Potentially bioactive organotin(IV) compounds: Synthesis, characterization, in vitro bioactivities and interaction with SS-DNA

Article abstract of DOI:10.1016/j.ejmech.2014.07.028

Fourteen new organotin(IV) complexes with general formula R ₂SnL₂ or R₃SnL where R = CH₃, C ₂H₅, C₄H₉, C₆H ₅, C₆H₁₁, CH

Full text of DOI:10.1016/j.ejmech.2014.07.028

European Journal of Medicinal Chemistry 84 (2014) 343e363
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Potentially bioactive organotin(IV) compounds: Synthesis,
characterization, in vitro bioactivities and interaction with SS-DNA
,
Muhammad Sirajuddin a, Saqib Ali a *, Vickie McKee b, Manzar Sohail c, Hammad Pasha d
a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
b Department of Chemistry, Loughborough University, Loughborough, Leics LE11 3TU, UK
c Center of Excellence for Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
d Department of Biochemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
Fourteen new organotin(IV) complexes with general formula R2SnL2 or R3SnL where R ¼ CH3, C2H5, C4H9,
C6H5, C6H11, CH2eC6H5, C(CH3)3, C8H17 and L ¼ N-[(2-methoxyphenyl)]-4-oxo-4-[oxy]butanamide were
synthesized and characterized by elemental analyses, FT-IR, NMR (1H, 13C and 119Sn), mass spectrometry
and single crystal X-ray structural analysis. Crystallographic data for four triorganotin(IV) complexes
(R3SnL, R ¼ CH3, C2H5, C4H9, CH2eC6H5) showed the tin has approximate trigonal bipyramidal geometry
with the R groups in the trigonal plane. The carboxylate groups of ligands L bridge adjacent tin atoms,
resulting in polymeric chains. In case of the diorganotin(IV) derivatives a six-coordinate geometry at the
tin atom is proposed from spectroscopic evidence. The MeeSneMe bond angle in complex 7 was
determined from the 2J[119Sne1H] value as 166.3ꢀ that falls in the range of six-coordinate geometry. The
ligand and its complexes (1e14) were screened for their antimicrobial, antitumor, cytotoxic and anti-
leishmanial activities and found to be biologically active. The ligand and its complexes bind to DNA
via intercalative interactions resulting in hypochromism and minor bathochromic shifts as confirmed by
UVevisible spectroscopy. Based on in vitro studies such as the potato disc method, the synthesized
compounds were found to possess significant antitumor activity. Also, from cytotoxicity and DNA
interaction studies, these compounds can also be used for the prevention and treatment of cancer. Gel
electrophoresis assay was used to investigate the damage to double stranded super coiled plasmid
pBR322 DNA by the synthesized compounds and compounds 1 and 7 were found to cause the maximum
damage. All the synthesized compounds exhibit strong antileishmanial activity that was even higher
than that of Amphotericin B, with significant cytotoxicity. This study, therefore, demonstrated the po-
tential use of these compounds as source of novel agents for the treatment of leishmaniasis.
© 2014 Elsevier Masson SAS. All rights reserved.
Received 14 December 2013
Received in revised form
1 July 2014
Accepted 8 July 2014
Available online 9 July 2014
Keywords:
Organotin(IV) compound
DNA interaction
Antitumor activity
Antimicrobial activity
Cytotoxicity
Antileishmanial activity
1. Introduction
and to avoid serious side-effects caused by platinum chemothera-
peutics. Among these, organotins have appeared as biologically
The chemistry of organotin compounds is gaining attention on
account of their interesting structural features, schizonticidal,
antimalarial, fungicidal activities and their potential as agricultural
biocides [1]. Organotin(IV) compounds of carboxylic acids are being
extensively studied with special reference to their methods of
synthesis, structural elucidation, and biological activity [2,3].
Encouraged by the initial success of platinum chemotherapeutic
metallopharmaceuticals, concentration was first shifted to non-
platinum chemotherapeutics starting from the basic cis-platin
framework, with the aim to optimize the competence of such drugs
active metallopharmaceuticals [4]. It has well been established that
organotin(IV) compounds are very important in cancer chemo-
therapy because of their apoptosis inducing character, while during
the last few years it is noticeable that organotin compounds occupy
an important place in cancer chemotherapy reports [5]. Recently,
Blower described thirty interesting inorganic pharmaceuticals, four
of which are tin compounds [6]. The organotin compounds have
also received considerable attention as antiproliferative, antitumor
and anticancer drugs. The activity is due to dissociated organo-
tin(IV) moieties. The biological activity usually associates with the
nature of organic ligand, since the organic ligand assists the
transportation of the complexes across the cell membrane [5,7e9].
The biological activity of organotin compounds is basically
determined by the number and nature of the organic groups bound
* Corresponding author.
E-mail addresses: m.siraj09@yahoo.com, msiraj09@gmail.com (M. Sirajuddin),
drsa54@yahoo.com (S. Ali).
http://dx.doi.org/10.1016/j.ejmech.2014.07.028
0223-5234/© 2014 Elsevier Masson SAS. All rights reserved.

344
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
to the central tin atom. The [R3Sn(IV)]þ and [Ar3Sn(IV)]þ derivatives
exert powerful toxic action on the central nervous system. Within
the series of [R3Sn(IV)]þ compounds, the lower homologues (Me,
Et) are the most toxic when administrated orally, and the toxicity
reduces progressively from propyl to octyl, the latter not being toxic
at all [10]. The presence of easily hydrolysable groups (easily
dissociable chelating ligands) producing intermediates such as
RnSn(4ꢁn)þ (n ¼ 2 or 3) moieties, which may bind with DNA or high-
affinity site of ATPase (histidine only), the low-affinity site of
ATPase, and haemoglobins (histidine and cystine), play an impor-
tant role in the determination of biological activity of the organotin
compounds. Therefore, substantial attempts have been made to
characterize model organotin compounds of ligands having hetero
donor atoms (O, N and S), and simultaneously several studies have
been focused on structureeactivity correlations during the last two
decades [11].
Keeping in view their biological applications, we are reporting a
series of 14 new organotin(IV) carboxylates of N-[(2-
methoxyphenyl)]-4-oxo-4-[oxy]butanamide. These compounds
were characterized successfully by elemental analysis, FT-IR, NMR
(1H, 13C, 119Sn) mass and single crystal analysis. They were screened
for biological applications including interaction with SS-DNA,
antimicrobial, antitumor, antileishmanial and cytotoxic activities.
utilizing an Advion TriVersa ™NanoMate sample introduction
system. The m/z values were evaluated assuming that H ¼ 1, C ¼ 12,
N ¼ 14, O ¼ 16, Cl ¼ 35, and Sn ¼ 120.
2.2. Synthesis
2.2.1. Synthesis of ligand: N-[(2-methoxyphenyl)]-4-oxo-4-[oxy]
butanamide (HL)
Stoichiometric amounts of o-anisidine (2-methoxyaniline) and
succinic anhydride were dissolved separately in glacial acetic acid.
The o-anisidine solution was added slowly to the solution of suc-
cinic anhydride and precipitate appeared [16] (Scheme 1). The
precipitates were filtered, washed thoroughly with distilled water
(to remove the unreacted succinic acid and succinic anhydride) and
HCl (to remove unreacted aniline) and air dried. Prism-like white
single crystals of the HL used in X-ray diffraction studies were
grown in an acetone solution by slow evaporation of solvent at
room temperature.
Yield: 90%: M.p. 141e142 ꢀC: Mol. Wt.: 223.23: Anal. Calc. for
C
11H13NO4: C, 59.2 (59.1); H, 5.9 (5.8); N, 6.3 (6.6): IR
(4000e100 cmꢁ1): 3200
1595 (COOasym); 1289
400 MHz)
n
(OH); 3368
n (NH); 1708 n (amide C]O);
n
n
(COOsym); 306 (Dn); 1H NMR (DMSO-d6,
d
(ppm): 12.12 (s, 1H; OH); 2.67 (t, 2H, H2, 3J[1H,
1H] ¼ 6.6 Hz); 2.53 (t, 2H, H3, 3J[1H, 1H] ¼ 6.6 Hz); 9.12 (s, 1H NH);
7.98 (d, 1H, H6, 3J[1H, 1H] ¼ 7.8 Hz); 6.91 (dd, 1H, H8, 4J[1H,
1H] ¼ 2.8 Hz); 7.08 (m, 2H, H7 and H9); 3.82 (s, 3H, H11): 13C NMR
2. Experimental section
2.1. Materials and methods
(DMSO-d6, 100 MHz) d (ppm): 174.4 (C1); 31.4 (C2); 29.4 (C3); 170.7
(C4); 127.9 (C5); 122.1 (C6); 120.6 (C7); 124.5 (C8); 111.5 (C9); 149.8
(C10); 56.1 (C11); ESI-MS, m/z (%): [C11H13NO4]þ 223 (30.1);
[C11H11NO3]þ 205 (11.3); [C7H9NO]þ 123 (100); [C7H8O]þ 108
(65.8); [C6H6N]þ 92 (5.5); [C5H5]þ 65 (7.1); [C3H3O]þ 55 (10.4).
Reagents Me3SnCl, Bu3SnCl, Ph3SnCl, Cy3SnCl, Me2SnCl2,
Bu2SnCl2, tert-Bu2SnCl2, Ph2SnCl2, n-Oct2SnO, o-anisidine, succinic
anhydride were obtained from Aldrich (USA) and were used
without further purification. All the solvents purchased from E.
Merck (Germany) were dried before use according to literature
procedures [12]. Dibenzyltin dichloride (Bz2SnCl2) and tribenzyltin
chloride (Bz3SnCl) were prepared according to the reported
method [13]. Sodium salt of Salmon fish sperm DNA (SS-DNA)
(Arcos) was used as received. The melting points were determined
in a capillary tube using a Gallenkamp (UK) electrothermal melting
point apparatus. IR spectra in the range of 4000e100 cmꢁ1 were
obtained on a Thermo Nicolet-6700 FT-IR Spectrophotometer.
Elemental analysis was done using a CE-440 Elemental Analyzer
(Exeter Analytical, Inc) and the experimentally found values are
given in parenthesis in experimental part. 1H, 13C and 119Sn NMR
were recorded on a 400 MHz JEOL ECS instrument, using DMSO as
an internal reference [1H (DMSO-d6) ¼ 2.50 and 13C (DMSO-
d6) ¼ 39.5 ppm]. Tetramethylsilane (for 1H and 13C NMR) and
Me4Sn (for 119Sn NMR) were used as external standards. For 119Sn
NMR the measurement was recorded at a working frequency of
37.29 MHz and the chemical shift was referenced to Me4Sn as an
external standard. Chemical shifts are given in ppm and coupling
constants (J) values are given in Hz. The multiplicities of signals in
1H NMR are given with chemical shifts; (s ¼ singlet, d ¼ doublet,
t ¼ triplet, q ¼ quartet, m ¼ multiplet). The absorption spectra were
measured on a Shimadzu 1800 UVevisible Spectrophotometer. X-
ray data for HL and complex 6 were collected at room temperature
while complexes 1 and 2 at 150 (2) K on a Bruker Apex II CCD
diffractometer. Complex 3 was collected at 190 (2) K on Agilent
Super Nova (Dual, Cu at zero, Eos) diffractometer. Details are given
in Table 2. All the non-hydrogen atoms were refined using aniso-
tropic atomic displacement parameters, and hydrogen atoms
bonded to carbon were inserted at calculated positions using a
riding model. Hydrogen atoms bonded to O or N were located from
difference maps and their coordinates refined. SHELXS-97 [14] was
used to solve and SHELX2012 [15] to refine the structures. The mass
spectra were recorded on a Thermo Scientific executive (orbitrap)
2.2.2. Synthesis of sodium salt of ligand: sodium N-[(2-
methoxyphenyl)]-4-oxo-4-[oxy]butanamide (NaL)
An aqueous solution of sodium hydrogen carbonate (NaHCO3)
was added to a suspended solution of HL in distilled water. The
mixture was stirred at room temperature to get a clear solution
which was then rotary evaporated to get the desired sodium salt of
the ligand. The chemical reaction is shown in Scheme 1.
2.2.3. Synthesis of organotin(IV) complexes R3SnL with R ¼ Me (1),
Bu (2), Ph (3), and [R2SnL2] with R ¼ Me (4), Bu (5)
Organotin(IV) carboxylates were synthesized by refluxing a
mixture of R3SnCl (5 mmol) or R2SnCl2 (2.5 mmol) and the sodium
salt of ligand NaL (5 mmol) in dry toluene for 8 h (Scheme 2). The
refluxed solution was kept overnight at room temperature. The
NaCl precipitate was removed by filtration and the solvent was
removed under reduced pressure. The product was purified by
recrystallization from chloroform at room temperature. The
numbering of HL and alkyl groups attached to Sn is given in
Scheme 3.
2.2.4. N-[(2-methoxyphenyl)]-4-oxo-4-[(trimethylstannyl)oxy]
butanamide (1)
Yield: 83%: M.p. 115e117 ꢀC: Mol. Wt.: 386.03: Anal. Calc. for
C
14H21NO4Sn: C, 43.6 (43.2); H, 5.5 (5.2); N, 3.6 (3.7): IR
(4000e100 cmꢁ1): 3418
(NH); 1689 (amide C]O); 1557
(COOasym); 1394 (COOsym); 146 (Dn); 546 (SneC); 455 (SneO):
(ppm): 2.55 (t, 2H, H2, 3J[1H,
n
n
n
n
n
n
1H NMR (DMSO-d6, 400 MHz)
d
1H] ¼ 6.8 Hz); 2.36 (t, 2H, H3, 3J[1H,1H] ¼ 6.8 Hz); 9.04 (s,1H NH); 8.02
(d, 1H, H6, 3J[1H, 1H] ¼ 7.8 Hz); 6.90 (dd, 1H, H8, 4J[1H, 1H] ¼ 2.8 Hz);
7.03 (m, 2H, H7 and H9); 3.81 (s, 3H, H11); 0.38 (s, 3H, H
a,
2J[119/
d (ppm):
117Sne1H
a
] ¼ 70, 68 Hz): 13C NMR (DMSO-d6, 100 MHz)
176.5 (C1);33.1 (C2);31.7(C3); 171.4(C4); 128.1 (C5);121.7(C6);120.6
(C7); 124.2 (C8); 111.4 (C9); 149.6 (C10); 56.0 (C11); 0.7 (Ca,
1J[119/

