Synthesis and antihypertensive activity of 2,4-dioxoimidazolidin-1-yl and perhydro-2,4-dioxopyrimidin-1-yl ergoline derivatives

Article abstract of DOI:10.1016/S0014-827X(98)00023-8

The synthesis and antihypertensive activity of a series of 2,4-dioxoimidazoldin-1-yl and perhydro-2,4-dioxopyrimidin-1-yl ergoline derivatives are reported. The oral antihypertensive activity was studied in spontaneously hypertensive rats (SHRs) by measuring systolic blood pressure by an indirect tail-cuff method at different times after treatment. The prolactin lowering activity (indirectly measured by the nidation test) in rats and the oral acute toxicity in mice were also studied. The results of this study revealed potent antihypertensive ergoline derivatives devoid of side-effects related to the dopaminergic stimulation and the importance of the Δ^9,10 double bond for conferring high potency within these compounds.

Full text of DOI:10.1016/S0014-827X(98)00023-8

Il Farmaco 53 (1998) 293–304
Synthesis and antihypertensive activity of 2,4-dioxoimidazolidin-1-yl and
perhydro-2,4-dioxopyrimidin-1-yl ergoline derivatives
*
Sergio Mantegani , Enzo Brambilla, Carla Caccia, Laura Chiodini, Daniela Ruggieri,
Ernesto Lamberti, Enrico Di Salle, Patricia Salvati
Pharmacia and Upjohn, Viale Pasteur 10, 20014 Nerviano (Milan), Italy
Received 8 July 1997; accepted 11 February 1998
Abstract
The synthesis and antihypertensive activity of a series of 2,4-dioxoimidazolidin-1-yl and perhydro-2,4-dioxopyrimidin-1-yl ergoline
derivatives are reported. The oral antihypertensive activity was studied in spontaneously hypertensive rats (SHRs) by measuring systolic
blood pressure by an indirect tail-cuff method at different times after treatment. The prolactin lowering activity (indirectly measured by the
nidation test) in rats and the oral acute toxicity in mice were also studied. The results of this study revealed potent antihypertensive ergoline
derivatives devoid of side-effects related to the dopaminergic stimulation and the importance of the D9,10 double bond for conferring high
potency within these compounds.
q 1998 Elsevier Science S.A. All rights reserved.
Keywords: Ergolines; Antihypertensive activity; Nidation inhibitory activity
1. Introduction
known that ergoline derivatives, besides stimulating DA
receptor sites, can exert complex pharmacological effects
involving simultaneous interaction with the different mono-
aminergic (adrenergic a1 and a2, and serotonergic 5-HT1 and
5-HT2) recognition sites [9]. A useful approach in devel-
oping antihypertensive agents from this chemical class has
been suggested which takes advantage of ergoline’s multi-
target activity such as a combination of the inhibition of
sympathetic tone via a1 adrenoceptor blockade and antago-
nism of 5-HT2 receptors that moreover facilitate the action
of thea1 adrenoceptorantagonist[10]. Inaddition,thepoten-
tial antihypertensive activity related to the agonistic 5-HT1
component, commonly present in this class of compounds in
different amounts, might contribute to the antihypertensive
effect [11]. On the other hand, the antihypertensive activity
of the various classes of ergoline derivatives has received no
systematic attention and very little is known about the struc-
tural requirements of the molecule to be selectively endowed
with this activity. In the identification of antihypertensive
ergolines, we have observed compounds 1 (FCE 22716) and
13 (FCE 22715) to be promising antihypertensive agents
[12]. These compounds have notable antihypertensiveactiv-
ity, the former being more potent than the latter, and are
almost devoid of unwanted side-effects such as depression of
the central nervous system, present in a high number of anti-
Ergot alkaloids and their derivatives have long been rec-
ognized for their potent pharmacological activities of which
the effects upon the endocrine and the central nervous system
(CNS) have been the most extensively studied [1]. A num-
ber of ergot derivatives are currently in clinical use for the
treatment of CNS and endocrine disorders, such as nicergo-
line [2], used in the treatment of senile mental impairment,
and the dopamine agonists pergolide [3] and cabergoline
[4], developed as effective agents in the management of
hyperprolactinemic states and Parkinson’s disease (Fig. 1).
An increasing body of experimental data supports the con-
cept that dopamine plays an important role in the control of
blood pressure [5]. Dopaminergic ergoline derivatives such
as bromocriptine [6], lergotrile [7] and pergolide [8] have
been shown to lower blood pressure when administered to
experimental animals or humans. It has therefore been sug-
gested that they exert their hypotensive effect by stimulating
dopamine receptors. However, while dopamine agonists
proved to be antihypertensive agents, their effects upon pro-
lactin secretion and nausea are serious side-effects, which
limit their use for an antihypertensive indication. It is well
* Corresponding author.
0014-827X/98/$19.00 q 1998 Elsevier Science S.A. All rights reserved.
PII S0014-827X(98)00023-8

294
S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
Fig. 1. (a) Nicergoline; (b) pergolide; (c) cabergoline.
D2, 5-HT1 and 5-HT2 receptor sites were evaluated for the
most interesting compounds 1, 10, 13 and 21, as an indication
of the mechanism of action. Among them, the D9,10-unsatu-
rated compounds 10 and 21 emerged as very potent antihy-
pertensive agents with a highly favourable selectivity ratio
when the blood pressure lowering potency, measured asED25
(dose lowering mean blood pressure (MPB) by 25 mmHg),
was compared with the prolactin inhibitory effect and toxic-
ity. Structure–activity relationships within the new classes of
compounds are discussed.
Fig. 2. (a) Compound 1 (FCE 22716); (b) 13 (FCE 22715).
hypertensive compounds, as well as decreasing prolactin
secretion and nausea mainly connected to central DA stimu-
lation (Fig. 2).
2. Chemistry
As far as the mechanism of action is concerned, prelimi-
nary findings indicated that 1 induced a1 adrenoceptor and
serotonin 5-HT2 blockade (a potent antagonistic activity
against 5-HT2 receptors in rabbit aorta was observed),
accompanied by weak stimulation of dopamine receptors
[13]. The identification of these antihypertensive ergoline
derivatives with minimal side-effects which we wished to
avoid, prompted the synthesis of analogues of 1 and 13 in the
search for more potent compounds with potential for human
hypertension therapy to enable us to gain more insight on the
structure–activity relationship within this series. The most
significant structural modifications carried out on 1 and 13
can be summarized as follows:
(a) replacement of a carbonyl either by a thiocarbonyl or
a sulfonyl group in the 2,4-dioxoimidazolidin-1-yl or in the
perhydro-2,4-dioxopyrimidin-1-yl ring system;
(b) investigation of the role of the imidic proton by sub-
stitution with a linear or branched alkyl group;
(c) investigation of the role of the distance of the hetero-
cyclic ring from the ergoline nucleus either by shortening or
lengthening the chain in position 8;
(d) modifications in positions 1, 6, 8, 9, 10 of the ergoline
skeleton.
Themostwidelyusedmethodforpreparingthecompounds
described in this paper (see Tables 1 and 2) was based on
the nucleophilic reaction of the corresponding ergolinyl or
ergolenylamine with methyl acrylate or ethyl bromoacetate.
The alkylation of the amineswithethylbromoacetateindime-
thylformamide in the presence of an acid scavenger such as
potassium carbonate or triethylamine at room temperature
afforded the corresponding glycine ethyl ester derivatives in
good yields [14]. These intermediates were subsequently
converted into the 2,4-dioxoimidazolidin-1-yl derivatives 1–
12 by treatment with cyanic or thiocyanic acid, generated by
the action of hydrochloric acid on potassiumcyanateorpotas-
sium thiocyanate, or by reaction with the appropriate alkyl
isocyanate [15]. When the ring closure of the a-ureido- or
thioureidoethyl acetate derivative did not spontaneously
occur, the intermediates were heated in vacuo for some
minutes. Condensation of the amines with methyl acrylate in
refluxing 1,4-dioxane afforded, through a Michael 1,4-addi-
tion, the b-alanine methyl ester derivatives [16]. These, in
turn, were converted into the perhydro-2,4-dioxopyrimidin-
1-yl derivatives 13–23 by means of the same treatment men-
tioned above [17]. In the case of the sulfonyl analogues 6,
18, the N-[(6-methylergolin-8b-yl)methyl]glycine ethyl
ester and the N-[(6-methylergolin-8b-yl)methyl]-b-alanine
methyl ester were melted with neat sulfonamide. The 6-nor
derivative 2 was obtained by action ofthe2,2,2-trichloroethyl
chloroformate on 1 to give the N-[(6-trichloroethyloxycar-
bonylergolin-8b-yl)methyl]glycine ethyl ester, which was
subsequently reduced to the 6-nor derivative by reaction with
Zn dust in acetic acid [18]. The 2,3-dihydro derivative 3 was
obtained in an acceptable yield by reduction of 1 using
The compounds synthesized were evaluated by screening
the arterial blood pressure in spontaneously hypertensive rats
(SHRs). Compoundsshowinginterestingactivitieswerealso
tested for effects upon prolactin secretion. As a measure of
lethality, the dose which produced death in 50% of mice
treated (LD50) was also determined for the selected com-
pounds. Some of these compounds markedly reduced blood
pressure in SHRs and are endowed with modest antiprolactin
activity and toxicity. The affinities towards the a1, a2, D1,

