Synthesis and biological activity of polyalthenol and pentacyclindole analogues

Article abstract of DOI:10.1016/j.ejmech.2013.12.012

A series of indole sesquiterpenes analogues of polyalthenol and pentacyclindole have been synthesized starting from ent-halimic acid in order to test their biological activity. These analogues include diverse oxidation levels at the sesquiterpenyl moiety and different functionalization on the indole ring. All synthetic derivatives were tested against a representative panel of Gram positive and Gram negative bacterial strains, and the human solid tumour cell lines A549 (non-small cell lung), HBL-100 (breast), HeLa (cervix), SW1573 (non-small cell lung), T-47D (breast) and WiDr (colon). Overall, the compounds presented activity against the cancer cell lines. The resulting lead, displaying a polyalthenol scaffold, showed GI₅₀ values in the range 1.2-5.7 μM against all cell lines tested.

Full text of DOI:10.1016/j.ejmech.2013.12.012

European Journal of Medicinal Chemistry 73 (2014) 265e279
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and biological activity of polyalthenol and pentacyclindole
analogues
,
a
a
a
a
Isidro S. Marcos a , Rosalina F. Moro , Isabel Costales , Pilar Basabe , David Díez ,
Ana Gil a, Faustino Mollinedo b, Fátima Pérez-de la Rosa c, Eduardo Pérez-Roth c,
José M. Padrón c
*
a Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain
b Instituto de Biología Molecular y Celular del Cáncer, Centro de Investigación del Cáncer, CSIC-Universidad de Salamanca, Campus Miguel de Unamuno,
37007 Salamanca, Spain
c BioLab, Instituto Universitario de Bio-Orgánica “Antonio González” (IUBO-AG), Centro de Investigaciones Biomédicas de Canarias (CIBICAN),
Universidad de La Laguna, C/ Astrofísico Francisco Sánchez 2, 38206 La Laguna, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of indole sesquiterpenes analogues of polyalthenol and pentacyclindole have been synthesized
starting from ent-halimic acid in order to test their biological activity. These analogues include diverse
oxidation levels at the sesquiterpenyl moiety and different functionalization on the indole ring. All
synthetic derivatives were tested against a representative panel of Gram positive and Gram negative
bacterial strains, and the human solid tumour cell lines A549 (non-small cell lung), HBL-100 (breast),
HeLa (cervix), SW1573 (non-small cell lung), T-47D (breast) and WiDr (colon). Overall, the compounds
presented activity against the cancer cell lines. The resulting lead, displaying a polyalthenol scaffold,
Received 16 September 2013
Received in revised form
10 December 2013
Accepted 12 December 2013
Available online 25 December 2013
Keywords:
showed GI50 values in the range 1.2e5.7
m
M against all cell lines tested.
Ó 2013 Elsevier Masson SAS. All rights reserved.
Indole sesquiterpenes
Pentacyclindole
Polyalthenol
Antitumourals
Ent-halimic acid
1. Introduction
12-epi-ent-pentacyclindole [5]. Furthermore, we demonstrated the
biogenetic relationship between polyalthenol and pentacyclindole
that had been proposed by Williams et al. [2]
As a follow up of our previous work, herein we report on the
synthesis and the biological evaluation of a series of indole ses-
quiterpenes analogues of polyalthenol and pentacyclindole. As a
model system to study the biological activity we selected antibac-
terial and anticancer assays. With the results of the biological tests
some structureeactivity relationships (SARs) could be inferred.
Polyalthenol and pentacyclindole (Fig. 1) are two indole ses-
quiterpenes present in Nature that display significant biological
activity including antimicrobial activity. Polyalthenol was isolated
in 1976 from the African plant Polyalthia oliveri Engl. Diels
(¼Greenwayodendron oliveri Verd.) [1] and exhibits activity against
clinical isolates of Staphylococcus aureus with a MIC90 of 8 mg/mL
[2]. Pentacyclindole, isolated in 2010 along with polyalthenol from
Polyalthia suaveolens (¼Greenwayodendron suaveolens), demon-
strated a MIC90 of 4 mg/mL [2].
2. Chemistry
In the past, our research group started diverse synthetic studies
on terpene alkaloids such as (þ)-agelasine C [3] and (þ)-thiersindole
C [4] (Fig. 2) amongothers. In the past fewyears, wehave focusedour
attention into indole sesquiterpenes. We have reported earlier the
synthesis of two polyalthenol analogues: 12-epi-ent-polyalthenol
and 12,19-bisepi-ent-polyalthenol, and the pentacyclindole epimer
For the synthesis of all indole sesquiterpenes analogues described
herein we used ent-halimic acid as starting material [6]. The syn-
thetic methodologies have been previously tuned up by our group in
the synthesis of indole diterpenes and sesquiterpenes [3e5,7].
2.1. Analogues of polyalthenol
As it has been said before starting from ent-halimic acid, the
synthesis of different polyalthenol analogues was achieved and the
* Corresponding author. Tel.: þ34 923 294474; fax: þ34 923294574.
E-mail address: ismarcos@usal.es (I.S. Marcos).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.12.012

266
I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
Fig. 1. Structures and stereochemistry of natural indole sesquiterpenes polyalthenol
and pentacyclindole.
compounds were classified into: 1. C-3 desoxygenated polyalthenol
analogues, 2. Analogues functionalised in the indole ring, 3. 2-
methylindole analogues and 4. Polyalthenol analogues as starting
materials for the synthesis of PLA2 inhibitors. Next, the synthesis of
these compounds will be described in detail.
Scheme 1. a) See Refs. [5,8]; b) NaBH4, 97%; c) Pb(OAc)4, 95%; d) Phenylhydrazine,
AcOH, 58%.
analogues 6e15 are also the synthetic precursors of the pentacy-
clindole analogues that we aim to obtain.
2.1.1. C-3 desoxygenated polyalthenol analogues
The first compound synthesized is
a C-3 desoxygenated
analogue of polyalthenol, which preparation, starting from ent-
halimic acid, is depicted in Scheme 1. After degradation to the
corresponding dinor derivative and reduction of the carboxylic
group to obtain compound 1 [5,8], a further degradation to the
trinor derivative aldehyde 3 is needed. This is carried out by
reduction of 1 with NaBH4 and reaction of the resultant diol 2 with
Pb(OAc)4. Then, a Fischer indolization of aldehyde 3 with phenyl-
hydrazine in AcOH afforded the C-3 desoxygenated polyalthenol
analogue 4.
2.1.3. 2-Methylindole analogues
Analogous reactions can be performed on methylketone 16
instead of aldehyde 5 to obtain, this way, the corresponding 2-
methylindoles. These compounds would permit us to obtain both
a new series of polyalthenol analogues and suitable precursors for
developing a series of phospholipase A2 inhibitors (IPLA2) that will
be briefly commented later.
In the same manner that compound 5, previously obtained in
our group, and transformed into different bioactive natural prod-
ucts [4], the methylketone 16, was treated with the adequate
phenylhydrazine or phenylhydrazine hydrochloride to afford 2-
methylindoles derivatives 17e26.
2.1.2. Analogues functionalised in the indole ring
Performing Fischer indolization reactions on aldehyde 5 using a
variety of differently functionalised phenylhydrazines [9] and
phenylhydrazines hydrochlorides [10] yields to the corresponding
indole derivatives 6e15 shown in Scheme 2. Compound 5 is an
important synthetic intermediate already used by our group in the
synthesis of polyalthenol, pentacyclindole and a wide variety of
bioactive natural products [4,5]. The synthesized polyalthenol
2.1.4. Polyalthenol analogues as starting materials for the synthesis
of PLA2 inhibitors
PLA2 inhibitors such as efipladib, giripladib and ecopladib are
compounds of enormous interest due to its biological activity, so
their analogues [11]. One of the most important considerations that
Fig. 2. Structures of (þ)-agelasine C, (þ)-thiersindole C and polyalthenol and pentacyclindole analogues.

I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
267
Scheme 2. a) See Ref. [4,5]; b) Phenylhydrazine, AcOH, 6 (95%); c) 4-methylphenylhydrazine hydrochloride, AcOH, 7 (45%); d) 4-bromophenylphydrazine hydrochloride, AcOH, 8
(40%); e) 4-chlorophenylhydrazine hydrochloride, AcOH, 9 (50%); f) 4-fluorophenylhydrazine hydrochloride, AcOH, 10 (53%); g) 4-methoxy phenylhydrazine hydrochloride, AcOH, 11
(44%); h) 4-trifluoromethylphenylhydrazine, AcOH, 12 (20%); i) 2-methylphenylhydrazine hydrochloride, AcOH, 13 (34%); j) 2-bromophenylhydrazine hydrochloride, AcOH, 14
(34%); k) 2-chlorophenylhydrazine hydrochloride, AcOH, 15 (27%).
Scheme 3. a) See Ref. [4]; b) Phenylhydrazine, AcOH, 17 (90%); c) 4-methylphenylhydrazine hydrochloride, AcOH, 18 (78%); d) 4-bromophenylphydrazine hydrochloride, AcOH, 19
(95%); e) 4-chlorophenylhydrazine hydrochloride, AcOH, 20 (94%); f) 4-fluorophenylhydrazine hydrochloride, AcOH, 21 (63%); g) 4-methoxy phenylhydrazine hydrochloride, AcOH,
22 (47%); h) 4-trifluoromethylphenylhydrazine, AcOH, 23 (27%); i) 2-methylphenylhydrazine hydrochloride, AcOH, 24 (62%); j) 2-bromophenylhydrazine hydrochloride, AcOH, 25
(87%); k) 2-chlorophenylhydrazine hydrocloride, AcOH, 26 (95%).
must be taken into account in order to ensure the biological activity
of these IPLA2 is that they must be functionalised at the C-2 position
of the indole. So we decided to add functionality to the methyl
group of the side chain on C-2. This can be achieved by oxidizing
the 2-methylindoles obtained with Na2CrO4 [7f], as depicted in
Scheme 4. Once aldehyde 27 is obtained in this way, it was
condensed with nitromethane in presence of ammonium acetate
[11d] to afford compound 28.
Other important requirement for the bioactivity of these com-
pounds is that the indole moiety should be functionalised and the N
Scheme 4. a) Na2CrO4, NaOAc, Ac2O, AcOH, 55 ꢀC, 30%; b) NH4OAc, CH3NO2, 100 ꢀC, 66%.

268
I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
t
Scheme 5. a) Bromodiphenylmethane, NaH, 38%; b) BuOK/tBuOH, 90 ꢀC, 95%.
in acid conditions. So all the analogues described for polyalthenol
can be easily transformed into pentacyclindoles by acidic treat-
ment. Following a similar classification as before, it is described the
synthesis of the different pentacyclindole analogues.
2.2.1. C-3 desoxygenated pentacyclindole analogues
Using polyalthenol analogue 4 as a starting material, a C-3
desoxygenated analogue of pentacyclindole can be obtained, as
seen in Scheme 6. Heating up compound 4 in C6H6 in the presence
of HI [7i,8] gave a pentacyclic compound with hexahydrocarbazole
structure 31. In order to regain the double bound, a mild oxidation
with TPAP [13] was performed, affording the pentacyclindole
analogue 32.
Scheme 6. a) HI 57%, benzene, 85 ꢀC, 81%; b) TPAP, NMO, 63%.
must bear a bulky protective group; the presence of a carboxylic
acid in the molecule is also essential. Taking this into account, we
decided to synthesize 30 (Scheme 5).
Reaction of 20 with bromodiphenylmethane [11b,11c] afforded
the N-protected indole derivative 29 which was hydrolysed [12] to
give 30. In this manner has been achieved the synthesis of com-
pounds 27e30 that are good starting materials for the synthesis of
PLA2 inhibitors analogues.
2.2.2. Analogues functionalised in the indole ring
The same sequence of reactions can be performed with the
aforementioned polyalthenol analogues 6e15, as depicted in
Scheme 7. Compounds 6e15, by heating with HI in C6H6, were
transformed into a series of hexahydrocarbazoles 33e39 and 45e47.
These compounds by TPAP oxidation led the corresponding penta-
cyclindole analogues, 40e44 and 48e50.
2.2. Analogues of pentacyclindole
2.3. Analogues functionalised in C-21
Our group has recently described the biomimetic synthesis of a
pentacyclindole by cyclisation of a polyalthenol derivative induced
Finally, a series of analogues with a different substituent at C-21
position were made, as seen in Scheme 8. Indole derivative 6 was
Scheme 7. a) HI 57%, benzene, 85 ꢀC; 33 (97%), 34 (99%), 35 (92%), 36 (91%), 37 (93%), 38 (90%), 39 (87%), 45 (93%), 46 (99%), 47 (99%); b) TPAP, NMO; 40 (36%), 41 (66%), 42 (50%), 43
(59%), 44 (79%), 48 (85%), 49 (46%), 50 (47%).

I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
269
Scheme 8. a) LAH, Et2O, 97%; b) Ac2O, Py, 95%; c) HI 57%, C6H6, 98%; d) TPAP, NMO, 54 (27%), 55 (5%).
transformed into the hydroxyderivative 51 by reduction with LAH.
3. Biological activity
Compound 51 was acetylated to afford 52, which under cyclisation
conditions, by heating with HI in C6H6, yielded hexahydrocarbazole
derivative 53. Oxidation of 53 with TPAP in presence of NMO
afforded 54 and 55.
Since antibacterial activity has been reported for naturally
occurring polyalthenol [1,2] and pentacyclindol [2], and we have
observed some preliminary antitumour activity for related
Table 1
Antiproliferative activity (GI50) against human solid tumour cells of compounds produced via Schemes 2e4.a
Compound
Cell line
A549
R1
R2
HBL-100
SW1573
HeLa
T-47D
WiDr
6
7
8
9
H
H
H
H
H
H
H
H
H
5.0 (ꢁ0.5)
17 (ꢁ1.0)
15 (ꢁ0.2)
16 (ꢁ1.0)
6.2 (ꢁ0.6)
2.2 (ꢁ0.9)
15 (ꢁ1.2)
11 (ꢁ0.4)
22 (ꢁ3.4)
22 (ꢁ2.6)
15 (ꢁ0.5)
26 (ꢁ1.4)
15 (ꢁ0.4)
17 (ꢁ1.0)
15 (ꢁ0.3)
16 (ꢁ0.9)
17 (ꢁ0.8)
14 (ꢁ1.6)
27 (ꢁ2.4)
20 (ꢁ6.1)
45 (ꢁ1.1)
13 (ꢁ2.3)
4.5 (ꢁ0.5)
18 (ꢁ1.3)
16 (ꢁ1.0)
17 (ꢁ1.6)
4.8 (ꢁ0.5)
2.1 (ꢁ1.1)
15 (ꢁ2.5)
8.0 (ꢁ2.3)
18 (ꢁ5.1)
19 (ꢁ4.9)
14 (ꢁ3.7)
25 (ꢁ9.3)
15 (ꢁ0.9)
15 (ꢁ0.6)
14 (ꢁ0.7)
16 (ꢁ1.6)
16 (ꢁ0.3)
16 (ꢁ2.2)
27 (ꢁ5.1)
22 (ꢁ8.4)
7.5 (ꢁ0.9)
16 (ꢁ0.9)
7.3 (ꢁ1.3)
15 (ꢁ3.4)
12 (ꢁ1.6)
11 (ꢁ3.3)
7.3 (ꢁ1.1)
1.3 (ꢁ0.2)
14 (ꢁ1.5)
7.8 (ꢁ1.2)
14 (ꢁ4.8)
14 (ꢁ2.6)
14 (ꢁ5.0)
18 (ꢁ5.5)
14 (ꢁ2.2)
14 (ꢁ2.5)
12 (ꢁ1.6)
15 (ꢁ1.2)
15 (ꢁ2.6)
15 (ꢁ0.9)
25 (ꢁ2.7)
19 (ꢁ1.8)
7.9 (ꢁ1.4)
13 (ꢁ3.1)
3.6 (ꢁ0.6)
14 (ꢁ1.2)
10 (ꢁ2.0)
11 (ꢁ1.6)
3.7 (ꢁ0.4)
1.2 (ꢁ0.7)
11 (ꢁ1.8)
4.9 (ꢁ0.8)
13 (ꢁ2.8)
14 (ꢁ1.8)
11 (ꢁ3.3)
17 (ꢁ4.5)
11 (ꢁ1.5)
12 (ꢁ1.7)
11 (ꢁ0.9)
12 (ꢁ0.9)
12 (ꢁ1.4)
14 (ꢁ0.7)
22 (ꢁ3.0)
17 (ꢁ2.6)
4.4 (ꢁ0.6)
6.9 (ꢁ2.1)
4.2 (ꢁ0.7)
20 (ꢁ2.0)
16 (ꢁ2.1)
17 (ꢁ0.8)
3.9 (ꢁ0.4)
3.7 (ꢁ0.3)
15 (ꢁ2.0)
18 (ꢁ2.0)
24 (ꢁ4.7)
24 (ꢁ4.6)
17 (ꢁ2.7)
31 (ꢁ5.3)
16 (ꢁ1.2)
17 (ꢁ2.0)
15 (ꢁ1.1)
15 (ꢁ1.1)
21 (ꢁ3.2)
19 (ꢁ4.3)
31 (ꢁ5.8)
27 (ꢁ9.3)
17 (ꢁ4.4)
15 (ꢁ3.3)
8.7 (ꢁ3.7)
22 (ꢁ2.0)
20 (ꢁ1.0)
20 (ꢁ0.5)
8.0 (ꢁ2.6)
5.7 (ꢁ1.1)
18 (ꢁ1.2)
26 (ꢁ2.2)
32 (ꢁ3.4)
31 (ꢁ2.9)
19 (ꢁ0.7)
28 (ꢁ2.9)
15 (ꢁ0.4)
18 (ꢁ1.4)
17 (ꢁ0.6)
17 (ꢁ2.1)
21 (ꢁ1.3)
21 (ꢁ4.0)
38 (ꢁ1.8)
29 (ꢁ6.1)
20 (ꢁ2.1)
21 (ꢁ2.7)
6-Me
6-Br
6-Cl
6-F
6-OMe
6-CF3
8-Me
8-Br
8-Cl
H
6-Me
6-Br
6-Cl
6-F
6-OMe
6-CF3
8-Me
8-Br
8-Cl
H
10
11
12
13
14
15
17
18
19
20
21
22
23
24
25
26
27
28
H
H
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
CHO
b
H
a
Values are given in mM and are means of two to five experiments; standard deviation is given in parentheses.
b
R1: CH]CHeNO2.

