Preparation and antimalarial activity of semisynthetic lycorenine derivatives

Article abstract of DOI:10.1016/j.ejmech.2013.03.018

A set of twenty one lycorenine derivatives has been prepared from the alkaloid hippeastrine (1). The modifications performed on hippeastrine included some functional group transformations, structural simplification and preparation of dimers. All alkaloids were tested as potential antimalarial agents, being the hippeastrine dimers the most active compounds.

Full text of DOI:10.1016/j.ejmech.2013.03.018

European Journal of Medicinal Chemistry 63 (2013) 722e730
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Preparation and antimalarial activity of semisynthetic lycorenine
derivatives
,
b
,
c
,
,b, ,1
Juan C. Cedrón a 1, David Gutiérrez d, Ninoska Flores d, Ángel G. Ravelo a
,
*
Ana Estévez-Braun a
,b, ,1
*
a Instituto Universitario de Bio-Orgánica “Antonio González”, Av. Astrofísico Francisco Sánchez 2, 38206 La Laguna, Tenerife, Spain
b Instituto Canario de Investigación del Cáncer (ICIC), Spain
c Universidad de Ingeniería & Tecnología (UTEC), Av. Cascanueces 2281, Santa Anita, Lima 43, Peru
d Instituto de Investigaciones Fármaco Bioquímicas, Facultad de Ciencias Farmacéuticas y Bioquímicas, Universidad Mayor de San Andrés, Av. Saavedra
2024, 2ꢀ piso, Miraflores, La Paz, Bolivia
a r t i c l e i n f o
a b s t r a c t
Article history:
A set of twenty one lycorenine derivatives has been prepared from the alkaloid hippeastrine (1). The
modifications performed on hippeastrine included some functional group transformations, structural
simplification and preparation of dimers. All alkaloids were tested as potential antimalarial agents, being
the hippeastrine dimers the most active compounds.
Received 14 December 2012
Received in revised form
8 March 2013
Accepted 9 March 2013
Available online 18 March 2013
Ó 2013 Elsevier Masson SAS. All rights reserved.
Keywords:
Lycorenine
Antiplasmodial activity
Amaryllidaceae alkaloids
Hippeastrine
1. Introduction
lycorine, ungeremine and haemanthamine are the most active al-
kaloids against both choloroquine-sensitive and chloroquine-
Malaria is still a main endemic disease in poorer countries,
especially in Africa, where 90% of deaths due to malaria occur [1]. In
the absence of effective antimalarial vaccines, low molecular
weight antimalarial drugs are important weapons against the dis-
ease [2]. Quinine, chloroquine, mefloquine, and artemisinin de-
rivatives have played an important role in fighting against malaria.
However, widespread drug resistance has made them less effective
with artemisinin derivatives as the only exception. Artemisinin
based combination therapies (ACT) recommended by World Health
Organization will help to delay the emergence of clinical resistance
against artemisinins, but reports of increased parasite clearance
times have emerged recently [3,4]. Therefore, it is important to
discover antimalarials with novel chemical entities that are effec-
tive against the multidrug resistant parasite strains.
resistant strains of Plasmodium falciparum [6,7]. Alkaloids from six
of the eight Amaryllidaceae alkaloids have been evaluated as anti-
malaric agents, showing that alkaloids with the lycorine-type are
the most active [8]. In previous publications our group has reported
the antimalarial activity of the haemanthamine- and lycorine-type
alkaloids [9,10]. However, to the best of our knowledge, no reports
for antimalarial activity have been published for the narciclasine-
and lycorenine-type alkaloids. Taking into account this information
and considering the large amount of hippeastrine (1) isolated during
the phytochemical study of Pancratium canariense (Amaryllidaceae)
[11], we decided to evaluate the antiplasmodial activity of a set of
semisynthetic lycorenine derivatives, and establish some structuree
activity relationships. This is the first report of the antimalarial ac-
tivity of lycorenine-type alkaloids, although other bioactivities, such
as cytotoxic [12] and antifungic [13] have been reported.
The Amaryllidaceae alkaloids, represented by a large group of
selected structures belonging to eight skeletons, exhibit a wide
range of biological activities, including antimalarial [5]. For example,
2. Results and discussion
* Corresponding authors. Instituto Universitario de Bio-Orgánica “Antonio Gon-
zález”, Av. Astrofísico Francisco Sánchez 2, 38206 La Laguna, Tenerife, Spain.
E-mail address: aestebra@ull.es (A. Estévez-Braun).
Sixteen alkaloids were isolated from the bulbs of P. canariense
[11,14]. Two of them, hippeastrine (1) (1.35 g) and pancratinine A
(2) (4.5 mg) present a lycorenine skeleton (Fig. 1).
1
http://www.icic.es.
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.03.018

J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
723
12
Cl-
Me
H 11
Br
4
H
H
H
H
O
H
H
N
Me
N
3
N
N
Me
Br
Me
4a
C
10
2OH
H
H
H
O
H
10a
9
O
O
O
O
O
O
O
O
R1
OH
OH
OH
A
H
O
O
O
6aO6
8
7
O
O
20 (25%)
18 (33%)
21 (20%)
Hippeastrine (1): R = H
Pancratinine A (2): R = OH
e
d
b
Fig. 1. Structures of lycorenine-type alkaloids isolated from Pancratium canariense.
O
Me
OH
H
N
H
N
H
H
N
Me
Me
Br
Because of the large amount of 1 isolated, several modifications
were achieved on its structure, as shown in Schemes 1e3. For the
most part, the transformations were carried out on the hydroxyl
group at C-2 or on the double bond presents in ring C. Trans-
formation of the lactone into lactam was made by using ammonium
acetate in acetic acid. Thus, compound 3 was obtained in high yield
with the same B/C cis ring fusion as 1. Compound 4 was obtained
quantitatively by acetylation of 1 with Ac2O/Py, while compounds
5e9 were prepared by acylation of 1 with several acyl chlorides of
different size, lipophilicity and stereoelectronic properties. Oxida-
tion of the hydroxyl group at C-2 of 1 to yield the cyclohexanone 10
was only achieved when the Jones reagent [15] was employed,
since the use of other oxidants, such as PCC [16], sulphur trioxide
[17] or manganese dioxide [18] was unsuccessful. Treatment of 1
with thionyl chloride yielded two products, 11 and 12, which have a
double bond at C-2eC-3 due to the corresponding elimination of
H
H
H
O
O
O
O
O
O
OH
f
OH
OH
a
H
H
O
O
O
O
O
O
1
17 (100%)
22 (17%)
g
c
OH
H
N
N
Me
Me
OH
OH
H
O
O
O
OAc
OMe
H
O
O
O
O
19 (20%)
23 (100%)
Scheme 2. Reagents and conditions: (a) 30% H2O2, MeOH, 24 h; (b) 1. HCl 12 M, MeOH,
30 min; 2. FeSO4$7H2O, MeOH, 0 ꢀC; 3. EDTA 0.1 M, 30 min; (c) Ac2O, DCM, reflux; (d)
H2, 10% Pd/C, THF; (e) Br2, DCM, 24 h; (f) CH3CONHBr, SnCl4, H2O, CH3CN, 0 ꢀC; (g)
OsO4, NMO, 24 h.
the hydroxyl group at C-2. The
b orientation for the chlorine group
of 12 was established for the value of the chemical shift of H-4a in
12 respect to that in 1, in agreement with the data published for 6-
membered ring with chorine atom and hydrogen in syn or anti
disposition [19]. With the aim of eliminate the NMe group, 1 was
reacted with ethyl chloroformiate, a useful reagent for this purpose
[20]. However, only derivative 13 was obtained, showing no
demethylation, but formation of a carbonate at C-2. Another
modification achieved at the hydroxyl group was the esterification
with p-vinylbenzoic acid, yielding 14. The methylenedioxy group of
1 was also modified. Reaction of 1 with BBr3 produced catechol
15, which reacted with trimethylsilyldiazomethane to yield
2a-hydroxyhomolycorine 16, an alkaloid isolated previously from
Leucojum vernum [21].
The nitrogen atom of 1 was also modified, as shown in Scheme
2. The N-oxide 17 was quantitatively obtained by reaction with
H
H
H
O
H
H
H
5: R=COC5H4N (100%)
N
N
N
Me
Me
Me
6: R=p-BrC6H4CO(100%)
7: R=COCH(CH3)2 (100%)
8: R=CO-C6H3-(CO2Me)2 (18%)
9: R=CO(CH2)2CH=CH2 (49%)
H
H
O
O
O
O
O
O
OH
OAc
OR
H
O
NH
O
O
O
4 (100%)
3 (95%)
a
c
b
H
N
Cl
H
N
H
N
N
H
Me
Me
Me
Me
H
H
H
O
H
O
O
O
O
O
O
O
O
OH
d
e
H
O
H
O
H
H
O
+
O
O
O
O
O
1
12 (47%)
10 (55%)
11 (43%)
f
h
g
H
N
H
H
H
N
H
H
N
Me
N
Me
Me
Me
O
H
H
H
HO
HO
MeO
MeO
O
O
O
O
j
OH
OH
OCO2Et
O
H
O
H
O
H
O
O
O
O
O
O
13 (12%)
14 (63%)
15 (55%)
16 (49%)
Scheme 1. Reagents and conditions: (a) CH3CO2NH4, CH3CO2H, reflux; (b) Ac2O, py; (c) RCl, NEt3, DCM; (d) Jones reagent, acetone; (e) SOCl2, DCM, reflux; (f) ClCO2Et, KOH(aq), DCM;
(g) p-vinylbenzoic acid, DCC, DCM; (h) BBr3, DCM; (j) Me3SiCHN2, MeOH.

724
J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
Me
N
Me
N
the D ring and the lactone ring openings occurred and the
H
H
N
Me
R
R
aromatization of the C ring was also detected. The treatment of
compounds 24 and 26 with trimethylsilyldiazomethane yielded the
methyl esters 28 and 29, respectively.
a
b
O
O
OAc
O
O
O
O
H
O
O
CO2H
CO2Me
Clivimine is the only dimeric alkaloid known isolated from
Amaryllidaceae [25]. This compound consists of two units of cli-
vonine (another lycorenine-type alkaloid) joined through 2,6-
dimethyl-pyridine-3,5-dicarboxylic acid [26]. With the aim of
preparing hippeastrine dimers, we decided to react 1 with some
aromatic diacyl dichlorides such as pyridine-2,6-dicarboxylic acid,
isophthalic acid, terephthalic acid and with the aliphatic hex-
anedioic acid. Under usual acylation conditions, four dimers 30e33
were obtained as shown in Scheme 3.