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
345
Scheme 1. Structural representation of the ligand (HL) and its sodium salt (NaL).
Scheme 2. General representation for synthesis of organotin(IV) compounds.
117Sne13C
d
a
¼ 524, 500 Hz]): 119Sn NMR (DMSO-d6, 400 MHz)
m/z ¼ 150 (25); [CH3Sn]þ, m/z ¼ 135 (23); [Sn]þ, m/z ¼ 120 (32);
[C13H18NO4Sn]þ, m/z ¼ 372 (41); [C12H18NO2Sn]þ, m/z ¼ 328 (3);
[C11H15NO2Sn]þ, m/z ¼ 313 (17); [C10H12NO2Sn]þ, m/z ¼ 298 (20).
(ppm): ꢁ10.2: ESI-MS, m/z (%): [C14H21NO4SnNa]þ, m/z ¼ 410 (38);
[C14H21NO4Sn]þ, m/z ¼ 387 (4); [C11H12O4N]þ, m/z ¼ 222 (7);
[C10H12NO2]þ, m/z ¼ 178 (16); [C3H9Sn]þ, m/z ¼ 165 (100); [C2H6Sn]þ,
2.2.5. N-[(2-methoxyphenyl)]-4-oxo-4-[(triethylstannyl)oxy]
butanamide (2)
Yield: 75%: M.p. 105e106 ꢀC: Mol. Wt.: 428.11: Anal. Calc. for
C
17H27NO4Sn: C, 47.7 (47.6); H, 6.4 (6.9); N, 3.3 (3.5): IR
(4000e100 cmꢁ1): 3434
(COOasym); 1392 (COOsym); 170 (Dn); 521
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1695
n
(amide C]O); 1562
(SneC); 481
n
n
n
n
d
(ppm): 2.58 (t, 2H, H2, 3J
[1H, 1H] ¼ 6.4 Hz); 2.41 (t, 2H, H3, 3J[1H, 1H] ¼ 6.4 Hz); 9.04 (s, 1H
NH); 8.00 (d, 1H, H6, 3J[1H, 1H] ¼ 7.8 Hz); 6.90 (dd, 1H, H8, 4J[1H,
1H] ¼ 2.4 Hz); 7.06 (m, 2H, H7 and H9); 3.81 (s, 3H, H11); 1.08 (q, 2H,
H
a
); 1.23 (t, 3H, H
b
,
3J[1H, 1H] ¼ 8.0 Hz): 13C NMR (DMSO-d6,
100 MHz)
d
(ppm): 176.7 (C1); 33.2 (C2); 31.6 (C3); 171.3 (C4); 128.1
(C5); 121.8 (C6); 120.6 (C7); 124.2 (C8); 111.3 (C9); 149.6 (C10); 56.0
(C11); 11.4 (C
(DMSO-d6, 400 MHz)
a
); 10.7 (C
b
,
d
2J[119Sne13C
(ppm): ꢁ18.8: ESI-MS, m/z (%):
b
] ¼ 32.3 Hz): 119Sn NMR
[C17H27NO4SnNa]þ, m/z ¼ 452 (42); [C17H27NO4Sn]þ, m/z ¼ 429 (2);
[C11H12O4N]þ, m/z ¼ 222 (24); [C10H12NO2]þ, m/z ¼ 178 (7);
[C6H15Sn]þ, m/z ¼ 207 (100); [C4H10Sn]þ, m/z ¼ 178 (7); [C2H5Sn]þ,
m/z ¼ 149 (5); [Sn]þ, m/z ¼ 120 (8); [C15H22NO4Sn]þ, m/z ¼ 400
Scheme 3. Numbering pattern of HL and organic moiety attached to Sn atom.

346
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
(98); [C14H22NO2Sn]þ, m/z ¼ 356 (4); [C12H17NO2Sn]þ, m/z ¼ 327
(2); [C10H12NO2Sn]þ, m/z ¼ 298 (15).
(15); [C11H12NO4]þ, m/z ¼ 222 (27); [C10H12NO2]þ, m/z ¼ 178 (18);
[C18H33Sn]þ, m/z ¼ 369 (100); [C12H22Sn]þ, m/z ¼ 287 (15);
[C6H11Sn]þ, m/z ¼ 197 (29); [Sn]þ, m/z ¼ 120 (15); [C23H34NO4Sn]þ,
m/z ¼ 508 (23); [C22H34NO2Sn]þ, m/z ¼ 464 (21); [C16H23NO2Sn]þ,
m/z ¼ 381 (14); [C10H12NO2Sn]þ, m/z ¼ 298 (18).
2.2.6. N-[(2-methoxyphenyl)]-4-oxo-4-[(tributylstannyl)oxy]
butanamide (3)
Yield: 76%: M.p. 52e54 ꢀC: C23H39NO4Sn Mol. Wt.: 512.27: Anal.
Calc. for C17H27NO4Sn: C, 53.9 (53.8); H, 7.7 (7.4); N, 2.7 (2.9): IR
2.2.9. N-[(2-methoxyphenyl)]-4-oxo-4-[(tribenzylstannyl)oxy]
butanamide (6)
(4000e100 cmꢁ1): 3426
(COOasym); 1372
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1694
n
(amide C]O); 1552
(SneC); 455
n
n
(COOsym); 180 (Dn); 569
n
n
Yield: 81%: M.p. 112e114 ꢀC: Anal. Calc. C32H33NO4Sn: Mol. Wt.:
d
(ppm): 2.55 (t, 2H, H2, 3J
614.3: C, 62.6; H, 5.4 (5.3); N, 2.3 (2.3): IR (4000e100 cmꢁ1): 3426
n
[1H, 1H] ¼ 6.8 Hz); 2.38 (t, 2H, H3, 3J[1H, 1H] ¼ 6.8 Hz); 9.00 (s, 1H
NH); 8.02 (d, 1H, H6, 3J[1H, 1H] ¼ 7.8 Hz); 6.88 (dd, 1H, H8, 4J[1H,
1H] ¼ 2.4 Hz); 7.02 (m, 2H, H7 and H9); 3.81 (s, 3H, H11); 1.07 (t, 3H,
(NH); 1685
202 (Dn); 542
400 MHz)
n (amide C]O); 1559 n (COOasym); 1357 n (COOsym);
n
(SneC); 447 n
(SneO): 1H NMR (DMSO-d6,
d
(ppm): 2.46 (t, 2H, H2, 3J[1H, 1H] ¼ 6.8 Hz); 2.31 (t, 2H,
Ha
, 3J[1H, 1H] ¼ 8.0 Hz); 1.56 (m, 2H, H
b
); 1.33 (m, 2H, H
g); 0.87 (t,
H3, 3J[1H, 1H] ¼ 6.8 Hz); 8.96 (s, 1H NH); 7.94 (d, 1H, H6, 3J[1H,
1H] ¼ 8.0 Hz); 6.97 (dd, 1H, H8, 4J[1H, 1H] ¼ 3.6 Hz); 7.44 (m, 2H, H7
3H, H
d
, 3J[1H, 1H] ¼ 6.8 Hz): 13C NMR (DMSO-d6, 100 MHz)
d
(ppm):
176.4 (C1); 33.2 (C2); 31.7 (C3); 171.3 (C4); 128.2 (C5); 121.6 (C6);
and H9); 3.73 (s, 3H, H11); 2.05 (s, 2H, H
a
, 2J[119Sne1H] ¼ 61); 7.14
120.5 (C7); 124.1 (C8); 111.3 (C9); 149.5 (C10); 56.0 (C11); 19.1 (C
28.1 (C ] ¼ 75 Hz);
, 2J[119Sne13C , 3J[119Sne13C
] ¼ 27 Hz) 26.9 (C
14.1 (C
): 119Sn NMR (DMSO-d6, 400 MHz)
(ppm): ꢁ17.6. ESI-MS,
a
);
(d, 1H, H
g
, 3J[1H, 1H] ¼ 7.6 Hz); 7.21 (t, 2H, H
d
, 3J[1H, 1H] ¼ 8.0 Hz);
b
b
g
g
6.84 (t, 1H, Hε, 3J[1H, 1H] ¼ 8.0 Hz): 13C NMR (DMSO-d6, 100 MHz)
d
d
d (ppm): 176.3 (C1); 31.5 (C2); 30.5 (C3); 171.2 (C4); 128.2 (C5);
m/z (%): [C23H39NO4SnNa]þ, m/z ¼ 536 (27); [C23H39NO4Sn]þ, m/
z ¼ 513 (20); [C11H12NO4]þ, m/z ¼ 222 (8); [C10H12NO2]þ, m/z ¼ 178
(11); [C12H27Sn]þ, m/z ¼ 291 (100); [C8H18Sn]þ, m/z ¼ 234 (26);
[C4H9Sn]þ, m/z ¼ 177 (20); [Sn]þ, m/z ¼ 120 (12); [C19H30NO4Sn]þ,
m/z ¼ 456 (22); [C18H30NO2Sn]þ, m/z ¼ 412 (7); [C14H21NO2Sn]þ, m/
z ¼ 355 (12); [C10H12NO2Sn]þ, m/z ¼ 298 (3).
121.9 (C6); 120.7 (C7); 124.3 (C8); 111.5 (C9); 149.7 (C10); 56.1
(C11); 21.6 (C 483 Hz); 143.7 (C
1J[119Sne13C 2J
119Sne13C , 3J[119Sne13C
] ¼ 72 Hz), 128.7 (C ] ¼ 62 Hz), 136.8 (C
4J[119Sne13C
400 MHz)
a
,
a
]
¼
b,
[
b
g
g
d,
d]
¼
46 Hz), 125.9 (Cε): 119Sn NMR (DMSO-d6,
d
(ppm): ꢁ256.9: ESI-MS, m/z (%): [C32H33NO4SnNa]þ, m/
z ¼ 638 (60); [C32H33NO4Sn]þ, m/z ¼ 615 (15); [C32H33NO4Sn]þ, m/
z ¼ 616 (98); [C11H12NO4]þ, m/z ¼ 222 (16); [C9H12NO2]þ, m/z ¼ 178
(23); [C32H32Sn]þ, m/z ¼ 393 (100); [C12H22Sn]þ, m/z ¼ 302 (23);
[C6H11Sn]þ, m/z ¼ 211 (9); [Sn]þ, m/z ¼ 120 (5); [C25H26NO4Sn]þ, m/
z ¼ 524 (21); [C25H26NO2Sn]þ, m/z ¼ 480 (26); [C16H17NO2Sn]þ, m/
z ¼ 389 (3); [C10H11N2O4Sn]þ, m/z ¼ 343 (21).
2.2.7. N-[(2-methoxyphenyl)]-4-oxo-4-[(triphenylstannyl)oxy]
butanamide (4)
Yield: 87%: M.p. 102e103 ꢀC: Mol. Wt.: 572.24: Anal. Calc. for
C
29H27NO4Sn: C, 60.9 (60.5); H, 4.8 (4.2); N, 2.5 (2.8): IR
(4000e100 cmꢁ1): 3425
(COOasym); 1382 (COOsym); 163 (Dn); 267
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1645
n
(amide C]O); 1545
(SneC); 444
n
n
n
n
2.2.10. Dimethylstannanediyl bis(4-(2-methoxyphenylamino)-4-
oxobutanoate) (7)
d
(ppm): 2.51 (t, 2H, H2, 3J
[1H, 1H] ¼ 6.4 Hz); 2.39 (t, 2H, H3, 3J[1H, 1H] ¼ 6.4 Hz); 9.02 (s, 1H
NH); 8.00 (d, 1H, H6, 3J[1H, 1H] ¼ 7.8 Hz); 6.91 (dd, 1H, H8, 4J[1H,
1H] ¼ 2.4 Hz); 7.05 (m, 2H, H7 and H9); 3.77 (s, 3H, H11); 7.91 (m, 15
Yield: 870%: M.p. 120e122 ꢀC: Mol. Wt.: 593.21: Anal. Calc. for
C
24H30N2O8Sn: C, 48.6 (62.6); H, 5.1 (5.3); N, 4.7 (4.4): IR
(4000e100 cmꢁ1): 3253
(NH); 1664 (amide C]O); 1526
(COOasym); 1386 (COOsym); 140 (Dn); 577 (SneC); 450 (SneO):
d
1H NMR (DMSO-d6, 400 MHz) (ppm): 2.66 (t, 2H, H2, 3J[1H,
n
n
n
H, SnePh): 13C NMR (DMSO-d6, 100 MHz)
d
(ppm): 176.3 (C1); 32.9
n
n
n
(C2); 31.6 (C3); 171.2 (C4); 128.1 (C5); 121.8 (C6); 120.6 (C7); 124.3
(C8); 111.4 (C9); 149.6 (C10); 56.0 (C11); 143.5 (Ca); 136.7 (Cb, 2J
1H] ¼ 6.6); 2.50 (t, 2H, H3, 3J[1H, 1H] ¼ 6.6); 9.11 (s, 1H NH); 8.0 (d, 3J
[
119Sne13Cb] ¼ 46 Hz); 128.6 (Cg, 3J[119Sne13Cd] ¼ 63 Hz); 129.4
[1H, 1H] ¼ 7.8 Hz, 1H, H6); 6.91 (dd, 1H, H8, 4J[1H, 1H] ¼ 2.4 Hz); 7.07
(Cd): 119Sn NMR (DMSO-d6, 400 MHz)
d
(ppm): ꢁ246.9: ESI-MS, m/z
(m, 2H, H7 and H9); 3.82 (s, 3H, H11); 0.76 (s, 3H, H
a
) [119/
d (ppm):
(%): [C29H27NO4SnNa]þ, m/z ¼ 596 (15); [C29H27NO4Sn]þ, m/z ¼ 573
(13); [C11H12NO4]þ, m/z ¼ 222 (9); [C10H12NO2]þ, m/z ¼ 178 (10);
[C18H15Sn]þ, m/z ¼ 351 (100); [C12H10Sn]þ, m/z ¼ 274 (25);
[C4H9Sn]þ, m/z ¼ 197 (23); [Sn]þ, m/z ¼ 120 (10); [C23H22NO4Sn]þ,
m/z ¼ 496 (12); [C22H22NO2Sn]þ, m/z ¼ 452 (24); [C16H17NO2Sn]þ,
m/z ¼ 375 (21); [C10H12NO2Sn]þ, m/z ¼ 298 (35).
117Sne1H] ¼ 102, 100 Hz): 13C NMR (DMSO-d6, 100 MHz)
178.8 (C1); 32.1 (C2); 30.1 (C3); 170.8 (C4); 128.0 (C5); 121.9 (C6);
120.6 (C7); 124.4 (C8); 111.4 (C9); 149.7 (C10); 56.0 (C11); 12.7 (C
a
):
119Sn NMR (DMSO-d6, 400 MHz)
d
(ppm): ꢁ281.7: ESI-MS, m/z (%):
[C24H30N2O8SnNa]þ, m/z ¼ 617 (34); [C24H30N2O8Sn]þ, m/z ¼ 594
(20); [C23H27N2O8Sn]þ, m/z ¼ 579 (18); [C12H15NO4Sn]þ, m/z ¼ 357
(19); [C11H12NO4Sn]þ, m/z ¼ 342 (20); [C11H12NO4]þ, m/z ¼ 222 (11);
[C9H12NO2]þ, m/z ¼ 178 (13); [C2H6Sn]þ, m/z ¼ 150 (10); [CH3Sn]þ, m/
z ¼ 135 (14); [Sn]þ, m/z ¼ 120 (4); [C13H18NO4Sn]þ, m/z ¼ 372 (100);
[C12H18NO2Sn]þ, m/z ¼ 328 (21); [C11H15NO2Sn]þ, m/z ¼ 313 (27);
[C10H12NO2Sn]þ, m/z ¼ 298 (25); [C22H27N2O6Sn]þ, m/z ¼ 535 (12).
2.2.8. N-[(2-methoxyphenyl)]-4-oxo-4-[(tricyclohexylstannyl)oxy]
butanamide (5)
Yield: 84%: M.p. 85e87 ꢀC: Mol. Wt.: 590.38: Anal. Calc.
C
29H45NO4Sn: C, 59.0 (58.7); H, 7.7 (7.5); N, 2.4 (2.6): IR
(4000e100 cmꢁ1): 3426
(COOasym); 1393 (COOsym); 184 (Dn); 569
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1694
n
(amide C]O); 1577
(SneC); 455
n
n
n
n
2.2.11. Dibutylstannanediyl bis(4-(2-methoxyphenylamino)-4-
oxobutanoate) (8)
d
(ppm): 2.58 (t, 2H, H2, 3J
[1H, 1H] ¼ 6.4); 2.46 (t, 2H, H3, 3J[1H, 1H] ¼ 6.4); 9.05 (s, 1H NH);
8.04 (d, 1H, H6, 3J[1H, 1H] ¼ 7.8 Hz); 6.88 (dd, 1H, H8, 4J[1H,
1H] ¼ 2.4 Hz); 7.01 (m, 2H, H7 and, H9); 3.82 (s, 3H, H11); 1.19 (m,
Yield: 80%: M.p. 115e117 ꢀC: Mol. Wt.: 677.37: Anal. Calc. for
C
30H42N2O8Sn: C, 53.2 (53.5); H, 6.3 (6.6); N, 4.1 (4.5): IR
(4000e100 cmꢁ1): 3312
(NH); 1698 (amide C]O); 1525
(COOasym); 1391 (COOsym); 134 (Dn); 571 (SneC); 477 (SneO):
(ppm): 2.65 (t, 2H, H2, 3J[1H,
n
n
n
1H, H
NMR (DMSO-d6, 100 MHz)
171.2 (C4); 128.2 (C5); 121.6 (C6); 120.5 (C7); 124.1 (C8); 111.3 (C9);
149.5 (C10); 56.0 (C11); 27.1 (C
, 1J[119Sne13C
] ¼ 512 Hz); 29.2 (C
2J[119Sne13C , 4J[119Sne13C
] ¼ 72 Hz) 36.1 (C ) 30.9 (C ] ¼ 47 Hz):
a
); 1.84 (m, 2H, H
b
); 1.62 (m, 2H, H
g
); 1.58 (m, 2H, H
d
): 13C
n
n
n
d
(ppm): 176.8 (C1); 33.2 (C2); 31.4 (C3);
1H NMR (DMSO-d6, 400 MHz)
d
1H] ¼ 6.4); 2.52 (t, 2H, H3, 3J[1H,1H] ¼ 6.4); 9.10 (s,1H NH); 8.04 (d, 3J
a
a
b,
[1H, 1H] ¼ 7.5 Hz, 1H, H6); 6.89 (dd, 1H, H8, 4J[1H, 1H] ¼ 2.4 Hz); 7.06
b
g
d
g
(m, 2H, H7 and H9); 3.82 (s, 3H, H11); 1.20 (t, 3H, H
a
d
,
3J(1H,
119Sn NMR (DMSO-d6, 400 MHz)
d
(ppm): ꢁ250.4: ESI-MS, m/z (%):
1H) ¼ 7.2 Hz); 1.46 (m, 2H, H
b
); 1.35 (m, 2H, H
g
); 0.77 (t, 3H, H
, 3J[1H,
[C29H45NO4SnNa]þ, m/z ¼ 614 (22); [C29H45NO4Sn]þ, m/z ¼ 591
1H] ¼ 7.2Hz): 13C NMR (DMSO-d6,100 MHz)
d (ppm): 179.5 (C1); 32.2

