Exploring the active site of phenylethanolamine N-methyltransferase: 3-alkyl-7-substituted-1,2,3,4-tetrahydroisoquinoline inhibitors

Article abstract of DOI:10.1016/j.bmc.2004.11.015

A series of 3-alkyl-7-substituted-1,2,3,4-tetrahydroisoquinolines was synthesized and these compounds were evaluated for their PNMT inhibitory potency and affinity for the α₂-adrenoceptor. 7-Nitro-, 7-bromo-, 7-aminosulfonyl-, or 7-N-2,2,2-trif

Full text of DOI:10.1016/j.bmc.2004.11.015

Bioorganic & Medicinal Chemistry 13 (2005) 1261–1273
Exploring the active site of phenylethanolamine
N-methyltransferase: 3-alkyl-7-substituted-
1,2,3,4-tetrahydroisoquinoline inhibitorsq
Gary L. Grunewald,* F. Anthony Romero, Alex D. Chieu, Kelcie J. Fincham,
Seema R. Bhat and Kevin R. Criscione
Department of Medicinal Chemistry, School of Pharmacy, Malott Hall, Room 4060, University of Kansas,
1251 Wescoe Hall Dr., Lawrence, KS 66045-7582, USA
Received 31 August 2004; revised 8 November 2004; accepted 8 November 2004
Available online 2 December 2004
Abstract—A series of 3-alkyl-7-substituted-1,2,3,4-tetrahydroisoquinolines was synthesized and these compounds were evaluated for
their PNMT inhibitory potency and affinity for the a2-adrenoceptor. 7-Nitro-, 7-bromo-, 7-aminosulfonyl-, or 7-N-2,2,2-tri-
fluoroethylaminosulfonyl-THIQs that possess a 3-alkyl substituent that is longer than a methyl group showed decreased
PNMT inhibitory potency, except for 3-propyl-7-aminosulfonyl-THIQ, which displayed excellent PNMT inhibitory potency.
The rank order for selectivity (PNMT vs the a2-adrenoceptor) is3-alkyl-7-aminouslfonyl-THIQs
fluoroethylaminosulfonyl-THIQs > 3-alkyl-7-nitro-THIQs > 3-alkyl-7-bromo-THIQs.
ꢀ 2004 Elsevier Ltd. All rights reserved.
ffi 3-alkyl-7-N-2,2,2-tri-
1. Introduction
OH
OH
HO
HO
NH2
HO
NHCH3
PNMT
Central nervous system (CNS) epinephrine (Epi) has
been implicated in the regulation of blood pressure,2 res-
piration,3,4 body temperature,3,4 the a1-adrenoceptor,5
HO
Epi (2)
NE (1)
and the a2-adrenoceptor,6,7 aswell asin osme of the
AdoMet (3)
AdoHcy (4)
8,9
neurodegeneration seen in Alzheimerꢀsdiesaes.
In
order to elucidate the role of CNS Epi (2) we have directed
our studies toward the development of an inhibitor of
Epi (2) biosynthesis. More specifically, we have targeted
phenylethanolamine N-methyltransferase10 (PNMT: EC
2.1.1.28), the enzyme that catalyzesthe terminal step in
Epi (2) biosynthesis in which an activated methyl group
istranfserred from S-adenosyl-L-methionine (3) to the
primary amine of norepinephrine (1) to form Epi (2)
and the cofactor product S-adenosyl-L-homocysteine
(AdoHcy; 4) (Fig. 1).
Figure 1. The terminal step in Epi (2) biosynthesis.
Some inhibitorsare too polar to penetrate the blood–
brain barrier (BBB), while othersexhibit affinity toward
other biologically relevant sites, most notably the a2-
adrenoceptor. Studies using a BBB model on a small
set of tetrahydroisoquinoline-type (THIQ-type) PNMT
inhibitorsindicate that a calculated log P (ClogP) value
of 0.5 or greater appearsto be required in order to ob-
serve significant BBB penetration.11–13 We have under-
taken a research program that is aimed at developing
a PNMT inhibitor that ispotent, eslective (PNMT
inhibitory potency vsthe a2-adrenoceptor affinity), and
capable of penetrating the BBB.
Problems associated with early PNMT inhibitors limit
their usefulness as pharmacological tools in the CNS.
Keywords: Phenylethanolamine N-methyltransferase; Enzyme inhibi-
tors; Tetrahydroisoquinolines; Structure-based design.
q See Ref. 1.
Many PNMT inhibitorscontain a THIQ nucleu.s We
have shown that disubstitution on the THIQ nucleus
at the 3- and 7-positions can result in dramatic increases
*
Corresponding author. Tel.: +1 785 864 4497; fax: +1 785 864
5326; e-mail: ggrunewald@ku.edu
0968-0896/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2004.11.015

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G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
Table 1. In vitro activitiesof some ( )-THIQ-type PNMT inhibitors
R
3
NH
R
7
Compd
R3
R7
PNMTa Ki (lM) SEM
Selectivity (a2/PNMT)
ClogPc
b
a2 Ki (lM) SEM
5d
CH3
CH2F
H
H
1.4 0.1
0.82 0.04
0.12 0.01
0.056 0.003
0.28 0.02
0.072 0.005
0.023 0.003
0.15 0.01
0.15 0.01
0.13 0.02
0.76 0.08
3.8 0.1
0.54
4.6
2.11
1.84
1.34
2.46
À0.29
1.86
2.70
1.58
0.00
1.41
6e
H
NO2
7f
0.23 0.13
4.3 0.3
100 10
1.9
8f
H
Br
77
360
9g
H
SO2NH2
NO2
Br
10h
11e
12e
13e
14i
CH3
CH2F
CH2F
CH2F
CH2F
31
6.4 0.2
76
1
430
280
NO2
SO2NH2
SO2NHCH2CF3
6
510
680 10
1200 100
4500
9200
a Reported in thistable for human recombinant PNMT.
b In vitro activitiesreported for the inhibition of binding of [ 3H]clonidine at the a2-adrenoceptor.
c Calculated logP.
d Ref. 15.
e Ref. 11.
f Ref. 16.
g Ref. 32.
h Ref. 14.
i Ref. 20.
in selectivity for PNMT versus the a2-adrenoceptor.14
The selectivity of 10,14 for example, ismuch greater than
that for mono-substituted 515 or 716 (Table 1). Quantita-
tive structure–activity relationship16 and comparative
molecular field analysis17 (CoMFA) studies on a series
of PNMT inhibitorspredicted that THIQscould bind
in the active site in one of two different orientations,
depending on the hydrophobic nature of the 7-substitu-
ent. Recently, we have published the crystal structure of
human PNMT (hPNMT) cocrystallized with AdoHcy
(4) and inhibitorscontaining either a lipophilic (7-
iodo-THIQ 15)18 or hydrophilic (SK&F 29661 9)19 7-
substituent. These crystal structures have shown that
our proposed CoMFA-derived hypothesis regarding a
change in the binding orientation of the inhibitorsin
the active site of PNMT was inaccurate, and that a con-
formational change in the enzyme active site occurs to
accommodate the two classes (hydrophilic vs lipophilic
aromatic substituents) of inhibitors.
Figure 2. This is a Connolly (solvent accessible) surface of the active
site exposing SK&F 29661 (9) and AdoHcy (4). A lipophilic potential
ismapped on the Connolly usrface of hPNMT whereby green is
neutral, blue ishydrophilic and brown islipophilic. Posible hydrogen
bondsare indicated by yellow lines. Carbon iswhite, nitrogen isblue,
oxygen is red and sulfur is yellow. Hydrogens are not shown for
clarity.
O
S
O
NH
NH
I
H2N
9
15
It was of interest to synthesize and evaluate 3-alkyl-7-
substituted-THIQs for two reasons. First, examination
of the hPNMT active site region surrounding the 3-po-
sition of the cocrystallized ligands revealed that the
channel between the AdoHcy (4) binding site and the
inhibitor binding site contains lipophilic amino acids
(Fig. 2). Docking studies indicated that 3-alkyl substitu-
entson 7-substituted-THIQsthat extend into thislipo-
philic channel may bind favorably, thusincreainsg
PNMT inhibitory potency (Figs. 3–5). Second, our pre-
viously reported a2-adrenoceptor CoMFA model on a
set of THIQs showed that there was steric bulk intoler-
ance around the 3-position of THIQ,17 and thus3-sub-
stituents longer than a methyl group should be
disfavored at the a2-adrenoceptor and a highly selective
PNMT inhibitor should result. Initially, we wished to
explore the 3-alkyl substituent on THIQs that possessed
either a hydrophilic or hydrophobic 7-substituent. 7-Ni-
tro- (7) and 7-bromo-THIQ (8) were chosen as templates
because they display excellent PNMT inhibitory
potency, but lack selectivity. We were also encouraged
by a previousobesrvation in which the addition of a
3-methyl substituent to 7 (10, 3-CH3, 7-NO2), led to

