Deeper Insight into the Six-Step Domino Reaction of Aldehydes with Malononitrile and Evaluation of Antiviral and Antimalarial Activities of the Obtained Bicyclic Products

Article abstract of DOI:10.1002/open.201700005

The straightforward and efficient synthesis of complex aza- and carbobicyclic compounds, which are of importance for medicinal chemistry, is a challenge for modern chemical methodology. An unprecedented metal-free six-step domino reaction of aldehydes with malononitrile was presented in our previous study to provide, in a single operation, these bicyclic nitrogen-containing molecules. Presented here is a deeper investigation of this atom-economical domino process by extending the scope of aldehydes, performing post-modifications of domino products, applying bifunctional organocatalysts and comprehensive NMR studies of selected domino products. The thermodynamic aspects of the overall reaction are also demonstrated using DFT methods in conjunction with a semi-empirical treatment of van der Waals interactions. Furthermore, biological studies of seven highly functionalized and artemisinin-containing domino products against human cytomegalovirus (HCMV) and Plasmodium falciparum 3D7 are presented. Remarkably, in vitro tests against HCMV revealed five domino products to be highly active compounds (EC₅₀ 0.071–1.8 μm), outperforming the clinical reference drug ganciclovir (EC₅₀ 2.6 μm). Against P. falciparum 3D7, three of the investigated artemisinin-derived domino products (EC₅₀ 0.72–1.8 nm) were more potent than the clinical drug chloroquine (EC₅₀ 9.1 nm).

Full text of DOI:10.1002/open.201700005

DOI: 10.1002/open.201700005
Deeper Insight into the Six-Step Domino Reaction of
Aldehydes with Malononitrile and Evaluation of Antiviral
and Antimalarial Activities of the Obtained Bicyclic
Products
Christina M. Bock,[a] Gangajji Parameshwarappa,[a] Simon Bçnisch,[b] Walter Bauer,[a]
Corina Hutterer,[c] Maria Leidenberger,[d] Oliver Friedrich,[d] Manfred Marschall,[c]
Barbara Kappes,[d] Andreas Gçrling,[b] and Svetlana B. Tsogoeva*[a]
The straightforward and efficient synthesis of complex aza-
and carbobicyclic compounds, which are of importance for
medicinal chemistry, is a challenge for modern chemical
methodology. An unprecedented metal-free six-step domino
reaction of aldehydes with malononitrile was presented in our
previous study to provide, in a single operation, these bicyclic
nitrogen-containing molecules. Presented here is a deeper in-
vestigation of this atom-economical domino process by ex-
tending the scope of aldehydes, performing post-modifications
of domino products, applying bifunctional organocatalysts and
comprehensive NMR studies of selected domino products. The
thermodynamic aspects of the overall reaction are also demon-
strated using DFT methods in conjunction with a semi-empiri-
cal treatment of van der Waals interactions. Furthermore, bio-
logical studies of seven highly functionalized and artemisinin-
containing domino products against human cytomegalovirus
(HCMV) and Plasmodium falciparum 3D7 are presented. Re-
markably, in vitro tests against HCMV revealed five domino
products to be highly active compounds (EC50 0.071–1.8 mm),
outperforming the clinical reference drug ganciclovir (EC50
2.6 mm). Against P. falciparum 3D7, three of the investigated ar-
temisinin-derived domino products (EC50 0.72–1.8 nm) were
more potent than the clinical drug chloroquine (EC50 9.1 nm).
1. Introduction
The domino process is a powerful tool to economically and
sustainably build complex molecular architectures.[1] The
number of work-up and purification steps is drastically re-
duced, therefore, the procedure is less time-consuming and
produces less waste compared to traditional stop-and-go syn-
thesis. Typical steps involved in known domino processes are
different CꢀC bond formation reactions, for example, Michael,
aldol or Knoevenagel reactions,[2] which in combination can
lead to highly substituted carbocyclic compounds,[3] spirocyclic
structures[4] or diverse heterocycles.[5]
exocyclic imine group (bicyclo[2.2.2]octan-2-imine) are found
as subunits in numerous natural products and bioactive com-
pounds,[6] but are not easy to access using common synthetic
methods. Only a few organocatalytic methods for generation
of these ring systems have been reported.[7] The known metal-
free and metal-catalyzed methods for the synthesis of azabicy-
cles and carbobicycles often use reagents that are not com-
mercially available and require laborious precursor synthesis
and isolation and/or purification of intermediate products in
most cases.[7,8] Notably, there are only a few examples in the
literature for the formation of isoquinuclidines starting from
readily available alkylidenemalononitriles under metal-cata-
Nitrogen-containing bicyclic systems, among them isoquinu-
clidine (2-azabicyclo[2.2.2]octane) and carbobicycles with an
[a] C. M. Bock, Dr. G. Parameshwarappa, Prof. Dr. W. Bauer,
Prof. Dr. S. B. Tsogoeva
[d] M. Leidenberger, Prof. Dr. O. Friedrich, Prof. Dr. B. Kappes
Institute of Medical Biotechnology
Institute of Organic Chemistry I and
Friedrich-Alexander-Universitꢁt Erlangen-Nꢀrnberg
Paul-Gordan-Straße 3, 91052 Erlangen (Germany)
Interdisciplinary Center for Molecular Materials
Friedrich-Alexander-University Erlangen-Nꢀrnberg
Henkestrasse 42, 91054 Erlangen (Germany)
E-mail: svetlana.tsogoeva@fau.de
Supporting Information and the ORCID identification number(s) for the
author(s) of this article can be found under:
https://doi.org/10.1002/open.201700005.
[b] S. Bçnisch, Prof. Dr. A. Gçrling
ꢀ 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
This is an open access article under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivs License, which permits use and
distribution in any medium, provided the original work is properly cited,
the use is non-commercial and no modifications or adaptations are
made.
Chair of Theoretical Chemistry and
Interdisciplinary Center for Molecular Materials
Friedrich-Alexander-Universitꢁt Erlangen-Nꢀrnberg
Egerlandstraße 3, 91058 Erlangen (Germany)
[c] Dr. C. Hutterer, Prof. Dr. M. Marschall
Institute for Clinical and Molecular Virology
Friedrich-Alexander-Universitꢁt Erlangen-Nꢀrnberg
Schlossgarten 4, 91054 Erlangen (Germany)
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lyzed conditions.[9] Recently, we reported the discovery of
a two-component multi-step domino reaction under metal-free
conditions providing both carbobicyclic compounds with exo-
cyclic imine groups and azabicycles (isoquinuclidines).[10] In this
context, we demonstrated the generation of intricate molecu-
lar architectures from simple aldehydes and malononitrile in
a single operation by a six-step domino reaction. Imidazole
was found to be the most suitable achiral catalyst for this
atom-economical reaction and was successfully applied to
study the reaction scope using substituted 2-phenylacetalde-
hydes.[10] Propanal as a representative aliphatic starting materi-
al showed that this reaction is not limited to phenylacetalde-
hyde derivatives. This study was complemented with mecha-
nistic investigations using mass spectrometry (MS) techniques
and DFT calculations taking into account van der Waals
interactions.
we demonstrated the broad substrate tolerance of this multi-
step domino reaction; propanal was the only aliphatic alde-
hyde tested. Starting from those results with propanal, in this
study we performed a series of experiments with homologous
aliphatic aldehydes (Table 1).
Table 1. Extended substrate scope of the imidazole-catalyzed multi-step
domino reaction.
Entry Aldehyde
Products Yield [%][c] d.r. a (anti/syn)[d] Ratio a/b[d]
1[a]
2[b]
3
1a, 1b
–
–
–
Developing such new and straightforward syntheses for
these classes of compounds is of great interest due to their
enormous potential as pharmaceuticals, demonstrated by
a number of studies on their biological activities.[6,11] Inspired
by naturally occurring alkaloids, compounds such as ibogaine
analogue A have recently been synthesized and biologically
evaluated (Figure 1).[6d] Isoquinuclidine analogue A has been
2a, 2b 25
3a, 3b 23
4a, 4b 13
5a, 5b 25
38:62
40:60
47:53
>99:1
11:1
2:1
1:1
1:3
4
5
[a] “–”: 0% yield. [b] The reaction has been previously reported.[10]
[c] Sum of yields of isolated products a and b. [d] Determined by H NMR
1
spectroscopy (see the Supporting Information).
Use of the shorter homologue acetaldehyde (1) did not lead
to the expected domino products 1a and 1b (Table 1, entry 1).
Instead, the cyclohexene derivative 6, bearing five nitrile
groups, was obtained in 60% yield (Scheme 1). Notably, similar
findings had been reported earlier in a study of base-catalyzed
condensation reactions with different alkylidenemalononi-
triles.[12] How can this reaction outcome be explained? Obvi-
ously, there is a change in the sequence of the reaction steps
in the catalytic cycle. The first step is a Knoevenagel reaction
of acetaldehyde and malononitrile (Scheme 1, step 1), similar
to the first step in the reaction mechanism previously pro-
Figure 1. Selected examples of bioactive azabicyclic (A and B) and carbobi-
cyclic compounds with exocyclic imine groups (C).
characterized as an opioid receptor agonist with potential anal-
gesic properties. Similar to its chloroquine-type parent com-
pound, isoquinuclidine derivative B (Figure 1) possesses anti-
malarial and antileishmanial activities.[6c] Carbobicyclic com-
pounds with an exocyclic imine function (C, Figure 1) appear
to have comparable antimalarial activities.[6a,b]
Motivated by these promising examples, we investigated
the potential antimalarial and antiviral activities of our domino
products. Herein, we present the results of these biological
studies in addition to our extended scope of substrates and bi-
functional catalysts for the six-step domino reaction, and an
extensive NMR spectroscopic analysis of a selected domino
product.
