Effect of structural modification in the amine portion of substituted aminobutyl-benzamides as ligands for binding σ1 and σ2 receptors

Article abstract of DOI:10.1016/j.bmc.2011.02.006

5-Bromo-N-[4-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-butyl)]-2, 3-dimethoxy-benzamide (1) is one of the most potent and selective σ₂ receptor ligands reported to date. A series of new analogs, where the amine ring fused to the aromatic ring was varied in size (5-7) and the location of the nitrogen in this ring was modified, has been synthesized and assessed for their σ₁/σ₂ binding affinity and selectivity. The binding affinity of an open-chained variant of 1 was also evaluated. Only the five-membered ring congener of 1 displayed a higher σ₁/σ₂ selectivity, derived from a higher σ₂ affinity and a lower σ₁ affinity. Positioning the nitrogen adjacent to the aromatic ring in the five-membered and six-membered ring congeners dramatically decreased affinity for both subtypes. Thus, location of the nitrogen within a constrained ring is confirmed to be key to the exceptional σ₂ receptor binding affinity and selectivity for this active series.

Full text of DOI:10.1016/j.bmc.2011.02.006

Bioorganic & Medicinal Chemistry 19 (2011) 1852–1859
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Effect of structural modification in the amine portion of substituted
aminobutyl-benzamides as ligands for binding r1 and r2 receptors
Kuo-Hsien Fan a, John R. Lever b,c,d, Susan Z. Lever a,e,
⇑
a Department of Chemistry, University of Missouri-Columbia, Columbia, MO, USA
b Department of Radiology, University of Missouri-Columbia, Columbia, MO, USA
c Department of Medical Pharmacology and Physiology, University of Missouri-Columbia, Columbia, MO, USA
d Harry S. Truman Veterans Administration Medical Center, Columbia, MO, USA
e Research Reactor Center, University of Missouri-Columbia, Columbia, MO, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
5-Bromo-N-[4-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-butyl)]-2,3-dimethoxy-benzamide (1)
is one of the most potent and selective r2 receptor ligands reported to date. A series of new analogs,
where the amine ring fused to the aromatic ring was varied in size (5–7) and the location of the nitrogen
Received 22 December 2010
Revised 29 January 2011
Accepted 3 February 2011
Available online 12 February 2011
in this ring was modified, has been synthesized and assessed for their r1
tivity. The binding affinity of an open-chained variant of 1 was also evaluated. Only the five-membered
ring congener of 1 displayed a higher r1 2 selectivity, derived from a higher 2 affinity and a lower r1
/r2 binding affinity and selec-
/
r
r
Keywords:
Sigma receptors
Structure–activity relationships
Aminobutyl-benzamides
affinity. Positioning the nitrogen adjacent to the aromatic ring in the five-membered and six-membered
ring congeners dramatically decreased affinity for both subtypes. Thus, location of the nitrogen within a
constrained ring is confirmed to be key to the exceptional
this active series.
r
2 receptor binding affinity and selectivity for
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
a class of tetrahydroisoquinolinyl benzamide ligands that rank
among the most selective for the r2 receptor subtype. Benzamide
1 (Fig. 1) displays high apparent affinity, Ki = 8.2 nM, for r2 sites
in vitro accompanied by 1573-fold selectivity over r1 sites. Ana-
logs of 1 reported by this research group have focused on substitu-
tions of the benzamide portion of the molecule, including 1a which
exhibits a higher selectivity of 8190.15–17 By contrast, we have ex-
plored variations in the tetrahydroisoquinoline ring.18 In the first
study, the two methoxy groups were replaced with methylene-,
ethylene- and propylenedioxy rings. These modifications de-
creased r2 affinity by 8- to 12-fold, with no major differences
noted with ring size. By contrast, the methylenedioxy analog
showed a 10-fold greater r1 affinity than 1, and progressively
poorer r1 affinities were then noted with increasing ring size. Of
more import, when the tetrahydroisoquinoline ring of 1 was
It has been approximately 20 years since the identification of
two subtypes to the sigma receptor.1 Advances have been made
with regard to the r1 subtype, including cloning,2–4 characteriza-
tion of the binding site,5,6 the search for putative endogenous
ligands,7 and the development of a knockout mouse.8 Such pro-
gress has not yet been made with the r2 receptor. Both subtypes,
however, are implicated in a variety of health related functions,
including addiction and cancer.9,10 Thus, this is a research area of
much current interest.
Glennon has reviewed structure–affinity relationships (SAR) for
r
1 and r
2 sites.11,12 Important features of the Glennon pharmaco-
phore for both r1 and r2 sites are an amine binding site flanked,
on each side, by hydrophobic binding pockets that display bulk tol-
erance. More recently, a model has been proposed based on 19
benzo[d]oxazol-2(3H)-one derivatives for the r2 binding site.13
In this model, fundamental attributes include an atom capable of
accepting a positive charge, and three hydrophobic areas, one of
which is aromatic and one which is aliphatic in nature. Although
a number of studies have investigated the effects of structure on
opened to study the effects of conformational flexibility on
r
receptor binding (Fig. 1, compound 2), there was no change in r1
affinity, but a dramatic decrease (1700-fold) in the r2 affinity
was observed. Thus, the constrained ring system appears to be a
crucial component to the exceptional r2 receptor binding affinity
and selectivity observed for this active series.
relative r1
/
r2 receptor binding affinity and selectivity, few truly
In order to gain a better understanding of the contribution of
the tetrahydroisoquinoline moiety to r2 affinity and selectivity,
we have extended our study to focus on structural modifications
at the amine portion of 1. The first goal was to modulate the
conformational freedom of the amine-containing ring fused to
the aromatic ring. We thus included the five-membered and
r2 selective compounds are known. Mach et al.14 have identified
⇑
Corresponding author. Tel.: +1 573 882 8395; fax: +1 573 882 2754.
E-mail address: levers@missouri.edu (S.Z. Lever).
0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2011.02.006

K.-H. Fan et al. / Bioorg. Med. Chem. 19 (2011) 1852–1859
1853
the appropriate primary butylamine derivative. The requisite
butylamine precursors (Scheme 1) were prepared through three
different two-step routes. The first route paralleled that reported
for compound 1; that is, alkylation with 4-bromobutryonitrile fol-
lowed by lithium aluminum hydride reduction. This route proved
successful in the synthesis of 12 in 68% yield. However, in the
preparation of other amines, this route was plagued by formation
of by-products that complicated purification (data not shown).
