3-[(S)-(2-tert-butyldimethylsilyloxy)propanoyl]-3-[4-methoxy-1,2-dihydrobenzocyclobuten-1-yl]-6,9-divinyl-1-oxaspiro[4,4]nonan-2-one 以18%的产率得到(8β,9α,14α)-11β-[2(S)-(tert-butyldimethylsilyloxy)propanoyl]-11α,13α-(γ-carbolactone)-3-methoxy-17α-vinylgona-1,3,5(10)-triene