Synthesis, binding affinity, and functional in vitro activity of 3-benzylaminomorphinan and 3-benzylaminomorphine ligands at opioid receptors

Article abstract of DOI:10.1021/jm3001086

A series of 3-benzylamino-3-desoxymorphinan (I) and 3-benzylamino-3- desoxymorphine (II) derivatives were synthesized and evaluated for their binding affinities, and functional activity data are presented at MOR, KOR, and DOR. Some of these ligands were found to have high binding affinity at MOR and KOR and displayed increased selectivity at MOR over KOR and DOR compared to butorphan or cyclorphan. The most selective compound, 3-(3′-hydroxybenzyl) amino-17-methylmorphinan (4g) (24-fold MOR to KOR and 1700-fold MOR to DOR) also showed high binding affinity (0.42 nM to MOR) and was a full agonist in the [³⁵S]GTPγS binding assay. 2-(3′-Hydroxybenzyl)amino-17- cyclopropylmethylmorphinan (17) was found to be a KOR-selective ligand (150-fold over MOR and >10000-fold over the DORs). Most 3-benzylaminomorphinan derivatives were partial agonists at MOR and full agonists at KOR in the [ ³⁵S]GTPγS binding assay.

Full text of DOI:10.1021/jm3001086

Article
pubs.acs.org/jmc
Synthesis, Binding Affinity, and Functional in Vitro Activity of 3-
Benzylaminomorphinan and 3-Benzylaminomorphine Ligands at
Opioid Receptors
John L. Neumeyer,*,† Bin Zhang,† Tangzhi Zhang,† Anna W. Sromek,† Brian I. Knapp,‡ Dana J. Cohen,‡
and Jean M. Bidlack‡
†Alcohol and Drug Abuse Research Center, McLean Hospital, Harvard Medical School, 115 Mill Street, Belmont, Massachusetts
02478-9106, United States
‡Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, New York
14642, United States
ABSTRACT: A series of 3-benzylamino-3-desoxymorphinan
(I) and 3-benzylamino-3-desoxymorphine (II) derivatives
were synthesized and evaluated for their binding affinities,
and functional activity data are presented at MOR, KOR, and
DOR. Some of these ligands were found to have high binding
affinity at MOR and KOR and displayed increased selectivity
at MOR over KOR and DOR compared to butorphan or cyclorphan. The most selective compound, 3-(3′-hydroxybenzyl)amino-
17-methylmorphinan (4g) (24-fold MOR to KOR and 1700-fold MOR to DOR) also showed high binding affinity (0.42 nM to
MOR) and was a full agonist in the [35S]GTPγS binding assay. 2-(3′-Hydroxybenzyl)amino-17-cyclopropylmethylmorphinan
(17) was found to be a KOR-selective ligand (150-fold over MOR and >10000-fold over the DORs). Most 3-
benzylaminomorphinan derivatives were partial agonists at MOR and full agonists at KOR in the [35S]GTPγS binding assay.
selective ligands. Our interest in exploring 3-benzylamino
derivatives is twofold: first, replacement of the phenolic
hydroxyl group may confer metabolic stability; second, the
presence of the 3-amino moiety allows for introduction of a
variety of functionalized benzyl groups, which may result in
analogues with increased selectivity and affinity for MOR. Here
we report the synthesis, binding affinity, and functional activity
of 3-benzylamino-3-desoxymorphinans and 3-benzylamino-3-
desoxymorphine analogues.
With a combination of affinity labeling experiments using S-
activated dihydromorphine derivatives and molecular mechan-
ics, Sagara et al.11 reported the binding site of the MOR, the
hydrogen bonding interaction between the phenolic hydroxyl
group of morphine and both the amino group of Lys303 at TM
VI and the phenolic hydroxyl group of Tyr148 at TM III.
Relatively small ligands, such as morphine, may be able to bind
at several different positions in the binding pocket of the
receptor. One of the docking models12 proposed that the
phenolic hydroxyl group is placed close to the imidazole group
of His297 at TM VI, forming hydrogen bonding interaction.
On the basis of these binding models, we speculated that
replacement of the OH group with an amino or a substituted
amino group would maintain partial hydrogen bonding.
Introduction of the aryl group on nitrogen may thus have a
π−π interaction with the phenyl group of Tyr148 or imidazole
group of His297 which may enhance the binding and increase
INTRODUCTION
■
Morphine is still the drug of choice for treating severe pain
caused by trauma.1 However, morphine has serious side effects,
including constipation, respiratory depression, dependence,
tolerance, and addiction. Most clinically available opioid
analgesics have MOR selective affinity, such as sufentanil,2
which is 600- to 800-fold more potent than morphine, with
100-fold selectivity for MOR over other opioid receptors.2b The
most commonly used centrally acting analgesics, hydrocodone3
and oxycodone,4 have only about one-tenth the affinity to KOR
and DOR as morphine, with good selectivity at MOR.
The free phenolic hydroxyl group in morphine, cyclorphan,
and butorphan (Scheme 1) is also a potential site for
metabolism, conjugation, and excretion, resulting in low oral
bioavailability and short duration of action.5 Although the
phenolic OH group was historically thought to be a
requirement for binding to opioid receptors serving as a
putative H-bond donor to a complementary site on the
protein.6 Schiller and co-workers7 reported that replacement of
the Tyr residue in TIPP peptides with a Bcp or Dbcp residue
resulted in a general increase in DOR binding affinity. We have
reported the modification of the phenolic hydroxyl group of
cyclorphan and butorphan, such as carbamate,8 oxazole,9 urea,9
and aminothiazole10 analogues, which maintain high binding
affinity. In continuing these studies on the development of
effective analgesics and/or treatment for opioid addiction, we
focused our interests on the structural modification and
pharmacological evaluation of analogues of cyclorphan and
butorphan, especially in the development of new MOR
Received: January 25, 2012
Published: March 22, 2012
© 2012 American Chemical Society
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Scheme 1. Synthesis of 3-Benzylaminomorphinan Analogues
the selectivity at the MOR. Wentland et al.13 had reported the
opioid receptor binding properties of a series of cyclazocine
analogues where the 8-OH group of cyclazocine was replaced
with amino groups. Several members of this new series had
surprisingly high affinity for the MOR and KOR. The NH2
group appears to be an effective bioisosteric replacement for the
prototypic 8-OH group in cyclazocine. The replacement of OH
with NH2 in morphine decreased the binding affinity
significantly, albeit with better selectivity at the MOR over
the other receptors.14 In our previous report,15 we also found
that replacement OH group of butorphan or cyclorphan
(Scheme 1) with NH2 resulted in a much lower binding affinity.
By incorporation of different substituted benzyl groups, ligands
with improved binding affinity and selectivity were synthesized.
Morphine analogues (11a, 11b, 11c, 12a, 12b, and 12c) with
substituted benzyl groups were generally less active at MOR.
Interestingly, 17, a 2-benzylamino-3-desoxymorphinan, was
found to be a highly KOR-selective ligand. Further methylation
of the 3-amino nitrogen of these morphinan ligands (i.e., 5a,
5b, 5c, 5d, 6b, and 6c) impaired their binding affinity, which
confirmed that the N−H bond participated in hydrogen
bonding between the ligand and the receptor.
CHEMISTRY
■
The synthetic route toward 3-benzylaminomorphinans is
described in Scheme 1. Levorphanol tartrate was converted to
its free base and then demethylated to afford norlevorphanol.16
The latter was then alkylated with either (bromomethyl)-
cyclobutane or (bromomethyl)cyclopropane to yield butorphan
or cyclorphan, respectively.16 The 3-hydroxy groups were
triflated (1a, 1b, 1c) with N-phenyl bistriflimide in the presence
of triethylamine, which could then be coupled in a Buchwald−
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Scheme 2. Synthesis of 3-Benzylamino-3-morphine Analogues
Scheme 3. Synthesis of 2-(3′-Hydroxybenzyl)amino-3-cyclorphan
Hartwig reaction17 to yield the 3-benzylamino-3-desoxymor-
phinan directly. For effective preparation of N-substituted 3-
aminomorphinans, the triflates were converted to their 3-
aminomorphinans (2a−c) with benzophenoneimine using
catalytic Pd(OAc)2 and rac-BINAP as ligand, followed by
hydrolysis and condensation with an aldehyde and reduction of
the resultant imine with NaBH4. The resulting amines (3a−k)
were methylated using paraformaldehyde/NaBH4/TFA.18 The
methoxybenzylaminomorphinans (3a−c, 3f−h) were demethy-
lated with BBr3 in anhydrous CH2Cl2 to yield hydroxybenzy-
laminomorphinan ligands (4a−c, 4d−f). For the synthesis of
morphine analogues (Scheme 2), morphine was treated with 1
equiv of PhNTf2 and Et3N in dichloromethane to selectively
afford morphine-3-triflate 7.21 The 6-hydroxy group was
protected by TBDPSCl/Et3N to afford 8.14 The triflate was
converted to 3-aminomorphine (9) by using Pd catalyzed
amination with benzophenoneimine, followed by hydrolysis
under acidic conditions. The resulting amine (9) was
condensed with the appropriate benzaldehyde to afford the
corresponding imine and reduced with NaBH4 to give 3-
benzylaminomorphine derivatives. TBDPS was routinely
removed with TBAF to yield the desired ligands (11a−c),
which after O-demethylation gave 12a−c. For the preparation
of 2-amino-3-desoxymorphinan (16), cyclorphan was first
nitrated with HNO3/HCOOH to afford 139 and then triflated
to yield 2-nitromorphinan-3-triflate (14). The triflate was
reduced to 2-nitro-3-desoxymorphinan (15) using Pd(OAc)2/
dppp/Et3SiH.20 Finally, the nitro group was reduced to the
amine (16) and converted to the corresponding imine with m-
anisaldehyde and reduced with NaBH4 to give the 2-
benzylamino-3-desoxymorphinan (17) (Scheme 3).
RESULTS AND DISCUSSION
■
Target compounds were screened for their affinity and
selectivity for MOR, KOR, and DOR with Chinese hamster
ovary (CHO) cell membranes stably expressing the human
opioid receptors. The data are summarized in Table 1. For
comparison purposes, opioid binding affinity data for
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a
Table 1. Ki for the Inhibition of MOR, KOR, and DOR Opioid Binding to CHO Membranes
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Table 1. continued
a
b
c
See ref 19. See ref 15. 17 is N-(cyclopropylmethyl)-2-(2-hydroxybenzyl)aminomorphinan.
levorphanol, butorphan, cyclorphan, compounds 8a and 8d,15
morphine, and hydrocodone were also included.
than butorphan (Ki = 0.23 nM). The m- and p-hydroxybenzyl
analogues 4b and 4c, on the other hand, had similar binding
and selectivity profiles as their methoxybenzyl derivatives (3b
and 3c), as did the methylenedioxybenzyl derivative 3e and m-
nitrobenzyl derivative 3k. The tertiary 3-amino analogues
showed a marked loss in affinity and selectivity to the MOR,
revealing that the 3-amino group as in 5a−c and 6b,c cannot be
fully substituted.
Replacement of the 3-phenolic group in cyclorphan (Ki at
MOR of 0.062 nM) for a 3-amino group (2c, Ki at MOR of
1.30 nM) resulted in a steep loss in affinity to the MOR.
However, introduction of a benzylic group to the nitrogen as in
8a15 (Ki at MOR of 0.26 nM) resulted in high affinity to the
MOR. In agreement with the methoxybenzylaminobutorphan
series (3a−c), methoxybenzylaminocyclorphan derivatives
(3f−h) also possessed subnanomolar affinity to MOR and
similar selectivities against DOR. The o-hydroxybenzylamino
derivatives 4a and 4d exhibited much lower affinity to MOR.
The m- and p- analogues 4e and 4f, however, had similar
affinities and selectivities as the butorphan derivatives 4b and
4c. The methylenedioxy analogue 3e followed the same trend.
