Synthesis and neuropharmacological evaluation of R(-)-N-alkyl-11- hydroxynoraporphines and their esters

Article abstract of DOI:10.1016/j.bmc.2004.04.029

We synthesized several N-substituted-11-hydroxynoraporphines and their esters of varying chain length, evaluated their binding affinity at dopamine (DA) receptor sites in rat caudate-putamen membranes, and quantified their effects on motor activity in normal adult male rats. The 11-hydroxyaporphines showed similar neuropharmacological properties to the corresponding 10,11-catecholaporphines. At moderate doses, their esters proved to have more prolonged behavioral actions and superior oral bioavailability.

Full text of DOI:10.1016/j.bmc.2004.04.029

Bioorganic & Medicinal Chemistry 12 (2004) 3553–3559
Synthesis and neuropharmacological evaluation of R())-N-alkyl-
11-hydroxynoraporphines and their esters
Csaba Csutoras,a Ao Zhang,a Kehong Zhang,b Nora S. Kula,b
Ross J. Baldessarinib and John L. Neumeyera,*
aAlcohol and Drug Abuse Research Center, McLean Division of Massachusetts General Hospital, Harvard Medical School,
115 Mill Street, Belmont, MA 02478-9106, USA
bMailman Research Center, McLean Division of Massachusetts General Hospital, Harvard Medical School,
115 Mill Street, Belmont, MA 02478-9106, USA
Received 27 February 2004; revised 22 April 2004; accepted 23 April 2004
Available online 18 May 2004
Abstract—We synthesized several N-substituted-11-hydroxynoraporphines and their esters of varying chain length, evaluated their
binding affinity at dopamine (DA) receptor sites in rat caudate-putamen membranes, and quantified their effects on motor activity in
normal adult male rats. The 11-hydroxyaporphines showed similar neuropharmacological properties to the corresponding 10,11-
catecholaporphines. At moderate doses, their esters proved to have more prolonged behavioral actions and superior oral bio-
availability.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
2
6a
N
H
1
N
H
R
R
During previous years, several laboratories including
ours have focused on the synthesis of mono-oxygenated
aporphines, especially the effects produced by elimina-
tion of the 10- or 11-hydroxyl groups in the catechola-
porphine, R())-apomorphine (APO, 1) and its N-alkyl
congener, R())-N-propylnorapomorphine (NPA, 2)
(Fig. 1). ( )-11-Hydroxyaporphines were first synthe-
sized in 1974 via a Reissert alkylation and Pschorr
cyclization route.1 Our earlier investigations indicated
that a hydroxyl group at the 11-position (analogous to
the meta-hydroxy group of dopamine) plays an impor-
tant role in receptor binding2 and that the catechol
system is not required for dopaminergic activity.
11
HO
HO
HO
10
R
CH3
CH2CH2CH3
CH2CH=CH2
R
3
4
5
1, R(-)-APO
2, R(-)-NPA
CH3
CH2CH2CH3
Figure 1.
their S-(+)-antipodes by a total synthesis strategy from
1-benzylisoquinoline and subsequent resolution of the
resulting aporphine racemates.4;5
We first synthesized optically pure R())-enantiomers of
some 11-hydroxyaporphines, by selective removal of the
10-hydroxyl group on the aporphine ring via a phenyl-
tetrazole ether.3 Later we prepared R())-N-n-propyl-
and R())-N-allyl-11-hydroxynoraporphine (4, 5) and
R())-APO (1) has some efficacy in the treatment of
Parkinson’s disease, but its poor oral bioavailability
limits its clinical utility.6 As a potential means of
avoiding this limitation, we found that several catechol
diesters and methylenedioxy prodrugs of 1 and 2 that
limited the first-pass metabolic inactivation of cate-
cholaporphines.7;8 Aporphines containing a single hyd-
roxyl group at C-11 such as 3, were reported by Schaus
et al.9 to have some affinity for the D1 dopamine
Keywords: Apomorphine; 11-Hydroxyaporphine; Parkinson’s disease;
Dopamine receptor; Motor activity; Bioavailability.
