Synthesis of mono-, bis-spiro- and dispiro-β-lactams and evaluation of their antimalarial activities

Article abstract of DOI:10.1016/j.tet.2011.09.041

Some new mono-, bis-spiro- and dispiro-β-lactams have been synthesized from imines derived from 9H-fluoren-9-one and a ketene derived from 9H-xanthene-9-carboxylic acid or phenoxyacetic acid by a [2+2] cycloaddition reaction in good to excellent yields va

Full text of DOI:10.1016/j.tet.2011.09.041

Tetrahedron 67 (2011) 8699e8704
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of mono-, bis-spiro- and dispiro-b-lactams and evaluation
of their antimalarial activities
,
a
b
c
c
Aliasghar Jarrahpour a , Edris Ebrahimi , Erik De Clercq , Veronique Sinou , Christine Latour ,
*
ꢀ
Lamia Djouhri Bouktab d, Jean Michel Brunel d
a Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
b Rega Institute for Medical Research, Katholieke Univeˇ rsiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium
c
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢁ
Universite de la Mediterranee, UMR-MD3 Relation hote-parasites, Physiopathologie & Pharmacologie, IRBA-Antenne Marseille, allee du medecin colonel Eugene Jamot,
Parc du Pharo, 13262 Marseille Cedex 07, France
d
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Universite de la Mediterranee, URMITE CNRS-IRD UMR 6236, Faculte de Medecine, 27 Bd Jean Moulin, 13385 Marseille Cedex 05, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 17 May 2011
Received in revised form 25 August 2011
Accepted 12 September 2011
Available online 17 September 2011
Some new mono-, bis-spiro- and dispiro-b-lactams have been synthesized from imines derived from 9H-
fluoren-9-one and a ketene derived from 9H-xanthene-9-carboxylic acid or phenoxyacetic acid by
a [2þ2] cycloaddition reaction in good to excellent yields varying from 45 to 83%. The biological activity
of these monocyclic b-lactams was successfully investigated against Plasmodium falciparum K14 resistant
strain with excellent EC50 values up to 5 mM.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
9H-Fluoren-9-one
Dispiro-b-lactams
9H-Xanthene-9-carboxylic acid
Phenoxyacetic acid
[2þ2] Cycloaddition
Antimalarial activities
1. Introduction
researchers have accomplished the synthesis of spiro-b-lactams
through cycloaddition reactions employing different ketenes and
The four-membered
structural unit of the most widely employed class of
b
-lactam ring is recognized as a key
-lactam an-
tibiotics.1 The constant need for new drugs showing broader bi-
ological activity and the necessity for new -lactam antibiotics to
imines in recent years.7 Spiro penicillins and cephalosporins have
b
been reported8 and only a few examples of simple spiro-
b-lactams
were known until 1990.9 Spiro-
b-lactams are interesting com-
b
pounds, which can act as antiviral,10 antibacterial agents.7h More
combat microorganisms that have built up resistance against tra-
ditional drugs,2 have maintained the interest of organic chemists
for almost half a century. A large number of methods are available
for the syntheses of newer 2-azetidinones and the topic has been
extensively reviewed.3 The [2þ2] cyclocondensation of ketenes
with imines, a procedure commonly known as the Staudinger re-
action is perhaps the most convenient procedure for the synthesis
recently, a cholesterol absorbtion inhibitor,11 such as Sch 58053 1
was discovered.12 The proline derived -lactams 213 were designed
b
as
b
-turn mimetics and used for synthetic applications.
a,a-Di-
substituted
b
-amino esters,14 diazabicyclic compounds15 and other
densely functionalized nitrogenated five-membered-ring sys-
tems16 have renewed the interest in these compounds.From a syn-
thetic point of view spiro-b-lactam derivatives, such as dispiro-
of the
b
-lactam ring skeleton.4,5 Also, several syntheses of spiro-
b
-
1,2,4-trioxolanes and dispiro-1,2,4,5-tetraoxanes have been re-
cently obtained by using different methodologies and found to
possess antimalarial activity.8,9,13,17e21 In this article we report the
lactams have been reported in the literature,6 and many
synthesis in a single step of new mono-, bis-spiro- and dispiro-b-
lactams by using a [2þ2] cycloadition reaction (Staudinger re-
action) and the evaluation of their potent antimalarial activity
against Plasmodium falciparum K14 resistant strain.