24: R=Me (73%)
25: R=Et (28%)
28 (from 24): R=Me (67%)
29 (from 26): R=C4H9 (79%)
26: R=C4H9 (29%)
27: R=C11H23 (45%)
H
H
H
N
H
N
Me
O
Me
O
O
O
c
O
R
O
H
H
O
1
O
O
O
O
O
Results of the antiplasmodial evaluation against F-32 Tanzania
(chloroquine sensitive) strains of P. falciparum are summarized in
Table 1. Only six lycorenine derivatives (8, 15, 30e33) showed
N
30 (20%) R=
32 (44%) R=
31 (43%) R=
33 (28%) R=
-(CH2)4-
antiplasmodial activity with IC50 values less than 10 mM. The dimers
30 and 32 resulted be the most active compounds being 9.8-fold
more active than the monomer (1).
Scheme 3. Reagents and conditions: (a) 1. RX, CH3CN, 24 h; 2. t-BuOK/t-BuOH, reflux,
4 h; (b) Me3SiCHN2, MeOH; (c) 0.5 equiv acyl chloride, NEt3, 24 h.
From the obtained results some structureeactivity relationships
can be outlined. The presence of a free hydroxyl group at C-2 seems
important for the activity since the acylated derivatives (4e7, 9, 10,
13 and 14) were less active than hippeastrine. The oxidation of the
hydroxyl group also led to a less active compound (1 vs. 10). Con-
cerning the modifications on the double bond at C-3eC-4 of the
ring C, derivatives 20e23 were less active than 1, indicating that
this double bond is important for the activity. A simplification of
the licorenine skeleton achieved by the formation of the biphenyls
24e29 produced a drastic loss of activity. The N-oxide derivative 17
hydrogen peroxide. Using 17 as starting material, we tried to obtain
the corresponding N-demethylated derivative. Thus, Polonovski
reaction was performed [22]. In this case, the ammonium derivative
18 was formed in 33% yield. Another reagent used for this type of
transformation is acetic anhydride. When 17 was refluxed with
Ac2O no demethylation was observed, being isolated only the
achiral compound 19 together with 2-acetylhippeastrine 4. 19
could be formed by lactone opening followed by aromatization.
Several modifications were also carried out on the double bond
C-3eC-4 of 1. Hydrogenation of 1 in the presence of 10% Pd/C
yielded 20 in low yield (25%), showing a cis union for the C and D
rings. The cis fusion was established by the value of the coupling
constant between H-4a and H-4 (J ¼ 5.8 Hz). Since the absolute
configuration of hippeastrine (1) is known [11,14], the stereo-
chemistry at C-4 was established as 4R. Bromination of the double
bond yielded the dibrominated derivative 21. Due to the small
coupling constant (J ¼ 3.3 Hz) between the axial hydrogen H-2 and
H-3, this last hydrogen must have an equatorial disposition and,
therefore, the bromine atom at C-3 is axial. According to the
mechanism for bromination of double bonds, the bromine at C-4 is
Table 1
In vitro activity of compounds 1e33 against Plasmodium
falciparum F32.
Compound
IC50 (m
M)a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
12.7 ꢁ 1.0
60.4 ꢁ 6.0
18.8 ꢁ 2.0
58.8 ꢁ 8.0
49.8 ꢁ 5.0
42.2 ꢁ 8.0
57.1 ꢁ 8.0
7.4 ꢁ 0.5
55.4 ꢁ 7.0
79.8 ꢁ 12.0
94.1 ꢁ 10.0
84.0 ꢁ 12.0
61.8 ꢁ 8.0
49.4 ꢁ 4.0
9.9 ꢁ 1.0
84.5 ꢁ 9.0
87.6 ꢁ 6.0
>100
b-axial, and the stereochemistry at C-3 and C-4 was established as
3S,4S. Haloamidation of the double bond following the procedure
described by Corey [23] yielded compound 22. In this case a bro-
mohydroxylation occurred instead of the expected bromoamida-
tion, probably because the cyclic bromonium ion intermediate was
opened by the water used instead of acetonitrile. In the 1H NMR
spectrum of compound 22, the hydrogen H-3 appeared as a singlet
17
18
at
d
4.80, indicating an almost null coupling with the axial hydrogen
-axial,
19
20
21
22
23
24
25
26
70.4 ꢁ 5.0
78.8 ꢁ 6.0
58.7 ꢁ 8.0
58.3 ꢁ 4.0
68.7 ꢁ 8.0
67.5 ꢁ 6.0
86.1 ꢁ 9.0
>100
H-2. Therefore, H-3 is equatorial and the bromine at C-3 is
a
and in agreement with the established mechanism of this reaction,
the hydroxyl at C-4 presents an anti orientation with respect to the
bromine. Thus, the absolute stereochemistry at C-3, C-4 was
determined as 3R, 4R. Treatment of 1 with osmium tetraoxide
produced quantitatively the cis-diol 23. The orientation of the hy-
droxyl groups was determined as
b on the basis of the large value
27
>100
for the coupling constant of H-3 (J ¼ 10.3 Hz), indicating a trans
disposition with H-2, and consequently the absolute stereochem-
istry 3S,4R.
28
29
30
31
32
33
67.6 ꢁ 6.0
76.2 ꢁ 8.0
1.3 ꢁ 0.1
3.9 ꢁ 0.9
1.3 ꢁ 0.1
4.0 ꢁ 1.0
0.03
Hofmann elimination [24] was performed on compound 4 in
order to achieve
a structural simplification. Thus, when 2-
Chloroquine
acetylhippeastrine was refluxed with different alkyl halides and
then treated with t-BuOK/t-BuOH the corresponding biphenyl de-
rivatives 24e27 were obtained. Under these reaction conditions,
a
Data are expressed as mean standard deviation of
three determinations.

J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
725
was inactive, indicating the importance of the unshared electron
pair on the nitrogen of hippeastrine. On the other hand, the
replacement of the methylenedioxy moiety by hydroxyl groups
(compound 15) produced a slight improvement in the anti-
plasmodial activity.
OCH2O), 5.73 (1H, s, H-3), 4.60 (1H, s, H-1), 4.34 (1H, s, H-2), 3.35
(1H, m, H-10b), 3.23 (1H, d, J ¼ 9.6 Hz, H-12), 2.86 (1H, d, J ¼ 9.5 Hz,
H-4a), 2.58 (2H, br s, H-11), 2.40 (1H, dd, J ¼ 9.7 Hz, J ¼ 18.4 Hz,
H-12), 2.00 (3H, s, NMe) 13C NMR (CDCl3)
d 164.3 (s, C-6), 151.7 (s,
C-9),147.8 (s, C-8),142.4 (s, C-4),138.4 (s, C-10a),119.3 (d, C-3),118.2
(s, C-6a), 109.7 (d, C-7), 108.5 (d, C-10), 101.9 (t, OCH2O), 81.6 (d, C-
1), 67.1 (d, C-2), 66.2 (d, C-4a), 55.4 (t, C-12), 42.6 (q, NMe), 37.6 (d,
C-10b), 27.2 (t, C-11). IR (neat, cmꢂ1): 3438, 1645, 1481, 1387, 1290,
1252, 1121, 1034, 936. HRMS m/z 314.1273 (calcd for C17H18N2O4
[M]þ 314.1267).
3. Conclusion
A set of 21 lycorenine derivatives has been prepared through
selective transformations. The modifications performed on the
structure of hippeastrine (1) indicate that only the elimination of
the methylenedioxy group produces a slight increase of the activity.
However, when different dimers of hippeastrine were evaluated,
the activity increased 10-fold compared to the single alkaloid. The
fact that dimers are significantly more potent than monomers may
suggest improved binding to their specific target than the mono-
mers or a possible hydrolysis of the dimer, giving place to two
molecules of 1 during the biological evaluation. Our results repre-
sent a starting point for preparing new lycorenine-type derivatives
with improved antiplasmodial activity.
4.3.2. 2-Acetylhippeastrine (4)
To 14 mg (0.044 mmol) of 1 in 1 mL of pyridine, 0.3 mL
(3.18 mmol) of acetic anhydride was added. After 3 h of stirring, the
solvent was evaporated and the residue was purified by preparative
TLC with DCM:MeOH 19:1, yielding 16 mg (100%) of 4 as an
20
amorphous white solid. [
d
a
]
D
¼ þ87.9 (c 1.4, EtOH). 1H NMR (CDCl3)
7.46 (1H, s, H-7), 6.97 (1H, s, H-10), 6.06 (2H, s, OCH2O), 5.59 (1H,
s, H-3), 5.42 (1H, s, H-2), 4.57 (1H, s, H-1), 3.16 (1H, m, H-12), 2.82
(1H, d, J ¼ 9.6 Hz, H-10b), 2.70 (1H, d, J ¼ 9.4 Hz, H-4a), 2.54 (2H, br
s, H-11), 2.27 (1H, dd, J ¼ 9.2 Hz, J ¼ 18.1 Hz, H-12), 2.06 (3H, s,
4. Experimental
OCOCH3), 2.04 (3H, s, NMe). 13C NMR (CDCl3)
d 169.4 (s, OCOCH3),
163.8 (s, C-6), 151.7 (s, C-9), 147.8 (s, C-8), 147.7 (s, C-4), 138.5 (s,
C-10a), 118.2 (s, C-6a), 114.6 (d, C-3), 109.6 (d, C-7), 108.5 (d, C-10),
101.9 (t, OCH2O), 79.2 (d, C-1), 68.5 (d, C-2), 66.5 (d, C-4a), 55.9 (t,
C-12), 43.3 (q, NMe), 40.7 (d, C-10b), 27.8 (t, C-11), 20.7 (c, OCOCH3).
IR (neat, cmꢂ1): 2926, 2852, 2791, 1728, 1616, 1503, 1481, 1450,
1383, 1292, 1226, 1121, 1031, 939, 755, 655. HRMS m/z 358.1282
(calcd for C19H20NO6 [M þ 1]þ 358.1291).
4.1. General
IR spectra were obtained using a Bruker IFS28/55 spectropho-
tometer. Optical rotations were measured with a PerkineElmer 241
automatic polarimeter. 1H and 13C NMR spectra were recorded,
unless any other indication, in CDCl3 or MeOD at 300 and 75 MHz
respectively. 2D NMR experiments were conducted on a Bruker
WP-400 SY NMR spectrometer at 400 MHz. High- and low-
resolution mass spectra were obtained on a VG Autospec spec-
trometer. Analtech Silica Gel GF preparative layer with UV254 was
used for TLC. Silica gel (0.2e0.63 mm) was employed for column
chromatography. Silica gel 60 (Merck) was used on a Harrison
Research 7924T Chromatotron.
4.3.3. General procedure for acylation of 1
To a solution of haemanthamine 1 in 5 mL of dry DCM were
added NEt3 and the corresponding acyl chloride. After 12 h of
stirring at rt, the solvent was evaporated and the residue was pu-
rified by preparative TLC using DCM:MeOH 9:1 as eluent, yielding
the corresponding esters 5e9.