The examination of 2-(m-hydroxybenzylamino)-3-desoxycy-
As described in Table 1, we began by investigating butorphan
and its derivatives. Butorphan has high affinity to the MOR
(0.23 nM), although it is not selective. Addition of a benzyl
group to the 3-amino moiety in compound 2b19 to yield 8d15
(see Table 1 for structures) improved the affinity and selectivity
to the MOR. We next investigated the effect of incorporation of
different functional groups on the benzyl ring. Introduction of
the methoxy group (3a−c and 3f−h) had a pronounced effect
on affinity and selectivity in this series. Thus, while an o-
methoxybenzyl derivative 3a had lower affinity and selectivity
for MOR compared to butorphan, the m-methoxy analogue 3b
restored MOR binding affinity to a subnanomolar level, along
with improved selectivity against the DOR. The p-methoxy
analogue 3c retained subnanomolar affinity to the MOR with
even better selectivity vs the DOR. In contrast, the p-
chlorobenzyl analogue 3d had no effect on selectivity and
exhibited weaker affinity to the MOR. Next, we investigated the
presence of a free phenolic group on the benzyl moiety. Much
to our surprise, the o-hydroxybenzyl analogue 4a (Ki = 1.7 nM)
possessed MOR binding affinity an order of magnitude lower
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Table 2. Ki for the Inhibition of MOR, KOR, and DOR Opioid Binding to CHO Membranes
a
Membranes from Chinese hamster ovary cells, expressing the human MOR, KOR, or DOR, were incubated with 12 different concentrations of the
compounds in the presence of receptor-specific radioligands at 25 °C in a final volume of 1 mL of 50 mM Tris-HCl, pH 7.5. Nonspecific binding was
determined using 10 μM naloxone. Data are the mean value SEM from three experiments, performed in triplicate.
clorphan 17 resulted in a loss of affinity to MOR, although it
had high affinity and selectivity to the KOR. Since the
hydroxybenzylamino moiety was shown to enhance affinity and
selectivity to the MOR for cyclorphan and butorphan, we also
examined the analogous derivative of levorphanol. Thus, 4g was
found to possess subnanomolar affinity to MOR (Ki = 0.42
nM), moderate affinity against KOR, and almost 2000-fold
lower affinity at DOR.
Because the methoxy- and hydroxybenzylamino substituted
morphinan derivatives were found to have high affinity and
selectivity to MOR, the corresponding derivatives of morphine
were also examined. In contrast to the morphinan derivatives
described above, which generally had MOR affinities in the
subnanomolar range and improved selectivities to the MOR,
the analogous morphine derivatives 11 and 12 suffered a loss of
affinity to the MOR. The morphine analogues 12a−c showed
only moderate binding affinity at MOR (Ki of 8.5, 13, 7.4 nM,
respectively) (Table 2).
Compounds that exhibited high affinity for the MOR were
screened for functional activity at MOR (Table 3) and KOR
(Table 4) using the [35S]GTPγS binding assay. Compound 4g,
which contained an N-methyl group, was a full agonist at the
MOR as shown in Table 3. The 3-benzylaminomorphinans
were partial agonists at the MOR. The 3-aminomorphine
derivatives (11a, 12b) were full agonists at the MOR, but they
were not very potent. While the 3-benzylaminomorphinans
were partial agonists at the MOR, they were full agonists at the
KOR as shown in Table 4. None of the compounds inhibited
U50,488-stimulated [35S]GTPγS binding mediated by the
KOR.
CONCLUSION
■
We have extended the SARs of cyclorphan and butorphan
analogues by introducing different substituted benzylamino
groups at the 3-position of morphinan. Replacing the N-methyl
substituent on the morphinan with cyclopropylmethyl or
cyclobutylmethyl substituents generally increased the binding
affinity at both the MOR and KOR. It was found that benzyl
substituents at the 3-amino nitrogen tended to increase the
binding affinity and selectivity of the compounds. Further
alkylation of 3′-nitrogen reduced the MOR affinity significantly,
which suggested that either hydrogen bonding was required or
the larger methyl group inhibited binding between the 3-amino
group of the compound and the MOR. In general, methoxy-,
hydroxyl-, and methylenedioxy-substituted benzylaminomor-
phinans exhibited the highest bindng affinities to MOR.
However, introduction of a free phenolic hydroxyl group may
open a potential site for metabolism. The increased selectivity
of morphine analogues supported the hypothesis that a
methoxybenzylamino or hydroxybenzylamino group at the 3-
position of an opioid ligand may interact with another site of
the MOR and may be a useful consideration when designing
new MOR selective opioid ligands. Functional activity was
determined for analogues that exhibited high binding affinity to
the MOR and KOR, and it was found that all morphinan
derivatives were partial agonists at the MOR and morphine
derivatives were full agonists at the MOR although with low
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Table 3. Effect of High Affinity Compounds on [35S]GTPγS
Binding Mediated by the μ Opioid Receptor
potency. All compounds proved to be full agonists at the KOR.
Our efforts led to the discovery of potent, selective MOR
agonists and also led to further insights into their structure−
activity relationship. Compounds 4a and 4g are promising lead
compounds for further evaluation and optimization, and they
may be used as chemical and pharmacological tools to elucidate
the pharmacodynamic features of opioid receptors. This class of
compounds, mixed κ/μ opioids, may have utility in the
treatment of cocaine abuse and, with further pharmacological
evaluation, may also prove to be useful as analgesics. Notably,
17, which has the benzylamino group attached to position 2
rather than position 3, was found to be highly selective at the
KOR and emerged as a promising lead compound for further
design and modification for the development of KOR selective
opioid ligands.
a
Emax (%
maximal
stimulation
over basal)
Imax (%
maximal
inhibition)
compd
EC50 (nM)
IC50 (nM)
b
b
DAMGO
55 5.0
1.6 0.15
0.80 0.40
3.8 0.37
7.8 0.29
3.6 0.65
NA
130 6.1
50 2.5
40 2.9
39 4.4
34 2.9
39 3.7
23 3.1
30 1.2
18 2.4
70 8.1
49 4.6
30 3.7
38 4.7
44 2.0
NI
NI
butorphan
20 2.7
1.7 0.40
80 16
150 20
94 17
2.0 0.93
10 2.2
0.21 0.065
6.8 1.6
810 9.4
4.8 0.48
75 13
160 5.7
3.5 0.14
7.6 3.5
NI
50 2.6
50 1.2
66 4.3
55 3.0
60 0.84
77 2.9
67 2.1
72 2.8
49 4.7
32 4.6
74 2.7
56 6.6
47 1.3
79 8.4
80 1.2
NI
cyclorphan
3b
3c
3e
3g
3h
6.8 0.53
NA
3i
3k
1.1 0.22
38 5.6
NA
4a
EXPERIMENTAL SECTION
■
4b
1
General Synthetic Methods. H (and 13C NMR) spectra were
4c
3.6 0.93
8.8 1.2
NA
recorded at 300 MHz (75 MHz) on a Varian Mercury 300
spectrometer. Chemical shifts are given as δ value (ppm) downfield
from tetramethylsilane as an internal reference. Melting points were
determined on a Thomas-Hoover capillary tube apparatus and are
reported uncorrected. Elemental analyses, performed by Atlantic
Microlabs, Atlanta, GA, were within 0.4% of theoretical values.
Analytical thin-layer chromatography (TLC) was carried out on 0.2
μm Kieselgel 60F-254 silica gel aluminum sheets (EM Science,
Newark, NJ). Flash chromatography was used for the routine
purification of reaction products. Eluent systems are described for
the individual compounds.
4d
4e
27
0
4f
NA
19 1.0
85 6.1
81 13
110 16
4g
6.5 1.5
210 97
550 53
11a
12b
NI
NI
NI
NI
a
Membranes from CHO cells that expressed the human μ opioid
receptor were incubated with 12 concentrations of the compound in
the presence of 0.08 nM [35S]GTPγS for 60 min at 30 °C. Nonspecific
binding was measured by the inclusion of 10 μM GTPγS. For the
inhibition experiments, [35S]GTPγS binding was stimulated by the
addition of 200 nM DAMGO. Data are the mean SEM from three
Representative Procedure for the Preparation of Mor-
phinans 3a−k and 10a−c. To a solution of N-cyclobutylmethyl-3-
aminomorphinan 2a (113 mg, 0.364 mmol) and p-anisaldehyde (59
mg, 0.437 mmol) in anhydrous methanol (10 mL) under nitrogen
atmosphere was added sodium sulfate (200 g, 1.4 mmol), and the
mixture was allowed to stir overnight at room temperature. Next,
sodium borohydride (59 mg, 1.54 mmol) was added and the mixture
was stirred at room temperature for 4 h. After the reaction was judged
complete, the mixture was concentrated under reduced pressure and
the residue was dissolved in ethyl acetate (50 mL) and washed
sequentially with water and brine. The organic layer was dried over
sodium sulfate, then filtered and concentrated, and the residue was
purified over silica gel using EtOAc/Et3N, 200:1, to afford 97 mg of N-
cyclobutylmethyl-3-(4-methoxybenzyl)aminomorphinan 3c as a pale
yellow oil, 62% yield. The oil was dissolved in a minimal amount of
ethyl acetate and treated with excess 1 N ethereal HCl. The resulting
solution was then concentrated and the residue was recrystallized from
methanol/diethyl ether to afford the corresponding dihydrochloride
salt (mp = 180−183 °C).
b
experiments performed in triplicate. NI = no inhibition of DAMGO-
stimulated [35S]GTPγS binding.
Table 4. Effect of High Affinity Compounds on [35S]GTPγS
a
Binding Mediated by the κ Opioid Receptor
compd
EC50 (nM)
Emax (% maximal stimulation over basal)
b
U50,488
4.2 0.38
1.3 0.4
0.19 0.4
39 8.4
140 10
80 6.8
90 10
b
butorphan
b
cyclorphan
3b
3c
3e
3g
3h
3i
120 13
120 7.1
130 12
130 14
130 3.3
120 4.3
140 16
130 7.1
130 4.8
110 4.9
98 1.9
100 2.7
140 9.0
160 6.4
50 2.6
27 2.9
0.43 0.18
5.3 0.56
0.077 0.014
0.79 0.11
47 1.8
(−)-17-(Cyclobutylmethyl)-N-(2-methoxybenzyl)morphinan-
1
3-amine (3a). Pale yellow oil (339 mg, 98%); H NMR (300 MHz,
CDCl3) δ 7.33−7.19 (m, 2H), 6.89 (dd, J = 5.8, 11.5, 3H), 6.56 (d, J =
2.0, 1H), 6.49 (dd, J = 1.8, 8.1, 1H), 4.29 (s, 2H), 4.02 (s, 1H), 3.86 (s,
3H), 2.99−2.78 (m, 2H), 2.73−2.44 (m, J = 19.4, 5H), 2.31−1.08 (m,
18H); 13C NMR (75 MHz, CDCl3) δ 157.4, 146.9, 140.6, 129.2,
128.2, 128.2, 127.4, 125.8, 120.4, 111.3, 110.2, 109.8, 61.0, 56.2, 55.2,
46.1, 44.4, 43.7, 41.2, 37.3, 36.4, 34.2, 27.8, 27.8, 26.7, 26.4, 24.0, 22.1,
3k
4a
4c
4d
4e
4f
38 3.8
2.3 0.28
3.9 0.53
1.8 0.32
230 19
27 2.5
18.7; mp
= 156−158 °C (HCl salt). Anal. Calcd for
C29H38N2O·2HCl·0.8H2O: C, 67.25; H, 8.10; N, 5.41. Found: C,
67.37, H, 8.15; N, 5.31.
4g
17
(−)-17-(Cyclobutylmethyl)-N-(3-methoxybenzyl)morphinan-
1
3-amine (3b). Colorless oil (195 mg, 71%); H NMR (300 MHz,
a
CDCl3) δ 7.25 (td, J = 2.0, 8.2, 1H), 7.02−6.86 (m, 3H), 6.80 (dd, J =
1.7, 8.2, 1H), 6.53 (d, J = 2.2, 1H), 6.46 (dd, J = 2.4, 8.1, 1H), 4.26 (s,
2H), 3.79 (s, 3H), 2.90 (d, J = 17.8, 1H), 2.78 (m, 1H), 2.60−2.37 (m,
5H), 2.23 (d, J = 10.8, 1H), 2.15−1.97 (m, 3H), 1.94−1.13 (m, 14H);
13C NMR (75 MHz, CDCl3) δ 159.8, 146.6, 141.3, 141.0, 129.5, 128.3,
126.5, 119.9, 113.1, 112.6, 110.8, 109.7, 61.2, 56.1, 55.1, 48.8, 46.0,
44.8, 41.6, 37.4, 36.5, 34.5, 27.8, 26.8, 26.5, 23.9, 22.1, 18.8; (HCl salt)
Membranes from CHO cells that expressed the human κ opioid
receptor were incubated with 12 concentrations of the compound in
the presence of 0.08 nM [35S]GTPγS for 60 min at 30 °C. Nonspecific
binding was measured by the inclusion of 10 μM GTPγS. Data are the
mean SEM from three experiments performed in triplicate. None of
the compounds produced any inhibition of [35S]GTPγS binding
b
stimulated by 100 nM U50,488. See ref 16.
