 – 19, August, 2001.
Original article submitted December 27, 2000.
Cl
Cl
Cl
Cl
Based on the mathematical (QSAR) predictions for
1-arylcycloalkyl-1-penicillins, we may expect that introduc-
tion of substituents such as F, Cl, and OH into the aromatic
nucleus of these compounds may lead to derivatives posses-
sing lower toxicity and higher acid resistance [1, 2]. Previo-
usly [3], we synthesized semisynthetic penicillins and cepha-
losporins with Cl and Br substituents in ortho, meta, and pa-
ra positions of the aromatic ring; the results of biological
tests with these compounds showed that the above predicti-
ons are generally valid.
In order to continue studying the relationship between
the chemical structure and biological properties of the afore-
mentioned compounds, we modified the acyl residues of pe-
nicillins and cephalosporins by introducing two chlorine sub-
stituents into the aromatic nucleus and by varying the size of
the cycloalkane ring.
The initial nitriles (Ia – Id) were synthesized by reactions
of 3,4-dichlorophenylacetonitrile (i) with dibromoethane and
1,3-chlorobromopropane in 50% aqueous NaOH solution in
the presence of triethylbenzylammonium chloride [4] or (ii)
with 1,4-dibromobutane and 1,5-dibromopentane in the pre-
sence of powdered NaOH [5]. The subsequent alkaline hyd-
rolysis of 1-(3,4-dichlorophenyl)cycloalkyl-1-carboxylic
acid nitriles Ia – Id led to the corresponding carboxylic acids
IIa – IId. Boiling carboxylic acids IIa – IId with thionyl chlo-
ride in anhydrous benzene yielded chloroanhydrides
IIIa – IIId.
The related 1-(3,4-dichlorophenyl)cycloalkyl-1-penicil-
lins (IVa – IVd) and -cephalosporins (Va – Vd, VIa – VId)
were synthesized by acylating 6-aminopenicillanic (6-APA),
7-aminodeacetoxycephalosporanic (7-ADCA), and 7-amino-
cephalosporanic (7-ACA) acids using chloroanhydride (A)
and mixed-anhydride (B) methods. The final products were
isolated in the form of sodium salts.
(CH2) Hal2
KOH
n
CN
(CH2)
CN
n
Ià – Id
Cl
Cl
Cl
SOCl2
COOH
(CH2)
COCl
(CH2)
Cl
n
n
IIà – IId
IIIà – IIId
Cl
Cl
S
CONH
(CH2)
A
N
n
O
COONa
IVà – IVd, VIà – VId
H3C
CH3
CH3
CH2OCOCH3
(VIà – VId)
(Và – Vd);
(IVà – IVd);
A =
n = 2 (a), 3 (b), 4 (c), 5 (d).
The proposed structures were confirmed by the data of
elemental analyses and the results of IR and 1H NMR spect-
roscopic measurements; purity of the reaction products was
checked by TLC on Silufol plates. The IR spectra of compo-
unds IV – VI showed the characteristic absorption bands of
b-lactam carbonyl (1760 – 1780 cm – 1), carboxy carbonyl
(1710 – 1725 cm – 1), amide carbonyl (1640 – 1660 cm – 1),
and NH groups (3300 – 3340 cm – 1).
EXPERIMENTAL CHEMICAL PART
The IR spectra were recorded on an UR-20 spectrophoto-
meter (Germany) using samples prepared as nujol mulls. The
1H NMR spectra were measured on a Varian T-60 spectro-
meter using TMS as the internal standard. The course of the
1
Mndzhoyan Institute of Fine Organic Chemistry, National Academy of
Sciences of the Republic of Armenia, Yerevan, Armenia.
