Iodinated analogs of trimetoquinol as highly potent and selective β2- adrenoceptor ligands

Article abstract of DOI:10.1021/jm960208o

A series of trimetoquinol (1, TMQ) analogs were designed and synthesized based on the lead compound 2, a diiodinated analog of trimetoquinol which exhibits improved selectivity for β₂-versus β₁-adrenoceptors (AR). To determine the in

Full text of DOI:10.1021/jm960208o

J . Med. Chem. 1996, 39, 3701-3711
3701
Iod in a ted An a logs of Tr im etoqu in ol a s High ly P oten t a n d Selective
â2-Ad r en ocep tor Liga n d s
J oseph E. De Los Angeles,† Victor I. Nikulin,†,‡ Gamal Shams,§ Anish A. Konkar,| Ratna Mehta,|
Dennis R. Feller,§ and Duane D. Miller*,†
Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee-Memphis, Memphis, Tennessee 38163,
Divisions of Medicinal Chemistry/ Pharmacognosy and Pharmacology, College of Pharmacy, The Ohio State University,
Columbus, Ohio 43210, and Department of Pharmacology, Research Institute of Pharmaceutical Sciences School of Pharmacy,
University of Mississippi, University, Mississippi 38677
Received March 14, 1996X
A series of trimetoquinol (1, TMQ) analogs were designed and synthesized based on the lead
compound 2, a diiodinated analog of trimetoquinol which exhibits improved selectivity for â2-
versus â1-adrenoceptors (AR). To determine the influence of 1-benzyl substituents of trime-
toquinol on â2-AR binding affinity and selectivity, we replaced and/or removed the 3′-, 4′-, and
5′-methoxy substituents of trimetoquinol. Replacement of the 4′-methoxy group of 2 with an
amino (21c) or acetamido (15) moiety did not significantly alter â2-AR and thromboxane A2/
prostaglandin H2 (TP) receptor affinity. Substitution with a 4′-hydroxy (18) or -iodo (21b) group
did not significantly alter â2-AR affinity, but greatly reduced TP receptor affinity (380- and
1200-fold, respectively). Further, the â2-AR can accommodate larger substituents such as a
benzamide at the 4′-position (26b). Other monoiodo derivatives (24, 26a ) have similar or slightly
lower affinity to both â2-AR and TP receptor compared to their diiodo analogs. Interestingly,
removal of the 4′-substituent of 3′,5′-diiodo analogs increased â2-AR affinity with little or no
effect on â1-AR and TP binding. Thus, analog 21a displayed highly potent (pKi 9.52) and
selective (â2/â1 ) 600) binding affinity for â2-AR. On the other hand, trifluoromethyl
substituents at the 3′- and 5′-positions (27) essentially abolished binding affinity at â2-AR and
TP receptors. The differential binding effects of the aforementioned trimetoquinol modifications
on the receptor systems may reflect differences in the binding pocket that interacts with the
benzyl portion of trimetoquinol analogs. Thus, manipulation of the 1-benzyl moiety of
trimetoquinol (1) has resulted in analogs that exhibit potent â2-AR binding affinity and
significantly lower â1-AR and TP receptor affinities.
In tr od u ction
Trimetoquinol (1) is a potent nonspecific â-adreno-
ceptor (â-AR) agonist clinically used in J apan as a
bronchorelaxant (Figure 1).1 Optical resolution of tri-
metoquinol and subsequent evaluation of the stereo-
isomers revealed that the (S)-(-)-isomer of trimeto-
quinol is a potent â-AR agonist in heart and lung tissues
whereas the (R)-(+)-isomer acts as a selective and highly
stereospecific TP receptor antagonist.2-5 Radioligand
competition binding studies at â-AR and TP receptors
show high stereoselective binding (>100-fold) for the (S)-
F igu r e 1.
(-)-isomer and (R)-(+)-isomer, respectively. This ste-
greatly diminished their ability to stimulate cAMP
accumulation.7 However, both the binding and func-
tional activities of isoproterenol are significantly re-
duced in the â2-AR Asn113, Ala204, and Ala207 mu-
tants. These results suggest that, although trimetoquinol
analogs may interact with the same amino acid residues
in the binding site as isoproterenol, the contribution of
catechol interactions with these mutated â2-ARs is less
significant in terms of ligand binding and may well be
overshadowed by the binding contributions of the tri-
methoxybenzyl group of trimetoquinol.
In previous studies, substitution with fluorine or
iodine on the 5- or 8-positions of trimetoquinol resulted
in only a modest (∼10-fold) increase in â2-AR versus â1-
AR selectivity as compared to trimetoquinol in func-
tional and binding studies.6,8 In addition, we have also
found that replacement of the 3′- and 5′-methoxy sub-
stituent of trimetoquinol with iodine atoms (i.e., 2) is
reoselectivity is also observed in the binding of fluori-
nated trimetoquinol analogs at â-AR.6
The basic structure of catecholamines, such as nore-
pinephrine and the â-adrenoceptor agonist isoproter-
enol, is incorporated within the tetrahydroisoquinoline
nucleus of trimetoquinol. In studies using mutated
hamster â2-AR expressed in Chinese hamster ovary
(CHO) cells, replacement of Asp113 with Asn113 abol-
ished receptor binding of trimetoquinol and its analogs.7
In addition, replacement of Ser204 and Ser207 with
Ala204 and Ala207 decreased the binding affinity of
trimetoquinol analogs in â2-AR to a lesser extent, but
† University of Tennessee-Memphis.
‡ Permanent address: Institute of Chemical Physics, Chernogolovka,
Moscow Region 142432, Russia.
§ University of Mississippi.
| The Ohio State University.
X Abstract published in Advance ACS Abstracts, J uly 15, 1996.
S0022-2623(96)00208-7 CCC: $12.00 © 1996 American Chemical Society

3702 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19
De Los Angeles et al.
Sch em e 1a
a
(a) Toluene, reflux (Dean-Stark trap), 72 h; (b) POCl3, MeCN, reflux; (c) NaBH4, MeOH; (d) TFAA, THF (6a ) or (Boc)2O, NaOH, THF
(6b); (e) H2, Pd/C (7a ) or Raney Ni (7b); (f) 1 equiv of BTMACl2I, MeOH, CH2Cl2, 20 h (8a ,b), or 4 equiv of BTMACl2I, CaCO3, MeOH,
CH2Cl2, 3 days (8a ); (g) 1. BBr3, CH2Cl2, 2. MeOH.
well tolerated on both â-AR8 and TP receptors.9,10
Interestingly, although its binding affinity at â1-AR is
slightly better than trimetoquinol, analog 2 displays a
much higher affinity than trimetoquinol for â2-AR.
These earlier findings suggest that trimetoquinol ana-
logs interact with an auxiliary site through the substi-
tuted benzyl group in addition to the binding site shared
by catecholamines. This subsite can be taken advantage
of in the development of more site-selective agents. The
high potency of 2 seems to suggest that this auxiliary
site is hydrophobic in nature. On TP receptors, the
complementary binding sites for trimetoquinol analogs
are essentially unknown. However, compound 2 is a
more potent TP receptor antagonist than trimetoquinol,
further suggesting that 1-benzyl ring modifications are
appropriate to develop agents with greater selectivity
on â-AR versus TP receptors and vice versa.
In this report, we describe the synthesis and evalu-
ation of iodinated trimetoquinol analogs designed as
probes for characterizing the receptor binding interac-
tions associated with the benzyl substituent of trime-
toquinol analogs and as site-selective â-AR and TP
ligands. These chemical modifications are expected to
provide us with a greater separation of the pharmaco-
logical activities for this class of compounds. Site-
selective â-AR agents have potential in the treatment
of cardiopulmonary diseases, non-insulin-dependent
diabetes (type II), and obesity;11 whereas highly selec-
tive TP receptor antagonists have value in the treat-
ment of thrombolytic disorders.5,9,12
The triple-protected isoquinoline intermediates were
synthesized as shown in Scheme 1. The tetrahydroiso-
quinolines 6a -c were synthesized from the O-methyl-
or O-benzyl-protected catecholamines 3a or 3b, respec-
tively, and 4-nitrophenylacetic acid (4a ) or 3,5-bis-
(trifluoromethyl)phenylacetic acid (4b) using methods
described previously.6,10,13 The amino groups of 6a and
6b were protected with trifluoroacetyl (TFA) and tert-
butyloxycarbonyl (t-BOC), respectively. The nitro groups
of 7a ,b were reduced via catalytic hydrogenation using
Pd/C or Raney Nickel, respectively, to give the aniline
derivatives 8a ,b. Iodination of 8a ,b with 1 equiv of
benzyltrimethylammonium dichloroiodate (BTMACl2I)
according to Kajigaeshi et al.14 led to the 3′-iodo analogs
9a ,b. An additional 3 equiv of BTMACl2I added in
portions over a 3 day period was required to convert 8a
completely to the diiodo derivative 10a . Interestingly,
the diiodo product 10a was often isolated as light pink
to reddish crystals. We found that the minor side
product 11 (Scheme 2) was responsible for the reddish
coloration. TLC analysis of the reaction mixture and
isolated crude product indicates that compound 11 is
formed mostly during workup. Compound 11 was
isolated by flash chromatography. The structure of 11
1
and its deacetylation product 12 was proven by H and
13C NMR and elemental analysis. Compound 11 was
also isolated in an attempt to convert the 4′-amino of
10a to a hydrazine group. Thus, diazotization of 10a
followed by reduction with H2SO3 gave compound 11
as the only isolated product in low yield.
While reaction of 10a with acetic anhydride at room
temperature did not give the desired 4′-acetamido
derivative 13, heating 10a in acetic anhydride at reflux
resulted in the diacetylation product 16 (Scheme 3).
Ch em istr y
We have composed a convenient protection scheme
for the synthesis of the desired trimetoquinol analogs.

Iodinated Analogs of Trimetoquinol
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19 3703
Sch em e 2a
a
(a) 5 equiv of BTMACl2I, MeOH, CH2Cl2, 5 days; (b) K2CO3, MeOH, H2O; (c) 1. NaNO2, H2SO4, AcOH, 2. H2SO3.
Sch em e 3a
a
(a) AcCl, Et3N, DMAP; (b) K2CO3, MeOH, H2O; (c) 1. BBr3, CH2Cl2, 2. MeOH; (d) Ac2O, reflux; (e) 1. NaNO2, H2SO4, AcOH, 2.
H3PO2 or KI.
