Synthesis and biological evaluation of novel azetidine derivatives as dopamine antagonist

Article abstract of DOI:10.1007/s00044-013-0579-3

In this study, azetidine derivatives were evaluated for their potency as dopaminergic antagonist. The study comprised derivatives substituted in 3-position with amide moiety. Further, the phenyl moiety of amide was modified at 2, 3, or 4-position. The substituted compounds were biologically evaluated for their affinity for D₂ and D₄ receptors. The most potent D₂ and D₄ antagonist among these compounds appeared to be the N-(1-benzhydryl-azetidin-3yl)-2-bromo-benzamide and N-(1-benzhydryl-azetidin-3yl)-4-bromo-benzamide, respectively. Various docking interactions of CPPMA with the D₄ receptor and the same for compound 5 i.e., N-(1-benzhydryl-azetidin-3yl)-4-bromo-benzamide were found to have good correlation with observed biological activity.

Full text of DOI:10.1007/s00044-013-0579-3

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-013-0579-3
ORIGINAL RESEARCH
Synthesis and biological evaluation of novel azetidine derivatives
as dopamine antagonist
•
Shashikant D. Metkar Manish S. Bhatia
•
Uday V. Desai
Received: 6 September 2012 / Accepted: 11 March 2013
Ó Springer Science+Business Media New York 2013
Abstract In this study, azetidine derivatives were eval-
uated for their potency as dopaminergic antagonist. The
study comprised derivatives substituted in 3-position with
amide moiety. Further, the phenyl moiety of amide was
modified at 2, 3, or 4-position. The substituted compounds
were biologically evaluated for their affinity for D2 and D4
receptors. The most potent D2 and D4 antagonist among
these compounds appeared to be the N-(1-benzhydryl-
azetidin-3yl)-2-bromo-benzamide and N-(1-benzhydryl-
azetidin-3yl)-4-bromo-benzamide, respectively. Various
docking interactions of CPPMA with the D4 receptor and
the same for compound 5 i.e., N-(1-benzhydryl-azetidin-
3yl)-4-bromo-benzamide were found to have good corre-
lation with observed biological activity.
tool in many drugs or bioactive compounds. (Pettersson
et al., 2011; Rajasekaran et al., 2010) Despite their
remarkable biological importance due to the difficulty in
formation of four member ring and strained nature, azeti-
dines have been relatively less explored class of compounds.
In fact, compounds bearing azetidine moiety find wide
application in reducing blood cholesterol levels (Kvarebo
et al., 2005), as human chymase inhibitors (Aoyana et al.,
2001), as gamma amino butyric acid reuptake inhibitors
(Faust et al., 2010; Metzner et al., 2004), as antifungals
(Singh et al., 2006), as antibacterials (O’Dowd et al., 2008),
as well as antidepressants (Melloni et al., 1979).
The literature survey revealed that sulpiride (Ratomp-
onirina et al., 2003) and a few compounds belonging to
FAUC series (Heindl et al., 2003; Abbas et al., 2009; Orr,
1986; Barth et al., 1997; Woodhead et al., 2006) have been
widely used as dopamine antagonists. Typically these
potentially bioactive compounds are characterized by the
presence of amide/peptide bond and a two to three carbon
bridge separating the amide nitrogen from nitrogen present
in a heterocycle.
Keywords Epichlorohydrin ꢀ Benzhydrylamines ꢀ
Azetidine ꢀ D2, D4 antagonist
Introduction
Azetidines are an important class of four-membered mono-
cyclic aza-heterocyclic compounds with remarkable bio-
logical activities, which made them an interesting synthetic
topic. Compared to their higher homologous counterparts,
azetidine ring finds wide application as a pharmacological
Cl
O
O
NH C3H7
N
N
O
H
SO2
O
N
H2N
Sulphiride
FAUC-21
S. D. Metkar ꢀ U. V. Desai
Department of Chemistry, Shivaji University, Vidyanagari,
Kolhapur 416004, India
Taking into account these facts as well as the structures
of azetidine motif, we planned to synthesize few deriva-
tives of azetidine having both of the aforesaid moieties.
And, our attention got focused on the synthesis of benz-
hydryl azetidines (BZA).