270
I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
Table 2
that natural products possess inherent drug-likeness and have
proven an extremely powerful source of potent and selective
antitumour drugs [15]. Overall, the resulting GI50 values were in the
Antiproliferative activity (GI50) against human solid tumour cells of compounds
produced via Scheme 5.a
Compound Cell line
range 1.2e78 mM.
All tested compounds can be grouped in three main categories
according to their chemical scaffold. Thus, we distinguish poly-
althenol (Tables 1 and 2), 2,3-dihydro pentacyclindole (Table 3) and
C3-unsaturated pentacyclindole analogues (Table 4). In Fig. 3, the
mean graph derived from the obtained dose-response data of all
tested products is displayed. In this plot, it is possible to observe
that the 2,3-dihydro pentacyclindole scaffold (Table 3) originates
the least active compounds (with the exception of compound 29).
Overall, the compounds show similar activity profile against drug
sensitive (A549, HBL-100, HeLa and SW1573) and resistant (T-47D
and WiDr) cell lines.
A549
HBL-100 SW1573 HeLa
T-47D
WiDr
20
29
30
17 (ꢁ1.0) 15 (ꢁ0.6) 14 (ꢁ2.5) 12 (ꢁ1.7) 17 (ꢁ2.0) 18 (ꢁ1.4)
>100 >100 >100 >100 >100 >100
9.1 (ꢁ1.6) 13 (ꢁ0.9) 13 (ꢁ2.3) 5.5 (ꢁ0.7) 13 (ꢁ1.1) 16 (ꢁ1.7)
a
Values are given in mM and are means of two to five experiments; standard
deviation is given in parentheses.
compounds [5], we decided to study the biological activity of the
synthetic analogues in two whole-cell screening models: a repre-
sentative panel of human solid tumour cell lines and a set of clin-
ically relevant bacteria species. The selected microbes included two
strains of Gram-positive and three Gram-negative bacteria.
From the results of the antiproliferative activity some struc-
tureeactivity relationships (SARs) could be inferred, and will be
discussed below.
For the polyalthenol analogues (Tables 1 and 2), the following
SAR was obtained. The presence of side chains (R1) in C-2 position
produces a slight loss in activity (6e15 vs 17e28). When consid-
ering the substituents on the benzene ring either at C-6 (7e12) or
C-8 (13e15), only the presence of a methoxy group enhances the
biological activity over the parent compound (11 vs 6). Finally, the
substitution on the nitrogen atom with a diphenylmethyl produces
a loss in activity (20 vs 29). However, if the methyl ester of com-
pound 29 is hydrolysed the resulting carboxylic acid 30 recovers
the biological activity. With this set of compounds it is not possible
to establish the role in the activity of the carboxylic acid group,
although we speculate that it might be favourable.
3.1. Antibacterial activity
Compounds were screened against strains of the Gram-positive
S. aureus and Enterococcus faecalis, and the Gram-negative Escher-
ichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.
Despite the fact of being analogues of known antimicrobial com-
pounds, the screening of compounds revealed some irrelevant ac-
tivity observed solely for compound 27 (MIC 50e100
against the bacterial strain S. aureus.
mM) and only
3.2. Antiproliferative activity
For the pentacyclindole analogues (Tables
following SAR was obtained. As aforementioned, the 2,3-dihydro
pentacyclindole derivatives (Table 3) show less activity than the
3 and 4), the
As a model to study the anticancer activity of the synthetic
compounds, we used the human solid tumour cell lines A549 (non-
small cell lung), HBL-100 (breast), HeLa (cervix), SW1573 (non-
small cell lung), T-47D (breast), and WiDr (colon). The in vitro
antiproliferative activity was evaluated after 48 h of drug exposure
using the sulforhodamine B (SRB) assay [14]. The results expressed
as GI50 (50% growth inhibition) are given in Tables 1e4. With the
exception of compound 29, all evaluated compounds induced cell
growth inhibition in all cell lines. This is consistent with the fact
corresponding
C3-unsaturated
pentacyclindole
analogues
(Table 4). Similar to what was observed for the polyalthenol ana-
logues, the presence of a methoxy group on the benzene ring
provides a minor enhancement on the antiproliferative activity, but
not in all cell lines (38 vs 33 and 44 vs 40).
4. Conclusions
In summary, we have described a straightforward synthetic
methodology to obtain a series of polyalthenol and pentacyclindole
analogues, with different functionalisation in sesquiterpenic and
indole fragments starting from ent-halimic acid. We evaluated their
ability to inhibit tumour cell growth and from the results some
structureeactivity relationships have been derived. Although the
experiments are preliminary, these compounds show remarkable
biological activity towards human cancer cell lines. Overall, the
compounds show active against drug sensitive and resistant cell
lines. More experiments are needed to establish the scope and
limitations of the methoxy group present in the most active com-
pound of the series.
Table 3
Antiproliferative activity (GI50) against human solid tumour cells of compounds
produced via Scheme 7.a
Compound
Cell line
R1
R2 A549
HBL-100 SW1573 HeLa
T-47D
WiDr
5. Experimental
33
H
H
H
H
H
H
H
39 (ꢁ17) 78 (ꢁ22) 30 (ꢁ20) 19 (ꢁ5.3) 35 (ꢁ12) 50 (ꢁ27)
27 (ꢁ3.2) 15 (ꢁ0.5) 23 (ꢁ5.5) 18 (ꢁ3.2) 23 (ꢁ4.3) 32 (ꢁ2.2)
40 (ꢁ3.2) 34 (ꢁ0.8) 45 (ꢁ15) 25 (ꢁ0.7) 31 (ꢁ7.1) 55 (ꢁ11)
35 (ꢁ0.7) 28 (ꢁ3.8) 38 (ꢁ11) 23 (ꢁ4.4) 28 (ꢁ5.1) 48 (ꢁ5.4)
25 (ꢁ1.9) 18 (ꢁ1.4) 27 (ꢁ5.7) 20 (ꢁ4.1) 27 (ꢁ5.2) 32 (ꢁ2.5)
22 (ꢁ9.7) 15 (ꢁ2.9) 25 (ꢁ5.5) 20 (ꢁ2.0) 19 (ꢁ6.8) 25 (ꢁ5.8)
5.1. General
34 Me
35 Br
36 Cl
37
38 OMe
45
46
47
Unless otherwise stated, all chemicals were purchased as the
highest purity commercially available and were used without
further purification. IR spectra were recorded on an AVATAR 370 FT-
IR Thermo Nicolet spectrophotometers. 1H and 13C NMR spectra
were performed in CDCl3 and referenced to the residual peak of
F
H
H
H
Me 30 (ꢁ0.5) 32 (ꢁ3.7) 31 (ꢁ4.7) 22 (ꢁ1.3) 29 (ꢁ2.9) 43 (ꢁ4.7)
Br 42 (ꢁ2.7) 40 (ꢁ8.3) 44 (ꢁ9.5) 22 (ꢁ2.4) 37 (ꢁ6.3) 54 (ꢁ10)
Cl 54 (ꢁ4.9) 52 (ꢁ8.2) 49 (ꢁ5.9) 31 (ꢁ5.2) 50 (ꢁ5.8) 67 (ꢁ11)
CHCl3 at
using Varian 200 VX and Bruker DRX 400 instruments. Chemical
d 7.26 ppm and d
77.0 ppm, for 1H and 13C, respectively,
a
Values are given in mM and are means of two to five experiments; standard
deviation is given in parentheses.

I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
271
Table 4
Antiproliferative activity (GI50) against human solid tumour cells of compounds produced via Scheme 7.a
Compound
Cell line
A549
R1
R2
HBL-100
SW1573
HeLa
T-47D
WiDr
40
41
42
44
48
49
50
H
H
H
H
H
Me
Br
Cl
4.6 (ꢁ0.1)
16 (ꢁ0.6)
17 (ꢁ0.3)
7.7 (ꢁ2.3)
16 (ꢁ0.5)
35 (ꢁ5.0)
21 (ꢁ2.4)
3.5 (ꢁ0.2)
11 (ꢁ2.0)
16 (ꢁ2.2)
5.0 (ꢁ0.6)
13 (ꢁ0.7)
26 (ꢁ5.2)
16 (ꢁ0.8)
8.3 (ꢁ1.1)
15 (ꢁ1.1)
12 (ꢁ1.1)
5.9 (ꢁ1.1)
16 (ꢁ2.3)
26 (ꢁ2.4)
17 (ꢁ0.2)
3.2 (ꢁ0.2)
11 (ꢁ0.8)
14 (ꢁ0.5)
3.9 (ꢁ0.5)
12 (ꢁ0.7)
18 (ꢁ4.9)
12 (ꢁ0.8)
3.4 (ꢁ0.7)
16 (ꢁ1.5)
21 (ꢁ2.1)
6.5 (ꢁ1.4)
23 (ꢁ1.8)
31 (ꢁ1.4)
21 (ꢁ1.7)
4.0 (ꢁ0.6)
19 (ꢁ1.0)
22 (ꢁ1.2)
1.2 (ꢁ2.2)
22 (ꢁ1.1)
37 (ꢁ2.8)
21 (ꢁ1.6)
Me
Br
OMe
H
H
H
a
Values are given in mM and are means of two to five experiments; standard deviation is given in parentheses.
shifts are reported in
d
parts per million and coupling constants (J)
5.2. General procedure for Fischer’s indolization reaction with
are given in hertz. MS were performed using a VG-TS 250 spec-
trometer at 70 eV ionising voltage. Mass spectra are presented as m/
z (% rel. int.). HRMS were recorded on a VG Platform (Fisons)
spectrometer using chemical ionization (ammonia as gas) or Fast
Atom Bombardment (FAB) technique. For some of the samples,
QSTAR XL spectrometer was employed for electrospray ionization
(ESI). Optical rotations were determined on a Perkin-Elmer 241
phenylhydrazines
To a 0.1 M solution of the corresponding aldehyde or ketone in
AcOH, 1.2 eq of phenylhydrazine were added and the reaction
mixture was stirred for 2 h at r.t. under Ar atmosphere; then it was
heated up to 130 ꢀC for further 2 h. It was let to cool down to r.t.,
diluted with EtOAc, washed with 6% NaHCO3 and brine and dried
over anhydrous Na2SO4. It was filtered and the solvent was
removed. The crude was purified through column chromatography
to afford the corresponding indole sesquiterpenes. Compound 17
could not be purified by column chromatography, so the crude was
polarimeter in 1 dm cells. Values are given in 10ꢂ1 deg cm2 gꢂ1
.
Diethyl ether and THF were distilled from sodium, and
dichloromethane was distilled from calcium hydride under Argon
atmosphere.
Fig. 3. Mean graph profiles for compounds 6e50. The middle line represents the median GI50 (mM) value of the set of compounds against each individual cell line.