Similar diacetylation has been reported with the reac-
tion of 2,6-dibromo-4-toluidine with refluxing acetic
anhydride while lower temperatures gave a mixture of
mono- and diacetylated products.15 With this result in
mind, monoacetylation was accomplished by reacting
10a with 5 equiv of acetyl chloride in the presence of
4-(dimethylamino)pyridine (DMAP) and triethylamine
at room temperature to afford 13. Basic hydrolysis of
the trifluoroacetyl protecting group of 10a and 13 gave
20c and 14, respectively. The methoxy derivatives 20c,
14, and 6c were demethylated with BBr3 to afford the
desired trimetoquinol analogs 21c, 15, and 27, respec-
tively, as hydrobromide salts (Schemes 1 and 3). In a
similar manner, the 6,7-bis(benzyloxy)-1-(3,5-diiodo-4-
methoxybenzyl)-1,2,3,4-tetrahydroisoquinoline10 (17) was
dealkylated with BBr3 to give 6,7-dihydroxy-1-(3,5-di-
iodo-4-hydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline (18),
the demethyl analog of 2. Diazotization of 10a (Scheme
3) followed by reaction of the diazonium salt with H3-
PO2 or potassium iodide (KI) gave the diiodo and triiodo

3704 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19
De Los Angeles et al.
Sch em e 4a
a
(a) AcCl, Et3N; (b) K2CO3, MeOH, H2O; (c) 1. BBr3, CH2Cl2, 2. MeOH; (d) Ac2O, 4 or PhCOCl, Et3N; (e) 1. TMSI, MeCN, 2. MeOH.
derivatives, 19a and 19b, respectively. Basic hydrolysis
of the trifluoroacetyl group of 19a ,b as before gave
20a ,b. Demethylation of 20a ,b with BBr3 proceeded
smoothly to give 21a ,b. Compound 9a was acylated
with acetic anhydride in refluxing benzene to give 22
which was deprotected in the same manner as 14 to give
23 (Scheme 4).
Resu lts a n d Discu ssion
We have modified the trimethoxybenzyl portion of
trimetoquinol by replacing one or more of the methoxy
groups with a variety of halogenated substitutions. The
effects of these modifications on the receptor binding
affinity of trimetoquinol analogs (Table 1) for human
â2-AR expressed in CHO cells and human TP receptors
(platelets) were determined by radioligand competition
binding assays using [125I]iodocyanopindolol (ICYP) and
[3H]-SQ 29548 as radioligands, respectively.
However, attempts to demethylate 23 with BBr3
failed to give the desired product 26a . Surprisingly, the
amide bond of 23 was cleaved to give aniline 24. This
indicates the importance of both o-iodine atoms as a
sterical hindrance toward cleavage of the acetamido
group of 14 by BBr3. Thus, we turned our attention to
trimethylsilyl iodide (TMSI) as a mild reagent for ether
cleavage. However, this agent was too weak to effect
demethylation of 23; therefore, the catechol O-methyl
ether protecting groups were changed to benzyl ethers.
Hence, compounds 26a and 26b were prepared from the
O-benzyl and N-t-BOC protected 9b (Scheme 4). The
acylated compounds 25a and 25b were deblocked using
TMSI. Initially, using the procedure of Lott16 (TMSI,
MeCN, 50 °C 2 h), amide 25a gave the desired amide
26a along with a significant amount of the deacetylation
product 24. Ordinarily, amides are stable to TMSI. To
optimize the selectivity, we monitored the TMSI depro-
tection reaction by NMR spectroscopy at room temper-
ature. The O-benzyl protecting groups were removed
within 6 h, and no cleavage of the amide bond was
observed at this temperature for 20 h. Thus, using the
reaction conditions 4-6 equiv of TMSI, MeCN, room
temperature, 6 h, we obtained 26a and 26b from 25a
and 25b, respectively.
â2-Ad r en ocep tor s. In this study, most of the modi-
fications made on the trimethoxybenzyl portion of
trimetoquinol resulted in enhancement of â2-AR affinity.
Previously, it was shown that replacement of the 3′- and
5′-methoxy groups of trimetoquinol with iodines [i.e., 1
(pKi ) 7.36) f 2 (pKi ) 8.69)] resulted in a greater than
20-fold increase in affinity.8 In the present study,
complete replacement of the 3′-, 4′-, and 5′-methoxy
groups of trimetoquinol (1) with iodine atoms to give
the triiodo analog 21b (pKi ) 8.82) enhanced â2-
adrenoceptor affinity 29-fold versus trimetoquinol (1),
but with respect to 2, the additional iodine substituent
at the 4′-position adds little to the binding affinity.
Studies on human â2-AR indicate that 4′-position
substituents reflecting varying size and chemical prop-
erties are well tolerated. Replacement of the 4′-methoxy
of 2 with an amino group [i.e., 2 f 21c (pKi ) 8.81)]
did not significantly alter affinity, and replacement with
a 4′-acetamido [i.e., 15 (pKi ) 8.06)] reduced affinity only
4-fold. A similar replacement with a hydroxy (i.e., 18,
pKi ) 7.93) reduced affinity about 5-fold as compared
to 2. The receptor binding pocket that interacts with
substituents at the 4′-position seems to be sufficiently
large to accommodate the 4′-benzamido moiety of 26b
(pKi ) 8.70). Interestingly, the diiodo analog 21a (pKi
) 9.52), which lacks a 4′-substituent, exhibits the most
potent affinity with a Ki value in the subnanomolar
range. Thus, while a wide range of substituents at the
4′-position are accepted by the receptor binding pocket,
these 4′-substituents contribute little to binding affinity.
Based on the present binding data, this binding pocket
is best left unoccupied for maximum binding affinity;
on the other hand, we are carrying out further inves-
tigations to find the optimum substituent at the 4′-
position that will take advantage of the pocket in this
region for additional binding interactions.
The proton NMR spectra of synthesized compounds
were quite complicated, especially the 2-t-BOC deriva-
tives which displayed complex splitting patterns reflect-
ing two relatively stable conformations with ratios
ranging from 5:2 to 5:4, similar to those observed for
N-Ac- and N-Me-substituted tetrahydroisoquinolines.17,18
However, the 13C NMR spectra of 1-benzyltetrahy-
droisoquinolines can be easily used for structure iden-
tification because of their relative simplicity. Assign-
ments of signals (final compounds) were made based on
the 13C NMR spectra of salsolinol,19 effects of substit-
uents on the benzene ring, and off-resonance spectra.
For 2-TFA derivatives, the chemical shift of the C-3
atom appears as a quartet (4J C-F ≈ 3.7 Hz) indicating
its close proximity to the CF3 group.

Iodinated Analogs of Trimetoquinol
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19 3705
Ta ble 1. Human â2-Adrenoceptors (AR) Expressed in CHO Cells and Platelet Thromboxane A2/Prostaglandin (TP) Receptor Binding
Affinities of Trimetoquinol (TMQ) Analogs
1-benzyl substituents
R2
human â2-AR CHOa
human TP receptorsb
compound
R1
R3
pKi ( SEM
PRc
pKi ( SEM
PRc
1
2
21c
24
15
26a
21a
21b
26b
18
OCH3
I
I
I
I
I
I
I
OCH3
OCH3
NH2
NH2
NHCOCH3
NHCOCH3
H
I
OCH3
I
I
H
I
H
I
I
7.36 ( 0.23
8.69 ( 0.16
8.81 ( 0.15
8.19 ( 0.27
8.06 ( 0.13
8.11 ( 0.16
9.52 ( 0.13
8.82 ( 0.18
8.70 ( 0.03
7.93 ( 0.03
5.36 ( 0.32
1.0
21
28
6.8
5.0
5.6
150
29
22
3.7
0.01
6.79 ( 0.09
7.33 ( 0.07
6.73 ( 0.12
6.00 ( 0.02
6.45 ( 0.11
5.83 ( 0.14
6.75 ( 0.07
4.22 ( 0.03
5.27 ( 0.13
4.72 ( 0.09
4.08 ( 0.02
1.00
3.5
0.87
0.16
0.46
0.11
0.91
0.003
0.03
0.009
0.002
I
I
NHCOPh
OH
H
H
I
CF3
27
CF3
a
b
Using [125I]ICYP as radioligand, N ) 4-9. Using [3H]-SQ 29548 as radioligand, N ) 4-9. c PR ) potency ratio relative to 1 (TMQ).
PR ) antilog [pKi(drug) - pKi(TMQ)].
Apparently, one m-iodo substituent is sufficient to
retain high affinity since removing one of the iodo
groups of either 21c or 15 [i.e., 21c f 24 (pKi ) 8.19)
or 15 f 26a (pKi ) 8.11)] resulted in only minor shifts
in affinity. To determine the nature (hydrophobic or
electronic) of the binding contributions of 3′- and 5′-
substituents (methoxy and iodo), we synthesized the bis-
(trifluoromethyl) analog 27. While the hydrophobic
property (π) of the trifluoromethyl group (π ) 0.88) is
similar to iodine (π ) 1.12), this functional group exerts
a much stronger electron-withdrawing effect. The bind-
ing affinity of the bis(trifluoromethyl)analog 27 (pKi )
5.36) was 4 orders of magnitude lower than the diiodo
analog 21a . Thus, trifluoromethyl substituents at the
3′- and 5′-positions abolish binding affinity. Since a
trifluoromethyl group is similar in size to an iodine
atom, the significantly stronger electron-withdrawing
property of the trifluoromethyl (σp ) 0.54 versus σp )
0.18 for iodine) is likely responsible for the greatly
reduced binding affinity of 27. The electron-withdraw-
ing effect of the trifluoromethyl substituents on the
π-electron system of the aromatic ring may interfere
with its capability to form aromatic interactions with
the receptor binding site. These aromatic interactions
may be more important for binding than hydrophobic
interactions.
â2/â1 Selectivity. Although replacement of the 3′-
and 5′-methoxy groups of trimetoquinol 1 with iodine
atoms (i.e., 2) resulted in a 21-fold increase in â2-AR
affinity, a similar increase in binding affinity was not
observed for â1-AR (Table 2). As a result, the diiodo
analog 2 exhibits moderate (ca. 40-fold) selectivity for
â2-AR versus â1-AR. More importantly, the influence
of a 4′-substituent is markedly different for â2-AR versus
â1-AR. While the absence of a 4′-substituent (i.e., 21a )
does not significantly alter â1-AR affinity (pKi ) 6.74),
the same feature increased â2-AR affinity. Conse-
quently, analog 21a displays more than 600-fold selec-
tivity for â2-AR versus â1-AR, and is the most selective
trimetoquinol analog yet reported. These results indi-
cate a remarkable difference in the receptor binding site
Ta ble 2. Selectivity of Trimetoquinol (TMQ) Analogs for
Human â2- and â1-Adrenoceptors (AR) Expressed in CHO Cells
pKi ( SEM
compound human â1 CHOa human â2 CHOa â2/â1 selectivityb
1
2
21a
6.49 ( 0.06
7.10 ( 0.06
6.74 ( 0.30
7.36 ( 0.23
8.69 ( 0.16
9.52 ( 0.13
7.4
39
600
a
Using [125I]ICYP as radioligand for â1- and â2-AR expressed
b
in CHO cells, N ) 4-9. â2/â1 selectivity ) Ki(â1-AR)/Ki(â2-AR).
or pocket of â2- and â1-AR that interacts with substit-
uents at the 4′-position of trimetoquinol analogs.
