Synthesis of quaternary ammonium salts of 16E-[4-(2-alkylaminoethoxy)-3- methoxybenzylidene]androstene derivatives as skeletal muscle relaxants

Article abstract of DOI:10.1016/j.steroids.2010.11.006

Synthesis of eighteen new quaternary ammonium salts of 16E-arylidene androstene derivatives as skeletal muscle relaxants is reported in the present study. The effects of possibly extended interonium distances on muscle relaxant activity are discussed. All

Full text of DOI:10.1016/j.steroids.2010.11.006

Steroids 76 (2011) 254–260
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Steroids
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Synthesis of quaternary ammonium salts of
16E-[4-(2-alkylaminoethoxy)-3-methoxybenzylidene]androstene derivatives as
skeletal muscle relaxants
Ranju Bansala,∗, Sheetal Guleriaa, Louise C. Youngb, Alan L. Harveyb
a University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh, 160014, India
b Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0NR, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 July 2010
Received in revised form
12 November 2010
Accepted 20 November 2010
Available online 27 November 2010
Synthesis of eighteen new quaternary ammonium salts of 16E-arylidene androstene derivatives as skele-
tal muscle relaxants is reported in the present study. The effects of possibly extended interonium
distances on muscle relaxant activity are discussed. All the quaternary ammonium steroids produced
reduction in the twitch responses, when screened for in vitro neuromuscular blocking activity using
isolated chick biventer cervicis muscle preparation. However, the variable interonium distance, which
˚
is believed to range from 11 to 17 A in these quaternary compounds and is associated with the built
in flexibility of these structures about the single bonds on the moieties linked to ring D of the steroid
skeleton, resulted in varied degrees of muscle relaxant activity. Some of the compounds also inhibited
acetylcholinesterase activity in low concentrations so that they would not be directly suitable for use as
muscle relaxants.
Key words:
Quaternary ammonium salts
16E-Arylidene steroids
Skeletal muscle relaxants
Anticholinesterase activity
© 2010 Elsevier Inc. All rights reserved.
1. Introduction
side effect-free neuromuscular junction blocker with shorter dura-
tion of action continues. Several research groups [5,9] are involved
Neuromuscular junction (NMJ) blockers are clinically used
as adjuncts to surgical anaesthesia to relax skeletal muscles to
avoid any complications arising due to muscle contractions of the
patients during surgery. Quaternary ammonium steroids represent
an important class of skeletal muscle relaxants. The rigid steroid
skeleton with onium centers at different positions has been an
excellent target for producing highly active and selective neu-
romuscular blocking drugs and provides an excellent method of
studying structure activity relationships within the series of these
agents [1–4]. There is a general assumption that neuromuscular
blocking activity is related to the optimal interonium distance of
in search for a therapeutically useful NMJ blocker and a number of
reports in this regard have also been originated from our laboratory
[10–12].
Recently, we have reported the synthesis of a new series of
16E-arylidene androstene derivatives (3, 4) (Fig. 1) with significant
cytotoxic activity [13]. The presence of accessible well placed bis-
tertiary amino functionalities in the steroid skeleton prompted us
to prepare their quaternary ammonium salts with longer intero-
nium distance and study them as muscle relaxants.
In continuation with earlier research work on steroidal NMJ
blockers reported from our laboratory, herein we present the
synthesis and skeletal muscle relaxant activity of quaternary
ammonium steroids with extended interonium distance in the 16-
arylidene series.
˚
about 10–14 A [5]. However, pipecuronium bromide (1) (Fig. 1)
has proved to be an extremely useful neuromuscular blocking
agent of medium to long duration of action without cardiovascular
side effects, even though the interonium distance is much longer
˚
˚
(16.07 A) [6,7] as compared to pancuronium bromide (11.00 A) (2)
(Fig. 1) [8] with moderate cardiovascular side effects. The lack of an
intact acetylcholine-like fragment in pipecuronium bromide has
not compromised its potency but rather increased it, presumably
due to increased interonium distance. The search for a more potent,
2. Experimental
2.1. General
Melting points were determined on a Veego melting point
apparatus and are uncorrected. UV (wavelengths in nm) were
recorded on Lambda 15 and IR (wave numbers in cm−1) spectra
on Perkin-Elmer spectrum RX 1, FT-IR spectrophotometer mod-
els using KBr pellets. 1H NMR spectra were recorded on Bruker
∗
Corresponding author. Tel.: +91 172 2541142; fax: +91 172 2543101.
E-mail address: ranju29in@yahoo.co.in (R. Bansal).
0039-128X/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
doi:10.1016/j.steroids.2010.11.006

R. Bansal et al. / Steroids 76 (2011) 254–260
255
H3C
H3C
O
O
O
O
H3C
H3C
+
N
CH3
+
+
N
N
N
+
N
O
N
CH3
H3C
H3C
_
_
2Br
O
2Br
H
H
H3C
O
H3C
(1)
O
(2)
R'
O
OCH2CH2R
OCH2CH2R
OMe
-N
N
OMe
CH3OCO
(4)
(3)
-N
,
R=
-N
,
Fig. 1. Structures of pipecuronium bromide (1), pancuronium bromide (2) and 16E-arylidene androstene derivatives (3, 4).
AC-300F, 300MHz using deuterated-chloroform (CDCl3) or deuter-
ated dimethylsulfoxide (DMSO-d6) containing tetramethylsilane as
internal standard (chemical shifts in ı, ppm). Elemental analyses
were carried out on a Perkin-Elmer-2400 model CHN analyzer.
Plates for TLC were prepared according to Stahl (E. Merck) using
EtOAc as solvent (activated at 110 ◦C for 30 min) and were visu-
alized by exposure to iodine vapors. Anhydrous sodium sulphate
was used as a drying agent. All solvents were distilled prior to use
according to standard procedures.
C40H62N2O3I2: C, 55.04; H, 7.16; N, 3.21. Found: C, 55.29; H, 7.56;
N, 3.58%.
