Artemisinin and its derivatives (ARTs) are being studied for their potential anti-tumor activity. Dimerization of artemisinin has been proposed as a promising means of enhancing drug efficacy. However, the sequential progression from monomers to dimers and trimers, retaining a consistent β-configuration, has not been previously investigated in terms of its effect on compound activity. To investigate the effect of various oligomeric forms on drug potency, we synthesized β-configuration-based ARTs, namely a monomer, dimer, and trimer, and rigorously characterized their structure. We evaluated the antitumor efficacy of these compounds against MCF-7 breast cancer cells. The artemisinin trimer 6a (β, β, β) exerted a stronger cytotoxic effects against MCF-7 breast cancer cells, with an IC