Diaryldimethylpiperazine ligands with μ- and δ-opioid receptor affinity: Synthesis of (+)-4-[(αR)-α -(4-allyl-(2S,5S)-dimethylpiperazin-1-yl)-(3-hydroxyphenyl)methyl] -N-ethyl-N-phenylbenzamide and (-)-4-[(αR)-α -(2S,5S)-dimethylpiperazin-1-yl)-(3-hydroxy

Article abstract of DOI:10.1016/S0968-0896(03)00496-6

We have explored the synthesis of compounds that have good affinity for both μ- and δ-opioid receptors from the (αR,2S,5S) class of diaryldimethylpiperazines. These non-selective compounds were related to opioids that have been found to interact selective

Full text of DOI:10.1016/S0968-0896(03)00496-6

Bioorganic & Medicinal Chemistry 11 (2003) 4761–4768
Diaryldimethylpiperazine Ligands with ꢀ- and ꢁ-Opioid Receptor
Affinity: Synthesis of (+)-4-[(ꢂR)-ꢂ-(4-allyl-(2S,5S)-
dimethylpiperazin-1-yl)-(3-hydroxyphenyl)methyl]-N-ethyl-N-
phenylbenzamide and (ꢀ)-4-[(ꢂR)-ꢂ-(2S,5S)-dimethylpiperazin-1-
yl)-(3-hydroxyphenyl)methyl]-N-ethyl-N-phenylbenzamide
In Jong Kim,a Thomas Ullrich,a,y James W. Janetka,a,{ M. Scott Furness,a,x
b
Arthur E. Jacobson,a,* RichardB. Rothman, Christina M. Dersch,b
c
a,
Judith L. Flippen-Anderson,c,k CliffordGeorge andKenner C. Rice *
aLaboratory of Medicinal Chemistry, Building 8, Room B1-23, National Institute of Diabetes and Digestive and Kidney Diseases,
National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
bClinical Psychopharmacology Section, National Institute on Drug Abuse, Addiction Research Center,
Department of Health and Human Services, Baltimore, MD 21224, USA
cLaboratory for the Structure of Matter, Naval Research Laboratory, Washington DC 20375, USA
Received5 June 2003; revised15 July 2003; accepted25 July 2003
Abstract—We have exploredthe synthesis of compounds that have goodaffinity for both
m- and d-opioidreceptors from the
(aR,2S,5S) class of diaryldimethylpiperazines. These non-selective compounds were related to opioids that have been found to
interact selectively with m- or d-opioidreceptors as agonists or antagonists. In our initial survey, we foundtwo compounds, (+)-4-
[(aR)-a-(4-allyl-(2S,5S)-dimethylpiperazin-1-yl)-(3-hydroxyphenyl)methyl]-N-ethyl-N-phenylbenzamide (14) andits N–H relative,
(ꢀ)-4-[(aR)-a-(2S,5S)-dimethylpiperazin-1-yl)-(3-hydroxyphenyl)methyl]-N-ethyl-N-phenylbenzamide (15), that interactedwith d-
receptors with good affinity, and, as we hoped, with much higher affinity at m-receptors than SNC80. The relative configuration of
the benzylic position in (+)-4-[(aR)-a-(4-allyl-(2S,5S)-dimethyl-1-piperazinyl)-(3-methoxyphenyl)methyl]-benzyl alcohol (10) was
determined by X-ray crystallographic analysis of a crystal that was an unresolved twin. The absolute stereochemistry of that
benzylic stereogenic center was unequivocally derived by the X-ray crystallographic analysis from the two other centers of asym-
metry in the molecule that were known. Those were established from the synthesis via a dipeptide cyclo-l-Ala-l-Ala in which the
absolute stereochemistry was established.
Publishedby Elsevier Ltd.
Introduction
Thus, much research has focusedon a search for highly
selective opioids.1,2 Side effects due to the interaction of
a ligandwith a specific type of opioidreceptor are,
however, unavoidable. For example, selective and high
affinity m-receptor opioids not only alleviate centrally
mediated pain, but also are well known to cause side
effects such as respiratory depression, tolerance, and
dependence. Many d-receptor agonists, like the m-ago-
nists, reduce centrally mediated pain, and, as well,
exhibit proconvulsant activity.1 Lastly, k-receptor
mediated agonists have also been found to mediate
analgesia, but these opioids have dysphoric effects.3
Compounds that act as antagonists via interaction with
opioidreceptors have been foundto have useful and
Compounds that are very selective and have high affi-
nity for a specific opioidreceptor are useful research
tools and, as therapeutic agents, avoid the side effects
due to activation of the other two opioid receptors.
*Corresponding author. Tel.:+1-301-496-1856; fax:+1-301-402-
0589e-mail: kr21f@nih.gov (K. R. Rice); e-mail: aej@helix.nih.gov
(A. E. Jacobson).
yCurrent address: Novartis Research Institute, A-1235 Vienna, Austria.
{Current address: AstraZeneca R & D Boston, Waltham, MA.
xCurrent address: Food and Drug Administration, Rockville, MD.
kCurrent address: PDB, Rutgers, the State University of New Jersey,
Piscataway, NJ 08854.
0968-0896/$ - see front matter Publishedby Elsevier Ltd.
doi:10.1016/S0968-0896(03)00496-6

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I. J. Kim et al. / Bioorg. Med. Chem. 11 (2003) 4761–4768
interesting activities. The m-antagonists will, of course,
block the antinociceptive action of m-agonists, but some
have been foundto be useful as treatment agents for the
the d-affinity, andconvert compounds from both the
benzylic aS and aR diaryldimethylpiperazine stereo-
chemical series of d-agonists to d-antagonists. In order
to increase m-receptor affinity, we modified the N,N-
diethylamide moiety to an N-ethyl,N-phenylbenzamide.
A similar N-methylanilide moiety, that was also moved
to the meta-position on the aromatic ring (i.e., 3, Chart
1), has been shown to increase m-agonist activity in this
series).9 The para-position of the N,N-diethylamide
moiety hadbeen hypothesizedto be an appropriate d-
receptor address.9,17ꢀ19 Since we eventually wouldwant
4
abuse of opioidagonists andalcohol.
The d-antago-
nists have been foundto attenuate or reverse m receptor-
mediated side effects such as respiratory depression,
tolerance, and dependence.5ꢀ8 Compounds with mixed
receptor properties (m and d) have recently been found
9
that actedas agonists. We thought that it might be of
interest to synthesize a different type of compound that
wouldinteract with goodaffinity at both
m- and d-
opioidreceptors. Those that didnot interact well with
k-receptors would, eventually, be further examined for
their actions as m-agonists and d-antagonists (i.e., as
analgesics with the m-agonist side effects of tolerance
and dependence blocked by the d-antagonist action).
