The invention relates to a compound of formula (I) ##STR1## wherein R.sub.1 is a sugar; R.sub.2 is --CH.sub.2 --O--(R.sub.7)m, R.sub.7 representing a sugar, or is --COOH; R.sub.3 is an epoxide-comprising group, or is C.sub.1 -C.sub.6 -alkyl or C.sub.2 -C.sub.6 -alkenyl, unsubstituted or substituted by at least one OH; R.sub.5 is H, C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl or C.sub.2 -C.sub.6 -alkynyl; R.sub.4 R.sub.6, R.sub.8 and R.sub.10 independently of one another are H; C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl, C.sub.2 -C.sub.6 -alkynyl, --X.sub.2 H, or --X.sub.2 R.sub.12, or R.sub.4 and R.sub.6 together and/or R.sub.8 and R.sub.10 together are =X.sub.2 ; X.sub.2 is O, NH, N--C.sub.1 -C.sub.6 -alkyl, N--C.sub.2 -C.sub.6 -alkenyl, N-C.sub.2 -C.sub.6 -alkynyl or S; R.sub.12 is C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 --alkenyl, C.sub.2 -C.sub.6 -alkynyl, aryl or acyl; and m and n are 1 or 2; in any of its stereochemical forms and mixtures of these forms in any ratio, and a physiologically acceptable salt or derivative thereof. The compounds are obtainable from a culture of the microorganism Actinomycetales species HAG 003959, DSM 12931, by fermentation. Accordingly, the invention relates to a process for their preparation and to the use of the compounds as pharmaceuticals, for example as antitumor agents.