A new class of potential chloroquine-resistance reversal agents for plasmodia: Syntheses and biological evaluation of 1-(3'-Diethylaminopropyl)-3-(substituted phenylmethylene)pyrrolidines

Article abstract of DOI:10.1021/jm000083u

1-(3'-Diethylaminopropyl)-3-(substituted phenylmethylene)pyrrolidines were synthesized and evaluated for CQ-resistant reversal activity. In general the compounds of the series elicit better biological response than their phenylmethyl analogues. The most a

Full text of DOI:10.1021/jm000083u

3428
J . Med. Chem. 2000, 43, 3428-3433
A New Cla ss of P oten tia l Ch lor oqu in e-Resista n ce Rever sa l Agen ts for
P la sm od ia : Syn th eses a n d Biologica l Eva lu a tion of
1-(3′-Dieth yla m in op r op yl)-3-(su bstitu ted p h en ylm eth ylen e)p yr r olid in es#
Sanjay Batra,*,† Pratima Srivastava,‡ Kamal Roy,†,| V. C. Pandey,§ and A. P. Bhaduri†
Divisions of Medicinal Chemistry, Pharmacokinetics and Metabolism, and Biochemistry, Central Drug Research Institute,
Lucknow 226 001, India
Received February 24, 2000
1-(3′-Diethylaminopropyl)-3-(substituted phenylmethylene)pyrrolidines were synthesized and
evaluated for CQ-resistant reversal activity. In general the compounds of the series elicit better
biological response than their phenylmethyl analogues. The most active compound 4b has been
evaluated in vivo in detail, and the results are presented. The possible mode of action of the
compounds of this series is by inhibition of the enzyme heme oxygenase, thereby increasing
the levels of heme and hemozoin, which are lethal to the parasite.
In tr od u ction
The disease malaria is caused by the protozoan
parasite of the genus Plasmodium and it leads to
mortality if subjects infected with P. falciparum are left
untreated. This disease affects around 300 million
subjects worldwide leading to more than 2 million
deaths per year. The treatment of falciparum malaria
has attracted global attention because of the growing
resistance of the parasites toward all the known anti-
malarial drugs. Complete compliance of the recom-
mended treatment by patients is desired for avoiding
such agents has led to biological evaluation of various
early development of the drug-resistant strains of the
calcium channel blockers,3 antidepressants,4 antihista-
parasite. In countries where hospital facilities cannot
mines,5 and prostaglandin oligomers6 as CQ-resistance
be extended to all patients, total compliance of recom-
reversal agents, but they could not be pursued further
mended treatment is not assured. As an emergency
since they were effective only in vitro.
measure, therefore, the most recent antimalarial drug,
The key point in designing the strategy toward the
such as artemisinin, in these countries is recommended
development of any such resistance reversal agent is
for hospital use only. The management for the control
the identification of the biochemical event, which may
of this disease is further complicated by the absence of
be correlated, with the development of resistance. The
either any prophylactic vaccine or a new drug, which
biochemical event identified at our institute is increased
targets plasmodial genes.1 The chemotherapy of malaria
capability of the CQ-resistant parasite to degrade heme
thus continues to be a matter of concern for medicinal
or hemozoin through heme oxygenase associated with
chemists. Better clinical experience with the easily
an increase in glutathione-S-transferase activity.7 Since
accessible antimalarial drug, chloroquine (CQ), does not
it is almost certain that the heme-CQ complex is toxic
help clinicians now because of the emergence of CQ-
to the parasite, our effort toward the development of a
resistant plasmodial strains. The present investigation,
resistance reversal agent is concerned with the discov-
therefore, aims toward discovering compounds which,
ery of compounds that may interfere with the heme
in combination with CQ, will make CQ-resistant plas-
degradation pathway of the CQ-resistant parasite. The
modia susceptible to this combination therapy leading
earlier works from this laboratory have concluded that
to the death of the resistant parasites. These com-
in comparison to the CQ-sensitive parasite, the CQ-
pounds, hereafter for the sake of simplicity, will be
resistant parasite has enhanced heme oxygenase and
addressed as CQ-resistance reversal agents.2 Search for
decreased levels of heme/hemozoin.7 In another obser-
vation from our group it has been reported that heme
oxygenase is responsible for heme and hemozoin deg-
#
CDRI Communication No. 6024.
* To whom correspondence should be addressed: Dr. Sanjay Batra,
radation generated during the intra-erythrocytic devel-
opment of malarial parasites of different species, viz.
