Opioid ligands with mixed properties from substituted enantiomeric N-phenethyl-5-phenylmorphans. Synthesis of a -agonist δ-antagonist and δ-inverse agonists

Article abstract of DOI:10.1039/b618875c

Enantiomeric N-phenethyl-m-hydroxyphenylmorphans with various substituents in the ortho, meta or para positions of the aromatic ring in the phenethylamine side-chain (chloro, hydroxy, methoxy, nitro, methyl), as well as a pyridylethyl and a indolylethyl m

Full text of DOI:10.1039/b618875c

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Opioid ligands with mixed properties from substituted enantiomeric
N-phenethyl-5-phenylmorphans. Synthesis of a l-agonist d-antagonist and
d-inverse agonists†‡
a
a
a
Kejun Cheng,§ In Jong Kim,¶ Mei-Jing Lee,§ꢀ Steven A. Adah,§∗∗a Tyler J. Raymond,b Edward J. Bilsky,b
Mario D. Aceto,c Everette L. May,c Louis S. Harris,c Andrew Coop,d Christina M. Dersch,e Richard B.
Rothman,e Arthur E. Jacobson§ and Kenner C. Rice*§
a
a
Received 2nd January 2007, Accepted 31st January 2007
First published as an Advance Article on the web 1st March 2007
DOI: 10.1039/b618875c
Enantiomeric N-phenethyl-m-hydroxyphenylmorphans with various substituents in the ortho, meta or
para positions of the aromatic ring in the phenethylamine side-chain (chloro, hydroxy, methoxy, nitro,
methyl), as well as a pyridylethyl and a indolylethyl moiety on the nitrogen atom, were synthesized and
their binding affinity to the l-, d-, and j-opioid receptors was examined. The higher affinity ligands
were further examined in the [35S]GTPcS assay to study their function and efficacy.
3-((1R,5S)-(−)-2-(4-Nitrophenethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10m) was found to be
a l-agonist and d-antagonist in that functional assay and was about 50 fold more potent than morphine
in vivo. 3-((1R,5S)-(−)-2-(4-Chlorophenethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10i) and
several other ligands displayed inverse agonist activity at the d-opioid receptor. The absolute
configuration of all of the reported compounds was established by chemical conversion of (−)-6 to
1R,5S-(−)-8b·HBr.
thetolerance and dependencecaused by the l-agonist.11,12 The dual
Introduction
effect could conceivably occur through a ligand that is fortuitously
able to fit to a binding site in both receptors, or perhaps to a
receptor that, when activated by a suitable ligand, can effect the
signaling properties of a related receptor.13,14 Interestingly, it has
been found that l- and d-receptors can exist as heterodimers.13–15
Further, Emmerson et al.,16 have noted that compounds with a d-
receptor inverse agonist profile may be useful as anorectants. Thus,
the interest in new ligands that interact with opioid receptors has
not abated, although the goals of the search have evolved.
The synthesis of compounds that act stereoselectively at each
of the opioid receptors and as potent, pure opioid agonists or
antagonists, has been a long-sought goal, and several non-peptidic
ligands with those properties have been found.2–10 More recently,
it has been suggested that ligands that display l-agonist and d-
antagonist activity may be useful as pharmacological tools or
medications. Theoretically, a l-agonist should induce analgesia
and the d-antagonist activity of the drug could reduce or eliminate
In an attempt at dissociating the undesirable effects of
morphine from its analgesic action in the 1950’s, May and
his collaborators examined the effect of simplification of the
structure of the rigid 5-ring morphine-like compounds (4,5-
epoxymorphinans).17 One of the first of the molecularly less
complex 5-phenylmorphan compounds that they synthesized and
examined,18 [( )-5-m-hydroxyphenyl-N-methylmorphan, (( )-3-
(2-methyl-2-aza-bicyclo[3.3.1]nonan-5-yl)-phenol, ( )-1] was
found to be as potent as the well-known analgesics in the
multicyclic rigid epoxymorphinan (e.g., morphine), morphinan
(e.g., levorphanol), and 6,7-benzomorphan (e.g., metazocine)
classes of antinociceptives. When the enantiomers of ( )-1
(Fig. 1) were examined by May et al.,19,20 they found that
the (+)-enantiomer showed potent antinociceptive activity in
mice (ca. 3 or 4 times more potent than morphine) and the
(−)-enantiomer showed both antinociceptive (morphine-like) and
narcotic antagonist activity (80 fold less potent than naloxone as
an antagonist in morphine-dependent Rhesus monkeys).
aDrug Design and Synthesis Section, Chemical Biology Research Branch,
National Institute on Drug Abuse, National Institutes of Health, Department
of Health and Human Services, Bethesda, Maryland, 20892-0815, USA.
E-mail: kr21f@nih.gov
bUniversity of New England, College of Osteopathic Medicine, Biddeford,
ME, 04005, USA
cDepartment of Pharmacology and Toxicology, School of Medicine, Virginia
Commonwealth University, Richmond, VA, 23298, USA
dDepartment of Pharmaceutical Sciences, University of Maryland School of
Pharmacy, Baltimore, MD, 21201, USA
eClinical Psychopharmacology Section, Intramural Research Program,
National Institute on Drug Abuse, National Institutes of Health, Department
of Health and Human Services, Baltimore, Maryland, 21224, USA
† Probes for Narcotic Receptor Mediated Phenomena. Part 35.1
‡ Electronic supplementary information (ESI) available: Further experi-
mental details. See DOI: 10.1039/b618875c
§ This work was initiated while these authors were members of the
Drug Design and Synthesis Section, Laboratory of Medicinal Chemistry,
National Institute of Diabetes, Digestive and Kidney Diseases, NIH, USA.
¶ Present address: ENANTA Pharmaceuticals, Inc. 500 Arsenal Street,
Watertown, MA 02472, USA
This is in sharp contrast to the epoxymorphinan opioids where
only the enantiomer with morphine’s absolute configuration, that
is, the natural product or a compound derived from it, interacts
ꢀ Present address: Formosa Laboratories, Taiwan
∗∗ Present address: NIAID, NIH, Department of Health and Human
Services, Rockville, Maryland, USA
This journal is
The Royal Society of Chemistry 2007
Org. Biomol. Chem., 2007, 5, 1177–1190 | 1177
©

View Article Online
interacting with both l- and d-opioid receptors and that would
act as a l-agonist and d-antagonist. Also, differently substituted
N-phenethyl phenylmorphans with varying affinity for opioid re-
ceptors and varying efficacy might provide greater insight into how
that moiety exerts its unusual antagonist effect. We substituted
various electron-withdrawing or donating groups (e.g., methoxy,
chloro, nitro, etc.) on the aromatic ring in the N-phenethyl side-
chain, and, as well, used a different heteroaromatic ring (Table 1).
We determined the affinity of these ligands to the l-, d-, and j-
opioid receptors and observed whether the electronic character of
the aromatic ring was as important for receptor interaction in the
5-phenylmorphans as we have previously postulated.27 The higher
affinity analogues were further evaluated for their efficacy using
the [35S]GTP-c-S assay (Tables 1 and 2).
Fig. 1 N-Methyl- and N-phenethyl-phenylmorphans.
well with opioid receptors and has significant analgesic activity.
Single-crystal X-ray analysis21 subsequently determined that the
(−)-enantiomer ((−)-5-m-hydroxyphenyl-2-methylmorphan hy-
drobromide) had the 1R,5S configuration. Prior to the work of
May et al., opioid antagonist activity had not been found in any
enantiomer from any opioid with a so-called “agonist” side-chain
on the nitrogen atom (e.g., N-methyl, N-phenethyl, N-pentyl),
nor have they often been found since that time among any of
the derivatives from the molecularly rigid series of opioids (e.g.,
in the epoxymorphinans, morphinans, or benzomorphans). This
novel and unexpected effect in the 5-phenymorphans has been
ascribed to the lack of rigidity of the aromatic ring, as well as to
its equatorially-oriented link to the piperidine ring rather than the
more common axial arrangement found in the rigid multicyclic
analgesics.20
In that context, it was interesting to note that racemic N-
phenethyl-9b-methyl-5-(3-hydroxyphenyl)morphan (3-(2-phen-
ethyl-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol) was reported by
Thomas et al.,22 to have high affinity for the l opioid receptor
and to have only opioid antagonist activity in the [35S]GTP-c-S
assay. The conversion to a pure l-opioid antagonist was said
to be due to the circumscribed rotation of the aromatic ring
by a properly situated, sterically interfering alkyl moiety. We
subsequently reported that one of the N-phenethyl-substituted
5-phenylmorphan enantiomers ((−)-2) without a 9b-methyl
substituent that was said to limit the rotation of the aromatic
ring, was also a selective l-opioid antagonist,23–25 as determined
in the same [35S]GTP-c-S assay as that used by Thomas et al.22
An N-phenethyl substituent apparently influences the activity of
the 5-phenylmorphan molecule26 much differently than in the more
rigid cyclic morphinan-type of opioids. We have now explored
this unusual effect of an N-phenethyl moiety, both with the hope
of finding 5-phenylmorphan ligands that might be capable of
Results and discussion
The synthesis of a key intermediate, 2-benzyl-5-(3-methoxy-
phenyl)-2-aza-bicyclo[3.3.1]nonane (( )-6), was achieved as
shown in Scheme 1.
Lithiation of 3-bromoanisole by n-BuLi followed by its addition
to 1-benzyl-4-piperidone gave a hydroxypiperidine intermediate
that, without purification, was dehydrated to tetrahydropyridine 3
in good yield (93% over 2 steps). The metalated enamine resulting
from lithiation of 3 by sec-BuLi was treated with allyl bromide
to give endocyclic enamine 4, which upon treatment with a 1 : 1
mixture of HCO2H and H3PO4 at room temperature for 72 h
gave an intermediate enamine 5. This enamine was immediately
reduced with NaBH4 to 2-benzyl-5-(3-methoxyphenyl)-2-aza-
bicyclo[3.3.1]nonane (( )-6). The desired enantiomeric salts were
obtained through resolution of ( )-6 with (+)- and (−)-di-O,Oꢁ-p-
toluyl-D-tartaric acid. The base (−)-6 obtained from the (−)-6.
di-O,Oꢁ-p-toluyl-L-tartaric acid salt showed slight levorotation
at the sodium D line (589 nm), and was dextrorotatory at
365 nm. Its hydrobromide salt ((−)-6·HBr) was levorotatory.
The enantiomeric purities of the corresponding bases ((−)-6 and
(+)-6 at [a]589 nm) were determined by chiral HPLC using a Daicel
Chiralcel OD column. The optical purity of both enantiomers
was shown to be greater than 99.8%. The experimental details are
presented in the Supplementary Information‡.
The absolute configuration of (−)-6 was determined to be 1R,5S
by chemical conversion to the known 3-((1R,5S)-2-methyl-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol·HBr ((−)-8b.HBr, Scheme 2), an
Scheme 1 Reagents and conditions: a) i) THF, −78 ◦C, n-BuLi, then 1-benzyl-4-piperidone, to −20 ◦C; ii) toluene, p-toluenesulfonic acid monohydrate,
reflux, 93% over 2 steps: b) THF, −40 ◦C, sec-BuLi, then allyl bromide, to 0 ◦C; c) H3PO4 : HCO2H (1 : 1), rt; d) MeOH, 0 ◦C, NaBH4, then rt, 60% over
3 steps; e) diastereomeric optical resolution with (+)-di-O,Oꢁ-p-toluyl-D-tartaric acid and (−)-di-O,Oꢁ-p-toluyl-L-tartaric acid, then NH4OH.