G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
1263
Figure 5. Thisfigure shows 27c docked into the active site of hPNMT
(from the hPNMT X-ray structure cocrystallized with AdoHcy 4 and
SK&F 29661 9)19 and the amino acid residues that could interact with
27c (see text). A Connolly surface mapped with a lipophilic potential
exposing 27c is also shown. Yellow lines indicate possible hydrogen
bonds. Carbon iswhite, nitrogen isblue, oxygen isred and sulfur is
yellow. Hydrogensare not shown for clarity.
Figure 3. Thisfigure shows 22b docked into the active site of hPNMT
(from the hPNMT X-ray structure cocrystallized with AdoHcy 4 and
7-iodo-THIQ 16)18 and the amino acid residues that could interact
with 22b. Although docking studies indicate that a 3-ethyl substituent
should bind favorably, the biochemical data indicated otherwise (see
text). A Connolly surface mapped with a lipophilic potential exposing
22b is also shown. Yellow lines indicate possible hydrogen bonds.
Carbon iswhite, nitrogen isblue and bromine isgreen. Hydrogensare
not shown for clarity.
nitrogen of 6.20 Therefore, it was also of interest to
determine if a 7-aminosulfonyl or a 7-N-2,2,2-tri-
fluoroethylaminosulfonyl moiety on 3-alkyl-THIQs also
result in increased selectivity compared to their 7-nitro
and 7-bromo analogues.
2. Chemistry
The synthesis of ( )-3-alkyl-7-bromo- (22a–f) and ( )-3-
alkyl-7-nitro-THIQs( 23b–f) ishsown in
Scheme 1.
Compounds 19a21 and 19b15 were prepared asreported
previously. The appropriate alkyl nitriles (16c–f) were
treated with benzyl magnesium chloride and the imine
salts were reduced in situ with lithium aluminum hy-
dride to form the corresponding phenethylamines
(17c–f).22 Treatment of amines 17c–f with K2CO3 and
methylchloroformate yielded carbamates 18c–f. Lac-
tams 19c–f were produced by the addition of carbamates
18c–f to polyphosphoric acid. Compounds 19a–f were
nitrated in the presence of sulfuric acid and potassium
nitrate to produce the 7-nitro-substituted-lactams
(20a–f). Compounds 20b–f were reduced with BH3ÆTHF
to yield the 3-alkyl-7-nitro-THIQs( 23b–f). The nitro
moietiesof 20a–f were transformed to bromo function-
alitiesby reduction of 20a–f to the aniline followed by
a Sandmeyer reaction to produce 21a–f. Subsequent
reduction of 21a–f yielded the corresponding 3-alkyl-7-
bromo-THIQs( 22a–f).
Figure 4. Thisfigure shows 23c docked into the active site of hPNMT
(from the hPNMT X-ray structure cocrystallized with AdoHcy 4 and
SK&F 29661 9)19 and the amino acid residues that could interact with
23c. Although docking studies indicate that a 3-ethyl substituent
should bind favorably, the biochemical data indicated otherwise (see
text). A Connolly surface mapped with a lipophilic potential exposing
23c is also shown. Yellow lines indicate possible hydrogen bonds.
Carbon iswhite, nitrogen isblue and oxygen isred. Hydrogensare not
shown for clarity.
The synthesis of ( )-3-alkyl-7-aminosulfonyl-THIQs
(27a–c) and 3-alkyl-7-N-(2,2,2-trifluoroethylaminosulfon-
yl)-THIQs( 28a–c) isshown in Scheme 2. Lactams 19a–c
were treated with chlorosulfonic acid to yield sulfonyl
chlorides 24a–c. Compounds 24a–c were dissolved in
acetonitrile and treated with ammonium hydroxide to
afford sulfonamides 25a–c. Compounds 26a–c were pro-
duced by treatment of 24a–c with 2,2,2-trifluoroethyl-
amine and pyridine in a biphasic mixture of EtOAc
and sodium carbonate. Reduction of 25a–c and 26a–c
with BH3ÆTHF afforded THIQs 27a–c and 28a–c.
an inhibitor with better PNMT inhibitory potency and
selectivity.
A previous study showed that the addition of a 7-amino-
sulfonyl substituent (13) to 3-fluoromethyl-THIQ (6)
increased selectivity for PNMT versus the a2-adrenocep-
tor compared to a 7-nitro (7) or 7-bromo (8) substituent
(e.g., 11 vs 13; Table 1).11 It was also observed that selec-
tivity could be further increased with the addition of a
2,2,2-trifluoroethyl (14) substituent to the sulfonamide

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G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
N
C
R
R
R
a, b
c
d
NHCO2Me
NH
NH2
R
16c–f
17c–f
18c–f
19c–f
O
R
R
R
e
g, h, i
f
19a–f
20b–f
NH
NH
NH
O2N
Br
Br
O
O
22a–f
20a–f
21a–f
a R = CH3
d R = CH(CH3)2
e R = CH2CH2CH2CH3
R
f
b R = CH2CH3
c R = CH2CH2CH3 f R = CH2CH2CH2CH2CH3
NH
O2N
23b–f
Scheme 1. Reagents: (a) BnMgCl, ether; (b) LiAlH4, THF; (c) K2CO3, ClCO2Me, THF; (d) PPA; (e) H2SO4, KNO3; (f) 1M BH3ÆTHF; (g) PtO2, H2;
(h) HBr, NaNO2; (i) CuBr, HBr.
R
R
the ligand to define a-adrenergic binding affinity to sim-
plify the comparison with previous results.
a
NH
NH
ClO2S
b
O
O
19a–c
24a–c
c
4. Results and discussion
R
R
Compounds 10, 22a–f, and 23b–f were prepared and
evaluated, and their biochemical results are shown in
Table 2. Three trendsare noted from the biochemical
data. First, similar trends in PNMT inhibitory potencies
are observed for both 3-alkyl-7-nitro- and -7-bromo-
THIQs( 10, 22a–f, and 23b–f). Second, 3-alkyl substitu-
entson 7-nitro- and 7-bromo-THIQsthat are longer
than a methyl substituent result in a significant decrease
in PNMT inhibitory potency. Third, 3-alkyl-7-nitro-
THIQs( 10, 23b–f) show less affinity for the a2-adreno-
ceptor ascompared to their 7-bromo analogues( 22a–
f), and therefore are more selective. This is consistent
with a previous QSAR study on 7-substituted-THIQs
whereby THIQs with hydrophilic 7-substituents show
less affinity for the a2-adrenoceptor than THIQswith
hydrophobic 7-substituents.16 The extension of the 3-
methyl substituent in both 3-alkyl-7-nitro- and -7-bro-
mo-THIQs did not lead to an increase in selectivity in
part because moderate a2-adrenoceptor affinity wasalso
observed.
O
S
O
O
NH
NH
S
N
H2N
F3C
O
O
O
H
25a–c
26a–c
d
d
R
R
O
S
O
O
S
O
NH
NH
H2N
F3C
N
H
27a–c
28a–c
a R = CH3
b R = CH2CH3
c R = CH2CH2CH3
Scheme 2. Reagents: (a) ClSO3H; (b) ammonium hydroxide, MeCN;
(c) 2,2,2-trifluoroethylamine, pyridine, EtOAc/satd Na2CO3; (d) 1M
BH3ÆTHF.
3. Biochemistry
Docking studies (AutoDock 3.0)27 were performed to
aid in the interpretation of the PNMT biochemical data
of these inhibitors. The docking of inhibitors into the
PNMT active site was performed on the S-enantiomer
since a previous study on 3-methyl-7-nitro-THIQ (10)
indicated that the S-enantiomer ispreferred over the
R-enantiomer in the hPNMT active site.28 The docking
studies on inhibitors that contain a 7-NO2, 7-SO2NH2,
and 7-SO2NHCH2CF3 substituent used the crystal
structure of PNMT cocrystallized with SK&F 29661
(9),19 whereas studies on inhibitors that possess a 7-Br
substituent used the crystal structure of PNMT cocrys-
tallized with 7-iodo-THIQ (15).18 Residues Lys57 and
Met258 move within the PNMT active site depending
on the hydrophobicity of the 7-substitutent.18 The ami-
In the current study, hPNMT with a C-teminal hexahis-
tidine tag wasexpresed in E. coli.20,23 The radiochemi-
cal assay conditions, previously reported for the bovine
enzyme,24 were modified to account for the high binding
affinity of some inhibitors.20,25 Inhibition constants were
determined using four concentrations of phenylethanol-
amine as the variable substrate, and three concentra-
tionsof inhibitor.
a2-Adrenergic receptor binding assays were performed
using cortex obtained from male Sprague–Dawley
rats.26 [3H]Clonidine wasused asthe radioligand to de-
fine the specific binding and phentolamine was used to
define the nonspecific binding. Clonidine was used as

G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
Table 2. In vitro activitiesof ( )-3-alkyl-7-nitro- and -7-bromo-THIQs
1265
R
3
NH
R
7
Compd
R3
R7
PNMT Ki (lM) SEM
Selectivity (a2/PNMT)
ClogPb
a
a2 Ki (lM) SEM
10c
23b
23c
23d
23e
23f
22a
22b
22c
22d
22e
22f
CH3
NO2
NO2
NO2
NO2
NO2
NO2
Br
0.072 0.005
0.49 0.03
0.53 0.02
4.6 0.3
31
1
430
57
1.86
2.39
2.91
2.79
3.44
3.97
2.98
3.51
4.03
3.90
4.56
5.09
CH2CH3
(CH2)2CH3
CH(CH3)2
(CH2)3CH3
(CH2)4CH3
CH3
28 0.3
6.8 0.2
13
36
3
7.8
1.2
0.44
65
6.6 0.4
9.8 0.3
8.0 0.7
4.3 0.2
1.1 0.1
1.2 0.1
1.1 0.1
3.9 0.3
0.93 0.09
2.2 0.2
0.017 0.005
0.48 0.02
0.48 0.02
4.4 0.3
CH2CH3
(CH2)2CH3
CH(CH3)2
(CH2)3CH3
(CH2)4CH3
Br
Br
2.5
2.3
0.89
0.12
0.20
Br
Br
7.6 0.2
11
Br
1
a In vitro activitiesreported for the inhibition of binding of [ 3H]clonidine at the a2-adrenoceptor.
b Calculated logP.
c Ref. 14.
no acid residues surrounding the 3-position of the
cocrystallized ligands SK&F 29661 (9) and 7-iodo-
THIQ (15) remain in similar positions for both crystal
structures.
Generally, a comparison of 27a–c and 28a–c with their
7-nitro (23c) and 7-bromo (22c) analogueshsowed a
similar trend, whereby lengthening the 3-alkyl chain also
results in a loss of PNMT inhibitory potency. 3-Methyl
analogues 27a (7-SO2NH2) and 28a (7-SO2NHCH2CF3)
display excellent PNMT inhibitory potency and moder-
ate selectivity. Surprisingly, 27c (3-Pr, 7-SO2NH2) dis-
played a 5-fold improvement in PNMT inhibitory
potency compared to its7-nitro and 7-bromo analogues.
Docking of 27c into the PNMT active site reveals that
this inhibitor could bind favorably, which is consistent
with itsPNMT Ki (Fig. 5). While docking studies show
that compounds 22c (3-Pr, 7-Br) and 23c (3-Pr, 7-NO2,
Fig. 4) should bind similarly to 27c, both compounds
show a loss in PNMT inhibitory potency.
Several observations are made from the docking studies
of 3-alkyl-7-nitro- and -7-bromo-THIQsin the PNMT
active site: (1) a 3-methyl, 3-ethyl, or 3-propyl substitu-
ent appearsto make a hydrophobic contact with Tyr222
(Fig. 3 shows a 3-ethyl), (2) a 3-propyl substituent ap-
pearsto make an additional hydrophobic contact with
Tyr35 (Fig. 4), (3) THIQs that possess larger 3-alkyl
substituents, such as an isopropyl, butyl, or pentyl sub-
stituent, do not fit within the PNMT active site (based
on docking studies), which is consistent with their signif-
icant loss in PNMT inhibitory potency, (4) the 7-nitro
moiety of 3-alkyl-THIQsappearsto mimic the us lfon-
amide moiety of SK&F 29661 (9) and may form a
hydrogen bond to Lys57 (Fig. 4), and (5) the 7-bromo
substituent of 3-alkyl-THIQs appears to mimic the iodo
group of 7-iodo-THIQ (2) and appearsto make hydro-
phobic contactswith Met258 and Val53 ( Fig. 3). We
have previously reported studies on the binding of a
3-fluoromethyl substituent20 and it appearsto make a
similar hydrophobic contact as the 3-methyl or 3-ethyl
substituent. It is not clear from the modeling why
the 3-ethyl-(25b, 24b) or 3-propyl-(25c, 24c)-7-nitro-
and -7-bromo-THIQsare equipotent at PNMT nor
why they are less potent than their methyl analogues.
An interesting and currently inexplicable trend in
PNMT inhibitory potency isobesrved for 27a–c. It is
not readily apparent from modeling why a dramatic de-
crease in PNMT inhibitory potency is observed for 27b
(3-Et, 7-SO2NH2) nor why 27c (3-Pr, 7-SO2NH2) isable
to regain PNMT inhibitory potency. An X-ray crystal
structure of PNMT cocrystallized with 27c may be re-
quired to explain thisanomalousresult.
Both 28a (3-CH3, 7-SO2NHCH2CF3) and 28b (3-Et, 7-
SO2NHCH2CF3) are more potent at PNMT than their
7-unsubstituted-sulfonamide analogues (27a, 27b). It
wasexpected that the addition of a 2,2,2-trifluoroethyl
substituent to 27c (3-Pr, 7-SO2NH2) would also result
in increased PNMT inhibitory potency; however, a
dramatic decrease in PNMT inhibitory potency was
observed for 28c (3-Pr, 7-SO2NHCH2CF3). Figure 6
shows the docking of 28a and it appearsthat the
2,2,2-trifluoroethyl substituent binds in an auxiliary
pocket, with possible hydrophobic contacts made be-
tween the sulfonamide substituent, and Val53 and
Arg44. These interactions are similar to those previously
reported for the binding of 14 (3-CH2F, 7-
SO2NHCH2CF3).20 Although it isnot clear from model-
ing, the biochemical data suggest that the PNMT active
It was observed in previous studies that a 7-aminosulfon-
yl11 or a 7-N-2,2,2-trifluoroethylaminosulfonyl20 substi-
tuent on 3-fluoromethyl-THIQ (6) increased selectivity
for PNMT versus the a2-adrenoceptor compared to a
7-nitro (11) or 7-bromo (12) substituent. Since a 3-
methyl, 3-ethyl, or 3-propyl substituent on 7-nitro and
7-bromo-THIQs( Table 2) resulted in compounds that
retained submicromolar PNMT inhibitory potency, it
was of interest to explore the effect of a 7-sulfonamide
substituent on these 3-alkyl-THIQs. The biochemical re-
sults for 27a–c and 28a–c are shown in Table 3.

