D1 agonist and/or D2 antagonist dopamine receptor properties of a series of ergoline derivatives: A structure-activity study

Article abstract of DOI:10.1016/S0223-5234(99)80045-2

A series of (3,5-dioxopiperazin-1-yl)ergoline derivatives has been synthesised and evaluated in vitro and in vivo for their dopaminergic D₁ and D₂ components. The structural contributions to the pharmacological profile of the ergoline skeleton, its substituents on positions 1, 2, 6, 9, and the 3,5-dioxopiperazin-1-yl portion of the molecule were examined. Structure- activity relationships within this series suggested that substitution on the ergoline skeleton in position 1 or 2 and on the 3,5-dioxopiperazin-4-nitrogen generated compounds with a spectrum of dopamine agonistic/antagonistic activity sensitive to both the nature and position of substituents.

Full text of DOI:10.1016/S0223-5234(99)80045-2

Eur. J. Med. Chem. 34 (1999) 107−124
© Elsevier, Paris
107
Original article
D1 Agonist and/or D2 antagonist dopamine receptor properties of a series
of ergoline derivatives: a structure–activity study
Sergio Mantegani*, Emanuele Arlandini, Tiziano Bandiera, Daniela Borghi, Enzo Brambilla,
Carla Caccia, Maria Antonietta Cervini, Paolo Cremonesi, Robert Albert McArthur,
Gabriella Traquandi, Mario Varasi
Pharmacia & Upjohn S.p.A., Viale L. Pasteur 10, 20014 Nerviano, Milano, Italy
(Received 14 May 1998; accepted 4 September 1998)
Abstract – A series of (3,5-dioxopiperazin-1-yl)ergoline derivatives has been synthesised and evaluated in vitro and in vivo for their
dopaminergic D1 and D2 components. The structural contributions to the pharmacological profile of the ergoline skeleton, its substituents on
positions 1, 2, 6, 9, and the 3,5-dioxopiperazin-1-yl portion of the molecule were examined. Structure–activity relationships within this series
suggested that substitution on the ergoline skeleton in position 1 or 2 and on the 3,5-dioxopiperazin-4-nitrogen generated compounds with a
spectrum of dopamine agonistic/antagonistic activity sensitive to both the nature and position of substituents. © Elsevier, Paris
ergoline derivatives / structure–affinity relationship / dopaminergic / antidopaminergic activity
1. Introduction
Semi-synthetic ergoline derivatives possess a wide and
divergent spectrum of pharmacological activities includ-
ing central, peripheral and neurohumoral effects, due
mainly to their capability to bind unselectively to adren-
ergic, dopaminergic and serotonergic receptor sites [1, 2].
Compounds of this class may act not only as agonists or
antagonists at the receptor sites of biogenic amine neu-
rotransmitters, but they may also assume a partial agonist
and antagonist role. Of particular significance for drug
Figure 1.
discovery and development is the dopamine agonist
activity of ergolines, which has many important clinical
implications [3–6]. Structure–activity studies have shown
management of hyperprolactinemic states and Parkin-
how the side chain at C-8 and suitable modifications of
son’s disease [9–12] respectively, while nicergoline is
the ergoline skeleton were determinant for the pharma-
used for the treatment of senile mental impairment [13,
cological profile of this class of compounds [7, 8]. Some
14] (figure 1).
semisynthetic ergolines are used to treat a number of
clinical conditions. The selective dopamine agonists per-
golide and cabergoline, for example, are used in the
In identifying antihypertensive ergolines, we have
observed that PNU 160425 had a very promising antihy-
pertensive activity [15, 16]. This prompted us to synthe-
sise analogues to discover more potent and selective
compound. Replacement of the perhydro-2,4-
dioxopyrimidin-1-yl by the isomer 3,5-dioxo-piperazin-
*Correspondence and reprints
1-yl moiety led to 1 (PNU 160260) (figure 2).

108
properties in denervated models in the same dose range.
In normal animals, 1 impairs Sidman avoidance in rats,
reduces spontaneous locomotion in mice and monkeys.
Compound 1 also antagonises apomorphine-induced
climbing behaviour in mice, yawning in rats, emesis in
dogs and amphetamine-induced toxicity in grouped mice.
However, after severely depleting central dopamine ex-
perimentally, 1 behaves as a powerful dopamine D1
receptor agonist. This compound induces contralateral
turning behaviour in 6-hydroxydopamine-lesioned rats
and reverses 1-methyl-4-phenyl-1,2,3,6-tetrahydro-
pyridine-induced akinesia in monkeys and reserpine-
induced hypokinesia in mice. Consequently 1 acts as a D2
receptor antagonist under normal physiological condi-
tions but is able to stimulate the D1 receptors preferen-
tially when endogenous dopamine is no longer available.
Mixed agonist/antagonist activity on brain dopamine
receptors has been reported for other ergot derivatives
Figure 2.
Thus, it was found that 1 was devoid of antihyperten-
sive activity but showed a unique central pharmacologi-
cal profile. This compound behaves as a full dopamine
antagonist in normal animals, but shows full agonist
Figure 3.

109
with different pharmacological profile, but to our knowl-
edge none of these change from antagonist to agonist
depending on the functional state of the substrate [17,
18]. These interesting findings prompted us to investigate
the biological properties of a series of analogues of 1.
Through systematic alteration of the parent molecule it
was hoped to define the features of the structure that may
be critical for the appearance of the unusual biological
activities endowed by the whole molecule. In order to
achieve this goal, a series of analogues presented in this
paper was prepared and characterised in vitro and in vivo.
The synthesis and the pharmacological properties of new
compounds are described and the structure–activity rela-
tionship explored [19].
tively to the dicarbamides II or to the diacylhydrazide
derivatives III respectively. These can be easily con-
verted into the 3,5-dioxopiperazin-1-yl derivatives IV,
1–4, 11–14 and V, 19, in high yield, by heating in phenol
at 160 °C in a flow of nitrogen. Electrophilic substitution
into the most reactive position 2, with N-bro-
mosuccinimide in tetrahydrofuran [20], or with methyl-
sulphenylchloride in dichloromethane [21], or with sul-
phurylchloride in presence of catalytic amount of
borotrifluoride in acetonitrile [22], converted 1 into 5–7
in almost quantitative yield, whilst reduction with sodium
borohydride in trifluoroacetic acid at low temperature
afforded, in acceptable yield, the indoline 8 accompanied
by a low amount of its 3α-H stereoisomer and by dimeric
products [23, 24]. Catalytic hydrogenation of 1, 2, 10, 15,
16 in acetic acid mainly provided the 10 α saturated
analogues 20–24, accompanied by their 10â-isomers
present in small amount. These cis and trans isomers were
readily separated using medium-pressure liquid chroma-
tography or fractional crystallisation from acetone. Ac-
cording to the von Braun methodology, the 6-desmethyl
derivative 9 was obtained in good yield by treatment of 1
with cyanogen bromide in dimethylformamide at room
temperature providing 6-cyano analogue IX, that was
subsequently reduced by Zn powder in acetic acid [25].
The propyl derivative 10 was prepared through alkylation
of 9 with propyliodide in dimethylformamide in presence
of triethylamine. A more versatile and efficient method
that allows the preparation of a wide variety of (3,5-
2. Chemistry
Compounds in tables I and II were prepared as
outlined in figures 3 and 4.
Condensation of ∆-9,10-ergolenylamines 27–35 with
ethylbromoacetate in dimethylformamide in the presence
of potassium carbonate yielded iminodiacetic acid diethyl
ester derivatives I as major product accompanied by a
small amount of N-(ethoxycarbonylmethyl)-N-(ethoxy-
carbonylmethoxycarbonyl)-lysergamine
derivatives,
stemming from carbonatation and subsequent alkylation
of the glycine ester intermediates. Reaction of the inter-
mediates I with ammonia in dimethylformamide or hy-
drazine hydrate in refluxing ethanol, led almost quantita-
Figure 4.

110
Table I. Chemical data of the ergoline derivatives 1–13.
Compound
R
R1
R2
R3
X–Y
Formula
M.p. (°C)
1
H
H
CH3
CH=CH
C20H22N4O2
208–210
2
CH3
H
CH3
CH=CH
CH=CH
CH=CH
CH=CH
CH=CH
CH=CH
CH=CH
CH=CH
CH=CH
C21H24N4O2
C22H26N4O2
C23H28N4O2
C20H21BrN4O2
C20H21ClN4O2
C21H24N4O2S
C20H24N4O2
C19H20N4O2
C22H26N4O2
216–218
129–131
137–140
242–245
239–240
206–208
135–140
212–214
250–253
3
CH3CH2
H
CH3
4
(CH3)2CH
H
CH3
5
H
H
H
H
H
H
Br
CH3
6
Cl
CH3
7
CH3S
2,3-H2
H
CH3
8
CH3
9
H
10
H
CH3CH2CH2
11
12
H
H
H
H
CH3
CH3
CH=CH
CH=CH
C20H22N4O2
231–235
237–238
C19H20N4O2
13
H
H
CH3
CH=CH
C19H20N4O2
145–160

111
Table II. Chemical data of the ergoline derivatives 14–26.
Compound
R
R1
R2
R3
X–Y
Formula
M.p. (°C)
14
H
H
CH3
CH=CH
C21H24N4O2
242–244
15
16
H
H
H
H
CH3
CH3
CH=CH
CH=CH
C21H24N4O2
227–229
240–242
C26H26N4O2
17
18
H
H
H
H
CH3
CH3
CH=CH
CH=CH
C28H30N4O2
239–241
265–268
C26H32N4O2
19
20
H
H
H
H
CH3
CH3
CH=CH
CH2–CH
C20H23N5O2
224–226
260–262
C20H24N4O2
21
22
CH3
H
H
CH3
CH2–CH
CH2–CH
C21H26N4O2
268–270
276–278
H
CH3CH2CH2
C22H28N4O2
23
24
25
26
H
H
H
H
H
H
H
H
CH3
CH3
CH3
CH3
CH2–CH
CH2–CH
CH2–CH
C21H26N4O2
C26H28N4O2
C20H25N5O2
C20H24N4O3
235–237
260–262
210–212
278–280