* Corresponding author. Tel.: +1-617-855-3388; fax: +1-617-855-2519;
e-mail: neumeyer@mclean.harvard.edu
0968-0896/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2004.04.029

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C. Csutoras et al. / Bioorg. Med. Chem. 12 (2004) 3553–3559
receptor and properties as D1 antagonists. More re-
cently, Hedberg et al.10 reported an efficient method for
the removal of the phenolic hydroxyl group on the
morphine nucleus, which they used to synthesize 11-
hydroxyaporphine (3). Our current studies focused on
the synthesis of several R())-11-hydroxyaporphines
with varying N-substituents, and preliminary investiga-
tions of their dopamine receptor affinities in rat brain
tissue as well as their oral bioavailability and duration of
action indicated as locomotor behavioral activation in
normal adult male rats.
dopaminergic potency and prolonged duration of
action.12 Accordingly, we prepared a series of esters of
varying chain length, in an effort to improve the bio-
availability and duration of action of the 11-hydroxy-
aporphines. Esters of representative long- (docosa-
hexaenoyl), intermediate- (valeryl), and short-chain
(acetyl) acids were prepared by reacting the appropriate
acid with N-ethyl-(14) or N-propyl-11-hydroxynor-
aporphine (4) in the presence of dicyclohexyl carbodi-
imide (DCC). Thus, esters 16–19 were obtained in 63–
75% yield (Scheme 1).
2.2. Pharmacology
2. Results and discussion
2.1. Chemistry
In vitro affinity of R())-N-alkyl-11-hydroxynorapor-
phines and their esters for the dopamine D1 and D2
receptors was determined using competition assays in
rat forebrain tissue (Table 1). The binding affinity of
R())-N-propylnorapomorphine (2) for the dopamine D2
receptor (Ki ¼ 9:9 nM) was very similar to that of R())-
apomorphine (1) (Ki ¼ 13:2 nM), whereas its D1 affinity
was somewhat lower. Among the four R())-N-alkyl-11-
hydroxynoraporphines 4, 5, 14, and 15, R())-N-n-pro-
pyl-11-hydroxynoraporphine (4) had the highest D2
affinity (Ki ¼ 28:5 nM), and lowest D1 affinity, and so
was selected for esterification. Affinity for the dopamine
D2 receptor decreased with increasing size of the ester
moiety: it was highest with acetyl (19), intermediate with
valeryl (18), and lowest with the docosohexanoyl ester
(17), suggesting increasing steric hindrance with
increasing chain length of the ester group.
Selective, catalytic removal of the 3-hydroxyl group
from morphine (6) employing
a modification of
Hedberg’s procedure10 via 3-O-[(trifluoromethyl)sulfo-
nyl]morphine (7) resulted in a high yield of 3-deoxy-
morphine (8)19 (Scheme 1). N-demethylation of 8 was
carried out with methyl chloroformate to yield 3-de-
oxynormorphine (9).19 N-alkylation of 9 with an
appropriate alkyl halide led to the N-substituted-3-de-
oxynormorphines 10–13. Acid-catalyzed rearrange-
ment11 of 10–12 with methanesulfonic acid at 90 ꢁC
yielded the corresponding R())-N-alkyl-11-hydroxyno-
raporphines 4, 5, 14. In the case of N-cyclopropyl-
methyl-3-deoxynormorphine (13), the desired aporphine
15 was not obtained, presumably due to the instability
of its N-substituent at this temperature. However, the N-
cyclopropylmethyl-11-hydroxynoraporphine (15) was
obtained by conducting the rearrangement at 60 ꢁC.
