Compounds of formula I are described, ##STR1## wherein: R.sub.1 and R.sub.2, that can be the same or different, are hydrogen or acyl groups; R.sub.3 and R.sub.4, that can be the same or different, are hydrogen or optionally substituted alkyl groups. The compounds of formula I are prepared by oxydation of the compounds of formula II: ##STR2## wherein the groups R'.sub.1, R'.sub.2, R'.sub.3 and R'.sub.4 have the same meanings as R.sub.1, R.sub.2, R.sub.3 and R.sub.4 or groups convertible to the latter. The compounds of formula I have remarkable antitumor activity.
化合物的
化学式I如下所述,##STR1##其中:R.sub.1和R.sub.2,可以相同也可以不同,是氢或酰基基团;R.sub.3和R.sub.4,可以相同也可以不同,是氢或可选择性取代的烷基基团。化合物的
化学式I是通过氧化
化学式II的化合物制备的:##STR2##其中基团R'.sub.1、R'.sub.2、R'.sub.3和R'.sub.4具有与R.sub.1、R.sub.2、R.sub.3和R.sub.4相同的含义或可转化为后者的基团。
化学式I的化合物具有显著的抗肿瘤活性。