Synthesis and antimicrobial activity of new 1-alkyl/cyclohexyl-3,3-diaryl-1′-methylspiro[azetidine-2,3′-indoline]-2′,4-diones

Article abstract of DOI:10.1016/j.ejmech.2008.06.007

The paper describes the synthesis of new 1-alkyl/cyclohexyl-3,3-diaryl-1′-methylspiro[azetidine-2,3′-indoline]-2′,4-diones from the reactions of the 2-diazo-1,2-diarylethanones with 1-methyl-3-(alkyl/cyclohexylimino)indolin-2-ones under thermal condition.

Full text of DOI:10.1016/j.ejmech.2008.06.007

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 44 (2009) 2265e2269
http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and antimicrobial activity of new 1-alkyl/cyclohexyl-3,
3-diaryl-10-methylspiro[azetidine-2,30-indoline]-20,4-diones
*
Girija S. Singh , Patrick Luntha
Department of Chemistry, University of Botswana, Private Bag 0022, Gaborone, Botswana
Received 18 March 2008; received in revised form 10 June 2008; accepted 13 June 2008
Available online 21 June 2008
Abstract
The paper describes the synthesis of new 1-alkyl/cyclohexyl-3,3-diaryl-10-methylspiro[azetidine-2,30-indoline]-20,4-diones from the reactions
of the 2-diazo-1,2-diarylethanones with 1-methyl-3-(alkyl/cyclohexylimino)indolin-2-ones under thermal condition. The compounds, character-
ized by satisfactory analytical and spectral (IR, 1H NMR and 13C NMR) data, have been screened for their antibacterial and antifungal activities.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords: Spiroazetidinones; Diarylketenes; 3-Iminoindolin-2-ones; Cycloaddition; Antimicrobial activity
1. Introduction
a scarce class of compounds. There are only a few reports in
the literature on the synthesis, reactivity and biological activity
of such 2-azetidinones [12e27]. The diverse types of
biological activities associated with indoline-2,3-dione (isatin)
derivatives and their interesting chemistry [28e31] prompted
us to synthesize 2-azetidinones spiro-fused to 1-methylindo-
lin-2-one ring and study its antimicrobial activity. Accordingly,
the present paper reports the synthesis and antimicrobial activ-
ity of 10 new 1-alkyl/cyclohexyl-3,3-diaryl-10-methylspiro
[azetidine-2,30-indoline]-20,4-diones from the reactions of 1-
methyl-3-(alkyl/cyclohexylimino)indolin-2-ones with three 2-
diazo-1,2-diarylethanones e 2-diazo-1,2-diphenylethanone,
2-diazo-1,2-bis(4-methylphenyl)ethanone and 2-diazo-1,2-
bis(4-methoxyphenyl)ethanone.
There are several methods reported in the literature for the
synthesis of 2-azetidinones [9,10]. However, the Staudinger
keteneeimine cycloaddition reaction is one of the most
common methods to synthesize 2-azetidinones [32]. It in-
volves reaction of an imine with acid chloride in the presence
of a tertiary base, usually triethylamine at temperatures
ranging from ꢀ78 ꢁC to reflux temperature in various solvents
such as dichloromethane, acetonitrile, toluene, etc. (Scheme
1). In the present study, diarylketenes are generated in situ
by thermal decomposition of a-diazoketones because their
reactions appeared versatile, simpler to carry out requiring
The 2-azetidinones, commonly known as b-lactams, are
among the most useful azaheterocyclic compounds from both
synthetic and medicinal chemistry points of views. Most of
the researches up to early 90s focused on synthesis of 2-azeti-
dinones and study of their antibacterial property [1e3]. Later
researches have shown some other useful biological activities
of such compounds, e.g. cholesterol absorption inhibition,
enzymes inhibition, hypoglycemic, and anticancer activity
[4,5]. Ezetimibe, a monocyclic 2-azetidinone, is now in clinical
use as a cholesterol absorption inhibitor [6]. Recent years have
shown extensive investigation on use of 2-azetidinones as syn-
thons for diverse types of biologically important compounds
such as b-aminoacids, g-aminoalcohols, azetidines, pyrimi-
dones, etc. [7e11]. However, most of these studies are under-
taken either on monocyclic or fused bicyclic 2-azetidinones. It
is due to the fact that the first 2-azetidinone-containing antibi-
otics penicillin and cephalosporin had fused bicyclic skeletons
whereas monobactams and nocardicins, observed in late 70s
and early 80s to have antibacterial activity, had monocyclic
2-azetidinone ring. The spiro-fused 2-azetidinones constitute
* Corresponding author. Tel.: þ267 3552501; fax: þ267 3552836.