We considered the possibility that the affinity of the
esters, especially the acetate 19 may reflect hydrolysis to
the parent phenolic aporphine 4 under the conditions of
the radioreceptor labeling experiments. For this pur-
pose, we examined the products of the binding experi-
Long-chain fatty acid derivatives of clozapine are active
after oral administration, with greatly enhanced anti-
OH
OH
OH
OH
i
N
N
N
N
ii
iii, iv
H3C
O
H3C
O
H3C
H
O
O
OH
N
OSO2CF3
7
9
8
morphine 6
OH
N
H
R1
v
N
H
R1
R1
vi
vii
O
R2
O
HO
O
1
1
2
R
1
R
R
-C
R
H
-CH CH
-CH CH
21 31
-CH CH
-CH CH CH
3
-CH CH=CH
16
17
18
10
2
3
2
3
2
3
14
4
5
-C
H
-CH CH CH
21 31
2
2
3
3
2
2
-CH CH CH
3
11
2
2
-C H
4
-CH CH CH
9
2
2
2
2
-CH CH=CH
2
2
12
13
19 -CH CH CH
-CH
3
2
2
3
15
-H C
2
-H C
2
Scheme 1. Synthesis of N-alkylated-11-hydroxynoraporphines and their esters. Reagents and conditions: (i) PhNTf2, Et3N, CH2Cl2, overnight; (ii)
Pd(OAc)2, Ph3P, Et3N, HCOOH, DMF, 60 ꢁC; (iii) ClCOOCH3, NaHCO3 ; (iv) NH2NH2, reflux; (v) R1X, K2CO3, EtOH; (vi) CH3SO3H; (vii)
R2COOH, DCC, DMAP, CH2Cl2.

C. Csutoras et al. / Bioorg. Med. Chem. 12 (2004) 3553–3559
3555
Table 1. R())-N-alkyl-11-hydroxynoraporphines: affinity at rat brain dopamine receptors
Agents
Ki ꢀ SEM (nM)
D1
D2
Aporphines (comparison standards)
(1) R())-apomorphine
(2) R())-N-n-propylnorapomorphine (NPA)
(3) R())-11-hydroxyaporphine
214 18
733 74
26.5 1.0
13.2 2.1
9.9 1.0
108 10.8
R())-N-alkyl-11-hydroxynoraporphines
(4) R())-N-n-propyl-11-hydroxynoraporphine
(5) R())-N-allyl-11-hydroxynoraporphine
(14) R())-N-ethyl-11-hydroxynoraporphine
(15) R())-N-cyclopropylmethyl-11-hydroxynoraporphine
699 118
397 51
177 13
272 18
28.5 12.8
41.1 11.0
88.0 15.5
96.3 15.8
Esters of N-n-propyl-11-hydroxynoraporphine
(17) R())-N-n-propyl-11-docosahexanoyloxynoraporphine
(19) R())-N-n-propyl-11-acetyloxynoraporphine
(18) R())-N-n-propyl-11-valeryloxynoraporphine
>20,000
>10,000
>20,000
>10,000
72.3 6.8
340 65
ments after 1 h of incubation under the same conditions
as used in the radioligand competition assays (see
experimental section). We found by thin layer chroma-
tography (TLC, CHCl3/MeOH ¼ 10/1) that acetate 19
was partially hydrolyzed to its phenolic precursor 4.
despite its similar affinity at the D2 receptor and lower
D1 affinity. However, in contrast to R())-apomorphine
(1), the N-n-propyl analog (2) had unexpected oral
behavioral activity at a dose of 20 lmol/kg. Removing
the hydroxyl group from the 10-position as in 4 did not
significantly change its in vitro receptor-affinity profile.
Esterification of 4 significantly improved the oral bio-
availability, especially the acetate 19 and valerate 18.
The longer chain valerate ester 18 had somewhat lower
In vivo experiments (Table 2) indicated that R())-N-n-
propylnorapomorphine (2) produced significantly
greater behavioral arousal than R())-apomorphine (1)
Table 2. Motor activation induced by N-alkyl R-())-11-hydroxyaporphines and their esters in rats
Agent
Dose (lmol/kg)
Route
N
Activity score
Duration (h)
Catecholaporphine standard agents
(1) R())-apomorphine
4
4
i.p.
i.g.
i.g.
4
4
6
1
1
Inactive
Inactive
NA
NA
20
(2) R())-N-n-propylnoraporphine (NPA)
4
4
i.p.
i.g.
i.g.
8
8
6
12 5.2
Inactive
68 20.8
8
NA
14
20
N-alkyl R())-11-OH-aporphines
(4) R())-11-OH-N-n-propylnoraporphine
4
4
i.p.
i.g.
i.g.
4
4
5
24 12.3
Inactive
76 27.9
8
NA
18
20
(14) R())-11-OH-N-ethylnoraporphine
4
4
i.p.
i.g.
i.g.