* Corresponding author. Tel.: þ98 711 228 4822; fax: þ98 711 228 0926; e-mail
addresses: aliasghar6683@yahoo.com, jarrah@susc.ac.ir (A. Jarrahpour).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.09.041

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A. Jarrahpour et al. / Tetrahedron 67 (2011) 8699e8704
aeruginosa and fungi, such as Candidaalbicans and Candida glabrata
with MICs values greater than 125 g/mL in all cases. On the other
OH
Cl
m
N
O
hand, none of the compounds exhibited specific antiviral activity,
which means that they did not inhibit the replication (induction of
viral cytopathogenicity) of any of the viruses tested (herpes sim-
plex, vesicula stomatitis, vaccinia and coxsackie viruses) at a con-
centration that was ꢁfivefold lower than the minimum cytotoxic
concentration which has been determined against HEL, VERO or
R2
O
N
F
N
HO
N
R1
H
O
2
1
HeLa cells and which varied from 4 mM to >100 mM. Nevertheless,
good to excellent antimalarial activities have been obtained against
Prolinederived
β-turn mimetics
Sch 58053
chloroquine-resistant P. falciparum K14 strain as outlined in Table 2
for spiro- and dispiro-
5 to 32.2 M. It is also noteworthy that the best derivatives 4d and
5e present a low cytotoxicity up to 100 M whatever the considered
cells. On the other hand, no significant antimalarial activity was
encountered for bis-spiro- and dispiro- -lactams 7, 8a,b, all of this
b-lactams compounds with IC50 varying from
2. Results and discussion
The synthesis of spiro- and dispiro-
was achieved according to the outlined procedure in Scheme 1.
Typically, imines 3aeg were prepared from 9H-fluoren-9-one and
substituted anilines with catalytic acetic acid in refluxing ethanol. It
is noteworthy that ortho and meta substituted amines do not react
under these conditions. These Schiff bases were subsequently
treated with 9H-xanthene-9-carboxylic acid or phenoxyacetic acid
in the presence of triethylamine and tosyl chloride to afford the
m
m
b-lactams 4aef and 5aeg
b
suggesting a quite strong influence of the structure of the consid-
ered lactam derivative on the mechanism of action.
3. Conclusion
expected spiro- and dispiro-
b
-lactams 4aef and 5aeg in good to
In conclusion, we have been able to prepare some new mono-,
excellent isolated yields varying from 45 to 83%.
bis-spiro- and dispiro-b-lactams from imines derived from 9H-
O
OH
O
O
O
O
OH
N
N
N
O
O
O
CH2Cl2, Et3N, TsCl
CH2Cl2, Et3N, TsCl
X
X
X
3a-g
5a-g
4a-f
d = (Et)2N
e = OEt
a = CH3
b = OCH3
c = Cl
f = (Me)2N
g = CH(CH3)2
Scheme 1. Synthesis of spiro- and dispiro-
b-lactams.
The reaction progress was monitored by TLC and the presence of
a new compound was easily confirmed. As an example, the IR
fluoren-9-one and ketenes derived from 9H-xanthene-9-carboxylic
acid or phenoxyacetic acid and presenting good to excellent anti-
malarial activities against a P. falciparum K14 resistant strain. Fur-
ther work is now under current investigation in order to improve
the structure of potent more active compounds and elucidate the
mechanism of action of these derivatives since this latter remains
unclear to date.
spectrum for 5a showed the characteristic absorption of a b-lactam
carbonyl at 1755 cmꢀ1. The 1H NMR spectrum exhibited the methyl
protons as a singlet at 2.02 ppm, and aromatic protons as a multi-
plet at 6.53e8.32 ppm. The absence of doublets of H3 and H4 for
the b
-lactam ring confirms the spiro structure of 5a. The 13C NMR
spectrum exhibited the following signals: methyl group at
20.8 ppm, C-3 at 64.2 ppm, C-4 at 69.1 ppm, and aromatic carbons
4. Experimental section
4.1. General
at 116.3e164.3 ppm, the b-lactam carbonyl appearing at 169.1 ppm.
The GCeMS analysis showed m/z¼477 [Mþ] as expected for this
derivative. According to this methodology, we have been able to
prepare numerous other spiro- and dispiro-b-lactams in good to
moderate yield (Table 1), which have been unambiguously char-
acterized by IR and NMR spectroscopy.
On the other hand, we envisioned, according to the same
strategy, performing the synthesis of new bis-spiro- and bis-dis-
piro-b-lactams derivatives. Thus, treatment of imines 6a,b with 9H-
All needed chemicals were purchased from Merck, Fluka and
Acros chemical companies. All reagents and solvents were dried
prior to use according to standard methods.22 IR spectra were run
on a Shimadzu FT-IR 8300 spectrophotometer. 1H NMR and 13C
NMR spectra were recorded in DMSO-d6 and CDCl3 using a Bruker
Avance DPX instrument (1H NMR 250 MHz, 13C NMR 62.9 MHz).
xanthene-9-carboxylic acid or phenoxyacetic acid in the presence
of triethylamine and tosyl chloride afforded the expected bis-spiro
and bis-dispiro-b-lactams 7 and 8a,b in 45e48% isolated yields,
Chemical shifts were reported in parts per million (d) downfield
from TMS. All of the coupling constants (J) are in hertz. The mass
spectra were recorded on a Shimadzu GCeMS QP 1000 EX in-
strument. Elemental analyses were run on a Thermo Finnigan Flash
EA-1112 series. Melting points were determined in open capillaries
with Buchi 510 melting point apparatus. Thin-layer chromatogra-
phy was carried out on silica gel F254 analytical sheets obtained
from Fluka. Column chromatography was performed on Merck
Kieselgel (230e270 mesh).
respectively (Scheme 2).
