Synthetic Studies Related to Ezomycins and Octosyl Acids: Synthesis of Heptofuranose Nucleosides

1-[Ethyl (E)-5,6-dideoxy-2,3-O-isopropylidene--D-ribo-hept-5-enofuranosyluronate] uracil(12) was synthesized. Other various heptofuranose uncleosides were also synthesized from uridine and adenosine by two-carbon chain extension using Witting reaction.