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mp = 151−154 °C. Anal. Calcd for C29H38N2O·2HCl·0.8H2O: C,
67.25; H, 8.10; N, 5.41. Found: C, 67.19, H, 8.00; N, 5.47.
(−)-17-(Cyclobutylmethyl)-N-(4-methoxybenzyl)morphinan-
C28H36N2O·2HCl·H2O: C, 66.26; H, 7.94; N, 5.52. Found: C, 66.06,
H, 7.63; N, 5.52.
( − ) - 1 7 - ( C y c l o p r o p y l m e t h y l ) - N - ( 3 , 4 -
methylenedihydroxybenzyl)morphinan-3-amine (3i). Pale yel-
low oil (47 mg, 67%); 1H NMR (300 MHz, CDCl3) δ 6.87−6.75 (m,
3H), 6.53 (d, J = 2.2, 1H), 6.45 (dd, J = 2.3, 8.1, 1H), 5.94 (s, 2H),
4.19 (s, 2H), 3.11 (s, 1H), 2.84 (d, J = 18.2, 1H), 2.74 (d, J = 9.3, 1H),
2.54 (m, 2H), 2.35 (dd, J = 6.6, 12.6, 1H), 2.25 (d, J = 11.4, 1H), 2.07
(m, 1H), 1.78 (m, 2H), 1.62 (d, J = 10.5, 1H), 1.34−1.12 (m, 9H),
0.88 (m, 1H), 0.50 (d, J = 6.8, 2H), 0.12 (d, J = 4.4, 2H); 13C NMR
(CDCl3, 75 MHz) δ 147.8, 146.6, 146.5, 141.2, 133.5, 128.3, 126.7,
120.8, 110.8, 109.8, 108.2, 100.9, 59.8, 55.8, 48.6, 45.9, 45.0, 41.7, 37.6,
36.6, 26.8, 26.6, 23.8, 22.2, 9.2, 4.1, 3.7; mp = 166−170 °C (HCl salt).
Anal. Calcd for C28H34N2O2·2HCl·1.4H2O: C, 63.61; H, 7.40; N, 5.30.
Found: C, 63.29, H, 7.13; N, 5.25.
1
3-amine (3c). Pale yellow oil (276 mg, 85%); H NMR (300 MHz,
CDCl3) δ 7.34−7.26 (m, 2H), 6.94−6.84 (m, 3H), 6.52 (d, J = 2.4,
1H), 6.46 (dd, J = 2.4, 8.1, 1H), 4.20 (s, 2H), 3.79 (s, 3H), 2.90 (d, J =
18.0, 1H), 2.78 (dd, J = 3.0, 5.3, 1H), 2.59−2.37 (m, 6H), 2.24 (d, J =
10.7, 1H), 2.13 −1.16 (m, 17H); 13C NMR (75 MHz, CDCl3) δ
158.7, 146.6, 141.2, 131.6, 128.9, 128.2, 127.0, 113.9, 110.7, 109.7,
61.4, 56.0, 55.2, 48.2, 46.0, 45.2, 41.9, 37.5, 36.6, 34.9, 27.89, 27.87,
26.9, 26.6, 23.9, 22.2, 18.8; mp = 180−183 °C (for HCl salt). Anal.
Calcd for C29H38N2O·2HCl·1.3H2O: C, 66.10; H, 8.15; N, 5.32.
Found: C, 66.50, H, 8.13; N, 5.05.
(−)-17-(Cyclobutylmethyl)-N-(4-chlorobenzyl)morphinan-3-
1
amine (3d). Pale yellow oil (99 mg, 71%); H NMR (300 MHz,
(−)-17-Methyl-N-(3′-methoxybenzyl)morphinan-3-amine
(3j). White solid (HCl salt, 110 mg, 44%); 1H NMR (300 MHz,
CDCl3) δ 7.24 (d, J = 7.9 Hz, 1H), 7.07−6.72 (m, 4H), 6.60−6.37 (m,
2H), 4.27 (s, 2H), 3.98−3.61 (m, 4H), 2.94 (d, J = 18.1 Hz, 1H), 2.78
(s, 1H), 2.65−2.07 (m, 8H), 1.85−1.14 (m, 12H); 13C NMR (75
MHz, CDCl3) δ 159.76, 146.53, 141.29, 141.02, 129.48, 128.28,
126.87, 119.86, 113.06, 112.58, 110.74, 109.72, 58.01, 55.11, 48.76,
47.33, 45.57, 42.75, 42.10, 37.04, 36.66, 26.74, 26.56, 23.22, 22.18.; mp
= 146−149 °C (HCl salt). Anal. Calcd for C25H32N2O·2HCl·4H2O:
C, 57.58; H, 8.12; N, 5.37. Found: C, 57.93, H, 7.98; N, 4.87.
(−)-3-(3′-Nitrobenzyl)amino-17-cyclobutylmethylmor-
CDCl3) δ 7.30 (m, 4H), 6.91 (d, J = 8.1, 1H), 6.49 (s, 1H), 6.44 (d, J
= 8.1, 1H), 4.27 (s, 2H), 3.89 (s, 1H), 2.90 (d, J = 18.0, 1H), 2.77 (s,
1H), 2.60−2.36 (m, 5H), 2.20 (d, J = 11.6, 1H), 2.06 (t, J = 10.6, 3H),
1.93−1.07 (m, 14H); 13C NMR (75 MHz, CDCl3) δ 147.0, 139.5,
137.8, 132.8, 128.69, 128.65, 128.6, 123.5, 11.5, 109.5, 59.6, 56.7, 47.8,
46.4, 42.0, 39.3, 36.6, 35.6, 32.1, 27.85, 27.76, 26.2, 25.8, 24.1, 21.7,
18.6; mp
= 160−163 °C (HCl salt). Anal. Calcd for
C28H35N2Cl·2HCl·0.4H2O: C, 65.28; H, 7.40; N, 5.44. Found: C,
65.28, H, 7.46; N, 5.39.
(−)-17-(Cyclobutylmethyl)-N-(3,4-methylenedioxybenzyl)-
morphinan-3-amine (3e). Yellow oil (42 mg, 51%); 1H NMR (300
MHz, CDCl3) δ 6.84 (m, J = 8.0, 17.0, 29.7, 4H), 6.51 (d, J = 2.2, 1H),
6.45 (dd, J = 2.3, 8.1, 1H), 5.93 (s, 2H), 4.19 (s, 2H), 2.86 (m, 2H),
2.48 (m, 5H), 1.87 (m, 10H), 1.25 (m, 8H); 13C NMR (CDCl3, 75
MHz) δ 147.8, 146.6, 146.4, 141.2, 133.5, 128.3, 127.0, 120.8, 110.7,
109.8, 108.20, 108.19, 100.9, 61.3, 55.9, 48.6, 45.9, 45.1, 41.8, 37.5,
36.6, 34.8, 27.9, 26.8, 26.6, 23.9, 22.2, 18.8; mp = 165−168 °C (HCl
salt). Anal. Calcd for C29H36N2O2·2HCl·0.4H2O: C, 65.04; H, 7.53; N,
5.23. Found: C, 64.91, H, 7.33; N, 5.12.
1
phinan (3k). Pale yellow oil (215 mg, 71%); H NMR (300 MHz,
CDCl3) δ 8.21 (s, 1H), 8.18 (d, J = 8.1, 1H), 7.71 (d, J = 8.2, 1H),
7.52 (t, J = 8.5, 1H), 6.90 (d, J = 8.2, 1H), 6.51 (s, 1H), 6.45 (d J = 8.5,
1H), 4.40 (s, 2H), 4.18−4.10 (m, 1H), 2.90 (d, J = 18.1, 1H), 2.80−
2.71 (m, 1H), 2.60−2.37 (m, 5H), 2.10−1.97 (m, 4H), 1.94−1.13 (m,
14H); 13C NMR (75 MHz, CDCl3) δ 148.5, 145.7, 142.3, 141.5,
133.4, 129.4, 128.4, 127.8, 122.2, 122.1, 110.8, 109.9, 6q.5, 55.9, 48.0,
45.9, 45.2, 41.9, 37.6, 36.6, 34.9, 27.9, 27.8, 26.8, 26.8, 23.9, 22.1, 18.8;
mp = 145−148 °C (HCl salt). Anal. Calcd for C28H35N3O2·2HCl: C,
64.86; H, 7.19; N, 8.10. Found: C, 65.14, H, 7.28; N, 8.04.
(−)-17-(Cyclopropylmethyl)-N-(2-methoxybenzyl)-
1
morphinan-3-amine (3f). Pale yellow oil (118 mg, 84%); H NMR
Representative Procedure for the Preparation of Mor-
phinans 4a−f and 6b,c. To a solution of N-cyclobutylmethyl-3-
(4-methoxybenzyl)aminomorphinan 3c (149 mg, 0.347 mmol) in
anhydrous dichloromethane (3 mL) under nitrogen atmosphere at 0
°C was added slowly dropwise a solution of BBr3 (3 mL, 1 M in
anhydrous dichloromethane). After addition was complete, the
resulting solution was allowed to warm to room temperature and
stirred for 1.5 h. Next, the solution was diluted with excess diethyl
ether and allowed to precipitate at 0 °C. The residue was washed with
ethyl acetate, then dissolved in 3 M aqueous HCl (10 mL) and washed
with ethyl acetate (10 mL). The aqueous layer was basified with
saturated sodium bicarbonate solution and extracted with dichloro-
methane (2 × 20 mL). The combined dichloromethane extracts were
dried over sodium sulfate, then filtered and concentrated. The residue
was purified over silica gel using EtOAc/Et3N (100:1) as eluent to
afford 90 mg of N-cyclobutylmethyl-3-(4-hydroxybenzyl)-
aminomorphinan 4c as a pale yellow oil, 74% yield. The oil was
then dissolved in a minimal amount of EtOAc and treated with excess
1 N ethereal HCl, and then the mixture was concentrated to afford a
white solid. The solid was washed with a small amount of EtOAc and
ether and dried under reduced pressure to afford 94 mg of the
dihydrochloride salt (mp = 165−168 °C).
(300 MHz, CDCl3) δ 7.31 (d, J = 7.2, 1H), 7.23 (t, J = 7.5, 1H), 6.89
(t, J = 9.4, 3H), 6.57 (s, 1H), 6.47 (d, J = 8.1, 1H), 4.29 (s, 2H), 3.85
(s, 3H), 3.07 (s, 1H), 2.83 (d, J = 18.0, 1H), 2.70 (d, J = 9.2, 1H),
2.52−2.48 (m, 2H), 2.31 (m, 2H), 2.05 (m, 1H), 1.81−1.60 (m, 3H),
1.34−1.13 (m, 8H), 0.87 (m, 1H), 0.49 (d, J = 7.6, 2H), 0.11 (s, 2H);
13C NMR (CDCl3, 75 MHz) δ 157.3, 146.8, 141.0, 129.2, 128.2, 128.1,
127.5, 126.6, 120.4, 111.1, 110.2, 109.9, 59.8, 55.7, 55.2, 45.8, 45.2,
43.7, 41.8, 37.6, 36.6, 26.8, 26.6, 23.7, 22.2, 9.3, 4.0, 3.6; mp = 151−
153 °C (HCl salt). Anal. Calcd for C28H36N2O·2HCl·1.6H2O: C,
64.88; H, 8.01; N, 5.40. Found: C, 65.15, H, 7.79; N, 5.14.
