Investigations on the synthesis and pharmacological properties of 4-alkoxy-2-[2-hydroxy-3-(4-aryl-1-piperazinyl)propyl]-6-methyl-1H-pyrrolo [3,4-c]pyridine-1,3(2H)-diones

Article abstract of DOI:10.1016/S0014-827X(02)01302-2

Synthesis of 2-[2-hydroxy-3-(4-aryl-1-piperazinyl)propyl] derivatives of 4-alkoxy-6-methyl-1H-pyrrolo[3,4-c]pyridine-1,3(2H)-diones (8-12) is described. The chlorides used in the above synthesis can exist in two isomeric forms: chain (18-20) and cyclic (19a, 20a). The compounds 8-12 exhibited potent analgesic activity which was superior than that of acetylsalicylic acid in two different tests. Most of the investigated imides suppressed significantly spontaneous locomotor activity in mice.

Full text of DOI:10.1016/S0014-827X(02)01302-2

Il Farmaco 57 (2002) 897Á908
/
www.elsevier.com/locate/farmac
Investigations on the synthesis and pharmacological properties of 4-
alkoxy-2-[2-hydroxy-3-(4-aryl-1-piperazinyl)propyl]-6-methyl-1H-
pyrrolo[3,4-c]pyridine-1,3(2H)-diones
a,
Helena Sladowska *, Barbara Filipek , Dominika Szkatula , Aleksandra Sabiniarz ,
b
a
a
´
b
a
c
d
Malgorzata Kardasz , Joanna Potoczek , Maria Sieklucka-Dziuba , Gra z˙ yna Rajtar ,
Zdzislaw Kleinrok , Tadeusz Lis
d
e
a
Department of Chemistry of Drugs, Wroclaw University of Medicine, Tamka 1, 50-137 Wroclaw, Poland
Laboratory of Pharmacological Screening, Faculty of Pharmacy, Jagiellonian University, Collegium Medicum, Medyczna 9, 30-688 Krak o´ w, Poland
b
c
Department of Hygiene, Medical School, Radziwillowska 11, 20-085 Lublin, Poland
d
Department of Pharmacology, Medical School, Jaczewskiego 8, 20-090 Lublin, Poland
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw, Poland
e
Received 3 May 2002; accepted 29 June 2002
Abstract
Synthesis of 2-[2-hydroxy-3-(4-aryl-1-piperazinyl)propyl] derivatives of 4-alkoxy-6-methyl-1H-pyrrolo[3,4-c]pyridine-1,3(2H)-
diones (8Á12) is described. The chlorides used in the above synthesis can exist in two isomeric forms: chain (18Á20) and cyclic (19a,
0a). The compounds 8Á12 exhibited potent analgesic activity which was superior than that of acetylsalicylic acid in two different
tests. Most of the investigated imides suppressed significantly spontaneous locomotor activity in mice.
/
/
2
/
´
2002 Editions scientifiques et m e´ dicales Elsevier SAS. All rights reserved.
#
Keywords: 4-Alkoxy-6-methyl-1H-pyrrolo[3,4-c]pyridine-1,3(2H)-diones; N-[2-hydroxy-3-(4-aryl-1-piperazinyl)propyl] derivatives; Synthesis;
Analgesic and sedative activities; Derivatives of 7-aza-4-azoniaspiro[3.5]nonane chloride
1
. Introduction
analgesic effect in the ‘writhing syndrome’ test at the
dose of 200 mg/kg whereas compound 4 increased the
time of appearance of the pain reaction at the dose of
68.09 mg/kg in the ‘hot-plate’ test. Among the studied
substances only imide 5 increased the number of head
twitches, induced by 5-HTP in mice, at the dose of 126.6
mg/kg. All the investigated compounds did not affect
the pulse rate and arterial blood pressure in rats.
It has been reported previously [1,2] that N-[2-
hydroxy-3-(4-phenyl(2-pyrimidinyl)-1-piperazinyl)pro-
pyl] derivatives of the suitable 1H-pyrrolo[3,4-c]pyri-
dine-1,3(2H)-diones (3,4-pyridinedicarboximides) (1Á5)
/
significantly suppressed spontaneous locomotor activity
in mice. Compounds 1 and 2 decreased significantly
their amphetamine induced hyperactivity (Fig. 1). Com-
pound 1 caused hypothermia in normothermic mice.
Most of the investigated imides did not display analgesic
activity in ‘writhing syndrome’ and ‘hot-plate’ tests.
Only the compounds 1 and 4 substituted at the position
From our earlier published findings [3] it follows that
the replacement of the piperidino group in compound 6
[
4] by a methoxy one (imide 7) caused appearance of
strong analgesic activity (Fig. 2). Compound 7 was
effective in the ‘writhing syndrome’ test up to the dose of
6
.25 mg/kg. In the ‘hot-plate’ test it showed analgesic
2 of the pyridine ring by the piperidino group were
active in one of these tests. The imide 1 showed a weak
action in doses 200 and 100 mg/kg whereas compound 6
was inactive as an analgesic agent in both tests. At the
same time the above mentioned modification resulted in
a non-toxic substance (LD50 for 6ꢀ
2000 mg/kg).
/
1750 mg/kg, for 7ꢀ
/
* Corresponding author
E-mail address: helena@bf.uni.wroc.pl (H. Sladowska).
´
´
0
014-827X/02/$ - see front matter # 2002 Editions scientifiques et m e´ dicales Elsevier SAS. All rights reserved.
PII: S 0 0 1 4 - 8 2 7 X ( 0 2 ) 0 1 3 0 2 - 2

´
898
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á908
/
c]pyridine-1,3(2H)-diones reported in Fig. 3 with the
expectation that the compounds obtained (8Á12) would
exhibit analgesic activity. Furthermore, the 2-hydroxy-
-(4-aryl-1-piperazinyl)propyl substituent has similar
/
3
structure to that of the side chains of b-blockers.
Therefore, we also evaluated the influence of imides
8
Á12 on the arterial blood pressure in rats.
/
2
8
. Chemistry
The starting materials for the synthesis of compounds
Á12 were 4-methoxy- and 4-ethoxy-6-methyl-1H-pyr-
/
rolo[3,4-c]pyridine-1,3(2H)-diones (13, 14) synthesized
previously [3]. They were transformed into the imides 8Á
2 according to the reactions presented in Scheme 1
methods ‘a’, ‘b ’ and ‘b ’, ‘c’). In the method ‘a’
/
1
(
Fig. 1.
1
2
compounds 13 and 14 were condensed with epichloro-
hydrin in the presence of anhydrous potassium carbon-
ate obtaining suitable N-2,3-epoxypropyl derivatives 15,
16 which in the reaction with N-arylpiperazines were
transformed into compounds 8Á11.