4.2. Biological assays
4.3.4. 2-Nicotylhippeastrine (5)
Following the procedure described above, 19.5 mg (0.062 mmol)
F-32 Tanzania (chloroquine sensitive) strains of P. falciparum
were cultured according to Trager and Jensen [27] on glucose-
enriched RPMI 1640 medium, supplemented with 10% human
serum at 37 ꢀC. After 24 h of incubation at 37 ꢀC, the medium was
replaced by fresh medium supplemented with the compound to be
evaluated in DMSO at three different concentrations (0.1, 1 and
of 1 was treated with 22 mL (2.5 equiv) of NEt3 and 17 mg (1.5 equiv)
of nicotyl chloride. After purification, 26 mg (100%) of 5 was ob-
20
tained as an amorphous white solid. [
a
]
¼ þ131.6 (c 1.6, EtOH). 1H
D
NMR (CDCl3)
d
9.18 (1H, s, CCHN), 8.78 (1H, dd, J ¼ 1.5 Hz, J ¼ 4.8 Hz,
NCHCHCHC), 8.27 (1H, d, J ¼ 6.1 Hz, NCHCHCHC), 7.48 (1H, s, H-7),
7.39 (1H, dd, J ¼ 4.8 Hz, J ¼ 7.7 Hz, NCHCHCHC), 6.97 (1H, s, H-10),
6.07 (1H, br s, OCH2O), 6.05 (1H, br s, OCH2O), 5.71 (2H, s, H-2, H-3),
4.73 (1H, s, H-1), 3.18 (1H, m, H-12), 2.91 (1H, d, J ¼ 10.2 Hz, H-10b),
2.75 (1H, d, J ¼ 9.3 Hz, H-4a), 2.57 (2H, m, H-11), 2.30 (1H, dd,
J ¼ 9.2 Hz, J ¼ 18.5 Hz, H-12), 2.09 (3H, s, NMe). 13C NMR (CDCl3)
10 mg/mL) and incubation was continued for further 48 h. On the
third day of the test, a blood smear was taken from each well and
parasitaemia was calculated for each concentration of sample
compared to the control. IC50 values were determined graphically
by plotting concentrations vs. percent inhibition. Chloroquine
d
163.8 (s, C-6), 163.7 (s, C]O), 153.4 (d, CCHN), 151.7 (s, C-9), 150.7
(0.03
in triplicate.
m
M) was used as a positive control. All tests were performed
(d, NCHCHCHC), 148.3 (s, C-4), 147.9 (s, C-8), 138.3 (s, C-10a), 137.2
(d, NCHCHCHC), 125.5 (s, CCHN), 123.2 (d, NCHCHCHC), 118.1 (s,
C-6a), 114.0 (d, C-3), 109.6 (d, C-7), 108.6 (d, C-10), 101.9 (t, OCH2O),
79.0 (d, C-1), 69.5 (d, C-2), 66.5 (d, C-4a), 55.9 (t, C-12), 43.4 (q,
NMe), 40.9 (d, C-10b), 27.9 (t, C-11). IR (neat, cmꢂ1): 2926, 2853,
2791, 1724, 1617, 1592, 1480, 1385, 1254, 1112, 1034, 937, 881, 749,
701, 664. HRMS m/z 421.1398 (calcd for C23H21N2O6 [M]þ 421.1400).
4.3. Chemistry
Alkaloids 1 and 2 were extracted from the bulbs of P. canariense
as described in Ref. [11].
4.3.1. Hippeastrine lactam (3)
4.3.5. 2-(p-Bromobenzoyl)-hippeastrine (6)
20 mg (0.064 mmol) of 1 and 100 mg (20 equiv) of ammonium
acetate dissolved in 5 mL of acetic acid were refluxed for 2 h. The
solvent was then evaporated and the residue was purified by pre-
Following the procedure described above, 18.7 mg (0.6 mmol) of
1 was reacted with 21
mL (2.5 equiv) of NEt3 and 19.5 mg (1.5 equiv)
of p-bromobenzoyl chloride to yield, after purification, 29 mg
20
parative TLC using DCM:MeOH 17:3 as eluent. 19 mg (85%) of 3 was
(100%) of 6 as an amorphous white solid. [
1H NMR (CDCl3)
7.85 (2H, d, J ¼ 8.3 Hz, COC(CH)2), 7.54 (2H, d,
J ¼ 8.3 Hz, (CH)2CBr), 7.46 (1H, s, H-7), 7.00 (1H, s, H-10), 6.06 (2H, s,
a
]
¼ þ96.6 (c 1.6, EtOH).
D
20
obtained as an amorphous white solid. [
a]
¼ þ57.6 (c 0.27, EtOH).
d
D
1H NMR (CDCl3)
d
7.45 (1H, s, H-7), 7.03 (1H, s, H-10), 6.06 (2H, s,

726
J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
OCH2O), 5.70 (1H, s, H-3), 5.67 (1H, s, H-2), 4.71 (1H, s, H-1), 3.23
(1H, br s, H-12), 2.95 (1H, d, J ¼ 8.3 Hz, H-10b), 2.77 (1H, d,
J ¼ 8.4 Hz, H-4a), 2.58 (2H, br s, H-11), 2.34 (1H, dd, J ¼ 9.2 Hz,
CH2), 118.1 (s, C-6a), 115.4 (t, CH2CH2CH]CH2), 114.6 (d, C-3), 109.6
(d, C-7), 108.4 (d, C-10), 101.9 (t, OCH2O), 79.1 (d, C-1), 68.3 (d, C-2),
66.5 (d, C-4a), 55.8 (t, C-12), 43.3 (q, NMe), 40.6 (d, C-10b), 33.2 (t,
CH2CH2CH]CH2), 28.5 (t, CH2CH2CH]CH2), 27.7 (t, C-11). IR (neat,
cmꢂ1): 2922, 2850, 1729, 1615, 1481, 1291, 1251, 1160, 1118, 1034,
936, 785, 652, 610. HRMS m/z 398.1606 (calcd for C22H24NO6
[M þ 1]þ 398.1604).
J ¼ 18.3 Hz, H-12), 2.12 (3H, s, NMe). 13C NMR (CDCl3)
d 164.3 (s,
C-6), 163. 8 (s, C]O), 151.7 (s, C-9), 147.9 (s, C-4), 147.4 (s, C-8), 138.2
(s, C-10a), 131.5 (d, COC(CH)2), 131.0 (d, (CH)2CBr), 128.3 (s,
COC(CH)2), 128.2 (s, (CH)2CBr), 118.1 (s, C-6a), 114.5 (d, C-3), 109.6
(d, C-7), 108.6 (d, C-10), 102.0 (t, OCH2O), 78.9 (d, C-1), 69.1 (d, C-2),
66.6 (d, C-4a), 55.9 (t, C-12), 43.3 (q, NMe), 40.7 (d, C-10b), 27.8 (t,
C-11). IR (neat, cmꢂ1): 2927, 2790, 1722, 1618, 1590, 1481, 1386,
1293, 1255, 1099, 1036, 1010, 938, 846, 756, 664. HRMS m/z
497.0466 (calcd for C24H20NO6Br [M]þ 497.0474).
4.3.9. 2-Oxohippeastrine (10)
To a solution of 37.9 mg (0.12 mmol) of 1 in acetone (2 mL) in
an ice bath, was added the Jones reagent dropwise, until the so-
lution turned orange. The reaction mixture was stirred for 30 min
and then isopropanol was added. The solution was filtered
through Florisil and the residue was concentrated and purified by
4.3.6. 2-Isobutyrylhippeastrine (7)
Following the procedure described above, 15.5 mg (0.05 mmol)
preparative TLC using DCM:MeOH 9:1 as eluent, to yield 20 mg
20
of 1 was treated with 18
mL (2.5 equiv) of NEt3 and 8
mL (1.5 equiv) of
(55%) of 10 as an amorphous white solid. [
a
]
¼ þ16.0 (c 0.3,
D
isobutyryl chloride. After purification, 18 mg (100%) of 7 were ob-
EtOH). 1H NMR (CDCl3)
d 7.50 (1H, s, H-7), 6.92 (1H, s, H-10), 6.10
20
tained as an amorphous white solid. [
a
]
¼ þ94.0 (c 0.5, EtOH). 1H
(2H, s, OCH2O), 6.09 (1H, s, H-3), 4.59 (1H, s, H-1), 3.28 (1H, m, H-
4a), 3.18 (2H, s, H-12, H-10b), 2.80 (2H, d, J ¼ 8.4 Hz, H-11), 2.42
(1H, dd, J ¼ 9.3 Hz, J ¼ 18.4 Hz, H-12), 2.07 (3H, s, NMe). 13C NMR
D
NMR (CDCl3)
d
7.46 (1H, s, H-7), 7.00 (1H, s, H-10), 6.07 (2H, s,
OCH2O), 5.59 (1H, s, H-3), 5.42 (1H, s, H-2), 4.55 (1H, s, H-1), 3.23
(1H, br s, H-12), 2.86 (1H, d, J ¼ 8.7 Hz, H-10b), 2.73 (1H, d,
J ¼ 8.7 Hz, H-4a), 2.50 (3H, m, H-11, CH(CH3)2), 2.27 (1H, dd,
J ¼ 9.5 Hz, J ¼ 18.1 Hz, H-12), 2.10 (3H, s, NMe),1.13 (3H, d, J ¼ 4.3 Hz,
CH(CH3)2), 1.08 (3H, d, J ¼ 4.3 Hz, CH(CH3)2). 13C NMR (CDCl3)
(CDCl3)
d 188.5 (s, C-2), 163.0 (s, C-6), 152.1 (s, C-9), 148.3 (s, C-8),
135.8 (s, C-10a), 121.1 (d, C-3), 117.8 (s, C-6a), 109.7 (d, C-7), 108.4
(d, C-10), 102.1 (t, OCH2O), 77.8 (d, C-1), 67.4 (d, C-4a), 56.2 (t, C-
12), 45.5 (d, C-10b), 43.3 (q, NMe), 29.7 (t, C-11). IR (neat, cmꢂ1):
2957, 2927, 2855, 1730, 1646, 1454, 1386, 1251, 1170, 1065, 1035,
d
175.5 (s, C]O),163.8 (s, C-6),151.7 (s, C-9),147.9 (s, C-8, C-4),138.3
(s, C-10a), 118.2 (s, C-6a), 115.0 (d, C-3), 109.6 (d, C-7), 108.6 (d,
C-10), 101.9 (t, OCH2O), 79.2 (d, C-1), 68.1 (d, C-2), 66.6 (d, C-4a),
55.9 (t, C-12), 43.3 (q, NMe), 33.7 (d, C-10b), 31.5 (d, CH(CH3)2), 27.7
(t, C-11), 18.6 (q, CH(CH3)2). IR (neat, cmꢂ1): 2928, 2789, 1731, 1617,
1481, 1386, 1291, 1251, 1189, 1151, 1119, 1035, 939, 755, 663. HRMS
m/z 385.1585 (calcd for C21H23NO6 [M]þ 385.1525).
