STUDIES ON PLANT BILE PIGMENTS. II. REGIOSELECTIVE PHOTOCHEMICAL AND ACID CATALYZED Z,E ISOMERIZATION OF DIHYDROBILINDIONE AS PHYTOCHROME MODEL

The (4 Z, 10 Z, 15E)-2,3-dihydrobilindione 4, along with the fully unsaturated (E, Z, Z)-analogue 8, has been prepared from the corresponding (Z, Z, Z)-isomer by a variation of Falk's method (Falk et aL, 1980). The photochemical and acid-catalyzed back-reactions have been studied by UV-vis and 1H-NMR spectroscopy.