(−)-17-(Cyclopropylmethyl)-N-(3-methoxybenzyl)-
morphinan-3-amine (3g). Pale yellow oil (130 mg, 93%); 1H NMR
(300 MHz, CDCl3) δ 7.24 (t, J = 6.8, 1H), 6.92 (dd, J = 8.9, 19.9, 3H),
6.80 (d, J = 8.2, 1H), 6.54 (s, 1H), 6.46 (d, J = 8.1, 1H), 4.26 (s, 2H),
3.78 (s, 3H), 3.12 (s, 1H), 2.84 (d, J = 18.1, 1H), 2.75 (d, J = 11.5,
1H), 2.55−2.47 (m, 2H), 2.36 (dd, J = 6.8, 12.2, 1H), 2.25 (d, J = 11.1,
1H), 2.04 (m, 1H), 1.83−1.63 (m, 2H), 1.62 (d, J = 9.7, 1H), 1.29−
1.12 (m, 8H), 0.90 (m, 1H), 0.51 (d, J = 7.8, 2H), 0.12 (s, 2H); 13C
NMR (CDCl3, 75 MHz) δ 159.7, 146.6, 141.2, 141.0, 129.5, 128.2,
126.5, 119.8, 113.0, 112.5, 110.7, 109.6, 59.6, 55.8, 55.1, 48.7, 45.8,
44.8, 41.6, 37.5, 36.5, 26.7, 26.5, 23.7, 22.1, 9.0, 4.0, 3.6; mp = 158−
160 °C (HCl salt). Anal. Calcd for C28H36N2O·2HCl·1.2H2O: C,
65.79; H, 7.97; N, 5.48. Found: C, 65.87, H, 7.88; N, 5.50.
(−)-17-(Cyclobutylmethyl)-N-(2-hydroxybenzyl)morphinan-
1
3-amine (4a). Pale yellow oil, 23 mg (82%); H NMR (300 MHz,
(−)-17-(Cyclopropylmethyl)-N-(4-methoxybenzyl)-
morphinan-3-amine (3h). Pale yellow oil (116 mg, 83%); 1H NMR
(300 MHz, CDCl3) δ 7.29 (d, J = 7.1, 2H), 6.88 (m, 3H), 6.53 (s,
1H), 6.46 (d, J = 8.2, 1H), 4.20 (s, 2H), 3.79 (s, 3H), 3.14 (s, 1H),
2.81 (t, J = 17.6, 2H), 2.57 (m, 2H), 2.40 (d, J = 6.0, 1H), 2.25 (d, J =
11.1, 1H), 2.05 (m, 1H), 1.84 (m, 2H), 1.60−1.12 (m, 9H), 0.90 (m,
1H), 0.51 (d, J = 6.9, 2H), 0.13 (s, 2H). 13C NMR (CDCl3, 75 MHz)
δ 158.7, 146.7, 140.9, 131.5, 128.9, 128.2, 126.3, 113.9, 110.8, 109.6,
59.6, 55.8, 55.2, 48.2, 45.8, 44.7, 41.5, 37.5, 36.5, 26.8, 26.5, 23.8, 22.2,
8.9, 4.0, 3.7; mp = 162−164 °C (HCl salt). Anal. Calcd for
CDCl3) δ 7.13 (dd, J = 14.2, 21.8, 1H), 6.83−6.62 (m, 4H), 6.48−6.26
(m, 2H), 4.19 (s, 2H), 3.90 (s, 1H), 2.99−2.66 (m, 2H), 2.66−2.40
(m, 4H), 2.39−2.22 (m, 1H), 2.18−0.90 (m, 18H); 13C NMR (75
MHz, CDCl3) δ 156.1, 147.4, 138.5, 128.7, 128.6, 128.6, 123.7, 123.1,
119.5, 116.1, 113.5, 111.1, 58.7, 57.0, 46.5, 40.7, 38.2, 36.2, 35.0, 30.9,
27.7, 27.6, 25.8, 25.4, 21.5, 18.5; mp = 172−174 °C (HCl salt). Anal.
Calcd for C28H36N2O·2HCl·1.3H2O: C, 61.21; H, 7.63; N, 5.10.
Found: C, 60.95; H, 7.35; N, 5.22.
(−)-17-(Cyclobutylmethyl)-N-(3-hydroxybenzyl)morphinan-
3-amine (4b). Pale yellow foam; 34 mg (96%); 1H NMR (300 MHz,
3885
dx.doi.org/10.1021/jm3001086 | J. Med. Chem. 2012, 55, 3878−3890

Journal of Medicinal Chemistry
Article
CDCl3) δ 8.92 (s, 1H), 7.11 (dd, J = 14.1, 21.8, 1H), 6.85−6.60 (m,
4H), 6.48−6.27 (m, 2H), 4.16 (s, 2H), 3.91 (s, 1H), 2.97−2.69 (m,
2H), 2.69−2.40 (m, 4H), 2.37−2.20 (m, 1H), 2.17−0.92 (m, 18H).
13C NMR (75 MHz, CDCl3) δ 157.6, 146.9, 141.2, 140.3, 129.6, 128.3,
CH2Cl2 (3 × 20 mL). The combined organic layers were dried over
Na2SO4, then filtered and concentrated to afford 212 mg of N-
cyclobutylmethyl-3-(4-methoxybenzyl)-3-methylaminomorphinan 5c
as a pale yellow oil, 98% yield. The oil (64 mg) was converted to
the dihydrochloride salt as described above to afford 70 mg of a white
solid (mp = 146−148 °C).
(−)-17-(Cyclobutylmethyl)-N-methyl-N-(2-methoxybenzyl)-
morphinan-3-amine (5a). Pale yellow oil (102 mg, 82%); 1H NMR
(300 MHz, CDCl3) δ 7.20−7.10 (m, 1H), 7.07 (d, J = 7.2, 1H), 6.88−
6.76 (m, 3H), 6.50 (dd, J = 3.0, 11.3, 2H), 4.46−4.31 (dd, J = 18, 24,
2H), 3.79 (s, 3H), 2.93 (s, 3H), 2.84 (d, J = 17.8, 1H), 2.71 (s, 1H),
2.43 (m, 5H), 2.15 (d, J = 10.1, 1H), 2.07−1.93 (m, 3H), 1.84−1.49
(m, 7H), 1.35−1.12 (m, 7H); 13C NMR (75 MHz, CD3OD) δ 157.6,
149.0, 140.1, 128.2, 127.9, 127.9, 126.9, 125.2, 120.3, 111.2, 110.2,
109.5, 61.3, 56.2, 54.7, 52.2, 46.3, 44.9, 41.5, 38.5, 37.6, 36.8, 34.7,
28.2, 28.0, 27.1, 26.8, 23.7, 22.4, 18.7; mp = 133−135 °C (HCl salt).
Anal. Calcd for C30H40N2O·2HCl·1.1H2O: C, 67.05; H, 8.29; N, 5.21.
Found: C, 66.79, H, 8.30; N, 5.03.
124.9, 118.2, 114.8, 114.5, 110.5, 109.6, 60.5, 55.9, 48.1, 46.1, 43.4,
40.5, 37.0, 36.1, 33.3, 28.2, 27.9, 26.6, 26.2, 23.7, 22.0, 18.7; mp =
177−180 °C (HCl salt). Anal. Calcd for C28H36N2O·2HCl·0.9H2O: C,
62.03; H, 7.58; N, 5.17. Found: C, 62.10; H, 7.62; N, 5.08.
(−)-17-(Cyclobutylmethyl)-N-(4-hydroxybenzyl)morphinan-
3-amine (4c). Pale yellow foam (90 mg, 74%); 1H NMR (300 MHz,
CDCl3) δ 7.22 (d, J = 8.3, 2H), 6.91 (d, J = 8.1, 1H), 6.77 (d, J = 8.4,
2H), 6.50 (m, 2H), 4.19 (s, 2H), 2.90 (m, J = 13.7, 2H), 2.55 (m, 5H),
2.14 (m, 4H), 1.72 (m, 7H), 1.26 (m, 8H); 13C NMR (CDCl3, 75
MHz) δ 156.5, 146.9, 140.7, 129.9, 129.1, 128.3, 126.0, 115.9, 110.9,
109.6, 61.1, 55.9, 48.4, 46.0, 44.1, 41.1, 37.3, 36.4, 34.1, 28.1, 26.7,
26.4, 23.8, 22.1, 18.7; mp = 165−168 °C (HCl salt). Anal. Calcd for
C28H36N2O·2HCl·1.3H2O: C, 65.56; H, 7.98; N, 5.46. Found: C,
65.41, H, 7.73; N, 5.50.
( − ) - 1 7 - ( C y c l o b u t y l m e t h y l ) - N - m e t h y l - N - ( 4 -
methyloxybenzyl)morphinan-3-amine (5c). Pale yellow oil (212
mg, 98%); 1H NMR (300 MHz, CDCl3) δ 7.09 (d, J = 8.7, 2H), 6.86
(d, J = 8.2, 1H), 6.78−6.69 (m, 2H), 6.58−6.45 (m, J = 2.5, 8.2, 2H),
4.30 (s, 2H), 3.69 (s, 3H), 2.88−2.75 (m, 4H), 2.69 (dd, J = 3.0, 5.4,
1H), 2.53−2.27 (m, 5H), 2.21−2.08 (m, 1H), 2.05 −0.93 (m, 17H);
13C NMR (75 MHz, CDCl3) δ 158.4, 148.5, 140.9, 131.3, 128.1, 128,1,
(−)-17-(Cyclopropylmethyl)-N-(2-hydroxybenzyl)-
morphinan-3-amine (4d). Pale yellow foam (68 mg, 90%). 1H
NMR (300 MHz, CDCl3) δ 7.18 (dd, J = 7.4, 14.6, 2H), 6.95 (d, J =
8.1, 1H), 6.87 (dd, J = 2.9, 7.7, 2H), 6.71 (d, J = 2.1, 1H), 6.64 (dd, J =
2.2, 8.1, 1H), 4.39 (s, 2H), 3.19 (s, 1H), 2.87 (d, J = 18.3, 1H), 2.80
(m, 1H), 2.64 (dd, J = 6.6, 19.4, 1H), 2.55 (m, 1H), 2.40 (dd, J = 6.8,
12.5, 1H), 2.22 (d, J = 13.0, 1H), 2.11 (m, 1H), 1.94 (d, J = 12.6, 1H),
1.84 (td, J = 4.3, 12.7, 1H), 1.62 (d, J = 9.3, 1H), 1.19 (m, 8H), 0.52
(m, 2H), 0.16 (q, J = 4.8, 2H); 13C NMR (CDCl3, 75 MHz) δ 156.8,
145.7, 141.1, 128.9, 128.6, 128.4, 123.4, 119.7, 116.4, 113.5, 112.6,
59.6, 55.8, 48.7, 45.8, 44.4, 41.2, 37.5, 36.4, 26.7, 26.4, 23.9, 22.0, 8.8,
4.1, 3.8; mp = 170−173 °C (HCl salt). Anal. Calcd for
C27H34N2O·2HCl·1.4H2O: C, 64.77; H, 7.81; N, 5.59. Found: C,
64.50, H, 7.67; N, 5.46.
128.0, 126.2, 113.7, 113.7, 110.8, 109.7, 61.5, 56.8, 56.0, 55.2, 46.0,
45.3, 42.0, 38.5, 37.6, 36.7, 35.0, 27.9, 27.8, 26.8, 26.6, 23.8, 22.2, 18.8;
mp
= 146−148 °C (for HCl salt). Anal. Calcd for
C30H40N2O·2HCl·H2O: C, 67.28; H, 8.28; N, 5.23. Found: C,
67.38, H, 8.23; N, 5.19.
(−)-17-(Cyclobutylmethyl)-N-methyl-N-(4-chlorobenzyl)-
1
morphinan-3-amine (5d). Pale yellow oil (61 mg, 92%); H NMR
(300 MHz, CDCl3) δ 7.23−7.14 (m, 2H), 7.13−7.07 (m, 2H), 6.91−
6.83 (m, 1H), 6.54−6.46 (m, 2H), 4.33 (s, 2H), 2.88 (s, 3H), 2.84 (d,
J = 17.8 Hz, 1H), 2.71 (m, 1H), 2.52−2.31 (m, 5H), 2.11 (d, J = 12.8,
1H), 1.99 (m, 3H), 1.86−1.48 (m, 13H); 13C NMR (75 MHz,
CD3OD) δ 148.7, 140.2, 138.7, 132.4, 128.7, 128.7, 128.5, 128.5,
128.4, 126.0, 111.8, 110.1, 61.3, 56.7, 56.1, 46.2, 44.9, 41.5, 38.7, 37.6,
36.8, 34.7, 28.2, 28.0, 27.0, 26.7, 23.7, 22.3, 18.6; mp = 135−139 °C
(HCl salt). Anal. Calcd for C29H37ClN2·2HCl·1.3H2O: C, 63.86; H,
7.69; N, 5.14. Found: C, 63.69, H, 7.70; N, 5.02.