272
I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
dissolved in EtOH, cooled down to 0 ꢀC and 3 eq of NaBH4 was
added. After stirring for 40 min at r.t. it was cooled down again to
0 ꢀC and 2 M HCl was added. It was diluted with H2O and 1 M NaOH
was added until pH ¼ 7. It was extracted with EtOAc, washed with
brine and dried over anhydrous Na2SO4. After filtering and
removing the solvent the crude was purified by column
chromatography.
117.2, 111.6, 110.2, 52.1, 45.5, 45.0, 39.2, 39.0, 35.1, 32.0, 28.5, 23.6,
22.7, 22.4, 17.9, 16.5, 13.2 (MeC-2); HRMS calcd for C26H32NO2NaF3
(Mþ þ Na) 470.2277, found 470.2281.
5.3. General procedure for Fischer’s indolization with
phenylhydrazine hydrochlorides
To 1.2 eq. of the corresponding phenylhydrazine hydrochloride
under Ar atmosphere, 1.2 eq of aqueous 1 M NaOH were added and
the mixture was stirred for 10 min. Then, a 0.1 M solution of
aldehyde 5 or ketone 16 in AcOH was added and the mixture was
stirred under Ar atmosphere and at r.t. for 2 h and then heated up to
130 ꢀC for further 2 h. In the case of the reactions with ketone 16 the
mixture was stirred at r.t. for 7 h and at 130 ꢀC for 16 h. It was let to
cool down to r.t. and diluted with EtOAc. The organic layer was
washed with 6% NaHCO3 and brine, dried over anhydrous Na2SO4,
filtered and the solvent was removed. The crude was purified
through column chromatography affording the corresponding
indole derivatives.
5.2.1. Aureanindol-16-ene (4)
Yield 58%; [
a]
D
22-59.1 (c 0.23, EtOH); IR (film, cmꢂ1): 3400, 3043,
2947, 2913, 1456, 1383, 746; 1H NMR (400 MHz, CDCl3):
d
7.92 (1H,
br s, NeH), 7.66 (1H, d, J ¼ 7.8 Hz), 7.33 (1H, d, J ¼ 7.8 Hz), 7.20 (1H, t,
J ¼ 7.8 Hz), 7.15 (1H, t, J ¼ 7.8 Hz), 6.94 (1H, s), 5.32 (1H, br s), 3.12
(1H, d, J ¼ 14.4 Hz), 2.98 (1H, d, J ¼ 14.4 Hz),1.02 (3H, s), 0.94 (3H, s),
0.92 (3H, s), 0.88 (3H, d, J ¼ 7.0 Hz); 13C NMR (100 MHz, CDCl3):
d
142.0, 135.6, 129.3, 122.8, 121.3, 120.2, 119.5, 119.0, 113.6, 110.8,
44.5, 43.3, 38.1, 34.9, 34.8, 31.8, 29.1, 28.9, 24.6 , 23.5, 23.1, 23.0,16.0;
HRMS calcd for C23H32N (Mþ þ H) 322.5229, found 322.2512.
5.2.2. Methyl aureanindol-16-ene-21-oate (6)
Yield 95%; mp: 129e132 ꢀC; [
a
]
22-45.7 (c 0.81, CHCl3); IR (film,
5.3.1. Methyl 6-metil-aureanindol-16-ene-21-oate (7)
D
cmꢂ1): 3399, 3052, 2949, 1727, 1457, 1434, 1379, 1255, 1232, 1198,
Yield 45%; [
2949, 2924, 2872, 1701, 1431, 1256, 1232, 1113; 1H NMR (200 MHz,
CDCl3):
a]
22-47.6ꢀ (c 0.34, CHCl3); IR (film, cmꢂ1): 3408,
D
1112, 739; 1H NMR (200 MHz, CDCl3):
d
8.01 (1H, br s, NeH), 7.63
(1H, d, J ¼ 7.6 Hz), 7.34 (1H, d, J ¼ 7.6 Hz), 7.16 (1H, t, J ¼ 7.6 Hz), 7.10
(1H, t, J ¼ 7.6 Hz), 6.94 (1H, s), 5.25 (1H, br s), 3.72 (3H, s), 3.09 (1H,
d, J ¼ 14.2 Hz), 2.98 (1H, d, J ¼ 14.2 Hz), 1.18 (3H, s), 2.39e1.04 (10H,
m), 0.88 (3H, s), 0.83 (3H, d, J ¼ 6.8 Hz); 13C NMR (50 MHz, CDCl3,
d
7.91 (1H, br s), 7.41 (1H, s), 7.22 (1H, d, J ¼ 8.0 Hz), 6.99
(1H, dd, J ¼ 8.0, 1.0 Hz), 6.89 (1H, d, J ¼ 2.2 Hz), 5.25 (1H, br s), 3.72
(3H, s), 3.07 (1H, d, J ¼ 14.4 Hz), 2.94 (1H, d, J ¼ 14.4 Hz), 2.48 (3H, s,
MeC-6), 2.30e1.20 (10H, m), 1.19 (3H, s), 0.90 (3H, s), 0.85 (3H, d,
d
ppm): 179.2, 141.4, 135.6, 129.5, 123.3, 121.5, 120.2, 119.7, 119.2,
J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3):
d 179.3, 141.4, 134.2, 129.8,
113.6, 111.0, 52.1, 45.4, 44.7, 38.9, 37.9, 35.2, 31.9, 28.7, 23.6, 23.0,
22.9, 18.8, 16.3; HRMS calcd for C24H31NO2 (Mþ) 365.2353, found
365.2355.
128.3, 123.6, 123.2, 120.2, 119.3, 113.1, 110.7, 52.1, 45.5, 44.6, 38.9,
38.0, 35.2, 31.9, 28.7, 23.7, 23.0, 22.9, 21.8 (MeC-6), 18.7, 16.3; HRMS
calcd for C25H33NO2Na (Mþ þ Na) 402.2403, found 402.2385.
5.2.3. Methyl 6-trifluoromethyl-aureanindol-16-ene-21-oate (12)
5.3.2. Methyl 6-bromo-aureanindol-16-ene-21-oate (8)
Yield 5%; [
a
]
22-26.9 (c 0.32, CHCl3); IR (film, cmꢂ1): 3368, 2928,
Yield 40%; [
2949, 2928, 2872, 1709, 1458, 1379, 1251, 1113, 739; 1H NMR
(400 MHz, CDCl3): 8.17 (1H, br s, NeH), 7.72 (1H, s), 7.21 (1H, d,
a]
22-44.5 (c 0.38, CHCl3); IR (film, cmꢂ1): 3421, 3373,
D
D
2874, 1699, 1329, 1258, 1159, 1113; 1H NMR (400 MHz, CDCl3)
d
8.20
(1H, s, NeH), 7.90 (1H, s), 7.41 (2H, s), 7.01 (1H, s), 5.24 (1H, br s),
3.71 (3H, s), 3.18 (1H, d, J ¼ 14.4 Hz), 3.04 (1H, m), 2.94 (1H, d,
J ¼ 14.4 Hz), 2.30e1.25 (9H, m), 1.16 (3H, s), 0.85 (3H, s), 0.84 (3H, d,
d
J ¼ 8.3 Hz), 7.17 (1H, d, J ¼ 8.3 Hz), 6.91 (1H, s), 5.20 (1H, br s), 3.71
(3H, s), 3.06 (1H, d, J ¼ 14.5 Hz), 3.01 (1H, br s), 2.82 (1H, d,
J ¼ 14.4 Hz), 2.20e1.20 (9H, m), 1.17 (3H, s), 0.84 (3H, s), 0.83 (3H, d,
J ¼ 6.8 Hz); 13C NMR (50 MHz, CDCl3)
d 179.1, 141.0, 137.1, 128.9,
124.9, 121.8 (d, J ¼ 30.0 Hz, C-6), 120.6, 118.4, 115.3, 114.8, 111.3, 52.1,
45.4, 44.6, 38.8, 38.4, 34.9, 31.7, 28.6, 23.5, 23.0, 22.9, 19.0, 16.3;
HRMS calcd for C25H30NO2F3Na (Mþ þ Na) 456.2121, found
456.2112.
J ¼ 6.8 Hz); 13C NMR (50 MHz, CDCl3):
d 179.3, 141.0, 134.5, 131.3,
124.7, 124.3, 122.2, 120.5, 113.4, 112.6, 112.5, 52.1, 45.5, 44.5, 38.8,
38.2, 35.1, 31.8, 28.6, 23.5, 22.9, 22.8, 18.9, 16.3; HRMS calcd for
C
24H30NO2NaBr (Mþ þ Na) 466.1352, found 466.1368.
5.2.4. Methyl 2-methyl-aureanindol-16-ene-21-oate (17)
5.3.3. Methyl 6-chloro-aureanindol-16-ene-21-oate (9)
Yield 50%; [
22-46.9 (c 0.29, CHCl3); IR (film, cmꢂ1): 3373, 2949,
1708, 1458, 1251, 1113, 733; 1H NMR (200 MHz, CDCl3)
Yield: 14%; [
a]
22-33.7 (c 1.04, CHCl3); IR (film, cmꢂ1): 3398,
a]
D
D
2926, 1709, 1460, 1437, 1251, 1113; 1H NMR (200 MHz, CDCl3)
d
7.84
d 8.06 (1H, br
(1H, br s, NeH), 7.53 (1H, d, J ¼ 7.0 Hz), 7.22 (1H, d, J ¼ 7.0 Hz), 7.08
(1H, t, J ¼ 7.0 Hz), 7.07 (1H, t, J ¼ 7.0 Hz), 5.22 (1H, br s), 3.75 (3H, s),
3.15 (1H, m), 3.01 (1H, d, J ¼ 14.6 Hz), 2.92 (1H, d, J ¼ 14.6 Hz), 2.34
(3H, s, MeC-2), 2.10e1.25 (9H, m), 1.19 (3H, s), 0.87 (3H, s), 0.83 (3H,
s, NeH), 7.56 (1H, d, J ¼ 1.8 Hz), 7.23 (1H, d, J ¼ 8.0 Hz), 7.09 (1H, dd,
J ¼ 8.4, 1.8 Hz), 6.95 (1H, dd, J ¼ 2.2 Hz), 5.21 (1H, br s), 3.70 (3H, s),
3.07 (1H, d, J ¼ 13.8 Hz), 2.85 (1H, d, J ¼ 13.8 Hz), 2.30e1.25 (10H,
m), 1.16 (3H, s), 0.85 (3H, s), 0.83 (3H, d, J ¼ 6.6 Hz); 13C NMR
d, J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3)
d
179.4, 141.7, 135.3, 133.0,
(50 MHz, CDCl3) d 179.2, 141.0, 134.2, 130.7, 125.1, 124.8, 121.8, 120.5,
130.8, 120.7, 119.8, 119.7, 118.9, 110.4, 110.1, 52.2, 45.6, 45.2, 39.1,
38.6, 35.2, 32.1, 28.7, 23.6, 22.8, 22.6, 18.1, 16.6, 13.2 (MeC-2); HRMS
calcd for C25H33NO2Na (Mþ þ Na) 402.2404, found 402.2412.
119.2, 113.6, 112.0, 52.1, 45.4, 44.5, 38.8, 38.2, 35.1, 31.8, 28.6, 23.5,
23.0, 22.9, 18.9, 16.3; HRMS calcd for C24H30NO2NaCl (Mþ þ Na)
422.1857, found 422.1843.
5.2.5. Methyl 6-trifluoro-2-methyl-aureanindol-16-ene-21-oate
(23)
5.3.4. Methyl 6-fluoro-aureanindol-16(17)-ene-21-oate (10)
Yield 53%; [
1712, 1485, 1456, 1251, 1114, 910, 733; 1H NMR (200 MHz, CDCl3)
7.97 (1H, br s, NeH), 7.25e7.20 (2H, m), 6.98 (1H, s), 6.89 (1H, m),
a]
22-45.1 (c 0.34, CHCl3), IR (film, cmꢂ1): 3383, 2949,
D
Yield: 27% calculated from transformed reagent; [
0.31, CHCl3); IR (film, cmꢂ1): 3367, 2926, 2872, 1701, 1449, 1331,
1256, 1157, 1111; 1H NMR (200 MHz, CDCl3)
7.95 (1H, br s, NeH),
a]
22-31.5 (c
D
d
d
5.23 (1H, br s), 3.71 (3H, s), 3.08e3.06 (1H, m); 3.04 (1H, d,
J ¼ 14.2 Hz), 3.03 (1H, m), 2.88 (1H, d, J ¼ 14.2 Hz), 2.30e1.25 (9H,
m), 1.17 (3H, s), 0.86 (3H, s), 0.83 (3H, d, J ¼ 7.2 Hz); 13C NMR
7.78 (1H, s), 7.29 (2H, m), 5.19 (1H, br s), 3.74 (3H), 3.05 (1H, d,
J ¼ 14.4 Hz), 2.86 (1H, d, J ¼ 14.4 Hz), 2.37 (3H, s, MeC-2), 2.15e1.30
(9H, m), 1.17 (3H, s), 0.83 (3H, s), 0.82 (3H, d, J ¼ 6.6 Hz); 13C NMR
(100 MHz, CDCl3)
129.7 (d, J ¼ 5.0 Hz, C-4), 125.0, 120.1, 113.5, 111.4, 111.2 (J ¼ 10.0 Hz,
d
179.0, 157.6 (d, J ¼ 115.0 Hz, C6-F), 141.0, 132.1,
(50 MHz, CDCl3)
d
179.2, 141.2, 138.0, 136.7, 134.7, 130.2, 120.2, 117.7,