P. falciparum, P. knowlesi, P. yoelii, and P. berghei.8,9
In light of these observations, it was envisaged that
compounds capable of inhibiting heme degradation
could increase the levels of the heme-CQ complex and
could thus cause the death of the CQ-resistant parasites
Medicinal Chemistry Division, Central Drug Research Institute, P.O.
Box 173, Chattar Manzil Palace, Lucknow 226 001, India. Tel: 0522-
212411-18 (EPABX) ext. 4368, 4383. Fax: 91-0522-223405, 223938.
E-mail: root@cscdri.ren.nic.in, batra_san@yahoo.co.uk.
† Medicinal Chemistry Division.
‡ Pharmacokinetics and Metabolism Division.
§ Biochemistry Division.
| Current address: Torrent Pharmaceuticals Pvt. Ltd., P.O. Village
Bhat, Gandhinagar, Gujarat, India.
10.1021/jm000083u CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/22/2000

CQ-Resistance Reversal Agents for Plasmodia
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3429
Sch em e 1a
P. berghei K173 strain infected erythrocytes suspended
in acid citrate dextrose solution using M. coucha. The
CQ-resistant strain of P. berghei was developed by
exposing the sensitive strain infected animals to in-
creasing doses of CQ and repassaging the infected blood
into healthy animals. This was continued till the
animals maintained a parasitemia even after orally
receiving 65 mg/kg body wt of CQ. The degree of drug
pressure was periodically checked in infected mastomys.
Simultaneously, P. yoelii nigeriensis infection was main-
tained in Swiss albino mice having CQ tolerance up to
120 mg/kg body wt. Infection was ascertained by moni-
toring the Giemsa-stained blood smears of infected
animals microscopically. The isolation of the parasites
was carried out from infected animal blood through
density gradient centrifugation and saponin lysis as
described earlier. Heme oxygenase activity was assayed
following the bilirubin formation in the post-mitochon-
drial fraction. Different concentrations (10-100 µM) of
test compounds were supplemented in the assay system
and preincubated for 10 min before starting the enzyme
reaction.
In Vivo Assa y. CQ/compound 4b was administered
orally in aqueous medium to mastomys having 4-5%
parasitemia of CQ-resistant P. berghei and mice having
1-2% parasitemia of P. yoelii nigeriensis for 10 consecu-
tive days. For studying the effect of compound 4b,
infected animals were divided into 4 groups of 10 mice
each. The first group received CQ alone (10 mg/kg body
wt); the second group received compound 4b alone (15
mg/kg body wt); the third group received a combination
of compound 4b and CQ (15 and 10 mg/kg body wt,
respectively); the fourth group was kept as a control
without any treatment. The parasitemia was monitored
periodically. The feeding experiments of CQ/compound
4b were repeated with fresh batches of CQ-resistant P.
berghei (5 times) or P. yoelii nigeriensis (4 times)
infected animals on different days, and the cured
mastomys/mice blood was reinoculated into fresh nor-
mal animals for validation of resurgence of infection.
a
(a) LiAlH4, dry ether; (b) MsCl, Et3N, dry benzene; (c) N,N′-
diethylaminopropylamine, Et3N, dry benzene; (d) Na, liquid NH3,
dry ether; (e) 2-(pyrrolidin-1-yl)ethyl chloride hydrochloride, K2CO3,
dry acetone.
if given in combination with CQ. We have earlier
reported a novel pyrrolidinoaminoalkane (CDRI 87/209),
which was found to be a CQ-resistance reversal agent
both in vitro10,11 and in vivo.12 In the study directed
toward delineating its possible mode of action, it has
been observed that CDRI 87/209 showed inhibition
against heme oxygenase and heme polymerase, the
two enzymes involved in the heme degradation path-
way. In our search for identification of newer molecular
structures, it was desired to synthesize compounds
analogous to CDRI 87/209. The central point of design-
ing new analogues was to bring restricted rotation
around the position 3 of the pyrrolidine ring and then
evaluate the biological activity. This led to the synthesis
and evaluation of 1-(3′-diethylaminopropyl)-3-(substi-
tuted phenylmethylene)pyrrolidines as CQ-resistance
reversal agents. The details of this study are presented
here.
