tert-butyl (2R)-2-[(2S)-1,4-dioxaspiro[4.5]dec-2-yl]cyclopent-3-ene-1-carboxylate

tert-butyl (3R)-2-allyl-3-[(2S)-1,4-dioxaspiro[4.5]dec-2-yl]pent-4-enoate

tert-butyl (1R,2S)-2-[(2S)-1,4-dioxaspiro[4.5]dec-2-yl]-1-(phenylthio)cyclopent-3-ene-1-carboxylate

(3S,2'S)-(1',4'-dioxa-spiro[4.5]dec-2'-yl)-pent-4-enoic acid ethyl ester