2.2.2. 16-[3-Methoxy-4-{2-(piperidin-1-yl)ethoxy}benzylidene]-
3ˇ-pyrrolidino-5-androsten-17ˇ-yl acetate dimethiodide
(5b)
Yield: 48.28%; m.p. 268–270 ◦C. UVmax (MeOH): 261.8 nm (log ε
4.31); IR: 2933, 1722, 1620, 1511, 1456, 1370, 1243, 1130,
1038, 946 cm−1 1H NMR (CDCl3 + DMSO-d6): ı 0.77 (s, 3H, 18-
;
CH3), 1.07 (s, 3H, 19-CH3), 2.19 (s⊕, 3H, –OCOCH3), 2.98 (s, 3H,
⊕
2.2. General procedure for the synthesis of quaternary ammonio
salts of 16-arylidene steroids 5–7a–d and 8–10a,b
–N–CH3, pyr⊕rolidine), 3.33 (s, 3H, –N–CH3, piperidine), 3.55–3.77
(m, 8H, 2x–N–(CH2)2–, piperidine and pyrrolidine), 3.84 (s, 3H,
Methyl iodide/allyl bromide (1 mL) was added to a solution
of bistertiary/monotertiary steroids (3, 4) [13] (0.4 mmol) in dry
dichloromethane (50 mL). The reaction mixture was kept aside at
room temperature for days as mentioned in Table 1. The crystalline
material obtained was filtered, washed with dry dichloromethane,
dried and recrystallized from appropriate solvent (Table 1) to afford
their corresponding quaternary ammonium salts.
Table 1
Quaternization time and crystallizing solvent used for various quaternary ammo-
nium steroids.
Compound no.
Days for quaternization
Crystallizing solvent
5a
5b
5c
5d
6a
6b
6c
6d
7a
7b
7c
7d
8a
8b
9a
9b
10a
10b
4
3
3
3
7
7
7
7
1
3
3
3
6
6
7
7
3
7
B
B
A
A
B
B
A + B
A
B
2.2.1. 16-[3-Methoxy-4-{2-(piperidin-1-yl)ethoxy}benzylidene]-
3ˇ-pyrrolidino-5-androsten-17ˇ-ol dimethiodide
(5a)
Yield: 53.98%; m.p. 278–280 ◦C. UVmax (MeOH): 261.8 nm (log ε
4.26); IR: 3410, 2936, 1626, 1512, 1464, 1264, 1231, 1140, 1076,
B
1026, 938, 820 cm−1 1H NMR (CDCl3 + DMSO-d6): ı 0.72 (s, 3H, 18-
;
A + B
B + D
C
C
C
C
C + D
C + D
CH3), 1.08 (s, 3H, 19-CH3), 2.60 (s) and 3.02 (s) (1.2:1 area ratio, 3H,
⊕
⊕
–N–CH3, pyr⊕rolidine), 3.40 (s, 3H, –N–CH3, piperidine), 3.66–3.72
(m, 8H, 2x–N–(CH2)2–, piperidine and pyrrolidine), 3.84 (s, 3H,
⊕
–OCH3), 4.08 (m, 3H, 17␣-H and –CH2Nꢀ), 4.46 (t, 2H, J = 4.32 Hz,
–OCH2–), 5.57 (s, 1H, 6-CH), 6.47 (s, 1H, vinylic-H, 16-arylidene),
6.92–6.95 (m, 3H, 2-CH, 5-CH and 6-CH, aromatic); Anal. Calc. for
A = dry dichloromethane, B = absolute alcohol, C = dry diethyl ether, D = dry acetone.

256
R. Bansal et al. / Steroids 76 (2011) 254–260
⊕
2.2.6. 16-[3-Methoxy-4-{2-(pyrrolidin-1-
–OCH3), 4.01 (t, 2H, J = 4.35 Hz, –CH2Nꢀ), 4.44 (t, 2H, J = 4.37 Hz,
–OCH2–), 5.28 (s, 1H, 17␣-H), 5.55 (d, 1H, J = 4.23 Hz, 6-CH), 6.10
(s, 1H, vinylic-H, 16-arylidene), 6.89 (m, 2H, 2-CH and 5-CH, aro-
matic), 6.98 (d, 1H, Jo = 8.26 Hz, 6-CH, aromatic); Anal. Calc. for
C42H64N2O4I2: C, 55.14; H, 7.05; N, 3.06. Found: C, 55.29; H, 7.16;
N, 3.36%.
yl)ethoxy}benzylidene]-3ˇ-pyrrolidino-5-androsten-17ˇ-yl
acetate dimethiodide (6b)
Yield: 51.36%; m.p. 197–200 ◦C. UVmax (MeOH): 262.6 nm (log ε
4.37); IR: 2938, 1727, 1601, 1513, 1461, 1371, 1237, 1141, 1038,
927 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ␦ 0.80 (s, 3H, 18-CH3), 1.08
⊕
(s, 3H, 19⊕-CH3), 2.21 (s, 3H, –OCOCH3), 2.96 (s, 3H, 3–N–CH3), 3.29
⊕
(s, 3H,⊕–N–CH3,), 3.68 (m, 2H, 3–N–CH2–, pyrrolidine), 3.73 (m,
⊕
2H, 3–N–CH2–, pyrrolidine), 3.79 (m, 4H, –N–(CH2)2–, pyrrolidine),
⊕
2.2.3. 16-[3-Methoxy-4-{2-(piperidin-1-yl)ethoxy}benzylidene]-
3ˇ-pyrrolidino-5-androsten-17ˇ-ol diallyl bromide
(5c)
3.85 (s, 3H, –OCH3), 3.98 (t, 2H, J = 4.44 Hz, –CH2Nꢀ), 4.44 (t, 2H,
Yield: 56.7%; m.p. 263–266 ◦C. UVmax (MeOH): 262.0 nm (log ε
4.43); IR: 3408, 2942, 1626, 1511, 1463, 1266, 1228, 1140,
J = 4.8 Hz, –OCH2–), 5.33 (s, 1H, 17␣-H), 5.54 (d, 1H, J = 5.1 Hz, 6-
CH), 6.14 (s, 1H, vinylic-H, 16-arylidene), 6.91–6.98 (m, 3H, 2-CH,
5-CH and 6-CH, aromatic); Anal. Calc. for C41H62N2O4I2: C, 54.67;
H, 6.94; N, 3.11. Found: C, 54.72; H, 6.88; N, 3.49%.