I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
273
C-7), 104.2 (d, J ¼ 10.0 Hz, C-5), 51.8, 45.2, 44.4, 38.6, 37.7, 35.0, 31.5,
5.3.10. Methyl 6-bromo-2-methyl-aureanindol-16-ene-21-oate
28.4, 23.3, 22.8, 22.6, 18.6, 16.0; HRMS calcd for C24H31NO2F
(19)
Yield: 95% calculated from conversion; [
(Mþ þ H) 384.2333, found 384.2336.
a
]
D
22-27.5 (c 0.40, CHCl3);
IR (film, cmꢂ1): 3397, 2949, 2926, 2872, 1709, 1449, 1379, 1250,
5.3.5. Methyl 6-methoxy-aureanindol-16-ene-21-oate (11)
1113; 1H NMR (200 MHz, CDCl3)
d 7.94 (1H, br s, NeH), 7.62 (1H, d,
Yield 44%; [
2872, 1718, 1485, 1256, 1213, 1113, 910, 733; 1H NMR (200 MHz,
CDCl3)
a
]
D
22-52.6 (c 0.27, CHCl3); IR (film, cmꢂ1): 3412, 3949,
J ¼ 1.6 Hz), 7.13 (1H, dd, J ¼ 8.2, 1.6 Hz), 7.06 (1H, d, J ¼ 8.2 Hz), 5.17
(1H, br s), 3.75 (3H, s), 3.12 (1H, m, H-15), 2.99 (1H, d, J ¼ 14.6 Hz),
2.74 (1H, d, J ¼ 14.6 Hz), 2.31 (3H, s, MeC-2), 2.10e1.20 (9H, m), 1.17
(3H, s), 0.83 (3H, d, J ¼ 7.0 Hz), 0.82 (3H, s); 13C NMR (50 MHz,
d
7.97 (1H, br s, NeH), 7.20 (1H, d, J ¼ 8.8 Hz), 7.06 (1H, d,
J ¼ 2.2 Hz), 6.91 (1H, d, J ¼ 2.2 Hz), 6.83 (1H, dd, J ¼ 8.8, 2.2 Hz), 5.27
(1H, br s), 3.88 (3H, s, eOMe), 3.71 (3H, s, eCOOMe), 3.02 (1H, d,
J ¼ 14.4 Hz), 2.95 (1H, d, J ¼ 14.4 Hz), 2.30e1.25 (9H, m), 1.18 (3H, s),
0.89 (3H, s), 0.83 (3H, d, J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3)
CDCl3):
d 179.4, 141.0, 134.4, 133.9, 132.5, 123.4, 122.1, 120.3, 112.3,
111.5, 110.4, 52.2, 45.6, 45.0, 39.3, 39.0, 35.2, 32.2, 28.5, 23.6, 22.7,
22.4, 17.9, 16.6, 13.2 (MeC-2); HRMS calcd for C25H32NO2NaBr
(Mþ þ Na) 480.1509, found 480.1510.
d
179.2,154.0,141.5, 131.1, 130.0, 124.3,120.1, 113.4, 111.7, 111.6, 101.8,
56.2 (eOMe), 52.1 (eCOOMe), 45.4, 44.8, 38.9, 37.8, 35.3, 31.9, 28.7,
23.7, 23.0, 22.9, 18.9, 16.3; HRMS calcd for C25H33NO3Na (Mþ þ Na)
418.2364, found 418.2351.
5.3.11. Methyl 6-chloro-2-methyl-aureanindol-16-ene-21-oate (20)
Yield 94% calculated from transformed reagent; [
0.57, CHCl3); IR (film, cmꢂ1): 3372, 2953, 2872, 1719, 1449, 1263,
1113, 737; 1H NMR (200 MHz, CDCl3)
8.05 (1H, br s, NeH), 7.47
a]
22-39.4 (c
D
5.3.6. Methyl 8-methyl-aureanindol-16-ene-21-oate (13)
d
Yield, 34%; [
a
]
22-34.6 (c 0.28, CHCl3); IR (film, cmꢂ1): 3408, 2951,
(1H, d, J ¼ 2.0 Hz), 7.09 (1H, d, J ¼ 8.4 Hz), 6.99 (1H, dd, J ¼ 8.4,
2.0 Hz), 5.17 (1H, br s), 3.76 (3H, s), 3.14 (1H, m), 2.99 (1H, d,
J ¼ 14.4 Hz), 2.75 (1H, d, J ¼ 14.4 Hz), 2.30 (3H, s, MeC-2), 2.10e1.20
(9H, m), 1.19 (3H, s), 0.83 (3H, s), 0.82 (3H, d, J ¼ 7.0 Hz); 13C NMR
D
2872, 1699, 1448, 1379, 1255, 1115, 735; 1H NMR (200 MHz, CDCl3)
d
7.97 (1H, s, NeH), 7.49 (1H, d, J ¼ 7.4 Hz), 7.04 (1H, dd, J ¼ 8.0,
7.4 Hz), 6.97 (1H, d, J ¼ 8.0 Hz), 6.96 (1H, s), 5.27 (1H, br s), 3.72 (3H,
s), 3.08 (1H, m), 3.07 (1H, d, J ¼ 14.1 Hz), 3.03 (1H, d, J ¼ 14.1 Hz),
2.49 (3H, s, MeC-8), 2.40e1.25 (9H, m), 1.19 (3H, s), 0.89 (3H, s), 0.84
(50 MHz, CDCl3) d 179.4, 141.1, 134.7, 133.7, 131.9, 124.6, 120.7, 120.3,
119.0, 111.0, 110.4, 52.2, 45.6, 45.0, 39.2, 39.0, 35.2, 32.1, 28.5, 23.5,
22.7, 22.5, 17.9, 16.5, 13.1 (MeC-2); HRMS calcd for C25H32NO2NaCl
(Mþ þ Na) 436.2014, found 436.1995.
(3H, d, J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3)
d 179.2, 141.5, 135.4,
129.1, 123.1, 122.1, 120.1, 119.4, 117.5, 114.2, 114.1, 52.1, 45.5, 44.7,
38.9, 37.8, 35.4, 31.9, 28.7, 23.7, 23.0, 22.9, 18.8, 16.8, 16.3 (MeC-8);
HRMS calcd for C25H34NO2 (Mþ þ H) 380.2584, found 380.2590.
5.3.12. Methyl 6-fluoro-2-methyl-aureanindol-16-ene-21-oate (21)
Yield: 63% calculated from transformed reagent; [
0.40, CHCl3); IR (film, cmꢂ1): 3377, 2951, 2932, 2872, 1709, 1487,
1450, 1252, 1115, 910, 735; 1H NMR (200 MHz, CDCl3)
7.87 (1H, br
a]
22-44.5 (c
D
5.3.7. Methyl 8-bromo-aureanindol-16-ene-21-oate (14)
Yield 34%; [
2872, 1716, 1435, 1379, 1336, 1259, 1196, 1113, 733; 1H NMR
(200 MHz, CDCl3)
a
]
D
22-37.9 (c 0.39, CHCl3); IR (film, cmꢂ1): 3372, 2949,
d
s, NeH), 7.17 (1H, d, J ¼ 8.8 Hz), 7.10 (1H, d, J ¼ 8.8 Hz), 6.80 (1H, dt,
J ¼ 8.8, 2.2 Hz), 5.22 (1H, br s), 3.75 (3H, s), 3.11 (1H, m), 2.94 (1H, d,
J ¼ 14.6 Hz), 2.83 (1H, d, J ¼ 14.6 Hz), 2.32 (3H, s, MeC-2), 2.10e1.20
(9H, m), 1.18 (3H, s), 0.84 (3H, s), 0.82 (3H, d, J ¼ 8.4 Hz); 13C NMR
d
8.16 (1H, br s, NeH), 7.55 (1H, d, J ¼ 8.0 Hz), 7.30
(1H, d, J ¼ 7.2 Hz), 7.00 (1H, s), 6.98 (1H, dd, J ¼ 8.0, 7.2 Hz), 5.21 (1H,
br s), 3.71 (3H, s), 3.08 (1H, d, J ¼ 14.2 Hz), 3.03 (1H, m), 2.91 (1H, d,
J ¼ 14.2 Hz), 2.30e1.25 (9H, m), 1.18 (3H, s), 0.90 (3H, s), 0.84 (3H, d,
(50 MHz, CDCl3)
d
179.4, 157.5 (d, J ¼ 115.0 Hz, C6-F) 141.5, 135.0,
J ¼ 6.2 Hz); 13C NMR (50 MHz, CDCl3)
d
179.2, 141.1, 134.5, 130.8,
131.8, 131.1, 120.0, 110.9, 110.4 (d, J ¼ 10.0 Hz, C-8), 108.7 (d,
J ¼ 25.0 Hz, C-7), 104.7 (d, J ¼ 25.0 Hz, C-5), 52.2, 45.6, 45.2, 39.0,
38.8, 35.2, 32.0, 28.6, 23.5, 22.8, 22.6, 18.1, 16.5, 13.3 (MeC-2); HRMS
calcd for C25H32NO2NaF (Mþ þ Na) 420.2309, found 420.2313.
124.0, 123.9, 120.5, 120.4, 119.0, 114.9, 104.8, 52.1, 45.4, 44.7, 38.8,
38.2, 35.3, 31.8, 28.6, 23.5, 23.0, 22.9, 19.0, 16.3; HRMS calcd for
C
24H30NO2NaBr (Mþ þ Na) 466.1352, found 466.1365.
5.3.8. Methyl 8-chloro-aureanindol-16-ene-21-oate (15)
Yield: 27%: mp: 134e136 ꢀC; [ 22-37.7 (c 1.00, CHCl3); IR (film,
cmꢂ1): 3373, 2951, 2872, 1716, 1436, 1259, 1198, 1113, 733; 1H NMR
(200 MHz, CDCl3)
5.3.13. Methyl 2-methyl-6-methoxy-aureanindol-16-ene-21-oate
a
]
(22)
D
Yield: 47% calculated from transformed reagent; [
0.35, CHCl3); IR (film, cmꢂ1): 3401, 2949, 2872, 1713, 1485, 1452,
1254, 1215,1113, 733; 1H NMR (200 MHz, CDCl3)
7.71 (1H, s, NeH),
a]
22-53.4 (c
D
d
8.29 (1H, br s, NeH), 7.51 (1H, d, J ¼ 8.0 Hz), 7.15
(1H, d, J ¼ 8.0 Hz), 7.02 (1H, t, J ¼ 8.0 Hz), 7.00 (1H, s), 5.22 (1H, br s),
3.72 (3H, s), 3.09 (1H, d, J ¼ 14.2 Hz),3.03 (1H, m), 2.91 (1H, d,
J ¼ 14.2 Hz), 2.30e1.25 (9H, m), 1.18 (3H, s), 0.85 (3H, s), 0.83 (3H, d,
d
7.12 (1H, d, J ¼ 8.4 Hz), 7.10 (1H, d, J ¼ 2.0 Hz), 6.74 (1H, dd, J ¼ 8.4,
2.0 Hz), 5.28 (1H, br s), 3.86 (3H, s, eOMe), 3.73 (3H, s, eCOOMe),
3.10 (1H, m), 2.93 (1H, d, J ¼ 14.4 Hz), 2.86 (1H, d, J ¼ 14.4 Hz), 2.32
(3H, s, MeC-2), 2.15e1.20 (9H, m), 1.18 (3H, s), 0.87 (3H, s), 0.80 (3H,
J ¼ 6.6 Hz); 13C NMR (50 MHz, CDCl3)
d 179.2, 141.1, 133.1, 131.1,
124.1, 120.9, 120.5, 119.9, 118.4, 116.6, 114.8, 52.1, 45.5, 44.6, 38.8,
38.2, 35.2, 31.8, 28.7, 23.5, 23.0, 22.9, 19.0, 16.3; HRMS calcd for
d, J ¼ 6.6 Hz); 13C NMR (50 MHz, CDCl3)
d 179.3, 153.9, 142.0, 134.0,
C
24H30NO2NaCl (Mþ þ Na) 422.1857, found 422.1849.
131.3, 130.5, 119.6, 110.6, 110.4, 110.2, 102.5, 56.3, 52.1, 45.5, 45.4,
39.1, 38.3, 35.3, 32.0, 28.8, 23.7, 22.8, 22.6, 18.2, 16.5, 13.4 (MeC-2);
HRMS calcd for C26H35NO3Na (Mþ þ Na) 432.2509, found 432.2516.
5.3.9. Methyl 2,6-dimethyl-aureanindol-16-ene-21-oate (18)
Yield: 78%; [
22-40.3 (c 1.00, CHCl3); IR (film, cmꢂ1): 3397,
2922, 2872, 1713, 1449, 1437, 1254, 1238, 1113, 735; 1H NMR
(400 MHz, CDCl3) 7.65 (1H, br s, NeH), 7.37 (1H, s), 7.11 (1H, d,
a
]
D
5.3.14. Methyl 2,8-dimethyl-aureanindol-16-ene-21-oate (24)
d
Yield: 62% calculated from transformed reagent; [
0.62, CHCl3); IR (film, cmꢂ1): 3393, 2926, 2872, 1701, 1431, 1379,
1248, 1113, 1103; 1H NMR (200 MHz, CDCl3)
7.76 (1H, br s, NeH),
a]
22-28.4 (c
D
J ¼ 8.1 Hz), 6.89 (1H, d, J ¼ 8.1 Hz), 5.21 (1H, br s), 3.74 (3H, s), 3.15
(1H, m), 2.99 (1H, d, J ¼ 14.4 Hz), 2.83 (1H, d, J ¼ 14.4 Hz), 2.43 (3H,
s, MeC-6), 2.32 (3H, s, MeC-2),1.91e1.31 (9H, m),1.18 (3H, s), 0.87 (3H,
d
7.40 (1H, d, J ¼ 7.4 Hz), 6.99 (1H, d, J ¼ 7.0 Hz), 6.91 (1H, dd, J ¼ 7.4,
7.0 Hz), 5.25 (1H, br s), 3.74 (3H, s), 3.17 (1H, m), 2.95 (2H, br s), 2.46
(3H, s, MeC-8), 2.37 (3H, s, MeC-2), 2.15e1.20 (9H, m), 1.19 (3H, s),
0.87 (3H, s), 0.82 (3H, d, J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3)
s), 0.82 (3H, d, J ¼ 6.9 Hz); 13C NMR (100 MHz, CDCl3)
d 179.0, 141.2,
133.3, 132.7, 130.8, 127.7, 121.9, 119.6, 119.1, 109.8, 109.4, 51.8, 45.3,
44.9, 38.9, 38.7, 35.0, 31.8, 28.4, 23.4, 22.5, 22.3, 21.5 (MeC-6), 17.6,
16.3, 12.9 (MeC-2); HRMS calcd for C26H36NO2 (Mþ þ H) 394.2741,
found 394.2740.
d
179.4,141.8, 134.8,132.6,130.4,121.5, 119.7, 119.2,119.1,117.5,111.0,
52.1, 45.6, 45.2, 39.1, 38.6, 35.4, 32.1, 28.7, 23.6, 22.8, 22.6, 18.1, 16.8

