New oxapolycyclic cage amines with NMDA receptor antagonist and trypanocidal activities

Article abstract of DOI:10.1016/j.bmc.2009.11.017

The synthesis of several (1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-benzoxonin-3-yl)amines and related compounds is reported. Several of them display very similar activity to memantine as NMDA receptor antagonists. Several derivatives showed a significant level of trypanocidal activity.

Full text of DOI:10.1016/j.bmc.2009.11.017

Bioorganic & Medicinal Chemistry 18 (2010) 46–57
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
New oxapolycyclic cage amines with NMDA receptor antagonist
and trypanocidal activities
María D. Duque a, Pelayo Camps a, Eva Torres a, Elena Valverde a, Francesc X. Sureda b, Marta López-Querol b,
Antoni Camins c, S. Radhika Prathalingam d, John M. Kelly d, Santiago Vázquez a,
*
a Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia, and Institute of Biomedicine (IBUB), Universitat de Barcelona, Av. Diagonal, 643, Barcelona
E-08028, Spain
b Unitat de Farmacologia, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c./ St. Llorenç 21, Reus E-43201, Spain
c Unitat de Farmacologia i Farmacognòsia, Facultat de Farmàcia, Institute of Biomedicine (IBUB) and CIBERNED, Universitat de Barcelona, Av. Diagonal, 643, Barcelona E-08028, Spain
d London School of Hygiene and Tropical Medicine, Department of Infectious and Tropical Diseases, Keppel Street, London WC1E 7HT, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 July 2009
Revised 5 November 2009
Accepted 7 November 2009
Available online 14 November 2009
The synthesis of several (1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-benzoxonin-3-yl)amines and
related compounds is reported. Several of them display very similar activity to memantine as NMDA
receptor antagonists. Several derivatives showed a significant level of trypanocidal activity.
Ó 2009 Elsevier Ltd. All rights reserved.
Dedicated to Professor Josep Font Cierco on
his 70th birth anniversary
Keywords:
NMDA
Memantine
Amantadine
Trypanosoma
Polycyclic cage compounds
NGP1-01
Indantadol
1. Introduction
Therefore, memantine enters the open channel preferentially when
it is pathologically activated for long periods of time. The physio-
Neurodegerative disorders like Parkinson’s disease and Alzhei-
mer’s disease, which are caused by the degeneration of dopaminer-
gic and cholinergic neurons, respectively, are becoming more and
more problematic for the older population.1 Unfortunately, current
treatments neither prevent nor reduce the progression of neurode-
generation. Therefore, great efforts have been undertaken to devel-
op drugs that meet this impairment.2
With regard to Alzheimer’s disease, NMDA receptor antagonists
act by protecting neurons from excessive pathological calcium in-
flux, which leads to neuronal damage and finally to neuronal cell
death.3 Up to now, the polycyclic amine memantine is the only
NMDA receptor antagonist with low NMDA receptor affinity that
has been introduced for the treatment of Alzheimer’s disease.4
The particular advantage of memantine is the fast off-rate kinetics
which prevents the drug from accumulating in the ion channel.
logical neurotransmission is not disturbed by memantine resulting
in minimal adverse effects.5
Another polycyclic amine, amantadine, displays moderate
NMDA receptor affinity and is used for the treatment of Parkinson’s
disease.6 Moreover, amantadine also has prophylactic and thera-
peutic activity in influenza A virus infections.7 Interestingly, aman-
tadine, memantine and related polycyclic amines also possess
trypanocidal activity.8
Biological activity has also been found with other polycyclic cage
amines.9 For example, 1 displayed in vivo activity against herpex
simplex-II and influenza A2 virus,10 2 was studied as an anti-Parkin-
sonian agent,11 and cubylamine, 3, was found to be a MAO-B inhib-
itor (Fig. 1).12 Moreover, heteroatom substituted polycyclic cage
amines are an interesting and highly promising group of compounds
that are receiving intense scrutiny as potential scaffolds for
the development of new drugs. For example, a series of oxapentacy-
cloundecylamines, such as NGP1-01 and related compounds,
has showed neuroprotective properties through NMDA receptor
* Corresponding author. Tel.: +34 934024533; fax: +34 934035941.
E-mail address: svazquez@ub.edu (S. Vázquez).
0968-0896/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2009.11.017

M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
47
H
H
H
b
a
O
O
R
O
NH2
R
NH2
NHNH2
OH
EtHN
Me
R = H, amantadine
1
3
5
6
7
R = Me, memantine
c
H
O
NH2
H
O
O
O
+
H2N
C6H5
2
N
CH3
H
H
8
9
CH3
Figure 1. Polycyclic cage compounds with biological activity.
O
O
O
O
+
antagonist activity,13 and several azapentacycloundecylalcohols
such as TC1 and TC4, have high affinity for sigma receptors (Fig. 2).14
Recently, we have found that several (3-alkyl-2-oxaadamant-1-
yl)amines, such as 4, showed NMDA receptor antagonist activity.
They were more potent than amantadine against NMDA-induced
calcium increase in cerebellar granule neurons, although they were
less potent than memantine. Moreover, two tertiary amine analogs
of 4 displayed a significant level of trypanocidal activity. However,
they were devoid of any antiviral activity (Fig. 2).15
Following our work on the synthesis of oxapolycyclic com-
pounds as analogs of amantadine and memantine, we now de-
scribe the synthesis and biological evaluation of a series of (1,2,3,5,
6,7-hexahydro-1,5:3,7-dimethano-4-benzoxonin-3-yl)amines, and
show that they contain structural features necessary for NMDA
receptor antagonist activity and trypanocidal activity.
H
O
CH3
CH3
10
11
Scheme 1. Reagents and conditions: (a) NH2NH2ꢀH2O, concd HCl, reflux, 4 h, 79%;
(b) H2, PtO2, 1 atm, rt, 3 days, 82% yield; (c) acetonitrile, toluene, concd H2SO4,
reflux, 18 h, 47% of 8, 3% of 9, 2% of 10, 3% of 11, and 20% of recovered 5.
responding imidate. Taking into account the medium yield of the
Ritter reaction we did not carry out the hydrolysis of amide 8
(Scheme 1).
Starting from amine 7, we have prepared amines 12–18 using
classical methods in amine chemistry. Reductive alkylation of
amine 7 with benzaldehyde or phenylacetaldehyde and sodium
cyanoborohydride in methanol afforded secondary amines 12a
and 12b, respectively. Reductive alkylation of benzylamine 12a
with formaldehyde led to 13a in 91% yield, while alkylation of
12a with benzyl chloride led to the dibenzyl derivative 13b in
74% yield. Hydrogenolysis of amine 13a led to secondary amine
14 in 82% yield. Moreover, reductive alkylation of amine 7 with ex-
cess formaldehyde and formic acid led to the dimethyl derivative
17a, while reaction of 7 with excess of acetaldehyde and sodium
cyanoborohydride in methanol afforded the diethyl derivative
17b. Alkylation of 7 with propargyl bromide led to a mixture of
propargylamine 15 and dipropargylamine 16. Column chromatog-
raphy of this mixture gave pure 15 and 16 in 34 and 40% yield,
respectively. Finally, alkylation of 7 with 1,5-dibromopentane led
to the piperidine derivative 18 in 46% yield (Scheme 2).
2. Results and discussion
2.1. Synthesis
For the synthesis of the new amines, known alcohol 5 was used
as starting material.16 Reaction of alcohol 5 with several primary
amines led to the recovery of the starting material. However, reac-
tion of 5 with aqueous hydrazine led to the known hydrazine 6 in
79% yield, probably due to the
a-effect ensuring a higher nucleo-
philicity of hydrazine.17 Catalytic hydrogenation of 6 furnished
amine 7 in 82% yield (Scheme 1).
Recently, a new NMDA receptor antagonist, indantadol, has
been introduced in clinical trials for the treatment of neuropathic
pain. Worthy of note, indantadol also inhibits MAO-A and MAO-B
In order to explore an alternative route to amine 7 we carried
out a Ritter reaction of 5 with acetonitrile in toluene in acidic med-
ium that led, after column chromatography, to the expected amide,
8, in 47% yield, along with the recovery of 20% of starting material
and small quantities (2–3%) of compounds 9–11. The origin of 9
can be rationalized as an electrophilic attack of the bridgehead car-
bocation involved in the Ritter reaction to toluene. Regarding es-
ters 10 and 11, their formation may involve nucleophilic attack
of 5 and its corresponding keto-alcohol opened derivative, respec-
tively, to protonated acetonitrile followed by hydrolysis of the cor-
with IC50 values of 7.2 and 60.3
l
M, respectively.18 This com-
pound features an indane nucleus and an aminoacetamide chain
in its structure. On the other hand, another non-competitive
NMDA receptor antagonist with in vitro an in vivo neuroprotec-
tive properties, N20C, also features an aminoacetamide group in
its structure.19 After noticing the NMDA receptor antagonist
activity of several of our new amines, we synthesized acetamide
19 that shares structural elements with both indantadol and
N20C. Thus, reaction of amine 7 with chloroacetamide in the
presence of sodium iodide and potassium carbonate led to acet-
amide 19 in 55% yield (based on recovered starting material)
(Scheme 3).
F
H
N
OH
O
N
Taking into account that in our previous work with 2-oxaada-
mant-1-ylamines we found that 3-alkyl derivatives were more po-
tent than the corresponding 3-unsubstituted derivatives,15 we also
planned to carry out the synthesis and evaluation of 5-alkyl deriv-
atives of amine 7.
TC1
NGP1-01
F
OH
N
N
Reaction of the known16 diketone 20 with methylmagnesium
bromide and ethylmagnesium bromide led to alcohols 21a and
21b, respectively, in very high yields. While reaction of alcohol
21a with refluxing acetonitrile in the presence of concd H2SO4
led to the expected amide 22a in 81% yield, Ritter reaction of
O
4
TC4
Figure 2. Heteropolycyclic cage compounds with biological activity.

48
M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
H
H
H
O
6
13
12
H
5
8
7a
7
O
O
b or
c
O
d
1
a
R1
R1
CH3
11a
N
H
N
N
H
3
11
NH2
2
R2
14
12a, R1 = CH2C6H5
7
13a, R1 = CH2C6H5,R 2 = Me
, R1 = CH2CH2C6H5
H
, R1 = R2 = CH2C6H5
H
12b
h
13b
g
e or f
O
N
O
+
H
N
15
16
H
O
H
O
R1
N
R1
N
17a, R1 = Me
17b
18
, R1 = Et
Scheme 2. Reagents and conditions: (a) benzaldehyde or phenylacetaldehyde, NaBH3CN, AcOH, MeOH, rt, 18 h, 66% for 12a, 60% for 12b; (b) CH2O, NaBH3CN, AcOH,
acetonitrile, rt, 2 h, 91% for 13a; (c) benzyl chloride, K2CO3, NaI, acetonitrile, reflux, 24 h, 74% for 13b; (d) H2, Pd/C, 38 atm, 100 °C, 24 h, 82% yield; (e) HCO2H, 37% aq CH2O,
80 °C, 24 h, 92% for 17a; (f) acetaldehyde, NaBH3CN, AcOH, acetonitrile, rt, 2 h, 91% for 17b; (g) 1,5-dibromopentane, Et3N, DMF, 60 °C, 26 h, 46%; (h) propargyl bromide,
K2CO3, NaI, acetonitrile, reflux, 18 h, 34% of 15 and 40% of 16.
the alcohol group in 21b and loss of water the carbocation 24
O
H
NH2
O
may rearrange to a new carbocation, 27, through enone 25. Aceto-
nitrile attack to 27 followed by Ritter reaction of the remaining
alcohol may lead to the diamide 23 (Scheme 4).
N
NH2
NH
Acidic hydrolysis of amides 22a and 22b led to amines 28a and
28b in 87% and 90% yield, respectively. In view of the aforemen-
tioned problems for obtaining acetamide 22b, we developed an
alternative procedure for the synthesis of amine 28b from alcohol
21b. Thus, reaction of 21b with urea in trifluoroacetic acid led to
28b in 70% yield (Scheme 5).20
Starting from amines 28a and 28b, we prepared amines 29a,
29b, 30, 31a and 31b using similar procedures to those previ-
ously described starting from amine 7. Thus, reductive alkylation
of 28a with formaldehyde and formic acid or with acetaldehyde
and sodium cyanoborohydride led to 29a and 29b, respectively.
On the other hand, reductive alkylation of amine 28b with benz-
aldehyde and sodium cyanoborohydride in methanol afforded
secondary amine 30 in 81% yield. Finally, alkylation of 28b with
propargyl bromide led to a mixture of propargylamine 31a and
dipropargylamine 31b. Column chromatography of this mixture
furnished pure 31a and 31b in 35% and 22% yield, respectively
(Scheme 5).
N20C
Indantadol
H
H
O
O
a
NH2
N
H
NH2
7
19
O
Scheme 3. Indantadol and N20C, NMDA receptor antagonists bearing an aminoac-
etamide group and synthesis of analog 19. Reagents: (a) chloroacetamide, K2CO3,
NaI, acetonitrile, reflux, 18 h, 55% (brsm).
alcohol 21b furnished a mixture of two products, the expected
amide, 22b, isolated after column chromatography in 22% yield,
and the rearranged diamide 23, isolated in 13% yield. The forma-
tion of diamide 23 can be explained taking into account the mech-
anism of the Ritter reaction that involves the formation of a
carbocation at the bridgehead position. Thus, after protonation of
R1
R1
10
13
12
1
NHAc
9
11
5
O
a
c
11a
4a
H
CH3
NHAc
+
8
O
O
or b
O
7
OH
NHAc
4
6
21a, R1 = CH3
22a, R1 = CH3
20
23
21b, R1 = CH2CH3
22b, R1 = CH2CH3
H
H
CH3
+ H+
CH3
O H
CH3
- H+
+ H+
21b
O
O
- H2O
26
24
25
H
CH3
23
OH
27
Scheme 4. Reagents and conditions: (a) methylmagnesium bromide or ethylmagnesium bromide, anhyd toluene, 0 °C, overnight, 99% for 21a; (b) ethylmagnesium bromide,
anhyd toluene, 0 °C, overnight, 90% for 21b; (c) acetonitrile, H2SO4, reflux, 18 h; 81% for 22a; 22% for 22b and 13% for 23.

