Compounds represented by the following structure (I) are disclosed: as are methods for making such compounds, wherein said methods comprise reacting a diacyldiketopiperazine with a first aldehyde to produce an intermediate compound; and reacting the intermediate compound with a second aldehyde to produce the class of compounds with the generic structure, where the first aldehyde and the second aldehydes are selected from the group consisting of an oxazolecarboxaldeyhyde, imidazolecarboxaldehyde, a benzaldehyde, imidazolecarboxaldehyde derivatives, and benzaldehyde derivatives, thereby forming the above compound wherein R1, R1′, R1″, R2, R3, R4, R5, and R6, X1 and X2, Y, Z, Z1, Z2, Z3, and Z4 may each be separately defined in a manner consistent with the accompanying description. Compositions and methods for treating vascular proliferation are also disclosed.