Alkylalanes and methyl furanosides: regioselective O-debenzylation or acetal cleavage
摘要:
Perbenzylated methyl pentofuranosides were submitted to the action of three alkylalanes and regioselective debenzylation at O-2 of the four pentoses was observed when choosing the right match between anomeric configuration and aluminium reagent. Diisobutylalane (DIBAL-H) allowed an easy access to reduced open-chain compounds, whereas trimethylalane (TMAL) stereoselectively produced methylated open chain derivatives. (c) 2006 Elsevier Ltd. All rights reserved.
Study of the Endocyclic versus Exocyclic C–O Bond Cleavage Pathways of α- and β-Methyl Furanosides
作者:Olivier St-Jean、Michel Prévost、Yvan Guindon
DOI:10.1021/jo3027438
日期:2013.4.5
scaffolds (ribo, lyxo, arabino, and xylo) efficiently afforded acyclic thioacetals with high SN2-like selectivity at the acetal center in the presence of Me2BBr and thiophenol. The stereochemical outcome of these reactions provides important mechanisticinsights into the activation pathway of five-membered semicyclic acetals. The thioacetal products should find applications in oligosaccharides synthesis and
Perbenzylated methyl pentofuranosides were submitted to the action of three alkylalanes and regioselective debenzylation at O-2 of the four pentoses was observed when choosing the right match between anomeric configuration and aluminium reagent. Diisobutylalane (DIBAL-H) allowed an easy access to reduced open-chain compounds, whereas trimethylalane (TMAL) stereoselectively produced methylated open chain derivatives. (c) 2006 Elsevier Ltd. All rights reserved.
The Use of Grignard Reagents in the Synthesis of Carbohydrates. III. The One-way Anomerization of Methyl Glycofuranosides and the Opening of Their Furanose Rings
作者:Masajiro Kawana、Hiroyoshi Kuzuhara、Sakae Emoto
DOI:10.1246/bcsj.54.1492
日期:1981.5
The anomerization of methyl glycofuranoside derivatives with methylmagnesium iodide or t-butylmagnesium bromide occurred in a one-way manner. For example, methyl 5-O-benzyl-β-D-ribofuranoside (3β) was converted into the corresponding α-anomer (3α) in a 95% yield when a mixture of 3β and t-butylmagnesium bromide in benzene–ether was heated at about 75 °C to remove the ether; the reverse reaction (from