New high-molecular decomposition products of natamycin (pimaricin) with intact lactone-ring.

Mild acid treatment of natamycin (IV) results in biologically inactive aponatamycin (VI), an amphoteric substance with some natamycin-like chemical and physical properties. Aponatamycin contains one natamycin- and one natamycinolide-moiety. More drastic acid degradation of natamycin eliminates the aminosugar under formation of the dimer (VII) of the hypothetical aglycone of natamycin, natamycinolide (V) as well as a non-ionic compound, the dimer of the 12-decarboxy-11-anhydro analogue of natamycinolide.