Therefore, an alternate route, alkylation of 14, 17, 23 (accom-
plished through L
-proline assisted cuprous iodide coupling19), or
27 by N-(4-bromobutyl) phthalimide, followed by treatment with
hydrazine was utilized. Yields in this two-step route ranged from
29% for 28 to 63% for 24. The last route, specifically used for the
preparation of amine 21, concomitantly formed the indoline ring
and installed the 4-azidobutyl moiety with reaction of 4-azidobu-
tylamine and 1,2-bis(bromomethyl)-4,5-dimethoxybenzene. The
azide was then reduced to form amine 21 in 71% yield for the
two-step sequence. For the synthesis of 31, (Scheme 2) alkylation
of 2-(3,4-dimethoxyphenyl)ethanamine with 4-bromobutryonitri-
le was followed by formylation. Lithium aluminum hydride
achieved reduction of the N-formyl group to the N-methyl group
as well as the nitrile moiety to the primary amine in 47% yield
for the three-step sequence.
Figure 1. Lead compounds as subject of this study.
seven-membered variants of 1 (Fig. 2, compounds 3 and 4). Nitro-
gen can occupy more than one isomeric position in the five-, and
seven-membered rings, as well as in the six-membered ring of 1,
so we prepared these analogs as well (Fig. 2, compounds 5–8).
Compounds 3–8 represent all the unique possibilities for one nitro-
gen atom in the fused ring, in addition to 1. From these com-
3. Stability of compounds in assay solutions
All compounds for in vitro binding assays were first formulated
at a millimolar concentration in water containing 1% ethanol with
a small percent of acetic acid (0.1% for 4 and 9; 2.5% for 3, 5, 6, 7,
and 8). Purity was assessed by HPLC and compounds 3, 4, 6, 7
and 9 exceeded 95% after 25 days. However, it was found that com-
pound 5 was not stable during the monitoring period (86% remain-
ing after 16 h and totally decomposed after 25 days). In addition,
compound 8 was found to be unstable during the assay period
(90% remaining after 16 h, 38% left after 44 h and totally decom-
posed after 25 days). For both of these compounds, binding assays
used freshly prepared serial dilutions to insure accuracy of the re-
sults obtained from the binding studies. Solutions of these com-
pounds in deuterated solvents followed by analysis by 1H NMR
and LC/MS provided analytical support for demethylation of the
methoxy group ortho to the benzamide moiety in compounds 5
pounds, effects on r1/r2 affinity and selectivity from either the
orientation of the nitrogen in each respective ring or the inherent
basicity of the nitrogen, can be determined. The second goal of
the study was to prepare and evaluate 9, the N-methyl analog of
2. The rationale for this structure is that it maintains the conforma-
tional fluidity of 2, while it re-introduces the tertiary nitrogen that
might be required for optimum binding to the receptor.
2. Chemistry
In all cases, the ultimate step for the synthesis of compounds
3–9 is coupling 5-bromo-2,3-dimethoxybenzoyl chloride (32) to
Figure 2. Compounds synthesized and evaluated in this study.

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K.-H. Fan et al. / Bioorg. Med. Chem. 19 (2011) 1852–1859
Scheme 1. Reagents: (a) Br(CH2)3CN; (b) LiAlH4/THF; (c) NaN3/HCl; (d) N-(4-bromobutyl)phthalimide; (e) NH2NH2ÁxH2O; (f) BH3ÁTHF; (g) 4-azidobutylamine; (h) PPH3/THF/
H2O; (i) 10 mol % CuI, 20 mol % -proline, DMSO; (j) Fe(s)/AcOH.
L
Scheme 2. Reagents: (a) Br(CH2)3CN; (b) HCO2H, Ac2O; (c) LiAlH4/THF.
and 8 (spectra and LC/MS results are found in the Supplementary
data). It is not obvious why only these two compounds would
decompose; however, these results underscore the need to moni-
tor stability of all compounds prior to binding assays.
all selectivity for the r2 receptor based on the results for each ana-
log was quite modest overall (0.27–8.5), with the exception for
compound 3, which exhibited a selectivity of 1758.
5. Discussion
4. Receptor binding assays
Based upon previous work,18 it is known that opening the ring
of the tetrahydroisoquinolinyl ring ablates r2 affinity. In this
study, modulating the conformational freedom and seeing its effect
In vitro binding affinities to the r1 receptor for the series of
compounds varied over an order of magnitude, from 583 28 nM
to 5073 82 nM (Table 1). The range of affinities observed for
on binding affinity, especially the
r2 affinity, was one of the major
the
r2 receptor was much larger, on the order of 11,000. The over-
goals. The effect of ring size of the amine-containing component

K.-H. Fan et al. / Bioorg. Med. Chem. 19 (2011) 1852–1859
1855
Table 1
In vitro affinity and selectivity of compounds 3–9 for r1 and r2 receptorsa
Ki (nM)
r1
Ki (nM)
r2
Selectivity
Ki 1/Kir2
r
1 Mach lead
12,900
881 15
8.2
2.7 0.1
1573b
326c
2 (Open-ring)
880 60
4616 247
0.2c
3 (5R-2)
4 (7R-3)
5 (5R-1)
6 (7R-2)
7 (7R-1)
8 (6R-1)
9 (Open-ring-Me)
Haloperidol
SA4503
1442 88
5073 82
4521 45
2068 60
2564 175
4499 182
583 28
0.82 0.06
734 50
9681 522
315 15
8957 335
5823 224
2126 240
9.58 0.98
89.51 7.97
1758
8.5
0.47
6.58
0.29
0.77
0.27
11.5
20.6
0.83 0.03
4.34 0.31
a
b
c
Mean SEM; n = 4.
From Ref. 14.
From Ref. 18.
fused to the aromatic ring on the binding affinity was investigated
by preparing a seven-membered variant and a five-membered var-
iant. In the case of the seven-membered ring congener, 6 (7R-2),
results supported the hypothesis that increasing conformational
freedom in this portion of the molecule had a negative effect on
binding to the r2 subtype. A negative effect on the r1 subtype
was seen as well; and overall, only a modest selectivity for the
r2 subtype was observed. Also, in support of the hypothesis that
conformational constraint is helpful in binding to the r2 subtype,
decreasing the ring size from 6 to 5 in 3 (5R-2) improved
r2 affin-
ity over that of 1 by 70%. The decrease in r1 affinity was not that
dramatic, approximately 50%, with the overall effect of improving
the selectivity over that of the lead compound.
Figure 3. (a) Overlap of minimized structures 1 and 8; (b) overlap of minimized
structures 3 and 5; (c) overlap of minimized structures 1 and 9.