We decided to examine this in two stages, the initial
stage involvedtheir synthesis andthe evaluation of their
binding affinity to opioid receptors.
to obtain a compoundwith goodaffinity for the
receptor that woulddisplay d-antagonist activity, we
d-
then considered how a d-agonist couldbe convertedto a
d-antagonist in the diaryldimethylpiperazine series. The
normal methodology used for such conversions in the m-
series of morphinans, epoxymorphinans, and6,7-benzo-
morphans (e.g., by exchange of an N-methyl moiety for
an N-allyl group) was not thought to be applicable in
this series since both N-methyl and N-allyl compounds
are d-agonists in the SNC80-type of diaryldimethylpi-
perazines. However, a change in the configuration of the
5-methyl group, from 5R to 5S, might provide a differ-
ent steric interaction with the receptor, eliminating the
agonist effect. Such steric influences have been known to
dramatically modify m-agonists to m-antagonists in the
phenylpiperidine series of analgesics that were also
Our search for this type of ligandfocusedon com-
pounds with the diaryldimethylpiperazine molecular
structure (Chart 1) that have been extensively
reviewed.10,11 Well known compounds in this class
were [+]-4-[(aR)-a-[(2S,5R)-4-allyl-2,5-dimethyl-1-piper-
azinyl]-3-methoxybenzyl]-N,N-diethylamide (SNC 80,12
1), a highly d-selective agonist with good d-receptor
affinity,13,14 andthe much less selective andhigher affi-
nity13 phenolic d-agonist, the racemic 4-[(4-allyl-2,5-
dimethylpiperazin-1-yl)-(3-hydroxyphenyl)methyl]-N,N-
diethylbenzamide (racemic BW373U86, 2).15,16 This
racemate andits aR,2S,5R-(+)-enantiomer, exhibited
both d- and m-agonist effects. In general, in the
aR,2S,5R diaryldimethylpiperazine series, the 3-meth-
oxylphenyl derivatives were found to have increased d-
receptor selectivity anddecreasedaffinity when com-
20,21
unaffectedby moidfication of the N-substituent.
That a similar pharmacological change induced by a
steric effect might be applicable to d-ligands was indi-
cated by the mention, in a patent, of a diaryldi-
methylpiperazine compoundwith d-antagonist activity
(as ascertainedin the mouse vas deferens assay) that
hadan aR,2S,5S configuration,22 andthe experimental
determination of d-antagonist activity in a 3R,5S-dia-
ryldimethylpiperazine compound, [cis-4-(a-(4-((Z)-2-
butenyl)-3,5-dimethyl-1-piperazinyl)-3-hydroxybenzyl)-
N,N-diethylbenzamide, 4].9 We, thus, decided to syn-
thesize and determine the opioid receptor binding affi-
nities of aR N-H and aR N-allyl (2S,5S)-2,5-cis-
dimethylpiperazinyl)-(3-methoxyphenyl)methyl]-N-ethyl-
N-phenylbenzamides.
14
paredwith its phenolic relative. Somewhat less d-affi-
nity was observedfor
aS,2S,5R ligands than the
comparable aR,2S,5R ligands, but those that were
examinedretained d-agonist activity.14 We decided,
initially, to try to increase the affinity of these com-
pounds for the m-receptor (as agonists) while retaining
Chemistry
The synthesis of the intermediates leading to the
designed compounds was straightforward and accom-
plished according to a previously reported method.23 4-
Formyl-N,N-diethylbenzamide (5) was obtainedfrom
the condensation of 4-formylbenzoic acid with diethyl-
amine in the presence of 1-(3-dimethylaminopropyl)3-
ethylcarbodiimide (EDCI) in 88% yield. Reaction of 5
with (3-methoxyphenyl)magnesium bromide produced
benzhydryl alcohol 6, which was convertedto the cor-
responding chloride 7 after treatment with concentrated
hydrochloric acid (Scheme 1). Addition of (2S,5S)-
dimethylpiperazine,24 yielded an inseparable amine
mixture 8. Allylation of the mixture 8 gave a mixture 9,
from which pure 9a and 9b couldbe obtainedby pre-
parative HPLC. Pure 8a and 8b was obtainedfrom pure
9a and 9b, respectively, by catalytic hydrogenation.
Chart 1.

I. J. Kim et al. / Bioorg. Med. Chem. 11 (2003) 4761–4768
4763
This prevented the direct determination of absolute
configuration. However, the absolute stereochemistry of
the benzylic stereogenic center was unequivocally
establishedfrom this X-ray crystallographic analysis of
.
10 2HBr because the two other centers of asymmetry in
the molecule were known. The absolute configuration of
2S,5S-dimethylpiperazine was derived by its synthesis
from the dipeptide cyclo-l-Ala-l-Ala in which the
absolute stereochemistry hadbeen unambiguously
determined. The configuration of the benzylic (C11a)
center of asymmetry in 10 was, thus, assignedas R.
Benzyl alcohol 10 was convertedto the corresponding
carbamates 11 in high yieldfrom its reaction with aryl-
isocyanates. The benzyl amine analogue 13 was
obtainedfrom 12, andthe phenolic benzamides 14 and
15 were obtainedfrom 9a, as shown in Scheme 2.
Results and Discussion
Scheme 1. Conditions: (a) N-ethylaniline, EDCI, 10 ꢁC to rt, CH2Cl2,
88%; (b) 3-MeO–PhMgBr, 10 ꢁC to rt, THF, 78%; (c) HCl, CHCl3, rt,
97%; (d) (2S,5S)-dimethylpiperazine, NaHCO3, CH3CN, reflux, 72%;
(e) allyl bromide, NaHCO3, DMF, 80 ꢁC, 95%; (f) 10% Pd/C, cat
CH3CO2H, H2O, reflux.
We have succeeded in synthesizing (+)-4-[(aR)-a-(4-
allyl - (2S,5S) - dimethylpiperazin - 1 - yl) - (3 - hydroxy-
phenyl)methyl]-N-ethyl-N-phenylbenzamide (14) and
the N–H enantiomer, (ꢀ)-4-[(aR)-a-(2R,5R)-dimethyl-
piperazin-1-yl)-(3-hydroxyphenyl)methyl]-N-ethyl-N-
phenylbenzamide (15). The X-ray diffraction study of
(+)-4-[(aR)-a-(4-allyl-(2S,5S)-dimethyl-1-piperazinyl)-(3-
methoxyphenyl)methyl]-benzyl alcohol dihydrobromide
In order to determine the importance of the amide
function to the pharmacological effect of the ligand,
that moiety was reduced in 8a and 9a with lithium alu-
minum hydride (LAH). We were surprised to find that
.
(10 2HBr, Fig. 1), alloweddetermination of their abso-
they reactedidfferently. Compound
9a gave benzyl
lute configuration. These compounds were found to
have good(low nM) affinity to the d-receptor, about the
same as that of SNC80 (1, Table 1), andalso have much
higher affinity for the m-opioidreceptors than SNC80.