S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
295
Table 1
2,4-Dioxoimidazolidin-1-yl ergolines 1–12
Comp.
W
X
R1
R2
R3
R4
D
8,9, D9,10
Formula
M.p. (8C)
1
2
3
4
5
6
7
8
9
CH2
CH2
CH2
CH2
CH2
CH2
CO
CO
CO
CO
CO
SO2
CO
CO
CO
CO
CO
CO
H
H
H
H
H
H
H
H
CH3
H
H
H
H
H
H
H
H
H
H
H
H
C19H22N4O2
C18H20N4O2
C19H24N4O2
C22H28N4O2
C22H28N4O2
C18H22N4O3
C18H20N4O2
C20H24N4O2
C20H24N4O2
C19H20N4O2
C19H23N5O2
C20H24N4O3
)300
240–242
160–165
188–189
210–212
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
HH
n-C3H7
i-C3H7
H
H
H
H
H
NH2
H
)300
295–297
242–244
292–294
282–284
191–193
234–236
C2H4
CH2
CH2
CH2
CH2
CH3
H
H
10
11
12
9,10
H
OCH3
H
Compound 3 (2,3-dihydro derivative).
Table 2
Perhydro-2,4-dioxopyrimidin-1-yl ergolines 13–23
Comp.
W
X
R1
R2
R3
R4
D
8,9, D9,10
Formula
M.p. (8C)
13
14
15
16
17
18
19
20
21
22
23
CH2
CH2
CH2
CH2
CH2
CH2
CO
CO
CO
CO
CS
SO2
CO
CO
CO
CO
CO
H
H
H
H
H
H
H
H
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
CH3
n-C3H7
i-C3H7
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C20H24N4O2
C21H26N4O2
C23H30N4O2
C23H30N4O2
C20H24N4OS
C19H24N4O3S
C18H22N4O2
C21H26N4O2
C20H22N4O2
C20H22N4O2
C21H26N4O2
)300
117–119
201–203
175–177
)300
)300
)300
140–142
290–292
190–193
)300
C2H4
CH2
CH2
CH2
H
H
CH3
9,10
8,9
H
H
NaCNBH3 in acetic acid [19]. Reaction of N-[(6-methyler-
golin-8b-yl)methyl]glycine ethyl ester with p-nitrophenyl
chloroformate in pyridine afforded in almost quantitative
yield the N-(p-nitrophenyloxycarbonyl)-N-[(6-methyler-
golin-8b-yl)methyl]glycine ethyl ester, which was con-
verted into 11 in reasonable yield by the action of hydrazine
(Fig. 3).
The amines required for preparing the compounds listed in
Tables 1 and 2 were prepared as follows: 6-methylergoline-
8b-methanamine 24, 6-methylergoline-8b-methanamine-
10a-methoxy 25 and 1,6-dimethylergoline-8b-methanamine
26 were obtained by reduction of the corresponding primary
carboxamide by lithium aluminium hydride. 1,6-Dimethyler-
goline-8b-carboxamide, necessary for the preparation of the

296
S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
Fig. 3. (a) BrCH2COOC2H5, K2CO3, DMF, r.t.; (b) KOCN, 1 N HCl, 908C; (c) CCl3CH2OCOCl, KHCO3, toluene, reflux; (d) powder Zn, AcOH, 358C; (e)
NH2SO2NH2, 1508C; (f) RNCO, dioxane, reflux; (g) 1708C, vacuum; (h) CH2_CHCOOCH3, dioxane, reflux; (i) p-nitrophenyl chlorocarbonate, pyridine,
r.t.; (l) NH2NH2, pyridine, reflux.
last compound, was prepared by methylation of the indole
nitrogen of the 6-methylergoline-8b-carboxamide with
potassium amide and methyl iodide in liquid ammonia [20].
6-Methyl-D8,9-didehydroergoline-8-methanamine 28 and 6-
methyl-D9,10-didehydroergoline-8b-methanamine 27 were
prepared from elymoclavine and lysergol, after conversion
into the corresponding azide, followed by reduction with tin
chloride [21]; 6-methylergoline-8b-amine 29 was prepared
through a Curtius degradation carried out on the hydrazide
of dihydrolysergic acid [22]; 6-methylergoline-8b-ethyla-
mine 30 was provided by reduction of 6-methylergoline-8b-
acetonitrile [23] (Fig. 4).
egg nidation up to 32 mg/kg p.o. and showed low toxicity
(Table 3). The ED25 was found to be 1.9 (1.3–2.4) mg/kg
p.o. and lasted 6–8 h. The 6-desmethyl analogue 2 showed
weaker antihypertensive activity in comparison with 1. The
2,3-dihydro derivative 3 displayed a short-lastingactivitythat
disappeared 5 h after treatment. The disubstituted derivatives
4, 5 revealed interesting antihypertensive activity but had a
greater toxicity than 1. The sulfonyl derivative 6 showed a
substantial decrease of activity. Shortening the side-chain at
C-8 led to 7, which was less active than 1. Increasing the
distance of the 2,4-dioxoimidazolidin-1-yl ring from the
ergoline skeleton by a methylene unit gave 8. Compound 8
showed modest antihypertensive activity and an enhanced
toxicity and nidationinhibitoryeffect. Substitutionatposition
1, as in 9, markedly reduced activity and increased toxicity.
The introduction of a double bond in position 9,10 of the
ergoline nucleus afforded 10, displaying a very high antihy-
pertensive activity at 1 mg/kg p.o. andlackingnidationinhib-
itory activity up to 32 mg/kg p.o. The safety ratio of 10 was
very favourable, with an LD50 exceeding 800 mg/kg p.o.
3. Results and discussion
3.1. 2,4-Dioxoimidazolidin-1-yl ergoline derivatives 1–12
The prototype 1 significantly lowered MBP in a dose
dependent way. Furthermore, 1 lacked inhibitory activity on

