Synthesis of carbasugars from aldonolactones: Ritter-type epoxide opening in the synthesis of polyhydroxylated aminocyclopentanes

Using the cis-fused cyclopentane-1,4-lactone, (1R,5S,7R,8R)-7,8-dihydroxy-2 -oxabicyclo[3.3.0]oct-3-one (1), as starting material, 5-deoxycarba-beta-L- xylo-hexofuranose (6) together with alpha- (12) and beta-1-amino-1,5-dideox ycarba-L-xylo-hexofuranose (16) have been prepared using a number of stereo selective transformations. The key step was the regioselective opening of t he epoxide (1R,5S,7R,8R)-7,8-epoxy-2-oxabicyclo-[3.3.0]oct-3-one (4) with d ifferent nucleophiles.