421
0091-150X/01/3508-0421$25.00 © 2001 Plenum Publishing Corporation

422
S. G. Akopyan et al.
TABLE 1. The Yields and Characteristics of the Synthesized Nitriles Ia – Id and Acids IIa – IId
Com- Yield,
M.p.,°C;
b.p.,°C/Torr
Empirical
formula
Rf
1H NMR spectrum in CDCl3, d, ppm
pound
%
Ia
77
47
33
63
71
62
82
71
84 – 86
0.41
0.87
0.66
0.58
0.61
0.76
0.72
0.65
C10H7Cl2N
C11H9Cl2N
C12H11Cl2N
C13H13Cl2N
C10H8O2Cl2
C11H10O2Cl2
C12H12O2Cl2
C13H14O2Cl2
1.16 – 2.0 (m, 4H, 2,3-CH2), 7.0 – 7.6 (m, 3H, C6H3)
Ib
1.0 – 3.3 (m, 6H, 2,3,4-CH2), 7.0 – 7.7 (m, 3H, C6H3)
160 – 162/3
155 – 158/3
186 – 187/3
144 – 145
84 – 86
Ic
1.7 – 2.2 (m, 8H, 2,3,4,5-CH2), 6.9 – 7.1 (m, 3H, C6H3)
Id
1.5 – 2.9 (m, 10H, 2,3,4,5,6-CH2), 7.3 – 7.7 (m, 3H, C6H3)
IIa
IIb
IIc
IId
1.1 – 1.7 (m, 4H, 2,3-CH2), 7.1 – 7.5 (m, 3H, C6H3), 9.5 (s, 1H, COOH)
1.8 – 2.9 (m, 6H, 2,3,4-CH2), 7.1 – 7.6 (m, 3H, C6H3), 9.2 (s, 1H, COOH)
1.1 – 2.7 (m, 8H, 2,3,4,5-CH2), 7.6 – 7.8 (m, 3H, C6H3), 9.4 (s, 1H, COOH)
1.1 – 2.3 (m, 4H, 2,3,4,5,6-CH2), 7.2 – 7.5 (m, 3H, C6H3), 8.9 (s, 1H, COOH)
118 – 120
117 – 118
reactions was monitored by TLC on Silufol UV-254 plates
(Czech Republic) eluted in the propanol – water, 7 : 2 (for so-
dium salts IV – VI), and acetone – hexane, 2 : 3 (for compo-
unds I, II), systems and developed by treatment with iodine
vapor. The data of elemental analyses coincide with the re-
sults of analytical calculations using empirical formulas.
1-(3,4-Dichlorophenyl)cycloalkane-1-carboxylic acid
nitriles (Ia – Id). Method A. To a mixture of 0.2 mole of
3,4-dichlorophenylacetonitrile, 0.02 mole of triethylbenzy-
lammonium chloride, and 50 ml of a 50% aqueous NaOH so-
lution were slowly added 0.3 mole of dibromoalkane (n = 2,
3). Then the mixture was stirred for 2 h at 55 – 75°C and co-
oled. The precipitated oil was separated from the aqueous
layer, after which the latter phase was doubly extracted with
diethyl ether. The oil phase was combined with the ether ext-
racts, washed with water, and dried over anhydrous sodium
sulfate. Finally, residual ether was distilled to obtain the tar-
get compounds Ia and Ib (Table 1).
kane (n = 4, 5) and the mixture was stirred for 12 h at 120°C.
Upon cooling, the reaction mixture was diluted with water
and extracted with diethyl ether. The ether extracts were was-
hed with water and dried over anhydrous sodium sulfate. Fi-
nally, residual ether was distilled to obtain the target nitriles
Ic and Id (Table 1).
1-(3,4-Dichlorophenyl)cycloalkane-1-carboxylic acids
(IIa – IId). A mixture of 0.1 mole of the initial nitrile
(Ia – Id) and 0.5 mole of potassium hydroxide in 120 ml of
ethylene glycol was boiled for 10 h. Upon cooling, the reacti-
on mixture was diluted with water and washed with diethyl
ether. The aqueous layer was acidified (on cooling) with di-
luted aqueous hydrochloric acid (1 : 1) to pH 1 – 2. The pre-
cipitated crystals were filtered and washed with water (Tab-
le 1).