E-mail address: singhgs@mopipi.ub.bw (G.S. Singh).
0223-5234/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.06.007

2266
G.S. Singh, P. Luntha / European Journal of Medicinal Chemistry 44 (2009) 2265e2269
1
R1
CH N
R2
O
that the H NMR spectra of spiro-compounds 3c and g with
a-phenylmethyl group on azetidinone ring nitrogen showed
the signals in sets of two (approximately in the ratio of 9:1)
indicating two spatial arrangement of the groups in these com-
pounds. The N-methyl and methine signals for minor configu-
ration appeared slightly downfield than the signals for these
protons in major configurations whereas the signal for methyl
proton [CH(Me)Ph] appeared slightly upfield. The mass spec-
tra of the products recorded showed the quasimolecular ions
formed by addition of sodium (M þ Na)þ.
O
R3N, solvent
+
R1
C
H
N
R2
R
Cl
0°C - Δ
R
Scheme 1. The Staudinger method for the preparation of 2-azetidinones.
no temperature control, no acid or base treatment and also no
water work-up.
2. Results and discussion
The mechanism of formation of the product, which is sim-
ilar to the one proposed earlier for such reactions [28], is
shown in Scheme 2. Thermal decomposition of the 2-diazoke-
tones leads to the formation of a-ketocarbenes with extrusion
of nitrogen. The a-ketocarbenes are known to undergo the
Wolff rearrangement leading to in situ generation of ketenes
[33]. The reaction of imines with ketenes may lead to the for-
mation of a zwitterionic intermediate, which cyclizes to give
the product 2-azetidinones.
2.1. Chemistry
An equimolar reaction of 2-diazo-1,2-diphenylethanone
(1a) with 1-methyl-3-(isopropylimino)indolin-2-one (2a) in
dry benzene afforded a white crystalline compound character-
ized as 1-isopropyl-10-methyl-3,3-diphenylspiro[azetidine-
2,30-indoline]-20,4-dione (3a) on the basis of satisfactory
analytical and spectral data (see Section 4).
Similar reactions of 2-diazo-1,2-diphenylethanone (1a)
with 1-methyl-3-(N-substituted imino)indolin-2-ones (2bed)
also afforded spiro(azetidin-2,30-indoline)-20,4-diones (3bed)
in good yields (Table 1). The reactions of 2-diazo-1,2-bis(4-
methylphenyl)ethanone (1b) and of 2-diazo-1,2-bis(4-methox-
yphenyl)ethanone (1c) were carried out in a similar manner
with 1-methyl-3-(alkylimino)indolin-2-ones 2aed and with
2a and b, respectively, which yielded new spiro(azetidin-
2,30-indoline)-20,4-diones (3eeh) and (3i,j), respectively, in
good to excellent yields (Table 1) which have been character-
ized on the basis of satisfactory analytical and spectral data
discussed briefly in the succeeding paragraph.