TP Recep tor s. In general, replacement of the 3′-
and 5′-methoxy groups of trimetoquinol (1, pKi ) 6.79)
with iodine to give analog 2 (pKi ) 7.33) resulted in only
a slight increase (3-fold) in affinity. However, replace-
ment of all three methoxy groups of trimetoquinol with
iodines to give the triiodo analog 21b (pKi ) 4.22)
practically abolished binding to TP receptors. In addi-
tion, demethylation of the 4′-methoxy substituent of 2
to give 18 (pKi ) 4.72) resulted in a similar 380-fold
reduction in binding affinity. The very low binding
affinity of 18 contrasts with a recent observation20
where 6,7-dihydroxy-1-(4′-hydroxy-3′-nitrobenzyl)-1,2,3,4-
tetrahydroisoquinoline exhibited good binding affinity.
By contrast, substitution of the same methoxy group
with an amino moiety (i.e., 21c, pKi ) 6.73) resulted in
only a 3-fold decrease in affinity. Interestingly, removal
of the 4′-substituent of 2 or 21c to give 21a (pKi ) 6.75)
did not affect binding affinity significantly. Acetylation
of the 4′-amino group of 21c was also tolerated as 15
(pKi ) 6.45) displayed binding affinity similar to 21c.
Thus, while a primary amine, acetamide, or a methoxy
group is tolerated at the 4′-position, a free hydroxy
group or an iodo group is detrimental to binding affinity.
Removal of one of the iodines of 21c and 15 to give 24
(pKi ) 6.00) and 26a (pKi ) 5.83), respectively, resulted
in a 5-fold decrease in binding affinity, suggesting that
hydrophobic interactions of 3′- or 5′-substituents con-
tribute to binding. However, replacement of the 3′- and
5′-iodo groups of 21a with similarly hydrophobic tri-

3706 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19
De Los Angeles et al.
residue was taken up in CH2Cl2. The solution was washed
consecutively with 0.1 N HCl (30 mL), H2O (50 mL), 0.1 N
NaOH (30 mL), and H2O (50 mL) and dried over MgSO4. The
solvent was evaporated, and the crude solid was recrystallized
from toluene to give 3.44 g (79%) of the product as white
needles: mp 127-128 °C; 1H NMR (CDCl3) δ 7.79 (s, 1H, ArH),
7.72 (s, 2H, ArH), 6.75 (d, J ) 8.1 Hz, 1H, ArH), 6.67 (d, J )
1.9 Hz, 1H, ArH), 6.61 (dd, J ) 8.1 & 1.9 Hz, 1H, ArH), 5.55
(m, 1H, NH), 3.85 (s, 3H, OMe), 3.84 (s, 3H, OMe), 3.58 (s,
2H, CH2), 3.52 (q, J ) 6.9 Hz, 2H, CH2N), 2.75 (t, J ) 6.9 Hz,
CH2); 13C NMR (CDCl3) δ 168.72, 149.20, 147.87, 137.28,
131.90, 130.79, 129.47, 123.16, 121.20, 120.56, 111.72, 111.27,
55.83, 42.85, 40.90, 34.97; IR (KBr) 3323 (NH), 1651 (CdO)
cm-1. Anal. (C20H13F6NO3) C, H, N.
fluoromethyl substituents resulted in a drastic reduction
in binding affinity. As with â2-AR, in terms of contribu-
tion to the overall binding affinity, hydrophobic interac-
tions appear secondary to aromatic interactions.
Con clu sion s
In this study, we have shown that substitution on the
trimethoxybenzyl portion of trimetoquinol (1) has a
major role in the type and potency of biological activity
expressed. 3′- and 5′-diiodo substitution on the 1-benzyl
moiety significantly improved binding affinity at â2-AR,
while having very little effect on â1-AR and TP receptor
binding. The role of the 4′-position is particularly
interesting in that the binding pocket that interacts
with this substituent is more discriminating in TP
receptors, while that of the â2-AR can accommodate
more varied groups. Our studies indicate that these
modifications of trimetoquinol (1) have provided a
further separation of â2-AR versus TP receptor affinities,
and the presence of 3′,4′,5′-triiodo substitution on the
1-benzyl group (i.e., 21b) produced 25 000-fold selectiv-
ity for â2-AR. Moreover, the type (or the lack) of
substitution at the 4-position may be key to the design
of â2-AR selective ligands based on the parent drug,
trimetoquinol (1).
6,7-Dim eth oxy-1-(4-n itr oben zyl)-1,2,3,4-tetr a h yd r oiso-
qu in olin e (6a ). A mixture of 5a (8.0 g, 23.2 mmol) and POCl3
(15.6 mL, 167.4 mmol) in dry MeCN (160 mL) was heated at
reflux for 4 h. The solvent was evaporated in vacuo to give a
glassy residue which was taken up in methanol (250 mL) and
evaporated to dryness 3 times until the residue was a solid.
The solid residue was dissolved in MeOH (250 mL) and then
cooled in an ice bath. Excess NaBH4 (17.56 g, 167.4 mmol)
was carefully added in portions. The mixture was stirred at
room temperature overnight. The solvent was removed in
vacuo, and the solid residue was partitioned in CH2Cl2 (250
mL) and H2O (150 mL). The layers were separated, and the
H2O layer was extracted with CH2Cl2 (100 mL). The combined
organic fraction was washed successively with H2O (2 × 50
mL), 2 N NaOH (2 × 50 mL), and H2O (50 mL) and dried with
Na2SO4. The solvent was evaporated to give a reddish oil. The
oil was taken up in a minimum amount of methanol. The
product crystallized upon standing and was collected by
Exp er im en ta l Section
Ch em istr y. Melting points were determined on a Thomas-
Hoover capillary melting point apparatus and are uncorrected.
Infrared spectra were recorded on a Perkin Elmer System 2000
FT-IR. Proton and carbon-13 magnetic resonance spectra were
obtained on a Bruker AX 300 spectrometer (300 and 75 MHz
for 1H and 13C, respectively). Chemical shift values are
reported as parts per million (δ) relative to tetramethylsilane
(TMS). Spectral data are consistent with assigned structures.
Elemental analyses were performed by Atlantic Microlab Inc.,
Norcross, GA, and found values are within 0.4% of the
theoretical values. Routine thin-layer chromatography (TLC)
was performed on silica gel GHlF plates (250 m, 2.5 × 10 cm;
Analtech Inc., Newark, DE). Flash chromatography was
performed on silica gel (Merck, grade 60, 230-400 mesh, 60
Å). Tetrahydrofuran (THF) was dried by distillation from
sodium metal, and acetonitrile (MeCN), CHCl3, and methylene
chloride (CH2Cl2) were dried by distillation from P2O5. All
anhydrous solvents (except anhydrous Et2O and THF) were
stored over 3- or 4-Å molecular sieves.
1
filtration (3.02 g, 40%): mp 134-136 °C; H NMR (CDCl3) δ
8.18 (d, J ) 8.7 Hz, 2H, ArH), 7.43 (d, J ) 8.7 Hz, 2H, ArH),
6.62 (s, 1H, ArH), 6.61 (s, 1H, ArH), 4.44 (dd, J ) 9.5, 4.1 Hz,
ArCH-N), 3.87 (s, 3H, OMe), 3.84 (s, 3H, OMe), 3.28 (dd, J )
13.7, 4.1 Hz, 1H, ArCH2), 3.23-3.15 (m, 1H, NCH), 3.04 (dd,
J ) 13.7, 9.5 Hz, 1H, ArCH), 3.00-2.91 (m, 1H, NCH), 2.71
(m, 2H, ArCH2); IR (KBr) 3337 (NH), 1515, 1345 (NO2) cm-1
Anal. (C18H20N2O4) C, H, N.
.
6,7-Dim e t h oxy-1-[3,5-b is[(t r iflu or om e t h yl)b e n zyl]]-
1,2,3,4-tetr a h yd r oisoqu in olin e Hyd r och lor id e (6c‚HCl).
The amide 5c (1.31 g, 3 mmol) was cyclized in the same
manner as 6a (7 mL of 1 M HCl in ether was added to the
methanolic solution of a crude product) to give 6c (0.84 g, 60%)
1
as a hydrochloride salt: mp 104-115 °C (MeOH-ether); H
NMR (CDCl3) δ 10.34 (bs, 2H, NH), 7.82 (s, 1H, ArH), 7.75 (s,
2H, ArH), 6.61 (s, 1H, ArH), 5.87 (s, 1H, ArH), 4.77 (m, 1H,
CH), 3.91 (m, 1H, CH), 3.84 (s, 3H, OMe), 3.47 (s, 3H, OMe),
3.44 (m, 2H, CH), 3.28 (m, 2H, CH), 3.02 (m, 1H, CH); 13C
NMR (CDCl3) δ 149.29, 147.74, 138.74, 132.08, 130.39, 123.33,
123.07, 121.40, 111.71, 109.43, 55.92, 55.38, 54.94, 40.46,
N -(3,4-Dim e t h oxyp h e n e t h yl)-4-n it r op h e n yla ce t a m -
id e (5a ). A solution of 3,4-dimethoxyphenethylamine (5.0 g,
27.6 mmol) and 4-nitrophenylacetic acid (7.5 g, 41.4 mmol) in
toluene (150 mL) was heated at reflux for 72 h in a flask
equipped with a Dean-Stark trap under an argon atmosphere.
The solvent was evaporated in vacuo, and the residue was
taken up in CH2Cl2 (200 mL). The solution was washed
consecutively with H2O (100 mL), 10% HCl (2 × 100 mL), H2O
(2 × 100 mL), 10% NaHCO3 (2 × 200 mL), and H2O (2 × 100
mL) and dried over MgSO4. The solvent was evaporated, and
the crude solid was recrystallized from EtOAc to give 5.49 g
(58%) of the product as ivory-colored needles: mp 119-121
38.30, 24.80; IR (KBr) 3600-2400 (NH2), 1614, 1522 cm-1
Anal. (C20H19F6NO2‚HCl‚0.5H2O) C, H, N.
.
6,7-Dim et h oxy-1-(4-n it r ob en zyl)-2-(t r iflu or oa cet yl)-
1,2,3,4-tetr a h yd r oisoqu in olin e (7a ). A solution of 6,7-
dimethoxy-1-(4-nitrobenzyl)-1,2,3,4-tetrahydrisoquinoline (6a )
(3.0 g, 9.14 mmol) in dry THF (150 mL) was added to
trifluoroacetic anhydride (20 mL) with stirring at 0 °C. The
mixture was stirred at room temperature overnight with the
flask equipped with a CaCl2 drying tube. The reaction mixture
was poured onto ice (200 g) and the mixture stirred for 30 min.
CH2Cl2 (200 mL) was added, and stirring was continued for
10 min. The layers were separated, and the organic layer was
washed consecutively with H2O (50 mL), 0.2 N NaOH (100
mL), and H2O (100 mL) and then dried with Na2SO4. The
solvent was evaporated in vacuo to give a yellow solid.