1019 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ı⊕0.71 (s, 3H, 18-CH3),
1.06 (s, 3H, 19-CH3), 3.67–3.77 (m, 8H, 2x–N–(CH2)2–, piperidine
and pyrrolidine), 3.83 (s, 3H, –OCH3), 4.03 (brs, 3H, 17␣-H and
⊕
⊕
2.2.7. 16-[3-Methoxy-4-{2-(pyrrolidin-1-
–CH2Nꢀ), 4.18 (d, 2H, J = 7.01 Hz, –N–CH2–CH CH2, pyrrolidine),
4.42 (d, 2H, J = 7.22 Hz, –N–CH2–CH CH2, piperidine), 4.47 (t, 2H,
yl)ethoxy}benzylidene]-3ˇ-pyrrolidino-5-androsten-17ˇ-ol
diallyl bromide (6c)
⊕
Yield: 42.22%; m.p. 180–182 ◦C. UVmax (MeOH): 262.2 nm
(log ε 4.37); IR: 3405, 2936, 1628, 1513, 1462, 1264, 1142,
J = 4.8 Hz, –OCH2–), 5.54 (d, 1H, J = 4.15 Hz, 6-⊕CH), 5.72–5.90 (m, 4H,
⊕
2x–N–CH2–CH CH2), 6.04–6.13 (m, 2H, 2x–N–CH2–CH CH2), 6.46
1028 cm−1
;
1H NMR (CDCl3 + DMSO-d6):⊕ı 0.71 (s, 3H, 18-CH3),
(s, 1H, vinylic-H, 16-arylidene), 6.93 (m, 3H, 2-CH, 5-CH and 6-CH,
aromatic); Anal. Calc. for C44H66N2O3Br2: C, 63.60; H, 8.01; N, 3.37.
Found: C, 63.90; H, 8.09; N, 3.38%.
1.07 (s, 3H, 19-CH3), 3.70 (brs, 4H, 3–N–(CH2)2–, pyrrolidine),
⊕
3.78 (m, 4H, –N–(CH2)2–, pyrrolidine), 3.84 (s, 3H, –OCH3), 3.94
⊕
(t, 2H, J = 4.24 Hz, –CH2Nꢀ), 4.01 (d, 1H, J = 5.3 Hz, 17␣-H), 4.11
⊕
2.2.4. 16-[3-Methoxy-4-{2-(piperidin-1-yl)ethoxy}benzylidene]-
3ˇ-pyrrolidino-5-androsten-17ˇ-yl acetate diallyl bromide
(5d)
(d, 2H, J = 6.46 Hz, 3–N–CH2–CH CH2), 4.24 (d, 2H, J = 7.1 Hz,
⊕
–N–CH2–CH CH2), 4.45 (t, 2H, J = 4.17 Hz, –OCH2–), 5.54 (d,
⊕
1H, J = 4.39 Hz, 6-CH), 5.68–5.85 (m, 4H, 2x–N–CH2–CH CH2),
⊕
Yield: 75.17%; m.p. 271–273 ◦C. UVmax (MeOH): 262.2 nm (log ε
4.47); IR: 2937, 1731, 1626, 1514, 1461, 1237, 1142, 1036,
6.00–6.17 (m, 2H, 2x–N–CH2–CH CH2), 6.45 (s, 1H, vinylic-H, 16-
958 cm−1 1H NMR (CDCl3 + DMSO-d6): ı 0.75 (s, 3H, 18-CH3),
;
arylidene), 6.93 (m, 3H, 2-CH, 5-CH and 6-CH, aromatic); Anal. Calc.
for C43H64N2O3Br2: C, 63.23; H, 7.90; N, 3.43. Found: C, 63.32; H,
7.72; N, 3.61%.
1.04 (s, 3H, 19-CH3), 2.19 (s, 3H, –OCOCH3), 3.73–3.81 (m, 8H,
⊕
2x–N–(CH2)2–, piperidine and pyrrolidine), 3.83 (s, 3H, –OCH3),
⊕
⊕
4.07 (s, 2H, –CH2Nꢀ), 4.22 (d, 2H, J = 6.57 Hz, –N–CH2–CH CH2,
pyrrolidine), 4.47 (m, 4H, –OCH2 and –N–CH2–CH CH2, piperi-
⊕
2.2.8. 16-[3-Methoxy-4-{2-(pyrrolidin-1-
yl)ethoxy}benzylidene]-3ˇ-pyrrolidino-5-androsten-17ˇ-yl
acetate diallyl bromide (6d)
dine), 4.49 (t, 2H,), 5.26 (s, 1H, 17␣-H), 5.54 (d, 1H, J = 3.3 Hz,
⊕
Yield: 43.16%; m.p. 155–158 ◦C. UVmax (MeOH): 262.2 nm
(log ε 4.30); IR: 2967, 1731, 1626, 1514, 1461, 1371, 1237,
6-CH), 5.63 (d, 1H, Jc⊕is = 9.91 Hz, –N–CH2–CH CH(H)), 5.72
(d, 1H, Jcis = 10.55 Hz, –N–CH2–CH CH(H)), 5.7⊕9–5.91 (m, 2H,
1142, 1041 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ı 0.80 (s, 3H,
⊕
2x–N–CH2–CH CH(H)), 6.03–6.18 (m, 3H, 2x–N–CH2–CH CH2
18-CH3), 1.05 (s, 3H, 19-CH3), 2.21 (s, 3H, –⊕OCOCH3), 3.84
⊕
and s (merged), vinylic-H, 16-arylidene), 6.82 (s, 1H, 2-CH, aro-
matic), 6.89 (d, 1H, Jo = 8.50 Hz, 5-CH, aromatic), 7.00 (d, 1H,
Jo = 8.39 Hz, 6-CH, aromatic); Anal. Calc. for C46H68N2O4Br2: C,
63.29; H, 7.85; N, 3.21. Found: C, 63.52; H, 7.41; N, 3.57%.
(brs, 9H, –OCH3; 3–N–(CH2)⊕2–, pyrrol⊕idine and –N–CH2–, pyrro-
lidine), 4.13 (m, 4H, –CH2Nꢀ and –N–CH2–, pyrrolidine), 4.24
⊕
(d, 2H, J = 7.01 Hz, 3–N–CH2–CH CH2), 4.30 (d, 2H, J = 6.7 Hz,
⊕
–N–CH2–CH CH2), 4.47 (t, 2H, J = 4.31 Hz, –OCH2–), 5.35 (s,
1H, ⊕17␣-H), 5.55 (d, 1H, J = 4.71 Hz, 6-CH)⊕, 5.68–5.86 (m, 4H,
2.2.5. 16-[3-Methoxy-4-{2-(pyrrolidin-1-
yl)ethoxy}benzylidene]-3ˇ-pyrrolidino-5-androsten-17ˇ-ol
dimethiodide (6a)
2x–N–CH2–CH CH2), 5.99–6.20 (m, 3H, 2x–N–CH2–CH CH2 and
vinylic-H, 16-arylidene), 6.85 (s, 1H, 2-CH, aromatic), 6.94 (s, 2H,
5-CH and 6-CH, aromatic); Anal. Calc. for C45H66N2O4Br2: C, 62.93;
H, 7.75; N, 3.26. Found: C, 62.89; H, 7.55; N, 3.33%.
