Synthesis and biological evaluation of novel compounds within a class of 3-aminochroman derivatives with dual 5-HT1A receptor and serotonin transporter affinity

Article abstract of DOI:10.1021/jm060218h

Compounds containing a 5-carbamoyl-8-fluoro-3-amino-3,4-dihydro-2H-1- benzopyran and a 3-alkylindole moiety linked through a common basic nitrogen were prepared and evaluated for 5-HT_1A affinity, serotonin rat transporter affinity, and functional antagonist activity in vitro. 26a was found to be the most potent and selective compound in this series and was shown to possess neurochemical activity in vivo by producing acute and rapid increases in 5-HT in the rat frontal cortex.

Full text of DOI:10.1021/jm060218h

J. Med. Chem. 2006, 49, 4785-4789
4785
Synthesis and Biological Evaluation of Novel Compounds within a Class of 3-Aminochroman
Derivatives with Dual 5-HT1A Receptor and Serotonin Transporter Affinity
Nicole T. Hatzenbuhler,*,‡ Deborah A. Evrard,‡ Boyd L. Harrison,‡ Donna Huryn,‡,# Jennifer Inghrim,‡ Christina Kraml,‡
James F. Mattes,‡ Richard E. Mewshaw,† Dahui Zhou,‡ Geoffrey Hornby,§ Qian Lin,§ Deborah L. Smith,§ Kelly M. Sullivan,§
Lee E. Schechter,§ Chad E. Beyer,§ and Terrance H. Andree§
Chemical and Screening Sciences and DiscoVery Neuroscience, Wyeth Research, CN 8000, Princeton, New Jersey 08543, and
Chemical and Screening Sciences, Wyeth Research, 500 Arcola Road, CollegeVille, PennsylVania 19426
ReceiVed February 24, 2006
Compounds containing a 5-carbamoyl-8-fluoro-3-amino-3,4-dihydro-2H-1-benzopyran and a 3-alkylindole
moiety linked through a common basic nitrogen were prepared and evaluated for 5-HT1A affinity, serotonin
rat transporter affinity, and functional antagonist activity in vitro. 26a was found to be the most potent and
selective compound in this series and was shown to possess neurochemical activity in vivo by producing
acute and rapid increases in 5-HT in the rat frontal cortex.
Introduction
The discovery and development of new antidepressants
remain an active area of research. Selective serotonin (5-HT)
reuptake inhibitors (SSRIs) have become a primary mode of
therapy because of fewer side effects compared to the traditional
tricyclic antidepressants (TCAs),1,2 but they suffer from a 2-6
week delay in the onset of therapeutic efficacy.3 It is thought
that this activity onset delay is the result of activation of
somatodendritic 5-HT1A autoreceptors, which reduce cell-firing
activity, limiting the amount of synaptic 5-HT. Following
chronic antidepressant treatment, desensitization of the 5-HT1A
autoreceptors occurs, resulting in a more pronounced increase
in serotonergic activity compared to acute treatment.4 Antago-
nism of the 5-HT1A autoreceptor should block the reduced rate
Figure 1. Structures of 5-OMe-DPAC and NAD-299 and design
strategy.
of neuronal firing, thus allowing the effects of the SSRI to be
seen more rapidly.5 Several studies have shown that antidepres-
sant effects of an SSRI can be accelerated by the coadminis-
which was developed for the potential treatment of depression
tration of a 5-HT1A antagonist.6,7 For example, in animal models,
and anxiety.16
the 5-HT1A antagonist WAY-100635 was found to potentiate
Using the “overlapping type approach”, we found in pre-
the antidepressant effects of several SSRIs when given in
liminary studies that the combination of 5-methoxychroman with
combination.7,8 In some clinical studies,9 but not all,6 the mixed
a straight chain aminoalkylindole moiety, known to be a SSRI
5-HT1A/â-adrenoceptor antagonist pindolol in combination with
pharmacophore,17 generated compounds possessing dual affinity
SSRIs has shown acceleration of antidepressant effects. Sig-
for the 5-HT1A receptor and the 5-HT reuptake site (Figure 1,
nificant amounts of work in our laboratories10 and others11,12
I). In light of these results, we then chose to combine 5-car-
have focused on creating a single molecular entity possessing
bamoyl-8-fluoro-3-amino-3,4-dihydro-2H-1-benzopyran with the
5-HT1A antagonism and 5-HT reuptake inhibition through
straight chain alkylindole moiety (Figure 1, II). In this report,
utilization of a common basic nitrogen linking the 5-HT1A and
we discuss the synthesis and structure-activity relationships
SSRI moieties. This generic strategy was previously termed “the
of two new series of chroman derivatives I and II and outline
overlapping type approach”.11
their dual activities.
