Chemical Synthesis of Sialyl N‐Glycans and Analysis of Their Recognition by Neuraminidase

Abstract

The chemical synthesis of af ully sialylated tetraantennary N-glycan has been achieved for the first time by using the diacetyl strategy,i nw hich NHAc is protected as NAc 2 to improve reactivity by preventing intermolecular hydrogen bonds.A nother key was the glycosylation to the branched mannose in an ether solvent, which promoted the desired glycosylation by stabilizing the oxocarbenium ion intermediate.F urthermore,h igh a-selectivity of these glycosylation reactions was realized by utilizing remote participation. Tw o asymmetrically deuterium labeled sialyl N-glycans were also synthesized by the same strategy.T he synthesized N-glycans were used to probe the molecular basis of H1N1 neuraminidase recognition. The asymmetrically deuterated N-glycans revealed ad ifference in the recognition of sialic acid on each branch. Meanwhile,t he tetraantennary N-glycan was used to evaluate the effects of multivalency and steric hinderance by forming branching structures.

Divergent Enzymatic Assembly of a Comprehensive 64‐Membered IgG N‐Glycan Library for Functional Glycomics

“…Additionally, to further diversify the IgG N ‐glycan library, the core‐fucosylated N ‐glycans 1–32 were treated with a robust fucosidase FucA1 for the removal of fucoside to afford core‐unmodified N ‐glycans 33–64 , respectively. [ 9k ]…”

“…The structural complexity and heterogeneity of IgG N ‐glycans make it difficult to isolate adequate and structurally well‐defined glycans from serum or tissue samples for biological function studies. Although great efforts have been devoted to preparing complex N ‐glycans with asymmetrical or symmetrical structures through chemical and chemoenzymatic methods, [ 9 ] the easy‐to‐implement systematic synthesis of comprehensive IgG N ‐glycans has not yet been reported. The exact structural elucidations and precise functional investigations of IgG N ‐glycosylation are still hampered due to the absence of an extensive and systematic N ‐glycan library with well‐defined structures.…”

Validation and Application of an Innovative Protective Group Concept: Enhancing Substrate Reactivity in Glycosylations by Disrupting Intermolecular Interactions

“…This study sheds light on the often-underestimated impact of intermolecular interactions on reactivity and introduces a rational approach for improving the synthetic efficiency of intricate molecular constructs. (d,J = 11.8 Hz,1 H),5 H,2 H,5 H,3.87 (s,3 H,OCOCH 3 ),3 H),2 H),3.43 (d,J = 5.7 Hz,1 H),3.31 (d,J = 1.9 Hz,1 H),3 H),2.51 (dd,J = 12.4,5.4 Hz, 1 H, Sia-H3 eq ), 2.29 (s, 3 H, Ac), 2.16 (s, 3 H, Ac), 2.15 (s, 3 H, Ac), 1.96 (s, 3 H, Ac), 1.86 (s, 3 H, Ac), 1.60 (t, J = 12.4 Hz, 1 H, Sia-H3 aq ), 1.47 (s, 3 H, Ac), 1.28 (s, 9 H, t-BuBz), 1.17 (d, J = 6.4 Hz, 3 H, -CH 3 ). 13 C{ 1 H} NMR (125 MHz, CDCl 3 ):  = 174.…”

Diacetyl strategy for synthesis of NHAc containing glycans: enhancing glycosylation reactivity via diacetyl imide protection

“…Protection of the acetamide in sialic acid as a diacetyl moiety may have facilitated the efficient glycosylation of each fragment coupling. The problem of low selectivity in the two glycosylation steps was resolved by remote participation using O -3 and O -6 acyl protection of the mannose residue in the synthesis of N -glycans containing bisecting GlcNAc, along with the synthesis of the previously mentioned deuterated disialylated biantennary N -glycans and the fully sialylated tetraantennary N -glycan ( Manabe et al, 2018 ; Shirakawa et al, 2021 ).…”