274
I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
(MeC-8), 16.5, 13.2 (MeC-2); HRMS calcd for C26H35NO2Na (Mþ þ Na)
5.4.3. Methyl (2R,3R,17R)-6-methyl-2,3-dihydro-2,17-ciclo-
416.2560, found 416.2566.
aureanindol-15-ene-21-oate (34)
Yield: 99%; [
a
]
22þ63.1 (c 0.20, CHCl3); IR (film, cmꢂ1): 3365,
D
2922, 2872, 1726, 1491, 1431, 1379, 1250, 1130, 735; 1H NMR
5.3.15. Methyl 8-bromo-2-methyl-aureanindol-16-ene-21-oate
(200 MHz, CDCl3)
d
6.91 (1H, s), 6.83 (1H, d, J ¼ 7.8 Hz), 6.60 (1H, d,
(25)
J ¼ 7.8 Hz), 3.77 (1H, dd, J ¼ 5.8, 4.8 Hz), 3.67 (3H, s), 3.09 (1H, dt,
J ¼ 12.2, 5.8 Hz), 2.67 (1H, m), 2.00e1.25 (11H, m), 2.26 (3H, s, MeC-
6), 1.29 (3H, s), 1.09 (3H, s), 0.84 (3H, d, J ¼ 6.0 Hz); 13C NMR
Yield: 87% calculated from transformed reagent; [
0.33, CHCl3); IR (film, cmꢂ1): 3367, 2949, 2872, 1716, 1446, 1247,
1112, 908, 738; 1H NMR (200 MHz, CDCl3)
7.98 (1H, s, NeH), 7.45
a]
22-41.2 (c
D
d
(50 MHz, CDCl3) d 178.0,147.7, 136.6, 135.0, 132.5, 128.6, 127.7, 124.2,
(1H, d, J ¼ 7.8 Hz), 7.22 (1H, d, J ¼ 7.8 Hz), 6.91 (1H, t, J ¼ 7.8 Hz), 5.20
(1H, br s), 3.74 (3H, s), 3.11 (1H, m), 2.98 (1H, d, J ¼ 14.8 Hz), 2.86
(1H, d, J ¼ 14.8 Hz), 2.37 (3H, s, MeC-2), 2.30e1.20 (9H, m), 1.18 (3H,
s), 0.84 (3H, s), 0.82 (3H, d, J ¼ 7.2 Hz); 13C NMR (50 MHz, CDCl3)
110.7, 67.1, 52.1, 47.6, 41.7, 40.2, 39.0, 38.3, 33.4 (x2), 27.2, 26.7, 24.1,
23.7, 21.1 (MeC-6), 18.6, 16.4; HRMS calcd for C25H34NO2 (Mþ þ H)
380.2584, found 380.2602.
d
179.3, 141.4, 133.9, 133.8, 132.0, 123.1, 120.1, 120.0, 118.9, 111.9,
5.4.4. Methyl (2R,3R,17R)-6-bromo-2,3-dihydro-2,17-cyclo-
aureanindol-15-en-21-oate (35)
103.8, 52.1, 45.5, 45.1, 39.0, 38.9, 35.4, 32.1, 28.6, 23.5, 22.8, 22.5,
18.1, 16.5, 13.2 (MeC-2); HRMS calcd for C25H32NO2NaBr (Mþ þ Na)
480.1509, found 480.1510.
Yield: 92%; [
a
]
22þ93.1 (c 0.15, CHCl3); IR (film, cmꢂ1): 3368,
D
2924, 2873, 1718, 1451, 1379, 1254, 1379, 1254, 808, 737; 1H NMR
(200 MHz, CDCl3)
d
7.16 (1H, d, J ¼ 2.0 Hz), 7.09 (1H, dd, J ¼ 8.2,
5.3.16. Methyl 8-chloro-2-methyl-aureanindol-16-ene-21-oate (26)
2.0 Hz), 6.52 (1H, d, J ¼ 8.2 Hz), 3.79 (1H, dd, J ¼ 6.0, 4.6 Hz), 3.67
(3H, s), 3.11 (1H, dt, J ¼ 12.2, 6.0 Hz), 2.66 (1H, m), 2.30e1.25 (11H,
m), 1.29 (3H, s), 1.00 (3H, s), 0.84 (3H, d, J ¼ 6.0 Hz); 13C NMR
Yield: 95% calculated from transformed reagent; [
0.47, CHCl3); IR (film, cmꢂ1): 3368, 2949, 2922, 1717, 1449, 1250,
1200, 1113, 908, 733; 1H NMR (200 MHz, CDCl3)
8.05 (1H, br s, Ne
a]
22-44.0 (c
D
d
(50 MHz, CDCl3) d 177.9,149.2,138.3,134.6,132.8,129.9,126.5,111.8,
H), 7.41 (1H, d, J ¼ 7.4 Hz), 7.07 (1H, d, J ¼ 7.4 Hz), 6.97 (1H, t,
J ¼ 7.4 Hz), 5.20 (1H, br s), 3.75 (3H, s), 3.12 (1H, t, J ¼ 7.8 Hz), 2.98
(1H, d, J ¼ 14.4 Hz), 2.86 (1H, d, J ¼ 14.4 Hz), 2.37 (3H, s, MeC-2),
2.10e1.20 (9H, m), 1.18 (3H, s), 0.85 (3H, s), 0.82 (3H, d, J ¼ 7.4 Hz);
110.6, 67.0, 52.1, 47.5, 41.4, 40.2, 38.9, 38.2, 33.3, 33.2, 27.2, 26.7,
24.0, 23.7, 18.6, 16.4; HRMS calcd for C24H31NO2Br (Mþ þ H)
444.1533, found 444.1528.
13C NMR (50 MHz, CDCl3)
d 179.3, 141.4, 133.9, 132.5, 132.3, 120.1,
5.4.5. Methyl (2R,3R,17R)-6-chloro-2,3-dihydro-2,17-cyclo-
aureanindol-15-ene-21-oate (36)
120.0, 119.7, 118.3, 115.6, 111.9, 52.2, 45.5, 45.1, 39.0, 38.8, 35.3, 32.1,
28.6, 23.5, 22.8, 22.6, 18.1, 16.5, 13.2 (MeC-2); HRMS calcd for
22þ54.9 (c 0.32, CHCl3); IR (film, cmꢂ1): 3368,
C
25H32NO2NaCl (Mþ þ Na) 436.2014, found 436.1999.
Yield: 91%; [
a
]
D
2926, 2873, 1719, 1477, 1431, 1254, 908, 733; 1H NMR (200 MHz,
CDCl3)
d
7.01 (1H, d, J ¼ 2.2 Hz), 6.95 (1H, dd, J ¼ 8.2, 2.2 Hz), 6.65
5.4. General procedure for cyclisation reactions
(1H,d, J ¼ 8.2 Hz), 3.80 (1H, dd, J ¼ 5.8, 4.6 Hz), 3.67 (3H, s), 3.11 (1H,
dt, J ¼ 12.0, 5.8 Hz), 2.30e1.25 (11H, m), 1.29 (3H, s), 1.00 (3H, s),
0.84 (3H, d, J ¼ 6.0 Hz); 13C NMR (50 MHz, CDCl3)
d 177.9, 148.8,
To a 0.02 M solution of the indole derivative in C6H6, 1 eq. of HI
57% was added. The mixture was heated up to 85 ꢀC for 1 h. It was
cooled down to r.t. and diluted with EtOAc. The organic layer was
washed with 10% NaHSO3, 6% NaHCO3, H2O and brine, dried over
anhydrous Na2SO4 and filtered. Removal of the solvents affords the
corresponding pentacyclic derivatives.
137.8,134.6,132.7,127.0,123.7,123.4,111.2, 67.1, 52.1, 47.5, 41.4, 40.2,
39.0, 38.2, 33.3, 33.2, 27.2, 26.7, 24.1, 23.7, 18.5, 16.4; HRMS calcd for
C
24H31NO2Cl (Mþ þ H) 400.2038, found 400.2023.
5.4.6. Methyl (2R,3R,17R)-6-fluoro-2,3-dihydro-2,17-cyclo-
aureanindol-15-ene-21-oate (37)
22þ40.8 (c 0.26, CHCl3); IR (film, cmꢂ1): 3366,
5.4.1. (2R,3R,17R)-2,3-dihydro-2,17-cyclo-aureanindol-15-ene (31)
Yield: 93%; [
a
]
D
Yield: 81%; [
a]
22þ137.1 (c 0.28, MeOH); IR (film, cmꢂ1): 3359,
2926, 2873, 1719, 1485, 1379, 1253, 1219, 1123, 808, 737; 1H NMR
D
2920, 2868, 1310, 1481, 1458, 1382, 1245, 738; 1H NMR (400 MHz,
(400 MHz, CDCl3)
d
6.80 (1H, dd, J ¼ 8.2, 2.4 Hz), 6.69 (1H, dt, J ¼ 8.2,
CDCl3)
d
7.26 (1H, br s, NeH), 7.08 (1H, d, J ¼ 7.2 Hz), 7.00 (1H, dt,
2.4 Hz), 6.58 (1H, dd, J ¼ 8.2, 4.3 Hz), 3.80 (1H, t, J ¼ 5.3 Hz), 3.67
(3H, s), 3.11 (1H, dt, J ¼ 12.0, 4.0Hz), 2.67 (1H, m), 2.30e1.25 (9H, m),
1.76e1.71 (2H, dd, J ¼ 13.3, 5.7 Hz), 1.29 (3H, s), 1.01 (3H, s), 0.84
J ¼ 7.6, 7.2 Hz), 6.71 (1H, t, J ¼ 7.2), 6.67 (1H, d, J ¼ 7.6 Hz), 3.76 (1H,
dd, J ¼ 6.0, 4.8 Hz), 3.11 (1H, m), 2.66 (1H, m), 2.10e1.10 (10H, m),
1.04 (3H, s), 1.01 (3H, s), 1.00 (3H, s), 0.84 (3H, d, J ¼ 6.3 Hz); 13C
(3H, d, J ¼ 5.7 Hz); 13C NMR (100 MHz, CDCl3)
d 177.7, 156.9 (d,
NMR (100 MHz, CDCl3) d 149.9, 137.6, 135.8, 131.4, 127.0, 123.1, 118.7,
J ¼ 135.0 Hz, C-6), 145.6, 137.7 (d, J ¼ 5.0 Hz, C-4), 134.5, 132.5, 112.9
(d, J ¼ 10.0 Hz, C-7), 110.8 (d, J ¼ 5.0 Hz, C-5), 110.5, 67.0, 51.8, 47.3,
41.0, 39.9, 39.1, 38.0, 33.4, 33.0, 26.9, 26.4, 23.8, 23.4, 18.4, 16.1;
HRMS calcd for C24H31NO2F (Mþ þ H) 384.2333, found 384.2337.
110.1, 67.0, 41.7, 40.3, 38.5, 37.8, 37.4, 34.7, 33.5, 28.3, 27.7, 27.2, 25.6,
24.3, 18.2, 16.3; HRMS calcd for C23H32N (Mþ þ H) 322.2529, found
322.2407.
5.4.2. Methyl (2R,3R,17R)-2,3-dihydro-2,17-cyclo-aureanindol-15-
5.4.7. Methyl (2R,3R,17R)-6-methoxy-2,3-dihydro-2,17-cyclo-
en-21-oate (33)
aureanindol-15-ene-21-oate (38)
Yield: 97%; [
a
]
22þ49.2 (c 0.17, CHCl3); IR (film, cmꢂ1): 3367,
Yield: 90%; [
a
]
D
22þ71.2 (c 0.16, CHCl3); IR (film, cmꢂ1): 3360,
D
2924, 2873, 1724, 1610, 1456, 1379, 1251, 1132, 910, 736; 1H NMR
2934, 1719, 1491, 1225, 733; 1H NMR (400 MHz, CDCl3)
d
7.23 (1H, d,
(200 MHz, CDCl3)
d
7.08 (1H, d, J ¼ 7.4 Hz), 7.02 (1H, dd, J ¼ 7.8,
J ¼ 2.3 Hz), 6.34 (1H, d, J ¼ 8.3 Hz), 6.58 (1H, dd, J ¼ 8.3, 2.3 Hz), 3.77
(1H, m), 3.74 (3H, s, MeOe), 3.67 (3H, s, eCOOMe), 3.10 (1H, dt,
J ¼ 12.0, 6.0 Hz), 2.68 (1H, m), 2.30e1.30 (11H, m), 1.28 (3H, s), 1.01
7.4 Hz), 6.71 (1H, t, J ¼ 7.4 Hz), 6.67 (1H, d, J ¼ 7.8 Hz), 3.80 (1H, dd,
J ¼ 6.0, 4.8 Hz), 3.67 (3H, s), 3.14 (1H, dt, J ¼ 12.0, 6.0 Hz), 2.69 (1H,
m), 2.30e1.25 (11H, m), 1.30 (3H, s), 1.02 (3H, s), 0.85 (3H, d,
(3H, s), 0.84 (3H, d, J ¼ 6.1 Hz); 13C NMR (50 MHz, CDCl3)
d 178.0,
J ¼ 6.2 Hz); 13C NMR (50 MHz, CDCl3)
d
178.0, 150.2, 136.0, 135.0,
153.9, 143.8, 138.3, 134.9, 132.6, 112.0, 111.6, 110.5, 67.3, 56.1 (MeOe
), 52.1 (eCOOMe), 47.6, 41.5, 40.2, 39.6, 38.3, 33.4, 33.3, 27.2, 26.7,
24.1, 23.7, 18.6, 16.4; HRMS calcd for C25H34NO3 (Mþ þ H) 396.2533,
found 396.2538.
132.5, 127.3, 123.4, 119.0, 110.5, 66.9, 52.1, 47.6, 41.6, 40.2, 38.9, 38.2,
33.3 (x2), 27.3, 26.7, 24.1, 23.7, 18.5, 16.4; HRMS calcd for C24H32NO2
(Mþ þ H) 366.2428, found 366.2416.

