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6
Chemo-Enzymatic Cascade Reactions for the Synthesis of
Glycoconjugates

Ruben R. Rosencrantz, Bastian Lange, and Lothar Elling

6.1
Introduction

6.1.1
Impact of Glycoconjugates and Their Synthesis
Glycans cover the surface of virtually every eukaryotic cell. This sugar coat consists
of glycoconjugates where the glycans are covalently linked to nonsugar moieties.
In vivo, these glycoconjugates are the well-known glycoproteins – in fact more than
50% of all human proteins – proteoglycans and glycolipids [1]. Glycoconjugates are
among nature’s most structurally and functionally diverse and complex structures.
In contrast to other major native polymers like DNA and proteins their structure is
neither limited to linear sequences nor is their synthesis template driven. Glycan
structures are generally accepted as carriers of information that is encoded in the
sequence of different carbohydrate building blocks, the stereo- and regioselectiv-
ity of their linkages as well as the branching of sugar chains. More and more
human diseases are characterized to be related to aberrant glycosylation underlin-
ing the importance of glycoconjugates in cellular interaction, immunology, and
signaling events [2–4]. Progress in functional glycomics uncovers their role in
major biological processes. Tumor invasion and metastasis [5], pathogen–host
interactions [6, 7], cellular signal transduction and trafficking events [8, 9], and
the development of multicellular organisms [10] are prominent examples. In this
respect, glycoconjugates bear a high potential for biomedical applications. Among
them are carbohydrate-based drugs [11], potential biomarkers [12–14] as well as
cancer epitopes [15], and glycans from pathogens [16–19] as potential vaccine
candidates. Exposed on the cell surface, glycoconjugates are involved in cell–cell
and cell–matrix interactions [20] and are therefore of great importance for the
biofunctionalization of biomaterial surfaces in regenerative medicine and tissue
engineering [21]. Fostering our understanding of their biological roles and develop-
ing diagnostic and therapeutic applications are the driving forces for the synthesis
of well-defined glycoconjugates.

Cascade Biocatalysis: Integrating Stereoselective and Environmentally Friendly Reactions, First Edition.
Edited by Sergio Riva and Wolf-Dieter Fessner.
c 2014 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2014 by Wiley-VCH Verlag GmbH & Co. KGaA.