We synthesized UG-650, a novel non-Gemini analog of UVB1 that combines structural features of UVB1 and MC 1288. The evaluation of the bioactivities indicates that UG-650 dose-dependently inhibited MCF-7 cell proliferation. In comparison to calcitriol, slightly lower concentrations of UG-650 were needed to achieve equivalent levels of proliferation inhibition. Structural analysis revealed that the analog forms additional interactions stabilizing VDR active form.