Yield: 40.16%; m.p. 230 ◦C (decomp). UVmax (MeOH): 262.0 nm
(log ε 4.28). IR: 3397, 2931, 1599, 1512, 1463, 1316, 1264, 1229,
1139, 1075, 1025, 939 cm−1 1H NMR (CDCl3 + DMSO-d6): ı 0.78
;
(s, 3H, 18-CH3), 1.⊕08 (s, 3H, 19-CH3), 2.61 (s) and 3.24 (s) (1:1
2.2.9. 16-[4-(2-Diethylaminoethoxy)-3-methoxybenzylidene]-
3ˇ-pyrrolidino-5-androsten-17ˇ-ol dimethiodide
(7a)
⊕
area rat⊕io, 3H, 3–N–CH3), 2.97 (s, 3H, –N–CH3), 3.73–3.83 (m,
8H, 2x–N–(CH2)2–, pyrrolidine), 3.84 (s, 3H, –OCH3), 3.92 (t, 2H,
Yield: 50.93%; m.p. 266–270 ◦C. UVmax (MeOH): 265.8 nm (log ε
4.46); IR: 3399, 2931, 2365, 1602, 1513, 1464, 1266, 1229, 1142,
⊕
J = 4.44 Hz, –CH2Nꢀ), 3.97 (s, 1H, 17␣-H), 4.43 (t, 2H, J = 4.26 Hz,
1027, 805 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ı 0.7⊕2 (s, 3H, 18-
–OCH2–), 5.54 (d, 1H, J = 4.08 Hz, 6-CH), 6.41 (s, 1H, vinylic-H, 16-
arylidene), 6.91–6.99 (m, 3H, 2-CH, 5-CH and 6-CH, aromatic); Anal.
Calc. for C39H60N2O3I2: C, 54.55; H, 7.04; N, 3.26. Found: C, 54.39;
H, 7.22; N, 3.49%.
CH3), 1.07 (s, ⊕3H, 19-CH3), 1.46 (t, 6H, J = 7.14 Hz, –N(CH2CH3)2),
⊕
3.03 (s, 3H, –N–CH3, pyrrolidine), 3.31 (s, 3H, H3C–N(CH2CH3)2),

R. Bansal et al. / Steroids 76 (2011) 254–260
257
⊕
⊕
2.2.13. 16-[3-Methoxy-4-{2-(piperidin-1-
yl)ethoxy}benzylidene]-17-oxo-5-androsten-3ˇ-yl acetate
methiodide (8a)
3.68 (m, 8H, –N(CH2CH3)2 and –N–(CH2)2, pyrrolidine), 3.84 (s, 3H,
⊕
–OCH3), 3.97 (t, 2H, J = 4.29 Hz, –CH2N–), 4.04 (s, 1H, 17␣-H), 4.44 (t,
Yield: 92.94%; m.p. 250–253 ◦C. UVmax (MeOH): 332.8 nm (log ε
2H, J = 4.31 Hz, –OCH2–), 5.55 (d, 1H, J = 4.25 Hz, 6-CH), 6.47 (s, 1H,
vinylic-H, 16-arylidene), 6.92–6.95 (m, 3H, 2-CH, 5-CH and 6-CH,
aromatic); Anal. Calc. for C39H62N2O3I2: C, 54.42; H, 7.26; N, 3.26.
Found: C, 54.44; H, 7.66; N, 3.22%.
4.19); IR: 2938, 1724, 1621, 1596, 1511, 1462, 1371, 1247, 1140,
1098, 1029 cm−1
;
1H NMR (CDCl3): ı 0.89 (s, 3H, 18-CH3), 0.98 (s,
⊕
3H, 19-CH3), 2.04 (s, 3H, –OCOCH3), 3.54 (s, 3H, –N–CH3), 3.76–3.83
⊕
(m, 2H, –N–CH2–, piperidine), 3.93 (s, 3H, –OCH3), 3.9⊕4–4.01 (m,
2.2.10. 16-[4-(2-Diethylaminoethoxy)-3-methoxybenzylidene]-
3ˇ-pyrrolidino-5-androsten-17ˇ-yl acetate dimethiodide
(7b)
⊕
2H, –N–CH2–, piperidine), 4.31 (t, 2H, J = 4.25 Hz, –CH2Nꢀ), 4.56 (t,
2H, J = 4.26 Hz, –OCH2–), 4.62 (m, 1H, 3␣-H), 5.43 (d, 1H, J = 4.62 Hz,
6-CH), 7.02–7.04 (m, 2H, 2-CH and 5-CH, aromatic), 7.16 (dd, 1H,
Jm = 1.29 Hz, Jo = 8.56 Hz, 6-CH, aromatic), 7.35 (s, 1H, vinylic-H, 16-
Yield: 49.35%; m.p. 258–260 ◦C. UVmax (MeOH): 262.0 nm (log ε
4.50); IR: 2937, 1728, 1625, 1513, 1462, 1372, 1241, 1142,
1039 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ı 0.7⊕8 (s, 3H, 18-CH3),
arylidene); Anal. Calc. for C37H52NO5I: C, 61.92; H, 7.30; N, 1.95.
Found: C, 62.02; H, 7.38; N, 2.01%.
1.05 (s, 3H, 19-CH3), 1.37 (t, 6H⊕, J = 7.21 Hz, –N(CH2CH3)2), 2.21
(s, 3H, –OCOCH3), 3.06 (s, 3H, –N–⊕CH3, pyrrolidine), 3.35 (s, 3H,
2.2.14. 16-[3-Methoxy-4-{2-(pyrrolidin-1-
⊕
⊕
H3C–N(CH2CH3)2), 3.75 (q, 8H, –N(CH2CH3)2 and –N–(CH2)2–,
yl)ethoxy}benzylidene]-17-oxo-5-androsten-3ˇ-yl acetate
methiodide (9a)
⊕
pyrrolidine), 3.84 (s, 3H, –OCH3), 4.05 (t, 2H, J = 4.36 Hz, –CH2Nꢀ),
Yield: 67.85%; m.p. 157–159 ◦C. UVmax (MeOH): 327.2 nm (log ε
4.41); IR: 2940, 1720, 1624, 1513, 1462, 1371, 1253, 1141, 1098,
4.47 (t, 2H, J = 4.2 Hz, –OCH2–), 5.32 (s, 1H, 17␣-H), 5.56 (d, 1H,
J = 4.21 Hz, 6-CH), 6.15 (s, 1H, vinylic-H, 16-arylidene), 6.86 (s, 1H,
2-CH, aromatic), 6.93–6.99 (m, 2H, 5-CH and 6-CH, aromatic); Anal.
calcd. for C41H64N2O4I2: C, 54.55; H, 7.15; N, 3.10. Found: C, 54.70;
H, 7.29; N, 3.14%.
