Probes for narcotic receptor mediated phenomena. 43. Synthesis of the ortho-a and para-a, and improved synthesis and optical resolution of the ortho-b and para-b oxide-bridged phenylmorphans: Compounds with moderate to low opioid-receptor affinity

Article abstract of DOI:10.1016/j.bmc.2011.05.035

N-Phenethyl-substituted ortho-a and para-a oxide-bridged phenylmorphans have been obtained through an improved synthesis and their binding affinity examined at the various opioid receptors. Although the N-phenethyl substituent showed much greater affinity

Full text of DOI:10.1016/j.bmc.2011.05.035

Bioorganic & Medicinal Chemistry 19 (2011) 4330–4337
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Probes for narcotic receptor mediated phenomena. 43. Synthesis
of the ortho-a and para-a, and improved synthesis and optical
resolution of the ortho-b and para-b oxide-bridged phenylmorphans:
Compounds with moderate to low opioid-receptor affinity
Feng Li a, , John E. Folk a,z, Kejun Cheng a, Muneaki Kurimura a,à, Jason A. Deck a,§, Jeffrey R. Deschamps b,c
,
Richard B. Rothman d, Christina M. Dersch d, Arthur E. Jacobson a, Kenner C. Rice a,
⇑
a Drug Design and Synthesis Section, Chemical Biology Research Branch, National Institute on Drug Abuse and the National Institute on Alcohol Abuse and Alcoholism,
National Institutes of Health, Department of Health and Human Services, 5625 Fishers Lane, Room 4N03, Bethesda, MD 20892-9415, USA
b Center for Biomolecular Science and Engineering, Naval Research Laboratory, Washington DC 20375, USA
c Center for Molecular Modeling, Division of Computational Bioscience, CIT, National Institutes of Health, DHHS, Bethesda, MD 20892, USA
d Clinical Psychopharmacology Section, Chemical Biology Research Branch, National Institute on Drug Abuse, Addiction Research Center, National Institutes of Health,
Department of Health and Human Services, Baltimore, MD 21224, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
N-Phenethyl-substituted ortho-a and para-a oxide-bridged phenylmorphans have been obtained through
Received 7 April 2011
Revised 17 May 2011
Accepted 20 May 2011
Available online 24 May 2011
an improved synthesis and their binding affinity examined at the various opioid receptors. Although the
N-phenethyl substituent showed much greater affinity for
l- and j-opioid receptors than their N-methyl
relatives (e.g., Ki = 167 nM and 171 nM at - and -receptors vs >2800 and 7500 nM for the N-methyl
l
j
ortho-a oxide-bridged phenylmorphan), the a-isomers were not examined further because of their rela-
tively low affinity. The N-phenethyl substituted ortho-b and para-b oxide-bridged phenylmorphans were
also synthesized and their enantiomers were obtained using supercritical fluid chromatography. Of the
Keywords:
ortho-a and ortho-b oxide-bridged
phenylmorphans
para-a and para-b oxide-bridged
phenylmorphans
four enantiomers, only the (+)-ortho-b isomer had moderate affinity for
and 42 nM, respectively, and it was found to also have moderate - and -opioid antagonist activity in
the [35S]GTP-
-S assay (Ke = 31 and 26 nM).
l- and j-receptors (Ki = 49
l
j
c
Ó 2011 Published by Elsevier Ltd.
Synthesis
Optical resolution
1. Introduction
rac-(4R,6aS,11bR)-2,3,4,5,6,6a-hexahydro-3-methyl-1H-4,11b-met
hanobenzofuro[3,2-d]azocine-8-ol and 10-ol, Figure 1)1–4 was pre-
viously accomplished and provided four of the twelve possible race
mic ortho- and para-hydroxyphenyl substituted a through f oxide-
bridged phenylmorphans (Fig. 1). The a-isomers were among the
earliest compounds prepared2,3 and, at that time, we did not realize
that an N-methyl substituted compound was unlikely to interact
well with opioid receptors. An insufficient amount of the compound
was initially prepared and this did not allow us to pursue conversion
to other N-substituents. The b-isomers were prepared last4 because
of the difficulty of synthesizing the strained 5,6-trans-fused ring
junction that must be formed to obtain them. We have now obtained
the N-phenethyl-substituted ortho-a and para-a-isomers, have im-
proved the synthesis of the N-phenethyl substituted ortho and
para-b-isomers, optically resolved the b-isomers, and examined
the binding affinities as well as the efficacies of the compounds with
higher affinity. An N-phenethyl substituent usually, but not always,5
increases the affinity of benzomorphan or phenylmorphan-like
compounds for opioid receptors,4,6 as well as their activity as either
agonists or antagonists.4 We have previously reported that the
We have synthesized the structurally rigid oxide-bridged phe-
nylmorphans in order to gain further insight into the receptor-active
conformationof the various opioid receptor subtypes, and have been
correlating this information with their agonist, antagonist, or
inverse-agonist activity. The synthesis of the racemic ortho-a and
ortho-b, and para-a and para-b, N-methyl substituted oxide-bridged
phenylmorphans (rac-(4R,6aR,11bR)-2,3,4,5,6,6a-hexahydro-3-met
hyl-1H-4,11b-methanobenzofuro[3,2-d]azocin-8-ol and 10-ol and
⇑
Corresponding author. Tel.: +1 301 496 1856; fax: +1 301 402 0589.
E-mail addresses: kr21f@nih.gov, ricek@bdg8.niddk.nih.gov (K.C. Rice).
Current address: Department of Pharmacology, Toxicology and Therapeutics,
University of Kansas Medical Center, Kansas City, KS 66160, USA.
à
Current address: Qs’ Research Institute, Otsuka Pharmaceutical Co., Ltd, 463-10
Kagasuno Kawauchi-cho, Tokushima 771-0192, Japan.
§
Current address: Division of Food Contact Notifications, Office of Food Additive
Safety, Center for Food Safety and Applied Nutrition, US Food and Drug Administra-
tion, 5100 Paint Branch Parkway, College Park, MD 20740, USA.
z
Deceased 12/27/10.
0968-0896/$ - see front matter Ó 2011 Published by Elsevier Ltd.
doi:10.1016/j.bmc.2011.05.035

F. Li et al. / Bioorg. Med. Chem. 19 (2011) 4330–4337
4331
rac-(4R,6aR,11bR)-2,3,4,5,6,6a-hexahydro-3-phenethyl-1H-4,11b-
methanobenzofuro[3,2-d]azocin-10-ol (10).
