Abstract: A conversion product of polysuccinimide useful as coating material for medicinal preparations and foodstuffs having the structure: ##STR1## wherein A is hydrogen or a straight or branched alkyl or alkylene group of 1 to 8 carbon atoms, optionally substituted by cycloaliphatic or aromatic groups, wherein the cyclic substituent can also contain heteroatoms, or by R--O--, ##STR2## or R.sub.3 R.sub.4 N groups, wherein R, R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are hydrogen or branched alkyl or cycloalkyl groups each of which may contain oxygen and nitrogen atoms in the chain or in the ring of 1 to 10 carbon atoms;B is hydrogen or straight or branched chain alkyl or alkenyl, and is the same or different from A;D is hydrogen, NH.sub.4, ##STR3## wherein A and B have the aforementioned meanings, or an alkali metal ion; anda is 0.2 to 1 and b is 0.8 to 0.