/
In the method ‘b’ 4-methoxy- and 4-ethoxy-6-methyl-
H-pyrrolo[3,4-c]pyridine-1,3(2H)-diones (13, 14) were
1
condensed with appropriate 2-hydroxy-3-(4-aryl-1-pi-
perazinyl)propyl chlorides (18Á20) or their cyclic iso-
/
Fig. 2.
mers (19a, 20a) in anhydrous ethanol in the presence of
C H ONa (‘b ’) or C H OK (‘b ’). In this way all
2
5
1
2
5
2
In order to obtain further information concerning
structureÁactivity relationships (SAR) in this group of
compounds we modified the structure of 1H-pyr-
rolo[3,4-c]pyridine-1,3(2H)-diones (1Á3). The modifica-
tion consisted mainly in introduction of alkoxy groups
in the position 2 of the pyridine ring.
compounds (8Á12) were synthesized.
/
/
The compounds 8 and 9 were also obtained as a result
of condensation of 4-chloro-6-methyl-1H-pyrrolo[3,4-
c]pyridine-1,3(2H)-dione (17) [5] with 2-hydroxy-3-(4-
phenyl-1-piperazinyl)propyl chloride (method ‘c’). This
reaction was performed in anhydrous methanol or
ethanol in the presence of 2 mol of sodium methoxide
or ethoxide for 1 mol of starting imide 17.
/
In the further investigations we also introduced
pharmacophoric groups: OCH and CF into the phenyl
3
3
substituent at N-4 of the piperazine ring and investi-
gated the influence of this modification on the pharma-
cological action. According to the above we performed
the synthesis of the derivatives of 1H-pyrrolo[3,4-
According to the literature data [6,7] 2-hydroxy-3-(4-
aryl-1-piperazinyl)propyl chlorides were obtained in the
reaction of epichlorohydrin with suitable N-arylpipera-
zines. Often non-isolated products of this reaction were
Fig. 3.

´
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á
/
908
899
Scheme 1.
used as intermediates in the synthesis of other com-
pounds.
to the water-insoluble products the structures of
the suitable 2-hydroxy-3-(4-aryl-1-piperazinyl)propyl
Carrying out the above reaction with N-(o-methoxy-
phenyl)- and N-(m-trifluoromethylphenyl)piperazines
we observed that the structure of the formed products
was dependent on temperature. At room temperature
they reacted with epichlorohydrin affording water non-
soluble substances which elemental composition corres-
ponded to 2-hydroxy-3-[4-(o-methoxyphenyl)- and 2-
hydroxy-3-[(4-m -trifluoromethylphenyl)-1-piperazi-
nyl]propyl chlorides, respectively. In the case of N-(m-
trifluoromethylphenyl)piperazine a small amount of
isomeric water-soluble by-product was formed. The
same reaction performed at first at 40 8C for 0.5 h
and then at room temperature led to the isomeric
compounds which were soluble in water and gave
positive reaction for chloride ions with silver nitrate.
N-Phenylpiperazine reacted with epichlorohydrin giving
in both the cases the same water insoluble substance
having elemental composition corresponding to the
known [6] 2-hydroxy-3-(4-phenyl-1-piperazinyl)propyl
chloride.
chlorides (18Á20). Isomeric compounds (soluble in
/
water) were appropriate derivatives of 7-aza-4-azoni-
aspiro[3,5]nonane chloride (19a, 20a) (Scheme 1).
According to our knowledge the possibility of forma-
tion of cyclic structures (type 19a, 20a) in the reaction of
N-arylpiperazines with epichlorohydrin was not
hitherto taken into consideration.
2.1. Crystal structures of 18 and 20a
The perspective view of the structures 18 and 20a is
shown in Fig. 4a and b. Compound 18 is racemic and
one of enantiomers (with C2 atom in R absolute
configuration) was chosen to presentation. Atomic
coordinates and equivalent isotropic displacement para-
meters are listed in Table 1 and principal bond distances,
bond angles and torsion angles in Table 2.
Compound 18 is a molecular structure, whereas 20a is
a salt where cation is represented by 2-hydroxy-7-(3-
trifluoromethyl)phenyl-7-aza-4-azoniaspiro[3,5]nonane
and positive charge is located on the quaternary
nitrogen atom in position 4 of piperazine ring. The
anion is chloride ion.
In order to establish and dispel our doubts concerning
structures of the obtained compounds appropriate
investigations were performed. Based on the results of
the elemental, spectral and X-ray analyses we ascribed

´
900
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á908
/
Fig. 4. (a) A wiev of the molecule 18 (in the picture molecule exists in R conformation). (b) A view of cation and anion of 2-hydroxy-7-(3-
trifluoromethyl)phenyl-7-aza-4-azoniaspiro[3.5]nonane chloride (20a).
The structure of both compounds is extended with the
piperazine ring in chair conformation. The mutual
position of the phenyl and piperazine rings is different
3. Experimental
3.1. Chemistry
in both cases and may be described by C6Á
/
N7Á
/
C10Á
/
C60 torsion angle (59.7(3)8 for 18 and 2.1(3)8 for 20a).
The orientation of the phenyl with respect to the
piperazine ring is dependent on presence, location and
nature of substituents in the phenyl ring, which was
described earlier in the literature, i.e. Ref. [8].
In 18 the propyl group is staggered. Chlorine and C3
atoms are in synclinar conformation and simultaneously
Cl atom is in antiperiplanar position in relation to O
atom. The position of O atom with respect to N4 is
synperiplanar.
All the results of the C, H, N determinations (carried
out by a Carlo Erba elemental analyzer model NA-1500)
were within 90.4% of the theoretical values. All the
/
melting points are uncorrected. The IR spectra, in KBr
pellets, were measured with a Zeiss Jena specord model
1
IR 75 and specord M 80 (Jena). H NMR spectra were
determined in CDCl on a Tesla 587A spectrometer (80
3
MHz), when not otherwise indicated, using TMS as an
internal standard.
3
.1.1. General method for synthesis 2-(2,3-epoxypropyl)
The four-membered ring in 20a is not flat and the
angles within this ring are close to 908 similarly to
structure of diphenylmethyl-3-hydroxyazetidinium chlo-
ride (DPHA) [9]. The OH-group is located in the
derivatives of 4-methoxy- and 4-ethoxy-6-methyl-1H-
pyrrolo[3,4-c]pyridine-1,3(2H)-diones (15, 16)
4-Methoxy- or 4-ethoxy-6-methyl-1H-pyrrolo[3,4-
c]pyridine-1,3(2H)-dione (13, 14) (0.005 mol) and 0.006
mol of anhydrous potassium carbonate in 15 ml of
epichlorohydrin were refluxed for 14 h. Then inorganic
substances were collected on a filter. From the filtrate an
excess of epichlorohydrin was distilled off under dimi-
equatorial position. The N4Á
are close to an average of Csp3
similar values were found in derivative of morpholine
/
C5 and N4Á
/
C9 lengths
bond length and
ꢁ
Á
/
N
[
10].