5
4
4
12 5.2
Inactive
Inactive
4
NA
NA
20
Esters of N-propyl-11-hydroxynoraporphine
(17) R())-11-O-docosahexaenoyl-N-n-propyl
noraporphine
4
s.c.
4
Inactive
Inactive
NA
4
20
20
i.g.
s.c.
i.g.
4
4
4
NA
6
5 2.6
75 33.4
12
(18) R())-11-O-valeryl-N-n-propyl noraporphine
(19) R())-11-O-acetyl-N-n-propylnoraporphine
4
4
i.p.
i.g.
i.g.
4
4
4
53 10.0
Inactive
99 18.0
12
NA
14
20
4
4
i.p.
i.g.
i.g.
4
4
4
12 4.7
Inactive
168 33.5
8
NA
16
20
Activity score (total locomotor activity counts from start to return to baseline, normalized to a value of 1.0 for apomorphine, as mean SEM); NA:
not applicable; i.p.: intraperitoneal; i.g.: intragastric; s.c.: subcutaneous; N, number of rats.

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C. Csutoras et al. / Bioorg. Med. Chem. 12 (2004) 3553–3559
activity when given subcutaneously, and moderate oral
bioavailability (Table 2).
4.2. 3-O-[(Trifluoromethyl)sulfonyl]morphine (7)
A slurry of 6ÆH2O (10 g, 32.8 mmol) and Et3N (7 mL) in
anhydrous CH2Cl2 (500 mL) under nitrogen was stirred
for 1 h at rt. N-Phenyltrifluoro-methanesulfonimide
(14 g, 39.4 mmol) was added to the reaction mixture.
After stirring for 24 h, the reaction mixture was ex-
tracted with 10% (w/v) aqueous KHCO3 (3 · 70 mL).
The organic layer was dried on sodium sulfate, filtered,
and concentrated in vacuo. A solid product (24.5 g) was
obtained, which was dissolved in ether (80 mL), and
extracted with 1 M HCl (4 · 120 mL). The acidic layer
was basified with ammonium hydroxide. The mixture
was extracted with CH2Cl2 (3 · 100 mL). The organic
layer was washed with brine (100 mL), dried with
Na2SO4, filtered and evaporated, to afford a white solid
(13.13 g). The solid residue was washed with a small
amount of dry ether to yield 12.4 g (90%) of pure 7; mp:
122–124 ꢁC (Lit.10: 123–124 ꢁC), 1H and 13C NMR
spectra were identical with that of the literature data.10
3. Conclusions
We report an efficient procedure for the preparation of
N-substituted-R())-11-hydroxynoraporphines 4, 5, 14,
15 from morphine (6), by a sequence of selective re-
moval of a phenolic hydroxyl group, N-demethylation,
and realkylation with an appropriate alkyl halide fol-
lowed by methanesulfonic acid-catalyzed rearrange-
ment. Esterification of the mono hydroxyl- aporphine 4
with representative acids yielded the corresponding es-
ters 16–18.
Replacing the N-methyl group in R())-apomorphine (1)
with the n-propyl group slightly enhanced the affinity at
the D2 dopamine receptor, but decreased affinity at the
D1 receptor. Among the present series of 11-hydroxy-
aporphines, the N-n-propyl compound 4 gave the highest
affinity and selectivity at the D2 dopamine receptor, and
its affinity was lower than that of its catechol precursor
2. Esterification of 4 resulted in a slightly decreased
affinity at dopamine D2 receptors and substantial loss of
D1 affinity.