They are, accordingly, less selective for those receptors,
satisfying our primary initial goal. The phenolic com-
pound 14 displayed better affinity (Ki=55 nM) for the
m-opioidreceptor, than 15, its N-nor relative. Unfortu-
alcohol 10 on LAH reduction, while 8a gave benzyl-
amine 12, in goodyield( Scheme 2). We assumedthat
the difference in reactivity of 8a and 9a couldbe due to
a reduction of different complexes that might be formed
between 8a or 9a andLAH.
The relative configuration of the benzylic position in 10
(and, by extension, in all of the other compounds with
three centers of asymmetry (e.g., 8, 9, 14, and 15) was
determined by X-ray crystallographic analysis of a
crystal that was an unresolvedtwin. Many reflections
included overlap data from the other twin components.
Scheme 2. Conditions: (a) LiAlH4, Et2O, reflux; (b) arylisocyanate,
C6H6, rt, 89–94%; (c) allyl bromide, NaHCO3, DMF, 80 ꢁC, 97%;
(d) BBr3Me2S in CH2Cl2, 1,2-dichloroethane, 60 ꢁC, 52%; (e) 10% Pd-
C, cat CH3CO2H, H2O, reflux, 73%.
Figure 1. Displacement ellipsoidplot of (+)-4-[( aR)-a-(4-allyl-
(2S,5S)-dimethyl - 1 - piperazinyl) - (3 - methoxyphenyl)methyl] - benzyl
.
alcohol dihydrobromide (10 2HBr) drawn at 30% probability level.
The bromine ions have been omittedfor clarity.

4764
I. J. Kim et al. / Bioorg. Med. Chem. 11 (2003) 4761–4768
Table 1. Opioid receptor binding affinities of ligands [Ki nMꢃSEM)]
GA, USA All extractedsolutions were driedover mag-
nesium sulfate or sodium sulfate and concentrated to
dryness on a rotary evaporator under reduced pressure.
N-Ethyl-4-formyl-N-phenylbenzamide (5). 1-[3-(Dime-
thylamino)propyl] - 3 - ethylcarbodiimide hydrochloride
(230.1 g, 1.20 mol) was added portionwise to a vigor-
ously stirredmixture of 4-formylbenzoic acid(150 g, 1
mol) and N-ethylaniline (133 g, 1.1 mol) in anhydrous
CH2Cl2 (2.5 L) at 10 ꢁC. The mixture temperature was
maintainedfor 30 min andthen kept at room tempera-
ture for 16 h. After adding a saturated solution of
sodium bicarbonate (1 L), the aqueous layer was
8a, 8b, 9a, 9b, 12, 13, 14, 15: R3=N-ethyl-N-phenylamide; 10:
R3=hydroxymethyl; 11a: R3=phenylcarbamate methyl ester; 11b:
R3=4-bromophenylcarbamate methyl ester; 11c: R3=4-methoxy-
phenylcarbamate methyl ester
11a R1 R2
ma
db
kc
m/d
k/d
1d
8a
8b
9a
9b
10
11a
11b
11c
12
2470ꢃ200d 2.9ꢃ0.35d
—
857
—
extractedwith CHCl
(3ꢂ500 mL). The combined
3
R
S
R
S
R
R
R
R
R
R
R
R
H
H
Me
Me
>9200
>9200
>9200
>9200
>6540
35ꢃ5
99ꢃ6
17,800ꢃ1220 >262 509
organic extracts were washedwith water, 2N-hydro-
chloric acid, and brine, dried (MgSO4 /activatedchar-
coal), filtered, and evaporated. The crude material was
trituratedwith isopropyl etherꢁto affordcolorless crys-
27,000 >93 273
Allyl Me
Allyl Me
Allyl Me
Allyl Me
Allyl Me
Allyl Me
H
Allyl Me
Allyl
H
58ꢃ4
2480ꢃ180 >159
43
32
28
224ꢃ26
293ꢃ15
7260ꢃ410
8280ꢃ430
>6990
>41
>22
>5 >5
>1.3 >1.4
>5
>5
>5
18
>6540 1310ꢃ54
1
tals (224 g, 88%), mp 79–81 C. H NMR (CDCl3) d
>6540
>4850
>6990
8510ꢃ370
9.91 (s, 1H), 7.64 (d, J=7 Hz, 2H), 7.43 (d, J=7 Hz,
2H), 7.30–7.09 (m, 3H), 7.04 (d, J=7 Hz, 2H), 4.01 (q,
J=7 Hz, 2H), 1.26 (t, J=7 Hz, 3H); MS m/z 253 (M+).
>6540 1380ꢃ84
>6540 1210ꢃ68
>6540 1350ꢃ33
6
6
5
11
93
Me
>6990
>6990
13
14
15
H
H
55ꢃ6
3.2ꢃ0.18
36ꢃ4
.
Anal. calcdfor C 16H15NO2 1.0H2O: C, 75.86; H, 5.97;
N, 5.53. Found: C, 75.66; H, 6.09; N, 5.50.
232ꢃ14
2.9ꢃ0.27
271ꢃ19
80
aDisplacement of [3H]DAMGO (d-Ala2,MePhe4Gly-ol5)enkephalin), in rat
brain membranes.
bDisplacement of [3H]DADLE (d-Ala2,d-Leu5)enkephalin), in rat brain
membranes. DAMGO (100 nM) was usedto block m receptor binding.
cDisplacement of [3H]U69,593 (trans-3,4-dichloro-N-methyl[2-(1-pyrrolidi-
nyl)cyclohexyl]benzene acetamide), in guinea pig brain membranes.
dData for SNC80 (1) from ref 13.
N-Ethyl-4-[hydroxy-(3-methoxyphenyl)methyl]-N-phenyl-
benzamide (6). A solution of 5 (109 g, 430.3 mmol) in
anhydrous THF (350 mL) was added to a vigorously
stirredmixture of 3-methoxyphenylmagnesium bromide
(948 mL, 474 mmol, 0.5 M solution in THF) in anhy-
drous THF at 10 ꢁC. The mixture was allowedto warm
to room temperature andwas stirredfor 30 min. After
adding saturated NH4Cl (1 L), the aqueous layer was
extractedwith ethyl acetate (3 ꢂ300 mL). The combined
nately, 14 interactedas well with the k- (Ki=36 nM) as
with the m-receptor. None of the other compounds listed
in Table 1 hadthe desiredselectivity andaffinity for the
m- and d-receptors. The amide function, in this series,
was foundto be important for interaction with opioid
receptors, andthe phenolic compounds, not the meth-
oxy ethers, hadthe desiredselectivity andreasonable
affinity. The aS configuration as seen in 8b and 9b
(Table 1) did not appear to be advantageous. The two
most interesting compounds, 14 and 15, will, eventually,
be further examinedfor their agonist and/or antagonist
activity andthe pharmacological data will be reported
in due course.