The IR spectra of compounds 3aej showed two strong ab-
sorption bands e one at around 1745e1760 and the other at
around 1720e1730 cmꢀ1 corresponding to two lactam car-
bonyl groups. The 13C NMR spectra showed the two carbonyl
carbons at around d 173 and 169 ppm. In the IR and 13C spec-
tra of the products 3aej, the disappearance of the band at
around 1640 cmꢀ1 corresponding to azomethine linkage and
of signal at around d 155 ppm corresponding to azomethine
carbon, respectively, in substrates 2aed confirmed the reac-
tion at azomethine linkage of the substrates forming spiro[aze-
tidine-2,30-indoline]-20,4-diones. It is noteworthy to mention
2.2. Pharmacology
All the synthesized compounds were screened for their
antibacterial and antifungal activities (Table 2). The concen-
trations ranging from 1.0 to 100.0 mg mLꢀ1 of the test
compound were used for the screening. The bacterial strains
used were Gram-(þ) Bacillus subtilis, Staphylococcus aureus
and Gram-(ꢀ) Escherichia coli and Pseudomonas aeruginosa.
The antifungal screening was done on Candida albicans and
on Saccharomyces cerevisiae. Of the 10 compounds screened
against bacterial strains, four compounds showed activity on
E. coli (3d: MIC ¼ 100 mg mLꢀ1, 3e: MIC ¼ 10 mg mLꢀ1
,
3h: MIC ¼ 100 mg mLꢀ1, 3j: MIC ¼ 50 mg mLꢀ1) whereas
only one compound showed activity on P. aeruginosa (3e:
MIC ¼ 50 mg mLꢀ1). None of the compounds showed activity
on Gram-(þ) strains up to the maximum concentration of
100 mg mLꢀ1 used in the study. These results are in agreement
with previous studies on monocyclic 2-azetidinones which
reported higher activity of such 2-azetidinones against
Gram-(ꢀ) bacteria in comparison to that against Gram-(þ)
bacteria [34e36]. Although none of the compounds showed
activity up to 100 mg mLꢀ1 against C. albicans six compounds
(3a: MIC ¼ 50 mg mLꢀ1
,
3b. MIC ¼ 10 mg mLꢀ1
,
,
3e:
3i:
MIC ¼ mg mLꢀ1
,
50,
3f:
MIC ¼ 100 mg mLꢀ1
Table 1
Physical data of the spiro[azetidin-2,30-indoline]-20,4-diones 3aej
MIC ¼ 50 mg mLꢀ1, 3j: MIC ¼ 50 mg mLꢀ1) have been ob-
served active on S. cerevisiae. Only compound 3e with two
4-methylphenyl groups and an isopropyl group on 2-azetidi-
none ring carbon and nitrogen, respectively, showed activity
against three organisms out of five studied.
Compound Ar
number
R
Molecular
formula
M.p.
(ꢁC)
Yield
(%)
3a
3b
3c
3d
3e
3f
Ph
Ph
CHMe2
CHPh2
C26H24N2O2 200e202 69
C36H28N2O2 236e237 74
Ph
Ph
CH(Me)Ph C31H26N2O2 162e165 60
Cyclohexyl C29H28N2O2 155e158 50
3. Conclusions
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
CHMe2
CHPh2
C28H28N2O2 258e260 72
C38H32N2O2 194e195 78
In conclusion, the paper reports the synthesis of spiro-
compounds containing 2-azetidinone and 1-methylindolin-
2-one rings from the reactions of 1-methyl-3-(alkylimino)
indolin-2-ones with three diarylketenes e diphenylketene,
3g
3h
3i
CH(Me)Ph C33H30N2O2 214e216 68
Cyclohexyl C31H32N2O2 180e182 52
4-MeOC6H4 CHMe2
4-MeOC6H4 CHPh2
C28H28N2O4 255e258 77
C38H32N2O4 204e206 80
3j

G.S. Singh, P. Luntha / European Journal of Medicinal Chemistry 44 (2009) 2265e2269
2267
dry benzene
Ar
Ar
Wolff-
rearrangement
N2
O
Ar
Ar
Δ, 6-8 h
Ar
C
C
O
- N2
Ar
O
1a-c
N
R
Ar = 1a. Ph, 1b. 4-MeC6H4, 1c. 4-MeOC6H4
R = 2a. CHMe2, 2b. CHPh2, 2c. CH(Me)Ph,
2d. C-hex
O
N
Me
2a-d
O
Ar
Ar
Ar
Ar
Ar
Ar
N
R
cyclization
C
C
N
O
R
C
C
N
O
R
O
N
O
O
Me
N
Me
N
Me
3a-j
Scheme 2. Mechanism of formation of compounds 3aej.
bis(4-methylphenyl)ketene and bis(4-methoxyphenyl)ketene.