938, 755. HRMS m/z 313.0962 (calcd for C
17H15NO5 [M]þ
313.0950).
4.3.10. Reaction of hippeastrine with thionyl chloride
To a solution of 20 mg (0.064 mmol) of 1 in 5 mL of dry DCM,
100 mL (20 equiv) of thionyl chloride were added. The mixture was
refluxed for 5 h. Then, the solvent was evaporated and the residue
was purified using preparative TLC with DCM:MeOH 9:1 as eluent
to yield 8 mg (43%) of 11 and 10 mg (47%) of 12.
4.3.7. 2-[3,5-Bis(methoxycarbonyl)benzoyl]hippeastrine (8)
Following the procedure described above, 35 mg (0.11 mmol) of
1 was treated with 8
mL (0.5 equiv) of NEt3 and 6.6 mL (0.33 equiv) of
trimesyl chloride. After purification, 11.3 mg (18%) of 8 were ob-
4.3.11. 3,4-Dihydro-2-deoxy-2,3,4,11-tetradehydrohippeastrine (11)
20
20
tained as an amorphous white solid. [
a
]
¼ þ108.9 (c 0.28, MeOH).
White solid. [
a
]
¼ þ52.5 (c 0.8, EtOH). 1H NMR (CDCl3)
d 7.53
D
D
1H NMR (CDCl3)
d
8.85 (1H, s, CH(CCO2Me)2), 8.79 (2H, s, COC(CH)2),
(1H, s, H-7), 6.98 (1H, s, H-10), 6.57 (1H, d, J ¼ 9.5 Hz, H-3), 6.06 (2H,
s, OCH2O), 5.99 (1H, dd, J ¼ 5.7 Hz, J ¼ 9.6 Hz, H-11), 5.67 (1H, d,
J ¼ 1.9 Hz, H-2), 4.97 (1H, dd, J ¼ 2.0 Hz, J ¼ 3.3 Hz, H-1), 3.96 (1H, d,
J ¼ 15.4 Hz, H-12), 3.55 (1H, m, H-4a), 3.30 (1H, d, J ¼ 15.5 Hz, H-12),
7.48 (1H, s, H-7), 7.02 (1H, s, H-10), 6.08 (1H, br s, OCH2O), 6.06 (1H,
br s, OCH2O), 5.74 (2H, s, H-2, H-3), 4.76 (1H, s, H-1), 3.97 (6H, s,
OMe), 3.21 (1H, br s, H-12), 2.97 (1H, br s, H-10b), 2.79 (1H, s, H-4a),
2.61 (2H, d, J ¼ 5.4 Hz, H-11), 2.32 (1H, m, H-12), 2.12 (3H, s, NMe).
2.80 (1H, dd, J ¼ 3.2 Hz, J ¼ 7.5 Hz, H-10b), 2.04 (3H, s, NMe). 13
C
13C NMR (CDCl3)
d
165.0 (s, CO2Me), 163.8 (s, C-6), 163.5 (s, C]O),
NMR (CDCl3) d 164.1 (s, C-6), 151.8 (s, C-9), 147.6 (s, C-8), 137.3 (s,
151.7 (s, C-9), 147.8 (s, C-8), 138.2 (s, C-10a),134.7 (d, CH(CCO2Me)2),
134.4 (d, COC(CH)2), 131,0 (s, CH(CCO2Me)2), 130.4 (s, COC(CH)2),
118.1 (s, C-6a), 114.2 (d, C-3), 109.6 (d, C-7), 108.7 (d, C-10), 101.9 (t,
OCH2O), 78.9 (d, C-1), 69.6 (d, C-2), 66.5 (d, C-4a), 55.9 (t, C-12),
52.4 (q, OMe), 43.3 (q, NMe), 27.8 (t, C-11). IR (neat, cmꢂ1): 3057,
2954, 2850, 1730, 1615, 1449, 1385, 1292, 1119, 1036, 999, 937, 783,
738, 700. HRMS m/z 534.1389 (calcd for C28H24NO10 [M ꢂ 1]þ
534.1400).
C-4),137.0 (C-10a),127.6 (d, C-3),124.5 (d, C-2), 124.0 (d, C-11), 117.4
(s, C-6a), 109.3 (d, C-7), 108.6 (d, C-10), 101.7 (t, OCH2O), 74.4 (d,
C-1), 69.7 (d, C-4a), 63.3 (t, C-12), 45.1 (d, C-10b), 42.8 (q, NMe). IR
(neat, cmꢂ1): 3054, 2918, 1712, 1617, 1481, 1390, 1334, 1254, 1122,
1038, 935, 821, 734, 662. HRMS m/z 297.1007 (calcd for C17H15NO4
[M]þ 297.1001).
4.3.12. 4S-Chloro-2,3-dehydro-3,4-dihydro-2-deoxyhippeastrine (12)
20
White solid. [
a]
¼ þ19.7 (c 1.0, EtOH). 1H NMR (CDCl3)
d 7.54
D
4.3.8. 2-(4-Pentenoyl)hippeastrine (9)
(1H, s, H-7), 7.00 (1H, s, H-10), 6.23 (1H, d, J ¼ 9.8 Hz, H-3), 6.06 (1H,
br s, OCH2O), 6.05 (1H, br s, OCH2O), 5.97 (1H, dd, J ¼ 5.5 Hz,
J ¼ 9.8 Hz, H-2), 4.82 (1H, dd, J ¼ 3.5 Hz, J ¼ 5.5 Hz, H-1), 3.30 (1H,
dd, J ¼ 7.1 Hz, J ¼ 8.7 Hz, H-12), 3.21 (1H, d, J ¼ 10.4 Hz, H-4a), 2.97
(1H, m, H-11), 2.57 (1H, dd, J ¼ 3.2 Hz, J ¼ 10.4 Hz, H-10b), 2.33 (1H,
dd, J ¼ 5.5 Hz, J ¼ 13.3 Hz, H-12), 2.24 (1H, m, H-11), 2.19 (3H, s,
Following the procedure described above, 20 mg (0.064 mmol)
of 1 was treated with 23
mL (2.5 equiv) of NEt3 and 14 mL (2 equiv) of
4-pentenoyl chloride. After purification, 12.3 mg (49%) of 9 were
20
obtained as an amorphous white solid. [
a]
¼ þ94.3 (c 0.07,
D
MeOH). 1H NMR (CDCl3)
d
7.46 (1H, s, H-7), 6.97 (1H, s, H-10), 6.13
(2H, s, OCH2O), 5.78 (1H, m, CH2CH2CH]CH2), 5.58 (1H, s, H-3),
5.44 (1H, s, H-2), 5.01 (1H, d, J ¼ 18.0 Hz, CH2CH2CH]CH2), 4.96
(1H, d, J ¼ 10.5 Hz, CH2CH2CH]CH2), 4.56 (1H, s, H-1), 3.19 (1H, br
s, H-12), 2.83 (1H, d, J ¼ 8.6 Hz, H-10b), 2.70 (1H, d, J ¼ 8.6 Hz, H-4a),
2.54 (2H, s, H-11), 2.38 (5H, m, CH2CH2CH]CH2, H-12), 2.07 (3H, s,
NMe). 13C NMR (CDCl3)
d 164.3 (s, C-6), 151.6 (s, C-9), 147.6 (s, C-8),
137.0 (s, C-10a), 135.8 (d, C-3), 122.8 (d, C-2), 117.5 (s, C-6a), 109.3 (d,
C-7), 108.9 (d, C-10), 101.7 (t, OCH2O), 73.4 (d, C-1), 71.8 (d, C-4a),
64.6 (s, C-4), 53.6 (t, C-12), 44.4 (q, NMe), 43.8 (d, C-10b), 40.5
(t, C-11). IR (neat, cmꢂ1): 3023, 1644, 1479, 1387, 1293, 1256, 1121,
1035, 551. HRMS m/z 333.0762 (calcd for C17H16NO4Cl [M]þ
333.0768).
NMe). 13C NMR (CDCl3)
d
171.4 (s, C]O), 163.8 (s, C-6), 151.6 (s, C-9),
147.8 (s, C-4), 147.8 (s, C-8), 138.4 (s, C-10a), 136.1 (d, CH2CH2CH]

J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
727
4.3.13. Ethyl hippeastrinyl carbonate (13)
4.3.16. 8,9-Nor-8,9-dimethoxyhippeastrine (16)
A solution of 30 mg (0.095 mmol) of 1 in 4 mL of DCM was
treated with 46 mL (5 equiv) of ethyl chloroformiate and 4 mL of a
To 15 mg (0.05 mmol) of 15 in 5 mL of MeOH was added 1 mL
of a 2 M solution of trimethylsilyldiazomethane in Et2O. The
mixture was reacted for 24 h. After that period, the solvent was
evaporated and the residue was purified by preparative TLC us-
3 M solution of potassium hydroxide. The mixture was stirred at rt
for 24 h. After that time, both phases were separated ant the
aqueous phase was extracted with DCM. The organic phases were
combined, dried with magnesium sulphate and concentrated.
Further purification by preparative TLC using DCM:MeOH 9:1 as
ing DCM:MeOH 9:1 as eluent. 8 mg (49%) of 16 were obtained as
20
an amorphous white solid. [
(CDCl3)
a
]
¼ þ89.4 (c 0.5, MeOH). 1H NMR
D
d
7.52 (1H, s, H-7), 7.04 (1H, s, H-10), 5.68 (1H, s, H-3),
eluent yielded 4.1 mg (12%) of 13 as an amorphous white solid.
4.64 (1H, s, H-1), 4.41 (1H, s, H-2), 3.94 (3H, s, OMe), 3.92 (3H, s,
OMe), 3.20 (1H, ddd, J ¼ 5.0 Hz, J ¼ 9.3 Hz, J ¼ 9.3 Hz, H-12), 2.94
(1H, d, J ¼ 9.5 Hz, H-10b), 2.71 (1H, d, J ¼ 9.5 Hz, H-4a), 2.55 (2H,
br s, H-11), 2.28 (1H, dd, J ¼ 9.5 Hz, J ¼ 18.7 Hz, H-12), 2.05 (3H, s,
¼ þ48.2 (c 0.35, MeOH). 1H NMR (CDCl3)
d 7.47 (1H, s, H-7),
20
[
a]
D
7.04 (1H, s, H-10), 6.08 (1H, br s, OCH2O), 6.07 (1H, br s, OCH2O),
5.70 (1H, s, H-3), 5.30 (1H, s, H-2), 4.68 (1H, s, H-1), 4.20 (2H, q,
J ¼ 7.0 Hz, OCH2CH3), 3.29 (1H, br s, H-12), 2.98 (1H, br s, H-10b),
2.81 (1H, m, H-4a), 2.60 (2H, d, J ¼ 11.0 Hz, H-11), 2.35 (1H, dd,
J ¼ 8.8 Hz, J ¼ 17.6 Hz, H-12), 2.11 (3H, s, NMe),1.30 (3H, t, J ¼ 7.0 Hz,
NMe). 13C NMR (CDCl3)
d 164.9 (s, C-6), 153.0 (s, C-9), 148.8 (s,
C-8), 144.9 (s, C-4), 136.7 (s, C-10a), 118.4 (d, C-3), 116.4 (s, C-6a),
111.7 (d, C-7), 110.7 (d, C-10), 82.2 (d, C-1), 66.8 (d, C-2), 66.8 (d,
C-4a), 56.2 (q, OMe), 55.9 (t, C-12), 55.9 (q, OMe), 43.2 (q, NMe),
39.1 (d, C-10b), 27.6 (t, C-11). IR (neat, cmꢂ1): 3400, 2926, 2338,
1716, 1602, 1512, 1461, 1361, 1299, 1220, 1158, 1071, 1024, 975,
878, 733, 640. HRMS m/z 330.1365 (calcd for C18H20NO5 [M ꢂ 1]þ
330.1341).