1178 | Org. Biomol. Chem., 2007, 5, 1177–1190
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
Table 1 Binding affinity of N-substituted 5-phenylmorphans to opioid receptors
Ki (nM SD)a
[3H]DAMGO (l)
Cmpd.b
R
[3H]DADLE (d)
[3H]U69593 (j)
(+)-10a
(−)-10a
(+)-10b
(−)-10b
(+)-10c
(−)-10c
(+)-10d
(−)-10d
(+)-10e
(−)-10e
(+)-10f
(−)-10f
(+)-10g
(−)-10g
(+)-10h
(−)-10h
(+)-10i
(−)-10i
(+)-10j
(−)-10j
(+)-10k
(−)-10k
(+)-10l
(−)-10l
(+)-10m
(−)-10m
(+)-10n
(−)-10n
(+)-10o
(−)-10o
(+)-10p
(−)-10p
(+)-10q
(−)-10q
(+)-10r
(−)-10r
(+)-10s
(−)-10s
(+)-10t
(−)-10t
(+)-10u
(−)-10u
(+)-2
2-Me-phenyl
2-Me-phenyl
3-Me-phenyl
3-Me-phenyl
4-Me-phenyl
4-Me-phenyl
2-MeO-phenyl
2-MeO-phenyl
3-MeO-phenyl
3-MeO-phenyl
4-MeO-phenyl
4-MeO-phenyl
2-Cl-phenyl
2-Cl-phenyl
3-Cl-phenyl
3-Cl-phenyl
4-Cl-phenyl
4-Cl-phenyl
2,4-di-Cl-phenyl
2,4-di-Cl-phenyl
2-NO2-phenyl
2-NO2-phenyl
3-NO2-phenyl
3-NO2-phenyl
4-NO2-phenyl
4-NO2-phenyl
2-Pyridyl
2-Pyridyl
3-Pyridyl
3-Pyridyl
4-Pyridyl
4-Pyridyl
3-Indolyl
3-Indolyl
2-OH-phenyl
2-OH-phenyl
3-OH-phenyl
3-OH-phenyl
4-OH-phenyl
4-OH-phenyl
Vinyl
Vinyl
Phenyl
Phenyl
68
19 0.9
63
9.8 0.1
38
17 1.3
3
510 24
310 24
880 32
96
190 17
190
4
2
7
86
270
36
5
9
2
320 22
440 15
900 88
170 22
320 24
280 25
300 17
1100 68
880 76
180 14
330 30
2
52
25
104
2
2
4
680 47
390 13
1110 79
20 1.1
160
6
107
9
510 30
20 1.3
43 1.0
13 0.8
55
135
4
3
200 13
1140 63
160 15
300 13
103 13
87
4.1 0.4
65
6.3 0.5
3
200
4
290 21
500 19
180 17
1060 59
1063 68
2
79
50
83
3
3
3
170
5
178 23
390 13
250 24
1400 65
117 11
500 23
220
8
5.2 0.5
69
750 61
3
130
45
4
4
1.9 0.1
28 0.6
0.9 0.1
149 12
240 24
140
35
4
9
500 53
2400 127
1825 185
1040 92
710 35
1900 240
1100 71
260 12
510 23
540 39
350 45
550 27
430 23
470 41
1050 150
2800 250
600 60
540 48
300 10
1400 130
380 22
1340 133
1820 169
310 32
34
42
3
3
13 1.0
75
51
118
40
65
21
76
26
40
6
4
9
2
3
2
8
2
3
190
720 53
93
5
4
250 17
350 17
390 27
1000 45
1800 109
148 12
35
320 13
19
11 0.9
3
53
5
1370 108
2
54
75
4
5
(−)-2
a [3H]DAMGO (D-Ala2,MePhe4Gly-ol5)enkephalin; [3H]DADLE (D-Ala2,D-Leu5)enkephalin; [3H]U69593 trans-3,4-dichloro-N-methyl[2-(1-
pyrrolidinyl)cyclohexyl]benzeneacetamide. Rat brain membranes were used for l and d binding, and guinea pig brain membranes were used for
j binding. All results, n = 3. b The dextrorotatory and levorotatory compounds were 1S,5R and 1R,5S, respectively. All of the compounds were tested in
salt form except for the 10n, 10p and 10q enantiomers that were tested as bases.
methoxyphenyl)-2-methyl-2-aza-bicyclo[3.3.1]nonane (8a) ([a]D20
N-methyl-m-hydroxy-5-phenylmorphan salt that had previously
had its configuration established by X-ray crystallographic
analysis.21
Thus, the (−)-6 base (levorotatory at 589 nm) from the
(−)-6.di-O,Oꢁ-p-toluyl-L-tartaric acid salt was converted to the
secondary amine base (+)-8 ([a]2D0 +2.9 (c 0.81, EtOH)) by
catalytic hydrogenation with H2/Pd. The hydrochloride salt of
(+)-8 was levorotatory. The (+)-8 base was N-methylated through
reductive formylation (H2/Pd and HCHO) to (1R,5S)-(−)-5-(3-
20
−10.9 (c 0.70, EtOH), [a]
−21.1 (c 0.70, EtOH)),
365
that, like the known20 1S,5R-N-methyl base, 1S,5R-(+)-5-(3-
methoxyphenyl)-2-methyl-2-aza-bicyclo[3.3.1]nonane, was an oil.
The (−)-N-methyl compound was converted to its hydro-
bromide salt, (1R,5S)-(−)-5-(3-methoxyphenyl)-2-methyl-2-aza-
◦
bicyclo[3.3.1]nonane·HBr (8a·HBr, mp 195–197 C; [a]2D0 −5.1
20
365
(c 0.82, MeOH), [a] −15.4 (c 0.82, MeOH)). The melting
point was comparable to the known 1S,5R-(+)-hydrobromide salt
This journal is
The Royal Society of Chemistry 2007
Org. Biomol. Chem., 2007, 5, 1177–1190 | 1179
©

View Article Online
Table 2 Agonist and antagonist activity of selected ligands at opioid
receptors
l
d
j
Compound
% Sa
% Ib
% Ib
(−)-10a
(−)-10b
(−)-10c
(−)-10d
(−)-10e
(−)-10f
(−)-10g
(−)-10h
(−)-10i
(−)-10k
(−)-10l
(+)-10m
(−)-10m
(−)-10o
(−)-10r
(−)-10s
DAMGO
1.0
15
39
30
36
50
19
47
41
184
142
−8.3
124
164
23
100
94
82
92
86
74
89
98
100
60
87
100
99
57
98
99
97
89
82
91
88
74
93
93
93
83
84
96
90
62
96
84
Scheme 2 Reagents and conditions: a) H2/Pd; b) H2/Pd–HCHO; c) 48%
HBr.
◦
(199–201 C).20 The base 8a was O-demethylated to 3-((1R,5S)-
9.0
500
(−)-2-methyl-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol (8b)19 (mp
◦
20
365
151–153 C, [a]2D0 −11.7 (c 0.775, EtOH), [a] −26.8 (c 0.775,
a % Stimulation (agonist efficacy) compared with DAMGO (l). Negative
numbers indicate inverse agonist effect. b % Inhibition (antagonist efficacy)
after stimulation with SNC80 (d), or U50499 (j). Each value is the mean
of 3 independent determinations. Compounds were screened at a 10 lM
concentration.
◦
EtOH); lit.,19 153–154 C, [a]2D0 −12.7) and 8b was converted
◦
to its hydrobromide◦ salt (mp 228–229 C, [a]2D0 −4.6 (c 0.81,
H2O); lit.,21 232–233 C, [a]D20 −4.2 (H2O)), with the known 1R,5S
configuration.21 Thus, through the chemical conversion (Scheme 2)
of (−)-6 to 3-((1R,5S)-(−)-2-methyl-2-aza-bicyclo[3.3.1]nonan-5-
yl)phenol hydrobromide (8b·HBr) we were able to assign the
absolute configuration of all of the compounds reported herein.
As noted above, hydrogenation of (+)-6 in the presence of
10% Pd–C gave the methoxyphenylamine base ((−)-8), which was
converted to (+)-8·HCl in high yield (Scheme 3).
demethylation of (+)-6 followed by reprotection with (bromo-
methyl)cyclopropane and dehydrogenation. The amines 1R,5S-
(+)-8 and (−)-9 were also prepared from (−)-6 in the same
way. The arylethyl-O-tosylate 7a–n (Scheme 4), a very useful
intermediate for some of the N-arylethyl substituents, was syn-
thesized by the reaction of the corresponding arylethyl alcohol
and p-toluenesufonyl chloride in the presence of triethylamine.28
The cyclopropylmethoxyphenylamine (+)-9 was prepared
for selective protection during some N-derivatizations via
Scheme 3 Reagents and conditions: a) AcOH, 10% Pd–C, H2 (60 psi), rt, 93%; b) i) CH2Cl2, BBr3·SMe2 in CH2Cl2, 50 ◦C; ii) dry DMF, t-BuOK, 0 ◦C,
(bromomethyl)cyclopropane, 50 ◦C; iii) AcOH, 10% Pd–C, H2 (70 psi), 50 ◦C, 54–57% over 3 steps; c) i) dry DMF, 7, K2CO3, 50 ◦C; ii) 1,2-dichloroethane,
BBr3·SMe2 in CH2Cl2, reflux, 17–35% over 2 steps; d) i) dry DMF, 7, K2CO3, 50 ◦C; ii) MeOH, conc. HCl, reflux, 27–38% over 3 steps; e) i) CH2Cl2,
indole-3-acetic acid, EDCI·HCl, rt; ii) THF, LiAlH4, 0 ◦C; iii) 1,2-dichloroethane, BBr3·SMe2 in CH2Cl2, reflux, ∼20% over 3 steps; f) i) CH2Cl2,
3-pyridylacetic acid, EDCI·HCl, rt; ii) THF, LiAlH4, 0 ◦C; iii) MeOH, conc. HCl, reflux, 22% over 3 steps; g) i) dry DMF, 4-bromo-1-butene, K2CO3,
50 ◦C; ii) 1,2-dichloroethane, BBr3·SMe2 in CH2Cl2, reflux, ∼20% over 2 steps; h) i) dry DMF, 4-(2-bromoethyl)-pyridine, K2CO3, 50 ◦C; ii) MeOH, conc.
HCl, reflux, 25–58% over 2 steps.
1180 | Org. Biomol. Chem., 2007, 5, 1177–1190
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
Scheme 4
Experimental details for all of the above are given in the
Supplementary Information‡.
The target compounds, enantiomeric 10a–u were prepared using
one of several methods from the reaction of the corresponding
enantiomeric amines and N-arylethyl precursor (See Scheme 3
and Table 1). The reaction of enantiomeric amines 8 or 9 with
arylethyl-O-tosylate 7a–n in the presence of potassium carbonate
gave N-arylethyl derivatives, which were subsequently deprotected
to provide the enantiomeric phenolic compounds 10a–10n or 10r–
10t (Method A or B). Enantiomeric compounds 10o and 10q
were prepared from the reaction of enantiomeric amines 9 or 8,
respectively, and 3-pyridylacetic acid (for 10o) or indole-3-acetic
acid (for 10q) in the presence of 1-(3-dimethylaminopropyl)-3-
ethylcarbodiimide hydrochloride (EDCI) followed by reduction
and demethylation (Method C or E). Also, 1S,5R-(+)-10p and
1R,5S-(−)-10u were synthesized from the reaction of 1S,5R-(+)-9
or 1R,5S-8, respectively, and 4-(2-bromoethyl)-pyridine (for
(+)-10p) or 4-bromo-1-butene (for (−)-10u) followed by depro-
tection to give the phenolic compound.
Fig. 2 Effect of test drugs on basal [35S]GTP-c-S binding in hDOR-CHO
cells. [35S]GTP-c-S binding assays were conducted as described in Methods.
Each point is the mean SD (n = 3). *p < 0.05 when compared to control
(Students t-test).
In general, the compounds with the highest affinity for the l-
opioid receptor were levorotatory and had the 1R,5S configuration
(except for 10t, Table 1, the p-hydroxyphenethyl derivative).
This was also usually true at the d-receptor, but there were
many more exceptions (e.g., 10g, 10j, 10n, 10r, 10s, and 10t
in Table 1). At the j-receptor, all of the compounds with the
1S,5R configuration (except 10f), had higher affinity than those
with the 1R,5S configuration, as did the parent N-phenethyl
compound 2. This difference probably reflects the very different
binding sites for these compounds in the j- vs. l- or d-opioid
receptors.
The compound that had the highest affinity for the l-
opioid receptor, 1R,5S-(−)-3-{2-[2-(4-nitrophenyl)-ethyl]-2-aza-
bicyclo[3.3.1]non-5-yl}-phenol (1R,5S-(−)-10m), was the 4-
nitrophenylethyl substituted phenylmorphan (Ki = 0.9 nM,
Table 1). It also showed fair affinity for the d-receptor (Ki =
35 nm), and less affinity for the j-receptor (Ki = 140 nm). The
entire set of compounds was screened, at a 10 lM concentration,
for l agonism and d antagonism in the [35S]-GTP-c-S binding
assay (Table 2). Four compounds ((−)-10k, (−)-10l, (−)-10m
and (−)-10o) showed the greatest degree of l agonism, although
the stimulation was considerably less than that produced by
DAMGO. Among these four compounds, (−)-10m showed the
greatest degree of d antagonism, and was therefore selected for
additional study.
