815. Glycosides. Part II. The preparation of methyl 3,4,6-tri-O-acetyl-2-O-methyl-β-D-glucopyranoside

Abstract

Tri-0 -acetyl-2-0 -methyl -p -D -glucop yranoside.By P . A. FINAN and C. D. WARREN. Methylation of methyl 2,4,6-tri-O-acetyl-p-~-glucopyranoside with methyl iodide and silver oxide gave a high yield of methyl 3,4,6-tri-O-acetyl-2-O-methyl-P-D-ghcopyranoside, the structure of which was proved by an alternative synthesis.

New Factors Governing Stereoselectivity in Borohydride Reductions ofβ-D-Glycoside-2-uloses − The Peculiar Effect of “Activated” DMSO

“…Condensation of ethyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-1-thio-β--glucopyranoside [3e] and 2,4,6-tri-O-acetyl-3-O-benzyl-α--glucopyranosyl bromide [6] in dichloromethane/toluene, in the presence of silver triflate as a promoter, afforded disaccharide 7 ( Figure 2). Zemplén O-deacetylation of 7 (Ǟ 8), isopropylidenation with 2,2-dimethoxypropane (Ǟ 9), and oxidation of OH-2Ј using methyl sulfoxide/acetic anhydride after conventional workup (procedure A) afforded β--glucosidulose 4.…”

“…A solution of ethyl 3,6-di-O-benzyl-2-deoxy-2-phthalimido-1-thio-β--glucopyranoside [3f] (720 mg, 1.35 mmol) and 2,4,6-tri-Oacetyl-3-O-benzyl-α--glucopyranosyl bromide [6] (1.86 g, 4.05 mmol) in dichloromethane (13 mL) containing powdered 4A molecular sieves (3 g) was stirred for 30 min under argon. A solution of silver triflate (1.40 g, 5.44 mmol) in toluene (33 mL) was added dropwise in the dark during 1.5 h at Ϫ45°C and stirring was continued for 1 h at Ϫ40°C.…”

Chemistry of xylopyranosides

“…Peracetylated α-D-xylopyranosyl bromide 20 has been synthesized from peracetylated αand β-D-xylopyranose, or mixtures thereof, in high yields in the presence of HBr in AcOH, 144,192 Et2O, 193 or CH2Cl2, 162 or by treatment with HBr-AcOH in CH2Cl2 194 (Scheme 6). The latter method has proved to work well on perpivaloylated 195 and perlevulinated 188 The Koenigs-Knorr and Lemieux protocols are commonly used for glycosylation reactions with bromide donors.…”

Acceptor Specificity of Salmonella GDP-Man:αlRha1→3αdGal-PP-Und β1→4-Mannosyltransferase: A Simplified Assay Based on Unnatural Acceptors

“…The first analogue, p -nitrophenyl-β- l -Rha ( 3 ), is commercially available, whereas Koenigs−Knorr 9 synthesis of 5 (64% α, α/β = 9:1), from bromide 4 and 4-(4-nitrophenyl)-1-butanol, followed by Zémplen deacylation efficiently provided 6 (85%). Synthesis of the disaccharide analogue 12 was initiated with Koenigs−Knorr coupling of glycal 7 and 4 to give 8 (69% α, α/β = 10:1) .…”