Synthesis of new antimicrobial pyrrolo[2,1-a]isoquinolin-3-ones

Article abstract of DOI:10.1016/j.bmc.2012.09.033

The attractive structure of the pyrroloisoquinoline moiety, together with its potential antimicrobial activity, encouraged us to prepare six 8-substituted and seven 8,9-disubstituted-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinolin-3- ones in a few steps with good yields. We applied a convenient methodology via double intramolecular cyclization conducted by a Bischler-Napieralski cyclodehydration-imine reduction sequence, which is widely employed in the synthesis of isoquinoline alkaloids. Therefore, we synthesized three series of these pyrrolo[2,1-a]isoquinolin-3-ones characterized by the substituent at the 8-position or 8,9-positions of the aromatic ring: (a) different side chains are attached to an 8-OH group (series 1); (b) a chlorine atom is attached to the 8-position (series 2); and (c) 8- and 9-carbons are bearing an identical group (series 3). The compounds bearing a benzylic moiety at the 8-position, for example, 8-benzyloxy-pyrrolo[2,1-a]isoquinolin-3-one (1a) and 8-(4-fluorobenzyloxy)-pyrrolo[2,1-a]isoquinolin-3-one (1e), as well as, a 8-chloro-9-methoxy moiety including the 8-chloro-9-methoxy-pyrrolo[2,1-a] isoquinolin-3-one (2a), provided the most fungicide and bactericide agents, respectively.

Full text of DOI:10.1016/j.bmc.2012.09.033

Bioorganic & Medicinal Chemistry 20 (2012) 6589–6597
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis of new antimicrobial pyrrolo[2,1-a]isoquinolin-3-ones
Laura Moreno a, Javier Párraga a, Abraham Galán a, Nuria Cabedo b, Jaime Primo b, Diego Cortes a,
⇑
a Departamento de Farmacología, Facultad de Farmacia, Universidad de Valencia, 46100 Burjassot, Valencia, Spain
b Centro de Ecología Química Agrícola-Instituto Agroforestal Mediterraneo, UPV, Campus de Vera, Edificio 6C, 46022 Valencia, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 April 2012
Revised 13 September 2012
Accepted 15 September 2012
Available online 24 September 2012
The attractive structure of the pyrroloisoquinoline moiety, together with its potential antimicrobial activ-
ity, encouraged us to prepare six 8-substituted and seven 8,9-disubstituted-1,2,3,5,6,10b-hexahydropyr-
rolo[2,1-a]isoquinolin-3-ones in a few steps with good yields. We applied a convenient methodology via
double intramolecular cyclization conducted by a Bischler-Napieralski cyclodehydration-imine reduction
sequence, which is widely employed in the synthesis of isoquinoline alkaloids. Therefore, we synthesized
three series of these pyrrolo[2,1-a]isoquinolin-3-ones characterized by the substituent at the 8-position
or 8,9-positions of the aromatic ring: (a) different side chains are attached to an 8-OH group (series 1); (b)
a chlorine atom is attached to the 8-position (series 2); and (c) 8- and 9-carbons are bearing an identical
group (series 3). The compounds bearing a benzylic moiety at the 8-position, for example, 8-benzyloxy-
pyrrolo[2,1-a]isoquinolin-3-one (1a) and 8-(4-fluorobenzyloxy)-pyrrolo[2,1-a]isoquinolin-3-one (1e), as
well as, a 8-chloro-9-methoxy moiety including the 8-chloro-9-methoxy-pyrrolo[2,1-a]isoquinolin-3-
one (2a), provided the most fungicide and bactericide agents, respectively.
Keywords:
Pyrrolo[2,1-a]isoquinolin-3-ones
Bischler-Napieralski cyclodehydration
Bactericide
Fungicide
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Actually, pyrrolo[2,1-a]isoquinolines were synthesized long be-
fore they were isolated as natural products, and were incorporated
Isoquinoline alkaloids are a large family of natural products
with a variety of powerful biological activities,1 including inhibi-
tion of cellular proliferation.2 Within the isoquinoline family, pyr-
roloisoquinoline alkaloids have been paid considerable attention in
recent years because they display interesting biological activities
such as antidepressant,3 muscarinic agonist,4 antiplatelet5 and
antitumor activity.6 In 1968, the first natural pyrroloisoquinoline
alkaloids were isolated from the peyote cactus and were identified
as peyoglutam and mescalotam.7 Since then, the pyrrolo[2,1-a]iso-
quinoline ring system is the main core of a wide variety of biolog-
ically active alkaloids, including antitumor crispine A, isolated
from Carduus crispus,8 tetracyclic compounds such as antiglycemic
jamtine, isolated from the climbing shrub Cocculus hirsutus,9 and
erythrina type alkaloids with curare-like neuromuscular blocking
activities.10,11 In 1984, a tetracyclic framework bearing a pyrrolo-
isoquinoline lactam was found in nuevamine12 which displayed
anti-inflammatory, antimicrobial, anti-leukemic and antitumor
properties.13 In 2004, tricyclic lactam trolline was isolated from
Trollius chinensis. This alkaloid exhibited in vitro significant anti-
bacterial activity against some strains of Klebsiella pneumoniae,
Pseudomonas aeruginosa, Haemophilus influenza, Staphylococcus
aureus, Streptococcus pneumonia, S. pyogenes, and moderate antivi-
ral activity against influenza viruses A and B.14
into larger ring systems; for example, in the lamellarins skeleton.15
Nevertheless, given their attractive biological activities, the syn-
thesis of new compounds bearing this structural framework has
greatly increased in recent years.16 One representative synthetic
strategy involves the annulation of the pyrrole ring by intramolec-
ular reaction of a 1,3-difunctionalized three-carbon building block
with a 3,4-dihydroisoquinoline.17–19 Other strategies proceed prin-
cipally via phenethyl succinimides, in which a N-acyliminium ion
undergoes different types of intramolecular aromatic p-cyclization
reactions to provide the C10a–C10b bond formation. In this case,
some broadly used approaches involve: (1) tandem carbophilic
addition of the organolithium reagent-N-acyliminium ion cycliza-
tion sequence to obtain the isoquinolone skeleton;20 (2) applica-
tion of Parham-type cyclization to halogenated imides, giving the
corresponding enamides;21,22 and (3) the Pummerer/Mannich in-
duced cyclization cascade, which involves a thionium-N-acylimin-
ium ion cyclization to give the azabicyclic ring system.23
Our research group is focusing since a long time on isolating
and synthesizing isoquinoline-containing compounds to obtain a
variety of chemically diverse structures with dopaminergic activ-
ity.24–28 However, the discovery of new antimicrobial agents in
the last few years has become a need since some microorganisms
develop resistance to classic drugs due to their extensive use. As
mentioned above, previous works have shown the antimicrobial
properties of pyrroloisoquinolines, including the nuevamine-type
and trolline-type alkaloids.13,14 The attractive structure of the
⇑
Corresponding author.
E-mail address: dcortes@uv.es (D. Cortes).
0968-0896/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2012.09.033

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L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
pyrroloisoquinoline moiety, together with its potential antimicro-
bial activity, encouraged us to synthesize trolline analogs contain-
ing a lactam-ring pharmacophore similar to antibiotic b-lactams.
Although several methods have been portrayed for the synthesis
of this framework, we applied a typical methodology that we
widely employed in the course of our research into isoquinoline
synthesis. It is based on double intramolecular cyclization, con-
ducted by Bischler-Napieralski cyclodehydration from an ester
b-phenylethylamide and involves the subsequent reduction of
the imine intermediate. Therefore, we prepared six 8-substituted
and seven 8,9-disubstituted-1,2,3,5,6,10b-hexahydropyrrolo[2,1-
a]isoquinolin-3-ones, including the known alkaloid ( )-trolline, in
a few steps with good yields for the purpose of exploring their anti-
microbial activities. Specifically, we followed the same approach to
synthesize three series of these pyrrolo[2,1-a]isoquinolinones
characterized by the substituent at the 8-position of the aromatic
ring. In these series: (a) different side chains are attached to an
8-OH group (series 1); (b) a chlorine atom is attached to the 8-po-
sition (series 2); and (c) 8- and 9-carbons are bearing an identical
group (series 3). The biological results of these thirteen compounds
have enabled us to draw conclusions on these groups’ influence on
antimicrobial activity.
amine quickly attacked the carbonyl ester leading to C ring
closure by a second intramolecular cyclization to give 8-benzyl-
oxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinolin-3-one (1a),
8-chloro-9-methoxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]iso-
quinolin-3-one (2a) and 8,9-dimethoxy-1,2,3,5,6,10b-hexahydro-
pyrrolo[2,1-a]isoquinolin-3-one (3a) for series 1–3, respectively.
