Certain bacterial species of the genus Streptomyces produce structurally and biologically interesting higher-carbon sugars.The most striking feature of these compounds is a transfused perhydrofuropyran ring system,formally derived from the addition of two carbons to C5' of a ribonucleoside and the linkage of the two-carbon chain with the oxygen atom at C3'.These metabolites also contain a natural or modified pyrimidine base.The ezomycins(Fig.1),discovered in the early 1970's by Sakata and co-workers,are the most complex members of this family of natural products.
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