1-(3,4-Dichlorophenyl)cycloalkane-1-carboxylic acid
chloroanhydrides (IIIa – IIId). A mixture of 0.061 mole of
Method B. To a mixture of 0.2 mole of powdered sodium
hydroxide and 0.05 mole of 3,4-dichlorophenylacetonitrile
heated to 45°C were slowly added 0.05 mole of dibromoal-
TABLE 3. Antimicrobial Activity of the Synthesized Penicillins
and Cephalosporins
MIC, mg/ml
Compound
St. aureus
Sh. dysint.
B. typhi
79
P. vulg.
TABLE 2. The Yields and Characteristics of the Synthesized Peni-
209 p 25923 Smith G6858 121
cillins and Cephalosporins
IVa
0.9
1.9
7.8
1.9
0.9
3.9
3.9
3.9
1.9
3.9
125
250
250
250
250
125
250
250
62.5 250
Com-
pound
Yield,
%
M.p., °C*
(with decomp.)
Rf
Empirical formula
IVb
IVc
IVd
125
250
250
250
15.6
1.9
250
125
IVa
56
83
70
85
53
42
66
50
40
36
31
38
135 – 137
74 – 76
0.70
0.70
0.78
0.67
0.68
0.68
0.70
0.76
0.67
0.67
0.71
0.77
C18H17Cl2N2O4SNa
C19H19Cl2N2O4SNa
C20H21Cl2N2O4SNa
C21H23Cl2N2O4SNa
C18H15Cl2N2O4SNa
C19H17Cl2N2O4SNa
C20H19Cl2N2O4SNa
C21H21Cl2N2O4SNa
C20H17Cl2N2O6SNa
C21H19Cl2N2O6SNa
C22H21Cl2N2O6SNa
C23H23Cl2N2O6SNa
IVb
IVc
IVd
Va
Benzylpeni-
cillin
116 – 118
117 – 119
72 – 74
0.012 0.006 0.012 3.12
7.0
0.39
62.5
3.12
62.6
Va
3.9
1.9
7.8
3.9
7.8
1.9
0.9
0.9
3.9
0.12
1.9
1.9
3.9
3.9
1.56
3.9
3.9
1.9
7.8
0.12
7.8
3.9
7.8
7.8
7.8
7.8
1.9
0.9
1.9
0.48
31.2
62.5
31.2
62.5
Vb
62.5 125
62.5 31.2
62.5 125
125
Vb
168 – 170
164 – 165
188 – 189
109 – 111
84 – 186
44 – 45
Vc
62.5
Vc
Vd
62.5 125
Vd
Cefalexin
VIa
3.9
7.8
7.8
7.8
–
62.5
31.2
125
VIa
VIb
VIc
VId
62.5 125
VIb
125
62.5
250
15.6
62.5
VIc
62.5
125
3.9
–
62.5
125
124 – 126
VId
*
Cefamezin
31.2
7.8
31.2
Melting points are indicated for acids.

Synthesis And Antimicrobial Properties Of 1-(3,4-Dichlorophenyl)Cycloalkyl-1-Penicillins
423
acid IIa – IId and 0.125 mole thionyl chloride in anhydrous
benzene was boiled for 8 h. Upon cooling, the solvent is dis-
tilled off and the residue of chloroanhydride IIIa – IIId is
used in the subsequent stage without additional purification.
1-(3,4-Dichlorophenyl)cycloalkyl-1-penicillins (IVa –
IVd) and 1-cephalosporins (Va – Vd, VIa – VId). Method A.
To a mixture of 0.01 mole of 6-APA (7-ADCA, 7-ACA),
0.033 mole NaHCO3, 80 ml water, and 60 ml acetone, coo-
led to 0 – 2°C, was added with stirring 0.01 mole of the cor-
responding carboxylic acid chloroanhydride IIIa – IIId in
20 ml of anhydrous acetone. Upon completely adding the
chloroanhydride, the stirring was continued for 3 – 4 h at the
same temperature and then 2 h at room temperature. Then
the aqueous solution was washed with ethyl acetate and aci-
dified with 1 N HCl solution to pH 2. The precipitated acid
was extracted with ethyl acetate, washed with ice-cold water,
and dried over anhydrous sodium sulfate. Then the ethyl ace-
tate extract was treated with an 8% aqueous NaHCO3 soluti-
on to pH 7 – 7.5. The aqueous layer was washed with ether
and lyophilized to obtain the target sodium salts IV – VI.