´
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á
/
908
901
Table 1 (Continued)
Table 1
Fractional atomic coordinates and equivalent isotropic displacement
parameters with the e.s.d.’s in parentheses for 18 and 20a
Atom
x
y
z
Ueq/Uiso
H1A
H1B
H2
0.1642(8)
0.1628(7)
0.2300(6)
0.2224(7)
0.2404(7)
0.1697(6)
0.1565(7)
0.1073(7)
0.1081(7)
0.1484(8)
0.1335(7)
0.2002(8)
0.1957(7)
0.1157(6)
0.0064(6)
0.0041(8)
0.0550(7)
0.664(5)
0.692(4)
0.686(3)
0.446(4)
0.333(4)
0.137(4)
0.367(4)
0.373(5)
0.148(4)
0.127(5)
0.367(5)
0.339(5)
0.112(4)
0.629(5)
0.394(4)
0.605(3)
0.250(4)
0.446(4)
0.286(3)
0.210(4)
0.424(4)
0.319(4)
0.848(5)
0.771(4)
0.744(5)
0.615(4)
0.892(3)
0.831(4)
0.540(5)
0.433(4)
0.032(8)
0.015(6)
0.007(5)
0.022(6)
0.020(6)
0.009(5)
0.023(6)
0.024(7)
0.022(6)
0.032(7)
0.035(8)
0.032(7)
0.016(6)
0.006(5)
0.014(5)
0.037(8)
0.032(8)
Atom
x
y
z
Ueq/Uiso
18
H3A
H3B
H5A
H5B
H6A
H6B
H8A
H8B
H9A
H9B
H20
H40
H50
H60
Cl
0.38388(7)
0.7458(2)
0.5772(3)
0.5899(3)
0.4899(3)
0.5281(2)
0.4220(3)
0.4681(3)
0.4680(2)
0.5696(3)
0.5221(3)
0.4925(3)
0.6141(3)
0.6309(3)
0.5288(3)
0.4077(3)
0.3896(3)
0.803(4)
0.648(3)
0.602(2)
0.556(3)
0.504(2)
0.372(3)
0.314(3)
0.429(3)
0.576(3)
0.400(3)
0.563(3)
0.677(3)
0.595(2)
0.415(3)
0.688(4)
0.710(3)
0.540(3)
0.340(3)
0.309(3)
0.20909(9)
0.4366(2)
0.2919(4)
0.3819(3)
0.5692(3)
0.6885(3)
0.8585(3)
0.9919(4)
0.8814(3)
0.7067(4)
0.5758(4)
1.0047(3)
0.9743(4)
1.0963(4)
1.2485(4)
1.2796(4)
1.1606(4)
0.341(5)
0.165(4)
0.393(3)
0.279(3)
0.650(3)
0.527(3)
0.814(3)
0.934(3)
1.043(4)
1.102(4)
0.633(4)
0.744(3)
0.464(3)
0.520(3)
0.864(5)
1.065(4)
1.315(4)
1.387(4)
1.175(3)
0.521742(13)
0.56594(4)
0.52963(5)
0.56123(5)
0.56455(5)
0.59146(4)
0.59389(5)
0.62044(5)
0.64939(4)
0.64694(5)
0.62012(5)
0.67542(5)
0.69574(5)
0.72135(6)
0.72721(6)
0.70708(6)
0.68166(6)
0.5737(7)
0.5274(6)
0.5146(4)
0.5751(5)
0.5443(5)
0.5649(5)
0.5971(5)
0.5721(5)
0.6166(6)
0.6200(5)
0.6652(5)
0.6432(5)
0.6181(4)
0.6245(5)
0.6924(6)
0.7350(5)
0.7441(6)
0.7107(6)
0.6685(5)
0.0296(2)
0.0235(4)
0.0230(5)
0.0206(5)
0.0218(5)
0.0195(4)
0.0222(5)
0.0222(5)
0.0215(4)
0.0242(5)
0.0224(5)
0.0236(5)
0.0245(5)
0.0277(6)
0.0300(6)
0.0324(6)
0.0274(6)
0.059(10)
0.046(8)
0.012(5)
0.020(6)
0.014(6)
0.022(6)
0.018(6)
0.019(6)
0.033(7)
0.028(7)
0.023(6)
0.017(6)
0.004(5)
0.016(6)
0.062(10)
0.033(7)
0.037(8)
0.036(7)
0.023(6)
O
C1
C2
C3
N4
C5
C6
N7
C8
C9
ꢂ0.152(4)
ꢂ0.321(4)
ꢂ0.106(5)
0.100(5)
C10
C20
C30
C40
C50
C60
H1
nished pressure. The residue was crystallized from
ethanol with simultaneous decolorization with charcoal
in the case of the compound 15.
H1A
H1B
H2
The properties of compounds 15 and 16 are given in
1
Table 3 but the assignments in their H NMR spectra
are presented below.
H3A
H3B
H5A
H5B
H6A
H6B
H8A
H8B
H9A
H9B
H20
H30
H40
H50
H60
1
H NMR of 15: dꢀ
3.40 (m-1H, CH); 3.58Á
CH a); 7.19 (s-1H, H in pyridine ring).
/
2.63Á
/
2.84 (m-5H, CH ꢁCH g);
/
3
2
3.05Á
/
/
4.13 (m-5H, OCH ꢁ
/
3
2
1
H NMR of 16: dꢀ
2.62Á2.79 (m-5H, CH ꢁ
CH); 3.76Á
CH2ÁCH ); 7.18 (s-1H, H in pyridine ring).