112
Figure 5.
dioxopiperazin-1-yl)ergoline derivatives from iminodi-
acetic acid derivative V and aliphatic or aromatic primary
amines, under mild reactions condition, is shown in
figure 4.
late in accordance with the Mitsunobu methodology [28].
The amines required for compounds 1–4, 11–14, 26 listed
in tables I and II were prepared as shown in figure 5.
6-Methyl-∆-9,10-didehydroergolin-8â-methanamine
(lysergamine) 27 and 6-methyl-∆-9,10-didehydroergolin-
8α-methanamine (isolysergamine) 28 were synthesised
from lysergol and isolysergol, after conversion into the
phthalimido derivatives by reaction with phthalimide,
triphenylphosphine and diethylazodicarboxylate in tet-
rahydrofuran, followed by deblocking of the phthalimido
group with hydrazine hydrate [28]. Analogously, 1,6-
dimethyl-∆-9,10-didehydroergolin-8â-methanamine 29,
1-ethyl-6-methyl-∆-9,10-didehydroergolin-8â-methana-
mine 30 and 1-isopropyl-6-methyl-∆-9,10-didehydro-
ergolin-8â-methanamine 31 were prepared as for 28,
starting from the corresponding 1-alkyl-lysergols, ob-
tained by indole-nitrogen alkylation of lysergol with alkyl
iodides in DMSO in presence of ground potassium
hydroxyde [29]. 6-Methyl-∆-9,10-didehydroergolin-8â-
amine 32 and 6-methyl-∆-9,10-didehydroergolin-8α-
amine 33 were prepared through a Curtius degradation
This method, based on the reaction of a acylimida-
zolide with a amide to form the imidic bond, gave rise in
good yield to the 1-aryl or 1-heteroaryl-piperazin-2,6-
dione derivatives which are quite inaccessible employing
the former methodology. Mono saponification of I with
potassium hydroxyde in ethanol gave the monoesters V.
This intermediate was subsequently converted into the
desired amido-esters VI by way of the acylimidazolide
with 1,1’-carbonyldiimidazole in dioxane. Saponification
of the ester function gave the acid-amides VII quantita-
tively. Ring closure of VII, after addition of 1 equivalent
of 1,1’-carbonyldiimidazole, proceeded efficiently and
cleanly in dioxane at reflux providing the piperazindiones
15–18 [26, 27]. Alternatively, 3,5-dioxopiperazin-4-
nitrogen derivatives, such as 15 and 18, can be prepared
from 1 by reaction with methanol or cyclohexanol in
presence of triphenylphosphine and diethylazodicarboxy-

113
Table III. In vitro characterization for the ergoline derivatives 1–26. Affinities are expressed as IC50 in µM, standard errors are ±10 % of the
mean reported values.
Compound
α1
α2
D1
D2
5-HT1
5-HT2
1
2
3
4
5
6
7
8
0.113
0.213
0.664
1.593
0.007
0.006
0.031
6.404
0.175
0.732
0.634
2.450
1.80
0.157
0.507
0.453
0.786
0.321
2.407
1.705
0.302
0.795
1.302
1.20
0.004
0.059
0.022
0.011
0.019
0.015
0.004
0.612
0.351
0.012
0.073
0.231
0.355
0.031
0.042
0.031
0.021
0.078
0.342
0.503
0.364
0.071
1.311
0.377
0.201
0.568
0.055
0.064
0.097
0.112
0.173
0.121
0.231
1.015
0.234
0.090
0.632
2.467
5.13
0.643
0.418
0.286
> 10
0.145
> 10
0.006
0.007
0.018
0.043
0.002
0.0008
0.001
0.284
0.046
0.004
0.122
> 10
0.254
0.210
0.030
0.030
0.784
0.019
0.132
0.065
0.022
0.004
0.133
0.062
0.088
0.697
0.023
0.160
0.683
1.122
0.272
0.040
0.404
0.058
0.026
0.023
0.014
4.876
0.251
0.036
0.031
0.021
0.579
0.167
0.213
> 10
0.024
0.009
0.006
0.021
0.058
0.074
0.071
0.862
4.121
0.154
0.087
> 10
0.153
0.143
0.075
0.142
0.347
0.047
0.518
0.392
0.065
0.572
0.222
5.554
0.282
0.763
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
0.493
0.143
0.333
1.804
> 10
> 10
0.853
> 10
> 10
1.23
4.40
3.46
0.461
0.574
2.54
carried out on the hydrazides of lysergic acid [30],
whereas 6-methyl-∆-9,10-didehydroergolin-8â-ethyl-
amine 34 was provided by lithium aluminium hydride
reduction of 6-methyl-∆-9,10-didehydroergolin-8â-
3.1. In vitro characterization
The compounds described in this study were evaluated
for their α1, α2, D1, D2, 5-HT1 and 5-HT2 receptor
binding affinities assessed by measurement of the dis-
placement of [3H]-prazosin binding in rat frontal cor-
tex [33], [3H]-yohimbine binding in rat frontal cor-
tex [34], [3H]-SCH-23390 binding in rat striatum [35],
[3H]-spiroperidol binding in rat striatum [36], [3H]-5-HT
binding in rat hippocampus [37] and [3H]-ketanserin
binding in rat pre-frontal cortex [38] respectively, and the
results are reported in table III.
acetonitrile [31].
6-Methyl-9α-hydroxy-dihydrolyser-
gamine 35 was prepared from of 9α-hydroxy-
dihydrolysergol, stemming from oxidative hydroboration
of methyl lysergate [32], followed by conversion of
hydroxymethyl into aminomethyl as described previously
for the analogues.
3. Pharmacology
3.2. In vivo characterization
Screening in vitro was based on binding affinity studies
for the receptors of neurotransmitters. This work was
paralleled by in vivo evaluation of their antidopaminergic
(antagonism of the apomorphine-induced climbing be-
haviour in normal rat) and dopaminergic component
(contralateral turning behaviour in 6-hydroxydopamine
lesioned rat). Classical structural modifications of the
lead compound 1 were undertaken to investigate the role
of the different functionalities present in the molecule.
The functional evaluation of the antidopaminergic or
dopaminergic component present in the compounds ex-
amined was assessed as follows, and the results are
reported in table IV.
3.2.1. Antagonism of apomorphine-induced climbing
behaviour in rats
The inhibition of apomorphine-induced climbing be-
haviour was employed as a method for detecting potential

114
Table IV. In vivo characterization of the ergoline derivatives 1–26. Number of turns are the mean values of five experiments. APO:
apomorphine; 6-OH-DA: 6-hydroxydopamine: turning/treated: 6-OH-DA lesioned rats.
Compound Antagonism of APO-induced
climbing behaviour
Contralateral turning behaviour
in 6-OH-DA lesioned rats
Turning/treated rats
mg/kg s.c.
% Inhib.
mg/kg s.c.
Turns in 6 h
1
2
3
4
5
6
7
8
0.4
0.2
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
89
100
61
42
89
91
76
26
17
26
41
0
0.1
0.5
0.5
0.5
0.5
0.05
0.05
0.5
0.5
0.05
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1
2423
1668
391
1102
2075
3351
3567
–
10/10
4/4
1/4
3/5
4/4
7/7
5/5
0/4
0/4
3/4
5/5
0/5
0/5
0/4
4/4
4/4
5/5
0/5
5/5
1/5
4/4
4/4
4/4
4/4
2/4
0/4
9
–
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
1146
1058
–
–
–
1841
3056
1588
–
1687
312
710
2475
1828
1716
345
–
0
0
84
0
12
15
10
0
10
11
0
1
1
0.5
1
0.5
1
0
0
5
0.5
antipsychotic agents. In fact, both typical and atypical
antipsychotic agents antagonise the response [39]. Ex-
periments suggested that D2 receptors appear to be
primarily responsible for the mediation of climbing in the
rats, while the D1 receptors would appear to have a role
in potentiating the climbing response induced by D2
stimulation. The requirement for both D1 and D2 receptor
stimulation to produce climbing behaviour is experimen-
tally supported by the fact that both D1 and D2 antago-
nists will inhibit apomorphine-induced climbing [40–42].
receptor
supersensitivity
in
the
denervated
striatum [43–45]. This action can be blocked by their
respective antagonists [46]. Moreover, taking into ac-
count only dopaminergic mechanism, experimental re-
sults indicate a physiological interaction between D1 and
D2 receptors [47]. The result of this test is predictive for
a potential anti-Parkinson activity, inasmuch as the den-
ervation of catecholaminergic pathway, loss of neu-
rotransmitters from nerve terminals, and the development
of postsynaptic DA receptor supersensitivity, as a conse-
quence of injection of 6-OHDA, resemble the pathologi-
cal and biochemical manifestation of Parkinson’s disease.
3.2.2. Contralateral turning behaviour in 6-OHDA-
lesioned rats
The compounds were evaluated in rats with unilateral
6-OHDA-induced lesions of the nigro-striatal DA path-
way. This model is commonly used for in vivo screening
of potential dopamine agonists. In this preparation, either
directly acting non selective or selective D1- and D2-
agonists induce a rotational turning behaviour towards
the non-lesioned side (contralateral rotation), which is
brought about by the development of postsynaptic DA
4. Results
4.1. Modifications on the indole nitrogen 2–4
The D2 component was slightly decreased when the
indole nitrogen was substituted by a linear group, a
methyl or ethyl as in 2, 3, and more significantly by a
branched alkyl group, an isopropyl as in 4. On the