Several years ago, 5-methoxy-3-(di-n-propylamino)chroman
(5-OMe-DPAC) (Figure 1) was discovered as a selective 5-HT1A
Chemistry
ligand vs other 5-HT sites and D2 sites in rat brain membranes.13
The 5-HT1A template 3 was synthesized from the benzalde-
hyde 1 according to literature procedures18 (Scheme 1). The
synthesis of moiety 8 is shown in Scheme 2 following a slightly
modified synthetic route previously published by other research-
ers.19 A key improvement was the nitration of 6 carried out
using a phase transfer reagent, 18-crown-6, in the presence of
potassium nitrite and iodine under sonication conditions,20
resulting in an improved yield (60%) of the nitro derivative 7.
Reduction of the double bond of 7 followed by phase transfer
hydrogenation generated 8 as a racemate at the 3-position of
the chroman ring. The enantiomers were separated by chiral
Subsequently, different 3-amino-3,4-dihydro-2H-1-benzopyran
derivatives were explored and developed as 5-HT1A agonists.14
The combination of 5-carboxamide, 8-fluoro substitutions with
R stereochemistry at the 3-amino position generated potent
5-HT1A antagonists15 such as robalzotan (NAD-299) (Figure 1),
* To whom correspondence should be addressed. Phone: (732) 274-
4047. Fax: (732) 274-4505. E-mail: hatzenn@wyeth.com.
‡ Chemical and Screening Sciences, Wyeth Research, NJ.
# Current Address: Department of Chemistry, University of Pennsylvania.
§ Discovery Neuroscience, Wyeth Research, NJ.
† Chemical and Screening Sciences, Wyeth Research, PA.
10.1021/jm060218h CCC: $33.50 © 2006 American Chemical Society
Published on Web 06/29/2006

4786 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 15
Brief Articles
Scheme 1a
Scheme 4a
a Reagents: (i) nitroethanol, Bu2NH-HCl, isoamyl acetate; (ii) NaBH4,
i
SiO2, CHCl3, PrOH; (iii) NH2NH2-H2O, Raney Ni, EtOH.
Scheme 2a
a Reagents: (i) Br-alkylindole, TEA, DMSO; (ii) aldehyde alkylindole,
NaBH3CN, HOAc, MeOH; (iii) aldehyde or cyclobutanone, NaBH3CN,
HOAc, MeOH.
a Reagents: (i) trimethylorthoformate, H2SO4, MeOH; (ii) propargyl
bromide, K2CO3, acetone; (iii) N,N-diethylaniline; (iv) NaOH, EtOH-H2O;
(v) CDI, THF followed by NH3(g), THF; (vi) 18-crown-6, KNO2, I2, THF-
pyridine, sonication; (vii) NaBH4, SiO2, CHCl3-iPrOH; (viii) NH2NH2‚H2O,
Raney Ni, EtOH-THF.
In 14-19 and 22-26, we first investigated the effect of
substitution on the basic nitrogen and stereochemistry at C3 of
the chroman ring and found, as summarized in Table 1, that
tertiary amines were preferred for 5-HT1A affinity. In II, propyl
(24a,b), methylcyclopropyl (25a,b), and cyclobutyl (26a) were
found to be the best substituents while a secondary amine (19a)
and ethyl (23a,b) resulted in a 5- to 10-fold decrease in activity.
In contrast, methyl substitution (22) generated a less potent
compound. Similarly, in I, ethyl (15) and methylcyclopropyl
(17) were best while methyl (14), propyl (16), and cyclobutyl
(18) showed moderate affinity. These results suggest that the
steric environment of the basic nitrogen plays a significant role
within the binding pocket of the 5-HT1A receptor. Interestingly,
serotonin transporter affinity was minimally affected by sub-
stitution on the basic nitrogen in both series and most com-
pounds had excellent (14-18, 23a,b, 24a,b, 25a,b, 26a,b) to
good affinity (18a, 19a, 22) for the r-5HT reuptake site.