M. S. Bhatia (&)
Department of Pharmaceutical Chemistry, Bharati Vidyapeeth
College of Pharmacy, Kolhapur 416013, India
e-mail: manish_bhatia13@yahoo.co.in
123

Med Chem Res
H
Experimental
N
R'''
R'
N
O
General
R''
Melting points of synthesized compounds were determined
by an open capillary method and are uncorrected. Analyt-
ical TLC was performed on Silica gel-G. Spot was detected
using iodine vapors or under UV light (254 nm). The IR
(KBr) spectra were recorded on a Jasco-FTIR 4100
BZA
Retrosynthetic approach toward the synthesis of planned
azetidine derivatives is depicted in Fig. 1. During the
present studies, we planned to maintain R0, R00 = phenyl
and R000 as substituted phenyl.
1
instrument. The H NMR spectra of the compounds were
Figure 2 shows the reaction scheme for the synthesis of
targeted amide. The intermediate mesylate was synthesized
starting from corresponding secondary alcohol, which is
turn was synthesized by reaction of benzhydryl amine with
epichlorohydrin following reported protocols (Isoda et al.,
2006; Morimoto et al., 1973). The resulted mesylate on
conversion to azide followed by its in situ reduction fur-
nished the primary amine, essential in the synthesis of
targeted amide.
obtained on 400 MHz Varian NMR using CDCl3. The
mass spectra of the compounds were recorded on Q- Tof
micro (YA-105) and MDS Sciex (API 3000) LC-MSMS
spectrometer.
Synthesis of 3-hydroxy-1-benzhydryl azetidine
A glass reactor was charged with isopropylalcohol (IPA)
(30 ml) and benzhydrylamine (6.0 g, 32 mmol). To this
stirred solution, epichlorohydrin (3.5 g, 39 mmol) was
added over a period of 2 h, maintaining the temperature
below 30 °C. After the addition, the mixture was stirred for
24 h at the 25–30 °C. IPA was removed by distillation
below 45 °C under vacuum to obtain the residue of
Figure 2 Reagents and conditions: (a) = epichlorohy-
drin, acetonitril, triethylamine (TEA), (b) = mesylchloride,
Methylene chloride, 0–5 °C (c) = sodium azide, dimeth-
ylformamide (DMF), 90 °C (d) = NH4Cl/Zn, EtOH,
(e) = benzoyl choride, TEA.
O
Fig. 1 Retrosynthetic approach
O
O
Cl
R
HO
R
OH
N
HN
N
R
Cl
O
+
NH2
+
NH2
N
OH
OMs
Fig. 2 Scheme for synthesis of
compounds 1–10
NH2
Cl
O
N
N
a
b
c,d
O
HN
N
R
NH2
N
e
1-10
123

Med Chem Res
3-chloro-1-diphenylmethyl amino-2-hydroxypropane. To
this residue, acetonitrile (18 ml) was added, and the sus-
pension was cooled to 10–15 °C. Triethylamine (14 g,
135 mmol) was added slowly over the period of 30 min
maintaining the temperature 10–15 °C. Stirred for addi-
tional 1 h and reaction temperature was raised to reflux,
stirred for 48 h, Acetonitrile was removed by distillation
below 50 °C under vacuum to give crude compound 2. The
crude compound was recrystallised in methanol (18.0 ml)
and water (60.0 ml) over 1 h at room temperature (25–
35 °C). The slurry was stirred for 8 h at 25–30 °C and was
then filtered. The wet cake was washed with 12 ml of water.
The wet cake was dried under vacuum below 50 °C to
obtained white solid in 65 % yield, 4.3 g, m.p. 111–112 °C.
1HNMR (CDCl3 400 MHz): d = 3.58(H,br,s,OH); 3.96
(H,dd,j = 6.0&1.5 Hz,CH); 3.56(2H,dd,j = 6.0&1.8 Hz,
CH2); 3.57(2H,dd,j = 6.6&6.6 Hz,CH2); 4.87(1H,s,CH);
7.14–7.27(10H,m,Ar Hs).
water. Ethyl acetate was evaporated to dryness under
reduced pressure to get oily a product. The oil obtained was
dissolved in ethanol (25 ml) and the solution of ammonium
chloride (8 g, 18 mmol) in water was added. The reaction
mixture was stirred and charged with Zn powder (3 g) and
refluxed for 7 h. Upon completion of reaction, ethyl acetate
and liquor ammonia were added. The mixture was filtered,
and filtrate was separated. Organic layer washed with brine
and water. After distilling off solvent under vacuum, crude
amine as oil (1.1 g) was obtained. The resultant oil was
chromatographed over silica gel. Elution with ethyl acetate–
hexane (60:40) furnished the desired 3-amino-1-benzhydryl
azetidine as white solid. Yield 0.6 g; m.p. = 84–87 °C.