115
contrary, the 5-HT2 component was enhanced particularly
in 3 reaching nanomolar values. An appreciable increase
in the antidopaminergic activity was observed for 2,
whilst the dopaminergic activity was diminished or al-
most suppressed as in the case of 3.
was also observed for 16–18. As far as the dopaminergic
activity is concerned, only 16 maintained a significant
activity, albeit lower than 1. This compound was devoid
of the antidopaminergic component present in the parent.
It is interesting to note that increasing the bulkiness of the
substituent led to a substantial decrease in in vitro and in
vivo dopaminergic activity as observed for 17. Finally,
the cyclohexyl derivative 18 was inactive.
4.2. Modifications on the position 2 of the indole ring
5–8
Substitution by a halogen atom (chlorine or bromine),
or by a thiomethyl strongly enhanced the α1 and D2
affinities. A subnanomolar D2 affinity was revealed for 6.
Conversely, these substitutions appear to be detrimental
for the 5-HT1 and 5-HT2 serotonergic components. These
substitutions have virtually no influence on the in vivo
antidopaminergic activity, whilst the dopaminergic activ-
ity was remarkably increased in particularly the case of 6
and 7. Reduction of the 2, 3-indole double bond strongly
affected the affinities for all the receptor sites considered,
leading to the inactive compound 8.
4.6. Modification on the ∆-9,10 double bond 20–25
When the ∆-9,10 double bond was satured, the affini-
ties were strongly decreased with respect to the unsatur-
ated analogues 1, 2, 10, 15, 16 and 19. The antidopam-
inergic activity was abolished in all the compounds
considered. Conversely, the dopaminergic activity was in
some way retained as in the case of 22–24, albeit lower
than the unsaturated analogues.
4.7. Modification on position 9 of the ergoline skeleton
26
4.3. Modifications on position 6 of the ergoline
skeleton 9, 10
The introduction of a 9α-hydroxy group was very
deleterious for in vitro and in vivo activity. In fact, 26 was
totally inactive when compared to the unsaturated 1 and
saturated analogue 20.
The subset of compounds 2, 5–7, and 16, having high
affinity for dopaminergic receptor sites and potent in vivo
antidopaminergic and dopaminergic activity was evalu-
ated in more details at lower doses. In addition, interac-
tion studies using the selective D1 antagonist R-(+)-SCH-
23390 (R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,
3, 4, 5-tetrahydro-1H-3-benzazepine hydrochloride) and
D2 antagonist S-(–)-sulpiride (S-(–)-5-(aminosulphonyl)-
N-[(1-ethyl-2-pyrrolodinyl)-methyl]-2-methoxy-
Replacement of the 6-methyl by hydrogen was detri-
mental in term of in vitro and as well as in vivo activity.
In fact, the nor analogue 9 was completely inactive. On
the contrary, replacement with the n-propyl group seemed
not to have significantly affected the dopaminergic activ-
ity when 10 was compared to 1, whereas the antidopam-
inergic activity was strongly reduced.
4.4. Modifications of the length or of the
stereochemistry of the chain in position 8 11–14
A series of analogues which probes the influence of the
spacing between the ergoline skeleton and the 3,5-
dioxopiperazin-1-yl functionalities was examined. By
shortening or lengthening of one methylene unit the
spacer in position 8 as in the case of 12, 13 and 14, led to
compounds devoid of activity. A similar result was
encountered by changing the stereochemistry as in the
case of the 8-α analogue 11.
benzamide), were carried out to identify the dopamine
receptor site mediating contralateral turning behaviour
for these compounds, as reported in table V.
5. Discussion
The ergoline derivatives of the present study illustrate
many key points relevant for the structural requirements
necessary for the dopaminergic or antidopaminergic ac-
tivity within this series. The structural requirement for
retaining the antidopaminergic and dopaminergic activity
present in the parent appears to be quite strict. In fact,
only substitution in position 2 allows the maintenance of
the uncommon pharmacological profile presented by 1.
Compounds such as 5–7 exert a more pronounced agonist
and antagonist dopaminergic activity than the parent. The
turning behaviour induced by 5–7 was antagonised
4.5. Modifications on the 3,5-dioxopiperazin-4-
nitrogen 15–18
The effects of changes to the 3,5-dioxopiperazin-1-yl
functionality on binding profile as well as in vivo activity
were assessed. As illustrated by 15–18, substitution of the
imidic hydrogen of the 3,5-dioxopiperazin moiety re-
sulted in a decrease in binding affinities, in particular for
17. A notable diminution in the antidopaminergic activity

116
Table V. Evaluation of the ergoline derivatives 2, 5–7, 16. The number of turns are the mean values of five experiments. Turn./treat. =
Turning/treated 6-OH-DA lesioned rats.
Compound Anti-climbing
Turning behaviour
Interaction study
ED50
mg/kg s.c.
Dose
mg/kg s.c.
Turns in 6 h
Turn./treat.
animals
Dose
mg/kg s.c.
% inhibit.
SCH-23390
% inhibit.
S-sulpiride
1
2
5
6
7
16
0.18
0.03
0.02
0.06
0.14
–
0.1
0.1
0.1
0.1
0.1
0.1
2423
927
2600
2770
2874
1227
10/10
5/5
5/7
5/5
5/5
0.1
0.1
0.025
0.1
0.05
0.1
95
15
25
22
22
34
21
89
64
69
97
86
6/6
mainly by the D2 antagonist S-(–)-sulpiride and not
significantly by the selective D1 antagonist R-SCH-(+)-
23390. These results indicate that after a severe dopamine
depletion, 5–7 behave as D2 agonist, as opposed to 1 that
acts as D1 agonist. Of equal importance to the achieve-
ment of dopaminergic activity was the substitution of the
imidic proton of the 3,5-dioxopiperazinyl moiety with
phenyl group as in 16. This compound revealed to be a
potent D2 agonist as shown by the interaction experiment,
devoid of any antagonistic component. The considerable
reduction in dopaminergic activity in 17 relative to 16
suggests that the D2 receptor is sensitive to steric bulk in
agonists of this structural type. Interestingly, the cyclo-
hexyl analogue 18 was completely devoid of activity,
notwithstanding displaying higher D1 and D2 affinity than
16 and 17. The results show that the dopaminergic
component is strongly dependent on structural modifica-
tions on the ergoline skeleton and on the heterocyclic
moiety, and the exert of this activity is not always
paralleled by in vitro the dopaminergic affinity. These
results suggest, in first instance, the involvement of other
receptor components or a different central bioavailability.
In conclusion, in this study, we have reported a series of
compounds related to 1, whose dopamine anta-
gonistic/agonistic activity can be strongly affected by
the choice of the substituent in position 1 or 2 of the
ergoline skeleton leading to in vivo potent dopamine
antagonists/agonists, or by the 3,5-dioxopiperazin-4-
nitrogen substituent that mainly afforded in vivo potent
D2 agonists.
(intensity to base = 100) on a Finnigan MAT SSQ 7000
mass spectrometer. H NMR were recorded on a Bruker
1
AC 200 spectrometer at 200 MHz and Varian VXR 400
MHz. Chemical shifts are reported as δ values in part per
million (ppm) relative to tetramethylsilane (δ 0.00) used
as internal standard. Microanalyses were performed on
Carlo Erba autoanalyser and were within ±0.4% of the
calculated values.
6.1.1. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-9,10-dide-
hydro-6-methylergoline 1
A solution of ethylbromoacetate (67 g, 425 mmol) in
dimethylformamide (150 mL) was added dropwise to a
stirred solution of 27 (50 g, 197 mmol) and potassium
carbonate (60.8 g, 440 mmol) in dimethylformamide
(300 mL) at room temperature. After stirring for 3 h, the
suspension was evaporated in vacuo and the residue taken
up in ethylacetate was partitioned with water then washed
with brine and dried over sodium sulphate. Evaporation
of the solvent, filtration of the residue on a small pad of
silica gel by elution with acetone/cyclohexane 1:3 af-
forded after crystallisation from diethylether, 2.4 g of
N-(ethoxycarbonylmethyl)-N-(ethoxycarbonylmethyloxy-
carbonyl)-lysergamine, m.p. 124–126 °C. MS m/z: 469
(C25H31N3O6, 56, [M]+ ), 236 (36), 235 (24), 222 (38),
221 (41), 202 (100), 192 (34), 174 (15), 154 (19), 130
(33). 1H-NMR (200 MHz, CDCl3): δ 1.64 (t, J = 7.2 Hz,
6 H, COOCH2CH3), 2.23 (dd, J = 9.5, 11.4 Hz, 1 H,
H-7ax), 2.32 (s, 3 H, CH3N), 2.66 (m, 1 H, H-4ax), 2.87
(m, 1 H, H-8ax), 3.12 (m, 1 H, H-5ax), 3.16 (m, 1 H,
H-7eq), 3.56 (ddd, J = 5.3, 14.6 Hz, 1 H, H-4eq), 3.66 (m,
2 H, CH2-8), 4.15 (q, J = 7.2 Hz, 4 H, COOCH2CH3),
4.32 (s, 2 H, NCH2COO), 4.55 (d, J = 3.3 Hz, 2 H,
NCOOCH2COO), 6.56 (bs, 1 H, H-9), 6.73 (m, 1 H,
H-2), 7.32 (m, 3 H, H-12, H-13, H-14), 10.1 (bs, 1 H,
NH-1).
6. Experimental protocol
6.1. Chemistry
Analytical and spectroscopic data were consistent with
the structure of the corresponding compounds. Electron-
impact mass spectra were recorded in form of m/z
Continuing the elution with acetone/cyclohexane 1:2,
65 g of N-[(9,10-didehydro-6-methylergoline-8â-yl)me-
thyl]-iminodiacetic acid diethyl ester (77% yield), m.p.