S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
297
Fig. 4. (a) LiAlH4, THF, reflux; (b) K, liq. NH3, CH3I; (c) C6H5SO2Cl, pyridine, 08C; (d) NaN3, HMPA, 458C; (e) SnCl2, 2 N NaOH, 08C; (f) ClCOCOCl,
DMF/CH3CN, y708C; (g) NH2NH2, EtOH, reflux; (h) NaNO2, 1 N HCl, 08C/1508C; (i) KCN, DMSO, 508C.
When MPB was measured directly in chronically cannulated
SHRs, the strong antihypertensive effect observed during the
screening was confirmed (Fig. 5). The ED25 of 10 was deter-
mined and was found to be 142.0 (96.0–190.0) mg/kg p.o.
The antihypertensive effect had a prompt onset and was long
lasting. Increases of heart rate (HR) (Fig. 6) after adminis-
tration of 10 were modest even at the highest dose (250 mg/
kg p.o.) The N-amino derivative 11 was revealed to be a
potent antihypertensive but with a short duration of action.
Introduction of a methoxy group at position 10a led to 12
which was totally inactive.
3.2. Perhydro-2,4-dioxopyrimidin-1-yl ergoline derivatives
13–23
The prototype compound 13 lacking substitution on the
heterocyclic ring was a very potent and selective antihyper-
tensive agent. This compound had no effect on prolactin
secretion, even when it was administered at very high doses
(Table 4). The substituted compounds 14–16 showed that
the replacement of the imidic hydrogen by a linear or
branched alkyl group led to a similar antihypertensive activ-
ity. However, this was accompanied by increased toxicity.

298
S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
Table 3
Antihypertensive activity of 2,4-dioxoimidazolidin-1-yl ergolines 1–12
Comp.
Dose
(mg/kg p.o.)
Antihypertensive activity: SBP b after treatment, D
(mmHg)
Nidation inhibition
in rats: ED50
Approximate toxicity
in rats: LD50
(mg/kg p.o.)
(mg/kg p.o.)
1 h
5 h
Vehicle a
1
q3.7"2.4
q3.5"2.3
20
1
20
20
1
7.5
3.75
1
20
15
5
y60.0"12.4**
y16.5"8.3
y72.5"2.5
)32
)800
y37.5"7.7**
y35.0"6.1**
y8.7"8.2
y41.2"1.2**
y26.2"8.9
y26.2"11.9*
y13.7"13.9
y13.7"8.9
y55.0"5.0**
y7.5"8.3
y52.0"4.3**
y28.7"6.5*
y63.7"8.0**
y58.7"4.2**
y25.0"10.6
2
3
4
5
6
y43.7"8.7**
y40.6"6.7*
y43.7"2.3**
y37.5"14.0
y35.0"10.2*
y11.0*"12.3
y17.5"10.3
y50.0"15.0*
y6.2"6.5
y55.0"5.4**
y28.7"7.7
y55.0"15.7*
y40.0"4.5*
y17.5"8.7
)800
)800
)8
)8
)8
400–800
200–400
100–200
7
8
)800
)8
400–800
9
20
1
7.5
1
4–8
400–800
10
11
12
)32
)32
)800
)800
20
a Methocel 0.5% wt./vol., 2 ml/kg; *p-0.05; **p-0.01 from corresponding control values by Dunnet’s test.
b SBP, systolic blood pressure.
17, which possesses a perhydro-2-thioxo-4-oxopyrimidin-1-
yl moiety, exhibited potency similar to 13, although with an
increased nidation inhibitory effect and toxicity. By analogy
with the former series, a relevant decrease in activity was
observed by the sulfonyl analogue 18. In correlatingtheactiv-
ity with the distance of the dihydrouracyl to the ergoline
nucleus, it was shown that direct linking of the perhydro-2,4-
dioxopyrimidin-1-yl moiety to the ergoline skeleton led to
decreasedpotency, asshownby19. Lengtheningofonemeth-
ylene unit, as in the case of 20, resulted in a slight decrease
of activity and increase of toxicity. Similarly to 10, the anti-
hypertensive activity was remarkably enhanced by the pres-
ence of a D9,10 double bond as in 21. Shifting the double bond
from position 9,10 to position 8,9 gave 22. This compound
was still active, although a dose related correlation was not
found. Alkylation in position 1, as in the case of 23, reduced
the antihypertensive activity and dramatically increased tox-
icity. The extremely marked effect of the unsaturated com-
pound 21 in the screening test prompted us to investigate
further its antihypertensive activity by direct measurementof
MPB in chronically cannulated SHRs. As shown from the
data in Fig. 7, this compound is endowed with a marked
activity at very low doses (31.2–50.0) mg/kg p.o. The ED25
was 24.3 (6.2–44.0) mg/kg p.o. Similarly to 10, the antihy-
pertensive effect had a prompt onset and was long lasting,
reaching a peak 4–6 h after treatment at all dosages. Heart
rate was not significantly affected for animals treated with 21
compared with controls (Fig. 8). Interestingly, the ED25
(24.3 mg/kg p.o.) was about 100 timeslower thanthataffect-
ing prolactin secretion (2.4 mg/kg p.o.).
Fig. 5. Time course of effects on mean blood pressure (MPB) produced by
compound 10 in chronically cannulated SHRs. The results represent mean
changes " from pretreatment values (ns6–20/group). Solid symbols rep-
resent statistically (p-0.01) significant changesfrompre-drug status(Dun-
net’s test); s, control vehicle; h, 62; m, 125; d, 250 mg/kg p.o.
Fig. 6. Time course of effects on heart rate (HR) produced by compound
10 in chronically cannulated SHRs. The results represent mean changes "
from pretreatment values (ns6–20/group). Solid symbols represent statis-
tically (p-0.01) significant changes from pre-drug status (Dunnet’s test);
s, control vehicle; h, 62; m, 125; d, 250 mg/kg p.o.

