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Table 5. Binding Assays to Human Opiate m-, d- and k-Receptors of
Compound 8
tions were used: sϭsinglet, dϭdoublet, ddϭdouble doublet, dtϭdouble
triplet, tϭtriplet, qϭquartet, mϭmultiplet and brϭbroad. FAB-MS, electron
ionization mass spectrometry (EI-MS) or high-resolution mass spectra (HR-
MS) were obtained using JEOL JMS-DX303 or JEOL JMS-AX500 mass
spectrometer. TLC was performed by using Silica gel 60F254 (Merck). Col-
umn chromatography was performed with Silica gel 60 (70—230 mesh)
(Merck). Sodium sulfate was employed as the drying agent. Palladium hy-
droxide [20 wt%, Pd (dry basis) on carbon, wet] and hydrogen chloride,
1.0 M solution in diethyl ether were obtained from Aldrich Chemical Com-
pany, Inc. The yields, physical and spectral data for 7a(I)—7a(IV), 7b(I),
7c(I), 8—10, 14y, 14z, 15y and 15z are shown in Tables 1 and 2. The analyt-
ical data for the solid compounds among the above compounds, 7a(I),
7a(II), 7a(III), 8, 10, 15y and 15z, are shown in Table 3.
Compound
m, IC50 (nM)a)
d, IC50 (nM)b)
k, IC50 (nM)c)
Ͼ10000
8
4.2
360
Quantitative follow-up: IC50 assessed in three independent experiments over a
range of 5—6 concentrations: total 34 tubes. a) This assay measures binding of
[3H]Diprenorphine (DPN) to human opiate m-receptors. b) This assay measures bind-
ing of [3H]Naltrindole to human opiate d-receptors. c) This assay measures binding
of [3H]DPN to human opiate k-receptors.
4-Hydroxy-4-(3-hydroxyphenyl)piperidine (4b)4) Typical Procedure:
A solution of 1-benzyl-4-[3-(benzyloxy)phenyl]-4-hydroxypiperidine (3b)
(10.0 g, 26.8 mmol) in MeOH (100 ml) was hydrogenated in the presence of
Pd(OH)2 (3.0 g) under H2 atmosphere (4 atm) at room temperature for 6 h.
The catalyst was removed by filtration and the filtrate was concentrated in
1
vacuo to give 4b (4.00 g, 77%) as a colorless solid. mp 188—189 °C. H-
NMR (DMSO-d6) d: 1.42—1.52 (2H, m), 1.66—1.80 (2H, m), 2.62—2.76
(2H, m), 2.84—2.97 (2H, m), 4.40—4.80 (1H, br), 6.54—6.60 (1H, m), 6.85
(1H, dd, Jϭ7.8, 2.0 Hz), 6.89 (1H, t, Jϭ2.0 Hz), 7.07 (1H, t, Jϭ7.8 Hz),
8.00—10.00 (1H, br). EI-MS m/z: 193 (Mϩ). HR-MS m/z: 193.1097 (Calcd
for C11H15NO2: 193.1102). IR n (KBr) cmϪ1: 3410, 3265.
4-Hydroxy-4-(2-hydroxyphenyl)piperidine (4a): Colorless solid. mp
188—189 °C. Yield 95%. 1H-NMR (DMSO-d6) d: 1.57—1.72 (2H, m),
1.94—2.09 (2H, m), 2.67—2.82 (2H, m), 2.87—3.02 (2H, m), 4.20—6.60
(3H, br), 6.68—6.80 (2H, m), 7.05 (1H, dt, Jϭ7.6, 1.5 Hz), 7.22 (1H, dd,
Jϭ7.6, 1.5 Hz). EI-MS m/z: 193 (Mϩ). HR-MS m/z: 193.1090 (Calcd for
C11H15NO2: 193.1102). IR n (KBr) cmϪ1: 3410, 3263.
4-Hydroxy-4-(4-hydroxyphenyl)piperidine (4c): Yellowish solid. mp
206—207 °C. Yield 46%. 1H-NMR (DMSO-d6) d: 1.50—1.70 (2H, m),
1.80—2.00 (2H, m), 2.80—3.15 (4H, m), 3.20—5.40 (3H, br), 6.71 (2H, d,
Jϭ8.3 Hz), 7.24 (1H, d, Jϭ8.3 Hz). EI-MS m/z: 193 (Mϩ). HR-MS m/z:
193.1095 (Calcd for C11H15NO2: 193.1102). IR n (KBr) cmϪ1: 3385, 3231.
The above compounds 4a and 4c were synthesized according to the syn-
thetic procedure of 4b.
N,N-Dimethyl-2,2-diphenyl-4-[4-hydroxy-4-(hydroxyphenyl)piperidin-
1-yl]butanamide (6) (General Procedure A) A mixture of 4 (2.5 mmol),
dimethyl(tetrahydro-3,3-diphenyl-2,2-furylidene) ammonium bromide (5)
(2.8 mmol), sodium carbonate (500 mg, 4.7 mmol) and DMF (25 ml) was
stirred at 80 °C for 8 h. The reaction mixture was concentrated in vacuo and
then H2O was added into the residue. The mixture was extracted with
CHCl3, dried, concentrated in vacuo, purified by column chromatography on
silica gel, eluting with 3% MeOH in CHCl3 to give 6 as a solid or viscous
liquid.