M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
49
R1
R1
CH3
a
b
O
O
O
R2
or c
NHAc
NH2
N
22a, R1 = CH3
28a
28b
, R1 = CH3
R2
29a, R2 = CH3
22b, R1 = CH2CH3
1
29b, R2 = CH2CH3
, R = CH2CH3
f
d
e
Et
O
Et
O
Et
O
N
OH
R2
N
H
21b
, R2 = H
31a
30
31b, R2
=
CH -C CH
2
Scheme 5. Reagents and conditions: (a) HCl concd, reflux, 18 h, 87% for 28a; 90% for 28b; (b) HCO2H, 37% aq CH2O, 80 °C, 24 h, 72% of 29a; (c) acetaldehyde, NaBH3CN, AcOH,
acetonitrile, rt, 18 h, 91% of 29b; (d) urea, CF3CO2H, 115 °C, 18 h, 70%; (e) benzaldehyde, NaBH3CN, AcOH, MeOH, rt, 18 h, 81%; (f) propargyl bromide, K2CO3, NaI, acetonitrile,
reflux, 18 h, 35% of 31a and 22% of 31b.
Table 1
The structures of all new compounds were confirmed by ele-
IC50 (l
M) values for (2-oxaadamant-1-yl)amines as NMDA antagonistsa,b
mental analysis or accurate mass measurement, IR, 1H NMR, 13C
NMR and mass spectral data.
Compound
Glutamate (100
lM)
NMDA (100 lM)
7
14
15
16
408 110
28 4.5
115 17
>500
35 6.8
6.0 1.3
34 2.3
>200
2.2. NMDA receptor antagonist activity
NMDA receptors mediate most of the important actions of gluta-
mate as a neurotransmitter in the brain. The development of NMDA
receptor antagonists has been intensive in the last decades due to
its neuroprotective actions.3a However, drug development in this
area has been hindered due to important side-effects in clinical tri-
als. Nonetheless, memantine, a non-competitive and low-affinity
NMDA receptor antagonist, is being used as a neuroprotective drug
in Alzheimer’s disease.21 Memantine is an un-competitive antago-
nist with fast on-off kinetics. Another important feature is that glu-
tamate has to be present to activate the NMDA receptor before
memantine exerts its action as antagonist. Amantadine, a drug that
is used in Parkinson’s disease (PD) has also some NMDA antagonist
activity and it has been proposed that part of its beneficial actions
on PD are due to its effect on NMDA receptors.22 To evaluate if
the synthesized compounds were able to antagonize NMDA recep-
tors, we have measured their effect on the increase in intracellular
17a
17b
18
28a
28b
29a
29b
Amantadine
Memantine
39 1.5
96 13
168 54
167 36
>500
7.7 1.1
22 3.1
358 130
55 12
3.8 0.3
14 1.1
30 1.0
98 26
>200
3.9 0.4
7.7 1.0
92 29
1.5 0.1
a
Functional data were obtained from primary cultures of cerebellar granule
neurons using the method described in the experimental section by measuring the
intracellular calcium concentration. Cells were challenged with glutamate (second
column) or NMDA (third column) as indicated. Data shown are means SEM of at
least three separate experiments carried out on three different batches of cultured
cells.
b
Compounds 12a, 12b, 13a, 13b, 19, 30, 31a and 31b were found to have low
potency as glutamate (IC50 >500
>200 M).
lM) and NMDA receptor antagonists (IC50
l
calcium evoked by glutamate or NMDA (both 100
lM, in the pres-
ence of 10 M of glycine) on rat cultured cerebellar granule neu-
l
rons.23 Compounds 14, 17a, 29a and 29b had IC50 values (NMDA)
that were in the micromolar order, similar to memantine (Table 1).
From the inspection of the results shown in Table 1 several
trends are evident. First, all the benzyl derivatives, 12a, 13a, 13b
and 30, and the phenethyl derivative 12b, were devoid of activity,
in striking contrast with NGP1-01, a low micromolar NMDA recep-
tor antagonist that features a benzyl group in its structure. Also,
propargyl derivatives were either inactive (compounds 16, 31a
2.3. MAO inhibitory activity
It is well known that rasagiline and selegiline, two clinically ap-
proved drugs for the treatment of Parkinson’s disease, display
monoaminooxidase (MAO) inhibitory activity.24 Taking into ac-
count that both compounds feature a propargylamine unit and that
structure–activity studies have shown that this moiety is associ-
ated with inhibition of MAO, we envisaged that our new deriva-
tives 15, 16, 31a and 31b, which also include propargyl
substituents, may also inhibit MAO. On the other hand, since
indantadol also shows MAO inhibitory activity,18 we tested our
analog 19. However, none of the tested compounds (tested at 10
and 31b) or had only
IC50 = 34 M). On the other hand, in the active compounds, the po-
tency increases on going from primary amines to N-alkylated and
N-dialkylated derivatives (e.g., series 7/14/17a or 28a/29a/29b),
the methyl or dimethyl substituted amines being optimum for
NMDA receptor antagonism.
a moderate activity (compound 15,
l
and 50 lM) showed MAO inhibitory activity. Selegiline (10 lM)
was used as a positive control, yielding a 85.5 5.5% inhibition of
MAO activity (n = 3, mean SEM).
Worthy of note, amantadine is more than 60 times less active
than its dimethyl derivative, memantine, as a NMDA receptor
antagonist. The positive effect of having methyl groups directly at-
tached to the polycyclic structure was also noticed in our previous
work with (2-oxaadamant-1-yl)amines,15 with the 3-methyl and
3-ethyl derivatives being much more active than the unsubstituted
compounds. However, among the products reported here, the
introduction of a 5-methyl or a 5-ethyl group did not increase
the activity (e.g., series 7/28a/ 28b or 17a/29a or 15/31a).
2.4. Trypanocidal activity
Human African trypanosomiasis (HAT) is caused by infection
with protozoan parasites of the Trypanosoma brucei species com-
plex. The disease is endemic in many parts of sub-Saharan Africa,
with upwards of 60 million people at risk. A process of antigenic
variation prevents elimination of the parasite by the immune sys-

50
M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
Table 2
Chemical shits (d) are reported in ppm related to internal tetra-
IC50 and IC90 (lM) values for oxapolycyclic cage amines that display inhibitory
methylsilane (TMS). Assignments given for the NMR spectra are
based on DEPT, COSY 1H/1H, HETCOR 1H/13C (HSQC and HMBC se-
quences for one bond and long range 1H/13C heterocorrelations,
respectively) and NOESY experiments for selected compounds.
For the MS and GC/MS analyses the sample was introduced directly
or through a gas chromatograph. For GC/MS analyses a 30-meter
column [5% diphenyl–95% dimethylpolysiloxane, conditions:
10 psi, initial temperature: 35 °C (2 min), then heating at a range
of 8 °C/min till 300 °C, then isothermic at 300 °C] was used. The
electron impact (70 eV) or chemical ionization (CH4) techniques
were used. Only significant ions are given: those with higher rela-
tive ratio, except for the ions with higher m/z values. Accurate
mass measurements were obtained using ESI technic. Absorption
values in the IR spectra (KBr) are given as wave-numbers (cmꢁ1).
Only the more intense bands are given. Column chromatography
was performed on silica gel 60 Å (35–70 mesh). For the thin layer
chromatography (TLC) aluminum-backed sheets with Silica Gel
60 F254 were used and spots were visualized with UV light and/
or 1% aqueous solution of KMnO4.
activity against cultured bloodstream form T. bruceia
Compound
IC50
(
l
M)
IC90 (lM)
30
31a
31b
Rimantadine
Memantine
13.86 0.4
15.23 1.35
14.63 1.18
7.04 0.27
13.75 1.26
19.95 0.42
25.59 0.94
24.08 1.07
13.97 1.68
21.43 0.55
a
Compounds were tested for in vitro activity against bloodstream form T. brucei
at a range of concentrations and IC50 and IC90 values established (Section 4.3). Data
are the mean of triplicate experiments SEM. Values for rimantadine and
memantine are shown for comparison.
tem, and the prospects of developing a vaccine are thought to be
remote. New drugs against HAT are therefore a major priority.
Drugs currently available against HAT are characterized by prob-
lems including toxicity, limited efficacy, cost and the need to
administer under medical supervision.
The anti-influenza virus drug rimantadine has been shown to be
active in vitro against bloodstream form T. brucei and other amino-
adamantane derivatives have even greater activity.8 Moreover,
very recently, we found that several (3-alkyl-2-oxadamant-1-yl)a-
mines showed significant activity against bloodstream form T. bru-
cei.15 We therefore investigated if the newly synthesized
oxapolycyclic cage amines reported here also displayed significant
activity against this parasite.
4.1.2. (1,2,3,5,6,7-Hexahydro-1,5:3,7-dimethano-4-benzoxonin-
3-yl)amine hydrochloride, 7ꢀHCl
A mixture of hydrazine 6 (9.19 g, 34.5 mmol)17 and PtO2
(10 mg) in absolute EtOH (400 mL) was hydrogenated at atmo-
spheric pressure and room temperature for three days. The suspen-
sion was filtered, the residue was washed with EtOH and
concentrated in vacuo. To the obtained white solid, water
(225 mL) was added, the solution was made basic with 2 N NaOH
and extracted with ethyl acetate (5 ꢂ 100 mL). The combined or-
ganic extracts were dried with anhyd Na2SO4, filtered and concen-
trated in vacuo to about 25 mL. An excess of Et2OꢀHCl was added
and the solution was cooled at 4 °C whereupon 7 precipitated as
its hydrochloride (7.17 g, 82% yield), mp 274ꢁ276 °C (EtOAc). IR
3407, 2941, 2924, 2848, 2725, 2642, 2546, 2365, 2064, 1606,
A total of 17 compounds were tested. Of these the oxapolycyclic
cage amines 7, 12a, 12b, 13a, 13b, 14, 15, 16, 17a, 19, 28a, 28b, 29a
and 29b displayed little or no inhibitory activity against cultured
bloodstream form T. brucei at 5 l lM). However,
g mLꢁ1 (15–20
compounds 30, 31a and 31b significantly inhibited parasite
growth, at levels comparable to rimantadine and memantine (Ta-
ble 2), and at least 10-fold lower than amantadine.8 As selectivity
is a highly desired goal in pharmacology, it is noteworthy that
the compounds with trypanocidal activity are devoid of NMDA
receptor antagonist activity.
1508, 1223, 1149, 1043, 1007, 962, 770 cmꢁ1 1H NMR 1.73 [dd,
.
J = 13.5 Hz, J0 = 1.0 Hz, 2H, 6(13)-Hexo], 1.98 [d, J = 12.5 Hz, 2H,
2(12)-Hexo], 2.24 [dm, J = 12.5 Hz, 2H, 2(12)-Hendo], 2.30 (dt,
J = 13.5 Hz, J0 = 6.0 Hz, 2H, 6(13)-Hendo], 3.27 [t, J = 6.0 Hz, 2H,
1(7)-H], 4.53 (t, J = 5.5 Hz, 1H, 5-H), 4.86 (s, 3H, mobile H), 7.13–
7.16 [m, 2H, 9(10)-H], 7.17–7.19 [m, 2H, 8(11)-H]. 13C NMR 33.1
[CH2, C6(13)], 38.0 [CH2, C2(12)], 39.3 [CH, C1(7)], 73.6 (CH, C5),
82.5 (C, C3), 128.2 [CH, C9(10)], 129.7 [CH, C8(11)], 145.9 [C,
C7a(C11a)]. MS (EI), m/z (%): 215 (Mꢀ+, 17), 157 (19), 156
([MꢁC3H7O]+, 100), 141 (C11H9þ, 51), 129 (23), 128 (20), 115
(22), 59 (28). Anal. Calcd for C14H17NOꢀHClꢀ0.25H20 (256.26): C,
65.62; H, 7.28; N, 5.47. Found: C, 65.67; H, 7.32; N, 5.67.
3. Conclusions
In summary, we have synthesized and fully characterized sev-
eral oxapolycyclic amines. None of the tested compounds showed
MAO inhibitory activity. Several derivatives were more potent than
amantadine against NMDA-induced calcium increase in cerebellar
granule neurons, and four compounds showed a very similar po-
tency to memantine. All the benzyl derivatives were devoid of
NMDA receptor antagonism activity, a trend previously observed
in the (2-oxaadamant-1-yl)amines.11 In contrast with our previous
work with (2-oxaadamant-1-yl)amines, introduction of an alkyl
group at C-5 does not increase the potency. However, the introduc-
tion of an ethyl group in C-5 increases the trypanocidal activity.
Work is in progress in order to evaluate the neuroprotective
activity of compounds 14, 17a, 17b, 29a and 29b in vitro. In addi-
tion, the synthesis and pharmacological evaluation of related poly-
cyclic cage amines containing a methylene unit instead of the
oxygen atom are currently in progress.
4.1.3. N-(1,2,3,5,6,7-Hexahydro-1,5:3,7-dimethano-4-
benzoxonin-3-yl)acetamide hydrochloride, 8
A mixture of alcohol 5 (1.44 g, 6.67 mmol), toluene (2 mL), ace-
tonitrile (0.68 mL, 13.4 mmol) and concentrated H2SO4 (1.20 mL,
22.5 mmol) was stirred under reflux for 18 h. The cold solution
was concentrated in vacuo, water (40 mL) was added to the residue
and extracted with EtOAc (4 ꢂ 20 mL). The combined organic ex-
tracts were washed with water (2 ꢂ 30 mL) and brine (30 mL),
dried with anhyd Na2SO4, filtered and concentrated in vacuo to
give an oily residue (1.34 g). Column chromatography (hexane/
EtOAc mixtures) gave, in order of elution 9 (63 mg, 3% yield), 10
(29 mg, 2%), 11 (45 mg, 3%), 5 (282 mg, 20%) and the title acetam-
ide, 8 (810 mg, 47%).
4. Experimental
4.1. Chemistry
Compound 8, mp 200ꢁ201 °C (CH2Cl2). IR 3289, 3057, 3021,
2929, 2912, 2876, 2836, 1669, 1663, 1655, 1541, 1534, 1522,
1492, 1450, 1435, 1390, 1369, 1352, 1335, 1300, 1276, 1248,
4.1.1. General
Melting points were determined in open capillary tubes. Unless
otherwise stated, NMR spectra were recorded in CD3OD in the fol-
lowing spectrometers: 1H NMR (500 MHz), 13C NMR (75.4 MHz).
1215, 1196, 1169, 1112, 1072, 1036, 995, 865, 756, 699 cmꢁ1 1H
.
NMR (CDCl3) 1.69 [d, J = 13.0 Hz, 2H, 6(13)-Hexo], 1.93 (s, 3H,

