2,2-dimethyl-6-(6-trimethylsilylhex-5-ynyl)-1,3-dioxin-4-one

(2,2-dimethyl-1,3-dioxolan-4-yl)methyl 3-oxobutanoate

cyclopropylmethyl 3-oxobutanoate

but-1-ene-1,3-dione

ethyl (Z)-3-hydroxy-2-butenoate