Synthesis of 4-octuloses. Part 7: Highly stereoselective synthesis of 2,3-anhydrosugar derivatives as key intermediates in the preparation of sugar beta-lactams

Reaction of either 1 or 4 with (N,N-dibenzylcarbamoylmethylene)dimethylsulf urane 2 in DMSO afforded 2,3-anhydro-4,5-O-isopropylidene-D-arabino-pentona mide 3 or N,N-dibenzyl 2,3-anhydro-4,5:6,7-di-O-isopropylidene-beta -D-glyc ero -D-galacto-oct-4-ulo-4,8-pyranosonamide 5, respectively. The configurat ions of 3 and 5 were determined on the basis of their spectroscopic data, i n the first case, and by chemical transformation into the known 2,3-anhydro -4,5:6,7-di-O-isopropylidene-beta -D-glycero-D-galacto-oct-4-ulo-4,8-pyrano se 11. Treatment of 3 and 5 with lithium hexamethyldisilazide in THF provid ed the corresponding sugar beta -lactams 12, 13 and 14, respectively. (C) 2 000 Elsevier Science Ltd. All rights reserved.