S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
299
Table 4
Antihypertensive activity of perhydro-2,4-dioxopyrimidin-1-yl ergolines 13–23
Comp.
Dose
(mg/kg p.o.)
Antihypertensive activity: SBP b after treatment, D
(mmHg)
Nidation inhibition
in rats: ED50
Approximate toxicity
in rats: LD50
(mg/kg p.o.)
(mg/kg p.o.)
1 h
5 h
Vehicle a
13
q3.6"2.4
q3.7"2.4
20
1
7.5
7.5
1
1
20
5
20
20
20
1
20
20
5
y85.0"3.5**
y20.0"7.3
y65.0"3.5
y38.7"2.4**
y56.2"5.9**
y65.3"3.5**
y35.8"8.8**
y25.0"9.7
)32
)800
14
15
y55.0"7.6**
y51.8"8.0**
y31.2"8.6
200–400
16
17
y23.7"9.4
400–800
400–800
y62.5"4.8**
y38.7"13.9**
y26.2"13.0
y50.0"3.5
y66.2"4.7**
y66.7"15.9**
y12.5"3.3
4
18
19
20
)800
)800
400–800
y18.7"2.3
)8
16
y51.6"24.5**
y20.0"4.5**
y115.0"0**
y60.0"13.2
y32.5"9.2
y55.0"5.0**
y28.7"7.1*
y126.2"4.3**
y66.2"9.4**
y48.7"3.1**
y11.2"1.2
21
22
2.4
8
)800
)800
23
1
y18.7"4.3
50–100
a Methocel 0.5% wt./vol., 2 ml/kg; *p-0.05; **p-0.01 from corresponding control values by Dunnet’s test.
b SBP, systolic blood pressure.
According to the binding results in Table 5, some struc-
ture–affinity relationship can be drawn for the most interest-
ing compounds 1, 10 and 13, 21. The adrenergic a1, a2
components were higher in the 2,4-dioxoimidazolidin-1-yl
than in the perhydro-2,4-dioxopyrimidin-1-yl series. The
dopaminergic D1, D2 components were negligible in the two
series. The low D2 component was in accordance with the in
vivo nidation inhibiting activity data. This correlation was
further demonstrated by 21. Compound 21 has the highest D2
affinity among the compounds considered. This affinity was
accompanied by the highest activity in the nidation test. The
introduction of the D9,10 double bond remarkably affected
the serotonergic 5-HT1, 5-HT2 components. A noticeable
increase in affinity was observed when 1 and 13 were com-
pared with 10 and 21. Such enhancement was more pro-
nounced for the perhydro-2,4-dioxopyrimidin-1-yl series,
where the increase in 5-HT1 was more than thirtyfold and in
5-HT2 more than tenfold.
Fig. 7. Time course of effects on mean blood pressure (MPB) produced by
compound 21 in chronically cannulated SHRs. The results represent mean
changes " from pretreatment values (ns6–20/group). Solid symbols rep-
resent statistically (p-0.01) significant changesfrompre-drug status(Dun-
net’s test); s, control vehicle; h, 31.2; m, 125; d, 500 mg/kg p.o.
In conclusion, our results showed that either the perhydro-
2,4-dioxopyrimidin-1-yl or 2,4-dioxoimidazolidin-1-yl moi-
eties, introduced by way of a C–N bond, can be useful sub-
stituting groups in the search for novel ergoline derivatives
endowed with antihypertensive effect. With respect to com-
pounds 1 and 13, the antihypertensive activity is not substan-
tially affected by the substituent present in position 3 of the
2,4-dioxoimidazolidin-1-yl and perhydro-2,4-dioxopyrimi-
din-1-yl rings, whereas toxicity is increased. Decreasedactiv-
ity was observed by shortening the chain in position 8. On
the contrary, the antihypertensive activity was not affected
by lengthening the side-chain. The replacement of the car-
bonyl by a thiocarbonyl group did not affect the antihyper-
Fig. 8. Time course of effects on heart rate (HR) produced by compound
21 in chronically cannulated SHRs. The results represent mean changes "
from pretreatment values (ns6–20/group). Solid symbols represent statis-
tically (p-0.01) significant changes from pre-drug status (Dunnet’s test);
s, control vehicle; h, 31.2; m, 125; d, 500 mg/kg p.o.

300
S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
Table 5
were carried out before treatment, and at 1 and 5 h after
dosing. Control animals received the vehicle methocel 0.5%
wt./vol., 2 ml/kg b.w. The results were evaluated by means
of two-way analyses of variance. The significance of the
differences between means was evaluated by Dunnett’s mul-
tiple comparison test. This compared the blood pressure
changes (D mmHg) at different times after treatment with
the corresponding values of the control group. Intra-arterial
measurement of mean blood pressure was performedthrough
catheters implanted in the right carotid artery of 6–20 rats/
group under halothane anesthesia. Twenty-fourhoursfollow-
ing surgery, the animals were placed in a Ballman cage and
the arterial cannula was connected through a Statham P23 Db
pressuretransducertoaBeckmannDynographforcontinuous
recording of mean blood pressure and heart rate. Recordings
were made under basal conditions and up to 24 h after drug
or vehicle was orally administered.
Binding profile for the ergoline derivatives 1, 10, 13, 21
Structure
a1
a2
D1
D2
5-HT1 5-HT2
0.13
0.17
2.21
1.05
0.21
0.01
0.27
0.11
0.21
1.02
0.18
0.33
1.52
1.13
1.20
1.12
3.50
0.05
1.10
0.04
4.1.2. Prolactin inhibitory activity
The prolactin secretion inhibitory activity was evaluated
indirectly using the nidation inhibition test in rats. Adult
Sprague-Dawley female rats (C. River, Italy) were caged
with fertile male rats in the evening of the day of proestrus.
Only rats with spermatozoa in vaginal smears on the follow-
ing day (1 day of pregnancy) were included in the protocol.
Theyweretreatedorallyonthemorningofday5ofpregnancy
with a suspension of the test compounds in methocel (0.5%
wt./vol.) orally. On day 14, the animals were anesthetized
and the uteri were examined for the presence of implantation
sites [24]. Compounds were tested at different doses (6–8
animals per group) and the dose inhibiting nidation in 50%
of the animals (ED50) was determined.
0.79
0.32
1.03
0.45
Affinities are expressed as IC50 in mM; standard errors are "10% of the
mean reported values.
tensive activity, whilst the replacement by a sulfonyl group
led to a marked decrease in potency. A remarkable increase
in antihypertensive activity was achieved by introduction of
a double bond between positions 9 and 10 of the ergoline
nucleus in both series. Our results showed that the introduc-
tion of a methyl group in position 1 or a methoxy in position
10a of the ergoline nucleus almost abolished the antihyper-
tensive activity and increased the toxicity. Compounds 10
and 21 have been selected for further preclinical evaluation
on the basis of their in vitro profile implying a potential
serotonergic mechanism of action and their high antihyper-
tensive activity accompanied by very low toxicity.
4.1.3. Acute toxicity
The acute oral toxicity was evaluated in male Swiss mice
(C. River, Italy). Eachcompoundwassuspendedinmethocel
(0.5% wt./vol.) and administered at various dose levels
(three animals per dose). The dose causing the death of 50%
of the animals (LD50) within 7 days following treatment was
determined.
4.1.4. Binding profile
The compounds described in this study were evaluated for
their a1, a2, D1, D2, 5-HT1 and 5-HT2 receptor binding affin-
ities assessed by measuring the displacement of [3H]-pra-
zosin binding in rat frontal cortex [25], [3H]-yohimbine
binding in rat frontal cortex [26], [3H]-SCH-23390 binding
in rat striatum [27], [3H]-spiroperidol binding inratstriatum
[28], [3H]-5-HT binding in rat hippocampus [29] and
[3H]-ketanserin binding in rat prefrontal cortex [30],
respectively.
4. Experimental
4.1. Pharmacological methods
4.1.1. Antihypertensive activity
Indirect measurements of systolic blood pressure were car-
ried out in groups of 4–5 spontaneously hypertensive male
rats, age 8–10 weeks (SHR, Kyoto, Japan; C. River, Italy).
On the day of the experiment, the animals were maintained
in an environment of 368C for 15 min. Systolic bloodpressure
wasmeasured byan indirecttail-cuffmethodusingaWqW/
BP Recorder, model 8005. Each determination was averaged
from at least four readings. Blood pressure measurements
4.2. Chemical methods
Melting points were determined using a Buchi melting
¨
point apparatus and are uncorrected. IR spectrawererecorded