Some of the compounds selectively inhibited the microbes.
Microbial cultures were developed in the Department of Bio-
logical Sciences at the University of Botswana.
4.1.1. Preparation of 1-methyl 3-(alkylimino)indolin-2-ones
(2aed)
4. Experimental
An equimolar amount (10 mmol) of an appropriate amine
and 1-methylindolin-2,3-dione in ethanol was refluxed for
4e6 h. The reaction mixture was kept overnight at room tem-
perature to afford red crystalline products which were used as
such for the reaction.
4.1. Chemistry
Melting points have been recorded on a Stuart Scientific
melting point apparatus and are uncorrected. The IR spectra
were recorded on a PerkineElmer-781 IR spectrophotometer
using KBr disc of the sample. The H and 13C NMR spectra
1
4.1.2. Synthesis of 1-alkyl/cyclohexyl-3,3-diaryl-10-methylspiro
[azetidine-2,30-indoline]-20,4-diones (3aej)
were recorded in a CDCl3 solution at 300 and 75.4 MHz, re-
spectively, on a BrukerÔ spectrometer. The mass spectra
were recorded on Finnignan LC QDECA mass spectrometer
by electrospray ionization. The elemental analyses were per-
formed on Gmbh VarioEL elemental analyzer.
Benzil, 4,4-dimethylbenzil, 4,4-dimethoxylbenzil, 1-meth-
ylindolin-2,3-dione, isopropyl amine, diphenylmethanamine,
(ꢂ)-a-phenylethyl amine, cyclohexyl amine and hydrazine hy-
drate were Sigma products. The benzene was dried by reflux-
ing over NaH. 2-Diazo-1,2-diarylethanones 1 were prepared
by oxidation of appropriate benzil monohydrazones using yel-
low mercuric oxide according to the reported method [37].
An equimolar amount of 2-diazo-1,2-diarylethanones 1 and
iminoindolin-2-ones 2 (1 mmol of each) in 10 mL of dry ben-
zene was heated to reflux under an atmosphere of nitrogen for
6e8 h. The solvent was evaporated under reduced pressure us-
ing a rotary evaporator. The residue was triturated with ethanol
to afford the white crystalline products 3 which were checked
for purity by TLC using n-hexane: ethyl acetate (1:1) as elu-
ent. The analytical and spectral data are given below.
4.1.2.1.
1-Isopropyl-3,3-diphenyl-10-methylspiro[azetidine-
2,30-indoline]-20,4-dione (3a). (IR, KBr, cmꢀ1): 1745, 1720;
1H NMR (CDCl3, d ppm): 7.50e6.19 (14H, arom.), 3.70
(sept, 1H, methine), 3.27 (s, 3H, NeCH3), 1.25 (d,
J ¼ 6.0 Hz, 3H, CH3), 1.11 (d, J ¼ 6.0 Hz, 3H, CH3); 13C
NMR (CDCl3, d ppm): 174.7, 168.3, 143.8, 138.5, 130.2,
128.2, 128.1, 127.3, 127.2, 126.8, 126.8, 124.2, 122.0,
108.3, 75.8, 71.3, 46.7, 26.7, 21.7, 20.6; Mass (m/z, r.i.): 419
(M þ Na, 13)þ, 416 (20), 388 (15), 312 (16), 225 [(M þ Na)
e (Ph2C]C]O), 100]þ; Elemental analysis: Calcd for
C26H24N2O2: C 78.76, H 6.10, N 7.07%; Found: C 78.22, H
5.94, N 6.89%.