1HNMR (CDCl3 400 MHz): d = 2.31(2H,br,s,NH2); 2.65
(2H,dd,j = 6.0&1.5 Hz,CH2); 3.50(2H,dd,j = 6.0&1.8 Hz,
CH2); 3.57(1H,dd,j = 6.6&6.6 Hz,CH2); 4.87(1H,s,CH);
7.14–7.27(10H,m,Ar Hs).
13CNMR (CDCl3 400 MHz): d = 43.27(CH), 64.21
(2xCH2), 78.58(CH), 127.05(Ar CH), 127.40(Ar CH),
128.38(Ar CH), 142.20(Ar C).
13CNMR (CDCl3 400 MHz): d = 62.47(CH), 58.6(CH2),
87.40(CH), 127.05(Ar CH), 127.40(Ar CH), 128.38(Ar CH),
142.20(Ar C).
Procedure for the preparation of N-(1-benzhydryl-azetidin-
3yl)-benzamide derivatives
Synthesis of 1-benzhydrylazetidin-3-yl methanesulfonate
To a stirred solution of 3-hydroxy-1-benzhydryl azetidine
(4 g, 16.5 mmol) in methylene chloride (12 ml), triethyl-
amine (2.5 g, 25 mmol) was added over 15 min, main-
taining the temperature between 25 and 30 °C. The solution
was cooled to 0–5 °C, and methanesulfonyl chloride (2.8 g,
25 mmol) was added dropwise over 15 min, while main-
taining the temperature 0–5 °C. Reaction was stirred at
0–5 °C for 1 h. Upon completion of reaction by tlc, water
15 ml was added and the reaction mixture was extracted
using methylene chloride. The organic layer was washed
with aqueous saturated bicarbonate solution and water,
dried over sodium sulfate and solvent removed to give
white solids (4.5 g 90 % yield, m.p. 114–115 °C).
1HNMR (CDCl3 400 MHz): d = 3.16(H,s,CH3); 5.5
(H,dd,j = 6.0&1.5 Hz,CH); 3.56(2H,dd,j = 6.0&1.8 Hz,
CH2); 3.57(1H,dd,j = 6.6&6.6 Hz,CH2); 5.1(1H,s,CH);
7.14–7.27(10H,m,Ar Hs).
A solution of 3-amino-1-benzhydryl azetidine (0.5 g,
1.0 meq) in chloroform and triethylamine (1.1 meq) was
prepared and cooled to 0–5 °C. To the solution, dropwise
solution of acid chloride was added maintaining the tem-
perature at 0–5 °C reaction was monitored by TLC. Upon
completion of reaction, water was added and organic layer
was separated. Organic layer was washed with 5 % sodium
bicarbonate solution and water. The organic layer was
dried over anhydrous sodium sulfate, and the solvent was
distilled off to yield compounds 1–10. Analytical and
spectral data was obtained for all the compounds.
N-(1-Benzhydryl-azetidin-3yl)-2,4-dichloro-benzamide(1)
Yield 1.29 g; m.p: 118–122 °C; IR (KBr) Vmax/cm-1
1620 (C,O,str), 3440 (NH sec,str), 750 (C–Cl,str).
;
1HNMR (CDCl3 400 MHz): d = 3.05(2H,t,CH2); 3.65
(2H,t,CH2); 4.38(1H,s,CH); 4.75(1H,m,CH); 7.14–7.58
(13H,m,Ar H); 6.8(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 38.2(CH3), 60.9(CH),
55.48(CH2), 87.35(CH), 128.2(Ar CH), 129.40(Ar CH),
126.38(Ar CH), 142.20(Ar C).
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 128.2(Ar CH), 129.40(Ar CH), 126.18
(Ar CH), 130.8(Ar CH), 128.38(Ar CH), 124.4(Ar CH),
142.70(Ar C), 145.57(Ar C), 131.27(Ar C), 132.48(Ar C),
154.48(Ar C); m/z (M?1): 412.
