Chemistry of maduramicin. I. Salt formation and normal ketalization

The formation of monovalent and divalent salt complexes of maduramicin is described and the 13C NMR chemical shift assignments of these materials are tabulated and discussed. In the spectrum of the thallium salt, 20 of the 47 signals are split due to the thallium-carbon coupling. Similarly the preparation of both the free acid and the sodium salt complexes of the normal methyl and ethyl ketal derivatives of maduramicin are outlined. Their 13C NMR spectra are fully assigned together with discussion of displacements observed due to this derivatization.