S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
301
on a Perkin- Elmer 125 spectrophotometer. 1H NMR spectra
4.2.2. 1-[(6-Methylergoline-8b)methyl]-2,4-
dioxoimidazolidine 1
were recorded on a Varian XL-200 spectrometer in CDCl3 or
DMSO-d6 solutions. Chemical shifts are expressed in d (ppm
from zero tetramethylsilane(TMS)). Assignmentsweresup-
ported by suitable decoupling experiments. The chemical
shifts are reported only for protons with clear attribution. EI
were recorded at 70 eV on a Varian MAT 311-A spectrom-
eter. All compounds had IR, 1H NMR and mass spectra that
were fully consistent with their structure. The results of the
elemental analyses (C, H, N) were within "0.4% of the
theoretical values. The examples presented below are repre-
sentative of all synthetic procedures.
A solution of 9.4 g (0.116 mol) of potassium cyanate in
100 ml of water was slowly added dropwise to a stirred
solution of 20 g (0.058 mol) of N-[(6-methylergolin-8b-
yl)methyl]glycine ethyl ester in 116 ml of 1 N hydrochloric
acid. After stirring for 2 h at room temperature, the solution
was heated at 758C for 5 h then set aside overnight. The
precipitate was filtered off, washed with water then twice
crystallized from methanol, furnishing 18.5 g (94%) of 1.
Anal. (C19H22N4O2) C, H, N. IR (KBr): 3400 (n N–H
amide); 1750 (n C_O); 1705 (n C_O); 1465 (n N–H
amide) cmy1. 1H NMR (DMSO-d6, 200 MHz): d 0.94 (ddd,
Js12.3, 12.3, 12.3 Hz, 1H, H9-ax); 1.79 (dd, Js11.4, 11.4
Hz, 1H, H-7ax); 1.93 (dd, Js4.3, 9.2 Hz, 1H, H-8ax); 2.10
(m, 1H, H-9ax); 2.23 (ddd, Js4.3, 9.5, 11.5 Hz, 1H, H-
5ax); 2.32 (s, 3H, CH3N); 2.3–2.36 (m, 2H, H-4ax, H-9e);
2.75 (ddd, Js3.5, 9.5, 12.3 Hz, 1H, H-10ax); 2.88 (b d,
Js11.4, 1H, H-7e); 3.16 (m, 2H, CH2-8); 3.28 (dd, Js4.3,
14.6 Hz, 1H, H-4e); 3.99 (s, 2H, NCH2CO); 6.77 (d, Js8.0
Hz, 1H, H-12); 6.99 (t, Js8.0 Hz, 1H, H-13); 7.10 (d,
Js8.0 Hz, 1H, H-14); 10.59 (b s, 1H, NH-1); 10.74 (b s,
1H, CONHCO). MS (EI) m/z 338 (88, Mqy); 237 (12);
225 (22), 223 (27); 197 (19); 180 (23); 167 (27); 154
(61); 144 (100); 127 (22).
4.2.1. N-[(6-Methylergolin-8b-yl)methyl]glycine ethyl ester
A solution of 14.4 g (0.086 mol) of ethyl bromoacetate in
50 ml of dimethylformamide at room temperature wasslowly
added dropwise to a stirred solution of 20 g (0.078 mol) of
24 and 10.8 g (0.080 mol) of potassium carbonate in 250 ml
of dimethylformamide. After stirring for 5 h, the solvent was
removed in vacuo and the residue was partitioned between
ethyl acetate and brine. The organic layer was dried
(Na2SO4), then evaporated to dryness. The crude reaction
mixture was chromatographed on silica gel eluting with chlo-
roform. The first fractions provided 2.3 g of N-[(6-methyl-
ergoline-8b)methyl]iminodiacetic acid ethyl ester as a white
foam. Anal. (C24H33N3O4) C, H, N. IR (KBr): 3400 (n N–
H); 1745 (n C_O) cmy1. 1H NMR (CDCl3, 200 MHz): d
1.05 (ddd, Js12.1, 12.1, 12.0 Hz, 1H, H-9ax); 1.26 (t,
Js7.1 Hz, 6H, COOCH2CH3); 1.90 (dd, Js11.2, 11.2 Hz,
1H, H-7ax); 2.15 (m, 2H, H-5ax, H-8ax); 2.48 (s, 3H,
CH3N); 2.56 (dd, Js8.6, 12.7 Hz, 1H, CH(H)-8); 2.7 (m,
2H, H-4ax, H-9e); 3.41 (dd, Js4.2, 14.8 Hz, 1H, H-4e);
3.59 (m, 4H, CH2NCH2); 4.16 (q, Js7.1 Hz, 4H,
COOCH2CH3); 6.8–7.2 (m, 4H, aromatic protons); 7.92 (b
s, 1H, NH-1). MS (EI) m/z 427 (14, Mqy); 354 (8); 340
(6); 238 (31), 237 (31); 223 (23); 167 (100); 154 (33);
130 (48); 127 (11). Continuing the elution with a mixture
of chloroform/ethanol (98:2), 23 g (86% yield) of N-[(6-
methylergolin-8b-yl)methyl]glycine ethyl ester were recov-
ered after crystallization from ethyl acetate, m.p. 174–1768C.
Anal. (C20H27N3O2) C, H, N. IR (KBr): 3300 (n N–H);
4.2.3. 1-[(6-Methylergoline-8b)methyl]-2,4-dioxo-3-
propylimidazolidine 4
A solution of 3 g (0.01 mol) of N-[(6-methylergolin-8b-
yl)methyl]glycine ethyl ester and 1 g (0.011 mol) of n-
propyl isocyanate in 75 ml of 1,4-dioxane was refluxed for 2
h. After removal of the solvent, the crude a-ureido ester was
heated at 1508C in a vacuum of 10 mmHg for 30 min. The
resulting product was filtered over a small pad of silica gel
eluting with chloroform. Crystallization from acetone pro-
vided 2.7 g of 4 (81%). Anal. (C21H26N4O2) C, H, N. IR
(KBr): 1755 (n C_O); 1705 (n C_O); 1465 (n N–H
amide)cmy1. 1HNMR(CDCl3, 200MHz):d0.94(t,Js7.3
Hz, 3H, NCH2CH2CH3); 1.18 (ddd, Js12.2, 12.2, 12.2 Hz,
1H, H-9ax); 1.67 (m, 2H, NCH2CH2CH3); 2.02 (dd,
Js11.2, 11.2 Hz, 1H, H-7ax); 2.20 (m, 2H, H-5ax, H-8ax);
2.27 (ddd, Js1.7, 11.4, 14.8 Hz, 1H, H-4ax); 2.37 (s, 3H,
CH3N); 2.60 (m, 1H, H-9e); 2.95 (m, 2H, H-7e, H-10ax);
3.2–3.6 (m, 5H, H-4e, NCH2CH2CH3, CH2-8); 3.92 (m, 2H,
NCH2CO), 6.8–7.2 (m, 4H, aromatics), 7.99 (b s, 1H, NH-
1). MS (EI) m/z 366 (100, Mqy); 239 (17); 225 (36),
223 (34); 195 (18); 182 (22); 167 (32); 154 (50); 144
(94); 127 (21).
1
1725 (n C_O) cmy1. H NMR (DMSO-d6, 200 MHz): d
0.97 (ddd, Js12.3, 12.3, 12.3 Hz, 1H, H7-ax); 1.20 (t,
Js7.0 Hz, 3H, COOCH2CH3); 2.0 (m, 2H, H-8ax, H-8ax);
2.23 (ddd, Js4.3, 9.5, 11.5 Hz, 1H, H-5ax); 2.46 (s, 3H,
CH3N); 2.40–2.7 (m, 4H, H-9e, H-4ax, CH2-8); 2.88 (ddd,
Js3.5, 9.5, 12.3 Hz, 1H, H-10ax); 3.14 (b d, Js7.3 Hz,
1H, H-7e); 4.16 (q, Js7.1 Hz, 2H, COOCH2CH3); 6.79 (d,
Js8 Hz, 1H, H-12); 6.98 (s, 1H, H-2); 7.0 (t, Js8.0 Hz,
1H, H-13); 7.12 (d, Js8.0 Hz, 1H, H-14); 10.68 (b s, 1H,
NH-1). MS (EI) m/z 341 (76, Mqy); 268 (14); 238 (62),
225 (26); 223 (40); 183 (18); 167 (100); 154 (65); 144
(30); 127 (19).
4.2.4. 1-[(6-Methylergoline-8b)methyl]-2-S,S-dioxide
thiodiazolidine-3-one 6
A finely ground mixture of 5 g (0.014 mol) of N-[(6-
methylergolin-8b-yl)methyl]glycine ethyl ester and 5 g
(0.052 mol) of sulfamide was slowly heated until melting
with continuous stirring and kept at melting point for 10 min.