Recrystallization from EtOAc-MeOH gave 1.94 g (50%) of
yellow crystals: mp 162-164 °C; 1H NMR (CDCl3) δ 8.14 (m,
2H, ArH), 7.28 (m, 2H, ArH), 6.62 (s, 1H, ArH), 6.34 (s, 1H,
ArH), 5.64 (t, J ) 6.7 Hz, ArCH-N), 3.87 (s, 3H, OMe), 3.72
(s, 3H, OMe), 3.3-3.6 (m, 2H, N-CH2), 3.25 (d, 2H, ArCH2),
2.98-2.6 (m, 2H, ArCH2); IR (KBr) 1686 (CdO), 1519, 1340
1
°C (lit.22 130-132 °C, ethanol-2-propanol); H NMR (CDCl3)
δ 8.16 (d, J ) 8.8 Hz, 2H, ArH), 7.37 (d, J ) 8.8 Hz, 2H, ArH),
6.73 (d, J ) 8.1 Hz, 1H, ArH), 6.65 (d, J ) 1.9 Hz, 1H, ArH),
6.60 (dd, J ) 8.1 & 1.9 Hz, 1H, ArH), 5.40 (m, 1H, NH), 3.86
(s, 3H, OMe), 3.84 (s, 3H, OMe), 3.59 (s, 2H, CH2), 3.51 (q, J
) 6.9 Hz, 2H, CH2), 2.73 (t, J ) 6.9 Hz, CH2); IR (KBr) 3320
(NH), 1650 (CdO) cm-1. Anal. (C18H20N2O5) C, H, N.
N-(3,4-Dim eth oxyp h en eth yl)-3,5-bis(tr iflu or om eth yl)-
p h en yla ceta m id e (5c). A solution of 3,4-dimethoxyphen-
ethylamine (2.72 g, 15 mmol) and 3,5-bis(trifluoromethyl)-
phenylacetic acid (2.72 g, 10 mmol) in toluene (50 mL) was
heated at reflux for 80 h in a flask equipped with a Dean-
Stark trap. The solvent was evaporated in vacuo, and the
(NO2) cm-1
(C20H19F3N2O5) C, H, N.
;
MS m/e (M+) 423 (M+H, FAB). Anal.

Iodinated Analogs of Trimetoquinol
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19 3707
6,7-Bis(b e n zyloxy)-2-(t er t -b u t oxyca r b on yl)-1-(4-n i-
tr oben zyl)-1,2,3,4-tetr a h yd r oisoqu in olin e (7b). A solution
of (Boc)2O (2.84 g, 13 mmol) in THF (10 mL) was added to a
cold mixture (ice bath) of isoquinoline 6b (6.20 g, 12 mmol) in
THF (100 mL) and 1 N NaOH solution (30 mL). The ice bath
was removed, and stirring was continued at room temperature
overnight. THF was evaporated under reduced pressure,
water was added, and the product was extracted with CH2-
Cl2, dried over MgSO4, filtered, and evaporated again. The
oily residue was dissolved in ether and put in a refrigerator.
Pink crystals were filtered and washed with ether to give 6.00
g (86%) of the title compound: mp 150-152 °C; 1H NMR
(CDCl3) δ (the spectrum consists of two rotamers of 5:4 ratio)
8.11 and 8.06 (d, J ) 8.2 Hz, 2H, ArH), 7.47-7.27 and 7.21-
7.11 (m, 12H, ArH), 6.70 and 6.67 (s, 1H, H-5), 6.56 and 6.44
(s, 1H, ArH), 5.27-4.96 (m, 5H, CH2O + CH), 4.12 and 3.74
(m, 1H, CH), 3.25-3.00 (m, 3H, CH, CH2Ar), 2.87-2.60 (m,
1H, CH), 2.57-2.37 (m, 1H, CH), 1.38 and 1.25 (s, 9H, t-Bu);
ture of isoquinoline 8b (1.11 g, 3.2 mmol), BTMACl2I (1.1 g,
3.2 mmol), and CaCO3 (0.44 g, 4.4 mmol) in CH2Cl2 (50 mL)
and MeOH (20 mL) was stirred overnight at room tempera-
ture. CaCO3 was filtered and washed with CH2Cl2. The
filtrate was washed with a solution of Na2S2O3 (×2) and H2O
(×2), dissolved in CHCl3 and EtOH, and concentrated till the
beginning of crystallization to give 1.59 g (81%) of title
compound as pink crystals: mp 169-171 °C; 1H NMR (CDCl3)
δ (the spectrum consists of two rotamers of 2:1 ratio) 7.47-
7.25 (m, 11H, ArH), 6.81 (dd, J ) 8.1, 1.6 Hz, 1H, ArH), 6.70-
6.59 (m, 2H, ArH), 6.49 and 6.30 (s, 1H, ArH), 5.20-5.85 (m,
5H, CH2O + CH), 4.13 and 3.74 (m, 1H, CH), 4.01 (s, NH2),
3.30-3.10 (m, 1H, CH), 2.96-2.59 (m, 3H, CH2Ar + CH),
2.59-2.43 (m, 1H, CH), 1.44 and 1.32 (s, 9H, t-Bu); IR (KBr)
3453 and 3334 (NH2), 1667 (CdO), 1627 (NH bend), 1520 and
1498 (CdC Ar) cm-1. Anal. (C35H37IN2O4) C, H, N.
1-(4-Am in o-3,5-d iiod oben zyl)-2-(tr iflu or oa cetyl)-6,7-d i-
m eth oxy-1,2,3,4-tetr a h yd r oisoqu in olin e (10a ). To a solu-
tion of 8a (0.1 g, 2.54 mmol) in CH2Cl2 (50 mL) and methanol
(20 mL) was added BTMACl2I (2.0 g, 5.77 mmol) and CaCO3
(2.0 g). The mixture was stirred overnight at room tempera-
ture. A second portion of BTMACl2I (0.97 g, 2.8 mmol) was
added, and stirring was continued overnight. Analysis of the
reaction indicated a mixture of mono- and diiodinated prod-
ucts. The reaction mixture was filtered. The filtrate was
washed consecutively with aqueous 5% Na2S2O3 (40 mL) and
water (50 mL), and then dried with Na2SO4. Evaporation of
the solvent gave a reddish glassy solid. The desired diiodi-
nated product was purified from the crude mixture by flash
chromatography (CH2Cl2-EtOAc, 9:1). The appropriate frac-
tions were combined and evaporated in vacuo to give 0.72 g
IR (KBr) 1688 (CdO), 1518, 1345 (NO2) cm-1
.
Anal.
(C35H36N2O6) C, H, N.
1-(4-Am in ob en zyl)-6,7-d im et h oxy-2-(t r iflu or oa cet yl)-
1,2,3,4-tetr a h yd r oisoqu in olin e (8a ). A solution of 7a (5.20
g, 12.24 mmol) in ethyl acetate (200 mL) was hydrogenated
(60 psi) over 5% Pd/C (1 g) for 2 h. The catalyst was removed
by filtration, and the filtrate was evaporated to dryness to give
a beige solid. Recrystallization from ethyl acetate and hexane
gave 4.20 g (87%) of the product as light pink to white
crystals: mp 157-160 °C; 1H NMR (CDCl3) δ 6.88 (d, 2H,
ArH), 6.59 (d, 3H, ArH), 6.32 (s, 1H, ArH), 5.53 (t, 1H, ArCH-
N), 3.99 (m, 1H, CH), 3.86 (s, 3H, OMe), 3.71 (s, 3H, OMe),
3.60 (bs, 2H, NH2), 3.42-3.56 (m, 2H, CH), 2.85-3.20 (m, 3H,
CH), 2.59-2.73 (m, 1H, CH); IR (KBr) 3370 (m, NH2), 1689
1
(44%) of the product as a white solid: mp 183-184.5 °C; H
(CdO) cm-1
(C20H21F3N2O3) C, H, N.
;
MS m/e (M+) 395 (M+H, FAB). Anal.
NMR (CDCl3) δ 7.37 (s, 2H, ArH), 6.61 (s, 1H, ArH), 6.29 (s,
1H, ArH), 5.43 (m, 1H, ArH), 4.56 (bs, 2H, NH2), 3.87 (s, 3H,
OMe), 3.73 (s, 3H, OMe), 3.60 (m, 1H, CH), 2.91 (m, 4H, CH),
1-(4-Am in ob en zyl)-6,7-b is(b en zyloxy)-2-(ter t-b u t oxy-
ca r bon yl)-1,2,3,4-tetr a h yd r oisoqu in olin e (8b). The nitro
compound 7b (6.00 g, 10.3 mmol) was dissolved in EtOAc (230
mL) in a Parr bottle. The solution was charged with a slurry
of Raney-Ni (4 mL) and hydrogenated at 50 psi for 3 h. The
solution was filtered through Celite and evaporated to give
5.10 g (90%) of the crude compound. The product was purified
by flash chromatography (silica gel, hexane-EtOAc, 2:1) to
give a foamy glassy solid (4.51 g, 71%); 1H NMR (CDCl3) δ
(the spectrum consists of two rotamers of 5:2 ratio) 7.48-7.24
(m, 10H, 2×Ph), 6.82 (m, J ) 8.2 Hz, ArH), 6.68 and 6.64 (s,
1H, ArH), 6.58 (m, J ) 8.2 Hz, 2H, ArH), 6.49 and 6.32 (s,
1H, ArH), 5.12-4.81 (m, 5H, 2×CH2O + CH), 4.18-4.08 and
3.81-3.71 (m, 1H, CH), 3.27-3.09 (m, 1H, CH), 3.00-2.60 (m,
3H, CH2Ar, CH), 2.59-2.40 (m, 1H, CH), 1.43 and 1.32 (s, 9H,
t-Bu); IR (KBr) 3451 and 3365 (NH2), 1684 (CdO), 1624 (NH
bend), 1517 (CdC Ar) cm-1. Anal. (C35H38N2O4) C, H, N.
1-(4-Am in o-3-iod ob en zyl)-6,7-d im et h oxy-2-(t r iflu or o-
a cetyl)-1,2,3,4-tetr a h yd r oisoqu in olin e (9a ). A mixture of
isoquinoline 8a (6.26 g, 18 mmol), benzyltrimethylammonium
dichloroiodate (BTMAICl2) (8.15 g 18 mmol), and CaCO3 (2.30
g, 23 mmol) in CH2Cl2 (200 mL) and absolute MeOH (80 mL)
was stirred overnight at room temperature; then BTMAICl2
(0.31 g, 0.9 mmol) was added and stirred for 1 h. The solution
was filtered, washed with Na2S2O3 solution and water, dried
over MgSO4, and concentrated under reduced pressure. Re-
crystallization of the residue from AcOEt gave the title
compound (7.90 g, 84%): mp 198-200 °C (dec); 1H NMR
(CDCl3) δ 7.34 (d, J ) 2.0 Hz, 1H, ArH), 6.90 (dd, J ) 2.0, 8.1
Hz, 1H, ArH), 6.66 (d, J ) 8.1 Hz, 1H, ArH), 6.59 (s, 1H, ArH),
6.29 (s, 1H, ArH), 5.48 (t, J ) 6.6 Hz, 1H, CH), 4.03 (s, 2H,
NH2), 3.93 (m, 1H, CH), 3.86 (s, 3H, OMe), 3.71 (s, 3H, OMe),
3.53 (ddd, J ) 14.3, 10.8, 4.0 Hz, 1H, CH), 2.96 (m, 2H, CH2-
Ar), 2.90 (ddd, J ) 15.9, 10.6, 5.6 Hz, 1H, CH), 2.68 (dt, J )
16.2, 4.2 Hz, 1H, CH); 13C NMR (CDCl3) δ 155.75 (q), 148.10,
147.41, 145.63, 139.77, 130.64, 128.46, 126.45, 124.86, 116.47
(q), 114.51, 110.96, 110.30, 83.64, 55.86, 55.79, 55.48, 40.41,
28.52; IR (KBr) 3435 and 3344 (NH2), 1693 (CdO), 1627 (NH
bend), 1521 and 1501 (CdC Ar) cm-1. Anal. (C20H20F3IN2O3)
C, H, N.