As mentioned previously, isomeric compounds could be synthe-
sized where the position of nitrogen in the fused ring varied. For
the five- and six-membered rings, two isomers are possible and
for the seven-membered ring, three isomers are possible. Binding
results suggest the position of the nitrogen in the smaller ring
structures is critical to binding to both subtypes, but much more
sensitive for affinity to the r2 subtype. For example, in 8 (6R-1),
(Open-ring-Me) (Fig. 3c). Each compound was first subjected to en-
ergy minimization by the MMFF94 force field built in ChemBio 3D
(Cambridge Soft) and then each pair was overlaid. Clearly, com-
pound 1 can extend itself linearly; whereas, the placement of the
nitrogen next to the aromatic ring in 8 puts a definite twist in
the molecule. This effect is also seen when comparing compounds
3 and 5. Compound 3, the compound with the highest r2 affinity
and selectivity is extended like compound 1. Compound 5, simi-
larly as seen for 8, the placement of the nitrogen puts a twist into
the heterocyclic portion of the molecule, and the observed affini-
ties are much worse. These twists in the molecule may help ex-
plain the exceedingly poor affinity of 8 and 5 to the r2 receptor.
In the comparison of 1 with 9, the open-ringed analog with the ter-
tiary amine, the conformational freedom inherent in the latter
compound permits some rotation of the dimethoxy-substituted
aryl ring out of plane and may impact the binding affinity. Taken
together, the relative binding properties noted indicate the impor-
tance of these structural features to binding to the r1 and r2
receptor subtypes.
the isomer of the Mach Lead (1),
tor of 5 and 2 affinity was totally ablated; 7 (7R-1) versus 6 (7R-2)
20% poorer for r1 and almost 30 times poorer for 2; 3 (5R-2)
versus 5 (5R-1) three times poorer for r1 and over 11,000 times
poorer for r2
r1 affinity was decreased by a fac-
r
r
.
In the seven-membered ring isomeric cases, there is no trend
related to the position of the nitrogen. In r1 affinities, 4 (7R-3)
had poorest affinity by a factor of 2 compared to 6 (7R-2) and 7
(7R-1); whereas, for
r2, 4 (7R-3) had a poorer affinity that 6
(7R-2), but more than ten times higher than that of 7 (7R-1). Of
these three isomers, 6 (7R-2), where the position of the nitrogen
to the aromatic ring is similar to that of the Mach lead 1 and 3
(5R-2), has the best affinity for the r2 subtype. These results
suggest that the structural position of the amine relative to the
aromatic ring is important for optimum binding for the
r2 subtype.
Introduction of a methyl group on the open-ring compound
(9 over 2) improved affinity for both r1 and r2 subtypes. These
results support the need for a tertiary nitrogen for binding to the
receptor; however, in this series of compounds, this modification
does not counteract the structural flexibility provided by the open
chain structure, as affinity was still quite low and selectivity was
poor.
6. Conclusions
Binding affinities of
a novel set of ligands are affected
dramatically by the structural modification in the amine portion
of the parent molecule. The excellent binding affinity of compound
3 only to r2 receptor subtypes provides a highly selective r2
receptor subtype ligand (Kir1/Kir2 = 1758), and these results cor-
Qualitatively, three-dimensional models can provide a preli-
minary rationale to explain the differences observed in the
in vitro results in the pairs of the compounds (1 (Mach lead) and
8 (6R-1) (Fig. 3a), 3 (5R-2) and 5 (5R-1) (Fig. 3b) and 1 and 9
roborate the need of rigidity in this portion of this class of ligands.
In addition, structural features were identified that result in extre-
mely poor affinity and selectivity for both the r1 and r2 receptor
subtypes.

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K.-H. Fan et al. / Bioorg. Med. Chem. 19 (2011) 1852–1859
pressure. Water (100 mL) was added to the residue and extracted
7. Experimental
7.1. General procedures
with EtOAc (3 Â 100 mL). The combined organic layers were dried
over anhydrous Na2SO4, concentrated to give 2-(4-(7,8-dimethoxy-
4,5-dihydro-1H-benzo[c]azepin-2(3H)-yl)butyl)isoindoline-1,3-
dione (1.55 g, 83%) as a yellow gum. 1H NMR (CDCl3) d:
7.84–7.79 (m, 2H), 7.73–7.68 (m, 2H), 6.66 (s, 2H), 3.85 (s,
3H), 3.84 (s, 3H), 3.80 (s, 2H), 3.69 (t, J = 7.0 Hz, 2H), 3.09–3.04
(m, 2H), 2.83–2.79 (m, 2H), 2.40 (t, J = 7.2, 2H), 1.74–1.62 (m,
4H), 1.55–1.50 (m, 2H). This material was used without further
purification or characterization and was treated with hydrazine
hydrate (0.33 g, 6.60 mmol) in dry MeOH (10 mL) and the mix-
ture was refluxed for 3 h. The mixture was cooled and the MeOH
and hydrazine were removed under reduced pressure. Diethyl
ether (50 mL) was added to the residue, filtered and the filtrate
was evaporated to give 15 (0.46 g, 44%) as a colorless oil. 1H
NMR (CDCl3) d: 6.67 (s, 1H), 6.66 (s, 1H), 4.90 (br s, 2H), 3.85
(s, 3H), 3.84 (s, 3H), 3.83 (s, 2H), 3.09–3.07 (m, 2H), 2.83–2.80
(m, 2H), 2.74 (t, J = 6.5 Hz, 2H), 2.34 (t, J = 6.5 Hz, 2H), 1.72–
1.69 (m, 2H), 1.59–1.55 (m, 4H).
1H NMR spectra were determined on Bruker 250, 300, or
500 MHz spectrometers. Chemical shifts are reported as parts per
million (d) relative to internal Me4Si in CDCl3, with coupling con-
stants (J) given in hertz (Hz). Elemental analyses were determined
by Atlantic Microlab, Inc. (Norcross, GA), and were in agreement
with calculated values (C, H, N: 0.4%) with the exception of com-
pounds 6 and 9 (H 0.46%). Short-path silica gel (Merck 7729, <230
mesh) chromatography was conducted under N2 pressure. Analyt-
ical TLC was performed with Macherey-Nagel Silica Gel 60 UV-254
plates (250 mm). OptiPhaseÒ HiSafe
2 scintillation cocktail,
[3H](+)-pentazocine ([3H](+)-PTZ, 29 Ci/mmol) and [3H]1,3-di-
(2-tolyl)guanidine ([3H]DTG, 48.7 Ci/mmol) were from Perkin–
Elmer Life Sciences, Inc. (Boston, MA). Other chemicals and
solvents were the best grades available, and were used as received
from commercial sources.