In order to obtain different substitutions at the 8 and 9-positions
to explore their influence on antimicrobial activity, the benzylic
and the methoxy groups of 1a (series 1) and 2a (series 2) were
deprotected under acid medium to give 8-hydroxy-1,2,3,5,6,
10b-hexahydropyrrolo[2,1-a]isoquinolin-3-one (1b), and by BBr3
to obtain 8-chloro-9-hydroxy-1,2,3,5,6,10b-hexahydropyrrolo[2,
1-a]isoquinolin-3-one (2b) (Schemes 1 and 2). In addition, those
substituents that seemed to enhance the antimicrobial activity
were placed in both 8 and 9-positions on the aromatic A-ring
(series 3), also by previous deprotection of 3a by BBr3 to obtain
( )-trolline (3b) (Scheme 3).
Secondly, in series 1, one carbamate and three O-alkylated
derivatives were prepared from 8-hydroxy-pyrroloisoquinolone
1b (Scheme 4) to give: 8-ethylcarbamate- (1c), 8-(1-piperidineth-
oxy)- (1d), 8-(4-fluorobenzyloxy)- (1e) and 8-phenylacetamide-
1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinolin-3-ones (1f). In
series 2, one carbamate derivative was prepared from 8-chloro-9-
hydroxy-pyrroloisoquinolone 2b to obtain 8-chloro-9-ethylcarba-
mate-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinolin-3-one (2c)
(Scheme 2). In series 3, one 8,9-bis(4-fluorobenzyloxy)- (3c) and
2. Results and discussion
2.1. Chemistry
one
8,9-bis(phenylacetamide)-1,2,3,5,6,10b-hexahydropyrrol-
o[2,1-a]isoquinolin-3-ones (3d), were prepared from ( )-trolline
(3b) (Scheme 3). All the target compounds were synthesized using
a short approach with good yields. In addition, and to our knowl-
edge, compounds 1a–1f, 2a–2c, 3c and 3d are reported for the first
time. Their structures were confirmed by NMR spectral data and
MS spectrometry.
The general synthetic plan for these compounds focused on
preparing the appropriate b-phenyl acetamides (1–3) by standard
methods25,26 to be cyclized by Bischler-Napieralski cyclodehydra-
tion. Firstly, these were prepared by starting with benzaldehyde
derivatives: 3-hydroxybenzaldehyde (series 1, Scheme 1) and
3-chloro-4-methoxy-benzaldehyde (series 2, Scheme 2); and from
the 3,4-dimethoxy-b-phenyl-ethylamine (series 3, Scheme 3).
Therefore, by commencing with these benzaldehydes, and by a
successive nitromethane-reduction sequence, b-phenylethylamine
intermediates were obtained and then condensed with the ethyl
succinyl chloride under Shotten-Bauman conditions to give the
b-(3-benzyloxy-phenyl)acetamide (1), b-(3-chloro-4-methoxy-
phenyl)acetamide (2) and b-(3,4-dimethoxy-phenyl)-acetamide
(3), as outlined in Schemes 1–3, respectively. These amides 1–3
were treated with a POCl3 reagent to lead us to the expected
dihydroisoquinolines by Bischler-Napieralski cyclization. The ob-
tained imine was reduced with NaBH4 to give the tetrahydroiso-
quinoline skeleton and, simultaneously, the formed nucleophilic
2.2. Antimicrobial activity
All the synthesized pyrrolo[2,1-a]isoquinolines were assayed
in vitro for their ability to inhibit bacterial and fungal growth. In
the antimicrobial assays, our compounds were tested against sev-
eral human pathogenic and economically important phytopatho-
genic bacteria and/or fungi. The bacterial agents were distributed
over Gram(+) and Gram(ꢀ) bacteria: B. cereus, S. aureus, and
E. faecalis as Gram(+) and S. typhii, E. coli and E. carotovora as
Gram(ꢀ) (Table 1). The inhibition zones exhibited by compounds
1a–1f, 2a–2c and 3a–3c are summarized in Tables 1 and 2 for
O
BnO
NO2
BnO
RO
(b)
(c)
H
NH2
3-benzyloxy-
3-benzyloxy-
(97 %)
(87 %)
R=H 3-OH-benzaldehyde
(a)
β-nitrostyrene
phenyl-ethylamine
R=Bn
3-OBn-benzaldehyde
(98 %)
(d)
7
8
6
5
BnO
RO
BnO
BnO
A
B
9
N
NH
(f)
NH
O
N
C
3
2
(e)
O
10b
1
10
O
1
(43 %)
1a: R= Bn
(g)
O
OEt
O
OEt
(77 %)
(72 %) 1b:
R= H
EtO
Scheme 1. Synthesis of pyrroloisoquinolin-3-ones 1a,1b (series 1). Reagents and conditions: (a) Benzyl chloride, K2CO3, EtOH, reflux, 6 h; (b) Nitromethane, NH4OAc, AcOH,
reflux, overnight; (c) LiAlH4, THF/Et2O, N2, reflux, 2 h; (d) Ethyl succinyl chloride, NaOH 5%, CH2Cl2, rt, overnight; (e) POCl3, CH2Cl2, N2, reflux, 6 h; (f) NaBH4; MeOH, rt, 2 h; (g)
concd HCl–EtOH 1:1, reflux, 3 h.

L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
6591
O
Cl
Cl
NO2
Cl
(a)
(b)
H
NH2
H3CO
H3CO
H3CO
3-chloro-4-methoxy-
β-(3-chloro-4-methoxyphenyl)
3-chloro-4-methoxy-
benzaldehyde
(88 %)
β-nitrostyrene
ethylamine
(90 %)
(c)
Cl
Cl
Cl
Cl
NH
N
NH
N
O
H3CO
H3CO
(e)
H3CO
O
H3CO
(d)
2
2a
(36 %)
(53 %)
O
OEt
O
OEt
O
EtO
Cl
Cl
N
(f)
N
O
O
(g)
HO
O
N
O
2b
(91 %)
2c
(85 %)
H
Scheme 2. Synthesis of pyrroloisoquinolin-3-one 2a–2c (series 2). Reagents and conditions: (a) Nitromethane, NH4OAc, AcOH, reflux, 6 h; (b) LiAlH4, THF/Et2O, N2, reflux, 2 h;
(c) Ethyl succinyl chloride, NaOH 5%, CH2Cl2, rt, overnight; (d) POCl3, CH3CN, N2, reflux, 4 h; (e) NaBH4; MeOH, rt, 2 h; (f) BBr3, CH2Cl2, rt, 2 h; (g) Ethyl isocyanate, acetone,
reflux, 3 h.
MeO
MeO
MeO
MeO
MeO
MeO
(b)
(a)
NH
O
NH2
N
O
O
3,4-dimethoxy-
phenyl-ethylamine
3
3a
(88 %)
(54 %)
EtO
(c)
HO
HO
N
O
3b
(e)
(93 %)
O
O
O
N
H
(d)
N
O
H
N
3d
(63 %)
F
O
O
O
N
O
3c
(80 %)
F
Scheme 3. Synthesis of pyrroloisoquinolin-3-ones 3a–3d (series 3). Reagents and conditions: (a) Ethyl succinyl chloride, NaOH 5%, CH2Cl2, rt, overnight; (b) POCl3, CH2Cl2, N2,
reflux, 3 h; and NaBH4; MeOH, rt, 2 h; (c) BBr3, CH2Cl2, rt, 2 h; (d) p-fluorobenzyl chloride, K2CO3, EtOH, reflux, overnight; (e) 2-bromo-N-phenylacetamide, K2CO3, EtOH,
reflux, 6 h.
bactericidal and antifungal activity, respectively. In general, a
lipophilic group at the 8- and/or 9-position seemed to provide
moderate activity if compared with a free hydroxyl group such
as 1b and ( )-trolline (3b). The introduction of the O-benzyl group
(1a) was adequate for activity, and a halogen atom (1e) over the
benzyl moiety or even two p-fluorobenzyloxy groups (3c), did

6592
L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
O
H
N
HO
O
O
F
N
(b)
(a)
(c)
N
N
O
N
O
O
O
O
1b
1d
(82 %)
1c
(70 %)
(d)
O
O
N
H
N
N
O
O
1f
(80 %)
1e
(80 %)
Scheme 4. Synthesis of pyrroloisoquinolin-3-ones 1c–1f. Reagents and conditions: (a) Ethyl isocyanate, acetone, reflux, 3 h; (b) 2-bromo-1-(piperidin-1-yl)ethanone, K2CO3,
EtOH, reflux, 6 h; (c) p-fluorobenzyl chloride, K2CO3, EtOH, reflux, overnight; (d) 2-bromo-N-phenylacetamide, K2CO3, EtOH, reflux, 6 h.
