| abstract |
Compounds of formula I: **(See formula)** or a salt thereof, wherein: each R1 and R4 are independently H, or COR5; R2 and R3 are COR5; and each R5 is independently selected from the group of C3-C7 straight or branched chain alkyl, C4-C10 alkylcycloalkyl, and C3-C7 cycloalkyl; for use in treating cancer in a patient in need. |