Ethyl 2-ethylidene-3-oxohex-4-enoate

(3aS,8bR)-3-((E)-But-2-enoyl)-4,4-dimethyl-3,3a,4,8b-tetrahydro-indeno[2,1-d]oxazol-2-one

(E)-1-((3aR,6aR)-3-tert-Butyl-4,4-dioxo-3a,4,6,6a-tetrahydro-1-oxa-4λ6-thia-2,5-diaza-pentalen-5-yl)-but-2-en-1-one

(E)-1-((3R,3aR,6aR)-2-Benzyl-4,4-dioxo-3-pyren-1-yl-hexahydro-1-oxa-4λ6-thia-2,5-diaza-pentalen-5-yl)-but-2-en-1-one

But-3-enoic acid (1R,5S,6S)-6-(2,2-dimethyl-propionylamino)-spiro[4.4]non-1-yl ester