7.1.4. 7,8-Dimethoxy-2,3,4,5-tetrahydro-1H-benzo[b]azepine
(17)
7.1.1. 4-(7,8-Dimethoxy-4,5-dihydro-1H-benzo[d]azepin-3(2H)-
yl)butan-1-amine (12)
To a stirred solution of 1621 (0.82 g, 3.7 mmol) in dry THF
(10 mL), BH3ÁTHF solution (20 mL, 1 M) was added dropwise at
0 °C and stirred at rt for 1.5 h. The reaction mixture was cooled
to 0 °C and then quenched with HCl (4 N) until no H2 gas further
evolved. The solution was stirred at rt for 0.5 h and then the pH
of the solution was adjusted with 10% aqueous NaOH to pH >14.
The resulting solution was extracted with CHCl3 (3 Â 50 mL) to
give 17 (0.66 g, 87%) as a white solid. 1H NMR (CDCl3) d: 6.65
(s, 1H), 6.34 (s, 1H), 3.82 (s, 6H), 3.02–2.99 (m, 2H), 2.72–2.68
(m, 2H), 1.80–1.76 (m, 2H), 1.62–1.59 (m, 2H).
To a stirred solution of 7,8-dimethoxy-2,3,4,5-tetrahydro-1H-
benzo[d]azepine20 (11) (1.36 g, 6.6 mmol) and 4-bromobutyronit-
rile (0.98 g, 6.6 mmol) in DMF (40 mL), NaI (1.00 g, 6.6 mmol)
and K2CO3 (2.75 g, 19.9 mmol) were added and the mixture was
stirred at 60 °C overnight. The solvent was removed under reduced
pressure and the residue was diluted with H2O (150 mL) and ex-
tracted with ethyl acetate (3 Â 100 mL) to give 4-(7,8-dimethoxy-
4,5-dihydro-1H-benzo[d]azepin-3(2H)-yl)butanenitrile
(1.66 g,
92%) as a yellow oil. 1H NMR (CDCl3) d: 6.64 (s, 2H), 3.85 (s, 6H),
2.86–2.82 (m, 4H), 2.63–2.59 (m, 4H), 2.58 (t, J = 6.8 Hz, 2H), 2.47
(t, J = 6.8 Hz, 2H), 1.84 (tt, J = 6.9 Hz, 6.9 Hz, 2H). This material
(1.58 g, 5.7 mmol) was used without further purification and dis-
solved in dry THF (20 mL) for the following reaction. A solution
of LiAlH4 (0.65 g, 17.1 mmol) in dry THF (20 mL) was added drop-
wise at 0 °C. The mixture was stirred at rt overnight under N2. The
mixture was cooled to 0 °C and quenched by adding H2O (1 mL),
10% aqueous NaOH (2 mL), and H2O (2.5 mL) successively. The
inorganic salts were washed with EtOAc and filtered. The filtrate
was evaporated under reduced pressure to give 12 (1.18 g, 75%)
as yellow oil. 1H NMR (CDCl3) d: 6.64 (s, 2H), 3.85 (s, 6H),
2.87–2.83 (m, 4H), 2.72 (t, J = 6.9 Hz, 2H), 2.64–2.60 (m, 4H), 2.48
(t, J = 6.9 Hz, 2H), 1.57–1.45 (m, 4H).
7.1.5. 4-(7,8-Dimethoxy-2,3,4,5-tetrahydro-1H-benzo[b]azepin-
1-yl)butan-1-amine (18)
To a stirred solution of 17 (155 mg, 0.75 mmol) in DMF (10 mL),
N-(4-bromobutyl)-phthalimide (211 mg, 0.75 mmol), NaI (0.11 g,
0.75 mmol) and K2CO3 (0.31 g, 2.2 mmol) were mixed according
to the procedure described in the preparation of 15. After a short
path chromatography column (EtOAc/CH2Cl2 1:1), 2-(4-(7,8-dime-
thoxy-2,3,4,5-tetrahydrobenzo[b]azepin-1-yl)butyl)isoindoline-1,3-
dione (166 mg, 55%) was isolated as a yellow gum. 1H NMR (CDCl3)
d: 7.87–7.79 (m, 2H), 7.73–7.67 (m, 2H), 6.59 (s, 1H), 6.50 (s, 1H),
3.83 (s, 3H), 3.80 (s, 3H), 3.70 (t, J = 7.0, 2H), 3.11 (t, J = 6.6 Hz, 2H),
2.85–2.81 (m, 2H), 2.71–2.66 (m, 2H), 1.85–1.77 (m, 4H), 1.67–1.56
(m, 4H). This material (160 mg, 0.39 mmol) was added to dry
MeOH (10 mL), and hydrazine hydrate (34 mg, 0.69 mmol) was
added. The mixture was refluxed for 3 h, after which the MeOH
and hydrazine were removed under reduced pressure and diethyl
ether (50 mL) was added to the residue. The resulting mixture
was filtered and the filtrate was evaporated to give 18 (61 mg,
56%) as a light yellow oil. 1H NMR (CDCl3) d: 6.66 (s, 1H), 6.55 (s,
1H), 3.85 (s, 3H), 3.83 (s, 3H), 3.09 (t, J = 6.6 Hz, 2H), 2.87–2.84
(m, 2H), 2.73–2.69 (m, 4H), 1.71–1.66 (m, 2H), 1.61–1.54 (m, 8H).
7.1.2. 7,8-Dimethoxy-2,3,4,5-tetrahydro-1H-benzo[c]azepin-1-
one (13) and 7,8-dimethoxy-4,5-dihydro-1H-benzo[b]azepin-
2(3H)-one (16)
The isomeric amides 13 and 16 were prepared as a mixture by a
literature procedure21 and purified by short path chromatography
EtOAc/CHCl3 (9:1) to give 13 (2.77 g, 52%) and 16 (1.22 g, 23%) as
white solids. 13: 1H NMR (CDCl3) d: 7.27 (s, 1H), 6.68 (s, 1H),
6.48 (br t, 1H), 3.93 (s, 3H), 3.92 (s, 3H), 3.15 (dt, J = 6.3, 6.6 Hz,
2H), 2.82 (t, J = 6.9 Hz, 2H), 2.02 (tt, J = 6.9, 6.9 Hz, 2H). Compound
16: 1H NMR (CDCl3) d: 7.4 (br s, 1H), 6.72 (s, 1H), 6.53 (s, 1H), 3.89
(s, 3H), 3.86 (s, 3H), 2.74 (t, J = 6.9 Hz, 2H), 2.36–2.32 (m, 2H),
2.26–2.20 (m, 2H). The amide 13 was reduced according to the
literature procedure21 to provide 14.