Table 2
Antimicrobial activity of the compounds (MIC, mg mLꢀ1 a
)
Compound Ar
number
R
E. coli P. S.
aeruginosa cerevisiae
3a
3b
3d
3e
3f
Ph
Ph
CHMe2
CHPh2
Cyclohexyl 100
50
10
Ph
4-MeC6H4
4-MeC6H4
4-MeC6H4
CHMe2
CHPh2
Cyclohexyl 100
10
50
50
100
3h
3i
4-MeOC6H4 CHMe2
4-MeOC6H4 CHPh2
50
50
3j
Chloramphenicol
Miconazole
50
0.1
4.1.2.2. 1-Diphenylmethyl-3,3-diphenyl-10-methylspiro[azeti-
0.1
dine-2,30-indoline]-20,4-dione (3b). (IR, KBr, cmꢀ1): 1760,
0.1
1
1728; H NMR (CDCl3, d ppm): 7.47e6.07 (24H, arom.),
a
None of the compounds except reference compound chloramphenicol
(MIC ¼ 0.1 mg mLꢀ1) showed activity against B. subtilis and S. aureus whereas
miconazole showed activity against C. albicans (MIC ¼ 0.1 mg mLꢀ1).
5.88 (s, 1H, methine), 2.88 (s, 3H, NeCH3); 13C NMR
(CDCl3, d ppm): 174.0, 169.5, 143.9, 138.8, 136.2, 130.0,

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G.S. Singh, P. Luntha / European Journal of Medicinal Chemistry 44 (2009) 2265e2269
1
129.9, 128.3, 128.2, 127.7, 127.6, 127.5, 127.5, 127.4, 127.2,
127.1, 126.6, 123.9, 121.6, 107.9, 75.3, 71.4, 62.8, 26.3; Mass
(m/z, r.i): 544 (M þ Na, 35)þ, 543 (100); Elemental analysis:
Calcd for C36H28N2O2: C 83.05, H 5.42, N 5.38%; Found: C
82.1, H 5.30, N 5.30%.
cmꢀ1): H NMR (CDCl3, d ppm): 7.46e5.93 (17H, arom.),
4.64 (q, J ¼ 6.0 Hz, 1H, methine), 2.96 (s, 3H, NeCH3),
2.24 (s, 6H, Ph-CH3), 1.75 (d, J ¼ 6.0 Hz, 3H, CH3); 13C
NMR (CDCl3, d ppm): 174.0, 169.3, 143.9, 138.2, 136.9,
136.4, 135.8, 129.8, 128.8, 128.7, 128.3, 128.0, 127.8,
127.7, 127.2, 126.5, 123.9, 121.5, 107.8, 75.2, 71.4, 55.2,
26.3, 21.1, 21.0, 20.7; Mass (m/z, r.i.): 509 (M þ Na, 100)þ;
Elemental analysis: Calcd for C33H30N2O2: C 81.45, H 6.21,
N 5.76%; Found: C 80.94, 5.78, N 5.56%.
4.1.2.3. 1-(a-Phenylethyl)-3,3-diphenyl-10-methylspiro[azeti-
dine-2,30-indoline]-20,4-dione (3c). (IR, KBr, cmꢀ1): 1753,
1
1720; H NMR (CDCl3, d ppm): 7.46e5.93 (19H, arom.),
4.69 (q, J ¼ 6.0 Hz, 1H, methine), 2.96 (s, 3H, NeCH3),
1.76 (d, J ¼ 6.0 Hz, 3H, CH3); 13C NMR (CDCl3, d ppm):
173.9, 169.0, 143.9, 138.6, 138.5, 138.0, 129.9, 128.3,
128.2, 128.2, 128.1, 128.0, 127.7, 127.4, 127.1, 127.0,
126.7, 123.7, 121.6, 107.9, 75.5, 71.3, 55.2, 26.4, 20.6; Mass
(m/z, r.i.): 482 (M þ Na, 32)þ, 481 (100); Elemental analysis:
Calcd for C31H26N2O2: C 81.20, H 5.72, N 6.11%; Found: C
81.0, H 5.43, N 5.94%.