/
1.39Á
/
1.56 (t-3H, CH3Á
3.38 (mÁ
4.75 (q-2H, Á
/
CH2Á
/
);
/
/
CH g); 3.05Á
/
/1H,
3
2
/
3.91 (m-2H, CH a); 4.48Á
/
/
2
/
3
3.1.2. General methods for synthesis 2-[2-hydroxy-3-(4-
aryl-1-piperazinyl)propyl] derivatives of 4-methoxy- and
-ethoxy-6-methyl-1H-pyrrolo[3,4-c]pyridine-1,3(2H)-
diones (8Á12)
4
20a
Cl
/
0.185294(11)
0.09121(4)
0.03353(4)
0.06877(7)
0.22977(4)
0.17610(5)
0.21800(5)
0.22126(5)
0.18287(4)
0.15839(5)
0.12032(5)
0.12300(4)
0.14502(5)
0.18369(5)
0.09058(5)
0.09222(5)
0.06126(5)
0.02804(6)
0.02650(6)
0.05707(6)
0.06372(6)
0.2193(8)
0.76808(7)
0 (fixed)
1.1859(2)
1.1764(3)
1.0305(3)
0.3693(2)
0.5015(3)
0.4818(3)
0.3943(3)
0.4681(2)
0.3224(3)
0.4063(3)
0.5851(2)
0.7313(3)
0.6554(3)
0.6513(3)
0.8225(3)
0.8863(3)
0.7853(3)
0.6159(4)
0.5514(3)
1.0672(4)
0.265(5)
0.02025(9)
0.0426(4)
0.0503(5)
0.0621(6)
0.0220(3)
0.0165(3)
0.0182(3)
0.0175(3)
0.0135(3)
0.0160(3)
0.0197(3)
0.0176(3)
0.0183(3)
0.0164(3)
0.0180(3)
0.0191(3)
0.0216(4)
0.0266(4)
0.0296(4)
0.0251(4)
0.0282(4)
0.036(8)
F1
F2
ꢂ0.3256(3)
ꢂ0.3782(4)
ꢂ0.6062(3)
0.8561(2)
3
.1.2.1. Method ‘a’. 2-(2,3-Epoxypropyl)-4-methoxy- or
2-(2,3-epoxypropyl)-4-ethoxy-6-methyl-1H-pyrrolo[3,4-
F3
O
C1
c]pyridine-1,3(2H)-dione (15 or 16) (0.001 mol) and
0.002 mol of N-phenylpiperazine (8, 9), 0.0011 mol of
N-(m-trifluoromethylphenyl)piperazine (10), 0.0013 mol
of N-(o-methoxyphenyl)piperazine (11) in 30 ml (8, 9)
or 15 ml (10, 11) of anhydrous ethanol were refluxed for
1 h (8, 9), 15 min (10, 11). The crystals separated after
cooling of the reaction mixture were collected on a filter
and purified by crystallization from ethanol.
0.6345(3)
0.6747(3)
C2
C3
0.4379(3)
0.3836(2)
N4
C5
0.2716(3)
0.2303(3)
C6
N7
C8
0.0976(3)
0.2159(3)
0.2551(3)
C9
C10
C20
C30
C40
C50
C60
C70
H1
ꢂ0.0073(3)
ꢂ0.1382(3)
ꢂ0.2496(3)
ꢂ0.2422(4)
ꢂ0.1150(4)
0.0049(4)
3.1.2.2. Methods ‘b ’ and ‘b ’. Sodium (method ‘b ’)
(0.01 mol) or 0.01 mol of potassium (method ‘b ’) was
dissolved in 100 ml of anhydrous ethanol and to this
solution 0.01 mol of 4-methoxy- or 4-ethoxy-6-methyl-
1H-pyrrolo[3,4-c]pyridine-1,3(2H)-dione (13 or 14) was
added. The reaction mixture was refluxed for 15 min in
case of the imide 13 and to the obtained suspension or
1 2 1
2
ꢂ0.3900(4)
0.847(5)

´
902
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á908
/
Table 2 (Continued)
Table 2
˚
Principal bond distances (A), bond angles (8) and torsion angles (8)
with ESD’s in parentheses for 18 and 20a
1
8
20a
Torsion angles
1
8
20a
N4Á
N4Á
OÁC2Á
C1ÁC2Á
C2ÁC3Á
C2ÁC3Á
C2ÁC3Á
C2ÁC1Á
C2ÁC1Á
C2ÁC1Á
C9ÁN4Á
C3ÁN4Á
C1ÁN4Á
N4ÁC5Á
C5ÁC6ÁN7Á
C5ÁC6ÁN7Á
C10ÁN7ÁC8Á
C6ÁN7ÁC8Á
C5ÁN4ÁC9Á
C3ÁN4ÁC9Á
C1ÁN4ÁC9Á
N7ÁC8ÁC9Á
C6ÁN7Á
C8ÁN7Á
C6ÁN7Á
C8ÁN7Á
C20ÁC30Á
C20ÁC30Á
C20ÁC30Á
Cl ÁC1ÁC2Á
Cl ÁC1ÁC2Á
/
C1Á
C1Á
C3Á
C3Á
N4Á
N4Á
N4Á
N4Á
N4Á
N4Á
C5Á
C5Á
C5Á
C6Á
/
C2Á
/
O
136.1(2)
/
/
C2Á
/
C3
14.7(2)
ꢂ135.9(2)
ꢂ14.8(2)
ꢂ98.8(2)
133.6(2)
14.9(2)
Bond distances
/
/
/N4
ꢂ46.4(3)
F1Á
F2Á
F3Á
OÁ
C1Á
C1Á
C2Á
C3Á
N4Á
N4Á
C5Á
C6Á
N7Á
N7Á
C8Á
/
C70
C70
C70
1.346(3)
1.331(3)
1.329(3)
1.397(2)
1.536(2)
1.551(2)
1.541(3)
1.522(2)
1.494(2)
1.495(2)
1.521(3)
1.461(2)
1.411(2)
1.464(2)
1.520(3)
1.401(3)
1.410(2)
1.380(3)
1.394(3)
1.497(3)
1.388(3)
1.396(3)
/
/
/N4
ꢂ165.2(2)
ꢂ55.4(3)
ꢂ176.9(2)
/
/
/
/
C9
C5
C1
C9
C5
C3
C6
C6
C6
N7
C10
C8
/
/
/
/
/
C2
1.421(3)
/
/
/
/
N4
C2
C3
N4
/
/
/
98.8(2)
/
1.512(3)
1.536(3)
1.462(3)
1.465(3)
1.472(3)
1.520(3)
1.467(3)
1.423(3)
1.472(3)
1.523(3)
1.404(3)
1.397(3)
1.395(3)
1.378(4)
/
/
/
ꢂ132.5(2)
ꢂ14.8(2)
53.5(2)
/
/
/
/
/
/
/
/
59.7(2)
/
C9
C5
C6
N7
/
/
/
ꢂ175.8(2)
ꢂ178.2(2)
ꢂ75.9(2)
ꢂ56.7(2)
ꢂ162.9(2)
60.1(2)
/
/
/
/
/
/
/
/
ꢂ58.7(3)
ꢂ173.0(2)
56.2(3)
/
/
/
/
/
C10
C8
/
/
/
/
/
/
/
C9
174.3(2)
ꢂ162.3(2)
ꢂ60.8(2)
ꢂ53.6(2)
176.6(2)
77.9(2)
/
C9
/
/
/
C9
C8
C8
C8
N4
ꢂ56.0(3)
ꢂ60.1(2)
177.6(2)
C10Á
C10Á
C20Á
C30Á
C30Á
C40Á
C50Á
C1ÁCl
/
C60
C20
C30
C40
C70
