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Communication | Special issue | Vol 25, No. 1, 1987, pp.89-96
Published online, 1st January, 1970
DOI: 10.3987/S-1987-01-0089
Circular Dichroic Spectra and Ionization Processes of Some Tropolonic Alkaloids

Daniela Walterova, Petr Malon, Frantisek Grambal, and Vilím Simánek

*Institute of Medical Chemistry, Palacky University, 3, Hnevotínská, 775 15 Olomouc, Czech Republic

Abstract

Some tropolonic alkaloids have been investigated by circular dichroic (CD) spectroscopy in dependence on pH. Their pKa values in water-ethanol mixture (1:1) are given. Molar circular dichroism values ( δ ε ) are reported for all the measured alkaloids. The pH-depending changes in CD spectra are observed in demethylcolchicines and colchiceines. In the former they are associated with the ionization of phenolic groups in aromatic ring A, and in t h e latter with conformational changes of tropolonic rine C due to ionization of hydroxyl group at C-10.