Streptovaricins and Mitomycins

Streptovaridns and Mitomycins.—Consideration of the structures deduced for metabolites with the streptovaricin skeleton which lack in particular the extensive oxygenation of say streptovaricin D, has allowed a reasonable sequence of events for streptovaricin biosynthesis to be proposed. (The streptovaridns belong to the class of ansamydns. For earlier reviews on ansamycin biosynthesis see ref. 5, p. 52, and ref. 6, p. 45.) 

Both citrulline (156) and arginine (157) serve as effident precursors for mitomy-dns (155). An efficient incorporation of L-[NH2CO- N, C]dtrulline with high retention of both labels as doubly labelled mitomycin rather than a mixture of singly labelled species establishes an intact incorporation of this precursor. Moreover, dtrulline is not converted into arginine (157) or urea prior to incorporation since this would have resulted in a loss of half the N by interchange with the N in either compound. 

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