Total Synthesis of Repeating Unit of O-Polysaccharide of Providencia alcalifaciens O22 via One-Pot Glycosylation

Abstract

The first total synthesis of the phosphorylated trisaccharide repeating unit of Providencia alcalifaciens O22 is reported. The trisaccharide contains rare deoxyamino sugar AAT at the reducing end and d-glyceramide 2-phosphate at the other end. The efficient synthesis involves one-pot assembly of trisaccharide and late-stage phosphorylation as key steps.

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

“…The monosaccharide building blocks 3 , 6 , and 7 [ 43 ] were synthesized from previously reported compounds 8 [ 36 ], 9 [ 44 – 45 ], and 10 [ 46 ] as described in Scheme 2 .…”

“…Chheda and co-worker, in 2015, reported the total synthesis of the pentasaccharide repeating unit of the O -specific polysaccharide of Providencia alcalifaciens O28 [ 35 ]. In 2017, Kulkarni and co-worker accomplished the total synthesis of a O-polysaccharide of Providencia alcalifaciens O22 via a one pot assembly of the oligosaccharide unit [ 36 ]. Recently in 2020 Werz and co-workers completed the total synthesis of a tri-, hexa-, and heptasaccharide of the O-polysaccharide of Providencia rustigianii O34 [ 37 ].…”

Chemical Synthesis of Rare, Deoxy-Amino Sugars Containing Bacterial Glycoconjugates as Potential Vaccine Candidates

“…The main difficult tasks for the synthesis of trisaccharide are the construction of orthogonally protected rare sugar AAT building block and phosphorylation of the secondary alcohol adjacent to the amide functionality in the d -glyceramide unit. Kulkarni and co-workers reported first total synthesis of trisaccharide 151 in one-pot manner in highly regioselective fashion [ 85 ]. Coupling of 4-OH thiophenyl galactoside donor 145 and 3-OH AAT acceptor 146 using NIS, TMSOTf promoter led to the formation of 4′-OH disaccharide as a single α isomer.…”

Total Synthesis of the Phosphorylated Zwitterionic Trisaccharide Repeating Unit of Photorhabdus temperata cinerea 3240

“…Target molecule 1 can be obtained by hydrogenolysis of the fully functionalized phosphorylated trisaccharide 2 , which can be synthesized by phosphorylation of trisaccharide acceptor 3 with phosphoramidite 4 . Benzyl ester 3 could be accessed by regioselective glycosylation of orthogonally protected AAT donor 6 with disaccharide acceptor 5 followed by desilylation, oxidation of the primary alcohol to the carboxylic acid, and concomitant esterification. Disaccharide acceptor 5 could in turn be obtained by the assembly of suitably functionalized d -galactosamine donor 7 with 4-OH glucose acceptor 8 followed by ester hydrolysis.…”

“…The remaining 3-OH was capped with the Fmoc group by using FmocCl, pyridine to afford orthogonally protected d -galactosamine donor 7 in 95% yield. The key rare sugar building block AAT 6 was prepared by following our established protocol. Once we had all of the desired building blocks in hand, the stage was set for glycosylation.…”