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
347
(C2); 29.9 (C3); 170.8 (C4); 128.0 (C5); 121.8 (C6); 120.5 (C7); 124.3
(4000e100 cmꢁ1): 3425
(COOasym); 1397 (COOsym); 129 (Dn); 586 n
n
(NH); 1687
n
(amide C]O); 1526
(SneC); 455
n
n
(C8); 111.3 (C9); 149.6 (C10); 56.0 (C11): 21.4 (C
119Sne13C 3J[119Sne13C
¼ 27 Hz); 26.2 (C ] ¼ 75 Hz) 14.1 (C
119Sn NMR (DMSO-d6, 400 MHz)
a
); 28.1 (C
b
,
2J
n
[
b
g,
g
d):
(SneO): 1H NMR (DMSO-d6, 400 MHz)
d
(ppm): 2.66 (t, 2H, H2, 3J
d
(ppm): ꢁ296.7: ESI-MS, m/z (%):
[1H, 1H] ¼ 6.4); 2.52 (t, 2H, H3, 3J[1H, 1H] ¼ 6.4); 9.10 (s, 1H NH); 7.90
[C30H42N2O8SnNa]þ, m/z ¼ 701 (54); [C30H42N2O8Sn]þ, m/z ¼ 678
(12); [C26H33N2O8Sn]þ, m/z ¼ 621 (7); [C15H21NO4Sn]þ, m/z ¼ 399
(8); [C11H12NO4Sn]þ, m/z ¼ 342 (4); [C11H12NO4]þ, m/z ¼ 222 (11);
[C10H12NO2]þ, m/z ¼ 178 (12); [C8H18Sn]þ, m/z ¼ 234 (7); [C4H9Sn]þ,
m/z ¼ 177 (100); [Sn]þ, m/z ¼ 120 (12); [C19H30NO4Sn]þ, m/z ¼ 456
(24); [C18H30NO2Sn]þ, m/z ¼ 412 (6); [C14H21NO2Sn]þ, m/z ¼ 355 (5);
[C10H12NO2Sn]þ, m/z ¼ 298 (5); [C25H33N2O6Sn]þ, m/z ¼ 577 (4).
(d, 3J[1H, 1H] ¼ 8.0 Hz, 1H, H6); 6.85 (dd, 1H, H8, 4J[1H, 1H] ¼ 2.4);
7.02 (m, 2H, H7 and H9); 3.77 (s, 3H, H11); 1.23 (s, 9H, H
b,
3J
d (ppm): 180.9
[
119Sne1H
b
] ¼ 31 Hz): 13C NMR (DMSO-d6,100 MHz)
(C1); 32.0 (C2); 29.4 (C3); 170.6 (C4); 128.0 (C5); 122.1 (C6); 120.7
(C7); 124.6 (C8); 111.6 (C9); 149.9 (C10); 56.1 (C11): 30.6 (C
a
); 29.9
(C
b
): 119Sn NMR (DMSO-d6, 400 MHz)
d
(ppm): ꢁ215.8: ESI-MS, m/
z (%):[C30H42N2O8SnNa]þ, m/z ¼ 701 (100); [C30H42N2O8Sn]þ, m/
z ¼ 678 (20); [C30H43N2O8Sn]þ, m/z ¼ 679 (80); [C26H33N2O8Sn]þ,
m/z ¼ 621 (2); [C15H21NO4Sn]þ, m/z ¼ 399 (12); [C11H12NO4Sn]þ, m/
z ¼ 342 (1); [C11H12NO4]þ, m/z ¼ 222 (10); [C10H12NO2]þ, m/z ¼ 178
(8); [C8H18Sn]þ, m/z ¼ 234 (7); [C4H9Sn]þ, m/z ¼ 177 (77);
[C3H6Sn]þ, m/z ¼ 162 (12); [C2H3Sn]þ, m/z ¼ 147 (7); [Sn]þ, m/
z ¼ 120 (12); [C19H30NO4Sn]þ, m/z ¼ 456 (34); [C18H30NO2Sn]þ, m/
z ¼ 412 (16); [C14H21NO2Sn]þ, m/z ¼ 355 (13); [C10H12NO2Sn]þ, m/
z ¼ 298 (4); [C25H33N2O6Sn]þ, m/z ¼ 577 (15).
2.2.12. Diphenylstannanediyl bis(4-(2-methoxyphenylamino)-4-
oxobutanoate) (9)
Yield: 78%: M.p. 121e123 ꢀC: Mol. Wt.: 717.35: Anal. Calc. for
C
34H34N2O8Sn: C, 56.9 (56.2); H, 4.8 (4.4); N, 3.9 (3.6): IR
(4000e100 cmꢁ1): 3277
(COOasym); 1381 (COOsym); 160 (Dn); 280
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1646
n
(amide C]O); 1541
(SneC); 451
n
n
n
n
d
(ppm): 2.50 (t, 2H, H2, 3J
[1H, 1H] ¼ 6.6); 2.36 (t, 2H, H3, 3J[1H, 1H] ¼ 6.6); 9.02 (s, 1H NH);
8.00 (d, 3J[1H, 1H] ¼ 7.5 Hz, 1H, H6); 6.91 (dd, 1H, H8, 4J[1H,
1H] ¼ 2.2); 7.07 (m, 2H, H7 and H9); 3.77 (s, 3H, H11); 7.90 (m, 10 H,
2.2.15. Dioctylstannanediyl bis(4-(2-methoxyphenylamino)-4-
oxobutanoate) (12)
SnePh): 13C NMR (DMSO-d6, 100 MHz)
d
(ppm): 176.3 (C1); 32.9
Yield: 73%: M.p. 81e83 ꢀC: Mol. Wt.: 789.59: Anal. Calc. for
(C2); 31.7 (C3); 171.2 (C4); 128.0 (C5); 121.9 (C6); 120.6 (C7); 124.3
(C8); 111.4 (C9); 149.6 (C10); 56.0 (C11): 143.6 (C ), 136.7 (C
2J
119Sne13C 3J[119/117Sne13C
] ¼ 45.8 Hz), 128.6 (C ] ¼ 74, 68),
129.4 (C
400 MHz)
C38H58N2O8Sn: C, 57.8 (57.4); H, 7.4 (7.1); N, 3.5 (3.8): IR
a
b
,
(4000e100 cmꢁ1): 3322
(COOasym); 1376 (COOsym); 145 (Dn); 575
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1690
n
(amide C]O); 1521
(SneC); 474
n
[
b
,
d
g,
g
n
n
n
d
4J[119Sne13C
d]
¼
63 Hz]): 119Sn NMR (DMSO-d6,
d
(ppm): 2.65 (t, 2H, H2, 3J
(ppm): ꢁ256.7: ESI-MS, m/z (%): [C34H34N2O8SnNa]þ,
[1H, 1H] ¼ 6.4); 2.52 (t, 2H, H3, 3J[1H, 1H] ¼ 6.4 Hz); 9.10 (s, 1H NH);
8.04 (d, 3J[1H, 1H] ¼ 7.5 Hz, 1H, H6); 6.89 (dd, 1H, H8, 3J[1H,
1H] ¼ 2.4 Hz); 7.06 (m, 2H, H7 and H9); 3.82 (s, 3H, H11); 1.33 (t, 2H,
m/z ¼ 741 (20); [C34H34N2O8Sn]þ, m/z ¼ 718 (12); [C28H29N2O8Sn]þ,
m/z ¼ 641 (4); [C17H17NO4Sn]þ, m/z ¼ 419 (10); [C11H12NO4Sn]þ, m/
z ¼ 342 (11); [C11H12NO4]þ, m/z ¼ 222 (10); [C10H12NO2]þ, m/
z ¼ 178 (12); [C12H10Sn]þ, m/z ¼ 274 (13); [C6H5Sn]þ, m/z ¼ 197
(100); [Sn]þ, m/z ¼ 120 (9); [C23H22NO4Sn]þ, m/z ¼ 496 (12);
[C22H22NO2Sn]þ, m/z ¼ 452 (9); [C16H17NO2Sn]þ, m/z ¼ 375 (7);
[C10H12NO2Sn]þ, m/z ¼ 298 (3); [C27H29N2O6Sn]þ, m/z ¼ 597 (19).
H
g
a
, 3J[1H, 1H] ¼ 6.8 Hz); 1.40 (bs, 6H, H
b, g, d , ,
); 1.50 (bs, 6H, Ha0 b0
0); 0.83 (t, 3H, Hd0
,
3J[1H, 1H] ¼ 6.8 Hz): 13C NMR (DMSO-d6,
100 MHz)
d (ppm): 172.5 (C1); 32.0 (C2); 30.9 (C3); 169.8 (C4);
128.1 (C5); 121.9 (C6); 119.6 (C7); 124.0 (C8); 110.4 (C9); 148.7
(C10); 55.0 (C11): 24.6 (C ); 29.5 (C ); 34.1 (C ); 29.3 (C ); 29.2
(C
0); 31.9 (C 0); 22.8 (C 0); 13.7 (C
400 MHz)
m/z
a
g
b
g
d
a
b
d
0): 119Sn NMR (DMSO-d6,
2.2.13. Dibenzylstannanediyl bis[4-(2-methoxyphenylamino)-4-
oxobutanoate] (10)
d
(ppm): ꢁ298.7: ESI-MS, m/z (%): [C38H58N2O8SnNa]þ,
¼
813 (43); [C38H58N2O8Sn]þ, m/z
¼
790 (26);
Yield: 70%: M.p. 131e133 ꢀC: Mol. Wt.: 745.41: Anal. Calc. for
[C30H41N2O8Sn]þ, m/z ¼ 677 (14); [C19H29NO4Sn]þ, m/z ¼ 455 (7);
[C11H12NO4Sn]þ, m/z ¼ 342 (7); [C11H12NO4]þ, m/z ¼ 222 (9);
[C11H12NO4]þ, m/z ¼ 224 (100); [C10H12NO2]þ, m/z ¼ 178 (18);
[C16H34Sn]þ, m/z ¼ 346 (4); [C8H17Sn]þ, m/z ¼ 233 (5); [Sn]þ, m/
z ¼ 120 (8); [C27H46NO4Sn]þ, m/z ¼ 568 (47); [C26H46NO2Sn]þ, m/
z ¼ 524 (32); [C18H29NO2Sn]þ, m/z ¼ 411 (3); [C10H12N2O4Sn]þ, m/
z ¼ 298 (1); [C29H41N2O6Sn]þ, m/z ¼ 633 (2).
C
36H38N2O8Sn: C, 58.0 (58.2); H, 5.1 (4.9); N, 3.8 (3.6): IR
(4000e100 cmꢁ1): 3299
n
(NH); 1665
n
(amide C]O); 1530
n
(COOasym); 1371
n (COOsym); 159 (Dn); 538 n (SneC); 444
n
(SneO): 1H NMR (DMSO-d6, 400 MHz)
d
(ppm): 2.71 (t, 2H, H2, 3J
[1H, 1H] ¼ 6.8 Hz); 2.60 (t, 2H, H3, J[1H, 1H] ¼ 6.8 Hz); 9.01 (s, 1H
NH); 8.00 (d, 3J[1H, 1H] ¼ 7.6 Hz, 1H, H6); 6.91 (dd, 1H, H8, 4J[1H,
1H] ¼ 1.6 Hz); 7.01 (m, 2H, H7 and H9); 3.83 (s, 3H, H11); 1.18 (s, 2H,
3
Ha); 7.95 (d, 1H, H
g,
3J(1H, 1H) ¼ 8.0 Hz); 7.23 (t, 2H, H
d,
3J[1H,
2.2.16. (2,20-Bipyridine) N-[(2-methoxyphenyl)]-4-oxo-4-
[(trimethylstannyl)oxy]butanamide (13)
1H] ¼ 7.8 Hz); 6.80 (t, 1H, Hε, 3J[1H, 1H] ¼ 7.8 Hz): 13C NMR (DMSO-
d6, 100 MHz)
d
(ppm): 172.3 (C1); 32.2 (C2); 31.0 (C3); 169.7 (C4);
Yield: 75%: M.p. 110e112 ꢀC: Mol. Wt.: 542.2: Anal. Calc. for
127.5 (C5); 121.2 (C6); 120.8 (C7); 123.5 (C8); 110.4 (C9); 148.6 (C10);
55.0 (C11): 21.6 (C ); 143.5 (C ), 127.0 (C ), 136.6 (C ), 126.8 (Cε):
119Sn NMR (DMSO-d6, 400 MHz)
(ppm): ꢁ319.8: ESI-MS, m/z (%):
C24H29N3O4Sn: C, 53.2 (53.5); H, 5.4 (5.3); N, 7.8 (7.9): IR
a
b
g
d
(4000e100 cmꢁ1): 3416
(COOasym); 1392 (COOsym); 130 (Dn); 546
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1690
n
(amide C]O); 1522
(SneC); 452
n
d
n
n
n
[C36H38N2O8SnNa]þ, m/z ¼ 769 (9); [C36H38N2O8Sn]þ, m/z ¼ 746 (7);
[C29H31N2O8Sn]þ, m/z ¼ 655 (14); [C18H19NO4Sn]þ, m/z ¼ 433 (15);
[C11H12NO6Sn]þ, m/z ¼ 342 (4); [C11H12NO4]þ, m/z ¼ 222 (10);
[C11H13NO4]þ, m/z ¼ 224 (100); [C10H12NO2]þ, m/z ¼ 178 (12);
[C14H14Sn]þ, m/z ¼ 302 (17); [C7H7Sn]þ, m/z ¼ 211 (17); [CH3Sn]þ, m/
z ¼ 135 (45); [Sn]þ, m/z ¼ 120 (2); [C25H26NO4Sn]þ, m/z ¼ 524 (44);
[C25H26NO2Sn]þ, m/z ¼ 480 (12); [C17H19NO2Sn]þ, m/z ¼ 389 (5);
[C10H12NO2Sn]þ, m/z ¼ 298 (9); [C28H31N2O6Sn]þ, m/z ¼ 611 (5).
d
(ppm): 2.63 (t, 2H, H2, 3J
[1H, 1H] ¼ 6.8 Hz); 2.29 (t, 2H, H3, 3J[1H, 1H] ¼ 6.8 Hz); 8.98 (s, 1H
NH); 8.36 (d, 3J[1H, 1H] ¼ 7.6 Hz, 1H, H6); 6.85 (dd, 1H, H8, 3J[1H,
1H] ¼ 2.4); 7.01 (m, 2H, H7 and H9); 3.77 (s, 3H, H11); {8.66 (d,1H, 3J
[1H, 1H] ¼ 5.2 Hz); 7.93 (m, 1H); 7.70 (m, 1H); 9.2 (d, 1H, 3J[1H,
1H]
¼
5.2 Hz) (2,20-Bipy H)}; 0.33 (s, 3H, 2J[119/117/
Ha,
a
115Sne1H
] ¼ 70, 68, 30 Hz): 13C NMR (DMSO-d6, 100 MHz)
d
(ppm): 176.5 (C1); 33.2 (C2); 31.8 (C3); 171.5 (C4); 128.2 (C5);
121.8 (C6); 120.7 (C7); 124.3 (C8); 111.5 (C9), 149.7 (C10), 56.1 (C11);
2.2.14. Di-tert-butylstannanediyl bis[4-(2-methoxyphenylamino)-
4-oxobutanoate] (11)
{149.8, 124.7, 137.8, 121.0, 155.8 (2,20-Bipy C)}, 0.7 (C 1J [119/
a,
117Sne13C
a
] ¼ 521, 500 Hz); 119Sn NMR (DMSO-d6, 400 MHz)
Yield: 85%: M.p. 106e108 ꢀC: Mol. Wt.: 677.37: Anal. Calc. for
d
(ppm): ꢁ10.1: ESI-MS, m/z (%): [C24H29N3O4SnNa]þ, m/z ¼ 566
C
30H42N2O8Sn: C, 53.2 (53.5); H, 6.3 (6.0); N, 4.1 (4.6): IR
(15); [C24H29N3O4Sn]þ, m/z ¼ 543 (31), [C14H21NO4Sn]þ, m/z ¼ 387