M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
51
COCH3), 2.22 [dd, J = 12.5 Hz, J0 = 5.5 Hz, 2H, 2(12)-Hendo], 2.28 [dt,
J = 13.0 Hz, J0 = 5.5 Hz, 2H, 6(13)-Hendo], 2.48 [d, J = 13.0 Hz, 2H,
2(12)-Hexo], 3.12 [br s, 2H, 1(7)-H], 4.44 (t, J = 5.5 Hz, 1H, 5-H),
5.72 (s, 1H, NH), 7.11 [s, 4H, 9(10)-H and 8(11)-H]. 13C NMR
(CDCl3) 24.4 (CH3, COCH3), 32.8 [CH2, C6(13)], 37.8 [CH2, C2(12)],
38.5 [CH, C1(7)], 71.4 (CH, C5), 82.3 (C, C3), 126.6 [CH, C9(10)],
128.4 [CH, C8(11)], 145.5 [C, C7a(C11a)], 168.3 (C, CO). MS (EI),
m/z (%): 258 (13), 257 (Mꢀ+, 71), 198 (29), 180 (17), 157 (26), 156
(100), 155 (30), 142 (22), 141 (61), 129 (42), 128 (40), 115 (32),
43 (22). Anal. Calcd for C16H19NO2 (257.33): C, 74.68; H, 7.44; N,
5.44. Found: C, 74.51; H, 7.51; N, 5.43.
was extracted with Et2O (4 ꢂ 15 mL). The combined organic ex-
tracts were washed with 2 N NaOH (3 ꢂ 25 mL), brine
(2 ꢂ 25 mL), dried with anhyd Na2SO4, filtered and concentrated
in vacuo. The residue was taken in EtOAc and the amine 12a was
precipitated as its hydrochloride (225 mg, 66% yield) by adding
an excess of Et2OꢀHCl. The analytical sample was obtained by crys-
tallization from EtOAc, mp 275ꢁ276 °C. IR 3100–2300 (max. at
2952, 2926, 2784, 2687, 2612, 2548, 2366), 1564, 1495, 1456,
1437, 1360, 1335, 1302, 1200, 1075, 1040, 1004, 966, 774, 761,
700 cmꢁ1 1H NMR 1.78 [d, J = 14.0 Hz, 2H, 6(13)-Hexo], 2.09 [d,
.
J = 12.5 Hz, 2H, 2(12)-Hexo], 2.37 [dt, J = 13.5 Hz, J0 = 5.5 Hz, 2H,
6(13)-Hendo], 2.41–2.45 (m, 2 H, 2(12)-Hendo], 3.34 [t, J = 5.5 Hz,
2H, 1(7)-H], 4.29 (s, 2H, CH2–C6H5), 4.63 (t, J = 5.5 Hz, 1H, 5-H),
7.16 [m, 2H, 9(10)-H], 7.21 [m, 2H, 8(11)-H], 7.44–7.48 (complex
signal, 3H, Ar-Hmeta and Ar-Hpara), 7.51 (dd, J = 7.5 Hz, J = 2.0 Hz,
2H, Ar-Hortho). 13C NMR 33.2 [CH2, C6(13)], 36.1 [CH2, C2(12)],
39.3 [CH, C1(7)], 45.3 (CH2, CH2–C6H5), 74.1 (CH, C5), 87.0 (C,
C3), 128.3 [CH, C9(10)], 129.6 [CH, C8(11)], 130.2 (CH, Ar-Cmeta),
130.5 (CH, Ar-Cpara), 131.1 (CH, Ar-Cortho), 132.7 (C, Ar-Cipso),
145.9 [C, C7a(C11a)]. MS (EI), m/z (%): 306 ([M+H]+, 6), 305 (Mꢀ+,
4), 150 (36), 149 (30), 129 (19), 128 (16), 115 (17), 91 (100), 65
(22). Anal. Calcd for C21H23NOꢀHCl (341.88): C, 73.78; H, 7.08; N,
4.10; Cl, 10.37. Found: C, 73.82; H, 7.29; N, 4.01; Cl, 9.89.
1,2,3,5,6,7-Hexahydro-3-(p-tolyl)-1,5:3,7-dimethano-3-4-ben-
zoxonin, 9, mp 173ꢁ174 °C (Et2O). IR 3042, 3017, 2922, 2907,
2866, 2835, 1509, 1493, 1452, 1431, 1334, 1322, 1284, 1230,
1213, 1196, 1182, 1099, 1069, 1037, 1013, 968, 903, 810, 784,
767, 717 cmꢁ1. 1H NMR (CDCl3) 1.80 [d, J = 13.0 Hz, 2H, 6(13)-Hexo],
2.14 [complex signal, 4H, 2(12)-Hexo and 2(12)-Hendo], 2.33 (s, 3H,
CH3), 2.37 [overlapped dt, J = 12.5 Hz, J0 = 6.0 Hz, 2H, 6(13)-Hendo],
3.15 [m, 2H, 1(7)-H], 4.53 (t, J = 5.5 Hz, 1H, 5-H), 7.13–7.19 [com-
plex signal, 6H, 9(10)-H, 8(11)-H and Ar-3(5)-H], 7.33 [dm,
J = 8.0 Hz, 2H, Ar-2(6)-H]. 13C NMR (CDCl3) 21.0 (CH3, Ar-CH3),
33.2 [CH2, C6(13)], 39.3 [CH, C1(7)], 40.1 [CH2, C2(12)], 69.2 (CH,
C5), 72.0 (C, C3), 123.5 [CH, Ar-C2(6)], 126.5 [CH, C9(10)], 128.5
[CH, C8(11)], 128.8 [CH, Ar-C3(5)], 135.9 (C, Ar-C4), 146.4 [C,
C7a(C11a)], 146.9 (C, Ar-C1). MS (EI), m/z (%): 291 (6), 290 (Mꢀ+,
27), 156 (100), 141 (43), 119 (25), 91 (18). Anal. Calcd for
C21H22O (290.41): C, 86.85; H, 7.64. Found: C, 86.62; H, 7.76.
1,2,3,5,6,7-Hexahydro-1,5:3,7-dimethano-4-benzoxonin-3-yl
acetate, 10, mp 99ꢁ100 °C (Et2O). IR 3019, 2945, 2926, 2851, 1728,
1493, 1450, 1438, 1374, 1326, 1279, 1254, 1210, 1197, 1117, 1087,
1062, 1048, 1030, 1019, 977, 960, 937, 764, 741, 699 cmꢁ1. 1H NMR
(CDCl3) 1.67 [dd, J = 13.5 Hz, J0 = 1.5 Hz, 2H, 6(13)-Hexo], 2.05 (s, 3H,
COCH3), 2.21–2.26 [m, 2H, 2(12)-Hendo], 2.32 [dt, J = 13.5 Hz,
J0 = 5.5 Hz, 2H, 6(13)-Hendo], 2.59 [d, J = 12.5 Hz, 2H, 2(12)-Hexo],
3.20 [t, J = 6.0 Hz, 2H, 1(7)-H], 4.61 (t, J = 5.5 Hz, 1H, 5-H), 7.13 [s,
4H, 9(10)-H and 8(11)-H]. 13C NMR (CDCl3) 22.3 (CH3, COCH3),
32.5 [CH2, C6(13)], 37.1 [CH2, C2(12)], 39.0 [CH, C1(7)], 73.6 (CH,
C5), 102.1 (C, C3), 126.8 [CH, C9(10)], 128.5 [CH, C8(11)], 145.2
[C, C7a(C11a)], 168.5 (C, CO). MS (EI), m/z (%): 258 (Mꢀ+, 14), 216
(14), 198 (75), 157 (26), 156 (100), 141 (45), 129 (56), 128 (40),
115 (34), 43 (22). Anal. Calcd for C16H18O3 (258.32): C, 74.40; H,
7.02. Found: C, 74.58; H, 7.12.
4.1.5. N-(2-Phenylethyl)-(1,2,3,5,6,7-hexahydro-1,5:3,7-
dimethano-4-benzoxonin-3-yl)amine hydrochloride, 12bꢀHCl
To a solution of amine 7ꢀHCl (251 mg, 1.00 mmol) in MeOH
(20 mL), NaBH3CN (95%, 135 mg, 2.04 mmol), AcOH (0.3 mL) and
phenylacetaldehyde (120 mg, 1.00 mmol) were added and the
mixture was stirred at room temperature for 18 h. After concentra-
tion to dryness, water (15 mL) was added to the residue and the
mixture was extracted with Et2O (4 ꢂ 20 mL). The combined or-
ganic extracts were washed with 2 N NaOH (3 ꢂ 20 mL), brine
(2 ꢂ 20 mL), dried with anhyd Na2SO4, filtered and concentrated
in vacuo to give a residue which was subjected to column chroma-
tography (silica gel, hexane/EtOAc 9:1) furnishing amine 12b
(192 mg, 60% yield). From a solution of 12b in EtOAc, its corre-
sponding hydrochloride was precipitated by adding an excess of
Et2OꢀHCl. The analytical sample was obtained by crystallization
from MeOH/Et2O, mp 280ꢁ281 °C. IR 2951, 2921, 2900, 2786,
2753, 2720, 2439, 2362, 2340, 1579, 1484, 1456, 1361, 1332,
1218, 1100, 1065, 1041, 1004, 972, 763, 748, 702 cmꢁ1 1H NMR
.
11-endo-Acetoxi-5,6,8,9-tetrahydro-5,9-propanobenzocyclo-
hepten-7-one, 11, mp 186ꢁ187 °C (Et2O). IR 3021, 2931, 1726,
1691, 1493, 1455, 1428, 1403, 1374, 1247, 1216, 1202, 1180,
1.74 [dd, J = 14.0 Hz, J0 = 1.5 Hz, 2H, 6(13)-Hexo], 2.02 [d,
J = 13.0 Hz, 2H, 2(12)-Hexo], 2.30–2.36 [complex signal, 4H, 6(13)-
Hendo and 2(12)-Hendo], 3.00 (m, 2H, CH2–C6H5), 3.32 [complex sig-
nal, 4H, CH2–CH2–C6H5 and 1(7)-H], 4.58 (t, J = 5.5 Hz, 1H, 5-H),
7.14 [m, 2H, 9(10)-H], 7.18 [m, 2H, 8(11)-H], 7.27 (tt, J = 7.5 Hz,
J0 = 1.5 Hz, 1H, Ar-Hpara), 7.30 (dm, J = 7.5 Hz, 2H, Ar-Hortho), 7.34
(tm, J = 7.5 Hz, 2H, Ar-Hmeta). 13C NMR 33.1 [CH2, C6(13)], 33.6
(CH2, CH2–C6H5), 36.1 [CH2, C2(12)], 39.2 [CH, C1(7)], 42.5 (CH2,
CH2–CH2–C6H5), 74.0 (CH, C5), 86.7 (C, C3), 128.3 [CH, C9(10)
and Ar-Cpara], 129.66 [CH, C8(11)], 129.72 (CH, Ar-Cortho), 129.9
(CH, Ar-Cmeta), 137.8 (C, Ar-Cipso), 145.9 [C, C7a(C11a)]. MS (EI),
m/z (%): 320 ([M+H]+, 1), 319 (Mꢀ+, 1), 230 (20), 229 (100), 228
(27), 199 (73), 157 (39), 141 (22), 129 (49), 128 (19), 115 (25),
105 (23), 104 (33), 91 (28). Anal. Calcd for C22H25NOꢀHCl
(355.91): C, 74.24; H, 7.36; N, 3.94; Cl, 9.96. Found: C, 73.88; H,
7.39; N, 3.95; Cl, 10.17.
1092, 1068, 1036, 1023, 978, 933, 772 cmꢁ1 1H NMR (CDCl3)
.
2.01 (s, 3H, COCH3), 2.09 [dt, J = 15.0 Hz, J0 = 3.5 Hz, 2H, 10(12)-Hen-
do], 2.16 [dt, J = 15.0 Hz, J0 = 4.5 Hz, 2H, 10(12)-Hexo], 2.66 [dd,
J = 17.5 Hz, J0 = 4.5 Hz, 2H, 6(8)-Hexo], 2.90 [ddm, J = 17.5 Hz,
J0 = 4.0 Hz, 2H, 6(8)-Hendo], 3.22 [pseudo quint, J = 4.5 Hz, 2H,
5(9)-H], 5.24 (quint, J = 4.5 Hz, 1H, 11-H), 7.18 [m, 2H, 1(4)-H],
7.21 [m, 2H, 2(3)-H]. 13C NMR (CDCl3) 21.5 (CH3, COCH3), 34.9
[CH2, C10(12)], 39.6 [CH, C5(9)], 48.6 [CH2, C6(8)], 72.1 (CH, C11),
127.6 [CH, C2(3)], 128.5 [CH, C1(4)], 143.8 [C, C4a(C9a)], 170.1
(C, COCH3), 210.5 (C, C7). MS (EI), m/z (%): 258 (Mꢀ+, 0.2), 198
([MꢁAcOH]ꢀ+, 21), 156 (17), 142 (16), 141 (100), 129 (28), 128
(28), 115 (21), 43 (16). Anal. Calcd for C16H18O3 (258.32): C,
74.40; H, 7.02. Found: C, 74.10; H, 7.19.
4.1.4. N-Benzyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-
benzoxonin-3-yl)amine hydrochloride, 12aꢀHCl
4.1.6. N-Benzyl-N-methyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-
dimethano-4-benzoxonin-3-yl)amine hydrochloride, 13aꢀHCl
To a solution of 12aꢀHCl (341 mg, 1.00 mmol) in acetonitrile
(10 mL), formaldehyde (0.78 mL, 37 wt % in water solution,
10 mmol) and NaBH3CN (198 mg, 3.00 mmol) were added. The
mixture was stirred for 30 min at room temperature, acetic acid
(0.4 mL) was added and the mixture was stirred at room tempera-
To a solution of amine 7ꢀHCl (251 mg, 1.00 mmol) in MeOH
(10 mL), NaBH3CN (95%, 135 mg, 2.04 mmol), AcOH (0.3 mL) and
benzaldehyde (106 mg, 1.00 mmol) were added and the mixture
was stirred at room temperature for 18 h. After concentration to
dryness, water (10 mL) was added to the residue and the mixture