All of these newly synthesized b-lactams derivatives were sub-
sequently evaluated for their biological activities. First of all, it has
been demonstrated that these compounds do not possess signifi-
cant antimicrobial efficiency against Gram-positive Staphylococcus
aureus and Gram-negative bacteria Escherichia coli or Pseudomonas

A. Jarrahpour et al. / Tetrahedron 67 (2011) 8699e8704
8701
Table 1
Structures and isolated yields of synthesized spiro- and dispiro-
b-lactams
Entry Product
Yielda (%)
Entry
Product
Yielda (%)
1
73
4
76
2
70
5
75
O
O
3
72
6
48
N
4f
7
55
11
83
8
55
12
65
O
N
9
77
13
63
O
5g
10
80
a
Isolated yield of pure products.

8702
A. Jarrahpour et al. / Tetrahedron 67 (2011) 8699e8704
W
N
N
O
O
OH
OH
O
H
6a, W= CH2
6b, W= O
l
C
C
H
s
O
T
2 C
,
l
N
,
2
E
t 3
t
E
,
3 N
l 2
,
T
C
s
C
l
2
C
W
W
N
N
N
N
O
O
O
O
O
O
O
O
8a, W= CH2
8b, W= O
7, W= CH2
Scheme 2. Synthesis of bis-spiro- and dispiro-b-lactams 7, 8a,b.
6.34e7.95 (ArH, m, 17H). 13C NMR
86.9 (C-3), 114.8, 117.4, 120.3, 120.8, 121.9, 123.1, 126.2, 127.6, 127.7,
128.4, 129.1, 129.4, 129.7, 130.2, 133.8, 134.2, 138.1, 140.3, 140.6, 141.1,
d
(ppm): 20.7 (Me), 72.4 (C-4),
Table 2
Antimalarial activity and cytotoxicity of the new mono-, bis-spiro- and dispiro-
lactams
b-
Compound IC50
(
m
M)
Minimum cytotoxic concentration (mM)
156.4 (aromatic carbons), 162.2 (CO
b
-lactam). GCeMS m/z¼477
P. falciparum K14
[Mþ]. Analysis calculated for C28H21NO2: C, 83.35; H, 5.25; N, 3.47%.
Found: C, 83.30; H, 5.23; N, 3.53%.
HEL
100
VERO
HeLa
4a
4c
4d
4f
5a
5b
5c
5d
5e
5f
10.7
28.5
6.4
11.1
18.0
32.2
28.1
15.8
5.0
29.8
17.3
>50
>50
>50
100
ꢁ4
100
20
>100
>100
20
>100
ꢁ100
>100
>100
>100
>100
ꢁ100
>100
ꢁ100
ꢁ100
ꢁ100
ꢁ100
ꢁ100
4.3.2. 1-(4-Methoxyphenyl)-3-phenoxyspiro[azetidine-2,90-fluoren]-
4-one (4b). White crystal (yield 70%). Mp: 196e198 ꢂC. IR (KBr,
100
100
ꢁ20
100
4
cmꢀ1): 1758 (CO
b
-lactam). 1H NMR
d
(ppm): 3.60 (OMe, s, 3H), 5.56
>100
>4
(H-3, s, 1H), 6.05e8.18 (ArH, m, 17H). 13C NMR
d
(ppm): 55.2 (OMe),
100
100
>100
20
>20
100
100
>100
>100
>100
>100
>100
>100
>100
72.6 (C-4), 87.0 (C-3), 114.2, 114.9, 119.0, 120.3, 121.1, 123.2, 126.4,
127.8, 128.4, 129.2, 129.7, 130.2, 138.2, 140.4, 140.7, 141.1, 156.5, 156.6
(aromatic carbons), 162.0 (CO
Analysis calculated for C28H21NO3: C, 80.17; H, 5.05; N, 3.34%.
Found: C, 80.20; H, 5.11; N, 3.38%.
b
-lactam). GCeMS m/z¼419 [Mþ].