The synthesis of the racemic ortho and para-b series essentially
followed the reported route4 except for the modification of a few
procedures to improve the yield. rac-(1R,5R,6S)-5-(2-Fluoro-5-
nitrophenyl)-2-methyl-2-azabicyclo[3.3.1]nonan-6-ol (13) was
originally prepared from rac-(1R,5R,6S)-(5-(2-fluorophenyl)-2-
methyl-2-azabicyclo[3.3.1]nonan-6-ol (11) in 62% yield on
a
0.8 mmol scale without isolation of the intermediate acetate
(12).4 However, when the reaction was carried out on a larger scale
(ꢀ25 mmol) needed for optical resolution, the yields were lower
(<50%). TLC indicated that all of the starting material had been used
and a significant amount of a lower Rf compound was obtained.
This procedure was modified to provide 13 in two steps (Scheme
2). Using the path shown in Scheme 2, compound 11, prepared in
eight steps from rac-(S)-2-(2-(dimethylamino)ethyl)-2-(2-fluoro-
phenyl)cyclohexanone,11 was acetylated using Ac2O and AcOH
and nitrated with fuming nitric acid to give rac-(1R,5S,6R)-5-(2-
Figure 1. General structure of the a through f oxide-bridged phenylmorphans, and
the structures of the ortho- and para-a and ortho- and para-b oxide-bridged
phenylmorphans.
fluorophenyl)-2-methyl-2-azabicyclo[3.3.1]nonan-6-yl
acetate
(12) in 92–96% yields over several runs. The acetyl moiety was re-
moved with 2 N HCl to give the azabicyclo[3.3.1]nonan-6-ol (13) in
93–96% yields.
racemic N-phenethyl substituted ortho-b isomer exhibited moder-
ate affinity for
for -opioid receptors. Since it is theoretically possible for one enan-
tiomer to retain all of the -opioid receptor affinity and the other the
-affinity, we examined the enantiomers of both the ortho-b and
j
-opioid receptors (Ki = 26 nM),4 and less affinity
l
Conversion to the desired N-phenethyl substituent required an
N-demethylation step. In the reported route,4 14 was converted to
15 using 1-chloroethyl chlorformate (56% yield and 17% recovery
of starting material). Similarly, 1-chloroethyl chlorformate was used
to N-demethylate 17 to 18 in 52% yield with a 42% recovery of start-
ing material after chromatography. To improve the procedure, the
N-methyl compound 14 was first reacted with BrCN in acetonitrile,
then refluxed in glacial acetic acid and 2 N HCl to give 15 quantita-
tively (Scheme 2). Compound 15 was used to obtain the N-phenethyl
substituted para-b compound 16 in three additional steps.4 The
BrCN procedure was also used to convert 17 to 18 in 95% yield
(Scheme 2), and 18 was used to obtain the N-phenethyl substituted
ortho-b compound 19 in three further well-known steps.4
The racemic compounds 16 and 19 (Scheme 3) were optically
resolved by supercritical fluid chromatography14 to give the (+)-
and (ꢁ)-enantiomers of the N-phenethyl substituted para-b race-
mate (16a and 16b, respectively) and the (+)- and (ꢁ)-enantiomers
of the N-phenethyl substituted ortho-b racemate (19a and 19b,
respectively). X-ray crystallographic analysis determined the ste-
reochemistry of 16b, and 19b the levo enantiomers ((4S,6aR,11bS)-
2,3,4,5,6,6a-hexahydro-3-phenethyl-1H-4,11b-methanobenzofuro
[3,2-d]azocine-10-ol and ((4S,6aR,11bS)-2,3,4,5,6,6a-hexahydro-3-
phenethyl-1H-4,11b-methanobenzofuro[3,2-d]azocine-8-ol, respe-
ctively (Fig. 2)).
j
l
para-b isomers to see if there was enhanced receptor-selectivity.
Oxide-bridged phenylmorphans are structurally rigid molecules
and those that interact with opioid receptors probably do so by pre-
senting a specific spatial pattern in the binding pocket of the recep-
tor. The receptor binding pocket is likely to allow only a limited
number of orientations for these molecules and the structural rigid-
ity of the oxide-bridged phenylmorphans severely restricts that
number. The oxide-bridged phenylmorphans cannot change their
conformation to enable or facilitate receptor interaction. In our work
on the synthesis of all of the a through f-racemates1–4,7–13 we began
with the view that if an oxide-bridged phenylmorphan had high
affinity for an opioid receptor and acted as an opioid agonist or
antagonist we would separate the enantiomers, determine absolute
configuration through X-ray crystallographic structure analysis and,
via quantum chemical studies,13 examine the spatial characteristics
of a molecule needed for their activity. In order to explore the effects
of the ortho-a and para-a compounds on opioid receptors, the two
racemic N-methyl analogs were re-synthesized and a new N-substi-
tuent, the N-phenethyl, was introduced and evaluated in both. Sim-
ilarly, to examine the enantiomeric b-isomers, we resynthesized the
racemate, improving its synthesis, and separated the enantiomers
using supercritical fluid chromatography.14
3. Results and discussion
2. Chemistry
The racemic N-methyl analogs in the ortho- and para-a oxide-
bridged phenylmorphan series (1 and 6, respectively) did not have
The synthesis of the racemic N-methyl substituted ortho-a
and para-a isomers was carried out essentially as previously re-
ported.2,3 The spectral properties of intermediates were found to
be similar to those in the literature and those of the N-methyl
substituted ortho-a and para-a isomers were identical to the
previously prepared compounds.2,3 To prepare the N-phenethyl
analogs, rac-(4R,6aR,11bR)-3-methyl-2,3,4,5,6,6a-hexahydro-1H-
4,11b-methanobenzofuro[3,2-d]azocin-8-ol (1) was heated in
acetic anhydride to give acetate (2, Scheme 1). The acetate was
reacted with ethylchloroformate under basic conditions to give
the ethylcarbamate (3), and the secondary amine 4 was obtained
from 3 by refluxing in H2SO4 overnight. Reaction with phen-
ethylbromide in DMF under basic conditions gave the desired
ortho-a compound, rac-(4R,6aR,11bR)-2,3,4,5,6,6a-hexahydro-3-
much affinity at any of the opioid receptors (Ki >2800 nM at
1). The racemic N-phenethyl-substituted ortho-a analog 5 (Table 1)
had the same low affinity at both - and -receptors (Ki = 170 nM),
and the N-phenethyl-substituted para-a analog 10 had higher
affinity for -receptors
-receptors (Ki = ꢀ100 nM) than for
(Ki = ꢀ500 nM). The N-phenethyl-substituted ortho-a and para-a
isomers were weak or moderately potent -antagonists (Ke = 163
and 46 nM, respectively), and weak -antagonists (Table 2,
l, Table
l
j
j
l
j
l
Ke = 274, and 123 nM, respectively, Table 2). Although the N-phen-
ethyl analogs had markedly higher affinity than the comparable
N-methyl compounds (Table 1), the racemic a-isomers did not
have sufficient affinity at any opioid receptor to warrant separation
of their enantiomers or further pharmacological evaluation.