To characterize the interaction of (−)-10m with l and d
receptors in greater detail, we determined the effects of (−)-10m
on basal [35S]GTP-c-S binding. As reported in Fig. 2, (−)-10m
reduced basal [35S]-GTP-c-S binding by ∼30%, indicating that
this compound is an inverse d agonist.
Interestingly, naltrindole (NTI) also showed inverse d agonist
activity, suggesting that in this cell line the d receptors are
constitutively active. Also, (−)-10m was a partial l agonist. As
reported in Fig. 3, (−)-10m potently stimulated [35S]GTP-c-S
binding to l receptors with an EC50 value of 2.39 nM and an EMAX
Fig. 3 Effect of (−)-10m on [35S]GTP-c-S binding in hMOR-CHO cells.
[35S]GTP-c-S binding assays were conducted as described in Methods.
The data were fit to a dose-response equation for the best-fit estimates
of the EC50 and EMAX. Maximal stimulation was determined with 1 lM
DAMGO. Each point is the mean SD (n = 3).
value of 47 1%, where the 100% is defined as the [35S]GTP-c-S
stimulation produced by 1 lM DAMGO.
The EC50 of DAMGO at the l receptor in recent [35S]GTP-c-S
assays was 11 1 nM, indicating that (−)-10m is a more potent l
agonist than DAMGO. In order to determine the Ke (antagonist
Ki) value of (−)-10m at the d receptor, we generated SNC80 dose-
response curves in the absence and presence of two concentrations
of (−)-10m. As expected for a d antagonist, (−)-10m produced a
This journal is
The Royal Society of Chemistry 2007
Org. Biomol. Chem., 2007, 5, 1177–1190 | 1181
©

View Article Online
dose-dependent rightward shift in the SNC80 dose-response curve
without significantly altering the EMAX values (Fig. 4).
We also examined the compound in vivo (Fig. 5). It was found
to be approximately 50-times more potent than morphine in the
55 ◦C tail flick assay (in mice, in comparison of A50 values).
Fig. 4 Effect of (−)-10m on SNC80-stimulated [35S]GTP-c-S binding
in hDOR-CHO cells. [35S]GTP-c-S binding assays were conducted as
described in the Methods section. The data were fit to a dose-response
equation for the best-fit estimates of the EC50 and EMAX (see Table 3). Each
point is the mean SD (n = 4–10).
Fig. 5 Dose and time-response curve for subcutaneous (−)-10m in the
55 ◦C tail-flick test.
The time of peak effect was determined to be 20 min and the A90
dose was 0.32 mg kg−1. The calculated A50 value (95% confidence
interval) was 0.131 mg kg−1 (0.1016–0.1699 mg kg−1). Robust
increases in locomotion and Straub-tail were observed during
testing of the higher doses. The (−)-10m was further evaluated
in other antinociceptive assays in the mouse. It was found to
be 18 times more potent than morphine in the hot plate assay,
6 times more potent in the phenylquinone assay, 43 times more
potent in the tail flick assay (comparison via standard literature
assays29), and was inactive as an opioid antagonist in the tail flick
vs. morphine assay. Straub tail and increased locomotor activity
were also observed in these assays.
These data, reported in Table 3, show that the Ke value of
(−)-10m is ∼122 nM, indicating that (−)-10m is a much weaker d
antagonist than NTI (Ke = 0.23 nm).
The data indicate that (−)-10m is much more potent as a l
agonist than as a d antagonist. This profile is the opposite of that
reported for 4-chlorophenylpyridomorphinan, which was much
more potent as a dantagonist than as a l agonist.11 Despite having
lower affinity at j receptors than dreceptors (Table 1), the Ke value
of (−)-10m at j receptors was similar to that observed for the d
receptor (∼106 nm). As observed with the d receptor, (−)-10m is a
weak j antagonist as compared to nor-binaltorphimine (nor-BNI)
(Ke = 0.1 nm).
Three analogues with Ki values ca. 5 nM at the l-receptor, the
3-chlorophenyl (1R,5S-(−)-10h), 2-nitrophenyl (1R,5S-(−)-10k),
Table 3 Characterization of (−)-10m at d and j receptors in the [35S]GTP-c-S binding assaya
Conditions
EC50/nM SD
E
MAX (% maximal stimulation SD)
Ke/nM
Delta receptors
SNC80 (n = 10)
37.8 3.0
60.2 7.9
115 10
701 28
100
97
99
2
3
2
2
SNC80 + 100 nM (−)-10m (n = 5)
SNC80 + 250 nM (−)-10m (n = 4)
SNC80 + 4 nM naltrindole (n = 3)
Kappa receptors
169
122
0.23
114
(−)-U40488 (n = 7)
56.2 3.1
321 29
1140 63
111 7.3
97 1.1
(−)-U40488 +50 nM (−)-10m (n = 3)
(−)-U40488 +300 nM (−)-10m (n = 4)
(−)-U40488 +0.1 nM norBNI (n = 7)
105
3
3
2
106
155
0.10
123
102
a [35S]-GTP-c-S binding was conducted as described in the Methods section. Agonist dose–response curves (ten points/curve) were generated in the absence
and presence of the indicated concentrations of test agents. Since (−)-10m decreased basal [35S]-GTP-c-S binding in the hDOR-CHO cells, SNC80 dose
response curves were calculated relative to the depressed baseline. The data for each experimental condition were pooled and the best-fit estimates of the
EC50 and EMAX values determined using MLAB-PC. The Ke values were calculated according to the equation: [Test Drug]/(EC50-2/EC50-1 − 1), where
EC50-2 is the EC50 value in the presence of the test drug and EC50-1 is the value in the absence of the test drug. Each parameter value is SD.
1182 | Org. Biomol. Chem., 2007, 5, 1177–1190
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
and the 3-nitrophenyl compound (1R,5S-(−)-10l) (Ki = 4, 5,
and 2 nM, respectively), were all partial l-agonists, and a fourth
compound, the 3-methylphenyl analogue (1R,5S-(−)-10b), with a
Ki value ca. 10 nM for the l-receptor was found to be a selective
l-antagonist (Table 2). Neither the 2-nitrophenyl nor the 3-
nitrophenyl analogue was found to have d-antagonist activity in the
[35S]GTP-c-S assay, nor did any of the methoxyphenyl compounds.
The desired l-agonist d-antagonist activity was only found in a
compound bearing a 4-nitro substituent. That substituent is bulky
and together with its well-known inductive and electronic effects
could modify the aromatic ring’s ability to interact with amino
acids in receptors, suggesting that this mixture of pharmacological
activities might be sensitive to a combination of electronic and
steric effects in the N-phenethyl-5-phenylmorphans.
Three other compounds, besides the aforementioned 4-nitro
derivative, had fair (Ki <100 nm) affinity for the d-receptor,
the 4-methylphenyl (1R,5S-(−)-10c), 4-methoxyphenyl (1R,5S-
(−)-10f), and the 4-chlorophenyl (1R,5S-(−)-10i) analogues. 3-
((1R,5S)-(−)-2-(4-Chlorophenethyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((−)-10i) was of special interest, since it decreased
[35S]GTP-c-S binding to d receptors 18% below baseline (data not
shown), indicating that it is an inverse dagonist. In antinociceptive
assays, (−)-10i was equipotent with morphine in the hot plate
assay, 5 times more potent in the phenylquinone assay, and 4 times
more potent in the tail flick assay. It had no opioid antagonist
activity in the tail flick vs. morphine assay, presumably an assay
for l-opioid antagonists. The 4-chlorophenethyl analogue (−)-10i
might be a leading candidate for further research that might
provide a potent anorectant,16 and it is also interesting because
of its unusual combination of properties, a l-agonist and d-inverse
agonist.
the ortho- and the meta-phenolic compounds (−)-10r and (−)-10s
had similar, moderately high affinities for the l-receptor, but the
para-analogue (−)-10t had much less affinity. Thus, although it
is clear that the substituent on the N-phenethyl group affected
affinity, the mechanism underlying that effect is unclear.
Conclusions
Unlike previously synthesized N-phenethyl substituted phenyl-
morphans that were found to be promiscuous opioid antagonists
(Fig. 1), some of the new analogues were selective l-agonists with
good affinity at the l- and others had moderate affinity at the
d-opioid receptor. Several compounds with the 1R,5S absolute
configuration were found, in the [35S]GTP-c-S binding assay, to
have efficacy as partial l-agonists ((−)-10m, (−)-10h, (−)-10k,
and (−)-10l), and one was a l-antagonist ((−)-10b. Most useful
and interesting was the discovery that the 4-nitrophenyl analogue
(−)-10m had affinity and efficacy at l and dreceptors; it was found
to have both l-agonist and d-antagonist activity. Although much
more potent than morphine as an antinociceptive, it also showed
some signs that it might have undesired side-effects (Straub-tail at
higher doses). Also, the 4-chlorophenyl analogue (−)-10i, which
had lower affinity than the former compound at l and dreceptors,
was found to be an inverse agonist at the dopioid receptor and was
morphine-like in antinociceptive assays. Both of these analogues
will serve as model compounds for the synthesis of more efficacious
ligands.
Experimental
All melting points were determined on a Thomas-Hoover melting-
point apparatus and are uncorrected. Proton nuclear magnetic
resonance (1H NMR, 300 MHz) and carbon nuclear magnetic
resonance (13C NMR, 75 MHz) spectra were recorded on a
Varian Gemini-300 instrument in CDCl3 (unless otherwise noted)
with the values given in ppm (TMS as internal standard) and J
(Hz) assignments of 1H resonance coupling. The high-resolution
electrospray ionization (ESI) mass spectra were obtain on a Waters
LCT Premier time-of-flight (TOF) mass spectrometer. Thin-layer
chromatography (TLC) was performed on 0.25 mm Analtech
GHLF silica gel. Flash column chromatography was performed
with Bodman silica gel LC 60 A. Elemental analyses were per-
formed by Atlantic Microlabs, Inc., Norcross, GA. Enantiomeric
purity was assessed by HPLC (Shimadzu LC-6A with a Shimadzu
SPD-6AV UM detector (at 254 nm) using Daicel’s Chiralcel
OD column (250 × 4.6 mm). The mobile phase was hexanes–2-
propanol–diethylamine (95:5:0.25) at a flow rate of 0.6 mL min−1.
The experimental details for compounds 3, ( )-6 (and the
resolution to (+)- and (−)-6), 7, 7a through 7l, (+)- and (−)-8 and
(+)- and (−)-9 are included in the Supplementary Information‡.
In the substituted phenyl series, the 3-nitrophenyl com-
pound (−)-10l had fair affinity, and the 2-methylphenyl and
2-hydroxyphenyl analogues had a little less affinity for the j-
receptor (Ki = 45, 68 and 93 nM, respectively). Both the ((+)-10a
and (+)-10r, were in the 1S,5R enantiomeric series. Their 1R,5S
counterparts had some, but less, affinity for the j-receptor (Ki = ca.
190 and 250 nM, respectively). The higher affinity 2-methylphenyl
analogue (1S,5R-(+)-10a) was noted to have some efficacy as a
j-antagonist in the [35S]GTP-c-S binding assay.
The efficacies and affinities of the newly synthesized ligands
at the l-receptor were obviously influenced by the substituent
on the phenyl ring. These substituents are relatively distant from
the nitrogen atom, and would not be likely to have much direct
influence on a nitrogen atom known to be important for inter-
action with opioid receptors. The properties of the aromatic ring
itself must, then, influence receptor affinity and/or efficacy. The
steric bulk of an indolyl ((−)-10q) and a nitrophenethyl (−)-10k,
(−)-10l, or (−)-10m) moiety was unlikely to be the predominant
factor in receptor interaction, since (−)-10q had considerably less
affinity than the phenethyl analogue (−)-2, and, as noted above,
the 4-nitrophenyl analogue ((−)-10m) had the highest affinity at
the l-opioid receptor. The electronic influence of the substituent
on binding was also not obvious. The compounds with the next
highest affinities for the l-receptor were analogues with a 3-
chlorophenyl ((−)-10h, Ki = 4 nm) moiety and a 3-nitrophenyl
moiety ((−)-10l, Ki = 1.9 nm). It is likely that a 3-chloro, a 3-nitro
and a 4-nitro substituent would affect the electronic character of
the aromatic ring differently, yet all had high affinity. Also, both
General procedure for syntheses of 3-((1S,5R)-(+)-2-(2-(or 3- or
4-)arylethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10) and
3-((1R,5S)-(−)-2-(2-(or 3- or 4)-arylethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10)
Method A. A mixture of enantiomeric amine 8 (2–3 mmol),
corresponding arylethyl tosylate 7 (1.5 equiv.) and K2CO3 (3 equiv)
in dry DMF (∼0.2 M concentration) were heated at 50 ◦C for 6 h.