Ch em istr y
The starting materials, namely 3-(substituted phen-
ylmethylene)-4,5-dihydro-2(3H)-furanones 1 (Scheme 1),
used for the synthesis of possible CQ-resistance reversal
agents were obtained by reacting substituted benzal-
dehyde with γ-butyrolactone in the presence of sodium
methoxide. However, compound 1d was prepared by
reaction of 4-benzyloxybenzaldehyde with γ-butyrol-
actone in the presence of sodium hydride in dry benzene.
The next step was to obtain diols 2 by reductive ring
opening of the butyrolactone by slow addition of
LiAlH4 to compounds dissolved in dry ether under
nitrogen. The diols were then subjected to mesylation
in the presence of methanesulfonyl chloride to obtain
the dimesyl derivative 3. These compounds on refluxing
with primary amine in dry benzene cyclized to yield
pyrrolidines 4. Debenzylation of compound 4d with
sodium in liquid ammonia at -40 °C yielded the
hydroxy derivative 5 in quantitative yield. This was
alkylated with 1-(2-aminoethyl)pyrrolidine hydrochlo-
ride to yield compound 6. All the amines were converted
to their oxalate salts by reacting them with oxalic acid
in a methanol-toluene mixture and then adding dry
ether to precipitate them.
In a separate set of experiments, P. yoelii nigeriensis
(multidrug-resistant) and P. berghei (CQ-resistant)
infected mice and mastomys were orally fed compound
4b (15 mg/kg body wt) or CQ (10 mg/kg body wt) for 6
and 10 days, respectively. After attainment of para-
sitemia of about 70% in former and about 25% in latter,
the parasites were isolated and further processed for
determination of heme oxygenase, heme polymerase,
heme, and hemozoin as reported earlier.12
Resu lts a n d Discu ssion
The main concern of the present investigation was to
discover compounds capable of selective inhibition of
heme degradation in plasmodia. Since heme degrada-
tion involves heme oxygenase activity, all the com-
pounds were, therefore, screened to monitor the in vitro
effect on heme oxygenase activity of cell-free parasite
P. yoelii as well as infected hepatic host enzyme for
control. Among all the compounds screened in vitro,
compounds 4c, 4d , and 6 were found to be complete
inhibitors of parasite heme oxygenase but they did not
inhibit the host enzyme, while compounds 4a , 4b, and
4e inhibited both parasite and host heme oxygenase
(Table 1). The Ki values of heme oxygenase with
CQ-Resista n ce Rever sa l Activity. The parasitic
infection was maintained by routinely inoculating 107

3430 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18
Batra et al.
Ta ble 1. In Vitro Effect of Different Compounds on Heme
Oxygenase Activity of Cell-Free Parasite P. yoelii and the
Corresponding Infected Host
treatment schedule of CQ and compound 4b, percentage
of parasitemia at different time intervals, and mean
survival time of CQ-resistant P. berghei and multidrug-
resistant P. yoelii nigeriensis infected mastomys and
mice, respectively. Dividing the infected animals into
four groups followed the protocol of treatment. In the
fourth group of mastomys having no treatment, the
parasitemia increased with an increase in time and the
maximum parasitemia was about 30% on 20-22 day
post-infection, after which the animals started dying.
All the treatments of CQ-resistant plasmodia in infected
mice were started at 4-5% parasitemia. The first and
second groups of animals received CQ and compound
4b at 10 and 15 mg/kg body wt, respectively, for 10
consecutive days, and the parasitemia developed simi-
larly as in the control (fourth group). However, the third
group of mastomys having received a combination of CQ
and compound 4b (10 and 15 mg/kg body wt) for 10 days
showed clearance of parasitemia after about 1 week
after cessation of treatment. It was also observed that
there was no significant rise in parasitemia during the
schedule of treatment in this group. The survival time
of the third group of mastomys was about 3 months
(Table 3). Reinoculation of healthy animals with blood
of the third group of mastomys did not show any
recurrence of parasitemia.
% inhib in heme oxygenase
R
compd concn (µM)
parasite
host
H
4a
4b
4c
4d
4e
6
10
50
100
10
50
100
10
50
100
10
50
100
10
52
64
82
48
64
10
65
65
nil
21
31
nil
nil
nil
nil
nil
nil
24
63
69
nil
nil
nil
4-OMe
87
3,4-(OMe)2
3,4-OCH2O
4-OCH2Ph
100
100
100
100
100
100
28
37
64
100
100
100
50
100
10
50
100
chlorpromazine
diltiazem
50
100
50
100
50
85
100
12.5
29
100
100
nil
nil
41
84
15
19
verapamil
100
Similar to these observations, parallel results were
obtained when P. yoelii nigeriensis infected Swiss albino
mice were used in place of P. berghei infected mastomys.