117
156–158 °C, were recovered after crystallisation from a
small volume of ethanol. MS m/z: 425 (C24H31N3O4, 38,
[M]+ ), 352 (22), 236 (47), 235 (26), 222 (42), 221 (56),
202 (100), 192 (24), 174 (23), 154 (17), 130 (41).
1H-NMR (200 MHz, CDCl3): δ 1.27 (t, J = 7.1 Hz, 6 H,
COOCH2CH3), 2.23 (dd, J = 9.7, 11.4 Hz, 1 H, H-7ax),
2.57 (s, 3 H, CH3N), 2.66 (m, 1 H, H-4ax), 2.6–3.0 (m, 2
H, CH2-8), 2.87 (m, 1 H, H-8ax), 3.12 (m, 1 H, H-5ax),
3.16 (m, 1 H, H-7eq), 3.52 (ddd, J = 5.4, 14.6 Hz, 1 H,
H-4eq), 3.61 (s, 4 H, NCH2COO), 4.25 (q, J = 7.1 Hz, 4
H, COOCH2CH3), 6.39 (bs, 1 H, H-9), 6.88 (m, 1 H,
H-2), 7.15 (m, 3 H, H-12, H-13, H-14), 9.4 (bs, 1 H,
NH-1).
6.1.2. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-9,10-didehy-
dro-1,6-dimethyl methylergoline 2
Compound 2 was synthesised from 29 following the
procedure reported for 1. MS m/z: 364 (C21H24N4O2,
100, [M]+ ), 250 (11), 237 (72), 235 (46), 206 (34), 194
(13), 181 (12), 168 (13), 127 (12), 71 (17), 42 (92).
1H-NMR (200 MHz, CDCl3): δ 2.03 (dd, J = 10.2, 10.2
Hz, 1 H, H-7ax), 2.3–2.5 (m, 3 H, H-4ax, CH2-8), 2.42 (s,
3 H, CH3N-6), 2.7–3.0 (m, 3 H, H-5ax, H-7e, H-8ax),
3.37 (m, 4 H, N(CH2CO)2), 3.43 (dd, J = 5.4, 14.8 Hz, 1
H, H-4e), 3.71 (s, 3 H, CH3N-1), 6.25 (bs, 1 H, H-9),
6.9–7.2 (m, 4 H, H-12, H-13, H-14), 11.15 (bs, 1 H,
CONHCO).
6.1.3.
8â-(3,5-Dioxopiperazin-1-ylmethyl)-1-ethyl-
Gaseous ammonia was bubbled into a solution of
N-[(9,10-didehydro-6-methylergoline-8â-yl)methyl]-imi-
nodiacetic acid diethyl ester (25 g, 59 mmol) in dimeth-
ylformamide (100 mL) cooled at –10 °C until saturation.
After keeping at room temperature overnight, the solvent
was removed in vacuo and the residue was crystallised
from methanol to provide 17 g of N-[(9,10-didehydro-6-
methylergoline-8â-yl)methyl]-iminodiacetamide (78%
yield), m.p. 245–247 °C. MS-FD (EHC = 25 mA) m/z:
367 (C20H25N5O2, 100, [M]+ ). 1H-NMR (200 MHz,
DMSO-d6): δ 2.25 (dd, J = 9.6, 11.4 Hz, 1 H, H-7ax),
2.53 (s, 3 H, CH3N), 2.76 (m, 1 H, H-4ax), 2.5–3.1 (m, 2
H, CH2-8), 2.89 (m, 1 H, H-8ax), 3.17 (m, 1 H, H-5ax),
3.21 (m, 1 H, H-7eq), 3.45 (s, 4 H, NCH2CONH2), 3.52
(ddd, J = 5.4, 14.6 Hz, 1 H, H-4eq), 6.33 (bs, 1 H, H-9),
6.91 (m, 1 H, H-2), 7.16 (m, 3 H, H-12, H-13, H-14), 7.31
(bs, 4 H, CONH2), 9.4 (bs, 1 H, NH-1).
9,10-didehydro-6-methylergoline 3
Compound 3 was synthesised from 30 following the
procedure reported for 1.
MS m/z: 378 (C22H26N4O2, 58, [M]+ ), 263 (11), 251
(94), 249 (59), 235 (24), 221 (52), 220 (65), 208 (24), 195
(23), 182 (26), 127 (23), 71 (28), 42 (100). 1H-NMR (200
MHz, CDCl3): δ 1.43 (t, J = 7.3 Hz, 3 H, NCH2CH3),
2.18 (dd, J = 10.2, 10.2 Hz, 1 H, H-7ax), 2.51 (m, 2 H,
CH2-8), 2.56 (s, 3 H, CH3N), 2.69 (ddd, J = 1.6, 11.3,
14.3 Hz, 1 H, H-4ax), 2.93 (m, 1 H, H-8ax), 3.0–3.2 (m,
2 H, H-5ax, H-7e), 3.43 (m, 4 H, N(CH2CO)2), 3.50 (dd,
J = 5.4, 14.3 Hz, 1 H, H-4e), 4.11 (q, J = 5.4, 14.3 Hz, 1
H, H-4e), 4.11 (q, J = 7.3 Hz, 2 H, NCH2CH3), 6.28 (bs,
1 H., H-9), 6.81 (d, J = 1.6 Hz, 1 H, H-2), 7.1–7.2 (m, 3
H, H-12, H-13, H-14), 8.54 (bs, 1 H, CONHCO).
6.1.4. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-1-isopro-
pyl-9,10-didehydro-6-methylergoline 4
A stirred mixture of phenol (15 g) and N-[(9,10-
didehydro-6-methylergoline-8â-yl)methyl]-iminodiaceta-
mide (3 g, 8 mmol) was slowly heated at 160 °C in a flow
of nitrogen and kept at this temperature until the evolu-
tion of ammonia has ceased. After cooling, the solid was
taken up in diethyl ether and the suspension filtered. The
precipitated was dissolved in a small amount of
acetone/chloroform 1:1 and filtered on a small column of
silica gel eluting with acetone. The fractions containing
the product were pooled and evaporated to small volume
providing 1.9 g of 1 (63% yield) as shiny crystals. MS
m/z: 350 (C20H22N4O2, 95, [M]+ ), 236 (18), 223 (100),
221 (97), 207 (31), 192 (79), 180 (31), 167 (34), 154 (34),
127 (46), 71 (21), 42 (21). 1H-NMR (400 MHz, DMSO-
d6): δ 2.07 (dd, J = 9.5, 11.0 Hz, 1 H, H-7ax), 2.44 (s, 3
H, CH3N), 2.3–2.6 (m, 3 H, H-4ax, CH2-8), 2.84 (m, 1 H,
H-8ax), 2.95 (m, 2 H, H-5ax, H-7e), 3.40 (m, 4 H,
N(CH2CO)2), 3.44 (dd, J = 5.5, 14.5 Hz, 1 H, H-4e), 6.26
(bs, 1 H, H-9), 7.0–7.2 (m, 4 H, H-12, H-13, H-14), 10.69
(bs, 1 H, NH-1), 11.18 (bs, 1 H, CONHCO).
Compound 4 was synthesised from 31 following the
procedure reported for 1. MS m/z: 392 (C23H28N4O2, 32,
[M]+ ), 265 (49), 263 (23), 235 (23), 192 (19), 167 (13),
1
154 (12), 127 (15), 71 (25), 43 (83), 42 (100). H-NMR
(200 MHz, CDCl3): δ 1.50–1.51 (two d, J = 6.7 Hz, 6 H,
(CH3)2CHN), 2.18 (dd, J = 10.3, 10.3 Hz, 1 H, H-7ax),
2.52 (m, 2 H, CH2-8), 3.0–3.2 (m, 2 H, H-5ax, H-7e),
3.44 (m, 4 H, N(CH2CO)2), 3.50 (dd, J = 5.5, 14.4 Hz, 1
H, H-4e), 4.59 (m, 1 H, (CH3)2CH), 6.28 (bs, 1 H, H-9),
6.91 (d, J = 1.6 Hz, H-2), 7.1–7.2 (m, 3 H, H-12, H-13,
H-14), 8.20 (bs, 1 H, CONHCO).
6.1.5. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-2-bromo-
9,10-didehydro-6-methylergoline 5
A solution of N-bromosuccinimide (2.4 g, 14 mmol) in
dioxane (45 mL) was added dropwise to a stirred solution
of 1 (4.2 g, 12 mmol) in dioxane (60 mL) at 40 °C. After
1h, the solvent was removed and the residue taken up in
chloroform was washed with 0.1 M of ammonium
hydroxyde, then with brine and dried over sodium sul-

118
phate. The residue was chromatographed on silica gel
eluting with acetone/cyclohexane 1:1 to give after crys-
tallisation from acetone 3.1 of 5 (60% yield). MS m/z:
430 (56), 428 (C20H21BrN4O2, 56, [M]+ ), 301 (47), 299
(23), 205 (49), 192 (55), 191 (52), 154 (23), 153 (32), 152
127 (16), 47 (26), 42 (19). 1H-NMR (200 MHz, Py-d5): δ
2.14 (dd, J = 11.6, 11.6 Hz, 1 H, H-7ax), 2.44 (s, 3H,
CH3S), 2.46 (m, 2 H, CH2-8), 2.48 (s, 3 H, CH3N), 2.90
(dd, J = 11.2, 14.7 Hz, 1 H, H-4ax), 3.0–3.2 (m, 2 H,
H-7e, H-8ax), 3.22 (m, 1 H, H-5ax), 3.62 (m, 4 H,
N(CH2CO)2), 3.83 (dd, J = 5.3, 14.7 Hz, 1 H, H-4e), 6.57
(m, 1 H, H-9), 7.3–7.4 (m, 3 H, H-12, H-13, H-14), 12.23
(bs, 1 H, NH-1), 13.18 (bs, 1 H, CONHCO).
1
(30), 127 (100), 71 (27). H-NMR (200 MHz, DMSO-
d6): δ 2.04 (dd, J = 10.4, 10.4 Hz, 1 H, H-7ax), 2.3–2.4
(m, 3 H, H-4ax, CH2-8), 2.41 (s, 3 H, CH3N), 2.79 (m, 1
H, H-8ax), 2.9–3.0 (m, 2H, H-5ax, H-7e), 3.36 (m, 4 H,
N(CH2CO)2), 6.26 (bs, 1 H, H-9), 7.0–7.1 (m, 3 H, H-12,
H-13, H-14), 11.14 (bs, 1 H, CONHCO), 11.41 (bs, 1 H,
NH-1).
6.1.8. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-2,3â-dihy-
dro-9,10-didehydro-6-methylergoline 8
Sodium borohydride (0.5 g, 12 mmol) was slowly
added portionwise to a stirred solution of 1 (3.5 g,
10 mmol) in trifluoroacetic acid (30 mL) under nitrogen
at –10 °C. After stirring for 30 min, the solution was
diluted with ethylacetate and basified with 0.1 M ammo-
nium hydroxyde. The organic phase was dried over
sodium sulphate and the solvent removed off. The residue
was chromatographed on silica gel eluting with
acetone/cyclohexane 1:1.5 to provide, after crystallisation
from diethyl ether 1.3 g of 8 (37% yield). MS m/z: 352
(C20H24N4O2, 83, [M]+ ), 237 (19), 225 (66), 223 (100),
194 (23), 168 (31), 167 (23), 154 (16), 127 (64), 71 (19),
6.1.6. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-2-chloro-
9,10-didehydro-6-methylergoline 6
A solution of sulphurylchloride (1.3 g, 9.5 mmol) in
acetonitrile (10 mL) was added dropwise) to a stirred
solution of 1 (2.8 g, 8 mmol) in acetonitrile (50 mL) and
borotrifluoride etherate (0.1 mL) at 0 °C. After stirring for
3 h, the solvent was removed in vacuo and the residue
taken up in dichloromethane was washed with 0.1 M
ammonium hydroxyde and dried over sodium sulphate.
The solvent was removed, and the residue was twice
crystallised from ethylacetate to provide 2.1 g of 6 (68%
yield). MS m/z: 386 (29), 384 (C20H21ClN4O2, 86,
[M]+ ), 271 (11), 269 (19), 257 (85), 241 (19), 228 (26),
227 (41), 226 (32), 192 (26), 127 (24), 42 (37). 1H-NMR
(200 MHz, Py-d5): δ 2.13 (dd, J = 11.8, 11.8 Hz, 1 H,
H-7ax), 2.47 (s, 3 H, CH3N), 2.49 (m, 2 H, CH2-8), 2.77
(dd, J = 11.0, 14.6 Hz, 1 H, H-4ax), 3.0–3.2 (m, 3 H,
H-5ax, H7e, H-8ax), 3.62 (m, 4 H, N(CH2CO)2), 3.63
(dd, J = 5.6, 14.6 Hz, 1 H, H-4e), 6.55 (bs, 1 H, H-9),
73–7.4 (m, 3 H, H-12, H-13, H-14), 12.80 (bs, 1 H,
NH-1), 13.18 (bs, 1 H, CONHCO).
1
42 (31). H-NMR (200 MHz, CDCl3): δ 1.39 (ddd, J =
11.5, 11.5, 11.5 Hz, 1 H, H-4ax), 2.12 (dd, J = 10.8, 10.8
Hz, 1 H, H-7ax), 2.4-2.6 (m, 3 H, H-4e, CH2-8), 2.49 (s,
3 H, CH3N, 2.85 (m, 1 H, H-8ax), 2.93 (m, 1 H, H-5ax),
3.06 (dd, J = 48, 10.8 Hz, 1 H, H-7e), 3.1–3.3 (m, 2 H,
H-2α, H-3â), 3.42 (s, 4 H, N(CH2CO)2), 3.70 (dd, J =
6.7, 6.7 Hz, 1 H, H-2â), 6.22 (bs, 1 H, H-9), 6.50 (d, J =
7.2 Hz, 1 H, H-14), 6.9–7.1 (m, 2 H, H-12, H-13), 8.01
(bs, 1 H, CONHCO).
6.1.9. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-9,10-dide-
hydro-ergoline 9
6.1.7. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-2-methyl-
thio-9,10-didehydro-6-methylergoline 7
Cyanogen bromide (3.3 g, 31 mmol) was added to a
stirred solution of 1 (9 g, 26 mmol) in dimethylforma-
mide (75 mL) After stirring overnight, the solvent was
removed in vacuo and the residue was twice crystallised
from acetone to provide 7.3 g of 8â-(3,5-dioxopiperazin-
A solution of sulphurylchloride (2.2 g, 15 mmol)) in
dichloromethane (40 mL) was slowly added dropwise to
a stirred solution of dimethyldisulphide (0.8 g, 22 mmol)
in dichloromethane (50 mL) at –20 °C. The yellow solu-
tion was set aside at room temperature for 1 h, and was
then added dropwise to a stirred solution of 1 (1.75 g,
4.76 mmol) in dichloromethane (50 mL) at 0 °C. After
being kept for 1 h at this temperature, the solution was
slowly warmed to room temperature and partitioned with
0.1 M ammonium hydroxyde. The organic phase was
washed with brine and then dried. After removal of the
solvent, the residue was crystallised twice from ethylac-
etate to give 0.9 g of 7 (45% yield). MS m/z: 396
(C21H24N4O2S, 56, [M]+ ), 381 (23), 269 (100), 267 (93),
253 (51), 239 (36), 238 (32), 192 (19), 191 (22), 180 (11),
1-ylmethyl)-9,10-didehydro-6-cyanoergoline,
m.p.
234–237 °C MS-FD (EHC = 25 mA) m/z: 353. A suspen-
sion of 8â-(3,5-dioxopiperazin-1-ylmethyl)-9,10-dide-
hydro-6-cyanoergoline (7 g, 19 mmol) and Zn dust
(3.5 g, 54 mmol) in acetic acid (150 mL) was stirred for
5 h at 45 °C. After filtration, the solvent was removed in
vacuo, and the residue was taken up in dichlorometane
and washed with 0.1 M of ammonium hydroxyde. The
organic phase was dried over sodium sulphate and
evaporated. The residue was filtered on a small pad of
silica gel eluting with acetone/cyclohexane 1:1.5, to
furnish after crystallisation from ethylacetate 4.7 g of 9

