Compounds of the formula ##STR1## wherein R is alkyl, alkylthio or hydroxy, as well as, pharmaceutically acceptable salts of compounds of formula I are antiproliferative agents useful in the treatment of cancer.
                            公式为##STR1##的化合物,其中R是烷基,烷
硫基或羟基,以及公认为药用的I式化合物的盐是抗增殖剂,可用于治疗癌症。