RESUMO
Two structurally defined, functionalized glycans of lipoteichoic acid (LTA, also known as PS-III) from C. difficile, which have one or two repeating units of LTA linked to the core trisaccharide, were efficiently synthesized via a convergent [2 + 3] or [2 + 2 + 3] strategy. The α-linkage of both N-acetylglucosamine residues in the repeating unit were constructed with glycosyl imidates of azidosugars as donors, while the phosphodiester bridges between the oligosaccharides were fashioned using H-phosphonate chemistry. Both synthetic targets contained a 3-aminopropyl group at the core trisaccharide reducing end, facilitating their conjugation to other biomolecules to afford conjugates useful for various biological studies and applications.
Assuntos
Clostridioides difficile , Lipopolissacarídeos , Estrutura Molecular , Polissacarídeos , Ácidos TeicoicosRESUMO
An efficient synthesis of the 3-aminopropyl glycoside of the biological repeating unit of Streptococcus pneumoniae serotype 23F capsular polysaccharide (CPS) was accomplished. The synthetic target contained a tetrasaccharide with a phosphoglycerol branch. Its oligosaccharide backbone was assembled via linear glycosylation, and the challenging ß-rhamnosyl linkage in its structure was achieved stereospecifically through naphthylmethyl-assisted intramolecular aglycon delivery (IAD). The remaining 1,2-trans glycosylation reactions were executed in excellent yields and stereoselectivity based on neighboring group participation. The phosphoglycerol branch was installed by the phosphoramidite method with benzylidene-protected glycerol 2-phosphoramidite as the substrate. Eventually, the target molecule was synthesized from monosaccharide building blocks in 17 longest linear steps and a 3.85% overall yield. In addition, the synthetic target also contained a free amino group at its reducing end, facilitating its conjugation with other molecules for various biological studies and applications.