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G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
Table 3. In vitro activitiesof ( )-3-alkyl-7-aminosulfonyl-and -7- N-(2,2,2-trifluoroethylaminosulfonyl)-THIQs
R1
O
NH
S
R2HN
O
Compd
R1
R2
PNMT Ki (lM) SEM
Selectivity (a2/PNMT)
ClogPb
a
a2 Ki (lM) SEM
27a
27b
27c
28a
28b
28c
CH3
H
0.077 0.003
1.8 0.1
61 9
120 20
790
67
0.28
0.81
1.33
1.69
2.21
2.74
CH2CH3
(CH2)2CH3
CH3
H
H
0.12 0.01
0.034 0.003
0.51 0.02
0.92 0.06
37
23
20
14
5
4
3
2
310
680
39
CH2CF3
CH2CF3
CH2CF3
CH2CH3
(CH2)2CH3
15
a In vitro activitiesreported for the inhibition of binding of [ 3H]clonidine at the a2-adrenoceptor.
b Calculated logP.
7-nitro-THIQs( 10, 23b–f) > 3-alkyl-7-bromo-THIQs
(22a–f). It waspredicted that 3-alkyl-7-( N-2,2,2-tri-
fluoroethylaminosulfonyl)-THIQs
(28a–c)
would
display the highest selectivity, but it was observed
that these inhibitors were no more selective than their
7-unsubstituted-sulfonamide
analogues
(27a–c).
3-Methyl-7-(N-2,2,2-trifluoroethylaminosulfonyl)-THIQ
(28a) isone of the mots potent PNMT inhibitorsthat
displays good selectivity.
5. Experimental
Figure 6. Thisfigure shows 28a docked into the active site of hPNMT
(from the hPNMT X-ray structure cocrystallized with AdoHcy 4 and
SK&F 29661 9)19 and the amino acid residues that could interact with
28a. A Connolly surface mapped with a lipophilic potential exposing
28a is also shown. Yellow lines indicate possible hydrogen bonds.
Carbon iswhite, nitrogen isblue, oxygen isred, fluorine isgreen and
sulfur is yellow. Hydrogens are not shown for clarity.
All of the reagents and solvents used were reagent grade
or were purified by standard methods before use. Melt-
ing pointswere determined in open capillary tubeson a
Thomas-Hoover melting point apparatus calibrated
with known compoundsbut are otherwise uncorrected.
All proton (1H NMR) and carbon (13C NMR) nuclear
magnetic resonance spectra were taken on a Bruker
DRX-400 or a Bruker AM-500 spectrometer. High res-
olution mass spectra (HRMS) were obtained on a VG
Analytical ZAB. Elemental analyses were performed
by Quantitative Technologies, Inc. (Whitehouse, New
Jersey). Flash chromatography was performed using sil-
ica gel 60 (230–400 mesh) supplied by Universal Adsor-
bents, Atlanta, Georgia. Anhydrous tetrahydrofuran
(THF) and diethyl ether (Et2O) were distilled from so-
dium-benzophenone ketyl. Hexanesrefersto the mix-
ture of hexane isomers (bp 40–70ꢁC). All reactions
that required anhydrousconditionswere performed un-
der argon, and all glassware was either oven-dried or
flame-dried before use. AdoMet was obtained from Sig-
ma–Aldrich (St. Louis, MO). [methyl-3H]AdoMet and
[3H]clonidine were obtained from PerkinElmer (Boston,
MA).
site cannot simultaneously accommodate both the
favorable binding of the 3-propyl substituent and the
7-N-2,2,2-trifuoroethylaminosulfonyl substituent of
28c. As predicted, better selectivity is observed for
27a–c and 28a–c compared to their 7-nitro or 7-bromo
analogues. However, an increase in selectivity was not
observed for 28a–c compared to 27a–c, which isa differ-
ent trend that we had previously observed for the addi-
tion of
a
2,2,2-trifluroethyl substituent to the
sulfonamide nitrogen of 13 (3-CH2F, 7-SO2NH2).20
In summary, 3-methyl-THIQs that possess a 7-nitro
(10), 7-bromo (22a), 7-aminosulfonyl (27a), or a 7-N-
2,2,2-trifluoroethylaminosulfonyl (28a) substituent dis-
play excellent PNMT inhibitory potency. 7-Nitro and
7-bromo-THIQs that possess a 3-alkyl substituent that
islonger than a methyl group ( 23b–f, 22b–f) showed de-
creased PNMT inhibitory potency. The same general
trend is also observed for 7-aminosulfonyl- and 7-(N-
2,2,2-trifluoroethylaminosulfonyl)-THIQs (27a,b, 28a–
c), with the exception of 3-propyl-7-aminosulfonyl
(27c), which displayed excellent PNMT inhibitory
potency. Aspredicted, the rank order for eslectivity
(PNMT inhibitory potency vsthe a2-adrenoceptor affin-
ity) is3-alkyl-7-aminosulfonyl-THIQs( 27a–c) > 3-alkyl-
5.1. Radiochemical assay of PNMT inhibitors
The assay used in this study has been modified from that
described previously.24 A typical assay mixture consisted
of 25lL of 0.5M phosphate buffer (pH8.0), 25lL of
50lM unlabeled AdoMet, 5lL of [methyl-3H]AdoMet,
containing approximately 3 · 105 dpm (specific activity
approximately 15Ci/mmol), 25lL of substrate solution
(phenylethanolamine), 25lL of inhibitor solution,