(−)-17-(Cyclobutylmethyl)-N-methyl-N-(2-hydroxybenzyl)-
morphinan-3-amine (6a). Pale yellow foam (34 mg, 95%); 1H
NMR (300 MHz, CDCl3) δ 7.15−7.06 (m, 1H), 7.02−6.94 (m, 2H),
6.92−6.83 (m, 2H), 6.82−6.70 (m, 2H), 4.25 (s, 2H), 2.91 (m, 2H),
2.79−2.46 (m, 5H), 2.73 (s, 3H), 2.26−0.88 (m, 18H); 13C NMR (75
MHz, CDCl3) δ 157.0, 149.4, 140.4, 128.7, 128.4, 128.3, 122.2, 119.5,
116.6, 116.1, 115.6, 60.5, 59.4, 56.2, 46.0, 43.5, 40.8, 40.5, 37.2, 36.0,
33.5, 27.85, 27.81, 26.4, 26.1, 24.2, 21.8, 18.7; mp = 155−157 °C (HCl
salt). Anal. Calcd for C29H38N2O·2HCl·1.4H2O: C, 66.10; H, 8.15; N,
5.32. Found: C, 65.84, H, 7.89; N, 5.24.
(−)-17-(Cyclopropylmethyl)-N-(3-hydroxybenzyl)-
1
morphinan-3-amine (4e). Pale yellow oil (65 mg, 84%); H NMR
(300 MHz, CDCl3) δ 7.16 (t, J = 7.9, 1H), 6.81−6.72 (m, 4H), 6.48
(s, 1H), 6.40 (d, J = 8.1, 1H), 4.26 (s, 2H), 3.97 (s, 1H), 3.17 (s, 1H),
2.79 (d, J = 18.3, 1H), 2.61 (m, 1H), 2.41 (m, 2H), 2.25 (m, 2H), 1.97
(m, 2H), 1.67−1.06 (m, 10H), 0.88 (m, 1H), 0.47 (d, J = 7.6, 2H),
0.08 (m, 2H); 13C NMR (CDCl3, 75 MHz) δ 157.7, 146.8, 141.4,
140.7, 129.6, 128.3, 125.6, 118.0, 114.8, 114.3, 109.8, 109.7, 59.3, 55.5,
47.9, 45.7, 44.0, 41.2, 37.3, 36.3, 26.7, 26.3, 23.5, 22.1, 8.2, 4.1, 4.0; mp
= 171−175 °C (HCl salt). Anal. Calcd for C27H34N2O·2HCl·1.1H2O:
C, 65.47; H, 7.77; N, 5.66. Found: C, 65.61, H, 7.67; N, 5.27.
(−)-17-(Cyclopropylmethyl)-N-(4-hydroxybenzyl)-
1
morphinan-3-amine (4f). Pale yellow oil (69 mg, 79%); H NMR
(300 MHz, CDCl3) δ 6.82 (m, 4H), 6.68 (d, J = 8.0, 1H), 6.47 (s,
1H), 6.43 (d, J = 8.2, 1H), 4.14 (s, 2H), 3.28 (m, 2H), 2.72−2.42 (m,
5H), 2.12−0.91 (m, 14H), 0.53 (d, J = 7.6, 2H), 0.16 (d, J = 4.0, 2H);
13C NMR (CDCl3, 75 MHz) δ 156.4, 146.9, 140.7, 130.0, 129.1, 128.3,
126.0, 115.9, 111.0, 109.7, 59.5, 55.8, 48.4, 45.8, 44.2, 41.1, 37.5, 36.4,
26.8, 26.4, 23.8, 22.1, 8.5,4.2, 3.8; mp = 195 °C (dec) (HCl salt). Anal.
Calcd for C27H34N2O·2HCl·1.6H2O: C, 64.30; H, 7.83; N, 5.55.
Found: C, 64.23, H, 7.83; N, 5.28.
(−)-17-(Cyclobutylmethyl)-N-methyl-N-(4-hydroxybenzyl)-
morphinan-3-amine (6c). Pale yellow oil (107 mg, 74%); 1H NMR
(300 MHz, CDCl3) δ 7.08 (d, J = 8.7, 2H), 6.86 (d, J = 8.2, 1H), 6.75
(d, J = 8.7, 2H), 6.53 (dt, J = 2.5, 8.2, 2H), 4.30 (s, 2H), 3.69 (s, 3H),
2.88−2.76 (m, 4H), 2.69 (dd, J = 3.0, 5.3, 1H), 2.43 (m, 4H), 2.33
(dd, J = 3.1, 11.9, 1H), 2.15 (d, J = 11.9, 1H), 1.99 (m, 3H), 1.84−1.48
(m, 7H), 1.35−1.01 (m, 7H); 13C NMR (75 MHz, CDCl3) δ 156.1,
148.7, 140.2, 129.5, 128.2, 128.2, 128.1, 124.8, 115.9, 115.9, 110.9,
109.7, 60.9, 56.8, 56.0, 46.1, 43.9, 40.9, 38.5, 37.3, 36.3, 33.9, 28.1,
28.0, 26.6, 26.3, 23.7, 22.0, 18.7; mp = 174−178 °C (HCl salt). Anal.
Calcd for C29H38N2O·2HCl·0.8H2O: C, 67.25; H, 8.10; N, 5.41.
Found: C, 67.14, H, 8.13; N, 5.39.
(−)-N-Methyl-(3′-hydroxybenzyl)morphinan-3-amine (4g).
1
Pale yellow foam (55 mg, 78%); H NMR (300 MHz, CDCl3) δ
8.66 (s, 1H), 7.18 (t, J = 7.7 Hz, 1H), 6.91−6.67 (m, 4H), 6.49 (d, J =
2.2 Hz, 1H), 6.40 (dd, J = 8.2, 2.3 Hz, 1H), 4.29 (s, 2H), 4.11 (s, 1H),
2.99−2.76 (m, 2H), 2.64 (dd, J = 18.4, 5.8 Hz, 1H), 2.30 (s, 3H),
2.26−1.09 (m, 13H); 13C NMR (75 MHz, CDCl3) δ 158.2, 147.2,
141.7, 140.7, 130.0, 128.6, 125.4, 118.1, 115.0, 114.4, 110.2, 110.1,
58.5, 48.0, 47.3, 44.3, 42.2, 41.4, 36.9, 36.4, 26.8, 26.5, 23.6, 22.3; mp =
166−169 °C (HCl salt). Anal. Calcd for C24H30N2O·2HCl·3H2O: C,
58.89; H, 7.83; N, 5.72. Found: C, 59.02, H, 7.93; N, 5.40.
Representative Procedure for the Preparation of Mor-
phinans 5a−d. To a solution of N-cyclobutylmethyl-3-(4-
methoxybenzyl)aminomorphinan 3c (210 mg, 0.487 mmol), paraf-
ormaldehyde (141 mg, 4.87 mmol), and NaBH4 (93 mg, 2.44 mmol)
in anhydrous THF (5 mL) was added TFA dropwise (2.5 mL). The
solution was stirred for 3 days at room temperature, then poured into a
mixture of excess aqueous NaOH and ice chips and extracted with
Morphine-3-(trifluoromethanesulfonate) (7).21 Morphine-3-
(trifluomethanesulfonate) (7) was prepared according to the literature
1
procedure (4.415 g, 90% yield). H NMR (300 MHz, CDCl3) δ 6.89
(d, J = 8.4, 1H), 6.65 (d, J = 8.4, 1H), 5.69 (d, J = 9.9, 1H), 5.29 (d, J =
9.7, 1H), 5.02 (d, J = 6.3, 1H), 4.22 (s, 1H), 3.40 (s, 1H), 3.28 (s, 1H),
3.10 (d, J = 19.1, 1H), 2.72 (s, 1H), 2.63 (dd, J = 4.5, 12.2, 1H), 2.44
(s, 3H), 2.33 (m, J = 6.1, 19.0, 2H), 2.12 (td, J = 4.8, 12.5, 1H), 1.88
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(d, J = 12.5, 1H); 13C NMR (CDCl3, 75 MHz) δ 149.4, 135.6, 133.6,
133.4, 130.4, 128.2, (124.9, 120.6, 116.4, 112.1, q), 120.8, 120.1, 93.5,
66.4, 58.3, 45.9, 43.2, 42.8, 40.3, 35.1, 20.8.
1H), 2.95 (d, J = 18.5 Hz, 1H), 2.52−2.16 (m, 7H), 1.72 (d, J = 4.8
Hz, 2H), 1.10 (s, 9H); 13C NMR (CDCl3, 75 MHz) δ 157.3, 147.2,
135.8, 135.7, 134.0, 133.7, 133.1, 130.8, 129.70, 129.67, 128.9, 128.8,
128.3, 127.9, 127.6, 127.5, 123.5, 120.5, 118.6, 112.0, 110.0, 91.7, 69.3,
58.9, 55.2, 46.4, 43.6, 43.5, 43.1, 41.1, 35.7, 26.8, 20.3, 19.3.
(−)-3-N-(4′-Methoxybenzyl)amino-7,8-didehydro-6-(tert-bu-
tyldiphenylsilyl)-4,5-epoxy-17-methyl-(5α,6α)-morphinan-6-ol
(10c). Pale yellow oil (540 mg, 97%); 1H NMR (300 MHz, CDCl3) δ
7.81−7.73 (m, 2H), 7.70−7.61 (m, 2H), 7.46−7.25 (m, 8H), 6.97−
6.80 (m, 2H), 6.44 (s, 2H), 5.74 (d, J = 9.8 Hz, 1H), 5.25−5.06 (m,
1H), 4.36 (dd, J = 6.1, 1.2 Hz, 1H), 4.27 (d, J = 24.0 Hz, 2H), 4.25−
4.15 (m, 1H), 3.80 (s, 3H), 3.25 (dd, J = 6.1, 3.2 Hz, 1H), 2.97 (d, J =
18.5 Hz, 1H), 2.50−2.17 (m, 4H), 2.37 (s, 3H), 1.78−1.66 (m, 2H),
1.08 (s, 9H); 13C NMR (CDCl3, 75 MHz) δ 158.7, 147.0, 135.81,
135.75, 134.0, 133.8, 133.1, 131.9, 130.8, 129.7, 129.0, 128.8, 128.2,
127.6, 123.7, 118.6, 113.9, 111.7, 91.7, 69.1, 59.0, 55.2, 48.2, 46.5, 43.4,
43.1, 41.1, 35.7, 26.9, 20.3, 19.4.
Representative Procedure for the Preparation of 11a−c.
TBAF (2.1 mL, 1 M in THF) was added to a solution of 10a (910 mg,
1.42 mmol) in THF (5 mL). The solution was stirred at room
temperature overnight. Next, 1 M HCl (30 mL) was added to the
solution, which was then washed with ethyl acetate (3 × 20 mL). The
aqueous layer was basified with concentrated ammonium hydroxide
(28%) and extracted with dichloromethane (3 × 20 mL). The
combined organic extract was dried over Na2SO4, then filtered and
concentrated under reduced pressure. The residue was purified over
silica gel (EtOAc/Et3N, 10:1), and the product was dissolved in ethyl
acetate (60 mL), washed with water (4 × 10 mL), brine, and dried
over Na2SO4, then filtered and concentrated under reduced pressure
to afford the product as a yellow oil. The oil was dissolved in 10 mL of
ethyl acetate, and 1 N ethereal HCl (3 mL) was added and the mixture
concentrated. The resulting pale yellow solid was washed with minimal
ethyl acetate and CH2Cl2 to afford 525 mg of pure 11a as a
dihydrochloride 1.6 hydrate, 73% yield (mp = 195 °C, dec)
3-(2′-Methoxybenzyl)amino-7,8-didehydro-4,5-epoxy-17-
methyl-(5α,6α)-morphinan-6-ol (11a). Pale yellow solid (419 mg,
98%); 1H NMR (300 MHz, CDCl3) δ 7.25 (dd, J = 14.7, 7.7 Hz, 2H),
6.89 (t, J = 7.5 Hz, 2H), 6.46 (s, 2H), 5.62 (d, J = 9.9 Hz, 1H), 5.25 (d,
J = 9.7 Hz, 1H), 4.78 (d, J = 6.4 Hz, 1H), 4.29 (dd, J = 18.1, 9.0 Hz,
2H), 4.08 (s, 1H), 3.84 (s, 3H), 3.31 m, 1H), 3.00 (d, J = 18.5 Hz,
1H), 2.62−2.17 (m, 4H), 2.42 (s, 3H), 2.02 (td, J = 12.2, 5.1 Hz, 1H),
1.85 (d, J = 12.2 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 157.30,
146.16, 133.06, 130.67, 129.10, 128.98, 128.29, 127.48, 123.91, 120.40,
119.47, 112.75, 110.18, 90.99, 66.34, 58.95, 55.25, 46.50, 44.17, 43.04,
42.86, 40.86, 35.74, 20.25; mp = 194 °C (dec) (HCl salt). Anal. Calcd
for C25H28N2O3·2HCl·H2O: C, 60.61; H, 6.51; N, 5.65. Found: C,
60.50, H, 6.49; N, 5.44.