2. Results and Discussion
2.1. Extended Substrate and Catalyst Scope for the Domino
Reaction
In our previous study, we mainly focused on substituted phe-
nylacetaldehydes as substrates.[10] With 11 different examples,
Scheme 1. Imidazole-catalyzed five-step domino reaction of acetaldehyde
(1) with malononitrile.
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posed for the formation of bicyclic domino products.[10] Next
follows a 1,4-conjugate addition of malononitrile to the Knoe-
venagel product (Michael acceptor; Scheme 1, step 2).
of 40:60 were similar to the results obtained with propanal (2).
However, there was a loss of selectivity in the formation of the
two constitutional isomers 3a and 3b (their ratio was 2:1).
With a low yield of 13% and almost no selectivity towards any
isomer, use of 4 as the substrate led to the worst results. As
a final example of the substrate scope, 3-phenylpropanal (5)
was chosen. This substrate also contains a phenyl group, like
the originally used phenylacetaldehyde (7), although there is
no enhanced reactivity, because the benzylic position is not
a to the carbonyl group. Compared to the reaction with 7
(Table 2, entry 1), the yield for the reaction with 5 was lower at
25%, whereas the high diastereoselectivity was preserved, and
only the anti isomer of 5a was formed (Table 1, entry 5). Re-
markably, this was the only example for which the isoquinucli-
dine was formed in a lower amount than the iminocarbobicy-
clic compound (5a/5b=1:3). The lower yield could be ex-
plained by the less reactive aldehyde, but the steric demand of
the phenyl ring was apparently still sufficient to prevent the
formation of a syn-5a isomer.
The reaction with another Knoevenagel product molecule
leads, through subsequent three steps (Scheme 1, steps 3–5),
to the generation of cyclohexene 6. By contrast, the azabicycle
7a and carbobicycle 7b were likely formed when phenylacetal-
dehyde was used instead of acetaldehyde (Table 2, entry 1).
This is because a dimerization reaction (vinylogous Michael ad-
dition) of the Knoevenagel product (generated from phenyla-
cetaldehyde)[10] occurs before another molecule of malononi-
trile can attack it. These differences between the reaction
mechanisms indicate the complexity of this domino reaction
and demonstrate how drastically reaction outcome, and there-
fore the product, can change, even if there are only small dif-
ferences in aldehyde structure.
The experiments with butyraldehyde (3) and valeraldehyde
(4) showed that with longer chain length of the aliphatic alde-
hyde, yield and selectivity of the reaction decrease (Table 1, en-
tries 3 and 4). For 3, the yield of 23% and the d.r. (3a, anti/syn)
Table 2. Catalyst and solvent screening for the reaction of phenylacetaldehyde (7) with malononitrile.
Entry
1
Catalyst
Solvent
toluene
Time [h]
48
Yield [%][a]
Ratio 7a/7b[b,c]
d.r. 7a (anti/syn)
>99:1
d.r. 7b
52
4:1
50:50
2
3
toluene
toluene
24
26
52
70
1:11
1:22
>99:1
>99:1
33:67
50:50
4
toluene
25
83
1:25
>99:1
25:75[d]
5[e]
6
7
8
without catalyst
toluene
CH2Cl2
hexane
C6F6
22
24
72
24
23
–
–
–
–
IV
IV
IV
IV
79
53
69
50
1:19
2:1
1:2
1:7
>99:1
>99:1
>99:1
>99:1
33:67
50:50
33:67
50:50
9
MeOH
[a] Sum of yields of isolated products 7a and 7b. [b] 7a/7b ratio determined by HPLC. [c] HPLC conditions for the separation of enantiomers and determi-
nation of ee values of obtained products were not found. [d] Enantioselectivities of the major product 7b (48% and 47% ee for two diastereomers, respec-
tively) were determined by 1H NMR spectroscopy in presence of the chiral shift reagent Eu(hfc)3. [e] “–”: 0% yield.
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Although the focus of this work was not the development
of an enantioselective version of this new reaction, nonethe-
less we probed the potential of converting the formation reac-
tion of 7a and 7b into an enantioselective synthesis route.
Therefore, we also used tertiary-amine-based bifunctional
chiral organocatalysts II–IV (Table 2). However, we did not find
HPLC conditions for determination of the ee values of the ob-
tained products and hence we limited our studies to determi-
nation of yields, 7a/7b ratios and diastereoselectivities for 7a
and 7b. Nonetheless, to measure the enantioselectivity for
products obtained with the selected bifunctional chiral cata-
2.2. DFT Studies on the Thermodynamics of the Overall
Reaction
In our recent study, we considered the thermodynamic and ki-
netic aspects of the chemodivergent step.[10] From these calcu-
lations, one could deduce that the Michael reaction (D!H,
Figure 2) is faster, whereas the intermolecular addition reaction
(D!E, Figure 2) is thermodynamically favored. The reaction
barriers were somewhat moderate and the initial reaction from
D to both E and H is endergonic. Therefore, we concluded
that the subsequent steps might also play a role. To further
shed light on this reaction, we studied the thermodynamics of
the subsequent steps of both reaction pathways by calculating
the intermediates resulting in 7a, that is, F and G (the imine
tautomer of 7a), as well as the intermediates resulting in 7b,
that is, I and the more stable enamine tautomer J (Figure 2).
Computational details can be found in the Supporting
Information.
1
lyst IV (providing the best reaction outcome), we used H NMR
spectroscopy in the presence of chiral shift reagent Eu(hfc)3
[hfc=3-(heptafluoropropylhydroxymethylene)-d-camphorate].
The carbobicycle 7b dominates with chiral catalysts II–IV in
toluene as a solvent (the 7a/7b ratio ranges from 1:11 to 1:25,
see Table 2). This constitutes strong evidence for kinetic control
in the formation of 7b, also implied by the observed enantio-
meric excess of 7b (ee values of 48% and 47% for the two cor-
responding diastereomers of 7b, Table 2). Strikingly, the overall
yield (after all six steps) could be increased to a maximum of
83% using catalyst IV (Table 2, entry 4). Interestingly, in all in-
vestigated solvents (toluene, CH2Cl2, hexane, C6H6 and MeOH)
the constitutional isomer 7a was formed as a single diastereo-
mer (d.r.>99:1). However, although solvents have a strong
impact on yields and chemoselectivities, a clear trend is not
apparent (Table 2, entries 6–9).
The product of the initial ring closure (E!F or H!I) is ener-
getically lower by 17.7 kcalmolꢀ1 for the pathway to 7a. After
the tautomerization to the more stable enamine J, this effect is
only partly overcompensated and the intermediate F of the
pathway to 7a is, therefore, favored thermodynamically at this
stage by 5.4 kcalmolꢀ1 over intermediate J. The bicyclic G of
the pathway to 7a is thermodynamically slightly favored by
0.6 kcalmolꢀ1 over product 7b, whereas the reaction from F to
G is more exergonic with a reaction free energy of ꢀ2.2 kcal
molꢀ1 compared to ꢀ7.1 kcalmolꢀ1 for the formation of 7b
from J. Unlike 7b, the imine (G) can undergo tautomerization
to the enamine 7a, which is 11.7 kcalmolꢀ1 more stable than
7b. Without dispersion interactions the free energies of the
first intermediates E and H would be considerably higher
(Figure 2), whereas the subsequent reaction steps for both
pathways exhibit similar reaction free energies to those if dis-
persion is taken into account. The raising of the free energy of
In summary, the chemoselectivity and the reaction yield of
this domino process in toluene is highly dependent on the
choice of substrate and catalyst. Therefore, the control over
the chemoselectivity might be possible through the use of
a particular aldehyde or organocatalyst (see Tables 1 and 2).
Figure 2. Left: Modified version of the mechanism reported in our previous publication.[10] Right: Free energies [kcalmolꢀ1] of the most stable conformers of
the intermediates leading to 7a and 7b, respectively, relative to the reactants (D plus malononitrile), with (black) and without (gray) dispersion interactions
taken into account in the geometry optimization and calculation of free energies.
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the first intermediate indicated previously[10] is stronger for H
compared to E, which means the pathway leading to product
7b benefits more from dispersion interactions.
Table 3. Predicted and experimental 13C NMR chemical shifts for syn-2a.
C atom
NMRPredict [ppm]
Experiment [ppm]
Overall it seems that the path with the initial addition reac-
tion (D!E) is thermodynamically favored and its product 7a is
favored owing to the tautomerization to the enamine.
1
2
3
4
44.5
54.3
148.1
41.1
46.4
52.8
154.7
37.1
5
53.8
56.8
6
7
9
79.1
152.7
58.2
75.7
160.7
48.8
2.3. NMR Investigations of a Selected Domino Product
Selected findings of our extensive NMR spectroscopic study of
isoquinuclidine syn-2a was discussed in our previous publica-
tion[10] on this metal-free multi-step domino reaction. More de-
tails gained from the use of methods such as HMQC, HMBC,
correlation via long-range coupling (COLOC), COSY, NOESY, and
1H–13C heteronuclear NOESY (HOESY) are presented in this sec-
tion. For convenience, we refer to the atom numbering shown
in Figure 3.