Additionally, most of these derivatives had good functional
activity at the human transporter. The R stereochemistry at C3
of the chroman ring was very important for 5-HT1A antagonist
activity and desired in vitro properties for a dual-acting new
molecular entity. In the carboxamide series II, only the
cyclobutyl derivatives (26a,b) showed full antagonism for both
enantiomers, as measured by a cAMP assay, but with weaker
affinity of the S enantiomer (26b) at the 5-HT1A receptor. In
contrast, 23b, 24b, and 25b (S stereoisomers) had excellent
5-HT1A affinities, but they were found to be full or partial
agonists functionally. Interestingly analogues 23a and 25a (R
enantiomers) showed full antagonism at the 5-HT1A receptor,
but 24a was a partial agonist suggesting that substitution on
the basic nitrogen may have some effect on the agonist/
antagonist properties of these compounds. Surprisingly, in the
methoxy series I, partial agonism was seen with the racemic
cyclobutyl derivative 18 and its R enantiomer (18a) was a full
antagonist with moderate affinities at the 5-HT1A receptor and
5-HT reuptake site. In general, more antagonism at the 5-HT1A
receptor was observed for the carboxamide derivatives (II) than
the methoxychroman analogues (I). All of these compounds
showed acceptable binding selectivity over the R1 receptor.
Compounds 24-33 explored the effect of different chain
lengths between the carboxamide chroman headpiece and the
3-alkyl-5-fluoroindole moiety, with differing substitutions on
the basic nitrogen as summarized in Table 1. Linkers of three
(24-26) or four (30, 32, 33) carbons were preferred for desirable
in vitro properties with comparable affinities at the 5-HT1A
Scheme 3a
a Reagents: (i) 2,3-dihydrofuran, THF-H2O followed by ethylene glycol,
ZnCl2; (ii) 2,3-dihydropyran, dioxane-H2O; (iii) CBr4, PPh3, CH2Cl2; (iv)
NaCN, DMF; (v) KOH, EtOH-H2O; (vi) LAH, THF; (vii) TFA, pyridine,
DMSO-benzene, DCC.
resolution with tartaric acid or by chiral HPLC of the final target
molecule. The stereochemistry of moiety 8 was determined by
NMR studies and later confirmed by X-ray crystallography of
one of the final targets.
The synthesis of the 5-HT reuptake moieties 11 and 12 is
shown in Scheme 3. The two- and three-carbon linker analogues
9a and 9b were generated through a Fischer indole synthesis
and converted to the bromo (11) or aldehyde (12) derivative.
The four-carbon linker derivative 9c was prepared by homolo-
gation of 9b using straightforward chemistry.
Novel compounds 13-33 were synthesized using the route
shown in Scheme 4. After coupling of the chroman amine
moiety 3 or 8 to the alkylindole moiety 11 or 12 through
alkylation or reductive amination to generate the secondary
amine derivatives, the final products (R1 ) Me, Et, Pr, meth-
ylcyclopropyl, cyclobutyl) were obtained by reductive amination
with the desired aldehyde or cyclobutanone.
Results and Discussion
Here, we have explored the combination of two well-known
5-HT1A templates and a known serotonin transporter moiety
through a common basic nitrogen, which resulted in two series
of novel compounds, which possess affinity for the 5-HT1A and
serotonin rat transporter receptors. Serotonin transporter affinity,
functional activity at the h-5HT transporter, 5-HT1A receptor
affinity, 5-HT1A intrinsic activity (cAMP), and R1 receptor
affinity are summarized in Table 1.

Brief Articles
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 15 4787
Table 1. Affinities for h-5-HT1A Receptor, r-5HT Transporter, and R1 Receptor, Functional Activity at the h-5HT Transporter, and in Vitro 5-HT1A
Antagonist Activity in CHO Cells for 14-19 and 22-33a
5-HT transporter
5-HT1A receptor
affinityd cAMPe
affinityb
functionc
R1 receptorf
K1, nM
compd
R1
Me
Et
n
stereo
Ki (SEM), nM
IC50 (SEM), nM
Ki (SEM), nM
E
max IC50, nM
14
15
16
17
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
2
0
2
0
2
2
rac
rac
rac
rac
rac
R
R
R
R
S
rac
R
S
rac
R
S
rac
R
S
rac
rac
rac
rac
rac
rac
rac
6.8
15
64(5.0)
386(153)
