Chemoenzymatic Syntheses of Sialylated Oligosaccharides Containing C5‐Modified Neuraminic Acids for Dual Inhibition of Hemagglutinins and Neuraminidases

Abstract

A fast chemoenzymatic synthesis of sialylated oligosaccharides containing C5-modified neuraminic acids is reported. Analogues of GM3 and GM2 ganglioside saccharidic portions where the acetyl group of NeuNAc has been replaced by a phenylacetyl (PhAc) or a propanoyl (Prop) moiety have been efficiently prepared with metabolically engineered E. coli bacteria. GM3 analogues were either obtained by chemoselective modification of biosynthetic N-acetyl-sialyllactoside (GM3 NAc) or by direct bacterial synthesis using C5-modified neuraminic acid precursors. The latter strategy proved to be very versatile as it led to an efficient synthesis of GM2 analogues. These glycomimetics were assessed against hemagglutinins and sialidases. In particular, the GM3 NPhAc displayed a binding affinity for Maackia amurensis agglutinin (MAA) similar to that of GM3 NAc, while being resistant to hydrolysis by Vibrio cholerae (VC) neuraminidase. A preliminary study with influenza viruses also confirmed a selective inhibition of N1 neuraminidase by GM3 NPhAc, suggesting potential developments for the detection of flu viruses and for fighting them.

Chemobacterial Synthesis of a Sialyl‐Tn Cyclopeptide Vaccine Candidate

“…Finally, the electrospray ionisation (ESI) mass spectrum in the negative mode presents a [ M −H] − ion at m / z 549, which corresponds to the expected molecular weight. On the basis of the initial amount of GalNAc‐α‐propargyl ( 1 ), the production yield was calculated to be 25 %, which is similar to yields generally obtained in bacterial synthesis with lactoside acceptors . The strain derivative of E. coli K‐12 was able to uptake GalNAc‐α‐propargyl efficiently, which made it available for bioconversion into sialyl‐Tn‐propargyl.…”

“…On the basis of the initial amounto f GalNAc-a-propargyl (1), the production yield was calculated to be 25 %, which is similar to yields generally obtained in bacterial synthesis with lactosidea cceptors. [18] The strain derivative of E. coli K-12 was able to uptake GalNAc-a-propargyl efficiently, which made it available for bioconversion into sialyl-Tn-propargyl. E. coli K-12 is not able to grow on GalNAc owing to al arge deletion in the Aga operon expressing the genes involved in GalNAc catabolism.…”

“…After centrifugation, the oligosaccharide fraction was extracted by charcoal adsorption, as previously described, [4b] and was eluted with am ixture of ethanol/H 2 O( 1:1). The dry material recovered (450 mg) then underwent af inal step of purification on aC 18 reversed-phase silica-gel column.…”

“…After 1h,D MF was evaporated under reduced pressure, and the crude mixture was subsequently treated with as olution of trifluoroacetic acid (TFA)/CH 2 Cl 2 (1:1, 10 mL). After 20 min, the solution was concentrated, and the residue was purified by precipitation with diethyl ether.Y ield:7 7% (20 mg); analytical UPLC-MS: t R = 1.53 min (C 18 RAFT-PADRE (5) synthesis:C ompound 4 (20 mg, 0.014 mmol, 1equiv) was dissolved in am ixture of DMF (1 mL) and 20 mm sodium acetate buffer pH 4.5 (7 mL), and the mixture was degassed under argon. The PADRE-Cys peptide (28.5 mg, 0.018 mmol, 1.3 equiv) was added to the solution, and the mixture was stirred under argon until the reaction was complete (checked by MS-UPLC).…”

Synthetic Strategies for Modified Glycosphingolipids and Their Design as Probes

“…423 Using modified Neu5Ac precursors, modified GM2 analogues were produced. 424 Modifications to the lactoside were also tolerated, generating saccharide moieties of GM2 and GM3 that could be further conjugated. 425 Encoding Neu5Ac-synthesizing enzymes avoided the need for exogeneous Neu5Ac, which should further reduce the cost of production for ganglioside oligosaccharides; 426 however, complications may include the possibility of excess sialylation.…”