organic extracts were washedwith brine, dried(MgSO
4
/activated charcoal), filtered, and evaporated. The crude
material was crystallizedfrom isopropyl ether to afford
6 as colorless crystals (121 g, 78%), mp 106–108 ꢁC. H
1
NMR (CDCl3) d 7.40–7.21 (m, 8H), 7.14 (d, J=7 Hz,
2H), 6.98–6.83 (m, 3H), 5.90 (s, 1H), 4.08 (q, J=7 Hz,
2H), 4.93 (s, 3H), 1.31 (t, J=7 Hz, 3H); MS m/z 360
(M+). Anal. calcdfor C 23H25NO3: C, 76.43; H, 6.41; N,
3.88. Found: C, 76.39; H, 6.43; N, 3.87.
4-[Chloro-(3-methoxyphenyl)methyl]-N-ethyl-N-phenyl-
benzamide (7). A solution of 6 (201 g, 557 mmol) in
CHCl3 (800 mL) was added dropwise to 37% hydro-
chloric acid(2.2 L). The biphasic mixture was allowed
to stir at room temperature for 16 h. The organic layer
was separated, washed with water (2ꢂ200 mL), dried
(NaSO4 /activatedcharcoal), filtered, andevaporatedto
afford 7 as a redoil (205 g, 97%), 1H NMR (CDCl3) d
7.40–7.21 (m, 8H), 7.14 (d, J=7 Hz, 2H), 6.98–6.83 (m,
3H), 5.90 (s, 1H), 4.08 (q, J=7 Hz, 2H), 3.93 (s, 3H),
1.31 (t, J=7 Hz, 3H); MS m/z 379 (M+). Anal. calcd
Experimental
Melting points were determined on a Thomas-Hoover
capillary melting point apparatus andare uncorrected.
Proton nuclear magnetic resonance (1H NMR) spectra
were recorded in CDCl3 (unless otherwise noted) with
tetramethylsilane (TMS) as the internal standard on a
Varian Gemini-300 spectrometer. Chemical ionization
mass spectra (MS, CI-NH3) were recorded on a Finni-
gan 4600 spectrometer. Optical rotations were obtained
using a Perkin-Elmer 241 MC polarimeter. Thin layer
chromatography (TLC) was performedon Analtech
silica gel GHLF 0.25 mm plates. Flash column chro-
matography was performedwith Fluka silica gel 60
(220–240 mesh). Preparative HPLC were performed
using the Shimadzu LC-6A system. Elemental analyses
were performedby Atlantic Microlabs, Inc., Norcross,
.
for C23H22ClNO2 0.75H2O: C, 70.22; H, 6.02; N, 3.56.
Found: C, 70.44; H, 5.75; N, 3.55.
4-[((2S,5S)-Dimethyl-1-piperazinyl)-(3-methoxyphenyl)-
methyl]-N-ethyl-N-phenylbenzamide (8). (2S,5S)-Dime-
thylpiperazine24 (5.75 g, 50.39 mmol) andNaHCO
3
(4.23 g, 50.39 mmol) were suspended in anhydrous
CH3CN (80 mL) under argon and refluxed for 30 min.

I. J. Kim et al. / Bioorg. Med. Chem. 11 (2003) 4761–4768
4765
A solution of 7 (8.6 g, 22.68 mmol) in anhydrous
3H), 0.95 (d, J=8 Hz, 3H). Anal. calcdfor
.
CH3CN (30 mL) was added dropwise, and the mixture
was refluxedfor 16 h. Hydrochloric acid(2N, 300 mL)
was added, and the aqueous layer was washed with
ethyl acetate (3ꢂ200 mL). The aqueous phase was trea-
ted with ammonium hydroxide until pH 9, and extrac-
tedwith ethyl acetate (3 ꢂ300 mL). The combined
organic extracts were washedwith water andbrine,
dried (NaSO4/activatedcharcoal), filtered, andevapo-
ratedto affordcrude 8. It was purifiedby column chro-
matography (10% MeOH in CHCl3) to give 8 as a pale
C32H41Cl2N3O2 1.75H2O: C, 63.83; H, 7.45; N, 6.98.
Found: C, 63.91; H, 7.16; N, 6.85.
General procedure for deallylation of 9a and 9b. The
allyl-substitutedamine ( ꢄ0.4 mmol) was suspended in
glacial acetic acid(50 mg) andwater (3.0 mL), and10%
palladium on charcoal (15 mg) was added. The mixture
was stirredat reflux temperature for 16 h, cooledto
room temperature, filteredthrough Celite, treatedwith
ammonium hydroxide until pH 12 and extracted with
CHCl3 (3ꢂ5 mL). The combinedorganic extracts were
dried over Na2SO4, filtered, and evaporated to give the
crude material. Chromatographic purification of the
crude material with 10% MeOH in CHCl3 afforded 8a
or 8b as a colorless oil.
1
yellow oil (7.504 g, 72%), H NMR (CDCl3) d 7.18–
6.99 (m, 8H), 6.94–6.81 (m, 4H), 6.61 (d, J=7 Hz, 1H),
4.28 (s, 1H), 3.83 (q, J=7 Hz, 2H), 3.68 (s, 3H), 2.90–
3.07 (m, 1H), 2.88–2.53 (m, 3H), 2.39–2.25 (m, 1H),
2.18–2.08 (m, 1H), 1.97–1.80 (m, 1H), 1.60 (broads,
1H), 1.12 (t, J=7 Hz, 3H), 0.87–0.72 (m, 6H); MS m/z
458 (M+1)+. Anal. calcdfor C 29H37Cl2N3O2 2.25H2O:
.
C, 61.09; H, 7.32; N, 7.37. Found: C, 60.94; H, 6.95; N,
7.18.
4-[(ꢂR)-ꢂ-(2S,5S)-dimethyl-1-piperazinyl)-(3-methoxy-
phenyl)methyl]-N-ethyl-N-phenylbenzamide (8a). Deal-
lylation of 9a (200 mg, 0.402 mmol) gave 8a (130 mg,
73%); dihydrochloride salt from methanol, mp 174–
D
175 ꢁC, [a]20 ꢀ7.9 (c 0.47, MeOH); H NMR (free base)
(CDCl3) d 7.28-7.08 (m, 8H), 6.99 (d, J=8 Hz, 2H),
6.97- 6.88 (m, 2H), 6.69 (d, J=8 Hz, 1H), 4.37 (s, 1H),
3.97 (q, J=8 Hz, 2H), 3.76 (s, 3H), 3.13-3.03 (m, 1H),
2.95-2.83 (m, 1H), 2.82–2.76 (m, 1H), 2.75–2.63 (m,
1H), 2.22 (dd, J=15 Hz, J=4 Hz, 1H), 2.00–1.87 (m,
1H), 1.57 (broads, 1H), 1.22 (t, J=8 Hz, 3H), 0.96 (d,
J=8 Hz, 3H), 0.94 (d, J=8 Hz, 3H). Anal. calcdfor
1
(+)-4-[(ꢂR)-ꢂ-(4-Allyl-(2S,5S)-dimethyl-1-piperazinyl)-
(3-methoxyphenyl)methyl]-N-ethyl-N-phenylbenzamide
(9a) and (+)-4-[(ꢂS)-ꢂ-(4-Allyl-(2S,5S)-dimethyl-1-pi-
perazinyl)-(3-methoxy- phenyl)methyl]-N-ethyl-N-phenyl-
benzamide (9b). A suspension of 8 (750 mg, 1.64
mmol), allyl bromide (199 mg, 1.64 mmol) and
NaHCO3 (276 mg, 3.28 mmol) in anhydrous DMF (10
mL) was stirredunder argon for 2 h at 80 ꢁC. After the
solvent was removed, the residue was diluted with ethyl
acetate (50 mL). The organic layer was washedwith
water (3ꢂ5 mL) and brine, dried (sodium sulfate/acti-
.
