ethyl 4-hydroxy-3-methylbut-2-enoate

(E)-4-(tert-butyldimethylsilanyloxy)-3-methylbut-2-enoic acid ethyl ester

ethyl 2-((3R,8aS)-3-methyl-1,4-dioxohexahydro-1H-pyrrolo[2,1-c][1,4]oxazin-3-yl)acetate

(E)-(4-ethoxy-2-methyl-4-oxobut-2-enoyl)-L-proline

(S)-Iodo-((3S,8aS)-3-methyl-1,4-dioxo-hexahydro-pyrrolo[2,1-c][1,4]oxazin-3-yl)-acetic acid ethyl ester