ChemInform Abstract: SELEKTIVE SPALTUNG VON THIOGLYKOSIDEN MIT DICHLORMETHYL‐METHYLAETHER

Abstract

Die acetylierten Thio‐gluco‐ (Ia) und ‐galaktopyranoside (Ib) werden durch den Chloräther (II) in Gegenwart von ZnCIQ zu den Acetochlor‐zuckern (IIIa) bzw. (IIIb) gespalten.

Direct Synthesis of Glycosyl Chlorides from Thioglycosides

“…The residue was purified by column chromatography on silica gel (ethyl acetate -hexane gradient elution) to afford the title compound (185 mg, 83%) as a white amorphous solid. Analytical data for 29: R f = 0.55 (ethyl acetate/hexane 1/4, v/v); [α] Ethyl 6-O-Acetyl-2,3,4-tri-O-benzyl-1-thio-β-D-galactopyranoside (31). N,N-Dimethylaminopyridine (DMAP, 55.57 mg, 0.45 mmol) and acetic anhydride (57.2 μL, 0.61 mmol) were added to a solution of compound 41 (150 mg, 0.30 mmol) in CH 2 Cl 2 (2.0 mL), and the resulting mixture was stirred under argon for 2 h at rt.…”

“…Farkas et al converted acetylated thioglycosides into the corresponding glycosyl chlorides in the presence of dichloromethyl methyl ether and ZnCl 2 (Scheme 1A). 31 This reaction produced peracetylated glycosyl chlorides, but a variety of side products such as hydrochloric acid, methyl chloride, and methyl formate were also noted. Sugiyama and Diakur 32 treated 4chlorophenylthio glycosides with oxalyl chloride and methyl/ phenyl sulfoxide in dichloromethane (Scheme 1B).…”

“…Hence, some efforts have been made to discover methods for the direct conversion of thioglycosides into glycosyl chlorides. Farkas et al converted acetylated thioglycosides into the corresponding glycosyl chlorides in the presence of dichloromethyl methyl ether and ZnCl 2 (Scheme A) . This reaction produced per-acetylated glycosyl chlorides, but a variety of side products such as hydrochloric acid, methyl chloride, and methyl formate were also noted.…”

Formation of Ethyl 1‐Thiomannopyranosides from 2‐O‐Chloroacetylated and 2‐O‐Levulinoylated Synthons

“…[1,2] While they themselves are important glycosyl donors for the synthesis of glycosides and oligosaccharides, they can be converted into other glycosyl donors. [3][4][5] Thioglycosides containing free hydroxy groups can be used as glycosyl acceptors, either in combination with other classes of glycosyl donors or with 1-thioglycosides by applying the "armed-disarmed" concept. [6] The importance of haloacetyl and levulinoyl (levulinoyl ester, Lev) [7][8][9][10] protecting groups in carbohydrate chemistry lies in the fact that they can be selectively removed in the presence of other acyl groups.…”