Reductive Cleavage of Glycosides, Stereochemistry of Trapping of Cyclic Oxonium Ions
作者:
David Rolf,
JohnA. Bennek,
GaryR. Gray,
期刊:
Journal of Carbohydrate Chemistry
(Taylor Available online 1983)
卷期:
Volume 2,
issue 4
页码: 373-383
ISSN:0732-8303
年代: 1983
DOI:10.1080/07328308308057884
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Reductive cleavage of the glycosidic carbon-oxygen bonds of methyl 2,3,4,6-tetra-O-methyl-β-d-glucopyranoside (1), methyl 2,3,4,6-tetra-O-methyl-α-d-glucopyranoside (2), permethylated cellulose (6) and permethylated cyclohexaamylose (7) was carried out in the presence of deuteriotriethylsilane, and the configuration of deuterium in the l-deuterio-1,5-anhydro-d-glucitol derivatives (4, 5and9, 10) that were produced was established by1H- and2H-NMR spectroscopy. All reductions were carried out with boron trifluoride etherate as the catalyst as originally reported [D. Rolf and G. R. Gray,J. Am. Chem. Soc., 104, 3539 (1982)], as well as with trimethylsilyl trifluoromethanesulfon-ate which we now report efficiently catalyzes the regiospecific reductive cleavage of glycosides. Spectroscopic studies revealed that the configuration of deuterium in the products was independent of the configuration of the starting glycoside. The predominant (∼95%) axial configuration observed leads us to propose that free oxonium ions (3and8) are formed as intermediates in these reductions.
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