I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
275
5.4.8. Methyl (2R,3R,17R)-6-trifluoromethyl-2,3-dihydro-2,17-
5.5. General procedure for oxidation reactions
cyclo-aureanindol-15-ene-21-oate (39)
Yield: 87%; [
a
]
22þ1.9 (c 0.26, CHCl3); IR (film, cmꢂ1): 3368, 2926,
A 0.01 M solution of the pentacyclic hexahydro derivative with
NMO (3 eq.) and TPAP (2 mg), molecular sieves (500 mg/mmol) in
DCM was stirred at r.t. and under Ar atmosphere for 5e7 min. The
crude was filtered through a silica and celite column, using EtOAc as
eluent. After removing the solvent, the crude was purified through
column chromatography to afford the corresponding tetrahydro
carbazole derivatives.
D
1717, 1618, 1466, 1327, 1265, 1157, 1109; 1H NMR (200 MHz, CDCl3)
d
7.28 (1H, s), 7.25 (1H, s), 6.63 (1H, d, J ¼ 8.8 Hz), 3.87 (1H, dd,
J ¼ 6.2, 4.8 Hz), 3.67 (3H, s), 3.18 (1H, dt, J ¼ 12.0, 6.2 Hz), 2.69 (1H,
m), 2.40e1.30 (11H, m), 1.29 (3H, s), 1.01 (3H, s), 0.85 (3H, d,
J ¼ 5.8 Hz); 13C NMR (50 MHz, CDCl3)
d 177.9, 153.1, 143.0, 135.8,
132.9, 132.4, 126.3, 125.2, 120.6, 66.9, 52.1, 47.0, 41.3, 40.1, 38.3, 38.2,
33.0 (x2), 27.2, 26.7, 24.0, 23.6, 18.5, 16.4; HRMS calcd for
C
25H31NO2F3 (Mþ þ H) 434.2301, found 434.2297.
5.5.1. (17R)-2,17-cyclo-aureanindol-15-ene (32)
Yield: 63%; [
a]
22-53.1 (c 0.04, CHCl3); IR (film, cmꢂ1): 3412,
D
2962, 2927, 1460, 1384, 1093, 739; 1H NMR (200 MHz, CDCl3)
d
7.74
5.4.9. Methyl (2R,3R,17R)-8-methyl-2,3-dihydro-2,17-cyclo-
aureanindol-15-ene-21-oate (45)
(1H, br s, NeH), 7.44 (1H, d, J ¼ 7.0 Hz), 7.30 (1H, d, J ¼ 7.0 Hz), 7.15e
7.02 (2H, m), 2.66 (2H, br s), 1.04 (3H, s), 0.99 (6H, s), 0.98 (3H, d,
Yield: 93%; [
a
]
D
22þ11.5 (c 0.27, CHCl3); IR (film, cmꢂ1): 3366,
J ¼ 8.8 Hz); 13C NMR (50 MHz, CDCl3)
d 137.1, 136.8, 136.4, 131.7,
128.2, 121.1, 119.3, 118.1, 110.6, 108.8, 39.3, 38.6, 38.1, 36.4, 34.9, 34.1,
2924, 2872, 1719, 1449, 1232, 733; 1H NMR (200 MHz, CDCl3)
d
6.95
(1H, d, J ¼ 7.0 Hz), 6.87 (1H, d, J ¼ 7.4 Hz), 6.66 (1H, dd, J ¼ 7.4,
7.0 Hz), 3.81 (1H, dd, J ¼ 6.0, 4.8 Hz), 3.67 (3H, s), 3.16 (1H, dt,
J ¼ 12.0, 6.0 Hz), 2.70 (1H, m), 2.40e2.20 (2H, m), 2.15 (3H, s, MeC-8),
2.00e1.40 (8H, m), 1.80e1.71 (2H, dd, J ¼ 13.3, 5.5 Hz), 1.30 (3H, s),
1.02 (3H, s), 0.85 (3H, d, J ¼ 5.8 Hz); 13C NMR (100 MHz, CDCl3)
29.0, 27.3, 26.7, 26.0, 23.0, 21.8, 16.1; HRMS calcd for C23H30
N
(Mþ þ H) 320.2373, found 320.2391.
5.5.2. Methyl (17R)-2,17-cyclo-aureanindol-15-ene-21-oate (40)
Yield: 36%; [
a]
22-189.0 (c 0.12, CHCl3); IR (film, cmꢂ1): 3393,
D
d
177.8, 148.5, 135.1, 135.0, 132.4, 128.1, 121.0, 119.9, 118.8, 66.3, 51.7,
2932, 1699, 1450, 739; 1H NMR (400 MHz, CDCl3)
d
7.70 (1H, br s,
47.3, 41.4, 39.8, 38.8, 37.9, 33.3, 33.2, 27.0, 26.4, 23.9, 23.5, 18.3, 16.8
(MeC-8), 16.1 (C-24); HRMS calcd for C25H34NO2 (Mþ þ H) 380.2584,
found 380.2584.
NeH), 7.45 (1H, d, J ¼ 7.6 Hz), 7.30 (1H, d, J ¼ 7.6 Hz), 7.12 (1H, t,
J ¼ 7.6 Hz), 7.09 (1H, t, J ¼ 7.6 Hz), 3.57 (3H, s), 3.47 (1H, m), 2.76 (1H,
d, J ¼ 15.2 Hz), 2.67 (1H, d, J ¼ 15.2 Hz), 2.30e1.35 (9H, m), 1.33 (3H,
s), 1.03 (3H, d, J ¼ 6.8 Hz), 1.02 (3H, s); 13C NMR (100 MHz, CDCl3)
5.4.10. Methyl (2R,3R,17R)-8-bromo-2,3-dihydro-2,17-cyclo-
d 177.3, 136.2, 136.0, 135.1, 131.1, 127.9, 121.0, 119.1, 117.8, 110.4, 108.8,
aureanindol-15-ene-21-oate (46)
51.9, 46.9, 38.6, 38.1, 36.0, 35.1, 33.5, 26.8, 26.1, 25.2, 24.5, 21.7, 15.7;
Yield: 99%; [
a
]
D
22-91.2 (c 0.08, CHCl3); IR (film, cmꢂ1): 3385,
HRMS calcd for C24H30NO2 (Mþ þ H).364.2271, found 364.2256.
2924, 1717, 1452, 1234, 1103, 737; 1H NMR (200 MHz, CDCl3)
d
7.14
(1H, d, J ¼ 8.0 Hz), 6.97 (1H, d, J ¼ 6.8 Hz), 6.56 (1H, dd, J ¼ 8.0,
6.8 Hz), 3.85 (1H, t, J ¼ 5.5 Hz), 3.68 (3H, s), 3.25 (1H, dt, J ¼ 12.2,
6.0 Hz), 2.68 (1H, m), 2.30e1.30 (11H, m), 1.29 (3H, s), 1.01 (3H, s),
5.5.3. Methyl 17R-6-methyl-2,17-cyclo-aureanindol-15-ene-21-
oate (41)
Yield: 66%; [
a]
22-136.7 (c 0.90, CHCl3); IR (film, cmꢂ1): 3397,
D
0.85 (3H, d, J ¼ 5.8 Hz); 13C NMR (50 MHz, CDCl3)
d
177.9, 148.8,
2930, 1713, 1452, 1240, 1204, 733; 1H NMR (400 MHz, CDCl3)
d 7.61
137.0, 134.5, 132.8, 129.9, 122.2, 120.0, 104.1, 66.2, 52.1, 47.5, 41.3,
40.1, 39.9, 38.1, 33.4, 33.2, 27.2, 26.7, 24.0, 23.8, 18.6, 16.4; HRMS
calcd for C24H31NO2Br (Mþ þ H) 444.1533, found 444.1520.
(1H, br s, NeH), 7.24 (1H, d, J ¼ 1.6 Hz), 7.18 (1H, d, J ¼ 8.2 Hz), 6.94
(1H, dd, J ¼ 8.2, 1.6 Hz), 3.57 (3H, s), 2.74 (1H, dd, J ¼ 15.0, 1.8 Hz),
2.62 (1H, d, J ¼ 15.0 Hz), 2.44 (3H, s, MeC-6), 2.30e1.35 (9H, m), 1.33
(3H, s), 1.03 (3H, d, J ¼ 5.6 Hz), 1.01 (3H, s); 13C NMR (100 MHz,
CDCl3)
d 177.7, 136.4, 135.4, 134.8, 131.2, 128.6, 128.4, 122.6, 117.9,
5.4.11. Methyl (2R,3R,17R)-8-chloro-2,3-dihydro-2,17-cyclo-
110.4, 108.6, 52.1, 47.2, 38.8, 38.3, 36.3, 35.4, 33.8, 27.1, 26.3, 25.5,
24.7, 22.0, 21.7 (MeC-6), 16.0; HRMS calcd for C2.5H31NO2Na
(Mþ þ Na) 400.2247, found 400.2248.
aureanindol-15-ene-21-oate (47)
Yield: 99%; [
a]
22-10.7 (c 0.80, CHCl3); IR (film, cmꢂ1): 3356,
D
2924, 1726, 1611, 1458, 1236, 1105, 735; 1H NMR (200 MHz, CDCl3)
d
7.01 (1H, dd, J ¼ 7.8, 1.0 Hz), 6.95 (1H, dd, J ¼ 7.8, 1.0 Hz), 6.62 (1H,
5.5.4. Methyl 17R-6-bromo-2,17-cyclo-aureanindol-15-en-21-oate
t, J ¼ 7.8 Hz), 3.84 (1H, dd, J ¼ 6.0, 4.8 Hz), 3.68 (3H, s), 3.22 (1H, dt,
J ¼ 12.0, 6.0 Hz), 2.68 (1H, m), 2.30e1.30 (11H, m), 1.30 (3H, s), 1.01
(42)
Yield: 50%; [
a]
22-91.2 (c 0.08, CHCl3); IR (film, cmꢂ1): 3372,
D
(3H, s), 0.85 (3H, d, J ¼ 6.2 Hz); 13C NMR (50 MHz, CDCl3)
d 177.9,
2928,1719,1431,1204, 733; 1H NMR (200 MHz, CDCl3)
d
7.77 (1H, br
147.3, 137.2, 134.5, 132.8, 127.1, 121.7, 119.6, 115.6, 66.6, 52.1, 47.5,
41.3, 40.1, 39.7, 38.2, 33.4, 33.2, 27.2, 26.7, 24.0, 23.8, 18.6, 16.4;
HRMS calcd for C24H31NO2Cl (Mþ þ H) 400.2038, found 400.2030.
s, NeH), 7.56 (1H, s), 7.17 (2H, s), 3.58 (3H, s), 3.48 (1H, m), 2.66 (1H,
d, J ¼ 16.4 Hz), 2.60 (1H, d, J ¼ 16.4 Hz), 2.20e1.40 (8H, m), 1.33 (3H,
s), 1.02 (3H, d, J ¼ 7.2 Hz), 1.00 (3H, s); 13C NMR (50 MHz, CDCl3)
d
177.5, 137.7, 135.1, 134.9, 131.7, 130.0, 123.9, 120.8, 112.8, 112.6,
5.4.12. (2R,3R,17R)-2,3-dihydro-2,17-cyclo-aureanindol-15-ene-21-
108.9, 52.2, 47.2, 38.8, 38.3, 36.1, 35.3, 33.5, 27.0 26.3, 25.4, 24.7,
21.9, 16.0.
yl acetate (53)
Yield: 98%; [
a
]
D
22þ51.3 (c 0.52, CHCl3); IR (film, cmꢂ1): 3368,
2929, 1739, 1610, 1464, 1371, 1242, 1036, 738, 667; 1H NMR
5.5.5. Methyl 17R-6-fluoro-2,17-cyclo-aureanindol-15-ene-21-oate
(43)
(400 MHz, CDCl3)
d
7.07 (1H, d, J ¼ 7.4 Hz), 7.01 (1H, t, J ¼ 7.4 Hz),
6.70 (1H, t, J ¼ 7.4 Hz), 6.64 (1H, d, J ¼ 7.4 Hz), 4.08 (1H, d,
J ¼ 10.8 Hz), 3.99 (1H, d, J ¼ 10.8 Hz), 3.77 (1H, dd, J ¼ 6.0, 4.6 Hz),
3.11 (1H, dt, J ¼ 12.2, 6.0 Hz), 2.71e2.64 (1H, m), 2.03 (3H, s), 2.15e
1.18 (11H, m), 1.03 (3H, s), 1.02 (3H, s), 0.84 (3H, d, J ¼ 6.4 Hz); 13C
Yield: 59%; [
a]
D
22-110.8 (c 0.043, CHCl3); IR (film, cmꢂ1): 3379,
2931, 1699, 1450, 735; 1H NMR (200 MHz, CDCl3)
d
7.71 (1H, s, Ne
H), 7.18 (1H, dd, J ¼ 8.8, 4.4 Hz), 7.08 (1H, dd, J ¼ 9.4, 2.6 Hz), 6.84
(1H, dt, J ¼ 9.2, 2.6 Hz), 3.58 (3H, s), 2.73 (1H, dd, J ¼ 15.0, 1.8 Hz),
2.60 (1H, d, J ¼ 15.0 Hz), 2.30e1.35 (9H, m), 1.33 (3H, s), 1.03 (3H, d,
NMR (50 MHz, CDCl3)
d 171.4, 149.9, 135.7, 135.3, 133.3, 127.1, 123.1,
118.7, 110.0, 70.0, 66.6, 41.8, 40.2, 38.5 (x2), 38.0, 33.6, 31.7, 27.0,
J ¼ 6.2 Hz), 1.01 (3H, s); 13C NMR (50 MHz, CDCl3)
d 177.5, 158.9 (d,
25.7, 23.5, 23.0, 21.0 (eOOCMe), 18.1, 16.2; HRMS calcd for
J ¼ 140.0 Hz, C-6), 144.9, 138.3, 135.0, 132.9, 128.6 (d, J ¼ 5.0 Hz, C-4)
C
25H34NO2 (Mþ þ H) 380.2584, found 380.2574.
125.2, 111.1 (d, J ¼ 10.0 Hz, C-7), 109.1 (d, J ¼ 30.0 Hz, C-8), 103.3 (d,

276
I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
J ¼ 15.0 Hz, C-5), 52.2, 46.9, 38.8, 38.3, 36.2, 35.3, 33.8, 27.0, 26.3,
25.5, 24.7, 22.0, 16.0; HRMS calcd for C24H28NO2FNa (Mþ þ Na)
404.1996, found 404.1978.
20.8, 15.9; HRMS calcd for C25H31NO2Na (Mþ þ Na) 400.2247, found
400.2260.
5.5.11. 21-acetoxy-2,17-cyclo-aureanindol-14,16-diene-18-one (55)
5.5.6. Methyl 17R-6-methoxy-2,17-cyclo-aureanindol-15-ene-21-
Yield: 5%; [
299, 280, 195; IR (film, cmꢂ1): 3398, 2958, 2927, 1735, 1655, 1459,
1384, 1271, 1122, 1074, 1042; 1H NMR (400 MHz, CDCl3)
7.51 (1H,
a
]
22-180.0 (c 0.03, CHCl3); UVl
(nm): 434, 343,
D
max
oate (44)
Yield 79%; [
a
]
D
22-105.5 (c 0.10, CHCl3); IR (film, cmꢂ1): 3393,
d
2936, 1726, 1711, 1458, 1217; 1H NMR (200 MHz, CDCl3)
d
7.59 (1H,
d, J ¼ 7.2 Hz), 7.38 (1H, d, J ¼ 7.2 Hz), 7.16 (1H, t, J ¼ 7.2 Hz), 7.12 (1H,
t, J ¼ 7.2 Hz), 6.21 (1H, dd, J ¼ 6.4, 3.2 Hz), 4.23 (1H, d, J ¼ 11.2 Hz),
4.01 (1H, d, J ¼ 11.2 Hz), 3.08 (1H, d, J ¼ 16.0 Hz), 2.76 (1H, d,
J ¼ 16.0 Hz), 2.76 (1H, d, J ¼ 16.0 Hz), 2.50 (1H, d, J ¼ 16.0 Hz), 2.02
(3H, s), 1.16 (3H, s), 1.10 (3H, d, J ¼ 6.8 Hz), 1.04 (3H, s); 13C NMR
br s, NeH), 7.19 (1H, d, J ¼ 8.8 Hz), 6.92 (1H, d, J ¼ 2.6 Hz), 6.77 (1H,
dd, J ¼ 8.8, 2.6 Hz), 3.85 (3H, s, MeOe), 3.57 (H, s, eCOOMe), 2.74
(1H, d, J ¼ 14.2 Hz), 2.60 (1H, d, J ¼ 14.2 Hz), 2.30e1.35 (9H, m), 1.33
(3H, s),1.03 (3H, d, J ¼ 6.6 Hz),1.02 (3H, s); 13C NMR (50 MHz, CDCl3)
d
177.6, 154.1, 137.3, 135.3, 131.6, 131.3, 128.5, 111.3, 110.9, 109.0,
(100 MHz, CDCl3) d 198.1, 182.8, 170.1, 152.7, 136.8, 135.9, 132.1,
100.6, 56.2 (MeOe), 52.2 (eCOOMe), 47.2, 38.9, 38.3, 36.3, 35.4,
33.9, 27.0, 26.3, 25.5, 24.7, 22.0, 16.0; HRMS calcd for C25H32NO3
(Mþ þ H) 394.2377, found 394.2377.
129.3, 126.3, 121.9, 120.0, 118.2, 111.4, 108.9, 70.6, 46.8, 40.1, 40.1,
37.9, 32.5, 32.3, 24.1, 20.7 (eCOOMe), 15.3, 14.9, HRMS calcd for
C
25H27NO3Na (Mþ þ Na) 412.1883, found 412.1901.
5.5.7. Methyl 17R-8-methyl-2,17-cyclo-aureanindol-15-ene-21-
5.6. 14,15-dinor-ent-halim-1(10)-ene-13,16-diol (2)
oate (48)
Yield: 85%; [
a
]
D
22-125.6 (c 0.09, CHCl3); IR (film, cmꢂ1): 3393,
To an ice-cooled solution of 1 (630 mg, 2.27 mmol) in EtOH
(22 mL), NaBH4 (145 mg, 3.85 mmol) was added and it was stirred
for 1 h 30 min at r.t. The solvent vas removed and H2O and 2 M HCl
were added. It was then extracted with EtOAc, washed with brine
and dried over anhydrous Na2SO4. After filtering and evaporating
2965, 2934, 1699, 1452, 1202; 1H NMR (400 MHz, CDCl3)
d
7.58 (1H,
s, NeH), 7.30 (1H, d, J ¼ 7.4 Hz), 7.00 (1H, t, J ¼ 7.4 Hz), 6.92 (1H, d,
J ¼ 7.4 Hz), 3.57 (3H, s), 3.40 (1H, m), 2.77 (1H, dd, J ¼ 15.5, 2.2 Hz),
2.65 (1H, d, J ¼ 15.5 Hz), 2.47 (3H, s, MeC-8), 2.30e1.35 (9H, m), 1.34
(3H, s), 1.03 (3H, d, J ¼ 6.9 Hz), 1.02 (3H, s); 13C NMR (100 MHz,
the solvent compound 2 was obtained. Yield 97%; IR (film, cmꢂ1
)
CDCl3)
d
177.3, 135.7, 135.6, 135.2, 131.0, 127.4, 121.7, 119.5, 119.3,
3373, 3043, 2929, 2871,1456,1379,1065; 1H NMR (200 MHz, CDCl3)
5.27 (1H, t, J ¼ 3.4 Hz), 3.57 (2H, m), 3.41e3.30 (1H, m), 2.10e1.00
115.6, 109.4, 51.9, 46.9, 38.6, 38.1, 36.1, 35.1, 33.5, 26.8, 26.2, 25.2,
24.5, 21.7, 16.6 (MeC-8), 15.7; HRMS calcd for C25H32NO2 (Mþ þ H)
378.2428, found 378.2435.
d
(16H, m), 0.85 (3H, s), 0.83 (3H, s), 0.80 (3H, s), 0.78 (3H, d,
J ¼ 7.6 Hz); 13C NMR (50 MHz, CDCl3):
d 141.7, 120.0, 73.4, 67.1, 43.6,
43.0, 39.2, 35.0, 33.6, 31.6, 29.3, 28.4, 27.9, 26.2, 23.8, 23.3, 22.6,
15.9; HRMS calcd for C18H32O2Na (Mþ þ Na) 303.2295, found
303.2298.
5.5.8. Methyl 17R-8-bromo-2,17-cyclo-aureanindol-15-ene-21-oate
(49)
Yield: 46%; [
a]
22-163.3 (c 0.06, CHCl3); IR (film, cmꢂ1): 3356,
D
2928,1719,1452,1196, 733; 1H NMR (200 MHz, CDCl3)
d
7.83 (1H, br
5.7. 14,15,16-trinor-ent-halim-1(10)-en-13-al (3)
s, NeH), 7.38 (1H, d, J ¼ 8.2 Hz), 7.25 (1H, d, J ¼ 6.6 Hz), 6.95 (1H, dd,
J ¼ 8.2, 6.6 Hz), 3.58 (3H, s), 2.75 (1H, d, J ¼ 14.4 Hz), 2.63 (1H, d,
J ¼ 14.4 Hz), 2.30e1.35 (9H, m), 1.34 (3H, s), 1.03 (3H, d, J ¼ 6.6 Hz),
To a mixture of 2 (648 mg, 2.31 mmol) in C6H6 (21 mL), Pb(AcO)4
(2.55 g, 5.76 mmol) was added and the resultant mixture was
stirred at r.t. for 20 min. The bulk reaction was then filtered through
a pad of celite, using EtOAc as solvent. The organic layer was
washed with 6% NaHCO3 and brine, dried over anhydrous Na2SO4
1.01 (3H, s); 13C NMR (50 MHz, CDCl3)
d 177.5, 137.1, 134.9, 134.8,
131.8, 129.4, 123.5, 120.5, 117.3, 110.4, 104.5, 52.2, 47.2, 41.6, 38.8,
36.4, 35.3, 33.8, 27.0, 26.3, 25.4, 24.7, 21.9, 16.0; HRMS calcd for
C
24H28NO2BrNa (Mþ þ Na) 442.1376, found 442.1363.
and filtered to afford 3. Yield 95%; [
a
]
D
22þ73.5 (c 2.1, CHCl3); IR (film,
cmꢂ1): 2926, 2872, 2703, 1726, 1465, 1380; 1H NMR (200 MHz,
5.5.9. Methyl 17R-8-chloro-2,17-cyclo-aureanindol-15-ene-21-oate
CDCl3) d 9.69 (1H, br s, eCHO), 5.30 (1H, br s), 2.30e1.00 (14H, m),
(50)
0.83 (3H, s), 0.81 (3H, s), 0.78 (3H, d, J ¼ 7.0 Hz), 0.77 (3H, s); 13C
Yield: 47%; [
a]
22-186.0 (c 0.08, CHCl3); IR (film, cmꢂ1): 3356,
NMR (50 MHz, CDCl3) d 203.4, 141.0, 121.0, 43.5, 42.7, 39.8, 39.3,
33.6, 31.6, 30.7, 29.2, 28.4, 25.9, 23.6, 23.3, 22.6, 16.0.
D
2931, 1719, 1452, 1198, 733; 1H NMR (200 MHz, CDCl3)
d
7.89 (1H, br
s, NeH), 7.34 (1H, d, J ¼ 7.4 Hz), 7.12 (1H, d, J ¼ 7.4), 7.00 (1H, t,
J ¼ 7.4 Hz), 3.58 (3H, s), 2.76 (1H, dd, J ¼ 15.4, 2.2 Hz), 2.64 (1H, d,
J ¼ 15.4 Hz), 2.30e1.35 (9H, m), 1.34 (3H, s), 1.03 (3H, d, J ¼ 6.4 Hz),
5.8. Methyl 6-chloro-2-formyl-aureanindol-16-ene-21-oate (27)
1.01 (3H, s); 13C NMR (50 MHz, CDCl3)
d
177.5, 137.1, 134.9, 133.6,
To a solution of 17 (212 mg, 0.515 mmol) in C6H6 (2.9 mL),
Na2CrO4 (94 mg, 0.572 mmol), fused AcONa (85.5 mg, 1.03 mmol),
Ac2O (1.16 mL, 12.9 mmol) and AcOH (0.53 mL, 10.3 mmol) were
added and the mixture was heated up to 55 ꢀC for 30 min. It was
quenched with crushed ice and extracted with EtOAc. The organic
phase was washed with 6% NaHCO3, H2O and brine, it was dried
over anhydrous Na2SO4 and filtered and the solvent was removed.
The crude was purified by column chromatography (Hex/EtOAc
98:2) to afford 27. Yield: 30%; IR (film, cmꢂ1): 3314, 2951, 2872,
1724, 1647, 1450, 1381, 1246, 1113, 739; 1H NMR (400 MHz, CDCl3)
131.7, 129.7, 120.6, 120.1, 116.7, 116.2, 110.3, 52.2, 47.2, 39.0, 38.8,
36.3, 35.3, 33.8, 27.0, 26.3, 25.4, 24.7, 21.9, 16.0; HRMS calcd for
C
24H28NO2ClNa (Mþ þ Na) 420.1701, found 420.1694.
5.5.10. 17R-2,17-cyclo-aureanindol-15-ene-21-yl acetate (54)
Yield: 27%; [
22-183.0 (c 0.03, CHCl3); IR (film, cmꢂ1): 3388,
2925, 1720, 1461, 1384, 1241, 1094, 1034, 738; 1H NMR (400 MHz,
CDCl3)
a]
D
d
7.72 (1H, br s, NeH), 7.44 (1H, d, J ¼ 7.6 Hz), 7.28 (1H, d,
J ¼ 7.5 Hz), 7.15e7.05 (2H, m), 4.05 (1H, d, J ¼ 11.0 Hz), 3.88 (1H, d,
J ¼ 11.0 Hz), 2.95 (1H, d, J ¼ 15.6 Hz), 2.73 (1H, d, J ¼ 15.2 Hz), 2.65
(1H, d, J ¼ 15.6 Hz), 2.60 (1H, d, J ¼ 15.2 Hz), 2.49 (1H, d, J ¼ 15.2 Hz),
2.41 (1H, d, J ¼ 15.2 Hz), 1.93 (3H, s), 1.07 (3H, s), 1.03 (3H, d,
d
9.70 (1H, s, eCHO), 9.18 (1H, br s, NeH), 7.68 (1H, s), 7.31 (1H, d,
J ¼ 8.8 Hz), 7.28 (1H, dd, J ¼ 8.8, 1.7 Hz), 5.06 (1H, br s), 3.75 (3H, s),
3.42 (1H, d, J ¼ 14.1 Hz), 3.03 (1H, d, J ¼ 14.1 Hz), 3.02 (1H, m), 2.10e
1.20 (9H, m), 1.17 (3H, s), 0.90 (3H, d, J ¼ 6.9 Hz), 0.71 (3H, s); 13C
J ¼ 6.9 Hz), 0.99 (3H, s); 13C NMR (100 MHz, CDCl3)
d 171.0, 136.4,
136.2, 135.9, 132.1, 127.8, 120.4, 119.1, 117.8, 110.4, 108.4, 69.1, 39.0,
NMR (50 MHz, CDCl3) d 181.8 (eCHO), 178.7, 138.9, 135.4, 134.4,
38.7, 38.0, 36.0, 33.6, 33.0, 27.0, 25.4, 24.4, 23.8, 21.0 (eCOOMe),
130.2, 127.5, 126.0, 125.8, 122.0, 121.5, 113.3, 51.9, 45.2, 44.1, 40.0,