348
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
(32); [C11H12NO4]þ, m/z ¼ 222 (11); [C10H12NO2]þ, m/z ¼ 178 (12);
[C3H9Sn]þ, m/z ¼ 165 (43); [C2H6Sn]þ, m/z ¼ 150 (21); [CH3Sn]þ, m/
z ¼ 135 (24); [Sn]þ, m/z ¼ 120 (5); [C23H26N3O4Sn]þ, m/z ¼ 528
(13); [C22H26N3O2Sn]þ, m/z ¼ 484 (10); [C21H23N3O2Sn]þ, m/
z ¼ 469 (8); [C11H15NO2Sn]þ, m/z ¼ 313 (20); [C10H12NO2Sn]þ, m/
z ¼ 298 (10); [C10H8N2]þ, m/z ¼ 157 (100).
nutrient agar medium at 45 ꢀC and poured into sterile petri plates.
The medium was allowed to solidify. 5 L of the test compound
(40 mg/mL in DMSO) was poured on 4 mm sterile paper discs and
placed on nutrient agar plates. In each plate DMSO and standard
antibacterial drugs (Roxithromycin and Cefixim) served as negative
and positive controls, respectively. Test samples were checked at
m
200 mg/mL, 100 mg/mL and 50 mg/mL as final concentrations and
2.2.17. (1,10-Phenanthroline) N-[(2-methoxyphenyl)]-4-oxo-4-
[(trimethylstannyl)oxy]butanamide (14)
triplicate plates of each bacterial strain were prepared. The plates
were incubated at 37 ꢀC for 24 h and the antibacterial activity was
determined by measuring the diameter of zones showing complete
inhibition (mm). Growth inhibition was calculated with reference
to negative control [20].
Yield: 70%: M.p. 125e127 ꢀC: Mol. Wt.: 566.2: Anal. Calc. for
C
26H29N3O4Sn: C, 43.6 (43.7); H, 5.5 (5.1); N, 3.6 (3.2): IR
(4000e100 cmꢁ1): 3417
(COOasym); 1393 (COOsym); 126 (Dn); 546
(SneO): 1H NMR (DMSO-d6, 400 MHz)
n
(NH); 1688
n
(amide C]O); 1519
(SneC); 486
n
n
n
n
d
(ppm): 2.49 (t, 2H, H2, 3J
2.4.1. Minimum inhibitory concentration (MIC) determination
The MIC (minimum inhibitory concentration) of a bacterium to a
certain antimicrobial agent (test compounds) can be determined
and today gives the best quantitative estimate for susceptibility.
MIC is defined as the lowest concentration of antimicrobial agent
required to inhibit growth of the bacteria. The MIC tells about the
degree of resistance and might give important information about
the resistance mechanism and the resistance genes involved. The
principle of MIC determination employing the microdilution
method is that after an agar plate is inoculated with the bacteria, a
disk or paper strip with antimicrobial agent is placed on the sur-
face. During incubation the antimicrobial agent diffuses into the
agar and inhibits growth of the bacteria if sensitive. Diffusion tests
are cheap compared to most MIC-determination methods.
[1H, 1H] ¼ 6.8 Hz); 2.31 (t, 2H, H3, 3J[1H, 1H] ¼ 6.8 Hz); 9.0 (s, 1H
NH); 8.18 (d, 3J[1H, 1H] ¼ 8.4 Hz, 1H, H6); 6.83 (dd, 1H, H8, 3J[1H,
1H] ¼ 2.4 Hz); 7.04 (m, 2H, H7 and H9); 3.82 (s, 3H, H11); 0.40 (s, 3H,
H
a,
2J[119Sne1H
a
] ¼ 69 Hz); {9.08 (d, 1H, 3J[1H, 1H] ¼ 5.4 Hz); 7.76
(m, 1H); 8.48 (m, 1H); 7.96 (d, 1H, 3J[1H, 1H] ¼ 5.4 Hz) (1,10-phen
H)}: 13C NMR (DMSO-d6, 100 MHz)
d (ppm): 173.5 (C1); 33.0
(C2); 31.7 (C3); 171.4 (C4); 128.2 (C5); 121.9 (C6); 120.7 (C7); 124.3
(C8); 111.5 (C9), 149.7 (C10), 56.1 (C11): 0.4 (C
a
,
1J
[
119Sne13C
a
] ¼ 525 Hz); {150.5, 123.9, 136.8, 129.0, 145.9, 127.2
(1,10-phen C)}; 119Sn NMR (DMSO-d6, 400 MHz)
d
(ppm): ꢁ11.0:
590 (5);
ESI-MS, m/z (%): [C26H29N3O4SnNa]þ, m/z
¼
[C26H29N3O4Sn]þ, m/z ¼ 567 (23); [C14H21NO4Sn]þ, m/z ¼ 387 (22);
[C11H12NO4]þ, m/z ¼ 222 (6); [C10H12NO2]þ, m/z ¼ 178 (8);
[C3H9Sn]þ, m/z ¼ 165 (33); [C2H6Sn]þ, m/z ¼ 150 (13); [CH3Sn]þ, m/
z ¼ 135 (17); [Sn]þ, m/z ¼ 120 (2); [C25H26N3O4Sn]þ, m/z ¼ 552 (12);
[C24H26N3O2Sn]þ, m/z ¼ 508 (4); [C23H23N3O2Sn]þ, m/z ¼ 493 (5);
[C11H15NO2Sn]þ, m/z ¼ 313 (13); [C10H12NO2Sn]þ, m/z ¼ 298 (6);
[C12H7N2]þ, m/z ¼ 179 (100); [C12H8N2]þ, m/z ¼ 180 (9); [C12H9N2]þ,
m/z ¼ 181 (15).
Serial twofold dilutions were performed by addition of culture
broth to reach concentrations ranging from 200, 100, 50, and 25
mL. The concentration of 100 g/mL was chosen because it yielded
inhibition zones that are wide enough to be measured and suffi-
ciently narrow to be accurately determined. 20 L of each dilution
mg/
m
m
were distributed in 96-well plates, as well as a sterility control and
a growth control (containing culture broth plus DMSO, without
antimicrobial substance). Each test and growth control well was
2.3. DNA interaction study assay by UVevisible spectroscopy
inoculated with 5
mL of a bacterial suspension (108 CFU/mL or
SS-DNA (50 mg) was dissolved by overnight stirring in distilled
water (pH ¼ 7.0) and kept at 4 ꢀC. 20 mM Phosphate buffer
(NaH2PO4eNa2HPO4, pH ¼ 7.2) was prepared in distilled water. A
solution of (SS-DNA) in the buffer gave a ratio of UV absorbance at
260 and 280 nm (A260/A280) of 1.8, indicating that the DNA was
sufficiently free of protein [17]. The DNA concentration was deter-
mined via absorption spectroscopy using the molar absorption
coefficient of 6600 Mꢁ1 cmꢁ1 (260 nm) for SS-DNA [18] and was
found to be 1.4 ꢂ 10ꢁ4 M. The compound was dissolved in 60%
DMSO at a concentration of 1 mM. The UV absorption titrations
were performed by keeping the concentration of the compound
fixed while varying the SS-DNA concentration. Equivalent solutions
of SS-DNA were added to the complex and reference solutions to
eliminate the absorbance of DNA itself. Compound-DNA solutions
were allowed to incubate for about 10 min at room temperature
before measurements were made. Absorption spectra were recor-
ded using cuvettes of 1 cm path length at room temperature
(25 1 ꢀC).
105 CFU/well). All experiments were performed in triplicate and
the microdilution trays were incubated at 36 ꢀC for 18 h. The results
were expressed in micrograms per milliliters [21].
2.5. Antifungal assay
Antifungal activity of the compound was tested against five
fungal strains; Mucor species (FCBP 0400), Aspergillus niger (FCBP
0198), Aspergillus fumigates (FCBP 66), Aspergillus flavous (FCBP
0064) and Fusarium solani (FCBP0291) using the disc diffusion
method [21]. The organisms were cultured on SDA at 28 ꢀC for 24 h.
Autoclaved broth culture (3 mL) was allowed to cool down to room
temperature, poured into sterile Petri plates and the medium was
allowed to solidify. Then 5 mL of the test compound (40 mg/mL in
DMSO) was poured on 4 mm sterile paper discs and placed on SDA
plates. The discs treated with DMSO and Terbinafine were used as
negative and positive controls, respectively. Plates were incubated
at 28 ꢀC for 7 days and fungal growth was determined by measuring
growth diameter (mm) around each well. Growth inhibition was
calculated with reference to the negative control. The MIC value
was noted as lowest concentration at which no growth was
observed.
2.4. Antibacterial assay
The disc diffusion method [19] was used to check the antibac-
terial activity of the synthesized compounds against six bacterial
strains, namely: Staphylococcus aureus (ATCC 6538), Bacillus subtilis
(ATCC 6633), Escherichia coli (ATCC15224), Bordetella bronchiseptica
(ATCC 4617), Salmonella typhimurium (ATCC 14028) and Enter-
obacter aerogenes (ATCC 13048). The organisms were cultured in
nutrient broth at 37 ꢀC for 24 h. 1% broth culture containing approx.
106 colony-forming units (CFU/mL) of test strain was added to
2.6. Brine shrimp lethality assay
The shrimp's lethality bioassay was performed as developed by
Michael et al. [22], and later modified by Sleet and Brendel [23]. It
was based on the ability to kill laboratory-cultured Artemia nauplii
(brine shrimp, Artemia salina). Doxorubicin was used as standard