119
(74% yield). MS m/z: 336 (C19H20N4O2, 44, [M]+ ), 221
(10), 209 (100), 207 (84), 192 (61), 180 (16), 167 (18),
154 (19), 127 (49), 71 (29), 42 (75). 1H-NMR (200 MHz,
Py-d5): δ 2.45 (m, 2 H, CH2-8), 2.68 (dd, J = 9.7, 11.9
Hz, 1 H, H-7ax), 2.94 (m, 1 H, H-8ax), 3.05 (ddd, J = 1.7,
11.7, 14.6 Hz, 1 H, H-4ax), 3.3–3.5 (m, 2 H, H-4e, H-7e),
3.58 (s, 4 H, N(CH2CO)2), 4.06 (m, 1 H, H-5ax), 6.61
(bs, 1 H, H-9), 7.2–7.5 (m, 4 H, H-2, H-12, H-13, H-14),
11.66 (bs, 1 H, NH-1), 13.14 (bs, 1 H, CONHCO).
2.45 (s, 3 H, CH3N), 2.50 (dd, J = 9.5, 10.6 Hz, 1 H,
H-7ax), 2.81 (ddd, J = 1.6, 11.2, 14.5 Hz, 1 H, H-4ax),
3.01 (dd, J = 5.0, 10.6 Hz, 1 H, H-7e), 3.22 (m, 1 H,
H-5ax), 3.56 (dd, J = 5.7, 14.5 Hz, 1 H, H-4e), 3.80 (s, 4
H, N(CH2CO)2), 3.94 (m, 1 H, H-8ax), 6.65 (bs, 1 H,
H-9), 7.2–7.5 (m, 4 H, H-2, H-12, H-13, H-14), 11.74 (bs,
1 H, NH-1), 13.10 (bs, 1 H, CONHCO).
6.1.13. 8α-(3,5-Dioxopiperazin-1-yl)-9,10-didehydro-
6-methylergoline 13
6.1.10. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-9,10-dide-
hydro-6-propylergoline 10
Compound 13 was synthesised from 33 following the
procedure reported for 1.
A stirred solution of 9 (4.6 g, 14 mmol), triethylamine
(1.8 g, 17 mmol) and propyliodide (2.9 g, 17 mmol) in
dimethylformamide (50 mL) was heated at 50 °C for 2 h.
The solvent was removed in vacuo and the residue taken
up in ethylacetate was washed with 0.1 M of ammonium
hydroxyde, then dried over sodium sulphate. After re-
moval of the solvent, the residue was chromatographed
on silica gel eluting with ethylacetate to afford after
crystallisation from acetone 3.2 g of 10 (65% yield).
FD-MS (EHC = 22 mA) m/z: 378 (C22H26N4O2, 100,
MS m/z: 336 (C19H20N4O2, 10, [M]+ ), 293 (100), 221
(35), 207 (38), 206 (44), 205 (38), 192 (19), 180 (64), 167
1
(30), 154 (25), 43 (13), 42 (14). H-NMR (200 MHz,
Py-d5): δ 2.32 (s, 3 H, CH3N), 2.45 (dd, J = 4.1, 12.5 Hz,
1 H, H-7ax), 2.79 (ddd, J = 1.7, 11.2, 14.3 Hz, 1 H, H-ax),
3.0–3.1 (m, 2 H, H-5ax, H-7e), 3.45 (m, 1 H, H-8e), 3.52
(dd, J = 5.9, 14.3 Hz, 1 H, H-4e), 3.91 (s, 4 H,
N(CH2CO)2), 6.58 (bd, J = 5.7 Hz, 1 H, H-9), 7.2–7.5 (m,
4 H, H-2, H-12, H-13, H-14), 11.77 (bs, 1 H, NH-1),
12.91 (bs, 1 H, CONHCO).
1
[M]+ ). H-NMR (200 MHz, DMSO-d6): δ 0.86 (t, J =
6.1.14. 8â-(3,5-Dioxopiperazin-1-ylethyl)-9,10-dide-
hydro-6-methylergoline 14
7.1, 3 H, CH3CH2CH2N), 1.46 (m, 2 H, CH3CH2CH2N),
2.11 (dd, J = 9.4, 11.0 Hz, 1 H, H-7ax), 24–2.5 (m, 3 H,
H-4ax, CH2-8), 2.6–2.7 (m, 3 H, H-8ax, CH3CH2CH2N),
2.95 (dd, J = 4.2, 11.0 Hz, H-7e), 3.23 (m, 1 H, H-5ax),
3.36(s, 4 H, N(CH2CO)2), 3.39 (dd, J = 5.4, 14.5 Hz, 1 H,
H-4e), 6.21 (bs, 1 H, H-9), 6.9–7.2 (m, 4 H, H-2, H-12,
H-13, H-14), 10.65 (bd, J = 1.9 Hz, 1 H, NH-1), 11.16
(bs, 1 H, CONHCO).
Compound 14 was synthesised from 34 following the
procedure reported for 1. MS m/z: 364 (C21H24N4O2, 96,
[M]+ ), 237 (30), 223 (46), 221 (71), 206 (45), 194 (88),
192 (48), 167 (44), 154 (79), 127 (96), 71 (25), 44 (100),
42 (90). 1H-NMR (200 MHz, DMSO-d6): δ 1.47 (m, 2 H,
CH2CH2N 8â-chain), 2.04 (dd, J = 10.5, 10.5 Hz, 1 H,
H-7ax), 2.3–2.6 (m, 4 H, H-4ax, H-8ax, H-CH2CH2N
8â-chain), 2.40 (s, 3 H, CH3N), 2.8–3.0 (m, 2 h, H-5ax,
H-7e), 3.33 (s, 4 H, N(CH2CO)2), 342 (dd, J = 5.4, 14.8
Hz, 1 H, H-4e), 6.29 (bs, 1 H, H-9), 7.0–7.2 (m, 4 H, H-2,
H-12, H-13, H-14), 10.65 (bs, 1 H, NH-1), 11.12 (bs, 1 H,
CONHCO).
6.1.11. 8α-(3,5-Dioxopiperazin-1-ylmethyl)-9,10-dide-
hydro-6-methylergoline 11
Compound 11 was synthesised from 28 following the
procedure reported for 1.
MS m/z: 350 (C20H22N4O2, 100, [M]+ ), 235 (11), 223
(66), 221 (11), 207 (20), 193 (45), 192 (67), 180 (25), 167
1
6.1.15.
[8â-(3,5-dioxo-4-methylpiperazin-1-yl)-
(23), 154 (21), 127 (12), 42 (14). H-NMR (200 MHz,
methyl]-9,10-didehydro-6-methylergoline 15
Py-d5): δ 2.44 (s, 3 H, CH3N), 2.5–3.0 (m, 6 H, H-4ax,
CH2-7, H-8e, CH2-8), 3.21 (m, 1 H, H-5ax), 3.60 (s, 4 H,
N(CH2CO)2), 3.62 (dd, J = 5.5, 14.3 Hz, 1 H, H-4e), 6.59
(dd, J = 1.3, 4.8Hz, 1 H, H-9), 7.2–7.5 (m, 4 H, H-2,
H-12, H-13, H-14), 11.70 (bs, 1 H, NH-1), 13.14 (bs, 1 H,
CONHCO).
Diethylazodicarboxylate (1.8 g, 0.11 mmol) was
slowly added dropwise to a stirred solution of 1 (3 g,
8.6 mmol), triphenylphosphine (2.7 g, 10 mmol) and
methanol (0.8 g, 26 mmol) in tetrahydrofuran (50 mL) at
room temperature. After stirring for 3 h, the solvent was
evaporated and the residue was chromatographed on
silica gel eluting with acetone/cyclohexane 1:2. After
crystallisation from ethylacetate, 2.1 g of 15 (65% yield)
were obtained. MS m/z: 364 (C21H24N4O2, 67, [M]+ ),
236 (16), 235 (17), 223 (100), 221 (97), 192 (76), 180
(31), 167 (37), 154 (38), 141 (43), 113 (69), 42 (98).
1H-NMR (200 MHz, CDCl3): δ 2.18 (dd, J = 9.8, 10.8
Hz, 1 H, H-7ax), 2.47 8m, 2 H, CH2-8), 2.56 (s, 3 H,
6.1.12. 8â-(3,5-Dioxopiperazin-1-yl)-9,10-didehydro-
6-methylergoline 12
Compound 12 was synthesised from 32 following the
procedure reported for 1.
MS m/z: 336 (C19H20N4O2, 12, [M]+ ), 293 (100), 292
(45), 221 (21), 206 (36), 205 (26), 192 (14), 180 (70), 167
1
(29), 154 (25), 42 (30). H-NMR (200 MHz, Py-d5): δ

