A concise synthesis of two isomeric pentasaccharides, the O repeat units from the lipopolysaccharides of P. syringae pv. porri NCPPB 3364T and NCPPB 3365 Original Research Article

A concise synthesis of two isomeric pentasaccharides, α-l-Rhap-(1 → 2)-α-l-Rhap-(1 → 3)-α-l-Rhap-(1 → 3)-[β-d-GlcpNAc-(1 → 2)]-α-l-Rhap () and α-l-Rhap-(1 → 2)-α-l-Rhap-(1 → 3)-[β-d-GlcpNAc-(1 → 2)]-α-l-Rhap-(1 → 3)-α-l-Rhap (), the O repeats from the lipopolysaccharides of Pseudonomonas syringae pv. porri NCPPB 3364T and 3365 was achieved via assembly of the building blocks, allyl 3,4-di-O-benzoyl-α-l-rhamnopyranoside (), 2,3,4-tri-O-benzoyl-α-l-rhamnopyranosyl trichloroacetimidate (), allyl 4-O-benzoyl-3-O-chloroacetyl-α-l-rhamnopyranoside (), 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl trichloroacetimidate (), and allyl 2,4-di-O-benzoyl-α-l-rhamnopyranoside (). Coupling of with followed by deallylation and trichloroacetimidate formation gave the disaccharide donor , while condensation of with , followed by dechloroacetylation, offered the disaccharide acceptor . Then, was coupled with to obtain the trisaccharide , and subsequent deallylation and trichloroacetimidate formation furnished the trisaccharide donor . Coupling of with , followed by deprotection, afforded pentasaccharide , while condensation of with , followed by deallylation and trichloroacetimidate formation, gave the tetrasaccharide donor , whose coupling with and subsequent deprotection yielded another pentasaccharide .