1030 cm−1
;
1H NMR (CDCl3): ı 0.98 (s, 3H, 1⊕8-CH3), 1.09 (s, 3H,
19-CH3), 2.04 (s, 3H, –⊕OCOCH3), 3.46 (s, 3H, –N–CH3), 3.8⊕6 (s, 3H,
–OCH3), 3.95 (m, 2H, –N–CH2–, pyrrolidine), 4.09 (m, 2H, –N–CH2–,
⊕
2.2.11. 16-[4-(2-Diethylaminoethoxy)-3-methoxybenzylidene]-
3ˇ-pyrrolidino-5-androsten-17ˇ-ol diallyl bromide
(7c)
pyrrolidine), 4.33 (s, 2H, –CH2Nꢀ), 4.54 (s, 2H, –OCH2–), 4.58 (s,
1H, 3␣-H), 5.43 (d, 1H, J = 4.52 Hz, 6-CH), 7.02 (d, 2H, Jo = 8.57 Hz,
2-CH and 5-CH, aromatic), 7.17 (dd, 1H, Jm = 1.50 Hz, Jo = 8.42 Hz, 6-
CH, aromatic), 7.36 (s, 1H, vinylic-H, 16-arylidene). Anal. Calc. for
C36H50NO5I: C, 61.44; H, 7.16; N, 1.99. Found: C, 61.31; H, 7.28; N,
2.14%.
Yield: 56.34%; m.p. 250–253 ◦C. UVmax (MeOH): 262.4 nm (log ε
4.55); IR: 3362, 2936, 1629, 1514, 1463, 1260, 1141, 1025,
800 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ı 0.71 (s, 3H, 18-CH3),
⊕
1.07 (s, 3H, 19-C⊕H3), 1.45 (t, 6H, J = 7 Hz, –N(CH2CH3)2), 3.55 (q,
⊕
2.2.15. 16-[4-(2-Diethylaminoethoxy)-3-methoxybenzylidene]-
17-oxo-5-androsten-3ˇ-yl acetate methiodide
(10a)
4H, J = 7.24 Hz, –N(CH2CH3)2), 3.71 (brs,⊕4H, –N–(CH2)2–, pyrro-
lidine), 3.83 (brs, 5H, –OCH3 and –CH2Nꢀ), 4.04 (s, 1H, 17␣-H),
⊕
Yield: 86.28%; m.p. 178–181 ◦C. UVmax (MeOH): 327.2 nm (log ε
4.19); IR: 2942, 1724, 1619, 1512, 1466, 1239, 1145, 1098, 1029,
4.12 (d, 2H, J = 6.19 Hz, –N–CH2–CH CH2, pyrrolidine), 4.18 (d, 2H,
⊕
804 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ı 0.⊕98 (s, 3H, 18-CH3), 1.09
J = 6.28 Hz, H2C–HC H2C–N(CH2CH3)2⊕, 4.44 (sbr, 2H, –OCH2–), 5.55
(s, 1H, 6-CH), 5.68–5.86 (m, 4H, 2x–N–CH2–CH CH2), 6.01–6.09
(s, 3H, 19-CH3), 1.49 (t, 6H,⊕J = 7.22 Hz, –N–(CH2CH3)2), 2.04 (s,
⊕
⊕
(m, 2H, 2x–N–CH2–CH CH2), 6.46 (s, 1H, vinylic-H, 16-arylidene),
3H, –OCOCH3), 3.41 (s, 3H, –N–CH3), 3.78 (m, 4H,⊕–N–(CH2CH3)2)
6.92–6.95 (m, 3H, 2-CH, 5-CH and 6-CH, aromatic); Anal. Calc. for
C43H66N2O3Br2: C, 63.07; H, 8.13; N, 3.42. Found: C, 63.22; H, 8.50;
N, 3.49%.
3.86 (s, 3H, –OCH3), 4.19 (t, 2H, J = 4.4 Hz, –CH2Nꢀ), 4.55 (t, 2H,
J = 4.35 Hz, –OCH2–), 4.62 (m, 1H, 3␣-H), 5.43 (d, 1H, J = 4.67 Hz, 6-
CH), 7.03 (d, 2H, Jo = 8.42 Hz, 2-CH and 5-CH, aromatic), 7.17 (dd,
1H, Jm = 1.22 Hz, Jo = 8.54 Hz, 6-CH, aromatic), 7.36 (s, 1H, vinylic-H,
16-arylidene); Anal. Calc. for C36H52NO5I: C, 61.27; H, 7.43; N, 1.98.
Found: C, 62.22; H, 7.03; N, 1.77%.
