Syntheses and unusual spectroscopic properties of novel ketobacteriopurpurins

Nuclear Overhauser enhancement experiments show that migratory aptitudes of alkyl groups in various vic-dihydroxybacteriopurpurins are different for individual stereoisomers. Long wavelength absorption maxima of ketobacteriopurpurins obtained from pinacol-pinacolone rearrangements of the corresponding diols are influenced by the position of the keto group in the macrocycle; differences in these maxima are diminished by introduction of electron-withdrawing substituents.