OCH2CH3). 13C NMR (CDCl3)
d 163.7 (s, C-6), 153.7 (s, OCO2), 151.8 (s,
C-9), 147.7 (s, C-8), 143.2 (s, C-4), 138.5 (s, C-10a), 124.6 (s, C-6a),
117.9 (d, C-3),109.6 (d, C-7),108.6 (d, C-10),101.9 (t, OCH2O), 78.8 (d,
C-1), 71.5 (d, C-2), 66.7 (d, C-4a), 64.3 (t, OCH2CH3), 55.8 (t, C-12),
43.2 (q, NMe), 38.9 (d, C-10b), 27.6 (t, C-11), 13.9 (q, OCH2CH3). IR
(neat, cmꢂ1): 2923, 2852, 1740, 1615, 1481, 1385, 1250, 1197, 1117,
1033, 1007, 938, 875, 784, 670. HRMS m/z 388.1406 (calcd for
4.3.17. Hippeastrine N-oxide (17)
C
20H22NO7 [M]þ 388.1396).
To a solution of 25 mg (0.08 mmol) of 1 in 2 mL of MeOH, at 0 ꢀC,
0.1 mL (11 equiv) of 30% H2O2 were added dropwise. The mixture
was reacted for 24 h. Then, an excess of manganese dioxide was
added and the resulting mixture was filtered through Celite. After
4.3.14. 2-(p-Vinylbenzoyl)-hippeastrine (14)
To a solution of 20 mg (0.064 mmol) of 1 in 3 mL of DCM were
added 26.5 mg (2 equiv) of 1,3-dicyclohexylcarbodiimide (DCC) and
19 mg (2 equiv) of p-vinylbenzoic acid. The mixture was stirred for
24 h. Then, the solvent was evaporated. Further purification of the
evaporation of the solvent, 26 mg (100%) of 17 was obtained as an
20
amorphous white solid. [
(MeOD)
a]
¼ þ23.0 (c 0.3, MeOH). 1H NMR
D
d
7.42 (1H, s, H-7), 7.29 (1H, s, H-10), 6.13 (2H, s, OCH2O),
residue by preparative TLC using DCM:MeOH 9:1 as eluent yielded
5.90 (1H, s, H-3), 4.66 (1H, s, H-1), 4.12 (1H, d, J ¼ 9.5 Hz, H-2), 3.70
(2H, m, H-12), 3.55 (1H, t, J ¼ 9.3 Hz, H-10b), 3.30 (1H, s, H-4a), 3.00
(3H, s, NMe), 2.90 (1H, m, H-11), 2.77 (1H, m, H-11). 13C NMR
20
17.7 mg (63%) of 14 as an amorphous white solid. [
a
]
¼ þ228.6
D
(c 0.07, MeOH). 1H NMR (CDCl3)
d
7.94 (2H, d, J ¼ 8.2 Hz, COC(CH)2),
7.46 (2H, d, J ¼ 8.2 Hz, (CH)2CCH]CH2), 7.42 (1H, s, H-7), 6.98 (1H,
s, H-10), 6.73 (1H, dd, J ¼ 10.9 Hz, J ¼ 17.5 Hz, (CH)2CCH]CH2), 6.08
(1H, br s, OCH2O), 6.07 (1H, br s, OCH2O), 5.85 (1H, d, J ¼ 17.5 Hz,
(CH)2CCH]CH2), 5.70 (2H, s, H-2, H-3), 5.38 (1H, d, J ¼ 10.9 Hz,
(CH)2CCH]CH2), 4.73 (1H, s, H-1), 3.19 (1H, m, H-12), 2.93 (1H, d,
J ¼ 9.2 Hz, H-10b), 2.74 (1H, d, J ¼ 9.2 Hz, H-4a), 2.59 (2H, m, H-11),
(MeOD) d 164.4 (s, C-6), 152.2 (s, C-9), 148.8 (s, C-8), 138.0 (s, C-4),
137.4 (s, C-10a),122.0 (d, C-3), 118.1 (s, C-6a), 108.9 (d, C-7), 108.7 (d,
C-10), 102.5 (t, OCH2O), 81.6 (d, C-1), 76.7 (d, C-2), 69.1 (t, C-12),
65.3 (t, C-4a), 54.7 (q, NMe), 32.6 (d, C-10b), 24.9 (t, C-11). IR (neat,
cmꢂ1): 3405, 2925, 1718, 1619, 1506, 1487, 1455, 1389, 1296, 1257,
1124, 1040, 960, 940, 892, 785, 739. HRMS m/z 331.1060 (calcd for
2.30 (1H, dd, J ¼ 9.1 Hz, J ¼ 18.3 Hz, H-12), 2.10 (3H, s, NMe). 13
C
C
17H17NO6 [M]þ 331.1056).
NMR (CDCl3)
d 164.8 (s, C]O), 163.9 (s, C-6), 151.6 (s, C-9), 147.8 (s,
C-8), 147.7 (s, C-4), 142.1 (s, COC(CH)2), 138.5 (s, C-10a), 135.6 (d,
(CH)2CCH]CH2), 129.8 (d, COC(CH)2), 128.4 (s, (CH)2CCH]CH2),
125.9 (d, (CH)2CCH]CH2), 118.2 (s, C-6a), 116.5 (t, (CH)2CCH]CH2),
114.5 (d, C-3), 109.6 (d, C-7), 108.5 (d, C-10), 101.9 (t, OCH2O), 79.1
(d, C-1), 68.7 (d, C-2), 66.5 (d, C-4a), 55.9 (t, C-12), 43.3 (q, NMe),
40.9 (d, C-10b), 27.8 (t, C-11). IR (neat, cmꢂ1): 2924, 2360,1714,1611,
1480, 1255, 1179, 1098, 1036, 937, 782, 735. HRMS m/z 446.1605
(calcd for C26H24NO6 [M þ 1]þ 446.1604).
4.3.18. Preparation of the ammonium derivative (18)
To 25 mg (0.075 mmol) of 17 dissolved in 2 mL of MeOH was
added dropwise HCl 12 M until a pH ¼ 1 was reached. After 30 min
of stirring, the solvent was evaporated and the residue was dis-
solved in MeOH and 50 mg (2 equiv) of iron (II) sulphate hepta-
hydrate, at 0 ꢀC. The mixture was reacted for 2 h. After that period,
the solvent was removed and the residue was dissolved in 2 mL of a
basic solution (pH ¼ 10) of ethylenediamine tetraacetate. This so-
lution was stirred for 30 min and then was extracted with DCM.
The organic phase was dried over anhydrous magnesium sulphate
and then filtered and concentrated. Further purification of the
residue on preparative TLC with DCM:MeOH 9:1 and 1% NH3 as
4.3.15. 8,9-Norhippeastrine (15)
To a solution of 27.2 mg (0.086 mmol) of 1 in 8 mL of dry DCM, at
0
ꢀC, was added dropwise 0.13 mL (1.5 equiv) of a solution 1 M of
BBr3 in DCM. After 5 h stirring, the solvent was removed and the
residue was chromatographed using preparative TLC with
eluent yielded 10 mg (33%) of 18 as an amorphous white solid.
20
[a
]
¼ ꢂ14.4 (c 0.54, EtOH). 1H NMR (CDCl3)
d 7.49 (1H, s, H-7), 6.69
D
DCM:MeOH 4:1. 14 mg (55%) of 15 were obtained as an amorphous
(1H, br s, H-12), 6.31 (1H, s, H-10), 6.02 (2H, s, OCH2O), 5.98 (1H, d,
J ¼ 2.7 Hz, H-3), 4.68 (1H, dd, J ¼ 4.2 Hz, J ¼ 5.7 Hz, H-1), 4.51 (1H, d,
J ¼ 5.7 Hz, H-4a), 4.13 (1H, dd, J ¼ 6.8 Hz, J ¼ 11.3 Hz, H-2), 3.62 (3H,
s, NMe), 3.59 (1H, br s, H-10b), 3.05 (1H, dd, J ¼ 6.7 Hz, 8.9 Hz, H-11),
white solid. [
a
]
D
¼ þ8.7 (c 0.75, EtOH). 1H NMR (MeOD)
d 7.43 (1H,
20
s, H-7), 6.98 (1H, s, H-10), 5.78 (1H, s, H-3), 4.59 (1H, s, H-1), 4.27
(1H, s, H-2), 3.42 (1H, br s, H-12), 3.18 (1H, d, J ¼ 9.7 Hz, H-10b), 3.00
(1H, d, J ¼ 9.9 Hz, H-4a), 2.72 (3H, m, H-11, H-12), 2.34 (3H, s, NMe).
2.59 (1H, dd, J ¼ 6.7 Hz, J ¼ 8.9 Hz, H-11). 13C NMR (CDCl3)
d 162.8 (s,
13C NMR (MeOD)
d
164.9 (s, C-6), 148.5 (s, C-9), 146.2 (s, C-8), 145.5
C-6), 152.7 (s, C-9), 147.0 (s, C-8), 137.0 (s, C-10a), 123.5 (d, C-12),
123.4 (d, C-3),117.2 (s, C-6a),115.0 (s, C-4),109.5 (d, C-7),106.7 (d, C-
10), 101.8 (t, OCH2O), 81.6 (d, C-1), 66.5 (d, C-2), 33.8 (d, C-4a), 33.7
(d, C-10b), 33.6 (q, NMe), 29.8 (t, C-11). IR (neat, cmꢂ1): 3442, 2924,
1645, 1482, 1385, 1267, 1034, 569. HRMS m/z 313.0953 (calcd for
(s, C-4), 138.7 (s, C-10a), 122.5 (d, C-3), 118.9 (s, C-6a), 116.0 (d, C-7),
114.5 (d, C-10), 81.2 (d, C-1), 67.5 (d, C-2), 65.6 (d, C-4a), 55.3 (t, C-
12), 40.4 (q, NMe), 34.6 (d, C-10b), 25.8 (t, C-11). IR (neat, cmꢂ1):
3444, 2925, 2854, 1644, 1459, 1381, 1265, 576. HRMS m/z 304.1181
(calcd for C16H18NO5 [M þ 1]þ 304.1185).