52
M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
ture for 2 h. An additional portion of NaBH3CN (198 mg,
3.00 mmol) was added and the mixture was further stirred at room
temperature for 2 h. The mixture was concentrated to dryness, 2 N
NaOH (10 mL) was added and the suspension was extracted with
CH2Cl2 (3 ꢂ 15 mL). The combined organic phases were washed
with H2O (2 ꢂ 10 mL), dried with anhyd Na2SO4, filtered and con-
centrated in vacuo to give 13a (289 mg, 91% yield) as a white solid.
Its hydrochloride was obtained by adding an excess of Et2OꢀHCl to
a solution of the amine in EtOAc, followed by filtration of the
formed precipitate. The analytical sample was obtained by crystal-
lization from MeOH/CH2Cl2, mp 235ꢁ236 °C. IR 3500–2100 (max.
at 3428, 3031, 2945, 2933, 2845, 2399, 2304), 1624, 1496, 1456,
1436, 1410, 1396, 1361, 1333, 1306, 1222, 1197, 1176, 1131,
1079, 1059, 1033, 973, 958, 910, 868, 788, 778, 759, 737, 706,
699 cmꢁ1. 1H NMR 1.79 [dd, J = 14.0 Hz, J’ = 1.0 Hz, 2H, 6(13)-Hexo],
2.18–2.48 [br signal, 6H, 2(12)-Hexo, 2(12)-Hendo and 6(13)-Hendo],
2.74 (s, 3H, CH3–N), 3.40 [br s, 2H, 1(7)-H], 3.96 (br signal, 1H,
CHa–C6H5), 4.72 (t, J = 5.5 Hz, 1H, 5-H), 4.88 (br signal, 1H, CHb–
C6H5), 7.17 [m, 2H, 9(10)-H], 7.23 [m, 2H, 8(11)-H], 7.48–7.53
(complex signal, 5H, Ar-H benzyl). 13C NMR 33.0 [CH2, C6(13)],
33.4 (CH3, CH3–N), 33.8 [br CH2, C2(12)], 39.2 [CH, C1(7)], 54.8
(CH2, CH2–C6H5), 75.0 (CH, C5), 92.3 (C, C3), 128.4 [CH, C9(10)],
129.7 [CH, C8(11)], 130.3 (CH, Ar-Cmeta), 131.1 (CH, Ar-Cpara),
131.3 (C, Ar-Cipso), 132.6 (CH, Ar-Cortho), 146.0 [C, C7a(C11a)]. MS
(EI), m/z (%): 319 (Mꢀ+, 18), 164 (14), 163 (100), 162 (25), 91 (38).
Anal. Calcd for C22H25NOꢀHClꢀ0.25H2O (360.41): C, 73.32; H, 7.41;
N, 3.89; Cl, 9.84. Found: C, 73.30; H, 7.44; N, 4.00; Cl, 9.69.
vents from the filtrate in vacuo followed by crystallization of the
residue from MeOH/Et2O gave 14ꢀHClꢀ0.25H2O (287 mg, 82% yield),
mp 265–266 °C. IR 3500–2400 (max. at 3429, 2945, 2918, 2840,
2798, 2754, 2682, 2485, 2412), 1624, 1481, 1453, 1336, 1227,
1198, 1163, 1089, 1072, 1042, 971, 758 cmꢁ1 1H NMR 1.74 [dd,
.
J = 14.0 Hz, J0 = 1.0 Hz, 2H, 6(13)-Hexo], 2.00 [d, J = 13.0 Hz, 2H,
2(12)-Hexo], 2.24–2.28 [m, 2H, 2(12)-Hendo], 2.32 (dt, J = 13.5 Hz,
J0 = 5.5 Hz, 2H, 6(13)-Hendo], 2.67 (s, 3H, CH3–N), 3.30–3.33 [br t,
J = 5.5 Hz, 2H, 1(7)-H], 4.57 (t, J = 5.5 Hz, 1H, 5-H), 7.14–7.17 [m,
2H, 9(10)-H], 7.18–7.20 [m, 2H, 8(11)-H]. 13C NMR 25.7 (CH3,
CH3–N), 33.1 [CH2, C6(13)], 35.8 [CH2, C2(12)], 39.1 [CH, C1(7)],
74.0 (CH, C5), 85.9 (C, C3), 128.3 [CH, C9(10)], 129.7 [CH, C8(11)],
145.9 [C, C7a(C11a)]. MS (EI), m/z (%): 230 ([M+H]+, 21), 229 (Mꢀ+,
15), 156 (22), 141 (28), 129 (18), 115 (14), 75 (15), 74 (100), 73
(74). Anal. Calcd for C15H19NOꢀHClꢀ0.25H20 (270.29): C, 66.66; H,
7.64; N, 5.18; Cl, 13.12. Found: C, 66.67; H, 7.66; N, 5.23; Cl, 13.48.
4.1.9. N-Propargyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-
benzoxonin-3-yl)amine hydrochloride, 15ꢀHCl and N,N-dipro-
pargyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-benzo-
xonin-3-yl)amine hydrochloride, 16ꢀHCl
A suspension of 7ꢀHCl (275 mg, 1.09 mmol), K2CO3 (180 mg,
1.28 mmol), propargyl bromide (0.16 mL, 80% solution in toluene,
1.44 mmol) and NaI (15 mg, 0.1 mmol) in acetonitrile (15 mL)
was heated under reflux for 18 h. After concentration to dryness
in vacuo, the residue was taken in CH2Cl2 (20 mL) and the solution
was washed with water (3 ꢂ 10 mL). The organic layer was dried
with anhyd Na2SO4, filtered and concentrated in vacuo to give a
residue which was subjected to column chromatography (hex-
ane/EtOAc mixtures) affording 16 (hexane/EtOAc 97:3, 129 mg,
40% yield) and 15 (hexane/EtOAc 95:5, 108 mg, 34% yield). The
hydrochlorides of 15 and 16 were obtained by adding an excess
of Et2OꢀHCl to a solution of the amine in EtOAc, followed by filtra-
tion of the formed precipitate. 15: mp 230–231 °C (EtOAc/Et2O). IR
3500–2450 (max. at 3448, 3285, 3199, 2994, 2919, 2844, 2761,
2734, 2699, 2647, 2580, 2392), 2123, 1569, 1455, 1434, 1336,
1218, 1198, 1070, 1050, 1039, 1018, 1007, 964, 760, 740,
4.1.7. N,N-Dibenzyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-
4-benzoxonin-3-yl)amine hydrochloride, 13bꢀHCl
A suspension of 12aꢀHCl (200 mg, 0.59 mmol), K2CO3 (70 mg,
0.5 mmol), benzyl chloride (0.11 mL, 1.00 mmol) and NaI (65 mg,
0.43 mmol) in acetonitrile (10 mL) was heated under reflux for
24 h. To the cold mixture, AcOEt (30 mL) was added and the solu-
tion was washed with water (3 ꢂ 20 mL). The organic layer was
dried with anhyd Na2SO4, filtered and concentrated in vacuo to
give a residue which was subjected to column chromatography
(hexane/EtOAc 99:1) gave 13b (172 mg, 74% yield). Its hydrochlo-
ride was obtained by adding an excess of Et2OꢀHCl to a solution of
the amine in EtOAc, followed by filtration of the formed precipi-
tate. The analytical sample was obtained by crystallization from
MeOH/Et2O, mp 268–270 °C. IR 3500–2300 (max. at 3356, 3041,
2936, 2916, 2843, 2471), 1625, 1492, 1458, 1333, 1225, 1198,
705 cmꢁ1 1H NMR 1.74 [d, J = 14.0 Hz, 2H, 6(13)-Hexo], 1.99 [d,
.
J = 13.0 Hz, 2H, 2(12)-Hexo], 2.29–2.35 [complex signal, 4H, 2(12)-
Hendo and 6(13)-Hendo], 3.20 (t, J = 2.5 Hz, 1H, CH2C„CH), 3.31 [t,
J = 5.5 Hz, 2H, 1(7)-H], 4.03 (d, J = 2.5 Hz, 2H, CH2C„CH), 4.58 (t,
J = 5.5 Hz, 1H, 5-H), 7.15 [m, 2H, 9(10)-H], 7.19 [m, 2H, 8(11)-H].
13C NMR 30.6 (CH2, CH2C„CH), 33.0 [CH2, C6(13)], 36.0 [CH2,
C2(12)], 39.1 [CH, C1(7)], 74.2 (CH, CH2C„CH), 75.3 (CH, C5),
78.6 (C, CH2C„CH), 86.8 (C, C3), 128.4 [CH, C9(10)], 129.7 [CH,
C8(11)], 145.8 [C, C7a(C11a)]. MS (EI), m/z (%): 253 (Mꢀ+, 18), 252
(14), 238 (36), 210 (19), 157 (48), 156 (63), 155 (32), 143 (25),
142 (32), 141 (100), 129 (76), 128 (70), 115 (66), 97 (87), 96
(63). Anal. Calcd for C17H19NOꢀ1.05HCl (291.63): C, 70.02; H,
6.93; N, 4.80; Cl, 12.76. Found: C, 69.84; H, 7.01; N, 4.72; Cl,
12.81. Compound 16: mp 172–173 °C. IR 3276, 3227, 3167, 2930,
2911, 2429, 2221, 2117, 1731, 1491, 1452, 1433, 1358, 1335,
1260, 1218, 1135, 1122, 1075, 1065, 1034, 967, 905, 767, 729,
694 cmꢁ1. 1H NMR 1.67 [dd, J = 13.5 Hz, J0 = 1.5 Hz, 2H, 6(13)-Hexo],
2.06 [d, J = 13.5 Hz, 2H, 2(12)-Hexo], 2.22–2.27 [complex signal, 4H,
2(12)-Hendo and 6(13)-Hendo], 2.79 (s, 2H, 2CH2C„CH), 3.22 [t,
J = 6.0 Hz, 2H, 1(7)-H], 3.97 (s, 4H, 2CH2C„CH), 4.48 (t, J = 5.5 Hz,
1H, 5-H), 7.11 [m, 2H, 9(10)-H], 7.15 [m, 2H, 8(11)-H]. 13C NMR
33.5 [CH2, C6(13)], 36.17 (CH2, 2CH2C„CH), 36.21 [CH2, C2(12)],
39.8 [CH, C1(7)], 73.7 (CH, C5), 76.5 (CH, 2CH2C„CH), 78.7 (C,
2CH2C„CH), 88.7 (C, C3), 128.0 [CH, C9(10)], 129.5 [CH, C8(11)],
146.6 [C, C7a(C11a)]. MS (EI), m/z (%): 291 (Mꢀ+, 12), 290 (20),
276 (50), 209 (24), 195 (18), 181 (16), 169 (28), 168 (18), 167
(18), 157 (60), 155 (39), 154 (20), 153 (23), 143 (34), 142 (39),
141 (90), 135 (33), 134 (38), 130 (20), 129 (100), 128 (76), 127
(24), 116 (20), 115 (77), 91 (24). Accurate mass measurement
1078, 1064, 1041, 964, 853, 747, 696 cmꢁ1 1H NMR 1.81 [d,
.
J = 13.5 Hz, 2H, 6(13)-Hexo], 2.36–2.50 [complex signal, 4H, 2(12)-
Hexo and 6(13)-Hendo], 2.60 (br s, 2H, 2(12)-Hendo], 3.43 [br s, 2H,
1(7)-H], 4.22 (d, J = 12.5 Hz, 2H, 2CHa–C6H5), 4.80 (br s, 1H, 5-H),
4.89 (d, J = 12.5 Hz, 2H, 2CHb–C6H5), 7.13–7.20 [complex signal,
6H, 9(10)-H and 2 Ar-Hortho], 7.21–7.32 [complex signal, 6H,
8(11)-H and 2 Ar-Hmeta], 7.33–7.40 (br signal, 2H, 2 Ar-Hpara). 13C
NMR 33.0 [CH2, C6(13)], 34.3 [CH2, C2(12)], 39.3 [CH, C1(7)], 54.2
(CH2, 2CH2–C6H5), 75.0 (CH, C5), 94.8 (C, C3), 128.4 [CH, C9(10)],
129.7 [CH, C8(11)], 130.0 [CH, 2 Ar-Cmeta], 130.6 (CH, 2 Ar-Cpara),
132.4 (CH, 2 Ar-Cortho), 132.0 (C, 2 Ar-Cipso), 146.1 [C, C7a(C11a)].
MS (EI), m/z (%): 396 ([M+H]+, 6), 395 (Mꢀ+, 13), 239 (28), 148
(42), 129 (20), 106 (28), 91 (100). Anal. Calcd for
C28H29NOꢀHClꢀ0.5H2O (441.01): C, 76.26; H, 7.09; N, 3.18; Cl,
8.04. Found: C, 76.36; H, 7.11; N, 3.23; Cl, 8.06.
4.1.8. N-Methyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-
benzoxonin-3-yl)amine hydrochloride, 14ꢀHCl
A suspension of 13aꢀHClꢀ0.25H2O (465 mg, 1.29 mmol) and 5%
Pd/C (50% in water, 100 mg) in absolute EtOH (50 mL) was hydro-
genated at 38 atm and 100 °C for 24 h. The suspension was filtered,
the residue was washed with EtOH and to the combined organic
filtrates an excess of Et2OꢀHCl was added. Evaporation of the sol-