4.3. 3-Deoxymorphine (8)
Triphenylphosphine (1.2 g, 4.5 mmol) and palladium
acetate (0.48 g, 2.03 mmol) were added to a stirred mix-
ture of 7 (10.0 g, 23.98 mmol), triethylamine (15 mL,
106.9 mmol), and formic acid (1.8 mL, 45.1 mmol) in
DMF (32 mL) at 40 ꢁC under nitrogen. The mixture was
stirred under nitrogen for 5 h, at 60 ꢁC. After cooling to
room temperature (RT), the reaction mixture was added
dropwise to a cooled solution of HCl (30 mL) in water
(300 mL). The acidic solution was extracted with CH2Cl2
(4 · 100 mL). The aqueous layer was basified with
ammonium hydroxide upon cooling, and then extracted
with CH2Cl2 (3 · 100 mL). The organic layer was washed
with brine (100 mL), dried with sodium sulfate, filtered,
and evaporated. The solid residue was filtered from dry
ether, washed with ether, to provide 5.7 g (88%) of 8; mp:
224–227 ꢁC (Lit.10: 227–229 ꢁC). 1H and 13C NMR
spectra were identical to the reported values.10
In vivo potency and oral activity of the compounds
evaluated indicated greater behavioral potency and
duration of locomotor behavioral activation of system-
ically injected (i.p.) N-n-propyl (4) than N-ethyl (14) 11-
hydroxynoraporphine. We esterified the 11-hydroxyl
function of 4 with a series of short (acetic, 19), moderate
(valeric, 18), and long-chain (docosahexaenoic or DHA,
16) acids and evaluated their in vivo pharmacological
activity. We found maximal behavioral potency after
systemic injection with the intermediate valeryl ester (17)
following parenteral injection, but with the acetate ester
(19) after enteric (intragastric) administration.
4.4. 3-Deoxynormorphine (9)
4. Experimental
3-Deoxynormorphine (9) was prepared according to the
reported procedure.19
4.1. Chemical synthesis
Melting points were measured with a Thomas Hoover
Capillary Melting Point Apparatus, and are uncor-
rected. 1H and 13C NMR spectra were obtained on
Varian 300 spectrometer, chemical shifts are reported in
ppm (d) from internal TMS and coupling constants (J)
were measured in Hz. Thin layer chromatography (TLC)
was performed on precoated Merck 5554 Silica gel 40
F254 foils, and the spots were visualized with Drag-
endorff’s reagent. Mass spectra were measured with a
Hewlett Packard 5972 series GC–MS instrument. APO
(1) and NPA (2) were synthesized by the procedure of
Granchelli et al.11 and Berenyi et al.13 using the me-
thanesulfonic acid-catalyzed rearrangement of the
appropriate morphinanes.
4.5. General procedure for the synthesis of N-alkyl-3-
deoxynormorphines (10–13)19
To a stirred mixture of 9 (0.5 g, 1.96 mmol), and
NaHCO3 (0.25 g, 2.98 mmol) in anhydrous ethanol
(10 mL) the appropriate alkyl halide (2.5 mmol) was
added slowly, under nitrogen. The reaction mixture was
allowed to reflux at 80–90 ꢁC for 24 h. Water (40 mL)
was then added to the reaction mixture, followed by
extraction into ethyl acetate (3 · 20 mL). The organic
layer was washed with brine (20 mL), dried with sodium
sulfate, filtered, and evaporated in vacuo. The oily crude
product was purified by column chromatography with
9:1 (vols) chloroform:methanol to afford pure oils.

C. Csutoras et al. / Bioorg. Med. Chem. 12 (2004) 3553–3559
3557
4.6. General procedure for the synthesis of R())-N-alkyl-
11-hydroxynoraporphine hydrochlorides (4, 5, 14, 15)
H-2), 7.94 (1H, d, J ¼ 7:9 Hz, H-1); 13C NMR (base,
CDCl3) d 2.9, 5.0, 7.4, 29.1, 34.8, 49.1, 59.1, 59.2, 115.5,
120.4, 121.3, 124.3, 126.3, 127.6, 128.0, 131.3, 133.7,
136.1, 138.3, 152.7; MS m=z (rel. intensity) 291 (M,
70%), 290 (M-1, 100%). Anal. (C20H21NOꢁHCl) Calcd:
C, 73.27; H, 6.76; N, 4.27. Found: C, 73.25; H, 6.76; N,
4.25.
The appropriate N-alkyl-3-deoxynormorphine (10–13)
(1.45 mmol) was dissolved in 99% methanesulfonic acid
(4 mL, 62 mmol), under nitrogen at RT. The reaction
mixture was stirred for 30 min at 90 ꢁC, and then cooled
to RT. Ice-water (20 mL) was added and the mixture
was basified with ammonia, extracted with CH2Cl2
(3 · 20 mL), and the organic layer was washed with brine
(20 mL), dried over sodium sulfate and evaporated in
vacuo to provide an oily crude product. Purification by
column chromatography with 19:1 (vols) chloro-
form:methanol provided a pure oily product, which was
converted into the hydrochloride salt with 1 M HCl–
ether.