G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
1267
25lL of enzyme preparation (containing 30ng hPNMT
and 25lg of bovine serum albumin), and sufficient water
to achieve a final volume of 250lL. After incubation for
30min at 37ꢁC, the reaction mixture wasquenched by
addition of 250lL of 0.5M borate buffer (pH10.0)
and wasextracted with 2mL of toluene/isoamyl alcohol
(7:3). A 1mL portion of the organic layer wasremoved,
transferred to a scintillation vial and diluted with cock-
tail for counting. The mode of inhibition wasacser-
tained to be competitive in all cases reported in Tables
1–3 by examination of the correlation coefficients( r2)
for the fit routinesascalculated in the Enzyme Kinetics
module (version 1.1) in SigmaPlot (version 7.0).29 While
all Ki valuesreported were calculated using competitive
kinetics, it should be noted that there was not always a
great difference between the r2 valuesfor the competitive
model versus the noncompetitive model. All assays were
run in duplicate with three inhibitor concentrationsover
a 5-fold range. Ki valueswere determined by a hyper-
bolic fit of the data using the Single Substrate–Single
Inhibitor routine in the Enzyme Kineticsmodule (ver-
sion 1.1) in SigmaPlot (version 7.0). For inhibitors with
apparent IC50 valueslesthan 0.1 lM (asdetermined by
a preliminary screen of the compounds to be assayed),
the Enzyme KineticsTight Binding Inhibition routine
wasused to calculate the Ki values.
default settings for AutoDock were used. The docking
of inhibitorsthat contain a 7-NO , 7-SO2NH2, or 7-
2
SO2NHCH2CF3 substituent used the crystal structure
of PNMT cocrystallized with SK&F 29661 (9), whereas
inhibitors that contain a 7-Br substituent used the crys-
tal structure of PNMT cocrystallized with 7-iodo-THIQ
(15). The inhibitor to be docked wasinitially overlayed
with either cocrystallized ligand 9 or 15, and minimized
with the Triposforce field.
5.4. General procedure for 18c–d (selected procedure
for 18c)
Butyronitrile (16c, 6.29mL, 72.3mmol) wasdiluted with
20mL of ether and added dropwise to a 1M benzyl mag-
nesium chloride solution in ether (86.8mL, 86.8mmol)
under an argon atmosphere. The mixture was heated
to reflux for 2.5h, THF (30mL) wasadded to the reac-
tion flask, and the mixture was cooled to 0ꢁC. Lithium
aluminum hydride (3.29g, 86.7mmol) wasadded cau-
tiously and the solution was heated to reflux overnight.
The reaction was quenched using the Fieser and Fieser
method.31 For ng of LAH, nmL of H2O, nmL of 15%
NaOH, and 3nmL of H2O were added consecutively
to the solution and the mixture was stirred for 0.5h.
The solution was filtered through a Celite pad and con-
centrated in vacuo to yield the crude amine 17c22 (8.13g,
49.9mmol). The amine was dissolved in THF (50mL)
and K2CO3 wasadded. The oslution wascooled to
0ꢁC and methylchloroformate (4.62mL, 59.8mmol)
was added slowly by syringe. The reaction was stirred
under argon for 5h. Upon completion, the solution
wasfiltered through a Celite pad and concentrated in
vacuo to yield the crude carbamate.
5.2. a2-Adrenoceptor radioligand binding assay
The radioligand receptor binding assay was performed
according to the method of UꢀPrichard et al.26 Male
Sprague–Dawley ratswere decapitated, and the cortexes
were dissected out and homogenized in 20vol (w/v) of
ice-cold 50mM Tris/HCl buffer (pH7.7 at 25ꢁC).
Homogenateswere centrifuged thrice for 10min at
50,000g with resuspension of the pellet in fresh buffer be-
tween spins. The final pellet was homogenized in 200vol
(w/v) of ice-cold 50mM Tris/HCl buffer (pH7.7 at
5.4.1. ( )-N-(Methoxycarbonyl)-1-phenyl-2-aminopent-
ane (18c). The crude carbamate (18c) waspurified by
Kuge1rohr distillation (0.62mmHg, 92ꢁC) to yield a
clear oil that solidified on standing (4.63g, 29%): mp
3
25ꢁC). Incubation tubescontaining [ H]clonidine (spe-
1
cific activity approximately 55Ci/mmol, final concentra-
tion 2.0nM), variousconcentrationsof drugsand an
aliquot of freshly resuspended tissue (800lL) in a final
volume of 1mL were used. Tubes were incubated at
25ꢁC for 30min and the incubation wasterminated by
rapid filtration under vacuum through GF/B glass fiber
filters. The filters were rinsed with three 5mL washes of
ice-cold 50mM Trisbuffer (pH7.7 at 25 ꢁC). The filters
were counted in vialscontaining premixed csintillation
cocktail. Nonspecific binding was defined as the concen-
tration of bound ligand in the presence of 2lM of phen-
tolamine. All assays were run in quadruplicate with five
53–54ꢁC; H NMR (400MHz, CDCl3) d 7.32–7.29 (m,
2H), 7.25–7.19 (m, 3H), 4.73 (br ex s, 1H, NH), 3.91
(m, 1H), 3.63 (s, 3H), 2.89–2.75 (m, 2H), 1.51–1.31 (m,
4H), 0.91 (t, J = 6.7Hz, 3H); HRMS (FAB+) m/z calcd
for C13H20NO2 (MH+) 222.1494 obsd 222.1483.
5.4.2.
aminobutane (18d). Isobutyronitrile (6.30mL, 72.3
mmol) wasuesd to form 17d. The crude carbamate
( )-N-(Methoxycarbonyl)-3-methyl-1-phenyl-2-
waspurified by Kugelrohr dtisillation (0.62mmHg,
92ꢁC) to yield 18d asa white oslid (5.78g, 36%): mp
1
63–64ꢁC; H NMR (400MHz, CDCl3) d 7.36–7.20 (m,
inhibitor concentrationsover a 16-fold range. IC
5H), 4.50 (br ex s, 1H, NH), 3.82 (m, 1H), 3.62 (s,
3H), 2.85–2.68 (m, 2H), 1.81–1.76 (m, 1H), 1.00–0.94
(m, 6H); HRMS (FAB+) m/z calcd for C13H20NO2
(MH+) 222.1494 obsd 222.1494.
50
valueswere determined by a log-probit analyissof the
data and Ki valueswere determined by the equation
Ki = IC50/(1 + [Clonidine]/KD), asall Hill coefficients
were approximately equal to 1.
5.4.3. ( )-N-(Methoxycarbonyl)-1-phenyl-2-aminohexane
(18e). Valeronitrile (18.9mL, 180.7mmol) wasuesd to
form 17e. The crude carbamate waspurified by Kugel-
rohr distillation (0.3mmHg, 124ꢁC) to yield 18e asa
white solid (15.4g, 16%): mp 56–58ꢁC; 1H NMR
(400MHz, CDCl3) d 7.31–7.27 (m, 2H), 7.23–7.19 (m,
3H), 4.73 (br ex s, 1H, NH), 3.89 (m, 1H), 3.62 (s,
5.3. Molecular modeling
Calculated logP (ClogP) valuesand Connolly surfaces
were generated in SYBYLꢂ on a Silicon GraphicsOctane
workstation.30 Docking of the inhibitorsinto the PNMT
active site was performed using AutoDock 3.0.27 The

1268
G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
3H), 2.81–2.74 (m, 2H), 1.51–1.32 (m, 6H), 0.90 (t,
J = 6.7Hz, 3H); HRMS (FAB+) m/z calcd for
C14H22NO2 (MH+) 236.1651 obsd 236.1626.
chromatography (2:1 hexanes/EtOAc) to yield 19f asa
white solid (711mg, 82%): mp 80–81ꢁC; 1H NMR
(400MHz, CDCl3) d 8.05 (s, 1H), 7.38–7.31 (m, 3H),
7.17 (s, 1H), 3.66 (m, 1H), 2.97–2.94 (m, 1H), 2.80–
2.77 (m, 1H), 1.64–1.57 (m, 2H), 1.41–1.30 (m, 6H),
0.87 (s, 3H); HRMS (FAB+) m/z calcd for C14H20NO
(MH+) 218.1545 obsd 218.1539.
5.4.4. ( )-N-(Methoxycarbonyl)-1-phenyl-2-aminohept-
ane (18f). Hexanenitrile (2.48mL, 20.6mmol) wasused
to form 17f. The crude carbamate waspurified by Ku-
gelrohr distillation (0.7mmHg, 120ꢁC) to yield 18f as
a white solid (2.34g, 46%): mp 61–62ꢁC; 1H NMR
(400MHz, CDCl3) d 7.37–7.29 (m, 5H), 4.67 (br ex s,
1H, NH), 4.03 (m, 1H), 3.63 (s, 3H), 2.79 (m, 2H),
1.59–1.29 (m, 8H), 0.88 (t, J = 6.7Hz, 3H); HRMS
(FAB+) m/z calcd for C15H24NO2 (MH+) 250.1807 obsd
250.1798.
5.6. General procedure for 20b–f (selected procedure
for 20c)
Lactam 19c (200mg, 1.06mmol) was dissolved in H2SO4
(5mL) and cooled to 0ꢁC. Potassium nitrate (128mg,
1.27mmol) was added in small portions to the solution,
which wasstirred overnight. The reaction mixture was
poured onto ice and extracted with EtOAc
(3 · 75mL). The organic layerswere combined, washed
with saturated NaHCO3, washed with brine, and dried
over Na2SO4. The solvent was removed in vacuo to yield
the crude nitro lactam.
5.5. General procedure for 19c–f (selected procedure for
19c)
Polyphosporic acid (PPA, 20g) was heated in a flask to
140ꢁC and carbamate 18c (900mg, 4.07mmol) was
added. After stirring for 15min, the mixture was poured
onto ice. The mixture wasextracted with DCM
(3 · 75mL). The organic layerswere combined, washed
with brine, and dried over Na2SO4. The solvent was re-
moved in vacuo to yield the crude lactam.
5.6.1. ( )-3-Ethyl-7-nitro-3,4-dihydroisoquinolin-1-(2H)-
one (20b). Lactam 19b (200mg, 1.79mmol) and KNO3
(138mg, 1.93mmol) were used. The crude nitro lactam
wasrecrystallized in CHCl 3/hexanesto yield 20b asyel-
1
low crystals (181mg, 72%): mp 199–200ꢁC; H NMR
5.5.1.
( )-3-Propyl-3,4-dihydroisoquinolin-1-(2H)-one
(400MHz, CDCl3) d 8.93 (s, 1H), 8.32 (d, J = 8.4Hz,
1H), 7.43 (d, J = 8.3Hz, 1H), 6.09 (br ex s, 1H), 3.72–
3.69 (m, 1H), 3.17–3.12 (m, 1H), 2.98–2.91 (m, 1H),
1.75–1.68 (m, 2H), 1.07 (t, J = 7.4Hz, 3H); HRMS
(FAB+) m/z calcd for C11H13N2O3 (MH+) 221.0926
obsd 221.0921.
(19c). The crude lactam waspurified by recytsalliztion
in ether/hexanesto yield 19c aswhite crystals(613mg,
76%): mp 97–98ꢁC; 1H NMR (400MHz, CDCl3) d
8.03 (d, J = 7.2Hz, 1H), 7.80 (br ex s, 1H, NH), 7.38–
7.35 (m, 1H), 7.29–7.26 (m, 1H), 7.13 (d, J = 7.0Hz,
1H), 3.64 (m, 1H), 2.91 (m, 1H), 2.75–2.68 (m, 1H),
1.64–1.41 (m, 4H), 0.91 (t, J = 6.8Hz, 3H); HRMS
(FAB+) m/z calcd for C12H16NO (MH+) 190.1232 obsd
190.1233.
5.6.2.
( )-7-Nitro-3-propyl-3,4-dihydroisoquinolin-1-
(2H)-one (20c). The crude nitro lactam wasrecyrtsal-
lized in EtOH/hexanesto yield 20c aslight yellow crys-
tals(212mg, 85%): mp 205–206 ꢁC; 1H NMR (400MHz,
MeOH-d4) d 8.74 (s, 1H), 8.37 (d, J = 2.5Hz, 1H), 7.59
(d, J = 8.4Hz, 1H), 3.76–3.75 (m, 1H), 3.28–3.23 (m,
1H), 2.99–2.93 (m, 1H), 1.65–1.45 (m, 4H), 0.99 (t,
J = 7.3Hz, 3H); HRMS (FAB+) m/z calcd for
C12H15N2O3 (MH+) 235.1083 obsd 235.1083.
5.5.2.
( )-3-(1-Methyl)ethyl-3,4-dihydroisoquinolin-1-
(2H)-one (19d). Carbamate 18d (1.02g, 4.59mmol) was
dissolved in PPA (20g). The crude lactam was purified
by flash chromatography (3:1 EtOAc/hexanes) to yield
1
19d asa white oslid (5.63g, 63%): mp 124–126 ꢁC; H
NMR (400MHz, CDCl3) d 8.07 (d, J = 7.6Hz, 1H),
7.47–7.21 (m, 3H), 6.16 (s, 1H, NH), 3.52–3.47 (m,
1H), 2.91 (m, 2H), 1.90–1.83 (m, 1H), 1.05–1.02 (m,
6H); HRMS (FAB+) m/z calcd for C12H16NO (MH+)
190.1232 obsd 190.1241.
5.6.3. ( )-3-(1-Methyl)ethyl-7-nitro-3,4-dihydroisoquino-
lin-1-(2H)-one (20d). Lactam 19d (1.00g, 5.29mmol) and
KNO3 (641mg, 6.35mmol) were used. The crude nitro
lactam wasrecrystallized in EtOH to yield 20d asyellow
crystals (960mg, 77%): mp 200–201ꢁC; 1H NMR
5.5.3.
( )-3-Butyl-3,4-dihydroisoquinolin-1-(2H)-one
(400MHz, MeOH-d4) d 8.74 (s, 1H), 8.36 (d,
(19e). Carbamate 18e (1.2g, 5.11mmol) was dissolved
in PPA (22g). The crude lactam wasrecrytsallized in
ether/hexane to yield 19e aswhite crytsals(606mg,
61%): mp 92–93ꢁC; 1H NMR (400MHz, CDCl3) d
8.02 (d, J = 7.2Hz, 1H), 7.84 (br ex s, 1H, NH), 7.35–
7.34 (m, 1H), 7.28–7.27 (m, 1H), 7.12 (d, J = 7.0Hz,
1H), 3.61 (m, 1H), 2.93–2.89 (m, 1H), 2.74–2.68 (m,
1H), 1.63–1.53 (m, 2H), 1.37–1.31 (m, 4H), 0.87 (t,
J = 6.8Hz, 3H); HRMS (FAB+) m/z calcd for
C13H18NO (MH+) 204.1388 obsd 204.1401.
J = 8.3Hz, 1H), 7.60 (d, J = 8.4Hz, 1H), 3.57–3.52 (m,
1H), 3.21–3.04 (m, 2H), 1.90–1.85 (m, 1H), 1.03–1.00
(m, 6H); HRMS (FAB+) m/z calcd for C14H15N2O3
(MH+) 235.1083 obsd 235.1077.
5.6.4. ( )-3-Butyl-7-nitro-3,4-dihydroisoquinolin-1-(2H)-
one (20e). Lactam 19e (200mg, 0.985mmol) and KNO3
(119mg, 1.18mmol) were used. The crude nitro lactam
wasrecrystallized in EtOH/hexanesto yield 20e asyel-
1
low crystals (163mg, 67%): mp 196–197ꢁC; H NMR
(400MHz, acetone-d6) d 8.71 (s, 1H), 8.35–8.33 (m,
1H), 7.66 (d, J = 8.0Hz, 1H), 7.33 (br ex s, 1H, NH),
3.79 (m, 1H), 3.32–3.28 (m, 1H), 3.02–2.96 (m, 1H),
1.72–1.64 (m, 2H), 1.47–1.36 (m, 4H), 0.92 (t,
5.5.4. ( )-3-Pentyl-3,4-dihydroisoquinolin-1-(2H)-one
(19f). Carbamate 18f (1.0g, 4.02mmol) was dissolved
in PPA (22g). The crude lactam waspurified by flahs