42.6
400(169)
732
40(0.07)
2.3(0.07)
15.8(1.5)
1.68(0.2)
15.6(0.2)
2.14(1.1)
45.2(2.0)
266(65)
34.9(2.8)
18.6(3.2)
3.5(0.9)
1.5(0.1)
3.2(1.0)
2.3(0.8)
2.1(0.09)
0.1(0.03)
9.3(2.1)
1.2(0.35)
253(31)
33.2(5.5)
330(33)
17.6(0.5)
4.4(0.3)
7.3(0.7)
2.1(0.5)
4.8(0.02)
91
96
80
91
37
0(23)
85
nd
0(135)
91
84
78
97
0(66)
0(70)
69
0(61)
0(27)
0(926)
0(68)
0(>1000)
0(68)
0(125)
0(97)
0(51)
0(24)
610
207
820
44%
15%
15%
21%
37%
640
545
nd
1150
46%
32%
2023
26%
16%
21%
nd
2.2(1.3)
9.0(3.0)
4.3
13(4.0)
41
Pr
MecPr
cBu
cBu
H
Me
Et
Et
Pr
Pr
Pr
MecPr
MecPr
MecPr
cBu
cBu
cBu
Et
Et
Pr
Pr
18
18a
19a
22
23a
23b
24
24a
24b
25
25a
25b
26
20.4(3.8)
14.8(4.8)
3.4(1.1)
3.6(0.7)
7.1(1.7)
8.0(0.9)
4.7(0.7)
3.5(0.5)
3.9(0.7)
4.2(1.3)
3.0(0.5)
1.5(0.04)
5.3(0.3)
60.2(5.0)
0.4(0.2)
88(17)
197(54)
116(7)
42.7(9.6)
37.3(2.5)
128(44)
181(22)
59.9(14.3)
53.5(27.5)
59.7(35.3)
36.3(3.6)
25.2(8.3)
18.7(1.8)
17.4(10)
883(71)
24.1(10.5)
>1000
26a
26b
27
416
328
484
494
636
506
645
28
29
30
31
32
33
12.2(3.4)
97.8(9.6)
3.3(0.5)
10.4(4.6)
3.9(0.35)
217(43)
>1000
82.4(42.3)
300(110)
39.4(3.1)
MecPr
MecPr
cBu
fluoxetine
WAY-100635
0.96(0.21)
0(7.06)
a Ki and IC50 are the mean of at least two experiments ( SEM (performed in triplicate, determined from nine concentrations). Values without SEM are
for a single determination only: nd, not determined. Percentages represent inhibition of binding at 1 µM. b Binding affinity for the 5-HT transporter by
displacement of [3H]paroxetine from rat cortical membranes.21 Ki values were calculated from IC50 values using the method of Cheng and Prusoff.22 c Inhibition
of [3H]-5-HT uptake by human 5-HT transporter in Jar cells.23 d Binding affinity at human 5-HT1A receptor in CHO cells labeled with [3H]-8-OH-DPAT.24
e Maximal agonist effect relative to 5-HT in inhibiting forskolin-stimulated adenylate cyclase activity.25 f Binding affinity at rat cortical R1 adrenergic
receptor labeled with [3H]prazosin.26
receptor, the r-5-HT transporter, and good functional activity
at the human transporter. Although the two-carbon linker
derivatives (27, 29, 31) showed reduced affinity at the 5-HT
reuptake site, they retained moderate 5-HT1A affinity regardless
of the substitution on the basic nitrogen. Interestingly, two- and
four-carbon linker analogues were in general full antagonists
at 5-HT1A as racemates in contrast to the three-carbon derivatives
(24 vs 29 and 30). Regardless of the chain length, propyl,
methylcyclopropyl, and cyclobutyl were preferred substituents
on the basic nitrogen. In keeping with the SAR of this series,
these compounds again demonstrated acceptable binding selec-
tivity over the R1 receptor.
with three- and four-carbon linkers as most desirable and sec-
ondarily on the substitution on the basic nitrogen, and (3) the
stereochemistry at the 3-position of the chroman ring played
an important role in the 5-HT1A receptor agonist or antagonist
properties of these compounds with the R stereochemistry
usually favored for antagonism. One of the best compounds
having dual activities was 26a, which demonstrated excellent
5-HT1A and serotonin transporter binding affinities and full
antagonism at the 5-HT1A receptor. Additionally, 26a showed
greater than 100-fold selectivity when tested against appropriate
biogenic amine receptors and was selected for further evaluation
in vivo. Indeed, an oral microdialysis study (30 mg/kg) has
shown that 26a acutely elevates serotonin levels in the rat frontal
cortex (Figure 2) to a similar extent of chronic (14 day) SSRI
treatment.4 These results are consistent with the in vitro profile
of this compound and suggest that 26a readily antagonizes the
5-HT1A receptor and inhibits the 5-HT transporter. These neuro-
chemical results, with studies outlined in the Introduction, sug-
gest that this compound may exhibit a pharmacological profile
consistent with “rapid-onset” antidepressant activity. Additional
SAR studies on both series and a more complete in vivo pro-
filing of 26a will be the subjects of future publications.
