A convergent solid-phase synthesis of actinomycin analogues--towards implementation of double-combinatorial chemistry

The actinomycin antibiotics bind to nucleic acids via both intercalation and hydrogen bonding. We found this 'double-action attack' mechanism very attractive in our search for a novel class of nucleic acid binders. A highly convergent, solid-phase synthetic strategy has been developed for a class of peptide-aryl-peptide conjugates modeled upon natural actinomycins. The features of this method include the use of Fmoc solid-phase peptide synthesis, side-chain to side-chain cyclization on the solid phase, a chemoselective cleavage step and segment condensation. The synthetic scheme is consistent with the requirements for combinatorial synthesis and furthermore, the final segment condensation allows, for the first time, double-combinatorial chemistry to be performed where two combinatorial libraries can be reacted with each other.