Chemistry Reference
In-Depth Information
Sugar decorated receptors for
chiral anions
Jaros
"
aw M. Granda and Janusz Jurczak*
DOI: 10.1039/9781849739986-00445
In this contribution, we present anion receptors possessing binding pocket modified with
monosaccharides. We also discuss how incorporation of a sugar into host backbone affect
structural and binding properties of anion receptors, what is exemplified by recognition of
achiral anions. Following important factors in design of chiral receptors, are also discussed -
geometry and topology of anion binding pocket as well as the role of sugar moiety in
recognition processes. Application of sugar containing receptors in chiral recognition of
biologically important anions such as
a
-hydroxy and
a
-amino acids are presented.
1 Introduction
Anions are omnipresent in the natural world, and although frequently
unnoticed, perform important functions.
1
Chlorides are present in im-
mense amounts in the oceans, nitrates and sulfates are found in the acid
rains, and carbonates are key-element in biomineralized materials. An-
thropogenic anions, including pertechnetate, a radioactive product in
spent nuclear fuel, phosphate and nitrate from agriculture, constitute the
main pollution hazard. Anions are also crucial for maintenance of life.
Every imaginable biochemical process at some stage is related with rec-
ognition, transformation, and transport of anions. Anionic species are
essential in formation enzyme-substrate and enzyme-cofactor complexes
as well as in interaction of proteins with RNA and DNA. High energy
anionic polyphosphates are in the center of power processes in the cell
metabolism. Anion carriers and channels are involved in transport of
small anions such as chloride, phosphates, and sulfates in or out of the
cell, maintaining the osmotic pressure. Misregulation of anion transport
mechanism can have serious consequences. For example, mal-
functioning chloride transport channel is involved in cystic fibrosis.
The design of anion receptors is particularly di
cult when compared
to design of receptors for cations. There are number of reasons for this.
Anions are bigger than analogous isoelectronic cations and therefore
have a lower charge to radius ratio.
2
The more diffuse nature means that
electrostatic interactions are less ecient. Anions may be pH sensitive
(becoming protonated at low pH) and thus loosing negative charge. The
receptor must function within the pH window of the target anion.
Moreover, in contrast to cations, anionic species have a diversity of
geometries, and therefore a higher degree of design and comple-
mentarity is needed to construct anion receptors selective for a particular
anionic guest (Fig. 1).
Search WWH ::
Custom Search