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
349
drug. A stock solution of 40,000
prepared by dissolving 40 mg of test compound in 1 mL of DMSO.
From this stock solution, further dilutions (0.1 g/mL, 1 g/mL and
10 g/mL) were made by the serial dilution method.
Artificial sea water was prepared using sea salt 34 g/L under
m
g/mL of each test compound was
plasmid double-stranded DNA to open circular and linear forms
[29,30]. Briefly, the pBR322 plasmid DNA was incubated with the
synthesized compounds, FeSO4 and H2O2 at 37 ꢀC for 60 min. FeSO4
and H2O2 were used as a positive control. The assay was performed
m
m
m
at four different concentrations: 1, 10, 100 and 1000
mg/mL.
constant aeration for 48 h at room temperature. Brine shrimp eggs
(Ocean Star Inc., USA) were hatched in shallow rectangular dish
(22 ꢂ 32 cm) filled with prepared sea water, having a plastic
separator of 2 mm in which numerous holes were punched to make
two unequal sections in the dish. The eggs (about 25 mg) were
sprinkled in the larger section, which was darkened (covered with
aluminum foil) whereas the smaller section was illuminated. After
24 h of hatching, phototropic nauplii (brine shrimp larvae) were
collected by pipette from the lightened side. From each stock so-
Following incubation, the samples were immediately loaded on a
0.9% agarose gel (used for analysis of intensity of bands), and elec-
trophoresed for 60 min. After electrophoresis, the gels were visu-
alized and photographed. Quantification of closed-circular and
nicked DNA was performed using the UVP software. The measure-
ment of intensity of DNA protection of compound against hydroxyl
free radical can be explained with the help of following scale.
ꢃ (ꢁ) sign means DNA damage. No super coiled DNA found
ꢃ (þ) sign means low DNA protection. Super coiled DNA < open
circular DNA with or without linear band.
lution (0.1 mg/mL, 1 mg/mL and 10 mg/mL) 25 mL of the test com-
pound was placed in glass vials (25 mL) and 2 mL sea water was
added. 15 shrimps were transferred to each vial after counting
against light background, using Pasteur pipette, and volume was
raised up to 5 mL. The vials were kept under illumination at room
temperature (25e28 ꢀC). After 24 h of incubation, surviving
shrimps were observed with the help of 3ꢂ magnifying glasses. The
experiment was performed in duplicate. In case, where control
death occurred, the data was corrected using Abbott's formula [24]:
ꢃ (þþ) sign means mild DNA protection. Super coiled DNA > open
circular DNA with or without linear band.
ꢃ (þþþ) sign means good DNA protection. Super coiled
DNA > open circular with no linear band.
2.9. Antileishmanial assay
control ꢁ sample
Leishmanial major strain kwh 23 were used for in vitro anti-
leishmanial activity. The strains were incubated at 24 ꢀC as previously
described byNabi etal., with a bit modification [31]. The strainwas left
for 7days in 199mediumcontaining10%Fetal BovineSerum(PAALab,
Gmbh). Before starting the activity, stock solutions of 10,000 ppm of
the samples were prepared in DMSO. The culture containing about
100 promastigote were transferred to 96 well plates. First row of the
Percentage death ¼
ꢂ 100
control
Then LD50 (Lethal Dose that killed 50% of shrimps) was calcu-
lated by using Finny software [25].
2.7. Potato disc antitumor assay
96 wellplates contained 198
mLofculturewhiletheremainingwellsof
Antitumor activity of the synthesized compounds was tested by
performing modified potato disc antitumor assay [26,27]. A 48 h old
bacterial culture of At-10 strain of Agrobacterium tumefaciens, a Gram
negative soil bacterium, was used in this experiment. This assay was
performed with inoculums at four concentrations of test samples
the plate contained 180 L of culture. About 2 m
of each samples was transferred to first row of the plate to obtain a
200 ppm concentration. The concentrationswere then serially diluted
by transferring 20 mL to each well and then 20 mL were discarded from
the last wells. The DMSO concentrations were kept <5% which has no
toxic affect on the culture [32]. Negative and positive controls were
maintained containing DMSO and drug Amphotericin B, respectively.
The experiments were repeated 3 times and kept at 24 ꢀC for 72 h.
After required time the mortality rates were recorded by transferring
20 mL of the culture to the improved neobar counting chamber under
light microscope. For IC50 calculation the data were statistically
analyzed by Probit regression analysis on SPSS version 16.
m
L of the stock solution
(1000, 100, 10 and 1 mg/mL), containing bacterial culture and 1.5 mL
autoclaved distilled water. Red-skinned potatoes were surface ster-
ilized in 0.1% HgCl2 solution, washed three times with autoclaved
distilled water, and potato discs of size 8 mm ꢂ 4 mm were prepared
using a sterilized cork borer. Autoclaved plain agar solution (1.5%)
was poured into Petri plates and allowed to solidify. Ten discs were
placed on the agar surface of each Petri plate, and 50 mL of inoculum
was placed on the surface of each disc. The plates were sealed with
parafilm to avoid contamination and moisture loss and were incu-
bated at 28 ꢀC in dark. The experiment was carried out in triplicate
and in strict aseptic conditions. After 21 days of incubation, discs
were stained with Lugol's solution (10% KI and 5% I2) and tumors
were counted on each disc using dissecting microscope. Percent tu-
mor inhibition was calculated by the following equation [28]:
3. Results and discussion
3.1. FT-IR spectra
FT-IR data of organotin(IV) derivatives reveal valuable infor-
mation about the structures of the complexes in the solid state.
ꢀ
Average number of tumors in sample
Percent inhibition ¼ 100 ꢁ
ꢁ
ꢂ 100
Average number of tumors in negative control
2.8. Gel electrophoresis assay
Comparing the FT-IR spectrum of the free ligands with those of the
complexes showed the disappearance of the hydrogen from hy-
droxyl group at 3200 cmꢁ1 indicating the complexation through
the oxygen atom. The carboxylate groups in the organotin(IV) de-
rivatives generally adopt a bridged structure in the solid state
This assay was carried out to check the DNA protection potential
of the compound against (OHꢁ) free radical. The pBR322 plasmid
DNA strand breaks were measured by the conversion of super coiled

350
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
unless the organic substituents at tin are bulky or the carboxylate
group is branched at the -carbon [33e35]. The values of Dn Dn
(COOasym) ꢁ (COOsym)] can be divided into 3 groups; (a) In
for tetracoordinated tin compounds,
q
ꢄ 112ꢀ, for pentacoordinated
a
[
¼
n
tin,
q
¼ 115e130ꢀ and for hexacoordinated tin,
q
¼ 129e176ꢀ [41].
n
The methyl protons in trimethyltin(IV) complex (1) give a charac-
teristic signal at 0.38 ppm with 2J[119/117Sne1H] ¼ 70, 68 Hz which
indicates 5-coordinate geometry (trigonal bipyramidal geometry)
around the tin atom in solution [41]. The protons of triethyltin(IV)
compounds where Dn > 350 cmꢁ1, the carboxylate group binds in a
monodentate fashion. However, other very weak intra- and inter-
molecular interactions cannot be excluded. (b) When
Dn < 200 cmꢁ1, the carboxylate groups of these compounds can be
considered to be bidentate. (c) In compounds where Dn > 200 cmꢁ1
and <350 cmꢁ1 an intermediate state between monodentate and
bidentate (anisobidentate) occurs. It has also been suggested that
the Dn value in the chelating mode is less than that in a bridging
mode [36,37]. It has been found in literature that when the struc-
ture changes from four to five or higher coordinated symmetry, the
complex (2) give two peaks: a quartet for Ha and a triplet for Hb. In
the case of butyl groups, a clear triplet is observed for terminal
methyl groups at 0.87 and 0.84 ppm for complexes (3) and (8),
respectively while the protons of other carbon atoms appear as a
complex multiplet pattern. The aromatic protons in PheSn appear
in the range 7.91e7.15 and 7.90e7.37 ppm, respectively in com-
pounds 4 and 9 [40]. The protons of the cyclohexyl derivatives
(complex 5) give multiplets in aliphatic regions. The methyl protons
in the dimethyltin(IV) complex (7) give a signal at 0.73 ppm and 2J
n
(COOsym) frequencies shift to lower and n (COOasym) to higher
frequencies which cause decrease in the Dn value in compounds
[38]. The magnitude of Dn for the reported complexes is in the
range of 126e202 cmꢁ1 which reflects either chelating or bidentate
nature of the ligand. Thus, a decrease in the Dn values are observed
in this complex compared to the corresponding free acid. The Dn
value was also calculated from single crystal XRD data for HL,
complexes 1, 2, 3 and 6 by using the following equation [39]:
[
119Sne1H] for dimethyltin(IV) derivatives were found to be 100 Hz
that falls in the range of 6-coordinated octahedral geometry. H of
a
the benzyl group (complexes 6 and 10) gives a singlet while the
aromatic protons appear in their respective regions. The methyl
protons of the tertiary butyl group in complex 11, {C(CH3)3}, appear
as a singlet at 1.23 ppm. In case of octyltin(IV) complex (12), a
somewhat different and complex pattern is observed for the
methylene protons. The terminal protons give a triplet while the
remaining protons give broad and complex signals.
Dn ¼ 1818:1dr þ 16:47ðqOCO e 120Þ þ 66:8
The 13C NMR data of the ligand and their complexes were in
agreement with the 1H NMR and FT-IR data for the formation of
complexes. The C1 and C4 of the complexes were shifted downfield
compared with the position in the free ligand due to the decrease of
electron density at carbon atoms when oxygen is bonded to an
electropositive tin atom [40]. This observation provides further
evidence that the complexation occurred through the oxygen
atoms of the carboxylate group. However, the signals for eCeNe,
and eCH2eCH2e peaks for the alkyl as well as aryl groups attached
to the tin atom appeared in their specific regions [42]. The positions
of the phenyl carbons of ligand undergo minor changes in the
complex as compared to those observed in free ligand. In the tri-
methyltin complex (1), the coupling constants 1J[119/117Sne13C]
were observed at 523, 400 Hz that fall in the range of 5-coordinate
trigonal bipyramidal geometry. This is further supported by the
CeSneC bond angle (Table 1) calculated from 1J[119Sne13C] value
using the Lockhart equation [43] which is for complex 1 is 122.7ꢀ
that falls in range of 5-coordinated geometry around the tin
where
OCO is the OeCeO angle (◦).
A good correlation was found between the Dn value calculated
dr is difference between the two CeO bond lengths (Å) and
q
from FT-IR data (306, 141, 170, 180 and 202 for HL, complexes 1, 2, 3
and 6, respectively) and single crystal XRD data (317, 146, 177, 180
and 208 for HL, complex 2, 3 and 6, respectively).
Similarly the appearance of new peaks for
of 586e521 cmꢁ1 (for alkyl-Sn), 280e267 cmꢁ1 (for phenyl-Sn) and
for
(SneO) in the range of 481e444 cmꢁ1, respectively confirms
the synthesis of the new complexes [40]. The (NeH) band in the
spectrum of the ligand at 3368 cmꢁ1 is also present in the spectra of
the complexes in the range of 3434e3368 cmꢁ1
n (SneC) in the range
n
n
.
3.2. Multinuclear (1H, 13C and 119Sn) NMR spectroscopy
3.2.1. 1H and 13C NMR spectroscopy
The 1H NMR studies of compounds provide further support for
the formation of compounds. The characteristic peak for the OH
bond in the spectrum of the ligand at 12.12 ppm is not present in
spectra of the complexes consistent with complexation of the
deprotonated ligand to organotin(IV) species through oxygens of
carboxylate group. There is no significant change in the position of
the NH signal in the spectra of the complexes indicating that ni-
trogen is not involved in coordination to tin. The phenyl proton at
position 6 (H6) appears as a doublet (d) at 7.98 ppm (HL) and from
8.00 to 8.04 ppm in complexes with 3J(1H, 1H) ¼ 7.8 Hz. Proton at
position 8 (H8) appears as a doublet of doublets (dd) at 6.91 ppm
(HL) and from 6.88 to 6.91 ppm in complexes. Protons at positions 7
and 9 (H7 and H9) appear as a multiplet in the range of
7.08e7.00 ppm. A small upfield shift is observed for protons H7 and
H9 which is probably due to the ring current effect.
(
q
¼ 115e130ꢀ) [44]. For complex 6 the CeSneC bond angle
(Table 1) calculated from 1J[119Sne13C] value using the Lockhart
equation [43] is 119.2ꢀ that is comparable to that observed in single
crystal X-ray (119.6ꢀ). In case of complex 7, the CeSneC value
calculated from 2J[119/117Sne1H] coupling is 166.2 consistent with 6-
coordinate geometry in solution state for diorganotin(IV) de-
rivatives [45]. The ipso carbon (Ca) of the phenyl group attached to
tin(IV) (complexes 5 and 9) appears in the range of 5-coordinate
Table 1
(CeSneC) angles (ꢀ) based on NMR parameters of selected organotin(IV) derivatives.
Comp. no
1J(119Sn, 13C)
2J(119Sn, 1H)
Angle (ꢀ)
According to literature, coordination patterns of tin(IV) in di-
(Hz)
(Hz)
1J
2J
and tri-methyltin(IV) derivatives with the 1J[119Sne13C] and 2J
[
119Sne1H] coupling constant values are as follows: in tetra-
1
2
3
4
5
6
7
13
14
524
490
488
629
512
483
e
70
e
123
118
coordinated tin compounds 1J values are predicted to be smaller
than about 400 Hz, whereas 2J values should be below 59 Hz; for
pentacoordinated tin, 1J values fall in the range of 450e670 Hz and
2J values fall in the range of 65e80 Hz; finally, for hexacoordinated
tin 1J and 2J values are generally larger than 670 and 83 Hz,
respectively [41]. Another important parameter that decides the
120
e
e
123
e
115
e
e
121.7
119.1
e
e
61
102
70
70
100
166
118
118
521
525
122.5
122.9
geometry around the tin atom is
q (CeSneC angle). Its values are:

