Substrate-dependent chemoselective aldose–aldose and aldose–ketose isomerizations of carbohydrates promoted by a combination of calcium ion and monoamines
with the CaCl(2) system in CD(3)OD revealed that the C-2 epimerization proceeds via stereospecific rearrangement of the carbon skeleton, or 1,2-carbonshift, and ketose formation proceeds partially through an intramolecular hydrogen migration or 1,2-hydride shift and, in part, via an enediol intermediate. These simultaneous aldose-aldose and aldose-ketose isomerizations showed interesting substrate-dependent
Both non‐acidic LiNbMoO6 and strongly acidic HNbMoO6 efficiently catalyze the epimerization of sugars including glucose, mannose, xylose, and arabinose in water. The reactions over these oxides reached almost equilibrium within a few hours where yields of corresponding epimers from glucose, xylose, and arabinose were 24–29 %. The layered mixed oxides functioned as heterogeneous catalysts and could
Rearrangement of the carbon skeleton of aldoses is catalysed by nickel(II) complexes
作者:Robert E. London
DOI:10.1039/c39870000661
日期:——
Carbon-13 n.m.r. studies utilizing [1-13C]-D-glucose demonstrate that the apparent C-2 epimerization catalysed by [Ni(H2O)2(tmen)2]Cl2(tmen =N,N,N′-trimethylethylenediamine) in fact proceeds via a molecular rearrangement in which the C-1 carbon label is found at the C-2 position of the product mannose.