Solid-phase synthesis and biochemical evaluation of conformationally constrained analogues of deglycobleomycin A₅

Deglycobleomycin binds to and degrades the self-complementary oligonucleotide d(CGCTAGCG)₂ in a sequence selective fashion. A previous modeling study [J. Am. Chem. Soc. 120, (1998), 7450] had shown that, during binding to double stranded DNA, the conformation of the methylvalerate domain of deglycoBLM approximated that of S-proline. In the belief that an analogue of deglycoBLM structurally constrained to mimic the DNA-bound conformation might exhibit facilitated DNA binding and cleavage, an analogue of deglycoBLM was prepared in which the methylvalerate moiety was replaced by S-proline. This deglycoBLM analogue, as well as the related analogue containing R-proline, was synthesized on a TentaGel resin. Both of the analogues were found to be capable of binding Fe²⁺ and activating O₂ for transfer to styrene. However, both deglycoBLM analogues exhibited diminished abilities to effect the relaxation of supercoiled plasmid DNA, and neither mediated sequence selective DNA cleavage.