G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
1269
J = 7.3Hz, 3H); HRMS (FAB+) m/z calcd for
NH2+), 8.24 (s, 1H), 8.12 (d, J = 8.5Hz, 1H), 7.51 (d,
J = 8.5Hz, 1H), 4.49–4.37 (m, 2H), 3.47 (m, 1H),
3.28–3.23 (m, 1H), 2.98–2.91 (m, 1H), 1.85–1.78 (m,
1H), 1.67–1.58 (m, 1H), 1.52–1.42 (m, 2H), 0.93 (t,
J = 7.2Hz, 3H); 13C NMR (400MHz, DMSO-d6) d
146.9, 141.1, 131.7, 131.1, 123.0, 122.8, 52.6, 44.3,
35.0, 31.6, 18.6, 14.6; HRMS (FAB+) m/z calcd for
C12H17N2O2 (MH+) 221.1290 obsd 221.1264; Anal.
Calcd for C12H16N2O2ÆHClÆ0.25H2O: C, 55.17; H,
6.77; N, 10.73. Found: C, 55.34; H, 6.69; N, 10.69.
C13H17N2O3 (MH+) 249.1239 obsd 249.1236.
5.6.5. ( )-7-Nitro-3-pentyl-3,4-dihydroisoquinolin-1-(2H)-
one (20f). Lactam 19f (350mg, 1.14mmol) and KNO3
(195mg, 1.37mmol) were used. The crude nitro lactam
wasrecrystallized in EtOH/hexanesto yield
20f asyel-
1
low crystals (363mg, 85%): mp 188–189ꢁC; H NMR
(400MHz, MeOH-d4) d 8.74 (s, 1H), 8.37 (s, 1H), 7.60
(s, 1H), 3.73 (m, 1H), 3.3–3.24 (m, 1H), 2.99–2.95 (m,
1H), 1.66–1.59 (m, 2H), 1.46–1.36 (m, 6H), 0.94 (s,
3H); HRMS (FAB+) m/z calcd for C14H19N2O3
(MH+) 263.1396 obsd 263.1409.
5.7.3. ( )-3-(1-Methyl)ethyl-7-nitro-1,2,3,4-tetrahydro-
isoquinoline hydrochloride (23dÆHCl). Compound 20d
(251mg, 1.07mmol) and 1M BH3ÆTHF (4.29mL,
4.29mmol) were used. The crude residue was purified
by flash chromatography (5:1 hexanes/acetone). The
hydrochloride salt was recrystallized from EtOH/hex-
anesto yield 23dÆHCl aswhite crytsals(200mg, 73%):
mp > 300ꢁC; 1H NMR (400MHz, DMSO-d6) d 9.64
(br ex s, 2H, NH2+), 8.24 (s, 1H), 8.13–8.11 (m, 1H),
7.52 (d, J = 8.5Hz, 1H), 4.49–4.38 (m, 2H), 3.37 (m,
1H), 3.17–3.12 (m, 1H), 3.02–2.95 (m, 1H), 2.16–2.11
(m, 1H), 1.07–1.03 (m, 6H); 13C NMR (400MHz,
DMSO-d6) d 146.9, 141.4, 131.7, 131.1, 123.0, 122.7,
58.3, 45.4, 30.5, 28.2, 19.5, 17.8; HRMS (FAB+) m/z
calcd for C12H17N2O2 (MH+) 221.1290 obsd 221.1288;
Anal. Calcd for C12H16N2O2ÆHCl: C, 56.14; H, 6.67;
N, 10.91. Found: C, 56.17; H, 6.49; N, 10.67.
5.7. General procedure for 23b–f (selected procedure
for 23c)
Compound 20c (207mg, 0.885mmol) was dissolved in
THF (25mL) and 1M BH3ÆTHF (3.54mL, 3.54mmol)
wasadded. The solution washeated to reflux overnight,
wascooled to 0 ꢁC, and MeOH (10mL) wasadded drop-
wise. The solvent was removed in vacuo and to the
remaining residue a solution of 6N HCl (6mL) and
MeOH (25mL) wasadded. The mixture washeated to
reflux for 3h and the MeOH wasremoved in vacuo.
Water (25mL) wasadded to the mixture, and the mix-
ture was cooled in ice and made basic with KOH pellets.
The basic solution was extracted with EtOAc
(4 · 50mL) and the combined organic extractswere
washed with brine and dried over Na2SO4. The solvent
wasremoved in vacuo to yield a crude orange residue,
which waspurified by flahs chromatography (2:1
MeCN/DCM). The free amine was dissolved in EtOH
and dry HCl(g) wasbubbled through the solution.
5.7.4. ( )-3-Butyl-7-nitro-1,2,3,4-tetrahydroisoquinoline
hydrochloride (23eÆHCl). Compound 20e (155mg,
0.625mmol) and 1M BH3ÆTHF (2.50mL, 2.50mmol)
were used. The crude orange residue was purified by
flash chromatography (2:1 MeCN/DCM). The hydro-
chloride salt was recrystallized from EtOH/hexanes to
yield 23eÆHCl aswhite crystals(100mg, 59%): mp 290–
293ꢁC (dec); 1H NMR (400MHz, DMSO-d6) d 9.65
(br ex s, 2H, NH2+), 8.23 (s, 1H), 8.12 (d, J = 7.9Hz,
1H), 7.51 (d, J = 8.2Hz, 1H), 4.49–4.37 (m, 2H), 3.47
(m, 1H), 3.28–3.23 (m, 1H), 2.97–2.90 (m, 1H), 1.84
(m, 1H), 1.62 (m, 1H), 1.43–1.34 (m, 4H), 0.92 (t,
J = 6.9Hz, 3H); 13C NMR (400MHz, DMSO-d6) d
146.9, 141.1, 131.7, 131.2, 122.9, 122.7, 52.9, 44.4,
32.6, 31.7, 27.3, 22.7, 14.6; HRMS (FAB+) m/z calcd
for C13H19N2O2 (MH+) 235.1447 obsd 235.1444; Anal.
Calcd for C13H18N2O2ÆHCl: C, 57.67; H, 7.07; N,
10.35. Found: C, 57.46; H, 7.06; N, 10.16.
5.7.1. ( )-3-Ethyl-7-nitro-1,2,3,4-tetrahydroisoquinoline
hydrobromide (23bÆHBr). Compound 20b (166mg,
0.76mmol) and 1M BH3ÆTHF (3.02mL, 3.02mmol)
were used. After workup, the solvent was removed in
vacuo to yield a crude residue that was purified by flash
chromatography (3:1 hexanes/acetone). The free amine
was dissolved in EtOH and dry HBr(g) wasbubbled
through it. The solvent was removed and the solid was
recrystallized from EtOH/hexanes to yield 23bÆHBr as
white crystals (159mg, 73%): mp 255–256ꢁC; 1H
NMR (400MHz, DMSO-d6) d 8.90 (br ex s, 2H,
NH2+), 8.23 (s, 1H), 8.13 (d, J = 8.5Hz, 1H), 7.53 (d,
J = 8.6Hz, 1H), 4.53–4.40 (m, 2H), 3.32 (m, 1H),
2.90–2.83 (m, 1H), 1.81–1.77 (m, 1H), 1.67–1.60 (m,
1H), 1.04–1.00 (t, J = 7.4Hz, 3H); 13C NMR
(500MHz, DMSO-d6) d 146.0, 140.1, 130.9, 130.4,
122.2, 121.8, 53.4, 43.9, 30.5, 25.5, 9.3; HRMS
(FAB+) m/z calcd for C11H15N2O2 (MH+) 207.1134
obsd 207.1137; Anal. Calcd for C11H14N2O2ÆHBr: C,
46.01; H, 5.27; N, 9.76. Found: C, 45.87; H, 5.28; N,
9.54.
5.7.5. ( )-7-Nitro-3-pentyl-1,2,3,4-tetrahydroisoquinoline
hydrochloride (23fÆHCl). Compound 20f (320mg,
1.22mmol) and 1M BH3ÆTHF (4.89mL, 4.89mmol)
were used. The crude orange residue was purified by
flash chromatography (3:1 EtOAc/hexanes). The hydro-
chloride salt was recrystallized from EtOH/hexanes to
yield 23fÆHCl aswhite crystals(204mg, 67%): mp 271–
275ꢁC (dec); 1H NMR (400MHz, DMSO-d6) d 9.68
(br ex s, 2H, NH2+), 8.23 (s, 1H), 8.12 (d, J = 7.9Hz,
1H), 7.51 (d, J = 8.2Hz, 1H), 4.49–4.37 (m, 2H), 3.48
(m, 1H), 3.29–3.24 (m, 1H), 2.97–2.90 (m, 1H), 1.85
(m, 1H), 1.63 (m, 1H), 1.44 (m, 2H), 1.31 (s, 4H), 0.89
(m, 3H); 13C NMR (400MHz, DMSO-d6) d 146.9,
141.0, 131.7, 131.2, 123.0, 122.7, 52.9, 44.4, 32.9, 31.8,
31.6, 24.9, 22.8, 14.7; HRMS (FAB+) m/z calcd for
5.7.2. ( )-7-Nitro-3-propyl-1,2,3,4-tetrahydroisoquinoline
hydrochloride (23cÆHCl). The hydrochloride salt was
recrystallized from EtOH/hexanes to yield 23cÆHCl as
white crystals (173mg, 77%): mp 265–295ꢁC (dec); IR
(film) 2960, 2919, 2852, 1670, 1614, 1521, 1455, 1342;
1H NMR (400MHz, DMSO-d6) 9.75 (br ex s, 2H,

