| abstract |
The present invention relates to a compound of formula (I) wherein R1 and R2 are selected from lower alkyl groups having 1-6 carbon atoms, substituted or unsubstituted aryl groups, and unsaturated alkyl groups having 1-6 carbon atoms; R3 is a substituted or unsubstituted lower alkyl group having 1-6 carbons; and R4 is selected from substituted or unsubstituted lower alkyl groups having 1-6 carbon atoms, substituted or unsubstituted aryl groups, and unsaturated alkyl groups having 1-6 carbon atoms. The present invention also relates to a pharmaceutical composition comprising the above compound, as well as a method of treating tumor cells with the compound. |