5g
7
8a
8b
4.3.3. 1-(4-Chlorophenyl)-3-phenoxyspiro[azetidine-2,90-fluoren]-4-
one (4c). White solid (yield 72%). Mp: 126e128 ꢂC. IR (KBr, cmꢀ1):
4.2. General procedure for the preparation of Schiff bases
3aeg
1758 (CO
b
-lactam). 1H NMR
d
(ppm): 5.91 (H-3, s, 1H,), 6.27e8.36
(ArH, m, 17H). 13C NMR
d
(ppm): 72.7 (C-4), 87.1 (C-3), 114.9, 118.8,
A mixture of an aromatic amine (1.00 mmol) and 9H-fluoren-9-
one (1.50 mmol) with catalytic acetic acid (100 L) was refluxed in
ethanol (20 mL) for 12 h. Evaporation of the solvent afforded the
crude imines either as oil or solid, which were used for the next
step without further purification.
120.5, 121.0, 122.1, 123.1, 126.3, 127.9, 128.6, 129.1, 129.2, 129.8, 130.1,
130.4, 134.8, 137.7, 140.4, 140.7, 140.8, 156.5 (aromatic carbons),
m
162.5 (CO
b
-lactam). GCeMS m/z¼405 [Mþ, 37Cl], 403 [Mþ, 35Cl].
Analysis calculated for C27H18ClNO2: C, 76.50; H, 4.28; N, 3.30%.
Found: C, 76.54; H, 4.31; N, 3.32%.
4.3.4. 1-(4-(Diethylamino)phenyl)-3-phenoxyspiro[azetidine-2,90-
4.3. General procedure for the synthesis of spiro- and dispiro-
fluoren]-4-one (4d). Green crystal (yield 76%). Mp: 152e154 ꢂC. IR
b-lactams 4aef and 5aeg
(KBr, cmꢀ1): 1789 (CO
b
-lactam). 1H NMR
d
(ppm): 0.98 (Me, t, 6H,
J¼7), 3.13 (CH2, q, 4H, J¼7), 5.54 (H-3, s, 1H,), 6.30e7.78 (ArH, m,
17H). 13C NMR
(ppm): 12.5 (Me), 44.3 (CH2), 72.6 (C-4), 87.0 (C-3),
A mixture of the previous crude Schiff base, triethylamine
d
(5.00 mmol), 9H-xanthen-9-carboxylic acid or phenoxyacetic acid
(1.50 mmol) and tosyl chloride (1.50 mmol) in dry CH2Cl2 (15 mL)
was stirred at room temperature for 15 h. Then it was washed with
HCl 1 N (20 mL), saturated NaHCO3 (20 mL) and brine (20 mL). The
organic layer was dried (Na2SO4), filtered and the solvent was
evaporated to give the product as a crystal, which was then purified
by recrystallization from ethanol.
111.7, 114.1, 119.4, 120.3, 120.7, 121.8, 123.3, 125.3, 126.5, 127.7, 128.4,
129.1, 130.1, 138.7, 140.4, 140.7, 141.6, 145.1, 156.7 (aromatic car-
bons), 161.6 (CO
b
-lactam). GCeMS m/z¼475 [Mþ]. Analysis calcu-
lated for C31H28N2O2: C, 80.84; H, 6.13; N, 6.08%. Found: C, 80.81; H,
6.18; N, 6.05%.
4.3.5. 1-(4-Ethoxyphenyl)-3-phenoxyspiro[azetidine-2,90-fluoren]-4-
one (4e). Yellow crystal (yield 75%). Mp: 140e142 ꢂC. IR (KBr,
4.3.1. 3-Phenoxy-1-p-tolylspiro[azetidine-2,90-fluoren]-4-one
(4a). White solid (yield 73%). Mp: 140e142 ꢂC. IR (KBr, cmꢀ1): 1742
cmꢀ1): 1755 (CO
b
-lactam). 1H NMR
d
(ppm): 1.26 (Me, t, 3H, J¼7),
3.79 (CH2, q, 2H, J¼7), 5.56 (H-3, s, 1H), 6.60e8.32 (ArH, m, 17H). 13
C
(CO b d (ppm): 2.08 (Me, s, 3H), 5.57 (H-3, s, 1H),
-lactam). 1H NMR

A. Jarrahpour et al. / Tetrahedron 67 (2011) 8699e8704
8703
NMR
d
(ppm): 14.7 (Me), 63.4 (CH2), 72.6 (C-4), 87.0 (C-3), 114.3,
lactam). GCeMSm/z¼507[Mþ].AnalysiscalculatedforC35H25NO3:C,
114.8, 114.9, 119.0, 120.4, 120.9, 121.9, 123.2, 126.4, 127.8, 128.5,
129.2, 129.6, 129.9, 130.2, 138.2, 140.4, 140.7, 141.2, 155.9, 156.6
(aromatic carbons), 162.0 (CO
Analysis calculated for C29H23NO3: C, 80.35; H, 5.35; N, 3.23%.