This journal is
The Royal Society of Chemistry 2007
Org. Biomol. Chem., 2007, 5, 1177–1190 | 1183
©

View Article Online
After the cooled mixture was filtered and the solvent evaporated,
the residue was diluted with 5% MeOH in CH2Cl2, washed with
water and brine, dried over Na2SO4, passed through a pad of
silica gel and concentrated to dryness. The product was directly
used for demethylation, which used 1.0 M BBr3·SMe2 in CH2Cl2
(vide supra). Column chromatography of crude product with 1–2%
MeOH in CH2Cl2 gave 10 (17–35% yield over 2 steps).
(4 mL) was heated at 50 ◦C for 2 h. After the cooled mixture was
filtered and the solvent evaporated, the residue was diluted with
ethyl acetate, washed with water and brine, dried over Na2SO4,
passed through a pad of silica gel and concentrated to dryness.
The crude product was used for the demethylation (see method A)
to give 10 (∼20% yield over 2 steps).
3-((1S,5R)-(+)-2-(2-methylphenethyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((+)-10a) and 3-((1R,5S)-(−)-2-(2-methylphenethyl)-
2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10a)
Method B. A mixture of enantiomeric amine 9 (2–3 mmol), the
corresponding arylethyl tosylate 7 (2 equiv.) and K2CO3 (3 equiv.)
in dry DMF (∼0.15 M concentration) was heated at 60 ◦C for 4 h.
After the cooled mixture was filtered and the solvent evaporated,
the residue was diluted with ethyl acetate, washed with water and
brine, dried over Na2SO4, passed through a pad of silica gel and
concentrated to dryness. The product was used without further
purification in the demethylation procedure, in which the reaction
mixture in concentrated HCl–MeOH (1 : 1, 0.05 M solution) was
refluxed for 2 h. After cooling, it was basified with NH4OH (to
∼pH 10), extracted with 10% MeOH in CH2Cl2, washed with
water and brine, dried over Na2SO4 and concentrated to give a
crude product. Column chromatography of this crude product
with 2–5% MeOH in CH2Cl2 gave 10 (27–38% yield over 2 steps).
(+)-10a was obtained from◦the reaction of 1S,5R-8 and 7a by
method A. Mp 260–261.5 C as HCl salt; [a]2D0 +16.6 (c 0.42,
MeOH); 1H NMR (CDCl3, free base): d 7.18–7.09 (m, 5H), 6.81
(d, 1H, J = 8 Hz), 6.76 (br-t, 1H, J = 2 Hz), 6.63 (dd, 1H, J =
8 and 2 Hz), 3.31 (br, 1H), 3.10–3.00 (m, 2H), 2.90–2.70 (m, 4H),
2.29 (s, 3H), 2.18 (br-t, 2H, J = 12 Hz), 2.04–1.82 (m, 5H), 1.70–
1.54 (m, 2H), 1.47–1.36 (m, 1H); 13C NMR (CDCl3, free base):
d 156.68, 153.21, 138.25, 136.09, 130.22, 129.35, 129.24, 126.26,
126.01, 116.32, 113.58, 112.70, 56.28, 52.28, 49.55, 38.08, 34.70,
30.88, 24.30, 22.78, 19.22; HRMS (ESI): Found 336.2318 [MH]+,
C23H30NO requires 336.2327. Found: C, 73.58; H, 8.13; N, 3.70.
Calc. for C23H29NO·HCl·0.25H2O: C, 73.38; H, 8.17; N, 3.72%.
(−)-10a was obtained from the reaction of 1R,5S-8 and 7a
Method C. A mixture of enantiomeric amine (−)-9 (250 mg,
0.92 mmol), 3-pyridylacetic acid (209 mg, 1.2 mmol) and EDCI
(230 mg, 1.2 mmol) in CH2Cl2 (6 mL) was stirred at room
temperature overnight. The reaction was diluted with 5% 2-
propanol in CH2Cl2, washed with aqueous Na2CO3 solution (to
∼pH 10) and brine, dried over Na2SO4 and passed through a
pad of silica gel. After evaporation, the residue was used without
further purification in the following reduction. LiAlH4 (42 mg,
1.1 mmol) was added to a solution of amide (∼0.36 mmol) in dry
THF (3 mL) at 0 ◦C and the mixture was stirred for 2 h. The
reaction was quenched by addition of saturated NH4Cl solution,
filtered through a pad of celite, extracted with ethyl acetate, washed
with water and brine, dried over Na2SO4 and concentrated to
give a crude amine, which was subjected to deprotection using
concentrated HCl–MeOH (see method B) to provide (−)-10k
(60 mg, 22% over 3 steps).
◦
by method A. Mp 263–264 C as HCl salt; [a]2D0 −16.7 (c
0.42, MeOH); HRMS (ESI): Found 336.2304 [MH]+, C23H30NO
requires 336.2327. Found: C, 74.10; H, 8.24; N, 3.73. Calc. for
C23H29NO·HCl: C, 74.27; H, 8.13; N, 3.77%.
3-((1S,5R)-(+)-2-(3-Methylphenethyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((+)-10b) and 3-((1R,5S)-(−)-2-(3-methylphenethyl)-
2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10b)
(+)-10b was obtained f◦rom the reaction of 1S,5R-8 and 7b by
method A. Mp 248–249 C as HCl salt; [a]2D0 +13.8 (c 0.38, MeOH);
1H NMR (CD3OD, free base): d 7.26–7.07 (m, 5H), 6.84 (dq, 1H,
J = 8 and 1 Hz), 6.80 (br-t, 1H, J = 2 Hz), 6.66 (ddd, 1H, J = 8,
2 and 1 Hz), 3.95 (br, 1H), 3.74–3.52 (m, 2H), 3.47–3.04 (m, 2H),
2.34 (s, 3H), 2.40–2.02 (m, 7H), 1.92–1.70 (m, 3H); 13C NMR (d6-
DMSO, HCl salt): d 157.36, 151.04, 137.72, 136.94, 129.39, 129.30,
128.51, 127.44, 125.85, 115.13, 113.04, 111.61, 54.23, 54.16, 48.56,
36.69, 34.95, 33.89, 33.23, 29.80, 21.40, 20.96, 20.43; HRMS (ESI):
Found 336.2335 [MH]+, C23H30NO requires 336.2327. Found: C,
74.19; H, 8.21; N, 3.73. Calc. for C23H29NO·HCl: C, 74.27; H, 8.13;
N, 3.77%.
Method D. A mixture of enantiomeric amine 9 (∼2 mmol),
4-(2-bromoethyl)pyridine (∼3 equiv.) and K2CO3 (∼6 equiv.) in
◦
dry DMF (3 mL) was heated at 50 C for 2 h. After the cooled
mixture was filtered and the solvent evaporated, the residue was
diluted with ethyl acetate, washed with water and brine, dried over
Na2SO4, passed through a pad of silica gel and concentrated to
dryness. The crude product was subjected to deprotection using
concentrated HCl–MeOH (see method B) to provide 10 (25–58%
over 2 steps).
(−)-10b was obtained from the reaction of 1R,5S-8 and 7b
◦
by method A. Mp 205–206 C as HBr salt; [a]2D0 −13.6 (c
0.38, MeOH); HRMS (ESI): Found 336.2299 [MH]+, C23H30NO
requires 336.2327. Found: C, 66.17; H, 7.34; N, 3.35. Calc. for
C23H29NO·HBr: C, 66.34; H, 7.26; N, 3.36%.
Method E. A mixture of enantiomeric amine 8 (2–3 mmol),
indole-3-acetic acid (1.1 equiv.) and EDCI (1.3 equiv.) in CH2Cl2
(∼2 M concentration) was stirred at room temperature overnight.
The reaction was diluted with 5% 2-propanol in CH2Cl2, washed
with aqueous Na2CO3 solution (to ∼pH 10) and brine, dried over
Na2SO4 and passed through a pad of silica gel. The crude product
was used for the reduction (see method C) and demethylation (see
method A) to give 10 (∼20% yield over 3 steps).
3-((1S,5R)-(+)-2-(4-Methylphenethyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((+)-10c) and 3-((1R,5S)-(−)-2-(4-methylphenethyl)-
2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10c)
(+)-10c was obtained f◦rom the reaction of 1S,5R-8 and 7c by
method A. Mp 237–238 C as HCl salt; [a]2D0 +13.4 (c 0.32, MeOH);
1H NMR (CDCl3, free base): d 7.18–7.09 (m, 5H), 6.82 (d, 1H,
J = 8 Hz), 6.78 (br-t, 1H, J = 2 Hz), 6.62 (dd, 1H, J = 8 and
2 Hz), 3.31 (br, 1H), 3.10–3.00 (m, 2H), 2.90–2.70 (m, 4H), 2.31
Method F. A mixture of enantiomeric amine 8 (∼2 mmol),
4-bromobut-1-ene (2 equiv.) and K2CO3 (4 equiv.) in dry DMF
1184 | Org. Biomol. Chem., 2007, 5, 1177–1190
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
(s, 3H), 2.19 (br-t, 2H, J = 12 Hz), 2.04–1.82 (m, 5H), 1.72–
1.54 (m, 2H), 1.42–1.30 (m, 1H); 13C NMR (CDCl3, free base):
d 156.41, 153.32, 137.00, 135.61, 129.25, 129.09, 128.62, 116.57,
113.30, 112.54, 57.79, 52.30, 49.62, 38.17, 38.08, 36.83, 34.73,
33.26, 24.32, 22.70, 21.10; HRMS (ESI): Found 336.2329 [MH]+,
C23H30NO requires 336.2327. Found: C, 74.03; H, 8.33; N, 3.81.
Calc. for C23H29NO·HCl: C, 74.27; H, 8.13; N, 3.77%.
3-((1S,5R)-(+)-2-(4-Methoxyphenethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10f) and 3-((1R,5S)-(−)-2-
(4-methoxyphenethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol
((−)-10f)
(+)-10f was obtained from the reaction of 1S,5R-9 and 7f by
method B. Mp 214–215 ◦C as HCl salt; [a]2D0 +15.2 (c 0.33, MeOH);
1H NMR (CDCl3, free base): d 7.19–7.10 (m, 3H), 6.90–6.80 (m,
3H), 6.78 (t, 1H, J = 2 Hz), 6.64 (dd, 1H, J = 8 and 2 Hz),
3.78 (s, 3H), 3.25 (br, 1H), 2.86–2.75 (m, 4H), 2.16 (d, 2H, J =
12 Hz), 2.08–1.84 (m, 5H), 1.72–1.56 (m, 2H), 1.43–1.32 (m, 1H);
13C NMR (CDCl3, free base): d 157.94, 156.09, 153.74, 132.52,
129.63, 129.27, 116.87, 113.81, 113.07, 112.43, 58.01, 55.26, 52.19,
49.59, 38.49, 38.22, 37.13, 34.88, 33.16, 24.55, 22.81; HRMS (ESI):
Found 352.2274 [MH]+, C23H30NO2 requires 352.2278. Found: C,
71.05; H, 7.80; N, 3.54. Calc. for C23H29NO2·HCl: C, 71.21; H,
7.79; N, 3.61%.
(−)-10c was obtained from the reaction of 1R,5S-8 and 7c
◦
by method A. Mp 218–219 C as HBr salt; [a]2D0 −12.7 (c
0.37, MeOH); HRMS (ESI): Found 336.2343 [MH]+, C23H30NO
requires 336.2327. Found: C, 66.15; H, 7.37; N, 3.43. Calc. for
C23H29NO·HBr: C, 66.34; H, 7.26; N, 3.36%.
3-((1S,5R)-(+)-2-(2-Methoxyphenethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10d) and 3-((1R,5S)-
(−)-2-(2-methoxyphenethyl)-2-aza-bicyclo[3.3.1]nonan-5-
yl)phenol ((−)-10d)
(−)-10f was obtained from the reaction of 1R,5S-9 and 7f
◦
by method B. Mp 215–216 C as HCl salt; [a]2D0 −15.0 (c
0.33, MeOH); HRMS (ESI): Found 352.2274 [MH]+, requires
C23H30NO2 requires 352.2296. Found: C, 71.01; H, 7.96; N, 3.63.