Interestingly, the N-phenethyl substituted chiral ortho-b enan-
phenethyl-1H-4,11b-methanobenzofuro[3,2-d]azocin-8-ol (5).
A
tiomer 19b lost the racemate’s selectivity for
j-opioid receptors
similar series of reactions in the para-a series (Scheme 1) gave

4332
F. Li et al. / Bioorg. Med. Chem. 19 (2011) 4330–4337
Scheme 1. Synthesis of racemic N-phenethyl ortho- and para-a isomers. Reagents and conditions: (a) Ac2O, 60 °C, 1 h, 92–94%; (b) EtOCOCl, K2CO3, ClCH2CH2Cl, overnight,
92–93%; (c) H2SO4, overnight, 80–81%; (d) phenethyl bromide, DMF, 90 °C, 3 h, 68–70%.
Scheme 2. Improved steps in synthesis of ortho and para-b isomers. Reagents and conditions: (a) Ac2O, AcOH, 90 °C; (b) fuming HNO3, 92–96% from 11; (c) 2 N HCl, reflux 3 h,
5 N NaOH, 93–96%; (d) BrCN, K2CO3, acetonitrile, reflux 2H; (e) HCl, AcOH, reflux 18 h; (f) Ph(CH2)2Br, NaI, CH3CN, reflux; (g) 10% Pd-C, EtOH; (h) NaNO2, Cu(NO3)2ꢂ2.5H2O,
Cu2O, 35% H2SO4; (i) 10% Pd-C, HCO2NH4, EtOH. For experimental procedures used to prepare 15a, 15b, 18a, and 18b, see Kurimura et al.4
(Table 1). Kurimura et al.,4 reported that the N-phenethyl substi-
tuted ortho-b racemate was seven-fold selective for over
-receptors. This chiral ortho-b enantiomer 19b had considerably
little less affinity than the racemate at
j-receptors (Ki = 42 nM
j
(Table 1) vs 26 nM4 for the racemate). The enantiomer 19b was
l
found to be both a moderately potent j- and l-antagonist
higher affinity at
l-receptors than the racemate (Ki = 49 nM (Table
(Ke = 31 and 26 nM, respectively, Table 2) in the [35S]GTP-
c-S
1) vs 190 nM4 for the racemate) and about the same, or perhaps a
assay.

F. Li et al. / Bioorg. Med. Chem. 19 (2011) 4330–4337
4333
4. Experimental section
4.1. Chemistry
All melting points were determined on a Thomas–Hoover melt-
ing-point apparatus and are uncorrected. Proton nuclear magnetic
resonance (1H NMR, 300 or 500 MHz) and carbon nuclear magnetic
resonance (13C NMR, 75 or 125 MHz) spectra were recorded on a
Varian Gemini-300 or a Bruker DMX500 wide-bore spectrometer
((proton frequency 500.13 MHz) running XWINNMR v3.1, carbon
125.757) in CDCl3 (unless otherwise noted) with the values given
in ppm (TMS as internal standard) and J (Hz) assignments of 1H res-
onance coupling. The high resolution electrospray ionization (ESI)
mass spectra were obtained 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 chro-
matography was performed with Bodman silica gel LC 60 A. Elemen-
tal analyses were performed by Atlantic Microlabs, Inc., Norcross,
GA, or Micro-Analytics, Inc, Wilmington, DE. Optical resolution of
16 and 19 was carried out by Avery Discovery Services, Worcester,
MA, using supercritical fluid chromatography.
Scheme 3. Optical resolution of the N-phenethyl substituted ortho- and para-b
racemates. (a) Supercritical fluid chromatography, CO2–MeOH/2-propanol (1:1)
with 1% propan-2-amine.
The opioid receptor affinity and the agonist and antagonist activ-
ity of the rigid N-phenethyl substituted ortho- and para-a through -f
oxide-bridged phenylmorphans is likely to be related to their spe-
cific 3-dimensional molecular shape and the different interatomic
distances between their heteroatoms, and their aromatic ring, with
sets of amino acids in a receptor binding pocket. In our work with
the phenylmorphans, we have found that only the (ꢁ)-para-e iso-
mer had morphine-like agonist activity in vivo.13 The (ꢁ)-ortho-f
isomer was four times as potent as naloxone as a
and the rac ortho-c isomer had much higher affinity for the
tor than the (ꢁ)-ortho-f isomer, and was a very potent
nist.16 The (+)-ortho-b isomer was
considerably weaker
l
-antagonist,13
-recep-
-antago-
4.1.1. rac-(4R,6aR,11bR)-3-Methyl-2,3,4,5,6,6a-hexahydro-1H-
4,11b-methanobenzofuro[3,2-d]azocine-8-acetate (2)
A mixture of acetic anhydride (1.0 mL) and the phenol 1 (60 mg,
0.25 mmol) was heated at 80 °C for 1 h. After removal of the sol-
vent, the residue was diluted with CHCl3 (15 mL) and washed with
NH4OH, dried over MgSO4. The solvent was evaporated to provide
2 (66 mg, 92%) as a light yellow oil. This was used directly in the
next step. HRMS [M+H]+ calcd for C17H22NO3: 288.1600. Found:
288.1602
l
l
a
antagonist (Table 2). Future research on the oxide-bridged phenyl-
morphans will focus on the optical resolution of the rac ortho-c iso-
mer, as well as the use of different N-substituents that could
provide further data for our probe of the opioid receptor from the
viewpoint of the ligand.
Figure 2. X-ray crystallographic structures of (ꢁ)-(4S,6aR,11bS)-2,3,4,5,6,6a-hexahydro-3-phenethyl-1H-4,11b-methanobenzofuro[3,2-d]azocine-10-ol hydrochloride (top)
and -8-ol hydrobromide (bottom) (N-phenethyl para-b isomer, 16b, and N-phenethyl ortho-b isomer 19a).

4334
F. Li et al. / Bioorg. Med. Chem. 19 (2011) 4330–4337
Table 1
vacuo to afford carbamate 3 (73 mg, 92%) as light yellow oil. It
was used directly in the next step without further purification.
HRMS [M+H]+ calcd for C19H24NO5: 346.1654. Found: 346.1662.