Method B. To a solution of 0.01 mole of acid IIa – IId in
60 ml of anhydrous acetone was added, with stirring and co-
oling to 0 – 2°C, a solution of 0.026 mole triethylamine in
40 ml of the same solvent and 0.028 mole of ethyl chlorocar-
bonate. The reaction mixture was stirred for 30 min at 0°C,
then 2 h at room temperature, and filtered. The filtrate was
slowly added to a solution of 0.26 mole of 6-APA (7-ADCA,
7-ACA) in 100 ml of acetone and 200 ml of 3% NaHCO3.
The mixture was stirred for 4 h and then treated as in method
A. The melting temperatures were determined for the acids
(Tafle 2).
ris). The reference drugs were benzylpenicillin, cefalexin,
and cefamezin. Each test was repeated not less than thrice.
The acid resistance of penicillins IVa – IVd was studied
in an water – ethanol mixture at pH 1.3 and a temperature of
37°C. The amount of undecomposed penicillin was determi-
ned by iodometric titration. The rate of penicillin decomposi-
tion was characterized by halflife t/2.
It was found that penicillins IVa – IVd exhibit an antis-
taphylococcal activity (MIC = 0.9 – 3.9 mg/ml). The most
pronounced antibacterial effect was observed for compound
IVa (Table 3). At the same time the penicillins showed low
activity with respect to Gram-negative microbes
(MIC = 62.5 – 500 mg/ml). The halflife of the penicillins
studied was t/2 = 2 – 5 min (versus 2 min for benzylpenicil-
lin), which is evidence of the instability of these compounds
in acid media. A comparison of the properties of penicillins
IVa – IVd to those of monochlorophenylcycloalkyl penicil-
lins [5] indicates that introduction of the second chlorine into
the aromatic ring does not increase the antibacterial properti-
es of these compounds.
The derivatves of 7-ADCA (Va – Vd) also exhibited an
antibacterial activity with respect to St. aureus
(MIC = 1.9 – 7.8 mg/ml) that was comparable to the activity
of cefalexin. The deriatves of 7-ADCA (Va – Vd), in contrast
to monochlorophenylcycloalkyl cephalosporins [5], exhibi-
ted antibacterial properties relative to Gram-negative bacteri-
al species as well. The semisynthetic cephalosporins repre-
senting the 7-ACA derivatives VIa – VId were also active
with respect to the test microbes, although the antibacterial
effect was less pronounced as compared to that of cefamezin.
REFERENCES
EXPERIMENTAL BIOLOGICAL PART
1. A. A. Ordukhanyan, A. S. Sarkisyan, M. A. Landau, et al.,
Khim.-Farm. Zh., 24(1), 66 – 71 (1980).
2. A. A. Ordukhanyan, A. S. Sarkisyan, M. A. Landau, et al.,
Khim.-Farm. Zh., 27(1), 63 – 66 (1983).
3. Sh. L. Mndzhoyan, M. S. Kramer, S. G. Akopyan, et al.,
Khim.-Farm. Zh., 26(2), 53 – 55 (1992).
4. M. Makosha, Usp. Khim., 12, 2174 – 2202 (1977).
5. A. L. Mndzhoyan, G. L. Papayan, and M. A. Bagoyan, Izv. Akad.
Nauk. ArmSSR, Khim. Nauki, 26(4), 359 – 364 (1963).
The antibacterial activity of the synthesized sodium salts
of penicillins IVa – IVd and cephalosporins Va – Vd and
VIa – VId was studied by the conventional method of double
serial dilutions in a beef-infusion broth (pH 7.2 – 7.4) at a
bacterial load of 2 ´ 106 microbial cells/ml. The tests were
performed with standard strains of both Gram-positive (Stap-
hylococcus aureus 209p, Smith, 25923) and Gram-negative
bacteria (Bacillus typhi, Shigella dysinteriae, Proteus vulga-