Calc. for C23H29NO2·HCl: C, 71.21; H, 7.79; N, 3.61%.
(+)-10d was obtained from the reaction of 1S,5R-9 and 7d by
method B. Mp 244–245 ◦C as HCl salt; [a]2D0 +20.0 (c 0.42, MeOH);
1H NMR (CDCl3, free base): d 7.23–7.12 (m, 3H), 6.90–6.82 (m,
4H), 6.68 (dd, 1H, J = 8 and 2 Hz), 3.84 (s, 3H), 3.35 (br, 1H),
3.10–3.02 (m, 2H), 2.94–2.72 (m, 4H), 2.18 (br 2H), 2.04–1.88 (m,
5H), 1.70–1.56 (m, 2H), 1.43–1.36 (m, 1H); 13C NMR (CDCl3,
free base): d 157.72, 156.80, 153.43, 130.66, 129.40, 128.52, 127.70,
120.74, 116.64, 113.62, 112.94, 110.52, 55.82, 55.49, 52.30, 49.93,
38.33, 38.19, 36.91, 34.92, 28.22, 24.47, 22.90; HRMS (ESI):
Found 352.2274 [MH]+, C23H30NO2 requires 352.2277. Found: C,
70.73; H, 7.75; N, 3.62. Calc. for C23H29NO2·HCl·0.25H2O: C,
70.39; H, 7.83; N, 3.57%.
3-((1S,5R)-(+)-2-(2-Chlorophenethyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((+)-10g) and 3-((1R,5S)-(−)-2-(2-chlorophenethyl)-
2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10g)
(+)-10g was obtained f◦rom the reaction of 1S,5R-8 and 7g by
method A. Mp 204–205 C as HCl salt; [a]2D0 +18.7 (c 0.33, MeOH);
1H NMR (CDCl3, free base): d 7.35–7.30 (m, 1H), 7.22–7.08 (m,
4H), 6.83 (d, 1H, J = 8 Hz), 6.77 (m, 1H), 6.64 (dd, 1H, J = 8
and 2 Hz), 3.30 (br, 1H), 3.10–2.95 (m, 3H), 2.90–2.70 (m, 2H),
2.24–2.10 (m, 2H), 2.08–1.80 (m, 5H), 1.72–1.56 (m, 2H), 1.43–
1.32 (m, 1H); 13C NMR (CDCl3, free base): d 156.46, 153.40,
137.83, 133.95, 130.98, 129.41, 129.24, 127.64, 126.89, 116.52,
113.37, 112.61, 55.50, 52.28, 49.52, 38.16, 36.88, 34.74, 31.53,
24.52, 22.75; HRMS (ESI): Found 356.1785 [MH]+, C22H27ClNO
requires 356.1781. Found: C, 67.23; H, 7.13; N, 3.55. Calc. for
C22H26ClNO·HCl: C, 67.34; H, 6.94; N, 3.57%.
(−)-10d was obtained from the reaction of 1R,5S-9 and 7d
◦
by method B. Mp 241–242 C as HCl salt; [a]2D0 −20.2 (c
0.42, MeOH); HRMS (ESI): Found 352.2292 [MH]+, C23H30NO2
requires 352.2277. Found: C, 71.11; H, 7.78; N, 3.59. Calc. for
C23H29NO2·HCl: C, 71.21; H, 7.79; N, 3.61%.
3-((1S,5R)-(+)-2-(3-Methoxyphenethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10e) and 3-((1R,5S)-(−)-2-(3-
methoxyphenethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol
((−)-10e)
(−)-10g was obtained from the reaction of 1R,5S-8 and 7g
◦
by method A. Mp 215–216 C as HBr salt; [a]2D0 −17.2 (c 0.39,
MeOH); HRMS (ESI): Found 356.1801 [MH]+, C22H27ClNO
requires 356.1781. Found 356.1801. Found: C, 60.48; H, 6.22;
N, 3.20. Calc. for C22H26ClNO·HBr: C, 60.49; H, 6.23; N, 3.21%.
(+)-10e was obtained from the reaction of 1S,5R-9 and 7e by
method B. Mp 226–227 ◦C as HCl salt; [a]2D0 +13.9 (c 0.52, MeOH);
1H NMR (CDCl3, free base): d 7.23–7.12 (m, 2H), 6.84 (d, 1H, J =
8 Hz), 6.82–6.72 (m, 4H), 6.64 (dd, 1H, J = 8 and 2 Hz), 3.79 (s,
3H), 3.26 (br, 1H), 3.07–2.98 (m, 2H), 2.88–2.76 (m, 4H), 2.18 (d,
2H, J = 12 Hz), 2.08–1.84 (m, 5H), 1.72–1.56 (m, 2H), 1.43–1.32
(m, 1H); 13C NMR (CDCl3, free base): d 159.62, 156.31, 153.55,
142.01, 129.33, 129.26, 121.13, 116.68, 114.51, 113.24, 112.53,
111.38, 57.62, 55.14, 52.25, 49.58, 38.36, 38.18, 37.02, 34.82, 34.01,
24.46, 22.80; HRMS (ESI): Found 352.2264 [MH]+, C23H30NO2
requires 352.2277. Found: C, 70.99; H, 7.83; N, 3.56. Calc. for
C23H29NO2·HCl: C, 71.21; H, 7.79; N, 3.61%.
3-((1S,5R)-(+)-2-(3-Chlorophenethyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((+)-10h) and 3-((1R,5S)-(−)-2-(3-chlorophenethyl)-
2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10h)
(+)-10h was obtained from the reaction of 1S,5R-8 and 7h by
method A. Mp 227–229 ◦C as HBr salt; [a]2D0 +11.4 (c 0.33, MeOH);
1H NMR (CDCl3, free base): d 7.20–7.10 (m, 4H), 7.04 (dt, 1H, J =
6 and 2 Hz), 6.83 (d, 1H, J = 8 Hz), 6.75 (t, 1H, J = 2 Hz), 6.63 (dd,
1H, J = 8 and 2 Hz), 3.25 (br, 1H), 3.02 (dd, 2H, J = 9 and 3 Hz),
2.84–2.76 (m, 4H), 2.20–2.10 (m, 2H), 2.08–1.80 (m, 5H), 1.74–
1.54 (m, 2H), 1.43–1.32 (m, 1H); 13C NMR (CDCl3, free base):
d 156.46, 153.31, 142.24, 134.04, 129.60, 129.30, 128.78, 126.96,
126.26, 116.50, 113.42, 112.58, 57.29, 52.34, 49.48, 38.16, 38.09,
36.87, 34.71, 33.42, 24.35, 22.72; HRMS (ESI): Found 356.1783
(−)-10e was obtained from the reaction of 1R,5S-9 and 7e
◦
by method B. Mp 223–224 C as HCl salt; [a]2D0 −13.7 (c
0.52, MeOH); HRMS (ESI): Found 352.2271 [MH]+, C23H30NO2
requires 352.2277. Found: C, 71.04; H, 7.90; N, 3.53. Calc. for
C23H29NO2·HCl: C, 71.21; H, 7.79; N, 3.61%.
This journal is
The Royal Society of Chemistry 2007
Org. Biomol. Chem., 2007, 5, 1177–1190 | 1185
©

View Article Online
[MH]+, C22H27ClNO requires 356.1781. Found: C, 60.54; H, 6.37;
N, 3.19. Calc. for C22H26ClNO·HBr: C, 60.49; H, 6.23; N, 3.21%.
(−)-10h was obtained from the reaction of 1R,5S-8 and 7h
7.52–7.46 (m, 1H), 7.38–7.30 (m, 2H), 7.15 (t, 1H, J = 8 Hz), 6.88–
6.82 (m, 1H), 6.78 (t, 1H, J = 2 Hz), 6.65 (dd, 1H, J = 8 and 2 Hz),
3.22 (br, 1H), 3.19–2.76 (m, 5H), 2.22–2.10 (m, 2H), 2.08–1.82 (m,
4H), 1.74–1.55 (m, 2H), 1.48–1.35 (m, 1H); 13C NMR (CDCl3,
free base): d 156.29, 153.58, 149.43, 135.41, 133.02, 132.73, 129.29,
127.23, 124.62, 116.69, 113.28, 112.56, 56.34, 52.60, 49.31, 38.25,
38.20, 36.93, 34.75, 31.18, 24.67, 22.71; HRMS (ESI): Found
367.2037 [MH]+, C22H27N2O3 requires 367.2022. Found: C, 65.09;
H, 6.74; N, 6.77. Calc. for C22H26N2O3·HCl·0.25H2O: C, 64.86; H,
6.80; N, 6.88%.
◦
by method A. Mp 239–241 C as HCl salt; [a]2D0 −13.8 (c 0.44,
MeOH); HRMS (ESI): Found 356.1806 [MH]+, C22H27ClNO
requires 356.1781. Found: C, 66.99; H, 7.03; N, 3.46. Calc. for
C22H26ClNO·HCl: C, 67.34; H, 6.94; N, 3.57%.
3-((1S,5R)-(+)-2-(4-Chlorophenethyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((+)-10i) and 3-((1R,5S)-(−)-2-(4-chlorophenethyl)-
2-aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10i)
(−)-10k was obtained from the reaction of 1R,5S-8 and 7k
◦
by method A. Mp 217–218 C as HCl salt; [a]2D0 −2.2 (c 0.48,
(+)-10i was obtained f◦rom the reaction of 1S,5R-8 and 7i by
method A. Mp 251–252 C as HCl salt; [a]2D0 +13.5 (c 0.39, MeOH);
1H NMR (CDCl3, free base): d 7.24 (d, 2H, J = 8 Hz), 7.20–7.10
(m, 3H), 6.82 (d, 1H, J = 8 Hz), 6.79 (br, 1H), 6.63 (dd, 1H,
J = 8 and 2 Hz), 3.24 (br, 1H), 3.05–3.00 (m, 2H), 2.85–2.75
(m, 4H), 2.22–2.10 (m, 2H), 2.05–1.80 (m, 5H), 1.74–1.54 (m,
2H), 1.43–1.32 (m, 1H); 13C NMR (CDCl3, free base): d 156.29,
153.28, 138.53, 131.89, 130.08, 129.30, 128.49, 116.65, 113.24,
112.45, 57.34, 52.42, 49.54, 38.16, 38.05, 36.80, 34.70, 33.08,
24.36, 22.64; HRMS (ESI): Found 356.1784 [MH]+, C22H27ClNO
requires 356.1781. Found: C, 67.32; H, 7.03; N, 3.56. Calc. for
C22H26ClNO·HCl: C, 67.34; H, 6.94; N, 3.57%.
MeOH); HRMS (ESI): Found 367.2030 [MH]+, C22H27N2O3
requires 367.2022. Found: C, 65.24; H, 6.75; N, 6.84. Calc. for
C22H26N2O3·HCl: C, 65.58; H, 6.75; N, 6.95%.
3-((1S,5R)-(+)-2-(3-Nitrophenethyl)-2-aza-bicyclo[3.3.1]nonan-5-
yl)phenol ((+)-10l) and 3-((1R,5S)-(−)-2-(3-nitrophenethyl)-2-
aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10l)
(+)-10l was obtained f◦rom the reaction of 1S,5R-8 and 7l by
method A. Mp 270–272 C as HCl salt; [a]2D0 +13.6 (c 0.35, MeOH);
1H NMR (CDCl3, free base): d 8.12–8.03 (m, 2H), 7.56–7.52 (m,
1H), 7.43 (t, 1H, J = 8 Hz), 7.17 (t, 1H, J = 8 Hz), 6.88 (d,
1H, J = 8 Hz), 6.79 (t, 1H, J = 2 Hz), 6.65 (dd, 1H, J = 8 and
2 Hz), 3.20 (br, 1H), 3.10–2.76 (m, 6H), 2.18–1.84 (m, 7H), 1.74–
1.55 (m, 2H), 1.48–1.35 (m, 1H); 13C NMR (CDCl3, free base):
d 156.12, 153.54, 148.24, 142.42, 135.14, 129.33, 129.17, 123.54,
121.26, 116.78, 113.11, 112.34, 56.94, 52.53, 49.39, 38.37, 38.16,
37.02, 34.79, 33.53, 24.64, 22.70; HRMS (ESI): Found 367.2009
[MH]+, C22H27N2O3 requires 367.2022. Found: C, 65.58; H, 6.95;
N, 6.55. Calc. for C22H26N2O3·HCl: C, 65.58; H, 6.75; N, 6.95%.