[3H] opioid receptor binding dataa for ortho-a and para-a isomers 1, 5, 6, and 10 and
for ortho-b and para-b enantiomers 16a, 16b, 19a, and 19b
4.1.3. rac-(4R,6aR,11bR)-2,3,4,5,6,6a-Hexahydro-1H-4,11b-met
hanobenzofuro[3,2-d]azocin-8-ol (4)
H2SO4 (3.0 mL, 40% w/w) was added to compound 3 (73 mg,
0.21 mmol) and the mixture was heated to reflux and stirred over-
night. After cooling to 0 °C, the reaction mixture was made basic
with aqueous NaOH (pH 8). The basicity was raised to pH 9 with
NH4OH and the mixture was extracted with CHCl3/MeOH (10:1).
The organic solution was dried over MgSO4 and the solvent was re-
moved in vacuo to give the secondary amine 4 (38 mg, 80%) as a
white powder that was used directly for the next step without fur-
ther purification.
Compd
R1
R2
R3
Ki (nM)
l
d
j
rac 1
rac 5
rac 6
rac 10
16a: (+)-
OH
OH
H
H
H
H
H
Me
PhEt
>2800
>4900 7500 1029
>4900 171 14
>4900 >8600
>4900
>5,000
167 14
>2800
486 39
OH Me
OH PhEt
OH PhEt
98
5
250 28
352 28
384 38
199 10
4R,6aS,11bR
16b: (ꢁ)-
4S,6aR,11bS
19a: (ꢁ)-
4S,6aR,11bS
19b: (+)-
4R,6aS,11bR
Morphine
4.1.4. rac-(4R,6aR,11bR)-2,3,4,5,6,6a-Hexahydro-3-phenethyl-
1H-4,11b-methanobenzofuro [3,2-d]azocin-8-ol (5)
H
OH PhEt
>5,000
>5,000
>5,000
102
3
The secondary amine 4 (32 mg, 0.14 mmol) was dissolved in
DMF (1.0 mL), followed by the addition of NaHCO3 (13 mg,
0.154 mmol) and (2-bromoethyl)benzene (29 mg, 0.154 mmol).
The reaction mixture was stirred at 90 °C for 3 h. After removal of
the solvent in vacuo, the residue was diluted with CHCl3 (10 mL),
and the organic material was washed with H2O (2 ꢃ 4 mL). The or-
ganic phase was dried over MgSO4, evaporated and the resulting
residue was purified by flash column chromatography on silica
gel (CHCl3/MeOH 40:1) to afford compound 5 (32 mg, 70%) as a
white powder, mp 82–83 °C. 1H NMR (300 MHz, CDCl3) d 1.56–
1.73 (m, 4H), 1.78–1.89 (m, 2H), 2.11–2.24 (m, 2H), 2.50 (td,
J = 12.9 Hz, 3.3 Hz, 1H), 2.58–2.73 (m, 2H), 2.79–2.89 (m, 3H),
3.34 (br, 1H), 4.58 (t, J = 6.6 Hz, 1H), 6.64–6.79 (m, 3H), 7.18–7.33
(m, 5H); 13C NMR (75 MHz, CHCl3) d 16.1, 29.9, 34.5, 35.2, 36.6,
43.4, 44.2, 50.7, 56.9, 87.9, 115.0, 115.2, 121.5, 126.4, 128.7,
128.9, 140.4, 145.8, 146.0; HRMS [M+H]+ calcd for C22H26NO2:
336.1964. Found: 336.1957. Anal. Calcd for C22H25NO2ꢂ0.85CHCl3:
C, 62.81, H, 5.96, N, 3.21. Found: C, 62.84, H, 5.89, N, 3.28.
OH
OH
H
H
PhEt
PhEt
367 19
42 1.8
49
3
2.55 0.01
Assays were conducted15 using CHO cells, which were stably transfected and
a
express the l-, d- or j-opiate receptors, respectively. All results n = 3.
Table 2
Functional data ([35S]GTP-
c
-S) for N-phenethyl-substituted ortho-a and para-a
racemates 5 and 10 and for ortho-b and para-b enantiomers 16a, 16b, 19a, and 19b
ortho-a and para-a racemates
4.1.5. rac-(4R,6aR,11bR)-3-Methyl-2,3,4,5,6,6a-hexahydro-1H-
4,11b-methanobenzofuro[3,2-d]azocine-10-acetate (7)
Acetic anhydride (1.0 mL) and the phenol 6 (64 mg, 0.26 mmol)
were heated at 80 °C for 1 h. After removal of the solvent, the res-
idue was diluted with CHCl3 (16 mL) and the organic solution was
washed with NH4OH and dried over MgSO4. The solvent was evap-
orated to give 7 (70 mg, 94%) as a light yellow oil. This was used
directly in the next step. HRMS [M+H]+ calcd for C17H22NO3:
288.1600. Found: 288.1500.
ortho-b and para-b enantiomers
Compd
R1
R2
Ke (nM)a
-Antagonism -Antagonism
163 29
l
j
rac 5
rac 10
OH
H
H
H
OH
OH
H
274 49
23 10
4.1.6. rac-(4R,6aR,11bR)-3-Carboxylate-2,3,4,5,6,6a-hexahydro-
1H-4,11b-methanobenzofuro [3,2-d]azocine-10-acetate (8)
To a solution of 7 (70 mg, 0.24 mmol) in ClCH2CH2Cl (3.0 mL)
were added K2CO3 (168 mg, 1.21 mmol) followed by ethylchloro-
formate (131 mg, 1.21 mmol). The reaction mixture was refluxed
overnight. After filtration and removal of solvent, the residue was
diluted with H2O, extracted with CHCl3 (3 ꢃ 16 mL) and dried over
MgSO4. The solvent was evaporated to afford carbamate 8 (77 mg,
93%) as light yellow powder. It was used directly in the next step
without further purification. HRMS [M+H]+ calcd for C19H24NO5:
346.1654. Found: 346.1638.
OH
OH
OH
H
46
9
3
16a: (+)-4R,6aS,11bR
16b: (ꢁ)-4S,6aR,11bS
19a: (ꢁ)-4S,6aR,11bS
19b: (+)-4R,6aS,11bR
Naloxone
47
9
100
103 17
761 191
227 33
328 67
H
31
6
22
6
2.3 0.3
—
—
norBNI
0.11 0.02
a
[
35S]GTP-
c-S binding was performed using CHO hMOR cells which express the
human -opiate receptor, and were conducted as described in Section 4.2.1. All
l
values n = 3.
