Abstract
Chromomycin A3 (A3), chromomycinone (CHR), 2'-dihydrochromomycinone (H2CHR), and iso-chromomycinone (iCHR) gave 2-electron reduction waves due to the conjugated ketones at the 1-position and catalytic hydrogen waves in acid solutions, whereas 1-deoxochromomycinone (DOCHR) afforded no wave. Methyl ethers and acetates of A3 and CHR (A3Me, CHRMe2, A3Ac, CHRAc6) showed the 2-electron reduction waves even in alkaline solutions before their hydrolysis because of lack of hydroxyl to affect on the reduction of carbonyl. Chromomyciquinone (CHQ) afforded a 2-electron 2-proton redox wave to predict the structure of naphthoquinones. The wave was affected by borax to suggest the polyhydroxyl group. It was predicted by polarography, spectroscopy and titration that A3 forms copper chelates, Cu (A3)2 and Cu (A3) Ac, in which the pen-standing oxo-enol group will offer the site of chelation.
