Studies towards a Conjugate Vaccine for Anthrax: Synthesis of the Tetrasaccharide Side Chain of the Bacillus anthracis Exosporium |
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Authors: | Roberto Adamo,Rina Saksena,Pavol Kov
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Affiliation: | Roberto Adamo,Rina Saksena,Pavol Kováč |
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Abstract: | The first synthesis of β‐L ‐glycoside 17 of the tetrasaccharide β‐Ant‐(1 → 3)‐α‐L ‐Rhap‐(1 → 3)‐α‐L ‐Rhap‐(1 → 2)‐L ‐Rhap is described (Schemes 1–3). Its spacer can be functionalized to make it amenable to conjugation to proteins by different conjugation methods. The synthesis was performed in a stepwise manner starting from the aglycon‐bearing terminal saccharide with thioglycosides as glycosyl donors. To attach the upstream terminal anthrose residue, the assembled linker‐equipped trisaccharide was glycosylated with ethyl 4‐azido‐3‐O‐benzyl‐2‐O‐(bromoacetyl)‐4,6‐dideoxy‐1‐thio‐β‐D ‐glucopyranoside ( 11 ). Further functionalization of the tetrasaccharide thus obtained, followed by deprotection gave the target substance 17 . Synthesis of substructures of 17 equipped with the same spacer, namely β‐L ‐Rhap‐1‐O‐(CH2)5COOMe ( 21 ), α‐L ‐Rhap‐(1 → 2)‐β‐L ‐Rhap‐1‐O‐(CH2)5COOMe ( 22 ), and α‐L ‐Rhap‐(1 → 3)‐α‐L ‐Rhap‐(1 → 2)‐β‐L ‐Rhap‐1‐O‐(CH2)5COOMe ( 23 ), is also described (Scheme 4). |
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Keywords: | Anthrax Anthrose β ‐Rhamnopyranoside Thioglycoside Oligosaccharides Glycosides Vaccines Bacillus anthracis |
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