Table 1
Strains
Bactericidal activity
Inhibition zone (mm) 24 h (means SE)a
1ab
1bb
2ab
1cb
1eb
1fb
3bb
3cb
Tetracyclineb
B. cereus
S. aureus
8.66 0.20A
7.50 0.35B
7.33 0.41BC
7.83 0.20A
6.83 0.20AB
7.33 0.73B
6.83 0.20AB
10.33 0.41C
6.16 0.20A
6.50 0.35C
7.50 0.61B
8.83 0.20A
6.66 0.41BC
7.33 0.41BC
24.33 0.41D
27.0 0.71C
26.0 0.71D
24.33 0.41C
25.66 0.41C
13.33 0.41E
25.66 0.41B
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
6.33 0.20B
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
E. faecalis
S. typhii
E. coli 405
E. carotovora
E. coli 100
6.83 0.20AB
6.0 0A
8.50 0.35C
7.50 0.35B
6.83 0.54AB
8.83 0.20D
6.33 0.41A
0
0
0
0
7.33 0.41B
7.33 0.20B
7.50 0.35B
8.0 0.35BD
6.33 0.20A
5.83 0.20A
6.83 0.20AB
6.33 0.20A
6.16 0.20A
7.26 0.18AB
8.0 0.61B
7
0
0A
0
0
0
0
0
0
0
a
Each value represents the average and the standard error of three independent experiments. Within each line, the mean values labeled with the same superscript (A–E) do
not present statistically significant differences (P >0.05).
b
Dose: 0.2 mg/disk. Compounds 1d, 2b, 2c and 3d did not show bactericidal activity. Compound 3a showed bactericidal activity at 0.3 mg/disk for S. aureus, E. faecalis,
E. coli 405 and E. carotovora.
Table 2
Strains
Antifungal activity
Inhibition zone (mm) 72 h (means SE)a
1ab
2ab
1cb
1eb
Benomyl
A. parasiticus
T. viride
F. culmorum
G. candidum
P. citrophthora
6.83 0.20A
6.0 0A
7.50 0.35B
0
0
0
0
0
0
0
0
7.83 0.20B
8.10 0.25B
10.50 0.35C
7.0 0.35A
29.33 0.41C,c1
29.33 0.81C,c1
27.66 1.08D,c2
0
0
12.0 0.71A
6.16 0.20A
11.33 0.41A
7.50 0.35B
6.33 0.41A
6.83 0.20B
0
0
9.66 0.41C
10.66 0.41A
44.33 0.41D,c3
a
Each value represents the average and the standard error of three independent experiments. Within each line, the mean values labeled with the same superscript (A–D)
do not present statistically significant differences (P >0.05).
b
Dose: 0.2 mg/disk.
c1
Dose: 20
l
g/disk.
Dose: 0.2 mg/disk.
Dose: 30 g/disk. Compounds 1b, 1d, 1f did not show antifungal activity.
c2
c3
l
not significantly improve it. Moreover, a carbamate bond at the 8-
position (1c) also provided activity against most of the tested
strains but not at 9-position (2c) on the aromatic A-ring. A similar
effect was observed for 1f and 3d with one and two aromatic
amide side chains, respectively. However, saturated amide 1d at
8-position did not display any bactericidal activity. The most note-
worthy compound was 2a, which possessed both a chlorine atom
tion zone against S. aureus and E. carotovora among all the tested
pyrroloisoquinolines. For this latter microorganism, 2a possessed
a potency that almost fell in the same range as the reference com-
pound (tetracycline), suggesting that it could be a potential alter-
native bactericidal agent to this ubiquitous plant pathogen with
a wide host range. Thus, the presence in 2a of a chlorine atom
and a methoxyl group at the 8-position and the 9-position, respec-
tively, appeared to enhance activity.
which draws electron density away from the
p system and an elec-
tron donating methoxyl group at the 8- and 9-position, respec-
tively. This compound displayed bactericidal activity against all
the tested strains. However, the presence of two methoxyl groups
(3a) at 8 and 9-positions was detrimental to the activity of the
compound and doses of 0.3 mg/disk were required to get a moder-
ate bactericidal effect. Furthermore, 2a showed the highest inhibi-
Fungicide activity was tested against some phytopathogen fun-
gi strains: A. parasiticus, T. viridae, F. culmorum, G. candidum and
P. citrophthora (Table 2). Compounds 1a, 2a, 1c and 1e inhibited
fungal growth in vitro. Compounds 1d and 1f, in which the
substitution at the 8-position was an amide side chain, did not dis-
play growth inhibition of the selected fungi at 0.2 mg/disk, unlike

L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
6593
the bactericidal test. In series 1, the most active compounds were
1a and their fluorinated analog 1e, which showed similar potency.
Consequently, it seems that the benzylic moiety located at the 8-
position on the pyrroloisoquinoline structure contributed posi-
tively to its antifungal properties, even if there was, or was not, a
halogen atom. Compound 2a, which was seen to be the most po-
tent bactericidal agent among the tested pyrroloisoquinolines,
had a moderate antifungal effect. Its derivatives 2b and 2c did
not display any antifungal activity even at 0.4 mg/disk. Surpris-
ingly, other disubstituted series 3 analogous (3a–3d) also showed
no fungicidal effect at the highest dose tested (0.4 mg/disk).
In conclusion, we prepared new eleven 8-substituted pyrrol-
o[2,1-a]isoquinolinones together with the known 3a and trolline
(3b) via a double cyclization unleashed by Bischler-Napieralski
cyclodehydration and an imine reduction sequence in a few steps
with good yields. The SAR studies reveal that the benzylic moiety
at the 8-position, as in compounds 1a (O-benzyl group) and 1e
(O-p-fluoro-benzyl group), and the 8-chloro-9-methoxy substitu-
tion as in 2a, provide the most fungicide and bactericide agents,
respectively.
ness to obtain the 3-benzyloxy-b-nitrostyrene (1.2 g, 97%) as yel-
low needles, which was used in the following step with no
further purification. Mp: 80–83 °C; 1H NMR (300 MHz, CDCl3):
d = 7.88 (d, J = 13.8 Hz, 1H, H-b), 7.48 (d, J = 13.8 Hz, 1H, H-a),
7.40 (m, 7H, H-2, H-5, Ph), 7.01 (m, 2H, H-4, H-6), 5.11 (s, 2H,
OCH2Ph); 13C NMR (75 MHz, CDCl3) d = 159.6 (C-3), 139.4 (CH-b),
137.8 (C-1), 136.7 (C-10), 130.9 (CH-
a), 129.1-127.9 (6C, CH-5,
CH20-CH-60), 122.4 (CH-6), 119.2 (CH-4), 115.5 (CH-2), 70.6
(OCH2Ph); ESMS m/z (%): 256 (100) [M+1]+.
3.2.3. 3-Chloro-4-methoxy-b-nitrostyrene
3-Chloro-4-methoxy-benzaldehyde (1.0 g, 5.87 mmol) was sub-
mitted to the same conditions depicted above to obtain the 3-
chloro-4-methoxy-b-nitrostyrene (1.1 g, 88%) as yellow needles,
which was used in the following step with no further purifica-
tion.26 Mp: 143–145 °C; 1H NMR (400 MHz, CDCl3): d = 7.91 (d,
J = 13.7 Hz, 1H, H-b), 7.59 (d, J = 2.2 Hz, 1H, H-2), 7.52
(d, J = 13.7 Hz, 1H, H-
(d, J = 8.6 Hz, 1H, H-5), 3.90 (s, 3H, OCH3-4); 13C NMR (100 MHz,
CDCl3) d = 158.4 (C-4), 138.4 (CH-b), 136.4 (CH- ), 130.9 (CH-2),
a), 7.44 (dd, J = 8.6, 2.2 Hz, 1H, H-6), 6.97
a
130.1 (CH-6), 124.2 (C-1), 123.7 (C-3), 112.7 (CH-5), 56.8 (OCH3);
MS (EI) m/z (%): 213.5 (55) [M]+, 185 (100).