7.1.6. 2-(4-Azidobutyl)-5,6-dimethoxyisoindoline (20)
To a stirred solution of 1922 (0.48 g, 1.5 mmol) and 4-azidobu-
tylamine23 (0.17 g, 1.5 mmol) in DMF (15 mL), NaI (0.45 g, 3 mmol)
and K2CO3 (3.7 g, 9 mmol) were added. The resulting mixture was
stirred at 60 °C for 3 h and then the solvent was removed under
reduced pressure. Water (50 mL) was added to the residue and
then extracted with EtOAc (3 Â 50 mL). The combined organic
layers were dried over anhydrous Na2SO4 and evaporated to give
20 (0.38 g, 93%) as a dark red oil. 1H NMR (CDCl3) d: 6.75 (s, 2H),
3.93 (s, 4H), 3.86 (s, 6H), 3.34 (t, J = 6.3 Hz, 2H), 2.77 (t, J = 6.9 Hz,
2H), 1.73–1.66 (m, 4H).
7.1.3. 4-(7,8-Dimethoxy-4,5-dihydro-1H-benzo[c]azepin-2(3H)-
yl)butan-1-amine (15)
To a flask, N-(4-bromobutyl)-phthalimide (1.29 g, 4.58 mmol),
14 (0.95 g, 4.58 mmol), NaI (0.67 g, 4.58 mmol) and K2CO3
(0.93 g, 13.4 mmol) were added. The resulting mixture was stirred
at 60 °C for 2 h and then the solvent was removed under reduced

K.-H. Fan et al. / Bioorg. Med. Chem. 19 (2011) 1852–1859
1857
7.1.7. 4-(5,6-Dimethoxyisoindolin-2-yl)butan-1-amine (21)
7.1.11. 4-(6,7-Dimethoxy-3,4-dihydroquinolin-1(2H)-yl)butan-
1-amine (27)
To a stirred solution of 20 (0.53 g, 1.9 mmol) in THF (10 mL) and
H2O (0.2 mL) was added PPh3 (0.61 g, 2.3 mmol) slowly and the
resulting mixture was stirred at rt for 24 h. The mixture was
extracted with 1 M aqueous HCl (3 Â 15 mL) and the organic phase
was discarded. The combined aqueous phases were washed with
CH2Cl2 (2 Â 50 mL). The washed aqueous layer was basified with
2.5 M aqueous NaOH to pH >10 and then extracted with CH2Cl2.
The combined organic layers were dried over anhydrous Na2SO4
and evaporated to give 21 (0.36 g, 76%) as a brown oil. 1H NMR
(CDCl3) d: 6.74 (s, 2H), 3.88 (s, 4H), 3.86 (s, 6H), 2.75
(t, J = 6.9 Hz, 2H), 2.72 (t, J = 8.4 Hz, 2H), 1.62–1.51 (m, 6H).
The two-step procedure to introduce the N-butylamino moiety
onto 18 was followed. From 26 (175 mg, 0.91 mmol) and N-(4-
bromobutyl)-phthalimide (257 mg, 0.91 mmol), after a short path
column with ethyl acetate/hexane (2:1), 2-(4-(6,7-dimethoxy-
3,4-dihydroquinolin-1(2H)-yl)butyl)isoindoline-1,3-dione (158 mg,
44%) was obtained as an orange oil. 1H NMR (CDCl3) d: 7.86–7.82
(m, 2H), 7.73–7.70 (m, 2H), 6.52 (s, 1H), 6.22 (s, 1H), 3.86 (s, 3H),
3.80 (s, 3H), 3.73 (t, J = 7 Hz, 2H), 3.25–322 (m, 2H), 3.19–3.17
(m, 2H), 2.67 (t, J = 6.5 Hz, 2H), 1.94–1.86 (m, 2H), 1.80–1.73 (m,
2H), 1.67–1.55 (m, 2H). This material was used without further
characterization in the reaction with hydrazine hydrate (34.7 mg,
0.70 mmol). After filtration, 27 (70 mg, 67%) was obtained as a pale
yellow oil. 1H NMR (CDCl3) d: 6.54 (s, 1H), 6.23 (s, 1H), 3.84 (s, 3H),
3.79 (s, 3H), 3.23–3.18 (m, 4H), 2.74 (t, J = 7 Hz, 2H), 2.68 (t,
J = 6.5 Hz, 2H), 1.95–1.90 (m, 2H), 1.65–1.59 (m, 2H), 1.53–1.47
(m, 2H).
7.1.8. 5,6-Dimethoxyindoline (23)
A sealed round bottomed flask was charged with CuI (0.11 g,
0.55 mmol),
L-proline (0.13 g, 1.1 mmol) and K2CO3 (1.62 g,
11.1 mmol). The flask was evacuated and then backfilled with N2
(two cycles). A solution of 2-(2-bromo-4,5-dimethoxyphenyl)-
ethanamine (22)24 (1.45 g, 5.5 mmol) in DMSO (5.5 mL) was added
to the flask and the mixture was stirred at 70 °C under N2 for 45 h.
Water (100 mL) was added to the mixture and extracted with
CHCl3 (3 Â 100 mL). The combined organic layers were dried over
anhydrous Na2SO4, concentrated and applied to a short path chro-
matography column CHCl3/MeOH (60:1) to give 23 (0.36 g, 36%) as
a pale brown solid. 1H NMR (CDCl3) d: 6.76 (s, 1H), 6.35 (s, 1H),
3.82 (s, 3H), 3.81 (s, 3H), 3.54 (t, J = 8.4 Hz, 2H), 2.98 (t, J = 8.4 Hz,
2H). This material corresponded to the spectral data reported for
the compound prepared by a different method.25
7.1.12. 4-(3,4-Dimethoxyphenethylamino)butanenitrile (29)
The alkylation of 2-(3,4-dimethoxyphenyl)ethanamine (1.81 g,
10 mmol) (28) with 4-bromobutanenitrile (1.48 g, 10 mmol) fol-
lowed the procedure described in the preparation of 12 and yielded
29 (2.31 g, 93%) as a yellow oil. 1H NMR (CDCl3) d: 6.83–6.71 (m,
3H), 3.88 (s, 3H), 3.86 (s, 3H), 2.81–2.83 (m, 2H), 2.77–2.72 (m,
4H), 2.42 (t, J = 7.2 Hz, 2H), 1.83–1.73 (m, 2H).