4.1.7. rac-(4R,6aR,11bR)-2,3,4,5,6,6a-Hexahydro-1H-4,11b-meth
anobenzofuro[3,2-d]azocin-10-ol (9)
4.1.2. rac-(4R,6aR,11bR)-3-Ethylcarboxylate-2,3,4,5,6,6a-hexah
ydro-1H-4,11b-methanobenzofuro[3,2-d]azocine-8-acetate (3)
To a solution of 2 (66 mg, 0.23 mmol) in ClCH2CH2Cl (3.0 mL)
were added K2CO3 (159 mg, 1.15 mmol) followed by ethylchloro-
formate (124 mg, 1.15 mmol). The reaction mixture was refluxed
overnight. After filtration and removal of the solvent, the residue
was diluted with H2O, extracted with CHCl3 (3 ꢃ 15 mL), and the
organic layer dried over MgSO4. The solvent was removed in
H2SO4 (3.0 mL, 40% w/w) was added to compound 8 (77 mg,
0.22 mmol) and the mixture was heated to reflux and stirred
overnight. After cooling down to 0 °C, the reaction mixture was
made basic with aq NaOH (pH 8). The basicity was raised to
pH 9 using NH4OH and the mixture was extracted with CHCl3/
MeOH (10:1). The organic solution was dried over MgSO4 and

F. Li et al. / Bioorg. Med. Chem. 19 (2011) 4330–4337
4335
the solvent was evaporated in vacuo to give the secondary
amine 9 (41 mg, 81%) as a white powder that was used directly
in the next step without further purification.
acetonitrile was added with stirring a solution of cyanogen bro-
mide (2.44 g, 23.0 mmol) in 5 mL of acetonitrile, and the mixture
was refluxed for 2 h. After cooling, the solids were removed by
filtration and the solvent evaporated. To the residue was added
a mixture of 30 mL of glacial HOAc and 120 mL of 2 N HCl,
and the mixture was refluxed for 18 h. After cooling, the mixture
was basified with 5 N NaOH and extracted with CHCl3 (3ꢃ). The
combined extracts were washed with a small volume of H2O,
dried (MgSO4) and the solvent removed to give 15 (5 g, quanti-
tative) as a light yellow powder sufficiently pure for the next
reaction.
4.1.8. rac-(4R,6aR,11bR)-2,3,4,5,6,6a-Hexahydro-3-phenylethyl-
1H-4,11b-methanobenzofuro [3,2-d]azocin-10-ol (10)
The secondary amine 9 (40 mg, 0.18 mmol) was dissolved in DMF
(1.0 mL), followed by addition NaHCO3 (13 mg, 0.19 mmol) and (2-
bromoethyl)benzene (36 mg, 0.193 mmol). The reaction mixture
was stirred at 90 °C for 3 h. After removal of the solvent in vacuo,
the residue was diluted with CHCl3 (10 mL) and the organic material
was washed with H2O (2 ꢃ 4 mL). The organic phase was dried over
MgSO4 and the resulting residue was purified by flash column chro-
matography on silica gel (CHCl3/MeOH 40:1) to give compound 10
(40 mg, 68%) as off-white powder, mp 76–77 °C. 1H NMR
(300 MHz, CDCl3) d 1.66–1.87 (m, 6H), 2.10–2.26 (m, 3H), 2.54 (t,
J = 12.6 Hz, 1H), 2.69 (m, 2H), 2.84–2.93 (m, 2H), 3.39 (br, 1H),
4.84 (t, J = 8.5 Hz, 1H), 6.61–6.63 (m, 3H), 7.25–7.38 (m, 5H); 13C
NMR (75 MHz, CDCl3) d 16.7, 24.6, 24.7, 25.0, 29.9, 32.3,42.1, 44.9,
52.0, 56.0, 85.9, 109.8, 111.0, 115.6, 127.1, 128.9, 192.0, 129.2,
129.5, 151.9, 152.02. HRMS [M+H]+ calcd for C22H26NO2:
336.1964; found, 336.1962. Anal. Calcd for C22H25NO2 .0.85 CHCl3:
C, 62.81; H, 5.96; N, 3.21. Found: C, 62.73; H, 5.90; N, 3.22.
4.1.12. rac-(4R,6aS,11bR)-10-Chloro-2,3,4,5,6,6a-hexahydro-8-
nitro-1H-4,11b-methanobenzofuro[3,2-d]azocine (18)
The secondary amine 18 was prepared from rac-(4R,6aS,11bR)-
10-chloro-2,3,4,5,6,6a-hexahydro-3-methyl-8-nitro-1H-4,11b-
methanobenzofuro[3,2-d]azocine4 (17) using the procedure for the
preparation of compound 15 from 14, to give a yellow solid (95%)
sufficiently pure for the next reaction.
4.1.13. Optical resolution of rac-(4R,6aS,11bR)-2,3,4,5,6,6a-hexa
hydro-3-phenethyl-1H-4,11b-methanobenzofuro[3,2-
d]azocine-10-ol (16)
The racemic N-phenethyl substituted para-b (16, 366 mg) and
ortho-b (19, 295 mg) isomers were resolved using supercritical
fluid chromatography.14 Resolution of the racemic para-b isomer
16 was conducted on a preparative scale using a 3x25 cm (S,S)-
Whelk-01 column (Regis Technologies, Morton Grove, IL) using
65% liquid CO2 (solvent) and 35% isopropanol with 0.1% isopropyl-
amine (co-solvent) isocratically at 80 mL/min. The sample was ap-
plied in MeOH/CH2Cl2 (1:1) and retention times were 0.8 and
2.5 min for the para-b enantiomers 16a and 16b with recoveries
of 170 mg and 168 mg, respectively, and estimated ee values of
98% for both.
4.1.9. rac-(1R,5S,6R)-5-(2-Fluoro-5-nitrophenyl)-2-methyl-2-az
abicyclo[3.3.1]nonan-6-yl acetate (12)
A
mixture of rac-(1R,5R,6S)-(5-(2-fluorophenyl)-2-methyl-2-
azabicyclo[3.3.1]nonan-6-ol4 (11, 5.5 g, 22 mmol) and Ac2O
(3.96 mL, 42 mmol) in 14 mL of AcOH was stirred at 90 °C for
18 h. The AcOH was removed under reduced pressure and fuming
HNO3 (13 mL) was added slowly at ꢁ5 °C with stirring. The mix-
ture was allowed to warm to room temperature over 1 h. A second
portion of fuming HNO3 (15 mL) was then added. After stirring for
2 h at room temperature, the mixture was cooled (ꢁ5 to ꢁ10 °C)
and carefully basified with 5 N NaOH (ca. 100 mL), maintaining
the temperature between 0 and ꢁ5 °C. The product was extracted
with CH2Cl2 (2ꢃ) and the combined extracts were washed with
H2O and brine and dried (MgSO4). Removal of solvent gave 12
(7.09 g, 96%) as light yellow crystals. A sample was recrystallized
from EtOAc, mp 138.5–139 °C. 1H NMR (500 MHz; CDCl3) d 8.21
(dd, J = 6.9, 2.7 Hz, 1H), 8.10 (td, J = 6.1, 2.7 Hz, 1H), 7.12 (dd,
J = 11.8, 9.0 Hz, 1H), 5.36 (dd, J = 10.2, 7.6 Hz, 1H), 3.04 (td,
J = 12.1, 4.8 Hz, 1H), 3.00–2.90 (m, 2H), 2.71–2.64 (m, 1H), 2.54–
2.42 (m, 4H), 2.33–2.25 (m, 1H), 2.13–2.03 (m, 2H), 1.98 (d,
J = 13.0 Hz, 1H), 1.89–1.77 (m, 4H), 1.61–1.51 (m, 1H); 13C NMR
(125 MHz; CDCl3) d 170.2, 166.6, 164.5, 144.1, 144.1, 135.3,
135.2, 124.9, 124.8, 124.6, 124.5, 118.0, 117.8, 75.5, 75.5, 52.9,
50.6, 43.1, 39.7, 39.6, 37.9, 37.9, 37.8, 30.0, 28.7, 23.6, 21.0.