3. Material and methods
3.1. General instrumentation
3.2.4. b-(3-Benzyloxy-phenyl)ethylamine
A mixture of 3-benzyloxy-b-nitrostyrene (600 mg, 2.35 mmol)
in 10 mL of anhydrous THF was added dropwise to a well-stirred
suspension of LiAlH4 (0.3 g, 8.7 mmol) in 13 mL of anhydrous
Et2O under nitrogen atmosphere, and was refluxed for 2 h. Then
the reaction mixture was cooled and the excess of reagent de-
stroyed by a dropwise addition of H2O. After a partial evaporation
of the filtered portion, the aqueous solution was extracted with
CH2Cl2 (3 ꢁ 10 mL). The organic layers were washed with brine,
dried over Na2SO4 and the solvent was removed to give the b-(3-
benzyloxy-phenyl)ethylamine (465 mg, 87%) as a yellow oil. 1H
NMR (300 MHz, CDCl3): d = 7.20 (m, 6H, H-5, Ph), 6.83 (m, 3H, H-
2, H-4, H-6), 5.03 (s, 2H, OCH2Ph), 2.88 (t, J = 13.5 Hz, 2H, CH2-b),
Melting points were taken on a Cambridge microscope instru-
ment coupled with a Reichert-Jung. EIMS was recorded in a VG
Auto Spec Fisons spectrometer instrument (Fisons, Manchester,
United Kingdom). 1H NMR and 13C NMR spectra were recorded
with CDCl3 as a solvent in a Bruker AC-300, AC-400 or AC-500.
Multiplicities of 13C NMR resonances were assigned by DEPT
experiments. COSY, HSQC and HMBC correlations were recorded
at 400 and 500 MHz (Bruker AC-400 or AC-500). The assignments
of all compounds were made by COSY, DEPT, HSQC and HMBC.
All the reactions were monitored by analytical TLC with silica gel
60 F254 (Merck 5554). Residues were purified by silica gel 60
2.65 (t, J = 13.5 Hz, 2H, CH2-a
); 13C NMR (75 MHz, CDCl3):
(40–63 lm, Merck 9385) column chromatography. Solvents and
reagents were purchased from commercial sources. Quoted yields
are of purified material.
d = 159.3 (C-3), 140.1 (C-10), 137.4 (C-1), 130.0 (CH-5), 129.9 (CH-
30, CH-50), 128.3 (CH-40), 127.9 (CH-20, CH-60), 121.9 (CH-6), 116.0
(CH-2), 112.8 (CH-4), 70.3 (OCH2Ph), 43.7 (CH2-b), 40.3 (CH2-
a);
ESMS m/z (%): 228 (100) [M+1]+.
3.2. General procedure for the synthesis of amides (1–3)
3.2.1. 3-Benzyloxy-benzaldehyde
3.2.5. b-(3-Chloro-4-methoxyphenyl)ethylamine
A mixture of 3-hydroxybenzaldehyde (3 g, 24.59 mmol), benzyl
chloride (4.1 mL, 35.79 mmol) and anhydrous K2CO3 (2.4 g,
17.39 mmol) in absolute EtOH (30 mL) was refluxed for 6 h. Then
the reaction mixture was concentrated to dryness, redissolved in
10 mL of CH2Cl2 and washed with 5% aqueous NaOH (3 ꢁ 10 mL).
The organic layer was dried with anhydrous Na2SO4 and evapo-
rated to dryness. The residue was purified by silica gel column
chromatography (hexane/EtOAc, 8:2) to afford 5.1 g of 3-benzyl-
oxy-benzaldehyde (98%) as a white solid. Mp: 54–56 °C; 1H NMR
(300 MHz, CDCl3): d = 9.85 (s, 1H, CHO), 7.32 (m, 9H, H-2, H-4,
H-5, H-6, Ph), 5.11 (s, 2H, OCH2Ph); 13C NMR (75 MHz, CDCl3) d
192.5 (CHO), 159.7 (C-3), 138.2 (C-1), 136.7 (C-10), 130.5 (CH-5),
129.1 (CH-30, CH-50), 128.6 (CH-40), 127.9 (CH-20, CH-60), 124.1
(CH-6), 122.6 (CH-4), 113.6 (CH-2), 70.6 (OCH2Ph); ESMS m/z (%):
213 (100) [M+1]+.
3-Chloro-4-methoxy-b-nitrostyrene (1.0 g, 4.70 mmol) was
submitted to the same conditions depicted above to obtain the
2-(3-chloro-4-methoxyphenyl)ethylamine (905 mg, 90%) as a yel-
low oil. The compound was used in further reaction without puri-
fication.26 1H NMR (400 MHz, CDCl3): d = 7.30 (d, J = 2.2 Hz, 1H,
H-2), 7.20 (dd, J = 8.5, 2.2 Hz, 1H, H-6), 6.80 (d, J = 8.5 Hz, 1H,
H-5), 3.90 (s, 3H, OCH3-4), 3.10 (m, 2H, H-b), 2.80 (m, 2H, H-a);
13C NMR (100 MHz, CDCl3): d = 153.8 (C-4), 133.3 (C-1), 130.8
(CH-2), 128.4 (CH-6), 122.6 (C-3), 112.5 (CH-5), 56.5 (OCH3), 43.8
(CH2-a
), 39.1 (CH2-b); MS (EI) m/z (%): 185 (45) [M]+.
3.2.6. Ethyl [b-(3-benzyloxy)phenethylamino]-oxobutanoate (1)
An amount of 0.47 mL of ethyl succinyl chloride (3.31 mmol)
was added dropwise at 0 °C to a solution of b-(3-benzyloxy-
phenyl)ethylamine (446 mg, 2.12 mmol) in CH2Cl2 and 5% aqueous
NaOH (4 mL). The reaction was stirred at room temperature over-
night to be then extracted with CH2Cl2 (3 ꢁ 10 mL). The combina-
tion of the organic phases was washed with brine (2 ꢁ 10 mL) and
H2O (2 ꢁ 10 mL), dried over Na2SO4 and evaporated to dryness. The
residue was purified by silica gel column chromatography (hexane/
EtOAc 6:4) to afford 540 mg of amide 1 (77%) as a yellow powder.
Mp: 68–71 °C; 1H NMR (500 MHz, CDCl3): d = 7.22 (m, 6H, H-5, Ph),
6.76 (m, 3H, H-2, H-4, H-6), 5.09 (s, 2H, OCH2Ph), 4.01 (q, J = 7.9 Hz,
3.2.2. 3-Benxyloxy-b-nitrostyrene
A mixture of 3-benzyloxy-benzaldehyde (1 g, 4.71 mmol), nitro-
methane (0.7 mL, 12.89 mmol) and NH4OAc (0.8 g, 10.41 mmol) in
AcOH (12.5 mL) was refluxed overnight. After cooling, the mixture
was diluted with water and extracted with CH2Cl2 (3 ꢁ 10 mL). The
organic solution was washed with brine (2 ꢁ 10 mL) and water
(2 ꢁ 10 mL), dried with anhydrous Na2SO4 and evaporated to dry-

6594
L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
2H, CO2CH2CH3), 3.40 (q, J = 6.3 Hz, 2H, CH2-
a
), 2.81 (t, J = 6.3 Hz,
4.71 (t, J = 8 Hz, 1H, H-10b), 4.23 (ddd, J = 12.4, 5.8, 2.7 Hz, 1H, H-
), 3.05 (m, 1H, H-5b), 2.91 (m, 1H, H-6 ), 2.71 (m, 1H, H-6b),
2.61 (m, 1H, H-1 ), 2.54 (m, 1H, H-2 ), 2.45 (m, 1H, H-2b), 1.82
2H, CH2-b), 2.65 (t, J = 6.5 Hz, 2H, CH2CO), 2.37 (t, J = 6.5 Hz,
CH2CONH), 1.10 (t, J = 7.9 Hz, 3H, CO2CH2CH3); 13C NMR
(125 MHz, CDCl3): d = 172.9 (CO2CH2CH3), 171.3 (CONH), 159.0
(C-3), 140.5 (C-10), 136.9 (C-1), 129.6 (CH-5), 128.5 (CH-30, CH-
50), 127.9 (CH-40), 127.4 (CH-20, CH-60), 121.3 (CH-6), 115.3 (CH-
5a
a
a
a
(m, 1H, H-1b); 13C NMR (125 MHz, CDCl3): d = 173.2 (NCO), 157.4
(C-8), 136.7 (C-10), 134.8 (C-6a), 130.0 (C-10a), 128.5 (CH-30, CH-
50), 127.9 (CH-40), 127.3 (CH-20, CH-60), 125.8 (CH-10), 114.6 (CH-
7), 113.8 (CH-9), 69.9 (OCH2Ph), 56.3 (CH-10b), 36.8 (CH2-5),
31.6 (CH2-2), 28.7 (CH2-6), 27.5 (CH2-1); ESMS m/z (%): 293 (100)
[M]+.
2), 112.8 (CH-4), 69.8 (OCH2Ph), 60.6 (CO2CH2CH3), 40.5 (CH2-a),
35.6 (CH2-b), 31.0 (CH2CONH), 29.5 (CH2CO), 14.1 (CO2CH2CH3);
ESMS m/z (%): 356 (100) [M+1]+.