7.1.13. N-(3,4-Dimethoxyphenethyl)-N-(3-cyanopropyl)-
formamide (30)
Formic acid (12.56 g, 285.5 mmol) and acetic anhydride (9.35 g,
8.57 mmol) were added to 29 (2.31 g, 9.29 mmol) and the mixture
was stirred at 70 °C for 1 h. After the acid was evaporated under re-
duced pressure, the residue was diluted with H2O (100 mL) and ex-
tracted with CHCl3 (3 Â 100 mL). After a short path column with
ethyl acetate, 30 (1.75 g, 68%) was obtained as a light yellow oil.
1H NMR (CDCl3) d: 8.11, 7.87 (s, total 1H), 6.83–6.34 (m, 3H),
3.88, 3.87, 3.86 (s, total 6H), 3.55–3.41 (m, 3H), 2.86–2.77 (m,
2H), 2.38 (t, J = 7.2 Hz, 1H), 2.33–2.29 (m, 1H), 1.96–1.92 (m, 1H),
1.86–1.73 (m, 1H).
7.1.9. 4-(5,6-Dimethoxyindolin-1-yl)butan-1-amine (24)
The indoline 23 (152 mg, 0.85 mmol) and N-(4-bromobutyl)-
phthalimide (239 mg, 0.85 mmol) were mixed according to the
procedure described in the preparation of 15. After a short path
column with CHCl3/MeOH (40:1), 24 (240 mg, 74%) was obtained
as a dark brown oil. 1H NMR (CDCl3) d: 7.86–7.81 (m, 2H), 7.74–
7.70 (m, 2H), 6.72 (s, 1H), 6.19 (s, 1H), 3.86 (s, 3H), 3.79 (s, 3H),
3.74 (t, J = 6.3 Hz, 2H), 3.26 (t, J = 8.1 Hz, 2H), 3.03 (t, J = 7.2 Hz,
2H), 2.87 (t, J = 8.1 Hz, 2H), 1.86–1.78 (m, 2H), 1.70–1.62 (m, 2H).
This material was used without further purification and mixed
with hydrazine hydrate (54.6 mg, 1.10 mmol) in the procedure
used for the preparation of 15. After filtration, 24 (133 mg, 85%)
was obtained as a light brown oil. 1H NMR (CDCl3) d: 6.75 (s,
1H), 6.18 (s, 1H), 3.86 (s, 3H), 3.80 (s, 3H), 3.27 (t, J = 8.1 Hz, 2H),
3.00 (t, J = 7.2 Hz, 2H), 2.88 (t, J = 8.1 Hz, 2H), 2.77 (t, J = 6.9, 2H),
1.68–1.53 (m, 4H), 1.26 (br s, 2H).
7.1.14. N1-(3,4-Dimethoxyphenethyl)-N1-methylbutane-1,4-
diamine (31)
With the procedure described for the preparation of 12, 30
(1.46 g, 5.3 mmol) was reduced with 1 M LiAlH4 solution in THF
(15 mL, 15 mmol). After filtration, 31 (1.1 g, 75%) was obtained as
a yellow oil. 1H NMR (CDCl3) d: 6.81–6.73 (m, 3H), 3.88 (s, 3H),
3.85 (s, 3H), 2.78–2.64 (m, 4H), 2.62–2.54 (m, 2H), 2.44–2.38 (m,
2H), 2.30 (s, 3H), 1.55–1.37 (m, 6H).
7.1.10. 6,7-Dimethoxy-1,2,3,4-tetrahydroquinoline (26)
6,7-Dimethoxy-3,4-dihydroquinolin-2(1H)-one, was first pre-
pared by a literature procedure for a similar compound.26 To a
solution of 2527 (1.98 g, 7.0 mmol) in glacial acetic acid (40 mL)
at 80 °C was added iron powder (7.0 g, 125.3 mmol) and the result-
ing mixture was stirred manually at 80 °C for 30 min. After stirring,
the mixture was filtered through Celite and the filtrate was diluted
with water (150 mL). The diluted filtrate was extracted with CHCl3
(3 Â 150 mL) and evaporated to give 6,7-dimethoxy-3,4-dihydro-
quinolin-2(1H)-one as a pale yellow solid (1.11 g, 77%). 1H NMR
(CDCl3) d: 8.90 (s, 1H), 6.69 (s, 1H), 6.40 (s, 1H), 3.86 (s, 3H),
3.85 (s, 3H), 2.90 (t, J = 7.5 Hz, 2H), 2.62 (t, J = 7.5 Hz, 2H). A sample
of this material (0.58 g, 2.8 mmol) was treated with BH3ÁTHF
(20 mL, 1 M) following the procedure described for the preparation
of 17. After extraction, 26 (0.37 g, 68%) was obtained as a brown oil.
1H NMR (CDCl3) d: 6.51 (s, 1H), 6.09 (s, 1H), 3.78 (s, 3H), 3.77 (s,
3H), 3.26–3.22 (m, 2H), 2.68 (t, J = 6.5 Hz, 2H), 1.95–1.86 (m, 2H).
These spectral data are consistent with that reported by Toda
et al.28 for this compound prepared in a different manner.
7.2. General procedure for preparation of amides 3–9
To a stirred solution of amine (12, 15, 18, 21, 24, 27, 31) and
equimolar amount of Et3N in dry CH2Cl2, an equimolar amount of
acid chloride 3228,29 in dry CH2Cl2 was added dropwise. The mix-
ture was stirred at rt for overnight and then the solvent was re-
moved under reduced pressure.
