Regioselective Benzylation of 2‐Deoxy‐2‐aminosugars using Crown Ethers: Application to a Shortened Synthesis of Hyaluronic Acid Oligomers

Abstract

The combination of benzyl bromide, sodium hydroxide and 15-crown-5 in tetrahydrofuran is shown to be an efficient method for installing benzyl groups at both the 4- and 6-positions regioselectively directly from peracetylated N-trichloroacetyl-protected glucosamine and galactosamine. Application of this benzylation strategy proved to significantly shorten the synthetic route to hyaluronic acid tetra- and hexamers.

Threshold of Thioglycoside Reactivity Difference Is Critical for Efficient Synthesis of Type I Oligosaccharides by Chemoselective Glycosylation

“…The crude was purified by column chromatography on silica gel with EtOAc/hexanes (1/5 to 1/4, v/v) to yield the desired product 10 (228 mg, 63%) as a white amorphous solid. R f 0.28 (EtOAc/ hexanes = 1/3, v/v); [ (12). For reaction details, please see Scheme S5.…”

“…At the current stage, there are several formidable barriers in chemical synthesis of type I oligosaccharides. For example, the 3-hydroxyl GlcNAc acceptor is less active than the 4-hydroxyl GlcNAc acceptor in glycosylation reactions. − The glycosylation with Galβ1 → 3GlcNAc donor gave a lower yield, as compared to that with Galβ1 → 4GlcNAc donor . Furthermore, when the thioglycoside donor and acceptor with similar reactivity are subjected to chemoselective glycosylation, the transfer of the anomeric thiotoluenyl group usually occurs from the thioglycoside acceptor to the activated donor, leading to donor regeneration, and formation of acceptor oligomerization or/and acceptor hydrolysis.…”

4,6-O-Pyruvyl Ketal Modified N-Acetylmannosamine of the Secondary Cell Wall Polysaccharide of Bacillus anthracis Is the Anchoring Residue for Its Surface Layer Proteins

“…Furthermore, TCA at C-2 of 14 can perform neighboring group participation during glycosylations to give selectively 1,2- trans -glycosides. Subsequently, TCA can be reduced to the desired acetamido function by treatment with Bu 3 SnH and AIBN . The Cbz protecting groups can be removed by catalytic hydrogenation in the presence of Boc, allowing selective installation of a thiol spacer on the amine of the linker.…”

Multifunctional membranes based on photosensitive crown-ether derivatives with advanced properties

“…Moreover, the numerous works concerning self-assembled monolayers of macrocyclic complexes with inorganic and organic molecules and ions have been published recently by various research groups worldwide [38][39][40][41]. The numerous crown-containing compounds with various substituents are promissing for application in molecular devices [42], chromatography [43], catalysis [44,45], biomedical fields [46,47], photovoltaics [48,49], hybrids [50,51] and special [52][53][54] materials. …”