120
CH3N), 2.67 (ddd, J = 1.8, 11.3, 14.4 Hz, H-4ax), 2.91
(m, 1 H, H-8ax), 3.0–3.2 (m, 2 H, H-5ax, H-7e), 3.18 (s,
3 H, CON(CH3)CO), 3.47 (s, 4 H, N(CH2CO)2), 3.52
(dd, J = 5.3, 14.4 Hz, 1 H, H-4e), 6.29 (bd, 1 H, H-9),
6.90 (t, J = 1.8 Hz, 1 H, H-2), 7.1–7.2 (m, 3 H, H-12,
H-13, H-14), 7.91 (bs, 1 H, NH-1).
provide 2.9 g of N-[(9,10-didehydro-6-methylergoline-
8â-yl)methyl]-N-(phenylcarbamoylmethyl)-glycine
(77% yield), m.p. 252–255 °C. MS m/z: 444
(C26H28N4O3, 4, [M]+ ), 351 (3), 337 (4), 236 (13), 235
(14), 223 (11), 221 (16), 192 (17), 151 (15), 106 (16), 93
1
(100). H-NMR (200 MHz, DMSO-d6): δ 2.63 (s, 3 H,
CH3N), 3.39 (s, 4 H, N(CH2COOH)CH2CONHC6H5),
6.51 (bs, 1 H, H-9), 6.9–7.6 (m, 9 H, H-2, H-12, H-13,
H-14, N-phenyl hydrogen H-2’, H-3’, H-4’, H-5’, H-6’),
10.22 (bs, 1 H, CONH), 10.64 (d, J = 2.1 Hz, 1 H, NH-1).
1,1’-Carbonyldiimidazole (5.6 g, 34 mmol) was added
to a stirred suspension of N-[(9,10-didehydro-6-methyl-
ergoline-8â-yl)methyl]-N-(phenylcarbamoylmethyl)-gly-
cine (5 g, 11.4 mmol) in dioxane (75 mL), then refluxed
for 3 h. The solvent was removed and the residue was
chromatographed on silica gel eluting with
acetone/cyclohexane 3:2. After crystallisation from ac-
etone, 3.7 g of 16 (77% yield) were obtained. MS m/z:
426 (C26H26N4O2, 49, [M]+ ), 295 (14), 223 (67), 221
(100), 207 (28), 193 (51), 192 (63), 167 (39), 154 (35),
6.1.16.
[8â-(3,5-dioxo-4-phenylpiperazin-1-yl)-
methyl]-9,10-didehydro-6-methylergoline 16
1 M Potassium hydroxyde (60 mL, 60 mmol) was
added dropwise to a solution of N-[(9,10-didehydro-6-
methylergoline-8-yl)methyl]-iminodiacetic acid diethyl
ester (25 g, 59 mmol) in ethanol (100 mL). After stirring
for 3 h, the precipitate was filtered, dissolved in boiling
water and treated with 1 M hydrochloric acid (62 mL,
62 mmol). The precipitate was washed with a small
volume of water, then crystallised from ethanol/water 5:1
to
provide
18.3 g
of
N-[(9,10-didehydro-6-
methylergoline-8-yl)methyl]-iminodiacetic acid monoet-
hyl ester (79% yield), m.p. 248–251 °C. MS-FD (EHC =
25 mA) m/z: 397 (C21H28N4O4, 100, [M]+ ). 1,1’-
Carbonyldiimidazole (1.6 g, 10 mmol) was added to a
stirred suspension of N-(9,10-didehydro-8â-ylmethyl-6-
methylergoline)-iminodiacetic acid monoethyl ester
(3.5 g, 8.8 mmol) in dioxane (75 mL), then heated at
reflux for 15 min. After cooling, aniline (2 g, 24 mmol)
was added and the solution was refluxed for 3 h. The
solvent was removed and the residue was chromato-
graphed on silica gel eluting with ethyl-
acetate/cyclohexane 1:1 to give 2.4 g of N-[(9,10-
didehydro-6-methylergoline-8â-yl)methyl]-N-(phenyl-
carbamoylmethyl)-glycine ethyl ester (60% yield), m.p.
196–198 °C. MS-FD (EHC = 30 nA) m/z: 472
(C28H30N4O3, 100, [M]+ ). 1H-NMR (200 MHz, CDCl3):
δ 1.28 (t, J = 7.2 Hz, 3 H, COOCH2CH3), 2.25 (dd, J =
9.7, 11.4 Hz, 1 H, H-7-ax), 2.56 (s, 3 H, CH3N), 2.6–2.9
(m, 3 H, H-4ax, CH2-8), 2.90 (m, 1, H-8ax), 3.12 (m, 1 H,
H-5ax), 3.16 (dd, J = 5.4, 11.4 Hz, 1 H, H-4e), 3.43 (s, 2
H, NCH2CON), 3.51 (dd, J = 5.4, 11.4 Hz, 1 H, H-4e),
3.52 (s, 2 H, NCH2COOCH2CH3), 4.30 (q, J = 7.2 Hz, 2
H, COOCH2CH3), 6.39 (bs, 1 H, H-9), 6.89 (t, J = 1.9 Hz,
1 H, H-2), 7.0–7.4 (m, 6 H, H-12, H-13, H-14, N-phenyl
hydrogen H-3’, H-4’, H-5’), 7.68 (d, J = 8.0, Hz,
N-phenyl hydrogen H-2’, H-6’), 7.93 (bs, 1 H, NH-1),
9.79 (bs, 1 H, CONH).
1
106 (36). H-NMR (200 MHz, CDCl3): δ 2.24 (dd, J =
10.6, 10.6 Hz, 1 H, H-7ax), 2.59 (m, 2 H, CH2-8), 2.59 (s,
3 H, CH3N), 2.70 (ddd, J = 1.8, 11.4, 14.5 Hz, 1 H,
H-4ax), 2.98 (m, 1 H, H-8ax), 3.1–3.2 (m, 2 H, H-5ax,
H-7e), 3.54 (dd, J = 5.2, 14.5 Hz, 1 H, H-4e), 3.65 (s, 4
H, N(CH2CO)2), 6.34 (bs, 1 H, H-9), 6.92 (t, J = 1.8 Hz,
H-2), 7.2–7.5 (m, 9 H, H-2, H-12, H-13, H-14, N-phenyl
hydrogen H-2’, H-3’, H-4’, H-5’, H-6’), 7.91 (bs, 1 H,
NH-1).
6.1.17. [8â-(3,5-dioxo-4-(2,6-dimethylphenyl)pipera-
zin-1-yl)-methyl]-9,10-didehydro-6-methylergoline 17
Compound 17 was synthesised from N-(9,10-
didehydro-8â-ylmethyl-6-methylergoline)-iminodiacetic
acid monoethyl ester and 2,6-dimethylaniline following
the procedure reported for 16. MS m/z: 454
(C28H30N4O2, 100, [M]+ ), 236 (18), 231 (37), 223 (50),
221 (64), 193 (28), 192 (32), 167 (9), 154 (14), 42 (21).
1H-NMR (200 MHz, Py-d5): δ 2.20 (s, 6 H, N-xylyl
methyl CH3-2’, CH3-6’), 2.24 (dd, J = 11.2, 11.2 Hz, 1 H,
H-7ax), 2.50 (s, 3 H, CH3N), 2.65 (m, 2 H, CH2-8), 2.91
(ddd, J = 1.7, 11.2, 14.3 Hz, 1 H, H-4ax), 3.1–3.3 (m, 3
H, H-5ax, H-7e, H-8ax), 3.66 (dd, J = 5.1, 14.3 Hz,
H-4e), 3.95 (s, 4 H, N(CH2CO)2), 6.62 (bs, 1 H, H-9),
7.1–7.4 (m, 7 H, H-2, H-12, H-13, H-14, N-xylyl hydro-
gen H-3’, H-4’, H-5’), 11.68 (bs, 1 H, NH-1).
A solution of N-[(9,10-didehydro-6-methylergoline-
8â-yl)methyl]-N-(phenylcarbamoylmethyl)-glycine ethyl
ester (4 g, 8.6 mmol) and 1 M potassium hydroxyde
(10 mL, 10 mmol) in ethanol (50 mL) was heated at
50 °C for 3 h, then treated dropwise with 1 M of
hydrochloric acid (11 mL, 11 mmol). The precipitate was
filtered off, washed with water, then with acetone to
6.1.18.
[8â-(3,5-dioxo-4-cyclohexylpiperazin-1-yl)-
methyl]-9,10-didehydro-6-methylergoline 18
Compound 18 was synthesised from 1 and cyclohex-
anol following the procedure reported for 15. MS m/z:
432 (C26H32N4O2, 94, [M]+ ), 236 (27), 223 (100), 221

