3366-49-2Relevant articles and documents
Preparation of Unsaturated Carbohydrates by Ester Pyrolysis, II. - Thermal cis Eliminations from Completely Acetylated Aldopyranoses
Koell, Peter,Steinweg, Eberhard,Meyer, Bernd,Metzger, Juergen
, p. 1039 - 1051 (2007/10/02)
The pentaacetates 1, 2, 7, and 9 of β-D-glucose, α-D-mannose, β-D-allose, and β-D-galactose and the tetraacetates 13 and 18 of β-D-xylose and β-D-ribose eliminate when dissolved in acetone at temperatures about 350 deg C in a flow apparatus within 0.5 - 1 min regioselectively and stereoselectively the 1-O-acetate group.The respective anomers with trans-bound hydrogen in position 2 do not give this reaction corresponding to the pericyclic elimination mechanism.In a subsequent sigmatropic rearrangement the primarily formed 2,3,4,6-tetra-O-acetyl-1,5-anhydro-hex-1-enitols 3 (from 1 or 2), 8, and 10 as well as the 2,3,4-tri-O-acetyl-1,5-anhydro-pent-1-enitols 14 and 19 yield the α- or β-triacetyl-3-deoxy-hex-2-enopyranoses 4 or 5, 12 and the α- or β-triacetyl-3-deoxy-pent-2-enopyranoses 15 or 16, respectively.These products partially anomerize, e.g. 12 gives 11. - By further rearrangement with subsequent acetic acid anhydride elimination 5 and 16 are transformed into the enones 6 and 17. - 1,2,4,6-Tetra-O-acetyl-3-deoxy-β-D-threo-hex-2-enopyranose (12) is described for the first time.The 0H5(D)conformations of 11 and 12 are established by 13C NMR data.