(−)-10l was obtained from the reaction of 1R,5S-8 and 7l by
(−)-10i was obtained from the reaction of 1R,5S-8 and 7i by
◦
method A. Mp 239–241 C as HCl salt; [a]2D0 −13.6 (c 0.39,
MeOH); HRMS (ESI): Found 356.1790 [MH]+, C22H27ClNO
requires 356.1781. Found: C, 67.30; H, 7.03; N, 3.52. Calc. for
C22H26ClNO·HCl: C, 67.34; H, 6.94; N, 3.57%.
1S,5R-(+)-3-{2-[2-(2,4-Dichlorophenyl)-ethyl]-2-aza-
bicyclo[3.3.1]non-5-yl}-phenol ((+)-10j) and 1R,5S-(−)-3-
{2-[2-(2,4-Dichlorophenyl)-ethyl]-2-aza-bicyclo[3.3.1]non-5-yl}-
phenol ((−)-10j)
◦
method A. Mp 269–270 C as HCl salt; [a]2D0 −13.1 (c 0.35,
MeOH); HRMS (ESI): Found 367.2012 [MH]+, C22H27N2O3
requires 367.2022. Found: C, 64.93; H, 6.84; N, 6.63. Calc. for
C22H26N2O3·HCl·0.25H2O: C, 64.86; H, 6.80; N, 6.88%.
(+)-10j was obtained f◦rom the reaction of 1S,5R-8 and 7j by
method A. Mp 249–250 C as HBr salt; [a]2D0 +20.0 (c 0.32, MeOH);
1H NMR (CDCl3, free base): d 7.35 (br-s, 1H), 7.18–7.12 (m, 3H),
6.85 (d, 1H, J = 8 Hz), 6.77 (t, 1H, J = 2 Hz), 6.63 (dd, 1H,
J = 8 and 2 Hz), 3.25 (br, 1H), 3.10–2.90 (m, 4H), 2.88–2.66 (m,
2H), 2.15 (d, 2H, J = 12 Hz), 2.08–1.84 (m, 5H), 1.72–1.55 (m,
2H), 1.43–1.32 (m, 1H); 13C NMR (CDCl3, free base): d 156.22,
153.55, 136.56, 134.60, 132.50, 131.71, 129.29, 129.16, 127.12,
116.75, 113.24, 12.51, 59.88, 55.34, 52.35, 49.46, 38.31, 38.18,
36.99, 34.79, 31.14, 24.64, 22.75; HRMS (ESI): Found 390.1382
[MH]+, C22H26Cl2NO requires 390.1391. Found: C, 61.84; H, 6.15;
N, 3.25. Calc. for C22H25Cl2NO·HCl: C, 61.91; H, 6.14; N, 3.28%.
(−)-10j was obtained from the reaction of 1R,5S-8 and 7j by
3-((1S,5R)-(+)-2-(4-Nitrophenethyl)-2-aza-bicyclo[3.3.1]nonan-5-
yl)phenol ((+)-10m) and 3-((1R,5S)-(−)-2-(4-nitrophenethyl)-2-
aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10m)
(+)-10m was obtained from the reaction of 1S,5R-8 and 7m by
method A. Mp 242–243 ◦C as HCl salt; [a]2D0 +15.9 (c 0.42, MeOH);
1H NMR (CDCl3, free base): d 8.16–8.10 (m, 2H), 7.38–7.33 (m,
2H), 7.17 (t, 1H, J = 8 Hz), 6.88 (d, 1H, J = 8 Hz), 6.78 (t, 1H, J =
2 Hz), 6.63 (dd, 1H, J = 8 and 2 Hz), 3.21 (br, 1H), 3.10–2.78 (m,
◦
6H), 2.18–1.84 (m, 7H), 1.74–1.55 (m, 2H), 1.48–1.34 (m, 1H); 13
C
method A. Mp 242–243 C as HCl salt; [a]2D0 −19.7 (c 0.32,
NMR (CDCl3, free base): d 155.96, 153.66, 148.47, 146.49, 129.56,
129.35, 123.58, 116.93, 113.00, 112.30, 56.82, 52.52, 49.39, 38.47,
38.19, 37.08, 34.83, 34.02, 24.72, 22.70; HRMS (ESI): Found
367.2034 [MH]+, C22H27N2O3 requires 367.2022. Found: C, 65.37;
H, 6.89; N, 6.90. Calc. for C22H26N2O3·HCl: C, 65.58; H, 6.75; N,
6.95%.
MeOH); HRMS (ESI): Found 390.1394 [MH]+, C22H26Cl2NO
requires 390.1391. Found: C, 61.67; H, 6.28; N, 3.21. Calc. for
C22H25Cl2NO·HCl: C, 61.91; H, 6.14; N, 3.28%.
3-((1S,5R)-(+)-2-(2-Nitrophenethyl)-2-aza-bicyclo[3.3.1]nonan-5-
yl)phenol ((+)-10k) and 3-((1R,5S)-(−)-2-(2-nitrophenethyl)-2-
aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10k)
(−)-10m was obtained from the reaction of 1R,5S-8 and 7m
◦
by method A. Mp 244–245 C as HCl salt; [a]2D0 −16.0 (c 0.33,
(+)-10k was obtained from the reaction of 1S,5R-8 and 7k by
method A. Mp 218–219 ◦C as HCl salt; [a]2D0 +2.5 (c 0.48, MeOH);
1H NMR (CDCl3, free base): d 7.89 (dd, 1H, J = 8 and 2 Hz),
MeOH); HRMS (ESI): Found 367.2008 [MH]+, C22H27N2O3
requires 367.2022. Found: C, 65.47; H, 6.82; N, 7.00. Calc. for
C22H26N2O3·HCl: C, 65.58; H, 6.75; N, 6.95%.
1186 | Org. Biomol. Chem., 2007, 5, 1177–1190
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
3-((1S,5R)-(+)-2-(2-(Pyridin-2-yl)ethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10n) and 3-((1R,5S)-(−)-2-
(2-(pyridin-2-yl)ethyl)-2-aza-bicyclo[3.3.1]nonan-5-
yl)phenol ((−)-10n)
Found 323.2115 [MH]+, C21H27N2O requires 323.2123. Found: C,
76.24; H, 8.02; N, 8.41. Calc. for C21H26N2O·0.5H2O: C, 76.10; H,
8.21; N, 8.45%.
(−)-10p was obtained from the reaction of 1R,5S-9 and 7p by
method D. Mp 168–172 ◦C as HCl salt; [a]2D0 −7.8 (c 0.60, MeOH,
free base); HRMS (ESI): Found 323.2104 [MH]+, C21H27N2O
requires 323.2123. Found: C, 76.84; H, 8.01; N, 8.47. Calc. for
C21H26N2O·0.25H2O: C, 77.15; H, 8.17; N, 8.57%.
(+)-10n was obtained from the reaction of 1S,5R-8 and 7n by
◦
method A. Mp 103–104 C as free base; [a]2D0 +14.7 (c 0.33,
1
MeOH, HCl salt); H NMR (CDCl3, free base): d 8.52 (d, 1H,
J = 5 Hz), 7.61 (dt, 1H, J = 8 and 2 Hz), 7.20 (d, 1H, J = 8 Hz),
7.18–7.08 (m, 2H), 6.84–6.78 (m, 2H), 6.65 (dd, 1H, J = 8 and
2 Hz), 3.20 (br, 1H), 3.10–2.90 (m, 6H), 2.18–1.78 (m, 7H), 1.68–
1.52 (m, 2H), 1.42–1.26 (m, 1H); 13C NMR (CDCl3, free base):
d 160.36, 156.78, 153.62, 148.74, 136.76, 129.15, 123.62, 121.41,
116.22, 113.16, 112.57, 55.68, 52.60, 49.22, 38.34, 38.25, 36.94,
36.09, 34.79, 24.83, 22,62; HRMS (ESI): Found 323.2148 [MH]+,
C21H27N2O requires 323.2123. Found: C, 75.84; H, 8.21; N, 8.36.
Calc. for C21H26N2O·0.5H2O: C, 76.10; H, 8.21; N, 8.45%.
(−)-10n was obtained from the reaction of 1R,5S-8 and 7n by
method A. Mp 181–182 ◦C as HCl salt; [a]2D0 −14.7 (c 0.33, MeOH,
HCl salt); HRMS (ESI): Found 323.2128 [MH]+, C21H27N2O
requires 323.2123. Found: C, 73.83; H, 8.17; N, 8.20. Calc. for
C21H26N2O·H2O: C, 74.08; H, 8.29; N, 8.23%.
3-(1S,5R)-(+)-(2-(2-(1H-Indol-3-yl)ethyl)-2-aza-bicyclo-
[3.3.1]nonan-5-yl)phenol ((+)-10q) and 3-(1R,5S)-(−)-(2-
(2-(1H-indol-3-yl)ethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol
((−)-10q)
(+)-10q was obtained from the reaction of 1S,5R-8 and 7q by
◦
method E. Mp 203–205 C as free base; [a]2D0 +13.4 (c 0.38,
1
MeOH, free base); H NMR (d6-DMSO, free base): d 10.76 (s,
1H), 9.19 (s, 1H), 7.52 (d, 1H, J = 8 Hz), 7.33 (d, 1H, J = 8 Hz),
7.16 (d, 1H, J = 2 Hz), 7.13–6.94 (m, 3H), 6.77 (d, 1H, J =
8 Hz), 6.74 (d, 1H, J = 2 Hz), 6.57 (dd, 1H, J = 8 and 2 Hz),
3.15 (br, 1H), 3.04–2.94 (m, 2H), 2.88–2.71 (m, 4H), 2.12–2.00
(m, 2H), 1.98–1.70 (m, 5H), 1.67–1.44 (m, 2H), 1.40–1.28 (m,
1H); 13C NMR (d6-DMSO, free base): d 157.16, 153.72, 136.17,
128.97, 127.34, 122.42, 120.76, 118.27, 118.10, 115.23, 112.89,
112.36, 111.71, 111.30, 56.32, 51.90, 48.74, 38.44, 38.29, 37.09,
34.52, 24.77, 23.46, 22.42; HRMS (ESI): Found 361.2299 [MH]+,
C24H29N2O requires 361.2280. Found: C, 77.97; H, 7.90; N, 7.44.
Calc. for C24H28N2O·0.5H2O: C, 78.01; H, 7.91; N, 7.58%.
(−)-10q was obtained from the reaction of 1R,5S-8 and 7q by
method E. Mp 201–203 ◦C as free base; [a]2D0 −13.6 (c 0.38, MeOH,
free base); HRMS (ESI): Found 361.2287 [MH]+, C24H29N2O
requires 361.2280. Found: C, 77.94; H, 7.86; N, 7.54. Calc. for
C24H28N2O·0.25H2O: C, 78.98; H, 7.86; N, 7.54%.
3-((1S,5R)-(+)-2-(2-(Pyridin-3-yl)ethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10o) and
3-((1R,5S)-(−)-2-(2-(pyridin-3-yl)ethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10o)
(+)-10o was obtained from the reaction of 1S,5R-9 and 7o by
method C. Mp 243–245 ◦C as HCl salt; [a]2D0 +8.0 (c 0.60, MeOH,
free base); 1H NMR (CDCl3, free base): d 8.50–8.42 (m, 2H), 7.57
(dt, 1H, J = 8 and 2 Hz), 7.28–7.22 (m, 1H), 7.14 (t, 1H, J = 8 Hz),
6.86–6.80 (m, 2H), 6.67 (dd, 1H, J = 8 and 2 Hz), 3.18 (br, 1H),
3.10–2.94 (m, 2H), 2.88–2.72 (m, 4H), 2.16–1.82 (m, 7H), 1.72–
1.52 (m, 2H), 1.42–1.26 (m, 1H); 13C NMR (CDCl3, free base):
d 156.83, 153.55, 149.48, 146.89, 136.80, 136.27, 129.21, 123.54,
116.22, 113.01, 112.39, 57.04, 52.56, 49.33, 38.43, 38.27, 37.06,
34.81, 31.20, 24.81, 22.70; HRMS (ESI): Found 323.2143 [MH]+,
C21H27N2O requires 323.2123. Found: C, 76.08; H, 8.27; N, 8.54.
Calc. for C21H26N2O·0.5H2O: C, 76.10; H, 8.21; N, 8.45%.
