Abstract: The present invention relates to novel substituted thiosemicarbazonic acid esters of formula I ##STR1## wherein R.sub.1 is lower alkyl, lower alk-2-en-1-yl, lower alk-2-yn-1-yl, or aryl-lower alkyl, R.sub.2 is hydrogen, lower alkyl, aryl, aryl-lower alkyl, lower alk-2-en-1-yl, lower alk-2-yn-1-yl, unsaturated or saturated heterocyclyl-lower alkyl, lower alkoxycarbonyl-lower alkyl or the group --C(.dbd.O)-R.sub.3, wherein R.sub.3 is lower alkyl, aryl, aryl-lower alkyl, aryl-lower alkenyl, heteroaryl (hetaryl), aryloxy, aryl-lower alkoxy or lower alk-2-en-1-yloxy, and R.sub.4 is lower alkyl, lower alkoxy, lower alk-2-en-1-yl, lower alk-2-yn-1-yl, aryl-lower alkyl, aryl-lower alkenyl, or also lower alkoxycarbonyl-lower alkyl, and the salts thereof, to a process for the preparation of said compounds, to pharmaceutical compositions containing them, and to the use thereof as medicaments.

Abstract: Substituted piperazine dione oxyls and hydroxides are stabilizers for synthetic polymeric materials normally subject to deterioration caused by ultraviolet light. The compounds may be prepared by first preparing a substituted piperazine dione with subsequent oxidation of the piperazine dione to yield the oxyl and reduction of the oxyl to yield the hydroxide derivative. Polymeric compositions containing these stabilizers may also contain a hindered phenolic compound. A typical embodiment is 15-n-octadecyl-7-oxyl-7,15-diazadispiro[5,1,5,3]hexadecane-14,16-dione.