Phototransformations of Some 2‐Substituted 4 H‐Chromen‐4‐ones (4‐Chromones) Related to the Antitumor Antibiotic Hedamycin

The 2‐substituted 4 H‐chromen‐4‐ones (4‐chromones) 2 and 3 have epoxysubstituted side chains at C(2) resembling that of the antibiotic hedamycin (1). They were chosen as model compounds and subjected to photolysis either in the presence or in the absence of oxygen. The products obtained were isolated by repeated HPLC., and their structures were determined by spectroscopic methods, mainly 1H‐ and 13C‐NMR. Especially noteworthy are the oxygen dependent formation of the tertiary alcohols 11 and 12 as well as the transformation of the diepoxychromone 3 to the allylic alcohols 13 and 14, the spiro compounds 15 and 16, and the 2‐ethylchromone 19.