121
(96), 209 (28), 192 (38), 181 (16), 167 (17), 154 (15), 127
(27), 71 (32), 43 (41), 42 (41). H-NMR (200 Mhz,
6.1.21. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-1,6-dimethyl-
ergoline 21
1
Py-d5): δ 1.0–1.7 (m, 10 H, N-cyclohexyl hydrogen
H-2’ax, H-6’ax, CH2-3’, CH2-4’, CH2-5’), 2.14 (d, J =
11.9, 11.9 Hz, 1 H, H-7ax), 2.3–2.6 (m, 4 H, CH2-8,
N-cyclohexyl hydrogen H-2’e, H-6’e), 2.46 (s, 3 H,
CH3N), 2.89 (ddd, J = 1.5, 11.2, 14.2 Hz, 1 H, H-4ax),
3.0–3.2 (m, 2 H, H-7e, H-8ax), 3.23 (m, 1 H, H-5ax), 3.63
(dd, J = 5.3, 14.2 Hz, 1 H, H-4e), 3.65 (s, 4 H,
N(CH2CO)2), 4.72 (m, 1 H, N-cyclohexyl H-1’ax), 6.55
(bs, 1 H, H-9), 7.2–7.5 (m, 4 H, H-2, H-12, H-13, H-14),
11.69 (bs, 1 H, NH-1).
Compound 21 was synthesised from 2 following the
procedure reported for 20. MS m/z: 366 (C21H26N4O2,
43, [M]+ ), 251 (13), 239 (15), 237 (14), 194 (9), 181
(25), 168 (48), 158 (26), 127 (18), 44 (37), 42 (100).
1H-NMR (200 MHz, Py-d5): δ 0.93 (ddd, J = 12.2, 12.2,
12.2 Hz, 1 H, H9-ax), 1.81 (dd, J = 11.3, 11.3 Hz, 1 H,
H-7ax), 1.95 (dd, J = 4.3, 9.2 Hz, 1 H, H-8ax), 2.24 (ddd,
J = 4.5, 9.5, 11.6 Hz, 1 H, H-5ax), 2.14 (m, 1H, H-9ax),
2.34 (s, 3 H, CH3N), 2.3–2.4 (m, 2 H, H-4ax, H-9e), 2.61
(m, CH2-8), 2.77 (ddd, J = 3.5, 9.5, 12.3 Hz, 1 H,
H-10ax), 2.89 (bd, J = 11.3, 1 H, H-7e), 3.31 (dd, J = 4.3,
14.6 Hz, 1 H, H-4e), 3.35 (s, 4 H, N(CH2CO)2) 3.74 (s,
3 H, CH3-1), 6.87 (d, J = 7.8 Hz, 1 H, H-12), 6.96 (t, J =
7.8 Hz, 1 H, H-13), 7.15 (d, J = 7.8 Hz, 1 H, H-14), 11.25
(bs, 1 H, CONHCO).
6.1.19.
[8â-(3,5-dioxo-4-aminopiperazin-1-yl)-
methyl]-9,10-didehydro-6-methylergoline 19
Compound 19 was synthesised from N-(9,10-
didehydro-8â-ylmethyl-6-methylergoline)-iminodiacetic
acid diethyl ester and hydrazine hydrate following the
procedure reported for 1. MS m/z: 365 (C20H23N5O2, 76,
[M]+ ), 236 (17), 223 (95), 221 (100), 207 (26), 193 (70),
6.1.22. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-6-propyl-
ergoline 22
1
Compound 22 was synthesised from 10 following the
procedure reported for 20. MS m/z: 380 (C22H28N4O2,
29, [M]+ ), 265 (9), 253 (14), 251 (9), 223 (22), 167 (30),
154 (59), 153 (41), 144 (30), 127 (58), 71 (37), 44 (41),
43 (74), 42 (100). 1H-NMR (200 MHz, Py-d5): δ 0.85 (t,
J = 7.3. Hz, 3 H, CH3CH2CH2N), 1.18 (ddd, J = 12.2,
180 (23), 167 (26), 154 (27), 42 (38). H-NMR (200
MHz, DMSO-d6): δ 2.08 (dd, J = 9.8, 10.7 Hz, 1 H,
H-7ax), 2.42 (s, 3 H, CH3N), 2.84 (m, 1 H, H-8ax), 3.43
(dd, J = 5.5, 14.6 Hz, 1 H, H-4e), 3.55 (s, 4 H,
N(CH2CO)2), 5.12 (bs, 2 H, N–NH2), 6.22 (bs, 1 H, H-9),
6.9–7.2 (m, 4 H, H-2, H-12, H-13, H-14).
12.2, 12.2 Hz,
1 H, H-9ax), 1.42 (m, 2 H,
CH3CH2CH2N), 2.02 (dd, J = 11.2, 11.2 Hz, 1 H, H-7ax),
2.20 (m, 2 H, H-5ax, H-8ax), 2.27 (ddd, J = 1.7, 11.4,
14.8 Hz, 1 H, H-4ax), 2.45 (m, 2 H, CH3CH2CH2N), 2.50
(m, 2 H, CH2-8), 2.60 (m, 1 H, H-9e), 2.95 (m, 2 H, H-7e,
H-10ax), 3.35 (s, 4 H, N(CH2CO)2), 6.71 (d, J = 8.0 Hz,
1 H, H-12), 6.93 (t, J = 8.0 Hz, 1 H, H-13), 7.15 (d, J =
8.0 Hz, 1 H, H-14), 10.63 (bs, 1H, NH-1), 11.27 (bs, 1 H,
CONHCO).
6.1.20. 8â-(3,5-Dioxopiperazin-1-ylmethyl)-6-methyl-
ergoline 20
A solution of 1 (7 g, 20 mmol) in acetic acid (170 mL)
was hydrogenated at 3 atmosphere pressure over 2.5 g of
10% Pd/C. The calculated amount of H2 was taken up in
3 h. The catalyst was removed by filtration and the
solvent was evaporated off. The residue dissolved in
chloroform, was washed with dilute ammonium hy-
droxyde solution, then the organic phase was dried and
evaporated. The residue was crystallised from acetone to
afford 5.3 g of 20 (75% yield). MS m/z: 352
(C20H24N4O2, 93, [M]+ ), 237 (40), 225 (46), 223 (39),
207 (24), 194 (39), 167 (69), 154 (100), 144 (61), 127
(60), 44 (46), 42 (68). 1H-NMR (200 MHz, DMSO-d6): δ
0.96 (ddd, J = 12.3, 12.3, 12.3 Hz, 1 H, H9-ax), 1.79 (dd,
J = 11.4, 11.4 Hz, 1 H, H-7ax), 1.93 (dd, J = 4.3, 9.2 Hz,
1 H, H-8ax), 2.23 (ddd, J = 4.3, 9.5, 11.5 Hz, 1 H, H-5ax),
2.10 (m, 1H, H-9ax), 2.32 (s, 3 H, CH3N), 2.3–2.36 (m,
2 H, H-4ax, H-9e), 2.59 (m, CH2-8), 2.75 (ddd, J = 3.5,
9.5, 12.3 Hz, 1 H, H-10ax), 2.88 (bd, J = 11.4, 1 H, H-7e),
3.28 (dd, J = 4.3, 14.6 Hz, 1 H, H-4e), 3.38 (s, 4 H,
N(CH2CO)2), 6.77 (d, J = 8.0 Hz, 1 H, H-12), 6.99 (t, J
= 8.0 Hz, 1 H, H-13), 7.10 (d, J = 8.0 Hz, 1 H, H-14),
10.59 (bs, 1H, NH-1), 11.20 (bs, 1 H, CONHCO).
6.1.23.
[8â-(3,5-dioxo-4-methylpiperazin-1-yl)-
methyl]-6-methylergoline 23
Compound 23 was synthesised from 15 following the
procedure reported for 20.
MS m/z: 366 (C21H26N4O2, 100, [M]+ ), 237 (31), 225
(31), 223 (22), 167 (37), 154 (37), 144 (20), 141 (13), 127
1
(13), 44 (19), 42 (26). δ H-NMR (200 MHz, Py-d5): δ
0.98 (ddd, J = 12.2, 12.2, 12.2 Hz, 1 H, H9-ax), 1.76 (dd,
J = 11.4, 11.4 Hz, 1 H, H-7ax), 1.94 (dd, J = 4.2, 9.2 Hz,
1 H, H-8ax), 2.24 (ddd, J = 4.2, 9.5, 11.5 Hz, 1 H, H-5ax),
2.12 (m, 1H, H-9ax), 2.32 (s, 3 H, CH3N), 2.3–2.4 (m, 2
H, H-4ax, H-9e), 2.58 (m, CH2-8), 2.77 (ddd, J = 3.5, 9.5,
12.2 Hz, 1 H, H-10ax), 2.88 (bd, J = 11.4, 1 H, H-7e),
3.15 (s, 3 H, CON(CH3)CO), 3.28 (dd, J = 4.2, 14.6 Hz,
1 H, H-4e), 3.38 (s, 4 H, N(CH2CO)2), 6.77 (d, J = 8.0

