8-Bromo-7-(tert-butyl-diphenyl-silanyloxymethyl)-3,3-diethyl-1,5-dioxa-spiro[5.5]undeca-7,10-dien-9-one

(1R,6S)-3-(((tert-butyldiphenylsilyl)oxy)methyl)-5',5'-diethyl-4-((E)-pent-1-en-1-yl)-7-oxaspiro[bicyclo[4.1.0]heptane-2,2'-[1,3]dioxan]-3-en-5-one

(1R,6S)-4-bromo-3-(((tert-butyldiphenylsilyl)oxy)methyl)-5',5'-diethyl-7-oxaspiro[bicyclo[4.1.0]heptane-2,2'-[1,3]dioxan]-3-en-5-one

(1S,6R)-4-bromo-3-(((tert-butyldiphenylsilyl)oxy)methyl)-5',5'-diethyl-7-oxaspiro[bicyclo[4.1.0]heptane-2,2'-[1,3]dioxan]-3-en-5-one