10
11
12
13
16
17
20
16.5
20.6
13.3
112.0
115.3
115.3
118.5
14.3
21.4
13.8
116.0
115.0[a]
113.6[a]
113.8
[a] Assignment may be reversed.
13C NMR shifts; a good coincidence is evident. A discrepancy
was found for the chemical shift sequence of C-13 and C-20.
Here, our COLOC findings clearly indicate the experimental
values to be correct. Strong deviations were also found for the
olefinic carbons C-7 and C-9. These deviations might be ex-
plained by the mesomeric effects described below in reference
to the molecular dynamics.
Interesting observations were made on the intramolecular
dynamics in syn-2a. Our initial 13C and 15N spectra were record-
ed in [D6]DMSO. To our surprise, only two 13C signals and two
15N signals for the CN groups were observed under these con-
ditions. A closer inspection of these spectra showed the two
missing signals to be coalescing. However, if a mixture of
[D6]DMSO and CD3CN (1:2) were used, all four expected CN sig-
nals were resolved in the 13C and 15N spectra. Under these con-
ditions, the chemical exchange of the CN groups involving C-
16 and C-17 is considerably slower. Figure 3 shows the 13C
region of the CN signals. Figure 3a represents a spectrum re-
corded in [D6]DMSO. Note that there is coalescence of C-16
and C-17. All of the expected four signals were observed in the
spectrum recorded in the mixture of [D6]DMSO and CD3CN
(Figure 3b). Under these conditions, there is slow exchange of
the C-16 and C-17 positions.
Figure 3. Left: Zoomed 13C NMR spectra (125 MHz) of syn-2a at +258C,
showing the four CN signals. Numbering is as suggested by the NMRPredict
software.[13] a) Spectrum in [D6]DMSO; note the coalescence of the C-16 and
C-17 signals; b) spectrum in [D6]DMSO/CD3CN (1:2); note the slow exchange
rates of C-16 and C-17; c) the EXSY spectrum; the cross peaks indicate the
chemical exchange of positions 16 and 17; mixing time 2.5 s, measuring
time 7.7 h. Right: Two mesomeric structures of syn-2a. In pure [D6]DMSO,
structure VI is more preferred over structure V than in a mixture of
[D6]DMSO/CD3CN (1:2).
A
13C–13C exchange spectroscopy (EXSY) spectrum (Fig-
ure 3c) corroborates these findings: the cross peaks found
clearly indicate mutual exchange of these two CN positions.
From the cross peak intensities we conclude the exchange rate
to be in the order of approximately 1 sꢀ1. In contrast, by using
the difference in chemical shifts of C-16 and C-17 under slow-
As is often the case, the assignment of the quaternary
carbon signals in the 13C NMR spectrum of syn-2a was not
straightforward. In particular, the nitrile carbons presented
a challenge. However, in the COLOC spectrum (not shown)
there is an intense cross peak between the H-5 signal and the
exchange conditions, the Gutowsky–Holm equation (kexch
=
2.22Dn) leads to an estimated exchange rate of approximately
390 sꢀ1 in pure [D6]DMSO.
3
carbon signal at 116.00 ppm, originating from J coupling. This
carbon signal can therefore be assigned to C-13. Along with
the dynamics findings (see below), the other CN signals could
also be assigned.
The CSEARCH/NMRPredict software package[13] is a powerful
tool for estimating 13C NMR chemical shifts in a given structure.
Table 3 shows a comparison of predicted and experimental
We interpret these dramatic differences in exchange rates as
a consequence of different hydrogen bonding between NH
groups and the solvent. In classical terms, the structure of syn-
2a can be formulated as two mesomeric forms (Figure 3). In
structure V, there is a “true” double bond between C-7 and C-
9. By contrast, the zwitterionic structure VI shows a formal
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single bond between these two carbon atoms, with a much
lower barrier of exchange activation energy. Structure VI is
more preferred over structure V in pure [D6]DMSO as com-
pared to the solvent mixture. Tentatively, we interpret this ob-
servation as follows: it is well known that proton exchange is
considerably slower in pure DMSO.[14] In an NH group, the
proton “resides/sticks” at its nitrogen atom. Hence, the nitro-
gen is more prone to carry a positive charge as in structure VI,
leading to a higher single bond character of C-7ꢀC-9. If the sol-
vent ([D6]DMSO) is diluted with CD3CN, the NH proton ex-
change becomes more facile and rapid. The NH proton is con-
sidered more “loose” under these conditions. Thus, structure V
with its true C-7=C-9 double bond becomes more abundant,
thus the C-16–C-17 exchange rate is slower.
mentioning here is the exceptional stability of this imine func-
tion. Compound 7b, for instance, remained completely uncon-
verted upon treatment with mild reducing agents such as tri-
chlorosilane.
For isoquinuclidine 7a, the thermal degradation to highly
substituted pyridine derivatives[9b] was tested. The reaction was
conducted under neat conditions at a temperature of 1508C.
The formation of the elimination product 10 was confirmed by
comparison with literature data. Surprisingly, pyridine deriva-
1
tive 9 showed only two signals in the H NMR spectrum and
not three, as one might expect. It is likely that an intermolecu-
lar deprotonation of the dicyanomethyl group CH proton
through the nitrogen atom of the pyridine core occurred; only
a zwitterionic structure, which is detected in solution can ex-
plain the missing NMR signal.
The synthesis of hybrid compound 11, consisting of isoqui-
nuclidine and artesunic acid subunits, is the final example of
post-modification presented herein. The reaction to form the
amide bond was accomplished in the presence of N,N’-dicyclo-
2.4. Post-Modification of the Domino Products
As a further part of our investigations we were interested in
chemical post-modifications of our domino products to poten-
tially introduce these types of compounds to a wider field for
future applications. Three transformations that were performed
are depicted in Scheme 2.
hexylcarbodiimide
(DCC)
and
4-dimethylaminopyridine
(DMAP). Comparable amide-bond-forming reagents such as 1-
ethyl-3-(3-dimethylaminopropyl)carbodiimide and hydroxyben-
zotriazole were not able to successfully activate the substrates
in this case. Product 11 was obtained in 39% yield starting
from isoquinuclidine 7a and artesunic acid under DCC/DMAP
activation after stirring at 08C for 48 h.
2.5. Antiviral and Antimalarial Activities of Highly
Functionalized Domino Products
Currently, there is a requirement for novel antiviral and antima-
larial compounds with high efficacy and low unintended side
effects. Therefore, the development of such therapeutics has
concentrated on discovering drug candidates that operate se-
lectively and effectively against viruses and malaria.
A
promising and fundamentally novel approach to obtain new
and efficacious compounds with improved pharmacological
properties is the hybridization of bioactive natural products, in
which two or more natural product fragments are covalently
linked with each other to form new hybrid molecules.[15] These
synthetic hybrids containing partial structures of natural com-
pounds are in most cases more active than their parent com-
pounds.[16] Encouraged by our previous results and experience
with artemisinin-based hybrids[17] we demonstrate here the
high potential of our domino-product–artemisinin hybrid mol-
ecules 11, 12a/b and 13a/b (Figure 4) as antiviral and antima-
larial agents. For comparison, we also present the activities of
parent domino products 7a and 7b (not containing artemisi-
nin moieties) against human cytomegalovirus (HCMV) and Plas-
modium falciparum 3D7.
Scheme 2. Post-modifications of domino products 7a and 7b.
Iminocarbobicycle 7b was transformed in the presence of
sodium borohydride to bicyclo[2.2.2]-octa-diene 8 with the
elimination of one cyano group. As it was not possible to
obtain an X-ray crystal structure of 7b, the formation of 8 pro-
vides further evidence for the presence of the imine function
in the parent compound 7b. The two most downfield-shifted
signals in the 13C NMR spectrum of 8 at around 156 ppm fit
well the theoretical value of the two carbons adjacent to the
NH2 groups. Under the reducing conditions, this second amino
group can only originate from the imine function. Also worth
2.5.1. Antiviral Activity
The anti-HCMV activity of the new domino products and their
artemisinin-based hybrids was evaluated by the use of an es-
tablished GFP-reporter-based replication assay of HCMV (re-
combinant strain AD169-GFP) in primary human foreskin fibro-
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activity than the reference compounds (Table 4). Only isoquinu-
clidine 7a and the artesunic acid-derived hybrid 11 showed no
measurable activity (EC50 values >10 mm). An outstanding
result was obtained with the isoquinuclidine–artemisinin
hybrid 12a, as characterized by the HCMV-specific EC50 value
of 0.071 mm, which represents a 37-fold increase in in vitro effi-
cacy over the established therapeutic ganciclovir. Other active
domino products (7b, 12b, 13a and 13b) were effective, with
a range of EC50 values between 0.21 and 1.8 mm, thus showing
similar or higher activity than ganciclovir. This study shows the
eminent potential of the hybrid concept, as active hybrids
12a, 12b, 13a and 13b featured strong antiviral properties
against HCMV, outperforming the parent compounds (artemisi-
nin, 7a and 7b) and ganciclovir.
2.5.2. Antimalarial Activity
The antimalarial activities of the domino products 7a, 7b, 11,
12a, 12b, 13a and 13b (see Figure 4) were assessed by in vi-
tro cytotoxicity studies against the P. falciparum 3D7 strain
using chloroquine and dihydroartemisin (DHA) as reference
compounds (Table 5). Both control substances displayed EC50
Figure 4. The domino products evaluated against human cytomegalovirus
(HCMV) and the parasite P. falciparum 3D7 in this work.
