Full Papers
DOI: 10.1002/cplu.201800497
1
2
3
4
5
6
7
8
9
Synthesis of Thicolchicine-Based Conjugates: Investigation
towards Bivalent Tubulin/Microtubules Binders
Elisa Bonandi,[a] Francesca Foschi,[a] Cristina Marucci,[a] Federico Dapiaggi,[a] Maurizio Sironi,[a]
Stefano Pieraccini,[a] Michael S. Christodoulou,[a, b] Francisco de Asís Balaguer,[c]
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
Four different hybrid compounds have been efficiently synthe-
sized by conjugation of deacetylthiocolchicine with pironetin-
inspired derivatives. The modest bioactivity and the apparent
absence of interaction with α-tubulin is explained by a
posteriori in silico investigation, which suggests a relevant
distance between the thiocolchicine binding site and the
proper pocket on the α-tubulin. The modest activity on
resistant cells suggested that the lipophilic nature of the linker
used renders the resulting compounds better substrates for p-
Gp efflux pumps. The study better clarifies the design of
bivalent compounds that target hetero tubulin/microtubules.
Introduction
activities, which are regulated by tubulin post translational
modifications.[3] Depending on the mode of action, MT-target-
ing agents can be divided into two different families: MT-
stabilizing agents and MT-destabilizing agents. In the last
decade, both these classes have been successfully applied in
the treatment of several cancer types,[4] and the search of new
cytotoxic or neuroprotective agents is still of primary interest.
Thus, our interest in the obtainment of new molecules able to
target tubulin and MTs, prompted us to plan the synthesis of
new tubulin/microtubules-targeting bivalent compounds. Bi-
functional drugs, bearing chemical entities that are able to bind
to separate sites of the protein, recently attracted the attention
of the scientific community, thanks to their possible great
pharmacological potential. The idea of conjugating different
MTs binders into bivalent entities led to the obtainment of
novel antimitotic agents, including taxoid-colchicine,[5] vinca
alkaloid-taxoid hybrids,[6] colchicineÀ tubulizine,[7] colchicine-pir-
onetin,[8] podophyllotoxin-thiocolchicine and hybrids merging
histone deacetylase inhibitors with different tubulin binders.[9,10]
On one hand the use of too short or rigid linkers prevents the
interaction with the desired binding site and leads to steric
clashes. On the other hand, the use of a too long and flexible
linker may lead to solubility and cell internalization problems.[11]
As the linker seems to play a critical role tuning the bioactivity
of these class of molecules, we planned the synthesis of new
bivalent compounds, constituted by a well-known β-tubulin
binder (thiocolchicine) and a pironetin-inspired compound
(hybrid 1, Figure 1) connected by linkers of different types and
length, to investigate how their properties affect the binding
capability.
Microtubules (MTs) are highly dynamic structures, diffused in
eukaryotic cells, as well as in some bacteria.[1] They are
fundamental components of the cytoskeleton and they play
important roles in several essential cellular processes, such as
cell division, locomotion, intracellular transport and cell shape
definition. MTs are originated from the head-to-tail arrange-
ment of α,β-tubulin heterodimers, leading to the formation of
cylindrical assemblies. In physiological conditions, MTs are
characterized by alternating phases of growth and shrinkage, a
behaviour known as “dynamic instability”. This dynamism is
essential for MTs correct functionality, in particular for the
formation of the mitotic spindle during the mitosis process.[2]
The perturbation of this dynamic behaviour can result in
deleterious effects for the cells, halting the cell replication and
inducing cellular apoptosis. Therefore, MTs represent very
suitable drug target, for anticancer therapy and also for
neurodegenerative diseases treatment, as recently emerged. In
fact, MTs dynamic instability is essential in many neuronal
[a] Dr. E. Bonandi, Dr. F. Foschi, C. Marucci, Dr. F. Dapiaggi, Prof. M. Sironi,
Dr. S. Pieraccini, Dr. M. S. Christodoulou, Prof. D. Passarella
Dipartimento di Chimica
Università degli Studi di Milano
via Golgi 19, 20133 Milano (Italy)
E-mail: daniele.passarella@unimi.it
[b] Dr. M. S. Christodoulou
Dipartimento di Scienze Farmaceutiche
Università degli Studi di Milano
via Golgi 19, 20133 Milano (Italy)
[c] Dr. F. de Asís Balaguer, Dr. J. F. Díaz
Chemical and Physical Biology
Centro de Investigaciones Biológicas
Consejo Superior de Investigaciones Cientificas CIB–CSIC
Madrid 28040 (Spain)
Results and Discussion
[d] Dr. N. Zidar
Faculty of Pharmacy
University of Ljubljana
Askerceva cesta 7, 1000 Ljubljana (Slovenia)
For the first explorative studies a ten-atom all-carbon chain and
a 24-atom pseudo-peptidic chain were taken into account. As
active units, we choose thiocolchicine and hybrid compound 1
as models of β- and possible α-binder, respectively (Figure 1).
Supporting information for this article is available on the WWW under
ChemPlusChem 2019, 84, 98–102
98
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim