Carbohydrates in Peptide and Protein Design - Peptide and Protein Design for Biopharmaceutical Applications - page 176

oligosaccharides - to produce novel peptides, peptidomimetics and
de novo -designed proteins. These hybrid molecules, chimeras, have
properties arising largely from the combination of structural characteristics
of carbohydrates with the functional group diversity of peptides. This field
includes synthetic glycopeptides, sugar (carbohydrate) amino acids
as peptidomimetics (see also Chapter 3), carbohydrate scaffolds
for nonpeptidal peptidomimetics of cyclic peptides (see also Chapter 4),
cyclodextrin-functionalized peptides and carboproteins, i.e.
carbohydrate-based protein mimetics (see also Chapter 6). These successful
applications demonstrate the general utility of carbohydrates in peptide and
protein architecture.
In this chapter we will attempt to provide an overview of novel hybrid
molecules or chimeric compounds. We will cover carbohydrates in pep-
tide design, but not the reverse, i.e. not peptides in carbohydrate design
such as are found in the replacement of glycosidic linkages with amides.
There are exhaustive reviews on synthetic glycopeptides [1]; in this
chapter we only show a few applications of glycopeptides.
But why bother with 'carbohydrates in peptide and protein design'? In
a much-quoted review on peptidomimetics from 1993, Giannis and
Kolter anticipated: '...the potential of the carbohydrate skeleton in the
design of nonpeptide ligands. Carbohydrates offer advantages of struc-
tural diversity and the facile derivatization with a multitude of functional
groups' [2]. Very briefly, 'carbohydrates in peptide and protein design'
promises to combine the structural properties of carbohydrates with the
functional group diversity of peptides for the design and synthesis of new
peptidomimetics and proteinomimetics, as well as for functionalized
cyclodextrins.

5.2 CONFIGURATIONAL AND

CONFORMATIONAL PROPERTIES OF
CARBOHYDRATES

There is no sharp and unequivocal definition of what counts as a carbo-
hydrate. In fact, the very name 'carbohydrate' is slightly misleading as it
suggests the sole constituents to be carbon and water. While the formula
C x (H 2 O) x covers many carbohydrates, numerous others do not fit with
this, e.g. glucosamine (2-amino-2-deoxy- D -glucose). Carbohydrates, as a
wide group of compounds, can be described by Wittgenstein's concept of
'family resemblance', i.e. they are related not by unifying, underlying