Photocatalytic, site-selective oxidations of carbohydrates
作者:Daniel J. Gorelik、Victoria Dimakos、Timur Adrianov、Mark S. Taylor
DOI:10.1039/d1cc05124e
日期:——
Site-selective oxidations of carbohydrates, employing acridinium photocatalysis and quinuclidine hydrogen atom transfer catalysis, are presented. Protocols have been developed for oxidations of all-equatorial carbohydrates as well as those containing cis-1,2-diols. Site-selectivity reflects the relative rates of hydrogen atom transfer from the carbohydrate C–H bonds, and can be enhanced using a phosphate
C-2 and C-3 oxidation of d-Glc, and C-2 oxidation of d-Gal by pyranose dehydrogenase from Agaricus bisporus
作者:Jindřich Volc、Petr Sedmera、Petr Halada、Věra Přikrylova、Geoffrey Daniel
DOI:10.1016/s0008-6215(98)00151-7
日期:1998.8
The quinone-dependent sugar oxidoreductase, pyranose dehydrogenase purified from the basidiomycete Agaricus bisporus catalyzed C-2 and C-3 oxidation of D-Glc to D-arabino-hexos-2-ulose (2-keto-D-Glc) and, preferentially, D-ribo-hexos-3-ulose (3-keto-D-Glc). The two aldoketoses accumulated only transiently in the reaction mixture being continually converted to the same end-product, D-erythro-hexos-2,3-diulose (2,3-diketo-D-Glc). D-Gal was oxidized by pyranose dehydrogenase and 1,4-benzoquinone exclusively at C-2 to produce D-lyxo-hexos-2-ulose (2-keto-D-Gal). Structures of the enzyme reaction products were deduced from their N,N-diphenylhydrazone derivatives. (C) 1998 Elsevier Science Ltd. All rights reserved.
Synthesis of sucrose analogues and the mechanism of action of Bacillus subtilis fructosyltransferase (levansucrase)
Trp85, Asp247 and Arg246 stabilization of both acceptors and substrates. In addition we also describe the first FTF reaction, which catalyzes the beta-(1-->2)-fructosyl transfer to 2-OH of L-sugars (L-glucose, L-rhamnose, L-galactose, L-fucose, L-xylose) presumably in a (1)C(4) conformation. In those conformations, the L-glycopyranosides are stabilized by the same hydrogen network. Structures of the