Synthesis of 3-amino-1-benzhydryl azetidine
To a stirred solution of 1-benzhydrylazetidin-3-yl meth-
anesulfonate (2.0 g, 6.3 mmol) of DMF (10 ml) was added
sodium azide (1.8 g, 10 mmol). Stirred and raised temper-
ature to 90 °C. Upon completion of reaction (tlc), DMF was
distilled under reduced pressure below 80 °C to dryness.
The residue was dissolved in ethyl acetate and washed with
N-(1-Benzhydryl-azetidin-3yl)-3-methoxy-benzamide(2)
Yield 1.01 g; m.p. 166–168 °C; IR (KBr) Vmax/cm-1
1630 (C,O,str), 3540 (NH sec,str),1150 (C–O,str).
;
123

Med Chem Res
1HNMR (CDCl3 400 MHz): d = 3.06(2H,s,CH2); 3.66
(2H,t,CH2); 3.90(3H,s,CH3); 4.40(1H,s,CH); 4.78(1H,m,
CH); 7.02–7.43(14H,m,Ar H); 6.69(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 55.79 (CH3), 84.28(CH), 128.2(Ar CH), 129.40
(Ar CH), 126.18(Ar CH), 130.1(Ar CH), 113.88(Ar CH),
107.74(Ar CH), 111.10(Ar CH), 161.7(Ar C), 152.27
(Ar C), 154.48(Ar C); m/z (M?1): 373.
1HNMR (CDCl3 400 MHz): d = 3.05(2H,t,CH2); 3.65
(2H,t,CH2); 4.39(1H,s,CH); 4.78(1H,m,CH); 7.18–7.64
(14H,m,Ar H); 6.66(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 128.2(Ar CH), 129.40(Ar CH), 126.18
(Ar CH), 131.6(Ar CH), 126.9(Ar CH), 127.2(Ar CH),
124.1(Ar CH), 127.3(Ar C), 147.4(Ar C), 154.48(Ar C);
m/z (M?1): 377.5.
N-(1-Benzhydryl-azetidin-3yl)-4-iodo-benzamide(3)
N-(1-Benzhydryl-azetidin-3yl)-2-bromo-benzamide(7)
Yield 1.45 g; m.p. 154–158 °C; IR (KBr) Vmax/cm-1
1620 (C,O,str), 3530 (NH sec,str), 550 (C–I,str).
;
Yield 1.30 g; m.p.134–136 °C; IR (KBr) Vmax/cm-1
;
1672 (C,O str),3300 (NH sec. str),664 (C–Br, str).
1HNMR (CDCl3 400 MHz): d = 3.06(2H,s,CH2); 3.59
(2H,t,CH2); 4.35(1H,s,CH); 4.70(1H,m,CH); 7.17–7.33
1HNMR (CDCl3 400 MHz): d = 3.07(2H,t,CH2); 3.66
(2H,t,CH2); 4.21(1H,s,CH); 4.86(1H,m,CH); 7.18–7.67
(14H,m,Ar H); 6.69(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 128.2(Ar CH), 129.40(Ar CH), 126.18
(Ar CH), 133.4(Ar CH), 127.9(Ar CH), 128.1(Ar CH),
123.8(Ar CH), 116.4(Ar C), 148.8(Ar C), 154.48(Ar C);
m/z (M?1): 421.9.
(10H,m,ArH);
7.86–7.88(2H,t,ArH);
8.17–8.22(2H,t,
Ar H); 7.00(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 128.2(Ar CH), 129.40(Ar CH), 126.18
(Ar CH), 138.1(Ar CH), 123.4(Ar CH), 123.34(Ar CH),
138.10(Ar CH), 88.50(Ar C), 150.27(Ar C), 154.48(Ar C);
m/z (M?1): 468.9.
N-(1-Benzhydryl-azetidin-3yl)-2-methyl-benzamide(8)
N-(1-Benzhydryl-azetidin-3yl)-4-nitro-benzamide(4)
Yield 1.04 g; m.p. 120–124 °C; IR (KBr) Vmax/cm-1
;
Yield 1.28 g; m.p. 158–160 °C; IR (KBr) Vmax/cm-1
;
1625 (C,O str),3400 (N,H sec str),2950 (C–H str).
1660 (C,O,str), 3590 (NH sec, str),1330 (C–NO2, str).