Found: C, 80.33; H, 5.32; N, 3.25%.
82.82; H, 4.96; N, 2.76%. Found: C, 82.85; H, 4.93; N, 2.75%.
b
-lactam). GCeMS m/z¼433 [Mþ].
4.3.12. 1-(4-(Dimethylamino)phenyl)-dispiro[azetidine((2,90-fluo-
ren)(3,90-xanthen))]-4-one (5f). White solid (yield 65%). Dec:
230e232 ꢂC. IR (KBr, cmꢀ1): 1735 (CO
b
-lactam). 1H NMR
d
(ppm):
2.78 (Me, s, 6H), 6.44e8.32 (ArH, m, 20H). 13C NMR
d (ppm): 40.6
4.3.6. 1-(4-Isopropylphenyl)-3-phenoxyspiro[azetidine-2,90-fluoren]-
4-one (4f). White solid (yield 48%). Mp: 144e146 ꢂC. IR (KBr, cmꢀ1):
(Me), 69.2 (C-3), 78.6 (C-4), 112.7, 116.3, 117.1, 118.9, 120.0, 120.3,
121.5, 122.5, 122.8, 123.8, 125.5, 126.0, 126.8, 126.9, 127.5, 128.5,
128.8, 129.3, 129.5, 140.1, 140.2, 147.7, 153.6 (aromatic carbons),
1758 (CO
2.69(CH, m, 1H), 5.57 (H-3, s, 1H), 6.34e8.30 (ArH, m, 17H). 13C NMR
(ppm): 23.8 (Me), 33.5 (CH), 72.5 (C-4), 87.1 (C-3), 114.9, 117.6,
b
-lactam). 1H NMR
d
(ppm): 1.13 (Me, d, 6H, J¼3.8),
163.5 (CO
b
-lactam). GCeMS m/z¼507 [Mþ]. Analysis calculated for
d
C35H26N2O2: C, 82.98; H, 5.17; N, 5.53%. Found: C, 82.93; H, 5.21; N,
5.51%.
120.4, 120.9, 122.0, 123.2, 126.4, 127.0, 127.8, 128.5, 129.2, 129.9,
130.2, 134.2, 138.2, 140.4, 140.7, 141.2, 145.2, 156.6 (aromatic car-
bons), 162.4 (CO
culated for C30H25NO2: C, 83.50; H, 5.84; N, 3.25%. Found: C, 83.52;
H, 5.81; N, 3.30%.
b
-lactam). GCeMS m/z¼431 [Mþ]. Analysis cal-
4.3.13. 1-(4-Isopropylphenyl)-dispiro[azetidine((2,90-fluoren)(3,90-
xanthen))]-4-one (5g). White solid (yield 63%). Mp: 238e240 ꢂC. IR
(KBr, cmꢀ1): 1751 (CO -lactam). 1H NMR
b d (ppm): 1.25 (Me, d, 6H,
J¼3.8), 2.74 (CH, m, 1H), 6.42e8.05 (ArH, m, 20H). 13C NMR
d (ppm):
4.3.7. 1-(4-Methylphenyl)-dispiro[azetidine((2,90-fluoren)(3,90-
xanthen))]-4-one (5a). Yellow crystal (yield 55%). Dec: 222e224 ꢂC.
23.8 (Me), 33.5 (CH), 69.1 (C-3), 78.5 (C-4), 116.3, 117.0, 117.5, 119.8,
120.0, 122.2, 122.8, 123.8, 125.4, 126.0, 126.6, 126.9, 127.3, 128.6,
128.9, 129.3, 129.4, 134.3, 139.7, 140.0, 145.0, 151.0, 153.5 (aromatic
IR (KBr, cmꢀ1): 1755 (CO
b
-lactam). 1H NMR
d
(ppm): 2.02 (Me, s,
3H), 6.30e8.99 (ArH, m, 20H). 13C NMR
d
(ppm): 20.8 (Me), 61.7 (C-
carbons), 164.3 (CO
b
-lactam). GCeMS m/z¼506 [Mþ]. Analysis
3), 78.5 (C-4), 116.3, 116.7, 117.2, 117.4, 120.0, 122.2, 122.8, 123.1,
125.3, 126.0, 126.9, 127.3, 128.6, 128.9, 129.5, 134.1, 134.6, 139.7,
calculated for C36H27NO2: C, 85.52; H, 5.38; N, 2.77%. Found: C,
85.50; H, 5.34; N, 2.72%.
140.0, 152.0, 153.5, 164.3 (aromatic carbons), 169.1 (CO b-lactam).