C50
C60
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
59.0(3)
59.7(3)
57.4(2)
2.1(3)
/
/
/
C10Á
C10Á
C10Á
C10Á
/
C60
C60
C20
C20
/
1.389(4)
1.378(4)
1.805(2)
/
/
/
ꢂ172.4(2)
ꢂ121.9(2)
6.1(3)
136.1(2)
179.5(2)
ꢂ46.5(2)
ꢂ97.5(3)
142.4(2)
23.9(3)
/
/
/
/
/
/
/
/
Bond angles
N4ÁC1ÁC2
OÁC2Á
OÁC2Á
C3Á
N4Á
C9ÁN4Á
C9ÁN4Á
C5ÁN4Á
C9ÁN4Á
C5ÁN4Á
C3ÁN4Á
N4ÁC5Á
N7ÁC6Á
C10ÁN7Á
C10ÁN7Á
C6ÁN7Á
N7ÁC8Á
N4ÁC9Á
C60Á
C60Á
C20Á
C30Á
C20Á
C20Á
C40Á
C50Á
C40Á
C50Á
F3ÁC70Á
F3ÁC70Á
F2ÁC70Á
F3ÁC70Á
F2ÁC70Á
F1ÁC70Á
Cl ÁC1Á
/
/
C70Á
C70Á
C70Á
/
F3
F2
F1
/
/
88.89(12)
/
/
/
/
/C3
108.4(2)
118.4(2)
/
/
/
/
/C1
107.8(2)
111.8(2)
113.3(2)
108.4(2)
113.5(2)
109.8(2)
118.07(15)
88.12(13)
89.78(13)
110.76(13)
112.07(13)
114.94(14)
112.15(14)
116.09(13)
89.34(12)
111.35(14)
110.08(15)
116.97(15)
116.97(15)
110.27(14)
110.40(15)
110.73(14)
118.1(2)
/
/
/O
178.06(15)
/C2Á/C1
/
/
/C3
ꢂ62.8(2)
/
C3Á
/
C2
C5
C3
C3
C1
C1
C1
C6
C5
/
/
/
/
clear solution (imide 14) 0.012 mol of the appropriate
chloride was added. The mixture was refluxed until the
alkaline reaction disappeared. The crystals separated
after cooling were collected on a filter, washed with
distilled water and dried. Then they were purified by
crystallization from ethanol.
/
/
/
/
/
/
/
/
/
/
110.2(2)
111.2(2)
113.4(2)
115.5(2)
109.8(2)
110.6(2)
110.6(2)
117.9(2)
119.5(2)
122.5(2)
120.3(2)
121.1(3)
/
/
/
/
C6
C8
/
/
3.1.2.3. Method ‘c’. Sodium (0.01 mol) was dissolved in
/
/
C8
C9
C8
50 ml of anhydrous methanol or ethanol and to this
/
/
/
/
solution 0.005 mol of 4-chloro-6-methyl-1H-pyrrolo[3,4-
c]pyridine-1,3(2H)-dione (17) was added. The mixture
was refluxed for 15 min and after cooling 0.006 mol of 2-
hydroxy-3-(4-phenyl-1-piperazinyl)propyl chloride was
introduced. The mixture was refluxed for 10 h. Then the
substance separated after cooling was collected on a
filter, washed with distilled water and purified by
crystallization from ethanol.
/
C10Á
C10Á
C10Á
C20Á
C30Á
C30Á
C30Á
C40Á
C50Á
C60Á
/
C20
/
/N7
123.3(2)
/
/N7
118.5(2)
/
/
C10
C40
C70
C70
C30
C60
C10
119.7(2)
122.5(2)
118.9(2)
/
/
/
/
/
/
118.6(2)
/
/
118.8(3)
120.8(3)
121.0(2)
117.8(2)
120.9(2)
120.9(2)
/
/
The properties of the obtained compounds 8Á12 are
/
/
/
1
listed in Table 3 but the assignments of their H NMR
/
/
F2
105.8(2)
106.8(2)
/
/
F1
spectra are shown below.
1
/
/
F1
105.1(2)
H NMR of 8: dꢀ
); 3.13Á3.25 (distorted t-4H, Á
3.80 (d-2H, Ha of propyl); 3.80Á
H, OCH ꢁHb of propylꢁOH); 6.85Á
/
2.47Á
/
2.82 (m-9H, CH ꢁ
/
Á
/
CH2Á
/
3
/
/
C30
C30
C30
113.4(2)
112.6(2)
112.5(2)
N(CH ) Á
/
/
/
(CH ) NÁ
/
2
2
2 2
/
/
C H ); 3.73Á
/
/
4.30 (m-
6
5
/
/
5
/
/
/7.26 (m-6H,
/
/C2
111.5(2)
3
arom. H).

´
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á
/
908
903
Table 3
Properties of the investigated compounds
Comp. Formula
molecular
weight)
M.p. (8C) (solvent) Yield (%)
IR absorptions in KBr (cmꢂ1
)
(
CO
OH
Mono- and
disubstituted
benzene
1
5
6
8
9
0
1
2
C
12
H
12
N
2
2
4
4
O
O
O
O
4
4
4
4
126Á
78Á81 (ethanol)
190Á
188Á
165Á
175Á
167Á
/
128 (ethanol) 60Á
/
65
1720, 1780
1720, 1780
1730, 1780
1725, 1770
1724, 1772
1726, 1772
1720, 1770
(248.23)
1
C
H
13 14
N
/
50
(262.26)
C
H
22 26
N
/
192 (ethanol) 51 method ‘a’; 54 method ‘b
‘b ’; 61 method ‘c’
190 (ethanol) 55 method ‘a’; 71 method ‘b
‘b ’; 48 method ‘c’
1
1
2
2
’; 65 method
3380Á3420 700, 770
/
(410.46)
2
C
H
23 28
N
/
’; 75 method
3370Á/3410 690, 760
(424.49)
2
1
1
1
C
H
23 25
F
3
N
4
O
4
/167 (ethanol) 42 method ‘a’; 82 method ‘b
’
’
3088
692, 756
(478.46)
C
H
23 28
N
4
O
5
/177 (ethanol) 46 method ‘a’; 67 method ‘b
3060
752
(440.49)
C
H
24 27
F
3
N
4
O
4
/168 (ethanol) 80 method ‘b
2
’
3080Á/3120 690, 750
(492.49)
1
H NMR of 9: dꢀ
.46Á2.72 (m-9H, CH ꢁ
.24 (distorted t-4H, Á
/
1.37Á
/
1.55 (t-3H, CH3Á
NÁ(CH ) Á); 3.12Á
NÁC H ); 3.73Á
/
CH2Á
/
);
C H ClN O , M 284.78 (C, H, N determinations).