1HNMR (CDCl3 400 MHz): d = 2.43(3H,s,CH3); 3.06
(2H,t,CH2); 3.66(2H,t,CH2); 4.41(1H,s,CH); 4.81(1H,m,
CH); 7.18–7.43(14H,m,Ar H); 6.30(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 15.3 (CH3), 128.2(Ar CH), 129.40(Ar
CH), 126.18(Ar CH), 131.1(Ar CH), 125.4(Ar CH),
126.1(Ar CH), 121.5(Ar CH), 130.4(Ar C), 150.3(Ar C),
154.48(Ar C); m/z (M?1): 357.
1HNMR (CDCl3 400 MHz): d = 3.25(2H,s,CH2); 3.70
(2H,t,CH2); 4.46(1H,s,CH); 4.80(1H,m,CH); 7.19–7.44
(10H,m,Ar H); 7.96–7.99(2H,t,Ar H); 8.28-8.33(2H,t,
Ar H); 7.00 (1H, s, NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 128.2(Ar CH), 129.40(Ar CH), 126.18
(Ar CH), 125.38(Ar CH), 122.5(Ar CH), 144.7(Ar C),
157.4(Ar C), 154.48(Ar C); m/z (M?1): 388.
N-(1-Benzhydryl-azetidin-3yl)-2-methoxy-benzamide(9)
N-(1-Benzhydryl-azetidin-3yl)-4-bromo-benzamide(5)
Yield 1.03 g; m.p. 144–146 °C; IR (KBr) Vmax/cm-1
;
Yield 1.30 g; m.p. 162–166 °C; IR (KBr) Vmax/cm-1
;
1620 (C,O str),3240 (NH sec str), 1300 (C–O str).
1670 (C,O,str), 3420 (NH sec str), 660 (C–Br,str).
1HNMR (CDCl3 400 MHz): d = 2.98(2H,s,CH2); 3.71
(2H,t,CH2); 3.99(3H,s,CH3); 4.41(1H,s,CH); 4.80(1H,m,
CH); 7.05–8.19(14H,m,Ar H); 6.97(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 55.8(CH3), 128.2(Ar CH), 129.40(Ar
CH), 126.18(Ar CH), 114.9(Ar CH), 126.5(Ar CH),
121.4(Ar CH), 121.0(Ar CH), 151.7.4(Ar C), 134.2(Ar C),
154.48(Ar C); m/z (M?1): 373.
1HNMR (CDCl3 400 MHz): d = 3.05(2H,s,CH2); 3.62
(2H,t,CH2); 4.47(1H,s,CH); 4.75(1H,m,CH); 7.19–7.55
(10H,m,Ar H); 7.91–7.94(2H,t,Ar H); 8.23–8.28(2H,t,Ar
H); 6.95(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 128.2(Ar CH), 129.40(Ar CH), 126.18
(Ar CH), 131.9(Ar CH), 123.78(Ar CH), 119.9(Ar C),
150.4(Ar C), 154.48(Ar C); m/z (M?1): 421.9.
N-(1-Benzhydryl-azetidin-3yl)-2-chloro-benzamide(6)
N-(1-Benzhydryl-azetidin-3yl)-2-nitro-benzamide(10)
Yield 1.20 g; m.p.136–140 °C; IR (KBr) Vmax/cm-1
1630 (C,O; str),3410 (NH sec str),730 (C–Cl; str).
;
Yield 1.3 g; m.p. 144–148 °C IR (KBr) Vmax/cm-1
1600(C,O str), 3490(NH sec str), 1300(C–NO2 str).
;
123

Med Chem Res
1HNMR (CDCl3 400 MHz): d = 3.05(2H,t,CH2); 3.65
(2H,t,CH2); 4.37(1H,s,CH); 4.74(1H,m,CH); 7.17–7.58
(14H,m,Ar H); 6.46(1H,s,NH);
13CNMR (CDCl3 400 MHz): d = 44.07(CH), 60.01
(CH2), 84.28(CH), 128.2(Ar CH), 129.40(Ar CH), 126.18
(Ar CH), 127.3(Ar CH), 126.4(Ar CH), 135.2(Ar CH),
124.5(Ar CH), 140.4(Ar C), 120.3(Ar C), 154.48(Ar C); m/z
(M?1): 388.
˚
0.001 kcal/mol/A was reached, maintaining the template
structure rigid during the minimization. Molecules of the
dataset were aligned by the atom-fit technique, using atoms
common with the structure of CPPMA. Comparative
dataset for the various interactions of CPPMA with the D4
receptor and the same for compound 5 were generated.