2.2.12. 16-[4-(2-Diethylaminoethoxy)-3-methoxybenzylidene]-
5-androsten-17ˇ-yl acetate diallyl bromide
(7d)
Yield: 77.65%; m.p. 200–203 ◦C. UVmax (MeOH): 262.0 nm (log ε
4.38); IR: 2968, 1731, 1633, 1515, 1463, 1371, 1237, 1143, 1041,
2.2.16. 16-[3-Methoxy-4-{2-(piperidin-1-
957, 801 cm−1
;
1H NMR (CDCl3 + DMSO-d6): ı 0.80 (s, 3H, 18-
yl)ethoxy}benzylidene]-17-oxo-5-androsten-3ˇ-yl acetate allyl
bromide (8b)
⊕
CH3), 1.07 (s, 3H, 19-CH3), 1.42 (t, 6H, J = 7.06 Hz, –N(CH2CH3)2),
Yield: 92.55%; m.p. 216–220 ◦C. UVmax (MeOH): 312.0 nm (log ε
4.26); IR: 2937, 1716, 1623, 1513, 1461, 1370, 1327, 1256,
⊕
2.21 (s, 3H, –OCOCH3), 3.53 (q, 4H, J = 7.13 Hz, –N(CH2CH3)2), 3.82
⊕
1143, 1098, 1026 cm−1
;
1H NMR (CDCl3): ı 0.98 (s, 3H, 18-
(t, 2H, J = 8.92 Hz, –CH2Nꢀ), 3.84 (s, 3H, –OCH3), 3.67 (brs, 4H,
⊕
⊕
CH3), 1.09 (s, 3H, 19-CH3), 2.04 (s, 3H, –OCOCH3), 3.70 (m,
⊕
–N–(CH2)2–, pyrrolidine), 4.09 (d, 2H, J = 7.46 Hz, –N–CH2–CH CH2,
2H, –N–CH2–, piperidine), 3.84 (s, 3H, –OCH3), 3.97 (m, 2H,
⊕
⊕
⊕
pyrrolidine), 4.16 (d, 2H, J = 7.17 Hz, H2C–HC H2C–N(CH2CH3)2,
–N–CH2–, piperidine), 4.20 (t, 2H, J = 3.6 Hz, –CH2N <), 4.46 (d,
4.44 (t, 2H, J = 4.06 Hz, –OCH2–)⊕, 5.33 (s, 1H, 17␣-H), 5.54 (s,
⊕
2H, J = 7.18 Hz, –N–CH2–CH CH2), 4.58 (t, 2H, J = 3.93 Hz, –OCH2–),
1H, 6-CH), 5.67–5.86 (m, 4H, 2x–N–CH2–CH CH2), 6.03–6.09 (m,
4.61 (m, 1H, 3⊕␣-H), 5.42 (d, 1H, J = 4.36 Hz, 6-CH), 5.77 (d, 1H,
⊕
2H, 2x–N–CH2–CH CH2), 6.14 (s, 1H, vinylic-H, 16-arylidene),
6.88–6.94 (m, 3H, 2-CH, 5-CH and 6-CH, aromatic); Anal. Calc. for
45H68N2O4Br2: C, 62.78; H, 7.96; N, 3.25. Found: C, 62.49; H, 8.11;
Jci⊕s = 9.91 Hz, –N–CH2–CH CH(H)), 5.91 (d, 1H, Jtrans = 16.65 Hz,
⊕
C
–N–CH2–CH CH(H)), 6.09–6.17 (m, 1H, –N–CH2–CH CH2), 7.03
N, 3.38%.
(s, 1H, 2-CH, aromatic), 7.06 (d, 1H, Jo = 8.47 Hz, 5-CH, aromatic),

258
R. Bansal et al. / Steroids 76 (2011) 254–260
⊕
7.17 (dd, 1H, Jm = 1.09 Hz, Jo = 8.56 Hz, 6-CH, aromatic), 7.35 (s, 1H,
vinylic-H, 16-arylidene); Anal. Calc. for C39H54NO5Br: C, 67.23; H,
7.81; N, 2.01. Found: C, 67.01; H, 7.88; N, 2.39%.
Jci⊕s = 10.38 Hz, –N–CH2–CH CH(H)), 5.87 (d, 1H, Jtrans = 16.53 Hz,
–N–CH2–CH CH(H)), 6.07 (m, 1H, –⊕–CH –CH CH2), 7.01 (d,
N
2
1H, Jm = 1.20 Hz, 2-CH, aromatic), 7.09 (d, 1H, Jo = 8.48 Hz, 5-CH,
aromatic), 7.19 (d, 1H, Jo = 8.55 Hz, 6-CH, aromatic), 7.36 (s, 1H,
vinylic-H, 16-arylidene); Anal. Calc. for C38H54NO5Br: C, 66.65; H,
7.95; N, 2.06. Found: C, 66.66; H, 8.02; N, 2.13%.
2.2.17. 16-[3-Methoxy-4-{2-(pyrrolidin-1-
yl)ethoxy}benzylidene]-17-oxo-5-androsten-3ˇ-yl acetate allyl
bromide (9b)
Yield: 61.71%; m.p. 83–85 ◦C. UVmax (MeOH): 312.4 nm (log ε
4.35); IR: 2936, 1712, 1624, 1596, 1514, 1462, 1328, 1261, 1143,
2.3. Neuromuscular blocking activity
1060, 1027, 945, 875 cm−1 1H NMR (CDCl3): ı 0.98 (s, 3H, 18-CH3),
;
The chick biventer cervicis nerve–muscle preparations were set
up as described previously [14]. Muscles were removed from 4 to
10 day-old chicks killed by exposure to CO2. Preparations were
mounted in pairs with a resting tension of approximately 1.0 g in
10 mL tissue baths containing Krebs-Henseleit solution. The solu-
tion was maintained at 34 ◦C and bubbled with 95% O2 and 5% CO2.
The muscles were stimulated via their motor nerves at 0.1 Hz with
pulses of 0.2 ms duration and a voltage greater than that required
for maximal contractions. Responses to acetylcholine, carbachol
and KCl were obtained in the absence of nerve stimulation.
1.09 (s, 3H, 19-CH3), 2.00 (s, 3H, –OCOCH3), 3.85 (s, 3H, –OCH3), 3.80
⊕
⊕
(m, 2H, –N–CH2–, pyrrol⊕idine), 4.20 (m, 2H, –N–CH2–, pyrrolidine),
⊕
4.24–4.30 (m, 4H, –CH2N < and –N–CH2–CH CH2), 4.56–4.62 (m,
3H, –OCH2– and 3␣-H), 5.43 (d, 1H, J = 4.47 Hz, 6-CH), 5.76 (d,
⊕
1H, Jcis = 9.96 Hz, –N–CH2–CH CH(H)), 5.85 (d, 1H, Jtrans = 16.85 Hz,
⊕
–N–CH2–CH CH(H)), 6.16 (m, 1H, –⊕–CH –CH CH2), 7.02 (m, 2H,
N
2
2-CH and 5-CH, aromatic), 7.17 (dd, 1H, Jm = 1.10 Hz, Jo = 8.18 Hz, 6-
CH, aromatic), 7.36 (s, 1H, vinylic-H, 16-arylidene); Anal. Calc. for
C38H52NO5Br: C, 66.85; H, 7.68; N, 2.05. Found: C, 66.98; H, 7.52;
N, 2.22%.
2.4. Anticholinesterase activity
2.2.18. 16-[4-(2-Diethylaminoethoxy)-3-methoxybenzylidene]-
17-oxo-5-androsten-3ˇ-yl acetate allyl bromide
(10b)
The effect of compounds on the activity of acetylcholinesterase
from electric eel was monitored at room temperature by the
method of Ellman et al. [15] adapted to 96-well plates. Each assay
was repeated three times.