N,N-Dimethyl-2,2-diphenyl-4-[4-hydroxy-4-(2-hydroxyphenyl)piperidin-
1-yl]butanamide (6a): Yellowish solid. mp 128—130 °C. Yield 76%. 1H-
NMR (CDCl3) d: 1.86—1.96 (2H, m), 1.96—2.20 (4H, m), 2.20—2.55 (7H,
m), 2.63—2.80 (2H, m), 2.80—3.05 (3H, m), 6.73—6.83 (2H, m), 7.05 (1H,
dd, Jϭ7.8, 1.5 Hz), 7.12 (1H, dt, Jϭ8.3, 1.5 Hz), 7.22—7.32 (2H, m),
7.32—7.43 (8H, m). EI-MS m/z: 458 (Mϩ). HR-MS m/z: 458.2599 (Calcd
for C29H34N2O3: 458.2570). IR n (KBr) cmϪ1: 3237, 1637.
Fig. 2. Analgesic Effects of Compound 8 on the Freund’s Complete Adju-
vant (FCA) Induced Hyperalgesia in Rats
Compound 8 was injected by intraplantar route into the inflamed paw approximately
24 h after intraplantar injection of 150 ml of FCA. Naloxone methiodide (10 mg/kg)
was subcutaneously administered 15 min before compound 8 injection. Pressure thresh-
old on inflamed paw was measured before drug injection, 10, 30, 60 and 120 min after
the injection. Each point represents the ϮS.E. of 8 rats.
highest potency (Table 4B).
Next, we examined the affinities to the human MOR, DOR
and KOR to confirm the selectivity of the most potent MOR
agonist, 8 (Table 5). We then confirmed that it had the selec-
tivity to the MOR because it showed lower affinities to the
DOR and KOR than to the MOR.
Lastly, we examined the peripheral analgesic activity of
compound 8 in the Randal–Selitto method on rat as an in
vivo test. As shown in Fig. 2, compound 8 had peripheral
analgesic activity because the effect was inhibited by nalox-
one methiodide of the peripheral opioid receptor antagonist.
N,N-Dimethyl-2,2-diphenyl-4-[4-hydroxy-4-(3-hydroxyphenyl)piperidin-
1-yl]butanamide (6b): Colorless solid. mp 168—169 °C. Yield 74%. 1H-
NMR (CDCl3) d: 1.50—1.70 (2H, m), 1.70—2.66 (12H, m), 2.66—2.90
(2H, m), 2.90—3.20 (3H, br), 6.71 (1H, d, Jϭ7.8 Hz), 6.87 (1H, s), 6.97
(1H, d, Jϭ7.8 Hz), 7.16 (1H, t, Jϭ7.8 Hz), 7.25—7.34 (2H, m), 7.34—7.47
(8H, m). EI-MS m/z: 459 (Mϩ). HR-MS m/z: 459.2649 (Calcd for
C32H40N2O4: 459.2648). IR n (KBr) cmϪ1: 3385, 1625.
Conclusion
As mentioned above, we found compound 8 (SS620) hav-
ing a 10 times more potent MOR agonist activity than lop-
eramide and a potent peripheral analgesic activity in vivo.
Therefore, we selected compound 8 as one of the promising
N,N-Dimethyl-2,2-diphenyl-4-[4-hydroxy-4-(4-hydroxyphenyl)piperidin-
candidates for a peripheral analgesic of the MOR agonist and 1-yl]butanamide (6c): Yellowish solid. mp 154—155 °C. Yield 55%. 1H-
NMR (DMSO-d6) d: 1.63—1.80 (2H, m), 1.90—3.60 (16H, m), 4.82—5.15
(1H, br), 6.71 (2H, d, Jϭ8.3 Hz), 7.20 (2H, d, Jϭ8.3 Hz), 7.26—7.55 (10H,
m), 9.21 (1H, s). EI-MS m/z: 440 (MϩϪH2O). HR-MS m/z: 440.2473 (Calcd
for C29H34N2O3: 440.2464). IR n (KBr) cmϪ1: 3406, 1618.
are now running various pharmacological tests to confirm its
profile. Also, we are continuing to examine the precise struc-
ture-activity relationship, and some derivatives of compound
8 are now being synthesized and evaluated.
N,N-Dimethyl-2,2-diphenyl-4-[4-(2-hydroxyphenyl)piperidin-1-yl]bu-
tanamide (13y) Compound 13y was synthesized from 4-(2-hydroxy-
phenyl)piperidine (12y)4) and dimethyl(tetrahydro-3,3-diphenyl-2,2-furyli-
dene)ammonium bromide (5) according to the general procedure A. Color-
Experimental
Melting points were determined on a Yanaco micro melting point appara-
tus without correction. IR spectra were measured with a Perkin-Elmer 1600
FT-IR spectrometer. 1H-NMR spectra were recorded on a JEOL JNM-
EX400 FT-NMR spectrometer in CDCl3 or dimethyl sulfoxide (DMSO)-d6
using tetramethylsilane as the internal reference. The following abbrevia-
1
less solid. mp 221—222 °C. Yield 75%. H-NMR (CDCl3) d: 1.77—1.88
(2H, m), 2.06—2.22 (2H, m), 2.31 (3H, s), 2.52—2.79 (6H, m), 2.90—3.04
(1H, m), 3.01 (3H, s), 3.24—3.37 (2H, m), 6.72—7.78 (1H, m), 6.88—6.97
(2H, m), 7.03—7.08 (1H, m), 7.26—7.43 (10H, m). EI-MS m/z: 442 (Mϩ).