Table 5. EC50 values for chloroquine, dihydroartemisinin and compounds
7a, 7b, 11, 12a, 12b, 13a and 13b tested against the parasite P. falcipar-
um 3D7.
[a]
Compound
Molecular weight [Da]
EC50 [nm]
blasts (HFFs).[18] Ganciclovir, an approved drug mostly applied
in conventional anti-HCMV therapy, and artemisinin, represent-
ing the parent compound of our novel hybrid products, were
used as reference compounds. Whereas ganciclovir displayed
an EC50 value of inhibition of HCMV replication in the low mi-
cromolar range (EC50 2.6ꢁ0.5 mm), artemisinin exerted no
measurable inhibitory effect within the range of analysis (EC50
>10 mm). Remarkably, five (7b, 12a/b, 13a/b, see Figure 4)
out of seven tested domino products showed higher antiviral
Chloroquine
Dihydroartemisinin
7a
7b
319.87
284.35
402.46
402.46
768.87
967.13
967.13
814.94
814.94
9.1ꢁ1.0
2.3ꢁ0.4
>1 mm
>1 mm
11
1.8ꢁ0.6
17.0ꢁ3.0
63.0ꢁ25.0
1.5ꢁ0.3
0.72ꢁ0.2
12a
12b
13a
13b
[a] Mean values ꢁ SD were calculated from at least three independent
biological replicates (nꢂ3) and each of these data sets consisted of three
separate measurements (see the Experimental Section).
Table 4. EC50 values of anti-HCMV activity (AD169-GFP) displayed in virus-
infected HFFs: ganciclovir, artemisinin and compounds 7a, 7b, 11, 12a,
12b, 13a and 13b.
values in the low-nanomolar range (9.1 and 2.3 nm, respective-
ly). Domino products 7a and 7b, prepared from phenylacetal-
dehyde, possessed only a minor inhibitory activity in the lower
micromolar range against the 3D7 strain. With EC50 values of
17 and 63 nm, the hybrid domino products 12a and 12b ex-
hibited a higher antimalarial activity in the mid-nanomolar
range. However, these EC50 values were significantly higher
than that of their parent compound DHA. In contrast to these
findings, artesunic-acid–isoquinuclidine hybrid 11 nicely dem-
onstrated a cooperative and synergistic effect of the 1,2,4-triox-
ane and isoquinuclidine moieties. With an EC50 value of 1.8 nm,
it is nearly five times more active than the parent compound
artesunic acid (EC50 =8.9 nm) and comparable in activity to
DHA (EC50 =2.3 nm), although the parent isoquinuclidine 7a
was inactive.
Compound
Molecular weight [Da]
EC50 [mm][a]
Ganciclovir[b]
Artemisinin[b]
7a
7b
11
12a[c]
12b[c]
13a
255.23
282.34
402.46
402.46
768.87
967.13
967.13
814.94
814.94
2.6ꢁ0.50
>10
>10
1.84ꢁ0.15
>10
0.07ꢁ0.00
0.26ꢁ0.01
0.21ꢁ0.00
0.22ꢁ0.00
13b
[a] Mean values ꢁ SD were calculated from replicates, n=4 (all data sets
were confirmed by performing two independent experiments). [b] EC50
values have been previously reported.[19] [c] EC50 values have been previ-
ously reported.[10]
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The best result was that achieved with hybrid domino
product 13b, which outperformed both reference compounds,
with a remarkable EC50 value of 0.72 nm, followed by its consti-
tutional isomer 13a with a value of 1.5 nm.
Experimental Section
Chemistry
1
For details of the H and 13C NMR spectroscopy of compounds in
this manuscript and their spectra, see the Supporting Information.
Complete characterization of the following domino products has
been reported previously: anti-2a, syn-2a, 2b, anti-7a, 7b, 12a,
12b, 13a and 13b.[10]
3. Conclusions
In summary, we present a more thorough investigation of the
recently introduced imidazole-catalyzed six-step domino reac-
tion, providing a direct and convenient route to bioactive aza-
bicyclic and carbobicyclic compounds.[10] We have demonstrat-
ed the extension of the substrate scope towards aliphatic alde-
hydes with longer chain lengths and found a reversed chemo-
selectivity of this reaction in the case of 3-phenylpropanal (5).
As well as imidazole, different bifunctional organocatalysts
have been investigated for the reaction of phenylacetaldehyde
(7) with malononitrile. The most active catalyst in this screen-
ing was the dihydroquinine-derived thiourea IV, use of which
led to the domino products 7a and 7b in a high overall yield
of 83% and high chemoselectivity towards the carbobicycle
7b (7a/7b=1:25). It is apparent that the chemoselectivity of
this domino process is strongly dependent on the choice of
substrate and the catalyst and, therefore, the control over the
chemoselectivity might be possible through the use of a
particular aldehyde or organocatalyst.
General Procedure for the Metal-free Multi-Step Domino
Reaction
Imidazole (2.5 mg, 0.036 mmol) was added to a stirred solution of
the corresponding aldehyde (0.48 mmol) and malononitrile (24 mg,
0.72 mmol) in toluene (1 mL). The reaction mixture was stirred at
room temperature for 48 h. The solvent was removed under re-
duced pressure and the crude product was purified by silica gel
column chromatography (hexane/EtOAc, 5:1 to 3:1).
5-Amino-3-(dicyanomethylene)-7-ethyl-8-propyl-2-azabicy-
clo[2.2.2]oct-5-ene-4,6-dicarbonitrile (anti-3a)
1
White solid; H NMR (400 MHz, CD3OD): d=4.35 (d, J=1.9 Hz, 1H),
1.95–1.85 (m, 1H), 1.85–1.79 (m, 1H), 1.65 (dtd, J=10.3, 4.2, 2.0 Hz,
1H), 1.56–1.33 (m, 3H), 1.25–1.12 (m, 2H), 1.00 ppm (m, 6H);
13C NMR (100 MHz, CD3OD): d=163.9, 154.9, 116.8, 115.6, 114.0,
76.3, 54.0, 53.0, 50.1, 47.9, 36.4, 28.0, 21.0, 14.4, 11.7 ppm; IR (ATR,
solid): n˜ =3450, 3323, 3267, 3199, 2966, 2207, 1659, 1607, 1564,
1460, 1408, 1331, 1284, 1225, 1112, 995, 730, 591, 542 cmꢀ1; MS
[MALDI, sinapinic acid (sin), 2,5-dihydroxybenzoic acid (dhb)]: m/z:
307 [M+H]+, 329 [M+Na]+; HRMS (ESI): m/z: calcd for C17H18N6Na:
329.1485 [M+Na]+; found: 329.1487.
To further investigate the chemodivergent domino process,
and to understand the influence of dispersion interactions, we
studied the thermodynamics of the steps of both reaction
pathways (leading to 7a and 7b, correspondingly) by DFT cal-
culations of the intermediates both without and with disper-
sion interactions. We found that the pathway leading to prod-
uct 7b is more favored with dispersion interactions. Further-
more, a range of NMR techniques (HMQC, HMBC, COLOC,
5-Amino-3-(dicyanomethylene)-7-ethyl-8-propyl-2-azabicy-
clo[2.2.2]oct-5-ene-4,6-dicarbonitrile (syn-3a)
1
COSY, NOESY, and H–13C HOESY) was used for determining the
1
White solid; H NMR (400 MHz, (CD3)2CO): d=9.38 (s, 1H), 6.61 (s,
structure of the isoquinuclidine syn-2a, formed from propanal.
A strongly solvent-dependent exchange of the two nitrile
groups adjacent to the exocyclic double bond was detected.
The study was completed by post-modifications of domino
products 7a and 7b and the investigation of their antiviral
and antimalarial properties, as well as selected domino
product–artemisinin hybrid molecules 11, 12a, 12b, 13a and
13b. To our delight, biological tests against HCMV revealed
five domino products, 7b, 12a, 12b, 13a and 13b, as highly
active compounds (EC50 values 0.071–1.8 mm), outperforming
the clinical reference drug ganciclovir (EC50 2.6 mm). In this re-
spect it was found that artemisinin-derived azabicycle 12a was
the most active compound. With respect to the activity against
the parasite P. falciparum 3D7, three domino products 11, 13a
and 13b (EC50 values 0.72–1.8 nm) were more potent than the
clinically used drug chloroquine (EC50 9.1 nm). Among these
three hits, the artemisinin-derived iminocarbobicyclic com-
pound 13b was the most efficient against the P. falcipar-
um 3D7 strain. These results are another excellent proof of the
hybridization concept and confirm that the multi-step domino
reactions are convenient, sustainable, efficient, and direct
routes to novel lead structures for medicinal chemistry.
2H), 4.65 (d, J=1.6 Hz, 1H), 2.54 (td, J=9.8, 2.0 Hz, 1H), 2.31–2.19
(m, 1H), 1.76–1.45 (m, 5H), 1.34–1.21 (m, 1H), 1.05 (t, J=7.3 Hz,
3H), 0.99 ppm (t, J=7.2 Hz, 3H); 13C NMR (100 MHz, (CD3)2CO): d=
161.5, 154.9, 115.3, 114.5, 113.9, 112.8, 77.6, 53.4, 52.7, 50.7, 45.2,
45.2, 30.6, 23.3, 21.0, 13.4, 11.7 ppm; IR (ATR, solid): n˜ =3411, 3327,
3204, 2952, 2870, 2206, 1655, 1612, 1574, 1446, 1395, 1319, 1285,
1224, 1201, 1114, 986, 935, 780, 659, 601, 535, 453 cmꢀ1; MS
(MALDI, dhb): m/z: 329 [M+Na]+; HRMS (ESI): m/z: calcd for
C17H18N6Na: 329.1485 [M+Na]+; found: 329.1477.