1270
G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
C14H21N2O2 (MH+) 249.1603 obsd 249.1607; Anal.
Calcd for C14H20N2O2ÆHCl: C, 59.05; H, 7.43; N, 9.84.
Found: C, 59.19; H, 7.43; N, 9.76.
2H), 1.82 (m, 1H), 0.95 (m, 6H); HRMS (FAB+) m/z
calcd for C12H15BrNO (MH+) 268.0337 obsd 268.0329.
5.8.4.
( )-7-Bromo-3-butyl-3,4-dihydroisoquinolin-1-
5.8. General procedure for 21a and 21c–f (selected
procedure for 21c)
(2H)-one (21e). Lactam 20e (500mg, 2.02mmol), PtO2
(137mg, 0.604mmol), NaNO2 (153mg, 2.22mmol),
and CuBr (871mg, 6.05mmolmol) were used. Com-
pound 21e waspurified by flash chromatography eluting
with 3:1 hexanes/EtOAc ! 2:1 hexanes/EtOAc (423mg,
Platinum oxide (186mg, 0.794mmol) wasplaced in a
Parr shaker bottle. Methanol (30mL) and concentrated
HCl (3mL) were cautiously added. Compound 20c
(54mg, 0.238mmol) wasadded and the mixture was
hydrogenated at 50psi for 5h. The reaction mixture
wasfiltered over a Celite pad and washed with MeOH.
The solution was concentrated in vacuo. The crude ani-
line hydrochloride salt (191mg, 0.793mmol) was dis-
solved in HBr (5mL) and water (12mL) and the
solution was cooled in an ice-water bath. Sodium nitrite
(60mg, 0.870mmol) in water (10mL) wasadded drop-
wise. Excess HNO2 wasdestroyed by the addition of a
small portion of urea. Copper(I) bromide (126mg,
0.875mmol), HBr (10mL), and water (20mL) were com-
bined, added dropwise to the diazonium salt solution,
and the reaction mixture wasstirred overnight at room
temperature. Ethyl acetate (30mL) wasadded and stir-
red for 20min. The mixture wasfiltered over a Celite
pad, which waswashed with EtOAc. The organic phase
was separated and the aqueous phase was extracted with
EtOAc (3 · 50mL). The combined organic layerswere
washed with saturated sodium bicarbonate and brine,
and dried over sodium sulfate. The solvent was removed
in vacuo to yield the crude lactam.
1
74%): mp 135–136ꢁC; H NMR (400MHz, CDCl3) d
8.15 (s, 1H), 7.51 (d, J = 8.0Hz, 1H), 7.40 (ex s, 1H,
NH), 6.86 (d, J = 8.0Hz, 1H), 3.91–3.88 (br m, 1H),
2.93 (m, 1H), 2.71 (m, 1H), 1.64–1.54 (m, 2H), 1.36
(m, 4H), 0.90 (t, J = 6.6Hz, 3H); HRMS (FAB+) m/z
calcd for C13H17BrNO (MH+) 282.0494 obsd 282.0487.
5.8.5.
( )-7-Bromo-3-pentyl-3,4-dihydroisoquinolin-1-
(2H)-one (21f). Lactam 20f (500mg, 1.91mmol), PtO2
(130mg, 0.573mmol), NaNO2 (145mg, 2.16mmol),
and CuBr (824mg, 5.72mmol) were used. Compound
21f waspurified by flahs chromatography eluting with
1
3:1 hexanes/EtOAc (124mg, 22%): mp 134–135ꢁC; H
NMR (400MHz, CDCl3) d 8.20 (s, 1H), 7.56 (d,
J = 8.0Hz, 1H), 7.10 (d, J = 8.0Hz, 1H), 6.54 (ex s,
1H, NH), 3.69 (br m, 1H), 2.98–2.93 (m, 1H), 2.79–
2.72 (m, 1H), 1.65–1.55 (m, 2H), 1.43–1.34 (m, 6H),
0.92 (t, J = 6.4Hz, 3H); HRMS (FAB+) m/z calcd for
C13H19BrNO (MH+) 296.0632 obsd 296.0650.
5.8.6. ( )-7-Bromo-3-methyl-1,2,3,4-tetrahydroisoquino-
line hydrochloride (22aÆHCl). Compound 21a (100mg,
0.416mmol) wasreduced with 1M BH ÆTHF (1.67mL,
3
5.8.1.
( )-7-Bromo-3-methyl-3,4-dihydroisoquinolin-1-
1.67mmol) asdecsribed in the general procedure for
23b–f. The free amine waspurified by flahs chromato-
graphy eluting with 5:95 MeOH/EtOAc ! 20:80
MeOH/EtOAc. The hydrochloride salt was recrystal-
lized in EtOH/hexanesto yield 22aÆHCl aswhite crystals
(2H)-one (21a). Lactam 20a (200mg, 0.962mmol),
PtO2 (65mg, 0.026mmol), NaNO2 (73mg, 1.06mmol),
and CuBr (415mg, 2.88mmol) were used. Compound
21a waspurified by flash chromatography eluting with
1
1
3:1 hexanes/EtOAc (115mg, 50%): mp 135–136ꢁC; H
(62mg, 57%): mp dec 273–290ꢁC; H NMR (400MHz,
NMR (400MHz, MeOH-d4) d 8.05 (s, 1H), 7.66–7.64
(m, 1H), 7.24 (d, J = 8.1Hz, 1H), 3.86–3.77 (m, 1H),
3.03–2.99 (m, 1H), 2.77–2.70 (m, 1H), 1.31 (m, 3H);
HRMS (FAB+) m/z calcd for C10H11BrNO (MH+)
240.0024 obsd 240.0019.
DMSO-d6) d 9.84 (ex br s, 2H, NH2+), 7.50 (s, 1H),
7.45 (d, J = 8.2Hz, 1H), 7.17 (d, J = 8.3Hz, 1H), 4.28
(m, 2H), 3.54–3.47 (m, 1H), 3.04–2.98 (m, 1H), 2.81–
2.74 (m, 1H), 1.37 (m, 3H); 13C NMR (400MHz,
DMSO-d6) d 132.2, 132.0, 131.7, 131.1, 130.1, 120.1,
49.3, 43.8, 32.9, 18.9; HRMS (FAB+) m/z calcd for
C10H13BrN (MH+) 226.0231 obsd 226.0225; Anal.
Calcd for C10H12NBrÆHCl: C, 45.74; H, 4.99; N, 5.33.
Found: C, 45.72; H, 4.67; N, 5.20.
5.8.2.
( )-7-Bromo-3-propyl-3,4-dihydroisoquinolin-1-
(2H)-one (21c). Compound 21c waspurified by flahs
chromatography eluting with 3:1 hexanes/EtOAc
(160mg, 75%): mp 132–133ꢁC; 1H NMR (400MHz,
MeOH-d4) d 8.04 (s, 1H), 7.66–7.64 (m, 1H), 7.25 (d,
J = 8.1Hz, 1H), 3.69–3.64 (m, 1H), 3.10–3.05 (m, 1H),
2.81–2.75 (m, 1H), 1.62–1.43 (m, 4H), 0.97 (t,
J = 6.6Hz, 3H); HRMS (FAB+) m/z calcd for
C12H15BrNO (MH+) 268.0337 obsd 268.0355.
5.8.7. ( )-7-Bromo-3-ethyl-1,2,3,4-tetrahydroisoquinoline
hydrochloride (22bÆHCl). Compound 20b (75mg,
0.261mmol), Pd/C (55mg, 0.103mmol), NaNO2
(20mg, 0.288mmol), and CuBr (114mg, 0.792mmol)
were used to synthesize 21b asdescribed in the general
procedure for 21a and 21c–f. Crude 21b wascarried for-
ward to the reduction reaction with 1M BH3ÆTHF asde-
scribed in the general procedure for 23b–f. The free
amine waspurified by flahs chromatography eluting
with EtOAc. The hydrochloride salt was recrystallized
in MeOH/ether to yield 22bÆHCl aswhite crytsals
(23mg, 33%): mp > 300ꢁC; 1H NMR (400MHz,
MeOH-d4) d 7.56–7.48 (m, 2H), 7.21 (d, J = 8.9Hz,
1H), 4.40 (m, 2H), 3.46–3.44 (m, 1H), 3.22–3.17 (m,
1H), 2.88–2.81 (m, 1H), 1.90–1.76 (m, 2H), 1.16–1.12
5.8.3. ( )-7-Bromo-3-(1-methyl)ethyl-3,4-dihydroisoquin-
olin-1-(2H)-one (21d). Lactam 20d (500mg, 2.14mmol),
PtO2
2.35mmol), and CuBr (923mg, 6.41mmol) were used.
Compound 21d waspurified by flahs chromatography
eluting with 3:1 hexanes/EtOAc (300mg, 52%): mp
119–120ꢁC; 1H NMR (400MHz, CDCl3) d 8.28 (s,
1H), 7.68 (d, J = 8.0Hz, 1H), 7.11 (d, J = 8.0Hz, 1H),
5.90 (ex s, 1H, NH), 3.51–3.46 (br m, 1H), 2.86 (m,
(146mg,
0.643mmol),
NaNO2
(162mg,