I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
277
38.5, 33.9, 31.7, 27.8, 23.2, 22.4, 22.0, 17.7, 16.5; HRMS calcd for
C
Ph), 137.0, 134.9, 131.7, [128.8, 128.5, 128.3 and 127.9 (ePh)], 124.6,
120.5, 120.5, 119.0, 112.3, 111.1, 62.7 (Ph2CHe), 45.3, 45.0, 39.7, 38.8,
35.2, 32.0, 28.3, 23.6, 22.6, 22.3, 17.6, 16.7, 13.2 (MeC-2); HRMS calcd
for C37H40NO2NaCl (Mþ þ Na) 588.2940, found 588.2645.
25H30NO3ClNa (Mþ þ Na) 450.1806; found 450.1800.
5.9. Methyl 2-(2-nitro-vinyl)-aureanindol-16-ene-21-oate (28)
To a solution of aldehyde 27 (16 mg, 0.041 mmol) in nitro-
methane (0.5 mL), excess of NH4OAc was added and the mixture
was heated up to 100 ꢀC for 3 h. It was cooled down to r.t., diluted
H2O and extracted with EtOAc. The organic layer was washed with
brine, dried over anhydrous Na2SO4. After filtering and removing of
5.12. Aureanindol-16-ene-21-ol (51)
To an ice-cooled solution of 6 (316 mg, 0.87 mmol) in Et2O
(9 mL), LAH (33 mg, 0.87 mmol) was added, and the mixture was
stirred at r.t for 45 min. It was cooled down again to 0 ꢀC and the
excess of LAH was quenched by slow addition of wet Et2O. It was
dried over anhydrous Na2SO4 and filtered. Removal of the solvent
the solvent, 28 was obtained. Yield: 66%; [
IR (film, cmꢂ1): 3356, 2651, 2926, 1719, 1701, 1609, 1448, 1317, 966,
739; 1H NMR (400 MHz, CDCl3)
8.53 (1H, br s, NeH), 8.00 (1H, d,
a]
22-13.8 (c 0.04, CHCl3);
D
d
afforded 51. Yield: 97%; [
3415, 3052, 2925, 1457, 1378, 1040, 908, 737, 665; 1H NMR
(200 MHz, CDCl3)
a]
22-4.7 (c 0.94, CHCl3); IR (film, cmꢂ1):
D
J ¼ 13.4 Hz), 7.59 (1H, d, J ¼ 7.8 Hz), 7.51 (1H, d, J ¼ 13.4 Hz), 7.31
(2H, m), 7.09 (1H, t, J ¼ 7.8 Hz), 5.16 (1H, br s), 3.77 (3H, s), 3.10 (1H,
d, J ¼ 14.2 Hz), 3.07 (1H, m), 3.03 (1H, d, J ¼ 14.2 Hz), 2.10e1.20 (9H,
m), 1.18 (3H, s), 0.82 (3H, d, J ¼ 6.9 Hz), 0.74 (3H, s); 13C NMR
d
7.99 (1H, br s, NeH), 7.61 (1H, dd, J ¼ 6.8,1.6 Hz),
7.33 (1H, dd, J ¼ 6.8, 1.6 Hz), 7.15 (1H, dt, J ¼ 6.8, 1.6 Hz), 7.06 (1H, dt,
J ¼ 6.8,1.6 Hz), 6.95 (1H, d, J ¼ 2.2), 5.27 (1H, dd, J ¼ 4.0, 3.0 Hz), 3.47
(1H, d, J ¼ 10.8 Hz), 3.31 (1H, d, J ¼ 10.8 Hz), 3.17 (1H, d, J ¼ 14.6 Hz),
2.86 (1H, d, J ¼ 14.6 Hz), 2.36e1.02 (10H, m), 0.93 (3H, s), 0.86 (3H,
(50 MHz, CDCl3) d 179.3,140.5,138.6,132.9,130.1,128.4,128.0,127.6,
126.8, 122.1, 121.1, 120.6, 111.5, 53.3, 45.6, 44.5, 39.1, 39.0, 35.1, 31.7,
28.5, 23.9, 22.8, 22.4, 18.3, 16.5; HRMS calcd for C26H32N2O4Na
(Mþ þ Na) 459.2254, found 459.2271.
s), 0.84 (3H, d, J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3)
d 142.0, 135.8,
129.4, 123.1, 121.5, 120.5, 119.6, 119.2, 113.5, 111.1, 70.1, 44.9, 38.4,
37.5, 36.9, 34.9, 29.6, 29.5, 23.9, 23.2, 22.7, 20.3, 16.2; HRMS calcd
for C23H31NONa (Mþ þ Na) 360.2298, found 360.2296.
5.10. Methyl 6-chloro-N-diphenylmethyl-2-methyl-aureanindol-
16-ene-21-oate (29)
5.13. Aureanindol-16-en-21-yl acetate (52)
A solution of 20 (80 mg, 0.194 mmol) in DMF (0.7 mL) was
added, under Ar atmosphere, over an ice-cooled mixture of NaH
(60% in mineral oil, 16 mg, 0.41 mmol) in DMF (0.1 mL) and the
resulting mixture was stirred for 30 min. After that time, a solution
of bromodiphenylmethane (109 mg, 0.44 mmol) in DMF (0.5 mL)
was added, and the mixture was stirred at r.t. for 1 h 15 min. It was
cooled down again to 0 ꢀC and quenched by carefully addition of
H2O. It was extracted with Et2O and the organic layer was washed
with H2O, dried over anhydrous Na2SO4, filtered and the solvent
was removed. The residue was purified by column chromatography
(Hex/EtOAc 99:1) to yield 29. Starting material was also recovered.
To a solution of 51 (890 mg, 2.64 mmol) in pyridine (3.3 mL)
Ac2O (3.3 mL) was added and the mixture was stirred at r.t for 1 h
and 30 min. It was then quenched with crushed ice and extracted
with EtOAc. The organic layer was washed with 2 M HCl, 6%
NaHCO3, H2O and brine, dried over anhydrous Na2SO4, filtered and
the solvent was removed. It was purified by column chromatog-
raphy (Hex/EtOAc 9/1) to yield 11. Yield: 95%; [
a
]
22: ꢂ15.2 (c 0.97,
D
CHCl3); IR (film, cmꢂ1): 3409, 3052, 2926, 1740, 1458, 1376, 1242,
1035, 739, 666; 1H NMR (200 MHz, CDCl3)
d 8.10 (1H, br s, NeH),
7.59 (1H, dd, J ¼ 7.0, 1.6 Hz), 7.30 (1H, dd, J ¼ 7.0, 1.6 Hz), 7.14 (1H, dt,
J ¼ 7.0, 1.6 Hz), 7.08 (1H, dt, J ¼ 7.0, 1.6 Hz), 6.89 (1H, d, J ¼ 2.2), 5.29
(1H, dd, J ¼ 3.8, 2.6 Hz), 3.93 (1H, d, J ¼ 10.6 Hz), 3.78 (1H, d,
J ¼ 10.6 Hz), 3.12 (1H, d, J ¼ 14.8 Hz), 2.89 (1H, d, J ¼ 14.8 Hz), 1.97
(3H, s), 2.33e1.01 (10H, m), 0.92 (3H, s), 0.89 (3H, s), 0.82 (3H, d,
Yield: 38%; [
a]
22-42.4 (c 0.82, CHCl3); IR (film, cmꢂ1): 2949, 2872,
D
1719, 1449, 1248, 1111, 908, 733, 698; 1H NMR (200 MHz, CDCl3)
d
7.47 (1H, d, J ¼ 2.0 Hz), 7.31 (6H, m, ePh), (4H, m, ePh), 6.89 (1H, s,
Ph2CHe), 6.76 (1H, dd, J ¼ 8.8, 2.0 Hz), 6.51 (1H, d, J ¼ 8.8 Hz), 5.10
(1H, br s), 3.71 (3H, s), 3.09 (1H, d, J ¼ 14.6 Hz), 2.77 (1H, d,
J ¼ 14.6 Hz), 2.17 (3H, s, MeC-2), 2.00e1.20 (10H, m), 0.84 (3H, d,
J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3)
d 171.8, 141.8, 135.9, 129.4,
122.9, 121.6, 120.4, 119.5, 119.2, 113.4, 111.1, 71.3, 44.8, 38.4, 38.1,
35.4, 34.9, 29.6, 29.2, 23.7, 23.2, 22.6, 21.1 (eOOCMe), 20.7, 16.1;
HRMS calcd for C25H33NO2Na (Mþ þ Na) 402.2404, found 402.2403.
J ¼ 6.6 Hz), 0.81 (3H, s); 13C NMR (50 MHz, CDCl3)
d 179.2, 140.7,
139.4 and 139.3 (ePh), 137.0, 134.9, 131.7, [128.8, 128.5, 128.4 and
128.0 (ePh)], 124.6, 120.5, 120.4, 119.0, 112.3, 111.2, 62.7 (Ph2CHe),
52.1, 45.5, 44.9, 39.8, 39.1, 35.3, 32.0, 28.4, 23.6, 22.7, 22.3, 17.7, 16.7,
13.2 (MeC-2); HRMS calcd for C38H42NO2NaCl (Mþ þ Na) 602.2796,
found 602.2798.
5.14. Biology
All starting materials were commercially available research-
grade chemicals and used without further purification. RPMI
1640 medium was purchased from Flow Laboratories (Irvine, UK),
foetal calf serum (FCS) was from Gibco (Grand Island, NY), tri-
chloroacetic acid (TCA) and glutamine were from Merck (Darm-
stadt, Germany), penicillin G, streptomycin, DMSO and
sulforhodamine B (SRB) were from Sigma (St Louis, MO), and
Mueller Hinton broth was from Becton Dickinson (USA).
5.11. 6-chloro-N-diphenylmethyl-2-methyl-aureanindol-16-ene-
21-oic acid (30)
t
A solution of 29 (30 mg, 0.052 mmol) in BuOK/tBuOH (1.0 M,
2 mL) was heated up to 90 ꢀC for 16 h. It was let to cool down to r.t
and 3 M HCl was added (pH ¼ 1). A solution of 3 M NaOH was added
drop wise to pH ¼ 7. It was extracted with EtOAc and the organic
layer was washed with brine, dried over anhydrous Na2SO4 and
5.14.1. Microbiology
filtered. Removal of the solvent afforded 30. Yield: 95%; [
0.37, CHCl3); IR (film, cmꢂ1): 3500e2750 (br), 2926, 2872, 1701,
1449, 908, 735, 698; 1H NMR (200 MHz, CDCl3)
7.46 (1H, d,
a
]
22-27.3 (c
The Gram-negative bacterial strains E. coli (ATCC35218), Kleb-
siella pneumonia (ATCC700603), and P. aeruginosa (ATCC27853),
and the Gram-positive E. faecalis (ATCC29212), and S. aureus
(ATCC29213) were used in this study. Bacteria were grown on
nutrient agar plates at 35e37 ꢀC. After 24 h of incubation, cells were
suspended in normal saline at a concentration of approximately
5.0 ꢃ 105 cfu mLꢂ1 by matching with 0.5 McFarlands standards.
Whole cell antimicrobial activity of compounds was determined in
D
d
J ¼ 2.0 Hz), 7.31 (6H, m, ePh), 7.07 (4H, m, ePh), 6.87 (1H, br s,
Ph2CHe), 6.75 (1H, dd, J ¼ 8.8, 2.0 Hz), 6.50 (1H, d, J ¼ 8.8 Hz), 5.10
(1H,s), 3.09 (1H, d, J ¼ 14.4 Hz), 2.77 (1H, d, J ¼ 14.4 Hz), 2.16 (3H, s,
MeC-2), 2.10e1.30 (10H, m), 1.17 (3H, s), 0.84 (3H, d, J ¼ 7.0 Hz), 0.81
(3H, s); 13C NMR (50 MHz, CDCl3)
d 184.4, 140.6, 139.4 and 139.3 (e