14 21 2 2 W
1
2
3
(
/
/
Á
/
H CÁ
/
/
/
/
H NMR of 19: dꢀ
(CH ) Á); 2.95Á3.25 (mÁ
CH2ÁClꢁ
); 6.93 (m-4H, H of phenyl).
/
2.52Á
4H, Á
OH); 3.86Á4.16 (m-4H,
/
2.95 (m-6H, Á
/
H CÁ
/
NÁ
/
3
2
2 2
2
/
(H C) Á
/
/
/
3.91
4.37 (mÁ
4.83 (q-2H, CH3ÁCH2Á);
/
/
/
/
(H C) ÁN-Aryl); 3.50Á
/
/
2
2
6
5
2 2
2
2
distorted d-3H, Ha of propylꢁ
/
OH); 3.92Á
/
/
3.68 (m-3H,
OCH ꢁ CHÁ
Á
/
/
/
/
1
H, Hb of propyl); 4.48Á
.813Á7.25 (m-6H, arom. H).
H NMR of 10: dꢀ2.45Á2.70 (m-9H, CH ꢁ
NÁ(CH ) Á); 3.15Á3.20 (distorted t-4H, Á
C H Ám-CF ); 3.73Á3.80 (distorted d-2H, Ha of pro-
4.12 (m-5H, Hb of propylꢁOHꢁOCH );
7.43 (m-5H, arom. H).
H NMR of 11: dꢀ2.45Á
NÁ(CH ) Á); 3.00Á3.10 (m-4H, Á
OCH ); 3.72Á
/
/
/
/
Á
/
/
3
6
/
/
/
/
Á
/
H CÁ
/
3
2
3.1.4. Chloride of 2-hydroxy-7-(2-methoxy)phenyl-7-
/
/
/
/
(H C) Á
/
NÁ
/
2
2
2
2
aza-4-azoniaspiro[3.5]nonane (19a)
/
/
6
4
3
In this case the same amount of reagents was used as
described in Section 3.1.3. The reaction mixture was
stirred at 40 8C for 0.5 h, then at r.t. for 8 h. A few
mililiters of diethyl ether were added to a cold solution
and the mixture was left overnight. The resulting solid
substance was collected on a filter and washed with
ethanol. The analytical sample was obtained after
pyl); 3.85Á
.018Á
/
/
/
3
7
/
/
/
2.80 (m-9H, CH ꢁ
/
Á
/
H CÁ
/
3
2
/
/
/
/
(H C) Á
/
NÁ
/
C H Áo-
/
2
2
2
2
6
4
/
4.13 (m-10H, Ha and Hb of propylꢁ
/
3
OHꢁ
/
2ꢃ
H NMR of 12: dꢀ
.51Á2.92 (m-9H, CH ꢁ
distorted t-4H, Á
/
OCH ); 6.91Á
/
7.20 (m-5H, arom. H).
1.38Á
H CÁ
3
1
/
/
1.56 (t-3H, CH3Á
/
CH2Á
/);
crystallization from ethanol. It melted at 125Á
/
127 8C,
2
/
/
Á
/
/
NÁ
C H Ám-CF ); 3.52 (s-
4 3
/
(CH ) Á
/
); 3.20-3.31
3
2
2 2
67% of yield.
(
/
(H C) Á
/
NÁ
/
/
2
2
6
The compound 19a was water-soluble and gave
positive reaction for chloride ions with silver nitrate.
C H ClN O , M 284.78 (C, H, N determinations).
1
4
H, OH); 3.73Á
.05Á4.24 (m-1H, Á
7.36 (m-5H, arom. H).
/
3.80 (distorted d-2H, Ha of propyl);
/
/
CHÁ); 4.47Á4.74 (q-2H, Á
/
/
/
CH2Á
/
1
4
21
2
2
W
1
CH ); 7.09Á
/
3
H NMR of 19a: dꢀ
/
3.15Á
/
3.42 (m-4H, Á
/
(H C) ÁN-
/
2
2
Aryl); 3.72Á4.12 (m-7H, Á
/
/
OCH ꢁ
/
); 4.39Á
/
3.1.3. 2-Hydroxy-3-[4-(2-methoxyphenyl)-1-
piperazinyl]propyl chloride (19)
3
4.93 (m-6H,
arom. H).
); 6.69Á
/
7.20 (m-4H,
Epichlorohydrin (0.012 mol) was added to a solution
containing 0.012 mol of N-(2-methoxyphenyl)piperazine
in 30 ml of anhydrous ethanol. The reaction mixture was
vigorously stirred at room temperature (r.t.) for 2 h. The
separated solid substance was collected on a filter and
3.1.5. 2-Hydroxy-3-[4-(3-trifluoromethylphenyl)-1-
piperazinyl]propyl chloride (20)
washed with ethanol. It melted at 103Á
0%.
The compound 19 was not soluble in water and gave
no chloride ions test with silver nitrate.
/
104 8C, yield
Epichlorohydrin (0.01 mol) was added to a vigorously
stirred solution of N-(3-trifluoromethylphenyl)pipera-
zine (0.01 mol) in 40 ml of anhydrous ethanol. The
mixture was stirred at room temperature, monitoring
8

´
904
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á908
/
the reaction through TLC on silica gel (ethyl acetate as
eluant). Then ethanol was evaporated at r.t. A residue
was a crude colorless oily product which was purified by
Table 4
Data referring to the crystal structure analysis of 18 and 20a
1
8
20a
column chromatography on silica gel (70Á
using ethyl acetate as eluant. The obtained in this way
compound 20 melted at 67Á69 8C after crystallization
from n-hexane. Yield 85%. R ꢀ0.71.
C H ClF N O, M 322.75 (C, H, N determina-
/
230 mesh)
Formula
C
254.75
13
H
19ClN
2
O
C
14
H
18ClF
322.75
orthorhombic
Pna2
3 2
N O
Molecular weight
Crystal system
Space group
/
orthorhombic
/
f
Pbca
1
1
4
18
3
2
W
Unit cell dimensions
a ( A˚ )
tions).
8.703(3)
6.709(3)
43.737(9)
2553.7(15)
8
36.421(6)
5.975(2)
6.842(2)
1488.9(7)
4
1
˚
H NMR of 20: dꢀ
CH ) Á); 3.01Á3.42 (t-4H, Á
.67 (distorted d-3H, ÁCH2ÁClꢁ
H, ÁCHÁ); 6.86Á7.53 (m-4H, H of phenyl).
