Derivatives of the epoxy-β-aminoketone containing natural product eponemycin have been prepared in order to study the molecular mode of action of this anti-angiogenic compound. Synthesis and use of a biotinylated dihydroeponemycin analogue demonstrated that dihydroeponemycin forms a covalent adduct with at least two intracellular proteins in human endothelial cells. Pretreatment of cells with a five equivalent excess of dihydroeponemycin precluded biotin-dihydroeponemycin binding indicating a specific interaction between natural product and the target proteins. This biotin-dihydroeponemycin derivative will prove useful in the purification and identification of eponemycin receptors.