278
I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
[3] I.S. Marcos, N. García, M.J. Sexmero, D. Díez, P. Basabe, J.G. Urones, Synthesis of
(þ)-agelasine C. A structural revision, Tetrahedron 61 (2005) 11672e11678.
[4] I.S. Marcos, M.A. Escola, R.F. Moro, D. Díez, F. Mollinedo, J.G. Urones, Synthesis
of (þ)-thiersindole C, Synlett (2007) 2017e2033.
96-well microtiter plates by a broth microdilution procedure using
Mueller Hinton broth. Proper growth and sterile screening controls
were included. Pure compounds were initially dissolved in DMSO at
400 times the desired final maximum test concentration, that is,
[5] (a) I.S. Marcos, R.F. Moro, I. Costales, P. Basabe, D. Díez, F. Mollinedo,
J.G. Urones, Synthesis of 12-epi-ent-polyalthenol an antitumour indole
sesquiterpene alkaloid, Tetrahedron 68 (2012) 7932e7940;
100
mM. Each compound was tested in duplicates at eight different
10-fold serial dilutions ranging from 100 to 0.05
mM. The microtiter
(b) I.S. Marcos, R.F. Moro, I. Costales, P. Basabe, D. Díez, F. Mollinedo,
J.G. Urones, Biomimetic synthesis of an antitumour indole sesquiterpene
alkaloid, 12-epi-ent-pentacyclindole, Tetrahedron 69 (2013) 7285e7289.
[6] J.G. Urones, J. de Pascual Teresa, I.S. Marcos, D. Díez, P. Basabe, N.M. Garrido,
R. Alfayate, Diterpenoids from Halimium viscosum, Phytochemistry 26 (1987)
1077e1079.
[7] (a) I.S. Marcos, A.B. Pedrero, M.J. Sexmero, D. Díez, P. Basabe, F.A. Hernández,
H.B. Broughton, J.G. Urones, Synthesis and absolute configuration of the
supposed structure of cladocoran A and B, Synlett (2002) 105;
plates were incubated at 35e37 ꢀC in a moist dark chamber. After
incubation, plates were shaken and the optical density values were
recorded spectrophotometrically. Plates were read at 630 nm after
24 h of incubation. The minimum inhibitory concentration (MIC)
was established as the concentration of compound that inhibited
visible growth of the microorganism.
(b) I.S. Marcos, A.B. Pedrero, M.J. Sexmero, D. Díez, P. Basabe, N. García,
R.F. Moro, H.B. Broughton, F. Mollinedo, J.G. Urones, Synthesis of bioactive
5.14.2. Tumour cell lines
sesterterpenolides from ent-halimic acid. 15-Epi-ent-cladocoran
J. Org. Chem. 68 (2003) 7496e7504;
A and B,
The human solid tumour cell lines A549, HBL-100, HeLa,
SW1573, T-47D and WiDr were used in this study. These cell lines
were a kind gift from Prof. G. J. Peters (VU Medical Center,
Amsterdam, The Netherlands). Cells were maintained in 25 cm2
culture flasks in RPMI 1640 supplemented with 5% heat inactivated
(c) I.S. Marcos, A.B. Pedrero, M.J. Sexmero, D. Díez, N. García, M.A. Escola,
P. Basabe, A. Conde, R.F. Moro, J.G. Urones, Synthesis of ent-halimanolides
from ent-halimic acid, Synthesis (2005) 3301e3310;
(d) I.S. Marcos, M.A. Escola, R.F. Moro, P. Basabe, D. Díez, F. Sanz, F. Mollinedo,
J. de la Iglesia-Vicente, B.G. Sierra, J.G. Urones, Synthesis of novel antitumoural
analogues of dysidiolide from ent-halimic acid, Bioorg. Med. Chem. 15 (2007)
5719e5737;
foetal calf serum and 2 mM L
-glutamine in a 37 ꢀC, 5% CO2, 95%
humidified air incubator. Exponentially growing cells were trypsi-
nized and re-suspended in antibiotic containing medium (100 units
penicillin G and 0.1 mg of streptomycin per mL). Single cell sus-
pensions displaying >97% viability by trypan blue dye exclusion
were subsequently counted. After counting, dilutions were made to
give the appropriate cell densities for inoculation onto 96-well
(e) I.S. Marcos, F.A. Hernández, M.J. Sexmero, D. Díez, P. Basabe, A.B. Pedrero,
N. García, F. Sanz, J.G. Urones, Synthesis and absolute configuration of
(ꢂ)-chettaphanin II, Tetrahedron Lett. 43 (2002) 1243e1245;
(f) I.S. Marcos, F.A. Hernández, M.J. Sexmero, D. Díez, P. Basabe, A.B. Pedrero,
N. García, J.G. Urones, Synthesis and absolute configuration of (ꢂ)-chetta-
phanin I and (ꢂ)-chettaphanin II, Tetrahedron 59 (2003) 685e694;
(g) I.S. Marcos, A. Conde, R.F. Moro, P. Basabe, D. Díez, J.G. Urones, Synthesis of
quinone/hydroquinone sesquiterpenes, Tetrahedron 66 (2010) 8280e8290;
(h) I.S. Marcos, J.L. González, M.J. Sexmero, D. Díez, P. Basabe, D.J. Williams,
microtiter plates. Cells were inoculated in a volume of 100 mL per
well at densities of 10,000 (A549, HBL-100, HeLa and SW1573),
15,000 (T-47D), and 20,000 (WiDr) cells per well, based on their
doubling times.
M.S.J. Simmonds, J.G. Urones, Diterpenic
antifeedant activity: semisynthesis and absolute configuration, Tetrahedron
Lett. 41 (2000) 2553e2557;
(i) I.S. Marcos, R.F. Moro, I. Costales, M.A. Escola, P. Basabe, D. Díez, J.G. Urones,
Synthesis of hexahydrocarbazoles by cyclisation of 3-(but-3-enyl) indole de-
rivatives, Tetrahedron 65 (2009) 10235e10242.
a- and b-hydroxybutanolides with
5.14.3. Chemosensitivity testing
[8] I.S. Marcos, A.B. Pedrero, M.J. Sexmero, D. Díez, P. Basabe, F.A. Hernández,
J.G. Urones, Synthesis and absolute configuration of three natural ent-hal-
imanolides with biological activity, Tetrahedron Lett. 44 (2003) 369e372.
[9] (a) C.U. Rogers, B.B. Corson, Org. Synthesis Coll. 4 (1967) 884;
(b) B. Robinson, in: The Fischer Indole Synthesis, Wiley-Interscience, New
York, 1982;
Compounds were initially dissolved in DMSO at 400 times the
desired final maximum test concentration. Control cells were
exposed to an equivalent concentration of DMSO (0.25% v/v,
negative control). Each agent was tested in triplicate at different
dilutions in the range of 1e100
on day 1 after plating. Drug incubation times were 48 h, after which
time cells were precipitated with 25 L ice-cold TCA (50% w/v) and
mM. The drug treatment was started
(c) M.L. Trudell, N. Fukada, J.M. Cook, Hydrazine-mediated one-pot amina-
tioneoxidation reaction: facile synthesis of 4-amino-beta-carbolines and 4-
aminoisoquinolines, J. Org. Chem. 52 (1987) 4293e4296.
m
[10] (a) R. Sheng, L. Shen, Y.-Q. Chen, Y.-Z. Yu, Convenient and efficient synthesis of
1-oxo-1,2,3,4-tetrahydrocarbazoles via Fischer indole synthesis, Synth. Com-
mun. 39 (2009) 1120e1127;
(b) O.A. Luzina, M.P. Polovinka, N.F. Salakhutdinov, G.A. Tolstikov, Chemical
modification of usnic Acid: III.* Reaction of (þ)-usnic acid with substituted
phenylhydrazines, Russ. J. Org. Chem. 45 (2009) 1783e1786.
[11] (a) J.C. McKew, F. Lovering, J.D. Clark, J. Bemis, Y.-B. Xiang, M. Shen, W. Zhang,
J. Alvarez, D. Joseph-McCarthy, Structureeactivity relationships of indole
fixed for 60 min at 4 ꢀC. Then the SRB assay was performed [14]. The
optical density (OD) of each well was measured at 492 nm, using
BioTek’s PowerWave XS Absorbance Microplate Reader. Values
were corrected for background OD from wells only containing
medium.
cytosolic phospholipase
Chem. Lett. 13 (2003) 4501e4504;
A2a inhibitors: substrate mimetics, Bioorg. Med.
Acknowledgements
(b) J.C. McKew, M.A. Foley, P. Thakker, M.L. Behnke, F.E. Lovering, F.-W. Sum,
S. Tam, K. Wu, M.W.H. Shen, W. Zhang, M. Gonzalez, S. Liu, A. Mahadevan,
H. Sard, S.-P. Khor, J.D. Clark, Inhibition of cytosolic phospholipase A2a: hit to
lead optimization, J. Med. Chem. 49 (2006) 135e158;
This research was co-financed by the EU Research Potential
(FP7-REGPOT-2012-CT2012-31637-IMBRAIN),
the
European
(c) K.L. Lee, M.A. Foley, L. Chen, M.L. Behnke, M.L. Lovering, S.J. Kirincich,
W. Wang, J. Shim, M.W.H. Shen, S.-P. Khor, X. Xu, D.G. Goodwin,
M.K. Ramarao, C. Nickerson-Nutter, F. Donahue, M.S. Ku, J.D. Clark, J.C. McKew,
Regional Development Fund (FEDER), the Spanish Red Temática de
Investigación Cooperativa en Cáncer (RD06/0020/1037), the Span-
ish Instituto de Salud Carlos III (PI11/00840), and the Spanish Junta
de Castilla y León (GR-178, SA063A07, GR-15, CSI052A11-2). I.C.
acknowledges Junta de Castilla y León for a doctoral fellowship. The
authors gratefully acknowledge the help of A. Lithgow (NMR) and C.
Raposo (MS) of Universidad de Salamanca.
Discovery of ecopladib, an indole inhibitor of cytosolic phospholipase A2a
J. Med. Chem. 50 (2007) 1380e1400;
,
(d) J.C. McKew, K.L. Lee, M.W.H. Shen, P. Thakker, M.A. Foley, M.L. Behnke,
B. Hu, F.-W. Sum, S. Tam, Y. Hu, L. Chen, S.J. Kirincich, R. Michalak,
J. Thomason, M. Ipek, K. Wu, L. Wooder, M.K. Ramarao, E.A. Murphy,
D.G. Goodwin, L. Albert, X. Xu, F. Donahue, M.S. Ku, J. Keith, C.L. Nickelson-
Nutter, W.M. Abraham, C. Williams, M. Hegen, J.D. Clark, Indole cytosolic
phospholipase A2
a inhibitors: discovery and in vitro and in vivo character-
References
ization of 4-{3-[5-chloro-2-(2-{[(3,4-dichlorobenzyl)sulfonyl]amino}ethyl)-1-
(diphenylmethyl)-1H-indol-3-yl]propyl} benzoic acid, efipladib, J. Med. Chem.
51 (2008) 3388e3413;
(e) K.L. Lee, M.L. Behnke, M.A. Foley, L. Chen, W. Wang, R. Vargas, J. Nunez,
S. Tam, N. Mollova, X. Xu, M.W.H. Shen, M.K. Ramarao, D.G. Goodwin,
C.L. Nickerson-Nutter, W.M. Abraham, C. Williams, J. Clark, J.C. McKew, Ben-
zenesulfonamide indole inhibitors of cytosolic phospholipase A2a: optimiza-
tion of in vitro potency and rat pharmacokinetics for oral efficacy, Bioorg.
Med. Chem. 16 (2008) 1345e1358;
[1] M. Lebeoulf, M. Hamonnière, A. Cavé, H.E. Gottlieb, N. Kunesch, E. Wenkert,
The structure of polyalthenol, an indolosesquiterpene, Tetrahedron Lett. 17
(1976) 3559e3562.
[2] R.B. Williams, J.-F. Hu, K.M. Olson, V.L. Norman, M.G. Goering, M. O’Neil-
Johnson, G.R. Eldridge, C.M. Starks, Antibiotic indole sesquiterpene alkaloid
from Greenwayodendron suaveolens with a new natural product framework,
J. Nat. Prod. 73 (2010) 1008e1011.

I.S. Marcos et al. / European Journal of Medicinal Chemistry 73 (2014) 265e279
279
(f) L. Chen, W. Wang, K.L. Lee, M.W.S. Shen, E.A. Murphy, W. Zhang, X. Xu,
S. Tam, C. Nickerson-Nutter, D.G. Goodwin, J.D. Clark, J.C. McKew, Reactions of
functionalized sulfonamides: application to lowering the lipophilicity of
cytosolic phospholipase A2a inhibitors, J. Med. Chem. 52 (2009) 1156e1171.
[12] P.G. Gassman, W.N. Schenk, A general procedure for the base-promoted hydrolysis
of hindered esters at ambient temperatures, J. Org. Chem. 42 (1977) 918e920.
[13] S.V. Ley, J. Norman, W.P. Griffith, S.P. Marsden, Tetrapropylammonium per-
ruthenate, Pr4NþRuOꢂ4 , TPAP: a catalytic oxidant for organic synthesis, Syn-
thesis (1994) 639e666.
[14] P.O. Miranda, J.M. Padrón, J.I. Padrón, V.S. Martín, Prins-type synthesis and
SAR study of cytotoxic alkyl chloro dihydropyrans, ChemMedChem 1 (2006)
323e329.
[15] (a) L. Costantino, D. Barlocco, Privileged structures as leads in medicinal
chemistry, Curr. Med. Chem. 13 (2006) 65e85;
(b) R.W. DeSimone, K.S. Currie, S.A. Mitchell, J.W. Darrow, D.A. Pippin, Privi-
leged structures: applications in drug discovery, Comb. Chem. High
Throughput Screen. 7 (2004) 473e494.