GCeMS m/z¼477 [Mþ]. Analysis calculated for C34H23NO2: C, 85.51;
4.4. General procedure for the preparation of bis-Schiff bases
6a,b
H, 4.85; N, 2.93%. Found: C, 85.30; H, 4.73; N, 3.13%.
4.3.8. 1-(4-Methoxyphenyl)-dispiro[azetidine((2,90-fluoren)(3,90-
xanthen))]-4-one (5b). White crystal (yield 77%). Dec: 238e240 ꢂC.
A mixture of 9H-fluoren-9-one (3.00 mmol) and bisamine
(1.00 mmol) with catalytic amount of acetic acid was refluxed in
ethanol (20 mL) for 12 h. Evaporation of the solvent afforded the
crude imines as oil, which were used for the next step without
further purification.
IR (KBr, cmꢀ1): 1751 (CO
b
-lactam). 1H NMR
d
(ppm): 3.64 (OMe, s,
3H), 6.30e8.36 (ArH, m, 20H). 13C NMR
d (ppm): 55.3 (OMe), 69.2
(C-3), 78.6 (C-4), 114.2, 116.4, 118.9, 120.0, 122.3, 122.8, 125.4, 126.1,
127.3, 128.6, 128.9, 130.0, 139.7, 140.1, 153.5, 156.3 (aromatic car-
bons), 164.0 (CO
culated for C34H23NO3: C, 82.74; H, 4.70; N, 2.84%. Found: C, 82.65;
H, 4.71; N, 2.81%.
b
-lactam). GCeMS m/z¼493 [Mþ]. Analysis cal-
4.5. General procedure for the synthesis of bis-spiro- and
dispiro-b-lactams 7 and 8a,b
A mixture of previous crude Schiff base 6a,b, triethylamine
(10.00 mmol), 9H-xanthen-9-carboxylic acid or phenoxyacetic acid
(3.00 mmol) and tosyl chloride (3.00 mmol) in dry CH2Cl2 (15 mL)
was stirred at room temperature for 24 h. Then it was washed with
HCl 1 N (20 mL), saturated NaHCO3 (20 mL) and brine (20 mL). The
organic layer was dried over Na2SO4, filtered and the solvent was
evaporated to give the product as a solid, which was then purified
by column chromatography, EtOAc/petroleum ether (8/2) as the
eluent solvent.
4.3.9. 1-(4-Chlorophenyl)-dispiro[azetidine((2,90-fluoren)(3,90-
xanthen))]-4-one (5c). White solid (yield 61%). Dec: 226e228 ꢂC. IR
(KBr, cmꢀ1): 1758 (CO
b
-lactam). 1H NMR
d
(ppm): 6.40e8.05 (ArH,
m, 20H). 13C NMR
d
(ppm): 69.5 (C-3), 78.7 (C-4), 116.5, 117.2, 118.4,
120.2, 121.0, 122.0, 122.9, 124.0, 125.3, 126.2, 127.2, 128.8, 129.1,
129.2, 129.4, 129.6, 135.0, 139.2, 140.1, 153.5 (aromatic carbons),
164.7 (CO
b
-lactam). GCeMS m/z¼499 [Mþ, 37Cl], 497 [Mþ, 35Cl].
Analysis calculated for C33H20ClNO2: C, 79.59; H, 4.05; N, 2.81%.
Found: C, 79.54; H, 4.12; N, 2.85%.
4.5.1. (4-(4(4-Oxo-3-phenoxyspiro[azetidine-2,90-fluoren]1-yl)ben-
zyl)phenyl)3-phenoxyspiro[azetidine-2,90-fluoren]-4-one (7). White
4.3.10. 1-(4-(Diethylamino)phenyl)-dispiro[azetidine((2,90-fluo-
ren)(3,90-xanthen))]-4-one (5d). White solid (yield 80%). Dec:
solid (yield 45%). Mp: 188e190 ꢂC. IR (KBr, cmꢀ1): 1735 (CO
b
-lac-
(ppm): 3.56 (CH2, s, 2H), 5.53 (H-3, s, 2H),
6.32e8.21 (ArH, m, 34H). 13C NMR
(ppm): 40.6 (CH2) 72.4 (C-4),
220e222 ꢂC. IR (KBr, cmꢀ1): 1739 (CO
b
-lactam). 1H NMR
d
(ppm):
1.01 (Me, t, 6H, J¼7), 3.15 (CH2, q, 4H, J¼7), 6.35e8.39 (m, ArH, 20H).