M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
53
(ESI+) calcd for [C20H22NO+H]+: 292.1696. Found: 292.1689. Anal.
Calcd for the free base C20H21NO (291.39): C, 82.44; H, 7.26; N,
4.81. Found: C, 82.12; H, 7.39; N, 4.58.
271 (Mꢀ+, 6), 141 (19), 129 (30), 128 (19), 116 (38), 115 (100),
100 (46), 72 (19). Anal. Calcd for C18H25NOꢀC4H6O6ꢀ1.5H2O
(448.51): C, 58.92; H, 7.64; N, 3.12. Found: C, 58.68; H, 7.76; N,
2.79.
4.1.10. N,N-Dimethyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-dimeth-
ano-4-benzoxonin-3-yl)amine hydrochloride, 17aꢀHCl
4.1.12. N-(1,2,3,5,6,7-Hexahydro-1,5:3,7-dimethano-4-benzo-
xonin-3-yl)piperidine hydrochloride, 18ꢀHCl
To a cold (0 °C) solution of 7 (503 mg, 2.00 mmol) in Et2O
(10 mL), formaldehyde (3.5 mL, 37 wt % in water solution,
44.4 mmol) and, dropwise, formic acid (3.0 mL, 80 mmol) were
added and the mixture was stirred at 80 °C for 24 h. The mixture
was allowed to cool to room temperature, was diluted with Et2O
(20 mL), 5 N NaOH (10 mL) was added dropwise and the suspen-
sion was stirred at room temperature for 15 min. The organic layer
was separated and the aqueous phase was extracted with Et2O
(4 ꢂ 20 mL). The combined organic phases were washed with brine
(30 mL), dried with anhyd Na2SO4, filtered and concentrated in va-
cuo to give 17a (447 mg, 92% yield). Its hydrochloride was obtained
by adding an excess of Et2OꢀHCl to a solution of the amine in EtOAc,
followed by filtration of the formed precipitate. The analytical sam-
ple was obtained by crystallization from MeOH/Et2O, mp 263–
264 °C. IR 3500–2300 (max. at 3370, 3320, 3016, 2961, 2946,
2915, 2844, 2612, 2583, 2507, 2401), 1616, 1479, 1452, 1433,
1390, 1361, 1335, 1222, 1196, 1166, 1154, 1122, 1074, 1051,
To a solution of 7ꢀHCl (590 mg, 2.37 mmol) in DMF (8.0 mL), an-
hyd Et3N (1.32 mL, 9.45 mmol) was added and the suspension was
stirred at room temperature for 2 h. 1,5-Dibromopentane (0.53 mL,
3.88 mmol) was added and the mixture was heated at 60 °C for
26 h. To the cold mixture, water (30 mL) was added and the solu-
tion was extracted with EtOAc (4 ꢂ 30 mL). The combined organic
extracts were washed with water (5 ꢂ 15 mL), dried with anhyd
Na2SO4 and filtered. Excess of Et2OꢀHCl was added and the solution
was concentrated in vacuo to dryness to give 18ꢀHCl (348 mg, 46%
yield). The analytical sample of 18ꢀHCl was obtained by crystalliza-
tion from MeOH/Et2O, mp 187ꢁ188 °C. IR 3016, 2946, 2914, 2856,
2643, 2599, 2543, 2480, 2459, 2375, 1492, 1452, 1440, 1426, 1331,
1220, 1198, 1113, 1098, 1077, 1048, 1029, 1014, 970, 896, 753,
674 cmꢁ1 1H NMR 1.54 (br s, 1H, piperidine 4-Hax), 1.74 [dd,
.
J = 14.0 Hz, J0 = 1.0 Hz, 2H, 6(13)-Hexo], 1.76–1.99 [complex signal,
5H, piperidine 4-Heq, 3(5)-Hax and 3(5)-Heq], 2.14 [d, J = 12.5 Hz,
2H, 2(12)-Hexo], 2.30–2.35 [complex signal, 4H, 2(12)-Hendo and
6(13)-Hendo], 2.96 [br s, 2H, piperidine 2(6)-Hax], 3.34 [t, J = 5.5 Hz,
2H, 1(7)-H], 3.71 [br s, 2H, piperidine 2(6)-Heq], 4.63 (t, J = 5.5 Hz,
1H, 5-H), 7.15 [m, 2H, 9(10)-H], 7.19 [m, 2H, 8(11)-H]. 13C NMR
23.4 (CH2, piperidine C4), 24.5 [CH2, piperidine C3(5)], 33.1 [CH2,
C6(13)], 33.9 [CH2, C2(12)], 39.1 [CH, C1(7)], 47.7 [CH2, piperidine
C2(6)], 74.6 (CH, C5), 91.4 (C, C3), 128.4 [CH, C9(10)], 129.7 [CH,
C8(11)], 146.0 [C, C7a(C11a)]. MS (EI), m/z (%): 283 (Mꢀ+, 20), 141
(15), 129 (18), 128 (27), 127 (100), 115 (13), 112 (18). Anal. Calcd
for C19H25NOꢀHCl (319.87): C, 71.34; H, 8.19; N, 4.38; Cl, 11.08.
Found: C, 70.91; H, 8.28; N, 4.27; Cl, 10.96.
1030, 1003, 965, 956, 909, 790, 613 cmꢁ1 1H NMR 1.75 [dd,
.
J = 14.0 Hz, J0 = 1.0 Hz, 2H, 6(13)-Hexo], 2.14 [d, J = 13.0 Hz, 2H,
2(12)-Hexo], 2.23–2.27 [m, 2H, 2(12)-Hendo], 2.32 (dt, J = 13.5 Hz,
J0 = 5.5 Hz, 2H, 6(13)-Hendo], 2.85 (s, 6H, CH3–N), 3.34–3.37 [br t,
J = 5.5 Hz, 2H, 1(7)-H], 4.63 (t, J = 5.5 Hz, 1H, 5-H), 7.16 [m, 2H,
9(10)-H], 7.21 [m, 2H, 8(11)-H]. 13C NMR 32.9 [CH2, C6(13)], 33.4
[CH2, C2(12)], 36.8 (CH3, CH3–N), 39.0 [CH, C1(7)], 74.6 (CH, C5),
90.8 (C, C3), 128.3 [CH, C9(10)], 129.7 [CH, C8(11)], 145.8 [C,
C7a(C11a)]. MS (EI), m/z (%): 243 (Mꢀ+, 19), 141 (19), 129 (17),
128 (17), 115 (19), 87 (100), 72 (24). Anal. Calcd for
C16H21NOꢀHClꢀ0.5H2O (288.82): C, 66.54; H, 8.03; N, 4.85; Cl,
12.28. Found: C, 66.74; H, 8.10; N, 4.93; Cl, 11.93.
4.1.13. 2-[(1,2,3,5,6,7-Hexahydro-1,5:3,7-dimethano-4-
4.1.11. N,N-Diethyl-(1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-
4-benzoxonin-3-yl)amine (2R,3R)-tartrate, 17bꢀ(2R,3R)-tartrate
benzoxonin-3-yl)amino]acetamide hydrochloride, 19ꢀHCl
A suspension of 7ꢀHCl (190 mg, 0.75 mmol), K2CO3 (123 mg,
0.88 mmol), 2-chloroacetamide (93 mg, 0.94 mmol) and NaI
(15 mg, 0.1 mmol) in acetonitrile (10 mL), was heated under reflux
for 18 h and then it was concentrated in vacuo to dryness. CH2Cl2
(20 mL) was added to the residue, the organic solution was washed
with water (3 ꢂ 10 mL), was dried with anhyd Na2SO4, filtered and
concentrated in vacuo to give an oily residue. Column chromatog-
raphy (silica gel) gave starting amine 7 (hexane/EtOAc 4:6, 31 mg)
and acetamide 19 (EtOAc/MeOH 95/5, 91 mg, 55% yield based on
unrecovered starting material). Its hydrochloride was obtained by
adding an excess of Et2OꢀHCl to a solution of the amine in Et2O, fol-
lowed by filtration of the precipitated solid, mp 254–255 °C. IR
3600–2400 (max. at 3563, 3322, 3176, 3057, 2934, 2722, 2613,
2402), 1683, 1622, 1558, 1493, 1453, 1435, 1418, 1400, 1361,
To
a
solution of 7ꢀHCl (251 mg, 1.00 mmol) in methanol
(13 mL), NaBH3CN (95%, 145 mg, 2.19 mmol), AcOH (0.4 mL) and
acetaldehyde (0.33 mL, 5.9 mmol) were added and the mixture
was stirred at room temperature for 8 h. An additional portion of
NaBH3CN (95%, 77 mg, 1.16 mmol) and acetaldehyde (0.16 mL,
2.9 mmol) were added, the mixture was stirred at room tempera-
ture for 10 h and then it was concentrated in vacuo to dryness.
Water (20 mL) was added to the residue, the suspension was basi-
fied with 1 N NaOH (8 mL) and was extracted with EtOAc
(3 ꢂ 10 mL). The combined organic extracts were washed with
brine (2 ꢂ 10 mL), dried with anhyd Na2SO4, filtered and concen-
trated in vacuo to give 17b as an oil (246 mg, 91% yield). An analyt-
ical sample of the (2R,3R)-tartrate of 17b was obtained by adding
1 equiv of (2R,3R)-(+)-tartaric acid in MeOH (15 mL) to a solution
of 17b in EtOAc (15 mL), evaporation to dryness and crystallization
from 2-propanol, mp 167ꢁ168 °C. IR 3600–2500 (max. at 3321,
3277, 2926, 2857, 2666), 1733, 1579, 1417, 1335, 1306, 1264,
1335, 1304, 1219, 1197, 1075, 1039, 969, 759 cmꢁ1 1H NMR 1.74
.
[d, J = 13.5 Hz, 2H, 6(13)-Hexo], 1.99 [d, J = 13.0 Hz, 2H, 2(12)-Hexo],
2.28–2.34 [complex signal, 4H, 2(12)-Hendo and 6(13)-Hendo], 3.30
[t, J = 5.5 Hz, 2H, 1(7)-H], 3.90 (s, 2H, CH2CONH2), 4.57 (t,
J = 5.5 Hz, 1H, 5-H), 7.15 [m, 2H, 9(10)-H], 7.19 [m, 2H, 8(11)-H].
13C NMR 33.1 [CH2, C6(13)], 36.1 [CH2, C2(12)], 39.2 [CH, C1(7)],
42.0 (CH2, CH2CONH2), 74.1 (CH, C5), 86.5 (C, C3), 128.3 [CH,
C9(10)], 129.7 [CH, C8(11)], 145.9 [C, C7a(C11a)], 168.9 (C, CO).
MS (EI), m/z (%): 274 (6), 273 ([M+H]+, 10), 272 (Mꢀ+, 6), 256 (12),
231 (14), 230 (45), 229 (69), 228 (41), 201 (30), 200 (49), 199
(34), 158 (46), 157 (68), 156 (41), 155 (32), 143 (23), 142 (38),
141 (80), 130 (50), 129 (100), 128 (52), 117 (38), 116 (97), 115
(59), 99 (50). Anal. Calcd for C16H20N2O2ꢀHClꢀ0.75H2O (322.32): C,
59.62; H, 7.04; N, 8.69; Cl, 11.00. Found: C, 59.94; H, 6.96; N,
8.61; Cl, 10.95.
1216, 1135, 1076, 1067, 1034, 968, 901, 789, 772, 680 cmꢁ1 1H
.
NMR 1.39 (t, J = 7.5 Hz, 6H, 2CH2CH3), 1.74 [dd, J = 14.0 Hz,
J0 = 1.0 Hz, 2H, 6(13)-Hexo], 2.16 [d, J = 12.5 Hz, 2H, 2(12)-Hexo],
2.30–2.36 [complex signal, 4H, 6(13)-Hendo and 2(12)-Hendo],
3.30–3.38 [complex signal, 6H, 2CH2–CH3 and 1(7)-H], 4.40 (s, 2
H, 2CHOH tartaric acid), 4.63 (t, J = 5.5 Hz, 1H, 5-H), 7.15 [m, 2H,
9(10)-H], 7.20 [m, 2H, 8(11)-H]. 13C NMR 12.4 (CH3, CH2CH3),
33.0 [CH2, C6(13)], 34.0 [CH2, C2(12)], 39.1 [CH, C1(7)], 45.9
(CH2, 2CH2–CH3), 74.0 (CH, 2CHOH tartaric acid), 74.5 (CH, C5),
93.0 (C, C3), 128.3 [CH, C9(10)], 129.7 [CH, C8(11)], 146.0 [C,
C7a(C11a)], 176.5 (C, 2CO2H). MS (EI), m/z (%): 272 ([M+H]+, 13),