HRMS [M+H]+ calcd for C17H22N2O4F: 337.1564. Found:
337.1560. Anal. Calcd for C17H22N2O4F: C, 60.70, H, 6.29; N, 8.33.
Found: C, 60.89; H, 6.32; N, 8.32.
4.1.13.1.
rac-(4R,6aS,11bR)-2,3,4,5,6,6a-Hexahydro-3-phen-
ethyl-1H-4,11b-methanobenzofuro[3,2-d]azocine-10-ol
(16a). Compound 16a (base): ½a D23
ꢄ
+52.1 (c 0.87, CHCl3); 1H NMR
(500 MHz, CDCl3) d 7.28 (t, J = 7.5 Hz, 2H), 7.23–7.17 (m, 3H), 6.72
(d, J = 8.4 Hz, 1H), 6.69 (d, J = 2.4 Hz, 1H), 6.62 (dd, J = 8.4, 2.4 Hz,
1H), 4.09 (dd, J = 11.6, 6.6 Hz, 1H), 3.15 (s, 1H), 2.93–2.87 (m,
1H), 2.86–2.68 (m, 5H), 2.51 (d, J = 12.4 Hz, 1H), 2.35 (dd, J = 14.8,
1.7 Hz, 1H), 2.26–2.16 (m, 1H), 1.87–1.77 (m, 2H), 1.74–1.65 (m,
1H), 1.53–1.43 (m, 1H); 13C NMR (125 MHz, CDCl3) d 153.2,
150.6, 140.4, 138.7, 128.9, 128.6, 126.3, 114.9, 110.9, 110.4, 91.7,
58.1, 52.8, 49.4, 44.0, 38.1, 34.5, 31.8, 27.6, 22.6; HRMS [M+H]+
calcd for C22H26NO2: 336.1964. Found: 336.1955.
4.1.13.2. rac-(4S,6aR,11bS)-2,3,4,5,6,6a-Hexahydro-3-phenethyl-
1H-4,11b-methanobenzofuro[3,2-d]azocine-10-ol (16b). Com-
pound 16b (base):
½
a 2D3
ꢄ
ꢁ55.7 (c 0.94, CHCl3); 1H NMR
(500 MHz, CDCl3) d 7.28 (t, J = 7.4 Hz, 2H), 7.25–7.16 (m, 3H),
6.72 (d, J = 8.4 Hz, 1H), 6.67 (s, 1H), 6.61 (d, J = 8.7 Hz, 1H), 4.09
(dd, J = 11.9, 6.3 Hz, 1H), 3.13 (s, 1H), 2.94–2.88 (m, 1H), 2.86–
2.66 (m, 5H), 2.49 (d, J = 12.2 Hz, 1H), 2.35 (d, J = 14.1 Hz, 1H),
2.27–2.16 (m, 2H), 1.87–1.77 (m, 2H), 1.75–1.65 (m, 1H), 1.52–
1.43 (m, 1H); 13C NMR (125 MHz, CDCl3) d 153.2, 150.6, 140.4,
138.7, 128.9, 128.6, 126.3, 114.9, 110.9, 110.4, 91.7, 58.1, 52.8,
49.4, 44.0, 38.1, 34.5, 31.8, 27.6, 22.6; HRMS [M+H]+ calcd for
4.1.10. rac-(1R,5R,6S)-5-(2-Fluoro-5-nitrophenyl)-2-methyl-2-
azabicyclo[3.3.1]nonan-6-ol (13)
The acetate 12 (7 g, 20 mmol) in 2 N HCl (140 mL) was refluxed
for 3 h. The mixture was cooled, basified with 5 N NaOH (ca.
70 mL), extracted with CH2Cl2 (2ꢃ), and the combined extracts
were washed with H2O and brine and dried (MgSO4). The solvent
was removed to give 13 (5.95 g, 96%), identical with the known
compound.4
C22H26NO2: 336.1964. Found: 336.1955.
Enantiomers 16a and 16b were converted to their HBr salts in
4.1.11. rac-(4R,6aS,11bR)-2,3,4,5,6,6a-Hexahydro-10-nitro-3-N-
phenethyl-1H-4,11b-methanobenzofuro[3,2-d]azocine (15)
To a mixture of rac-(4R,6aS,11bR)-2,3,4,5,6,6a-hexahydro-3-
methyl-10-nitro-1H-4,11b-methanobenzofuro[3,2-d]azocine4 (14,
5.26 g, 19.2 mmol) and K2CO3 (2.16 g, 15.6 mmol) in 125 mL of
2-propanol-H2O. Compound 16aꢂHBr: ½a D23
ꢄ
+57.2 (c 0.51, MeOH:-
H2O, 1:1); mp 276–280 °C. Anal. Calcd for C22H26BrNO2: C, 63.46,
H, 6.29, N, 3.36. Found: C, 63.16, H, 6.28, N, 3.32. Compound
16bꢂHBr: ½a 2D3
ꢄ
-55.8 (c 0.51, MeOH:H2O, 1:1); mp 276–278 °C. Anal.