7.2.1. 5-Bromo-N-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-2,3-
dimethoxybenzamide (3)
Compound 3 was prepared according to the general procedure
with 21 (136 mg, 0.55 mmol). After a short path column with
CHCl3/MeOH (10:1), 3 (147 mg, 59.8%) was obtained as a light yel-
low gum. 1H NMR (CDCl3) d: 8.09 (br t, 1H), 7.77 (d, J = 2.4 Hz, 1H),
7.09 (d, J = 2.4 Hz, 1H), 6.73 (s, 2H), 3.88 (s, 4H), 3.87 (s, 6H), 3.86 (s,
3H), 3.85 (s, 3H), 3.50 (dt, J = 6.3, 6.3 Hz, 2H), 2.76 (t, J = 6.6 Hz, 2H),
1.74–1.67 (m, 4H). 13C NMR (CDCl3) d: 163.84, 153.16, 148.24,

1858
K.-H. Fan et al. / Bioorg. Med. Chem. 19 (2011) 1852–1859
146.38, 131.46, 128.42, 125.15, 118.06, 116.96, 105.71, 61.29,
59.11, 56.20, 56.00, 55.66, 39.69, 27.36, 26.40. Anal. Calcd for
3.12 (t, J = 6.5 Hz, 2H), 2.86–2.84 (m, 2H), 2.71–2.69 (m, 2H),
1.73–1.61 (m, 6H), 1.57–1.55 (m, 2H). 13C NMR (CDCl3) d:
163.63, 153.18, 146.95, 146.41, 145.34, 143.34, 129.12, 128.06,
125.34, 118.20, 117.07, 113.72, 103.73, 61.21, 56.23, 56.14, 56.07,
54.61, 53.48, 39.59, 34.27, 30.44, 27.08, 26.28, 26.03. Anal. Calcd
for C25H33BrN2O5: C, 57.58; H, 6.38; N, 5.37. Found: C, 57.85; H,
6.52; N, 5.36.
C23H29BrN2O5: C, 55.59; H, 5.92; N, 5.68. Anal. Calcd for
C
23H29BrN2O5ÁH2O (corrected): C, 54.02; H, 6.11; N, 5.48. Found:
C, 54.32; H, 5.79; N, 5.48.
7.2.2. 5-Bromo-N-(4-(7,8-dimethoxy-4,5-dihydro-1H-benzo[d]-
azepin-3(2H)-yl)butyl)-2,3-dimethoxybenzamide (4)
Compound 4 was prepared according to the general procedure
with 12 (0.36 g, 1.3 mmol). The residue was applied to a short path
chromatography column and eluted with acetone to give 4 (0.30 g,
45%) as a pale yellow gum. The free base was converted into the
HCl salt and recrystallized from a mixture of ethanol and diethyl
ether. Mp 135–137 °C. 1H NMR of the free base (CDCl3) d: 7.93
(br t, 1H), 7.81 (d, J = 2.4 Hz, 1H), 7.13 (d, J = 2.4 Hz, 1H), 6.63 (s,
2H), 3.89 (s, 3H), 3.88 (s, 3H), 3.85 (s, 6H), 3.48 (dt, J = 6, 6 Hz,
2H), 2.85–2.81 (m, 4H), 2.63–2.60 (m, 4H), 2.51 (t, J = 6.6 Hz, 2H),
1.64–1.60 (m, 4H). 13C NMR of the free base (CDCl3) d: 163.71,
153.18, 146.60, 134.13, 128.23, 125.31, 118.19, 117.08, 112.81,
61.28, 58.51, 56.24, 55.91, 55.49, 39.62, 36.04, 27.55, 24.34. Anal.
Calcd for C25H33BrN2O5ÁHCl: C, 53.82; H, 6.14; N, 5.02. Anal. Calcd
for C25H33BrN2O5ÁHClÁ1.5 H2O (corrected): C, 51.33; H, 6.38; N,
4.79. Found: C, 51.40; H, 6.29; N, 4.83.
7.2.6. 5-Bromo-N-(4-(6,7-dimethoxy-3,4-dihydroquinolin-1(2H)-
yl)butyl)-2,3-dimethoxybenzamide (8)
Compound 8 was prepared according to the general procedure
with 27 (70 mg, 0.26 mmol). After a short path column with
CH2Cl2/ethyl acetate (1:1), 8 (66 mg, 62%) was obtained as a light
yellow gum. 1H NMR (CDCl3) d: 7.91 (br t, 1H), 7.82 (d, J = 2.5 Hz,
1H), 7.13 (d, J = 2.5 Hz, 1H), 6.54 (s, 1H), 6.22 (s, 1H), 3.88 (s, 3H),
3.83 (s, 3H), 3.81 (s, 3H), 3.78 (s, 3H), 3.51 (dt, J = 6.5, 6.5 Hz, 2H),
3.27–3.24 (m, 2H), 3.20–3.18 (m, 2H), 2.68 (t, J = 6.5 Hz, 2H),
1.95–1.90 (m, 2H), 1.71–1.64 (m, 4H). 13C NMR (CDCl3) d:
163.69, 153.18, 148.15, 146.44, 140.07, 139.85, 127.90, 125.34,
118.29, 117.10, 114.36, 114.16, 97.57, 61.23, 56.76, 56.24, 56.15,
51.84, 49.31, 39.54, 27.45, 27.38, 24.02, 22.39. Anal. Calcd for
C24H31BrN2O5: C, 56.81; H, 6.16; N, 5.52. Found: C, 56.88; H,
6.15; N, 5.53.
7.2.3. 5-Bromo-N-(4-(5,6-dimethoxyindolin-1-yl)butyl)-2,3-
dimethoxybenzamide (5)
7.2.7. 5-Bromo-N-(4-((3,4-dimethoxyphenethyl)(methyl)-
amino)butyl)-2,3-dimethoxybenzamide (9)
Compound 5 was prepared according to the general procedure
with 24 (133 mg, 0.53 mmol). After a short path column with
CHCl3/MeOH (55:1), 5 (128 mg, 49%) was obtained as a light
brown gum. 1H NMR (CDCl3) d: 7.93 (br t, 1H), 7.82 (d,
J = 2.4 Hz, 1H), 7.13 (d, J = 2.4 Hz, 1H), 6.74 (s, 1H), 6.18 (s, 1H),
3.91 (s, 3H), 3.86 (s, 3H), 3.84 (s, 3H), 3.80 (s, 3H), 3.52 (dt,
J = 6.3, 6.3 Hz, 2H), 3.27 (t, J = 8.1 Hz, 2H), 3.03 (t, J = 6.6 Hz, 2H),
2.88 (t, J = 8.1 Hz, 2H), 1.77–1.69 (m, 4H). 13C NMR (CDCl3) d:
163.73, 153.18, 148.94, 147.13, 146.44, 141.59, 127.98, 125.32,
120.54, 118.26, 117.09, 110.54, 94.08, 61.26, 57.12, 56.23, 56.16,
53.99, 50.18, 39.50, 28.40, 27.22, 25.11. Anal. Calcd for
Compound 9 was prepared according to the general procedure
with 31 (0.32 g, 1.2 mmol). After a short path column with
CH2Cl2/ethyl acetate (1:1), 9 (112 mg, 11%) was obtained as a yel-
low oil. The free base was converted into the oxalate salt and
recrystallized from a mixture of ethanol, ethyl acetate and diethyl
ether. Mp 115–117 °C. 1H NMR of the oxalate salt (CDCl3) d: 8.05 (t,
J = 6 Hz, 1H), 7.77 (d, J = 2.5 Hz, 1H), 7.14 (d, J = 2.5 Hz, 1H),
6.81–6.71 (m, 3H), 3.89 (s, 3H), 3.88 (s, 3H), 3.87 (s, 3H), 3.85 (s,
3H), 3.49 (dt, J = 6.5, 6.5 Hz, 2H), 3.24 (br s, 2H), 3.19 (br s, 2H),
3.00 (t, J = 8.5 Hz, 2H), 2.84 (s, 3H), 1.89–1.82 (m, 2H), 1.69 (tt,
J = 6.5, 6.5 Hz, 2H). 13C NMR of the oxalate salt (CDCl3) d: 164.25,
163.09, 153.26, 149.22, 148.19, 146.58, 128.10, 127.40, 125.13,
120.55, 118.55, 117.06, 111.71, 111.44, 61.33, 57.65, 56.27, 55.87,
55.84, 55.81, 40.09, 38.21, 30.02, 27.00, 20.93. Anal. Calcd for
C23H29BrN2O5: C, 55.99; H, 5.92; N, 5.68. Anal. Calcd for
C
23H29BrN2O5Á0.25H2O (corrected): C, 55.48; H, 5.97; N, 5.63.