C29H37Cl2N3O2 2.0H2O: C, 59.76; H, 7.40; N, 7.21.
Found: C, 60.03; H, 7.06; N, 6.81.
vatedcharcoal), filteredandevaporatedto afford
9 as a
4-[(ꢂS)-ꢂ-(2S,5S)-Dimethyl-1-piperazinyl)-(3-methoxy-
phenyl)methyl]-N-ethyl-N-phenylbenzamide (8b). Deal-
lylation of 9b (210 mg, 0.422 mmol) gave 8b (140 mg,
73%); dihydrochloride salt from methanol, mp 177–
178 ꢁC, [a]D20 ꢀ10.0ꢁ (c 0.38, MeOH); 1H NMR (free
base) (CDCl3) d 7.28–7.08 (m, 8H), 7.05–6.87 (m, 4H),
6.69 (d, J=8 Hz, 1H), 4.35 (s, 1H), 3.97 (q, J=8 Hz,
2H), 3.78 (s, 3H), 3.13–3.03 (m, 1H), 2.88–2.78 (m, 1H),
2.77–2.62 (m, 2H), 2.21 (dd, J=15 Hz, J=4 Hz, 1H),
2.05–1.83 (m, 1H), 1.52 (broads, 1H), 1.20 (t, J=8 Hz,
3H), 0.95 (d, J=8 Hz, 3H), 0.87 (d, J=8 Hz, 3H). Anal.
yellow oil, a mixture of two diastereomers (777 mg,
95%). Separation of the diastereomeric mixture was
accomplishedby preparative HPLC (Alltech econo-
sphere column (silica, 10 mm, 22ꢂ250 mm), UV detec-
tion at 254 nm). The mixture was dissolved in 40% ethyl
acetate in hexanes (ꢄ50 mg/mL), filteredthrough a 0.45
mm filter, and ꢄ50 mg (1 mL/injection) was separated
at a time. The mobile phase contained40% ethyl ace-
tate in hexanes with a flow rate of 5 mL/min. The
retention time of 9a and 9b was about 28 and30 min,
respectively, and ꢄ70% separation was achievedin
each injection. 9a: dihydrochlorꢁide salt from diethyl
.
calcdfor C 29H37Cl2N3O2 1.25H2O: C, 63.08; H, 7.19;
N, 7.61. Found: C, 63.00; H, 7.11; N, 7.55.
D
ether, mp 192–193 ꢁC; [a]20 +5.9 (c 0.44, MeOH); H
NMR (free base) (CDCl3) d 7.30–7.08 (m, 8H), 6.97 (d,
J=8 Hz, 2H), 6.91–6.82 (m, 2H), 6.71 (d, J=8 Hz, 1H),
5.93–5.77 (m, 1H), 5.22–5.08 (m, 2H), 4.42 (s, 1H), 3.97
(q, J=8 Hz, 2H), 3.75 (s, 3H), 3.44–3.31 (m, 1H), 2.98–
2.84 (m, 1H), 2.83–2.71 (m, 1H), 2.57 (dd, J=15 Hz,
J=4 Hz, 1H), 2.44–2.28 (m, 1H), 2.22–2.15 (m, 1H),
1.21 (t, J=8 Hz, 3H), 1.00 (d, J=8 Hz, 3H), 0.92 (d,
1
(+)-4-[(ꢂR)-ꢂ-(4-Allyl-(2S,5S)-dimethyl-1-piperazinyl)-
(3-methoxyphenyl)methyl]-benzyl alcohol (10). 1 M-
LiAlH4 in THF (0.957 mL, 0.957 mmol was added
dropwise to a solution of 9a (396.3 mg, 0.798 mmol) in
Et2O (10 mL) at 0 ꢁC. After refluxing 2 h, the reaction
ꢁ
mixture was cooledto 0 C andquenchedby addition of
saturatedNH Cl solution. The heterogeneous mixture
4
.
J=8 Hz, 3H). Anal. calcdfor C 32H41Cl2N3O2 1.75H2O:
was filteredthrough a padof Celite andwashedwith
EtOAc. The combinedfiltrate was washedwith water
andbrine, driedover Na 2SO4, filteredandconcentrated
to dryness. Chromatography of the crude with 40%
ethyl acetate in hexanes gave 10 as a colorless oil (303.6
mg, quantitative), [a]D20 +23.3ꢁ (c 0.45, CHCl3); 1H
NMR (CDCl3) d 7.44 (br-d, J=8 Hz, 2H), 7.24 (br-d,
J=8 Hz, 2H), 7.15 (t, J=8 Hz, 1H), 7.01–6.97 (m, 2H),
6.69 (br-dd, J=8 and2 Hz, 2H), 5.92–5.78 (m, 1H),
5.19–5.10 (m, 2H), 4.60 (br–s, 2H), 4.51 (br-s, 1H), 3.75
C, 63.83; H, 7.45; N, 6.98. Found: C, 63.86; H, 7.26; N,
6.79. 9b: dihydrochloride salt from diethyl ether, mp
159–160 ꢁC, [a]2D0 +12.2ꢁ (c 0.36, MeOH); 1H NMR
(free base) (CDCl3) d 7.28–7.05 (m, 8H), 7.05–6.88 (m,
4H), 6.91–6.82 (m, 2H), 6.71 (d, J=8 Hz, 1H), 5.93–
5.77 (m, 1H), 5.22–5.08 (m, 2H), 4.40 (s, 1H), 3.97 (q,
J=8 Hz, 2H), 3.77 (s, 3H), 3.44–3.31 (m, 1H), 2.84–2.66
(m, 2H), 2.62–2.48 (m, 1H), 2.47–2.29 (m, 2H), 2.29–
2.16 (m, 1H), 1.21 (t, J=8 Hz, 3H), 0.97 (d, J=8 Hz,

4766
I. J. Kim et al. / Bioorg. Med. Chem. 11 (2003) 4761–4768
(s, 3H), 3.41 (br-dd, J=14 and5 Hz, 1H), 3.03–3.00 (m,
1H), 2.80 (dd, J=14 and 8 Hz, 1H), 2.60 (dd, J=11 and
3 Hz, 1H), 2.47–2.38 (m, 3H), 2.28–2.21 (m, 1H), 1.03
(d, J=6 Hz, 3H), 0.95 (d, J=6 Hz, 3H); MS m/z 381
(M+1)+; HRMS (FAB) m/z calcdfor C 12H24N2O2,
381.2543; found, 381.2541. The dihydrobromide salt
was preparedandcrystallizedslowly from ethanol in a
diethyl ether atmosphere (mp 159–160 ꢁC) for X-ray
crystallographic analysis (Fig. 1).