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
351
Table 2
Crystal data and structure refinement parameters for HL, 1, 2, 3 and 6.
Parameters
HL
Complex 1
Complex 2
Complex 3
Complex 6
Empirical formula
Formula weight
C11H13NO4
223.22
0.71073
C14H21NO4Sn
386.01
0.71073
C17H27NO4Sn
428.08
0.71073
C23H39NO4Sn
512.24
1.5418
C32H33NO4Sn
614.28
0.71073
Wavelength (
l
/Aꢀ)
Temperature/K
Crystal system
Space group
a/Å
296(2)
Orthorhombic
Pbca
11.9448(9)
10.0633(8)
18.2987(18)
90, 90, 90
2199.6(3)
8
1.348
0.103
944.0
0.35 ꢂ 0.3 ꢂ 0.25
4.46e52ꢀ
8785
150(2)
Monoclinic
C2/c
12.473(2)
9.6832(16)
26.208(4)
90, 100.269(2), 90
3114.7(9)
8
1.646
1.652
1552.0
0.47 ꢂ 0.42 ꢂ 0.16
3.158e61.144ꢀ
18,215
150(2)
Monoclinic
P21/c
14.595(4)
9.877(3)
14.236(4)
90, 115.062(5), 90
1859.0(10)
4
1.530
1.393
872.0
0.17 ꢂ 0.09 ꢂ 0.03
3.08e52.434ꢀ
15,653
190(2)
Monoclinic
P21/n
18.2080(5)
10.3193(2)
27.3873(8)
90, 98.580(2), 90
5088.3(2)
8
1.337
8.189
2128.0
0.15 ꢂ 0.1 ꢂ 0.04
6.28e124.56ꢀ
27,410
296(2)
Monoclinic
P21/n
14.0610(4)
10.6556(3)
19.7087(7)
90, 101.761(10), 90
2890.93(16)
4
1.411
0.920
1256.0
0.32 ꢂ 0.22 ꢂ 0.2
3.27e55.694ꢀ
25,738
b/Å
c/Å
ꢀ
a
,
b
,
g/
Volume/Å3
Z
rcalcmg/mm3
m/mmꢁ1
F(000)
Crystal size/mm3
2
Q range for data collection
Reflections collected
Independent reflections
2161 [Rint ¼ 0.0277,
Rsigma ¼ 0.0235]
2161/0/148
1.050
4772 [Rint ¼ 0.0514,
Rsigma ¼ 0.0475]
4772/0/184
1.013
3714 [Rint ¼ 0.1360,
Rsigma ¼ 0.1138]
3714/0/212
0.986
8016 [Rint ¼ 0.0355,
Rsigma ¼ 0.0354]
8016/0/523
1.024
6835 [Rint ¼ 0.0340,
Rsigma ¼ 0.0339]
6832/0/344
1.003
Data/restraints/parameters
Goodness-of-fit on F2
Final R indexes [I ꢅ 2
s
(I)]
R1 ¼ 0.0389,
R1 ¼ 0.0323,
R1 ¼ 0.0601,
R1 ¼ 0.0369,
R1 ¼ 0.0286,
wR2 ¼ 0.1019
wR2 ¼ 0.0652
wR2 ¼ 0.1106
wR2 ¼ 0.0962
wR2 ¼ 0.0612
geometry [46,47]. The CH3eSn signal in complex 7 is broadened
and 1J(13Ce119Sn) coupling cannot be determined accurately from
the spectrum. For complexes 13 and 14 some additional peaks
appear in both in 1H and 13C NMR spectra for 2,2-bipyridine and
1,10-phenanthroline protons and carbons.
(ꢁ18.8 ppm), 3 (ꢁ17.6 ppm), 13 (ꢁ10.1 ppm), 14 (ꢁ11 ppm) is
caused by the influence of electron withdrawing and donating
ability of the groups attached to ligand as well as electronegativity
of the substituent at the tin atom. If the substituent has lone-pair
electrons or
p electrons of multiple bonds, then an increase in
119Sn shielding will be observed due to the partial filling of the
empty 5d orbital of the tin atom (dep or dpepp interaction). The
combination of these competitive effects leads to the tin shielding
minimum for the series Sn(CH3)3, Sn(C2H5)3, Sn(C4H9)3 [48,49]. The
values of 119Sn NMR for complexes 4, 5 and 6 fall in the normal
range of 5-coordinated geometry. In case of diorganotin(IV) de-
rivatives (complexes 7e12) the 119Sn NMR values range
from ꢁ256.7 ppm to ꢁ298.7 ppm falling in the range of 6-
coordinate geometry.
3.2.2. 119Sn NMR spectroscopy
119Sn NMR spectroscopy is one of the most potent methods for
the study of molecular structure and bonding in organotin com-
pounds. This is due to the wide range of tin chemical shifts and to
the strong dependence of tin chemical shifts upon the substituent
groups and intermolecular effects [48,49]. The low field displace-
ment of tin chemical shifts in case of complexes 1 (ꢁ10.2 ppm), 2
3.3. X-ray crystallography
Table 3
Selected bond lengths (Å) for HL, 1, 2, 3 and 6.
Crystal data and structure refinement parameters for all six
structures are shown in Table 2 while the selected bond lengths and
bond angles are given in Table 3.
Bond lengths for HL
O1eC1
C1eC2
N1eC4
1.305(2)
1.498(2)
1.338(2)
O2eC1
C2eC3
N1eC5
1.196(2)
1.522(2)
1.417(2)
Bond lengths for complex 1
O-1eSn1
O2eSn1
C1eC2
2.3333(17)
C12eSn1
C13eSn1
C14eSn1
C1eO2
2.132(2)
2.128(3)
2.129(2)
1.271(3)
2.2149(17)
1.510(3)
1.251(3)
C1eO1
Bond lengths for complex 2
O1eSn1
O2eSn1
C1eC2
2.199(6)
C12eSn1
C14eSn1
C16eSn1
C1eO2
2.138(3)
2.135(9)
2.143(9)
1.24(1)
2.351(6)
1.50(1)
1.28(1)
C1eO1
Bond lengths for complex 3
O1eSn1
O2eSn1
C1eC2
2.185(2)
C12eSn1
C16eSn1
C20eSn1
C1eO2
2.138(5)
2.137(4)
2.128(4)
1.246(4)
2.392(2)
1.505(5)
1.279(4)
C1eO1
Bond lengths for complex 6
O1eSn1
O2eSn1
C1eC2
2.156(2)
C19eSn1
C12eSn1
C26eSn1
C1eO2
2.149(3)
2.138(3)
2.141(2)
1.230(3)
2.451(2)
1.507(3)
1.275(3)
Fig. 1. A perspective view of the HL molecule showing the crystallographic numbering
scheme. All H-atoms have been omitted for clarity.
C1eO1

352
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
Fig. 2. Packing diagram with unit cell of HL viewed along b-axis. Hydrogen bonds are shown as dashed lines and H atoms have been omitted for clarity.
3.3.1. HL
N-[(2-methoxyphenyl)]-4-oxo-4-[oxy]butanamide, crystallizes
Table 4
as a monomer in the orthorhombic space group Pbca. The molec-
ular structure is shown in Fig. 1 while its unit cell packing is shown
in Fig. 2. Crystal data and structure refinement parameters are
shown in Table 2 while selected bond lengths and bond angles are
given in Tables 3 and 4, respectively. The conformations of the NeH
and the C]O bonds in the amide segment are anti to each other. In
the side chain, the amide C]O bond is anti to the adjacent CeH
bond, while the carboxyl C]O bond is syn to the adjacent CeH
Selected bond angles (ꢀ) for HL, 1, 2, 3 and 6.
Bond angles for HL
O1eC1
C1eC2
N1eC4
O1eC1
C1eC2
N1eC4
O1eC1
C1eC2
N1eC4
O1eC1
C1eC2
N1eC4
Bond angles for complex 1
O1eSn1eC12
O1eSn1eC13
O1eSn1eC14
O1eSn1eO2
O1eC1eO2
85.43(8)
C12eSn1eO2
C13eSn1eO2
C14eSn1eO2
C12eSn1eC13
C12eSn1eC14
C13eSn1eC14
88.26(8)
94.22(9)
94.13(8)
117.28(10)
118.75(10)
123.50(11)
87.58(8)
90.01(8)
173.57(6)
122.3(2)
120.2(2)
O1eC1eC2
Bond angles for complex 2
Table 5
Hydrogen-bond angles and bond lengths (Å,ꢀ) for HL, 1, 2, 3 and 6.
O1eSn1eC12
O1eSn1eC14
O1eSn1eC16
O1eSn1eO2
O1eC1eO2
93.5(3)
91.3(3)
93.8(3)
174.8(2)
122.3(8)
117.0(7)
C12eSn1eO2
C14eSn1eO2
C16eSn1eO2
C12eSn(1)eC14
C12eSn1eC16
C14eSn1eC16
90.1(3)
83.7(3)
86.9(3)
115.0(3)
128.7(3)
115.5(3)
DeH/A
DeH
H/A
D/A
DeH/A
HL
O1eH1/O3i
N1eH1A/O4
C6eH6/O3
Complex 1
C11eH11/O3i
Complex 3
N1eH1/O4
N2eH2/O8
Complex 6
C6eH6/O3i
0.82
0.86
0.93
1.80
2.23
2.28
2.606(2)
2.6028(2)
2.841(2)
167.0
106.0
118.0
O1eC1eC2
Bond angles for complex 3
O1eSn1eC12
O1eSn1eC16
O1eSn1eC20
O1eSn1eO2
O1eC1eO2
96.6(1)
88.6(1)
95.6(1)
173.8(9)
122.7(3)
116.3(3)
C12eSn1eO2
C16eSn1eO2
C20eSn1eO2
C20eSn1eC16
C20eSn1eC12
C16eSn1eC12
87.8(1)
85.4(1)
85.8(1)
118.7(2)
121.4(2)
118.7(2)
0.98
2.41
3.201(4)
137.4
0.86
0.86
2.19
2.17
2.606(5)
2.569(6)
110.0
108.0
O1eC1eC2
Bond angles for complex 6
0.93
2.30
2.882(4)
120.0
O1eSn1eC12
O1eSn1eC19
O1eSn1eC26
O1eSn1eO2
O1eC1eO2
95.8(8)
96.3(9)
91.7(8)
169.3(6)
123.6(2)
114.6(2)
C12eSn1eO2
C19eSn1eO2
C26eSn1eO2
C19eSn1eC26
C12eSn1eC19
C12eSn1eC26
88.4(8)
90.1(9)
77.7(8)
118.5(1)
119.5(1)
120.1(1)
Symmetry transformations used to generate equivalent atoms for HL: (i)
3/2 ꢁ x,1/2 þ y,þz.
Symmetry transformations used to generate equivalent atoms for complex 1: (i)
1/2 þ x,ꢁ1/2 þ y,þz.
Symmetry transformations used to generate equivalent atoms for complex 6: (i)
1/2 ꢁ x,ꢁ1/2þy,1/2 ꢁ z.
O1eC1eC2