13C NMR
(ppm): 12.6 (Me), 44.3 (CH2), 69.1 (C-3), 78.7 (C-4), 111.8,
tam). 1H NMR
d
d
d
86.9 (C-3), 114.8, 117.5, 120.3, 120.8, 121.9, 122.3, 123.1, 126.3, 127.7,
128.4, 129.1, 129.2, 129.8, 130.1, 134.4, 136.9, 137.9, 140.2, 140.5,
140.9, 156.4 (aromatic carbons), 162.3 (CO b-lactam). Analysis cal-
culated for C55H38N2O4: C, 83.52; H, 4.84; N, 3.54%. Found: C, 83.55;
H, 4.87; N, 3.51%.
116.4, 116.8, 119.3, 120.0, 120.4, 122.6, 122.8, 123.2, 125.6, 125.7,
126.0, 127.0, 128.6, 128.9, 129.8, 140.2, 140.3, 145.0, 153.6 (aromatic
carbons), 163.4 (CO
calculated for C37H30N2O2: C, 83.12; H, 5.66; N, 5.24%. Found: C,
83.20; H, 5.62; N, 5.21%.
b
-lactam). GCeMS m/z¼534 [Mþ]. Analysis
4.5.2. (4(4(4-Oxo-dispiro[azetidine((2,90-fluoren)(3,90-xanthen))]1-
yl)benzyl)phenyl)dispiro[azetidine((2,90-fluoren)(3,90-xanthen))]4-
one (8a). Yellow solid (yield 45%). Dec: 210e212 ꢂC. IR (KBr, cmꢀ1):
4.3.11. 1-(4-Ethoxyphenyl)-dispiro[azetidine((2,90-fluoren)(3,90-
xanthen))]-4-one (5e). White solid (yield 83%). Mp: 228e230 ꢂC. IR
(KBr, cmꢀ1): 1751 (CO
b
-lactam). 1H NMR
d
(ppm): 1.30 (Me, t, 3H,
1735 (CO
b
-lactam). 1H NMR
d
(ppm): 3.74 (CH2, d, 2H, J¼10.8),
J¼7), 3.83 (CH2, q, 2H, J¼7), 6.60e8.32 (ArH, m, 20H). 13C NMR
6.80e7.80 (ArH, m, 40H). 13C NMR
d
(ppm): 40.6 (CH2), 69.1 (C-3),
d
(ppm): 14.7 (Me), 63.5 (CH2), 69.2 (C-3), 78.7 (C-4), 114.8, 116.4,
78.5 (C-4), 116.4, 117.1, 117.5, 119.8, 120.0, 122.1, 122.8, 123.8, 125.4,
126.0, 127.2, 128.6, 128.9, 129.1, 129.3, 129.4, 134.7, 136.9, 139.6,
140.0, 153.4 (aromatic carbons), 164.4 (CO b-lactam). Analysis
116.8, 118.9, 120.1, 122.3, 122.8, 123.2, 125.4, 126.1, 127.4, 128.7, 129.0,
129.7,130.0,139.8,140.1,153.5,155.7 (aromatic carbons),164.0 (CO
b-

8704
A. Jarrahpour et al. / Tetrahedron 67 (2011) 8699e8704
Yamamoto, Y.; Asao, N.; Tsukuda, N. In Advances in Asymmetric Synthesis; Hassner,
A. H., Ed.; JAI: Stamford, CT,1998;Vol. 3; (g) Muller, T. E.;Beller, M. Chem. Rev.1998,
98, 675e703; (h) Doyle, M. P. Pure Appl. Chem. 1998, 70, 1123e1128.
calculated for C67H42N2O4: C, 85.69; H, 4.51; N, 2.98%. Found: C,
85.71; H, 4.56; N, 2.93%.
6. (a) Dalla-Croce, P.; La Rosa, C.; Ferraccioli, R. Tetrahedron 1999, 55, 201e210; (b)
Anklam, S.; Liebscher, J. Tetrahedron 1998, 54, 6369e6384; (c) Fetter, J.; Bertha,
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Zaks, A.; Chackalmannil, S.; Dugar, S. J. Org. Chem. 1996, 61, 8341e8343; (e)
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Guest, A. W.; Bateson, J. H. Tetrahedron Lett. 1993, 34, 1799e1802; (g) Ishibashi,
I.; Nakamura, N.; Sato, T.; Takeuchi, M.; Ikeda, M. Tetrahedron Lett. 1991, 32,
1725e1728; (h) Sharma, M. K.; Durst, T. Tetrahedron Lett. 1990, 31, 3249e3252;
(i) Ikeda, M.; Uchino, T.; Ishibashi, H.; Tamura, Y.; Ikeda, M. J. Chem. Soc., Chem.
