Product of a Novel Carbocyclic Enlargement in Aqueous Media: 9[beta]-tert-Butoxy-4-(E)-ethylidene-8[beta]-methyl-5-oxobicyclo[6.3.0]undecan-2[beta]-carboxylic Acid Methyl Ester

The title compound, C₂₀H₃₂O₄, is the major diastereomer obtained by the two-carbon ring expansion of a precursor containing fused five- and six-membered rings. It is shown to have the methyl, tert-butoxy and carboxymethyl substituents in mutually cis dispositions.

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