Yield: 98.8%; m.p. 175–177 ◦C. UVmax (MeOH): 327.4 nm (log ε
4.21); IR: 2936, 1712, 1624, 1514, 1463, 1371, 1329, 1260,
1143, 1098, 1059, 1028, 940, 813 cm−1 1H NMR (CDCl3 + DMSO-
;
3. Results and discussion
d6):
ı 0.98 (s, 3H, 18-CH3), 1.09 (s, 3H, 19-CH3), 1.52 (t,
⊕
3.1. Chemistry
6H, J = 7.18 Hz, –N(CH2CH3)2), 2.04 (s, 3H, –OCOCH3), 3.63 (m,
⊕
4H, –⊕N(CH2CH3)2), 3.85 (s, 3H, –OCH3), 4.20 (t, 2H, J = 4.57 Hz,
The bisquaternary ammonium salts 5–7a–d (Scheme 1) were
prepared from their respective bistertiary amines (3) [13] by treat-
ment with alkyl halides such as methyl iodide or allyl bromide in
⊕
–CH2Nꢀ), 4.28 (d, 4H, J = 7.11 Hz, –N–CH2–CH CH2), 4.60 (m, 3H,
–OCH2– and 3␣-H), 5.43 (d, 1H, J = 4.36 Hz, 6-CH), 5.78 (d, 1H,
R
_
Y
OCH2CH2
2X
+
N
OMe
R'
+
N
+
N
+
Y
=
N
R'
R'
R'
7a-d
5a-d
6a-d
(a)
R = OH, R' = CH3,
X = I
(b)
(c)
R = OCOCH ,
R' = CH3, X = I
CH2-CH=CH2,
3
X = Br
R' =
R = OH,
X = Br
CH2-CH=CH2,
R = OCOCH3,
R' =
(d)
Scheme 1. Structures of bisquaternary steroidal derivatives 5–7a–d.

R. Bansal et al. / Steroids 76 (2011) 254–260
259
Table 2
O
Skeletal muscle relaxant activity of quaternary ammonium steroids.
Compound no.
Concentration (␮M)
t50 (min)
5a
5b
5c
5d
2
10
11
49
_
X
8–10
6–8
2
OCH2CH2R
1
OMe
H3COCO
6a
5
10
6b
5
8
6c
5
7
6d
7a
7b
7c
5
10
5
0.4
5
6.5
+
N
+
N
+
7–9
3–4
16–17
4
R
=
N
R'
R'
7d
R'
8a
8b
9a
9b
>150
200
10
10
>300
35
No block
5–7
9a,b
10a,b
8a,b
t20 = 23 min
t20 = 23 min
No block
45–50
R' = CH3,
CH2-CH=CH2,
(a)
(b)
X = I
10a
10b
Pancuronium
Pipecuronium
R' =
X = Br
0.011a
0.01a
7a
6a
Scheme 2. Structures of monoquaternary steroidal derivatives 8–10a–b.
All compounds were tested on the twitch responses of chick biventer cervicis prepa-
rations to stimulation of the motor nerve. t50 = time in which 50% block is achieved;
each compound was tested against 2 preparations: the range of times to reach t50
is given; where a single value appears, both preparations blocked at the same rate.
dry dichloromethane at room temperature for a variable period
of time (Table 1). The structures of these quaternary compounds
were established using various spectral and elemental analyses.
In the 1H NMR spectra of 5–7a, protons of methyl group attached
to quaternary nitrogen of 3-pyrrolidino functionality appeared as
split singlets for compounds 5 and 6a while only one singlet was
observed for protons of the methyl group attached to quaternary
nitrogen of other heterocyclic ring at 16-position. However, in case
a
Ref. [16].
3.2. Pharmacological activity
3.2.1. Neuromuscular blocking activity
of 7a the two methyl groups attached to quaternary heads appeared
Quaternary ammonium steroids 5–7a–d and 8–10a,b were
screened for in vitro neuromuscular blocking activity using an iso-
lated nerve–muscle preparation, the chick biventer cervicis [14].
Muscles were stimulated indirectly at 0.1 Hz to monitor effects of
the compounds on twitch height.
⊕
as single singlets. The singlets for –N–CH3 of two heterocyclic rings
in compounds 5–7b also appeared downfield at ı ∼ 3 and 3.33 ppm.
The presence of a singlet at ı ∼ 2.2 ppm in 5–7b,d confirmed the
acetylation at 17-position. Terminal methylenes and methine pro-
ton of both the allyl groups attached to the quaternary nitrogens of
pyrrolidine and piperidine rings appeared as multiplets at about ı
5–6 ppm in the proton NMR of the diallyl⊕quaternary ammonium
All the bisquaternary ammonium compounds (5–7a–d) reduced
twitch responses to stimulation of the motor nerve, although there
were marked differences in potency (Table 2). The most active com-
pound was allyl salt 5d, which reduced twitch responses to 50% of
control height in 2 min when added at 1 ␮M. In contrast, 10 ␮M of
methiodide 5b took 8–10 min to give a similar reduction in twitch
height. The monoquaternary compounds (8a–10b) were virtually
inactive on the chick biventer cervicis muscle preparation (Table 2).
When compounds had reduced responses to nerve stimulation,
they also had reduced the sensitivity of the muscle preparations
to the cholinoceptor agonists acetylcholine and carbachol. How-
ever, muscle contractility (as judged by responses to depolarization
induced by KCl) was not affected by the compounds. The twitch
blocking effects were reversed on washout of the compounds.
Although there is no marked difference in the muscle relax-
ant properties of the three series i.e. pyrrolidinyl, piperidinyl and
diethylamino groups as the quaternary nitrogen heads on side
chain at 16-position of steroid skeleton, the bisquaternary 17-
acetoxy piperidinyl derivative 5d exhibited the maximum potency
by blocking 50% of the twitch response in 2 min at 1 ␮M. In gen-
eral the 17-acetoxy derivatives 5–7b,d exhibited higher potency
in comparison to their 17-hydroxy counterparts 5–7a,c. Out of
dimethiodides or diallyl salts, the later looked more promising in
agreement with earlier reports [11]. The greatest loss of potency
was on changing from bisquaternary 5–7a–d to monoquaternary
mononitrogen compounds 8–10a,b. Lack of an intact acetylcholine-
like fragment in these compounds has not compromised their
potency, presumably due to increased interonium distance, which
salts 5–7c and 5–7d. The triplets of –CH2Nꢀ and –OCH2– protons
of all these quaternary ammonium derivatives 5–7a–d appeared at
ı ∼ 4 and 4.4 ppm, respectively. N-Methylenes of pyrrolidino and
piperidino functionalities were also observed at downfield values
due to quaternization of nitrogen.