However, the parasitemia for starting the treatment
schedule was 1-2%, the maximum parasitemia attained
by the animals was about 60-70%, and the mean
survival time was about 1 week in the first, second, and
fourth groups of mice. The third group of mice receiving
a combination therapy of CQ and compound 4b (10 and
15 mg/kg body wt, respectively) for 10 consecutive days
survived for more than 1 month (Table 4).
In the study directed toward evaluation of status of
heme oxygenase, heme, and hemozoin in the parasites
isolated from animals treated with compound 4b, it was
observed that CQ-resistant P. berghei has about 10
times higher activity of heme oxygenase as compared
to its CQ-sensitive counterpart. Heme and hemozoin
levels showed about 6- and 2-fold decreases, respec-
tively, in the CQ-resistant plasmodia as compared to
the CQ-sensitive strain (Table 5). The multidrug-
resistant P. yoelii nigeriensis isolated from the infected
animals also showed complete inhibition of heme oxy-
genase, and the levels of heme and hemozoin were
increased and decreased, respectively (Table 6).
Ta ble 2. Status of Heme Oxygenase and
Glutathione-S-transferase Activities in P. yoelii nigeriensis
Isolated from Infected Mice Orally Treated with the
Compounds
% inhibition in
compd (15 mg/kg
heme
glutathione-
S-transferase
body wt for 5 days)
oxygenase
4a
4b
4c
4d
4e
6
nil
100
100
nil
nil
79
nil
99
80
10
nil
90
compound 4b for CQ-resistant was found to be almost
one-half that of the CQ-sensitive strain of P. berghei.
Since the main aim of this study was to find a CQ-
resistance reversal agent which is active in vivo and has
a better activity profile than our earlier reported
compound CDRI 87/209, all the compounds were first
evaluated for their in vivo heme oxygenase inhibitory
activity in P. yoelii nigeriensis isolated from infected
mice. In this study, apart from heme oxygenase, the
effect on another enzyme, namely glutathione-S-trans-
ferase, was also monitored because the level of this
enzyme was found to be higher in resistant plasmodia.
Of all the compounds, 4b showed complete inhibition
of both the enzymes, while compounds 4c and 6 exhib-
ited potent inhibition; the remaining compounds did not
show any inhibitory activity (Table 2). Upon the basis
of these observations compound 4b was selected for
detailed in vivo evaluation for CQ-resistance reversal
activity.
Con clu sion
A new series of CQ-resistance reversal agents was
synthesized and evaluated. Preliminary results indicate
that of all the synthesized compounds, 1-(3′-diethylami-
nopropyl)-3-((4-methoxyphenyl)methylene)pyrrolidine
(4b) is the most active compound. The ability of this
compound in combination with CQ to eliminate para-
sitemia in experimental animals infected with the CQ-
resistant plasmodia indicated the possibility of combat-
ing drug-resistant plasmodia on the basis of the
envisaged concept delineated earlier in the text. This
observation offers a new strategy for chemotherapy.
However, more detailed studies, particularly with drug-
To evaluate the in vivo CQ-resistance reversal effect
of compound 4b, it was screened against CQ-resistant
P. berghei and multidrug-resistant P. yoelii nigeriensis
infected mastomys and mice, respectively, to ascertain
the susceptibility of plasmodia to CQ in the combination
therapy. The results in Tables 3 and 4 show the

CQ-Resistance Reversal Agents for Plasmodia
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18 3431
Ta ble 3. In Vivo Evaluation of Compound 4b as a Resistance Reversal Agent in CQ-Resistant P. berghei Infected M. couchaa
parameter
group I
4-5%
CQ: 10 mg/kg
body wt
group II
4-5%
4b: 15 mg/kg
body wt
group III
group IV
parasitemia before treatment
dose of CQ and/or compound 4b
4-5%
4-5%
nil
CQ: 10 mg/kg body wt
and 4b: 15 mg/kg body wt
period of treatment
10 days
15-17%
>25-30%
20-22 days
10 days
20-22%
>25-30%
20-22 days
10 days
nil
nil
observed for 3 months,
no death
not applicable
20-22%
>25-30%
20-22 days
parasitemia on day 10 of treatment
parasitemia 1 week after 10-day treatment
mean survival time
a
Each group constituted 20 mastomys infected with CQ-resistant P. berghei K173 strain (able to tolerate 65-70 mg/kg body wt of CQ
base orally; sensitive strain could tolerate 8 mg/kg body wt). The experiment was repeated 5 times. CQ and compound were fed orally in
aqueous solution.