6-Amino-8-ethyl-2-imino-7-propylbicyclo[2.2.2]oct-5-ene-
1,3,3,5-tetracarbonitrile (3b, Mixture of Diastereomers)
1
White solid; H NMR (300 MHz, (CD3)2CO): d=12.58–11.81 (2ꢁs, 2ꢁ
1H), 6.79–6.75 (2ꢁs, 2ꢁ2H), 3.96–3.90 (1ꢁs, 1ꢁd, J=1.8 Hz, 2ꢁ
1H), 2.00–1.95 (m, 2H), 1.88–1.38(m, 11H), 1.34–1.17(m, 3H), 1.09–
1.03 (2ꢁt, J=7.4, 7.4 Hz, 2ꢁ3H), 1.00–0.94 ppm (2ꢁt, J=7.1,
7.2 Hz, 2ꢁ3H); 13C NMR (100 MHz, (CD3)2CO): d=161.7, 160.4,
155.4, 154.2, 116.6, 116.5, 113.8, 113.7, 113.3, 113.1, 112.8, 112.4,
69.4, 68.8, 58.1, 56.3, 46.9, 46.7, 43.8, 43.2, 43.0, 43.0, 42.0, 36.4,
36.3, 28.7, 28.6, 20.7, 20.6, 13.9, 13.8, 11.5, 11.3, 11.3 ppm; IR (ATR,
solid): n˜ =3395, 3327, 3238, 2929, 2203, 2157, 1645, 1592, 1458,
1416, 1313, 1244, 1195, 1078, 985, 889, 836, 782, 741, 594, 528,
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437 cmꢀ1; MS (MALDI, dhb): m/z: 329 [M+Na]+; HRMS (ESI): m/z:
calcd for C17H18N6Na: 329.1485 [M+Na]+; found: 329.1487.
6-Amino-8-benzyl-2-imino-7-phenethylbicyclo[2.2.2]oct-5-ene-
1,3,3,5-tetracarbonitrile (5b, Mixture of Diastereomers)
1
White solid; H NMR (400 MHz, (CD3)2CO): d=12.63–11.90 (2ꢁs, 2ꢁ
1H), 7.52–7.10 (m, 20H), 6.91–6.87 (2ꢁs, 4H), 3.57–3.51 (1ꢁs, 1ꢁd,
J=2.1 Hz, 2H), 3.03–2.98 (2ꢁd, J=4.9 Hz, 1H, J=4.9 Hz, 1H), 2.91–
2.78 (m, 4H), 2.72–2.66 (m, 2H), 2.63–2.51 (m, 2H), 2.36–2.27 (m,
2H), 2.26–2.15 (m, 1H), 2.14–2.05 (m, 1H), 1.73–1.53 ppm (m, 2H);
13C NMR (100 MHz, (CD3)2CO): d=161.2, 160.2, 155.3, 154.2, 141.2,
141.1, 138.2, 138.2, 129.5, 129.5, 129.3, 129.3, 128.9, 128.9, 128.6,
128.6, 127.4, 127.4, 126.6, 126.6, 116.6, 116.5, 113.6, 113.4, 113.1,
113.0, 112.5, 112.2, 69.3, 68.7, 58.0, 58.0, 56.3, 45.9, 45.9, 44.2, 43.7,
43.6, 43.3, 43.3, 42.0, 41.3, 41.2, 36.3, 33.5, 33.4 ppm; IR (ATR, solid):
n˜ =3433, 3343, 3220, 2922, 2856, 2201, 1644, 1598, 1495, 1453,
1412, 1233, 1121, 1056, 1030, 890, 841, 800, 748, 700, 570, 529,
470, 439 cmꢀ1; MS (MALDI, om): m/z: 453 [M+Na]+; HRMS (ESI):
m/z: calcd for C27H22N6Na: 453.1798 [M+Na]+; found: 453.1798.
5-Amino-8-butyl-3-(dicyanomethylene)-7-propyl-2-azabicy-
clo[2.2.2]oct-5-ene-4,6-dicarbonitrile (anti-4a)
1
White solid; H NMR (400 MHz, (CD3)2CO): d=9.37 (s, 1H), 6.67 (s,
2H), 4.55 (d, J=1.7 Hz, 1H), 1.99–1.86 (m, 2H), 1.58–1.26 (m, 10H),
0.92 ppm (t, J=6.9 Hz, 6H); 13C NMR (100 MHz, (CD3)2CO): d=
162.7, 153.0, 115.4, 112.9, 77.2, 53.1, 52.0, 52.0, 49.2, 48.0, 47.1, 36.3,
33.0, 22.9, 20.1, 13.7, 13.6 ppm; IR (ATR, solid): n˜ =3462, 3423,
3259, 3228, 3182, 2956, 2926, 2859, 2213, 2200, 1655, 1571, 1442,
1396, 1217, 1114, 1058, 985, 867, 638, 590, 544, 448 cmꢀ1; MS
[MALDI, om (without matrix)]: m/z: 357.2 [M+Na]+; HRMS (ESI):
m/z: calcd for C19H22N6Na: 357.1798 [M+Na]+; found: 357.1792.
5-Amino-8-butyl-3-(dicyanomethylene)-7-propyl-2-azabicy-
clo[2.2.2]oct-5-ene-4,6-dicarbonitrile (syn-4a)
4-Amino-2,6-dimethylcyclohex-4-ene-1,1,3,3,5-pentacarbo-
nitrile (6, Mixture of Diastereomers)
1
White solid; H NMR (400 MHz, (CD3)2CO): d=9.42 (s, 1H), 6.62 (s,
The reaction was performed according to the general procedure
for the metal-free multi-step domino reaction with acetaldehyde
and malononitrile as starting compounds. The reaction was stirred
at room temperature for 24 h. The crude product was purified by
column chromatography (pure CH2Cl2) to afford 6 as a white solid.
2H), 4.61 (d, J=1.7 Hz, 1H), 2.53 (td, J=10.0, 2.1 Hz, 1H), 2.40–2.29
(m, 1H), 1.85–1.72 (m, 1H), 1.71–1.49 (m, 4H), 1.48–1.24 (m, 5H),
0.94 ppm (2ꢁt, J=6.8 Hz, 6H); 13C NMR (75 MHz, (CD3)2CO): d=
161.8, 155.2, 115.7, 114.9, 114.3, 113.2, 78.0, 53.9, 53.8, 51.1, 45.8,
43.8, 32.8, 30.8, 29.0, 23.0, 21.3, 14.3, 14.1 ppm; IR (ATR, solid): n˜ =
3418, 3324, 3228, 2957, 2868, 2207, 1657, 1571, 1460, 1400, 1218,
1136, 1061, 977, 938, 872, 648, 597, 536, 455 cmꢀ1; MS (MALDI,
dhb): m/z: 357.2 [M+Na]+; HRMS (ESI): m/z: calcd for C19H22N6Na:
357.1822 [M+Na]+; found: 357.1792.
1
M.p. 1058C; H NMR (400 MHz, (CD3)2CO): d=7.04–6.97 (s, 2ꢁ2H),
3.62 (2ꢁq, J=6.8 Hz, 2ꢁ1H), 3.41 (2ꢁq, J=7.0 Hz, 2ꢁ1H), 1.88 (d,
J=6.8 Hz, 3H), 1.83 (d, J=6.8 Hz, 3H), 1.60 (d, J=6.9 Hz, 3H),
1.55 ppm (d, J=7.0 Hz, 4H); 13C NMR (100 MHz, (CD3)2CO): d=
144.5, 143.3, 116.2, 115.6, 113.2, 112.6, 112.6, 112.3, 112.3, 110.3,
109.9, 109.8, 79.3, 79.3, 42.9, 40.5, 39.8, 39.7, 39.4, 36.4, 36.3, 35.5,
17.3, 17.2, 15.4, 15.1 ppm; IR (ATR, solid): n˜ =3432, 3350, 3230,
2981, 2943, 2884, 2207, 2159, 1648, 1617, 1458, 1372, 1311, 1226,
1155, 1099, 998, 946, 816, 731, 674, 419 cmꢀ1; MS (MALDI, dctb):
m/z: 273.1 [M+Na]+; HRMS (ESI): m/z: calcd for C13H10N6Na:
273.0859 [M+Na]+; found: 273.0856.
