novel methods for treatment of neoplastic disease states in animals , which methods comprise administering a therapeutically effective amount of a compound of the formula iv , ## str1 ## wherein : y is hydrogen or lower alkyl ; and z is a radical of the formula -- o -- r , wherein r is : a substituted lower alkyl radical selected from the group consisting of mono - and di - hydroxy lower alkyl , cyano lower alkyl , halo lower alkyl , lower alkyl amino lower alkyl , hydroxy lower alkylthio lower alkyl , hydroxy lower alkyldithio lower alkyl , di - lower alkoxy lower alkyl , hydroxy or lower alkoxy substituted lower alkoxy lower alkyl , and cyclo lower alkyl substituted lower alkyl ; or a lower alkenyl radical ; or a lower alkynyl radical ; or a substituted or unsubstituted oxygen - containing heterocyclic radical selected from the group consisting of tetrahydro furanyl or lower alkyl substituted derivatives thereof , lower alkyl substituted oxiranyl , lower alkyl substituted dioxolanyl , lower alkyl substituted pyranyl , or lower alkyl substituted furanyl .