Biological activity
The synthesized compounds were tested for in vivo Dopa-
minergic antagonist activity. Wistar albino rat of either sex,
weighing 200–250 g were procured from National Institute of
Bioscience, Pune. The animals were maintained under stan-
dard laboratory condition (temperature 23 20° C, relative
humidity 55 10 %) throughout the experiments. The ani-
mals were shifted from animal house to the laboratory one
hour prior to the start of the experiment. The test compounds
were administered intraperitoneally to rats at the dose of 10
and 20 mg/kg of bodyweight. Haloperidol (0.3 and 1 mg/kg,
i.p.) was used to induce catalepsy and clozapine (1 and 5 mg/
kg, i.p.) as a standard drug and was administered. Catalepsy,
defined as the acceptance and retention of abnormal posture,
was measured by means of the bar test. In brief, rat forepaws
were gently placed over a horizontal bar, fixed at a height of
9 cm above the working surface (Okuyama et al., 1993). The
length of time during which the animal retained this position
was recorded by an observer blind to the treatment, and by
measuring the time elapsing from the placement of the rat
until the removal of one of its forepaws. Rats were removed
from the bar if their latency on the bar test exceeded 300 s
(i.e., cutoff = 300 s). Results were expressed as percentage
vs the cutoff time (i.e., catalepsy % = latency on bar test
(s)/cutoff (300 s) 9 100). Rats were injected with the dif-
ferent drugs in their home cage, where they were maintained
until the three consecutive trials on bar test latency were
scored (90 min after antipsychotic injection).
Fig. 3 Docking of CPPMA and compound 5 in D4 receptor
Data were analyzed using ANOVA followed by the
Newman–Keuls post hoc test [*P \ 0.05, **P \ 0.001 vs
CLP (5 mg/kg, i.p.)]. The percentage catalepsy is men-
tioned in Table 2.
Docking studies
Structure of compound 5 which was the most active
compound was used as the template to build the molecules
in the dataset of the molecular design software Vlife MDS
3.5. The ligand geometries were optimized by energy
minimization using MMFF94 force field and Gasteiger-
Fig. 4 Interactions of CPPMA in the D4 receptor site
Marsili charges for the atoms, till
a gradient of
123

Med Chem Res
Results and discussion
The entire products described herein were prepared by the
conventional method; in the synthetic scheme, the various
derivatives of 3-amino-1-benzhydryl azetidines were pre-
pared. In step 1, the cyclization reaction takes place
between the epichlorohydrin and benzhydryl amine
resulting in the formation of a four-membered heterocyclic
ring azetidine, which is confirmed by the presence of peak
at 3,550–3,200 (OH), the absence of peaks in the region
3,400–3,300 and 3,330–3,250 cm-1 of the IR spectra,
which indicates that the primary amine is cyclized to ter-
tiary amines and occurrence of peak at 4.31 ppm in NMR
spectra which further confirms the formation of azetidine.
In step two, the 3-hydroxy benzhydryl azetidine is reacted
with the mesyl chloride in the presence of methylene
chloride to get the mesylated product. This mesylated
further reacted with sodium azide in DMF followed by
in situ reduction to get the 3-amino-1-benzhydryl azetidine
which is confirmed by the presence of prominent peak 0.5–
3.0 ppm in NMR spectra for aliphatic amine. In last step,
the 3-amino-1-benzhydryl azetidine is reacted with various
acid chlorides and amide formation is confirmed by the
presence of peak at 1,680–1,630 cm-1 in the IR spectra
and an amide peak is observed at 6.9 ppm in NMR spectra.
The purity of the product obtained was around 90–95 %.
Fig. 5 Interactions of compound 5 in the D4 receptor site
Both compound docked into D4 receptor are shown in
Fig. 3, the interactions of CPPMA in the receptor site are
shown in Fig. 4 while those of compound 5 are shown in
Fig. 5.
