Total Synthesis of the All-Rare Sugar-Containing Pentasaccharide Repeating Unit of the O-Polysaccharide of Plesiomonas shigelloides Strain 302-73 (Serotype O1)

Abstract

First total synthesis of the conjugation-ready pentasaccharide repeating unit of Plesiomonas shigelloides strain 302-73 (serotype O1) is reported. The complex target pentasaccharide is composed of all-rare amino sugars such as orthogonally functionalized D-bacillosamine, L-fucosamine, and L-pneumosamine linked through four consecutive α-linkages. The poor nucleophilicity of axial 4-OH of L-fucosamine and stereoselective glycosylations are the key challenges in the total synthesis, which was completed via a longest linear sequence of 27 steps in 3% overall yield.

Total Synthesis of the Repeating Units of O-Specific Polysaccharide of Pseudomonas chlororaphis subsp. aureofaciens UCM B-306 via One-Pot Glycosylation

“…To the best of our knowledge, the synthesis of Gal p NAcAN-containing oligosaccharides has so far not been reported in literature. In a continuation of our ongoing efforts toward the synthesis of rare sugars containing bacterial oligosaccharides, − herein we report the first total syntheses of two trisaccharide repeating units via an expedient one-pot assembly.…”

“…Both d -bacillosamine and d -fucosamine thioglycoside donors are readily accessible in excellent overall yields through our established protocol via the sequential one-pot displacement of corresponding 2,4-bistriflates. , Recent work by Bennett and co-workers demonstrated that the 2-naphthylmethyl (Nap) group and PMP groups can be orthogonally cleaved to facilitate chain extension of the RUs in complex oligosaccharide assembly. Indeed, the reducing-end PMP ether can be easily cleaved using CAN to reveal the anomeric hemiacetal, which can be transformed into either a variety of donors for further attachment with a saccharide or a linker for protein conjugation …”

“…Indeed, the reducing-end PMP ether can be easily cleaved using CAN to reveal the anomeric hemiacetal, which can be transformed into either a variety of donors for further attachment with a saccharide or a linker for protein conjugation. 17 Initially we attempted the synthesis of bacillosamine acceptor 6 from the known 25 bacillosamine thioglycoside building block 7. The glycosylation of donor 7 and acceptor pmethoxyphenol (PMPOH) using NIS, TfOH as the promoter, and Et 2 O as a cosolvent was expected to give the α-linked bacillosamine derivative 8.…”

Total Synthesis of Trisaccharide Repeating Unit of Staphylococcus aureus Type 8 (CP8) Capsular Polysaccharide

“…Such a trisaccharide can be used for making larger glycans in the quest for finding the optimal length of the antigen for vaccine development. Earlier, we have established efficient protocols involving a one-pot double displacement of 2,4-bistriflates derived from d - as well as l -sugars, which allowed a facile and expedient access to a variety of rare deoxy amino sugars, , and the glycoconjugates thereof, − including CP5 trisaccharide. Herein, we report an efficient total synthesis of CP8 trisaccharide RU 1 .…”

Total Synthesis of the Repeating Units of Proteus penneri 26 and Proteus vulgaris TG155 via a Common Disaccharide

“…An efficient protocol of regioselective one-pot S N 2 displacements of pyranosidic 2,4-bis-triflates has been developed in our lab to access a range of rare 6-deoxy d -hexoses and later on extended to 6-deoxy l -hexoses as well. This strategy enabled the synthesis of various rare sugar building blocks that could be assembled into a variety of complex glycans. − Here, we report the first total synthesis of linker appended trisaccharide and tetrasaccharide repeating units of P. penneri 26 ( 1 ) and P. vulgaris TG155 ( 2 ). The main challenges associated with the syntheses are (1) synthesis of rare sugar building blocks i.e.…”