Novel practical synthesis of Kdn2en and its C-4 nitrogen-modified derivatives

A practical synthesis of Kdn2en and 4-amino-4-deoxy-Kdn2en has been achieved via a key intermediate, methyl 4,5,7,8,9-penta-O-acetyl-2,6-anhydro-3-deoxy-d-glycero-d-galacto-non-2-enonate, which has been prepared from Kdn in three steps in 91% overall yield.