Found: C, 55.42; H, 5.64; N, 5.58.
C
24H33BrN2O5ÁCOOH: C, 54.16; H, 6.18; N, 5.05. Anal. Calcd for
7.2.4. 5-Bromo-N-(4-(7,8-dimethoxy-4,5-dihydro-1H-benzo[c]-
azepin-2(3H)-yl)butyl)-2,3-dimethoxybenzamide (6)
C24H33BrN2O5ÁCOOHÁ1.5H2O (corrected): C, 51.64; H, 6.41; N,
4.82. Found: C, 51.72; H, 5.95; N, 4.55.
Compound 6 was prepared according to the general procedure
with 15 (306 mg, 1.1 mmol). After a short path column with
CHCl3/MeOH (10:1), 6 (480 mg, 92%) was obtained as a light yellow
gum. 1H NMR (CDCl3) d: 7.96 (br t, 1H), 7.78 (d, J = 2.4 Hz, 1H), 7.12
(d, J = 2.4 Hz, 1H), 6.67 (s, 1H), 6.66 (s, 1H), 3.88 (s, 6H), 3.86 (s, 6H),
3.84 (s, 2H), 3.45 (dt, J = 5.7, 5.7 Hz, 2H), 3.15–3.11 (m, 2H),
2.85–2.81 (m, 2H), 2.46 (t, J = 6.6 Hz, 2H), 1.75–1.72 (m, 2H),
1.63–1.61 (m, 4H). 13C NMR (CDCl3) d: 163.73, 153.19, 149.59,
146.53, 146.45, 134.99, 128.16, 125.25, 118.19, 117.01, 113.80,
112.80, 61.41, 58.97, 58.25, 56.35, 56.13, 55.99, 52.22, 39.65,
7.3. Receptor binding assays
Competition binding assays for ligands at r1 and r2 receptors
were performed using [3H](+)-PTZ ( 1), [3H]DTG/500 nM (+)-PTZ
r
(r2) and membranes from fresh-frozen, male English Hartley gui-
nea pig brains (Rockland Immunochemicals, Inc., Gilbertsville, PA)
as previously described.30 Experiments were performed in dupli-
cate, and repeated four times. Ki values were calculated from the
inhibition data using the Cheng–Prusoff equation,31 and a r1 Kd
of 2.3 nM for [3H](+)-PTZ and a r2 Kd of 23.9 nM for [3H]DTG.30
35.52, 27.43, 24.67, 24.53. Anal. Calcd for
C25H33BrN2O5: C,
57.58; H, 6.38; N, 5.37. Anal. Calcd for C25H33BrN2O5Á1.5H2O
(corrected): C, 54.75; H, 6.62; N, 5.11. Found: C, 54.84; H, 6.16;
N, 5.10.
7.4. Compound stability studies for in vitro binding assays
All analogs except 4 and 9 were dissolved in stock buffer (2.5%
AcOH, 1% EtOH in water) at the concentration of 10À3 M. The 2.5%
AcOH was used to increase solubility of the compounds in aqueous
solution. Because 4 and 9 were prepared as the HCl and oxalate
salt, respectively, they were dissolved in less concentrated acidic
stock buffer (0.1% AcOH, 1% EtOH in water) at the concentration
of 10À3 M. After 25 days in the stock buffer, each compound’s pur-
ity was analyzed by analytical HPLC.
7.2.5. 5-Bromo-N-(4-(7,8-dimethoxy-2,3,4,5-tetrahydro-1H-
benzo[b]azepin-1-yl)butyl)-2,3-dimethoxybenzamide (7)
Compound 7 was prepared according to the general procedure
with 18 (61 mg, 0.22 mmol). After a short path column with
CH2Cl2/ethyl acetate (2:1), 7 (81 mg, 81%) was obtained as a light
yellow gum. 1H NMR (CDCl3) d: 7.86 (br t, 1H), 7.81 (d, J = 2 Hz,
1H), 7.12 (d, J = 2.5 Hz, 1H), 6.65 (s, 1H), 6.54 (s, 1H), 3.88 (s, 3H),
3.84 (s, 3H), 3.83 (s, 3H), 3.82 (s, 3H), 3.47 (dt, J = 6.5, 6.5 Hz, 2H),

K.-H. Fan et al. / Bioorg. Med. Chem. 19 (2011) 1852–1859
1859
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We acknowledge a grant award from the National Institute on
Drug Abuse (DA028477, J.R.L., PI) for partial support of this
research. We also acknowledge grant awards from the National
Science Foundation (US) and the National Institutes of Health
(US) (NSF CHE-89-08304, CHE-95-31247, CHE-92-2183526 and
NIH 1S10RR11962-01) which supported the purchase of the NMR
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Supplementary data (1H NMR spectra of intermediates, as well
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in the supplementary data. In addition, HPLC chromatograms of
compounds 3, 4, 6, 7 and 9 in stock buffer after 25 days can be
found. HPLC chromatograms and 1H NMR spectra that monitor
the decomposition of compounds 5 and 8 as a function of time
are included, along with LC/MS analyses of the decomposition
products) associated with this article can be found, in the online
version, at doi:10.1016/j.bmc.2011.02.006.
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