Stereoselective synthesis of the 5′-aminofuranoside part of polyoxins via (3,3)-sigmatropic rearrangement of allylic thiocyanates

A new and stereoselective route for the synthesis of the benzyl 5-(R)-N-Cbz-5,6-dideoxy-2,3-O-isopropylidene-β-d-ribo-hept-6-enfuranoside 5e and 5-(R)-N-acetyl-5,6-dideoxy-1,3-O-isopropylidene-β-d-ribo-hept-6-enfuranoside 12 as useful protected precursors of the 5′-aminofuranoside part of polyoxins is presented. The key-step involves diastereoselective introduction of the amino group at C-5 of the ribose and xylose by (3,3)-sigmatropic rearrangements of the corresponding allylic thiocyanates.