54
M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
4.1.14. 1,2,3,5,6,7-Hexahydro-5-methyl-1,5:3,7-dimethano-4-
benzo-xonin-3-ol, 21a
COCH3). MS (EI), m/z (%): 272 (20), 271 (Mꢀ+, 100), 253 (16), 212
(44), 198 (33), 197 (19), 194 (25), 170 (88), 169 (42), 157 (46),
156 (30), 155 (74), 142 (26), 129 (56), 128 (40), 115 (30). Anal. Calcd
for C17H21NO2ꢀ0.15CH2Cl2 (284.10): C, 72.51; H, 7.56; N, 4.93.
Found: C, 72.16; H, 7.54; N, 4.82.
To a flask containing anhyd toluene (100 mL) at 0 °C, methyl-
magnesium bromide (84 mL, 3 M in Et2O, 0.25 mol) was added.
Then, a solution of 20 (11.00 g, 51.4 mmol) in anhyd toluene
(300 mL) was added dropwise, keeping the temperature between
ꢁ10 and 0 °C. The mixture was allowed to reach room temperature
with stirring overnight. An aqueous solution of NH4Cl (10%) was
added until the resulting precipitate was completely dissolved.
The organic phase was separated and the aqueous one was ex-
tracted with CH2Cl2 (4 ꢂ 20 mL). The combined organic extracts
were dried with anhyd Na2SO4, filtered and concentrated in vacuo
to give a white solid (11.7 g, 99% yield), mp 169–170 (lit. 167–
169).16
4.1.17. N-(5-Ethyl-1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-
benzoxonin-3-yl)acetamide, 22b
A mixture of alcohol 21b (3.50 g, 14.3 mmol), acetonitrile
(75 mL) and concentrated H2SO4 (0.6 mL, 11.3 mmol) was stirred
under reflux for 18 h. The solution was allowed to cool to room
temperature, water (150 mL) was added and the mixture was ex-
tracted with EtOAc (3 ꢂ 100 mL). The combined organic extracts
were washed with brine (2 ꢂ 50 mL), dried with anhyd Na2SO4, fil-
tered and concentrated in vacuo to give a residue (1.62 g), which
was subjected to column chromatography (hexane/EtOAc mix-
tures) to give, in order of elution, acetamide 22b (860 mg, 22%
yield) and 23 (630 mg, 13% yield) as white solids. The analytical
samples of 22b and 23 were obtained by crystallization from
CH2Cl2.
4.1.15. 5-Ethyl-1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-
benzoxonin-3-ol, 21b
To a flask containing anhyd toluene (50 mL) at 0 °C, ethylmag-
nesium bromide (40 mL, 3 M in Et2O, 0.12 mol) was added. Then,
a solution of 20 (5.00 g, 23.4 mmol) in anhyd toluene (150 mL)
was added dropwise, keeping the temperature between ꢁ10 and
0 °C. The mixture was allowed to reach room temperature with
stirring overnight. An aqueous solution of NH4Cl (10%) was added
until the resulting precipitate was completely dissolved. The or-
ganic phase was separated and the aqueous one was extracted
with CH2Cl2 (4 ꢂ 50 mL). The combined organic extracts were
dried with anhyd Na2SO4, filtered and concentrated in vacuo to
give a white solid (5.14 g, 90% yield), mp 155 °C (methanol/Et2O).
IR 3321, 3071, 3026, 2973, 2958, 2934, 2912, 2874, 2837, 1495,
1458, 1439, 1426, 1357, 1347, 1279, 1246, 1164, 1140, 1125,
Compound 22b, mp 191ꢁ192 °C. IR 3219, 3029, 2919, 2841,
1639, 1537, 1493, 1451, 1435, 1369, 1347, 1279, 1220, 1199,
1166, 1145, 1056, 1045, 1028, 988, 944, 840, 833, 764, 736, 627,
609 cmꢁ1 1H NMR (CDCl3) 0.87 (t, J = 7.5 Hz, 3H, CH2CH3), 1.50
.
[q, J = 7.5 Hz, 2H, CH2CH3], 1.64 [d, J = 13.0 Hz, 2H, 6(13)-Hexo],
1.86 [dd, J = 13.0 Hz, J0 = 5.5 Hz, 2H, 6(13)-Hendo], 1.93 (s, 3H,
COCH3), 1.99 [dd, J = 13.0 Hz, J0 = 5.5 Hz, 2H, 2(12)-Hexo], 2.59 [d,
J = 13.0 Hz, 2H, 2(12)-Hendo], 3.14 [t, J = 5.5 Hz, 1H, 1(7)-H], 5.78
(s, 1H, NH), 7.08–7.12 [complex signal, 4H, 9(10)-H and 8(11)-H].
13C NMR (100.6 MHz, CDCl3) 7.1 (CH3, CH2CH3), 24.3 (CH3, COCH3),
36.3 [CH2, C6(13)], 37.1 (CH2, CH2CH3), 37.6 [CH2, C2(12)], 38.5
[CH, C1(7)], 75.7 (C, C5), 84.0 (C, C3), 126.6 [CH, C9(10)], 128.3
[CH, C8(11)], 145.3 [C, C7a(C11a)], 168.1 (C, CH3CO). MS (EI), m/z
(%): 286 (16), 285 (Mꢀ+, 81), 226 (44), 208 (22), 198 (59), 197
(35), 185 (27), 184 (74), 170 (34), 169 (92), 157 (60), 156 (50),
155 (100), 154 (32), 143 (26), 142 (25), 141 (35), 129 (80), 128
(59), 115 (44), 43 (42). Anal. Calcd for C18H23NO2 (285.39): C,
75.76; H, 8.12; N, 4.91. Found: C, 75.88; H, 8.22; N, 4.84.
1112, 1007, 970, 945, 910, 760, 662 cmꢁ1 1H NMR (CDCl3) 0.88
.
(t, J = 7.7 Hz, 3H, CH2CH3), 1.56 (q, J = 7.7 Hz, 2H, CH2CH3), 1.62 [un-
solved dt, J = 13.5 Hz, 2H, 6(13)-Hexo], 1.84 [ddm, J = 13.5 Hz,
J0 = 6.0 Hz, 2H, 6(13)-Hendo], 1.91 [dt, J = 13.0 Hz, J0 = 1.5 Hz, 2H,
2(12)-Hexo], 1.99 [ddm, J = 13.0 Hz, J0 = 6.0 Hz, 2H, 2(12)-Hendo],
3.1–3.5 (br signal, 1H, OH), 3.22 [tt, J = 6.0 Hz, J0 = 1.5 Hz, 1H,
1(7)-H], 7.14 [pseudo s, 4H, 9(10)-H and 8(11)-H]. 13C NMR
(100.6 MHz, CDCl3) 7.4 (CH3, CH2CH3), 35.9 [CH2, C6(13)], 37.0
(CH2, CH2CH3), 39.4 [CH, C1(7)], 39.8 [CH2, C2(12)], 78.3 (C, C5),
94.7 (C, C3), 126.7 [CH, C9(10)], 128.4 [CH, C8(11)], 145.3 [C,
C7a(C11a)]. MS (EI), m/z (%): 245 (18), 244 (Mꢀ+, 100), 215 (18),
184 (38), 172 (26), 169 (29), 157 (35), 156 (28), 155 (33), 129
(85), 128 (42), 115 (47). Anal. Calcd for C16H20O2 (244.33): C,
78.65; H, 8.25. Found: C, 78.59; H, 8.20.
7,9-Bisacetamido-6,7,8,9,10,11-hexahydro-8-methyl-5,9:7,11-
dimethano-5H-benzocyclononene, 23, mp 261ꢁ262 °C. IR 3406,
3291, 3081, 2969, 2923, 2862, 1662, 1560, 1496, 1446, 1368,
1348, 1320, 1297, 1130, 1074, 1034, 970, 942, 759, 657,
601 cmꢁ1 1H NMR 1.01 (d, J = 7.5 Hz, 3H, C8–CH3), 1.91 (s, 6H,
.
2COCH3), 1.95 [d, J = 13.5 Hz, 2H, 6(13)-Hexo], 2.06 [dm, 4H,
10(12)-Hexo and 2(13)-Hendo], 2.58 [ddd, J = 13.5 Hz, J0 = 6.5 Hz,
J” = 2.5 Hz, 2H, 10(12)-Hendo], 3.07 (overlapped t, J = 7.0 Hz, 1H, 5-
H), 3.09 (overlapped t, J = 7.0 Hz, 1H, 11-H), 3.16 (q, J = 7.5 Hz,
1H, 8-H), 5.09 (s, 2H, 2 NH), 7.01–7.11 (complex signal, 4H, Ar-
H). 13C NMR 8.6 (CH3, C8–CH3), 24.6 (CH3, COCH3), 33.3 [CH2,
C6(13)], 39.0 [CH2, C10(12)], 39.6 (CH) and 39.8 (CH) (C5 and
C11), 40.9 (CH, C8), 57.7 [C, C7(9)], 126.5 (CH) and 126.7 (CH)
(C2 and C3), 127.8 (CH) and 128.2 (CH) (C1 and C4), 145.3 (C)
and 145.9 (C) (C4a and C11a), 169.1 (C, 2COCH3). MS (EI), m/z
(%): 327 (23), 326 (Mꢀ+, 100), 283 (22), 267 (31), 224 (23), 209
(25), 208 (92), 198 (20), 193 (50), 186 (41), 179 (22), 169 (42),
168 (79), 167 (31), 156 (42), 141 (48), 129 (26), 128 (31), 115
(24). Anal. Calcd for C20H26N2O2ꢀ1.25H2O (348.96): C, 68.84; H,
8.23; N, 8.03. Found: C, 68.98; H, 8.27; N, 8.01.
4.1.16. N-(1,2,3,5,6,7-Hexahydro-5-methyl-1,5:3,7-dimethano-
4-benzoxonin-3-yl)acetamide hydrochloride, 22a
A mixture of alcohol 21a (500 mg, 2.17 mmol), acetonitrile
(10 mL) and concentrated H2SO4 (0.1 mL, 1.87 mmol) was stirred
under reflux for 18 h. The mixture was allowed to cool to room tem-
perature, water (20 mL) was added and the solution was extracted
with EtOAc (3 ꢂ 10 mL). The combined organic extracts were
washed with brine (2 ꢂ 10 mL), dried with anhyd Na2SO4, filtered
and concentrated in vacuo to give 22a as a white solid (477 mg,
81% yield). The analytical sample of 22a was obtained by crystalli-
zation from CH2Cl2, mp 172ꢁ177 °C. IR 3239, 3042, 2973, 2917,
1635, 1540, 1495, 1448, 1432, 1372, 1284, 1226, 1174, 1040, 982,
841, 762, 738, 603 cm-1 1H NMR (CDCl3) 1.22 (s, 3H, CH3), 1.65
.
[dm, J = 13.5 Hz, 2H, 6(13)-Hexo], 1.91 [overlapped dd, J = 13.5 Hz,
J0 = 6.0 Hz, 2H, 6(13)-Hendo], 1.93 (s, 3H, COCH3), 2.01 [dd,
J = 13.5 Hz, J0 = 5.5 Hz, 2H, 2(12)-Hexo], 2.56 [d, J = 13.5 Hz, 2H,
2(12)-Hendo], 3.12 (t, J = 6.0 Hz, 2H, 1(7)-H], 5.76 (s, 1H, NH), 7.08–
7.12 [complex signal, 4H, 9(10)-H and 8(11)-H]. 13C NMR (CDCl3)
24.4 (CH3, COCH3), 31.4 (CH3, C5–CH3), 37.2 [CH2, C2(12)], 38.68
[CH, C1(7)], 38.72 [CH2, C6(13)], 73.7 (C, C5), 84.1 (C, C3), 126.6
[CH, C9(10)], 128.3 [CH, C8(11)], 145.1 [C, C7a(C11a)], 168.1 (C,
4.1.18. (1,2,3,5,6,7-Hexahydro-5-methyl-1,5:3,7-dimethano-4-
benzoxonin-3-yl)amine hydrochloride, 28a
A mixture of acetamide 22a (4.00 g, 14.7 mmol), water (188 mL)
and concentrated HCl (24 mL, 288 mmol) were heated under reflux
for 24 h. The solution was cooled to 0 °C and the title compound
precipitated as a white solid that was filtered and washed with
cold water (2 ꢂ 20 mL) and EtOAc (1 ꢂ 20 mL) to give 28aꢀHCl