3 Hz), 0.97 (d, J=6 Hz, 3H); MS m/z 530 (M+1)+.
Dihydrochloride salt from methanol, mp 160–161 ꢁC
.
(dec). Anal. calcd for C32H41Cl2N3O4 1.0H2O: C, 61.73;
H, 7.29; N, 6.75. Found: C, 61.96; H, 6.89; N, 6.44.
(+)-4-[(ꢂR)-ꢂ-(2S,5S)-dimethyl-1-piperazinyl)-(3-meth-
oxyphenyl)methyl]-N-ethyl-N-phenylbenzylamine (12).
To a mixture of 8a (88 mg, 0.193 mmol) in THF (2
mL) was added dropwise 1.0 M-LiAlH4 in THF (0.23
mL, 0.23 mmol) at 0 ꢁC, andthe mixture was refluxed
for 2 h. The reaction was quenchedby adition of
saturated. NH4Cl solution, filteredthrough a padof
Celite andwashedwith EtOAc. The combinedfiltrate
General procedure for syntheses of carbamates 11. A
mixture of benzyl alcohol 10 (ꢄ0.12 mmol), arylisocya-
nate (ꢄ0.125 mmol) anda catalytic amount of dibutyl
dilaurate (3 mL) in benzene (1.5 mL) was stirredat room
temperature overnight. The reaction mixture was dilu-
tedwith ethyl acetate (20 mL), washedwith water and
brine, dried over Na2SO4, filtered, and concentrated to
dryness. Column chromatography of the crude product
with 20% ethyl acetate in hexanes afforded carbamates
11 as a colorless film (89–94%).
was washedwith water andbrine, driedover Na
2SO4,
filtered, and concentrated to dryness. Column chroma-
tography of the crude with 10% MeOH in CHCl3 pro-
vided 8 (61.0 mg, 72%) as a colorless oil, [a]D20 +2.2ꢁ (c
0.55, CHCl3); 1H NMR (CDCl3) d 7.36 (br-d, J=8
Hz, 2H), 7.19–7.10 (m, 5H), 7.03–6.99 (m, 2H), 6.72–
6.62 (m, 4H), 4.43 (br-s, 3H), 3.77 (s, 3H), 3.42 (q,
J=7 Hz, 2H), 3.15 (dd, J=12 and3 Hz, 1H), 3.00–
2.86 (m, 2H), 2.73 (dd, J=12 and2 Hz, 1H), 2.43
(dd, J=12 and3 Hz, 1H), 2.03 (t, J=11 Hz, 1H),
1.17 (t, J=7 Hz, 3H), 0.99 (d, J=6 Hz, 3H), 0.98 (d,
J=6 Hz, 3H); MS m/z 444 (M+1)+. Trihydrochloride
salt from diethyl ether, mp 173 ꢁC (dec). Anal. calcd for
Carbamate 11a. Reaction of benzyl alcohol 10 (44. 6
mg, 0.117 mmol) andphenylisocyanate (13 mL, 0.12
mmol) gave carbamate 11a (52.3 mg, 89%), [a]2D0
+23.3ꢁ (c 0.49, CHCl3); 1H NMR (CDCl3) d 7.47 (br-d,
J=8 Hz, 2H), 7.38–7.26 (m, 6H), 7.18–6.96 (m, 3H),
6.71–6.64 (m, 2H), 5.93–5.79 (m, 1H), 5.20–5.15 (m,
2H), 5.13 (br-s, 2H), 4.53 (br-s, 1H), 3.76 (s, 3H), 3.42
(dd, J=14 and 5 Hz, 1H), 3.03–3.01 (m, 1H), 2.83 (dd,
J=14 and 8 Hz, 1H), 2.63 (dd, J=11 and3 Hz, 1H),
2.50–2.39 (m, 3H), 2.31–2.23 (m, 1H), 1.04 (d, J=6 Hz,
3H), 0.97 (d, J=6 Hz, 3H); MS m/z 500 (M+1)+.
Dihydrochloride salt from methanol, mp 168 ꢁC (dec).
.
C29H40Cl3N3O 2.25H2O: C, 58.68; H, 7.56; N, 7.08.
Found: C, 58.76; H, 7.37; N, 6.72.
(+)-4-[(ꢂR)-ꢂ-(4-Allyl-(2S,5S)-dimethylpiperazin-1-yl)-
(3-methoxyphenyl)methyl]-N-ethyl-N-phenylbenzylamine
(13). Allylation was performedaccording to the proce-
dure described in conversion of 8 to 9. Reaction of 12
(32.3 mg, 0.073 mmol) andallyl bromide (6.6 mL, 0.077
mmol)ꢁgave 13 (34.1 mg, 97%) as a colorless oil, [a]2D0
.
Anal. calcdfor C 31H39Cl2N3O3 0.5H2O: C, 64.02; H,
6.93; N, 7.23. Found: C, 64.10; H, 6.97; N, 7.23.
1
+24.2 (c 0.99, CHCl3); H NMR (CDCl3) d 7.37 (br–
Carbamate 11b. Reaction of benzyl alcohol 10 (46.7 mg,
0.123 mmol) and p-bromophenylisocyanate (24.8 mg,
0.125 mmol) gave carbamate 11b (66.8 mg, 94%), [a]2D0
+22.0ꢁ (c 0.45, CHCl3); 1H NMR (CDCl3) d 7.47 (br-d,
J=8 Hz, 2H), 7.41–7.38 (m, 2H), 7.29–7.24 (m, 3H),
7.16 (t, J=8 Hz, 1H), 7.00–6.96 (m, 2H), 6.72–6.68 (m,
1H), 6.62 (br–s, 1H), 5.92–5.79 (m, 1H), 5.20–5.12 (m,
4H), 4.53 (s, 1H), 3.76 (s, 3H), 3.42 (dd, J=14 and5 Hz,
1H), 3.03–3.00 (m, 1H), 2.82 (dd, J=14 and8 Hz, 1H),
2.2 (dd, J=11 and3 Hz, 1H), 2.49–2.38 (m, 3H), 2.32–
2.23 (m, 1H), 1.03 (d, J=6 Hz, 3H), 0.97 (d, J=6 Hz,
3H); MS m/z 578 (M+). Dihydrochloride salt from
methanol, mp 165 ꢁC (dec). Anal. calcd for
C31H38BrCl2N3O3: C, 57.15; H, 5.88; N, 6.45. Found:
C, 56.83; H, 6.08; N, 6.14.