Conclusion
The combination of a known 5-HT1A antagonist (5-carbam-
oyl-8-fluoro-3-amino-3,4-dihydro-2H-1-benzopyran) template
and a transporter moiety (aminoalkylindole) sharing a common
basic nitrogen resulted in compounds with desirable affinities
at the serotonin reuptake site and 5-HT1A receptor. A structure-
activity relationship study of this series has shown that (1) the
activity for the 5-HT1A receptor was dependent on the substitu-
tion on the basic nitrogen, with cyclobutyl and methylcyclo-
propyl being preferred for 5-HT1A affinity (the chain length had
minimal effect except for ethyl substitution on the four-carbon
linker derivative resulting in diminished 5-HT1A binding affin-
ity), (2) the transporter affinity was primarily dependent on the
length of the alkyl chain linking the 5-HT1A and indole moieties
Experimental Section
Chemistry. Melting points were determined on a MEL-TEMP
apparatus and are uncorrected. 1H NMR spectra were recorded on
a Varian Unity Plus 400 spectrometer or a Unity INOVA Varian

4788 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 15
Brief Articles
1
generated a white solid: mp 134 °C, dec; H NMR (400 MHz,
DMSO-d6) δ 2.93-3.16 (m, 2H), 3.18-3.53 (m, 5H), 3.78-3.99
(m, 1H), 4.24-4.55 (m, 2H), 6.84-7.01 (m, 1H), 7.09-7.26 (m,
2H), 7.30-7.49 (m, 4H), 7.82 (s, 1H), 9.18 (s, 1H), 11.08 (s, 1H);
MS (ES) m/z 370.2 ([M - H]-). Anal. (C20H19F2N3O2‚1HCl‚
0.25H2O) C, H, N.
General Procedure C (Introduction of Cyclobutyl on Basic
Nitrogen): 3-{Cyclobutyl[3-(5-fluoro-1H-indol-3-yl)propyl]-
amino}-8-fluorochromane-5-carboxamide (26). To 19 (0.14 g,
0.35 mmol) in anhydrous MeOH (6 mL) under nitrogen at room
temperature were added cyclobutanone (0.070 mL, 0.876 mmol),
acetic acid (0.050 mL, 0.84 mmol), and sodium cyanoborohydride
(0.044 g, 0.70 mmol). The mixture was stirred at room temperature
overnight. More cyclobutanone (0.026 mL), acetic acid (0.21 mL),
and sodium cyanoborohydride (0.22 g) were added after 24 and
48 h, at which time the reaction went to completion. The workup
was the same as for Procedure B. Chromatography (5:4:1 EtOAc/
hexane/MeOH (1% NH4OH)) afforded 0.12 g (78%) of 26 as a
sticky gum. Conversion to the mono-HCl salt generated an off-
Figure 2. Acute in vivo microdialysis study of 26a. Oral treatment
with 30 mg/kg significantly (p < 0.05) increased 5-HT levels compared
to the lower dose (3 mg/kg) or vehicle-treated rats, suggesting that
this compound crosses the blood-brain barrier to activate the 5-HT1A
receptor and 5-HT transporter. These results are consistent with
published literature showing that combining SSRI treatment with a
5-HT1A antagonist increases 5-HT levels in this brain region.8
1
white solid: mp 109 °C, dec; H NMR (500 MHz, DMSO-d6) δ
1.51-1.75 (m, 2H), 1.85-2.57 (m, 7H), 2.59-2.76 (m, 2H), 3.06-
3.48 (m, 3H), 3.88-4.14 (m, 2H), 4.31-4.43 (m, 1H), 4.45-4.59
(m, 1H), 6.84-6.95 (m, 1H), 7.10-7.25 (m, 3H), 7.26-7.35 (m,
2H), 7.38-7.49 (m, 1H), 7.72-7.89 (m, 1H), 10.11-10.42 (m, 1H),
10.93 (s, 1H); MS (ES) m/z 438.2 ([M - H]-). Anal. (C25H27F2N3O2‚
1.10HCl‚0.50H2O) C, H, N. The enantiomers of 26 were separated
by chiral HPLC using a Chiralcel AD column (2 cm × 25 cm) and
16% IPA in hexane/DEA as the mobile phase. They were isolated
and characterized as mono-HCl salts. 26a (white solid): mp 129
°C, dec; [R]25D -26.76° (c 1%, DMSO); 99.5% ee by chiral HPLC;
MS (ES) m/z 440.1 ([M + H]+). Anal. (C25H27F2N3O2‚1HCl‚
500 MHz spectrometer. Chemical shifts δ are reported in ppm
relative to DMSO-d6 at 2.49 ppm or CHCl3-d at 7.27 ppm as an
internal standard. Mass spectra were recorded on a Micromass LCT
spectrometer. CHN combustion analyses were determined on a
Perkin-Elmer 2400 analyzer or were performed by Robertson
Microlit (Madison, NJ). All analyzed compounds are within (0.4%
of the theoretical value unless otherwise indicated. Optical rotations
were measured using a Jasco P-1020 polarimeter. Solvents and
reagents were used as purchased. All final targets were converted
to the HCl salt by dissolution in ethyl acetate and addition of 1 M
HCl/Et2O, followed by filtration unless otherwise indicated.