4336
F. Li et al. / Bioorg. Med. Chem. 19 (2011) 4330–4337
Calcd for C22H26BrNO2: C, 63.46, H, 6.29, N, 3.36. Found: C, 63.36, H,
6.36, N, 3.33.
buffer ‘B’ is buffer A plus 1.67 mM DTT and 0.15% BSA. 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 leu-
peptin, 2 g/mL chymostatin, 10 g/mL bestatin and 100 l
l
l
g/mL
4.1.14. Optical resolution of rac-(4R,6aS,11bR)-2,3,4,5,6,6a-hexa
hydro-3-phenethyl-1H-4,11b-methanobenzofuro[3,2-
d]azocine-8-ol (19)
Optical resolution of the racemic ortho-b isomer 19 was
achieved in the same manner as with 16, above. The sample was
applied in 2-propanol and retention times were 2.6 and 3.1 min
for ortho-b fractions 1 and 2 (19a and 19b, respectively) with
recoveries of 121 and 126 mg and estimated ee values of 99.9%
and 98.5%, respectively.
bacitracin. The homogenate was centrifuged at 30,000ꢃg for
10 min at 4 °C, and the supernatant discarded. The membrane pel-
lets were resuspended in buffer B and used for [35S]GTP-
assays. Test tubes received the following additions: 50
c
l
-S binding
L buffer A
plus 0.1% BSA, 50
tion = 40 M), 50
S in buffer A/0.1% BSA (final concentration = 50 pM), and 300
cell membranes (50 g of protein) in buffer B. The final concentra-
tions of reagents in the [35S]GTP-
-S binding assays were: 50 mM
Tris–HCl, pH 7.4, containing 100 mM NaCl, 10 mM MgCl2, 1 mM
EDTA, 1 mM DTT, 40 M GDP and 0.1% BSA. Incubations proceeded
for 3 h at 25 °C. Nonspecific binding was determined using GTP- -S
(40 -S were separated by vacuum
M). Bound and free [35S]GTP-
l
l
L GDP in buffer A/0.1% BSA (final concentra-
L drug in buffer A/0.1% BSA, 50
L [35S]-GTP-
L of
l
l
c-
l
l
c
4.1.14.1.
rac-(4R,6aS,11bR)-2,3,4,5,6,6a-Hexahydro-3-phen-
l
ethyl-1H-4,11b-methanobenzofuro[3,2-d]azocine-8-ol
c
(19a). Compound 19a (base): ½a D23
ꢄ
ꢁ64.1 (c 1.0, CHCl3); 1H NMR
l
c
(500 MHz, CDCl3) d 7.28 (t, J = 7.5 Hz, 2H), 7.22–7.17 (m, 3H),
6.80 (t, J = 7.6 Hz, 1H), 6.74 (d, J = 7.9 Hz, 1H), 6.68 (d, J = 7.2 Hz,
1H), 5.60 (br s, 1H), 4.15 (dd, J = 12.6, 5.7 Hz, 1H), 3.11 (s, 1H),
2.99–2.93 (m, 1H), 2.85 (td, J = 11.7, 5.9 Hz, 1H), 2.81–2.68 (m,
4H), 2.46 (d, J = 12.4 Hz, 1H), 2.38–2.32 (m, 1H), 2.32–2.18 (m,
2H), 1.87–1.73 (m, 3H), 1.51–1.42 (m, 1H); 13C NMR (125 MHz,
CDCl3) d 146.0, 141.0, 140.6, 138.9, 128.9, 128.5, 126.2, 122.2,
115.3, 114.0, 92.6, 58.2, 53.0, 49.3, 44.3, 38.3, 34.7, 31.9, 27.5,
23.0; HRMS [M+H]+ calcd for C22H26NO2: 336.1964. Found:
336.1967.
filtration (Brandel) through GF/B filters. The filters were punched
into 24-well plates to which was added 0.6 mL LSC-cocktail (Cyto-
scint). Samples were counted, after an overnight extraction, in a Tri-
lux liquid scintillation counter at 27% efficiency.
4.3. X-ray crystal data on compounds 16b and 19a
Single-crystal X-ray diffraction data on compounds 16b and 19a
were collected using MuK
a radiation and a Bruker Platinum 135
CCD area detector. Crystals were prepared for data collection by
coating with high viscosity microscope oil. The oil-coated crystal
was mounted on a micro-mesh mount (Mitergen, Inc.) and trans-
ferred to the diffractometer. The structures were solved by direct
methods and refined by full-matrix least squares on F2 values using
the programs found in the SHELXTL suite (Bruker, SHELXTL v6.10,
2000, Bruker AXS Inc., Madison, WI). Corrections were applied for
Lorentz, polarization, and absorption effects. Parameters refined in-
cluded atomic coordinates and anisotropic thermal parameters for
all non-hydrogen atoms. Hydrogen atoms on carbons were included
using a riding model [coordinate shifts of C applied to H atoms] with
C–H distance set at 0.96 Å. Complete information on data collection
and refinement is available in the Supplementary data.
4.1.14.2. rac-(4S,6aR,11bS)-2,3,4,5,6,6a-Hexahydro-3-phenethyl-
1H-4,11b-methanobenzofuro[3,2-d]azocine-8-ol (19b). Com-
pound 19b (base): ½a D23
ꢄ
+63.4 (c 1.1, CHCl3); 1H NMR (500 MHz,
CDCl3) d 7.28 (t, J = 7.4 Hz, 2H), 7.22–7.17 (m, 3H) 6.80 (t,
J = 7.6 Hz, 1H), 6.74 (d, J = 8.0 Hz, 1H), 6.68 (d, J = 7.2 Hz, 1H),
5.78, (br s, 1H), 4.15 (dd, J = 12.6, 5.7 Hz, 1H), 3.11 (s, 1H), 2.96
(dd, J = 10.9, 8.2 Hz, 1H), 2.85 (td, J = 11.7, 5.9 Hz, 1H), 2.81–2.68
(m, 4H), 2.47 (d, J = 12.2 Hz, 1H), 2.39–2.32 (m, 1H), 2.32–2.17 (m,
2H), 1.87–1.73 (m, 3H), 1.52–1.42 (m, 1H); 13C NMR (125 MHz,
CDCl3) d 146.1, 141.0, 140.5, 138.8, 128.9, 128.5, 126.2, 122.2,
115.3, 114.0, 92.6, 58.2, 53.0, 49.3, 44.3, 38.2, 34.7, 31.8, 27.5,
22.9; HRMS [M+H]+ calcd for C22H26NO2: 336.1964. Found:
336.1960.
For compound 16b a 0.643 ꢃ 0.104 ꢃ 0.026 mm3 crystal was
prepared for data collection and a data set collected at room tem-
perature. The crystal was orthorhombic in space group P 212121,
with unit cell dimensions a = 7.4195(2), b = 12.5090(3), and
c = 20.7761(5) Å. Data was 98.5% complete to 68.26° h with an
average redundancy of 4.98. The final anisotropic full matrix
least-squares refinement on F2 with 235 variables converged at
R1 = 4.56%, for the observed data and wR2 = 13.56% for all data.