4.11. General procedure for the synthesis of R())-N-
alkyl-11-hydroxynoraporphine esters (16–19)14
The appropriate R())-N-alkyl-11-hydroxynoraporphine
(4, 14) (0.5 mmol), corresponding acid (0.6 mmol) and a
catalytic amount of 4-dimethylaminopyridine (DMAP)
were dissolved in anhydrous dichloromethane (20 mL)
under nitrogen. To the stirred mixture, a solution of
N,N0-dicyclohexyl-carbodiimide (130 mg, 0.6 mmol) in
anhydrous dichloromethane (6 mL) was added at RT.
After stirring for 4 h, the reaction mixture was
filtered and evaporated to dryness. The crude oily
product was purified by column chromatography with
5:2 (vols) hexane–ethyl acetate to obtain a pure oily
product.
4.7. R())-N-ethyl-11-hydroxynoraporphine hydrochloride
(14)
White solid (53%), mp>250 ꢁC (dec.); 1H NMR
(CD3OD) d 1.47 (3H, t, CH3), 2.85 (1H, m, C–H), 3.30
(5H, m, C–H), 3.97 (2H, m, C–H), 4.43 (1H, m, C–H),
6.88 (2H, m, H-8, H-10), 7.12 (1H, t, H-9), 7.18 (1H, d,
J2;3 ¼ 9 Hz, H-3), 7.37 (1H, t, H-2), 8.40 (1H, d,
J1;2 ¼ 9 Hz, H-1); MS m=z (rel. intensity) 265 (M, 60%).
Anal. (C18H19NOꢁHCl) Calcd: C, 71.64; H, 6.63; N,
4.64. Found: C, 71.58; H, 6.65; N, 4.62.
4.12. R())-N-ethyl-11-docosahexaenoyloxynoraporphine
(16)
Starting from R())-N-ethyl-11-hydroxynoraporphine
(14) and cis-4,7,10,13,16,19-docosahexaenoic acid
1
4.8. R())-N-n-propyl-11-hydroxynoraporphine hydro-
chloride (4)
(DHA), the product is a syrupy oil (180 mg, 63%): H
NMR (CDCl3) d 0.97 (3H, t, CH3), 1.16 (3H, t, CH3),
2.07 (2H, m, C–H), 2.50 (8H, m, C–H), 2.85 (10H, s, C–
H), 3.15 (4H, m, C–H), 3.48 (1H, m, C–H), 5.37 (12H, s,
@C–H), 7.00 (1H, d, J9;10 ¼ 8 Hz, H-10), 7.07 (1H, d,
J8;9 ¼ 8 Hz, H-8), 7.21 (3H, m, H-2, H-3, H-9), 7.74
(1H, d, J1;2 ¼ 8 Hz, H-1). Anal. (C40H49NO2) Calcd: C,
83.43; H, 8.58; N, 2.43. Found: C, 83.22; H, 8.60; N,
2.43.
White solid (52%); mp>250 ꢁC (dec.) (Lit. [4]: 257–
258 ꢁC).
4.9. R())-N-allyl-11-hydroxynoraporphine hydrochloride
(5)
White solid (50%), mp: 186–190 ꢁC. 1H NMR (CD3OD)
d 2.86 (1H, m, C–H), 3.30 (4H, m, C–H), 3.98 (2H, m,
C–H), 4.38 (2H, m, C–H), 5.72 (2H, m,@C–H), 6.09
(1H, m, @C–H), 6.89 (2H, d, J ¼ 8:5 Hz, H-8, H-10),
7.12 (1H, t, H-9), 7.18 (1H, d, J ¼ 8:2 Hz, H-3), 7.36
(1H, t, H-2), 8.41 (1H, d, J ¼ 8:2 Hz, H-1); MS m=z (rel.
intensity) 277 (M, 50%). Anal. (C18H17NOꢁHClꢁH2O)
Calcd: C, 65.16; H, 6.03; N, 4.22. Found: C, 65.25; H,
6.04; N, 4.23.