Monoquaternary salts (Scheme 2) of the monotertiary coun-
terparts (4) [13] of 16-arylidenosteroids were also prepared to
observe the difference in muscle relaxant activity of the compounds
among this class and to study the structure-activity relationships.
Monoquaternary ammonium salts 8–10a,b were prepared by quat-
ernizing their respective monotertiary amines with methyl iodide
and allyl bromide in dry dichloromethane at room temperature
for a variable time period as shown in Table 1. These quaternary
compounds exhibited IR absorption bands near 1720 cm−1 and 1
H
NMR signal at ␦ 2.04 ppm (3␤-OCOCH3). The proton resonance sin-
glets for the –CH3 attached to quaternary nitrogen head of 8–10a
appeared at ␦ 3.54, 3.46 and 3.41 ppm, respectively.
The proton resonance doublets of terminal methylenes of the
allyl groups in the mono allyl quaternary ammonio salts 8–10b
were found in the region ı ∼ 5.77 (Jcis = 9.95 Hz) and 5.9 ppm
(Jtrans = 16.65 Hz). A multiplet at ı ∼ 6.1 ppm for the methine pro-
ton of the allyl group was also seen in the 1H NMR spectra of all of
these mono allylated quaternary ammonio derivatives.
The interonium distances of these quaternary compounds were
estimated from drieding models, which indicated a wide range of
˚
was found to be ranging from 11 to 17 A due to free rotation of side
˚
values of 11–17 A. This may be associated with the built in flexibility
chain.
of these structures about the single bonds on the moieties linked
to ring D of the steroid skeleton (Fig. 1).
The compounds are acting by a non-depolarizing mechanism
because they do not themselves cause contracture of the chick

260
R. Bansal et al. / Steroids 76 (2011) 254–260
Table 3
augmentation of transmission because of the reduced metabolism
of the released acetylcholine.
Anticholinesterase activity of the compounds.
Compound no.
Ki (␮M)a
Overall, the tested compounds displayed varied degrees of
muscle relaxant activity with the monoquaternary salts exhibit-
ing less potency as compared to bisquaternary ones. The present
series represents a new class of steroidal neuromuscular block-
ers with variable interonium distance, but the compounds
ability to inhibit the activity of acetylcholinesterase means
that they would not themselves be candidates for potential
development.
5a
5b
5c
5d
6a
6b
6c
6d
7a
7b
7c
7d
8a
8b
9a
9b
6.0 (4.1–8.6)
2.7 (1.2–5.8)
7.5 (3.9–14.5)
0.35 (0.1–3.0)
0.64 (0.06–6.5)
4.3 (0.07–27)
1.3 (0.3–5.0)
2.0 (0.6–6.1)
1.0 (0.4–2.7)
6.7 (2.8–16.2)
0.46 (0.03–7.0)
0.2 (0.1–0.4)
4.2 (2.9–6.2)
0.21 (0.12–0.38)
3.6 (0.9–2.8)
2.2 (0.9–4.9)
2.6 (1.7–3.8)
0.34 (0.23–0.5)
7.4b
Acknowledgements
The financial support provided by Council of Scientific and
Industrial Research, India to Sheetal Guleria, Senior Research Fellow
is gratefully acknowledged. We are thankful to Cipla India Limited
for the free supply of steroids. This work is dedicated to the memory
of our esteemed teacher Prof. D.P. Jindal.
10a
10b
Pancuronium
Pipecuronium
5.9b
References
a
Values are mean 95% confidence limits (n = 4).
Determined against acetylcholinesterase from human erythrocytes [17].
b
[1] Feldman S. DrugsToday 1990;32:159–69.
[2] Davis M, Parnell EW, Rosenbaum JR. J Chem Soc Perkin Trans 1967;1:1045–52.
[3] Alauddin M, Caddy B, Lewis JJ, Martin-Smith M, Sugrue MF. J Pharm Pharmacol
1965;17:55–8.
[4] M. Riesz M, Karpati E, Szporny L. New neuromuscular blocking agents. In:
Kharkevich DA, editor. Handbook of experimental pharmacology, vol. 79. 1986.
p. 301–22.
[5] Tuba Z, Maho S, Vizi ES. Curr Med Chem 2002;9:1507–36.
[6] Tuba Z, Maho S. Acta Pharm Hung 1992;62:73–81.
[7] Foldes FF, Nagashima H, Nguyen HD, Duncalf D, Goldiner PL. Can J Anaesth
1990;37:549–55.
biventer cervicis preparations, as would suxamethonium, and
because they also decreased responses to the cholinoreceptor ago-
nist carbachol (data not shown). However, the compounds also
displayed nonparallel shifts of dose response curve to carbachol.
This implies that the compounds may also be acting by some other
mechanism, such as block of receptor ion channel.
[8] Savage DS. J Chem Soc 1971;3:410–5.
[9] Larijani GE, Zefeiridis A, Goldberg ME. Pharmacotherapy 1999;19:1118–20.
[10] Singh H, Jindal DP. J Chem Soc Perkin Trans 1974;1:1475–9.
3.2.2. Anticholinesterase activity
The compounds were also tested for their ability to inhibit the
activity of electric eel acetylcholinesterase [15]. All compounds,
mono- and bis-quaternary, inhibited theenzymeand Ki values were
found between 0.2 (for 8b) and 7.5 (for 5c) ␮M (Table 3).
The compounds are not only acting as antagonists at
acetylcholine receptors (Table 2) but are also inhibiting acetyl-
cholinesterase activity at low concentrations (Table 3). Thus, there
are two functionally opposite effects: reduction of neuromuscular
transmission because of the block of acetylcholine receptors and
[11] Jindal DP, Piplani P, Fajrak H, Prior C, Marshall IG. Eur
2002;37:901–8.
J Med Chem
[12] Dubey S, Jindal DP, Piplani P, Young LC, Fathi B, Harvey AL. Med Chem Res
2005;14:229–40.
[13] Bansal R, Guleria S. Steroids 2008;73:1391–9.
[14] Ginsborg BL, Warriner JN. Br J Pharmacol Chemother 1960;15:410–1.
[15] Ellman GL, Courtney KD, Andres V, Featherstone RM. Biochem Pharmacol
1961;7:88–95.
[16] Karpati E, Biro K. Arzneim-Forsch/Drug Res 1980;30:346–54.
[17] Kato M, Hashimoto Y, Horinouchi T, Ando T, Ito J, Yamanaka H. J Anesth
2000;14:30–4.