/
2.51Á
/
3.01 (m-6H, Á
/
H CÁ
/
NÁ
/
b (A)
2
˚
c (A)
(
3
1
/
/
/
(H C) ÁN-Aryl); 3.47Á
/
/
2
2
2
2
3
V (A )
˚
/
/
/
OH); 3.77Á4.17 (m-
/
Z
T (K)
/
/
/
100(2)
1.325
0.285
100(2)
1.440
0.289
3
D
calc (g/cm )
ꢂ1
3.1.6. Chloride of 2-hydroxy-7-(3-trifluoromethyl)-
phenyl-7-aza-4-azoniaspiro[3.5]nonane (20a)
m (mm )
Measured reflections
15560 (2975
unique)
2031
16981 (4485
unique)
4236
Epichlorohydrin (0.025 mol) was added to a solution
of 0.025 mol of N-(3-trifluoromethylphenyl)piperazine
in 30 ml of anhydrous ethanol. The mixture was stirred
at first at 40 8C for 0.5 h, then at r.t. for 24 h. The
separated white solid substance was collected on a filter
Reflections with I ꢀ2s(I)
Reflections used in refine-
ment
2975
4485
Flack parameter
Parameters refined
Max./min. height in final F
0.01(6)
262
230
ꢂ0.31, 0.37
ꢂ0.37,ꢁ0.70
and washed with ethanol. It melted at 147Á
/
149 8C, 55%
3
map (e/A )
˚
of the yield.
R
0.0561
0.0986
0.0429
0.0916
The substance was water-soluble and gave positive
reaction for chloride ions with silver nitrate.
C H ClF N O, M 322.75 (C, H, N determina-
Rw
1
4
18
3
2
W
tions).
1
standard pellet diet, tap water was given ad libitum.
Control and experimental groups consisted of six to
eight animals each. The investigated compounds were
administered intraperitoneally as a suspension in 3%
Tween 80 or 0.5% methylcellulose at a constant volume
of 10 ml/kg (mice) and 5 ml/kg (rats).
H NMR of 20a in DMSO-d (300 MHz): dꢀ
/
3.49Á
3.70 and 3.74Á
CH of piperazine fragment);
/
6
3
3
4
.56 (m-4H, Á
.82 (2 distorted t-4H, 2ꢃ
.22Á4.33 (dd-2H, CH2Á); 4.55Á
4.74 (m-1H, ÁCHÁ); 6.73Á
.55 (4H, arom. H).
/
(H C) Á
/
N-Aryl); 3.63Á
/
/
2
2
/
2
/
/
/
4.64 (m-3H, Á
/
CH2Á
/
ꢁ
/
OH); 4.64Á
/
/
/
/
6.78 and 7.15Á
/
7
3.2.1.3. Statistical analysis. The statistical significance
3
.1.7. X-ray analysis of 18 and 20a
The crystals of 18 and 20a suitable for X-ray analysis
was calculated using a one-way ANOVA or Student’s t-
test. The ED50 values and their confidence limits were
calculated according to the method of Litchfield and
Wilcoxon [15].
were grown from chloroform (18) or ethanol (20a). Both
structures were solved by direct methods using the
SHELXS-97 program [11] and refined using SHELXL-97
Acute toxicity was assessed by the methods of
Litchfield and Wilcoxon [15] and presented as LD50
calculated from the mortality of mice after 24 h.
Pain reactivity was measured in the ‘hot-plate’ test
according to the method of Eddy and Leimbach [16].
The animals were placed individually on a metal plate
heated to 56 8C. The time (s) of appearance of the pain
reaction (licking of the forepaws or jumping) was
recorded by a stop-watch. The experiments were per-
formed 30 min after administration of the investigated
compounds.
Pain reactivity was also measured by the ‘writhing
syndrome’ test of Koster et al. [17]. The test was
performed in mice by the i.p. injection of a 0.6%
solution of acetic acid, in a volume of 10 ml/kg 60 min
after the administration of investigated compounds. The
number of writhing episodes was counted for 30 min
after the injection of 0.6% acetic acid.
[
12]. The molecular graphics were prepared using XP [13]
and ORTEP3 [14]. The experimental and crystal data are
listed in Table 4.
3
3
3
.2. Pharmacology
.2.1. Materials and methods
.2.1.1. Substances. Acetylsalicylic acid (ZF-Starogard
Gdaski, PL), morphine (Morphinum hydrochloricum,
Polfa-Kutno, PL).
3
.2.1.2. Animals. The experiments were carried out on
male and female AlbinoÁSwiss mice (body weight 18Á26
g) and male Wistar rats (body weight 180Á250 g). The
/
/
/
animals were housed in constant temperature facilities
exposed to 12:12 h light-dark cycle and maintained on a

´
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á
/
908
905
Spontaneous locomotor activity in mice was mea-
sured in circular photoresistor actometers (32 cm in
diameter). The investigated compounds were injected
‘writhing’ tests. All investigated compounds possessed
analgesic action in both tests (Tables 5 and 6).
In the ‘hot-plate’ test the imides 8 and 12 produced a
significant effect up to the dose of 12.5 mg/kg, whereas
the compounds 9 and 10 had analgesic activity in doses
up to 25 mg/kg. Also 11 increased significantly the times
of appearance of the pain reaction but only in doses up
to 100 mg/kg. All the investigated compounds showed
more potent analgesic activity than acetylsalicylic acid
intraperitoneally in doses 200Á12.5 mg/kg. Thirty min
/
after the injection of the investigated compounds mice
were placed in the actometers for 30 min. Each crossing
of the light beam was recorded automatically. The
amount of impulses was noted after 30 min.
Arterial blood pressure was determined according to
the method of Gerold and Tschirky [18] using UGO-
BASILE equipment (blood pressure recorder, cat. no.
80006). Systolic blood pressure on the tail artery was
measured 30 min after administration of investigated
compounds.
(
Table 5).
The compounds 8Á
/
11 possessed very strong activity
in the ‘writhing’ method. The most potent effect was
produced by the imide 8 which was effective up to a dose
of 0.39 mg/kg. The compound 10 was active up to the
dose of 0.78 mg/kg, while 9 and 11 decreased the pain
sensitivity in mice in this test up to the dose of 1.56 mg/
kg. Also the compound 12 showed strong analgesic
activity in the ‘writhing syndrome’ test up to the dose of
4
. Results and discussion
4
.1. Acute toxicity
3
.125 mg/kg. The summarized data are shown in Table
. It was interesting to observe that in the ‘writhing’ test
6
All investigated compounds were not toxic (LD ꢀ
/
5
0
all the investigated compounds displayed activity supe-
rior to that of acetylsalicylic acid. What more, the results
reported in Table 6 indicate that the compounds 8, 10,
2
000 mg/kg).
