3,6-Cyclopropylene-Δ4-tetrahydrophthalic Anhydride is an intermediate in synthesizing Tecovirimat (T137330), an orally bioavailable antipoxvirus compound inhibits extracellular virus formation and protects mice from lethal orthopoxvirus, including vaccinia, monkeypox, camelpox, cowpox, ectromelia (mousepox), and variola viruses.