Chemical synthesis of the O-antigen repeating unit of Actinobacillus actinomycetemcomitans serotype f

Abstract

Herein, we report the total synthesis of the trisaccharide repeating unit of the O-antigen of Actinobacillus actinomycetemcomitans serotype f. The trisaccharide comprising of α-(1–2) and α-(1–3)-linked L-rhamnopyranosides backbone with the latter rhamnose containing a branching N-acetyl-d-galactosaminopyranoside at the C2–O via a β-glycosidic bond was synthesized by two methods. Initially, the protected trisaccharide has been synthesized by step-wise assembly of the monosaccharide building blocks and subsequently the former was synthesized by the one-pot assembly of the latter components. The synthesized trisaccharide contains an aminoethyl linker appended as an O-glycoside at the reducing end, thereby providing scope for further conjugation for different applications.