2-<(methoxycarbonyl)oxy>-3-<(trimethylsilyl)methyl>-3-butenoic acid

(4R*,14R*,17S*)-16-methyl-14-(phenylsulfonyl)-2-oxo-3-oxatricyclo<12.2.1.04,17>heptadec-1-ene

(4S*,8R*,11S*)-10-methylene-8-(phenylsulfonyl)-2-oxo-3-oxatricyclo<6.2.1.04,11>undec-1-ene

(4R*,10R*,13S*)-12-methyl-10-(phenylsulfonyl)-2-oxo-3-oxatricyclo<8.2.1.04,13>tridec-1-ene

(4S*,9R*,12S*)-11-methyl-9-(phenylsulfonyl)-2-oxo-3-oxatricyclo<7.2.1.04,12>dodec-1-ene