302
S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
After cooling, the mixture was extracted with chloroform/
methanol (10:2) and the solution was washed with brine and
dried. The solvent was removed and the dark residue was
chromatographed on silica gel eluting with acetone. The
eluted product was crystallized from methanol, affording 2.8
g (53%) of 6. Anal. (C18H22N4O3S) C, H, N. IR (KBr):
3100–3700 (n N–H); 1640 (n C_O); 1280 (n SO2 anti-
sym.); 1140 (n SO2 sym.) cmy1. 1H NMR (DMSO-d6, 200
MHz): d 1.31 (ddd, Js12.0, 12.0,12.0 Hz, 1H, H-9ax); 2.96
(s, 3H, CH3Nq); 3.49 (m, 2H, NCH2C_O); 6.8–7.2 (m,
4H, aromatic protons); 9.71 (b s, 1H, SO2NH); 10.5 (b s,
1H, NH-1). MS (EI) m/z 374 (23, Mqy); 310 (4); 269
(10), 255 (16); 237 (35); 223 (68); 167 (81); 154 (100);
144 (54); 127 (58).
NCH2CO); 4.30 (m, 1H, H-8ax); 6.77 (d, Js7.0 Hz, 1H,
H-12); 6.96 (d, Js1.7 Hz, 1H, H-2); 7.0 (m, Js7.0 Hz,
1H, H-13); 7.12 (d, Js7.0, 1H, H-14); 10.62, 10.80 (two
b s, 2H, NH-1, CONHCO). MS (EI) m/z 324 (31, Mqy);
224 (59); 223 (100), 209 (9); 197 (8); 181 (12); 167 (57);
155 (37); 154 (77); 127 (36).
4.2.7. 1-[(6-Methylergolin-8b-yl)methyl]-2,4-dioxo-3-
aminoimidazolidine 11
A solution of 2.4 g (0.012 mol) of p-nitrophenyl chloro-
formate dissolved in 25 ml of tetrahydrofuran was added
dropwise to a stirred solution of 3 g (0.008 mol) of N-[(6-
methylergolin-8b-yl)methyl]glycine ethyl ester in 30 ml of
pyridine. After stirring for 2 h at room temperature, 5 ml of
hydrazine hydrate were added and the solution was refluxed
for 1 h. The solvent was removed then the residue was taken
up in ethyl acetate and washed several times with a 10%
solution of potassium carbonate. After drying and removal
of the solvent, the crude product was chromatographed over
silica gel eluting with chloroform. Crystallization from eth-
anol gave 1.9 g (61% yield) of 11. Anal. (C19H23N5O2) C,
H, N. IR (KBr): 3390 (n N–H); 1770 (n C_O); 1710 (n
4.2.5. N-(6-Methylergolin-8b-yl)glycine ethyl ester
A solution of 3.1 g (0.018 mol) of ethyl bromoacetate in
20 ml of dimethylformamide at room temperature wasslowly
added dropwise to a stirred solution of 4 g (0.167 mol) of
29 and 2.29 g (0.167 mol) of potassium carbonate in 50 ml
of dimethylformamide. After 3 h, the solution was diluted
with ethyl acetate and washed several times with brine. Dry-
ing and removal of the solvent afforded a residue that was
twice crystallized from a small volume of ethanol, affording
3.9 g (75% yield) of N-(6-methylergolin-8b-yl)glycine
ethyl ester, m.p. 231–2338C. Anal. (C19H25N3O2) C, H, N.
IR (KBr): 3340 (n N–H); 1740 (n C_O) cmy1. 1H NMR
(CDCl3, 200 MHz): d 1.29 (ddd, Js12.2, 12.2, 12.2 Hz,
1H, H-9ax); 1.30 (t, Js7.1 Hz, 3H, COOCH2CH3); 2.04
(dd, Js10.5, 10.5 Hz, 1H, H-7ax); 2.18 (ddd, Js4.3, 9.6,
11.0 Hz, 1H, H-5ax); 2.49 (s, 3H, CH3N); 2.67(ddd, Js1.7,
11.0, 14.7 Hz, 1H, H-4ax); 2.8–3.1 (m, 3H, H-8ax, H-9e, H-
10ax); 3.17 (ddd, Js2.1, 4.0, 10.5 Hz, 1H, H-7e); 3.40 (dd,
Js4.3, 14.7 Hz, 1H, H-4e); 3.55 (s, 2H, NHCH2COO);
4.22 (q, Js7.1 Hz, 2H, COOCH2CH3); 6.8–7.2 (m, 4H,
aromatic protons); 8.08 (b s, 1H, NH-1). MS (EI) m/z 327
(16, Mqy); 253 (5); 223 (8), 209 (4); 198 (26); 181 (16);
167 (18); 155 (35); 154 (100); 127 (24).
1
C_O); 1465 (n N–H amide) cmy1. H NMR (DMSO-d6,
200 MHz): d 0.94 (ddd, Js12.2, 12.2, 12.2 Hz, 1H, H-9ax);
1.81 (dd, Js11.1, 11.1 Hz, 1H, H-7ax); 1.94 (ddd, Js4.2,
9.4, 10.7 Hz, 1H, H-5ax); 2.13 (m, 1H, H-8ax); 2.30 (s, 3H,
CH3N); 2.4–2.6 (m, 2H, H-4ax, H-9e); 2.76 (m, 1H, H-
10ax); 2.82 (m, 1H, H-7e); 3.1–3.3 (m, 3H, CH2-8H, H-
4e); 3.97 (s, 2H, NCH2CO); 4.75 (s, 2H, NNH2); 6.67 (d,
Js7.0 Hz, 1H, H-13); 6.95 (s, 1H, H-2); 6.99 (t, Js7 Hz,
1H, H-13); 7.10 (d, Js7.0 Hz, 1H, H-14); 10.60 (b s, 1H,
NH-1). MS (EI) m/z 353 (100, Mqy); 237 (14); 225 (20),
223 (23); 197 (13); 182 (11); 167 (20); 154 (46); 144
(59); 127 (18).
4.2.8. N-[(6-Methylergolen-D9,10-8b-yl)methyl]-b-alanine
methyl ester
A solution of 10 g (0.04 mol) of 27 and 3.75 g (0.043
mol) of methylacrylatein150mlof1,4-dioxanewasrefluxed
for 5 h. After removal of the solvent, the residue was filtered
through a pad of silica gel eluting with acetone. The first
fractions afforded, after evaporation of the solvent and crys-
tallization from diethyl ether, 0.7 g of N-(b-methoxycar-
bonylethyl)-N-[(6-methylergolen-D9,10-8b-yl)methyl]-b-
alanine methyl ester, m.p. 157–1598C. Anal. (C24H31N3O4)
4.2.6. 1-(6-Methylergolin-8b-yl)-2,4-dioxoimidazolidine 7
A solution of 1.5 g (0.018 mol) of potassium cyanate in
10 ml of water was added dropwise to a stirred solution of 3
g (0.009 mol) of N-(6-methylergolin-8b-yl)glycine ethyl
ester in 18.0 ml of 1 N hydrochloric acid. After stirring for 1
h at room temperature, the solution was heated at 908C for 3
h. After cooling, the precipitate was filtered off, washed with
water and subsequently crystallized twice from ethanol, pro-
viding 2.7 g of 7. Anal. (C18H20N4O2) C, H, N. IR (KBr):
3390 (n N–H); 1750 (n C_O); 1700 (n C_O); 1460 (n N–
C, H, N. IR (KBr): 3430 (n N–H); 1725 (n C_O) cmy1
.
1H NMR (CDCl3, 200 MHz): d 2.12 (dd, Js10.2 Hz, 1H,
H-7ax); 2.1-2.5 (m, 6H, CH2-8, 2 CH2COO); 2.56 (s, 3H,
CH3N); 2.68 (ddd, Js1.7, 11.3, 14.4 Hz, 1H, H-4ax); 2.70
(m, 1H, H-8); 2.89 (m, 4H, NCH2yCH2); 3.02 (dd, Js5.0,
10.2 Hz, 1H, H-7e); 3.12 (m, 1H, H-5ax); 3.52 (dd, Js5.4,
14.4Hz, 1H, H-4e); 3.67 (s, 6H, COOCH3); 6.36 (b s, 1H,
H-9); 6.89 (dd, Js1.7, 1.7 Hz, 1H, H-2); 7.18 (s, 3H, H-
12, H-13, H-14); 7.92 (b s, 1H, NH-1). MS (EI) m/z 425
(3.5, Mqy); 352 (4); 221 (11); 203 (11), 202 (100); 192
1
H amide) cmy1. H NMR (DMSO-d6, 200 MHz): d 1.50
(ddd, Js12.2, 12.2, 12.2 Hz, 1H, H-9ax); 1.98 (ddd, Js4.3,
9.4, 10.8 Hz, 1H, H-5ax); 2.21 (dd, Js11.0, 11.0 Hz, 1H,
H-7ax); 2.35 (s, 3H, CH3N); 2.49 (ddd, Js1.7, 11.0, 14.9
Hz, 1H, H-4ax); 2.60–3.0 (m, 3H, H-7e, H-9e, H-10ax);
3.28 (dd, Js4.3, 14.9 Hz, 1H, H-4e); 3.98 (m, 2H,