6-Amino-7-butyl-2-imino-8-propylbicyclo[2.2.2]oct-5-ene-
1,3,3,5-tetracarbonitrile (4b, Mixture of Diastereomers)
1
White solid; H NMR (400 MHz, (CD3)2CO): d=12.58–11.82 (2ꢁs, 2ꢁ
1H), 6.80–6.75 (2ꢁs, 2ꢁ2H), 3.94–3.87 (1ꢁs, 1ꢁd, J=2.2 Hz, 2ꢁ
1H), 2.17–2.09 (m, 2H), 2.00–1.95 (m, 2H), 1.92–1.73 (m, 2H), 1.60–
1.20 (m, 18H), 0.98–0.89 ppm (m, 12H); 13C NMR (100 MHz,
(CD3)2CO): d=161.7, 160.5, 155.4, 154.2, 116.6, 116.5, 113.8, 113.7,
113.3, 113.2, 112.9, 112.5, 69.5, 68.8, 58.1, 56.4, 47.0, 46.9, 44.0, 43.2,
43.2, 42.0, 40.8, 37.8, 37.7, 33.9, 33.8, 22.8, 22.8, 20.1, 20.1, 13.5,
13.4 ppm; IR (ATR, solid): n˜ =3402, 3333, 3226, 2960, 2931, 2863,
2200, 1647, 1594, 1461, 1417, 1315, 1245, 1090, 1007, 1055, 1007,
918, 894, 836, 813, 745, 708, 585, 524, 509, 439 cmꢀ1; MS (MALDI,
om): m/z: 357.2 [M+Na]+; HRMS (ESI): m/z: calcd for C19H22N6Na:
357.1798 [M+Na]+; found: 357.1808.
Reduction with Sodium Borohydride: 2,6-Diamino-7-benzyl-8-
phenylbicyclo[2.2.2]octa-2,5-diene-1,3,5-tricarbonitrile (8)
Carbobicycle 7b (29 mg, 0.072 mmol, 1 equiv) was dissolved in
methanol (0.6 mL) and cooled to 08C. Sodium borohydride (27 mg,
0.72 mmol, 10 equiv.) was added and the reaction mixture was
stirred for 30 min, before it was allowed to warm to room tempera-
ture. After 5.5 h the reaction was quenched by the addition of sa-
turated NaHCO3 (1 mL). The organic layer was separated and the
aqueous phase was extracted with CH2Cl2 (3ꢁ5 mL). The combined
organic phases were washed with brine (15 mL) and dried over
Na2SO4. The solvent was removed under reduced pressure and the
crude product was purified by column chromatography (hexane/
EtOAc, 4:1 to 2:1) to give 8 as a white solid (15 mg, 0.040 mmol,
56%). M.p. decomposition >3008C; 1H NMR (400 MHz, (CD3)2CO):
d=7.19–7.10 (m, 2H), 7.11–6.92 (m, 6H), 6.92–6.82 (m, 2H), 6.40–
3.40 (2ꢁs, 4H), 3.40 (dd, J=13.0, 3.7 Hz, 1H), 3.19 (d, J=2.5 Hz,
1H), 3.08 (dd, J=4.8, 2.5 Hz, 1H), 3.04–2.97 (m, 1H), 2.52 ppm (dd,
J=13.0, 11.6 Hz, 1H); 13C NMR (100 MHz, (CD3)2CO): d=156.9,
(156.8), 154.7, (154.6), 142.2, 137.9, 129.7, 128.6, 128.4, 128.0, 126.8,
117.1, 116.8, 114.8, 80.5, (80.4), 78.4, (78.4), 54.3, (54.2), 53.5, 51.6,
45.4, 40.0 ppm; IR (ATR, solid): n˜ =3458, 3395, 3332, 3221, 2917,
2848, 2197, 1658, 1615, 1495, 1454, 1224, 1185, 1161, 1080, 1032,
974, 737, 696, 650, 581, 552, 506 cmꢀ1; HRMS (ESI): m/z: calcd for
C24H19N5Na: 400.1533 [M+Na]+; found: 400.1539.
5-Amino-7-benzyl-3-(dicyanomethylene)-8-phenethyl-2-aza-
bicyclo[2.2.2]oct-5-ene-4,6-dicarbonitrile (anti-5a)
White solid; 1H NMR (400 MHz, CD3CN): d=7.42–7.10 (m, 10H),
5.86 (s, 2H), 4.12 (d, J=1.9 Hz, 1H), 2.70 (dd, J=13.9, 6.4 Hz, 1H),
2.62–2.37 (m, 4H), 2.27–2.19 (m, 1H), 2.17–1.96 (m, 2H), 1.49–
1.38 ppm (m, 1H); 13C NMR (100 MHz, CD3CN): d=163.0, 153.3,
142.5, 139.6, 130.5, 129.8, 129.6, 129.4, 127.9, 127.3, 116.1, 115.1,
115.0, 113.7, 78.6, 54.0, 52.4, 50.6, 49.5, 47.3, 40.2, 35.9, 33.1 ppm;
IR (ATR, solid): n˜ =3470, 3369, 3200, 3134, 2924, 2859, 2199, 1644,
1582, 1495, 1447, 1394, 1325, 1277, 1217, 1033, 913, 747, 699, 545,
502 cmꢀ1
; MS [MALDI, trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-
prop enylidene]malononitrile (dctb)]: m/z: 453 [M+Na]+; HRMS
(ESI): m/z: calcd for C27H22N6Na: 453.1798 [M+Na]+; found:
453.1790; calcd for C27H22N6K: 469.1538 [M+K]+; found: 469.1523.
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nant human cytomegalovirus (HCMV AD169-GFP) as described pre-
viously.[18a,19b] All data represent mean values of determinations in
quadruplicate [HCMV infections performed in duplicate, GFP meas-
urements of total cell lysates performed in duplicate using auto-
mated quantitative GFP fluorometry in a Victor 1420 Multilabel
Counter (PerkinElmer Wallac GmbH, Freiburg, Germany), as de-
scribed].[21] Processing and evaluation of data was performed by
the use of Excel (means and standard deviations).
4-Amino-2-(dicyanomethyl)pyridine-3,5-dicarbonitrile (9)
Neat domino product 7a was heated at 1508C for 17 h. Then, the
resulting material was suspended in CH2Cl2. After centrifugation
(3 min), the precipitate and supernatant were separated. This pro-
cedure was repeated twice. The precipitate was dried under high
vacuum to afford the pyridine derivative 9 in satisfactory purity as
a
beige solid (15 mg, 0.072 mmol, 79%). M.p. decomposition
1
>2508C; H NMR (400 MHz, (CD3)2SO): d=8.27 (s, 2H), 8.23 ppm (s,
1H); 13C NMR (100 MHz, (CD3)2SO): d=157.9, 155.0, 149.4, 117.3,
116.2, 113.8, 113.1, 86.7, 78.0, 42.3 ppm; IR (ATR, solid): n˜ =3317,
3207, 3076, 2207, 1655, 1623, 1570, 1510. 1404, 1316, 1259, 1224,
1081, 877, 781, 748, 684, 664, 581, 553, 458, 422 cmꢀ1; HRMS (ESI,
negative): m/z: calcd for C10H3N6: 207.0425 [MꢀH]ꢀ; found:
207.0426.
Cytotoxicity Studies against P. falciparum 3D7 Strains
P. falciparum Culture
P. falciparum 3D7 parasites were cultured in type-A-positive human
erythrocytes at a hematocrit of 5% in RPMI 1640 supplemented
with HEPES (25 mm), hypoxanthine (0.1 mm), gentamycin
(50 mgmLꢀ1) and 0.5% albumax I. Cultures were incubated at 378C
under controlled atmospheric conditions of 5% O2, 3% CO2, and
92% N2 at 95% relative humidity.
Removal of the solvent of the supernatant under reduced pressure
afforded the byproduct (E)-prop-1-ene-1,3-diyldibenzene (10)[20] as
a colorless oil (6.0 mg, 0.031 mmol, 33%); 1H NMR (400 MHz,
CDCl3): d=7.37–7.26 (m, 7H), 7.23–7.15 (m, 3H), 6.45 (d, J=
15.8 Hz, 1H), 6.39–6.25 (m, 1H), 3.54 ppm (d, J=6.6 Hz, 2H);
13C NMR (100 MHz, CDCl3): d=140.2, 137.5, 131.1, 129.3, 128.7,
128.6, 128.5, 127.2, 126.2, 126.2, 39.3 ppm; HRMS (APPI): m/z: calcd
In Vitro Antimalarial Activity Assay
for C15H14: 194.1090 [M] +; found: 194.1096.
C
Cultures used in cell proliferation assays were synchronized by
treatment with sorbitol.[22] Effective concentrations to inhibit para-
site growth by 50% (EC50) were determined using the SYBR Green I
malaria drug-sensitivity assay.[23] Aliquots (50 mL) of a cell suspen-
sion containing ring stages at a parasitemia of 0.2% and a hema-
tocrit of 2% were added to the wells of 96-well microtiter plates.
Plates were incubated for 72 h in the presence of drugs at various
concentrations. Subsequently, cells of each well were lysed with
2ꢁ lysis buffer [Tris (40 mm, pH 7.5), EDTA (10 mm), 0.02% saponin,
0.08% Triton X-100; 50 mL] containing SYBR green (8.3 mm). Plates
were incubated for 1 h in the dark at room temperature with con-
stant mixing before the fluorescence (excitation wavelength
485 nm; emission wavelength >520 nm) was measured using a mi-
crotiter plate fluorescence reader (Victor X4, PerkinElmer). Drugs
were serially diluted (1:3), with initial drug concentrations of
243 nm for chloroquine and 81 nm for dihydroartemisinin and it
derivatives. Each drug concentration was tested in triplicate and re-
peated at least three times. Uninfected erythrocytes (hematocrit
2%) and infected erythrocytes without drug served as controls and
were investigated in parallel. Percent growth was calculated as de-
scribed by Beez and co-workers.[24] Data were analyzed using the
SigmaPlot (version 12.0; Hill function, three parameters) and Sig-
maStat (version 13.0) programs.
