ISMSC 2007 - Università degli Studi di Pavia

OP 19
Pyrrolic Tripodal Receptors for Molecular Recognition of Monosaccharides:
Tuning Selectivity
Martina Cacciarini, a Oscar Francesconi, a Cristina Nativi, a Stefano Roelens b
a Dipartimento di Chimica Organica, Università di Firenze, and b CNR – IMC, Polo Scientifico e
Tecnologico, Via della Lastruccia, 13 – 50019 Sesto Fiorentino, Firenze, Italy
There has been a considerable interest in recent years for synthetic receptors for molecular
recognition of carbohydrates. [1] The research in this field was fuelled by the discovery of the
ubiquitary presence of carbohydrates on cell surfaces, exerting a number of roles relying on
molecular recognition processes that are crucial for cell’s life, such as, among others, adhesion,
infection and immune response. [2] Although encouraging results have been obtained, mostly in
organic solvents, with receptors possessing significant affinities for mono or oligosaccharides,
selectivity, the most relevant and ambitious target, is still a challenging goal far to be reached.
Benzene based tripodal architectures have been frequently employed in the last decade to
develop synthetic receptors for monosaccharides, leading to interesting results. [1] In this
context, we recently reported a new generation of cyclic (1) and acyclic (2) receptors featuring
pyrrolic binding sites, which were shown to effectively bind to monosaccharides. [3]
NH HN HN
NH
HN
HN
HN
NH HN
1
In an effort to explore the potentials of this new family of receptors, we found that selectivity can
be directed toward specific monosaccharides by strategically introduce appropriate substituents
into the architecture of the receptor, preserving the flexibility of the tripodal scaffold. In the
present communication, the results obtained with this versatile family of hosts, endowed with
recognition properties among the best reported in the recent literature, will be discussed,
showing how affinity and selectivity are modulated by an appropriate combination of functional
groups and substituents.
[1] For a recent comprehensive review on the subject, see: A. P. Davis, T. D. James, in
Functional Synthetic Receptors; T. Schrader, A. D. Hamilton, Eds.; WileyVCH: Weinheim,
2005; pp.45-109.
[2] B. Ernst, W. Hart, P. Sinaÿ, Carbohydrates in Chemistry and Biology; WileyVCH:
Weinheim, 2000; Part I, Vol. 2 and Part II, Vol. 4.
[3] (a) O. Francesconi, A. Ienco, G. Moneti, C. Nativi, S. Roelens, Angew. Chem. Int. Ed. 2006,
45, 6693-6696. (b) C. Nativi, M. Cacciarini, O. Francesconi, A. Vacca, G. Moneti, A. Ienco, S.
Roelens, J. Am. Chem. Soc., 2007, ASAP 16/3/2007.
NH
H
N
HN
2
HN
H
N
HN
Threading of molecular handcuffs to obtain new interlocked twodimensional
species
O
O
O
O
O
O
O
N N
Cu
N N N
Cu
N N N N N
O
O
O
O
O
O
O
O
O
a [2]-catenane
N
N
O
O
N
N
molecular handcuffs
O
O
O
O
2+
N
N
O
O
O
O
MeO
MeO
O
O
O
O
O
O
O
O
O
O
O
O
O
O
N N
Cu
N N
N N
N N
Cu
N N
N N
N N
N N
Cu
Cu
N N N N
O
O
O
O
O
O
O
O
O
O
O
O
a non-stoppered [4]rotaxane
OP 20
Valérie Heitz a , Jean-Paul Collin a , Julien Frey a , Tomàs Kraus b , Jean-Pierre Sauvage a , Christian
Tock a
a. Institut de Chimie de Strasbourg, Laboratoire de Chimie Organo-Minérale, Université Louis
Pasteur, 4, rue Blaise Pascal, 67000 Strasbourg, France.
b. Dr. Tomàs Kraus, Institute of Organic Chemistry and Biochemistry, Flemingovo nam. 2,
16610 Prague, Czech Republic.
Elaboration of multirotaxanes or multicatenanes incorporating several rings and several threadlike
fragments is very challenging, as synthetic targets or as prototypes of molecular machines.
The copper(I) templated strategy used in the group long ago has been extended to more and
more complex molecules, incorporating several metal centres. We have described recently the
synthesis of a handcuffs-like bis-macrocycle consisting of two back-to back rigidly connected
1,10-phenanthroline units as the central core, each phenanthroline being part of a 30membered
macrocycle. [1] Threading this bis-macrocycle with a large ring gave a [2]catenane
with an unusual topology as represented below. The bis-macrocycle can also be utilised for
constructing more complex systems such as, in particular, a rotaxane tetramer or its nonstoppered
analogue, as depicted in the scheme. [2]
[1]. "A catenane consisting of a large ring threaded through both cyclic units of a handcuff-like
compound". J. Frey, T. Kraus, V. Heitz, J.-P. Sauvage, Chem. Commun., 2005, 5310-5312.
[2]. "Copper(I)-induced threading of two bis-macrocycles on two rods: a cyclic [4]rotaxane".
J.-P. Collin, J. Frey, V. Heitz, E. Sakellariou, J.-P. Sauvage, C. Tock, New J. Chem. 2006,
30, 1386-1389.
4+
OMe
OMe