Morphine-6-(tert-butyldiphenylsilyl)oxy-3-(trifluorometha-
nesulfonate) (8).14 Morphine-3-(trifluomethanesulfonate) (7) (2.02
g, 4.85 mmol), TBDPSCl (1.60 g, 5.82 mmol), and imidazole (792
mg, 11.6 mmol) were stirred overnight in dichloromethane. Next,
ethyl acetate (100 mL) was added to the solution, and it was washed
sequentially with water (50 mL) and brine (10 mL). The organic layer
was dried over Na2SO4. The organic layer was filtered and
concentrated under reduced pressure, and the crude product was
purified on silica gel (EtOAc/Et3N, 200:1) to give the title product 8
1
as a white foam (2.94 g, 93%). H NMR (300 MHz, CDCl3) δ 7.82
(dd, J = 7.4, 1.6 Hz, 2H), 7.68 (dd, J = 7.6, 1.3 Hz, 2H), 7.53−7.31 (m,
6H), 6.93 (d, J = 8.4 Hz, 1H), 6.56 (d, J = 8.4 Hz, 1H), 5.74 (d, J = 9.7
Hz, 1H), 5.18 (dt, J = 9.7, 2.6 Hz, 1H), 4.51 (d, J = 5.0 Hz, 1H), 4.18
(dd, J = 5.2, 2.7 Hz, 1H), 3.28 (dd, J = 5.9, 3.0 Hz, 1H), 3.03 (d, J =
19.1 Hz, 1H), 2.52−2.21 (m, 4H), 2.37 (s, 3H), 1.85−1.63 (m, 2H),
1.12 (s, 9H); 13C NMR (CDCl3, 75 MHz) δ 150.8, 135.9, 135.7,
135.3, 133.6, 133.5, 133.3, 130.5, 129.86, 129.76, 128.1, 127.68,
127.66, 121.5, 120.9, 119.1, 116.6, 94.0, 69.2, 58.3, 45.9, 43.9, 43.0,
40.8, 35.4, 26.7, 21.0, 19.2.
3-Amino-6-(tert-butyldiphenylsilyl)oxymorphine (9). Under
nitrogen atmosphere, morphine-6-(tert-butyldiphenylsilyl)oxy-3-(tri-
fluoromethanesulfonate) (8) (2.93 g, 4.47 mmol) was dissolved in
anhydrous THF (50 mL), and Pd(OAc)2 (50 mg, 0.224 mmol), rac-
BINAP (279 mg, 0.448 mmol), and benzophenone imine (1.05 g, 5.81
mmol) were added to the stirring solution. The reaction mixture was
refluxed for 24 h under N2. After the reaction was complete, THF was
removed under reduced pressure and the residue was taken up in
dichloromethane (200 mL), washed with water, and dried over
Na2SO4. The organic layer was filtered and concentrated under
reduced pressure, and the crude product (orange oil) was used for the
next step directly. The residue was dissolved in MeOH (30 mL), and
NaOAc (880 mg, 10.7 mmol) and hydroxylamine hydrochloride (560
mg, 8.04 mmol) were added. The resulting reaction mixture was
stirred at room temperature for 3 days. After completion, the methanol
was removed under reduced pressure and the residue was dissolved in
ethyl acetate (200 mL), washed with brine, dried over Na2SO4, then
filtered and concentrated under reduced pressure. The residue was
purified on silica gel (eluted by EtOAc and EtOAc/Et3N, 100/1) to
afford 9 as a white solid (1.77 g, 76%). 1H NMR (300 MHz, CDCl3) δ
7.88−7.79 (m, 2H), 7.75−7.66 (m, 2H), 7.42 (m, 6H), 6.47 (dd, J =
22.1, 7.9 Hz, 2H), 5.76 (d, J = 9.7 Hz, 1H), 5.27−5.16 (m, 1H), 4.40
(d, J = 5.9 Hz, 1H), 4.28−4.19 (m, 1H), 3.46 (s, 2H), 3.26 (d, J = 3.0
Hz, 1H), 2.98 (d, J = 18.5 Hz, 1H), 2.57−2.18 (m, 4H), 2.39 (s, 3H),
1.73 (s, 2H), 1.14 (d, J = 8.3 Hz, 9H); 13C NMR (CDCl3, 75 MHz) δ
147.3, 135.8, 135.7, 134.0, 133.7, 133.1, 129.7. 129.6, 128.2, 127.6,
124.9, 118.6, 115.9, 91.6, 69.1, 58.8, 46.4, 43.3, 43.0, 41.0, 35.6, 26.8,
20.4, 19.3.
3-(3′-Methoxybenzyl)amino-7,8-didehydro-4,5-epoxy-17-
methyl-(5α,6α)-morphinan-6-ol (11b). White solid (525 mg,
1
83%); H NMR (300 MHz, CDCl3) δ 7.25 (dd, J = 8.5, 5.3 Hz,
1H), 6.93 (d, J = 12.6 Hz, 2H), 6.81 (d, J = 8.2 Hz, 1H), 6.46 (dd, J =
19.3, 7.9 Hz, 2H), 5.67 (d, J = 9.8 Hz, 1H), 5.29 (d, J = 8.0 Hz, 1H),
4.82 (d, J = 5.9 Hz, 1H), 4.29 (s, 2H), 4.13 (s, 1H), 3.78 (s, 3H),
3.39−3.21 (m, 1H), 3.01 (d, J = 18.6 Hz, 2H), 2.69−2.20 (m, 7H),
2.13−1.93 (m, 1H), 1.86 (d, J = 12.5 Hz, 1H); 13C NMR (75 MHz,
CDCl3) δ 159.76, 145.73, 141.23, 133.03, 130.46, 129.55, 129.07,
128.47, 124.06, 119.78, 119.60, 113.07, 112.58, 112.27, 91.12, 66.41,
58.95, 55.14, 48.75, 46.51, 43.07, 42.95, 40.92, 35.83, 20.26; mp = 195
°C (dec) (HCl salt). Anal. Calcd for C25H28N2O3·2HCl·1.6H2O: C,
59.31; H, 6.61; N, 5.53. Found: C, 59.37, H, 6.29; N, 5.47.
3-(4′-Methoxybenzyl)amino-7,8-didehydro-4,5-epoxy-17-
methyl-(5α,6α)-morphinan-6-ol (11c). Pale yellow solid (380 mg,
100%); 1H NMR (300 MHz, CD3OD) δ 7.26 (d, J = 8.3 Hz, 2H), 6.92
(d, J = 8.1 Hz, 1H), 6.82 (d, J = 8.2 Hz, 2H), 6.71 (d, J = 8.1 Hz, 1H),
5.69 (d, J = 9.3 Hz, 1H), 5.31 (d, J = 10.1 Hz, 1H), 5.10 (d, J = 6.0 Hz,
1H), 4.43 (s, 2H), 4.35 (s, 1H), 4.18 (s, 1H), 3.69 (s, 3H), 3.31 (t, J =
18.5 Hz, 2H), 3.24−3.06 (m, 3H), 3.02−2.78 (m, 1H), 2.92 (s, 3H),
2.44 (t, J = 11.1 Hz, 1H), 2.04 (d, J = 13.7 Hz, 1H); 13C NMR (75
MHz, CDCl3) δ 158.78, 145.67, 133.06, 131.47, 130.59, 129.02,
128.89, 128.47, 123.96, 119.57, 113.92, 112.10, 91.08, 66.38, 58.96,
(−)-3-N-(3′-Methoxybenzyl)amino-7,8-didehydro-6-(tert-bu-
tyldiphenylsilyl)-4,5-epoxy-17-methyl-(5α,6α)-morphinan-6-ol
(10a). Pale yellow oil (920 mg, 95%); 1H NMR (300 MHz, CDCl3) δ
7.78 (dd, J = 7.9, 1.4 Hz, 2H), 7.68 (dd, J = 7.8, 1.5 Hz, 2H), 7.49−
7.19 (m, 7H), 6.98 (m, 2H), 6.80 (dd, J = 8.1, 2.5 Hz, 1H), 6.49−6.34
(m, 2H), 5.75 (d, J = 9.8 Hz, 1H), 5.23−5.13 (m, 1H), 4.36 (2, 2H),
4.38−4.36 (m, 1H), 4.24−4.17 (m, 2H), 3.77 (s, 3H), 3.27 (dd, J =
6.0, 3.1 Hz, 1H), 2.96 (d, J = 18.5 Hz, 1H), 2.56−2.16 (m, 4H), 2.38
(s, 3H), 1.74 (t, J = 7.4 Hz, 2H), 1.08 (s, 9H); 13C NMR (CDCl3, 75
MHz) δ 159.8, 147.0, 141.6, 135.8, 135.7, 133.9, 133.7, 133.2, 130.7,
129.7, 129.5, 128.9, 128.1, 127.6, 127.5, 123.5, 119.8, 118.7, 112.8,
112.6, 111.7, 91.7, 69.1, 59.0, 55.1, 48.7, 46.4, 43.4, 43.0, 40.9, 35.6,
26.8, 20.4, 19.4.
(−)-3-N-(2′-Methoxybenzyl)amino-7,8-didehydro-6-(tert-bu-
tyldiphenylsilyl)-4,5-epoxy-17-methyl-(5α,6α)-morphinan-6-ol
(10b). Pale yellow oil (610 mg, 100%); 1H NMR (300 MHz, CDCl3)
δ 7.80 (dd, J = 7.9, 1.4 Hz, 2H), 7.69 (dd, J = 7.8, 1.5 Hz, 2H), 7.44−
7.28 (m, 7H), 7.26−7.17 (m, 1H), 6.95−6.82 (m, 2H), 6.47−6.35 (m,
2H), 5.75 (d, J = 9.8 Hz, 1H), 5.22−5.13 (m, 1H), 4.48−4.33 (m,
3H), 4.20 (d, J = 2.4 Hz, 1H), 3.82 (s, 3H), 3.24 (dd, J = 5.8, 3.0 Hz,
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55.24, 48.20, 46.53, 43.10, 42.95, 40.94, 35.85, 20.25; mp = 198 °C
(dec) (HCl salt). Anal. Calcd for C25H28N2O3·2HCl·H2O: C, 60.61;
H, 6.51; N, 5.65. Found: C, 60.40, H, 6.64; N, 5.52.
EtOAc/Et3N = 70:30:1) to give 2.8 g of 14 in 88% yield, as a slightly
yellow oil. 1H NMR (300 MHz, CDCl3) δ 7.94 (s, 1H), 7.27 (s, 1H),
3.23−3.12 (m, 1H), 3.05 (d, J = 19.1, 1H), 2.82−2.64 (m, 2H), 2.53−
2.42 (m, 1H), 2.38−2.25 (m, 2H), 2.03−0.77 (m, 11H), 0.54 (d, J =
7.9, 2H), 0.12 (d, J = 4.7, 2H). 13C NMR (75 MHz, CDCl3) δ 150.91,
140.10, 139.91, 138.45, 125.56, 121.31, 59.85, 54.86, 44.98, 44.09,
41.28, 38.94, 36.40, 26.68, 26.09, 24.42, 21.79, 9.24, 4.09, 3.66.
Synthesis of 2-Nitro-N-cyclopropylmethylmorphinan (15).
Triflate 14 (142 mg, 0.3 mmol), Pd(OAc)2 (7.8 mg, 0.03 mmol), and
dppp (12.4 mg, 0.03 mmol) were dissolved in anhydrous DMF (0.8
mL) under nitrogen atmosphere. Next, Et3SiH (120 μL, 0.75 mmol)
was added to the mixture and stirred at 60 °C overnight. The cooled
reaction mixture was directly purified over silica gel (hexanes/EtOAc/
Representative Procedure for the Preparation of 12a−c. To
a solution of 11b (425 mg, 0.89 mmol) in dichloromethane (10 mL)
under nitrogen atmosphere was added BBr3 (1M, 2 mL in
dichloromethane) at room temperature. Then the mixture was stirred
at room temperature for 3 days. After completion, the reaction was
carefully quenched with methanol, and the solvent was removed under
reduced pressure. The product was then dissolved in 1 M HCl (30
mL) and washed with CH2Cl2 (2×). Then the aqueous layer was
basified with concentrated ammonium hydroxide (28%), extracted
with CH2Cl2 (3×), and the combined organic extracts were dried over
Na2SO4, then filtered and concentrated. The crude product was
purified over silica gel (EtOAc/Et3N, 10:1, EtOAc/Et3N/MeOH,
10:1:0.1, EtOAc/Et3N/MeOH, 10:1:1) to give a purple foam. The
foam was dissolved in a minimal amount of dichloromethane and
stirred with excess 1 N ethereal HCl. The mixture was concentrated
and the resulting white solid was washed with CH2Cl2 and dried to
afford 125 mg of the pure 12b as a dihydrochloride 1.6 hydrate, 30%
yield (mp = 190 °C, dec).
3-(2′-Hydroxybenzyl)amino-7,8-didehydro-4,5-epoxy-17-
methyl-(5α,6α)-morphinan-6-ol (12a). Pale yellow solid (112 mg,
41%); 1H NMR (300 MHz, CD3OD) δ 7.23 (m, 2H), 7.03 (d, J = 8.2
Hz, 1H), 6.89 (d, J = 7.9 Hz, 1H), 6.82−6.72 (m, 2H), 5.77 (d, J = 9.8
Hz, 1H), 5.38 (d, J = 9.7 Hz, 1H), 5.18 (d, J = 6.2 Hz, 1H), 4.56 (q, J
= 12.6 Hz, 2H), 4.44 (s, 1H), 4.26 (s, 1H), 3.49−2.86 (m, 6H), 3.01
(s, 1H), 2.53 (t, J = 11.5 Hz, 1H), 2.10 (d, J = 11.5 Hz, 1H), 0.10 (s,
1H); 13C NMR (75 MHz, CD3OD) δ 157.68, 153.74, 135.67, 135.16,
133.10, 132.41, 132.01, 126.25, 124.92, 121.57, 120.62, 118.37, 116.84,
116.12, 94.16, 66.97, 61.68, 51.27, 42.91, 41.77, 39.48, 33.69, 22.91;
1
Et3N = 70:30:1) to afford 52 mg of 15 as a yellow oil, 53% yield. H
NMR (300 MHz, CDCl3) δ 8.00 (m, 2H), 7.42 (d, J = 8.5, 1H), 3.07
(m, 2H), 2.72 (m, 2H), 2.40 (m, 2H), 1.91 (m, 2H), 1.25 (m, 10H),
0.53 (m, 2H), 0.12 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 149.02,
145.67, 139.43, 126.54, 122.51, 121.27, 59.83, 55.22, 45.23, 44.55,
41.44, 38.51, 36.40, 26.78, 26.28, 24.94, 22.07, 9.18, 4.09, 3.68.
Synthesis of 2-Amino-N-cyclopropylmethylmorphinan (16).
Compound 16 was prepared according to the published procedure.10a
Synthesis of 2-Amino-N-cyclopropylmethyl-N′-m-hydroxy-
benzylmorphinan (17). m-Anisaldehyde (99 μL, 0.85 mmol) and
anhydrous Na2SO4 (10 mg) were added to the solution of 16 (50 mg,
0.17 mmol) in MeOH (2 mL). The resulting mixture was stirred at
room temperature overnight. NaBH4 (32.3 mg, 0.8 mmol) was then
added and stirred at room temperature for 4 h. The solvent was
removed under reduced pressure, and the residue was dissolved in 10
mL of 1 N HCl and washed with ethyl acetate (2 × 10 mL), then
basified with ammonium hydroxide until pH ≈ 11 was reached. The
aqueous solution was then extracted with CH2Cl2 (3 × 10 mL). The
organic layer was washed with brine and dried over anhydrous
Na2SO4. The solvent was removed under reduced pressure and the
residue was purified over silica gel (hexane/EtOAc/Et3N = 40/30/1)
to afford 17 as a colorless oil (52 mg, 73%)
mp
= 190 °C (dec) (HCl salt). Anal. Calcd for
C24H26N2O3·2HCl·1.6H2O: C, 58.56; H, 6.39; N, 5.69. Found: C,
58.46, H, 6.46; N, 5.33.
3-(3′-Hydroxybenzyl)amino-7,8-didehydro-4,5-epoxy-17-
methyl-(5α,6α)-morphinan-6-ol (12b). Pale yellow solid (125 mg,
30%); 1H NMR (300 MHz, CD3OD) δ 7.20 (t, J = 7.8 Hz, 1H), 7.07
(dd, J = 8.2, 2.9 Hz, 1H), 6.95−6.76 (m, 4H), 5.79 (d, J = 9.9 Hz, 1H),
5.39 (d, J = 10.0 Hz, 1H), 5.19 (d, J = 6.2 Hz, 1H), 4.49 (m, 3H), 4.45
(s, 1H), 4.27 (s, 1H), 3.48−2.87 (m, 7H), 3.01 (s, 3H), 2.53 (t, J =
11.5 Hz, 1H), 2.14 (d, J = 13.9 Hz, 1H), 1.42−1.25 (m, 1H), 0.07 (d, J
= 15.3 Hz, 1H); 13C NMR (75 MHz, CD3OD) δ 159.03, 153.76,
135.65, 135.24, 133.36, 132.12, 131.12, 126.28, 124.87, 122.27, 121.74,
118.24, 117.54, 116.81, 94.26, 66.98, 61.70, 55.03, 42.95, 41.78, 39.54,
33.69, 22.93; mp = 190 °C (dec) (HCl salt). Anal. Calcd for
C24H26N2O3·2HCl·1.6H2O: C, 58.56; H, 6.39; N, 5.69. Found: C,
58.58, H, 6.66; N, 5.75.
3-(4′-Hydroxybenzyl)amino-7,8-didehydro-4,5-epoxy-17-
methyl-(5α,6α)-morphinan-6-ol (12c). Pale yellow solid (71 mg,
26%); 1H NMR (300 MHz, CD3OD) δ 7.25 (d, J = 8.5 Hz, 2H), 7.02
(d, J = 8.2 Hz, 1H), 6.79 (m, 3H), 5.78 (d, J = 9.9 Hz, 1H), 5.40 (d, J
= 9.8 Hz, 1H), 5.19 (d, J = 6.3 Hz, 1H), 4.48 (s, 3H), 4.27 (s, 1H),
3.50−2.87 (m, 6H), 3.02 (s, 3H), 2.53 (m, 1H), 2.14 (d, J = 12.9 Hz,
1H), 0.10 (s, 1H); 13C NMR (75 MHz, CD3OD) δ 159.05, 152.90,
134.66, 134.43, 132.19, 131.16, 125.28, 124.14, 121.40, 120.71, 115.63,
115.47, 93.26, 65.96, 60.70, 54.00, 41.93, 40.77, 38.56, 32.69, 21.93;
To a solution of 17 (52 mg, 0.12) in anhydrous CH2Cl2 (2 mL)
under nitrogen atmosphere was added BBr3 (2 mL, 1 M in CH2Cl2) at
0 °C. Then the mixture was stirred at room temperature for 2 h. The
reaction was carefully quenched with excess MeOH, and the solvent
was removed under reduced pressure. The resulting dark oil was
dissolved in MeOH (3 mL), refluxed for 15 min. Next, the solvent was
removed under reduced pressure, and the product was dissolved in 10
mL of 1 M HCl and washed with ethyl acetate twice. Then the
aqueous layer was basified with ammonium hydroxide (28% aqueous
solution) and extracted with CH2Cl2 (2×). The combined organic
extracts were dried over Na2SO4, then filtered and concentrated under
reduced pressure. The crude product was purified over silica gel
(EtOAc/MeOH/Et3N = 50/1/1) to afford 17) as a white foam (37
1
mg, 78%). H NMR (300 MHz, CDCl3) δ 7.23 (m, 1H), 6.88 (d, J =
8.2, 1H), 6.76 (m, 3H), 6.34 (m, 2H), 4.34 (s, 2H), 4.06 (s, 1H), 3.14
(s, 1H), 2.77 (d, J = 18.5, 1H), 2.58 (m, 1H), 2.41 (m, 1H), 2.12 (m,
4H), 1.62 (m, 2H), 1.21 (m, 8H), 0.76 (d, J = 12.8, 1H), 0.53 (m,
2H), 0.11 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 157.72, 145.56,
141.60, 137.87, 129.70, 128.80, 126.42, 117.31, 114.70, 113.26, 111.80,
109.73, 59.50, 55.47, 46.95, 45.58, 43.93, 41.54, 36.47, 36.05, 26.64,
26.39, 24.33, 21.95, 8.41, 4.18, 4.13; (HCl salt) mp = 173−175 °C.
Anal. Calcd for C20H28N3·2HCl·0.7H2O: C, 66.44; H, 7.72; N, 5.74.
Found: C, 66.43, H, 7.87; N, 5.68
Opioid Binding to the Human κ, δ, and μ Opioid Receptors.
Chinese hamster ovary (CHO) cells stably transfected with the human
κ opioid receptor (hKOR-CHO) were obtained from Dr. Liu-Yuan
Liu-Chen (Temple University, Philadelphia, PA). CHO cells
expressing the human δ-opioid receptor (hDOR-CHO) were obtained
from Dr. Larry Toll (SRI International, Palo Alto, CA), and the μ-
opioid receptor (hMOR-CHO) was obtained from Dr. George Uhl
(NIDA Intramural Program, Baltimore, MD). The cells were grown in
100 mm dishes in Dulbecco’s modified Eagle’s medium (DMEM)
supplemented with 10% fetal bovine serum (FBS) and penicillin−
streptomycin (10 000 U/mL) at 37 °C in a 5% CO2 atmosphere. The
affinity and selectivity of the compounds for the multiple opioid
mp
= 198 °C (dec) (HCl salt). Anal. Calcd for
C24H26N2O3·2HCl·1.6H2O: C, 54.57; H, 6.72; N, 5.30. Found: C,
54.76, H, 6.63; N, 5.52.
2-Nitro-3-trifluoromethylsulfonyloxy-N-cyclopropylmethyl-
morphinan (14). 2-Nitro-3-hydroxy-N-cyclopropylmethylmorphinan
139 (2.4 g, 6.7 mmol) was dissolved in anhydrous dichloromethane
(50 mL) and Et3N (3.2 mL, 19.3 mmol). The mixture was cooled to 0
°C, and then Tf2O (1.8 mL, 9.6 mmol) was added. The mixture was
allowed to warm to room temperature and stirred overnight. The
solution was diluted with dichloromethane (60 mL), washed
sequentially with saturated sodium carbonate solution and brine, and
then dried over anhydrous Na2SO4. The organic layer was filtered and
concentrated under reduced pressure to afford a crude product, which
was purified by column chromatography on silica gel (hexanes/
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Journal of Medicinal Chemistry
Article
receptors were determined by incubating the membranes with
radiolabeled ligands and 12 different concentrations of the compounds
at 25 °C in a final volume of 1 mL of 50 mM Tris-HCl, pH 7.5.
Incubation times of 60 min were used for the κ-selective peptide
[3H]DAMGO and the μ-selective ligand [3H]U69,593. A 3 h
incubation was used with the δ-selective antagonist [3H]naltrindole.