Domino Isoquinuclidine–Artesunate Hybrid (11)
Artesunic acid (28 mg, 0.073 mmol, 1 equiv) and isoquinuclidine 7a
(29 mg, 0.073 mmol, 1 equiv.) were dissolved in acetonitrile
(2.8 mL) under inert conditions (in a nitrogen atmosphere). This so-
lution was cooled to 08C, then, DMAP (4.5 mg, 0.037 mmol,
0.5 equiv.) and DCC (20 mg, 0.095 mmol, 1.3 equiv.) were added se-
quentially. The reaction mixture was stirred for 48 h at 08C. The
mixture containing a precipitate was filtered and the filtrate was
concentrated under reduced pressure. The crude product was puri-
fied by column chromatography (hexane/EtOAc, 6:1 to 3:1) to
afford 11 as a white solid (22 mg, 0.029 mmol, 39%). M.p. decom-
position >1908C; 1H NMR (300 MHz, (CD3)2CO): d=9.90 (s, 1H),
9.89 (s, 1H), 9.23 (s, 2ꢁ1H), 7.18–6.95 (m, 2ꢁ10H), 5.73 (d, J=
9.8 Hz, 1H), 5.69 (d, J=9.9 Hz, 1H), 5.47 (s, 2ꢁ1H), 4.67 (d, J=
1.0 Hz, 2ꢁ1H), 3.63–3.52 (m, 2ꢁ1H), 3.46 (ddd, J=11.3, 7.6, 3.6 Hz,
2ꢁ1H), 3.35–3.25 (m, 2ꢁ1H), 3.05–2.73 (m, 2ꢁ3H), 2.55–2.17 (m,
2ꢁ3H), 1.99–1.37 (m, 2ꢁ8H), 1.29 (s, 3H), 1.28 (s, 3H), 1.25–0.97
(m, 2ꢁ3H), 0.93 (d, J=6.3 Hz, 3H), 0.92 (d, J=6.3 Hz, 3H), 0.85 (d,
J=7.1 Hz, 3H), 0.84 ppm (d, J=7.0 Hz, 3H); 13C NMR (100 MHz,
(CD3)2CO): d=172.9, 171.1, 170.2, 169.7, 162.7, 162.4, 152.4, 152.3,
140.2, 139.3, 137.0, 136.9, 129.8, 129.7, 129.2, 128.9, 128.6, 128.6,
128.5, 128.2, 128.0, 127.4, 127.2, 126.9, 125.3, 120.3, 115.2, 112.8,
112.5, 112.5, 109.3, 108.6, 104.2, 104.1, 93.0, 92.5, 91.6, 91.5, 80.3,
80.2, 77.9, 77.8, 57.8, 57.1, 53.6, 52.7, 52.3, 52.3, 52.0, 50.8, 50.7,
50.1, 49.2, 48.3, 45.6, 45.6, 39.3, 39.0, 37.1, 37.1, 36.4, 34.6, 34.4,
32.2, 32.1, 30.9, 26.6, 25.5, 24.9, 22.8, 21.8, 21.8, 20.0, 13.8, 11.9,
11.8 ppm; IR (ATR, solid): n˜ =3449, 3347, 3206, 3134, 2926, 2873,
2202, 1720, 1647, 1570, 1495, 1451, 1405, 1379, 1221, 1179, 1158,
1099, 1013, 945, 875, 825, 752, 694, 647, 564, 539, 511 cmꢀ1; HRMS
(ESI): m/z: calcd for C44H44N6NaO7: 791.3164 [M+Na]+; found:
791.3163; elemental analysis calcd (%) for C44H46N6O8 (M+H2O): C
67.16, H 5.89, N 10.68; found: C 66.97, H 5.68, N 10.50.
Acknowledgements
S.B.T. and A.G. gratefully acknowledge financial support from the
Deutsche Forschungsgemeinschaft (DFG) by grants TS 87/17-
1 and GO 523/16-1 (SPP 1807, Priority Programme “Control of
London Dispersion Interactions in Molecular Chemistry”). S.B.T. is
also grateful for funding from the DFG (grants TS 87/15-1 and TS
87/16-3) and the Wilhelm Sander-Stiftung (grant 2014.019.1).
M.M. and C.H. thank the financial support of the DFG (grant MM
1289/7-3), the Wilhelm Sander-Stiftung (grant 2011.085.2) and
the Bayerische Forschungsstiftung (ForBIMed-Biomarker in der In-
fektionsmedizin, grant I1). We also thank the Graduate School
Molecular Science (GSMS), Interdisciplinary Center for Molecular
Materials (ICMM) and Emerging Fields Initiative (EFI) “Chemistry
in Live Cells” supported by Friedrich-Alexander-Universitꢁt Erlan-
HCMV GFP-Based Replication Assay
An HCMV GFP-based replication assay was performed over a dura-
tion of seven days (multi-round infection) using primary human
foreskin fibroblasts (HFFs) infected with a GFP-expressing recombi-
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Funel, G. Schmidt, S. Abele, Org. Process Res. Dev. 2011, 15, 1420–1427;
g) I. Wauters, A. De Blieck, K. Muylaert, T. S. A. Heugebaert, C. V. Stevens,
Eur. J. Org. Chem. 2014, 1296–1304.
gen-Nꢀrnberg for research funding and the Elite Network of Ba-
varia for a doctoral research fellowship for C.M.B.
[9] a) M. Igarashi, Y. Nakano, K. Takezawa, T. Watanabe, S. Sato, Synthesis
1987, 68–70; b) Y. Nakano, W.-Y. Shi, Y. Nishii, M. Igarashi, J. Heterocycl.
Chem. 1999, 36, 33–40; c) Y. Nakano, Y. Kaneko, W. A. Fen, Heterocycles
1999, 51, 169–177; d) N. Mahajan, V. Gupta, P. Kotwal, A. S. Pannu, T. K.
Razdan, J. Chem. Crystallogr. 2011, 41, 552–556.
Conflict of Interest
The authors declare no conflict of interest.
[10] C. M. Bock, G. Parameshwarappa, S. Bçnisch, C. Neiss, W. Bauer, F.
Hampel, A. Gçrling, S. B. Tsogoeva, Chem. Eur. J. 2016, 22, 5189–5197.
[11] a) I. Iriepa, F. J. Villasante, E. Gꢅlvez, L. Labeaga, A. Innerarity, A. Orjales,
Bioorg. Med. Chem. Lett. 2002, 12, 189–192; b) M. E. Kuehne, L. He, P. A.
Jokiel, C. J. Pace, M. W. Fleck, I. M. Maisonneuve, S. D. Glick, J. M. Bidlack,
J. Med. Chem. 2003, 46, 2716–2730; c) L. S. Aitken, N. R. Arezki, A. Dell’I-
sola, A. J. A. Cobb, Synthesis 2013, 45, 2627–2648; d) E. Cifuentes-
Pagano, J. Saha, G. Csanyi, I. Al Ghouleh, S. Sahoo, A. Rodriguez, P. Wipf,
P. J. Pagano, E. M. Skoda, MedChemComm 2013, 4, 1085–1092; e) Y. Wa-
tanabe, S. Kitazawa, H. Fujii, T. Nemoto, S. Hirayama, T. Iwai, H. Gouda,
S. Hirono, H. Nagasea, Bioorg. Med. Chem. Lett. 2014, 24, 4980–4983.
[12] M. R. S. Weir, J. B. Hyne, Can. J. Chem. 1965, 43, 772–782.
[13] CSEARCH/NMRPredict software package, W. Robien, University of
Vienna, Austria; http://nmrpredict.orc.univie.ac.at/ last accessed Octo-
ber 24, 2015.
Keywords: antimalarial agents · antiviral agents · density
functional calculations · domino reactions · organocatalysis
[1] a) L. F. Tietze, Chem. Rev. 1996, 96, 115–136; b) H.-C. Guo, J.-A. Ma,
Angew. Chem. Int. Ed. 2006, 45, 354–366; Angew. Chem. 2006, 118,
362–375; c) L. F. Tietze, G. Brasche, K. M. Gericke, Domino Reactions in
Organic Synthesis, Wiley-VCH, Weinheim, 2006; d) H. Pellissier, Tetrahe-
dron 2006, 62, 1619–1665; e) H. Pellissier, Tetrahedron 2006, 62, 2143–
2173; f) K. C. Nicolaou, D. J. Edmonds, P. G. Bulger, Angew. Chem. Int. Ed.
2006, 45, 7134–7186; Angew. Chem. 2006, 118, 7292–7344; g) C. J.
Chapman, C. G. Frost, Synthesis 2007, 1–21; h) D. Enders, C. Grondal,
M. R. M. Hꢂttl, Angew. Chem. Int. Ed. 2007, 46, 1570–1581; Angew.
Chem. 2007, 119, 1590–1601; i) C. Vaxelaire, P. Winter, M. Christmann,
Angew. Chem. Int. Ed. 2011, 50, 3605–3607; Angew. Chem. 2011, 123,
3685–3687; j) Ł. Albrecht, H. Jiang, K. A. Jørgensen, Angew. Chem. Int.
Ed. 2011, 50, 8492–8509; Angew. Chem. 2011, 123, 8642–8660; k) L. F.
Tietze, Domino Reactions: Concepts for Efficient Organic Synthesis, Wiley-
VCH, Weinheim, 2014; l) C. M. R. Volla, I. Atodiresei, M. Rueping, Chem.
Rev. 2014, 114, 2390–2431.
[14] M. Hoshino, H. Katou, K.-i. Yamaguchi, Y. Goto, Biochim. Biophys. Acta
Biomembranes 2007, 1768, 1886–1899.