General Procedure A (Alkylation Reaction): 8-Fluoro-3-
{[3-(5-fluoro-1H-indol-3-yl)propyl]amino}chromane-5-carbox-
amide (19). A solution of 8 (0.81 g, 3.8 mmol), 11 (n ) 1) (0.55
g, 2.1 mmol), and triethylamine (0.60 mL, 4.2 mmol) in anhydrous
DMSO (20 mL) was stirred at 90 °C for 9.5 h. The mixture was
cooled to room temperature, diluted with EtOAc, and extracted with
H2O (2×). The organic layer was treated with brine, dried over
anhydrous MgSO4, filtered, and concentrated. Chromatography (5:
4:1 EtOAc/hexane/MeOH (1% NH4OH)) afforded 0.48 g (60%)
of 19 as a peach solid. Conversion to the mono-HCl salt generated
an off-white solid: mp 122 °C, dec; 1H NMR (500 MHz, DMSO-
d6) δ 1.90-2.08 (m, 2H), 2.68-2.82 (m, 2H), 2.98-3.25 (m, 3H),
3.27-3.45 (m, 2H), 3.71-3.88 (m, 1H), 4.27-4.46 (m, 2H), 6.82-
6.98 (m, 1H), 7.08-7.21 (m, 2H), 7.22-7.27 (m, 1H), 7.27-7.37
(m, 2H), 7.43 (s, 1H), 7.81 (s, 1H), 9.00 (s, 1H), 10.95 (s, 1H);
>99.9% ee by chiral HPLC; MS (ESI) m/z 384([M - H]-). Anal.
(C21H21F2N3O2‚1.20HCl) C, H, N. Chiral separation of 19 was
carried out by SFC on a Chiralcel AS column (2 cm × 25 cm)
using 40% MeOH in CO2 (100 bar). The enantiomers were isolated
and characterized as mono-HCl salts. 19a (white solid): mp 89
°C, dec; [R]25D +19.8° (c 1%, DMSO); MS (ES) m/z 384.2 ([M -
H]-). Anal. (C21H21F2N3O2‚1HCl‚1.20H2O) C, H. N: calcd 9.47,
0.40H2O) C, H, N. 26b (white solid): mp 129 °C, dec; [R]25
D
+27.56° (c 1%, DMSO); 95% ee by chiral HPLC; MS (ES) m/z
438.2([M - H]-). Anal. (C25H27F2N3O2‚1HCl‚0.50H2O) C, H, N.
Acknowledgment. The authors thank Discovery Analytical
Chemistry for HPLC and NMR studies, and Dr. Douglas M.
Ho for X-ray studies. We thank Dr. Minsheng Zhang and Mr.
Andrew Steiner for the synthesis of some intermediates and final
compounds.
Supporting Information Available: Details of synthesis and
analytical data for all final targets, biological assays, and in vivo
microdialysis. This material is available free of charge via the
Internet at http://pubs.acs.org.
References
(1) Blackwell, B. Adverse effects of antidepressant drugs. Part 1:
Monoamine oxidase inhibitors and tricyclics. Drugs 1981, 21, 201-
219.
(2) Evrard, D. A.; Harrison, B. L. Recent approaches to novel antidepres-
sant therapy. Annu. Rep. Med. Chem. 1999, 34, 1-9.
(3) Katz, M. M.; Tekell, J. L.; Bowden, C. L.; Brannan, S.; Houston, J.
P.; Berman, N.; Frazer, A. Onset and early behavioral effects of
pharmacologically different antidepressants and placebo in depression.
Neuropsychopharmacology 2004, 29, 566-579 and references
therein.
(4) Kreiss, D. S.; Lucki, I. Effects of acute and repeated administration
of antidepressant drugs on extracellular levels of 5-hydroxytryptamine
measured in vivo. J. Pharmacol. Exp. Ther. 1995, 274, 866-876.
