The new sesquiterpene alkaloids 1α-benzoyloxy-6β-nicotinoyloxy-9β-acetoxy-4β-hydroxydihydro-β-agarofuran, 1α-cinnamoyloxy-6β-nicotinoyloxy-9β-acetoxy-2β,4β-dihydroxydihydro-β-agarofuran, 1α-benzoyloxy-6β-nicotinoyloxy-8β,9α-diacetoxy-4β-hydroxydihydro-β-agarofuran and 1α-benzoyloxy-6β-nicotinoyloxy-9α-acetoxy-8β,4β-dihydroxydihydro-β-agarofuran were isolated from the aerial part of Orthosphenia mexicana and from the root bark of Rzedowskia tolantonguensis and their structures determined by spectroscopic and chemical studies. © 1987.