S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
303
(4); 189 (3); 167 (3); 154 (4). Continuing the elution with
the same solvent, 11.4 g (85%) of N-[(6-methylergolen-
D
CH2); 6.22 (b s, 1H, H-9); 7.02–7.2 (m, 3H, H-12, H-13,
H-14); 10.11, 10.67 (two b s, 2H, NHCO, NH-1). MS (EI)
m/z 350 (100, Mqy); 292 (9); 235 (32); 223 (64), 221
(59); 205 (25); 192 (71); 180 (64); 167 (24); 154 (38).
9,10-8b-yl)methyl]-b-alanine methyl ester were recovered
after crystallization from acetone, m.p. 187–1908C. Anal.
(C20H25N3O2) C, H, N. IR (KBr): 3520 (n N–H); 1735 (n
1
C_O) cmy1. H NMR (CDCl3, 200 MHz): d 2.24 (dd,
Js10.2 Hz, 1H, H-7ax); 2.5–2.8 (m, 5H, H-4ax, CH2-8,
CH2COO); 2.57 (s, 3H, CH3N); 2.68 (ddd, Js1.7, 11.3,
14.4 Hz, 1H, H-4ax); 2.84 (m, 1H, H-8); 2.95 (m, 2H,
NCH2-CH2); 3.10 (m, 2H, H-7e, H-5ax); 3.51 (dd, Js5.4,
14.4 Hz, 1H, H-4e); 3.70 (s, 3H, COOCH3); 6.38 (b s, 1H,
H-9); 6.88 (dd, Js1.9, 1.9 Hz, 1H, H-2); 7.18 (m, 3H, H-
12, H-13, H-14); 8.07 (b s, 1H, NH-1). MS (EI) m/z 339
(61, Mqy); 236 (21); 224 (100); 221 (46), 193 (59); 192
(55); 180 (15); 167 (20); 154 (20).
References
[1] W.T. Rall, in: P.B. Molinoff, W.R. Ruddon (Eds.), The Pharmaco-
logical Basis of Therapeutics, 8th ed., MacMillan, New York, 1990,
pp. 933–953.
[2] B. Saletu, E. Paulus, L. Linzmayer, Nicergoline in senile dementia of
Alzheimer type and multi-infarct dementia: a double-bind placebo-
controlled, clinical and EEG/ERP mapping study, Psychopharmacol-
ogy 117 (1995) 385–395.
[3] W. Fuller, J.A. Clemens, E.C. Kornfeld, H.D. Snoddy, E.B. Smalstig,
N.G. Bach, Effects of (8b)-8-[(methylthio)methyl]-6-propylergo-
line on dopaminergic function and brain dopamine turnover in rats,
Life Sci. 24 (1979) 375–382.
4.2.9. Perhydro-1-[(6-methylergolin-8b-yl)methyl]-2-
thioxo-4-oxopyrimidine 17
[4] E. Brambilla, E. Di Salle, G. Briatico, S. Mantegani, A. Temperilli,
Synthesis and nidation inhibitory activity of a new class of ergoline
derivatives, Eur. J. Med. Chem. 24 (1989) 421–426.
[5] A. Berkowitz, Dopamine and dopamine receptors as target sites of
cardiovascular drug action, Fed. Proc. Fed. Am. Soc. Exp. Biol. 42
(1983) 3019–3021.
[6] A. Luchsinger, M. Velasco, A. Urbina, J. Morillo, E. Romero, R.
Alvarez, O.H. Pieretti, Comparative effects of dopaminergic agonists
on cardiovascular, renal, and renin–angiotensin system in hyperten-
sive patients, J. Clin. Pharmacol. 32 (1992) 55–60.
[7] F. Alan, G. Sved, J.D. Fernstrom, Evidence for a peripheral dopami-
nergic mechanism in the antihypertensive action of lergotrile, Life
Sci. 27 (1980) 349–354.
Potassium isothiocyanate 2.25 g (0.023 mol) was added
portionwise to a stirred solution of 5 g (0.015 mol) of N-
[(6-methylergolin-8b-yl)methyl]-b-alanine methyl ester in
75 ml of glacial acetic acid. The resulting red solution was
heated for 2 h at 908C. The solvent was removed, then the
crude mixture was partitioned between chloroform and a
solution of 1 M of potassium carbonate. The organic phase
was dried and evaporated to dryness. The residue was chro-
matographed on silica gel eluting with chloroform. The frac-
tions containing the compound were pooled and concentrated
to a small volume, affording 3.7 g (67%) of 17. Anal.
(C20H24N4OS) C, H, N. IR (KBr): 3440 (n N–H amide);
[8] T. Yen, N.B. Stamm, J.A. Clemens, Pergolide: a potent dopaminergic
antihypertensive, Life Sci. 25 (1979) 209–216.
1
1710 (n C_O); 1545 (n C–N thioamide) cmy1. H NMR
[9] K. Fuxe, S.O. Ogren, L.F. Agnati, K. Andersson, C. Kohler, B. Fred-
holm, Central monoamine synapses as sites of action of ergot deriv-
atives, in: M. Goldstein, D.B. Calne, A. Lieberman, M.O. Thorner
(Eds.), Advances in Biochemistry and Psychopharmacology, vol. 23,
Raven Press, New York, 1980, pp. 41–74.
[10] J.A. Van der Starre, R.S. Reneman, The a adrenergic receptor block-
ing effect of ketanserin and the interaction between a-adrenergic and
S2-serotonin receptor blockade, J. Cardiovasc. Pharmacol. 11 (1)
(1988) 54–61.
(DMSO-d6, 200 MHz): d 1.08 (ddd, Js12.0, 12.0, 12.0 Hz,
1H, H-9ax); 2.35 (s, 3H, CH3N); 2.67 (m, 2H, CH2CONH);
3.73 (m, 2H, NCH2CH2); 2.95 (m, 2H, NCH2-CH2); 6.8–
7.1 (m, 4H, aromatic protons); 10.61, 10.94 (two b s, 2H,
NH-1, CSNHCO). MS (EI) m/z 368 (69, Mqy); 335
(100); 237 (46); 223 (33), 194 (17); 167 (49); 155 (28);
154 (68); 144 (29); 127 (28).
[11] E. Schliker, K. Classen, M. Gothert, Presynaptic serotonin receptors
and alpha-adrenoceptors on central serotonergic and noradrenergic
neurons of normotensive and spontaneously hypertensive rats, J. Car-
diovasc. Pharmacol. 11 (5) (1988) 518–528.
[12] Eur. Patent Appl. 126 968 (1984) [Chem. Abstr. 102 (1984)
149582y].
[13] P. Salvati, G.P. Bondiolotti, C. Caccia, F. Vaghi, G. Bianchi, Mech-
anism of the antihypertensive effect of FCE 22716, a new ergoline
derivative, in spontaneously hypertensive rat, Pharmacology 38
(1989) 78–92.
[14] J. March, Advanced Organic Chemistry, 2nd ed., McGraw-Hill, New
York, 1985, p. 364.
[15] C. Elderfield, Heterocyclic Compounds, vol. 5, Wiley, New York,
1957, p. 256.
[16] W.F. Holcomb, C.S. Hamilton, Derivatives of 4-amino-6-methoxy-
quinaldine, J. Am. Chem. Soc. 64 (1942) 1309–1311.
[17] D.J. Brown, F. Mason, Chemistry of Heterocyclic Compounds, vol.
16, Wiley, New York, 1962, p. 434.
[18] T. Montzka, J.D. Matiskella, R.A. Patyka, 2,2,2-Trichloroethyl chlo-
roformate: a general reagent for demethylation of tertiary methyla-
mines, Tetrahedron Lett. 14 (1974) 1325–1327.
4.2.10. Perhydro-1-[(6-methylergolen-D9,10-8b-yl)methyl]-
2,4-pyrimidinedione 21
A solution of 3.75 g (0.046 mol) of potassium cyanate in
20 ml of water was added dropwise to a stirred solution of
7.5 g (0.023 mol) of N-[(6-methylergolen-D9,10-8b-
yl)methyl]-b-alanine methyl ester in 46 ml of 1M hydroch-
loric acid at room temperature. The solution was heated at
808C for 3 h, then, after cooling, the precipitate was filtered
off, washed thoroughly with water and subsequently crystal-
lized from methanol yielding 6.8 g (84%) of pure compound
9 as shiny crystals. Anal. (C20H22N4O2) C, H, N. IR (KBr):
3440 (n N–H amide); 1710, 1685 (n C_O); 1490 (n C–N
amide) cmy1. 1H NMR (DMSO-d6, 200 MHz): d 2.10 (dd,
Js12.1, 12.1, 12.0 Hz, 1H, H-7ax); 2.42 (m, 1H, H-4ax);
2.43 (s, 3H, CH3N); 2.56 (m, 2H, CH2CO); 2.80–3.0 (m,
3H, H-5x, H-7e, H-8); 3.2–3.5 (m, 5H, H-4e, CH2-8, NCH2-