C
17H15NO5 [M ꢂ 1]þ 313.0950).

728
J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
4.3.19. Methyl 6-[5-(acetyloxy)-1-methyl-2,3-dihydro-1H-indol-7-
yl]-1,3-benzodioxole-5-carboxylate (19)
To a solution of 29.2 mg (0.08 mmol) of 17 in 3 mL of DCM was
added 11 mL (2 equiv) of acetic anhydride. After 24 h of reflux, the
solvent was evaporated and the residue was purified using a
chromatotron with DCM:MeOH 19:1 as eluent to obtain 16 mg
(51%) of 4 and 6.4 mg (20%) of 19 as an amorphous white solid. 1H
OCH2O), 4.80 (1H, s, H-3), 4.72 (1H, s, H-1), 4.62 (2H, s, eOH, H-2),
3.63 (2H, m, H-10b, H-12), 3.08 (1H, d, J ¼ 10.9 Hz, H-4a), 2.83 (1H,
dd, J ¼ 10.0 Hz, J ¼ 23.0 Hz, H-11), 2.60 (1H, t, J ¼ 10.0 Hz, H-12), 2.14
(1H, dd, J ¼ 6.3 Hz, J ¼ 13.4 Hz, H-11), 1.85 (3H, s, NMe). 13C NMR
(MeOD) d 163.7 (s, C-6), 152.8 (s, C-9), 148.3 (s, C-8), 136.5 (s, C-10a),
117.6 (s, C-6a), 108.4 (d, C-10), 108.2 (d, C-7), 102.3 (t, OCH2O), 81.4
(d, C-1), 77.5 (s, C-4), 73.5 (d, C-2), 66.9 (d, C-4a), 53.6 (t, C-12), 52.2
(d, C-3), 43.4 (q, NMe), 38.4 (t, C-11), 38.3 (d, C-10b). IR (neat,
cmꢂ1): 3431, 2922, 2853, 1718, 1616, 1481, 1450, 1392, 1290, 1255,
1202, 1110, 1035, 934, 883, 734, 667. HRMS m/z 434.0017 (calcd for
NMR (CDCl3)
d 7.36 (1H, s, H-7), 6.83 (1H, s, H-10), 6.79 (1H, d,
J ¼ 3.7 Hz, H-3), 6.47 (1H, d, J ¼ 2.0 Hz, H-1), 6.05 (2H, s, OCH2O),
3.62 (3H, s, OMe), 3.28 (2H, m, H-12), 2.95 (2H, t, J ¼ 8.2 Hz, H-11),
2.28 (3H, s, NMe), 2.22 (3H, s, OCOCH3). 13C NMR (CDCl3)
d
169.9 (s,
C
17H18NO6BrNa [M þ Na]þ 434.0038).
OCOCH3), 166.9 (s, C-6), 149.7 (s, C-9), 146.6 (s, C-8), 142.2 (s, C-4),
141.2 (s, C-2), 136.0 (s, C-10a), 132.1 (s, C-10b), 131.9 (s, C-4a), 124.0
(s, C-6a), 121.3 (d, C-1), 116.6 (d, C-3), 111.0 (d, C-10), 109.4 (d, C-7),
101.6 (t, OCH2O), 57.2 (t, C-12), 51.7 (q, OMe), 38.9 (q, NMe), 28.5 (t,
C-11), 13.8 (c, OCOCH3). IR (neat, cmꢂ1): 2921, 2852, 2360, 1755,
1726, 1615, 1484, 1436, 1372, 1210, 1123, 1034, 930, 874, 733, 670.
HRMS m/z 369.1224 (calcd for C20H19NO6 [M]þ 369.1212).
4.3.23. 3S,4R-Dihydroxyhippeastrine (23)
A solution of 20 mg (0.064 mmol) of 1 in 5 mL of t-butanol/THF/
H2O 7:2:1 was treated with 24.5 mg (3.3 equiv) of N-methyl-
morpholine N-oxide (NMO) and 0.4 mg (2.5% mol) of osmium
tetraoxide. The reaction mixture was stirred for 24 h. Then, a
saturated solution of sodium bisulphate was added and the mixture
was extracted several times with DCM. The organic phases were
4.3.20. 3,4R-Dihydrohippeastrine (20)
dried over anhydrous MgSO4, filtered and concentrated to afford
20
14.9 mg (0.047 mmol) of 1 in 4 mL of THF were hydrogenated in
the presence of catalytic amounts of 10% Pd/C. The reaction mixture
was stirred for 5 days. The solution was then filtered through Celite
and the solvent was evaporated. After purification by preparative
TLC with DCM:MeOH 9:1 as eluent, 3.5 mg (25%) of 20 were ob-
tained as an amorphous white solid. [
22 mg (100%) of 23 as an amorphous white solid. [
a
]
¼ þ18.8 (c
D
1.5, MeOH). 1H NMR (MeOD)
d
7.38 (1H, s, H-7), 7.05 (1H, s, H-10),
6.06 (2H, s, OCH2O), 4.63 (1H, t, J ¼ 4.2 Hz, H-1), 3.97 (1H, dd,
J ¼ 4.2 Hz, J ¼ 10.3 Hz, H-2), 3.55 (1H, d, J ¼ 10.3 Hz, H-3), 3.05 (2H,
m, H-10b, H-11), 2.60 (2H, m, H-4a, H-12), 1.98 (3H, s, NMe), 1.96
20
a
]
¼ ꢂ6.4 (c 0.7, EtOH). 1H
(2H, m, H-11, H-12). 13C NMR (MeOD)
d 164.5 (s, C-6), 152.2 (s, C-9),
D
NMR (CDCl3)
d
7.51 (1H, s, H-7), 6.95 (1H, s, H-10), 6.05 (2H, s,
147.5 (s, C-8), 136.6 (s, C-10a), 117.2 (s, C-6a), 108.3 (d, C-10), 107.9
(d, C-7), 102.0 (t, OCH2O), 80.4 (s, C-4), 77.8 (d, C-1), 74.4 (d, C-4a),
72.3 (d, C-3), 71.8 (d, C-2), 54.2 (t, C-12), 41.9 (q, NMe), 38.4 (d,
C-10b), 37.1 (t, C-11). IR (neat, cmꢂ1): 3398, 2924, 1705, 1616, 1482,
1450, 1393, 1261, 1123, 1037, 938, 883, 736, 651. HRMS m/z 349.1169
(calcd for C17H19NO7 [M]þ 349.1162).
OCH2O), 4.64 (1H, t, J ¼ 4.9 Hz, H-1), 3.97 (1H, m, H-2), 3.38 (1H, t,
J ¼ 5.0 Hz, H-10b), 3.30 (1H, br s, H-12), 2.70 (1H, dd, J ¼ 5.6 Hz,
J ¼ 5.8 Hz, H-4a), 2.34 (2H, m, H-12, H-4), 2.26 (3H, s, NMe), 2.00
(2H, m, H-11), 1.63 (2H, m, H-3). 13C NMR (CDCl3)
d 163.9 (s, C-6),
152.3 (s, C-9), 147.0 (s, C-8), 137.0 (s, C-10a), 118.3 (s, C-6a), 109.5 (d,
C-7), 106.4 (d, C-10), 101.8 (t, OCH2O), 81.0 (d, C-1), 68.4 (d, C-2),
66.7 (d, C-4a), 54.8 (t, C-12), 41.6 (q, NMe), 36.2 (d, C-10b), 34.6 (d,
C-4), 33.3 (t, C-3), 29.9 (t, C-11). IR (neat, cmꢂ1): 3403, 2925, 2852,
1710, 1617, 1482, 1450, 1263, 1123, 1036, 934, 757, 651. HRMS m/z
317.1238 (calcd for C17H19NO5 [M]þ 317.1263).
4.3.24. General procedure for the preparation of biphenyl
derivatives 24e27
A solution of 4 (2-acetylhippeastrine) in 5 mL of CH3CN was
treated with an excess of the corresponding alkyl halide. After 24 h
of reflux, the solvent was evaporated and the residue was dissolved
in 5 mL of t-butanol. An excess of potassium t-butoxide (10 equiv)
was added and the mixture was refluxed for 4 h. Then a saturated
solution of NH4Cl was added and the mixture was extracted with
DCM. The organic phase was concentrated and purified by pre-
parative TLC using DCM:MeOH 99:1 as eluent.
4.3.21. 3S,4S-Dibromohippeastrine (21)
A solution of 20 mg (0.063 mmol) of 1 in 5 mL of dry DCM
was treated with 4 mL (1 equiv) of Br2. The reaction mixture was
stirred for 24 h. Then, the solvent was evaporated and the residue
was purified by preparative TLC using DCM:MeOH 9:1 as eluent to
obtain
6 mg (20%) of 20 as an amorphous orange solid.
20
[
a]
¼ ꢂ13.5 (c 0.6, EtOH). 1H NMR (CDCl3)
d
7.51 (1H, s, H-7), 6.98
4.3.25. 6-[2-(Dimethylamino)-3-vinylphenyl]-1,3-benzodioxole-5-
carboxylic acid (24)
D
(1H, s, H-10), 6.07 (2H, s, OCH2O), 5.07 (1H, d, J ¼ 3.3 Hz, H-3), 4.67
(1H, t, J ¼ 3.0 Hz, H-1), 4.30 (1H, t, J ¼ 3.3 Hz, H-2), 3.36 (1H, m,
H-12), 2.90 (2H, m, H-4a, H-10b), 2.74 (2H, m, H-11), 2.44 (1H, m,
Following the general procedure, 35.8 mg (0.1 mmol) of 4 was
treated with 0.5 mL (8 mmol) of methyl iodide, to yield 22.6 mg
H-12), 2.34 (3H, s, NMe). 13C NMR (CDCl3)
d
164.0 (s, C-6), 152.3 (s,
(73%) of 24 as an amorphous white solid. 1H NMR (CDCl3)
d 7.42 (2H,
C-9), 148.0 (s, C-8), 138.2 (s, C-10a), 117.5 (s, C-6a), 109.8 (d, C-7),
108.7 (d, C-10), 102.0 (t, OCH2O), 77.6 (d, C-1), 71.3 (d, C-2), 68.5 (s,
C-4), 66.2 (d, C-3), 66.0 (C-4a), 52.9 (d, C-10b), 45.7 (q, NMe), 41.4 (t,
C-12), 29.5 (t, C-11). IR (neat, cmꢂ1): 3439, 1645, 1480, 1419, 1288,
1252, 1117, 1030, 604. HRMS m/z 470.9429 (calcd for C17H17NO5Br2
[M]þ 476.9433).
s, H-3, H-7), 6.96 (3H, m, H-1, H-2, H-11), 6.62 (1H, s, H-10), 6.05
(2H, s, OCH2O), 5.61 (1H, d, J ¼ 17.5 Hz, H-12), 5.25 (1H, d, J ¼ 9.7 Hz,
H-12), 2.52 (6H, s, NMe).13C NMR (CDCl3)
d 162.3 (s, C-6),150.4 (s, C-
9), 147.2 (s, C-4a), 146.2 (s, C-8), 138.5 (s, C-10b), 138.3 (s, C-10a),
135.4 (d, C-11), 135.2 (s, C-4), 129.6 (d, C-1), 126.6 (d, C-3), 123.2 (d,
C-2), 122.4 (s, C-6a), 113.4 (t, C-12), 111.3 (d, C-10), 110.1 (d, C-7),
101.7 (t, OCH2O), 43.2 (q, NMe). IR (neat, cmꢂ1): 2912, 1668, 1615,
1489, 1440, 1408, 1359, 1270, 1234, 1142, 1086, 936, 905, 879, 803,
762, 608. HRMS m/z 311.1159 (calcd for C18H17NO4 [M]þ 311.1158).