[15] a) L. F. Tietze, H. P. Bell, S. Chandrasekhar, Angew. Chem. Int. Ed. 2003,
42, 3996–4028; Angew. Chem. 2003, 115, 4128–4160; b) G. Mehta, V.
Singh, Chem. Soc. Rev. 2002, 31, 324–334; c) A. Ganesan, Curr. Opin. Bio-
technol. 2004, 15, 584–590; d) B. Meunier, Acc. Chem. Res. 2008, 41,
69–77.
[2] a) D. Enders, M. R. M. Hꢂttl, C. Grondal, G. Raabe, Nature 2006, 441,
861–863; b) L. Zu, H. Li, H. Xie, J. Wang, W. Jiang, Y. Tang, W. Wang,
Angew. Chem. Int. Ed. 2007, 46, 3732–3734; Angew. Chem. 2007, 119,
3806–3808; c) Ł. Albrecht, B. Richter, C. Vila, H. Krawczyk, K. A. Jørgen-
sen, Chem. Eur. J. 2009, 15, 3093–3102; d) K. Jiang, Z.-J. Jia, X. Yin, L.
Wu, Y.-C. Chen, Org. Lett. 2010, 12, 2766–2769; e) D. B. Ramachary, C.
Venkaiah, P. Murali, Krishna, Chem. Commun. 2012, 48, 2252–2254.
[3] a) Y. Hayashi, T. Okano, S. Aratake, D. Hazelard, Angew. Chem. Int. Ed.
2007, 46, 4922–4925; Angew. Chem. 2007, 119, 5010–5013; b) E. Reyes,
H. Jiang, A. Milelli, P. Elsner, R. G. Hazell, K. A. Jørgensen, Angew. Chem.
Int. Ed. 2007, 46, 9202–9205; Angew. Chem. 2007, 119, 9362–9365.
[4] a) W.-B. Chen, Z.-J. Wu, Q.-L. Pei, L.-F. Cun, X.-M. Zhang, W.-C. Yuan, Org.
Lett. 2010, 12, 3132–3135; b) W. Sun, G. Zhu, C. Wu, L. Hong, R. Wang,
Chem. Eur. J. 2012, 18, 6737–6741.
[5] a) O. Mahꢃ, I. Dez, V. Levacher, J.-F. Briꢄre, Angew. Chem. Int. Ed. 2010,
49, 7072–7075; Angew. Chem. 2010, 122, 7226–7229; b) C. Yu, Y.
Zhang, A. Song, Y. Ji, W. Wang, Chem. Eur. J. 2011, 17, 770–774.
[6] a) W. Seebacher, C. Schlapper, R. Brun, M. Kaiser, R. Saf, R. Weis, Eur. J.
Pharm. Sci. 2005, 24, 281–289; b) W. Seebacher, C. Schlapper, R. Brun,
M. Kaiser, R. Saf, R. Weis, Eur. J. Med. Chem. 2006, 41, 970–977; c) M. O.
Faruk Khan, M. S. Levi, B. L. Tekwani, N. H. Wilson, R. F. Borne, Bioorg.
Med. Chem. 2007, 15, 3919–3925; d) T. S. Banerjee, S. Paul, S. Sinha, S.
Das, Bioorg. Med. Chem. 2014, 22, 6062–6070.
[16] a) S. B. Tsogoeva, Mini-Rev. Med. Chem. 2010, 10, 773–793; b) T. Frçhlich,
A. C¸apcı Karagçz, C. Reiter, S. B. Tsogoeva, J. Med. Chem. 2016, 59,
7360–7388.
[17] a) C. Horwedel, S. B. Tsogoeva, S. Wei, T. Efferth, J. Med. Chem. 2010, 53,
4842–4848; b) C. Reiter, A. Herrmann, A. C¸apci, T. Efferth, S. B. Tsogoeva,
Bioorg. Med. Chem. 2012, 20, 5637–5641; c) C. Reiter, A. C¸apcı Karagçz,
T. Frçhlich, V. Klein, M. Zeino, K. Viertel, J. Held, B. Mordmꢂller, S. Emir-
˘
dag ꢆztꢂrk, H. Anıl, T. Efferth, S. B. Tsogoeva, Eur. J. Med. Chem. 2014,
75, 403–412; d) C. Reiter, T. Frçhlich, L. Gruber, C. Hutterer, M. Marschall,
C. Voigtlꢇnder, O. Friedrich, B. Kappes, T. Efferth, S. B. Tsogoeva, Bioorg.
Med. Chem. 2015, 23, 5452–5458; e) C. Reiter, T. Frçhlich, M. Zeino, M.
Marschall, H. Bahsi, M. Leidenberger, O. Friedrich, B. Kappes, F. Hampel,
T. Efferth, S. B. Tsogoeva, Eur. J. Med. Chem. 2015, 97, 164–172.
[18] a) M. Marschall, M. Freitag, S. Weiler, G. Sorg, T. Stamminger, Antimicrob.
Agents Chemother. 2000, 44, 1588–1597; b) M. Marschall, T. Stamminger,
A. Urban, S. Wildum, H. Ruebsamen-Schaeff, H. Zimmermann, P. Lischka,
Antimicrob. Agents Chemother. 2012, 56, 1135–1137.
[19] a) S. J. F. Kaptein, T. Efferth, M. Leis, S. Rechter, S. Auerochs, M. Kalmer,
C. A. Bruggeman, C. Vink, T. Stamminger, M. Marschall, Antiviral Res.
2006, 69, 60–69; b) S. Chou, G. Marousek, S. Auerochs, T. Stamminger,
J. Milbradt, M. Marschall, Antiviral Res. 2011, 92, 364–368.
[20] E. Alacid, C. Nꢅjera, Org. Lett. 2008, 10, 5011–5014.
[21] C. Hutterer, I. Niemann, J. Milbradt, T. Frçhlich, C. Reiter, O. Kadioglu, H.
Bahsi, I. Zeittrꢇger, S. Wagner, J. Einsiedel, P. Gmeiner, N. Vogel, S. Wan-
dinger, K. Godl, T. Stamminger, T. Efferth, S. B. Tsogoeva, M. Marschall,
Antiviral Res. 2015, 124, 101–109.
[22] C. Lambros, J. P. Vanderberg, J. Parasitol. 1979, 65, 418–420.
[23] M. Smilkstein, N. Sriwilaijaroen, J. X. Kelly, P. Wilairat, M. Riscoe, Antimi-
crob. Agents Chemother. 2004, 48, 1803–1806.
[7] a) M. Rueping, C. Azap, Angew. Chem. Int. Ed. 2006, 45, 7832–7835;
Angew. Chem. 2006, 118, 7996–7999; b) H. Yang, R. G. Carter, J. Org.
Chem. 2009, 74, 5151–5156; c) H. Yang, R. G. Carter, Tetrahedron 2010,
66, 4854–4859; d) N. Holub, H. Jiang, M. W. Paix¼o, C. Tiberi, K. A. Jør-
gensen, Chem. Eur. J. 2010, 16, 4337–4346; e) D. Wu, Y. H. He, X. Deng,
Z. Guan, J. Heterocycl. Chem. 2013, 50, 425–429; f) A. Alizadeh, V. Sade-
ghi, F. Bayat, L.-G. Zhu, Synlett 2014, 25, 2609–2612.
[8] a) D. Schinzer, M. Kalesse, Tetrahedron Lett. 1991, 32, 4691–4694; b) Y.-S.
Lin, S.-Y. Chang, M.-S. Yang, C. P. Rao, R. K. Peddinti, Y.-F. Tsai, C.-C. Liao,
J. Org. Chem. 2004, 69, 447–458; c) V. Thornqvist, S. Manner, M. Wing-
strand, T. Frejd, J. Org. Chem. 2005, 70, 8609–8612; d) J. Carreras, A.
Avenoza, J. H. Busto, J. M. Peregrina, J. Org. Chem. 2007, 72, 3112–
3115; e) H. Nakano, K. Osone, M. Takeshita, E. Kwon, C. Seki, H. Matsuya-
ma, N. Takano, Y. Kohari, Chem. Commun. 2010, 46, 4827–4829; f) J.-A.
[24] D. Beez, C. P. Sanchez, W. D. Stein, M. Lanzer, Antimicrob. Agents Chemo-
ther. 2011, 55, 50–55.
Received: January 11, 2017
Revised: March 1, 2017
Published online on && &&, 2017
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FULL PAPERS
C. M. Bock, G. Parameshwarappa,
S. Bçnisch, W. Bauer, C. Hutterer,
M. Leidenberger, O. Friedrich,
M. Marschall, B. Kappes, A. Gçrling,
S. B. Tsogoeva*
The domino effect: Investigations of
the metal-free six-step domino reaction
of aldehydes with malononitrile are re-
ported, extending the scope of alde-
hydes and organocatalysts. NMR studies
of selected products and DFT calcula-
tions of the thermodynamics of this re-
action are presented. Evaluation of
seven highly functionalized and artemi-
sinin-containing domino products
against human cytomegalovirus and
Plasmodium falciparum 3D7 reveals high
activity, with the compounds outper-
forming the clinical drugs ganciclovir
and chloroquine.
&& – &&
Deeper Insight into the Six-Step
Domino Reaction of Aldehydes with
Malononitrile and Evaluation of
Antiviral and Antimalarial Activities of
the Obtained Bicyclic Products
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ÝÝ These are not the final page numbers!