122
Hz, 1 H, H-12), 6.96 (t, J = 8.1 Hz, 1 H, H-13), 7.15 (d,
J = 8.1 Hz, 1 H, H-14), 10.59 (bs, 1H, NH-1).
7.08 (d, J = 8.0 Hz, 1 H, H-12), 7.54 (d, J = 7.0 Hz, 1 H,
H-14), 10.53 (bs, 1 H, NH-1), 11.20 (bs, 1 H, CONHCO).
6.1.24.
[8â-(3,5-dioxo-4-phenylpiperazin-1-yl)-
6.2. Pharmacology
methyl]-6-methylergoline 24
Compound 24 was synthesised from 16 following the
procedure reported for 20. MS m/z: 428 (C26H28N4O2,
34, [M]+ ), 237 (22), 225 (27), 223 (21), 167 (44), 154
All binding studies were performed in rat brain areas.
Male Wistar rats weighing 175–200 g, were killed by
decapitation under light anesthesia and the various brain
regions dissected out very quickly on an ice-cold plate.
Depending on the receptor to be studied the different
areas were used following the methods reported.
1
(47), 144 (32), 127 (14), 106 (18), 42 (100). H-NMR
(200 MHz, Py-d5): δ 0.92 (ddd, J = 12.2, 12.2, 12.2 Hz,
1 H, H9-ax), 1.75 (dd, J = 11.2, 11.2 Hz, 1 H, H-7ax),
1.94 (dd, J = 4.2, 9.1 Hz, 1 H, H-8ax), 2.23 (ddd, J = 4.2,
9.5, 11.6 Hz, 1 H, H-5ax), 2.12 (m, 1H, H-9ax), 2.31 (s,
3 H, CH3N), 2.3–2.5 (m, 2 H, H-4ax, H-9e), 2.53 (m,
CH2-8), 2.69 (ddd, J = 3.4, 9.5, 12.2 Hz, 1 H, H-10ax),
2.88 (bd, J = 11.4, 1 H, H-7e), 3.28 (dd, J = 4.2, 14.6 Hz,
1 H, H-4e), 3.38 (s, 4 H, N(CH2CO)2), 7.1–7.5 (m, 9 H,
H-2, H-12, H-13, H-14, N-phenyl hydrogen H-2’, H-3’,
H-4’, H-5’, H-6’), 10.89 (bs, 1H, NH-1).
6.2.1. α1 Adrenergic binding assay
Brain cortex was homogenized in 30 volumes (w/v) of
ice-cold 50 mM Tris-HCl buffer (pH 7.2 at 25 °C) using
a Polytron PT10 (setting 5 for 20 sec). Homogenates were
centrifuged twice for 10 min at 50000 g with resuspen-
sion of the pellet in fresh buffer. The final pellet was
resuspended in ice-cold 50 mM Tris-HCl (pH 7.4 at
25 °C). Each assay tube contained 50 mL of drug solu-
tion, 50 mL of [3H]-prazosin to achieve a final concen-
tration of 0.4 nM, and 900 mL of resuspended mem-
branes (10 mg fresh tissue). The tubes were incubated for
30 min at 25 °C and the incubation was termined by rapid
filtration under vacuum through Whatman GF/B glass
fibre filters. The filters were washed three times with
5 mL of ice-cold 50 mM Tris-HCl buffer (pH 7.2 at
25 °C). The radioactivity bound to the filters was mea-
sured by liquid scintillation counter. Specific [3H]-
prazosin binding was defined as the difference between
binding in the absence or presence of 1 µM phentolamine.
6.1.25.
[8â-(3,5-dioxo-4-aminopiperazin-1-yl)-
methyl]-6-methylergoline 25
Compound 25 was synthesised from 19 following the
procedure reported for 20.
MS m/z: 367 (C20H25N5O2, 71, [M]+ ), 237 (49), 225
(51), 223 (68), 194 (24), 181 (25), 167 (74), 154 (88), 144
(52), 127 (43), 115 (28), 44 (96), 42 (100). 1H-NMR (200
MHz, DMSO-d6): δ 0.93 (ddd, J = 12.3, 12.3, 12.3 Hz, 1
H, H9-ax), 1.86 (dd, J = 11.2, 11.2 Hz, 1 H, H-7ax), 1.94
(dd, J = 4.2, 9.2 Hz, 1 H, H-8ax), 2.24 (ddd, J = 4.2, 9.5,
11.5 Hz, 1 H, H-5ax), 2.13 (m, 1H, H-9ax), 2.37 (s, 3 H,
CH3N), 2.3–2.4 (m, 2 H, H-4ax, H-9e), 2.61 (m, CH2-8),
2.69 (ddd, J = 3.5, 9.5, 12.2 Hz, 1 H, H-10ax), 2.88 (bd,
J = 11.2, 1 H, H-7e), 3.28 (dd, J = 4.2, 14.6 Hz, 1 H,
H-4e), 3.41 (s, 4 H, N(CH2CO)2), 5.23 (bs, 2 H, N-NH2),
6.64 (d, J = 8.2 Hz, 1 H, H-12), 6.93 (t, J = 8.2 Hz, 1 H,
H-13), 7.18 (d, J = 8.2Hz, 1 H, H-14), 10.71 (bs, 1H,
NH-1).
6.2.2. α2 Adrenergic binding assay
Brain cortex was homogenized in 30 volumes (w/v) of
ice-cold 5 mM Tris-HCl, 5 mM EDTA buffer (pH 7.3 at
25 °C) using a Polytron PT10 (setting 5 for 20 sec).
Homogenates were centrifuged three times for 10 min at
50000 g with resuspension of the pellet in fresh buffer.
The final pellet was resuspended in ice-cold 50 mM
Tris-HCl, 0.5 mM EDTA (pH 7.5 at 25 °C). Each assay
tube contained 50 mL of drug solution, 50 mL of [3H]-
yohimbine to achieve a final concentration of 1 nM, and
900 mL of resuspended membranes (10 mg fresh tissue).
The tubes were incubated for 30 min at 25 °C and the
incubation was termined by rapid filtration under vacuum
through Whatman GF/B glass fibre filters. The filters
were washed three times with 5 mL of ice-cold 50 mM
Tris-HCl, 0.5 mM EDTA buffer (pH 7.5 at 25 °C). The
radioactivity bound to the filters was measured by liquid
scintillation counter. Specific [3H]-yohimbine binding
was defined as the difference between binding in the
absence or presence of 10 µM phentolamine.
6.1.26.
8â-(3,5-Dioxopiperazin-1-ylmethyl)-9α-
hydroxy-6-methylergoline 26
Compound 26 was synthesised from 35 following the
procedure reported for 1.
MS m/z: 368 (C20H24N4O3, 36, [M]+ ), 254 (40), 253
(93), 241 (34), 239 (37), 223 (62), 214 (83), 193 (38), 183
(27), 154 (80), 127 (56), 71 (27), 44 (60), 42 (100).
1H-NMR (200 MHz, DMSO-d6): δ 1.92 (m, 2 H, H-8ax,
H-7ax), 2.01 (ddd, J = 4.0, 10.0, 11.0 Hz, 1 H, H-5), 2.29
(s, 3 H, CH3N), 2.54 (ddd, J = 1.0, 11.0, 14.0 Hz, 1 H,
H-4ax), 2.80 (dd, J = 10.0, 10.0 Hz, 1 H, H-10), 2.92 (m,
1 H, H-7eq), 3.24 (dd, J = 4.0, 14.0 Hz, 1H, H-4eq), 3.39
(s, 4 H, N(CH2CO)2), 3.51 (m, 1 H, H-9), 4.82 (d, J = 7.7
Hz, 1 H, OH-9), 6.91 (m, 1 H, H-2), 6.94 (m, 1 H, H-13),

123
6.2.3. D1 Dopaminergic binding assay
zation buffer and the suspension incubated 10 min at
37 °C. After other two centrifugations and washing the
final pellet was resuspended in ice-cold Tris-HCl 50 mM
containing 4 mM CaCl2, 0.1% ascorbic acid and 10 µM
pargyline (pH 7.4 at 25 °C). Each assay tube contained
50 mL of drug solution, 50 mL of [3H]-8-OH-DPAT to
achieve a final concentration of 0.8 nM, and 900 mL of
resuspended membranes (10 mg fresh tissue). The tubes
were incubated for 30 min at 25 °C and the incubation
was termined by rapid filtration under vacuum through
Whatman GF/B glass fibre filters. The filters were washed
three times with 5 mL of ice-cold 50 mM Tris-HCl buffer
(pH 7.2 at 25 °C). The radioactivity bound to the filters
was measured by liquid scintillation counter. Specific
[3H]-8-OH-DPAT binding was defined as the difference
between binding in the absence or presence of 10 µM
5-HT.
Striata were homogenized in 30 volumes (w/v) of
ice-cold 50 mM Tris-HCl buffer (pH 7.7 at 25 °C) using
a Polytron PT10 (setting 5 for 20 sec). Homogenates were
centrifuged twice for 10 min at 50000 g with resuspen-
sion of the pellet in fresh buffer. The final pellet was
resuspended in ice-cold Tris-HCl 50 mM containing
120 mM NaCl, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2,
0.1% ascorbic acid and 10 µM pargyline (pH 7.1 at
37 °C). Each assay tube contained 50 mL of drug solu-
tion, 50 mL of [3H]-SCH 23390 to achieve a final
concentration of 0.4 nM, and 900 mL of resuspended
membranes (3 mg fresh tissue). The tubes were incubated
for 15 min at 37 °C and the incubation was termined by
rapid filtration under vacuum through Whatman GF/B
glass fibre filters. The filters were washed three times
with 5 mL of ice-cold 50 mM Tris-HCl buffer (pH 7.7 at
25 °C). The radioactivity bound to the filters was mea-
sured by liquid scintillation counter. Specific [3H]-SCH
23390 binding was defined as the difference between
binding in the absence or presence of 0.1 µM piflutixol.
6.2.6. 5-HT2 Serotonergic binding assay
Prefrontal cortex was homogenized in 30 volumes
(w/v) of ice-cold 50 mM Tris-HCl buffer (pH 7.2 at
25 °C) using a Polytron PT10 (setting 5 for 20 sec).
Homogenates were centrifuged three times for 10 min at
50000 g with resuspension of the pellet in fresh buffer.
The final pellet was resuspended in ice-cold 50 mM
Tris-HCl (pH 7.4 at 37 °C). Each assay tube contained
50 mL of drug solution, 50 mL of [3H]-ketanserin to
achieve a final concentration of 0.8 nM, and 900 mL of
resuspended membranes (5 mg fresh tissue). The tubes
were incubated for 15 min at 37 °C and the incubation
was termined by rapid filtration under vacuum through
Whatman GF/B glass fibre filters. The filters were washed
three times with 5 mL of ice-cold 50 mM Tris-HCl buffer
(pH 7.2 at 25 °C). The radioactivity bound to the filters
was measured by liquid scintillation counter. Specific
[3H]-ketanserin binding was defined as the difference
between binding in the absence or presence of 1 µM
methysergide. The binding profile is reported in table III.
6.2.4. D2 Dopaminergic binding assay
Striata were homogenized in 30 volumes (w/v) of
ice-cold 50 mM Tris-HCl buffer (pH 7.7 at 25 °C) using
a Polytron PT10 (setting 5 for 20 sec). Homogenates were
centrifuged twice for 10 min at 50000 g with resuspen-
sion of the pellet in fresh buffer. The final pellet was
resuspended in ice-cold Tris-HCl 50 mM containing
120 mM NaCl, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2,
0.1% ascorbic acid and 10 µM pargyline (pH 7.1 at
37 °C). Each assay tube contained 50 mL of drug solu-
tion, 50 mL of [3H]-spiroperidol to achieve a final con-
centration of 0.4 nM, and 900 mL of resuspended mem-
branes (3 mg fresh tissue). The tubes were incubated for
15 min at 37 °C and the incubation was termined by rapid
filtration under vacuum through Whatman GF/B glass
fibre filters. The filters were washed three times with
5 mL of ice-cold 50 mM Tris-HCl buffer (pH 7.7 at
25 °C). The radioactivity bound to the filters was mea-
sured by liquid scintillation counter. Specific [3H]-
spiroperidol binding was defined as the difference be-
tween binding in the absence or presence of 1 µM
(+)-butaclamol.
6.2.7. Antagonism of apomorphine-induced climbing
behaviour in rats
60 and 30 min after s.c. administration of the test
compounds, rats (175–200 g) were injected s.c. with
1.5 mg/kg of apomorphine (APO), and put into individual
cylindrical cages with walls of smooth metal bars. The
animals were observed 15 min after apomorphine admin-
istration according to the method of Protais et al. [29].
6.2.5. 5-HT1A Serotonergic binding assay
Hippocampus was homogenized in 30 volumes (w/v)
of ice-cold 50 mM Tris-HCl buffer (pH 7.2 at 25 °C)
using a Polytron PT10 (setting 5 for 20 sec). Homoge-
nates were centrifuged twice for 10 min at 50000 g with
resuspension of the pellet in fresh buffer. After the second
centrifugation the pellet was resuspended in homogeni-
6.2.8. Contralateral turning behaviour in 6-OHDA-
lesioned rats
After 6-OHDA nigral lesion, rats were selected for
further testing on the basis of completing at least 250
contralateral turns after injection of apomorphine

124
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test compounds, turning behaviour was recorded for at
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