N-Acetyl-Neuraminic Acid

The mechanism of oxidative deamination of N‑nitroso‑N‑acetyl sialyl glycosides to KDN glycosides with overall retention of configuration was studied. No evidence was found for stereodirecting participation by ester groups at the 4‑ and 7‑positions. A common mechanism involving 1‑oxabicyclo[3.1.0]hexyl oxonium ion intermediates following pyranoside ring oxygen participation is proposed. In β‑thiosialosides, a minor pathway involves 4‑O‑acetyl exchange with glacial acetic acid, proposed to occur via thioglycoside participation at the diazoalkane stage.

Fig. 1 Synthesis of NeuAc Derivatives Selectively Functionalized at the 4-Position. (Buda S, Crich D, 2016)

A method combining metabolic labeling, click chemistry, 16S rRNA gene sequencing, and whole‑genome sequencing was developed to track and identify sialic acid (SA)‑presenting microbes in complex microbiomes. Using this approach, a new E. coli strain was isolated that incorporates SA onto its surface and encodes nanT, neuA, and neuS genes for SA harvesting and presentation. This method is applicable to identifying SA‑presenting bacteria from human, animal, and environmental microbiomes.

Fig. 2 Metabolic labeling and isolation of SA-presenting microbes from a fecal microbiome sample. (Han Z, et al., 2021)