Praly, J P and Brendle, J C and Klett, J and Pequery, F (2001) Synthesis of peracetylated D-galactopyranosylidene dihalides. Comptes Rendus - Academie des Sciences Paris Serie 2 Chimie Fascicule C, 4 (7). pp. 611-617. ISSN 1387-1609Full text not available in this repository. (Request a copy from the Strathclyde author)
Upon treatment with aluminium trichloride in absolute chloroform, beta -D-galactopyranose penta-O-acetate was converted in high yield into tetra-O-acetyl-beta -D-galactopyranosyl chloride. In the presence of N-bromosuccinimide in boiling carbon tetrachloride, homolytic substitution of the anomeric hydrogen atom in this beta -chloride occurred selectively to afford tetra-O-acetyl-1-bromo-beta -D-galactopyranosyl chloride, in admixture with minor amounts of tetra-O-acetyl-D-galactopyranosylidene chloride. Bromine substitution by fluorine took place with a low stereoselectivity in tetra-O-acetyl-1-bromo-beta -D-galactopyranosyl chloride when treated with 1.25 equiv silver fluoride in acetonitrile, whereas tetra-O-acetyl-beta -galactopyranosylidene fluoride could be prepared in 54% yield with 3.3 equiv AgF. The gem-difluoride could be deacetylated quantitatively. Upon treatment with 1,4-diazabicyclo[2.2.2] octane, peracetylated 1-bromo-beta -D-galactopyranosyl chloride underwent 1,2-elimination of hydrogen bromide to afford 2,3,4,6-tetra-0-acetyl-D-lyxo-hex-1-enopyranosyl chloride in 33 % yield. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
|Keywords:||radical bromination of tetra-O-acetyl-beta-D-galactopyranosyl chloride, pyranosylgem-dihalides, sugars, spectroscopy, fluoride, glycals, Chemistry, Chemistry(all)|
|Subjects:||Science > Chemistry|
|Department:||Faculty of Science > Pure and Applied Chemistry|
|Depositing user:||Pure Administrator|
|Date Deposited:||18 Oct 2011 13:10|
|Last modified:||06 Jan 2017 10:03|