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
353
Fig. 3. Polymeric structure of R3SnL.
bond. The observed rare anti conformation of the C]O and OeH
bonds of the acid group is similar to that examined in N-(4-
Methoxyphenyl)maleamic acid [50]. There is an intramolecular
CeH—O and NeH—O interaction within the polymeric chain of the
HL. An intermolecular CeH—O interaction along b-axis links the
polymeric chains in zigzag form (Fig. 2) which are linked into a
one-dimensional polymeric chain [51]. The geometry around the tin
atom is distorted trigonal bipyramidal. The values of
t
(
t
¼ (
b
ꢁ
a
)/
60, where is the largest basal angle around the tin atom while
b
a
is
the next largest angle around the tin atom) for the complexes 1, 2, 3,
and 6 are 0.83, 0.80, 0.87 and 0.82, respectively that are typical for
distorted trigonal bipyramidal geometry [52]. The geometry around
the tin atom is defined by three R groups and two oxygen atoms. The
three R groups occupy the equatorial positions with essentially
identical bond distances [SneC ¼ 2.125e2.149 Å]. The OeSneO
angle is approximately linear [OeSneO ¼ 169.33e174.8ꢀ]. The
CeSneC and OeSneC angles are within the expected range of values
[CeSneC ¼ 115.5(18)ꢀe121.43(19)ꢀ and OeSneC ¼ 85.40e96.34ꢀ]
[53]. The sum of the CeSneC angles in the equatorial plane equals
359.5ꢀ, 359.5ꢀ, 359.3ꢀ and 358.1ꢀ, respectively for complexes 1, 2, 3,
6, indicating slight distortion. This distortion from ideal trigonal
bipyramidal geometry is found in the axial angle [OeSneO]. The
intramolecular SneO1 separation of 2.333(17) Å, 2.199(6) Å,
2.184(3) Å, 2.156(2) Å, respectively for complexes 1, 2, 3, 6 is
significantly shorter than the intermolecular SneO2 distance of
2.215(17) Å, 2.351(6) Å, 2.392(3) Å, 2.451(2) Å, respectively for
complexes 1, 2, 3, 6. The asymmetric SneO separations are reflected
in the associated CeO1 and CeO2 distances of 1.251(3) Å,1.280(1) Å,
1.278(5) Å, 1.257(3) Å and 1.271(3) Å, 1.24(1) Å, 1.246(5) Å,
1.230(3) Å, respectively for complexes 1, 2, 3, 6 [54]. The Sn1eO1,
Sn1eO2 (another Sn atom bonded by O2 of the bridging carboxylate
ligand) bond distances involving the bridging carboxylate ligand are
exactly same indicating a symmetrical bridge. The anisobidentate
bidentate carboxylate has a difference of 0.058 Å between its CeO
bonds while for the bidentate carboxylate this difference is only
0.021 Å; the variations in the CeO bond distances suggest charge
delocalization over the carboxylate group COO. The different modes
of bonding of the acetates, i.e., bridging or chelating, are thus easily
differentiated by the relevant bond lengths [55]. There is an intra-
molecular CeH—O (O of amide carbonyl group) interaction within
the polymeric chain. An intermolecular CeH—O interaction links the
polymeric chains into sheets form (Figs. 7 and 9) or zigzag form
(Figs. 5 and 11) which are linked into a three-dimensional network
three-dimensional network via CeH—p interactions. The detail of
intramolecular H-bonds is given in Table 5.
3.3.2. Complexes 1, 2, 3 and 6
The general polymeric structure of R3SnL is shown in Fig. 3. The
perspective diagrams of the complexes 1, 2, 3 and 6 are given in
Figs. 4, 6, 8 and 10 while their unit cell packing diagrams are shown
in Figs. 5, 7, 9 and 11, respectively. Crystal data and structure
refinement parameters are shown inTable 2 while the selected bond
lengths and bond angles are given inTables 3 and 4, respectively. The
presence of a bidendate ligand, 4-(2-methoxyphenylamino)-4-
oxobutanoate, leads to the formation of the polymeric structure.
In other words, the central R3Sn (R ¼ CH3, C2H5, C4H9 and C7H7)
group bridges the two neighboring 4-(2-methoxyphenylamino)-4-
oxobutanoate ligands via carboxylate (Fig. 3) moieties to form
via CeH—
p interactions. The details of intramolecular H-bonds
existing within the structure are given in Table 5.
3.4. Mass spectrometry
The general fragmentation patterns for HL, tri- and di-organo-
tin(IV) complexes are shown in Schemes 4e6, respectively. In the
mass spectrum of HL the molecular ion peak undergoes the elim-
ination of a water molecule generating a mass fragment of m/
Fig. 4. A perspective view of the complex 1 showing the crystallographic numbering
scheme. All H-atoms have been omitted for clarity.

354
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
Fig. 5. Packing diagram with unit cell of complex 1 viewed along b-axis.
z ¼ 205 that further undergoes the elimination of 2CO and C2H2
molecules to give base peak of m/z ¼ 123. The base peak undergoes
fragmentation in two different ways: in one case it gives a mass
fragment of m/z ¼ 108 by the elimination of NH fragment while in
second way it gives a mass fragment of m/z ¼ 92 by the elimination
of OCH3 and H. [MNa]þ fragment of 45% intensity is also observed.
In the mass spectra of all the compounds, each fragment ion
occurs in a group of peaks as a result of tin isotopes. For simplicity
the mass spectral fragmentation data reported here are related to
the principal isotope 120Sn [56]. The low-intensity molecular ion
peaks, Mþ were observed in all synthesized organotin carboxylates
(1e12). Also, the [MNa]þ Fragment is observed in all spectra. The
fragmented ions are in good agreement with the expected structure
of the compounds and consistent with the literature [57,58].
In triorganotin compounds, three primary fragmentation pat-
terns are proposed, based on observed m/z in their spectra. Elimi-
nation of different groups like COOR0 and R, gave [Sn]þ as end
product in one of the pathways. The other two pathways after
primary elimination of [R]þ and [R3Sn]þ groups and then elimina-
tion of COO and successive R (in one of the pathway) results in the
formation of [R']þ, which shows similar pattern for the further
elimination of different groups [59].
A bit different scheme of mass fragmentation pattern has been
suggested for the diorganotin compounds but these pathways end
up in similar manner as suggested for the triorganotin compounds.
In addition, the following ions: [C4H9]þ, [C6H5]þ, [C7H7]þ, and
[C8H17]
þ are also observed with reasonable intensities in the mass
spectra of all organotin(IV) derivatives [59].
3.5. DNA binding study by UVevisible spectroscopy
Electronic absorption spectra were initially used to examine the
interaction between the compounds and SS-DNA. Figs. 12 and 13
(also Figs. S1eS5: Supplementary data) show the UVevisible
spectra observed when representative compounds interact with
different concentrations of DNA. It was observed that all
Fig. 6. A perspective view of the complex 2 showing the crystallographic numbering
scheme. All H-atoms have been omitted for clarity.

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
355
Fig. 8. A perspective view of the complex 3 showing the crystallographic numbering
scheme. All H-atoms have been omitted for clarity.
hence results hypochromic shift. Since hypochromism due to pep*
stacking interactions may appear in the case of the intercalative
binding mode, while bathochromism may be observed when the
DNA duplex is stabilized [1,63].
Based upon the variation in absorbance, the intrinsic binding
constant of the compound with DNA were determined according to
BenesieHildebrand equation [64]:
A0
εG
εG
1
¼
þ
ꢂ
A ꢁ A0 εHꢁG ꢁ εG εHꢁG ꢁ εG K½DNAꢆ
where K is the association/binding constant, Ao and A are the ab-
sorbances of the compound and its complex with DNA, respec-
tively, and εG and εHꢁG are the absorption coefficients of the
compound and the compound-DNA complex, respectively. The
association constants were obtained from the intercept-to-slope
ratios of Ao/(A ꢁ Ao) vs. 1/[DNA] plots. The Gibb's free energy (
DG)
was determined from the equation:
Fig. 7. Packing diagram with unit cell of complex 2 viewed along b-axis.
DG ¼ ꢁRT ln K
where R is general gas constant (8.314 JKꢁ1 molꢁ1) and T is the
temperature (298 K). The binding constants and calculated Gibb's
free energies are given in Table 6.
From the interaction study with SS-DNA it is concluded that the
synthesized compounds could be used as an anticancer drug.
compounds have one strong absorption peak at 280e283 nm. In
case of compound 4 a shoulder at 267.40 nm also appeared. After
interaction with increasing amounts of DNA, all the peaks
decreased gradually and there was a minor red shift of upto 1 nm
for all compounds. Long et al. [60], have pointed out that the peak
shift of the small molecules after they interacted with DNA could be
clues to judge the binding mode between the small molecules and
DNA. If the binding involves a typical intercalative mode, an
hypochromism (decrease in absorption or molar absorptivity) ef-
fect coupled with obvious bathochromism (shift of wavelength
toward longer wavelength side, i.e. red shift) for the characteristic
peaks of the small molecules will be found due to the strong
stacking between the chromophore and the base pairs of DNA
[61,62]. Therefore, based on this viewpoint, the interaction between
compounds and SS-DNA could be noncovalent intercalative bind-
3.6. Biological activities
3.6.1. Antibacterial activity
Invitro antibacterial screening tests of the synthesized ligand and
its organotin(IV) derivatives were carried out against 6 bacterial
strains; 2 g-positive [B. subtilis, and S. aureus] and 4 g-negative [E.
coli, B. bronchiseptica, S. typhimurium, Enterobacter aerogens]. The
disc diffusion method [21,22] was used in this assay and each
experiment was performed in triplicate. Readings of the zone of
inhibition represent the mean value of 3 readings, which are shown
in Table 7. Roxithromycin and Cefixime were used as standard drugs
in these assays. The data obtained show that the synthesized com-
pounds have antibacterial activity. Compounds 1, 2, 7,11 and 13 have
maximum antibacterial activity against all 6 strains. Their activity is
ing. After intercalating the base pairs of DNA, the
intercalated ligand could couple with orbital of base pairs, thus
decreasing the * transition energy, and further resulting in the
bathochromism. On the other hand, the coupling of a orbital with
partially filled electrons decreases the transition probabilities
p* orbital of the
p
pep
p

356
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
Fig. 9. Packing diagram with unit cell of complex 3 viewed along b-axis.
Fig. 10. A perspective view of the complex 4 showing the crystallographic numbering scheme. All H-atoms have been omitted for clarity.
even higher than the standard drugs (Roxithromycin and Cefixime).
Some of the compounds have no activity against some strains but
show good activity against the other strains. MIC (minimum inhib-
itory concentration) values for each compound against each strain
are shown in Table 8. The antibacterial activity and inhibition zone
around the tested compounds can be caused by their bactericide
effects (killing the bacteria) or from their bacteriostatic effects
(inhibiting multiplication of bacteria by blocking their active sites on
surface or inside bacterial cell). Comparing the biological activity of
the ligand and its organotin(IV) complexes with the standard drugs,
it is observed that the synthesized compounds have good activity
against the studied bacterial strains. A pictorial representation of

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
357
Fig. 11. Packing diagram with unit cell of complex 6 viewed along c-axis.
Scheme 4. General fragmentation pattern of HL.
Scheme 5. General fragmentation pattern of triorganotin(IV) complexes.

358
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
Scheme 6. General fragmentation pattern of diorganotin(IV) complexes.
Fig. 12. Absorption spectrum of 1 mM compound 2 in the absence (a) and presence of 9 (b), 18 (c), 27 (d), 36 (e), 45 (f), 54 (g), 63 (h), 72 (i), 81 (j) and 90 (k)
m
M DNA. The arrow
indicates the increasing conc. of DNA. The inset graph represents the plot of Ao/A ꢁ Ao vs. 1/[DNA] (
m
M)ꢁ1 for the calculation of binding constant (K) and Gibb's free energy (
DG).

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
359
Fig. 13. Absorption spectrum of 1 mM compound 5 in the absence (a) and presence of 9 (b), 18 (c), 27 (d), 36 (e), 45 (f), 54 (g), 63 (h), 72 (i), 81 (j) and 90 (k)
indicates the increasing conc. of DNA. The inset graph represents the plot of Ao/A ꢁ Ao vs. 1/[DNA] (
m
M DNA. The arrow
m DG).
M)ꢁ1 for the calculation of binding constant (K) and Gibb's free energy (
zone of inhibition of antibacterial activity of one the representative
It is concluded from the antibacterial and antifungal activities
compound is shown in Fig. S6 (supplementary data).
that some of the synthesized compounds show good antibacterial
and antifungal activities even higher than the standards so they can
be used as a potent antimicrobial drug.
3.6.2. Antifungal activity
All synthesized compounds were also subjected to in vitro
antifungal activity testing against 4 fungal strains [Mucor species, A.
niger, Aspergillus flavus and Aspergillus fumigatus] using the disk
dilution method [65]. The results are shown in Table 9. Turbinafine
was used as the reference drug. All the compounds, except HL and
12, have shown antifungal activity against the various strains.
Compound 3 shows higher activity than the reference drug. Their
MIC values against each strain are given in Table 10. A pictorial
representation of zone of inhibition of antifungal activity of one the
representative compound is shown in Fig. S7 (supplementary data).
Percentage inhibition and MIC value of biological active samples
was evaluated by following formula:
3.6.3. Cytotoxic activity
This assay is used for preliminary screening which shows
cytotoxic effects as well as wide range of pharmacological activ-
ities, i.e., pesticidal, anticancer, and antifungal activities [9]. The
cytotoxic activity of ligand HL and its organotin(IV) complexes
(1e14) were studied in vitro against the brine shrimp lethality
method by using Doxorubicin as a standard drug and the results
are summarized in Table 11. The data is based on mean value of 2
duplicates. The mechanism of toxic effect of organotin(IV) com-
pounds is quite complicated, and it cannot be regarded as thor-
oughly studied. It is assumed that these compounds are capable of
reacting with cell membranes, finally leading to their decay, speed
up the ion exchange processes, and inhibiting oxidative and
photochemical phosphorylation. Generally, among RnSnX4-n com-
pounds, the most toxic are the R3SnX [66]. Toxicity in the R3Sn
series is related to total molecular surface area and to the octa-
nol:water partition coefficient, KOW, which is a measure of hy-
drophobicity. The high lipid solubility of organotins ensures cell
penetration and association with intracellular sites, while cell wall
components also play an important role [67]. Also the
donoreacceptor interactions between the organotin species and
the target organism played an important role in the toxicity
mechanism [68]. The brine shrimp cytotoxicity assay is considered
as a useful tool for preliminary assessment of toxicity. Cytotoxicity
can be considered significant if the LD50 value is less than
Percent inhibition of fungal growth
ꢀ
ꢁ
Growth diameter in test compoundðmmÞ
Growth diameter in controlðmmÞ
¼
ꢂ 100
Table 6
Overall binding constant and Gibb's free energy data of the selected compounds.a
Compound no.
K (Mꢁ1
)
ꢁ
D )
G (KJ molꢁ1
HL
1
2
3
4
5
9
12
8.26 ꢂ 103
9.9 ꢂ 103
1.19 ꢂ 104
1.24 ꢂ 104
1.25 ꢂ 104
1.81 ꢂ 104
8.7 ꢂ 103
3.85 ꢂ 103
22.34
22.80
23.25
23.35
23.37
24.3
20e30
cancer cells are rapidly dividing and multiplying. In the present
study the LD50 value for the tested compounds is less than 4 g/mL
mg/mL [69]. Cytotoxic drugs work best in cancers where the
22.6
20.5
m
(except compound 12) so they can be consider as cytotoxic. Thus
these compounds can also used for the treatment of cancer.
a
Numbering of compounds is in accordance to Scheme 2.

