(1R,3R,4S,6S)-3-acetyl-3-(2-(2-oxolanyl)ethyl)-6-acetoxybicyclo[2.2.2]octan-2-one

(1R,3S,4S,6S)-spiro[6-acetoxybicyclo[2.2.2]octan-2-one-3,1'-cyclohex-3'-en]-2'-one

(1R,3S,4S,6S)-spiro[6-hydroxybicyclo[2.2.2]octan-2-one-3,1'-cyclohex-3'-en]-2'-one

(1S,2S,4R,5S)-2',3-dioxospiro[bicyclo[2.2.2]octane-2,1'-cyclohexan]-3'-en-5-yl (2R,3S)-3-benzamido-2-(methoxymethoxy)-3-phenylpropanoate