[35S]GTPγS Binding Studies To Determine the Pharmaco-
logical Properties of the Compounds. Membranes from CHO
cells stably expressing either the human κ or μ opioid receptor were
used in the experiments. Cells were scraped from tissue culture plates
and then centrifuged at 1000g for 10 min at 4 °C. The cells were
resuspended in phosphate-buffered saline, pH 7.4, containing 0.04%
EDTA. After centrifugation at 1000g for 10 min at 4 °C, the cell pellet
was resuspended in membrane buffer, which consisted of 50 mM Tris-
HCl, 3 mM MgCl2, and 1 mM EGTA, pH 7.4. The membranes were
homogenized with a Dounce homogenizer, followed by centrifugation
at 40000g for 20 min at 4 °C. The membrane pellet was resuspended
in membrane buffer, and those transfected with the centrifugation step
were repeated. The membranes were then resuspended in assay buffer,
which consisted of 50 mM Tris-HCl, 3 mM MgCl2, 100 mM NaCl,
and 0.2 mM EGTA, pH 7.4. The protein concentration was
determined by the Bradford assay using bovine serum albumin as
the standard. The membranes were frozen at −80 °C until used.
CHO cell membranes expressing either the human κ opioid
receptor (15 μg of protein per tube) or μ opioid receptor (7.5 μg of
protein per tube) were incubated with 12 different concentrations of
the agonist in assay buffer for 60 min at 30 °C in a final volume of 0.5
mL. The reaction mixture contained 3 μM GDP and 80 pmol of
[35S]GTPγS. Basal activity was determined in the presence of 3 μM
GDP and in the absence of an agonist, and nonspecific binding was
determined in the presence of 10 μM unlabeled GTPγS. Then the
membranes were filtered onto glass fiber filters by vacuum filtration,
followed by three washes with 3 mL of ice-cold 50 mM Tris-HCl, pH
7.5. Samples were counted in 2 mL of ScintiSafe 30% scintillation fluid.
Data represent the percent of agonist-stimulation [35S]GTPγS binding
over the basal activity, defined as [(specific binding/basal binding) ×
100] − 100. All experiments were repeated at least three times and
were performed in triplicate. To determine antagonist activity of a
compound at the μ opioid receptors, CHO membranes expressing the
μ opioid receptor were incubated with the compound in the presence
of 200 nM agonist DAMGO. To determine antagonist activity of a
compound at the κ opioid receptors, CHO membranes expressing the
κ opioid receptor were incubated with the compound in the presence
of 100 nM κ agonist U50,488.
REFERENCES
■
(1) Mercadante, S.; Villari, P.; Ferrera, P.; Casuccio, A.; Fulfaro, F.
Rapid Titration with Intravenous Morphine for Severe Cancer Pain
and Immediate Oral Conversion. Cancer 2002, 95, 203−208.
(2) (a) Colpaert, F. C.; Niemegeers, C. J.; Janssen, P. A.; Van Ree, J.
M. Narcotic Cueing Properties of Intraventricularly Administered
Sufentanil, Fentanyl, Morphine, and met-Enkephalin. Eur. J.
Pharmacol. 1978, 47, 115−119. (b) Niemegeers, C. J.; Schellekens,
K. H.; Van Bever, W. F.; Janssen, P. A. Sufentanil, a Very Potent and
Extremely Safe Intravenous Morphine-like Compound in Mice, Rats,
and Dogs. Arzneim. Forsch. 1976, 26, 1551−1556.
(3) Chen, Z. R.; Irvine, R. J.; Somogyi, A. A.; Bochner, F. Mu
Receptor Binding of Some Commonly Used Opioids and their
Metabolites. Life Sci. 1991, 48, 2165−2171.
(4) Riley, J.; Eisenberg, E.; Muller-Schwefe, G.; Drewes, A. M.;
̈
Arendt-Nielsen, L. Oxycodone: A Review of Its Use in the
Management of Pain. Curr. Med. Res. Opin. 2008, 24, 175−192.
(5) Aldrich, J. V.; Vigil-Cruz, S. C. Narcotic Analgesics. In Burger’s
Medicinal Chemistry and Drug Discovery; Abraham, D., Ed.; John Wiley
& Sons: New York, 2003; Vol. 6, Chapter 7, pp 329−481.
(6) (a) Furst, S.; Hosztafi, S.; Friedmann, T. Structure−Activity
Relationships of Synthetic and Semisynthetic Opioid Agonists and
Antagonists. Curr. Med. Chem. 1995, 1, 423−440. (b) Aldrich, J. V.
Analgesics. In Burger’s Medicinal Chemistry and Drug Discovery; Wolff,
M. E., Ed.; John Wiley & Sons: New York, 1996; Vol. 3, pp 321−441.
(c) Mascarella, S. W.; Bai, X.; Williams, W.; Sine, B.; Bowen, W. D.;
Carroll, F. I. (+)-cis-N-(Para-, Meta-, and Ortho-substituted benzyl)-N-
normetazocines: Synthesis and Binding Affinity at the [3H]-
(+)-Pentazocine-Labeled (σ1) Site and Quantitative Structure−
Activity Relationship Studies. J. Med. Chem. 1995, 38, 565−569.
(d) Reden, J.; Reich, M. F.; Rice, K. C.; Jacobson, A. E.; Brossi, A.
Deoxymorphines: Role of the Phenolic Hydroxyl in the Antinoci-
ception and Opiate Receptor Interactions. J. Med. Chem. 1979, 22,
256−259. (e) Hedberg, M. H.; Johansson, A. M.; Fowler, C. J.;
Terenius, L.; Hacksell, U. Palladium-Catalyzed Synthesis of C3-
Substituted 3-Deoxymorphines. Bioorg. Med. Chem. Lett. 1994, 4,
2527−2532. (f) Kubota, H.; Rothman, R. B.; Dersch, C.; McCullough,
K.; Pinto, J.; Rice, K. C. Synthesis and Biological Activity of 3-
Substituted 3-Deoxynaltrindole Derivatives. Bioorg. Med. Chem. Lett.
1999, 8, 799−804.
(7) Berezowska, I.; Chung, N. N.; Lemieux, C.; Wilkes, B. C.;
Schiller, P. W. Agonist vs. Antagonist Behavior of δ Opioid Petides
Containing Novel Phenylalanine Analogues in Place of Tyr. J. Med.
Chem. 2009, 52, 6941−6945.
(8) Peng, X.; Knapp, B. I.; Bidlack, J. M.; Neumeyer, J. L. High-
Affinity Carbamate Analogues of Morphinan at Opioid Receptors.
Bioorg. Med. Chem. Lett. 2007, 15, 1508−1511.
(9) Peng, X.; Knapp, B. I.; Bidlack, J. M.; Neumeyer, J. L. In-Vitro
Investigation of Oxazol and Urea Analogues of Morphinan at Opioid
Receptors. Bioorg. Med. Chem. 2007, 15, 4106−4112.
AUTHOR INFORMATION
■
Corresponding Author
*Phone: 1-617-855-3388. Fax: 1-617-855-3887. E-mail:
jneumeyer@mclean.harvard.edu.
(10) (a) Zhang, A.; Xiong, W.; Hilbert, J. E.; DeVita, E. K.; Bidlack, J.
M.; Neumeyer, J. L. 2-Aminothiazole-Derived Opioids. Bioisosteric
Replacement of Phenols. J. Med. Chem. 2004, 47, 1886−1888.
(b) Zhang, A.; Vliet, S. V.; Neumeyer, J. L. Synthesis of aminothiazole
derived morphinans. Tetrahedron Lett. 2003, 44, 6459−6462.
(c) Zhang, T.; Yan, Z.; Sromek, A.; Knapp, B. I.; Scrimale, T.;
Bidlack, J. M.; Neumeyer, J. L. Aminothiazolomorphinans with Mixed
κ and μ Opioid Activity. J. Med. Chem. 2011, 54, 1903−1913.
(11) Sagara, T.; Egashira, H.; Okamura, M.; Fujii, I.; Shimohigashi,
Y.; Kanematsu, K. Ligand Recognition in mu Opioid Receptor:
Experimentally Based Modeling of mu Opioid Receptor Binding Sites
and Their Testing by Ligand Docking. Bioorg. Med. Chem. 1996, 4,
2151−2166.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by NIH Grants R01-
DA14251(J.L.N.) and K05-DA00360 (J.M.B.)
ABBREVIATIONS USED
■
MOR, μ opioid receptor; KOR, κ opioid receptor; DOR, δ
opioid receptor; BINAP, 2,2′-bis(diphenylphosphino)-1,1′-
binaphthyl; TBDPS, tert-butyl(diphenyl)silyl; TBAF, tetrabuty-
lammonium fluoride; TM, transmembrane domain; TIPP, H-
Tyr-Tic-Phe-Phe-OH; Bcp, 4-[N-((4′-phenyl)phenethyl)-
carboxamido]phenylalanine; Dbcp, 2′,6,-dinaphthyl-4′-[N-((4′-
phenyl)phenethyl)carboxamido]phenylalanine
(12) Pogozheva, I. D.; Lomize, A. L.; Mosberg, H. I. Opioid Receptor
Three-Dimensional Structures from Distance Geometry Calculations
with Hydrogen Bonding Constraints. Biophys. J. 1998, 75, 612−634.
(13) Wentland, M. P.; Xu, G.; Cioffi, C. L.; Ye, Y.; Duan, W.; Cohen,
D. J.; Colasurdo, A. M.; Bidlack, J. M. 8-Aminocyclazocine Analogues:
3889
dx.doi.org/10.1021/jm3001086 | J. Med. Chem. 2012, 55, 3878−3890

Journal of Medicinal Chemistry
Article
Synthesis and Structure−Activity Relationships. Bioorg. Med. Chem.
Lett. 2000, 9, 183−187.
(14) Wentland, M. P.; Duan, W.; Cohen, D. J.; Bidlack, J. M.
Selective Protection and Functionalization of Morphine: Synthesis and
Opioid Receptor Binding Properties of 3-Amino-3-desoxymorphine
Derivatives. J. Med. Chem. 2000, 43, 3558−3565.
(15) Decker, M.; Si, Y. G.; Knapp, B. I.; Bidlack, J. M.; Neumeyer, J.
L. Synthesis and Opioid Receptor Binding Affinities of 2-Subtituted
and 3-Aminomorphinans: Ligands for μ, κ, and δ Opioid Receptors. J.
Med. Chem. 2010, 53, 402−418.
(16) Neumeyer, J. L.; Bidlack, J. M.; Zong, R.; Bakthavachalam, V.;
Gao, P.; Cohen, D. J.; Negus, S. S.; Mello, N. K. Synthesis and Opioid
Receptor Affinity of Morphinan and Benzomorphan Derivatives:
Mixed κ Agonists and μ Agonists/Antagonists as Potential
Pharmacotherapeutics for Cocaine Dependence. J. Med. Chem. 2000,
43, 114−122.
(17) Wolfe, J. P.; Buchwald, S. L. Palladium-Catalyzed Amination of
Aryl Triflates. J. Org. Chem. 1997, 62, 1264−1267.
(18) Gribble, G. W.; Nutaitis, C. F. Reactions of Sodium Borohydride
in Acidic Media: N-Methylation of Amines with Paraformaldehyde/
Trifluoroacetic Acid. Synthesis 1987, 1987, 709−711.
(19) Zhang, A.; Xiong, W.; Bidlack, J. M.; Hilbert, J. E.; Knapp, B. I.;
Wentland, M. P.; Neumeyer, J. L. 10-Ketomorphinan and 3-
Substituted-3-desoxymorphinan Analogues as Mixed κ and μ Opioid
Ligands: Synthesis and Biological Evaluation of Their Binding Affinity
at Opioid Receptors. J. Med. Chem. 2004, 47, 165−174.
(20) Hupp, C. D.; Neumeyer, J. L. Rapid Access to Morphinones:
Removal of 4,5-Ether Bridge with Pd-Catalyzed Triflate Reduction.
Tetrahedron Lett. 2010, 51, 2359−2361.
(21) Csutoras, C.; Zhang, A.; Zhang, K.; Kula, N. S.; Baldessarini, R.
J.; Neumeyer, J. L. Synthesis and Pharmacological Evaluation of R(−)-
N-Alkyl-11-hydroxynoraporphines and Their Esters. Bioorg. Med.
Chem. Lett. 2004, 12, 3553−3559.
3890
dx.doi.org/10.1021/jm3001086 | J. Med. Chem. 2012, 55, 3878−3890