304
S. Mantegani et al. / Il Farmaco 53 (1998) 293–304
[19] G.W. Gribble, P.D. Lord, J. Skotnicki, S.E. Dietz, J.T. Eato, J.R.
Johnson, Reactions of sodium borohydride in acidic media. I. Reduc-
tion of indoles and alkylation of aromatic amines, with carboxylic
acids, J. Am. Chem. Soc. 96 (1974) 7812–7814.
[20] L. Bernardi, B. Camerino, B. Patelli, S. Redaelli, Derivati della D-6-
methyl-8b-aminomethyl-10a-ergolina, Gazz. Chim. Ital. 94 (1964)
936–946.
[25] P. Greengrass, R. Bremner, Binding characteristic of [3H]-prazosin
to rat brain a-adrenergic receptors, Eur. J. Pharmacol. 55 (1979) 323–
326.
[26] B.D. Perry, D.C. U’Prichard, [3H]-Rauwolscine (a-yohimbine): a
specific antagonist radioligand for brain a2-adrenergic receptors, Eur.
J. Pharmacol. 76 (1981) 461–464.
[27] W. Billard, V. Ruperto, G. Grosby, L. Iorio, C.A. Barnett, Character-
ization of the binding of [3H]-SCH 23390, a selective D-1 receptor
antagonist ligand, in rat striatum, Life Sci. 35 (1984) 1885–1893.
[28] I. Creese, R. Schneider, S.H. Snyder, [3H]-Spiroperidol labels dopa-
mine receptors in pituitary and brain, Eur. J. Pharmacol. 46 (1977)
377–381.
[29] M.W. Pedigo, H.I. Yamamura, D.L. Nelson, Discrimination of mul-
tiple [3H]-5-hydroxytryptamine binding sites by the neuroleptic spi-
perone in rat brain, J. Neurochem. 36 (1981) 220–226.
[30] J.E. Leysen, C.J.E. Niemegeers, J.M. van Nueten, P.M. Laduron,
[3H]-Ketanserin (R 41 468), a selective 3H-ligand for serotonin2
receptor binding sites, Mol. Pharmacol. 21 (1981) 301–314.
[21] T. Fehr, P. Stutz, P.A. Stadler, R. Hummel, R. Salzmann, Antihyper-
tensiv Wirksame Harnstoffderivate des 8b-Aminomethyl-6-Methyl-
Ergolens, Eur. J. Med. Chem. 9 (1974) 597–601.
¨
[22] A. Hofman, Uber den Curtius’schen Abbau der Isomeren Lysergsa¨u-
ren und Dihydro-Lysergsa¨uren, Helv. Chim. Acta 30 (1947) 44–51.
[23] M. Semonsky’, N. Kucharczyk, Synthesis of nitrile and amide of D-
6-methyl-8-ergolinylacetic acid, Collect. Czech. Chem. Commun. 33
(1968) 577–601.
[24] E. Fluckiger, E. Del Pozo, in: B. Berde, H.O. Schild(Eds.), Handbook
of Experimental Pharmacology, vol. 49, Springer, Berlin, 1978, p.
615.