cis-4,5-dihydroxy-5-[[(tert-butyldimethylsilyl)oxy]methyl]-2-cyclopentenone

t-4-[(tert-butyldimethylsilyl)oxy]-5-hydroxy-r-5-[[(tert-butyldimethylsilyl)oxy]methyl]-2-cyclopentenone

(2RS,3RS,4SR)-3,4-dihydroxy-4-t-butyldimethylsilyloxy-2-t-butyldimethylsilyloxymethylcyclopentan-1-one

(5S,9S)-9-hydroxy-2,2-dimethyl-1,3-dioxaspiro[4.4]non-7-en-6-one

6-carbethoxy-1,4-dioxaspiro[4.4]non-6-ene