Ta ble 4. In Vivo Evaluation of Compound 4b as a Resistance Reversal Agent in Multidrug-Resistant P. yoelii nigerienses Infected
Swiss Albino Micea
parameter
group I
1-2%
CQ: 10 mg/kg
body wt
group II
1-2%
4b: 15 mg/kg
body wt
group III
group IV
parasitemia before treatment
dose of CQ and/or compound 4b
1-2%
1-2%
nil
CQ: 10 mg/kg body wt
and 4b: 15 mg/kg body wt
period of treatment
6 days
6 days
10 days
nil
nil
observed for 1 month,
no death
not applicable
70-80%
no survival
1 week
parasitemia on day 6/10 of treatment
parasitemia 1 week after 10-day treatment
mean survival time
70-80%
no survival
1 week
70-80%
no survival
1 week
a
Each group constituted 20 mice infected with multidrug-resistant P. yoelii nigerienses (able to tolerate 120 mg/kg body wt of CQ base
orally).
Ta ble 5. Status of Heme Oxygenase, Heme, and Hemozoin in CQ-Sensitive, CQ-Resistant, and CQ-Resistant P. berghei Treated with
Compound 4b (15 mg/kg body wt) for 10 Days
sample
heme oxygenasea
hemeb
hemozoinb
CQ-sensitive P. berghei
CQ-resistant P. berghei
CQ-resistant P. berghei treated with 4b
7.32 ( 0.71
80.17 ( 14.24
no activity
344 ( 12.17
60.29 ( 9.32
321.13 ( 24.86
101.36 ( 10.13
51.39 ( 7.18
71.14 ( 13.32c
a
b
Values are mean ( SD of 4 separate observations. Specific activity in nmol/h/mg protein. Specific activity in pmol/mg protein. P <
0.001. c P ) NS.
Ta ble 6. Status of Heme Oxygenase, Heme, and Hemozoin in CQ-Sensitive, CQ-Resistant, and CQ-Resistant P. yoelii nigeriensis
Treated with Compound 4b (15 mg/kg body wt) for 10 Days
sample
heme oxygenasea
hemeb
hemozoinb
CQ-sensitive P. yoelii
CQ-resistant P. yoelii
CQ-resistant P. yoelii treated with 4b
10.23 ( 1.81
101.86 ( 13.14
no activity
218.13 ( 15.64
109.31 ( 12.13
172.14 ( 19.86
109.18 ( 17.14
43.29 ( 13.74
45.15 ( 12.62c
a
b
Values are mean ( SD of 4 separate observations. Specific activity in nmol/h/mg protein. Specific activity in pmol/mg protein. P <
0.001. c P ) NS.
ylene)-1,4-butanediol (2a ). To an ice-cooled stirred suspension
of furanone 1a (1.0 g, 5.7 mmol) in 150 mL of dry ether was
added LiAlH4 (0.2 g, 5.5 mmol) in portions over a period of 10
min under nitrogen. After the reaction mixture was stirred
for 45 min. in an ice jacket, it was decomposed with chilled
1% aq sodium hydroxide solution (10 mL) slowly. The precipi-
tate was filtered and rejected. The organic layer of the filtrate
was separated and dried over sodium sulfate. On evaporation,
the pure diol was obtained in good yield and was used for
further reaction without any purification (0.78 g, 76%): IR
resistant field isolates of P. falciparum, are required
before new drug developmental activities are initiated.
The possible mode of action of compound 4b relates to
the heme or hemozoin degradation pathway and more
specifically to heme oxygenase of the CQ-resistant
parasite thus increasing the concentration of heme in
the food vacuole. This increased heme leads to enhanced
levels of the heme-CQ complex that is lethal to the
parasite.
1
(neat) 3350 cm-1; H NMR (CDCl3) δ 2.55 (t, 2H, J ) 8 Hz,
CH2), 3.55 (t, 2H, J ) 8 Hz, CH2), 4.11 (s, 2H, CH2), 6.53 (s,
1H, dCH), 7.19 (m, 5H, Ar-H); MS (EI) m/z 178 (1.8). Anal.
(C11H14O2) C, H.
Exp er im en ta l Section
Melting points are uncorrected and were determined in
capillary tubes on a hot stage apparatus containing silicon oil.