3.2.7. Ethyl [b-(3-chloro-4-methoxy)phenethylamino]-oxobut-
anoate (2)
3.3.2. 8-Chloro-9-methoxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-
a]isoquinolin-3-one (2a)
b-(3-Chloro-4-methoxyphenyl)ethylamine (1 g, 5.39 mmol)
was submitted to the same conditions depicted above. The residue
was purified by silica gel column chromatography (hexane/EtOAc
5:5) to afford 900 mg of amide 2 (53%) as a yellow powder. Mp:
109–112 °C; 1H NMR (500 MHz, CDCl3): d = 7.17 (d, J = 2.1 Hz, 1H,
H-2), 7.04 (dd, J = 8.3, 2.1 Hz, 1H, H-6), 6.84 (d, J = 8.3 Hz, 1H, H-
5), 4.11 (q, J = 7.9 Hz, 2H, CO2CH2CH3), 3.85 (s, 3H, OCH3–4), 3.43
Ethyl b-(3-chloro-4-methoxy-phenethylamino)-4-oxobutano-
ate (2) (100 mg, 0.31 mmol) was submitted to the same conditions
depicted above. The residue was purified by silica gel column chro-
matography (toluene/EtOAc/MeOH/Et3N, 6:3:1:0.1) to obtain
28 mg of 8-chloro-9-methoxy-pyrrolo[2,1-a]isoquinolin-3-one 2a
(36%) as a yellow oil. 1H NMR (500 MHz, CDCl3): d = 7.15 (s, 1H,
H-7), 6.62 (s, 1H, H-10), 4.72 (t, J = 8.0 Hz, 1H, H-10b), 4.28 (ddd,
(q, J = 6.3 Hz, 2H, CH2-a), 2.70 (t, J = 6.3, 2H, CH2-b), 2.60 (t,
J = 12.9, 6.2, 2.7 Hz, 1H, H-5
H-5b), 2.84 (m, 1H, H-6 ), 2.68 (m, 1H, H-6b), 2.66 (m, 1H,
H-1 ), 2.56 (m, 1H, H-2 ), 2.48 (m, 1H, H-2b), 1.85 (m,
a), 3.86 (s, 3H, OCH3), 2.99 (m, 1H,
J = 6.5 Hz, 2H, CH2CO), 2.41 (t, J = 6.5 Hz, CH2CONH), 1.22 (t,
J = 7.9 Hz, 3H, CO2CH2CH3); 13C NMR (125 MHz, CDCl3): d = 173.1
(CO2CH2CH3), 171.8 (CONH), 153.5 (C-4), 131.9 (C-1), 130.3 (CH-
2), 127.8 (CH-6), 122.2 (CH-3), 112.1 (CH-5), 60.7 (CO2CH2CH3),
a
a
a
1H, H-1b); 13C NMR (125 MHz, CDCl3): d = 173.0 (NCO), 153.6
(C-9), 136.9 (C-10a), 130.5 (CH-7), 127.8 (C-6a), 121.1 (C-8),
108.3 (CH-10), 56.2 (CH-10b), 56.1 (OCH3), 36.9 (CH2-5), 31.6
(CH2-2), 27.5 (CH2-6), 27.4 (CH2-1); ESMS m/z (%): 251 (100) [M]+.
56.1 (OCH3), 40.6 (CH2-a), 34.3 (CH2-b), 30.9 (CH2CONH), 29.5
(CH2CO), 14.0 (CO2CH2CH3); ESMS m/z (%): 314.5 (100) [M+1]+.
3.2.8. Ethyl [b-(3,4-dimethoxy)phenethylamino]-oxobutanoate
(3)
3.3.3. 8,9-Dimethoxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a
]isoquinolin-3-one (3a)
b-(3,4-Dimethoxyphenyl)ethylamine (1 g, 5.52 mmol) was sub-
mitted to the same conditions depicted above. The residue was
purified by silica gel column chromatography (hexane/EtOAc 5:5)
to afford 1.5 g of amide 3 (88%) as a white powder. Mp: 48–
51 °C. 1H NMR (500 MHz, CDCl3): d = 6.81 (d, J = 2.1 Hz, 1H, H-5),
6.70 (m, 2H, H-2, H-6), 4.11 (q, J = 7.9 Hz, 2H, CO2CH2CH3), 3.85
(s, 3H, OCH3-4), 3.84 (s, 3H, OCH3-3), 3.43 (q, J = 6.3 Hz, 2H,
Ethyl b-(3,4-dimethoxy-phenethylamino)-4-oxobutanoate (3)
(1.2 g, 3.88 mmol) was submitted to the same conditions depicted
above. The residue was purified by silica gel column chromatogra-
phy (CH2Cl2/MeOH/NN4OH, 95:5:0.1) to obtain 520 mg of 8, 9-
dimethoxy-pyrrolo[2,1-a]isoquinolin-3-one 3a (54%) as a green
oil. 1H NMR (500 MHz, CDCl3): d = 6.59 (s, 1H, H-7), 6.54 (s, 1H,
H-10), 4.70 (t, J = 8.0 Hz, 1H, H-10b), 4.26 (ddd, J = 12.9, 6.2,
CH2-a), 2.70 (t, J = 6.3, 2H, CH2-b), 2.60 (t, J = 6.5 Hz, 2H, CH2CO),
2.7 Hz, 1H, H-5
(m, 1H, H-5b), 2.85 (m, 1H, H-6
1H, H-1 ), 2.55 (m, 1H, H-2
a
), 3.83 (s, 3H, OCH3-9), 3.82 (s, 3H, OCH3-8), 2.99
), 2.65 (m, 1H, H-6b), 2.60 (m,
), 2.44 (m, 1H, H-2b), 1.80 (m, 1H,
2.41 (t, J = 6.5 Hz, CH2CONH), 1.22 (t, J = 7.9 Hz, 3H, CO2CH2CH3);
13C NMR (125 MHz, CDCl3): d = 173.4 (CO2CH2CH3), 171.9 (CONH),
149.4 (C-3), 148.0 (C-4), 131.9 (C-1), 121.1 (CH-6), 112.4 (CH-5),
a
a
a
H-1b); 13C NMR (125 MHz, CDCl3): d = 173.1 (NCO), 148.0 (C-8),
147.8 (C-9), 129.2 (C-10a), 125.4 (C-6a), 111.6 (CH-7), 107.6 (CH-
10), 56.5 (CH-10b), 55.9 (OCH3-8), 55.8 (OCH3-9), 36.9 (CH2-5),
31.6 (CH2-2), 27.9 (CH2-6), 27.6 (CH2-1); ESMS m/z (%): 247 (100)
[M]+.
111.8 (CH-2), 61.0 (CO2CH2CH3), 56.2 (2ꢁ OCH3), 41.2 (CH2-
a),
35.6 (CH2-b), 31.4 (CH2CONH), 29.8 (CH2CO), 14.5 (CO2CH2CH3);
ESMS m/z (%): 310 (100) [M+1]+.
3.3. General procedure for the synthesis of 1,2,3,5,6,10b-
pyrrolo[2,1-a]isoquinolin-3-ones (1a–3a)
3.4. General procedure for the synthesis of 1,2,3,5,6,10b-
hexahydropyrrolo[2,1-a]isoquinolin-3-ones (1b–1f)
3.3.1. 8-Benzyloxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a
]isoquinolin-3-one (1a)
3.4.1. 8-Hydroxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a
]isoquinolin-3-one (1b)
A solution of ethyl 4-[b-(3-benzyloxyphenyl)ethylamino]-4-
oxobutanoate (1) (300 mg, 0.84 mmol) in dry CH2Cl2 (30 mL) was
treated with POCl3 (0.39 mL, 4.20 mmol) and was refluxed for 6 h
in a nitrogen atmosphere. The reaction mixture was diluted with
H2O (10 mL) and extracted with CH2Cl2 (3 ꢁ 10 mL). The organic
solution was dried over Na2SO4 and evaporated to dryness. The
residue was dissolved in MeOH (25 mL) and treated with NaBH4
(400 mg, 10.57 mmol) at room temperature. The reaction mixture
was stirred for 2 h. Afterward, H2O (5 mL) was added and the or-
ganic solvent was removed under reduced pressure. The aqueous
mixture was made basic and extracted with CH2Cl2 (3 ꢁ 10 mL),
dried over Na2SO4 and concentrated. The residue was purified by
silica gel column chromatography (toluene/EtOAc/MeOH/Et3N,
6:3:1:0.1) to obtain 105 mg of the 8-benzyloxy-pyrrolo[2,1-a]iso-
quinolin-3-one 1a (43%) as a yellow oil. 1H NMR (500 MHz, CDCl3):
d = 7.36 (m, 5H, Ph), 7.02 (d, J = 8.5 Hz, 1H, H-10), 6.87 (dd, J = 8.5,
2.5 Hz, 1H, H-9), 6.75 (d, J = 2.5 Hz, 1H, H-7), 5.04 (s, 2H, OCH2Ph),
8-benzyloxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinolin-
3-one (1a) (200 mg, 0.68 mmol) was refluxed for 3 h in a mixture
of equal volumes of ethanol and concentrated HCl (50 mL). The
reaction mixture was evaporated to dryness and the residue puri-
fied by silica gel column cromatography (CH2Cl2/MeOH 94:6) to
give 101 mg of 8-hydroxy-pyrrolo[2,1-a]isoquinolin-3-one 1b
(72%) as a white oil. 1H NMR (500 MHz, CDCl3): d = 6.76 (d,
J = 8.3 Hz, 1H, H-10), 6.53 (dd, J = 8.3, 2.0 Hz, 1H, H-9), 6.42 (d,
J = 2.0 Hz, 1H, H-7), 4.56 (t, J = 8 Hz, 1H, H-10b), 3.90 (m, 1H, H-
5a), 2.91 (m, 1H, H-5b), 2.67 (m, 1H, H-6
a), 2.56 (m, 1H, H-6b),
2.45 (m, 1H, H-1 ), 2.37 (m, 1H, H-2
a
a), 2.22 (m, 1H, H-2b), 1.65
(m, 1H, H-1b); 13C NMR (125 MHz, CDCl3): d = 174.0 (NCO), 155.3
(C-8), 134.2 (C-6a), 128.0 (C-10a), 125.4 (CH-10), 114.7 (CH-7),
113.9 (CH-9), 56.5 (CH-10b), 36.9 (CH2-5), 31.3 (CH2-2), 28.1
(CH2-6), 27.1 (CH2-1); ESMS m/z (%): 203 (100) [M]+.