2.70 (m, 1H, CH); IR (KBr) 3429, 3348 (NH), 1685 (CdO) cm-1
.
Anal. (C20H19F3I2N2O3) C, H, N.
4′,4′′-Azobis[1-(4-am in o-3,5-diiodoben zyl)-6,7-dim eth oxy-
2-(tr iflu or oa cetyl)-1,2,3,4-tetr a h yd r oisoqu in olin e] (11)
was isolated from the above mixture as a bottom spot, deep
purple solid: mp 229-232 °C; 1H NMR (CDCl3) δ 7.78 (s, 2H,
ArH), 6.65 (s, 1H, ArH), 6.18 (s, 1H, ArH), 5.53 (dd, J ) 7.9,
5.6 Hz, 1H, ArH), 3.99 (m, 1H, CH), 3.88 (s, 3H, OMe), 3.74
(m, 1H, CH), 3.72 (s, 3H, OMe), 3.16 (dd, J ) 13.0, 5.3 Hz,
1H, CH), 2.96 (m, 2H, CH), 2.80 (dt, J ) 16.2, 4.5 Hz, 1H,
CH); 13C NMR (CDCl3) δ 156.14 (q), 148.89, 148.54, 147.59,
142.27, 141.53, 125.60, 125.05, 116.47 (q), 111.28, 110.42,
89.83, 56.15, 56.01, 55.54, 40.88 (q), 40.60, 28.45; IR (KBr) 1688
(CdO), 1520 (CdC Ar) cm-1
. Anal. (C40H34F6I4N4O6) C, H,
N.
The same product was obtained via diazotization of 10a
(0.32 g, 0.5 mmol, see below) and stirring overnight with 20
mL of 6% H2SO3 at room temperature, yield 0.03 g (10%) after
flash column chromatography.
4′,4′′-Azobis[1-(4-am in o-3,5-diiodoben zyl)-6,7-dim eth oxy-
1,2,3,4-tetr a h yd r oisoqu in olin e] (12). A solution of azo
compound 11 (0.26 g, 0.2 mmol) in 35 mL of MeOH and 0.85
g of K2CO3 in 11 mL was refluxed for 4 h and evaporated. Flash
chromatography on silica gel (CH2Cl2, CH2Cl2-MeOH, 50:1,
30:1) gave 0.15 g (70%) of the product: mp 176-177 °C (dec);
1H NMR (300 MHz, CDCl3) δ 7.96 (s, 2H, ArH), 6.62 (s, 1H,
ArH), 6.61 (s, 1H, ArH), 4.20 (dd, J ) 9.6, 4.0 Hz, 1H, ArH),
3.87 (s, 3H, OMe), 3.86 (s, 3H, OMe), 3.10-3.30 (m, 2H, CH),
3.00 (m, 1H, CH), 2.68-2.90 (m, 2H, CH); 13C NMR (CDCl3) δ
148.43, 147.75, 147.21, 144.05, 141.87, 129.76, 127.43, 112.03,
109.34, 90.43, 56.61, 56.16, 55.88, 41.65, 40.51, 29.36; IR (KBr)
1515 (CdC, Ar) cm-1. Anal. (C36H36I4N4O4) C, H, N.
1-(4-Aceta m id o-3,5-d iiod oben zyl)-6,7-d im eth oxy-2-(tr i-
flu or oa cetyl)-1,2,3,4-tetr a h yd r oisoqu in olin e (13). A solu-
tion of acetyl chloride (0.80 g, 7.8 mmol) in dry THF (2 mL)
was added dropwise to a stirred solution of 10a (1.0 g, 1.56
mmol), Et3N (0.40 g, 7.8 mmol), and (N,N-dimethylamino)-
pyridine (DMAP, at 10 mg) in dry THF (20 mL) at 0 °C under
an argon atmosphere. After the addition, the reaction mixture
was allowed to warm to room temperature, and stirring was
continued overnight (14 h). The reaction was quenched with
1-(4-Am in o-3-iod oben zyl)-6,7-bis(ben zyloxy)-2-(ter t-bu -
toxycar bon yl)-1,2,3,4-tetr ah ydr oisoqu in olin e (9b). A mix-

3708 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19
De Los Angeles et al.
H2O (20 mL) and stirred for 30 min. The solution was
extracted with Et2OAc (3 × 75 mL). The organic extract was
washed with H2O (20 mL), dried (Na2SO4), and evaporated in
vacuo to give a tan solid. Recrystallization of the crude product
from EtOH and H2O gave 0.93 g (87%) of the title compound
as light beige needles: mp 218-219 °C; 1H NMR (CDCl3) δ
7.5-7.75 (bm, 2H, ArH), 6.96 (s, 1H, CONH), 6.62 (s, 1H, ArH),
6.24 (s, 1H, ArH), 5.47 (t, J ) 6.7 Hz, 1H, CH), 3.98 (m, 1H,
CH), 3.87 (s, 3H, OMe), 3.73 (s, 3H, OMe), 2.83-3.18 (m, 4H,
CH), 2.74 (m, 1H, CH), 2.22 (s, 3H, Ac); 13C NMR (CDCl3) δ
168.14, 156.02 (q), 148.39, 147.68, 140.58, 140.31, 139.35,
125.71, 124.85, 116.4 (q), 98.73, 56.09, 55.93, 55.44, 40.63 (q),
40.48, 28.43, 23.62; IR (KBr) 3387 (NH), 1683 (CO). Anal.
(C22H21F3I2N2O4) C, H, N.
washed with water, and dried over MgSO4. The solution was
filtered, evaporated, and dried under vacuum. The residue
was dissolved in CH2Cl2 (4 mL), and 1 M BBr3 in CH2Cl2 (1.39
mL, 1.39 mmol) was added at -78 °C under an argon
atmosphere. The mixture was stirred overnight at room
temperature followed by addition of MeOH (1 mL) and stirring
for 5 h. The resulting solution was evaporated with MeOH 5
times, and the residue was recrystallized from MeOH-ether
to give 0.078 g (45%) of white crystals: mp 235-237 °C (dec);
1H NMR (DMSO-d6) δ 9.50 (s, 1H, OH), 9.14 (s, 1H, OH), 8.89
(s, 1H, OH), 8.78 (br s, 1H, NH+), 8.43 (br s, 1H, NH+), 7.76
(s, 2H, ArH), 6.64 (s, 1H, ArH), 6.55 (s, 1H, ArH), 4.55 (m,
1H, CH), 3.40-3.05 (m, 3H, CH), 2.92-2.68 (m, 3H, CH); 13
C
NMR (CD3OD) δ 156.59 (C-4′), 146.96 and 145.85 (C-6 and
C-7), 141.69 (C-2′ and C-6′), 132.30 (C-1′), 123.71 and 123.24
(C-4a and C-8a), 116.25 (C-5), 114.14 (C-8), 85.85 (C-3′ and
C-5′), 57.55 (C-1), 41.08 (C-3), 39.12 (CH2Ar), 25.68 (C-4); IR
1-(4-Acetam ido-3,5-diiodoben zyl)-6,7-dim eth oxy-1,2,3,4-
tetr a h yd r oisoqu in olin e Hyd r och lor id e (14‚HCl). A solu-
tion of 13 (1.22 g, 1.78 mmol) in methanol (60 mL) was added
to a solution of K2CO3 (5.6 g) in 80 mL of 1:1 methanol and
water. The mixture was stirred at room temperature for 3 h.
The resulting solution was concentrated and then extracted
with ethyl acetate (3 × 80 mL). The organic solution was dried
(Na2SO4) and evaporated in vacuo to give 0.79 g (75%) of the
product as the free base. The free base converted to the
hydrochloride salt and recrystallized from anhydrous ethanol
and ethyl ether: mp 196-200 °C (dec); 1H NMR (DMSO-d6) δ
9.85 (s, 1H, CONH), 9.35 (bm, 2H, NH+), 7.98 (s, 1H, ArH),
7.96 (s, 1H, ArH), 6.78 (s, 1H, ArH), 6.65 (s, 1H, ArH), 4.65
(bm, 1H, CH), 3.83 (s, 3H, OMe), 3.73 (s, 3H, OMe), 3.35-
3.43 (m, 1H, CH), 2.8-3.2 (m, 5H, CH), 2.01 (s, 3H, Me); IR
(KBr) 1677 (CdO), 1514 (CdC Ar) cm-1; MS m/e (M+) 592 (M-
HCl, EI). Anal. (C20H22I2N2O3‚HCl‚0.5Et2O) C, H, N.
1-(4-Acetam ido-3,5-diiodoben zyl)-6,7-dih ydr oxy-1,2,3,4-
tetr a h yd r oisoqu in olin e Hyd r obr om id e (15‚HBr ). To a
solution of 14 (0.50 g, 0.88 mmol) in dry CH2Cl2 (50 mL) at 0
°C (ice bath) was added dropwise 1 M BBr3 (4 mL, 4 mmol) in
CH2Cl2 under an argon atmosphere. The mixture was then
allowed to reach room temperature, and stirring was continued
overnight. The reaction mixture was cooled with an ice bath,
and methanol (20 mL) was added carefully. The solution was
stirred for 10 min and then evaporated in vacuo. This was
repeated 4 times to give a solid which was stirred with ether
overnight. The crude product was collected by filtration and
recrystallized from methanol and ethyl ether to give 0.51 g
(90%) of the desired product as an off-white solid: mp 202-
206 °C (dec); 1H NMR (DMSO-d6) δ 9.82 (s, 1H, CONH), 9.15
(bm, 1H, OH), 8.91 (bm, 2H, NH+), 8.55 (bm, 1H, OH), 7.97
(s, 1H, ArH), 7.94 (s, 1H, ArH), 6.71 (s, 1H, ArH), 6.56 (s, 1H,
ArH), 4.66 (bm, 1H, CH), 3.27-3.35 (m, 2H, CH), 3.10-3.16
(m, 2H, CH), 2.70-2.93 (m, 4H, CH), 2.02 (s, 3H, Me); 13C NMR
(CD3OD) δ 172.51 (CdO), 147.04 and 145.89 (C-6 and C-7),
142.34 (C-4′), 141.90 and 141.73 (C-2′ and C-6′), 140.18 (C-1′),
123.67 and 123.09 (C-5a and C-8a), 116.32 (C-5), 114.11 (C-
8), 100.61 and 100.46 (C-3′ and C-5′), 57.51 (C-1), 41.10 (C-3),
39.31 (CH2Ar), 25.70 (C-4), 23.09 (COCH3); IR (KBr) 1652 (CO),
1524 (C-N) cm-1; MS m/e (M+) 565 (M+H, FAB). Anal.