IR spectra were carried out on a Beckman Acculab-1 spectr-
photometer and 1H NMR were recorded on a Perkin-Elmer
R-32 or Bruker 400 FT NMR spectrometer, using TMS as
internal standard (chemical shifts in δ values, J in Hz). Mass
spectrometry was carried out on a J EOL J MS-D-300 spec-
trometer. Elemental analyses were performed by a Carlo Erba
1108 microanalyzer and were within (0.4% of calculated
values in all cases.
2-[(4-Meth oxyp h en yl)m eth ylen e]-1,4-bu ta n ed iol (2b).
Similarly to the procedure described for 2a , the title compound
was prepared starting from 1b. The product was obtained as
a low-melting solid (93%): IR (neat) 3400 cm-1 1H NMR
;
(CDCl3) δ 2.54 (t, 2H, J ) 8 Hz, CH2), 3.72 (m, 5H, CH2 merged
with Ar-OCH3), 4.10 (s, 2H, CH2), 6.45 (s, 1H, dCH), 6.75 (d,
2H, J ) 9 Hz, Ar-H), 7.10 (d, 2H, J ) 9 Hz, Ar-H); MS (EI)
m/z 208 (18.9). Anal. (C12H16O3) C, H.
2-[(3,4-Dim et h oxyp h en yl)m et h ylen e]-1,4-b u t a n ed iol
(2c). Similarly to the procedure described for 2a , the title
compound was prepared starting from 1c. The product was
Gen er a l P r oced u r e for P r ep a r a tion of Diols 2a-e. This
procedure is illustrated for the preparation of 2-(phenylmeth-

3432 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 18
Batra et al.
obtained as an oil (85%): IR (neat) 3400 cm-1; 1H NMR (CDCl3)
δ 2.57 (t, 2H, J ) 8 Hz, CH2), 3.55 (t, 2H, J ) 8 Hz, CH2), 3.82
(s, 6H, 2 × Ar-OCH3), 4.12 (s, 2H, CH2), 6.47 (s, 1H, dCH),
6.75 (m, 2H, Ar-H), 6.92 (m, 1H, Ar-H); MS (EI) m/z 238
(21.7). Anal. (C13H18O4) C, H.
2-[(3,4-Meth ylen ed ioxyp h en yl)m eth ylen e]-1,4-bu ta n e-
d iol (2d ). Similarly to the procedure described for 2a , the title
compound was prepared starting from 1d . The product was
obtained as an oil (74%): IR (neat) 3400 cm-1; 1H NMR (CDCl3)
δ 2.51 (t, 2H, J ) 8 Hz, CH2), 3.58 (t, 2H, J ) 8 Hz, CH2), 4.08
(s, 2H, CH2), 5.81 (s, 2H, OCH2O), 6.47 (s, 1H, dCH), 6.75 (m,
2H, Ar-H), 6.92 (m, 1H, Ar-H); MS (EI) m/z 222 (16.8). Anal.
(C12H14O4) C, H.
described for 4b, the title compound was prepared starting
from 1c. The product was obtained as an oil (65%): 1H NMR
(CDCl3) δ 1.04 (t, 6H, J ) 8 Hz, 2 × CH3), 1.72 (m, 4H, 2 ×
CH2), 2.52 (m, 10H, 5 × CH2), 3.31 (s, 2H, CH2), 3.89 (s, 6H,
2 × Ar-OCH3), 6.28 (brs, 1H, dCH), 6.75 (m, 2H, Ar-H), 6.84
(m, 1H, Ar-H); MS (EI) m/z 332 (21.9). Oxalate salt: mp 143-
44 °C. Anal. [C20H32N2O2‚2(CO2H)2] C, H, N.
3-[(3,4-Meth ylen ed ioxyp h en yl)m eth ylen e]-1-(3-N,N-d i-
eth yla m in op r op yl)p yr r olid in e (4d ). Similarly to the pro-
cedure described for 4b, the title compound was prepared
starting from 1d . The product was obtained as an oil (59%):
1H NMR (CDCl3) δ 1.04 (t, 6H, J ) 8 Hz, 2 × CH3), 1.68 (m,
4H, 2 × CH2), 2.58 (m, 10H, 5 × CH2), 3.31 (s, 2H, CH2), 5.87
(s, 2H, OCH2O), 6.28 (brs, 1H, dCH), 6.44 (m, 2H, J ) 8 Hz,
Ar-H), 6.81 (m, 2H, J ) 8 Hz, Ar-H); MS (EI) m/z 316 (21.9).