G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
1271
(m, 3H); 13C NMR (500MHz, MeOH-d4) d 132.4, 132.3,
132.2, 131.8, 130.6, 121.7, 56.5, 45.8, 31.6, 27.4, 9.8;
HRMS (FAB+) m/z calcd for C11H15BrN (MH+)
NBrÆHCl: C, 51.25; H, 6.29; N, 4.60. Found: C, 51.27;
H, 6.33; N, 4.45.
240.0388
obsd
240.0398;
Anal.
Calcd
for
5.8.11. ( )-7-Bromo-3-pentyl-1,2,3,4-tetrahydroisoquino-
line hydrochloride (22fÆHCl). Compound 21f (120mg,
C11H14NBrÆHCl: C, 47.76; H, 5.47; N, 5.06. Found: C,
47.40; H, 5.44; N, 4.92.
0.405mmol) wasreduced with 1M BH ÆTHF (1.62mL,
3
1.62mmol) asdecsribed in the general procedure for
23b–f. The free amine waspurified by flahs chromato-
graphy eluting with 3:2 EtOAc/hexanes. The hydrochlo-
ride salt was recrystallized in EtOH/hexanes to yield
22fÆHCl aswhite crystals(60mg, 47%): mp 219–220 ꢁC;
1H NMR (500MHz, DMSO-d6) d 9.59 (ex br s, 2H,
NH2+), 7.51 (s, 1H), 7.45 (d, J = 8.3Hz, 1H), 7.19 (d,
J = 8.3Hz, 1H), 4.29 (s, 2H), 3.42 (m, 1H), 3.07 (m,
1H), 2.78 (m, 1H), 1.82 (m, 1H), 1.61 (m, 1H), 1.43–
1.31 (m, 6H) 0.90 (t, J = 7.2Hz, 3H); 13C NMR
(500MHz, DMSO-d6) d 131.7, 131.7, 131.3, 130.6,
129.5, 119.6, 52.7, 43.6, 32.4, 31.3, 30.5, 24.4, 22.3,
14.2; HRMS (FAB+) m/z calcd for C14H21BrN (MH+)
5.8.8. ( )-7-Bromo-3-propy1-1,2,3,4-tetrahydroisoquino-
line hydrochloride (22cÆHCl). Compound 21c (634mg,
2.36mmol) wasreduced with 1M BH ÆTHF (7.09mL,
3
7.09mmol) asdecsribed in the general procedure for
23b–f. The free amine waspurified by flahs chromato-
graphy eluting with 2:1 EtOAc/hexanes. The hydrochlo-
ride salt was recrystallized in EtOH/hexanes to yield
22cÆHCl aswhite crytsals(229mg, 35%): mp 224–
1
225ꢁC; H NMR (400MHz, DMSO-d6) d 9.81 (ex m,
2H, NH2+), 7.51 (s, 1H), 7.44 (d, J = 8.3Hz, 1H), 7.17
(d, J = 8.3Hz, 1H), 4.26 (s, 2H), 3.46–3.38 (m, 3H),
3.05 (m, 1H), 2.79 (m, 1H), 1.86–1.79 (m, 1H), 1.65–
1.56 (m, 1H), 0.93 (t, J = 7.2Hz, 3H); 13C NMR
(400MHz, DMSO-d6) d 132.31, 132.26, 131.8, 131.3,
130.0, 120.1, 52.9, 44.0, 35.0, 30.9, 18.7, 14.6;
HRMS (FAB+) m/z calcd for C12H17BrN (MH+)
254.0544 obsd 254.0538; Anal. Calcd for C12H16-
NBrÆHCl: C, 49.59; H, 5.90; N, 4.82. Found: C, 49.56;
H, 5.77; N, 4.66.
282.0857
obsd
282.0864;
Anal.
Calcd
for
C14H20NBrÆHCl: C, 52.76; H, 6.64; N, 4.40. Found: C,
52.47; H, 6.65; N, 4.16.
5.9. General procedure for 24a–c (selected procedure
for 24c)
Lactam 19c (500mg, 2.64mmol) wastreated with
ClSO3H (5mL) and stirred at 50ꢁC for 8h. The mixture
waspipetted cautioulsy onto ice (50mL). The aqueous
mixture wasextracted with EtOAc (3 · 50mL). The
combined organic layers were washed with saturated so-
dium bicarbonate and brine, and dried over sodium sul-
fate. The solvent was removed in vacuo to yield sulfonyl
chloride 24c, which required no further purification.
5.8.9. ( )-7-Bromo-3-(1-methyl)ethyl-1,2,3,4-tetrahydro-
isoquinoline hydrochloride (22dÆHCl). Compound 21d
(290mg, 1.08mmol) wasreduced with 1M BH 3ÆTHF
(4.33mL, 4.33mmol) asdescribed in the general proce-
dure for 23b–f. The free amine waspurified by flahs
chromatography eluting with 2:1 EtOAc/hexanes. The
hydrochloride salt was recrystallized in EtOH/hexanes
to yield 22dÆHCl aswhite crytsals(219mg, 76%): mp
dec 305–308ꢁC; 1H NMR (400MHz, DMSO-d6) d
9.53 (ex br s, 2H, NH2+), 7.54 (s, 1H), 7.45 (d,
J = 8.3Hz, 1H) 7.20 (d, J = 8.3Hz, 1H), 4.30 (m, 2H),
3.33 (m, 1H), 2.95 (m, 1H), 2.85 (m, 1H), 2.13 (m,
1H), 1.03 (m, 6H); 13C NMR (500MHz, DMSO-d6) d
132.1, 131.9, 131.4, 130.5, 129.5, 119.6, 58.2, 44.7,
30.0, 27.0, 19.1, 17.3; HRMS (FAB+) m/z calcd for
C12H17BrN (MH+) 254.0544 obsd 254.0539; Anal.
Calcd for C12H16NBrÆHCl: C, 49.59; H, 5.90; N, 4.82.
Found: C, 49.61; H, 5.80; N, 4.68.
5.9.1. ( )-3-Methyl-7-chlorosulfonyl-3,4-dihydroisoquino-
lin-1-(2H)-one (24a). Lactam 19a (696mg, 4.32mmol)
wastreated with chlorouslfonic acid (7mL) to yield
24a (313mg, 28%): mp 109–110ꢁC; 1H NMR
(400MHz, CDCl3) d 8.76 (s, 1H), 8.12 (m, 1H), 7.50
(m, 1H), 6.42 (ex s, 1H), 3.95 (m, 1H), 3.11–2.95 (m,
2H), 1.42 (m, 3H);HRMS (FAB+) m/z calcd for
C10H11NO3SCl (MH+) 260.0148 obsd 260.0145.
5.9.2. ( )-3-Ethyl-7-chlorosulfonyl-3,4-dihydroisoquino-
lin-1-(2H)-one (24b). Lactam 19b (1.18g, 6.73mmol)
wastreated with chlorouslfonic acid (10mL) to yield
24b (345mg, 19%): mp 169–170ꢁC; 1H NMR
(400MHz, CDCl3) d 8.76 (s, 1H), 8.11 (m, 1H), 7.50
(d, J = 8.1Hz, 1H), 6.46 (ex s, 1H), 3.74–3.69 (m, 1H),
3.19–3.14 (m, 1H), 2.99–2.93 (m, 1H), 1.80–1.67 (m,
2H), 1.08 (t, J = 7.4Hz, 3H); HRMS (FAB+) m/z calcd
for C11H13NO3SCl (MH+) 274.0305 obsd 274.0314.
5.8.10. ( )-7-Bromo-3-butyl-1,2,3,4-tetrahydroisoquino-
line hydrochloride (22eÆHCl). Compound 21e (415mg,
1.47mmol) wasreduced with 1M BH ÆTHF (5.89mL,
3
5.89mmol) asdecsribed in the general procedure for
23b–f. The free amine waspurified by flahs chromato-
graphy eluting with 2:1 EtOAc/hexanes. The hydrochlo-
ride salt was recrystallized in EtOH/hexanes to yield
22eÆHCl aswhite crytsals(331mg, 74%): mp 229–
1
230ꢁC; H NMR (400MHz, DMSO-d6) d 9.77 (ex m,
5.9.3. ( )-3-Propyl-7-chlorosulfonyl-3,4-dihydroisoquino-
lin-1-(2H)-one (24c). Lactam 19c (500mg, 2.64mmol)
wastreated with chlorouslfonic acid (5mL) to yield
24c (608mg, 80%): mp 159–160ꢁC; 1H NMR
(500MHz, CDCl3) d 8.76 (s, 1H), 8.11 (s, 1H), 7.50 (s,
1H), 6.23 (ex s, 1H), 3.86 (m, 1H), 3.17–3.14 (m, 1H),
2.98–2.93 (m, 1H), 1.66–1.49 (m, 4H), 0.95 (m, 3H);
HRMS (FAB+) m/z calcd for C12H15NO3SCl (MH+)
288.0461 obsd 288.0469.
2H, NH2+), 7.51 (s, 1H), 7.44 (d, J = 8.3Hz, 1H), 7.17
(d, J = 8.3Hz, 1H), 4.27 (s, 2H), 3.39 (m, 1H), 3.05
(m, 1H), 2.79 (m, 1H), 1.86 (m, 1H), 1.61 (m, 1H),
1.41–1.32 (m, 4H) 0.92 (t, J = 7.2Hz, 3H); 13C NMR
(500MHz, DMSO-d6) d 131.8, 131.8, 131.3, 130.5,
129.5, 119.6, 52.6, 43.5, 32.1, 30.5, 26.9, 22.3, 14.1;
HRMS (FAB+) m/z calcd for C13H19BrN (MH+)
268.0701 obsd 268.0695; Anal. Calcd for C13H18-

