Cu(ClO₄)₂·6H₂O catalyzed solvent free per-O-acetylation and sequential one-pot conversions of sugars to thioglycosides

Abstract

The solvent free per-O-acetylation of various reducing and non-reducing sugars has been carried out using stoichiometric amounts of acetic anhydride and copper(ii) perchlorate hexahydrate as the catalyst.

Diazepinium perchlorate: a neutral catalyst for mild, solvent-free acetylation of carbohydrates and other substances

“…The importance of this observation lies in the fact that all these compounds are extremely vulnerable to acetolytic conditions (Ac 2 O-acidic catalyst systems) usually employed for the reaction. Further, alcohols such as b-cholesterol (31), (À)-menthol (33), glycerol (35), dithiothreitol (37) and benzyl alcohol (39) Table 4) in excellent yields. Thus, no chemoselectivity towards acetylation under the above condition was observed in the case of the phenolic hydroxyl and sulydryl groups.…”

Immobilization of UDP‐Galactose on an Amphiphilic Resin

“…Glucose, 4 , was acetylated in a quantitative yield with acetic anhydride, catalysed by 4‐ N , N ‐dimethylaminopyridine (DMAP) . Sugar 5 was produced by the glycosylation reaction of p ‐toluenethiol with the C1‐hydroxyl in a good yield of 78 % over two steps , . The remaining acetyl groups were removed and an acetal introduced to C4 and C6 formed sugar 6 in a good yield of 66 % over two steps .…”

“…BF 3 · OEt 2 (771 µL, 6.25 mmol) was added at 0 °C and the reaction mixture warmed to room temperature before being stirred for 2 d. The reaction mixture was washed with NaHCO 3 (20 mL) and the aqueous phase extracted with CH 2 Cl 2 (3 × 10 mL) and the combined organic phases were dried and concentrated in vacuo. Purification by flash chromatography (8:2, hexane/ethyl acetate) gave the product as a yellow solid (445 mg, 78 %) , . The sugar (135 mg, 0.30 mmol) and NaOMe (10 mg, 0.18 mmol) were stirred in MeOH (3 mL) for 1.5 h. The reaction mixture was quenched with Dowex, filtered and concentrated in vacuo to yield the product as a yellow solid (80 mg, 94 %) .…”

“…[28] Sugar 5 was produced by the glycosylation reaction of p-toluenethiol with the C1-hydroxyl in a good yield of 78 % over two steps. [29,30] The remaining acetyl groups were removed and an acetal introduced to C4 and C6 formed sugar 6 in a good yield of 66 % over two steps. [30] Benzylation of C2 and C3 followed by the removal of the acetal group under acidic conditions gave sugar 7 in an excellent yield of 94 % over two steps.…”

“…Purification by flash chromatography (8:2, hexane/ethyl acetate) gave the product as a yellow solid (445 mg, 78 %). [29,30] The sugar (135 mg, 0.30 mmol) and NaOMe (10 mg, 0.18 mmol) were stirred in MeOH (3 mL) for 1.5 h. The reaction mixture was quenched with Dowex, filtered and concentrated in vacuo to yield the product as a yellow solid (80 mg, 94 %). [30] The sugar (492 mg, 1.71 mmol), PhCH(OMe) 2 (520 mL, 3.44 mmol) and camphorsulfonic acid (cat.…”