4.1.2.8. 1-Cyclohexyl-3,3-bis(4-methylphenyl)-10-methylspir-
o[azetidine-2,30-indoline]-20,4-dione (3h). (IR, KBr, cmꢀ1):
1
1750, 1720; 1H NMR (CDCl3, d ppm): H NMR (CDCl3,
d ppm): 7.35e6.24 (12H, arom.), 3.36 (tt, 1H, NeCH), 3.26
(s, 3H, NeCH3), 2.27 and 2.25 (2s, 6H, Ph-CH3), 2.05e1.05
(m, 10H, C-hex); 13C NMR (CDCl3, d ppm): 174.9, 168.6,
143.7, 136.9, 136.5, 135.8, 130.0, 128.9, 128.8, 128.0,
127.0, 126.5, 124.4, 121.9, 108.2, 75.5, 71.3, 54.3, 31.8,
30.7, 26.7, 25.2, 25.1, 21.1, 21.0; Mass (m/z, r.i.): 487
(M þ Na, 20)þ, 265 (100), 247 (20), 145 (30), 118 (20); Ele-
mental analysis: Calcd for C31H32N2O2: C 80.14, H 6.94, N
6.03%; Found: C 79.70, H 6.33, N 5.64%.
4.1.2.4. 1-Cyclohexyl-3,3-diphenyl-10-methylspiro[azetidine-
2,30-indoline]-20,4-dione (3d). (IR, KBr, cmꢀ1): 1750, 1721;
1H NMR (CDCl3, d ppm): 7.49e6.18 (14H, arom.), 3.37 (tt,
1H, NeCH), 3.27 (s, 3H, NeCH3), 2.05e1.05 (m, 10H, C-
hex); 13C NMR (CDCl3, d ppm): 174.7, 168.3, 143.8, 138.5,
130.2, 128.2, 128.2, 127.3, 127.2, 126.9, 126.8, 124.2,
122.0, 108.3, 75.8, 71.3, 54.3, 31.8, 30.7, 26.7, 25.2, 25.1; El-
emental analysis: Calcd for C29H28N2O2: C 79.79, H 6.46, N
6.42%; Found: C 79.39, H 6.26, N 6.26%.
4.1.2.9. 1-Isopropyl-3,3-bis(4-methoxyphenyl)-10-methylspir-
o[azetidine-2,30-indoline]-20,4-dione (3i). (IR, KBr, cmꢀ1):
1747, 1720; 1H NMR (CDCl3, d ppm): 7.38e6.28 (12H,
arom.), 3.78 (s, 6H, OCH3), 3.71 (sept, J ¼ 6.0 Hz, 1H, me-
thine), 3.25 (s, 3H, NeCH3), 1.25 (d, J ¼ 6.0 Hz, 3H, CH3),
1.11 (d, J ¼ 6.0 Hz, 3H, CH3); 13C NMR (CDCl3, d ppm):
174.7, 168.7, 158.6, 158.4, 143.8, 131.0, 130.9, 130.0,
129.3, 127.9, 126.9, 124.4, 122.0, 113.6, 113.5, 108.2, 74.9,
71.4, 55.2, 55.1, 46.6, 26.6, 21.7, 20.6; Mass (m/z, r.i.): 479
(M þ Na, 12)þ, 225 (100); Elemental analysis: Calcd for
C28H28N2O4: C 73.66, H 6.18, N 6.14%; Found: C 73.25, H
5.94, N 5.94%.