d, J=8 Hz, 2H), 7.19–7.10 (m, 5H), 7.00–6.97 (m, 2H),
6.72–6.20 (m, 4H), 5.92–5.78 (m, 1H), 5.19–5.10 (m,
2H), 3.76 (m, 3H), 3.46–3.37 (m, 3H), 3.00–2.98 (m,
1H), 2.79 (br-dd, J=14 and 8 Hz, 1H), 2.59 (dd, J=11
and3 Hz, 1H), 2.46–2.36 (m, 3H), 2.27–2.20 (m, 1H),
1.17 (t, J=7 Hz, 3H), 1.02 (d, J=6 Hz, 3H), 0.96 (d,
J=6 Hz, 3H); MS m/z 484 (M+1)+. Trihydrochloride
salt from diethyl ether, mp 187 ꢁC (dec). Anal. calcd for
.
C32H44Cl3N3O 1.50H2O: C, 61.98; H, 7.64; N, 6.78.
Found: C, 61.98; H, 7.73; N, 6.52.
(+)-4-[(ꢂR)-ꢂ-(4-Allyl-(2S,5S)-dimethylpiperazin-1-yl)-
(3-hydroxyphenyl)methyl]-N-ethyl-N-phenylbenzamide
(14). To a solution of 9a (179 mg, 0.3596 mmol) in 1,2-
dichloroethane (4.5 mL) was added dropwiseꢁ 1 M-
.
BBr3 Me2S in CH2Cl2 (1.26 mL, 1.26 mmol) at 0 C and
Carbamate 11c. Reaction of benzyl alcohol 10 (47.9 mg,
0.126 mmol) and p-methoxyphenylisocyanate (16.6 mL,
0.128 mmol) gave carbamate 11c (60.1 mg, 91%), [a]2D0
the mixture was heatedat 60 ꢁC for 3.5 h. The reaction
mixture was pouredinto ice-coldammonia solution and
extractedwith 10% MeOH in ethyl acetate (2 ꢂ). The
combinedorganic layer was washedwith water and
brine, dried over Na2SO4, filteredandconcentratedto
dryness. Column chromatography of the crude with
40% ethyl acetate in hexanes provided 14 (91.2 mg,
52%) as a colorless oil, [a]D20 +16.8ꢁ (c 0.41, CHCl3); 1H
NMR (CDCl3) d 7.23–6.56 (m, 8H), 5.88–5.75 (m, 1H),
5.18–5.09 (m, 2H), 4.46 (s, 1H), 3.96 (q, J=7 Hz, 2H),
3.33 (br-dd, J=14 and5 Hz, 1H), 2.90–2.77 (m, 2H),
+21.7ꢁ (c 0.30, CHCl3); H NMR (CDCl3) d 7.46 (br–
1
d, J=9 Hz, 2H), 7.29–7.25 (m, 3H), 7.16 (t, J=8 Hz,
1H), 7.00–6.96 (m, 2H), 6.86–6.82 (m, 2H), 6.71–6.68
(m, 1H), 6.51 (br-s, 1H), 5.92–5.79 (m, 1H), 5.20–5.11
(m, 4H), 4.53 (s, 1H), 3.77 (s, 3H), 3.76 (s, 3H), 3.42 (br-
dd, J=14 and 5 Hz, 1H), 3.03–3.01 (m, 1H), 2.82 (dd,
J=14 and 8 Hz, 1H), 2.62 (dd, J=11 and3 Hz, 1H),
2.49–2.39 (m, 3H), 2.30–2.23 (m, 1H), 1.03 (d, J=6 Hz,

I. J. Kim et al. / Bioorg. Med. Chem. 11 (2003) 4761–4768
4767
2.55 (dd, J=11 and4 Hz, 1H), 2.43–2.34 (m, 2H),
2.20–2.11 (m, 2H), 1.20 (t, J=7 Hz, 3H), 0.99 (d,
J=6 Hz, 3H), 0.93 (d, J=6 Hz, 3H); MS m/z 484
(M+1)+. Dihydrochloride salt from methanol, mp
synthesis from a peptide of established configuration.
Crystallographic data (excluding structure factors) have
been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication no CCDC
21160. Copies of the data can be obtained, free of
charge, on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44-1223-336033 or
email: deposit@ccdc.cam.ac.uk).
173–174 ꢁC. Anal. calcdfor C 31H39Cl2N3O2 0.5H2O:
.
C, 65.83; H, 7.13; N, 7.43. Found: C, 65.95; H, 7.08;
N, 7.44.
(ꢀ) - 4 - [(ꢂR) - ꢂ - (2S,5S) - dimethylpiperazin - 1 - yl) - (3-
hydroxyphenyl) - methyl] - N - ethyl - N - phenylbenzamide
(15). A mixture of 14 (52.0 mg, 0.1075 mmol), glacial
acetic acid(three drops) andwater (2.0 mL) and10%
palladium on charcoal (10 mg) was refluxed for 14 h.
The reaction was filteredthrough Celite, washedwith
10% MeOH in ethyl acetate andtreatedwith ammo-
nium hydroxide until pH 12. The organic extracts were
dried over Na2SO4, filteredandevaporatedto give the
crude material. Chromatographic purification of the
crude material with 10% MeOH in CHCl3 afforded 15
Opioid binding assays
Opioid binding assays proceeded according to pub-
27,28
lishedprocedures.
Mu receptors were labeledwith
[3H]DAMGO (d-Ala2,MePhe4Gly-ol5)enkephalin,
2
nM). Rat membranes for mu and delta receptor bind-
ing assays were preparedeach ady using a partially
thawedfrozen rat brain that was homogenizedwith a
polytron in 10 mL/brain of ice-cold10 mM Tris–HCl,
pH 7.0. Membranes were then centrifugedtwice at
30,000g for 10 min andresuspeneddwith ice-cold
buffer following each centrifugation. After the second
centrifugation, the membranes were resuspended in 50
mM Tris–HCl, pH 7.4 (60 mL/brain), at 25 ꢁC. Incu-
bations proceeded for 2 h at 25 ꢁC in 50 mM Tris–
HCl, pH 7.4, along with a protease inhibitor cocktail
(PIC). The nonspecific binding was determined using
20 mM of levallorphan. Delta binding sites were
as a colorless oil, [a]D20 ꢀ2.8ꢁ (c 0.88, MeOH); H NMR
1
(CD3OD) d 7.32–6.60 (m, 8H), 4.54 (s, 1H), 3.94 (q,
J=7 Hz, 2H), 3.32–3.27 (m, 3H), 3.12 (br-d, J=11 Hz,
1H), 2.56–2.34 (m, 2H), 1.20–1.15 (m, 6H), 1.08 (d, J=7
Hz, 3H); MS m/z 444 (M+1)+. Dihydrochloride salt
from methanol, mp 176–177 ꢁC. Anal. calcdfor
.