(5) (a) Briner, K.; Dodel, R. C. New approaches to rapid onset
antidepressants. Curr. Pharm. Des. 1998, 4, 291-302. (b) Schechter,
L. E.; Kelly, M. G. An overview of 5-HT1A receptor antagonists:
historical perspective and therapeutic targets. Serotonin 1997, 2, 299-
309.
(6) Ballesteros, J.; Callado, L. F. Effectiveness of pindolol plus serotonin
uptake inhibitors in depression, a meta-analysis of early and late
outcomes from randomized controlled trials J. AffectiVe Disord. 2004,
79, 137-147 and references therein.
found 10.06. 19b (white solid): mp 87°C, dec; [R]25 -16.0° (c
D
1%, DMSO); >99.9% ee by chiral HPLC; MS (ES) m/z 386.1 ([M
+ H]+).
General Procedure B (Reductive Amination): 8-Fluoro-3-
{[2-(5-fluoro-1H-indol-3-yl)ethyl]amino}chromane-5-carbox-
amide (20). To 8 (0.38 g, 1.8 mmol) in anhydrous MeOH (29 mL)
under nitrogen at room temperature were added 12 (n ) 0) (0.33
g, 1.89 mmol), acetic acid (0.23 mL, 4.32 mmol), and sodium
cyanoborohydride (0.23 g, 3.6 mmol). The mixture was stirred at
room temperature overnight, quenched with 1 N NaOH/H2O, and
concentrated. The residue was taken up in CH2Cl2/H2O and
extracted with CH2Cl2 (3×). The organic layer was treated with
brine, dried over anhydrous MgSO4, filtered, and concentrated.
Chromatography (5:4:1 EtOAc/hexane/MeOH (1% NH4OH)) af-
forded 0.53 g (79%) of 20. Conversion to the mono-HCl salt
(7) Romero, L.; Artigas, F. Preferential potentiation of the effects of
serotonin uptake inhibitors by 5-HT1A receptor antagonists in the
dorsal Raphe pathway: role of somatodendritic autoreceptors. J.
Neurochem. 1997, 68, 2593-2603.

Brief Articles
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 15 4789
(8) Beyer, C. E.; Boikess, S.; Luo, B.; Dawson, L. A. Comparison of
the effects of antidepressants on norepinephrine and serotonin
concentrations in the rat frontal cortex: an in-vivo microdialysis
study. J. Psychopharmacol. 2002, 16, 297-304.
(9) Blier, P.; Bergeron, R. J. The use of pindolol to potentiate antidepres-
sant medication. J. Clin. Psychiatry 1998, 59 (Suppl. 5), 16-23.
(10) Evrard, D. A.; Zhou, P.; Yi, S. Y.; Zhou, D.; Smith, D. L.; Sullivan,
K. M.; Hornby, G. A.; Schechter, L. E.; Andree, T. H.; Mewshaw,
R. E. Studies towards the next generation of antidepressants. Part 4:
Derivatives of 4-(5-fluro-1H-indol-3-yl)cyclohexylamine with affinity
for the serotonin transporter and the 5-HT1A receptor. Bioorg. Med.
Chem. Lett. 2005, 15, 911-914 and references therein.
(11) Perez, M.; Pauwels, P. J.; Pallard-Sigogneau, I,; Fourrier, C.; Chopin,
P.; Palmier, C.; Colovray, V.; Halazy, S. Design and synthesis of
new potent, silent 5-HT1A antagonists by covalent coupling of
aminopropanol derivatives with selective serotonin reuptake inhibi-
tors. Bioorg. Med. Chem. Lett. 1998, 8, 3423-3428.
(12) Rocco, V. P.; Spinazze, P. G.; Kohn, T. J.; Honigschmidt, N. A.;
Nelson, D. L.; Wainscott, D. B.; Ahmad, L. J.; Shaw, J.; Threlkeld,
P. G.; Wong, D. T. Advances toward new antidepressants beyond
SSRIs: 1-aryloxy-3-piperidinylpropan-2-ols with dual 5-HT1A recep-
tor antagonism/SSRI activities. Part 4. Bioorg. Med. Chem. Lett. 2003,
13, 3939-3942 and references therein.
(17) Mewshaw, R. E.; Zhou, D.; Zhou, P.; Shi, X.; Hornby, G.; Spangler,
T.; Scerni, R.; Smith, D.; Schechter, L. R.; Andree, T. H. Studies
toward the discovery of the next generation of antidepressants. 3.
Dual 5-HT1A and serotonin transporter affinity within a class of
N-aryloxyethylindolylalkylamines. J. Med. Chem. 2004, 47, 3823-
3842.