4.13. R())-N-n-propyl-11-docosahexaenoyloxynorapor-
phine (17)
Starting from R())-N-propyl-11-hydroxynoraporphine
(4) and cis-4,7,10,13,16,19-docosahexaenoic acid (DHA),
the product was obtained as a syrupy oil (210 mg, 71%):
1H NMR (CDCl3) d 0.97 (6H, t, 2 · CH3), 1.58 (2H, m,
C–H), 2.07 (2H, m, C–H), 2.55 (9H, m, C–H), 2.85
(10H, s, C–H), 3.10 (3H, m, C–H), 3.41 (1H, d, C–H)
5.37 (12H, s, @C–H), 7.00 (1H, d, J9;10 ¼ 8 Hz, H-10),
7.07 (1H, d, J8;9 ¼ 8 Hz, H-8), 7.21 (3H, m, H-2, H-3, H-
9), 7.72 (1H, d, J1;2 ¼ 8.5 Hz, H-1). Anal. (C41H51NO2)
Calcd: C, 83.49; H, 8.71; N, 2.37. Found: C, 83.25; H,
8.74; N, 2.36.
4.10. R())-N-cyclopropylmethyl-11-hydroxynoraporphine
hydrochloride (15)
The reaction was conducted at 60 ꢁC and the hydro-
chloride was obtained as a white solid (36%); mp: 195–
1
200 ꢁC (dec.). H NMR (base, CDCl3) d 0.20 (2H, m,
cyclopropyl C–H), 0.56 (2H, m, cyclopropyl C–H), 1.00
(1H, m, cyclopropyl C–H), 2.40 (1H, q, C–H), 2.58 (2H,
m, C–H), 2.79 (1H, m, C–H), 3.08 (3H, m, C–H), 3.45
(2H, m, C–H), 6.78 (1H, d, J ¼ 8:5 Hz, H-8), 6.84 (1H,
d, J ¼ 8:5 Hz, H-10), 7.06 (2H, t, H-9, H-3), 7.26 (1H, t,
4.14. R())-N-n-propyl-11-valeryloxynoraporphine
hydrochloride (18)
Starting
from
porphine (4) and valeric acid, the oily product was
R())-N-n-propyl-11-hydroxynora-

3558
C. Csutoras et al. / Bioorg. Med. Chem. 12 (2004) 3553–3559
converted to the hydrochloride salt with HCl–ether to
provide a white solid product (150 mg, 75%): mp: 232–
234 ꢁC (dec.). H NMR (base, CDCl3) d 0.95 (6H, m,
In vivo pharmacology: In vivo potency and oral bio-
availability of synthesized aporphine derivatives were
determined by measuring stimulation of motor activity
in adult male Sprague–Dawley rats using a microcom-
puter-controlled photobeam activity monitoring system
(San Diego Instruments; San Diego, CA), as was de-
tailed previously.18 The number of rats in each experi-
mental group ranged from 4 to 8. Oral delivery of test
agents was achieved using a permanently surgically
preimplanted polyethylene gastric tube to avoid stress
associated with conventional oral intubation. For this
surgery, rats were anesthetized with 60 mg/kg sodium
pentobarbital (injected intraperitoneally, i.p.). PE50
tubing was inserted and sutured to the stomach, and led
subcutaneously to a point of access on the back of the
neck, where it was sutured in place. Animals were al-
lowed at least two weeks to recover prior to behavior
testing. At the end of the experiments, rats were sacri-
ficed with carbon dioxide. The function of the gastric
tube was checked postmortem by injecting dye to ensure
that drugs delivered using this method did not reach
sites other than the gastric lumen.
1
2 · CH3), 1.37 (2H, m, C–H), 1.75 (4H, m, C–H), 2.50
(5H, m, C–H), 2.75 (1H, d, C–H), 2.90 (1H, m, C–H),
3.18 (3H, m, C–H), 3.41 (1H, d, J ¼ 13 Hz, C–H), 7.00
(1H, d, J9;10 ¼ 8 Hz, H-10), 7.07 (1H, d, J8;9 ¼ 7 Hz, H-8),
7.21 (3H, m, H-2, H-3, H-9), 7.74 (1H, d, J1;2 ¼ 7:5 Hz,
H-1); 13C NMR (base, CDCl3) d 12.0, 13.6, 19.5, 22.2,
26.7, 29.3, 34.3, 35.0, 48.8, 56.5, 59.1, 122.1, 124.7,
125.8, 125.9, 127.3, 127.6, 128.1, 130.6, 133.6, 135.8,
138.6, 147.3, 171.9; MS m=z (rel. intensity) 363 (M,
60%); HPLC: 99% purity. Anal. (C24H29NO2ÆHCl)
Calcd: C, 72.07; H, 7.56; N, 3.50. Found: C, 71.91; H,
7.58; N, 3.51.
