A synthesis of functionalised tricyclo[5.2.2.0]undecenes related to the isoeremolactone skeleton

Abstract

Synthesis of methyl 4,8-dimethyltricyclo[5.2.2.0^1,5]undeca-4(and 5),8-diene-9-carboxylate (3), as a synthon for isoeremolactone, is described. The key steps are the double Michael addition of the enolate of 3-[3,3-ethylenedioxybutyl]cyclohex-2-en-1-one (9), prepared from m-methoxyphenylbut-3-en-2-one (4), to methyl 2-(ethylthio)but-2-enoate leading to the bicyclo[2.2.2]octanone intermediate (12) and the intramolecular aldol condensation of the deprotected diketone (13) to construct the third five-membered carbocyclic ring.