360
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
Table 7
Zone of inhibition (mm) of antibacterial activity of HL and its organotin(IV) derivatives.a
Compound no.
E. coli
S. aureus
E. aerogens
S. typhimurium
B. bronchiseptica
B. subtilis
HL
1
2
3
4
5
16
26
34
0
0
9
11
25
28
12
0
0
20
22
18
11
0
8
23
26
0
0
8
9
26
38
12
32
0
10
27
36
19
0
0
0
6
7
8
9
10
11
12
13
16
16
17
14
16
24
10
16
13
24
14
17
17
14
16
20
17
0
20
10
26
14
13
21
27
15
14
40
0
18
14
10
12
15
16
17
0
13
19
20
11
19
30
11
19
7
13
18
22
17
11
40
9
20
16
25
10
0
26
12
28
10
26
16
14
Cefiximeb
Roxithromicineb
13
19
a
Numbering of compounds is in accordance to Scheme 2.
Reference drugs.
b
3.6.4. Antitumor activity
antitumor activity that the synthesized compounds might be used
as a potent antitumor as well anticancer agent.
The antitumor activity of the synthesized compounds was
studied using the potato disc bioassay technique. Minimum
inhibitory concentration (MIC) of samples on A. tumefaciens are
shown in Table 12. The exact mechanism of action is not known but
antitumor properties of organotin(IV) compounds are due to inhi-
bition of mitochondrial oxidative phosphorylation (the process of
the synthesis of ATP by phosphorylation of ADP for which energy is
obtained by electron transport and which takes place in the mito-
chondria during aerobic respiration) [64,70]. The A. tumefaciens-
induced potato disc tumor assay is an effective indicator of anti-
tumor activity regardless of the mechanism of drug action. Thus,
this assay would be acceptable as a primary general screen for
antitumor activity of the synthesized compounds, regardless of
mode of inhibitory action on tumor formation. Compounds 2, 3, 7,
8, 11, and 13 were found with the highest tumor inhibitions among
the tested compounds. A pictorial presentation for one of the
representative compound is shown in Fig. S8 (supplementary data).
It can be concluded from the DNA interaction, cytotoxicity and
3.6.5. Detection of plasmid pBR322 DNA damage by agarose gel
electrophoresis
In this assay plasmid pBR322 DNA was used to determine the
antioxidant potential of the compound on DNA. The aim of this
work was to know the ability of selected organotin(IV) derivatives
to unwind or condense a super coiled DNA. The capability of the
synthesized compounds to mediate pBR322 DNA damage was
investigated using agarose gel electrophoresis at neutral pH and
temperature conditions. The mix solution containing compound
and DNA were incubated in the presence of FeSO4 and H2O2 as a
reducing agent for certain time. The electrophorogram of pBR322
DNA damage in presence of different concentrations of the two
representative compounds 7 and 1 incubated for 60 min were
shown in Fig. 14 while the overall data is shown in Table 13. The
treated pBR322 DNA showed two bands on agarose gel electro-
phoresis. The foremost moving band corresponded to the native
Table 8
MIC values (m
g/mL) of antibacterial activity of HL and its organotin(IV) derivatives.a
Compound no.
Minimum inhibitory concentration (mg/mL)
E. coli
S. aureus
E. aerogens
S. typhimurium
B. bronchiseptica
B. subtilis
HL
1
2
3
4
5
6
7
8
9
10
11
12
13
14
100
25
6.25
150
e
100
50
50
150
e
e
200
25
6.25
100
e
200
12.5
6.25
100
12.5
e
200
25
6.25
50
50
6.25
100
25
e
200
50
50
50
25
50
12.5
200
12.5
e
e
200
200
150
50
e
100
100
100
100
100
12.5
e
150
100
25
150
150
6.25
e
100
50
50
200
50
12.5
e
200
100
50
100
200
12.5
200
100
100
e
e
e
6.25
150
25
200
e
50
100
e
50
100
e
100
200
e
150
e
Cefiximeb
Roxithromicineb
e
e
e
e
e
e
a
Numbering of compounds is in accordance to Scheme 2.
Reference drugs.
b

M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
361
Table 9
Table 11
Zone of inhibition (mm) of antifungal activity of HL and its organotin(IV)
Cytotoxicity data of HL and its organotin(IV) derivatives.a
derivatives.a
Compound
no.
No. of shrimps killed out of 30 per dilutionb
LD50
(mg/mL)
Compound no.
A. niger
A. fumigates
A. flavus
M. species
200 ppm 66.6 ppm 22.2 ppm 7.4 ppm 2.4 ppm
HL
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0
28
48
40
40
0
15
15
14
30
11
24
0
0
22
58
32
28
16
15
0
12
32
0
18
0
0
28
46
32
26
18
12
0
0
26
0
20
0
26
25
35
0
24
34
20
23
18
12
0
0
22
0
14
0
0
HL
1
2
3
4
5
4
7
8
16
30
30
30
30
30
30
27
30
30
30
30
21
30
30
13
30
30
30
30
30
30
26
30
30
30
27
23
30
30
30
e
12
27
30
30
30
30
30
21
28
28
30
24
20
30
28
27
e
11
24
30
28
29
30
28
18
26
26
30
20
17
27
25
25
e
9
21
28
26
25
29
26
13
23
25
27
14
20
22
24
24
e
192.2
1.09
0.881
0.433
0.793
0.493
0.793
2.89
0.611
0.403
1.105
3.114
6.19
9
10
11
12
13
14
26
24
35
16
16
35
1.17
0.499
0.434
0
32
Terbinafineb
Doxorubicinc 30
a
Numbering of compounds is in accordance to Scheme 2.
Reference drug.
Vehicle
control
e
e
b
a
b
c
Numbering of compounds is in accordance to Scheme 2.
Against brine-shrimps (in vitro).
Standard drug.
form of super coiled circular and the slower moving band was the
open circular form. Double stranded super coiled structure of
plasmid pBR322 DNA with
mobility is disrupted upon formation of strand breaks, resulting in
an open-circle conformation with reduced electrophoretic
mobility in agarose [29,30]. The amount of DNA damage markedly
was enhanced with increasing the concentration of the compound
(Fig. 14).
a relatively high electrophoretic
interference with the function of parasite mitochondria. This study,
therefore, demonstrated the potential use of these compounds as
source of novel agents for the treatment of leishmaniasis.
a
4. Conclusions
3.6.6. Antileishmanial activity
The ligand, N-[(2-methoxyphenyl)]-4-oxo-4-[oxy]butanamide,
coordinates to tin via oxygen atoms of the carboxylate group. In the
case of triorganotin(IV) derivatives the geometry around the tin
atom is distorted trigonal-bipyramidal both in solution and solid
states. While in case of diorganotin(IV) derivatives the geometry
around the tin atom is octahedral. A good correlation was found
between the Dn value calculated from FT-IR data and single crystal
XRD data. From the single crystal X-ray structural analysis it is
revealed that these compounds have packing diagrams like den-
drimers with characteristics that make them useful for numerous
biological applications. Biological studies reveal that generally the
triorganotin(IV) complexes have higher activity than their
The antiprotozoal activity of the HL and its organotin(IV) de-
rivatives against the pathogenic Leishmania was obtained and data
are given in Table 14. The synthesized compounds produced a
significant reduction in viable promastigotes. The minimum pro-
tozoa concentration (IC50) for promastogotes, defined as that con-
centration which produced 50% reduction in parasites after 72 h of
incubation [71]. It is evidenced from the data that the tri-
organotin(IV) derivatives have higher activity than their diorgano
analogues. Potential toxicity, costs, and drug-resistant pathogens
necessitate the development of new antileishmanial agents. All the
synthesized compounds exhibit strong antileishmanial activity that
was even higher than that of amphotericin B with significant
cytotoxicity. Their antileishmanial activity may be due the
Table 12
Potato disc antitumor data of HL and its organotin(IV) derivatives.a
Table 10
MIC values (m
g/mL) of antifungal activity of HL and its organotin(IV) derivatives.a
Compound
no.
Percentage inhibition standard deviation
1000 g/mL 100 g/mL 10 g/mL
IC50
m
g/mL
m
m
m
Compound no.
Minimum inhibitory concentration (mg/mL)
HL
1
2
3
4
5
6
7
8
9
10
11
12
13
14
62.64 0.27
69.88 0.17
84.14 0.17
87.82 0.17
77.47 0.14
80.91 0.29
76.12 0.23
91.37 0.26
88.27 0.20
85.28 0.26
87.12 0.23
92.41 0.15
65.47 0.14
84.82 0.25
66.68 0.23
100
31.14 0.40
54.82 0.26
70.33 0.29
72.39 0.20
54.94 0.24
57.35 0.23
62.0 0.17
62.87 0.18
65.51 0.23
62.18 0.20
52.0 0.17
71.49 0.08
44.94 0.24
66.66 0.23
45.63 0.42
100
5.63 0.24
30.22 0.23
48.26 0.20
52.28 0.40
32.18 0.26
36.55 0.32
20.32 0.26
43.21 0.24
50.22 0.32
43.90 0.23
19.31 0.26
53.44 0.28
31.18 0.26
46.78 0.29
27.12 0.31
100
410.37
82.24
13.52
10.35
59.29
40.77
60.34
21.70
12.28
21.36
83.24
8.78
A. niger
A. fumigates
A. flavus
M. species
HL
1
2
3
4
5
6
7
8
e
e
e
e
12.5
0.78
1.56
3.12
200
150
200
150
1.56
200
100
e
50
50
50
0.78
3.12
6.25
150
150
e
0.78
3.12
6.25
150
200
e
12.5
12.5
25
100
200
e
200
6.25
e
e
e
9
6.25
e
100
e
10
11
12
13
14
69.25
14.77
72.87
100
e
100
e
200
e
Vincristineb
50
100
100
150
100
50
200
200
a
Numbering of compounds is in accordance to Scheme 2.
Reference drug.
a
b
Numbering of compounds is in accordance to Scheme 2.

362
M. Sirajuddin et al. / European Journal of Medicinal Chemistry 84 (2014) 343e363
Fig. 14. Effects of compounds 7 and 1 on plasmid (pBR322) DNA.
corresponding diorganotin(IV) complexes, possibly due to their
Table 13
greater lipophilicity and permeability through the cell membrane.
The high lipid solubility of organotins ensures cell penetration and
association with intracellular sites. In solution, triorganotin com-
pounds may undergo spontaneous disproportionation into the
corresponding diorganotin and tetraorganotin derivatives while,
in vivo, the loss of one alkyl or aryl group may occur through the
intervention of enzymes such as aromatase. UVeVis spectroscopic
results show that the synthesized compounds bind to DNA via
intercalative mode of interaction resulting in hypochromism and
minor red shift. The synthesized compounds may represent a new
line of antitumor agents for prevention and treatment of cancer and
also serve as a potential source of chemoprotective agent(s). The
oxidative DNA damage by the synthesized compounds in the
presence of FeSO4 and H2O2 (used as a positive control) was
explored using agarose gel electrophoresis. The extent of pBR322
DNA damage was enhanced significantly with increasing concen-
tration of the compounds. The antileishmanial data clearly indicate
that these compounds have a strong antileishmanial activity and
might be developed a new antileishmanial drug. Their anti-
leishmanial activity may be due the interference with the function
of parasite mitochondria.
Plasmid pBR322 DNA damage by agarose Gel Electrophoresis data.a
Compound no.
DNA protection activity at different concentration
1000
m
g/mL
100
m
g/mL
10
m
g/mL
1
mg/mL
HL
1
2
3
4
5
6
7
8
ꢁ
ꢁ
ꢁ
ꢁ
þþþ
þ
þþþ
þ
þþ
þ
þþ
þ
ꢁ
ꢁ
ꢁ
ꢁ
þþþ
ꢁ
þþ
ꢁ
þ
þ
ꢁ
ꢁ
þþ
þþþ
ꢁ
þþ
þþþ
ꢁ
þþ
þ
þþþ
ꢁ
þþ
ꢁ
9
þþ
þ
þþ
þ
þ
þ
10
11
13
14
þþ
þ
þþ
þ
þþ
ꢁ
þþ
ꢁ
ꢁ
ꢁ
þþþ
þþ
þþ
þ
(ꢁ)
¼
no protection, (þ)
¼
Slight protection, (þþ)
¼
Moderate protection,
(þþþ) ¼ Good protection.
a
Numbering of compounds is in accordance to Scheme 2.
Table 14
Acknowledgment
Antileishmanial data of HL and its organotin(IV) derivativesa.
Compound no.
IC50 (mg/mL)
Muhammad Sirajuddin gratefully acknowledges the Higher
Education Commission (HEC) Islamabad, Pakistan, for financial
support (PIN#117-7338-PS7-017).
HL
1
2
3
4
5
6
7
8
9
10
11
12
13
14
3.42 ꢂ 10ꢁ3
7.59 ꢂ 10ꢁ5
9.19 ꢂ 10ꢁ5
4.17 ꢂ 10ꢁ5
8.70 ꢂ 10ꢁ5
3.90 ꢂ 10ꢁ5
9.96 ꢂ 10ꢁ5
5.89 ꢂ 10ꢁ4
6.65 ꢂ 10ꢁ4
6.60 ꢂ 10ꢁ4
7.96 ꢂ 10ꢁ4
1.92 ꢂ 10ꢁ3
1.04 ꢂ 10ꢁ3
1.56 ꢂ 10ꢁ2
9.22 ꢂ 10ꢁ2
0.56
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2014.07.028.
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