4.15. R())-N-n-propyl-11-acetyloxynoraporphine
hydrochloride (19)
Starting from R())-N-propyl-11-hydroxynoraporphine
(4) and glacial acetic acid, column chromatographic
purification was carried out with 19:1 (vols) chloro-
form:methanol, and an oily product obtained was con-
verted to the hydrochloride salt with HCl–ether to
provide a white solid product (120 mg, 67%); mp: 250–
Potency of aporphine test agents was expressed as the
sum of behavioral scores at each time of rating until
locomotor responses returned to their pre-injection
baseline levels, and relative to that (standard score ¼ 1)
produced by i.p. injection of 4 lmol/kg R())-apomor-
phine (1), the effects of which lasted for one hour. In
addition to the activity sum-score, duration of action is
also shown in Table 2.
1
252 ꢁC (dec.). H NMR (base, CDCl3) d 0.96 (3H, t,
CH3), 1.65 (2H, m, C–H), 2.27 (3H, s, COCH3), 2.50
(3H, m, C–H), 2.75 (1H, m, C–H), 2.90 (1H, m, C–H),
3.12 (3H, m, C–H), 3.40 (1H, m, C–H), 7.02 (1H, d,
J9;10 ¼ 8 Hz, H-10), 7.07 (1H, d, J8;9 ¼ 8 Hz, H-8), 7.21
(3H, m, H-2, H-3, H-9), 7.75 (1H, d, J1;2 ¼ 7:5 Hz, H-1);
13C NMR (base, CDCl3) 12.0, 19.5, 21.3, 29.3, 35.0,
48.8, 56.5, 59.2, 122.0, 124.5, 125.9, 126.0, 127.3, 127.7,
128.2, 130.6, 133.7, 135.9, 138.6, 147.2, 169.2; MS m=z
(rel. intensity) 321 (M, 70%); HPLC: 97% purity. Anal.
(C21H23NO2ꢂHCl) Calcd: C, 70.48; H, 6.76; N, 3.91.
Found: C, 70.42; H, 6.80; N, 3.89.
Acknowledgements
The authors acknowledge the Branfman Family Foun-
dation, as well as the Bruce J. Anderson Foundation
and the McLean Private Donors Neuropharmacology
Research Fund for financial support of this work.
Morphine was generously supplied by Mallinkrodt Inc.
We also thank Jane McNeil for the mass spectroscopy
determinations and Xuemei Peng for assistance in the
preparation of the manuscript.
4.16. Pharmacology
In vitro neuropharmacology: Affinity of R())-N-alkyl-11-
hydroxynoraporphines (4, 5, 14, 15) and their esters (17–
19) for dopamine D1 and D2 receptors was determined
in radioligand competition assays, using membrane
preparations from DA-rich corpus striatum (caudatop-
utamen) tissue from rat forebrain. Adult male Sprague–
Dawley rats were sacrificed by decapitation following
carbon dioxide narcosis. Brains were quickly removed
and dissected on ice. Tissue was homogenized in 50 mM
Tris–HCl buffer (pH 7.4) containing 150 mM NaCl,
washed twice and resuspended in the same buffer. For
the D1 receptor assay, homogenate was incubated with
300 pM [3H]SCH-23390 (NEN; Boston, MA) for 30 min
at 30 ꢁC; nonspecific binding was defined with excess
(10 lM) cis-flupenthixol.15 For the D2 receptor assay,
homogenate was incubated with 75 pM [3H]nemona-
pride (NEN; Boston, MA) for 90 min at 30 ꢁC; non-
specific binding was defined with 10 lM haloperidol.16;17
Experiments were carried out in triplicate. Results
from these radioligand competition assays are shown in
Table 1.
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