For compound 19a a 0.364 ꢃ 0.085 ꢃ 0.042 mm3 crystal was
prepared for data collection and a data set collected at room tem-
perature. The crystal was monoclinic in space group P 21, with unit
cell dimensions a = 9.1613(3), b = 11.7449(4), c = 18.4218(6) Å, and
b = 90.721°. Data was 91.2% complete to 68.04° h with an average
redundancy of 3.09. The final anisotropic full matrix least-squares
refinement on F2 with 476 variables converged at R1 = 4.99%, for
the observed data and wR2 = 14.94% for all data.
Enantiomers 19a and 19b was converted to their HBr salts in 2-
propanol. Compound 19aꢂHBr: ½a D23
ꢄ
-53.3 (c 0.59, MeOH/H2O, 1:1);
mp 298–300 °C. Anal. Calcd for C22H26BrNO2: C, 63.46, H, 6.29, N,
3.36. Found: C, 63.57, H, 6.20, N, 3.32. Compound 19bꢂHBr: ½a D23
ꢄ
+52.6 (c 0.53, MeOH:H2O, 1:1); mp 298–300 °C. Anal. Calcd for
C22H26BrNO2: C, 63.46, H, 6.29, N, 3.36. Found: C, 63.51, H, 6.23,
N, 3.32.
4.2. Binding and Efficacy assays. Cell culture and membrane pre
paration
As noted previously,15 the recombinant CHO cells (hMOR–
CHO, hDOR–CHO and hKOR–CHO) were produced by stable
transfection with the respective human opioid receptor cDNA,
and were 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 at ꢁ80 °C.
Atomic coordinates for 16b and 19a have been deposited with
the Cambridge Crystallographic Data Centre (deposition numbers
816329 and 816330, respectively). Copies of the data can be ob-
tained, free of charge, on application to CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK [fax: +44(0) 1223 336033 or e-mail:
deposit@ccdc.cam.ac.uk.
4.2.1. [35S]GTP-
c-S binding assays
Acknowledgments
The assays were conducted with minor modifications of pub-
lished methods.17 In this description, buffer ‘A’ is 50 mM Tris–HCl,
pH 7.4, containing 100 mM NaCl, 10 mM MgCl2, 1 mM EDTA and
The work of the Drug Design and Synthesis Section, CBRB, NIDA,
& NIAAA, was supported by the NIH Intramural Research Programs

F. Li et al. / Bioorg. Med. Chem. 19 (2011) 4330–4337
4337
3. Yamada, K.; Flippen-Anderson, J. L.; Jacobson, A. E.; Rice, K. C. Synth. Stuttg.
2002, 2359.
4. Kurimura, M.; Liu, H.; Sulima, A.; Przybyl, A. K.; Ohshima, E.; Kodato, S.;
Deschamps, J. R.; Dersch, C.; Rothman, R. B.; Lee, Y. S.; Jacobson, A. E.; Rice, K. C.
J. Med. Chem. 2008, 51, 7866.
5. May, E. L. J. Org. Chem. 1956, 21, 899.
6. Zhang, Y.; Lee, Y. S.; Rothman, R. B.; Dersch, C. M.; Deschamps, J. R.; Jacobson, A.
E.; Rice, K. C. J. Med. Chem. 2009, 52, 7570.
7. Burke, T. R., Jr.; Jacobson, A. E.; Rice, K. C.; Silverton, J. V. J. Org. Chem. 1984, 49,
2508.
8. Linders, J. T.; Burke, T. R.; Jacobson, A. E.; Rice, K. C. In Problems of Drug
Dependence, 1990; Harris, L. S., Ed.; National Institute on Drug Abuse Research
Monograph 105: Washington, DC, 1991, p 388.
9. Kodato, S.; Linders, J. T. M.; Gu, X.-H.; Yamada, K.; Flippen-Anderson, J. L.;
Deschamps, J. R.; Jacobson, A. E.; Rice, K. C. Org. Biomol. Chem. 2004, 2, 330.
10. Tadic, D.; Linders, J. T. M.; Flippen-Anderson, J. L.; Jacobson, A. E.; Rice, K. C.
Tetrahedron 2003, 59, 4603.
11. Hashimoto, A.; Przybyl, A. K.; Linders, J. T. M.; Kodato, S.; Tian, X. R.;
Deschamps, J. R.; George, C.; Flippen-Anderson, J. L.; Jacobson, A. E.; Rice, K. C. J.
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of the National Institute on Drug Abuse (NIDA) and the National
Institute of Alcohol Abuse and Alcoholism. The Clinical Psychophar-
macology Section, CBRB, NIDA, was supported by the NIH Intramu-
ral Research Program of the National Institute on Drug Abuse
(NIDA). We thank the Averica Discovery Services, J.P. Kiplinger,
President, Worcester, MA, for carrying out the supercritical fluid
chromatography used to obtain the enantiomers of 16 and 19. We
also thank Dr. Klaus Gawrisch and Dr. Walter Teague (Laboratory
of Membrane Biochemistry and Biophysics, NIAAA, for NMR spec-
tral data. The authors express their thanks to Noel Whittaker and
Wesley White, Laboratory of Analytical Chemistry, NIDDK, for mass
spectral data and 1H NMR spectral data. The X-ray crystallographic
work was supported by NIDA through an Interagency Agreement
#Y1-DA1101 with the Naval Research Laboratory (NRL).
12. Zezula, J.; Jacobson, A. E.; Rice, K. C. Heterocycles 2007, 71, 881.
13. Zezula, J.; Singer, L. B.; Przybyl, A. K.; Hashimoto, A.; Dersch, C. M.; Rothman, R.
B.; Deschamps, J.; Lee, Y. S.; Jacobson, A. E.; Rice, K. C. Org. Biomol. Chem. 2008,
6, 2868.
14. White, C.; Burnett, J. J. Chromatogr. A 2005, 1074, 175.
15. Fontana, G.; Savona, G.; Rodriguez, B.; Dersch, C. M.; Rothman, R. B.; Prisinzano,
T. E. Tetrahedron 2008, 64, 10041.
16. Kim, J.-H.; Deschamps, J. R.; Rothman, R. B.; Dersch, C. M.; Folk, J. E.; Cheng, K.;
Jacobson, A. E.; Rice, K. C. Bioorg. Med. Chem. 2011. doi:10.1016/
j.bmc.2011.04.028.
17. Xu, H.; Hashimoto, A.; Rice, K. C.; Jacobson, A. E.; Thomas, J. B.; Carroll, F. I.; Lai,
J.; Rothman, R. B. Synapse 2001, 39, 64.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2011.05.035.
References and notes
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