2-[(4-Ben zyloxyp h en yl)m eth ylen e]-1,4-bu ta n ed iol (2e).
Similarly to the procedure described for 2a , the title com-
pound was prepared starting from 1e. The product was
o
Oxalate salt: mp 167-69 C. Anal. [C20H32N2O2‚2(CO2H)2] C,
1
obtained as a solid (74%): mp 89 °C; IR (neat) 3320 cm-1; H
H, N.
NMR (CDCl3) δ 2.61 (t, 2H, J ) 8 Hz, CH2), 3.79 (t, 2H, J )
8 Hz, CH2), 4.19 (s, 2H, CH2), 5.04 (s, 2H, CH2Ph), 6.53 (s,
1H, dCH), 7.09 (m, 9H, Ar-H); MS (EI) m/z 284 (17.8). Anal.
(C18H20O3) C, H.
3-[(4-Ben zyloxyph en yl)m eth ylen e]-1-(3-N,N-dieth ylam i-
n op r op yl)p yr r olid in e (4e). Similarly to the procedure de-
scribed for 4b, the title compound was prepared starting from
1e. The product was obtained as an oil (52%): 1H NMR (CDCl3)
δ 1.02 (t, 6H, J ) 8 Hz, 2 × CH3), 1.43 (m, 2H, CH2), 1.65 (m,
2H, CH2), 2.56 (m, 10H, 5 × CH2), 3.26 (s, 2H, CH2), 4.99 (s,
2H, CH2Ph), 6.23 (brs, 1H, dCH), 7.11 (m, 9H, Ar-H); MS
(EI) m/z 378 (13.2). Oxalate salt: mp 141-42 °C. Anal.
[C25H34N2O‚2(CO2H)2] C, H, N.
Gen er a l P r oced u r e for P r ep a r a t ion of Dim esyla t es
3a -e. This procedure is illustrated for the preparation of 2-[(4-
benzyloxyphenyl)methylene]-1,4-dimethanesulfonyloxybu-
tane (3e). To an ice-cooled stirred solution of diol (2.5 g, 8.8
mmol) in 80 mL dry benzene were simultaneously added
dropwise a solution of triethylamine (2.46 mL, 17.6 mmol) and
methanesulfonyl chloride (1.37 mL, 17.6 mmol) in dry benzene.
The reaction was allowed to stir at 0-5 °C for 6 h. On
completion the reaction mixture was extracted with water. The
organic layer was separated and dried over sodium sulfate.
The evaporation of solvent furnished the dimesyl derivative
3e as an oil (yield 3.3 g, 96%). Since these dimesylates were
not very stable they were immediately utilized for further
reaction: 1H NMR (CDCl3) δ 1.92 (t, 2H, CH2), 2.95 (s, 6H, 2
× SO2CH3), 4.22 (m, 4H, 2 × -CH2), 4.99 (s, 2H, CH2-Ph),
7.14 (m, 10H, Ar-H & dCH); MS (EI) m/z 440 (11.2). Anal.
(C20H24S2O7) N. D.
Typ ica l P r oced u r e for P r ep a r a tion of Com p ou n d 5.
Ammonia was first condensed in a round-bottom flask and was
allowed to distill through a passing tube into another flask
containing compound 4e (2.0 g, 5.3 mmol) in 30 mL of dry
ether. Small amount of sodium chips was then added at a
temperature between -40 and -45 °C till the reaction mixture
turned blue black. The reaction was stirred at the same
temperature for 45 min. On completion, the reaction mixture
was allowed to come to room temperature (30 °C) and then
solid ammonium chloride was added till the solution became
clear. Thereafter, the ammonia was boiled off and the solution
was filtered. The filtrate was evaporated to give the hydroxy
derivative as an oil (1.48 g, 98%): IR (neat) 3380 cm-1 1H
;
Gen er a l P r oced u r e for P r ep a r a tion of P yr r olid in es
4a -e. This procedure is illustrated for the preparation of 3-[(4-
methoxyphenyl)methylene]-1-(3-N,N-diethylaminopropyl)pyr-
rolidine (4b). A mixture of dimesylate 3b (2.0 g, 5 mmol), N,N′-
diethylaminopropylamine (4.8 mL, 30 mmol) and triethylamine
(2.8 mL, 20 mmol) in 50 mL of dry benzene was heated at
reflux with stirring for 10 h. The solvent was evaporated, and
the residue was partitioned between water and ethyl acetate.