L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
6595
3.4.2. 8-Ethylcarbamate-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a
]isoquinolin-3-one (1c)
2.46 (m, 1H, H-2b), 1.82 (m, 1H, H-1b); 13C NMR (125 MHz, CDCl3):
1
d = 173.4 (NCO), 162.5 (C-40, JCF = 246 Hz), 157.3 (C-8), 135.0 (C-
A solution of 8-hydroxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]-
isoquinolin-3-one (1b) (35 mg, 0.17 mmol) in dry acetone (10 mL)
was treated with ethyl isocyanate (0.34 mmol, 0.03 mL). After
refluxing for 3 h, the reaction mixture was concentrated to dryness,
redissolved in 10 mL of CH2Cl2 and washed with H2O (3 ꢁ 10 mL).
The organic layer was dried with anhydrous Na2SO4, filtered and
evaporated under reduced pressure. The residue was purified
through a silica gel column (CH2Cl2/MeOH 97:3) to afford 8-ethylc-
arbamate-pyrrolo[2,1-a]isoquinolin-3-one 1c (34 mg, 70%) as a
yellow oil. 1H NMR (500 MHz, CDCl3): d = 7.09 (d, J = 8.3 Hz, 1H,
H-10), 7.00 (dd, J = 8.3, 2.0 Hz, 1H, H-9), 6.91 (d, J = 2.0 Hz, 1H, H-
10), 132.5 (C-6a), 130.2 (C-10a), 129.3 (2CH, CH-20, CH-60), 125.9
2
(CH-10), 115.5 (2CH, CH-30, CH-50, JCF = 21.7 Hz), 114.5 (CH-7),
113.9 (CH-9), 69.3 (OCH2Ph), 56.4 (CH-10b), 36.9 (CH2-5), 31.7
(CH2-2), 28.7 (CH2-6), 27.6 (CH2-1); ESMS m/z (%): 311 (100) [M]+.
3.4.5. 8-Phenylacetamide-1,2,3,5,6,10a-hexahydropyrrolo[2,1-a
]isoquinolin-3-one (1f)
A
mixture of 8-hydroxy-1,2,3,5,6,10a-hexahydropyrrolo[2,1-
a]isoquinolin-3-one (1b) (30 mg, 0.14 mmol), 2-bromo-N-phenyl-
acetamide (29 mg, 0.14 mmol) and anhydrous K2CO3 (19 mg,
0.14 mmol) in EtOH (10 mL) was refluxed for 6 h. Then the reaction
mixture was concentrated to dryness, redissolved in 10 mL of
CH2Cl2 and washed with 5% aqueous NaOH (3 ꢁ 10 mL). The organ-
ic layer was dried with anhydrous Na2SO4 and evaporated to dry-
ness. The residue was purified by silica gel column
chromatography (toluene/EtOAc/MeOH/Et3N, 6:3:1:0.1) to afford
40 mg of 8-phenylacetamide-pyrrolo[2,1-a]isoquinolin-3-one 1f
(80%) as a yellow oil. 1H NMR (500 MHz, CDCl3): d = 7.58 (d, 2H,
J = 7.6 Hz, H-20, H-60), 7.36 (t, 2H, J = 7.5 Hz, H-30, H-50), 7.16 (t,
1H, J = 7.5 Hz, H-40), 7.10 (d, J = 8.5 Hz, 1H, H-10), 6.90 (dd, J = 8.5,
2.5 Hz, 1H, H-9), 6.78 (d, J = 2.5 Hz, 1H, H-7), 4.74 (t, J = 7.9 Hz,
1H, H-10b), 4.60 (s, 2H, OCH2CO), 4.28 (ddd, J = 12.9, 6.2, 2.7 Hz,
7), 4.71 (t, J = 8.0 Hz, 1H, H-10b), 4.26 (m, 1H, H-5
CH3CH2NHCO), 3.07 (m, 1H, H-5b), 2.92 (m, 1H, H-6
1H, H-6b), 2.63 (m, 1H, H-1 ), 2.53 (m, 1H, H-2 ), 2.45 (m, 1H,
a), 3.30 (m, 2H,
a), 2.77 (m,
a
a
H-2b), 1.86 (m, 1H, H-1b), 1.20 (m, 3H, CH3CH2NHCO); 13C NMR
(125 MHz, CDCl3): d = 173.2 (NCO), 154.4 (C-8), 149.6 (NHCO),
134.8 (C-6a), 134.4 (C-10a), 128.7 (CH-10), 125.1 (CH-7), 120.3
(CH-9), 56.5 (CH-10b), 36.8 (CH2-5), 36.7 (CH3CH2NHCO), 31.3
(CH2-2), 28.5 (CH2-6), 27.5 (CH2-1), 15.0 (CH3CH2NHCO); ESMS
m/z (%): 297 (100) [M+Na]+.
3.4.3. 8-(1-Piperidinethoxy)-1,2,3,5,6,10b-
hexahydropyrrolo[2,1-a]isoquinolin-3-one (1d)
1H, H-5a), 3.06 (m, 1H, H-5b), 2.93 (m, 1H, H-6a), 2.87 (m, 1H,
A
mixture of 8-hydroxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-
H-6b), 2.65 (m, 1H, H-1
a
), 2.57 (m, 1H, H-2 ), 2.47 (m, 1H, H-
a
a]isoquinolin-3-one (1b) (30 mg, 0.14 mmol), 2-bromo-1-(piperi-
din-1-yl)ethanone (19 mg, 0.14 mmol) and anhydrous K2CO3
(19 mg, 0.14 mmol) in absolute EtOH (10 mL) was refluxed for
6 h. Afterward, the reaction mixture was concentrated to dryness,
redissolved in 10 mL of CH2Cl2 and washed with 5% aqueous NaOH
(3 ꢁ 10 mL). The organic layer was dried with anhydrous Na2SO4,
filtered and evaporated to dryness. The residue was purified by sil-
ica gel column chromatography (toluene/EtOAc/MeOH/Et3N,
6:3:1:0.1) to afford 40 mg of 8-(1-piperidinethoxy)-pyrrolo[2,
1-a]isoquinolin-3-one 1d (82%) as a green oil. 1H NMR (500 MHz,
CDCl3): d = 7.02 (d, J = 8.5 Hz, 1H, H-10), 6.84 (dd, J = 8.5, 2.6 Hz,
1H, H-9), 6.70 (d, J = 2.6 Hz, 1H, H-7), 4.71 (t, J = 6.7 Hz, 1H, H-
2b), 1.84 (m, 1H, H-1b); 13C NMR (125 MHz, CDCl3): d = 173.2
(PhNCO), 166.0 (NCO-3), 155.7 (C-8), 136.7 (C-10), 135.6 (C-6a),
131.8 (C-10a), 129.1 (2CH, CH-20, CH-60), 126.3 (CH-10), 124.9
(CH-40), 120.1 (2CH, CH-30, CH-50), 114.9 (CH-7), 113.7 (CH-9),
67.7 (OCH2CO), 56.3 (CH-10b), 36.8 (CH2-5), 31.7 (CH2-2), 28.7
(CH2-6), 27.6 (CH2-1); ESMS m/z (%): 336 (100) [M]+.