1272
G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
5.10. General procedure for 27a–c (selected procedure
for 27c)
4.39–4.36 (m, 2H), 3.50–3.41 (m, 1H), 3.19–3.13 (m,
1H), 2.93–2.86 (m, 1H), 1.86–1.79 (m, 1H), 1.64–1.58
(m, 1H), 1.50–1.43 (m, 2H), 0.93 (t, J = 7.2Hz, 3H);
13C NMR (DMSO-d6) d 143.2, 136.9, 130.5, 130.4,
125.4, 124.7, 52.8, 44.4, 35.0, 31.4, 18.6, 14.6; HRMS
(FAB+) m/z calcd for C12H19N2O2S (MH+) 255.1167
obsd 255.1175; Anal. Calcd for C12H18N2O2ÆHCl: C,
49.56; H, 6.59; N, 9.63. Found: C, 49.34; H, 6.37; N,
9.40.
Sulfonyl chloride 24c (390mg, 1.36mmol) was dissolved
in acetonitrile (6mL), ammonium hydroxide (6mL) was
added, and the reaction stirred overnight. The acetoni-
trile wasremoved in vacuo and water (10mL) was
added. The aqueousmixture wasextracted with EtOAc
(3 · 25mL). The combined organic extractswere
washed with brine and dried over sodium sulfate. The
solvent was evaporated in vacuo to yield sulfonamide
25c (326mg), which required no further purification.
Sulfonamide 25c wasreduced with 1M BH 3ÆTHF
(4.53mL, 4.53mmol) asdescribed in the general proce-
dure for 23b–f except the free amine wasextracted from
the aqueouslayer at pH10. The free amine waspurified
by column chromatography eluting with 10:1 DCM/
MeOH.
5.11. General procedure for 28a–c (selected procedure
for 28c)
Sulfonyl chloride 24c (200mg, 0.695mmol) wasdi-s
solved in a biphasic mixture of EtOAc (25mL) and sat-
urated sodium carbonate (12mL). Pyridine (3mL) and
2,2,2-trifluoroethylamine (0.166mL, 2.09mmol) were
added and the reaction stirred overnight. The organic
layer was separated and washed with 3N HCl
(2 · 15mL), saturated sodium bicarbonate, and brine.
The organic layer was dried over sodium sulfate and
evaporated in vacuo to yield sulfonamide 26c (216mg),
which required no further purification. Sulfonamide
26c wasreduced with 1M BH 3ÆTHF (1.85mL,
1.85mmol) asdecsribed in the general procedure for
23b–f, except the free amine wasextracted from the
aqueouslayer at pH10. The free amine waspurified
by flash chromatography eluting with 20:1 DCM/
MeOH ! 10:1 DCM/MeOH.
5.10.1. ( )-7-Aminosulfonyl-3-methyl-1,2,3,4-tetrahydro-
isoquinoline hydrochloride (27aÆHCl). Sulfonyl chloride
24a (150mg, 0.578mmol) was used to produce sulfon-
amide 25a (122mg), which was subsequently reduced
with 1M BH3ÆTHF (2.31mL, 2.31mmol). The free
amine waspurified by flahs chromatography eluting
with 20:1 DCM/MeOH. The hydrochloride salt was
recrystallized in EtOH/hexanes to yield 27aÆHCl
(69mg, 45%): mp 221–222ꢁC; 1H NMR (400MHz,
DMSO-d6) d 9.63 (br ex s, 2H), 7.71–7.69 (m, 2H),
7.41–7.40 (m, 3H), 4.39–4.29 (m, 2H), 3.60–3.55 (m,
1H), 3.15–3.09 (m, 1H), 2.93–2.86 (m, 1H), 1.40–1.38
(m, 3H); 13C NMR (400MHz, DMSO-d6) d 143.3,
136.8, 130.3, 130.2, 125.4, 124.7, 49.2, 44.2, 33.3, 18.9;
HRMS (FAB+) m/z calcd for C10H15N2O2S (MH+)
227.0854 obsd 227.0869; Anal. Calcd for C10H14N2O2-
SÆHCl: C, 45.71; H, 5.75; N, 10.66. Found: C, 45.74;
H, 5.80; N, 10.46.
5.11.1. ( )-3-Methyl-7-N-(2,2,2-trifluoroethylaminosulfon-
yl)-1,2,3,4-tetrahydroisoquinoline hydrochloride (28aÆHCl).
Sulfonyl chloride 24a (145mg, 0.558mmol) and 2,2,2-
trifluoroethylamine (0.133mL, 1.67mmol) were used to
produce sulfonamide 26a (146mg), which wasreduced
with 1M BH3ÆTHF (1.81mL, 1.81mmol). The free
amine waspurified by flahs chromatography eluting
with 20:1 DCM/MeOH. The hydrochloride salt was
recrystallized in EtOH/hexanes to yield 28aÆHCl
(65mg, 34%): mp 270–271ꢁC; 1H NMR (400MHz,
DMSO-d6) d 9.65 (br ex s, 2H), 8.70 (ex s, 1H), 7.75–
7.70 (m, 2H), 7.44 (d, J = 8.1Hz, 1H), 4.44–4.33 (m,
2H), 3.71–3.65 (m, 2H), 3.60–3.55 (m, 1H), 3.17–2.94
(m, 1H), 2.94–2.87 (m, 1H), 1.39 (m, 3H); 13C NMR
(500MHz, DMSO-d6) d 139.3, 137.5, 130.2, 130.1,
125.5, 125.2, 124.7 (q, J = 279Hz, CF3), 48.6, 43.7 (q,
J = 31Hz, CF3CH2), 43.6, 32.9, 18.4; HRMS (FAB+)
m/z calcd for C12H16N2O2SF3 (MH+) 309.0885 obsd
309.0878; Anal. Calcd for C12H15N2O2SF3ÆHCl: C,
41.80; H, 4.68; N, 8.12. Found: C, 42.06; H, 4.67; N,
7.93.
5.10.2. ( )-7-Aminosulfonyl-3-ethyl-1,2,3,4-tetrahydro-
isoquinoline hydrochloride (27bÆHCl). Sulfonyl chloride
24b (150mg, 0.548mmol) was used to produce sulfon-
amide 25b (130mg), which was subsequently reduced
with 1M BH3ÆTHF (2.19mL, 2.19mmol). The free
amine waspurified by flahs chromatography eluting
with 20:1 DCM/MeOH ! 10:1 DCM/MeOH. The
hydrochloride salt was recrystallized in EtOH/hexanes
to yield 27bÆHCl (79mg, 52%): mp 244–245ꢁC; 1H
NMR (400MHz, DMSO-d6) d 9.65 (br ex s, 2H),
7.72–7.69 (m, 2H), 7.43–7.40 (m, 3H), 4.38 (m, 2H),
3.43–3.36 (m, 1H), 3.19–3.14 (m, 1H), 2.92–2.85 (m,
1H), 1.90–1.87 (m, 1H), 1.67–1.64 (m, 1H) 1.04–1.00
(m, 3H); 13C NMR (400MHz, DMSO-d6) d 143.3,
136.8, 130.4, 130.4, 125.4, 124.7, 54.4, 44.5, 31.0, 26.1,
10.2; HRMS (FAB+) m/z calcd for C11H17N2O2S
(MH+) 241.1011 obsd 241.1016; Anal. Calcd for
C11H16N2O2SÆHCl: C, 47.73; H, 6.19; N, 10.12. Found:
C, 47.94; H, 6.13; N, 10.00.
5.11.2. ( )-3-Ethyl-7-N-(2,2,2-trifluoroethylaminosulfon-
yl)-1,2,3,4-tetrahydroisoquinoline hydrochloride (28bÆHCl).
Sulfonyl chloride 24b (150mg, 0.548mmol) and 2,2,2-tri-
fluoroethylamine (0.131mL, 1.64mmol) were used to
produce sulfonamide 26b (154mg), which was subse-
quently reduced with 1M BH3ÆTHF (1.83mL,
1.83mmol). The free amine waspurified by flash chroma-
tography eluting with 3:1 MeCN/DCM. The hydrochlo-
ride salt was recrystallized in EtOH/hexanes to yield
28bÆHCl (97mg, 49%): mp 259–260ꢁC; 1H NMR
(400MHz, DMSO-d6) d 9.73 (br ex s, 2H), 8.70 (ex s,
5.10.3. ( )-7-Aminosulfonyl-3-propyl-1,2,3,4-tetrahydro-
isoquinoline hydrochloride (27cÆHCl). The hydrochloride
salt was recrystallized in EtOH/hexanes to yield 27cÆHCl
1
(220mg, 54%): mp 205–206ꢁC; H NMR (DMSO-d6) d
9.72 (br ex s, 2H), 7.71–7.69 (m, 2H), 7.42–7.39 (m, 3H),

G. L. Grunewald et al. / Bioorg. Med. Chem. 13 (2005) 1261–1273
1273
7. Stolk, J. M.; Vantini, G.; Guchait, R. B.; UꢀPrichard, D.
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1H), 7.77–7.70 (m, 2H), 7.46 (d, J = 8.1Hz, 1H), 4.45–
4.34 (m, 2H), 3.74–3.65 (m, 2H), 3.42 (m, 1H), 3.22–
3.17 (m, 1H), 2.92–2.85 (m, 1H), 1.90–1.84 (m, 1H),
1.71–1.60 (m, 1H), 1.02 (t, J = 7.5Hz, 3H); 13C NMR
(500MHz, DMSO-d6) 139.4, 137.4, 130.3, 130.3, 125.5,
125.2, 124.7 (q, J = 277Hz, CF3), 53.9, 44.0, 43.7 (q,
J = 34Hz, CF3CH2), 30.6, 25.6, 9.7; HRMS (FAB+)
m/z calcd for C13H18N2O2SF3 (MH+) 323.1041 obsd
323.1041; Anal. Calcd for C13H17N2O2SF3ÆHCl: C,
43.52; H, 5.06; N, 7.81. Found: C, 43.53; H, 4.98; N, 7.62.
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5.11.3. ( )-3-Propyl-7-N-(2,2,2-trifluoroethylaminosulfon-
yl)-1,2,3,4-tetrahydroisoquinoline hydrochloride (28cÆHCl).
The hydrochloride salt was recrystallized in EtOH/hex-
anesto yield 28cÆHCl (51mg, 20%): mp 224–225ꢁC;
1H NMR (400MHz, DMSO-d6) d 9.49 (br ex s, 2H),
8.70 (ex s, 1H), 7.76–7.70 (m, 2H), 7.45 (d, J = 8.0Hz,
1H), 4.45–4.35 (m, 2H), 3.71–3.65 (m, 2H), 3.50 (m,
1H), 3.23–3.17 (m, 1H), 2.92–2.82 (m, 1H), 1.78 (m.
1H), 1.65–1.39 (m, 3H), 0.94 (t, J = 7.5Hz, 3H); 13C
NMR (400MHz, DMSO-d6) d 139.8, 137.9, 130.8.
130.8, 126.0, 125.7, 125.2 (q, J = 277Hz, CF3), 52.8,
44.4, 44.2 (q, J = 34Hz, CF3CH2), 35.1, 31.4, 18.6,
14.5; HRMS (FAB+) m/z calcd for C14H20N2O2SF3
(MH+) 337.1198 obsd 337.1202; Anal. Calcd for
C14H19N2O2SF3ÆHCl: C, 45.10; H, 5.41; N, 7.51. Found:
C, 44.95; H, 5.26; N, 7.52.
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Acknowledgements
This research was supported by NIH Grant HL 34193.
We thank David VanderVelde and Sarah Neuenswander
of the Nuclear Magnetic Resonance Laboratory for
their assistance. The 500MHz NMR spectrometer was
partially funded by NSF Grant CHE-9977422. We also
thank Gerald Lushington of the Molecular Graphics
and Modeling Laboratory and Todd Williamsof the
Mass Spectrometry Laboratory for their assistance.
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