The new sesquiterpenes 1 ct-benzoyloxy-9fl-acetoxy-4fl,6fl-dihydroxydihydro-fl-agarofuran, lct-benzoyloxy-6fl,9fl-diacetoxy-4fl-hydroxydihydro-fl-agarofuran, l~t-benzoyloxy-6fl,9fl,15-triacetoxy-4fl-hydroxydihydro-fl-agarofuran, l~-benzoyloxy-6fl,8fl,9~t-triacetoxy-4/~-hydroxydihydro-/~-agarofuran, l~t-benzoyloxy-6B,9~t-diacetoxy-4fl,8fl-dihydroxydihydro-fl-agarofuran and l ot-cinnamoyloxy-2fl,6fl,9fl-triacetoxy-4fl-hydroxydihydro-fl-agarofuran were isolated from the aerial part of Orthosphenia mexicana and their structures determined by spectroscopic and chemical studies.