M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
55
(2.72 g, 87% yield, based on unrecovered starting compound). The
aqueous layer was extracted with EtOAc (3 ꢂ 40 mL) and the com-
bined organic extracts were dried with anhyd Na2SO4, filtered and
concentrated in vacuo to give starting 22a as a white solid (0.8 g).
The analytical sample of 28aꢀHCl was obtained by crystallization
from MeOH/Et2O, mp >285 °C (dec). IR 3500–2500 (max. at 3439,
3187, 3131, 3075, 3019, 2985, 2924, 2845, 2731, 2666, 2621,
2554, 2504), 2039, 1602, 1516, 1490, 1451, 1286, 1236, 1214,
added and the mixture was stirred at 80 °C for 24 h. The mixture
was allowed to cool to room temperature, was diluted with Et2O
(20 mL), 5 N NaOH (15 mL) was added dropwise and the mixture
was stirred at room temperature for 15 min. The organic layer
was separated and the aqueous phase was extracted with Et2O
(4 ꢂ 10 mL). The combined organic phases were washed with brine
(1 ꢂ 30 mL), dried with anhyd Na2SO4, filtered and concentrated in
vacuo to give 29a (276 mg, 72% yield). Its hydrochloride was ob-
tained by adding an excess of Et2OꢀHCl to a solution of the amine
in EtOAc, followed by filtration of the precipitated solid. The ana-
lytical sample was obtained by crystallization from MeOH/Et2O,
mp 208–209 °C. IR 3014, 2974, 2924, 2840, 2588, 2532, 2509,
2436, 2306, 1499, 1474, 1454, 1434, 1345, 1239, 1219, 1183,
1177, 1046, 1020, 993, 836, 755 cmꢁ1 1H NMR 1.29 (s, 3H, CH3),
.
1.71 [d, J = 14.0 Hz, 2H, 6(13)-Hexo], 1.93 [d, J = 13.0 Hz, 2H, 2(12)-
Hexo], 1.98 [dd, J = 13.0 Hz, J0 = 6.0 Hz, 2H, 6(13)-Hendo], 2.15 [dd,
J = 11.5 Hz, J0 = 6.5 Hz, 2H, 2(12)-Hendo], 3.30 (t, J = 5.5 Hz, 2H,
1(7)-H], 4.87 (s, mobile H), 7.14–7.19 [complex signal, 4H, 9(10)-
H and 8(11)-H]. 13C NMR 31.3 (CH3, C5–CH3), 37.3 [CH2, C2(12)],
39.0 [CH2, C6(13)], 39.6 [CH, C1(7)], 76.5 (C, C5), 84.0 (C, C3),
129.3 [CH, C9(10)], 129.6 [CH, C8(11)], 145.7 [C, C7a(C11a)]. MS
(EI), m/z (%): 230 ([M+H]+, 26), 229 (Mꢀ+, 30), 171 (25), 170 (100),
155 (67), 143 (18), 129 (27), 128 (23), 115 (21). Anal. Calcd for
C15H19NOꢀ1.1HClꢀ0.4H2O (276.63): C, 65.13; H, 7.62; N, 5.06; Cl,
14.10. Found: C, 65.05; H, 7.66; N, 5.40; Cl, 13.84.
1163, 1132, 1076, 1062, 1022, 914, 900, 783 cmꢁ1 1H NMR 1.32
.
(s, 3H, CH3), 1.72 [d, J = 14.0 Hz, 2H, 6(13)-Hexo], 2.00 [ddm,
J = 14.5 Hz, J0 = 5.5 Hz, 2H, 6(13)-Hendo], 2.09 [d, J = 13.0 Hz, 2H,
2(12)-Hexo], 2.16 [ddm, J = 13.0 Hz, J0 = 5.5 Hz, 2H, 2(12)-Hendo],
2.85 [s, 6H, N(CH3)2], 3.38 [t, J = 6.0 Hz, 2H, 1(7)-H], 4.86 (s, mobile
H), 7.16 [m, 2H, 9(10)-H], 7.20 [m, 2H, 8(11)-H]. 13C NMR 31.1
(CH3, C5–CH3), 32.8 [CH2, C2(12)], 36.8 [CH3, N(CH3)2], 38.9 [CH2,
C6(13)], 39.4 [CH, C1(7)], 77.9 (C, C5), 92.6 (C, C3), 128.4 [CH,
C9(10)], 129.6 [CH, C8(11)], 145.6 [C, C7a(C11a)]. MS (EI), m/z
(%): 258 (11), 257 (Mꢀ+, 58), 155 (28), 129 (15), 128 (15), 87
(100). Anal. Calcd for C17H23NOꢀHCl (293.84): C, 69.49; H, 8.23;
N, 4.77; Cl, 12.07. Found: C, 69.32; H, 8.28; N, 4.58; Cl, 11.98.
4.1.19. (5-Ethyl-1,2,3,5,6,7-hexahydro-1,5:3,7-dimethano-4-
benzoxonin-3-yl)amine hydrochloride, 28b
(a) From 22b: A mixture of acetamide 22b (380 mg, 1.33 mmol),
water (18 mL) and concentrated HCl (2.3 mL, 27.6 mmol) was
heated under reflux for 24 h. The solution was cooled to 0 °C and
the title compound precipitated as a white solid that was filtered
and washed with cold water (5 mL) and EtOAc (2 ꢂ 5 mL) to give
28bꢀHCl (300 mg, 81% yield, 90% based on unrecovered starting
compound). The combined organic phase was dried with anhyd
Na2SO4, filtered and concentrated in vacuo to give starting 22b as
a white solid (40 mg). The analytical sample of 28bꢀHCl was ob-
tained by crystallization from MeOH/Et2O, mp >300 °C (dec). IR
3600–2500 (max. at 3501, 2967, 2879, 2676, 2623, 2535), 1592,
1508, 1494, 1465, 1453, 1436, 1354, 1335, 1286, 1237, 1218,
4.1.21. N,N-Diethyl-(1,2,3,5,6,7-hexahydro-5-methyl-1,5:3,7-
dimethano-4-benzoxonin-3-yl)amine (2R,3R)-tartrate,
29bꢀ(2R,3R)-tartrate
To a solution of 28aꢀHCl (265 mg, 0.9 mmol) in MeOH (15 mL),
NaBH3CN (95%, 132 mg, 2.0 mmol), AcOH (0.3 mL) and acetalde-
hyde (0.34 mL, 6.0 mmol) were added and the mixture was stirred
at room temperature for 8 h. An additional portion of NaBH3CN
(95%, 66 mg, 1.0 mmol) and acetaldehyde (0.17 mL, 3.0 mmol)
were added, the mixture was stirred at room temperature for
18 h and then it was concentrated in vacuo to dryness. Water
(20 mL) was added to the residue, the suspension was basified with
1 N NaOH and was extracted with EtOAc (3 ꢂ 10 mL). The com-
bined organic extracts were washed with brine (2 ꢂ 10 mL), dried
with anhyd Na2SO4, filtered and concentrated in vacuo to give 29b
as an oil (258 mg, 91% yield). An analytical sample of the (2R,3R)-
tartrate of 29b was obtained by adding 1 equiv of (2R,3R)-(+)-tar-
taric acid in methanol (15 mL) to a solution of 29b in EtOAc
(15 mL), concentration to dryness and crystallization from 2-pro-
panol, mp 111ꢁ112 °C. IR 3600–2400 (max. at 3321, 3271, 2974,
2935, 2649, 2476), 1871, 1734, 1580, 1409, 1337, 1305, 1261,
1174, 1057, 1033, 985, 897, 836, 754 cmꢁ1 1H NMR 0.93 (t,
.
J = 7.5 Hz, 3H, CH2CH3), 1.58 [q, J = 7.5 Hz, 2H, CH2CH3], 1.67 [d,
J = 13.5 Hz, 2 H, 6(13)-Hexo], 1.93 [d, J = 12.5 Hz, 2H, 2(12)-Hexo],
1.97 [overlapped dd, J = 13.5 Hz, J0 = 6.0 Hz, 2H, 6(13)-Hendo], 2.14
[ddm, J = 13.5 Hz, J0 = 5.5 Hz, 2H, 2(12)-Hendo], 3.31 [t, J = 6.0 Hz,
2H, 1(7)-H], 4.86 (s, mobile H), 7.14 [m, 2H, 9(10)-H], 7.17 [m,
2H, 8(11)-H]. 13C NMR 7.3 (CH3, CH2CH3), 36.7 [CH2, C6(13)],
37.5 (CH2, CH2CH3), 37.6 [CH2, C2(12)], 39.4 [CH, C1(7)], 78.5 (C,
C5), 84.0 (C, C3), 128.3 [CH, C9(10)], 129.6 [CH, C8(11)], 145.8 [C,
C7a(C11a)]. MS (EI), m/z (%): 243 (Mꢀ+, 49), 185 (21), 184 (100),
172 (26), 169 (51), 156 (42), 155 (91), 143 (26), 131 (28), 129
(42), 128 (35), 115 (32). Anal. Calcd for C16H21NOꢀHClꢀ0.33H2O
(285.75): C, 67.25; H, 7.99; N, 4.90; Cl, 12.41. Found: C, 67.24; H,
7.87; N, 4.98; Cl, 12.41. (b) From 21b: To a mixture of alcohol
21b (300 mg, 1.23 mmol) and urea (148 mg, 2.46 mmol) trifluoro-
acetic acid (0.9 mL, 12.3 mmol) was added and the suspension was
heated at 115 °C for 18 h. To the cold (0 °C) solution water (10 mL)
and 1 N NaOH till basic pH were added. The solution was extracted
with Et2O (4 ꢂ 5 mL) and the combined organic extracts were
washed with water (2 ꢂ 5 mL), dried with anhyd Na2SO4, filtered
and concentrated in vacuo to give 28b as a yellow solid (253 mg)
that was crystallized from EtOAc. Its hydrochloride was obtained
by adding an excess of Et2OꢀHCl to a solution of the amine in
Et2O and filtration of the precipitated white solid (240 mg, 70%
yield).
1213, 1132, 1068, 1003, 788, 763, 679, 618 cmꢁ1 1H NMR 1.32
.
(s, 3H, C5–CH3), 1.38 (t, J = 7.5 Hz, 6H, 2CH2CH3), 1.72 [d,
J = 13.5 Hz, 2H, 6(13)-Hexo], 2.01 [dd, J = 13.5 Hz, J0 = 6.0 Hz, 2H,
6(13)-Hendo], 2.10 [d, J = 13.5 Hz, 2H, 2(12)-Hexo], 2.24 [ddm,
J = 13.5 Hz, J0 = 5.5 Hz, 2H, 2(12)-Hendo], 3.36 [complex signal, 6H,
2CH2CH3 and 1(7)-H], 4.39 (s, 2H, 2CHOH tartrate), 4.86 (s, mobile
H), 7.16 [m, 2H, 9(10)-H], 7.19 [m, 2H, 8(11)-H]. 13C NMR
(100.6 MHz) 12.5 (CH3, 2CH2CH3), 31.1 (CH3, C5–CH3), 33.5 [CH2,
C2(12)], 38.9 [CH2, C6(13)], 39.5 [CH, C1(7)], 45.9 (CH2, 2CH2CH3),
74.1 (CH, 2CHOH tartrate), 77.7 (C, C5), 94.7 (C, C3), 128.4 [CH,
C9(10)], 129.6 [CH, C8(11)], 145.7 [C, C7a(C11a)], 176.8 (C,
2CO2H tartrate). MS (EI), m/z (%): 285 (Mꢀ+, 23), 155 (17), 129
(15), 115 [Et2NCH(CH3)2ꢀ+, 100], 100 (Et2N@CHCH3þ, 39), 72 (11).
Anal. Calcd for C23H33NO7ꢀ0.5H2O (444.53): C, 62.15; H, 7.71; N,
3.15. Found: C, 61.96; H, 7.94; N, 3.14.
4.1.20. N,N-Dimethyl-(1,2,3,5,6,7-hexahydro-5-methyl-1,5:3,7-
dimethano-4-benzoxonin-3-yl)amine hydrochloride, 29aꢀHCl
To a cold (0 °C) solution of 28a (343 mg, 1.50 mmol) in Et2O
(10 mL), formaldehyde (2.6 mL, 37 wt % in water solution,
33 mmol) and, dropwise, formic acid (2.3 mL, 61 mmol) were
4.1.22. N-Benzyl-(5-ethyl-1,2,3,5,6,7-hexahydro-1,5:3,7-
dimeth-ano-4-benzoxonin-3-yl)amine hydrochloride, 30ꢀHCl
To a solution of amine 28bꢀHCl (320 mg, 1.14 mmol) in MeOH
(10 mL), NaBH3CN (95%, 152 mg, 2.30 mmol), AcOH (0.3 mL) and