3-(1S,5R)-(+)-(2-(2-Hydroxyphenethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10r) and 3-(1R,5S)-(−)-(2-
(2-hydroxyphenethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol
((−)-10r)
(−)-10o was obtained from the reaction of 1R,5S-9 and 7o by
method C. Mp 237–241 ◦C as HCl salt; [a]2D0 −7.9 (c 0.60, MeOH,
free base); HRMS (ESI): Found 323.2138 [MH]+, C21H27N2O
requires 323.2123. Found: C, 76.17; H, 8.15; N, 8.39. Calc. for
C21H26N2O·0.5H2O: C, 76.10; H, 8.21; N, 8.45%.
(+)-10r was obtained from the reaction of 1S,5R-8 and 7d by
◦
method A. Mp 186–188 C as HBr salt; [a]2D0 +14.3 (c 0.38,
MeOH); 1H NMR (CDCl3, free base): d 7.16–7.08 (m, 2H), 6.99
(d, 1H, J = 7 Hz), 6.89–6.80 (m, 3H), 6.73 (d, 1H, J = 7 Hz),
6.69 (d, 1H, J = 8 Hz), 3.27 (br, 1H), 3.15–3.02 (m, 1H), 2.98–
2.95 (m, 1H), 2.77–2.29 (m, 2H), 2.18–1.90 (m, 8H), 1.77–1.64
(m, 2H), 1.57–1.50 (m, 1H); 13C NMR (CDCl3, free base): d
157.68, 156.80, 152.48, 130.94, 129.22, 128.53, 127.91, 118.88,
117.85, 116.35, 112.93, 112.35, 56.92, 54.15, 48.93, 37.87, 37.75,
36.43, 34.51, 31.35, 24.07, 22.64; HRMS (ESI): Found 338.2123
[MH]+, C22H28NO2 requires 338.2120. Found: C, 63.24; H, 7.23;
N, 2.89. Calc. for C22H27NO2·HBr·0.75THF: C, 63.56; H, 7.25;
N, 2.96%.
3-((1S,5R)-(+)-2-(2-(Pyridin-4-yl)ethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10p) and 3-((1R,5S)-(−)-2-(2-
(pyridin-4-yl)ethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol
((−)-10p)
(+)-10p was obtained from the reaction of 1S,5R-9 and 7p by
method D. Mp 170–174 ◦C as HCl salt; [a]2D0 +7.4 (c 0.60, MeOH,
free base); 1H NMR (CDCl3, free base): d 8.54–8.46 (m, 2H), 7.20–
7.12 (m, 3H), 6.86 (d, 1H, J = 8 Hz), 6.83 (t, 1H, J = 2 Hz), 6.60
(dd, 1H, J = 8 and 2 Hz), 3.17 (br, 1H), 3.10–2.92 (m, 2H), 2.88–
2.76 (m, 4H), 2.16–1.82 (m, 7H), 1.76–1.54 (m, 2H), 1.46–1.32
(m, 1H); 13C NMR (CDCl3, free base): d 156.47, 153.70, 150.17,
149.20, 129.25, 124.40, 116.52, 112.89, 112.28, 56.30, 52.57, 49.32,
38.50, 38.29, 37.13, 34.85, 33.60, 24.90, 22.70; HRMS (ESI):
(−)-10r was obtained from the reaction of 1R,5S-8 and 7d
◦
by method A. Mp 187–188 C as HBr salt; [a]2D0 −14.7 (c
0.38, MeOH); HRMS (ESI): Found 338.2135 [MH]+, C22H28NO2
requires 338.2120. Found: C, 62.99; H, 7.16; N, 2.92. Calc. for
C22H27NO2·HBr·0.25THF: C, 63.30; H, 6.93; N, 3.21%.
This journal is
The Royal Society of Chemistry 2007
Org. Biomol. Chem., 2007, 5, 1177–1190 | 1187
©

View Article Online
3-(1S,5R)-(+)-(2-(3-Hydroxyphenethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10s) and 3-(1R,5S)-(−)-(2-
(3-hydroxyphenethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol
((−)-10s)
[MH]+, C18H26NO requires 272.2014. Found: C, 69.99; H, 8.46; N,
4.49. Calc. for C18H25NO·HCl: C, 70.22; H, 8.51; N, 4.55%.
(−)-10u was obtained from the reaction of 1R,5S-8 and
◦
7u by method F. Mp 225–227 C as HCl salt; [a]2D0 −6.3 (c
0.35, MeOH); HRMS (ESI): Found 272.2010 [MH]+, C18H26NO
requires 272.2014. Found: C, 69.57; H, 8.51; N, 4.45. Calc. for
C18H25NO·HCl·0.25H2O: C, 69.21; H, 8.55; N, 4.48%.
(+)-10s was obtained from the reaction of 1S,5R-8 and 7e by
method A. Mp 250–252 ◦C as HCl salt; [a]2D0 +16.7 (c 0.30, MeOH,
free base); 1H NMR (d6-acetone free base): d 7.27–7.16 (m, 2H),
6.99–6.93 (m, 2H), 6.88–6.85 (m, 1H), 6.82 (d, 1H, J = 8 Hz),
6.79–6.73 (m, 2H), 3.27 (br, 1H), 3.21–3.02 (m, 2H), 2.98–2.78
(m, 4H), 2.28–1.92 (m, 7H), 1.80–1.64 (m, 2H), 1.57–1.44 (m,
1H); 13C NMR (CDCl3, free base): d 158.31, 158.22, 155.04,
143.49, 130.08, 129.99, 120.78, 116.74, 116.64, 113.73, 113.35,
112.83, 58.56, 53.63, 49.87, 39.53, 39.44, 38.27, 35.72, 35.16,
26.00, 23.51; HRMS (ESI): Found 338.2105 [MH]+, C22H28NO2
requires 338.2120. Found: C, 70.42; H, 7.59; N, 3.58. Calc. for
C22H27NO2·HCl: C, 70.67; H, 7.55; N, 3.75%.
Pharmacological methods
Antinociceptive (hot plate, tail-flick, phenylquinone) assays in
mice. These assays were run as previously noted.29
Cell culture and membrane preparation
The recombinant CHO cells (hMOR-CHO, hDOR-CHO and
hKOR-CHO) were produced by stable transfection with the
respective human opioid receptor cDNA, and provided by Dr
Larry Toll (SRI International, CA). The cells were grown on
plastic flasks in DMEM (100%) (hDOR-CHO and hKOR-CHO)
or DMEM–F-12 (50%–50%) medium (hMOR-CHO) containing
10% FBS, and G-418 (0.10-0.2 mg/ml) under 95% air–5% CO2 at
37 ◦C. Cell monolayers were harvested and frozen in −80 ◦C.
(−)-10s was obtained from the reaction of 1R,5S-8 and 7e
◦
by method A. Mp 242–243 C as HBr salt; [a]2D0 −11.7 (c
0.36, MeOH); HRMS (ESI): Found 338.2124 [MH]+, C22H28NO2
requires 338.2120. Found: C, 63.41; H, 6.87; N, 3.44. Calc. for
C22H27NO2·HBr: C, 63.16; H, 6.75; N, 3.35%.
3-(1S,5R)-(+)-(2-(4-Hydroxyphenethyl)-2-aza-
bicyclo[3.3.1]nonan-5-yl)phenol ((+)-10t) and 3-(1R,5S)-(−)-(2-
(4-hydroxyphenethyl)-2-aza-bicyclo[3.3.1]nonan-5-yl)phenol
((−)-10t)
[35S]GTP-c-S binding assays
On the day of the assay, cells were thawed on ice for 15 min
and homogenized using a polytron in 50 mM Tris-HCl, pH 7.4,
containing 4 lg mL−1 leupeptin, 2 lg mL−1 chymostatin, 10 lg
mL−1 bestatin and 100 lg mL−1 bacitracin, The homogenate was
centrifuged at 30000g for 10 min at 4 ◦C, and the supernatant
discarded. The membrane pellets were resuspended in binding
buffer and used for [35S]GTP-c-S binding assays. [35S]GTP-c-S
binding was determined as described previously.30 Briefly, test
tubes received the following additions: 50 lL buffer A (50 mM
Tris-HCl, pH 7.4, containing 100 mM NaCl, 10 mM MgCl2, 1 mM
EDTA), 50 lL GDP in buffer A–0.1% BSA (final concentration =
10 lM), 50 lL drug in buffer A–0.1% BSA, 50 lL [35S]GTP-
c-S in buffer A–0.1% BSA (final concentration = 50 pM), and
300 lL of cell membranes (50 lg of protein) in buffer B. The
final concentrations of reagents in the [35S]GTP-c-S binding assays
were: 50 mM Tris-HCl, pH 7.4, containing 100 mM NaCl, 10 mM
MgCl2, 1 mM EDTA, 1 mM DTT, 10 lM GDP and 0.1%
BSA. Incubations proceeded for 3 h at 25 ◦C. Nonspecific binding
was determined using GTP-c-S (40 lM). Bound and free [35S]-
GTP-c-S were separated by vacuum filtration through GF/B
filters. The filters were punched into 24-well plates to which was
added 0.6 mL LSC-cocktail (Cytoscint). Samples were counted,
after an overnight extraction, in a Trilux liquid scintillation
counter at 27% efficiency.
(+)-10t was obtained from the reaction of 1S,5R-8 and 7f by
◦
method A. Mp 265–267 C as HCl salt; [a]2D0 +14.9 (c 0.38,
1
MeOH); H NMR (d6-acetone free base): d 7.27–7.16 (m, 3H),
6.99–6.93 (m, 2H), 6.88–6.83 (m, 2H), 6.79–6.73 (m, 1H), 3.25 (br,
1H), 3.21–3.02 (m, 2H), 2.96–2.76 (m, 4H), 2.28–1.90 (m, 7H),
1.80–1.60 (m, 2H), 1.56–1.40 (m, 1H); 13C NMR (CDCl3, free
base): d 158.22, 156.45, 155.13, 132.62, 130.54, 129.98, 116.75,
115.95, 113.32, 112.82, 59.07, 53.65, 49.85, 39.59, 39.51, 38.37,
35.76, 34.42, 26.11, 23.51; HRMS (ESI): Found 338.2113 [MH]+,
C22H28NO2 requires 338.2120. Found: C, 70.44; H, 7.58; N, 3.76.
Calc. for C22H27NO2·HCl: C, 70.67; H, 7.55; N, 3.75%.
(−)-10t was obtained from the reaction of 1R,5S-8 and 7f
◦
by method A. Mp 265–266 C as HCl salt; [a]2D0 −15.1 (c
0.38, MeOH); HRMS (ESI): Found 338.2102 [MH]+, C22H28NO2
requires 338.2120. Found: C, 70.56; H, 7.70; N, 3.73. Calc. for
C22H27NO2·HCl: C, 70.67; H, 7.55; N, 3.75%.