(C18H18N2O3I2‚HBr‚0.25Et2O) C, H, N.
(KBr) 3600-2600 (OH, NH), 1527 (CdC, Ar) cm-1
(C16H15I2NO3‚HBr‚0.1Et2O) C, H, N.
. Anal.
1-(3,5-Diiod oben zyl)-6,7-d im eth oxy-2-(tr iflu or oa cetyl)-
1,2,3,4-tetr a h yd r oisoqu in olin e (19a ). A solution of iso-
quinoline 10a (1.29 g, 2 mmol) in glacial acetic acid (30 mL)
was added to a cold solution of NaNO2 (0.19 g, 2.8 mmol) in
concentrated (d 1.84) H2SO4 (3.4 mL); the temperature was
kept within 0-5 °C. The solution was poured into ice-water
(60 g), and H3PO2 (12 mL) was added in 30 min. The cooling
bath was removed, and the solution was allowed to stand at
room temperature for 2 days. The precipitate was filtered,
dried, and chromatographed on silica gel (hexane-AcOEt, 8:1).
Recrystallization from AcOEt-hexane gave 0.50 g (40%) of
white crystals: mp 162-163 °C; 1H NMR (CDCl3) δ 7.93 (t, J
) 1.5 Hz, 1H, ArH), 7.43 (d, J ) 1.5 Hz, 2H, ArH), 6.62 (s,
1H, ArH), 6.24 (s, 1H, ArH), 5.48 (t, J ) 6.7 Hz, 1H, CH), 3.95
(m, 1H, CH), 3.87 (s, 3H, OMe), 3.72 (s, 3H, OMe), 3.61 (m,
1H, CH), 3.06-2.86 (m, 3H, CH), 2.70 (m, 1H, CH); 13C NMR
(CDCl3) δ 155.98 (q), 148.46, 147.67, 143.60, 141.25, 137.98,
125.86, 125.00, 116.41 (q), 111.20, 110.19, 94.58, 55.96, 55.93,
55.37, 41.13, 40.61 (q), 28.44; IR (KBr) 1686 (CdO), 1541, 1520
(CdC Ar) cm-1. Anal. (C18H19I2NO2) C, H, N.
1-(3,4,5-Tr iiod ob e n zyl)-6,7-d im e t h oxy-2-(t r iflu or o-
a cetyl)-1,2,3,4-tetr a h yd r oisoqu in olin e (19b). Compound
10a (1.29 g, 2 mmol) was diazotized in the usual manner. The
resulting solution was poured in ice-water (60 g) followed by
addition of KI (0.47 g, 2.8 mmol) in water (10 mL). The
mixture was heated to 80 °C and allowed to cool. The
precipitate was filtered, dried, and purified by column chro-
matography (silica gel, hexane-AcOEt, 3:1): yield 0.51 g
(34%); mp 215-216 °C; 1H NMR (CDCl3) δ 7.59 (s, 2H, ArH),
6.63 (s, 1H, ArH), 6.31 (s, 1H, ArH), 5.46 (t, J ) 6.7 Hz, 1H,
ArH), 3.93 (m, 1H, CH), 3.88 (s, 3H, OMe), 3.75 (s, 3H, OMe),
3.61 (ddd, J ) 13.8, 9.9, 4.1 Hz, 1H, CH), 3.02-2.85 (m, 3H,
CH2Ar + CH), 2.70 (dt, J ) 16.2, 4.3 Hz, 1H, CH); 13C NMR
(CDCl3) δ 156.07 (q), 148.48, 147.71, 140.45, 139.90, 125.67,
125.08, 118.91, 116.39 (q), 111.16, 110.08, 106.78, 55.97, 55.10,
40.68 (q), 40.32 28.43; IR (KBr) 1685 (CdO), 1519 (CdC Ar)
cm-1. Anal. (C20H17F3I3NO3) C, H, N.
1-(4-Dia cet a m id o-3,5-d iiod ob en zyl)-6,7-d im et h oxy-2-
(tr iflu or oa cetyl)-1,2,3,4-tetr a h yd r oisoqu in olin e (16). A
solution of 10a (0.70 g, 1.08 mmol) in acetic anhydride (10 mL)
was heated at reflux for 2 h. The solvent was evaporated in
vacuo to give an oily residue. The residue was taken up in
hot ethanol. The product crystallized upon cooling to give 0.78
g (99%) of the product as white crystals: mp 190-192 °C; 1H
NMR (CDCl3) δ 7.70 (s, 2H, ArH), 6.64 (s, 1H, ArH), 6.39 (s,
1H, ArH), 5.53 (t, J ) 6.7 Hz, 1H, CH), 3.96 (m, 1H, CH), 3.87
(s, 3H, OMe), 3.79 (s, 3H, OMe), 2.68 (m, 1H, CH), 2.94-3.07
(m, 3H, CH), 2.77 (m, 1H, CH), 2.28 (s, 6H, Ac); 13C NMR
(CDCl3) δ 171.23, 155.93 (q), 148.48, 147.86, 142.66, 141.36,
141.12, 125.65, 124.83, 116.31 (q), 111.14, 109.88, 99.21, 56.08,
55.93, 55.31, 40.58, 40.44 (q), 28.43, 26.60; IR (KBr) 1719, 1683
(CdO), 1235, 1207 (C-O) cm-1. Anal. (C24H23F3I2N2O5) C, H,
N.
1-(3,5-Diiod oben zyl)-6,7-d im eth oxy-1,2,3,4-tetr a h yd r o-
isoqu in olin e (20a ). A mixture of isoquinoline 19a (0.38 g,
0.6 mmol) in MeOH (35 mL) and K2CO3 (0.85 g) in water (11
mL) was refluxed for 1.5 h. MeOH was evaporated, and a
white precipitate was filtered and dried. The crude product
was purified by flash chromatography (silica gel) using a
gradient (EtOAc-hexanes, 1:2; EtOAc, EtOAc-MeOH, 30:1)
and recrystallized from EtOAc-hexanes to give 0.25 g (76%)
of white crystals: mp 122-124 °C; 1H NMR (CDCl3) δ 7.94 (t,
J ) 1.4 Hz, 1H, ArH), 7.60 (d, J ) 1.4 Hz, 2H, ArH), 6.60 (s,
1H, ArH), 6.57 (s, 1H, ArH), 4.10 (m, 1H, CH), 3.86 (s, 3H,
OMe), 3.84 (s, 3H, OMe), 3.18 (m, 1H, CH), 3.08 (dd, J ) 4.1
and 13.7 Hz, 1H, CH), 2.95 (m, 1H, CH), 2.82-2.61 (m, 3H,
CH); 13C NMR (CDCl3) δ 147.68, 147.17, 143.78, 143.15,
137.64, 129.86, 127.42, 111.98, 109.32, 94.99, 56.57, 56.06,
55.87, 42.20, 40.55, 29.39; IR (KBr) 3325 (NH), 1516 (CdC Ar)
cm-1. Anal. (C18H19I2NO2) C, H, N.
6,7-Dih yd r oxy-1-(4-h yd r oxy-4,3,5-d iiod oben zyl)-1,2,3,4-
tetr a h yd r oisoqu in olin e Hyd r obr om id e (18‚HBr ). Hy-
drochloride 1710 (0.21 g, 0.28 mmol) was dissolved in CHCl3
and washed with 1 N NaOH; the organic layer was separated,
6,7-Dim et h oxy-1-(3,4,5-t r iiod ob en zyl)-1,2,3,4-t et r a h y-
d r oisoqu in olin e (20b). A mixture of isoquinoline 19b (0.454
g, 0.6 mmol) in MeOH (35 mL) and K2CO3 in water (11 mL)

Iodinated Analogs of Trimetoquinol
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19 3709
was refluxed for 1.5 h. MeOH was evaporated, and a white
precipitate was filtered and dried. Recrystallization from
CHCl3-hexane gave 0.300 g (76%) of white crystals: mp 168-
170 °C (dec); 1H NMR (CDCl3) δ 7.79 (s, 2H, ArH), 6.60 (s,
1H, ArH), 6.58 (s, 1H, ArH), 4.09 (dd, J ) 9.8, 3.8 Hz, 1H,
CH), 3.86 (s, 3H, OMe), 3.85 (s, 3H, OMe), 3.17 (m, 1H, CH),
3.04-2.88 (m, 2H, CH), 2.82-2.60 (m, 3H, CH); 13C NMR
(CDCl3) δ 147.66, 147.15, 143.00, 139.68, 129.67, 127.42,
118.18, 111.92, 109.14, 107.09, 56.35, 56.06, 55.85, 41.38,
40.56, 29.35; IR (KBr) 3312 (NH), 1516 (CdC Ar) cm-1. Anal.
(C18H18I3NO2) C, H, N.
