Chemical Fucosylation of a Polysaccharide: A Semisynthetic Access to Fucosylated Chondroitin Sulfate Antonio Laezza, † Alfonso Iadonisi, † Cristina De Castro, ‡ Mario De Rosa, § Chiara Schiraldi, § Michelangelo Parrilli, ∥ and Emiliano Bedini* ,† † Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario Monte S.Angelo, via Cintia 4, I-80126 Napoli, Italy ‡ Department of Soil, Plant, Environmental, and Animal Production Sciences, University of Naples Federico II, via Universita ̀ 100, I-80055 Portici, Italy § Department of Experimental Medicine, Second University of Naples, via de Crecchio 7, I-80138 Napoli, Italy ∥ Department of Biology, University of Naples Federico II, Complesso Universitario Monte S.Angelo, via Cintia 4, I-80126 Napoli, Italy * S Supporting Information ABSTRACT: Chemical O-glycosylation of polysaccharides is an almost unexplored reaction. This is mainly due to the difficulties in derivatizing such complex biomacromolecules in a quantitative manner and with a fine control of the obtained structural parameters. In this work, chondroitin raw material from a microbial source was chemo- and regioselectively protected to give two polysaccharide intermediates, that acted in turn as glycosyl acceptors in fucosylation reactions. Further manipulations on the fucosylated polysaccharides, including multiple de-O-benzylation and sulfation, furnished for the first time nonanimal sourced fucosylated chondroitin sulfates (fCSs)−polysaccharides obtained so far exclusively from sea cucumbers (Echinoidea, Holothuroidea) and showing several very interesting biological activities. A semisynthetic fCS was characterized from a structural point of view by means of 2D-NMR techniques, and preliminarily assayed in an anticoagulant test. ■ INTRODUCTION Chondroitin sulfate (CS) is a biomacromolecule with a linear backbone constituted of glucuronic acid (GlcA) and N-acetyl- galactosamine (GalNAc), linked together through alternating β- 1 → 3 and β-1 → 4 glycosidic bonds. The resulting 4)-β-GlcA-(1 → 3)-β-GalNAc-(1→ disaccharide repeating unit could be decorated with one or more sulfate groups to give different sulfation patterns. 1 Sulfated L-fucose (Fuc) branches have been found α-glycosidically linked at position O-3 of GlcA units in CS polysaccharides extracted from sea cucumbers (Echinoidea, Holothuroidea) (Figure 1). 2 Different varieties of sea cucumbers from the seawater of different geographical zones show fucosylated chondroitin sulfates (fCSs) with different Fuc branches. In particular, a variation in Fuc and/or GalNAc sulfation pattern has been observed. 3 fCSs have been shown to possess several interesting activities in biological events related to atherosclerosis, cellular growth, angiogenesis, inflammation, fibrosis, cancer metastasis, virus infection, hyperglycemia, and, above all, coagulation and thrombosis. 2 It is noteworthy that most of these biological activities strictly require the presence of sulfated Fuc branches on CS backbone. 4 The anticoagulant and antithrombotic activity of fCS seems to be driven by a serpin-dependent mechanism in which thrombin inhibition is mediated by both antithrombin (AT) and heparin cofactor II (HC-II). 4c Nonetheless, a serpin- independent mechanism was proposed too, as fCS showed anticoagulant activity also when tested on AT- and HCII-free plasmas. 5 Furthermore, the antithrombotic action of fCS was discovered to be retained even when it was orally taken up. 6 These unique activities greatly support fCS as a strong candidate for a new anticoagulant and antithrombotic drug. Nonetheless, two drawbacks must be taken into account: the severe Received: May 13, 2015 Revised: June 12, 2015 Published: June 17, 2015 Figure 1. General structure of natural fCSs. Article pubs.acs.org/Biomac © 2015 American Chemical Society 2237 DOI: 10.1021/acs.biomac.5b00640 Biomacromolecules 2015, 16, 2237−2245