3-((1S,5R)-(+)-2-(But-3-enyl)-2-aza-bicyclo[3.3.1]nonan-
5-yl)phenol ((+)-10u) and 3-((1R,5S)-(−)-2-(but-3-enyl)-2-
aza-bicyclo[3.3.1]nonan-5-yl)phenol ((−)-10u)
(+)-10u was obtained f◦rom the reaction of 1S,5R-8 and 7u by
method F. Mp 226–227 C as HCl salt; [a]2D0 +6.6 (c 0.35, MeOH);
1H NMR (CDCl3, free base): d 8.46 (br-s, 1H), 7.08 (t, 1H, J =
8 Hz), 6.76 (d, 1H, J = 8 Hz), 6.70 (m, 1H), 6.56 (dd, 1H, J = 8 and
2 Hz), 5.85–5.70 (m, 1H), 5.10–4.95 (m, 2H), 3.21 (br, 1H), 3.04–
2.92 (m, 2H), 2.73–2.24 (m, 2H), 2.38–2.25 (m, 2H), 2.20–2.07 (m,
2H), 2.02–1.95 (m, 5H), 1.72–1.47 (m, 2H), 1.45–1.29 (m, 1H);
13C NMR (CDCl3, free base): d 156.69, 153.14, 136.16, 129.09,
116.06, 115.82, 113.42, 112.71, 54.82, 51.98, 49.51, 38.06, 37.90,
36.64, 34.60, 31.32, 24.22, 22.67; HRMS (ESI): Found 272.2022
Opioid binding assays
Opioid binding assays proceeded according to published
procedures.31,32 l-Receptors were labeled with [3H]DAMGO. Rat
membranes for l- and d-receptor binding assays were prepared
each day using a partially thawed frozen rat brain that was homog-
enized with a polytron in 10 mL per brain of ice-cold 10 mM Tris-
HCl, pH 7.0. Membranes were then centrifuged twice at 30000g
for 10 min and resuspended with ice-cold buffer following each
1188 | Org. Biomol. Chem., 2007, 5, 1177–1190
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
centrifugation. After the second centrifugation, the membranes
were resuspended in 50 mM Tris-HCl, pH 7.4 (60 mL per brain),
at 25 ◦C. Incubations proceeded for 2 h at 25 ◦C in 50 mM Tris-
HCl, pH 7.4, along with a protease inhibitor cocktail [bacitracin
(100 lg mL−1), bestatin (10 lg mL−1), leupeptin (4 lg mL−1) and
chymostatin (2 lg mL−1)]. The nonspecific binding was determined
using 20 lM of levallorphan. Delta binding sites were labeled using
[3H]DADLE (2 nm) and rat brain membranes. Rat membranes
were prepared each day as described above. After the second
centrifugation, the membranes were resuspended in 50 mM Tris-
HCl, pH 7.4 (50 mL per brain), at 25 ◦C. Incubations proceeded
for 2 h at 25 ◦C in 50 mM Tris-HCl, pH 7.4, containing 100 mM
choline chloride, 3 mM MnCl2, 100 nM DAMGO to block binding
to l-sites, and the protease inhibitor cocktail. Nonspecific binding
was determined using 20 lM levallorphan. j-Binding sites were
labeled using [3H]U69593 (2 nm). Guinea pig brain membranes
were prepared each day using partially thawed guinea pig brain
that was homogenized with a polytron in 15 mL per brain of
ice-cold 10 mM Tris-HCl, pH 7.0. The membranes were then
centrifuged twice at 30000g for 10 min and resuspended with
ice-cold buffer following each centrifugation. After the second
centrifugation, the membranes were resuspended in 50 mM Tris-
HCl, pH 7.4 (85 mL per brain), at 25 ◦C. Incubations proceeded
for 2 h at 25 ◦C in 50 mM Tris-HCl, pH 7.4, containing 1 lg
mL−1 of captopril and the protease inhibitor cocktail. Nonspecific
binding was determined using 1 lM U69593. Each radioligand
was displaced by 8–10 concentrations of test drug. Compounds
were stored as a 10 mM stock solution in 100% DMSO. All drug
dilutions were done in 10 mM Tris-HCl, pH 7.4, containing 1 mg
mL−1 bovine serum albumin. All washes were done with ice-cold
10 mM Tris-HCl, pH 7.4.
mouse was first tested for baseline latency by immersing its tail in
the water and recording the time to response. Mice not responding
within 5 s were excluded from further testing. Mice were then
administered the test compound and tested for antinociception
at 10, 20, 30, 45, 60, 90, 120, 150 and 180 min post-injection. A
cutoff of 10 s was used to avoid tissue damage. Antinociception
was calculated by the following formula: % antinociception =
100 × (test latency − control latency)/(10 − control latency).
Dose–response lines were constructed at times of peak agonist
effect and analyzed by linear regression using FlashCalc software
(Dr Michael Ossipov, University of Arizona, Tucson, AZ). All
A50 values (95% confidence limits) shown are calculated from the
linear portion of the dose–response curve. A minimum of three
doses per curve and 10 mice per dose were used.
Acknowledgements
Authors from the Drug Design and Synthesis Section (DDS) and
the Clinical Psychopharmacology Section of the Chemical Biology
Research Branch in NIDA Intramural were supported by the NIH
Intramural Research Program of the National Institute on Drug
Abuse, and the members of DDS were also supported by the
NIH Intramural Research Program of the National Institute of
Diabetes and Digestive and Kidney Diseases. We also thank Dr
John Lloyd (NIDDK, NIH) for the mass spectral data. Some of
the pharmacological data were obtained under the auspices of
the Drug Evaluation Committee, College on Problems of Drug
Dependence. Dr A. Coop is the recipient of an independent
scientist award from NIDA DA K02-19634.
References
Data analysis and statistics
1 A. C. Hiebel, Y. S. Lee, E. J. Bilsky, D. Giuvelis, J. R. Deschamps,
M. D. Aceto, E. L. May, E. M. Harris, A. Coop, C. M. Dersch, R. B.
Rothman, A. E. Jacobson and K. C. Rice, J. Med. Chem., 2006, in
review.
2 S. N. Calderon and A. Coop, Curr. Pharm. Des., 2004, 10, 733–742.
3 J. R. Carson, S. J. Coats, E. E. Codd, S. L. Dax, J. Lee, R. P. Martinez,
L. A. McKown, L. A. Neilson, P. M. Pitis, W. N. Wu and S. P. Zhang,
Bioorg. Med. Chem. Lett., 2004, 14, 2113–2116.
4 J. R. Carson, S. J. Coats, E. E. Codd, S. L. Dax, J. Lee, R. P. Martinez,
L. A. Neilson, P. M. Pitis and S. P. Zhang, Bioorg. Med. Chem. Lett.,
2004, 14, 2109–2112.
5 S. N. Calderon, K. C. Rice, R. B. Rothman, F. Porreca, J. L. Flippen-
Anderson, H. Kayakiri, H. Xu, K. Becketts, L. E. Smith, E. J. Bilsky,
P. Davis and R. Horvath, J. Med. Chem., 1997, 40, 695–704.
6 S. N. Calderon, R. B. Rothman, F. Porreca, J. L. Flippen-Anderson,
R. W. McNutt, H. Xu, L. E. Smith, E. J. Bilsky, P. Davis and K. C.
Rice, J. Med. Chem., 1994, 37, 2125–2128.
7 D. Delorme, C. Berthelette, R. Lavoie and E. Roberts, Tetrahedron:
Asymmetry, 1998, 9, 3963–3966.
8 G. Dondio, S. Ronzoni and P. Petrillo, Expert Opin. Ther. Pat., 1997,
7, 1075–1098.
9 G. Dondio, S. Ronzoni and P. Petrillo, Expert Opin. Ther. Pat., 1999,
9, 353–374.
10 R. B. Rothman, V. Bykov, A. Reid, B. R. de Costa, A. H. Newman,
A. E. Jacobson and K. C. Rice, Neuropeptides (Edinburgh), 1988, 12,
181–187.
For [35S]GTP-c-S binding experiments, the percent stimulation of
[35S]GTP-c-S binding was calculated according to the following
formula: (S − B)/B × 100, where B is the basal level of [35S]GTP-
c-S binding and S is the stimulated level of [35S]GTP-c-S binding.33
EC50 values (the concentration that produces fifty percent maximal
stimulation of [35S]GTP-c-S binding) and Emax (% of maximal
stimulation in the [35S]-GTP-c-S binding) were determined using
either the program MLAB-PC (Civilized Software, Bethesda,
MD) or KaleidaGraph (Version 3.6.4, Synergy Software, Reading,
PA). For opioid binding experiments, the data were fit to the two-
parameter logistic equation for the best-fit estimates of the IC50
and N values: Y = 100/(1 + ([INHIBITOR]/IC50)N), where “Y”
is the percent of control value.
Sources
[35S]GTP-c-S (SA = 1250 Ci mmol−1) was obtained from DuPont
NEN (Boston, MA). Various opioid peptides were provided by
Multiple Peptide System via the Research Technology Branch,
NIDA. The sources for the reagents used in the opioid binding
assays have been described.31,32
11 S. Ananthan, N. K. Khare, S. K. Saini, L. E. Seitz, J. L. Bartlett, P.
Davis, C. M. Dersch, F. Porreca, R. B. Rothman and E. J. Bilsky,
J. Med. Chem., 2004, 47, 1400–1412.
12 E. E. Abdelhamid, M. Sultana, P. S. Portoghese and A. E. Takemori,
J. Pharmacol. Exp. Ther., 1991, 258, 299–303.
13 I. Gomes, A. Gupta, J. Filipovska, H. H. Szeto, J. E. Pintar and L. A.
Devi, Proc. Natl. Acad. Sci. U. S. A., 2004, 101, 5135–5139.
Warm water tail-flick test
Antinociception was assessed at 55 ◦C. The latency to the first sign
of a rapid tail-flick was taken as the behavioral endpoint. Each
This journal is
The Royal Society of Chemistry 2007
Org. Biomol. Chem., 2007, 5, 1177–1190 | 1189
©

View Article Online
14 C. D. Rios, B. A. Jordan, I. Gomes and L. A. Devi, Pharmacol. Ther.,
2001, 92, 71–87.
15 R. B. Rothman, J. A. Danks, M. Herkenham, A. E. Jacobson, T. R. J.
Burke and K. C. Rice, Neuropeptides (Amsterdam, Neth.), 1985, 6,
227–237.
16 P. J. Emmerson, J. H. McKinzie, P. L. Surface, T. M. Suter, C. H. Mitch
and M. A. Statnick, Eur. J. Pharmacol., 2004, 494, 121–130.
17 E. L. May and J. G. Murphy, J. Org. Chem., 1954, 19, 618–622.
18 E. L. May and J. G. Murphy, J. Org. Chem., 1955, 20, 1197–1201.
19 E. L. May and M. Takeda, J. Med. Chem., 1970, 13, 805–807.
20 H. Ong, T. Oh-ishi and E. L. May, J. Med. Chem., 1974, 17, 133–134.
21 T. Cochran, J. Med. Chem., 1974, 17, 987–989.
25 A. Hashimoto, A. E. Jacobson, R. B. Rothman, C. M. Dersch, C.
George, J. L. Flippen-Anderson and K. C. Rice, Bioorg. Med. Chem.,
2002, 10, 3319–3329.
26 E. L. May, J. Org. Chem., 1956, 21, 899–901.
27 I. J. Kim, C. M. Dersch, R. B. Rothman, A. E. Jacobson and K. C.
Rice, Bioorg. Med. Chem., 2004, 12, 4543–4550.
28 J. Tholander and J. Bergman, Heterocycles, 1999, 51, 1275–1282.
29 M. D. Aceto, E. R. Bowman, L. S. Harris, L. D. Hughes, B. R. Kipps,
S. L. Lobe and E. L. May, in Problems of Drug Dependence 2004, ed.
W. L. Dewey, National Institute on Drug Abuse Research Monograph
185; NIH Publication No. 05-5290, Washington DC, 2005, p. 160–
200.
22 J. B. Thomas, X. L. Zheng, S. W. Mascarella, R. B. Rothman, C. M.
Dersch, J. S. Partilla, J. L. Flippen-Anderson, C. F. George, B. E.
Cantrell, D. M. Zimmerman and F. I. Carroll, J. Med. Chem., 1998, 41,
4143–4149.
23 A. Hashimoto, A. Coop, R. B. Rothman, C. Dersch, H. Xu, R. Horel,
C. George, A. E. Jacobson and K. C. Rice, in Problems of Drug
Dependence, 1999, ed. L. S. Harris, National Institute on Drug Abuse
Research Monograph 180, NIH Publication No. 00-4737, Washington
DC, 2000, p. 250.
30 H. Xu, A. Hashimoto, K. C. Rice, A. E. Jacobson, J. B. Thomas, F. I.
Carroll, J. Lai and R. B. Rothman, Synapse (N. Y.), 2001, 39, 64–69.
31 S. Ananthan, H. S. Kezar, R. L. Carter, S. K. Saini, K. C. Rice, J. L.
Wells, P. Davis, H. Xu, C. M. Dersch, E. J. Bilsky, F. Porreca and R. B.
Rothman, J. Med. Chem., 1999, 42, 3527–3538.
32 J. B. Thomas, M. J. Fall, J. B. Cooper, R. B. Rothman, S. W. Mascarella,
H. Xu, J. S. Partilla, C. M. Dersch, K. B. McCullough, B. E. Cantrell,
D. M. Zimmerman and F. I. Carroll, J. Med. Chem., 1998, 41, 5188–
5197.
24 A. Hashimoto, R. B. Rothman, C. Dersch, R. Horel, A. E. Jacobson
and K. C. Rice, Drug Alcohol Depend., 2000, 60, S86.
33 H. Xu, X. Wang, J. Wang and R. B. Rothman, Synapse (N. Y.), 2004,
52, 209–217.
1190 | Org. Biomol. Chem., 2007, 5, 1177–1190
This journal is
The Royal Society of Chemistry 2007
©