The organic layer was washed with brine, dried over sodium
sulfate and concentrated. The residue was column chromato-
graphed over basic alumina using chloroform:methanol (99:1,
v/v) as eluent to yield the pyrrolidine 4b in 57% yield as an
oil: 1H NMR (CDCl3) δ 0.90 (t, 6H, J ) 8 Hz, 2 × CH3), 1.70
(m, 4H, 2 × CH2), 2.53 (m, 10H, 5 × CH2), 3.20 (s, 2H, CH2),
3.73 (s, 3H, Ar-OCH3), 6.19 (brs, 1H, dCH), 6.88 (d, 2H, J )
8 Hz, Ar-H), 7.16 (d, 2H, J ) 8 Hz, Ar-H); MS (EI) m/z 302
(18.1).
Gen er a l P r oced u r e for P r ep a r a tion of Oxa la te Sa lts
of P yr r olid in es. This procedure is illustrated for the prepa-
ration of the oxalate salt of compound 4b. To the solution of
compound 4b (3.0 g) in dry methanol (5 mL) was added a
solution of oxalic acid dihydrate (1.25 g) in dry methanol (10
mL). The mixture was hand shaked for 10 min and then dry
ether was added freely to precipitate the salt. This crude salt
was recrystallized from dry methanol (2.54 g, 53%): mp 184-
85 °C. Anal. [C19H30N2O‚2(CO2H)2] C, H, N.
NMR (CDCl3) δ 0.98 (t, 6H, J ) 8 Hz, 2 × CH3), 1.53 (m, 4H,
2 × CH2), 2.49 (m, 10H, 5 × CH2), 3.24 (s, 2H, CH2), 6.32 (brs,
1H, dCH), 6.83 (m, 4H, Ar-H); MS (EI) m/z 288 (33). Anal.
(C18H28N2O) ND.
Typ ica l P r oced u r e for P r ep a r a tion of Com p ou n d 6.
To a stirred solution of compound 5 (0.5 g, 1.73 mmol) in 30
mL of dry acetone were added baked potassium carbonate (0.4
g, 6.8 mmol) and N,N′-diethylaminoethylpyrrolidine hydro-
chloride (0.35 g, 2 mmol). The reaction mixture was refluxed
for 20 h; after cooling the inorganic material was filtered and
the filtrate was evaporated to furnish a residue. This oil upon
chromatography over basic alumina using methanol:chloro-
form (1:99, v/v) as an eluent furnished 3-[(4-(2-pyrrolidin-1-
yl)methoxyphenyl)methylene]-1-(3-N,N-diethylaminopropyl)-
pyrrolidine as an oil (0.45 g, 68%): 1H NMR (CDCl3) δ 1.02 (t,
6H, J ) 8 Hz, 2 × CH3), 1.78 (m, 8H, 4 × CH2), 2.58-(m, 14H,
7 × CH2), 2.88 (t, 2H, CH2), 3.42(s, 2H, CH2), 4.11 (t, 2H, CH2),
6.40 (brs, 1H, dCH), 6.88 (d, 2H, J ) 8 Hz, Ar-H), 7.11 (d,
2H, J ) 8 Hz, Ar-H); MS (EI) m/z 385 (43.2). Oxalate salt:
mp 118-21 °C. Anal. [C25H34N2O‚H2O‚3(CO2H)2] C, H, N.
Ack n ow led gm en t. Two of the authors (P.S. and
K.R.) are grateful to CSIR, New Delhi, for financial
support in the form of fellowships. Technical assistance
by R. Arora in the preparation of starting materials is
gratefully acknowledged.
3-(P h en ylm et h ylen e)-1-(3-N,N-d iet h yla m in op r op yl)-
p yr r olid in e (4a ). Similarly to the procedure described for 4b,
the title compound was prepared starting from 1a . The product
was obtained as an oil (62%): 1H NMR (CDCl3) δ 0.98 (t, 6H,
J ) 8 Hz, 2 × CH3), 1.70 (m, 4H, 2 × CH2), 2.53 (m, 10H, 5 ×
CH2), 3.29 (s, 2H, CH2), 6.28 (brs, 1H, dCH), 7.22 (m, 5H, Ar-
H); MS (EI) m/z 272 (20.9). Oxalate salt: mp 143-44 °C. Anal.
[C18H28N2‚2(CO2H)2] C, H, N.
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