1-(4-Aceta m id o-3-iod oben zyl)-6,7-d im eth oxy-2-(tr iflu o-
r oa cetyl)-1,2,3,4-tetr a h yd r oisoqu in olin e (22). To a solu-
tion of isoquinoline 9a (0.52 g, 1 mmol) in hot benzene (15 mL)
was added Ac2O (0.51 g, 5 mmol). The solution was refluxed
for 1 h. The reaction mixture was allowed to cool. White
crystals were filtered. Mother liquor was concentrated, and
hexane was added. Slightly creamy crystals were filtered,
total yield 0.53 g (94%). To get an analytical sample, the
compound was recrystallized from EtOAc-hexane: mp 174-
175 °C; 1H NMR (CDCl3) δ 8.11 (d, J ) 8.3 Hz, 1H, H-5′), 7.52
(d, J ) 1.5 Hz, 1H, H-2′), 7.36 (s, 1H, NH), 7.10 (dd, J ) 8.3,
1.5 Hz, 1H, ArH), 6.60 (s, 1H, ArH), 6.32 (s, 1H, ArH), 5.23 (t,
J ) 6.6 Hz, CH), 3.94 (m, 1H, CH), 3.87 (s, 3H, OMe), 3.72 (s,
3H, OMe), 3.54 (ddd, OMe ) 14.1, 10.4 Hz, 3.8 Hz, 1H, CH),
3.06 (m, 2H, CH), 2.90 (ddd, J ) 15.9, 10.4, 5.2 Hz, 1H, CH),
2.68 (dt, J ) 16.0, 4 Hz, 1H, CH), 2.23 (s, 3H, Ac); 13C NMR
(CDCl3) δ 168.12, 155.90 (q), 148.30, 147.63, 139.63, 137.12,
134.95, 130.53, 126.19, 124.95, 121.73, 116.44 (q), 111.10,
110.17, 89.68, 55.91, 55.33, 40.75, 40.50 (q), 28.51, 24.75; IR
1-(4-Am in o-3,5-d iiod oben zyl)-6,7-d im eth oxy-1,2,3,4-tet-
r a h yd r oisoqu in olin e (20c). A slurry of the isoquinoline 10a
(1.94 g, 3 mmol) in MeOH (260 mL) and K2CO3 (11.2 g) in
H2O (80 mL) was refluxed for 1 h. MeOH was evaporated
under reduced pressure, and crystals were filtered, dried, and
recrystallized from EtOAc-hexane to give the title compound
(1.39 g, 84%): mp 169-171 °C; 1H NMR (CDCl3) δ 7.55 (s,
2H, ArH), 6.61 (s, 1H, ArH), 6.51 (s, 1H, ArH), 4.54 (s, 2H,
NH2), 4.04 (dd, J ) 9.6, 4.0 Hz, 1H, CH), 3.86 (s, 3H, OMe),
3.84 (s, 3H, OMe), 3.18 (m, 1H, CH), 3.03 (dd, J ) 13.8, 4.0
Hz, 1H, CH), 2.92 (ddd, J ) 12.1, 6.8, 5.2 Hz, 1H, CH), 2.82-
2.61 (m, J ) 13.8, 9.6 Hz, 3H, CH); 13C NMR (CDCl3) δ 147.51,
147.05, 144.66, 139.97, 132.36, 130.14, 127.38, 111.88, 109.28,
81.59, 56.79, 56.01, 55.83, 40.87, 40.72, 29.47; IR (KBr) 3416
(KBr) 3395 (NH), 1688 (CdO), 1519 (CdC Ar) cm-1
. Anal.
(C22H22F3IN2O4) C, H, N.
1-(4-Acet a m id o-3-iod ob en zyl)-6,7-d im et h oxy-1,2,3,4-
tetr a h yd r oisoqu in olin e (23). The title compound (0.57 g,
69%) as a glassy solid was obtained from the isoquinoline 22
(0.99 g, 1.76 mmol) in the same manner as 20c: 1H NMR
(CDCl3) δ 8.12 (d, J ) 8.3 Hz, 1H, H-5′), 7.70 (d, J ) 1.7 Hz,
1H, ArH), 7.38 (s, 1H, NH), 7.26 (dd, J ) 8.3, 1.7 Hz, 1H, ArH),
6.63 (s, 1H, ArH), 6.60 (s, 1H, ArH), 4.11 (dd, J ) 9.6, 3.8 Hz,
1H, CH), 3.10-3.25 (m, 2H, CH), 2.92 (m, 1H, CH), 2.63-2.86
(m, 3H, CH2Ar, CH), 2.25 (s, 3H, Ac); 13C NMR (CDCl3) δ
168.19, 147.54, 147.05, 139.31, 137.30, 136.66, 130.12, 129.92,
127.28, 122.25, 111.85, 109.27, 90.50, 56.64, 55.99, 55.79,
41.63, 40.61, 29.30, 24.66; IR (KBr) 3391 (NH), 1676 (CdO),
1515 (CdC Ar) cm-1. Anal. (C20H23IN2O3) C, H, N.
(NH), 3331 (NH), 1607 (NH bend), 1571, 1512 (CdC Ar) cm-1
.
Anal. (C18H20N2I2) C, H, N.
6,7-Dih yd r oxy-1-(3,5-d iiod oben zyl)-1,2,3,4-tetr a h yd r o-
isoqu in olin e Hyd r obr om id e (21a ‚HBr ). The isoquinoline
20a (0.19 g, 0.35 mmol) was demethylated using the same
procedure as 15. Recrystallization from MeOH-ether gave
0.20 g (96%) of the title compound: mp 157-159 °C (dec); 1H
NMR (DMSO-d6) δ 9.13 (bs, 1H, OH), 8.88 (bm, 2H, NH+OH),
8.57 (bm, 1H, NH), 8.02 (t, J ) 1.4 Hz, 1H, ArH), 7.80 (d, J )
1.4 Hz, 2H, ArH), 6.61 (s, 1H, ArH), 6.56 (s, 1H, ArH), 4.63
(bm, 1H, CH), 3.22-3.41 (m, 2H, CH), 3.14 (m, 1H, CH), 2.71-
2.96 (m, 3H, CH); 13C NMR (CD3OD) δ 147.01 and 145.79 (C-6
and C-7), 145.69 (C-4′), 139.18 (C-2′ and C-6′), 141.15 (C-1′),
123.76 and 123.03 (C-4a and C-8a), 116.30 (C-5), 114.21 (C-
8), 96.14 (C-3′ and C-5′), 57.25 (C-1), 41.02 (C-3), 40.08 (CH2-
Ar), 25.60 (C-4); IR (KBr) 3600-2700 (br OH, NH), 1617, 1521
(CdC Ar) cm-1. Anal. (C16H15BrI3NO2) C, H, N.
1-(4-Am in o-3-iodoben zyl)-6,7-dih ydr oxy-1,2,3,4-tetr ah y-
d r oisoqu in olin e Dih yd r och lor id e (24‚2HCl). The title
compound was obtained in the same manner as 21c from the
isoquinoline 23 (0.42 g, 0.90 mmol). The product was recrys-
tallized from MeOH (twice) to give 0.32 g (64%). The com-
pound was dissolved in NaHCO3 solution and extracted with
EtOAc (×5). The solution was dried (MgSO4) and evaporated;
1 M HCl in ether (2 mL) was added to the methanol solution
of the residue. The solution was concentrated and put in a
refrigerator. The white crystals were filtered, washed with
6,7-Dih yd r oxy-1-(3,4,5-t r iiod ob en zyl)-1,2,3,4-t et r a h y-
d r oisoqu in olin e Hyd r obr om id e (21b‚HBr ). The isoquino-
line 20b (0.23 g, 0.35 mmol) was demethylated using the same
procedure as 15. Recrystallization from MeOH-ether gave
0.24 g (97%) of the title compound: mp 210-213 °C (dec); 1H
NMR (MeOH-d4) δ 7.92 (s, 2H, ArH), 6.63 (s, 1H, ArH), 6.56
(s, 1H, ArH), 4.64 (dd, J ) 5.7 and 3.1 Hz, 1H, CH), 3.42-
3.53 (m, 1H, CH), 3.2-3.34 (m, 2H, CH), 2.83-3.07 (m, 3H,
CH); 13C NMR (CD3OD) δ 147.11 and 145.90 (C-6 and C-7),
141.06 (C-2′ and C-6′), 140.21 (C-1′), 123.70 and 122.98 (C-4a
and C-8a), 120.90 (C-4′), 116.31 (C-5), 114.14 (C-8), 108.68 (C-
3′ and C-5′), 57.04 (C-1), 41.01 (C-3), 39.38 (CH2Ar), 25.62 (C-
4); IR (KBr) 3600-2700 (br OH, NH), 1617, 1540 (CdC Ar)
cm-1. Anal. (C16H16BrI2NO2) C, H, N.
1
EtOAc, and dried: dec.p. 186-190 °C; H NMR (DMSO-d6) δ
9.05 (bs, 1H, OH), 7.68 (d, J ) 1.7 Hz, 1H, ArH), 7.16 (dd, J )
8.2, 1.7 Hz, 1H, ArH), 6.94 (d, J ) 8.2 Hz, 1H, ArH), 6.57 (s,
1H, ArH), 6.55 (s, 1H, ArH), 4.46 (m, 1H, CH), 3.27 (m, 1H,
CH), 3.00-3.20 (m, 2H, CH), 2.80-3.00 (m, 2H, CH), 2.74 (dt,
J ) 16.8, 5.9 Hz, CH); 13C NMR (CD3OD) δ 147.00 and 145.76
(C-6 and C-7), 1412.68 (C-2′), 138.21 (C-4′), 136.27 (C-1′),
132.35 (C-6′), 123.82 and 123.10 (C-4a and C-8a), 116.27 (C-
5), 114.33 (C-8), 124.24 (C-5′), 91.49 (C-3′), 57.27 (C-1), 40.90
(C-3), 39.87 (CH2Ar), 25.659 (C-4); IR (KBr) 3600-2300 (br,
OH, NH), 1607 (NH bend), 1526 (CdC Ar) cm-1
(C16H17IN2O2‚2HCl) C, H, N.
. Anal.
1-(4-Acetam ido-3-iodoben zyl)-6,7-bis(ben zyloxy)-2-(ter t-
bu toxyca r bon yl)-1,2,3,4-tetr a h yd r oisoqu in olin e (25a ). To
a cold solution (0 °C) of isoquinoline 9b (0.68 g, 1 mmol) and
Et3N (0.34 g, 3 mmol) in CH2Cl2 (10 mL) was added AcCl (0.16
g, 2 mmol). The cooling bath was removed, and the mixture
was stirred overnight. The solution was washed with water
(2×), dried over MgSO4, filtered, and evaporated. Ether was
added and evaporated again to give a glassy solid (0.65 g,
90%): mp 62-64 °C; 1H NMR (CDCl3) δ (the spectrum consists
of two rotamers of 5:3 ratio) 8.12 and 8.06 (d, J ) 8.2), 7.59-
7.25 (m, 11H, ArH), 7.06 and 6.98 (m, 1H, ArH), 6.70 and 6.65
(s, 1H, ArH), 6.48 and 6.35 (s, 1H, ArH), 5.24-4.87 (m, 5H,
CH2O + CH), 4.12 and 3.73 (m, 1H, CH), 3.27-3.11 (m, 1H,
CH), 2.98-2.60 (m, 3H, CH2Ar + CH), 2.60-2.37 (m, 1H, CH),
2.22 (s, 3H, Ac), 1.43 and 1.31 (s, 9H, t-Bu); IR (KBr) 3389
(NH), 1688 (CdO), 1512 (CdC Ar) cm-1. Anal. (C37H39IN2O5)
C, H, N.
1-(4-Am in o-3,5-d iiod oben zyl)-6,7-d ih yd r oxy-1,2,3,4-tet-
r a h yd r oisoqu in olin e Dih yd r och lor id e (21c‚2HCl). The
isoquinoline 20c (1.21 g, 2.2 mmol) was demethylated in the
same manner as 20b to give 1.14 g (76%) of the dihydrobro-
mide salt: mp 155-157 °C (dec). The product was dissolved
in MeOH, chromatographed (silica gel, EtOAc-NH4OH, 100:
1), and evaporated with EtOH (×5). To an ethanol solu-
tion was added a 1 N etherial solution of HCl (3 mL),
concentrated, precipitated with EtOAc, and recrystallized from
1
MeOH-i-PrOH: mp 176-178 °C (dec); H NMR (DMSO-d6)
δ 9.15 (br s, 1H, OH), 8.89 (br s, 1H, NH2+), 7.68 (s, 2H, H-2′),
6.64 (s, 1H, H-5), 6.55 (s, 1H, H-8), 5.06 (br s, 2H, NH2), 4.47
(m, 1H, H-1), 3.40-2.67 (m, 6H, H-3 + H-4 + CH2Ar); 13C NMR
(CD3OD) δ 147.99 (C-4′), 146.84 and 145.75 (C-6 and C-7),
141.60 (C-2′ and C-6′), 128.78 (C-1′), 123.75 and 123.33 (C-4a
and C-8a), 116.24 (C-5), 114.16 (C-8), 81.86 (C-3′ and C-5′),
57.59 (C-1), 41.07 (C-3), 39.07 (CH2Ar), 25.68 (C-4); IR (KBr)
3600-2500 (br, OH, NH), 1607 (NH bend), 1529 (CdC Ar)
cm-1. Anal. (C16H16I2N2O2‚2HCl‚H2O) C, H, N.
