Abstract: Rhizoxin and rhizoxin-2-ene derivatives of formula (I): ##STR1## in which: n is 1 to 25: A is an extra bond or oxygen, X is oxygen, sulfur, nitrogen or carbonyl; and R is hydrogen, carboxylic acyl having from 1 to 25 carbon atoms, alkoxycarbonyl group having from 2 to 26 carbon atoms, phosphono, alkylphosphono group in which the alkyl part has from 1 to 25 carbon atoms, dialkylphosphono group in which each alkyl part has from 1 to 25 carbon atoms, alkyl group having from 1 to 25 carbon atoms, aralkyl, cycloalkyl, heterocyclic, alkylthio group in which the alkyl part has from 1 to 25 carbon atoms, aralkylthio, or heterocyclylthio, or when X represents a nitrogen atom, R is R.sup.1 and R.sup.2, where R.sup.1 and R.sup.2 are hydrogen, alkyl, acyl, alkoxycarbonyl, phosphono, alkylphosphono or dialkylphosphono have valuable anti-tumor activity. They may be prepared by acylation of rhizoxin or rhizoxin-2-ene.

Abstract: Rhizoxin and rhizoxin-2-ene derivatives of formula ##STR1## in which: n is 1 to 25; A is an extra bond or oxygen, X is oxygen, sulfur, nitrogen or carbonyl; and R is hydrogen, carboxylic acyl having from 1 to 25 carbon atoms, alkoxycarbonyl group having from 2 to 26 carbon atoms, phosphono, alkylphosphono group in which the alkyl part has from 1 to 25 carbon atoms, dialkylphosphono group in which each alkyl part has from 1 to 25 carbon atoms, alkyl group having from 1 to 25 carbon atoms, aralkyl, cycloalkyl, heterocyclic, alkylthio group in which the alkyl part has from 1 to 25 carbon atoms, aralkylthio, or heterocyclylthio, or when X represents a nitrogen atom, R is R.sup.1 and R.sup.2, where R.sup.1 and R.sup.2 are hydrogen, alkyl, acyl, alkoxycarbonyl, phosphono, alkylphosphono or dialkylphosphono, have valuable anti-tumor activity. They may be prepared by acylation of rhizoxin or rhizoxin-2-ene.