4.5.3. (4(4(4-Oxo-dispiro[azetidine((2,90-fluoren)(3,90-xanthen))]1-
yl)phenoxy)phenyl)dispiro[azetidine((2,90-fluoren)(3,90-xant hen))]
4-one (8b). White solid (yield 48%). Mp: 188e190 ꢂC. IR (KBr,
cmꢀ1): 1735 (CO
40H). 13C NMR
b
-lactam). 1H NMR
d
(ppm): 6.63e8.33 (ArH, m,
d
(ppm): 69.3 (C-3), 78.6 (C-4), 116.4, 117.1, 118.5,
118.9, 119.2, 120.0, 121.4, 122.1, 122.8, 123.9, 125.4, 126.1, 127.2, 128.7,
129.0, 129.4, 132.1, 139.4, 140.1, 153.4, 153.5 (aromatic carbons),
164.2 (CO b-lactam). Analysis calculated for C66H40N2O5: C, 84.24;
ꢀ €
Commun. 1984, 758e759; (j) Csaky, A. G.; Medel, R.; Murcia, M. C.; Plumet, J.
Helv. Chim. Acta 2005, 88, 1387e1396; (k) Jarrahpour, A.; Ebrahimi, E. Molecules
2010, 15, 515e531.
H, 4.28; N, 2.98%. Found: C, 84.25; H, 4.31; N, 2.95%.
7. (a) Alcaide, B.; Almendros, P.; Rodriguez-Acebes, R. Chem.dEur. J. 2005, 11,
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ugopalan, P.; Bhasin, K. K.; Bari, S. S. Tetrahedron 2007, 63, 3195e3204; (n) Al-
caide, B.; Almendros, P.; Rodríguez-Acebes, R. J. Org. Chem. 2006, 71,
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4.6. General procedure for antimalarial activity
measurements
The chloroquine-resistant P. falciparum strain K14 (Southeast
Asia) was cultured in vitro in complete medium consisting of RPMI
1640 (In Vitrogen) supplemented with 27.5 mM NaHCO3, 20 mg/L
gentamycin, and 10% human serum.23 Parasites were grown at
37 ꢂC in human Oþ red blood cells at a 6% haematocrit under a 5%
CO2,10% O2 and 85% N2 atmosphere. Cultures were synchronized by
sorbitol treatments.24 Stock solutions of lactam derivatives were
prepared in sterile DMSO (10 mM) and later dilutions were with
complete culture medium. Increasing concentrations of lactam
derivatives (100
uted in a 96-well plate; DMSO (0.5% vol/vol, top concentration) was
distributed for control. Then,100 L from a culture containing >95%
ring (0e20 h postinvasion) at a 0.8% parasitaemia and 3% haema-
tocrit in complete medium was added per well along with 1.0 Ci of
mL/well, top concentration¼50
mM) were distrib-
m
m
3H-hypoxanthine with a specific activity of 14.1 Ci/mmol (Per-
kineElmer, Courtaboeuf, France). Parasites were grrown for 42 h at
37 ꢂC. Plates were then freeze-thawed and harvested on filters.
Dried filters were moistened in scintillation liquid mixture
ꢀ
Csaky, A. G.; Murcia, M. C.; Plumet, J. Tetrahedron Lett. 2002, 43, 6405e6408.
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11. Wu, G.; Tormos, W. J. Org. Chem. 1997, 62, 6412e6414.
12. Repa, J. J.; Drestschy, J. M.; Turley, S. D. J. Lipid Res. 2002, 43, 1864e1874.
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(Microscint O; PerkineElmer) and counted in
a Top Count
Microbeta counter (PerkineElmer). Percentage growth inhibition
was calculated from the parasite-associtaed radioactivity. 100% 3H-
hypoxanthine incorporation was determined from a control grown
in the absence of lactam derivatives. The concentration of drug
giving 50% inhibition of label incorporation (IC50) was determined
by nonlinear regression analysis of log-based doseeresponse curve
(Riasmart; Packard). Each concentration was estimated from in-
dependent experiments in triplicate.
14. Alonso, E.; del Pozo, C.; Gonzalez, J. Synlett 2002, 69e72.
15. Alonso, E.; del Pozo, C.; Gonzalez, J.; Macias, A. Tetrahedron Lett. 2004, 45,
4657e4660.
Acknowledgements
16. Dalla-Croce, P.; La Rosa, C. Heterocycles 2000, 53, 2653e2660.
17. Barba, B.; Hernandez, C.; Rojas-Lima, S.; Farfan, N.; Santillan, R. Can. J. Chem.
1999, 77, 2025e2032.
The authors thank the Shiraz University Research Council for
financial support (Grant No. 88-GR-SC-23).
18. (a) Dalla Croce, P.; Ferraccioli, R.; La Rosa, C. Tetrahedron 1995, 51, 9385e9392;
(b) Khasanov, A. B.; Ramirez-weinhouse, M. M.; Webb, T. R.; Thirunazi, M. J. Org.
Chem. 2004, 69, 5766e5769.
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