4.3.22. 3R-Bromo-4R-hydroxyhippeastrine (22)
20 mg (0.064 mmol) of 1 was added to mixture of 10 mg
(1.2 equiv) of N-bromoacetamide, 26
mL (0.4 equiv) of a 1 M solution
of tin chloride (SnCl4) in DCM, and 1.4
m
L (1.2 equiv) of H2O in 5 mL
4.3.26. 6-[2-(Ethylmethylamino)-3-vinylphenyl]-1,3-benzodioxole-
5-carboxylic acid (25)
of MeCN at 0 ꢀC. After 2 h stirring, water was added and the mixture
was extracted with DCM. The organic phase was concentrated and
Following the general procedure, 43.2 mg (0.12 mmol) of 4 was
treated with 0.5 mL (6.7 mmol) of ethyl bromide, to yield 11 mg
purified by preparative TLC, using DCM:MeOH 9:1 as eluent, to
20
yield 4.4 mg (17%) of 22. White solid. [
NMR (MeOD)
a]
¼ ꢂ3.3 (c 0.3, MeOH). 1H
(28%) of 25 as an amorphous white solid. 1H NMR (CDCl3)
d
7.43
D
d
7.41 (1H, s, H-7), 7.09 (1H, s, H-10), 6.10 (2H, s,
(1H, s, H-7), 7.41 (1H, d, J ¼ 7.2 Hz, H-3), 6.97 (3H, m, H-1, H-2, H-11),

J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
729
6.61 (1H, s, H-10), 6.06 (1H, br s, OCH2O), 6.04 (1H, br s, OCH2O),
5.60 (1H, d, J ¼ 17.5 Hz, H-12), 5.23 (1H, d, J ¼ 10.9 Hz, H-12), 2.69
(2H, m, NCH2CH3), 2.55 (3H, s, NMe), 0.88 (3H, t, J ¼ 7.0 Hz,
(CDCl3)
d
7.43 (1H, d, J ¼ 7.7 Hz, H-3), 7.41 (1H, s, H-7), 6.98 (3H, m,
H-1, H-2, H-11), 6.64 (1H, s, H-10), 6.07 (1H, br s OCH2O), 6.05 (1H,
br s, OCH2O), 5.63 (1H, d, J ¼ 17.6 Hz, H-12), 5.25 (1H, d, J ¼ 10.9 Hz,
NCH2CH3). 13C NMR (CDCl3)
d
162.7 (s, C-6), 150.2 (s, C-9), 147.6 (s,
H-12), 3.60 (3H, s, OMe), 2.55 (6H, s, NMe). 13C NMR (CDCl3)
d 166.8
C-4a), 146.2 (s, C-8), 139.0 (s, C-10b), 138.7 (s, C-10a), 135.8 (s, C-4),
135.6 (d, C-11), 129.7 (d, C-1), 126.4 (d, C-3), 123.3 (d, C-2), 122.7 (s,
C-6a), 113.3 (t, C-12), 110.1 (d, C-7), 101.6 (t, OCH2O), 49.7 (t,
NCH2CH3), 39.9 (q, NMe), 13.3 (q, NCH2CH3). IR (neat, cmꢂ1): 3394,
3080, 2971, 1685, 1615, 1486, 1443, 1407, 1235, 1135, 1084, 1037, 933,
806, 762, 737. HRMS m/z 325.1305 (calcd for C19H19NO4 [M]þ
325.1314).
(s, C-6), 149.8 (s, C-9), 147.0 (s, C-4a), 146.2 (s, C-8), 138.6 (s, C-10b),
138.5 (s, C-10a), 135.3 (s, C-4), 135.1 (d, C-11), 129.7 (d, C-1), 126.2
(d, C-3), 123.2 (s, C-6a), 123.0 (d, C-2), 113.5 (t, C-12), 111.1 (d, C-10),
109.7 (d, C-7), 101.6 (t, OCH2O), 51.5 (q, OMe), 43.5 (q, NMe). IR
(neat, cmꢂ1): 3060, 2921, 1726, 1617, 1486, 1370, 1245, 1129, 1084,
1037, 930, 880, 759, 728, 675. HRMS m/z 325.1302 (calcd for
C
19H19NO4 [M]þ 325.1314).
4.3.27. 6-[2-(Butylmethylamino)-3-vinylphenyl]-1,3-benzodioxole-
5-carboxylic acid (26)
4.3.31. Methyl 6-[2-(butylmethylamino)-3-vinylphenyl]-1,3-
benzodioxole-5-carboxylate (29)
Following the general procedure described above, 53.1 mg
(0.15 mmol) of 4 was treated with 0.5 mL (4.66 mmol) of 1-
bromobutane, to yield 14.7 mg (29%) of 26 as an amorphous white
8 mg (0.023 mmol) of 26 was reacted as described in the general
procedure, to yield 6.5 mg (79%) of 29 as an amorphous white solid.
1H NMR (CDCl3)
d
7.45 (1H, d, J ¼ 7.5 Hz, H-3), 7.41 (1H, s, H-7), 7.03
solid. 1H NMR (CDCl3)
d
7.43 (1H, s, H-7), 7.42 (1H, d, J ¼ 7.2 Hz, H-3),
(2H, m, H-1, H-11), 6.93 (1H, t, J ¼ 6.5 Hz, H-2), 6.63 (1H, s, H-10), 6.07
(1H, br s, OCH2O), 6.05 (1H, br s, OCH2O), 5.62 (1H, d, J ¼ 17.7 Hz, H-
12), 5.22 (1H, d, J ¼ 10.9 Hz, H-12), 3.59 (3H, s, OMe), 2.58 (3H, s,
NMe), 2.56 (2H, m, NCH2CH2CH2CH3),1.16 (4H, m, NCH2CH2CH2CH3),
6.98 (3H, m, H-1, H-2, H-11), 6.60 (1H, s, H-10), 6.06 (1H, br s, OCH2O),
6.04 (1H, br s, OCH2O), 5.61 (1H, dd, J ¼ 1.1 Hz, J ¼ 17.5 Hz, H-12), 5.23
(1H, d, J ¼ 10.9 Hz, H-12), 2.59 (3H, s, NMe), 2.57 (2H, m,
NCH2CH2CH2CH3), 1.27 (2H, m, NCH2CH2CH2CH3), 1.06 (2H, m,
NCH2CH2CH2CH3), 0.75 (3H, t, J ¼ 7.2 Hz, NCH2CH2CH2CH3). 13C NMR
0.77 (3H, t, J ¼ 7.2 Hz, NCH2CH2CH2CH3). 13C NMR (CDCl3)
d 166.6 (s,
C-6), 149.6 (s, C-9), 148.0 (s, C-4a), 146.3 (s, C-8), 139.3 (s, C-10b),
139.2 (s, C-10a), 135.9 (s, C-4), 135.5 (d, C-11), 129.8 (d, C-1), 125.9
(d, C-3), 123.2 (s, C-6a), 122.9 (d, C-2), 113.0 (t, C-12), 111.2 (d,
C-10), 109.6 (d, C-7), 101.5 (t, OCH2O), 55.1 (t, NCH2CH2CH2CH3),
51.4 (q, OMe), 41.1 (q, NMe), 30.4 (t, NCH2CH2CH2CH3), 19.8 (t,
NCH2CH2CH2CH3), 13.6 (q, NCH2CH2CH2CH3). IR (neat, cmꢂ1): 3081,
2926, 1727, 1617, 1485, 1437, 1369, 1244, 1127, 1082, 1037, 931, 878,
804, 761. HRMS m/z 367.1784 (calcd for C22H25NO4 [M]þ 367.1784).
(CDCl3)
d 164.6 (s, C-6), 150.2 (s, C-9), 147.8 (s, C-4a), 146.2 (s, C-8),
139.2 (s, C-10b),139.0 (s, C-10a),135.8 (s, C-4),135.6 (d, C-11),129.8 (d,
C-1), 126.3 (d, C-3), 123.1 (d, C-2), 122.8 (s, C-6a), 113.2 (t, C-12), 111.3
(d, C-10), 110.2 (d, C-7), 101.6 (t, OCH2O), 55.2 (t, NCH2CH2CH2CH3),
40.9 (q, NMe), 30.2 (t, NCH2CH2CH2CH3), 19.8 (t, NCH2CH2CH2CH3),
13.6 (q, NCH2CH2CH2CH3). IR (neat, cmꢂ1): 2957, 2928, 1687, 1615,
1486,1443,1407,1235,1137,1082,1038, 934, 806, 762, 737, 673. HRMS
m/z 353.1612 (calcd for C21H23NO4 [M]þ 353.1627).
4.3.32. General procedure for preparation of dimers 30e33
To a solution of 1 in 5 mL of dry DCM, NEt3 (1.5e2.5 equiv) and
0.5 equiv of the corresponding acyl dichloride were added. After
stirring at rt for 24 h, the solvent was evaporated and the residue
was purified by preparative TLC using DCM:MeOH 9:1 as eluent to
obtain the corresponding dimers 30e33.
4.3.28. 6-[2-(Methylundecylamino)-3-vinylphenyl]-1,3-
benzodioxole-5-carboxylic acid (27)
Following the general procedure described above, 42.5 mg
(0.12 mmol) of 4 was treated with 0.5 mL (2.24 mmol) of 1-
bromoundecane, to yield 24 mg (45%) of 27 as an amorphous
white solid. 1H NMR (CDCl3)
s, H-7), 6.97 (3H, m, H-1, H-2, H-11), 6.62 (1H, s, H-10), 6.06 (1H, br
d
7.43 (1H, d, J ¼ 8.1 Hz, H-3), 7.42 (1H,
4.3.33. Dihippeastrinyl isophthalate (30)
s, OCH2O), 6.04 (1H, br s, OCH2O), 5.61 (1H, d, J ¼ 17.6 Hz, H-12),
Following the procedure described above, 30 mg (0.095 mmol)
5.22 (1H, d, J ¼ 11.4 Hz, H-12), 3.95 (2H, t,
J
¼ 6.3 Hz,
of 1 was treated with 20
mL (1.5 equiv) of NEt3 and 9.7 mg of iso-
NCH2(CH2)9CH3), 2.59 (3H, s, NMe), 1.25 (18H, s, NCH2(CH2)9CH3),
phthaloyl chloride. After purification, 7.1 mg (20%) of 30 were ob-
20
0.87 (3H, t, J ¼ 5.7 Hz, NCH2(CH2)9CH3). 13C NMR (CDCl3)
d
167.0 (s,
tained as an amorphous white solid. [
a]
¼ þ147.3 (c 0.22, MeOH).