56
M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
benzaldehyde (0.18 mL, 1.73 mmol) were added and the mixture
was stirred at room temperature for 2 h. Then, an additional
amount of NaBH3CN (95%, 76 mg, 1.15 mmol) and benzaldehyde
(0.09 mL, 0.86 mmol) were added and the mixture was stirred
at room temperature for 18 h and concentrated in vacuo to dry-
ness. Water (15 mL) was added to the residue, and the mixture
was extracted with Et2O (4 ꢂ 15 mL). The combined organic ex-
tracts were washed with 1 N NaOH (1 ꢂ 25 mL), brine
(2 ꢂ 25 mL), dried with anhyd Na2SO4, filtered and concentrated
in vacuo. The residue was taken in EtOAc and the amine 30 was
precipitated as its hydrochloride (341 mg, 81% yield) by adding
an excess of Et2OꢀHCl. The analytical sample was obtained by
crystallization from EtOAc, mp 246–248 °C. IR 3500–2400 (max.
at 3418, 3030, 2935, 2691, 2614, 2549, 2396), 1564, 1495, 1456,
10.91. Found: C, 70.17; H, 7.51; N, 4.21; Cl, 11.11. Compound
31b: mp 177–178 °C. IR 3500–2150 (max. at 3428, 3180, 2967,
2948, 2925, 2880, 2418, 2385, 2355, 2203), 2119, 1494, 1463,
1454, 1435, 1350, 1222, 1202, 1028, 1006, 985, 962, 919, 837,
774, 723, 675 cmꢁ1 1H NMR 0.95 (t, J = 7.5 Hz, 3H, CH2CH3),
.
1.64 (q, J = 7.5 Hz, 2H, CH2CH3), 1.68 [d, J = 15.5 Hz, 2H, 6(13)-
Hexo], 2.00 [dd, J = 12.5 Hz, J0 = 6.0 Hz, 2H, 6(13)-Hendo], 2.18 [d,
J = 13.0 Hz, 2H, 2(12)-Hexo], 2.30 [ddm, J = 13.5 Hz, J0 = 6.0 Hz, 2H,
2(12)-Hendo], 3.25 (br s, 2H, CH2C„CH), 3.37 [t, J = 6.0 Hz, 2H,
1(7)-H], 4.32 (d, J = 2.5 Hz, 4H, CH2C„CH), 7.16 [m, 2H, 9(10)-
H], 7.19 [m, 2H, 8(11)-H]. 13C NMR 7.4 (CH3, CH2CH3), 34.8
[CH2, C2(12)], 36.6 [CH2, C6(13)], 37.5 (CH2, CH2CH3), 37.6 (CH2,
2CH2C„CH), 39.4 [CH, C1(7)], 74.6 (C, 2CH2C„CH), 80.4 (C,
2CH2C„CH and C5), 94.8 (C, C3), 128.4 [CH, C9(10)], 129.5 [CH,
C8(11)], 145.7 [C, C7a(C11a)]. MS (EI), m/z (%): 319 (Mꢀ+, 6), 318
(10), 290 (24), 248 (14), 237 (19), 222 (20), 185 (40), 169 (56),
155 (55), 143 (47), 141 (52), 135 (100), 134 (60), 129 (82), 128
(70), 115 (57). Anal. Calcd for C22H25NOꢀHClꢀ0.25H2O (360.41):
C, 73.32; H, 7.41; N, 3.89; Cl, 9.84. Found: C, 73.39; H, 7.37; N,
3.86; Cl, 9.85.
1352, 1216, 1026, 999, 984, 758, 698 cmꢁ1 1H NMR 0.97 (t,
.
J = 7.5 Hz, 3H, CH2CH3), 1.65 [q, J = 7.5 Hz, 2H, CH2CH3], 1.71 [d,
J = 14.0 Hz, 2H, 6(13)-Hexo], 2.03 [overlapped dd, 2H, 6(13)-Hendo],
2.04 [d, J = 12.5 Hz, 2H, 2(12)-Hexo], 2.34 [ddm, J = 13.0 Hz,
J0 = 6.0 Hz, 2H, 2(12)-Hendo], 3.38 [t, J = 6.0 Hz, 2H, 1(7)-H], 4.28
(s, 2H, CH2–C6H5), 4.86 (s, mobile H), 7.17 [m, 2H, 9(10)-H],
7.21 [m, 2H, 8(11)-H], 7.43–7.50 (complex signal, 5H, Ar-H ben-
zyl). 13C NMR 7.4 (CH3, CH2CH3), 35.8 [CH2, C2(12)], 36.8 [CH2,
C6(13)], 37.5 (CH2, CH2CH3), 39.4 [CH, C1(7)], 45.3 (CH2, CH2–
C6H5), 79.2 (C, C5), 88.6 (C, C3), 128.3 [CH, C9(10)], 129.6 [CH,
C8(11)], 130.3 (CH, Ar-Cmeta), 130.5 (CH, Ar-Cpara), 131.1 (CH, Ar-
Cortho), 132.9 (C, Ar-Cipso),145.8 [C, C7a(C11a)]. MS (EI), m/z (%):
334 (15), 333 (Mꢀ+, 49), 304 (15), 184 (14), 169 (18), 155 (23),
150 (21), 149 (100), 91 (73). Anal. Calcd for C23H27NOꢀHClꢀ0.4H2O
(377.14): C, 73.25; H, 7.70; N, 3.71; Cl, 9.40. Found: C, 73.23; H,
7.56; N, 3.56; Cl, 9.75.
4.2. NMDA receptor antagonist activity
The functional assay of antagonist activity at NMDA receptors
was performed using primary cultures of cerebellar granule neu-
rons, which were prepared according to established protocols.23
Cells were grown on 10 mm poly-
slips, and used for the experiments after 7–14 days in vitro. Cells
were loaded with 6 M Fura-2 AM (invitrogen-molecular probes)
L-lysine coated glass cover
l
for 45 min. Afterwards the coverslip was mounted on a quartz
cuvette containing a Locke-Hepes buffer using a special holder.
Measurements were performed using a Perkin–Elmer LS-50B
fluorometer equipped with a fast-filter accessory, under mild
agitation and at 37 °C. Analysis from each sample was recorded
real-time during 1200 s. After stimulation with NMDA or gluta-
4.1.23. N-Propargyl-(5-ethyl-1,2,3,5,6,7-hexahydro-1,5:3,7-
dimethano-4-benzoxonin-3-yl)amine hydrochloride, 31aꢀHCl
and N,N-dipropargyl-(5-ethyl-1,2,3,5,6,7-hexahydro-1,5:3,7-
dimetha-no-4-benzoxonin-3-yl)amine hydrochloride, 31bꢀHCl
A suspension of 28bꢀHCl (920 mg, 3.29 mmol), K2CO3 (459 mg,
3.29 mmol), propargyl bromide (0.32 mL, 80% solution in toluene,
2.88 mmol) and NaI (40 mg, 0.27 mmol) in acetonitrile (35 mL)
was heated under reflux for 18 h and concentrated in vacuo to
dryness. To the residue, CH2Cl2 (50 mL) was added and the solu-
tion was washed with water (3 ꢂ 20 mL). The organic layer was
dried with anhyd Na2SO4, filtered and concentrated in vacuo.
The residue was subjected to column chromatography (hexane/
EtOAc mixtures) to give 31b (hexane/EtOAc 98:2, 202 mg, 22%
yield) and 31a (hexane/EtOAc 95:5, 321 mg, 35% yield). The
hydrochlorides of 31a and 31b were obtained by adding an excess
of Et2OꢀHCl to a solution of the corresponding amine in EtOAc fol-
lowed by filtration of the formed precipitates. The analytical sam-
ples of 31a and 31b were obtained by crystallization from Et2O.
31a: mp 186–187 °C. IR 3500–2400 (max. at 3458, 3306, 3245,
3179, 2965, 2939, 2919, 2728, 2629, 2406), 2125, 1557, 1493,
mate (100 lM, in the presence of 10 lM glycine), increasing
cumulative concentrations of the compound to be tested were
added. The percentages of inhibition at every tested concentra-
tion were analyzed using a non-linear regression curve fitting
(variable slope) by using the software GraphPad Prism 4.0.
4.3. MAO inhibitory activity
The ability of the compounds to inhibit MAO activity was
measured using the MAO-Glo™ Assay (Promega). As a tissue
homogenate, we used a crude mitochondrial preparation from
mice cortex (NIH Swiss, Harlan).25 Compounds were tested for
non-specific MAO activity at a concentration of 10 and 50 lM.
The assays were carried out according to manufacturer’s protocol.
Readings were performed using a tube luminometer (Berthold
Lumat).
.
1451, 1350, 1217, 1031, 987, 764 cmꢁ1 1H NMR 0.94 (t,
J = 7.5 Hz, 3H, CH2CH3), 1.61 (q, J = 7.5 Hz, 2H, CH2CH3), 1.68 [d,
J = 13.5 Hz, 2H, 6(13)-Hexo], 1.94 [d, J = 13.0 Hz, 2H, 2(12)-Hexo],
1.99 [dd, J = 13.5 Hz, J0 = 5.5 Hz, 2H, 6(13)-Hendo], 2.23 [ddm,
J = 13.5 Hz, J0 = 5.5 Hz, 2H, 2(12)-Hendo], 3.19 (t, J = 3.0 Hz, 1H,
CH2C„CH), 3.35 [t, J = 5.5 Hz, 2H, 1(7)-H], 4.01 (d, J = 3.0 Hz, 2H,
CH2C„CH), 7.15 [m, 2H, 9(10)-H], 7.18 [m, 2H, 8(11)-H]. 13C
NMR (100.6 MHz) 7.3 (CH3, CH2CH3), 30.6 (CH2, CH2C„CH), 35.7
[CH2, C2(12)], 36.7 [CH2, C6(13)], 37.4 (CH2, CH2CH3), 39.2 [CH,
C1(7)], 75.3 (CH, CH2C„CH), 78.5 (C, C5), 79.4 (C, CH2C„CH),
88.3 (C, C3), 128.4 [CH, C9(10)], 129.6 [CH, C8(11)], 145.6 [C,
C7a(C11a)]. MS (EI), m/z (%): 281 (Mꢀ+, 29), 252 (28), 194 (25),
185 (35), 184 (82), 169 (63), 155 (100), 143 (30), 141 (35), 131
(27), 129 (62), 128 (57), 115 (47), 97 (61), 96 (34). Anal. Calcd
for C19H23NOꢀHClꢀ0.4H2O (325.06): C, 70.20; H, 7.69; N, 4.31; Cl,
4.4. T. brucei culturing and drug test
Cultures of bloodstream form T. brucei (strain 427) were main-
tained at 37 °C in modified Iscove’s medium (pH 7.4).26 Trypanoci-
dal activity was assessed by growing parasites for 48 h in the
presence of various drug concentrations to determine the levels
which inhibited growth by 50% (IC50) and 90% (IC90). In the case
of untreated cultures (volume 4 mL), cell densities increased from
0.5 ꢂ 104 to 1 ꢂ 106 cells mLꢁ1 over this period. Experiments were
performed in triplicate. Cell densities at each drug concentration
were determined using a hemocytometer (Weber Scientific Inter-
national Ltd), and drug sensitivity was expressed as a percentage
of growth of control cells.

M. D. Duque et al. / Bioorg. Med. Chem. 18 (2010) 46–57
57
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Acknowledgements
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A.C., P.C., F.X.S. and S.V. gratefully acknowledge financial sup-
port from Ministerio de Educación y Ciencia (P.C. and S.V.: Project
CTQ2008-03768; F.X.S.: Project SAF 2006-13092-C02-01; A.C.: Pro-
ject 2005-01604 and PI080400) and Comissionat per a Universitats
i Recerca (P.C. and S.V.: Project 2005-SGR-00180, F.X.S.: Project
2009-SGR-853). M.D.D. thanks to the Ministerio de Educación y
Ciencia (FPU Program).
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