(18) Al Neirabeyeh, M.; Reynaud, D.; Podona, T.; Ou, L.; Perdicakis,
C.; Coudert, G.; Guillaumet, G.; Pichat, L.; Gharib, A.; Sarda, N.
Methoxy and hydroxyl derivatives of 3,4-dihydro-3-(di-n-propyl-
amino)-2H-1-benzopyrans: new synthesis and dopaminergic activity.
Eur. J. Med. Chem. 1991, 26, 497-504.
(19) Hanson, S.; Johansson, L.; Sohn, D. D. Process for the Manufacture
of 3-N,N-Dicyclobutylamino-8-fluoro-3,4-dihydro-2H-1-benzopyran-
5-carboxamide. U.S. 6,197,978 B1, March 6, 2001.
(20) Ghosh, D.; Nichols, D. E. An improved method for the preparation
of cyclic conjugated nitroolefins. Synthesis 1996, 195-197.
(21) Cheetham, S. C.; Viggers, J. A.; Slater, N. A.; Heal, D. J.; Buckett,
W. R. [3H]-Paroxetine binding in rat frontal cortex strongly correlates
with [3H]5-HT uptake: effect of administration of various antidepres-
sant treatments. Neuropharmacology 1993, 32, 737-743.
(22) Cheng, Y.-C.; Prusoff, W. H. Relationship between the inhibition
constant (Ki) and the concentration of inhibitor which causes 50%
inhibition (IC50) of an enzymatic reaction. Biochem. Pharmacol. 1973,
22, 3099-3108.
(23) Ramamoorthy, J. D.; Ramamoorthy, S.; Papapetropoulos, A.; Catra-
vas, J. D.; Leibach, F. H.; Ganapathy, V. Cyclic AMP-independent
up-regulation of the human serotonin transporter by staurosporine
in chloriocarcinoma cells. J. Biol. Chem. 1995, 270, 17189-17195.
(24) Hall, M. D.; El Mestikawy, S.; Emerit, M. B.; Pichat, L.; Hamon,
M.; Gozlan, H. [3H]8-Hydroxy-2-(di-n-propylamino) tetralin binding
to pre- and postsynaptic 5-hydroxytryptamine sites in various regions
of the rat brain. J. Neurochem. 1985, 44, 1685-1696.
(13) Podona, T.; Guardiola-Lemaitre, B.; Caignard, D.-H.; Adam, G.;
Pfeiffer, B.; Renard, P.; Guillaumet, G. 3,4-Dihydro-3-amino-2H-1-
benzopyran derivatives as 5-HT1A receptor ligands and potential
anxiolytic agents. 1. Synthesis and structure-activity relationship
studies. J. Med. Chem. 1994, 37, 1779-1793.
(14) Hammarberg, E.; Nordvall, G.; Leideborg, R.; Nylof, M.; Hanson,
S.; Johansson, L.; Thorberg, S.-O.; Tolf, B.-R.; Jerning, E.; Svant-
esson, G. T.; Mohell, N.; Ahlgren, C.; Westlind-Danielsson, A.;
Csoregh, I.; Johansson, R. Synthesis of novel 5-substituted 3-amino-
3,4-dihydro-2h-1-benzopyran derivatives and their interactions with
the 5-HT1A receptor. J. Med. Chem. 2000, 43, 2837-2850.
(15) Evenden, J. L.; Hammarberg, E. M.; Hansson, H. S.; Hellberg, S.
E.; Johansson, L. G.; Lundkvist, J. R. M.; Ross, S. B.; Sohn, D. D.;
Thorberg, S. O. (R)-5-Carbamoyl-8-fluoro-3-N,N-disubstituted-amino-
3,4-dihydro-2H-1-benzopyrans. U.S. 5,616,610, April 1, 1997.
(16) Ross, S. B.; Thorberg, S.-O.; Jerning, E.; Mohell, N.; Stenfors, C.;
Wallsten, C.; Milchert, I. G.; Ojteg, G. A novel selective 5-HT1A
receptor antagonist. CNS Drug ReV. 1999, 5, 213-232.
(25) Dunlop, J.; Zhang, Y.; Smith, D. L.; Schechter, L. E. Characterization
of 5-HT1A receptor functional coupling in cells expressing the human
5-HT1A receptor as assessed with the cytosensor microphysiometer.
J. Pharmacol. Toxicol. Methods 1998, 40, 47-55.
(26) Morrow, A. L.; Creese, I. Characterization of R1-adrenergic receptor
subtypes in rat brain: a reevaluation of [3H]WB4104 and [3H]prazosin
binding. Mol. Pharmacol. 1986, 29, 321-330.
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