3.5. General procedure for the synthesis of 1,2,3,5,6,10b-
hexahydropyrrolo[2,1-a]isoquinolin-3-ones (2b and 3b)
3.5.1. 8-Chloro-9-hydroxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-
a]isoquinolin-3-one (2b)
10b), 4.65 (s, 2H, OCH2CO), 4.23 (m, 1H, H-5
2H, CH2N), 3.46 (t, J = 5.3 Hz, 2H, CH2N), 3.04 (m, 1H, H-5b), 2.89
(m, 1H, H-6 ), 2.73 (m, 1H, H-6b), 2.56 (m, 1H, H-1 ), 2.52 (m,
1H, H-2 ), 2.44 (m, 1H, H-2b), 1.82 (m, 1H, H-1b), 1.64–1.54 (m,
a
), 3.55 (t, J = 5.3 Hz,
8-Chloro-9-methoxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]iso-
quinolin-3-one (2a, 0.23 mmol, 60 mg) in dry CH2Cl2 was stirred at
ꢀ78 °C. Then, 0.10 mL of BBr3 were added under nitrogen atmo-
sphere and the resulting mixture was stirred for 2 h at room tem-
perature. The reaction mixture was evaporated to dryness and
purified by silica gel column chromatography (CH2Cl2/MeOH
90:10) to afford 50 mg of 8-chloro-9-hydroxy-1,2,3,5,6,10b-hexa-
hydropyrrolo[2,1-a]isoquinolin-3-one 2b (91%) as a colorless oil.
1H NMR (500 MHz, CDCl3): d = 7.18 (s, 1H, H-7), 6.97 (s, 1H, H-
10), 4.48 (t, J = 8.0 Hz, 1H, H-10b), 4.30 (ddd, J = 12.9, 6.2, 2.7 Hz,
a
a
a
6H, (CH2)3N); 13C NMR (125 MHz, CDCl3): d = 173.2 (NCO-3),
166.0 (NCOCH2O), 156.7 (C-8), 135.0 (C-6a), 130.6 (C-10a), 125.9
(CH-10), 114.5 (CH-7), 113.6 (CH-9), 67.5 (OCH2CO), 56.4 (CH-
10b), 46.3 and 43.2 (2 ꢁ CH2N), 36.9 (CH2-5), 31.7 (CH2-2), 28.6
(CH2-6), 27.5 (CH2-1), 26.4 and 25.4 (2 ꢁ CH2CH2N), 24.3
(CH2(CH2)2N); ESMS m/z (%): 328 (100) [M]+.
1H, H-5
a), 2.87 (m, 1H, H-5b), 2.67 (m, 1H, H-6
a), 2.51 (m, 1H,
3.4.4. 8-(4-Fluorobenzyloxy)-1,2,3,5,6,10a-
hexahydropyrrolo[2,1-a]isoquinolin-3-one (1e)
H-6b), 2.42 (m, 1H, H-1
a
), 2.35 (m, 1H, H-2 ), 2.31 (m, 1H, H-
a
2b), 1.62 (m, 1H, H-1b); 13C NMR (125 MHz, CDCl3): d = 172.5
(NCO), 149.3 (C-9), 138.1 (C-10a), 131.3 (CH-7), 130.3 (C-6a),
119.9 (C-8), 113.6 (CH-10), 56.2 (CH-10b), 37.0 (CH2-5), 31.7
(CH2-2), 27.5 (CH2-6), 27.4 (CH2-1); ESMS m/z (%): 237.5 (100)
[M]+.
A
mixture of 8-hydroxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-
a]isoquinolin-3-one (1b) (20 mg, 0.10 mmol), p-fluorobenzyl chlo-
ride (0.01 mL) and anhydrous K2CO3 (10 mg) in absolute ethanol
(10 mL) was refluxed overnight. Afterward, the reaction mixture
was concentrated to dryness, redissolved in 10 mL of CH2Cl2 and
washed with 5% aqueous NaOH (3 ꢁ 10 mL). The organic layer
was dried with anhydrous Na2SO4, filtered and evaporated to dry-
ness under reduced pressure. The residue was purified by silica gel
column chromatography (CH2Cl2/MeOH 97:3) to afford 25 mg of 8-
(4-fluorobenzyloxy)-pyrrolo[2,1-a]isoquinolin-3-one 1e (80%) as a
yellow oil. 1H NMR (500 MHz, CDCl3): d = 7.38 (m, 2H, PhF), 7.07
(m, 3H, PhF, CH-10), 6.86 (dd, J = 8.5, 2.5 Hz, 1H, H-9), 6.74 (d,
J = 2.5 Hz, 1H, H-7), 5.00 (s, 2H, OCH2Ph), 4.73 (t, J = 7.8 Hz, 1H,
3.5.2. ( )-Trolline (3b)
8,9-Dimethoxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquino-
lin-3-one (3a, 0.80 mmol, 200 mg) in dry CH2Cl2 was stirred at
ꢀ78 °C. Then, 0.25 mL of BBr3 were added under nitrogen atmo-
sphere and the resulting mixture was stirred for 2 h at room tem-
perature. The reaction mixture was evaporated to dryness and
purified by silica gel column chromatography (CH2Cl2/MeOH
85:15) to afford 165 mg of 8,9-dihydroxy-1,2,3,5,6,10b-hexahydro-
pyrrolo[2,1-a]isoquinolin-3-one 3b (93%) as a white powder. Mp:
245–247 °C; 1H NMR (500 MHz, CDCl3): d = 6.99 (s, 1H, H-7),
H-10b), 4.25 (m, 1H, H-5
a
), 3.04 (m, 1H, H-5b), 2.91 (m, 1H, H-
), 2.56 (m, 1H, H-2 ),
6a), 2.75 (m, 1H, H-6b), 2.63 (m, 1H, H-1
a
a

6596
L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
6.98 (s, 1H, H-10), 4.54 (t, J = 8.0 Hz, 1H, H-10b), 4.32 (ddd, J = 12.9,
6.2, 2.7 Hz, 1H, H-5 ), 2.89 (m, 1H, H-5b), 2.74 (m, 1H, H-6 ), 2.48
(m, 1H, H-6b), 2.43 (m, 1H, H-2 ), 2.35 (m, 1H, H-2b), 2.33 (m, 1H,
H-1
) 1.66 (m, 1H, H-1b); 13C NMR (125 MHz, CDCl3): d = 172.6
(NCO), 146.3 (C-8), 146.1 (C-9), 129.3 (C-10a), 124.7 (C-6a), 118.7
(CH-10), 116.5 (CH-7), 56.4 (CH-10b), 37.4 (CH2-5), 31.9 (CH2-2),
28.1 (CH2-6), 28.0 (CH2-1); ESMS m/z (%): 219 (100) [M]+.
the reaction mixture was concentrated to dryness, redissolved in
10 mL of CH2Cl2 and washed with 5% aqueous NaOH (3 ꢁ 10 mL).
The organic layer was dried with anhydrous Na2SO4 and evapo-
rated to dryness. The residue was purified by silica gel column
chromatography (CH2Cl2/MeOH, 98:2) to afford 40 mg of 8,9-
bis(phenylacetamide)-1,2,3,5,6,10a-hexahydropyrrolo[2,1-a]iso-
quinolin-3-one 3d (63%) as a brown oil. 1H NMR (500 MHz, CDCl3):
d = 7.52 (m, 4H, H-20, H-60, H-200, H-600), 7.26 (m, 4H, H-30, H-50, H-
300, H-500), 7.10 (m, 2H, H-40, H-400), 6.75 (s, 1H, H-7), 6.72 (s, 1H,
H-10), 4.68 (s, 2H,OCH2CO), 4.67 (t, J = 7.9 Hz, 1H, H-10b), 4.25
a
a
a
a
3.6. General procedure for the synthesis of 9-substituted-
1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinolin-3-ones (2c, 3c
and 3d)
(ddd, J = 12.9, 6.2, 2.7 Hz, 1H, H-5
1H, H-6 ), 2.66 (m, 1H, H-6b), 2.62 (m, 1H, H-2
H-2b), 2.43 (m, 1H, H-1
), 1.74 (m, 1H, H-1b); 13C NMR
a), 2.98 (m, 1H, H-5b), 2.82 (m,
a
a), 2.53 (m, 1H,
3.6.1. 8-Chloro-9-ethylcarbamate-1,2,3,5,6,10b-
a
hexahydropyrrolo[2,1-a]isoquinoline-3-one (2c)
(125 MHz, CDCl3): d = 173.0 (NCO-3), 165.9 (PhNCO), 146.9 (C-9),
146.2 (C-8), 136.6 (C-10), 132.4 (C-10a), 128.9 (C-30, C-50, C-300,
C-500), 124.9 (CH-40, CH-400), 128.7 (C-6a), 120.0 (4CH, CH-20, CH-
60, CH-200, CH-600), 115.7 (CH-7), 111.9 (CH-10), 69.6 (OCH2CO),
56.2 (CH-10b), 36.7 (CH2-5), 31.6 (CH2-6), 27.9 (CH2-2), 27.4
(CH2-1); ESMS m/z (%): 485 (100) [M]+.