D
C-6), 149.5 (s, C-9), 148.0 (s, C-4a), 146.1 (s, C-8), 139.4 (s, C-10b),
138.6 (s, C-10a), 136.0 (s, C-4), 135.6 (d, C-11), 129.9 (d, C-1), 125.9
(d, C-3), 123.7 (s, C-6a), 122.9 (d, C-2), 113.0 (t, C-12), 111.1 (d, C-10),
109.8 (d, C-7), 101.5 (t, OCH2O), 64.7 (t, NCH2(CH2)9CH3), 41.0 (q,
NMe), 31.6, 29.2, 29.1, 29.0, 28.3, 28.0, 26.7, 25.6, 22.4 (t,
NCH2(CH2)9CH3), 13.9 (q, NCH2(CH2)9CH3). IR (neat, cmꢂ1): 3398,
2924, 2853, 1706, 1619, 1465, 1366, 1247, 1128, 1084, 1039, 937, 905,
807, 760. HRMS m/z 451.2713 (calcd for C28H37NO4 [M]þ 451.2723).
1H NMR (CDCl3)
d
8.58 (1H, s, H-10), 8.19 (2H, d, J ¼ 7.6 Hz, H-30), 7.51
(1H, t, J ¼ 7.6 Hz, H-40), 7.47 (2H, s, H-7), 7.06 (2H, s, H-10), 6.08 (2H,
br s, OCH2O), 6.06 (2H, br s, OCH2O), 5.71 (4H, s, H-2, H-3), 4.73 (2H,
s, H-1), 3.22 (2H, m, H-12), 2.95 (2H, d, J ¼ 8.1 Hz, H-10b), 2.76 (2H,
d, J ¼ 8.1 Hz, H-4a), 2.60 (4H, m, H-11), 2.30 (2H, dd, J ¼ 8.9 Hz,
J ¼ 18.0 Hz, H-12), 2.10 (6H, s, NMe). 13C NMR (CDCl3)
d 164.1 (s, C]
O), 163.8 (s, C-6), 151.7 (s, C-9), 147.8 (s, C-4), 147.8 (s, C-8), 138.3 (s,
C-10a), 134.0 (d, C-10), 130.7 (s, C-20), 129.9 (d, C-30), 128.7 (d, C-40),
118.0 (s, C-6a), 114.2 (d, C-3), 109.5 (d, C-7), 108.7 (d, C-10), 101.9 (t,
OCH2O), 79.0 (d, C-1), 69.2 (d, C-2), 66.5 (d, C-4a), 55.8 (t, C-12),
43.3 (q, NMe), 40.7 (d, C-10b), 27.8 (t, C-11). IR (neat, cmꢂ1): 3054,
2924, 1724, 1614, 1481, 1385, 1292, 1226, 1120, 1035, 938, 732, 564.
HRMS m/z 761.2357 (calcd for C42H37N2O12 [M þ 1]þ 761.2347).
4.3.29. General procedure for methylation to obtain derivatives 28
and 29
To a solution of the corresponding acid in 5 mL of DCM:MeOH
1:1, 0.5 mL of a solution 2 M of trimethylsilyldiazomethane in Et2O
was added. The reaction mixture was stirred for 24 h. Then, the
solvent was evaporated and the residue was purified by preparative
TLC using DCM:hexane 1:1 as eluent, to yield the corresponding
methyl esters 28 and 29.
4.3.34. Dihippeastrinyl-pyridine-2,6-dicarboxylate (31)
Following the procedure described above, 30 mg (0.095 mmol)
of 1 was reacted with 20
mL (1.5 equiv) of NEt3 and 9.7 mg of
2,6-pyridinedicarbonyl chloride to yield, after purification, 15.5 mg
20
4.3.30. Methyl 6-[2-(dimethylamino)-3-vinylphenyl]-1,3-
benzodioxole-5-carboxylate (28)
(43%) of 31. as an amorphous white solid. [
a]
¼ þ153.1 (c 0.26,
D
MeOH). 1H NMR (CDCl3)
d
8.25 (2H, d, J ¼ 7.7 Hz, H-20), 7.98 (1H, t,
11.3 mg (0.036 mmol) of 24 was treated as described in the
J ¼ 7.7 Hz, H-30), 7.45 (2H, s, H-7), 7.21 (2H, s, H-10), 6.06 (2H, br s,
general procedure, to yield 7.8 mg (67%) of 28. White solid. 1H NMR
OCH2O), 6.05 (2H, br s, OCH2O), 5.78 (2H, s, H-3), 5.71 (2H, s, H-2),

730
J.C. Cedrón et al. / European Journal of Medicinal Chemistry 63 (2013) 722e730
4.77 (2H, s, H-1), 3.25 (2H, m, H-12), 3.01 (2H, d, J ¼ 9.3 Hz, H-10b),
2.72 (2H, d, J ¼ 9.3 Hz, H-4a), 2.54 (4H, s, H-11), 2.25 (2H, dd,
J ¼ 9.1 Hz, J ¼ 18.5 Hz, H-12), 2.09 (6H, s, NMe). 13C NMR (CDCl3)
Acknowledgements
This work has been partly funded by the Spanish MEC (SAF
2009-13296-C02-01) and by the ICIC (Instituto Canario de Inves-
tigación del Cáncer).
d
163.9 (s, C-6), 163.0 (s, C]O), 151.6 (s, C-9), 148.6 (s, C-4), 147.7 (s,
C-10), 147.6 (s, C-8), 138.8 (s, C-30), 138.1 (d, C-10a), 128.1 (d, C-20),
118.0 (s, C-6a), 113.6 (d, C-3), 109.5 (d, C-7), 109.0 (d, C-10), 101.8 (t,
OCH2O), 78.9 (d, C-1), 69.8 (d, C-2), 66.7 (d, C-4a), 55.7 (t, C-12),
43.3 (q, NMe), 40.8 (d, C-10b), 27.8 (t, C-11). IR (neat, cmꢂ1): 2924,
2850, 1723, 1616, 1502, 1481, 1450, 1385, 1291, 1252, 1123, 1034, 937,
843, 783, 734, 699, 651. HRMS m/z 762.2275 (calcd for C41H36N3O12
[M þ 1]þ 762.2299).
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2013.03.018.
4.3.35. Dihippeastrinyl terephthalate (32)
References
Following the procedure described above, 25 mg (0.08 mmol) of
1 was treated with 28
ephthaloyl chloride. After purification, 13.2 mg (44%) of 32 were
m
L (2.5 equiv) of NEt3 and 8.1 mg of ter-
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20
obtained as an amorphous white solid. [
a
]
¼ þ92.5 (c 0.43,
D
MeOH). 1H NMR (CDCl3) 8.03 (4H, s, H-20), 7.47 (2H, s, H-7), 6.98
d
(2H, s, H-10), 6.07 (2H, br s, OCH2O), 6.05 (2H, br s, OCH2O), 5.70
(4H, s, H-2, H-3), 4.73 (2H, s, H-1), 3.19 (2H, m, H-12), 2.93 (2H, d,
J ¼ 9.1 Hz, H-10b), 2.74 (2H, d, J ¼ 9.1 Hz, H-4a), 2.59 (4H, m, H-11),
2.30 (2H, dd, J ¼ 9:2 Hz, J ¼ 18.5 Hz, H-12), 2.10 (6H, s, NMe). 13
C
NMR (CDCl3)
d 164.1 (s, C]O), 163.8 (s, C-6), 151.7 (s, C-9), 147.8 (s,
C-4), 147.8 (s, C-8), 138.4 (s, C-10a), 133.4 (s, C-10), 129.5 (d, C-20),
118.1 (s, C-6a), 114.3 (d, C-3), 109.6 (d, C-7), 108.6 (d, C-10), 101.9 (t,
OCH2O), 78.9 (d, C-1), 69.3 (d, C-2), 66.5 (d, C-4a), 55.8 (t, C-12),
43.3 (q, NMe), 27.8 (t, C-11). IR (neat, cmꢂ1): 2921, 1722, 1616, 1481,
1386, 1252, 1199, 1102, 1035, 937, 877, 732. HRMS m/z 761.2378
(calcd for C42H37N2O12 [M þ 1]þ 761.2347).
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4.3.36. Dihippeastrinyl adipate (33)
Following the procedure described above, 25 mg (0.08 mmol) of
1 was treated with 28 mL (2.5 equiv) of NEt3 and 5.8 mL of adipoyl
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Press, 2010, pp. 1e37.
chloride. After purification, 8.2 mg (28%) of 33 were obtained as an
20
¼ þ99.2 (c 0.38, MeOH). 1H NMR
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amorphous white solid. [
(CDCl3)
a]
D
d
7.45 (2H, s, H-7), 6.97 (2H, s, H-10), 6.07 (4H, s, OCH2O),
5.58 (2H, s, H-3), 5.41 (2H, d, J ¼ 1.6 Hz, H-2), 4.55 (2H, s, H-1), 3.18
(2H, m, H-12), 2.83 (2H, d, J ¼ 8.1 Hz, H-10b), 2.68 (2H, d, J ¼ 8.1 Hz,
H-4a), 2.53 (4H, s, H-11), 2.29 (4H, COCH2(CH2)2CH2CO), 2.07 (6H, s,
NMe), 1.61 (4H, br s, COCH2(CH2)2CH2CO). 13C NMR (CDCl3)
d 171.6
(s, C]O), 163.9 (s, C-6), 151.6 (s, C-9), 147.8 (s, C-8), 147.0 (s, C-4),
138.3 (s, C-10a),118.0 (s, C-6a),114.5 (d, C-3),109.5 (d, C-7),108.5 (d,
C-10), 101.9 (t, OCH2O), 79.1 (d, C-1), 68.3 (d, C-2), 66.5 (d, C-4a),
55.8 (t, C-12), 43.3 (q, NMe), 33.4 (t, COCH2(CH2)2CH2CO), 27.7 (t, C-
11), 23.9 (t, COCH2(CH2)2CH2CO). IR (neat, cmꢂ1): 3055, 2926, 1729,
1615, 1481, 1450, 1385, 1291, 1252, 1122, 1035, 937, 901, 783, 734,
610. HRMS m/z 741.2629 (calcd for C40H41N2O12 [M þ 1]þ 741.2660).
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