Cyclization ofN(Tetra-O-acetyl-d-gluco- andd-Mannopyranosyl)-Pyridinium Salts in a Methanolic Solution of Sodium Methylate

Phenanthroline Catalysis in Stereoselective 1,2-cis Glycosylations

“…25 It has been reported that the anomeric hydrogen of βglucosylpyridinium bromide appeared at 6.10 ppm in D 2 O. 26 In addition, an anomeric mixture of mannosylpyridinium species, wherein the anomeric hydrogens have been established to resonate at δ H = 6.63 and 6.49 ppm in CD 2 Cl 2 was identified. 27 The 1 H NMR spectra of glycosyl bromide 29 and C8 showed the C1-anomeric hydrogens of the phenanthrolinium ion intermediates, Int 1 (β) and Int 2 (α), appeared at 8.44 and 8.18 ppm, respectively.…”

“…In general, if there is a hydrogen bond between the C1-anomeric hydrogen and the second nitrogen of phenanthroline, it is expected that the chemical shift of the C1-hydrogen should be shifted more downfield in the 1 H NMR . It has been reported that the anomeric hydrogen of β-glucosylpyridinium bromide appeared at 6.10 ppm in D 2 O . In addition, an anomeric mixture of mannosylpyridinium species, wherein the anomeric hydrogens have been established to resonate at δ H = 6.63 and 6.49 ppm in CD 2 Cl 2 was identified .…”

A Mechanistic Probe into 1,2‐cis Glycoside Formation Catalyzed by Phenanthroline and Further Expansion of Scope

“…Conversely, if the C1 anomeric proton is hydrogen bonding to the second nitrogen of phenanthroline, the chemical shift should appear more downfield in the 1 H NMR. It has been reported that the anomeric proton of β‐glucosyl pyridinium bromide resonances at δ H =6.10 ppm in D 2 O [17] . In addition, Gin and coworker established anomeric mixture of glycosyl pyridinium species, wherein the anomeric protons resonance at δ H =6.63 and 6.49 ppm in CD 2 Cl 2 at −60 °C [18] .…”

“…It has been reported that the anomeric proton of β-glucosyl pyridinium bromide resonances at δ H = 6.10 ppm in D 2 O. [17] In addition, Gin and coworker established anomeric mixture of glycosyl pyridinium species, wherein the anomeric protons resonance at δ H = 6.63 and 6.49 ppm in CD 2 Cl 2 at À 60 °C. [18] However, the 1 H NMR spectra of a 1:1 mixture of glycosyl bromide 1* and C2 taken at À 60 °C (see Figure S3) showed the anomeric protons of the intermediates, Int 1 (β) and Int 2 (α), resonance at δ H = 8.44 and 8.18 ppm, respectively (Figure 2).…”

Rapid Access to 1,6-Anhydro-β-l-hexopyranose Derivatives via Domino Reaction: Synthesis of l-Allose and l-Glucose

“…Several efficient methods have been devised to gain access to 1,6-anhydro-β-hexopyranoses belonging to d -series, including cyclization of hexose derivatives under acidic or alkaline conditions and Lewis acid or halonium ion-catalyzed intramolecular rearrangement of d -glycal derivatives. Conversely, only a few approaches for the synthesis of l -series 1,6-anhydrosugars are reported; nevertheless, considering their potential use as chiral building blocks in rare sugar-containing natural product synthesis, their preparation still represents a challenging subject of investigation.…”