Table 1 Physical properties of synthesized compounds 1 to 10
Compound
R
Molecular formula
Mol. weight
M.p (°C)
118-122
Yield (%)
75
Elemental analysis
C
H
N
1
Cl
C23H20ON2Cl2
411
67.20
5.00
6.70
(67.15)
(4.90)
(6.83)
Cl
2
C24H24O2N2
C23H21ON2I
C23H21O3N3
372
166-168
154-158
158-160
65
74
73
78.32
7.10
7.30
(77.39)
(6.49)
(7.52)
OMe
3
4
467.9
387
58.91
4.30
5.70
(58.99)
(4.52
(5.98)
I
70.00
5.44
10.00
(71.30)
(5.49)
(10.85)
NO2
5
C23H21ON2Br
420
162-166
74
66.01
5.10
6.69
(65.57)
(5.02)
(6.65)
Br
123

Med Chem Res
Table 1 continued
Compound
R
Molecular formula
C23H21ON2Cl
Mol. weight
376.5
M.p (°C)
136-140
Yield (%)
75
Elemental analysis
C
H
N
6
74.35
5.50
7.40
Cl
(73.30)
(5.62)
(7.43)
Br
7
C23H21ON2Br
C24H24ON2
C24H24O2N2
C23H21O3N3
420
356
372
387
134-136
120-124
144-146
144-148
74
70
62
73
63.60
5.10
6.60
(65.57)
(5.20)
(6.65)
CH3
OMe
NO2
8
79.00
6.23
7.80
(80.87)
(6.79)
(7.86)
9
76.96
6.30
7.45
(77.39)
(6.49)
(7.52)
10
70.32
5.30
10.10
(71.30)
(5.46)
(10.85)
Table 1 shows the different substituent which is used in the
present study. All the synthesized compounds were
screened for dopaminergic activity.
Table 2 % Catalepsy for com-
pounds 1–10
Compounds
Catalepsy (%)
1
2
46.9 5.28
73.4 4.23
40.6 3.30
72.7 5.22
79.8 5.12
33.1 2.35
48.8 4.33
62.9 4.34
39.1 3.88
75.4 4.01
The results are summarized in Table 2. The selected
experimental model predicts the therapeutic activity of a
particular drug class i.e., D2 antagonists. Even the diversity
of in vivo models utilized by others might not, arguably, be
appropriate to the prediction of antipsychotic activity for
agents lacking D2 receptor affinity; specifically, D4 receptor
antagonists. Haloperiodol (0.3 mg/kg, i.p.) produced mini-
mal cataleptic effect per se, and was used as the-sub-cata-
leptic dose of the drug. The present results showed a
different effect on rat catalepsy induced by sub-cataleptic
dose of haloperidol (0.3 mg/kg, i.p.) when co-administered
with clozapine (1 and 5 mg/kg, i.p.) or with different series
of compounds (10 and 20 mg/kg, i.p.). As seen in Table 2
compounds substituted at 4-phenyl show D4 affinity.
CPPMA is a reported D4 antagonist (Kulagowski et al.,
1996). Docking studies carried out with CPPMA and
compound 5 indicate that the nitrogen of CPPMA has
charged interaction with Leucine 187 of the D4 receptor.
Similarly, in compound 5, the nitrogen in azetidine ring
showed charge interaction with Leucine 187. Furthermore,
3
4
5
6
7
8
9
10
molecules, respectively. Thus, the similarity of the designed
ligands with CPPMA could explain the observed D4
antagonist activity of the synthesized compounds.
Conclusion
The structural information available from reported anti-
dopaminergic compounds lead to the design of novel az-
etidine derivatives. Subsequently, retrosynthetic approach
was successfully used to plan the synthetic route. The
observed anti-dopaminergic activity of some of the azeti-
dine analogs had a good correlation with the similarity in
structure with CPPMA and virtual interactions with the D4
receptor. Thus, the observed anti-dopaminergic activity of
designed compounds and the structural requirements for
such activity established in this work can be used as a
˚
the aromatic ring in CPPMA is 5.824 A away from the
nitrogen showing charge interaction, where as in compound
˚
5, the distance is 5.636 A. Second aromatic ring of com-
˚
pound is at 4.860 A as compared to the distance of pyrazole
˚
ring in CPPMA which is at 4.825 A from the nitrogen
˚
showing charged interaction. Halogen is placed at 8.403 A
˚
in CPPMA and at 10.253 A in compound 5. Nitrogens are
˚
placed at 2.880 and 3.061 A in CPPMA and designed
123

Med Chem Res
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Acknowledgments The authors express their sincere thanks to
Head, Department of Chemistry, Shivaji University and Principal,
Bharati Vidyapeeth College of Pharmacy, Kolhapur for providing
necessary facilities, and Sarex Chemicals Ltd., Andheri (W), Mum-
bai—400 058, India for providing benzhydrylamine for this work.
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