A solution of 8-chloro-9-hydroxy-1,2,3,5,6,10b-hexahydropyr-
rolo[2,1-a]isoquinolin-3-one 2b (20 mg, 0.084 mmol) in dry ace-
tone (10 mL) was treated with ethyl isocyanate (0.17 mmol,
0.01 mL). After refluxing for 3 h, the reaction mixture was concen-
trated to dryness, redissolved in 10 mL of CH2Cl2 and washed with
H2O (3 ꢁ 10 mL). The organic layer was dried with anhydrous
Na2SO4, filtered and evaporated under reduced pressure. The resi-
due was purified through a silica gel column (CH2Cl2/MeOH 95:5)
to afford 8-chloro-9-ethylcarbamate-1,2,3,5,6,10b-hexahydropyr-
rolo[2,1-a]isoquinolin-3-one 2c. (85%) as a yellow oil. 1H NMR
(500 MHz, CDCl3): d = 7.10 (s, 1H, H-7), 6.78 (s, 1H, H-10), 4.68 (t,
3.7. Pharmacological assays
3.7.1. Target microorganisms
Fungicidal activity was measured against 5 phytopathogens:
Aspergillus parasiticus (CECT 2681), Trichoderma Viride (CECT
2423), Fusarium culmorum (CCM 172), Phytophthora citrophthora
(CECT 2353) and Geotrichum candidum (CCM 245). Seven different
bacterial strains were used to determine bactericidal activity:
Bacillus cereus (CECT 148), Staphylococcus aureus (CECT 86), Entero-
coccus faecalis (CECT 481), Salmonella typhi (CECT 409), Escherichia
coli (CECT 405), Escherichia coli (CECT 100) and Erwinia carotovora
(CECT 225). The strains were provided by the Colección Española
de Cultivos Tipo (CECT) or by the Colección de la Cátedra de Micro-
biología (CMM) of the Biotechnology Department (Universidad
Politécnica de Valencia).
J = 8.0 Hz, 1H, H-10b), 4.42 (ddd, J = 12.9, 6.2, 2.7 Hz, 1H, H-5
3.72 (m, 2H, CH3CH2NHCO), 3.01 (m, 1H, H-5b), 2.83 (m, 1H, H-
), 2.63 (m, 1H, H-6b), 2.61 (m, 1H, H-1 ), 2.55 (m, 1H, H-2 ),
a),
6a
a
a
2.46 (m, 1H, H-2b), 1.80 (m, 1H, H-1b), 1.20 (m, 3H, CH3CH2NHCO);
13C NMR (125 MHz, CDCl3): d = 173.3 (NCO), 158.5 (C-9), 150.5
(NHCO), 137.4 (C-10a), 130.6 (CH-7), 126.0 (C-6a), 119.3 (C-8),
112.5 (CH-10), 56.5 (CH-10b), 37.4 (CH3CH2NHCO), 37.0 (CH2-5),
31.7 (CH2-2), 27.4 (CH2-6), 27.3 (CH2-1), 15.4 (CH3CH2NHCO);
ESMS m/z (%): 308.5 (100) [M]+.
3.6.2. 8,9-Bis(4-fluorobenzyloxy)-1,2,3,5,6,10a-
hexahydropyrrolo[2,1-a]isoquinolin-3-one (3c)
3.7.2. Antifungal and antibacterial activities
A mixture of 8, 9-dihydroxy-1,2,3,5,6,10b-hexahydropyrrol-
o[2,1-a]isoquinolin-3-one (3b) (50 mg, 0.22 mmol), p-fluorobenzyl
chloride (0.04 mL) and anhydrous K2CO3 (40 mg) in absolute etha-
nol (20 mL) was refluxed overnight. Afterward, the reaction mix-
ture was concentrated to dryness, redissolved in 10 mL of CH2Cl2
and washed with 5% aqueous NaOH (3 ꢁ 10 mL). The organic layer
was dried with anhydrous Na2SO4, filtered and evaporated to dry-
ness under reduced pressure. The residue was purified by silica gel
column chromatography (CH2Cl2/MeOH 97:3) to afford 70 mg of 8-
(4-fluorobenzyloxy)-pyrrolo[2,1-a]isoquinolin-3-one 1e (80%) as a
yellow oil. 1H NMR (500 MHz, CDCl3): d = 7.38 (m, 4H, PhF), 7.04
(m, 4H, PhF, CH-10), 6.69 (s, 1H, H-7), 6.64 (s, 1H, H-10), 5.05 (s,
These assays were determined in triplicate by the paper disk-
agar diffusion assay according to Cole.29 The doses used in the as-
says were 10, 15 or 20 l
g/mm2 (0.2, 0.3 or 0.4 mg/disk). Fungal
strains were seeded in Petri dishes containing PDA culture medium
and were incubated for 7 days at 28 °C. Then, a Tween 80 solution
(0.05%) in sterile distilled water was used to obtain a suspension
containing ꢂ106 conidia/mL. Next 1 mL of this conidia suspension
was added to 15 mL of PDA in a Petri dish. After solidification, four
Whatman disks (No. 113, 0.5 cm diameter) impregnated with the
tested products, at appropriate doses, were added to these Petri
dishes. The PDA plates containing disks impregnated with only
the solvent used to dissolve the tested compounds were used as
negative controls, and the disks with benomyl (methyl-1-[butylc-
arbamoyl]-2-benzimidazolecarbamate) (Sigma), at different con-
centrations according to the fungal species assayed, were used as
positive controls. Fungicidal activity was determined by measuring
the inhibition zone developed around the paper disk, indicating a
zone of no growth.
In the bactericidal tests, 24-h cultures of each bacterium, main-
tained in inclined tubes on solid culture medium, were reactivated
with a Nutrient Broth (Difco) and were incubated for 24 h at 28 or
37 °C according to the bacterium. Then, 1 mL of this suspension
was inoculated in a Petri plate, and 15 mL of the culture medium
Plate Count Agar (Difco) was added. When the medium was com-
pletely solidified, five paper disks loaded with the tested products
were placed in the dish. These plates were incubated for 24 h in the
dark at 28 or 37 °C, according to the bacterium. The plate Count
Agar plates containing disks impregnated with only the solvent
used to dissolve the tested compounds were used as negative
4H, OCH2Ph), 4.66 (t, J = 7.8 Hz, 1H, H-10b), 4.26 (m, 1H, H-5
2.99 (m, 1H, H-5b), 2.84 (m, 1H, H-6 ), 2.65 (m, 1H, H-6b), 2.56
(m, 1H, H-1 ), 2.51 (m, 1H, H-2 ), 2.42 (m, 1H, H-2b), 1.76 (m,
1H, H-1b); 13C NMR (125 MHz, CDCl3): d = 173.1 (NCO), 163.4 (C-
a),
a
a
a
1
1
40, JCF = 246 Hz), 161.4 (C-400, JCF = 246 Hz), 147.9 (C-8), 147.7 (C-
9), 132.8 (C-10, C-100), 130.4 (C-10a), 129.2 (4CH, CH-30, CH-50,
CH-300, CH-500), 126.9 (C-6a), 115.4 (4CH, CH-20, CH-60, CH-200, CH-
600), 115.2 (CH-7), 112.2 (CH-10), 71.2 (OCH2Ph), 70.7 (OCH2Ph),
56.4 (CH-10b), 36.9 (CH2-5), 31.7 (CH2-2), 28.0 (CH2-6), 27.5
(CH2-1); ESMS m/z (%): 435 (100) [M]+.
3.6.3. 8,9-Bis(phenylacetamide)-1,2,3,5,6,10a-
hexahydropyrrolo[2,1-a]isoquinolin-3-one (3d)
A mixture of 8, 9-dihydroxy-1,2,3,5,6,10b-hexahydropyrrol-
o[2,1-a]isoquinolin-3-one (3b) (30 mg, 0.13 mmol), 2-bromo-N-
phenylacetamide (61 mg, 0.26 mmol) and anhydrous K2CO3
(30 mg, 0.22 mmol) in EtOH (10 mL) was refluxed for 6 h. Then

L. Moreno et al. / Bioorg. Med. Chem. 20 (2012) 6589–6597
6597
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