Syntheses of brostallicin starting from distamycin A

Two syntheses of brostallicin, a DNA minor groove binder now undergoing phase II studies, starting from distamycin A are described. One approach is based upon the selective hydrolysis via imide activation of the C-terminus amide. Besides employing traditional solution-phase synthesis, the convenient use of a polymer-supported reagent is also discussed. The other one is based upon the Curtius rearrangement of the C-terminus side chain of a convenient intermediate, easily prepared in two steps by straightforward functional group manipulation of distamycin A.