C28H35Cl2N3O2 1.5H2O: C, 61.87; H, 7.05; N, 7.73.
Found: C, 61.77; H, 6.96; N, 7.50.
3
Single-crystal X-ray diffraction analysis of (+)-4-[(ꢂR)-
ꢂ-(4-allyl-(2S,5S)-dimethyl-1-piperazinyl)-(3-methoxy-
labeledusing [ H]DADLE (d-Ala2, d-Leu5)enkephalin,
2 nM) andrat brain membranes. Rat membranes were
prepared each day as described above. After the sec-
ondcentrifugation, the membranes were resuspended
in 50 mM Tris–HCl, pH 7.4 (60 mL/brain), at 25ꢁ C.
Incubations proceeded for 2 h at 25 ꢁC in 50 mM
Tris–HCl, pH 7.4, containing 100 mM choline chlor-
ide, 3 mM MnCl2, 100 nM DAMGO to block binding
to mu sites, and PIC. Nonspecific binding was deter-
minedusing 20 mM levallorphan. Kappa binding sites
were labeledusing [ 3H]U69,593 (trans-3,4-dichloro-N-
methyl[2-(1-pyrrolidinyl)cyclohexyl]benzene acetamide,
2 nM). Guinea pig brain membranes were prepared
each day using partially thawed guinea pig brain that
was homogenizedwith a polytron in 15 mL/brain of
ice-cold10 mM Tris–HCl, pH 7.0. The membranes
were then centrifugedtwice at 30,000 g for 10 min and
resuspended with ice-cold buffer following each cen-
trifugation. After the secondcentrifugation, the mem-
branes were resuspended in 50 mM Tris–HCl, pH 7.4
(85 mL/brain), at 25ꢁ C. Incubations proceeded for 2 h
at 25 ꢁC in 50 mM Tris–HCl, pH 7.4, containing 1 mg/
mL of captopril andPIC. Nonspecific binidng was
determined using 1 mM U69,593. Each radioligand was
displaced by 8-10 concentrations of test drug. Com-
pounds were prepared as 1 mM solution with 10 mM
Tris buffer (pH 7.4) containing 10% DMSO before
drug dilution. All drug dilutions were done in 10
mM Tris–HCl, pH 7.4, containing 1 mg/mL bovine
serum albumin. All washes were done with ice-cold
10 mM Tris–HCl, pH 7.4. The IC50 andslope factor
(N) were obtainedby using the program MLAB-PC
.
phenyl)methyl]-benzyl alcohol dihydrobromide (10 2HBr).
2+
C24 H34 N2
O2 2(Brꢀ) F.W.=542.35, monoclinic
space group P21, a=7.444(1), b=9.046(1), c=21.471(1)
A, b=98.17(1)ꢁ. V=1431.1(3) A3, Z=2, rcalc=1.259
mg mmꢀ3, l (Cu Ka)=1.54178 A, m=3.736 mmꢀ1
F(000)=556, T=293 K.
,
A clear colorless 0.27ꢂ0.12ꢂ0.02 mm crystal was used
for data collection with a Bruker SMART 6K CCD
detector on a Platform goniometer. The Rigaku rotat-
ing Cu anode source was equipped with incident beam
Gobel mirrors. Lattice parameters were determined
using SAINT25 from 4214 reflections within
5.31<y<61.37ꢁ. Data were collectedto 2 y=133.9ꢁ. A
set of 7113 reflections was collectedin the o scan mode.
There were 3882 unique reflections. Corrections were
appliedfor Lorentz, polarization, andabsorption
26
effects. The structure was solvedwith SHELXTL and
26
refinedwith the aidof the SHELX97
system of pro-
grams. The full-matrix least-squares refinement on F2
used3 restraints andvaried230 parameters including
atom coordinates and anisotropic thermal parameters.
H atoms were included using a riding model [coordinate
shifts of C appliedto attachedH atoms, C-H distances
set to 0.96–0.93 A, H angles idealized, Uiso(H) were set
to 1.2ꢁ to 1.5 Ueq(C). Final residuals were R1=0.099 for
the 3132 observeddata with Fo>4ꢀ(Fo) and0.109 for all
data. Final difference Fourier excursions of 1.82 and
ꢀ0.74 eAꢀ3. A definitive assignment was made for the
thirdcenter of asymmetry in Fig. 1 assuming the 2S,5S
absolute configuration of the methyl groups on the
piperazine molecule. This absolute configuration of the
(2S,5S)-2,5-dimethylpiperazine was assured by its
(CivilizedSoftware, Bethesad, MD).
calculatedaccording to the equation Ki=IC50/(1+[L]/
Kd).
Ki values were

4768
I. J. Kim et al. / Bioorg. Med. Chem. 11 (2003) 4761–4768
13. Calderon, S. N.; Rice, K. C.; Rothman, R. B.; Porreca, F.;
Acknowledgements
Flippen-Anderson, J. L.; Kayakiri, H.; Xu, H.; Becketts, K.;
Smith, L. E.; Bilsky, E. J.; Davis, P.; Horvath, R. J. Med.
Chem. 1997, 40, 695.
14. Calderon, S. N.; Rothman, R. B.; Porreca, F.; Flippen-
Anderson, J. L.; McNutt, R. W.; Xu, H.; Smith, L. E.; Bilsky,
E. J.; Davis, P.; Rice, K. C. J. Med. Chem. 1994, 37, 2125.
15. Chang, K. J.; Rigdon, G. C.; Howard, J. L.; McNutt,
R. W. J. Pharmacol. Exp. Ther. 1993, 267, 852.
The authors (LMC, NIDDK) thank the National Insti-
tute on Drug Abuse, NIH, DHHS, for partial financial
support of our research program, andthank Noel
Whittaker andVictor Livingood(NIDDK, DHHS) for
the mass spectral data. The X-ray crystallographic work
was supportedin part by the National Institute on Drug
Abuse, NIH, DHHS, andthe Office of Naval Research.
16. Wild, K. D.; McCormick, J.; Bilsky, E. J.; Vanderah, T.;
McNutt, R. W.; Chang, K. J.; Porreca, F. J. Pharmacol. Exp.
Ther. 1993, 267, 858.
17. Dondio, G.; Ronzoni, S.; Eggleston, D. S.; Artico, M.;
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18. Portoghese, P. S.; Sultana, M.; Nagase, H.; Takemori,
A. E. J. Med. Chem. 1988, 31, 281.
19. Schwyzer, R. Biochemistry 1986, 25, 6335.
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References and Notes
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