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Alternative synthesis of methylated sugars. XIV. Synthesis of methyl 3,4-di-O-acetyl-β-D-xylopyranoside

P. Kováč and R. Palovčík

Institute of Chemistry, Slovak Academy of Sciences, 809 33 Bratislava

 

Abstract:  The amount of per-O-acetyl-2-O-benzyl-D-xylopyranoses and xylofuranoses in the product of acetylation of 2-O-benzyl-D-xylose (/) depends greatly on the method of acetylation applied. While standard acetylation with acetic acid anhydride in the presence of sodium acetate at 100°C results in the formation of an appreciable amount of furanoses, the product of acetylation of I with acetic acid anhydride in pyridine contains minimum amount of furanoses and crystalline l,3,4-tri-0-acetyl-2-0-benzyl-β-D-xylopyranose (//) can be isolated from it. When II was treated with hydrogen bromide in dichloromethane the β-bromide was fornted first; anomerization then produced the thermodynamically more stable a-bromide (///). Methanolysis of /// afforded methyl 3,4-di-0-acetyl-2-0-benzyl-β-D-xylopyranoside (IV) identical with methyl 3,4-di-0-acetyl-2-0-benzyl-ß-D-xylopyranoside obtained by acetyla­ tion of the known, independently prepared, methyl 2-O-benzyl-ß-D-xylopyranoside. The title glycoside V was obtained by hydrogenolysis of the benzyl ether IV. Synthesis of the hitherto unknown crystalline 1,3,4-tri-O-acetyl-ß-D-xylopyranose is also described.

Full paper in Portable Document Format: 311a98.pdf

 

Chemical Papers 31 (1) 98–105 (1977)

Tuesday, July 27, 2021

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