2.2.3.3. Kedarcidin Chromophore

Kedarcidin is a new chromoprotein antitumor antibiotic that was isolated from the fermentation broth of a novel actinomycete strain. It consists of an apoprotein and a cytotoxic, highly labile, non protein chromophore. The apoprotein is water soluble while the chromophore is solvent-extractable, cytotoxic and highly unstable. As with NCS, the antitumor activity of kedarcidin is due primarily to the chromophore. The enediyne core is activated by chemical reduction (e.g. sodium borohydride) followed by spontaneous cyclization to a biradical intermediate and DNA cleavage (Scheme 6).