1-(4-(Ben zoyla m in o)-3-iod oben zyl)-6,7-bis(ben zyloxy)-
2-(ter t-b u t oxyca r b on yl)-1,2,3,4-t et r a h yd r oisoq u in olin e
(25b). To a cold solution (0 °C) of isoquinoline 9b (0.68 g, 1

3710 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 19
De Los Angeles et al.
mmol) and Et3N (0.30 g, 3 mmol) in 10 mL of CH2Cl2 was
added benzoyl chloride (0.28 g, 2 mmol). The cooling bath was
removed, and the mixture was stirred overnight. CH2Cl2 was
added (30 mL), the solution was washed with water, dried over
MgSO4, filtered, and evaporated till dryness. The oily residue
was dissolved in ether and evaporated to give 0.60 g (76%) of
a glassy solid. The compound was purified by column chro-
matography (silica gel, EtOAc-hexane 1:2): mp 151-153 °C;
1H NMR (CDCl3) δ 8.42-6.36 (m, 18H, Ar), 5.20-4.90 (m, 5H,
2 × CH2O + H-1), 4.20-2.15 (m, 6H, aliphatic), 1.56-1.25 (m,
9H, t-Bu); IR (KBr) 3397 (NH), 1687 (CdO), 1513 (CdC Ar)
cm-1. Anal. (C42H41IN2O5) C, H, N.
150-mL flasks and were detached into Ham’s F-12 medium
after treatment with 0.05% trypsin-0.53 mM EDTA solution.
The cells were then pelleted and washed 3 times with Tris-
EDTA buffer (50 mM Tris-HCl, 150 mM NaCl, 20 mM EDTA,
pH 7.4) and resuspended in the same buffer. Competition
binding experiments were performed in duplicate using these
whole cells. Aliquots (150 µL) of cells were added to tubes
containing 50 µL of [125I]ICYP [(1.5-5) × 104 cells/20-60 pM
ICYP] and varying concentrations of competing drugs. The
final volume in each tube was 0.25 mL. Nonspecific binding
(5-30%) was determined in the presence of 1 µM (()-
propranolol. Incubations were carried out for 60 min at 37
°C. Binding reactions were terminated by rapid filtration
through Whatman GF/B glass fiber filters on a Brandel Model
12-R tissue harvester. Filters were washed twice with ice-
cold Tris-EDTA buffer to remove free ICYP. The filters were
dried under tissue harvester vacuum, and radioactivity was
measured by gamma scintillation spectrometry (Beckman
Model 8000 gamma counter; Palo Alto, CA). Specific binding
to â-AR in these cells varied from 94 to 100%.
Th r om boxan e A2/P r ostaglan din H2 (TP ) Receptor Sites
in Hu m a n P la telets. For binding experiments, human
platelet-rich plasma (PRP) was centrifuged and resuspended
in 50 mM Tris-saline buffer, pH 7.4.9 Platelets were incu-
bated with 5 nM [3H]-SQ 29548 in a final volume of 0.5 mL as
described by Hedberg et al.21 Unlabeled SQ 29548 (50 µM)
was used to determine nonspecific binding. Varying concen-
trations of each competing drug were used to quantify the
inhibition of specific [3H]-SQ 29548 binding. Samples were
incubated 30 min at room temperature, and rapidly filtered
by vacuum through Whatman GF/C glass fiber filters on a
Brandel cell harvester and washed for 10 s with ice-cold Tris-
saline buffer. Filters were placed in plastic scintillation vials
containing 10 mL of an emulsion-type scintillation mixture,
and radioactivity was measured by liquid scintillation spec-
trometry. Specific binding to human platelets varied between
88 and 95%.
1-(4-Aceta m ido-3-iod oben zyl)-6,7-dih yd r oxy-1,2,3,4-tet-
r a h yd r oisoqu in olin e Hyd r oiod id e (26a‚HI). To a solution
of isoquinoline 25a (0.40 g, 0.5 mmol) in anhydrous MeCN (5
mL) was added TMSI (0.40 g, 2 mmol) via a syringe in an
argon atmosphere. The solution was stirred for 6 h followed
by MeOH (1 mL) addition, and stirring was continued for 30
min. CH2Cl2 (30 mL) was added to the reaction mixture, and
yellow crystals were filtered; yield 0.19 g (67%). The compound
was dissolved in MeOH, AcOEt was added, and the solution
was concentrated under reduced pressure. The crystals were
filtered: dec.p. 172-174 °C; 1H NMR (DMSO-d6) δ 9.39 (s, 1H,
NH), 8.86 (bs, 1H, OH), 8.50 (bs, 1H, OH), 7.90 (d, J ) 1.7 Hz,
1H, ArH), 7.41 (d, J ) 8.2 Hz, 1H, ArH), 7.35 (dd, J ) 8.2, 1.7
Hz, 1H, ArH), 6.63 (s, 1H, ArH), 6.56 (s, 1H, ArH), 4.63 (m,
1H, CH), 3.43-2.70 (m, 6H, CH), 2.06 (s, 3H, Ac); 13C NMR
(CD3OD) δ 172.65 (CdO), 146.98 and 145.81 (C-6 and C-7),
142.68 (C-2′), 140.11 (C-4′), 137.15 (C-1′), 131.30 (C-6′), 129.10
(C-5′), 123.63 and 123.27 (C-4a and C-8a), 116.27 (C-5), 114.15
(C-8), 91.49 (C-3′), 57.60 (C-1), 41.01 (C-3), 39.98 (CH2Ar),
25.68 (C-4), 23.09 (COCH3); IR (KBr) 3600-2400 (br, OH, NH),
1655 (CdO), 1624 (NH bend), 1522 (CdC Ar) cm-1; MS m/z
(M+) 439. Anal. (C18H19IN2O3‚HI‚0.25EtOAc) C, H, N.
1-(4-(Ben zoylam in o)-3-iodoben zyl)-6,7-dih ydr oxy-1,2,3,4-
tetr a h yd r oisoqu in olin e Hyd r oiod id e (26b‚HI). To a mix-
ture of isoquinoline 25b (0.16 g, 2 mmol) in MeCN (4 mL) was
added TMSI (0.16 g, 0.8 mmol) under argon atmosphere, and
the solution was stirred at room temperature for 7 h. MeOH
(1 mL) was added and stirred for 1 h followed by ether (40
mL) addition, and the yellow precipitate was filtered to give
0.10 g (80%) of the product. The compound was dissolved in
MeOH, and EtOAc was added and concentrated until the
Da ta An a lysis. Competitive binding data were analyzed
using the PC-version of the radioligand binding program
LIGAND (McPherson, 1985). Inhibitory concentration-50
(IC50) value of each competing drug was determined graphi-
cally from individual plots of percent radioligand bound versus
log drug concentration on â-adrenoceptors and human plate-
lets. Dissociation constants (Ki) for each competing drug were
calculated using the equation: Ki ) IC50/(1 + [L]/KL) and the
data expressed as pKi (i.e., -log Ki) values. The KL values
used in the above equation are 17 pM, 10 pM, and 3.1 nM for
â1-AR, â2-AR, and TP receptors, respectively.
1
beginning of crystallization: mp 185-188 °C (dec); H NMR
(DMSO-d6) δ 9.98 (s, 1H, NHCOPh), 9.18 (s, 1H, NH), 8.88
(br, 2H, OH + NH), 8.54 (br, 1H, OH), 8.03-7.93 (m, 3H, ArH),
7.64-7.42 (m, 3H, ArH), 7.49 (d, J ) 8.1 Hz, 1H, ArH), 7.41
(dd, J ) 8.1, 1.4 Hz, 1H, ArH), 6.65 (s, 1H, ArH), 6.58 (s, 1H,
ArH), 3.43-2.70 (m, 6H, CH); IR (KBr) 3500-2700 (br, NH,
OH), 1649 (CdO), 1518 (CdC Ar) cm-1. Anal. (C23H21IN2O3‚
HI‚0.33EtOAc) C, H, N.
Ack n ow led gm en t. The authors thank the National
Institutes of Health (USPHS Grant HL-22533) for
support of this work.
1-[3,5-Bis(tr iflu or om eth yl)ben zyl]-6,7-dih ydr oxy-1,2,3,4-
tetr a h yd r oisoqu in olin e Hyd r och lor id e (27‚HCl). The
title compound was obtained from 6c in the same manner as
15 (85%). The product was converted to the hydrochloride salt,
and recrystallization from methanol-ether gave the product
as white crystals: mp 239-242 °C; 1H NMR (CD3OD-d4) δ 7.95
(s, 3H, ArH), 6.65 (s, 1H, ArH), 6.44 (s, 1H, ArH), 4.77 (t, J )
7.7 Hz), 3.51 (dt, J ) 6.88, 12.74 Hz), 3.33 (m, 2H, CH), 3.0
(m, 2H, CH); 13C NMR (CD3OD) δ 147.15 and 145.81 (C-6 and
C-7), 140.21 (C-1′), 133.21 (C-3′ and C-5′), 131.61 (C-2′ and
C-6′), 124.79 (CF3), 123.79 and 122.63 (C-4a and C-8a), 122.58
(C-4′), 116.40 (C-5), 114.35 (C-8), 57.11 (C-1), 41.77 (C-3), 40.55
(CH2Ar), 25.56 (C-4); IR (KBr) 3600-2400 (N+H, OH), 1282
(C-O) cm-1. Anal. (C18H16ClF6NO2) C, H, N.
Ra d ioliga n d Bin d in g Stu d ies w ith â1- a n d â2-AR Ex-
p r essed in CHO Cells. Competition binding experiments on
â1- and â2-AR expressed in CHO cells were performed as
described previously.8 CHO cells expressing human â1- and
â2-AR (provided by A. D. Strosberg, Institut Cochin de Gene-
tique Moleculaire, Paris, France, and David Bylund, University
of Nebraska, Omaha, NE, respectively) were cultured in Ham’s
F-12 medium supplemented with 10% fetal bovine serum, 50
units/mL-50 µg/mL penicillin-streptomycin, 2 mM L-glut-
amine, and 50 µg/mL Geneticin in a humidified atmosphere
of 5% CO2-95% air. CHO cells were grown to a confluence in
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