4
.2. Pain reactivity
11 and 9 were about 6 to 1.7 times more potent than
morphine, but the anti-writhing activity of 12 was
comparable to that reported for morphine.
In order to screen the compounds for analgesic
activity two methods were chosen: the ‘hot-plate’ and
Table 5
The influence of the investigated compounds on the pain reactivity in ‘hot-plate’ test in mice
Comp.
Dose (mg/kg) i.p.
25
% Prolongation of the time reaction
ED50 (mg/kg)
11.9 (6.6Á13.1)
8
85.8***
75.5***
6.8
/
1
2.5
.25
50
6
9
101.7****
59.9****
28.8
17.6 (12.6Á
/
23.8)
2
1
5
2.5
10
75
79.3**
43.3*
53.6 (42.1Á/64.0)
5
2
1
0
5
2.5
41.6*
1
1
2
150
00
85.0*
49.1*
7.5
96.8 (72Á121)
/
1
5
0
1
25
2.5
.25
400
87.5**
62.5*
21.8
10.6 (5.9Á18.8)
/
1
6
Acetylsalicylic acid
Morphine
116.0**
35.0
9.45
266.7 (148.2Á/533.4)
2
1
00
00
6
66.0**
61.0*
5.4
2.55 (1.59Á/4.08)
3
1
Results are expressed as a mean9SEM, nꢀ6Á8.
/
*
*
*
*
p B0.05.
* p B0.02.
** p B001.
*** p B0.001.

´
906
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á908
/
Table 6
Effects of investigated compounds on the ‘writhing syndrome’ induced by acetic acid on mice
Comp.
Dose (mg/kg) i.p.
% inhibition of writhing
ED50 (mg/kg)
0.40 (0.27Á0.69)
8
6.25
97.8****
94.0****
88.7****
88.7****
45.45*
/
3
1
.125
.56
0
.78
.39
0
0
.195
9
25
1
96.7****
90.0****
1.4 (0.79Á/1.8)
2.5
****
6.25
3.125
1.56
0.78
86.7
80.0****
65.3****
11.7
1
0
1
12.5
96.7****
93.8***
62.1***
59.7***
45.3*
1.04 (0.4Á
/
2.7)
6
3
.25
.125
.56
.78
.39
1
0
0
23.0
1
50
89.7****
80.6****
72.8***
72.0***
60.0***
56.8**
37.4
1.35 (0.33Á5.57)
/
2
1
5
2.5
6
3
1
0
.25
.125
.56
.78
12
50
91.3****
85.0****
76.3***
62.8**
54.5**
41.9
2.49 (1.7Á5.6)
/
2
1
5
2.5
6
3
1
.25
.125
.56
Acetylsalicylic acid
Morphine
100
83.5****
56.0**
41.6
39.15 (29.1Á
/
48.4)
5
3
0
0
10
3
93.7****
61.0**
15.6
2.44 (1.18Á
/
5.02)
1
Results are expressed as a mean9SEM, nꢀ6Á8.
/
*
*
*
*
p B0.05.
* p B0.02.
** p B0.01.
*** p B0.001.
4
.3. Locomotor activity
The compounds 10, 11 and 12 suppressed significantly
From the data presented above it can be seen that all
the studied compounds 8Á12 displayed strong analgesic
/
properties and were non-toxic. In the ‘writhing’ test the
most active substance was the imide 8, containing
methoxy group in position 2 of the pyridine ring and
unsubstituted phenyl at N-4 of piperazine. The replace-
ment of methoxy group by ethoxy one (imide 9) caused
almost fourfold decrease of the analgesic activity in this
test. Similarly the imide 10 with methoxy group in the
pyridine ring was more active than its ethoxy analog 12.
It indicates that the kind of the alkoxy group in
position 4 of 1H-pyrrolo[3,4-c]pyridine-1,3(2H)-dione
derivatives has influence on the strength of the analgesic
action in the ‘writhing’ test. Introduction of trifluoro-
methyl or methoxy groups into the phenyl substituent at
the spontaneous locomotor activity of mice during a 30
min observation period up to the dose of 12.5 mg/kg.
The imide 9 was active at the dose of 200 mg/kg while 8
also inhibited spontaneous locomotor activity in mice by
ca. 37Á23%, but this effect was not significant (Table 7).
/
4
.4. Arterial blood pressure
All the tested compounds administered at the dose of
00 mg/kg did not affect the pulse rate and arterial
blood pressure in rats.
2

´
H. Sladowska et al. / Il Farmaco 57 (2002) 897Á
/
908
907
Table 7
Influence of the investigated compounds on the spontaneous locomo-
tor activity in mice
tion did not influence the toxicity of the mentioned
compounds. All had LD ꢀ2000 mg/kg.
/
5
0
Comp. Dose (mg/ % inhibition of locomotor
activity
ED50 (mg/kg)
kg)
5
. Conclusion
8
9
200
36.9
23.5
1
00
200
00
The analgesic action of new derivatives of 1H-
84.4***
45.8
107.9 (91Á121)
/
pyrrolo[3,4-c]pyridine-1,3(2H)-dione was investigated
on mice, using the ‘hot-plate’ and ‘writhing’ tests. All
of the compounds studied exhibited analgesic activity
which was superior to that of acetylsalicylic acid in the
both tests. Furthermore they caused significant suppres-
sion of the spontaneous locomotor activity in mice.
It is accepted that analgesics are generally considered
to act centrally, peripherally or both centrally and
peripherally. Narcotic analgesics such as morphine
produce their analgesic actions by a central mechanism,
but non-steroidal antiinflammatory agents, such as
aspirin-by a peripheral mechanism [19]. However, it is
supposed that salicylates produce their analgesic effects
partly by a central mechanism [20].
1
5
2
0
5
38.6
38.4
10
11
12
50
84.9***
73.3**
64.3*
82.9***
76.0**
68.7*
64.5***
58.3***
39.9*
34.1
6.15 (3.8Á8.2)
/
2
1
5
2.5
50
7.2 (5.1Á10.4)
/
2
1
5
2.5
50
19.7 (15.2Á23.3)
/
2
1
5
2.5
6
.25
Each group consisted of 6Á8 animals.
/
*
*
*
p B0.05.
* p B0.02.
** p ꢀ0.01.
Our results suggest that the investigated compounds
can show analgesic activity across central and peripheral
mechanism. The explanation of the exact mechanism of
action will demand of the further pharmacological
investigations.
N-4 of piperazine in the compound 8 (imides 10 and 11)
also weakens the analgesic properties, more in case of
11. Similar relationship was observed in the case of the
compounds 9 and 12.
Among the five studied substances the compound 12
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substance in the ‘hot-plate’ test. Compound 11 contai-
ning in its structure two methoxy groups was endowed
with the weakest analgesic properties in this test.
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