4.1.2.5. 1-Isopropyl-3,3-bis(4-methylphenyl)-10-methylspiro[a-
zetidine-2,30-indoline]-20,4-dione (3e). (IR, KBr, cmꢀ1):
1748, 1720; 1H NMR (CDCl3, d ppm): 7.31e6.25 (12H,
arom.), 3.71 (sept, J ¼ 6.0 Hz, 1H, methine), 3.26 (s, 3H,
NeCH3), 2.27 and 2.26 (2s, 6H, Ph-CH3), 1.25 (d,
J ¼ 6.0 Hz, 3H, CH3), 1.11 (d, J ¼ 6.0 Hz, 3H, CH3); 13C
NMR (CDCl3, d ppm): 174.8, 168.6, 143.8, 136.9, 136.5,
135.8, 130.0, 128.9, 128.8, 128.0, 127.0, 126.5, 124.4,
121.9, 108.2, 75.5, 71.3, 46.6, 26.7, 21.7, 21.1, 21.0, 20.6;
Mass (m/z, r.i.): 447 (M þ Na, 11)þ, 278 (38), 225 (100); El-
emental analysis: Calcd for C28H28N2O2: C 79.22, H 6.65,
N 6.60%; Found: C 78.92, H 6.57, N 6.54%.
4.1.2.10. 1-Diphenylmethyl-3,3-bis(4-methoxyphenyl)-10-meth-
ylspiro[azetidine-2,30-indoline]-20,4-dione (3j). (IR, KBr,
cmꢀ1): 1759, 1728; 1H NMR (CDCl3, d ppm): 7.35e6.15
(22H, arom.), 5.86 (s, 1H, methine), 3.78 and 3.75 (2s, 6H,
Ph-OCH3), 2.86 (s, 3H, NeCH3); 13C NMR (CDCl3,
d ppm): 174.1, 169.8, 158.7, 158.4, 143.9, 138.9, 136.4,
131.3, 130.0, 129.7, 129.4, 127.7, 127.6, 127.5, 127.3,
127.3, 124.1, 121.6, 113.6, 113.5, 107.8, 74.4, 71.6, 62.8,
55.2, 55.1, 26.3; Elemental analysis: Calcd for C38H32N2O4:
C 78.60, H 5.55, N 4.82%; Found: C 78.80, H 5.42, N 4.77%.
4.1.2.6. 1-Diphenylmethyl-3,3-bis(4-methylphenyl)-10-methyl-
spiro[azetidine-2,30-indoline]-20,4-dione
(3f). (IR,
KBr,
cmꢀ1): 1759, 1726; 1H NMR (CDCl3, d ppm): 7.33e6.13
(22H, arom.), 5.86 (s, 1H, methine), 2.87 (s, 3H, NeCH3),
2.29 and 2.26 (2s, 6H, Ph-CH3); 13C NMR (CDCl3, d ppm):
174.0, 169.0, 143.9, 138.9, 137.0, 136.5, 136.4, 136.1,
136.0, 130.0, 129.7, 128.9, 128.9, 128.1, 128.1, 127.7,
127.5, 127.3, 126.4, 124.0, 121.5, 107.8, 75.0, 71.5, 62.8,
26.3, 21.1, 21.0; Mass (m/z, r.i.): 571 (M þ Na, 100)þ, 555
(25), 497 (38), 480 (42), 468 (50), 451 (52), 367 (33), 349
(32), 325 (15), 265 (25); Elemental analysis: Calcd for
C38H32N2O2: C 83.18, H 5.88, N 5.11%; Found: C 82.74, H
5.55, N 4.91%.
4.2. Pharmacology
4.2.1. Antimicrobial activities
Using microlitre syringes, different amounts (0.5, 5, 10, 50
and 100mg) of each compound and standards were spotted on
different glass-backed plates coated with silica-gel (Merck) 60
F254. Nutrient agar was inoculated with respective pure
microbial cultures, overlaid on the above plates and incubated
appropriately. Inhibition of the bacterial and fungal growth
was evaluated based on a simple and rapid bioautographic
4.1.2.7. 1-(a-Phenylethyl)-3,3-bis(4-methylphenyl)-10-methyl-
spiro[azetidine-2,30-indoline]-20,4-dione
(3g). (IR,
KBr,

G.S. Singh, P. Luntha / European Journal of Medicinal Chemistry 44 (2009) 2265e2269
2269
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[38,39].
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Acknowledgements
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The authors are thankful to the Department of Chemistry,
University of Botswana (UB), for providing the necessary re-
search facilities. The financial assistance from the Office of
Research and Development at the UB is gratefully
acknowledged.
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